Oxidative stress and mitochondrial dysfunction mediated Cd-induced hepatic lipid accumulation in zebrafish Danio rerio Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-17 Ya-Xiong Pan, Zhi Luo, Mei-Qing Zhuo, Chuan-Chuan Wei, Guang-Hui Chen, Yu-Feng Song
The present study was performed to determine the effect of waterborne CdCl2 exposure influencing lipid deposition and metabolism, oxidative stress and mitochondrial dysfunction, and explore the underlying molecular mechanism of cadmium (Cd)-induced disorder of hepatic lipid metabolism in fish. To this end, adult zebrafish were exposed to three waterborne CdCl2 concentrations (0(control), 5 and 25 μg Cd/l, respectively) for 30 days. Lipid accumulation, the activities of enzymes related to lipid metabolism and oxidative stress, as well as the expression level of genes involved in lipid metabolism and mitophagy were determined in the liver of zebrafish. Waterborne CdCl2 exposure increased hepatic triglyceride (TG) and Cd accumulation, the activities of fatty acid synthase (FAS), 6-phosphogluconate dehydrogenase (6PGD), glucose 6-phosphate dehydrogenase (G6PD) and malic enzyme (ME), and the mRNA level of fatty acid synthase (fas), acetyl-CoA carboxylase alpha (acaca), glucose 6-phosphate dehydrogenase (g6pd) and malic enzyme (me), but reduced the mRNA level of carnitine palmitoyl transferase 1 (cpt1), hormone-sensitive lipase alpha (hsla), and adipose triacylglyceride lipase (atgl). The activities of superoxide dismutase (SOD), glutathoinine peroxidase (GPx) and cytochrome c oxidase (COX) and the ATP level were significantly reduced after CdCl2 exposure. CdCl2 exposure significantly increased the mRNA level of genes (microtubule-associated protein light chain 3 alpha (lc3a), PTEN-induced putative kinase 1 (pink1), NIP3-like protein X (nix) and PARKIN (parkin) related to mitophagy. To elucidate the mechanism, reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC) and the mitochondrial permeability transition (MPT) inhibitor cyclosporine A (CsA) were used to verify the role of ROS and mitochondrial dysfunction in Cd-induced disorder of lipid metabolism. NAC pretreatment reversed the Cd-induced up-regulation of TG accumulation and activities of lipogenic enzymes, and the Cd-induced down-regulation of mRNA levels of lipolytic genes. Meanwhile, NAC pretreatment also blocked the mitochondrial membrane potential (MMP) collapse and decreased the ATP level, suggesting that ROS played a crucial role in regulating the Cd-induced mitochondrial dysfunction. Taken together, our findings, for the first time, highlight the importance of the oxidative stress and mitochondrial dysfunction in Cd-induced disorder of hepatic lipid metabolism, which proposed a novel mechanism for elucidating metal element exposure inducing the disorder of lipid metabolism in vertebrates.
Microcystin-leucine arginine mediates apoptosis and engulfment of Leydig cell by testicular macrophages resulting in reduced serum testosterone levels Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-17 Yabing Chen, Jing Wang, Xiang Chen, Dongmei Li, Xiaodong Han
Microcystin-leucine arginine (MC-LR) causes decline of serum testosterone levels resulting in impaired spermatogenesis; however, the underlying molecular mechanisms are not fully understood. In this study, we aimed to investigate the effects of MC-LR exposure on the number of Leydig cells (LCs) in testis. Following chronic low dose exposure to MC-LR, the number of LCs was markedly decreased while macrophages were significantly increased. Then, we established a co-culture system to study the interaction between macrophages and LCs in the presence of MC-LR. No significant apoptosis of LCs cultured alone was observed after MC-LR (< 5 000 nM) treatment; however, apoptosis was robustly increased when LCs were co-cultured with macrophages in the presence of MC-LR. Further studies identified that MC-LR could stimulate macrophage to produce TNF-α, and secreted TNF-α induced LC apoptosis by binding to the tumor necrosis factor receptor 1 (TNFR1) on the LCs and thus activating reactive oxygen species (ROS)-p38MAPK signaling pathway. Furthermore, we also examined increased expression of Axl receptor and growth arrest-specific 6 (Gas6) in macrophages after MC-LR treatment. GAS6 mediates phagocytosis of apoptotic LCs by binding to the Axl receptor on macrophages and phosphatidylserine (PtdSer) on apoptotic LCs. Together, these results suggested that reduced serum testosterone levels may be associated with decrease of LCs as a result of LC apoptosis and phagocytosis by immune cells in MC-LR-treated mice.
A protective role for autophagy in TDCIPP-induced developmental neurotoxicity in zebrafish larvae Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-15 Ruiwen Li, Ling Zhang, Qipeng Shi, Yongyong Guo, Wei Zhang, Bingsheng Zhou
Tris (1, 3-dichloro-2-propyl) phosphate (TDCIPP), an extensively used organophosphorus flame retardant, is frequently detected in various environmental media and biota, and has been demonstrated as neurotoxic. Autophagy has been proposed as a protective mechanism against toxicant-induced neurotoxicity. The purpose of the present study was to investigate the effect of TDCIPP exposure on autophagy, and its role in TDCIPP-induced developmental neurotoxicity. Zebrafish embryos (2–120 h post-fertilization [hpf]) were exposed to TDCIPP (0, 5, 50 and 500 μg/l) and a model neurotoxic chemical, chlorpyrifos (CPF, 100 μg/l). The developmental endpoints, locomotive behavior, cholinesterase activities, gene and protein expression related to neurodevelopment and autophagy were measured in the larvae. Our results demonstrate that exposure to TDCIPP (500 μg/l) and CPF causes developmental toxicity, including reduced hatching and survival rates and increased malformation rate (e.g., spinal curvature), as well as altered locomotor behavior. The expression of selected neurodevelopmental gene and protein markers (e.g., mbp, syn2a, and α1-tubulin) was significantly down-regulated in CPF and TDCIPP exposed zebrafish larvae. Treatment with CPF significantly inhibits AChE and BChE, while TDCIPP (0–500 μg/l) exerts no effects on these enzymes. Furthermore, the conversion of microtubule-associated protein I (LC3 I) to LC3 II was significantly increased in TDCIPP exposed zebrafish larvae. In addition, exposure to TDCIPP also activates transcription of several critical genes in autophagy (e.g. Becn1, atg3, atg5, map1lc3b and sqstm1). To further investigate the role of autophagy in TDCIPP induced developmental neurotoxicity, an autophagy inducer (rapamycin, Rapa, 1 nM) and inhibitor (chloroquine, CQ, 1 μM) were used. The results demonstrate that the hatching rate, survival rate, and the expression of mbp and а1-tubulin proteins were all significantly increased in larvae treated with TDCIPP (500 μg/l) and Rapa compared to TDCIPP alone. In contrast, co-treatment with the autophagy inhibitor CQ results in exacerbated neurodevelopmental toxicity. Taken together, our results confirm that exposure to TDCIPP induces autophagy, which plays a protective role in TDCIPP-induced developmental neurotoxicity in zebrafish embryos and larvae.
Tris (2-butoxyethyl) phosphate affects motor behavior and axonal growth in zebrafish (Danio rerio) larvae Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-13 Fan Jiang, Jue Liu, Xinyue Zeng, Liqin Yu, Chunsheng Liu, Jianghua Wang
Tris (2-butoxyethyl) phosphate (TBOEP) is an environmental contaminant that poses serious risks to aquatic organisms and their associated ecosystem. Recently, the reproductive and developmental toxicology of TBOEP has been reported. However, fewer studies have assessed the neurotoxic effects in zebrafish (Danio rerio) larvae. In this study, zebrafish embryos were subjected to waterborne exposure of TBOEP at 0, 50, 500, 1500 and 2500 μg/L from 2 to 144-h post-fertilization (hpf). Behavioral measurements showed that TBOEP exposure reduced embryonic spontaneous movement and decreased swimming speed of larvae in response to dark stimulation. In accordance with these motor effects, TBOEP treatment reduced neuron-specific GFP expression in transgenic Tg (HuC-GFP) zebrafish larvae and inhibited the growth of secondary motoneurons, as well as decreased expression of marker genes related to central nervous system development in TBOEP treated group. Furthermore, increased concentrations of reactive oxygen species (ROS) and malondialdehyde (MDA), as well as reduction of SOD activity were detected in TBOEP exposure group. The present results showed that the alteration in motor neuron and oxidative stress could together lead to the motor behavior alterations induced by TBOEP.
Tissue-specific molecular and cellular toxicity of Pb in the oyster (Crassostrea gigas): mRNA expression and physiological studie Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-13 Jie Meng, Wen-Xiong Wang, Li Li, Guofan Zhang
Lead (Pb) is one of the ubiquitous and toxic elements in aquatic environment. In oysters, gills and digestive glands are the main target organs for Pb-induced toxicity, but there is limited information on the molecular mechanisms underlying its toxicity. The present study investigated the Pb-induced toxicity mechanisms in the Pacific oyster (Crassostrea gigas) based on transcriptome, phenotypic anchoring, and validation of targeted gene expression. Gene ontology and pathway enrichment analyses revealed the differential Pb toxicity mechanisms in the tissues. In the gills, Pb disturbed the protein metabolism, with the most significant enrichment of the “protein processing in endoplasmic reticulum” pathway. The main mechanism comprised of a Pb-stimulated calcium (Ca2+) increase by the up-regulation of transporter-Ca-ATPase expression. The disturbed Ca2+ homeostasis then further induced high expressions of endoplasmic reticulum (ER) chaperones, leading to ER stress in the oysters. Unfolded proteins induced ER associated degradation (ERAD), thereby preventing the accumulation of folding-incompetent glycoproteins. However, Pb mainly induced oxidative reduction reactions in the digestive gland with high accumulation of lipid peroxidation products and high expression of antioxidant enzymes. Further, Pb induced fatty acid β-oxidation and CYP450 catalyzed ω-oxidation due to increased metabolic expenditure for detoxification. The increased content of arachidonic acid indicated that Pb exposure might alter unsaturated fatty acid composition and disturb cellular membrane functions. Taken together, our results provided a new insight into the molecular mechanisms underlying Pb toxicity in oysters.
Alterations of secondary sex characteristics, reproductive histology and behaviors by norgestrel in the western mosquitoﬁsh (Gambusia affinis) Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-13 Li-ping Hou, Hongxing Chen, Chang-en Tian, Ye Liang, Rong-rong Wu, Xing-mei Zhang, Xu-wen Fang, Cui-ping Zhang, Jun-jie Hu, Li-ying Song, Yan-qiu Liang, Daniel Schlenk, Lingtian Xie
Synthetic hormones in wastewater effluents released into the aquatic environments may interfere with the normal endocrine systems of fish in receiving streams. Norgestrel (NGT) is a synthetic progestin widely used in oral contraceptives and frequently detected in wastewater effluents. In this study, adult female mosquitofish (Gambusia affinis) were exposed to three environmentally relevant concentrations of norgestrel (NGT) (i.e., 3.6, 35.8, and 368.0 ng L−1) for 42 d, fin morphology, histology of the ovary, and reproductive behaviors were evaluated. The results showed that NGT at all three concentrations caused an increased frequency of atretic follicular cells in ovaries and impaired mating behaviors exhibited by males toward the NGT-exposed females. In mosquitofish exposed to NGT at 35.8 and 368 ng L−1, the anal fin of females had an increased length ratio of ray4/ray 6, an increased width of ray 3, and increased number of segments in ray 3. The histopathological analysis showed that exposure to NGT increased the incidence of spermatogenesis in ovaries. Mating behavior was impaired 58.4%, 65.7%, and 76.4% (P < 0.01 in all cases) in when mosquitofish were exposed to NGT at 3.6, 35.6 and 368.0 ng L−1, respectively. The rapid masculinization, the increased frequency of atretic follicles, the incidence of spermatogenesis in the ovary of female fish, and the altered reproductive behaviors suggest that wild populations of mosquitofish could be similarly affected inhabiting in NGT contaminated environments.
Microplastic does not magnify the acute effect of PAH pyrene on predatory performance of a tropical fish (Lates calcarifer) Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-12 Olgac Guven, Lis Bach, Peter Munk, Khuong V. Dinh, Patrizio Mariani, Torkel Gissel Nielsen
Microplastic (MP) leads to widespread pollution in the marine ecosystem. In addition to the physical hazard posed by ingestion of microplastic particles, concern is also on their potential as vector for transport of hydrophobic contaminants. We studied experimentally the single and interactive effects of microplastic and pyrene, a polycyclic aromatic hydrocarbon, on the swimming behaviour and predatory performance of juvenile barramundi (Lates calcarifer). Juveniles (18+ days post hatch) were exposed to MPs, or pyrene (100 nM), or combination of both and feeding rate and foraging activity (swimming) were analyzed. Exposure to MPs alone did not significantly influence feeding performance of the juveniles, while a concentration-response series of pyrene showed strong effect on fish behaviour when concentrations were above 100 nM. In the test of combined MP and pyrene exposure we observed no effect on feeding while swimming speed showed a significant decrease. Thus, our results confirm that short-time exposure to pyrene impacts performance of fish juveniles, while additional exposure to microplastic influenced their activity but not their feeding rate at the given conditions. Further studies on microplastics and other pollutants outlining their combined effects on behaviour and survival of tropical fish are encouraged.
Complex role of titanium dioxide nanoparticles in the trophic transfer of arsenic from Nannochloropsis maritima to Artemia salina nauplii Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-10 Fan Yang, Liqing Zeng, Zhuanxi Luo, Zaosheng Wang, Fuyi Huang, Qiuquan Wang, Damjana Drobne, Changzhou Yan
Increasing concern has been focused on the potential risks associated with the trophic transfer to aquatic organisms of ambient contaminants in the presence of titanium dioxide nanoparticles (nano-TiO2). This study investigated the influence of nano-TiO2 on the trophic transfer of arsenic (As) from the microalgae Nannochloropsis maritima to the brine shrimp Artemia salina nauplii. We found that nano-TiO2 could significantly facilitate As sorption on N. maritima within an exposure period of 24 h, and this sorption subsequently led to higher As trophic transfer from the algae to A. salina according to trophic transfer factors (TTFAs+nano-TiO2 > TTFAs). However, after 48 h of depuration, the retention of As in A. salina fed As-nano-TiO2-contaminated algae was even lower than that in A. salina fed As-contaminated algae at the same exposure concentrations. This result indicates that the increased food chain transfer of As in the presence of nano-TiO2 can be explained by adsorption of As onto nano-TiO2 in contaminated food (algae), but the bioavailability of As in A. salina is reduced after the introduction of nanoparticles. Although the stress enzyme activities of superoxide dismutase (SOD) and acetylcholinesterase (AChE) in A. salina at a lower As concentration treatment in the presence of nano-TiO2 were not significantly changed, they increased with higher exposure concentrations of As with or without nano-TiO2. Our study highlighted the complex role of nanomaterials in the transfer of ambient contaminants via trophic chains and the potential of nano-TiO2 to reduce the bioavailability of As via trophic transfer to saltwater zooplankton.
Miniaturised Marine Algae Test with Polycyclic Aromatic Hydrocarbons − Comparing Equilibrium Passive Dosing and Nominal Spiking Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-09 Nora Claire Niehus, Carolin Floeter, Henner Hollert, Gesine Witt
In this study the miniaturised Marine Algae Test (mMAT) using passive dosing was developed based on the ISO EN DIN10253 to investigate the growth inhibition of the marine diatom Phaeodactylum tricornutum caused by polycyclic aromatic hydrocarbons (PAHs). Risk assessment of hydrophobic organic compounds (HOCs) like PAHs in aquatic toxicity tests is very difficult due to their low aqueous solubilities, losses via sorption to the wells and volatilisation. However, passive dosing can overcome these challenges. In this study biocompatible silicone O-rings were used as PAH reservoir. Individual PAHs at saturation were tested using passive dosing and in comparison with nominal spiking. Additionally, a recreated mixture of PAHs reflecting the field composition of the sediment pore water was tested with passive dosing. PAHs revealed strong growth inhibiting effects on algal growth in passive dosing tests, while nominal spiking had only slightly growth inhibiting effects in the highest concentration. The recreated PAH mixture revealed slightly inhibiting effects using passive dosing when tested with a factor of 5000 of the field concentration. This study demonstrates the superiority of passive dosing to spiking and further the successful implementation of passive dosing in the marine algae test maintaining a constant concentration for HOCs with a log KOW > 4.6.
Phototoxic effects of PAH and UVA exposure on molecular responses and developmental success in coral larvae Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-09 Sebastian Overmans, Mikaela Nordborg, Ruben Diaz Rua, Diane L. Brinkman, Andrew P. Negri, Susana Agustí
Exposure to polycyclic aromatic carbons (PAHs) poses a growing risk to coral reefs due to increasing shipping and petroleum extraction in tropical waters. Damaging effects of specific PAHs can be further enhanced by the presence of ultraviolet radiation, known as phototoxicity. We tested phototoxic effects of the PAHs anthracene and phenanthrene on larvae of the scleractinian coral Acropora tenuis in the presence and absence of UVA (320–400 nm). Activity of superoxide dismutase (SOD) enzyme was reduced by anthracene while phenanthrene and UVA exposure did not have any effect. Gene expression of MnSod remained constant across all treatments. The genes Catalase, Hsp70 and Hsp90 showed increased expression levels in larvae exposed to anthracene, but not phenanthrene. Gene expression of p53 was upregulated in the presence of UVA, but downregulated when exposed to PAHs. The influence on stress-related biochemical pathways and gene expresson in A. tenuis larvae was considerably greater for anthracene than phenanthrene, and UVA-induced phototoxicity was only evident for anthracene. The combined effects of UVA and PAH exposure on larval survival and metamorphosis paralleled the sub-lethal stress responses, clearly highlighting the interaction of UVA on anthracene toxicity and ultimately the coral’s development.
RIBE at an inter-organismic level: a study on genotoxic effects in Daphnia magna exposed to waterborne uranium and a uranium mine effluent Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-09 P. Reis, J. Lourenço, F.P. Carvalho, J. Oliveira, M. Malta, S. Mendo, R. Pereira
Cardiometabolic response of juvenile rainbow trout exposed to dietary selenomethionine Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-08 Connor M. Pettem, Jennifer M. Briens, David M. Janz, Lynn P. Weber
Selenium (Se) is considered as an essential trace element, involved in important physiological and metabolic functions for all vertebrate species. Fish require dietary concentrations of 0.1 to 0.5 μg Se/g dry mass (d.m.) to maintain normal physiological and selenoprotein function, however concentrations exceeding 3 μg/g d.m. have been shown to cause toxicity. As Se is reported to have a narrow margin between essentiality and toxicity, there is growing concern surrounding the adverse effects of elevated Se exposure caused by anthropogenic activities. Previous studies have reported that elevated dietary exposure of fish to selenomethionine (Se-Met) can cause significant cardiotoxicity and alter aerobic metabolic capacity, energy homeostasis and swimming performance. The goal of this study aims to further investigate mechanisms of sublethal Se-Met toxicity, particularly potential underlying cardiovascular and metabolic implications of chronic exposure to environmentally relevant concentrations of dietary Se-Met in juvenile rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout were fed either control food (1.3 μg Se/g dry mass [d.m.]) or Se-Met spiked food (6.4, 15.8 or 47.8 μg Se/g d.m.) for 60 d at 3% body weight per day. Following exposure, ultrahigh resolution B-mode and Doppler ultrasound was used to characterize cardiac function in vivo. Chronic dietary exposure to Se-Met significantly increased stroke volume, cardiac output, and ejection fraction. Fish fed with Se-Met spiked food had elevated liver glycogen and triglyceride stores, suggesting impaired energy homeostasis. Exposure to Se-Met significantly decreased mRNA abundance of citrate synthase (CS) in liver and serpin peptidase inhibitor, clad H1 (SERPINH) in heart, and increased mRNA abundance of sarcoplasmic reticulum calcium ATPase (SERCA) and key cardiac remodelling enzyme matrix metalloproteinase 9 (MMP9) in heart. Taken together, these responses are consistent with a compensatory cardiac response to increased susceptibility to oxidative stress, namely a decrease in ventricular stiffness and improved cardiac function. These cardiac alterations in trout hearts were linked to metabolic disruption in other major metabolic tissues (liver and skeletal muscle), impaired glucose tolerance with increased levels of the toxic glucose metabolite, methylglyoxal, increased lipid peroxidation in skeletal muscle, development of cataracts and prolonged feeding behaviour, indicative of visual impairment. Therefore, although juvenile rainbow trout hearts were apparently able to functionally compensate for adverse metabolic and anti-oxidant changes after chronic dietary exposure Se-Met, complications associated with hyperglycemia in mammalian species were evident and would threaten survival of juvenile and adult fish.
Metabolomic and oxidative effects of quantum dots-indolicidin on three generations of Daphnia magna Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-08 Annarita Falanga, Flavia A. Mercurio, Antonietta Siciliano, Lucia Lombardi, Stefania Galdiero, Marco Guida, Giovanni Libralato, Marilisa Leone, Emilia Galdiero
Metabolomic analysis of short term sulfamethazine exposure on marine medaka (Oryzias melastigma) by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-08 Yawen Liu, Xinhong Wang, Yongyu Li, Xixi Chen
Toxicological effects of sulfamethazine (SM2) have garnered increasing concern due to its wide applications in aquaculture and persistence in the aquatic environment. Most studies have main focused on freshwater fish (i.e. zebrafish), while information regarding effects of SM2 on marine species is still scarce. Here, the hepato-toxicities in marine medaka (Oryzias melastigma) with an increasing SM2 concentrations (0.01 mg/L, 0.1 mg/L and 1 mg/L) were assessed by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOF/MS) based metabolomics. Significant metabolites belonging to different metabolites classes were identified by multivariate statistical analysis. The increases levels of amino acids including alanine, asparagine, ornithine, proline, threonine, glutamic acid, lysine, tyrosine and phenylalanine were found in at least two exposure levels. Pathway analysis revealed that amino acids played important biological roles during SM2 exposure: up-regulation of high energy-related amino acids for energy regulation; permutations of glutamine and glutamic acid for oxidative stress; immune function disorder and corresponding toxicities defenses. The down regulations of sugar and fatty acids metabolism were observed with an increasing level of SM2 exposure, suggesting that extra energy for cellular defense and detoxification was demanded for different stress request. This study proposed an innovative perspective to explore possible SM2 induced hepatic damages at three exposure levels on a nontarget aquatic specie.
Toxicity of sediment-bound lufenuron to benthic arthropods in laboratory bioassays Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-06 T.C.M. Brock, J.D.M. Belgers, M-C. Boerwinkel, L. Jollie, M.H.S. Kraak, M.J. Papo, J.A. Vonk, I. Roessink
This paper deals with species sensitivity distributions (SSDs) for the lipophilic insecticide lufenuron and benthic arthropods based on sediment-spiked laboratory toxicity tests. This compound that inhibits chitin synthesis and moulting of arthropods persists in sediment. Using field-collected sediment, toxicity tests were conducted with three macro-crustaceans and six insects. The Hazardous Concentration to 5% of the tested species, the HC5 (and 95% confidence limit), derived from an SSD constructed with 10d-LC50’s was 2.2 (1.2-5.7) μg/g organic carbon (OC) in dry sediment. In addition, HC5 values derived from SSDs constructed with 28d-LC10 and 28-d LC50 values were 0.13 (0.02-1.50) μg/g OC and 2.0 (1.3-5.5) μg/g OC, respectively. In 28d toxicity tests with Chironomus riparius and Hyalella azteca, a higher sensitivity was observed when using lufenuron-spiked field-collected sediment than in lufenuron-spiked artificial sediment. Overall, the non-biting midge C. riparius appeared to be a representative and sensitive standard test species to assess effects of lufenuron exposure in sediment. The Tier-1 (based on standard test species), Tier-2 (based on standard and additional test species) and Tier-3 (model ecosystem approach) regulatory acceptable concentrations (RACs) for sediment-spiked lufenuron did not differ substantially. The Tier-2 RAC was the lowest. Since to our knowledge this study is the first in the open literature that evaluates the tiered approach in the sediment effect assessment procedure for pesticides, we advocate that similar evaluations should be conducted for pesticides that differ in toxic mode-of-action.
Short-term developmental effects and potential mechanisms of azoxystrobin in larval and adult zebrafish (Danio rerio) Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-06 Fangjie Cao, Peizhuo Wu, Lan Huang, Hui Li, Le Qian, Sen Pang, Lihong Qiu
Previous study indicated that azoxystrobin had high acute toxicity to zebrafish, and larval zebrafish were more sensitive to azoxystrobin than adult zebrafish. The objective of the present study was to investigate short-term developmental effects and potential mechanisms of azoxystrobin in larval and adult zebrafish. After zebrafish embryos and adults were exposed to 0.01, 0.05 and 0.20 mg/L azoxystrobin (equal to 25, 124 and 496 nM azoxystrobin, respectively) for 8 days, the lethal effect, physiological responses, liver histology, mitochondrial ultrastructure, and expression alteration of genes related to mitochondrial respiration, oxidative stress, cell apoptosis and innate immune response were determined. The results showed that there was no significant effect on larval and adult zebrafish after exposure to 0.01 mg/L azoxystrobin. However, increased ROS, MDA concentration and il1b in larval zebrafish, as well as increased il1b, il8 and cxcl-c1c in adult zebrafish were induced after exposure to 0.05 mg/L azoxystrobin. Reduced mitochondrial complex III activity and ATP concentration, increased SOD activity, ROS and MDA concentration, decreased cytb, as well as increased sod1, sod2, cat, il1b, il8 and cxcl-c1c were observed both in larval and adult zebrafish after exposure to 0.20 mg/L azoxystrobin; meanwhile, increased p53, bax, apaf1 and casp9, alteration of liver histology and mitochondrial ultrastructure in larval zebrafish, and alteration of mitochondrial ultrastructure in adult zebrafish were also induced. The results demonstrated that azoxytrobin induced short-term developmental effects on larval zebrafish and adult zebrafish, including mitochondrial dysfunction, oxidative stress, cell apoptosis and innate immune response. Statistical analysis indicated that azoxystrobin induced more negative effects on larval zebrafish, which might be the reason for the differences of developmental toxicity between larval and adult zebrafish caused by azoxystrobin. These results provided a new insight into potential mechanisms of azoxystrobin in larval zebrafish and adult zebrafish.
The role of marine biotoxins on the trophic transfer of Mn and Zn in fish Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-05 Simon Pouil, Rachel Clausing, Marc Metian, Paco Bustamante, Marie-Yasmine Dechraoui Bottein
Essential nutrients are critical for organismal physiological processes. In fish, they are obtained primarily from the diet, and their transfer and accumulation are known to be impacted by environmental variables such as water temperature, pH and salinity, as well as by diet composition and matrices. Yet, prey items consumed by fish may also contain toxic compounds such as marine toxins associated with harmful algae. These biotoxins have the potential to affect essential trace element assimilation in fish through chemical interactions such as the formation of trace element-toxin complexes or by affecting general fish physiology as in the modification of ion-specific transport pathways. We assessed the influence of dietary exposure to brevetoxins (PbTxs), ichthyotoxic neurotoxins produced by the dinoflagellate Karenia brevis, on trophic transfer of two essential trace elements, Mn and Zn in a fish model. Using ecologically relevant concentrations of PbTxs and trace elements in controlled laboratory conditions, juvenile turbots Scophthalmus maximus were given food containing PbTxs before or at the same time as a feeding with radiotracers of the chosen essential elements (54Mn and 65Zn). Treatments included simultaneous exposure (PbTxs + 54Mn + 65Zn) in a single-feeding, and 3-week daily pre-exposure to dietary PbTx followed by a single feeding with 54Mn and 65Zn, and a control (54Mn and 65Zn only). After a 21-day depuration period, turbot tissue brevetoxin levels were quantified and assimilation efficiencies of 54Mn and 65Zn were assessed. PbTxs were found in turbot tissues in each exposure treatment, demonstrating dietary trophic transfer of these toxins; yet, no differences in assimilation efficiencies of Mn or Zn were found between treatments or the control (p > 0.05). These results indicate that, in our experimental conditions, PbTx exposure does not significantly affect the trophic transfer of Mn and Zn in fish.
The Cytotoxicity and Genotoxicity of Particulate and Soluble Hexavalent Chromium in Leatherback Sea Turtle Lung Cells Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-04 Rachel M. Speer, Catherine F. Wise, Jamie L. Young, Abou El-Makarim Aboueissa, Mark Martin Bras, Mike Barandiaran, Erick Bermúdez, Lirio Márquez-D’Acunti, John Pierce Wiser Sr.
Hexavalent chromium [Cr(VI)] is a marine pollution of concern as recent studies show it has a global distribution, with some regions showing high Cr concentrations in marine animal tissue, and it is extensively used. Leatherback sea turtles (Dermochelys coriacea) are an endangered marine species that may experience prolonged exposures to environmental contaminants including Cr(VI). Human activities have led to global Cr(VI) contamination of the marine environment. While Cr(VI) has been identified as a known human carcinogen, the health effects in marine species are poorly understood. In this study, we assessed the cytotoxic and genotoxic effects of particulate and soluble Cr(VI) in leatherback sea turtle lung cells. Both particulate and soluble Cr(VI) induced a concentration-dependent increase in cytotoxicity. Next, using a chromosome aberration assay, we assessed the genotoxic effects of Cr(VI) in leatherback sea turtles. Particulate and soluble Cr(VI) induced a concentration-dependent increase in clastogenicity in leatherback sea turtle lung cells. These data indicate that Cr(VI) may be a health concern for leatherback sea turtles and other long-lived marine species. Additionally, these data provide foundational support to use leatherback sea turtles are a valuable model species for monitoring the health effects of Cr(VI) in the environment and possibly as an indicator species to assess environmental human exposures and effects.
Multi biomarker analysis of pollution effect on resident populations of blue mussels from the Baltic Sea Aquat. Toxicol. (IF 4.129) Pub Date : 2018-03-01 Josefine Larsson, Katarzyna Smolarz, Justyna Świeżak, Magda Turower, Natalia Czerniawska, Mats Grahn
Anthropogenic pollution including metals, petroleum, toxins, nutrients and many others is a growing problem in the marine environment. These are important factors altering the environment and by that the fate of many local populations of marine organisms. The aim of this study was to assess the impact of selected point pollution sources on resident populations of the blue mussel (Mytilus edulis trossulus) in the Baltic Sea using multiple biomarker approach. The study used a nested sampling scheme in which sites from reference (REF) habitats are geographically paired with selected sites from sewage treatment plants (STP) and harbors (HAR). The results showed that mussels from harbors had a higher frequency of histological abnormalities in the digestive gland compared to mussels from sewage effluent affected areas and reference sites. However these mussels together with mussels from STPs had higher lipid content, body mass index (BMI) and gonado-somatic index (GSI) compared to mussels from reference sites. A marked spatial variability was found with a stronger toxicity of ambient environment affecting resident mussel populations in the Gulf of Gdańsk area, while an opposite pattern was found in Tvärminne area. Yet the blue mussels sampled in the Gulf of Gdańsk were characterized by the highest GSI and BMI values compared to Askö and Tvärminne populations. No differences in analyzed biomarker response related to species identity, measured by a species-specific genetic marker, were found indicative of strong genetic introgression in the Baltic Proper.
Early life stages of Northern shrimp (Pandalus borealis) are sensitive to fish feed containing the anti-parasitic drug diflubenzuron Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-28 Renée Katrin Bechmann, Emily Lyng, Stig Westerlund, Shaw Bamber, Mark Berry, Maj Arnberg, Alfhild Kringstad, Piero Calosi, Paul J. Seear
Increasing use of fish feed containing the chitin synthesis inhibiting anti-parasitic drug diflubenzuron (DFB) in salmon aquaculture has raised concerns over its impact on coastal ecosystems. Larvae of Northern shrimp (Pandalus borealis) were exposed to DFB medicated feed under Control conditions (7.0 °C, pH 8.0) and under Ocean Acidification and Warming conditions (OAW, 9.5 °C and pH 7.6). Two weeks’ exposure to DFB medicated feed caused significantly increased mortality. The effect of OAW and DFB on mortality of shrimp larvae was additive; 10% mortality in Control, 35% in OAW, 66% in DFB and 92% in OAW + DFB. In OAW + DFB feeding and swimming activity were reduced for stage II larvae and none of the surviving larvae developed to stage IV. Two genes involved in feeding (GAPDH and PRLP) and one gene involved in moulting (DD9B) were significantly downregulated in larvae exposed to OAW + DFB relative to the Control. Due to a shorter intermoult period under OAW conditions, the OAW + DFB larvae were exposed throughout two instead of one critical pre-moult period. This may explain the more serious sub-lethal effects for OAW + DFB than DFB larvae. A single day exposure at 4 days after hatching did not affect DFB larvae, but high mortality was observed for OAW + DFB larvae, possibly because they were exposed closer to moulting. High mortality of shrimp larvae exposed to DFB medicated feed, indicates that the use of DFB in salmon aquaculture is a threat to crustacean zooplankton.
Genotoxicity and physiological effects of CeO2 NPs on a freshwater bivalve (Corbicula fluminea) Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-27 Vanessa Koehle-divo, Carole Cossu-Leguille, Sandrine Pain-Devin, Cécile Simonin, Carole Bertrand, Bénédicte Sohm, Catherine Mouneyrac, Simon Devin, Laure Giamberini
The rapid development of nanotechnology and the increased use of nanomaterials in products used in everyday life have raised the question of the potential release of nanoparticles into the aquatic environment. Their fate and effects in natural ecosystems are not currently well understood but harmful effects of nanoparticles have been demonstrated at low concentrations on some freshwater and marine species. Cerium dioxide nanoparticles (CeO2 NPs) are produced in large quantities and used in products in many different fields, such as automotives or optics. Because of their widespread use in daily products, CeO2 NPs are included in the OECD priority list of manufactured nanomaterials for human and environmental assessment. Indeed some studies have been conducted to assay various enzymatic biomarkers, which showed the CeO2 NPs potential to modify anti-oxidative defenses and cellular membrane stability. Nevertheless, only a few studies were performed on their genotoxic potential. The aim of this work was to evaluate the genotoxic and physiological effects of CeO2 NPs on a widespread freshwater bivalve Corbicula fluminea by using comet assay and a multi-enzymatic biomarker approach. Exposure to two CeO2 NP concentrations during a short term experiment (6 days) was set up. The first one (10 μg/L) was chosen in order to work with low but measurable concentrations whereas the second one was ten times higher (100 μg CeO2 NPs/L). DNA damage was significantly more pronounced compared with control for both concentrations tested as early as two days of exposure and seemed to increase with time. Some enzymatic biomarkers of anti-oxidative defenses (total antioxidant capacity, catalase activity), anti-toxic mechanisms (glutathione-S-transferase activity, caspase-3 activity) or metabolism (lactate dehydrogenase activity) tended to increase after 6 days of exposure but only the induction of caspase pathway and DNA damages appeared significant for exposed organisms. In this study, time and concentration effects of CeO2 NPs were highlighted by coupling genotoxic and cellular biomarker assessments.
The influence of natural dissolved organic matter on herbicide toxicity to marine microalgae is species-dependent Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-27 Nathalie Coquillé, Dominique Ménard, Julien Rouxel, Valentin Dupraz, Mélissa Éon, Patrick Pardon, Hélène Budzinski, Soizic Morin, Édith Parlanti, Sabine Stachowski-Haberkorn
Microalgae, which are the foundation of aquatic food webs, may be the indirect target of herbicides used for agricultural and urban applications. Microalgae also interact with other compounds from their environment, such as natural dissolved organic matter (DOM), which can itself interact with herbicides. This study aimed to evaluate the influence of natural DOM on the toxicity of three herbicides (diuron, irgarol and S-metolachlor), singly and in ternary mixtures, to two marine microalgae, Chaetoceros calcitrans and Tetraselmis suecica, in monospecific, non-axenic cultures. Effects on growth, photosynthetic efficiency (Ф’M) and relative lipid content were evaluated. The chemical environment (herbicide and nutrient concentrations, dissolved organic carbon and DOM optical properties) was also monitored to assess any changes during the experiments. The results show that, without DOM, the highest irgarol concentration (I0.5: 0.5 mg L−1) and the strongest mixture (M2: irgarol 0.5 μg L−1 + diuron 0.5 μg L−1 + S-metolachlor 5.0 μg L−1) significantly decreased all parameters for both species. Similar impacts were induced by I0.5 and M2 in C. calcitrans (around −56% for growth, −50% for relative lipid content and −28% for Ф’M), but a significantly higher toxicity of M2 was observed in T. suecica (−56% and −62% with I0.5 and M2 for growth, respectively), suggesting a possible interaction between molecules. With DOM added to the culture media, a significant inhibition of these three parameters was also observed with I0.5 and M2 for both species. Furthermore, DOM modulated herbicide toxicity, which was decreased for C. calcitrans (−51% growth at I0.5 and M2) and increased for T. suecica (-64% and −75% growth at I0.5 and M2, respectively). In addition to the direct and/or indirect (via their associated bacteria) use of molecules present in natural DOM, the characterization of the chemical environment showed that the toxic effects observed on microalgae were accompanied by modifications of DOM composition and the quantity of dissolved organic carbon excreted and/or secreted by microorganisms. This toxicity modulation in presence of DOM could be explained by (i) the modification of herbicide bioavailability, (ii) a difference in cell wall composition between the two species, and/or (iii) a higher detoxification capacity of C. calcitrans by the use of molecules contained in DOM. This study therefore demonstrated, for the first time, the major modulating role of natural DOM on the toxicity of herbicides to marine microalgae.
Evaluation of biomarkers in Mytilus galloprovincialis as an integrated measure of biofilm-membrane bioreactor (BF-MBR) system efficiency in mitigating the impact of oily wastewater discharge to marine environment: a microcosm approach Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-24 Cristina Pirrone, Federica Rossi, Simone Cappello, Marina Borgese, Giuseppe Mancini, Giovanni Bernardini, Rosalba Gornati
The large volumes of oily wastewater discharged to marine environment cause heavy impacts on the coastal marine ecosystem. The selection of an appropriate technology to reduce these impacts should be based on the respects of the discharge limits and on the effective assessment and monitoring of its effects on biological organism preservation. To this aim, we set up a controlled microcosm-scale system to compare the effects of a treated and untreated oily wastewater discharge in which the restore process is performed through a Membrane Bio-Reactor. The system is completed by other three microcosms to control and isolate any possible concurrent effect on the Mytilus galloprovincialis, used as sentinel organism. Mytilus galloprovincialis have been kept in all these microcosms, and then mRNA expression and morphology were evaluated on gills and digestive gland. The genes considered in this work are Heat Shock Protein 70 and Metallothionein 10, involved in response to physicochemical sublethal stressors and Superoxide dismutase 1, Catalase, and a Cytochrome P450 involved in oxidative stress response. Our results evidenced a significant overexpression, both in gills and digestive gland, of HSP70 in samples maintained in the microcosm receiving the treated effluent, and of MT10 in those animals kept in microcosm where the effluent was treated. Even though the mRNA modifications are considered “primary” and transient responses which do not always correspond to protein content, the study of these modifications can help to gain insights into the mechanisms of action of xenobiotic exposure. Morphological analysis suggested that, although different depending on the microcosm, the most serious damages were found in the gill epithelium accompanied with severe haemocyte infiltration, whilst in digestive gland the tissue architecture alterations and the haemocyte infiltration were less pronounced. These observations suggest that the immune system was activated as a general response to stressful stimuli such as the presence of toxic compounds. Moreover, the results indicate that the treatment process is useful. In fact, samples derived from the microcosm receiving the treated effluent, even though presenting some signs of stress, seemed to partially recover the normal structure, although their mRNA expression indicated some cellular suffering.
Melanomacrophage response and hepatic histopathologic biomarkers in the guppy Poecilia reticulata exposed to iron oxide (maghemite) nanoparticles Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-21 Gabriel Qualhato, Simone Maria Teixeira de Sabóia-Morais, Luciana Damacena Silva, Thiago Lopes Rocha
Effects of atrazine on vitellogenesis, steroid levels and lipid peroxidation, in female red swamp crayfish Procambarus clarkii Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-21 Gabriela Romina Silveyra, Patricia Silveyra, Itzick Vatnick, Daniel Alberto Medesani, Enrique Marcelo Rodríguez
Atrazine, a widely use herbicide, has been classified as a potential endocrine disruptor, especially for freshwater species. In this study, we tested the hypothesis that atrazine can affect reproduction in crayfish through dysregulation of vitellogenin expression and hormone synthesis. Adult female crayfish (Procambarus clarkii) were exposed during one month to atrazine at concentrations of either 1 or 5 mg/L. At the end of the exposure, ovaries, hepatopancreas, and hemolymph samples were harvested for analysis of vitellogenin expression and steroid hormone levels. Ovarian tissue was also sampled for both biochemical and histological analyses. Our results show that atrazine-exposed crayfish had a lower expression of vitellogenin in the ovary and hepatopancreas, as well as smaller oocytes, and reduced vitellogenin content in the ovary. Despite these effects, circulating levels of estradiol increased in females exposed to 5 mg/L of atrazine, showing that the inhibiting effect of atrazine on vitellogenin production was not related to a lower secretion of sexual steroids. Instead, some early stimulating effects of estradiol on vitellogenesis could have occurred, particularly in the hepatopancreas. On the other hand, atrazine caused a higher metabolic effort, in terms of lactate production, presumably triggered to provide the energy needed to face the unspecific stress produced by the herbicide. Lipid peroxidation was not affected by atrazine, but glutathione levels were significantly increased.
Azoles additively inhibit cytochrome P450 1 (EROD) and 19 (aromatase) in rainbow trout (Oncorhynchus mykiss) Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-21 Kristina Beijer, Maria Jönsson, Siraz Shaik, Daphné Behrens, Björn Brunström, Ingvar Brandt
Antifungal azoles are widely used in medicine, agriculture, and material protection and several antifungal azoles have been found in environmental samples. Although these compounds were designed to inhibit fungal enzymes such as lanosterol-14-demethylase (cytochrome P450 (CYP) 51), it is well established that the inhibitory actions of azoles are not specific for fungal CYP isozymes. We refined a gill filament assay to determine the inhibition of CYP1, measured as reduced 7-ethoxyresorufin-O-deethylase (EROD) activity, in rainbow trout (Oncorhynchus mykiss) gill tissue ex vivo. The advantage of this method is that both induction and inhibition of EROD are performed ex vivo. Among thirteen azoles studied, the five that caused the strongest inhibition of gill EROD activity at a concentration of 5 μM were selected for concentration–response assessment. These compounds (bifonazole, clotrimazole, imazalil, miconazole, and prochloraz) showed IC50 values ranging from 0.1 to 1.5 μM. CYP19 (aromatase) inhibition was measured using microsomes from rainbow trout brains. Concentration-response curves for CYP19 inhibition were determined for letrozole, bifonazole, clotrimazole, imazalil, miconazole and prochloraz, which gave IC50 values ranging from 0.02 to 3.3 μM. It was further found that mixtures of the five most potent azoles reduced both CYP1 and 19 catalytic activity in an additive fashion (IC50 = 0.7 μM and 0.6 μM, in the respective assay). Bifonazole (IC50 = 0.1 μM) is not previously known to inhibit CYP1 activity. The additive inhibition of CYP1 and CYP19 catalytic activity is an important finding of the present study. We conclude that this additive action of azoles could mediate adverse impacts on CYP regulated physiological functions in environmentally exposed fish.
Influence of microplastics on the toxicity of the pharmaceuticals procainamide and doxycycline on the marine microalgae Tetraselmis chuii Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-21 Joana C. Prata, Beatriz R.B.O. Lavorante, Maria da Conceição B.S.M. Montenegro, Lúcia Guilhermino
Microplastics and pharmaceuticals are considered ubiquitous and emergent pollutants of high concern but the knowledge on their effects on primary producers is still limited, especially those caused by mixtures. Thus, the goal of the present study was to investigate if the presence of microplastics (1–5 μm diameter) influences the toxicity of the pharmaceuticals procainamide and doxycycline to the marine microalga Tetraselmis chuii. Bioassays (96 h) to investigate the toxicity of those substances individually and in mixtures (i.e. microplastics-procainamide mixtures and microplastics-doxycycline mixtures) were carried out. Effect criteria were the average specific growth rate (growth rate) and chlorophyll a concentration (chlorophyll). EC10, EC20 and EC50 were determined. Microplastics alone had no significant effects on growth rate up to 41.5 mg/l, whereas chlorophyll was significantly reduced at 0.9 and 2.1 mg/l of microplastics, but not at higher concentrations. The 96 h EC50 (growth rate and chlorophyll, respectively) determined for the other bioassays were: 104 and 143 mg/l for procainamide alone; 125 and 31 mg/l for procainamide in the presence of microplastics; 22 and 14 mg/l for doxycycline alone; 11 and 7 mg/l for doxycycline in the presence of microplastics. Significant differences (p < 0.001) between the toxicity curves of each pharmaceutical alone and in mixture with microplastics were found for procainamide (chlorophyll), and doxycycline (both parameters). Thus, both pharmaceuticals were toxic to T. chuii in the low ppm range, and microplastics-pharmaceutical mixtures were more toxic than the pharmaceuticals alone. Very high decreases of doxycycline concentrations in test media were found, indicating degradation of the antibiotic. Thus, although the biological results are expressed in relation to doxycycline concentration, the effects were likely caused by a mixture of the parental compound and its degradation products. The concentrations of microplastics and pharmaceuticals tested (low ppm range) are higher than those expected to be found in waters of the most part of marine ecosystems (ppt or ppb ranges). However, considering the widespread contamination by microplastics and pharmaceuticals, the concentrations already found in waters, sediments and/or organism of heavily polluted areas, the long-term exposure (over generations) of wild populations to such substances in polluted ecosystems and the possibilities of bioaccumulation and toxicological interactions, these findings are of concern and further research on microplastics-pharmaceuticals toxicological interactions is needed.
Nrf2a Modulates the Embryonic Antioxidant Response to Perfluorooctanesulfonic Acid (PFOS) in the Zebrafish, Danio rerio Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-20 Karilyn E. Sant, Paul P. Sinno, Haydee M. Jacobs, Alicia R. Timme-Laragy
The glutathione redox system undergoes precise and dynamic changes during embryonic development, protecting against and mitigating oxidative insults. The antioxidant response is coordinately largely by the transcription factor Nuclear factor erythroid-2 (Nrf2), an endogenous sensor for cellular oxidative stress. We have previously demonstrated that impaired Nrf family signaling disrupts the glutathione redox system in the zebrafish embryo, and that impaired Nrf2 function increases embryonic sensitivity to environmental toxicants. Here, we investigated the persistent environmental toxicant and reported pro-oxidant perfluorooctanesulfonic acid (PFOS), and its impact on the embryonic glutathione-mediated redox environment. We further examined whether impaired Nrf2a function exacerbates PFOS-induced oxidative stress and embryotoxicity in the zebrafish, and the potential for Nrf2-PPAR crosstalk in the embryonic adaptive response. Wild-type and nrf2afh318−/− mutant embryos were exposed daily to 0 (0.01% v/v DMSO), 16, 32, or 64 μM PFOS beginning at 3 hours post fertilization (hpf). Embryonic glutathione and cysteine redox environments were examined at 72 hpf. Gross embryonic toxicity, antioxidant gene expression, and apoptosis were examined at 96 hpf. Mortality, pericardial edema, and yolk sac utilization were increased in wild-type embryos exposed to PFOS. Embryonic glutathione and cysteine redox couples and gene expression of Nrf2 pathway targets were modulated by both exposure and genotype. Apoptosis was increased in PFOS-exposed wild-type embryos, though not in nrf2a mutants. In silico examination of putative transcription factor binding site suggested potential crosstalk between Nrf2 and PPAR signaling, since expression of PPARs and gene targets was modulated by both PFOS exposure and Nrf2a genotype. Overall, this work demonstrates that nrf2a modulates the embryonic response to PFOS, and that PPAR signaling may play a role in the embryonic adaptive response to PFOS.
Effects of single and combined exposure of pharmaceutical drugs (carbamazepine and cetirizine) and a metal (cadmium) on the biochemical responses of R. philippinarum Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-19 Ângela Almeida, Vânia Calisto, Valdemar I. Esteves, Rudolf J. Schneider, Amadeu M.V.M. Soares, Etelvina Figueira, Rosa Freitas
In the aquatic environment, organisms are exposed to complex mixtures of contaminants which may alter the toxicity profile of each compound, compared to its toxicity alone. Pharmaceutical drugs (e.g. carbamazepine (CBZ) and cetirizine (CTZ)), and metals (e.g. cadmium (Cd)), are among those contaminants that co-occur in the environment. However, most studies concerning their toxicity towards aquatic species are based on single exposure experiments. Thus, the present study aimed to evaluate single and combined effects of Cd and CBZ or CTZ (single conditions: Cd, CTZ, CBZ; combined conditions: CTZ + Cd, CBZ + Cd) on biomarkers related to oxidative stress and energy metabolism in the edible clam Ruditapes philippinarum, by exposing the organisms for 28 days to environmentally relevant concentrations of these contaminants. The biomarkers studied were: i) the electron transport system activity, protein and glycogen content (indicators of organisms’ metabolic status); ii) lipid peroxidation and the ratio between reduced and oxidized glutathione (indicators of oxidative stress); iii) superoxide dismutase and catalase activities (indicators of antioxidant defence) and iv) activities of glutathione S-transferases (indicator of biotransformation capacity). Results obtained showed that the uptake of Cd and CBZ was not affected by the combined presence of the contaminants. However, for CTZ, the uptake was higher in the presence than in the absence of Cd. Concerning toxicity data in general, the combined exposures (CTZ + Cd, CBZ + Cd) had lower biological effects than the contaminants alone. Nevertheless, our data showed that despite the low concentrations tested, they were enough to exert biological effects that differed between single and combined treatments, evidencing the need to conduct more co-exposure studies to increase the environmental relevance of the gathered data.
Metoprolol induces oxidative damage in common carp (Cyprinus carpio) Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-18 Héctor Martínez-Rodríguez, Kingsley Donkor, Sharon Brewer, Marcela Galar-Martínez, Nely SanJuan-Reyes, Hariz Islas-Flores, Livier Sánchez-Aceves, Armando Elizalde-Velázquez, Leobardo Manuel Gómez-Oliván
During the last decade, β-blockers such as metoprolol (MTP) have been frequently detected in surface water, aquatic systems and municipal water at concentrations of ng/L to μg/L. Only a small number of studies exist on the toxic effects induced by this group of pharmaceuticals on aquatic organisms. Therefore, the present study aimed to evaluate the oxidative damage induced by MTP in the common carp Cyprinus carpio, using oxidative stress biomarkers. To this end, indicators of cellular oxidation such as hydroperoxide content (HPC), lipid peroxidation (LPX) and protein carbonyl content (PCC) were determined, as well as the activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). Also, concentrations of MTP and its metabolite O-desmethyl metoprolol were determined in water as well as carp gill, liver, kidney, brain and blood, along with the partial uptake pattern of these compounds. Results show that carp takes up MTP and its metabolite in the different organs evaluated, particularly liver and gill. The oxidative stress biomarkers, HPC, LPX, and PCC, as well as SOD and CAT activity all increased significantly at most exposure times in all organs evaluated. Results indicate that MTP and its metabolite induce oxidative stress on the teleost C. carpio and that the presence of these compounds may constitute a risk in water bodies for aquatic species.
Bioaccumulation and Physiological effects of Copepods sp. (Eucyclop sp.) fed Chlorella ellipsoides Exposed to Titanium dioxide (TiO2) Nanoparticles and Lead (Pb2+). Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-18 Matouke Matouke Moise, Mushood Mustapha
The demand for manufactured products and the derivatives of nanomaterials and non essential metals continue to increase, and as a consequence their presence in fisheries and aquaculture has therefore become a major concern for the risks to which our environment is exposed. The bioaccumulation profile of binary compounds (Titanium dioxide nanoparticles and lead) and their effects on the feeding behaviour of copepods were assessed in a simplified food chain including, the freshwater alga Chlorella ellipsoides and the cyclopoids copepods sp. Our results indicated that Pb and TiO2 NPs individually and mixed can be transferred from alga to copepods via dietary pathway. The highest bioconcentration factor (748.5) was recorded for Pb in the combined compounds (Pb15 + Ti16.5) μg L−1 and the highest BCF (5.57) recorded for TiO2 NPs was found in TiO2 NPs (16.5) alone. Ingestion and filtration rate decreased significantly (p < 0.05) in all treatments. Analysis of variance (ANOVA) showed that the combination of these metals significantly (p < 0.05) decreased ingestion and filtration rate. In addition, the individual compounds and their combinations significantly (p < 0.05) increased carbohydrate and total lipid content. The antioxidant activities showed significant (p < 0.05) effect of Glutathione peroxidase (GPx), Glutathione reductase (GR), catalase (CAT) however, SOD and MDA were not significant (p > 0.05) in both single and binary treatments. The results demonstrate that the co-exposure of TiO2 NPs and Pb inhibit the ingestion and filtration of microalgae by cyclopoid copepods sp. and also induce increase of carbohydrate, lipid; GPx, GR and CAT due to stress.
The effects of chronic acetaminophen exposure on the kidney, gill and liver in rainbow trout (Oncorhynchus mykiss) Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-15 Eugene Choi, Derek Alsop, Joanna Y. Wilson
In this study, we examined if rainbow trout chronically exposed to acetaminophen (10 and 30 μgL−1) showed histological changes that coincided with functional changes in the kidney, gill and liver. Histological changes in the kidney included movement and loss of nuclei, non-uniform nuclei size, non-uniform cytoplasmic staining, and loss of tubule integrity. Histological effects were more severe at the higher concentration and coincided with concentration dependent increases in urine flow rate and increased urinary concentrations of sodium, chloride, potassium, calcium, urea, ammonia, glucose, and protein. Yet, glomerular filtration rate was not altered with acetaminophen exposure. In the gill, filament end swelling, whole filament swelling, and swelling of the lamellae were observed in exposed fish. Lamellar spacing decreased in both exposure groups, but lamellar area decreased only with 30 μgL−1 exposure. At faster swimming speeds, oxygen consumption was limited in acetaminophen exposed fish, and critical swimming speed was also decreased in both exposure groups. The liver showed decreased perisinusoidal spaces at 10 and 30 μgL−1 acetaminophen, and decreased cytoplasmic vacuolation with 30 μgL−1 acetaminophen. A decrease in liver glycogen was also observed at 30 μgL−1. There was no change in plasma concentrations of sodium, chloride, potassium, calcium, magnesium, and glucose with exposure, suggesting compensation for urinary loss. Indeed, an increase in Na+-K+-ATPase activity in the gills was found with 30 μgL−1 acetaminophen exposure. Chronic exposure of rainbow trout to the environmentally relevant pharmaceutical acetaminophen, alters both histology and function of organs responsible for ion and nutrient homeostasis.
Binary Effect of Titanium Dioxide Nanoparticles (nTiO2) and Phosphorus on Microalgae (Chlorella ‘ellipsoides Gerneck, 1907) Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-14 M.M Matouke, Elewa Dorcas, A. Karimatu
The wide application of titanium dioxide nanoparticles and phosphorus in the manufacturing of many industrial products mainly used in agricultural sector has resulted in the release of considerable amounts of these compounds into freshwater aquatic ecosystem. These compounds may cause some unexpected effects to aquatic organisms. This study assessed the binary effects of Titanium nanoparticles (nTiO2) and Phosphorus on Chlorella ellipsoides. Toxicological assay test of the compounds nTiO2 (1.25 μM) alone and the combination of Titanium dioxide (1.25 μM) and Phosphorus (16, 32, 80, 160, 240 μM) was assessed, after 96 h exposures, for optical density (OD680), specific growth rate, chlorophyll levels and lipid peroxidation via Malondialdehyde (MDA) activity. Superoxide dismutase (SOD), peroxidase (POD) and glutathione-s-transferase (GST) activities were also measured. Two-way ANOVA showed a significant interaction (P < 0.05) between binary mixture. Co-exposure showed a decreased phosphorus bioconcentration in the microalgae with significant increase (P < 0.05) in chlorophyll a/b and total chlorophyll contents. A significant decrease (P < 0.05) in specific growth rate and optical density were recorded whereas, antioxidant enzymes (MDA, SOD, POD, GST) activities were significantly (P < 0.05) increased. These results showed that the addition of nTiO2 to Phosphorus affected the physiology of microalgae and should be of great concern for freshwater biodiversity.
A critical review of histopathological findings associated with endocrine and non-endocrine hepatic toxicity in fish models Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-12 Jeffrey C. Wolf, James R. Wheeler
Although frequently examined as a target organ for non-endocrine toxicity, histopathological evaluation of the liver is becoming a routine component of endocrine disruption studies that utilize various fish species as test subjects. However, the interpretation of microscopic liver findings can be challenging, especially when attempting to distinguish adverse changes associated with endocrine disrupting substances from those caused by systemic or direct hepatic toxicity. The purpose of this project was to conduct a critical assessment of the available peer-reviewed and grey literature concerning the histopathologic effects of reproductive endocrine active substances (EAS) and non-endocrine acting substances in the livers of fish models, and to determine if liver histopathology can be used to reliably distinguish endocrine from non-endocrine etiologies. The results of this review suggest that few compound-specific histopathologic liver effects have been identified, among which are estrogen agonist-induced increases in hepatocyte basophilia and proteinaceous intravascular fluid in adult male teleosts, and potentially, decreased hepatocyte basophilia in female fish exposed to substances that possess androgenic, anti-estrogenic, or aromatase inhibitory activity. This review also used published standardized methodology to assess the credibility of the histopathology data in each of the 117 articles that reported liver effects of treatment, and consequently it was determined that in only 37% of those papers were the data considered either highly credible or credible. The outcome of this work highlights the value of histopathologic liver evaluation as an investigative tool for EAS studies, and provides information that may have implications for EAS hazard assessment.
Acetylcholinesterase of mangrove oyster Crassostrea rhizophorae: A highly thermostable enzyme with promising features for estuarine biomonitoring Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-12 Paula Rayane de Souza, Kelma Sirleide de Souza, Caio Rodrigo Dias de Assis, Marlyete Chagas de Araújo, Kaline Catiely Campos Silva, Julliet de Fátima Xavier da Silva, Andreia Cybelle Marques Ferreira, Valdir Luna da Silva, Mônica Lúcia Adam, Luiz Bezerra Carvalho Jr., Ranilson de Souza Bezerra
Enzyme biomarkers from several aquatic organisms have been used for assessing the exposure to contaminants at sublethal levels. Amongst them, the cholinesterases are commonly extracted from several organisms to evaluate/measure organophosphate and carbamate neurotoxic effects. Acetylcholinesterase (AChE; EC 126.96.36.199) is an enzyme of the group of serine esterases that acts on the hydrolysis of the neurotransmitter acetylcholine allowing the intermittence of the nerve impulses responsible for the neuronal communication. This enzyme is the main target for the action of some pesticides and the inhibition of its activity in bivalve mollusks may be used as biomarker due to their filter-feeding habit. In this context, the present study aimed to characterize physicochemical and kinetic parameters of the AChE extracted from gills and viscera of the oyster Crassostrea rhizophorae and investigate the in vitro effect of pesticides (dichlorvos, diazinon, chlorpyrifos, methyl-parathion, temephos, carbaryl, carbofuran, aldicarb, diflubenzuron and novaluron) in search for assessing its potential as biomarker. Specific substrates and inhibitors evidenced the predominance of AChE in both tissues. The optimum pH found for gills and viscera AChE were 8.0 and 8.5, respectively. The maximum peak of activity occurred at 70 °C for gill AChE and 75 °C for viscera AChE. The enzymes of both tissues presented remarkable thermostability. The Michaelis-Menten constant for both enzymes were 1.32 ± 0.20 mM for gills and 0.43 ± 0.12 mM for viscera. The Vmax values for gills and viscera were 53.57 ± 1.72 and 27.71 ± 1.15 mU/mg, respectively. The enzymes were able to reduce the activation energy to 9.75 kcal mol−1 (gills) and 11.87 kcal mol−1 (viscera) obtaining rate enhancements of 3.57 × 105 and 1.01 × 104, respectively, in relation to non-catalyzed reactions. Among the pesticides under study, the carbamates carbaryl and carbofuran exerted the strongest inhibitory effects on the enzyme activity achieving important degrees of inhibition at concentrations below national and international current regulations. The first observation of the effects of benzoylurea pesticides (diflubenzuron and novaluron) on AChE from mollusks is reported here. The gills AChE of C. rhizophorae showed potential to be specific biomarker for the carbamate carbaryl while the viscera AChE showed it for carbofuran. According to their features, these enzymes may be proposed as promising tools for estuarine monitoring as well as biocomponent of biosensor devices.
Gemfibrozil and carbamazepine decrease steroid production in zebrafish testes (Danio rerio) Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-10 Shamaila Fraz, Abigail H. Lee, Joanna Y. Wilson
Gemfibrozil (GEM) and carbamazepine (CBZ) are two environmentally relevant pharmaceuticals and chronic exposure of fish to these compounds has decreased androgen levels and fish reproduction in laboratory studies. The main focus of this study was to examine the effects of GEM and CBZ on testicular steroid production, using zebrafish as a model species. Chronic water borne exposures of adult zebrafish to 10 μg/L of GEM and CBZ were conducted and the dosing was confirmed by chemical analysis of water as 17.5 ± 1.78 and 11.2 ± 1.08 μg/L respectively. A 67 day exposure led to reduced reproductive output and lowered whole body, plasma, and testicular 11-ketotestosterone (11-KT). Testicular production of 11-KT was examined post exposure (42 days) using ex vivo cultures to determine basal and stimulated steroid production. The goal was to ascertain the step impaired in the steroidogenic pathway by each compound. Ex vivo 11-KT production in testes from males chronically exposed to GEM and CBZ was lower than that from unexposed males. Although hCG, 25-OH cholesterol, and pregnenolone stimulation increased 11-KT production in all treatment groups over basal levels, hCG stimulated 11-KT production remained significantly less in testes from exposed males compared to controls. 25-OH cholesterol and pregnenolone stimulated 11-KT production was similar between GEM and control groups but the CBZ group had lower 11-KT production than controls with both stimulants. We therefore propose that chronic GEM and CBZ exposure can reduce production of 11-KT in testes through direct effects independent of mediation through HPG axis. The biochemical processes for steroid production appear un-impacted by GEM exposure; while CBZ exposure may influence steroidogenic enzyme expression or function.
Linking mode of action of the model respiratory and photosynthesis uncoupler 3,5-dichlorophenol to adverse outcomes in Lemna minor Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-10 Li Xie, Tânia Gomes, Knut Asbjørn Solhaug, You Song, Knut Erik Tollefsen
Standard chemical toxicity testing guidelines using aquatic plant Lemna minor have been developed by several international standardisation organisations. Although being highly useful for regulatory purposes by focusing on traditional adverse endpoints, these tests provide limited information about the toxic mechanisms and modes of action (MoA). The present study aimed to use selected functional assays in L. minor after exposure to 3,5-dichlorophenol (3,5-DCP) as a model to characterize the toxic mechanisms causing growth inhibition and lethality in primary producers. The results demonstrated that 3,5-DCP caused concentration-dependent effects in chloroplasts and mitochondria. Uncoupling of oxidative phosphorylation (OXPHOS), reduction in chlorophyll (Chlorophyll a and b) content, reproduction rate and frond size were the most sensitive endpoints, followed by formation of reactive oxygen species (ROS), lipid peroxidation (LPO), reduction of carotenoid content and impairment of photosynthesis efficiency. Suppression of photosystem II (PSII) efficiency, electron transport rate (ETR), chlorophyll (a and b) contents and oxidative phosphorylation (OXPHOS) were closely correlated while ROS production and LPO were negative correlated with ETR, carotenoid content and growth parameters. A network of conceptual Adverse Outcome Pathways (AOPs) was developed to decipher the causal relationships between molecular, cellular, and apical adverse effects occurring in L. minor to form a basis for future studies with similar compounds.
Trophic transfer potential of two different crystalline phases of TiO2 NPs from Chlorella sp. to Ceriodaphnia dubia Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-07 V. Iswarya, M. Bhuvaneshwari, N. Chandrasekaran, Amitava Mukherjee
Owing to the increase in the usage of titanium dioxide nanoparticles (TiO2 NPs), their release into the aquatic environment is inevitable. In the aquatic ecosystem, TiO2 NPs can bio-magnify at various trophic levels in the food chain through dietary exposure. In the current study, the trophic transfer potential of two crystalline phases of TiO2, anatase and rutile nanoparticles (individual as well as a binary mixture) has been evaluated in the lake water matrix using algae–daphnia system. Chlorella sp. and Ceriodaphnia dubia were used as test organisms to represent the algae–daphnia food chain of the freshwater ecosystem. Other than crystallinity, the effect of irradiation (visible and UV-A) was also investigated at the test concentrations, 75, 300, and 1200 μM. TiO2 NPs treated algal diet produced significant mortality only at the test concentrations, 300 and 1200 μM. The type of irradiation and crystallinity doesn’t have any impact on the mortality of daphnids through the dietary exposure of TiO2 NPs. Comparing the mixture with individual NPs, binary mixture induced less mortality on C. dubia which signifies the antagonistic effect of NPs when they coexist. Statistical modeling confirmed the antagonistic effect of the binary mixture on C. dubia. As individual NPs, anatase and rutile forms showed a maximum Ti accumulation under UV-A and visible irradiation, respectively. BMF of TiO2 NPs has been in validation with the bioaccumulation noted in C. dubia. Individual NPs (75 μM) showed higher BMF value of ∼23 under both UV-A (anatase) and visible (rutile) irradiation. Individual NPs showing higher BMF confirmed their trophic transfer potential in the aquatic food chain, primarily through the diet. In contrast, the binary mixture obtained a higher BMF of 1.9 and 0.79 at 75 and 300 μM under visible and UV-A irradiation, respectively. The plausible reason behind this decrement was the antagonistic effect of the mixture which significantly reduced their Ti bioaccumulation on C. dubia.
Uptake and effects of cerium(III) and cerium oxide nanoparticles to Chlamydomonas reinhardtii Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-07 Lena A. Kosak née Röhder, Tanja Brandt, Laura Sigg, Renata Behra
Acute exposure to chlorpyrifos induces reversible changes in health parameters of Nile tilapia (Oreochromis niloticus) Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-06 Eman Zahran, Engy Risha, Walaa Awadin, Dušan Palić
Chlorpyrifos (CPF) is one of the most common insecticides found in freshwater ecosystems, and has been detected in agricultural and fishery products worldwide. This study focused on comprehensive panel of hematological, immunotoxic and pathology changes in Nile tilapia (Oreochromis niloticus) during and after exposure to CPF at 15 μg/L (0.043 μM) (1/10 LC50, group CPF1), or 75 μg/L (0.21 μM) (1/2 LC50, group CPF2) for 14 days, followed by 2 weeks recovery. Different endpoints were used to determine effects of CPF on fish health: hematological parameters; antioxidant levels in liver and gills; innate immune parameters; expression levels of pro-inflammatory cytokine genes at mRNA level in anterior kidney and spleen; and histopathological assessment of gills, liver, and kidney tissues. RBCs were significantly decreased in CPF1 group compared to other groups only at day 3. Blood packed cell volume (PCV) and mean corpuscular volume (MCV) showed significant increase at day 3 and 14 of CPF exposure. TLC (Total Leukocytic Counts), neutrophil counts were significantly increased in CPF exposed groups at days 3, 7, 14 compared to the control. While, lymphocytes counts were significantly increased at CPF1 group compared to other groups at day 14. Antioxidant enzyme activity in liver and gills showed significant increase of Malondialdehyde (MDA) and glutathione (GSH), and significant decrease in (catalase/CAT/, glutathione S-transferase/GST/, and superoxide dismutase/SOD/); in CPF exposed groups. Serum bactericidal and lysozyme activity was nominally and significantly decreased, respectively, and whole blood respiratory burst was significantly increased in CPF2 group. The cytokine expression levels showed complex changes in expression patterns. In kidney, cytokine interleukin-8 (IL-8) was significantly upregulated at day 1 in both exposed group. Interleukin-1β (IL-1β) and Tumor necrosis factor-α (TNFα) were significantly upregulated at day 1 in CPF1 group, and then IL-8 and TNFα downregulated at day 3 in same group. At day 7, only TNFα was up and downregulated in CPF1 and CPF2, respectively compared to control. All gene expression levels in spleen were upregulated on day 7 of exposure in the high exposed group. Histopathology showed dose-dependent changes in CPF treated groups, indicating gill, liver, and posterior kidney changes associated with oxidative stress damages. Following recovery period, all measured parameters showed varying degrees in their reversibility to the control level. These findings provide important insights about the acute toxic effects of CPF on fish and show potential to be used as biomarkers in further toxicological evaluation studies.
Comparative assessment of toxicity of ZnO and amine-functionalized ZnO nanorods toward Daphnia magna in acute and chronic multigenerational tests Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-05 Renata Amanda Gonçalves, Ana Letícia de Oliveira Franco Rossetto, Diego José Nogueira, Denice Schulz Vicentini, William Gerson Matias
Zinc oxide nanomaterials (ZnO NM) have been used in a large number of applications due to their interesting physicochemical properties. However, the increasing use of ZnO NM has led to concerns regarding their environmental impacts. In this study, the acute and chronic toxicity of ZnO nanorods (NR) bare (ZnONR) and amine-functionalized (ZnONR@AF) toward the freshwater microcrustacean Daphnia magna was evaluated. The ZnO NR were characterized by transmission electron microscopy (TEM), X–Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and the zeta potential and hydrodynamic diameter (HD). The acute EC50(48h) values for D. magna revealed that the ZnONR@AF were more toxic than the ZnONR. The generation of reactive oxygen species (ROS) was observed in both NM. Regarding the chronic toxicity, the ZnONR@AF were again found to be more toxic than the ZnONR toward D. magna. An effect on longevity was observed for ZnONR, while ZnONR@AF affected the reproduction, growth and longevity. In the multigenerational recovery test, we observed that maternal exposure can affect the offspring even when these organisms are not directly exposed to the ZnO NR.
Environmentally-realistic concentration of cadmium combined with polyunsaturated fatty acids enriched diets modulated non-specific immunity in rainbow trout Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-03 Valérie Cornet, Abderrahim Ouaach, S.N.M. Mandiki, Enora Flamion, Aline Ferain, Mélusine Van Larebeke, Benjamin Lemaire, Felipe E. Reyes López, Lluis Tort, Yvan Larondelle, Patrick Kestemont
Nutrition is crucial to grow healthy fish particularly in a context of pollution, overcrowding and pathogen risks. Nowadays, the search for food components able to improve fish health is increasingly developing. Here, the influence of four dietary polyunsaturated fatty acids (PUFAs) that are alpha-linolenic acid (ALA, 18:3n-3), linoleic acid (LA, 18:2n-6), eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) on the sensitivity of rainbow trout (Oncorhynchus mykiss) juveniles to environmentally realistic cadmium (Cd, 0.3 μg/L) concentration was investigated. Fish diets were designed to ensure the specific abundance of one of these individual PUFAs, and were given for a 4-week pre-conditioning period followed by a 6-week Cd exposure period. Focus was put on growth performance and immune responses following a short (24 h) and a long-term (6 weeks) Cd exposure. For each experimental condition, some fish were submitted to a bacterial challenge (24 h) with Aeromonas salmonicida achromogenes at the end of Cd conditioning period. DHA-enriched diet improved growth performances as compared to LA-enriched diet, but also increased ROS production (after short-term exposure to Cd) that could lead to a higher inflammation status, and some immunity-related genes (at short and long-term exposure). We notably highlighted the fact that even a low, environmentally-realistic concentration, Cd can strongly impact the immune system of rainbow trout, and that specific dietary PUFA enrichment strategies can improve growth performance (DHA-enriched diet), provide protection against oxidative stress (ALA- and EPA-enriched diet) and stimulate non-specific immunity.
Characterization of AHR2 and CYP1A Expression in Atlantic Sturgeon and Shortnose Sturgeon Treated with Coplanar PCBs and TCDD Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-02 Nirmal K. Roy, Allison Candelmo, Melissa DellaTorre, R. Christopher Chambers, Arthur Nadas, Isaac Wirgin
Atlantic sturgeon and shortnose sturgeon co-occur in many estuaries along the Atlantic Coast of North America. Both species are protected under the U.S. Endangered Species Act and internationally on the IUCN Red list and by CITES. Early life-stages of both sturgeons may be exposed to persistent aromatic hydrocarbon contaminants such as PCBs and PCDD/Fs which are at high levels in the sediments of impacted spawning rivers. Our objective was to compare the PCBs and TCDD sensitivities of both species with those of other fishes and to determine if environmental concentrations of these contaminants approach those that induce toxicity to their young life-stages under controlled laboratory conditions. Because our previous studies suggested that young life-stages of North American sturgeons are among the more sensitive of fishes to coplanar PCB and TCDD-induced toxicities, we were interested in identifying the molecular bases of this vulnerability. It is known that activation of the aryl hydrocarbon receptor 2 (AHR2) in fishes mediates most toxicities to these contaminants and transcriptional activation of xenobiotic metabolizing enzymes such as cytochrome P4501A (CYP1A). Previous studies demonstrated that structural and functional variation in AHRs are the bases for differing sensitivities of several vertebrate taxa to aromatic hydrocarbons. Therefore, in this study we characterized AHR2 and its expression in both sturgeons as an initial step in understanding the mechanistic bases of their sensitivities to these contaminants. We also used CYP1A expression as an endpoint to develop Toxicity Equivalency Factors (TEFs) for these sturgeons. We found that critical amino acid residues in the ligand binding domain of AHR2 in both sturgeons were identical to those of the aromatic hydrocarbon-sensitive white sturgeon, and differed from the less sensitive lake sturgeon. AHR2 expression was induced by TCDD (up to 6-fold) and by three of four tested coplanar PCB congeners (3-5-fold) in Atlantic sturgeon, but less so in shortnose sturgeon. We found that expression of AHR2 and CYP1A mRNA significantly covaried after exposure to TCDD and PCB77, PCB81, PCB126, but not PCB169 in both sturgeons. We also determined TEFs for the four coplanar PCBs in shortnose sturgeon based on comparison of CYP1A mRNA expression across all doses. Surprisingly, the TEFs for all four coplanar PCBs in shortnose sturgeon were much higher (6.4 to 162 times) than previously adopted for fishes by the WHO.
Sub-lethal effects of herbicides penoxsulam, imazamox, fluridone and glyphosate on Delta Smelt (Hypomesus transpacificus) Aquat. Toxicol. (IF 4.129) Pub Date : 2018-02-01 Jiali Jin, Tomofumi Kurobe, Wilson F. Ramírez-Duarte, Melissa B. Bolotaolo, Chelsea H. Lam, Pramod K. Pandey, Tien-Chieh Hung, Marie E. Stillway, Leanna Zweig, Jeffrey Caudill, Li Lin, Swee J. Teh
Concerns regarding non-target toxicity of new herbicides used to control invasive aquatic weeds in the San Francisco Estuary led us to compare sub-lethal toxicity of four herbicides (penoxsulam, imazamox, fluridone and glyphosate) on an endangered fish species Delta Smelt (Hypomesus transpacificus). We measured 17β-estradiol (E2) and glutathione (GSH) concentrations in liver, and acetylcholinesterase (AChE) activity in brain of female and male fish after 6 h of exposure to each of the four herbicides. Our results indicate that fluridone and glyphosate disrupted the E2 concentration and decreased glutathione concentration in liver, whereas penoxsulam, imazamox and fluridone inhibited brain AChE activity. E2 concentrations were significantly increased in female and male fish exposed to 0.21 μM of fluridone and in male fish exposed to 0.46, 4.2, and 5300 μM of glyphosate. GSH concentrations decreased in males exposed to fluridone at 2.8 μM and higher, and glyphosate at 4.2 μM. AChE activity was significantly inhibited in both sexes exposed to penoxsulam, imazamox, and fluridone, and more pronounced inhibition was observed in females. The present study demonstrates the potential detrimental effects of these commonly used herbicides on Delta Smelt.
Bisphenol risk in fish exposed to a contamination gradient: triggering of spatial avoidance Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-31 Daniel C.V.R. Silva, Cristiano V.M. Araújo, Fernanda M. França, Morun B. Neto, Teresa C.B. Paiva, Flávio T. Silva, Marcelo L.M. Pompêo
Bisphenol A (BPA) is an emerging contaminant widely used in various industrial products. Sublethal toxicity of BPA on aquatic organisms is expected to occur at a concentration of around 500 μg L−1, which is much higher than environmentally realistic concentrations found in water bodies (up to 0.41 μg L−1). However, there is no information concerning how a BPA contamination gradient could affect the spatial displacement of organisms. We hypothesized that fish might be able to detect an environmentally realistic BPA contamination gradient and avoid potential toxic effects due to continuous exposure. Therefore, the objectives of this work were: (i) to determine if BPA could trigger an avoidance response in the freshwater fish Poecilia reticulata; (ii) to assess whether BPA-driven avoidance occurs at environmentally relevant concentrations; and (iii) to estimate the population immediate decline (PID) at the local scale, considering avoidance and mortality as endpoints. Avoidance experiments were performed in a seven-compartment non-forced exposure system, in which a BPA contamination gradient was simulated. The results indicated that BPA triggered avoidance in P. reticulata. In a traditional forced acute toxicity test, lethal effects in 50% of the population occurred at a BPA concentration of 1,660 μg L−1, while in the non-forced system with a BPA concentration gradient, avoidance of 50% of the population occurred at a concentration four orders of magnitude lower (0.20 μg L−1). At environmentally relevant BPA concentrations, PID was mainly determined by the avoidance response. Avoidance in P. reticulata populations is expected to occur at BPA concentrations below those that cause sublethal effects on fish and are considered safe by international agencies (≤1 μg L−1). The approach used in the present study represents a valuable tool for use in environmental risk assessment strategies, providing a novel and ecologically relevant response that is complementary to traditional ecotoxicological tests.
Joint effects of nine antidepressants on Raphidocelis subcapitata and Skeletonema marinoi: a matter of amine functional groups Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-31 Laetitia Minguez, Ronan Bureau, Marie-Pierre Halm-Lemeille
Antidepressants are among the most prescribed pharmaceuticals throughout the world. Their presence has already been detected in several aquatic ecosystems worldwide and their effects on non-target organisms justify the growing concern of both the public and regulatory authorities. These emerging pollutants do not occur as isolated compounds but rather as multi-component mixtures, which may lead to increased adverse effects compared to individual compounds. Freshwater and marine algae seem particularly sensitive to pharmaceuticals, including antidepressants. Studies assessing the toxicity of antidepressant mixture to algae focused mainly on binary mixtures of selective serotonin reuptake inhibitors. In the present experiment, the freshwater algae Raphidocelis subcapitata (formerly known as Pseudokirchneriella subcapitata) and the marine diatom Skeletonema marinoi were exposed to equitoxic mixtures of 9 antidepressants (fluvoxamine, fluoxetine, sertraline, duloxetine, venlafaxine, clomipramine, amitriptyline, and citalopram) at different concentrations. The growth inhibition was measured. Results showed that the toxicity of this mixture was higher than the effects of each individual component, highlighting simple additivity or synergistic effects, whereas tested concentrations were below the 10% inhibition concentration (IC10) of each compound. Moreover, the QSAR analysis highlighted that antidepressants would act through narcosis (non-specific mode of action) towards the two species of algae. However, more specific effects can be observed by differentiating compounds with a primary/secondary amine from those with a tertiary amine. These mixture effects on algal species have to be assessed, especially since any impacts on phytoplankton could ultimately impact higher trophic levels (less food, secondary poisoning).
The effects of elevated environmental CO2 on nitrite uptake in the air-breathing clown knifefish, Chitala ornata Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-31 Le Thi Hong Gam, Frank Bo Jensen, Do Thi Thanh Huong, Nguyen Thanh Phuong, Mark Bayley
Nitrite and carbon dioxide are common environmental contaminants in the intensive aquaculture ponds used to farm clown knifefish (Chitala ornata) in the Mekong delta, Vietnam. Here we tested the hypothesis that hypercapnia reduces nitrite uptake across the gills, because pH regulation will reduce chloride uptake and hence nitrite uptake as the two ions compete for the same transport route via the branchial HCO3−/Cl− exchanger. Fish fitted with arterial catheters were exposed to normocapnic/normoxic water (control), nitrite (1 mM), hypercapnia (21 mmHg CO2), or combined hypercapnia (acclimated hypercapnia) and nitrite for 96 h. Blood was sampled to measure acid-base status, haemoglobin derivatives and plasma ions. Plasma nitrite increased for 48 h, but levels stayed below the exposure concentration, and subsequently decreased as a result of nitrite detoxification to nitrate. The total uptake of nitrite (evaluated as [NO2−] + [NO3−]) was significantly decreased in hypercapnia, in accordance with the hypothesis. Methemoglobin and nitrosylhemoglobin levels were similarly lower during hypercapnic compared to normocapnic nitrite exposure. The respiratory acidosis induced by hypercapnia was half-compensated by bicarbonate accumulation in 96 h, which was mainly chloride-mediated (i.e. reduced Cl− influx via the branchial HCO3−/Cl− exchanger). Plasma osmolality and main ions (Na+, Cl−) were significantly decreased by hypercapnia and by nitrite exposure, consistent with inhibition of active transport. We conclude that hypercapnia induces a long-lasting, and mainly chloride-mediated acid-base regulation that reduces the uptake of nitrite across the gills.
Novel aspects of uptake patterns, metabolite formation and toxicological responses in Salmon exposed to the organophosphate esters — Tris(2-butoxyethyl)- and Tris(2-chloroethyl) phosphate Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-31 Augustine Arukwe, Camilla Catarci Carteny, Trine Eggen, Monika Möder
Toxicity assessment of pyriproxyfen in vertebrate model zebrafish embryos (Danio rerio): A multi biomarker study Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-12 Kannan Maharajan, Sellamani Muthulakshmi, Bojan Nataraj, Mathan Ramesh, Krishna Kadirvelu
Pyriproxyfen (2-[1-methyl-2-(4-phenoxyphenoxy) ethoxy] pyridine) (PPF), is a pyridine-based pesticide widely used to control agricultural insect pests and mosquitoes in drinking water sources. However, its ecotoxicological data is limited in aquatic vertebrates particularly in fish. Hence, the present study aimed to evaluate the adverse effect of PPF in zebrafish embryo development (Danio rerio). In order to investigate the impact of PPF, embryos were exposed to 0.16, 0.33 and 1.66 μg/mL (0.52, 1.04 and 5.2 μM, respectively) for 96 hpf and various biomarker indices such as developmental toxicity (edema formation, hyperemia, heart rate and scoliosis), oxidative stress (reactive oxygen species (ROS), lipid peroxidation (LPO) and nitric oxide (NO)), antioxidant responses (superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione peroxidase (GPx) and reduced glutathione (GSH)), biochemical (lactate dehydrogenase (LDH) and acid phosphatase (AP)), neurotoxicity (acetylcholinesterase (AChE)), genotoxicity (apoptosis and DNA damage) and histopathological changes were determined. The results showed that severe developmental deformities and changes in heart rate were observed in embryos treated with highest (1.66 μg/mL) concentration than the control (P < 0.05). Heart size measurement showed that, significant change in heart size (P < 0.01) was observed in embryos of 96 hpf only at 1.66 μg/mL PPF exposure. The oxidative stress was apparent at highest test concentration (1.66 μg/mL) as reflected by the elevated ROS, LPO and NO and changes in antioxidant enzyme activities including SOD, CAT, GST and GPx (P < 0.05). Besides, GSH level and AChE activity were significantly lowered in 1.66 μg/mL PPF exposed group than the control. After 96 hpf of PPF exposure, no significant changes were found in AP activity whereas, a biphasic response was observed in he LDH activity. There was no genotoxic effect in embryos exposed to PPF at 0.16 and 0.33 μg/mL, while significant (P < 0.05) DNA damage and apoptosis were found in 1.66 μg/mL treated group. Histopathological analysis revealed that exposure to PPF at 1.66 μg/mL resulted in thinning of heart muscles, pericardial edema and hyperemia while there was no obvious changes were observed in other treatment groups. Hence, the results of the present study demonstrate that PPF could cause adverse effect on early developmental stages of zebrafish at higher concentration.
Copper bioaccumulation and biokinetic modeling in marine herbivorous fish Siganus oramin Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-10 Yanyan Zhou, Fangsan Wei, Wei Zhang, Zhiqiang Guo, Li Zhang
Marine herbivorous fish directly consume macroalgae, which commonly accumulate high levels of trace metals in polluted areas. We proposed that herbivorous fish could be better candidates for biomonitoring marine metal pollution than carnivorous fish. To date, the trophic transfer of Cu from macroalgae to marine herbivorous fish is unclear. In this study, the kinetics of Cu bioaccumulation in a widespread marine herbivorous fish, Siganus oramin, were investigated, and biokinetic modeling was applied to estimate the Cu levels in the fish sampled from different sites and seasons. The results showed that Cu accumulation in the fish was linearly correlated to the dietary Cu levels in the different prey species, which were proportional to the waterborne Cu concentrations. The Cu found in the subcellular trophically available metal fraction (TAM) in the prey contributed the largest proportion of accumulated Cu in S. oramin. The dietary assimilation efficiencies (AEs) of Cu were 15.56 ± 1.76%, 13.42 ± 2.86%, and 21.36 ± 1.47% for Ulva lactuca, Gracilaria lemaneiformis and Gracilaria gigas, respectively. The calculated waterborne uptake rate constant (ku) of Cu was 0.023 ± 0.011 L g−1 d−1, and the efflux rate constant (ke) was 0.055 ± 0.021 d−1. Dietary Cu accounted for 60%-75% of the body Cu in S. oramin, suggesting that dietary uptake could be the primary route for Cu bioaccumulation in herbivorous fish. The biokinetic model demonstrated that the Cu concentrations in the water and fish presented a positive linear relationship, which was in line with our field investigation along the coastal areas of South China. Therefore, we suggested that S. oramin could be used as a biomonitoring organism for Cu pollution in the marine environment. However, the heterogeneities between the predicted levels and the measured levels of Cu implied that seasonal changes should be taken into account to improve the accuracy of the model.
Oxidative and interactive challenge of cadmium and ocean acidification on the smooth scallop Flexopecten glaber Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-08 Alessandro Nardi, Maura Benedetti, Daniele Fattorini, Francesco Regoli
Effects of domestic effluent discharges on mangrove crab physiology: integrated energetic, osmoregulatory and redox balances of a key engineer species Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-06 Dimitri Theuerkauff, Georgina A. Rivera-Ingraham, Yann Mercky, Mathilde Lejeune, Elliott Sucré, Jehan-Hervé Lignot
Mangroves are increasingly used as biofiltering systems of (pre-treated) domestic effluents. However, these wastewater discharges may affect local macrofauna. This laboratory study investigates the effects of wastewater exposure on the mangrove spider crab Neosarmatium meinerti, a key engineering species which is known to be affected by waste waters in effluent-impacted areas. These effects were quantified by monitoring biological markers of physiological state, namely oxygen consumption, the branchial cavity ventilation rate, gill physiology and morphology, and osmoregulatory and redox balance. Adults acclimated to clean seawater (SW, 32 ppt) and freshwater (FW, ∼0 ppt) were compared to crabs exposed to wastewater for 5 hours (WW, ∼0 ppt). Spider crabs exposed to WW increased their ventilation and whole-animal respiration rates by 2- and 3-fold respectively, while isolated gill respiration increased in the animals exposed to FW (from 0.5 to 2.3 and 1.1 nmol O2 min−1 mgDW−1 for anterior and posterior gills, respectively) but was not modified in WW-exposed individuals. WW exposure also impaired crab osmoregulatory capacity; an 80 mOsm.kg−1 decrease was observed compared to FW, likely due to decreased branchial NKA activity. ROS production (DCF fluorescence in hemolymph), antioxidant defenses (superoxide dismutase and catalase activities) and oxidative damage (malondialdehyde concentration) responses varied according to animal gender. Overall, this study demonstrates that specific physiological parameters must be considered when focusing on crabs with bimodal breathing capacities. We conclude that spider crabs exposed to WW face osmoregulatory imbalances due to functional and morphological gill remodeling, which must rapidly exhaust energy reserves. These physiological disruptions could explain the ecological changes observed in the field.
Effects of lanthanum on Microcystis aeruginosa: Attention to the changes in composition and content of cellular microcystins Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-06 Fei Shen, Lihong Wang, Qing Zhou, Xiaohua Huang
Algal blooms threaten human health and aquatic ecosystem through the production of microcystins (MCs) by toxic strains. The accumulation of rare earth elements (REEs) in water affects the growth and physiological activities of algae. However, whether or how REEs affect cellular microcystins (MCs) is largely unknown. In this study, the effects of lanthanum ion [La(III)], a type of REE, on the MCs in Microcystis aeruginosa were investigated, and the mechanism of the effect was analyzed using ecological stoichiometry. The different concentrations of La(III) were selected to correlate environmental pollution status. Low-dose La(III) (0.2, 2.0, and 4.0 μM) exposure increased the total content of MCs and the percentage contents of microcystin-YR (MC-YR) and microcystin-LW (MC-LW) and decreased the percentage content of microcystin-LR (MC-LR). High-dose La(III) (8.0, 20, 40, and 60 μM) exposure decreased the total content of the MCs, increased the percentage content of MC-LR, and decreased the percentage contents of MC-YR and MC-LW. The changes in the total MCs content were positively associated with the ratios of C:P and N:P in algal cells. The composition of MCs was dependent on the ratio of C:N in algal cells; for example, the percentage content of MC-LR decreased and the percentage content of MC-YR and MC-LW increased as the ratio of C:N in algal cells increased. In conclusion, La(III) could affect the content and composition of MCs via changes in the growth and chlorophyll-a content of Microcystis aeruginosa, and these effects depended on the ratios of C:P, N:P, and C:N in Microcystis aeruginosa. Such changes may influence the toxicity of Microcystis blooms. The results provides a new insight into the mechanism of REEs effects on algal toxins and provide references for evaluating environmental risks of REEs pollution in aquatic ecosystems.
Effects of copper and butyltin compounds on the growth, photosynthetic activity and toxin production of two HAB dinoflagellates : the planktonic Alexandrium catenella and the benthic Ostreopsis cf. ovata Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-06 Douglas Couet, Olivier Pringault, Chrystelle Bancon-Montigny, Nicolas Briant, Françoise Elbaz Poulichet, Sophie Delpoux, Ons Kéfi-Daly Yahia, BenGharbia Hela, M’Rabet Charaf, Fabienne Hervé, Georges Rovillon, Zouher Amzil, Mohamed Laabir
Controlled laboratory experiments were conducted to test the effects of copper (Cu2+) and butyltins (BuT) on the growth, photosynthetic activity and toxin content of two HABs (Harmful Algal Blooms) dinoflagellates, the planktonic Alexandrium catenella and the benthic Ostreopsis cf. ovata. Microalgae were exposed to increasing concentrations of Cu2+ (10−4 to 31 nM) or BuT (0.084 to 84 nM) for seven days. When considering the growth, EC50 values were 0.16 (±0.09) nM and 0.03 (±0.02) nM of Cu2+ for A. catenella and O. cf. ovata, respectively. Regarding BuT, EC50 was 14.2 (±6) nM for O. cf. ovata, while A. catenella growth inhibition appeared at BuT concentrations ≥27 nM. Photosynthetic activity of the studied dinoflagellates decreased with increasing Cu and BuT concentrations. For O. cf. ovata, the response of this physiological parameter to contamination was less sensitive than the biomass. Cu exposure induced the formation of temporary cysts in both organisms that could resist adverse conditions. The ovatoxin-a and -b concentrations in O. cf. ovata cells increased significantly in the presence of Cu. Altogether, the results suggest a better tolerance of the planktonic A. catenella to Cu and BuT. This could result in a differentiated selection pressure exerted by these metals on phytoplankton species in highly polluted waters. The over-production of toxins in response to Cu stress could pose supplementary health and socio-economic threats in the contaminated marine ecosystems where HABs develop.
Effects of ocean acidification on copepods Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-05 Minghua Wang, Chang-Bum Jeong, Young Hwan Lee, Jae-Seong Lee
Ocean acidification (OA) leads to significant changes in seawater carbon chemistry, broadly affects marine organisms, and considered as a global threat to the fitness of marine ecosystems. Due to the crucial role of copepods in marine food webs of transferring energy from primary producers to higher trophic levels, numerous studies have been conducted to examine the impacts of OA on biological traits of copepods such as growth and reproduction. Under OA stress, the copepods demonstrated species-specific and stage-dependent responses. Notably, different populations of the same copepod species demonstrated different sensitivities to the increased pCO2. In copepods, the deleterious effects of OA are also reinforced by other naturally occurring co-stressors (e.g., thermal stress, food deprivation, and metal pollution). Given that most OA stress studies have focused on the effects of short-term exposure (shorter than a single generation), experiments using adults might have underestimated the damaging effects of OA and the long-term multigenerational exposure to multiple stressors (e.g., increased pCO2 and food shortage) will be required. Particularly, omics-based technologies (e.g., genomics, proteomics, and metabolomics) will be helpful to better understand the underlying processes behind biological responses (e.g., survival, development, and offspring production) at the mechanistic level which will improve our predictions of the responses of copepods to climate change stressors including OA.
Title: Vitamin C attenuates biochemical and genotoxic damage in common carp (Cyprinus carpio) upon joint exposure to combined toxic doses of fipronil and buprofezin insecticides Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-05 Madiha Ghazanfar, Sana Shahid, Irfan Zia Qureshi
Feeding inhibition in Corbicula fluminea (O.F. Muller, 1774) as an effect criterion to pollutant exposure: perspectives for ecotoxicity screening and refinement of chemical control Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-04 Bruno Branco Castro, Carlos Silva, Inês Patrunilho Efe Macário, Bruno Oliveira, Fernando Gonçalves, Joana Luísa Pereira
Bivalves are commonly used in biomonitoring programs to track pollutants. Several features, including its filter-feeding abilities, cumulatively argue in favour of the use of the Asian clam (Corbicula fluminea) as a biosentinel and an ecotoxicological model. Filtration in bivalves is very sensitive to external stimuli and its control is dictated by regulation of the opening/closure of the valves, which may be used as an avoidance defence against contaminants. Here, we investigate the filter-feeding behaviour of the Asian clam as an endpoint for assessing exposure to pollutants, driven by two complementary goals: (i) to generate relevant and sensitive toxicological information based on the ability of C. fluminea to clear an algal suspension, using the invasive species as a surrogate for native bivalves; (ii) to gain insight on the potential of exploring this integrative response in the refinement of chemical control methods for this pest. Clearance rates and proportion of algae removed were measured using a simple and reproducible protocol. Despite some variation across individuals and size classes, 50–90% of food particles were generally removed within 60–120 min by clams larger than 20 mm. Removal of algae was sensitive to an array of model contaminants with biocide potential, including fertilizers, pesticides, metals and salts: eight out of nine tested substances were detected at the μg l−1 or mg l−1 range and triggered valve closure, decreasing filter-feeding in a concentration-dependent manner. For most toxicants, a good agreement between mortality (96 h − LC50 within the range 0.4–5500 mg l−1) and feeding (2 h − IC50 within the range 0.005–2317 mg l−1) was observed, demonstrating that a 120-min assay can be used as a protective surrogate of acute toxicity. However, copper sulphate was very strongly avoided by the clams (IC50 = 5.3 μg l−1); on the contrary, dichlorvos (an organophosphate insecticide) did not cause feeding depression, either by being undetected by the clams’ chemosensors and/or by interfering with the valve closure mechanism. Such an assay has a large potential as a simple screening tool for industry, environmental agencies and managers. The ability of dichlorvos to bypass the Asian clam’s avoidance strategy puts it in the spotlight as a potential agent to be used alone or combined with others in eradication programs of this biofouler in closed or semi-closed industrial settings.
Copper induces expression and methylation changes of early development genes in Crassostrea gigas embryos Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-03 Rossana Sussarellu, Morgane Lebreton, Julien Rouxel, Farida Akcha, Guillaume Rivière
Copper contamination is widespread along coastal areas and exerts adverse effects on marine organisms such as mollusks. In the Pacific oyster, copper induces severe developmental abnormalities during early life stages; however, the underlying molecular mechanisms are largely unknown. This study aims to better understand whether the embryotoxic effects of copper in Crassostrea gigas could be mediated by alterations in gene expression, and the putative role of DNA methylation, which is known to contribute to gene regulation in early embryo development. For that purpose, oyster embryos were exposed to 4 nominal copper concentrations (0.1, 1, 10 and 20 μg L−1 Cu2+) during early development assays. Embryotoxicity was monitored through the oyster embryo-larval bioassay at the D-larva stage 24 h post fertilization (hpf) and genotoxicity at gastrulation 7 hpf. In parallel, the relative expression of 15 genes encoding putative homeotic, biomineralization and DNA methylation proteins was measured at three developmental stages (3 hpf morula stage, 7 hpf gastrula stage, 24 hpf D-larvae stage) using RT-qPCR. Global DNA content in methylcytosine and hydroxymethylcytosine were measured by HPLC and gene-specific DNA methylation levels were monitored using MeDIP-qPCR. A significant increase in larval abnormalities was observed from copper concentrations of 10 μg L−1, while significant genotoxic effects were detected at 1 μg L−1 and above. All the selected genes presented a stage-dependent expression pattern, which was impaired for some homeobox and DNA methylation genes (Notochord, HOXA1, HOX2, Lox5, DNMT3b and CXXC-1) after copper exposure. While global DNA methylation (5-methylcytosine) at gastrula stage didn’t show significant changes between experimental conditions, 5-hydroxymethylcytosine, its degradation product, decreased upon copper treatment. The DNA methylation of exons and the transcript levels were correlated in control samples for HOXA1 but such a correlation was diminished following copper exposure. The methylation level of some specific gene regions (HoxA1, Hox2, Engrailed2 and Notochord) displayed changes upon copper exposure. Such changes were gene and exon-specific and no obvious global trends could be identified. Our study suggests that the embryotoxic effects of copper in oysters could involve homeotic gene expression impairment possibly by changing DNA methylation levels.
Toxicokinetic and toxicodynamic of depleted uranium in the zebrafish, Danio rerio Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-30 Olivier Simon, Béatrice Gagnaire, Virginie Camilleri, Isabelle Cavalié, Magali Floriani, Christelle Adam-Guillermin
This study investigated the accumulation pattern and biological effects (genotoxicity and histopathology) to adult zebrafish (male and female) exposed to a nominal waterborne concentration of 20 μg L−1 of depleted uranium (DU) for 28 days followed by 27 days of depuration. Accumulation pattern showed that (i) DU accumulated in brain, (ii) levels in digestive tract were higher than those measured in gills and (iii) levels remained high in kidney, brain and ovary despite the 27 days of depuration period. Genotoxicity, assessed by comet assay, was significant not only during DU exposure, but also during depuration phase. Gonads, in particular the testes, were more sensitive than gills. The histology of gonads indicated severe biological damages in males. This study improved knowledge of ecotoxic profile of uranium, for which a large range of biological effects has already been demonstrated.
Novel approach for evaluating pharmaceuticals toxicity using Daphnia model: analysis of the mode of cytochrome P450-generated metabolite action after acetaminophen exposure Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-30 Ryeo-Ok Kim, Min-A Jo, Jinhaeng Song, Il-Chan Kim, Seokjoo Yoon, Woo-Keun Kim
Because of its widespread use, the pharmaceutical acetaminophen (APAP) is frequently detected in aquatic environments. APAP can have serious physiological effects, such as reduced reproduction, low growth rates, and abnormal behavior, in aquatic organisms. However, the methods available for evaluation of the aquatic toxicity of APAP are of limited usefulness. The present study aimed to develop reliable and sensitive markers for evaluation of APAP toxicity using Daphnia as a model organism. We focused on N-acetyl-p-benzoquinoneimine (NAPQI) production from APAP via cytochrome P450 metabolism because NAPQI causes APAP toxicity. Daphnia magna were exposed to APAP (0, 50, or 100 mg/L for 12 h or 24 h), and the total metabolites were extracted and analyzed for NAPQI. Direct detection of NAPQI was difficult because of its high reactivity, and its peak was close to that for APAP. Therefore, we tried to identify molecular and biochemical indicators associated with NAPQI generation, elimination, and its interactions with macromolecules. We identified changes in CYP370A13 gene expression, glutathione depletion, inhibition of thioredoxin reductase activity, and production of reactive oxygen species as indicators of D. magna exposure to APAP. These indicators could be used to develop sensitive and accurate techniques to evaluate the environmental toxicity of APAP.
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