Pharmacological characterization of the aminorex analogs 4-MAR, 4,4’-DMAR, and 3,4-DMAR Neurotoxicology (IF 3.076) Pub Date : 2019-02-15 Anna Rickli, Karolina Kolaczynska, Marius C. Hoener, Matthias E. Liechti
4,4’-Dimethylaminorex (4,4’-DMAR) is a novel psychoactive substance (NPS) that appeared on the illicit drug market in addition to the psychostimulant 4-methylaminorex (4-MAR). Both substances are methylated derivatives of aminorex, an amphetamine-like anorectic used in the 1960ies and withdrawn from the marked due to severe cardiovascular toxicity. The aim of the present study was to characterize the in vitro pharmacological profiles of 4-MAR, 4,4’-DMAR, and 3,4-dimethylaminorex (3,4-DMAR, direx). We assessed norepinephrine (NE), dopamine (DA), and serotonin (5-HT) transporter inhibition potencies and monoamine release in transporter-transfected human embryonic kidney (HEK) 293 cells. We also assessed monoamine receptor and transporter binding affinities. 4,4’-DMAR potently inhibited all monoamine transporters (IC50<1 µM) with greater potency than 3,4-methlyenedioxymethamphetaime (MDMA) and displayed a higher serotonergic over dopaminergic preference, relatively similar to MDMA (DA transporter / 5-HT transporter inhibition ratio of 0.4 and 0.08 for 4,4’-DMAR and MDMA, respectively). In contrast, 4-MAR preferentially inhibited the NE and DA transporter, exhibiting a pharmacological profile more similar to amphetamine. Both 4-MAR and 4,4’-DMAR were also substrate releasers at the DAT. 3,4-DMAR only weakly inhibited the NE transporter and showed no relevant activity at the DA and 5-HT transporter. Binding affinities of all three aminorex derivatives at various monoamine receptors were negligible (Ki values >2 µM). The in vitro pharmacological profiles indicate that 4,4’-DMAR has comparable psychoactive properties and serotonergic toxicity to MDMA and may be more potent. 4-MAR is a psychostimulant similar to amphetamine or methamphetamine. 3,4-DMAR likely has only weak psychostimulant properties.
A role of PSA-NCAM in the survival of retinal ganglion cells (RGCs) after kainic acid damage Neurotoxicology (IF 3.076) Pub Date : 2019-02-14 Natalia Lobanovskaya, Alexander Zharkovsky
Background Neural cell adhesion molecule (NCAM) belongs to the immunoglobulin superfamily of adhesion molecules. Polysialic acid (PSA) is attached to NCAM post-translationally. PSA residues are considered to reduce the adhesive properties of NCAM and play an important role in the regulation of cell interactions. PSA-NCAM is largely expressed in the mature retina by glial cells adjacent to retinal ganglion cells (RGCs) but its functions remain unclear. The objective of this study was to explore the role of PSA-NCAM with respect to RGC survival following kainic acid (KA)-induced excitotoxicity. Methods Experiments were performed on C57BL/6NTac male mice. KA was injected intravitreally to induce RGC damage. RGCs were visualized using an anti-Brn3a antibody. Endoneuraminidase N (NA) was administrated intravitreally to cleave PSA chains from NCAM. Results KA induced an 80% reduction in the density of RGCs that was accompanied by a decrease in PSA-NCAM in the RGC layer. KA treatment induced a pronounced increase in the level of matrix metalloproteinase-9 (MMP-9) in the inner layers of the retina. Inhibition of MMP-9 reduced both RGC death and PSA-NCAM shedding in the retina. PSA-NCAM cleavage induced by NA abolished the protective action of the MMP-9 inhibitor and decreased RGC survival following KA-treatment. Conclusions A decrease in retinal PSA-NCAM levels following KA administration is due to the induction of active MMP-9, which removes extracellular PSA-NCAM from the surface of astroglial and Müller cells. The MMP-9 induced shedding of PSA-NCAM enhances KA-induced toxicity and at least in part contributes to the observed loss of RGCs following excitotoxic damage.
d-Amphetamine and methylmercury exposure during adolescence alters sensitivity to monoamine uptake inhibitors in adult mice Neurotoxicology (IF 3.076) Pub Date : 2019-02-12 Steven R. Boomhower, M. Christopher Newland
Gestational exposure to methylmercury (MeHg), an environmental neurotoxicant, and adolescent administration of d-amphetamine (d-AMP) disrupt dopamine neurotransmission and alter voluntary behavior in adult rodents. We determined the impact of adolescent exposure to MeHg and d-AMP on monoamine neurotransmission in mice by assessing sensitivity to acute d-AMP, desipramine, and clomipramine, drugs that target dopamine, norepinephrine, and serotonin reuptake, respectively. Male C57Bl/6n mice were given 0 (control) or 3 ppm MeHg via drinking water from postnatal day 21 to 60 (murine adolescence). Within each group, mice were given once-daily injections of d-AMP or saline (i.p.) from postnatal day 28 to 42. This exposure regimen produced four treatment groups (n = 10-12/group): control, d-AMP, MeHg, and d-AMP + MeHg. As adults, the mice lever pressed under fixed-ratio schedules of reinforcement (FR 1, 5, 15, 30, 60, and 120). Acute i.p. injections of d-AMP (.3 – 1.7 mg/kg), desipramine (5.6 – 30 mg/kg), and clomipramine (5.6 – 30 mg/kg) were administered in adulthood after a stable behavioral baseline was established. Adolescent MeHg exposure increased saturation rate and minimum response time, an effect that was mitigated by chronic administration of d-AMP in adolescence. In unexposed mice, the three monoamine reuptake inhibitors had separable behavioral effects. Adolescent d-AMP increased sensitivity to acute d-AMP, desipramine, and clomipramine. Adolescent MeHg exposure alone did not alter drug sensitivity. Combined adolescent d-AMP + MeHg exposure enhanced sensitivity to acute d-AMP’s and desipramine’s effects on minimum response time. Adolescence is a vulnerable developmental period during which exposure to chemicals can have lasting effects on monoamine function and behavior.
Effects of norfloxacin exposure on neurodevelopment of zebrafish (Danio rerio) embryos Neurotoxicology (IF 3.076) Pub Date : 2019-02-12 Jinlei Xi, Juan Liu, Shijing He, Wanyao Shen, Cizhao Wei, Ke Li, Yufeng Zhang, Jiang Yue, Zheqiong Yang
In view of the wide application of fluoroquinolones (FQs), a group of broad-spectrum synthetic antibacterial agents, and their large ingress into the environment, the toxic effects on non-target organisms caused by FQs have received great attention. In this study, we used zebrafish embryo as a model, measured the general toxic effects of norfloxacin, a commonly used FQs, and investigated the effects of norfloxacin on the neurodevelopment of zebrafish embryos. Our data showed that norfloxacin significantly inhibited the hatching rate of zebrafish embryos, and increased the mortality and malformation rate of the embryos. To discuss the developmental neurotoxicity of norfloxacin, we measured the expression of several stem cell and neuron lineage markers in the zebrafish embryos. We found that norfloxacin exposure inhibited the expression of GFAP (glial cell marker), and enhanced the expression of Sox 2 (stem cell marker) and Eno2 (mature neuron marker). By measuring the level of active Caspase 3 and the expression ratio of Bax to Bcl2, we discovered that norfloxacin induced obvious cell apoptosis in the brain of zebrafish embryos. To explore the mechanism of the developmental neurotoxic effects of norfloxacin, we applied MK-801, a non-competitive NMDA receptors antagonist, to block the actions of NMDA receptors. The results indicated that MK-801 could rescue the upregulated cell apoptosis and disrupted balance of neuro-glial differentiation induced by norfloxacin in the brain of zebrafish embryos. Our results suggest that the activation of NMDA receptors mediates the developmental neurotoxicity of norfloxacin.
Rho-inhibition and neuroprotective effect on rotenone-treated dopaminergic neurons in vitro Neurotoxicology (IF 3.076) Pub Date : 2019-02-12 Letizia Mattii, Carla Pardini, Chiara Ippolito, Francesco Bianchi, Antonietta Raffaella, Maria Sabbatini, Francesca Vaglini
Mesencephalic cell cultures are a good model to study the vulnerability of dopaminergic neurons and reproduce, in vitro, experimental models of Parkinson’s disease. Rotenone associated as an environmental neurotoxin related to PD, is able to provoke dopaminergic neuron degeneration by inhibiting complex I of the mitochondrial respiratory chain and by inducing accumulation of α-synuclein. Recently, rotenone has been described to activate RhoA, a GTPase protein.In the present study we evaluated a possible neuroprotective effect of Rho-inhibitor molecules on rotenone-damaged dopaminergic (DA) neurons obtained from mouse primary mesencephalic cell culture.Our results showed that Clostridium Botulinum C3 toxin (C3) and simvastatin, as RhoA inhibitors, were able to protect DA neurons from rotenone damages. In fact, pretreatment with C3 or simvastatin significantly prevented the reduction of [3H]dopamine uptake, neurites injury and the expression patterns of proteins like α-syn, actin and connexin 43.
Protective role of metformin against methamphetamine induced anxiety, depression, cognition impairment and neurodegeneration in rat: The role of CREB/BDNF and Akt/GSK3 signaling pathways Neurotoxicology (IF 3.076) Pub Date : 2019-02-08 Saghar Keshavarzi, Sareh Kermanshahi, Leila Karami, Majid Motaghinejad, Manijeh Motevalian, Samira Sadr
Background Methamphetamine is a neuro-stimulant with neurodegenerative effects, and ambiguous mechanism of action. Metformin is an antidiabetic agent with neuroprotective properties but not fully understood mechanisms. The present study investigated the molecular basis of metformin neuroprotection against methamphetamine-induced neurodegeneration. Brief method Sixty adult male rats were randomly divided into six groups: group 1 (received normal saline), group 2 (received 10 mg/kg of methamphetamine) and groups 3, 4, 5 and 6 [received methamphetamine (10 mg/kg) plus metformin (50, 75, 100 and 150 mg/kg) respectively]. Elevated Plus Maze (EPM), Open Field Test (OFT), Forced Swim Test (FST), Tail Suspension Test (TST) and Morris Water Maze (MWM) were used to assess the level of anxiety, depression and cognition in experimental animals. Also animals’ hippocampus were isolated and oxidative stress and inflammatory parameters and expression of total and phosphorylated forms of cAMP response element binding (CREB), brain-derived neurotrophic factor (BDNF), protein kinase B (Akt) and glycogen synthase kinase 3 (GSK3) proteins were evaluated by ELISA method. Results According to the data obtained, methamphetamine caused significant depression, anxiety, motor activity disturbances and cognition impairment in experimental animals. Metformin, in all used doses, decreased methamphetamine induced behavioral disturbances. Also chronic administration of methamphetamine could increase malondialdehyde (MDA), tumor necrosis factor-Alpha (TNF-α) and interleukine-1 beta (IL-1β) in rats, while caused reduction of superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) activities. Metformin, especially in high doses, could prevent these malicious effects of methamphetamine. Also Metformin could activate CREB (both forms), BDNF and Akt (both forms) proteins’ expression and inhibited GSK3 (both forms) protein expression in methamphetamine treated rats. Significance According to obtained data, metformin could protect the brain against methamphetamine-induced neurodegeneration probably by mediation of CREB/BDNF or Akt/GSK3 signaling pathways. These data suggested that CREB/BDNF or Akt/GSK3 signaling pathways may have a critical role in methamphetamine induced neurotoxicity and/or neuroprotective effects of metformin.
Matrine ameliorates anxiety and depression-like behaviour by targeting hyperammonemia-induced neuroinflammation and oxidative stress in CCl4 model of liver injury Neurotoxicology (IF 3.076) Pub Date : 2019-02-08 Adnan Khan, Bushra Shal, Muhammad Naveed, Fawad Ali Shah, Ayesha Atiq, Naseem Ullah Khan, Yeong Shik Kim, Salman Khan
Identification of molecular targets for toxic action by persulfate, an industrial sulfur compound Neurotoxicology (IF 3.076) Pub Date : 2019-02-06 Takahisa Shimada, Kenji Takahashi, Makoto Tominaga, Toshio Ohta
Persulfate salts are broadly used as industrial chemicals and exposure to them causes occupational asthma, occupational rhinitis and contact dermatitis. However, the mechanisms underlying these toxic actions are not fully elucidated. Transient receptor potential (TRP) vanilloid 1 (V1), ankyrin 1 (A1) and melastatin 8 (M8) are non-selective cation channels preferentially expressing sensory neurons. These channels are known to be involved in respiratory and skin diseases. In the present study, we investigated the effects of sodium persulfate on these TRP channels. In wild-type mouse sensory neurons, persulfate evoked [Ca2+]i increases that were inhibited by removal of extracellular Ca2+ or blockers of TRPA1 but not by those of TRPV1 and TRPM8. Persulfate failed to evoke [Ca2+]i responses in neurons from TRPA1(-/-) mice, but did evoke them in neurons from TRPV1(-/-) mice. In HEK 293 cells expressing mouse TRPA1 (mTRPA1-HEK), persulfate induced [Ca2+]i increases. Moreover, in HEK 293 cells expressing mouse TRPV1 (mTRPV1-HEK), a high concentration of persulfate also evoked [Ca2+]i increases. Similar [Ca2+]i responses were observed in HEK 293 cells expressing human TRPA1 and human TRPV1. Current responses were also elicited by persulfate in mTRPA1- and mTRPV1-HEK. Analysis using mutated channels revealed that persulfate acted on electrophilic agonist-sensitive cysteine residues of TRPA1, and it indirectly activated TRPV1 due to the external acidification, because of the disappearance of [Ca2+]i responses in acid-insensitive mTRPV1 mutant. These results demonstrate that persulfate activates nociceptive TRPA1 and TRPV1 channels. It is suggested that activation of these nociceptive channels may be involved in respiratory and skin injuries caused by exposure to this industrial sulfur compound. Thus, selective TRPA1 and TRPV1 channel blockers may be effective to remedy persulfate-induced toxic actions.
Modulation Of Caspase-3 Gene Expression And Protective Effects Of Garlic And Spirulina Against CNS Neurotoxicity Induced By Lead Exposure In Male Rats Neurotoxicology (IF 3.076) Pub Date : 2019-01-28 Mona K. Galal, Ebtihal M.M. Elleithy, Mohamed I. Abdrabou, Noha A.E. Yasin, Youssef M. Shaheen
Difference in ability for extracellular Zn2+ influx between human and rat amyloid β1-42 and its significance Neurotoxicology (IF 3.076) Pub Date : 2019-01-18 Haruna Tamano, Hiroki Suzuki, Shuhei Kobuchi, Paul A. Adlard, Ashley I. Bush, Atsushi Takeda
The accumulation of amyloid-β1-42 (Aβ1-42), a constituively-generated peptide, in the brain is considered an upstream event in pathogenesis of Alzheimer’s disease. Aβ1-42-induced pathophysiology has been extensively studied in experimental mice and rats. However, neurotoxicity of murine Aβ1-42 is much less understood than human Aβ1-42. Here we report difference in ability for extracellular Zn2+ influx into dentate granule cells of rats between human and rat Aβ1-42 and its significance. Human Aβ1-42 rapidly increased intracellular Zn2+, which was determined with intracellular ZnAF-2, in dentate granule cells, 5 min after injection of Aβ1-42 (25 μM, 1 μl) into the dentate gyrus, while rat Aβ1-42 did not increase intracellular Zn2+. In vivo perforant pathway LTP was attenuated under pre-perfusion with 5 nM human Aβ1-42 in artificial cerebrospinal fluid (ACSF) containing 10 nM Zn2+, recapitulating the concentration of extracellular Zn2+, but not with 5 nM rat Aβ1-42 in ACSF containing 10 nM Zn2+. The present study suggests that rat Aβ1-42 has lower affinity for extracellular Zn2+ than human Aβ1-42 and does not capture Zn2+ in the extracellular compartment, resulting in no significant effect on cognitive activity of rat even in the range of very low nanomolar concentrations of endogenous Aβ1-42.
Prenatal exposure to organohalogen compounds and children’s mental and motor development at 18 and 30 months of age Neurotoxicology (IF 3.076) Pub Date : 2019-01-18 Michelle Vivienne Marlou Ruel, Arend Frederik Bos, Shalini Devi Soechitram, Lisethe Meijer, Pieter Jan Jacob Sauer, Sietske Annette Berghuis
Background Organohalogen compounds (OHCs), i.e. polychlorinated biphenyls (PCBs, are wide-spread environmental pollutants known to be neurotoxic for the developing brain. The hydroxylated metabolites of PCBs, OH-PCBs, might be even more toxic due to their structure and interference with thyroid hormone metabolism. We found that prenatal exposure to OH-PCBs was associated with thyroid hormone metabolism at toddler age. Little, however, is known about the neurotoxicity of OH-PCBs in humans. Objectives To determine whether prenatal background exposure to OHCs has an effect on mental and motor development in children at the age of 18 and 30 months. Methods One hundred and eighty-one healthy mother-infant pairs were included in this observational study performed in the Netherlands. We measured maternal pregnancy levels of PCB-153 and three OH-PCBs. In one part of the cohort we measured another nine PCBs and three OH-PCBs and in the other part we measured five brominated diphenyl ethers (BDEs), dichloro-diphenyldichloroethylene (p,p’-DDE), pentachlorophenol (PCP), and hexabromocyclododecane (HBCDD). We used the mental development index (MDI) and the motor development index (PDI) of the Bayley Scales of Infant Development II (BSID-II) to assess children’s mental and motor development (mean = 100; delayed score <85). Results Higher prenatal PCB-153 levels were associated with a delayed MDI score at 18 months. None of the other compounds were associated with a delayed score, but several associations were found between OHC levels and BSID-II scores. The sum of all six OH-PCBs and three individual OH-PCBs, 4-OH-PCB-107, 3-OH-PCB-153, and 4’-OH-PCB-172, correlated positively with MDI at 30 months. The compound 3’-OH-PCB-138 showed a similar trend. A higher 4-OH-PCB-187 was associated with a lower MDI at 18 months. We found a similar trend for higher BDE-99. Higher BDE levels were associated with higher PDI at 18 months. The levels of p,p’-DDE-, PCP, and HBCDD were not associated with BSID-II scores at 18 months. Conclusions Higher prenatal levels of PCB-153 were associated with a delayed MDI score at 18 months. None of the other compounds were associated with a delayed score, but several associations were found between OHC levels and BSID-II scores. Prenatal OH-PCBs were positively associated with mental development at 30 months, whereas one OH-PCB was negatively associated at 18 months. BDE levels were positively associated with psychomotor development. Prenatal p,p’-DDE, PCP, and HBCDD levels were not associated with neurodevelopment at 18 months.
Blockade of GluN2B-containing NMDA receptors reduces short-term brain damage induced by early-life status epilepticus Neurotoxicology (IF 3.076) Pub Date : 2019-01-11 Cássio Morais Loss, Natã Sehn da Rosa, Régis Gemerasca Mestriner, Léder Leal Xavier, Diogo Losch de Oliveira
Status epilepticus (SE) during developmental periods can cause short- and long-term consequences to the brain. Brain damage induced by SE is associated to NMDA receptors (NMDAR)-mediated excitotoxicity. This study aimed to investigate whether blockade of GluN2B-containing NMDAR is neuroprotective against SE-induced neurodegeneration and neuroinflammation in young rats. Forty-eight Wistar rats (16 days of life) were injected with pilocarpine (60 mg/kg; i.p.) 12-18 h after LiCl (3 mEq/kg; i.p.). Fifteen minutes after pilocarpine administration, animals received i.p. injections of saline solution (0.9% NaCl; SE + SAL group), ketamine (a non-selective and noncompetitive NMDAR antagonist; 25 mg/kg; SE + KET), CI-1041 (a GluN2B-containing NMDAR antagonist; 10 mg/kg; SE + CI group) or CP-101,606 (a NMDAR antagonist with great selectivity for NMDAR composed by GluN1/GluN2B diheteromers; 10 mg/kg; SE + CP group). Seven days after SE, brains were removed for Fluoro-Jade C staining and Iba1/ED1 immunolabeling. GluN2B-containing NMDAR blockade by CI-1041 or CP-101,606 did not terminate LiCl-pilocarpine-induced seizures. SE + SAL group presented intense neurodegeneration and Iba1+/ED1+ double-labeling in hippocampus (CA1 and dentate gyrus; DG) and amygdala (MePV nucleus). Administration of CP-101,606 did not alter this pattern. However, GluN2B-containing NMDAR blockade by CI-1041 reduced neurodegeneration and Iba1+/ED1+ double-labeling in hippocampus and amygdala similar to the reduction observed for SE + KET group. Our results indicate that GluN2B-containing NMDAR are involved in SE-induced neurodegeneration and microglial recruitment and activation, and suggest that stopping epileptic activity is not a condition required to prevent short-term brain damage in young animals.
The effect of repeated isoflurane exposure on serine synthesis pathway during the developmental period in Caenorhabditis elegans Neurotoxicology (IF 3.076) Pub Date : 2019-01-09 Sang-Hwan Do, Sue-Young Lee, Hyo-Seok Na
Background Serine synthetic pathway plays an essential role in the development and function of the nervous system. This study investigated whether the serine synthetic pathway was affected by repeated volatile anesthetic exposure using C. elegans and its relationship with anesthesia-induced neurotoxicity. Methods Synchronized worms were divided into two groups: the control and isoflurane groups. Worms in the isoflurane group were exposed to isoflurane for 1 h at each larval stage. The chemotaxis index was evaluated when they reached the young adult-stage in both groups. Also, RNA was extracted from the young adult-worms, and the expressions of C31C9.2, F26H9.5, and Y62E10 A.13 were evaluated using real-time polymerase chain reaction in both groups. At the same time, the L-serine level was measured. After phosphoserine phosphatase inhibitor – glycerophosphorylcholine (GPC) – and L-serine were treated, the change of chemotaxis index was determined. Results In young adult worms exposed to isoflurane, the genetic expressions of C31C9.2, F26H9.5, and Y62E10 A.13 were decreased, and a significant decrease was shown in Y62E10 A.13. The serine level in worms was also lower in the isoflurane group than in the control group (5.13 ± 1.44 vs. 7.65 ± 0.81 pM, n = 5 in each group, p = 0.009). Exposure to GPC reduced the chemotaxis index to a similar degree as repeated isoflurane exposure (52.9% in GPC group vs 58.7% in the isoflurane group). The chemotaxis index (61.1%) was not decreased by repeated isoflurane anesthesia in GPC-treated worms. In this condition, the L-serine level was low similarly in both groups (5.22 ± 1.19 vs. 4.90 ± 1.36 pM, n = 5 in each group, p = 0.702). When L-serine was supplied to C. elegans, the deteriorated chemotaxis index by isoflurane exposure recovered (78.1% in the control group vs. 75.5% in the isoflurane group, p = 0.465). Conclusion Serine synthetic pathway was negatively affected in C. elegans by repeated isoflurane exposure. Y62E10 A.13, which corresponds to phosphoserine phosphatase, was mostly influenced, followed by low L-serine level. Supplementation with L-serine could restore the chemotaxis index.
Involvement of β-catenin in cytoskeleton disruption following adult neural stem cell exposure to low-level silver nanoparticles Neurotoxicology (IF 3.076) Pub Date : 2018-12-31 Robert J. Cooper, Maya N. Menking-Colby, Kenneth A. Humphrey, Jack H. Victory, Daniel W. Kipps, Nadja Spitzer
Silver nanoparticles (AgNPs) are increasingly incorporated in consumer products to confer antibacterial properties. AgNPs are shed during everyday use of these products,resulting in ingestion or inhalation and bioaccumulation in tissues including the brain. While these low levels of AgNPs do not induce DNA fragmentation typical of apoptosis or necrosis, they do interfere with cytoskeletal structure and dynamics in cultured differentiating adult neural stem cells (NSCs). Moreover, these cells form f-actin inclusions in response to 1 μg/ml AgNPs. Here, we report that these cytoskeletal inclusions colocalize with aggregates of the signaling protein β-catenin, a modulator of cytoskeletal dynamics. Pharmacological alteration of β-catenin signaling reduced formation of f-actin inclusions. AgNP exposure also resulted in a reduction of neurite length in differentiating NSCs, which was mimicked by pharmacological activation of β-catenin signaling. Conversely, pharmacological inhibition of the Wnt/β-catenin signaling pathway resulted in increased neurite lengths in control cells, but did not reverse the neurite collapse induced by AgNP exposure. Substantial changes in neurite length, in response to low-level AgNP or pharmacological manipulation of β-catenin signaling, occurred within the first six hours of exposure and were most evident in cells differentiating towards neural-like morphologies. We conclude that low-level exposure to AgNP, such as that resulting from use of consumer products, may disrupt β-catenin signaling in neural cells in an indirect or non-additive manner. Exposure to AgNP shed from consumer products at levels currently considered safe, may therefore alter physiological function of neural cells. This is of concern particularly regarding children, whose brains contain many developing neurons, and who may face bioaccumulation of AgNP over decades of exposure.
Sevoflurane exposure has minimal effect on cognitive function and does not alter microglial activation in adult monkeys Neurotoxicology (IF 3.076) Pub Date : 2018-12-31 Jennifer L. Walters, Xuan Zhang, John C. Talpos, Charles M. Fogle, Mi Li, John J. Chelonis, Merle G. Paule
Postoperative Cognitive Dysfunction (POCD) is a complication that has been observed in a subset of adult and elderly individuals after general anesthesia and surgery. Although the pathogenesis of POCD is largely unknown, a growing body of preclinical research suggests that POCD may be caused by general anesthesia. A significant amount of research has examined the effects of general anesthesia on neurocognitive function in rodents, yet no studies have assessed the adverse effects of general anesthesia on brain function in adult nonhuman primates. Thus, this study sought to determine the effects of an extended exposure to sevoflurane anesthesia on cognitive function and neural inflammation in adult rhesus macaques. Five adult rhesus macaques (16-17 years of age) were exposed to sevoflurane anesthesia for 8 h and, and micro-positron emission tomography (PET)/computed tomography (CT) imaging and a battery of operant tasks were used to assess the effects of anesthesia exposure on 18F-labeled fluoroethoxybenzyl-N-(4-phenoxypyridin-3-yl) acetamide ([18F]-FEPPA) uptake, a biomarker of microglia activation, and aspects of complex cognitive function. Exposure to sevoflurane anesthesia for 8 h did not increase [18F]-FEPPA uptake in the adult monkey brain. Sevoflurane anesthesia significantly decreased accuracy (mean difference = 22.79) on a learning acquisition task 6 days after exposure [t(3) = 6.92, p = 0.006], but this effect did not persist when measured 1 week and 2 weeks after additional exposures. Further, sevoflurane anesthesia had no impact on performance in 4 additional cognitive tasks. These data suggest that exposure to anesthesia alone may not be sufficient to cause persistent POCD in adult populations.
Mechanistic comparison between MPTP and rotenone neurotoxicity in mice Neurotoxicology (IF 3.076) Pub Date : 2018-12-31 Sunil Bhurtel, Nikita Katila, Sunil Srivastav, Sabita Neupane, Dong-Young Choi
Animal models for Parkinson’s disease (PD) are very useful in understanding the pathogenesis of PD and screening for new therapeutic approaches. 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine (MPTP) and rotenone are common neurotoxins used for the development of experimental PD models, and both inhibit complex I of mitochondria; this is thought to be an instrumental mechanism for dopaminergic neurodegeneration in PD. In this study, we treated mice with MPTP (30 mg/kg/day) or rotenone (2.5 mg/kg/day) for 1 week and compared the neurotoxic effects of these toxins. MPTP clearly produced dopaminergic lesions in both the substantia nigra and the striatum as shown by loss of dopaminergic neurons, depletion of striatal dopamine, activation of glial cells in the nigrostriatal pathway and behavioral impairment. In contrast, rotenone treatment did not show any significant neuronal injury in the nigrostriatal pathway, but it caused neurodegeneration and glial activation only in the hippocampus. MPTP showed no such deleterious effects in the hippocampus suggesting the higher susceptibility of the hippocampus to rotenone than to MPTP. Interestingly, rotenone caused upregulation of the neurotrophic factors and their downstream PI3K-Akt pathway along with adenosine monophosphate-activated protein kinase (AMPK) activation. These results suggest that MPTP-induced dopaminergic neurotoxicity is more acute and specific in comparison to rotenone toxicity, and compensatory brain-derived neurotrophic factor (BDNF) induction and AMPK activation in the rotenone-treated brain might suppress the neuronal injury.
Involvement of brain GABAAR-coupled Cl-/HCO3-–ATPase in phenol-induced the head-twitching and tremor responses in rats Neurotoxicology (IF 3.076) Pub Date : 2018-12-24 Sergey A. Menzikov, Sergey G. Morozov
Phenol-induced neurotoxicity manifests as twitching/tremor and convulsions, but its molecular mechanisms underlying the behavioral responses remain unclear. We assessed the role of the brain Cl-/HCO3--ATPase in behavioral responses in rats following an in vivo intraperitoneal injection of phenol (20–160 mg/kg). Low concentrations of phenol (20–80 mg/kg) increased the ATPase activity as well as the head twitching responses in rat, whereas higher phenol concentrations (>60 mg/kg) increased the tremor but reduced the ATPase activity. At phenol concentrations >120 mg/kg, no ATPase activity was detected. Phenobarbital (10 mg/kg) and picrotoxin (1 mg/kg) as well as o-vanadate (2 mg/kg), significantly prevented (~55–70%) the phenol-induced change in the behavioral responses and completely restored the enzyme activity. In vitro experiments confirmed that phenol stimulated the Cl-/HCO3--ATPase activity at low concentrations, but had no stimulating effect on other transport ATPases. Low doses of phenol increased the formation of phosphoprotein and the rate of ATP-consuming Cl- transport by the reconstituted enzyme. The present findings provide evidence that phenol-induced neurotoxicity involves the Cl-/HCO3--ATPase in the behavioral responses in mammals and indicate the potential benefit of this enzyme as a target for the treatment of head twitching and other types of tremor diseases.
Predictors of seizure in Wilson disease: A clinico-radiological and biomarkers study Neurotoxicology (IF 3.076) Pub Date : 2018-12-21 Jayantee Kalita, Usha K. Misra, Vijay Kumar, Vasudev Parashar
Background There is paucity of studies on predictors of seizures in Wilson disease with neurological manifestation (WDNM), and none has evaluated the role of copper (Cu) induced oxidative stress, proinflammatory and excitotoxicity in the genesis of seizure. Objectives To report frequency, refractoriness, and outcome of seizure in WDNM. We also evaluate role of Cu induced oxidative stress, excitotoxicity and cytokines in predicting seizures. Methods The diagnosis of WDNM was based on clinical, MRI, KF ring and 24 hour urinary Cu. Detailed clinical examination including severity of WD, occurrence of seizure, seizure semiology, antiepileptic drug (AED) and breakthrough seizures were noted. Cranial MRI and electroencephalography findings were noted. Serum free-Cu, oxidative stress markers (glutathione, total antioxidant capacity, malondialdehyde), glutamate and cytokines (interleukin 6, 8 and 10 and tumour necrosis factor α) were measured by atomic absorption spectrophotometer, spectrophotometer, fluorometer and flow cytometer respectively, and correlated with seizures. Patients were treated with zinc with or without penicillamine, and those with epilepsy received second-generation antiepileptic drugs (AEDs). Results Out of 110 patients with WDNM, 16(14.5%) had seizures; focal in 11(68.7%) and generalized in 5(31.3%). Patients with seizure had higher serum free-Cu (35.87 ± 1.34 vs 31.72 ± 0.68; P = 0.02), severe dystonia (P = 0.04), and more frequent cortical (100% vs 6.4%; P < 0.01) and subcortical (81.3% vs 20.2%; P < 0.01) lesions on MRI compared to those without seizure. Oxidative stress markers (glutathione, total antioxidant capacity, malondialdehyde), cytokines and glutamate were elevated in WDNM compared to controls. On multivariate logistic regression analysis, cortical involvement (OR = 105.49; 95%CI = 8.74-1272.39; P < 0.01) and number of MRI lesions (OR = 1.99; 95% CI = 1.11-3.57; P = 0.02) were independent predictors of seizure. The seizures were controlled with single and dual AEDs in seven patients each, and two patients needed three AEDs. All the patients had seizure remission for a median follow up of 66(24-180) months. Conclusion About one-sixth WDNM patients have seizures especially in those with cortical and extensive MRI lesions. Seizures are easily controlled by AEDs.
Phosphorylation of extracellular signal-regulated kinase 1/2 in subepidermal nerve fibers mediates hyperalgesia following diabetic peripheral neuropathy Neurotoxicology (IF 3.076) Pub Date : 2018-12-21 Chiung-Hui Liu, Chyn-Tair Lan, Li-You Chen, Wen-Chieh Liao, Miau-Hwa Ko, To-Jung Tseng
Peripheral neuropathy, a chronic complication of diabetes mellitus (DM), is often accompanied by the onset of severe pain symptoms that affect quality of life. However, the underlying mechanisms remain elusive. In the present study, we used Sprague–Dawley rats to establish a rodent model of the human type 1 DM by a single intraperitoneal (i.p.) injection with streptozotocin (STZ) (60 mg/kg). Hypersensitivity, including hyperalgesia and allodynia, developed in the STZ-induced diabetic rats. Cutaneous innervation exhibited STZ-induced reductions of protein gene product 9.5-, peripherin-, and neurofilament 200-immunoreactivity (IR) subepidermal nerve fibers (SENFs). Moreover, the decreases of substance P (SP)- and calcitonin gene-related peptide (CGRP)-IR SENFs were distinct gathered from the results of extracellular signal-regulated kinase 1 and 2 (ERK1/2)- and phosphorylated ERK1/2 (pERK1/2)-IR SENFs in STZ-induced diabetic rats. Double immunofluorescence studies demonstrated that STZ-induced pERK1/2-IR was largely increased in SENFs where only a small portion was colocalized with SP- or CGRP-IR. By an intraplantar (i. pl.) injection with a MEK inhibitor, U0126 (1,4-Diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene), hyperalgesia was attenuated in a dose-responsive manner. Botulinum toxin serotype A had dose-dependent analgesic effects on STZ-induced hyperalgesia and allodynia, which exhibited equivalent results as the efficacy of transient receptor potential vanilloid (TRPV) channel antagonists. Morphological evidence further confirmed that STZ-induced SP-, CGRP- and pERK1/2-IR were reduced in SENFs after pharmacological interventions. From the results obtained in this study, it is suggested that increases of pERK1/2 in SENFs may participate in the modulation of TRPV channel-mediated neurogenic inflammation that triggers hyperalgesia in STZ-induced diabetic rats. Therefore, ERK1/2 provides a potential therapeutic target and efficient pharmacological strategies to address hyperglycemia-induced neurotoxicity.
Bilirubin-induced neurotoxic and ototoxic effects in rat cochlear and vestibular organotypic cultures Neurotoxicology (IF 3.076) Pub Date : 2018-12-19 Haibo Ye, Yazhi Xing, Ling Zhang, Jianhui Zhang, Haiyan Jiang, Dalian Ding, Haibo Shi, Shankai Yin
Exposure to high levels of bilirubin in hyperbilirubinemia patients and animal models can result in sensorineural deafness. However, the mechanisms underlying bilirubin-induced damage to the inner ear, including the cochlear and vestibular organs, remain unknown. The present analyses of cochlear and vestibular organotypic cultures obtained from postnatal day 3 rats exposed to bilirubin at varying concentrations (0, 10, 50, 100, or 250 μM) for 24 h revealed that auditory nerve fibers (ANFs) and vestibular nerve endings were destroyed even at low doses (10 and 50 μM). Additionally, as the bilirubin dose increased, spiral ganglion neurons (SGNs) and vestibular ganglion neurons (VGNs) exhibited gradual shrinkage in conjunction with nuclei condensation or fragmentation in a dose-dependent manner. The loss of cochlear and vestibular hair cells (HCs) was only evident in explants treated with the highest concentration of bilirubin (250 µM), and bilirubin-induced major apoptosis most likely occurred via the extrinsic apoptotic pathway. Thus, the present results indicate that inner ear neurons and fibers were more sensitive to, and exhibited more severe damage following, bilirubin-induced neurotoxicity than sensory HCs, which illustrates the underlying causes of auditory neuropathy and vestibulopathy in hyperbilirubinemia patients.
Genetic Effects of Welding Fumes on the Progression of Neurodegenerative Diseases Neurotoxicology (IF 3.076) Pub Date : 2018-12-17 Humayan Kabir Rana, Mst. Rashida Akhtar, Mohammad Bashir Ahmed, Pietro Lio’, Julian M.W. Quinn, Fazlul Huq, Mohammad Ali Moni
Background Welding involves exposure to fumes, gases and radiant energy that can be hazardous to human health. Welding fumes (WFs) comprise a complex mixture of metallic oxides, silicates and fluorides that may result in different health effects. Inhalation of WFs in large quantities over a long periods may pose a risk of developing neurodegenerative diseases (NDGDs), but the nature of this risk is poorly understood. To address this we performed transcriptomic analysis to identify links between WF exposure and NDGDs. Methods We developed quantitative frameworks to identify the gene expression relationships of WF exposure and NDGDs. We analyzed gene expression microarray data from fume-exposed tissues and NDGDs including Parkinson's disease (PD), Alzheimer's disease (AD), Lou Gehrig's disease (LGD), Epilepsy disease (ED) and multiple sclerosis disease (MSD) datasets. We constructed disease-gene relationship networks and identified dysregulated pathways, ontological pathways and protein-protein interaction sub-network using multilayer network topology and neighborhood-based benchmarking. Results We observed that WF associated genes share 18, 16, 13, 19 and 19 differentially expressed genes with PD, AD, LGD, ED and MSD respectively. Gene expression dysregulation along with relationship networks, pathways and ontologic analysis indicate that WFs may be linked to the progression of these NDGDs. Conclusions Our developed network-based approach to analysis and investigate the genetic effects of welding fumes on PD, AD, LGD, ED and MSD neurodegenerative diseases could be helpful to understand the causal influences of WF exposure for the progression of the NDGDs.
Bioluminescence imaging of Arc expression in mouse brain under acute and chronic exposure to pesticides Neurotoxicology (IF 3.076) Pub Date : 2018-12-15 Hironori Izumi, Tetsuya Ishimoto, Hiroshi Yamamoto, Hisashi Mori
Exposure to pesticides can induce neurobehavioral effects in rodents, as well as in other mammals, including humans. However, the effects of the toxicity of pesticides on the central nervous system (CNS) remain largely unclear. The expression of the activity-regulated cytoskeleton-associated protein gene (Arc) is induced in a neuronal-activity-dependent manner and is implicated in synaptic and experience-dependent plasticity. We previously developed Arc-promoter-driven luciferase transgenic (Tg) mouse strains to monitor the neuronal-activity-dependent gene expression under physiological and pathological conditions in vivo. In this study, we examined the effect of acute administration of four different pesticides (deltamethrin, glufosinate, methylcarbaryl, and imidacloprid) on neuronal activity using Arc-Luc Tg mice. The change in the bioluminescence signal in mouse brain upon treatment with deltamethrin and glufosinate occurred more slowly than that of kainic acid, a potent neuroexcitatory amino acid agonist. These two pesticides also caused convulsive responses in adult Arc-Luc Tg mice. In the case of glufosinate, we detected the long-term upregulation of bioluminescence signal intensity of Arc-Luc over 24 h after the treatment. Furthermore, we observed greater changes of bioluminescence signal in adults than in juveniles, and a lower incidence of convulsions at the juvenile stage. In contrast to the acute treatment, we detected a decrease of bioluminescence signal after low-dose chronic treatment with glufosinate, without neuronal overexcitation. From these results, we suggest that Arc-Luc Tg mice are useful for assessing the acute and chronic effects of pesticides on the CNS.
Bisphenol F causes disruption of gonadotropin-releasing hormone neural development in zebrafish via an estrogenic mechanism Neurotoxicology (IF 3.076) Pub Date : 2018-12-03 Kailee Weiler, Siddharth Ramakrishnan
Gonadotropin releasing hormone (GnRH) neurons in the brain are the main controllers of reproduction and reproductive behavior in most vertebrates, and are susceptible to endocrine disruption by different bisphenols. While the endocrine disrupting properties of bisphenol A have been well documented, commonly used analogues such as bisphenol F (BPF) are not as well studied. In this study we examined the effects of early, low-dose, chronic BPF exposure on the development of the GnRH neural system in the zebrafish embryo. Using a transgenic zebrafish model system with GnRH3 neurons tagged with green fluorescent protein (GFP), developing GnRH neurons in both the terminal nerve (TN) and preoptic area (POA) were observed. These are neuronal populations with the former associated with allied reproductive behaviors and the latter associated with pituitary-gonadal axis control. Embryos were exposed in vitro to 0.25, 0.5 and 1 μM BPF from fertilization to 3 days post fertilization (dpf). At 0.25 μM BPF exposure, both POA- and TN- GnRH3 neurons showed significant reductions in neural area at 2 dpf that did not persist to 3 dpf. The higher BPF doses did not show neuron size differences at 2 dpf, but showed reduction in TN-GnRH3 neuron area at 3 dpf. These effects of BPF were closely mimicked by different doses of estradiol. An estrogen antagonist, ICI, mitigated BPF effects on the embryo. This is the first study to show that BPF affects the developing GnRH neural system via an estrogen-mediated pathway.
Alpha-naphthoflavone induces apoptosis through endoplasmic reticulum stress via c-Src-, ROS-, MAPKs-, and arylhydrocarbon receptor-dependent pathways in HT22 hippocampal neuronal cells Neurotoxicology (IF 3.076) Pub Date : 2018-11-30 Ah-Ran Yu, Yeon Ju Jeong, Chi Yeon Hwang, Kyung-Sik Yoon, Wonchae Choe, Joohun Ha, Sung Soo Kim, Youngmi Kim Pak, Eui-Ju Yeo, Insug Kang
α-Naphthoflavone (αNF) is a prototype flavone, also known as a modulator of aryl hydrocarbon receptor (AhR). In the present study, we investigated the molecular mechanisms of αNF-induced cytotoxic effects in HT22 mouse hippocampal neuronal cells. αNF induced apoptotic cell death via activation of caspase-12 and -3 and increased expression of endoplasmic reticulum (ER) stress-associated proteins, including C/EBP homologous protein (CHOP). Inhibition of ER stress by treatment with the ER stress inhibitor, salubrinal, or by CHOP siRNA transfection reduced αNF-induced cell death. αNF activated mitogen-activated protein kinases (MAPKs), such as p38, JNK, and ERK, and inhibition of MAPKs reduced αNF-induced CHOP expression and cell death. αNF also induced accumulation of reactive oxygen species (ROS) and an antioxidant, N-acetylcysteine, reduced αNF-induced MAPK phosphorylation, CHOP expression, and cell death. Furthermore, αNF activated c-Src kinase, and inhibition of c-Src by a kinase inhibitor, SU6656, or siRNA transfection reduced αNF-induced ROS accumulation, MAPK activation, CHOP expression, and cell death. Inhibition of AhR by an AhR antagonist, CH223191, and siRNA transfection of AhR and AhR nuclear translocator reduced αNF-induced AhR-responsive luciferase activity, CHOP expression, and cell death. Finally, we found that inhibition of c-Src and MAPKs reduced αNF-induced transcriptional activity of AhR. Taken together, these findings suggest that αNF induces apoptosis through ER stress via c-Src-, ROS-, MAPKs-, and AhR-dependent pathways in HT22 cells.
Resveratrol treatment reduces the vulnerability of SH-SY5Y cells and cortical neurons overexpressing SOD1-G93A to Thimerosal toxicity through SIRT1/DREAM/PDYN pathway Neurotoxicology (IF 3.076) Pub Date : 2018-11-29 Giusy Laudati, Luigi Mascolo, Natascia Guida, Rossana Sirabella, Vincenzo Pizzorusso, Sara Bruzzaniti, Angelo Serani, Gianfranco Di Renzo, Lorella MT Canzoniero, Luigi Formisano
In humans, mutation of glycine 93 to alanine of Cu++/Zn++ superoxide dismutase type-1 (SOD1-G93 A) has been associated to some familial cases of Amyotrophic Lateral Sclerosis (ALS). Several evidence proposed the involvement of environmental pollutants that like mercury could accelerate ALS symptoms. SH-SY5Y cells stably transfected with SOD1 and G93 A mutant of SOD1 constructs were exposed to non-toxic concentrations (0.01 µM) of ethylmercury thiosalicylate (thimerosal) for 24 hours. Interestingly, we found that thimerosal, in SOD1-G93 A cells, but not in SOD1 cells, reduced cell survival. Furthermore, thimerosal-induced cell death occurred in a concentration dependent-manner and was prevented by the Sirtuin 1 (SIRT1) activator Resveratrol (RSV). Moreover, thimerosal decreased the protein expression of transcription factor Downstream Regulatory Element Antagonist Modulator (DREAM), but not DREAM gene. Interestingly, DREAM reduction was blocked by co-treatment with RSV, suggesting the participation of SIRT1 in determining this effect. Immunoprecipitation experiments in SOD1-G93 A cells exposed to thimerosal demonstrated that RSV increased DREAM deacetylation and reduced its polyubiquitination. In addition, RSV counteracted thimerosal-enhanced prodynorphin (PDYN) mRNA, a DREAM target gene. Furthermore, cortical neurons transiently transfected with SOD1-G93 A construct and exposed to thimerosal (0.5 µM/24 hours) showed a reduction of DREAM and an up-regulation of the prodynorphin gene. Importantly, both the treatment with RSV or the transfection of siRNA against prodynorphin signiﬁcantly reduced thimerosal-induced neurotoxicity, while DREAM knocking-down potentiated thimerosal-reduced cell survival. These results demonstrate the particular vulnerability of SOD1-G93 A neuronal cells to thimerosal and that RSV via SIRT1 counteracts the neurodetrimental effect of this toxicant by preventing DREAM reduction and prodynorphin up-regulation.
Increased serum levels of macrophage migration inhibitory factor in autism spectrum disorders Neurotoxicology (IF 3.076) Pub Date : 2018-11-29 Jun Ning, Li Xu, Chang-Qing Shen, Yu-Yan Zhang, Qing Zhao
Objective Macrophage migration inhibitory factor (MIF) has been suggested as a pivotal regulator of innate immunity and inflammatory. The aim of this study was to measure serum circulating levels of MIF in relation to the degree of the severity of autism spectrum disorders (ASD). Methods One hundred and two Chinese children with ASD and same their age-sex matched typical development children were included. Concentrations of MIF were tested by Quantikine Human MIF Immunoassay. Serum levels of homocysteine (HCY), C-reactive protein (CRP) and serum Interleukin 6 (IL-6) were also tested. The influence of serum levels of MIF on ASD risk and ASD severity were performed by binary logistic regression analysis. Results The serum levels of MIF in the children with ASD (24.7 ± 08.9 ng/ml) were significantly higher than those of control subjects (18.3 ± 5.5 ng/ml) (t = 6.134, P < 0.001). Levels of MIF increased with increasing severity of ASD as defined by the CARS score (P < 0.001). In multivariate model, MIF was associated with an increased risk of ASD (OR 1.11, 95% CI: 1.05-1.17; P < 0.001). MIF improved the combined model (HCY/CRP/IL-6) to predict ASD (P < 0.001). At admission, 68 children (66.7%) had a severe autism. In these children, the mean serum level of MIF was higher than in those children with mild to moderate autism (28.1 ± 8.5 ng/ml VS. 17.9 ± 4.7 ng/ml; t = 6.482, P < 0.001). In multivariate model, MIF was still associated with an increased risk of severe ASD (OR: 1.15, 95% CI: 1.04-1.19; P < 0.001). MIF improved the combined model (HCY/CRP/IL-6) to predict severe ASD (P < 0.001). Conclusions These results identify high serum MIF levels are associated with severity of ASD. Further study is warranted on the precise involvement of MIF in ASD, and the mechanism by which MIF contributes to ASD pathogenesis.
Inhibition of microRNA-124-3p as a novel therapeutic strategy for the treatment of Gulf War Illness: evaluation in a rat model Neurotoxicology (IF 3.076) Pub Date : 2018-11-29 Nicole R. Laferriere, Wendy E. Kurata, Cary T. Grayson, Kelsey M. Stecklow, Lisa M. Pierce
Gulf War Illness (GWI) is a chronic, multisymptom illness that continues to affect up to 30% of veterans deployed to the Persian Gulf during the 1990-1991 Gulf War. After nearly 30 years, useful treatments for GWI are lacking and underlying cellular and molecular mechanisms involved in its pathobiology remain poorly understood, although exposures to pyridostigmine bromide (PB) and pesticides are consistently identified to be among the strongest risk factors. Alleviation of the broad range of symptoms manifested in GWI, which involve the central nervous system, the neuroendocrine system, and the immune system likely requires therapies that are able to activate and inactivate a large set of orchestrated genes. Previous work in our laboratory using an established rat model of GWI identified persistent elevation of microRNA-124-3p (miR-124) levels in the hippocampus whose numerous gene targets are involved in cognition-associated pathways and neuroendocrine function. This study aimed to investigate the broad effects of miR-124 inhibition in the brain 9 months after completion of a 28-day exposure regimen of PB, DEET (N,N-diethyl-3-methylbenzamide), permethrin, and mild stress by profiling the hippocampal expression of genes known to play a critical role in synaptic plasticity, glucocorticoid signaling, and neurogenesis. We determined that intracerebroventricular infusion of a miR-124 antisense oligonucleotide (miR-124 inhibitor; 0.05-0.5 nmol/day/28 days), but not a negative control oligonucleotide, into the lateral ventricle of the brain caused increased protein expression of multiple validated miR-124 targets and increased expression of downstream target genes important for cognition and neuroendocrine signaling in the hippocampus. Off-target cardiotoxic effects were revealed in GWI rats receiving 0.1 nmol/day as indicated by the detection in plasma of 5 highly elevated protein cardiac injury markers and 6 upregulated cardiac-enriched miRNAs in plasma exosomes determined by next-generation sequencing. Results from this study suggest that in vivo inhibition of miR-124 function in the hippocampus is a promising, novel therapeutic approach to improve cognition and neuroendocrine dysfunction in GWI. Additional preclinical studies in animal models to assess feasibility and safety by developing a practical, noninvasive drug delivery system to the brain and exploring potential adverse toxicologic effects of miR-124 inhibition are warranted.
Neuroprotective action of Eicosapentaenoic (EPA) and Docosahexaenoic (DHA) acids on Paraquat intoxication in Drosophila melanogaster Neurotoxicology (IF 3.076) Pub Date : 2018-11-28 Anderson de Oliveira Souza, Carlos Antônio Couto-Lima, Carlos Henrique Rocha Catalão, Nilton Nascimento Santos-Júnior, Júlia Fernanda dos Santos, Maria Jose Alves da Rocha, Luciane Carla Alberici
Several studies have shown the protective effects of dietary enrichment of omega-3 (ω-3) long-chain fatty acids in several animal models of neurodegenerative diseases. Here we investigate if eicosapentaenoic (EPA) and Docosahexaenoic (DHA) acids (ω-3) protect against neurodegeneration mediated by the exposure to a widely used herbicide Paraquat (PQ) (1,1ʹ-dimethyl-4-4ʹ-bipyridinium dichloride), focusing on mitochondrial metabolism using Drosophila melanogaster as a model. Dietary ingestion of PQ for 3 days resulted in the loss of citrate synthase content, respiratory capacity impairment and exacerbated H2O2 production per mitochondrial unit related to complex I dysfunction, and high lactate accumulation in fly heads. PQ intoxication lead to 1) the loss of ELAV (embryonic lethal abnormal vision) and α-spectrin, essential proteins of neuronal viability and synaptic stability; 2) increased gamma-secretase activity, an enzyme related to APP release; and 3) increased the amyloid fibrils contents. All these toxic effects induced by PQ were prevented by concomitant dietary ingestion of EPA/DHA, suggesting that a neuroprotective effect of ω-3 also involves mitochondrial protection. In conclusion, concomitant EPA and DHA ingestion protects against PQ-induced neuronal and mitochondrial dysfunctions frequently found in neurodegenerative processes reinforcing its protective role against environmental neurodegenerative diseases.
Anesthesia affects Excitatory/Inhibitory Synapses during the Critical Synaptogenic Period in the Hippocampus of young Mice: Importance of Sex as a Biological Variable Neurotoxicology (IF 3.076) Pub Date : 2018-11-28 Xianshu Ju, Yunseon Jang, Jun Young Heo, Jiho Park, Sangwon Yun, Sangil Park, Yang Hoon Huh, Hyo-Jeong Kim, Yulim Lee, Yoon Hee Kim, Chae Seong Lim, Sun Yeul Lee, Youngkwon Ko, Gi Ryang Kweon, Woosuk Chung
Background Sex plays an important yet often underexplored role in neurodevelopment and neurotoxicity. While several studies report the importance of sex regarding anesthesia-induced neurotoxicity in neonatal mice, only few have focused on the late postnatal period. Here, to further understand the importance of sex regarding the neurobiological changes after early anesthesia during the critical synaptogenic period, we exposed postnatal day 16, 17 (PND 16, 17) mice to sevoflurane in pediatric patients and performed detailed evaluations in the hippocampus. Methods PND 16, 17 mice received a single exposure of oxygen with or without sevoflurane (2.5%) for 2 hours. Changes of the hippocampus were analyzed in male and female mice 6 hours after exposure: excitatory/inhibitory synaptic transmission, protein/mRNA expression levels of excitatory/inhibitory synaptic molecules (GluR1, GluR2, PSD95, gephyrin, GAD65), and number of excitatory synapses. Results Sevoflurane exposure increased the frequency of miniature excitatory postsynaptic currents specifically in male mice (control: 0.07 ± 0.04 [Hz]; sevoflurane: 14.72 ± 0.08 [Hz]), while miniature inhibitory postsynaptic currents were affected specifically in female mice. The protein/mRNA expression levels of excitatory synaptic molecules were also increased specifically in male mice. Unexpectedly, protein/mRNA expression levels of inhibitory synaptic molecules were increased in both sexes, and there was no male-specific increase of excitatory synapse number. Conclusions Exposure of mice to sevoflurane during the critical, late postnatal period induces sex-dependent changes in the hippocampus. Although often disregarded, our results confirm the importance of sex as a biological variable when studying the changes triggered by early anesthesia.
Ameliorative effect of alendronate against intracerebroventricular streptozotocin induced alteration in neurobehavioral, neuroinflammation and biochemical parameters with emphasis on Aβ and BACE-1 Neurotoxicology (IF 3.076) Pub Date : 2018-11-24 Saima Zameer, Madhu Kaundal, Divya Vohora, Javed Ali, Abul Kalam Najmi, Mohd Akhtar
Alzheimer’s disease (AD) is the most prevalent age related neurodegenerative disorder manifested by progressive cognitive decline and neuronal loss in the brain, yet precise etiopathology of majority of sporadic or late-onset AD cases is unknown. AD is associated with various pathological events such as Aβ deposition due to BACE-1 induced cleavage of APP, neuroinflammation, increased cholesterol synthesis, cholinergic deficit and oxidative stress. It was found that bone drug, alendronate (ALN) that cross blood brain barrier inhibits brain cholesterol synthesis and AChE enzyme activity. As cholesterol modifying agents have been supposed to alter AD like pathologies, the current study was designed to investigate the possible neuroprotective and therapeutic potential of ALN against ICV STZ induced experimental sporadic AD (SAD) in mice in a non-cholesterol dependent manner, using donepezil (5 mg/kg) as a reference standard. The preliminary study was done by molecular modelling to identify the binding affinity of ALN with BACE-1 in silico. The prevention of cognitive impairment in mice induced by ICV STZ (3 mg/kg) infused on first and third day, by ALN (1.76 mg/kg p.o.) administered for 15 consecutive days was assessed through Spontaneous Alternation Behavior (SAB) and Morris water maze (MWM) test. Additionally, the protective effect of ALN was also observed by the reversal of altered levels of Aβ1-42, BACE-,1 neuroinflammatory cytokines, AChE activity and oxidative stress markers (except TBARS) in ICV-STZ infused mice. However, the findings of the present study imply the therapeutic potential of ALN against SAD-like complications.
Soluble epoxide hydrolase inhibitor, APAU, protects dopaminergic neurons against rotenone induced neurotoxicity: Implications for Parkinson’s disease Neurotoxicology (IF 3.076) Pub Date : 2018-11-22 Navya Lakkappa, Praveen T. Krishnamurthy, M.D Pandareesh, Bruce D Hammock, Sung Hee Hwang
Epoxyeicosatrienoic acids (EETs), metabolites of arachidonic acid, play a crucial role in cytoprotection by attenuating oxidative stress, inﬂammation and apoptosis. EETs are rapidly metabolised in vivo by the soluble epoxide hydrolase (sEH). Increasing the half life of EETs by inhibiting the sEH enzyme is a novel strategy for neuroprotection. In the present study, sEH inhibitors APAU was screened in silico and further evaluated for their antiparkinson activity against rotenone (ROT) induced neurodegeneration in N27 dopaminergic cell line and Drosophila melanogaster model of Parkinson disease (PD). In the in vitro study cell viability (MTT and LDH release assay), oxidative stress parameters (total intracellular ROS, hydroperoxides, protein oxidation, lipid peroxidation, superoxide dismutase, catalase, glutathione peroxidise, glutathione reductase, glutathione, total antioxidant status, mitochondrial complex-1activity and mitochondrial membrane potential), inflammatory markers (IL-6, COX-1 and COX-2), and apoptotic markers (JNK, phospho-JNK, c-jun, phospho-c-jun, pro and active caspase-3) were assessed to study the neuroprotective effects. In vivo activity of APAU was assessed in Drosophila melanogaster by measuring survival rate, negative geotaxis, oxidative stress parameters (total intracellular ROS, hydroperoxides, glutathione levels) were measured. Dopamine and its metabolites were estimated by LC-MS/MS analysis. In the in silico study the molecule, APAU showed good binding interaction at the active site of sEH (PDB: 1VJ5). In the in vitro study, APAU significantly attenuated ROT induced changes in oxidative, pro-inflammatory and apoptotic parameters. In the in vivo study, APAU significantly attenuates ROT induced changes in survival rate, negative geotaxis, oxidative stress, dopamine and its metabolites levels (p < 0.05). Our study, therefore, concludes that the molecule APAU, has significant neuroprotection benefits against rotenone induced Parkinsonism.
Carbofuran hampers oligodendrocytes development leading to impaired myelination in the hippocampus of rat brain Neurotoxicology (IF 3.076) Pub Date : 2018-11-22 Brashket Seth, Anuradha Yadav, Ankit Tandon, Jai Shankar, Rajnish Kumar Chaturvedi
During the mammalian brain development, oligodendrocyte progenitor cells (OPCs) are generated from neuroepithelium and migrate throughout the brain. Myelination is a tightly regulated process which involves time framed sequential events of OPCs proliferation, migration, differentiation and interaction with axons for functional insulated sheath formation. Myelin is essential for efficient and rapid conduction of electric impulses and its loss in the hippocampus of the brain may result in impaired memory and long-term neurological deficits. Carbofuran, a carbamate pesticide is known to cause inhibition of hippocampal neurogenesis and memory dysfunctions in rats. Nonetheless, the effects of carbofuran on OPCs proliferation, fate determination, maturation/differentiation and myelination potential in the hippocampus of the rat brain are still completely elusive. Herein, we investigated the effects of sub-chronic exposure of carbofuran during two different time periods including prenatal and adult brain development in rats. We observed carbofuran hampers OPCs proliferation (BrdU incorporation) and oligodendroglial differentiation in vitro. Similar effects of carbofuran were also observed in the hippocampus region of the brain at both the time points. Carbofuran exposure resulted in reduced expression of key genes and proteins involved in the regulation of oligodendrocyte development and functional myelination. It also affects the survival of oligodendrocytes by inducing apoptotic cell death. The ultrastructural analysis of myelin architecture clearly depicted carbofuran-mediated negative effects on myelin compaction and g-ratio alteration. Conclusively, our study demonstrated that carbofuran alters myelination potential in the hippocampus, which leads to cognitive deficits in rats.
Saikosaponin d causes apoptotic death of cultured neocortical neurons by increasing membrane permeability and elevating intracellular Ca2+ concentration Neurotoxicology (IF 3.076) Pub Date : 2018-11-17 Jing Zheng, Juan Chen, Xiaohan Zou, Fang Zhao, Mengqi Guo, Hongbo Wang, Tian Zhang, Chunlei Zhang, Wei Feng, Isaac N. Pessah, Zhengyu Cao
Saikosaponins (SSs) are a class of naturally occurring oleanane-type triterpenoid saponins found in Radix bupleuri that has been widely used in traditional Chinese medicine. As the main active principals of Radix bupleuri, SSs have been shown to suppress mouse motor activity, impair learning and memory, and decrease hippocampal neurogenesis. In the present study, we investigated the effect of five SSs (SSa, SSb1, SSb2, SSc, and SSd) on neuronal viability and the underlying mechanisms in cultured murine neocortical neurons. We demonstrate that SSa, SSb1 and SSd produce concentration-dependent apoptotic neuronal death and induce robust increase in intracellular Ca2+ concentration ([Ca2+]i) at low micromolar concentrations with a rank order of SSd > SSa > SSb1, whereas SSb2 and SSc have no detectable effect on both neuronal survival and [Ca2+]i. Mechanistically, SSd-induced elevation in [Ca2+]i is the primary result of enhanced extracellular Ca2+ influx, which likely triggers Ca2+-induced Ca2+ release through ryanodine receptor activation, but not SERCA inhibition. SSd-induced Ca2+ entry occurs through a non-selective mechanism since blockers of major neuronal Ca2+ entry pathways, including L-type Ca2+ channel, NMDA receptor, AMPA receptor, Na+-Ca2+ exchanger, and TRPV1, all failed to attenuate the Ca2+ response to SSd. Further studies demonstrate that SSd increases calcein efflux and induces an inward current in neocortical neurons. Together, these data demonstrate that SSd elevates [Ca2+]i due to its ability to increase membrane permeability, likely by forming pores in the surface membrane, which leads to massive Ca2+ influx and apoptotic neuronal death in neocortical neurons.
Early life exposure to extended general anesthesia with isoflurane and nitrous oxide reduces responsivity on a cognitive test battery in the nonhuman primate Neurotoxicology (IF 3.076) Pub Date : 2018-11-14 John C. Talpos, John J. Chelonis, Mi Li, Joseph P. Hanig, Merle G. Paule
Despite the widespread use of general anesthesia, a growing body of research suggests that anesthesia exposure early in life may be associated with acute neurotoxicity and lasting behavioral changes. To better evaluate the risk posed by early life anesthesia on cognitive development, infant rhesus monkeys were exposed to an anesthesia regimen previously shown to be neurotoxic and their cognitive development was subsequently measured using a translational operant test battery. On postnatal day 5 or 6, animals were exposed to 8 hours of isoflurane (n = 6, 1% isoflurane in a vehicle gas of 70% nitrous oxide and 30% oxygen) or a control condition (n = 8). Starting at 7 months of age, the monkeys were continuously trained and assessed on the NCTR Operant Test Battery (OTB). The OTB consists of cognitive tests which also exist in near identical forms for use in rats and humans, and includes tests of learning, memory, color discrimination, and motivation. Monkeys previously exposed to anesthesia showed a clear decrease in responding in a measure of motivation, as well as a lower response rate in a learning task. These data further support the hypothesis that prolonged anesthesia early in life may increase the risk of developing cognitive impairments later in life.
OTILONIUM AND PINAVERIUM TRIGGER MITOCHONDRIAL-MEDIATED APOPTOSIS IN RAT EMBRYO CORTICAL NEURONS IN VITRO Neurotoxicology (IF 3.076) Pub Date : 2018-11-15 Fernanda García-Alvarado, Giulia Govoni, Ricardo de Pascual, Cristina Ruiz-Ruiz, Alicia Muñoz-Montero, Luis Gandía, Antonio M.G de Diego, Antonio G. García
In the frame of a repositioning programme with cholinergic medicines in clinical use searching for neuroprotective properties, we surprisingly found that spasmolytic antimuscarinics otilonium and pinaverium exhibited neurotoxic effects in neuronal cultures. We decided to characterize such unexpected action in primary cultures of rat embryo cortical neurons. Neurotoxicity was time- and concentration-dependent, exhibiting approximate EC50´s of 5 µM for both drugs. Seven antimuscarinic drugs endowed with a quaternary ammonium, and another 10 drugs with different cholinergic activities, carrying in their molecule a ternary ammonium did not exhibit neurotoxicity. Both drugs caused a concentration-dependent blockade of whole-cell inward currents through voltage-activated calcium channels (VACCs). Consistent with this, they also blocked the of K+-elicited [Ca2+] c transients. Neither antioxidant catalase, glutathione, n-acetylcysteine, nor melatonin protected against neurotoxicity of otilonium or pinaverium. However cyclosporine A, a blocker of the mitochondrial permeability transition pore, prevented the neurotoxic effects of otilonium and pinaverium monitored as the fraction of cells undergoing apoptosis. Furthermore, the caspase-9 and caspase-3 inhibitor Ac-LEHD-CHO mitigated the apoptotic neuronal death of both drugs by around 50%. Data are compatible with the hypothesis that otilonium and pinaverium elicit neuronal death by activating the intrinsic mitochondrial-mediated signaling pathway of apoptosis. This may have its origin in the mitigation of Ca2+ entry and the uncoupling of the Ca2+-dependent generation of mitochondrial bioenergetics, thus causing the opening of the mitochondrial mPTP to elicit apoptotic neuronal death.
Cannabinoid-like Effects of Five Novel Carboxamide Synthetic Cannabinoids Neurotoxicology (IF 3.076) Pub Date : 2018-11-12 Michael B. Gatch, Michael J. Forster
A new generation of novel cannabinoid compounds have been developed as marijuana substitutes to avoid drug control laws and cannabinoid blood tests. 5F-MDMB-PINACA (also known as 5F-ADB, 5F-ADB-PINACA), MDMB-CHIMICA, MDMB-FUBINACA, ADB-FUBINACA, and AMB-FUBINACA (also known as FUB-AMB, MMB-FUBINACA) were tested for in vivo cannabinoid-like effects to assess their abuse liability. Locomotor activity in mice was tested to screen for locomotor depressant effects and to identify behaviorally-active dose ranges and times of peak effect. Discriminative stimulus effects were tested in rats trained to discriminate Δ9-tetrahydrocannabinol (3 mg/kg, 30-min pretreatment). 5F-MDMB-PINACA (ED50 = 1.1 mg/kg) and MDMB-CHIMICA (ED50 = 0.024 mg/kg) produced short-acting (30 min) depression of locomotor activity. ADB-FUBINACA (ED50 = 0.19 mg/kg), and AMB- FUBINACA (ED50 = 0.19 mg/kg) depressed locomotor activity for 60-90 min; whereas MDMB-FUBINACA (ED50 = 0.04 mg/kg) depressed locomotor activity for 150 min. AMB-FUBINACA produced tremors at the highest dose tested. 5F-MDMB-PINACA (ED50 = 0.07), MDMB-CHIMICA (ED50 = 0.01 mg/kg), MDMB-FUBINACA (ED50 = 0.051 mg/kg), ADB-FUBINACA (ED50 = 0.075 mg/kg) and AMB-FUBINACA (ED50 = 0.029) fully substituted for the discriminative stimulus effects of Δ9-THC following 15-min pretreatment. All 5 compounds decreased locomotor activity and produced discriminative stimulus effects similar to those of Δ9-THC, which suggests they may have abuse liability similar to that of Δ9-THC. AMB-FUBINACA may have an increased risk of toxicities in recreational users.
The NLRP3 inflammasome is involved in the neuroprotective mechanism of neural stem cells against microglia-mediated toxicity in SH-SY5Y cells via the attenuation of tau hyperphosphorylation and amyloidogenesis Neurotoxicology (IF 3.076) Pub Date : 2018-11-05 Elaine Wan Ling Chan, Sangeetha Krishnansamy, Cindy Wong, Sook Yee Gan
Heterozygous huntingtin promotes cadmium neurotoxicity and neurodegeneration in striatal cells via altered metal transport and protein kinase C delta dependent oxidative stress and apoptosis signaling mechanisms Neurotoxicology (IF 3.076) Pub Date : 2018-11-03 Gunnar F. Kwakye, Jessica A. Jiménez, Morgan G. Thomas, Brett A. Kingsley, Matthew McIIvin, Mak A. Saito, Edmund M. Korley
Involvement of oxidative stress in di-2-ethylhexyl phthalate (DEHP)-induced apoptosis of mouse NE-4C neural stem cells Neurotoxicology (IF 3.076) Pub Date : 2018-11-03 Miaojing Wu, Linlin Xu, Chaxiang Teng, Xiao Xiao, Weihua Hu, Jiaxiang Chen, Wei Tu
Di-2-ethylhexyl phthalate (DEHP) has been widely used as a plasticizer in industry and can cause neurotoxicity; however, the underlying mechanism remains unclear. In the study, we found that DEHP significantly inhibited viability of mouse NE-4C neural stem cells and caused lactate dehydrogenase (LDH) release from the cells. DEHP dramatically increased the levels of apoptosis-related proteins such as cleaved Caspase-8, cleaved Caspase-3 and Bax, as well as decreased Bcl-2 protein level. DEHP could also significantly increase the total numbers of AnnexinV-positive/PI-negative and AnnexinV-positive/PI-positive staining cells. Hoechst 33342 staining showed that marked DNA condensation and apoptotic bodies could be found in the ZnO NPs-treated cells. These results indicated that DEHP could induce apoptosis of NE-4C cells. Meanwhile, DEHP could significantly increase malondialdehyde (MDA) level, and decrease the content of glutathione (GSH) and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX), respectively, implying that DEHP could induce oxidative stress of NE-4C cells. Furthermore, N-Acetyl-L-cysteine (NAC), an inhibitor of oxidative stress, could rescue the inhibition of cell viability and induction of apoptosis by DEHP. Taken together, our results showed that oxidative stress was involved in DEHP-induced apoptosis of mouse NE-4C cells.
CARVACROL AMELIORATES BEHAVIORAL DISTURBANCES AND DNA DAMAGE IN THE BRAIN OF RATS EXPOSED TO PROPICONAZOLE Neurotoxicology (IF 3.076) Pub Date : 2018-10-28 Mohamed A. Elhady, Abdel Azeim A. Khalaf, Mervat M. Kamel, Peter A. Noshy
Propiconazole (PCZ) is an ergosterol biosynthesis inhibiting fungicide. Carvacrol (CAR) is a monoterpenoid phenol that has various beneficial health effects. The current research was designed to study the impact of PCZ on the behavior of rats and its ability to induce DNA damage in neurons as well as to clarify the ameliorative effect of CAR against these toxic impacts. Sixty Sprague-Dawley rats were randomly and equally divided into 4 experimental groups and treated daily by oral gavage for 2 months as follows: Group 1 (control); group 2 treated with PCZ (75 mg/kg); group 3 treated with CAR (50 mg/kg) and group 4 treated with both PCZ and CAR. Behavioral tests demonstrated that exposure to PCZ had a deleterious effect on psychological, motor and cognitive neural functions. Additionally, antioxidant enzyme activities, SOD and GSH-Px, were declined in brain tissue following exposure to PCZ. Moreover, comet assay revealed a high percent of DNA damage in the brain of rats exposed to PCZ. On the other hand, CAR administration ameliorated the harmful effects induced by PCZ through a protective mechanism that involved the improvement of neural functions and attenuation of oxidative stress and DNA damage.
Adolescent methylmercury exposure: Behavioral mechanisms and effects of sodium butyrate in mice Neurotoxicology (IF 3.076) Pub Date : 2018-10-29 Steven R. Boomhower, M. Christopher Newland
Methylmercury (MeHg), an environmental neurotoxicant primarily found in fish, produces neurobehavioral impairment when exposure occurs during gestation. Whether other developmental periods, such as adolescence, display enhanced vulnerability to the behavioral effects of MeHg exposure is only beginning to be explored. Further, little is known about the effects of repeated administration of lysine deacetylase inhibitors, such as sodium butyrate (NaB), on operant behavior. In Experiment 1, male C57BL6/n mice were exposed to 0, 0.3, and 3.0 ppm MeHg (n = 12 each) via drinking water from postnatal days 21 to 60 (murine adolescence). As adults, mice were trained to lever press under an ascending series of fixed-ratio schedules of milk reinforcement selected to enable the analysis of three important parameters of operant behavior using the framework provided by Mathematical Principles of Reinforcement. Adolescent MeHg exposure dose-dependently increased saturation rate, a measure of the retroactive reach of a reinforcer, and decreased minimum response time relative to controls. In Experiment 2, the behavioral effects of repeated NaB administration both alone and following adolescent MeHg exposure were examined. Male C57BL6/n mice were given either 0 or 3.0 ppm MeHg during adolescence and, before behavioral testing, two weeks of once daily i.p. injections of saline or 0.6 g/kg NaB (n = 12 in each cell). Adolescent MeHg exposure again increased saturation rate but did not significantly alter minimum response time. NaB also increased saturation rate in both MeHg exposure groups. These data suggest that the behavioral mechanisms of adolescent MeHg exposure and NaB may be related to the impact of reinforcement on prior responses. Specifically, MeHg and NaB concentrated the effects of reinforcers onto the most recent responses.
ANTIAPOPTOTIC EFFECT OF TAURINE AGAINST NMDA-INDUCED RETINAL EXCITOTOXICITY IN RATS Neurotoxicology (IF 3.076) Pub Date : 2018-10-30 Lidawani Lambuk, Igor Iezhitsa, Renu Agarwal, Nor Salmah Bakar, Puneet Agarwal, Nafeeza Mohd Ismail
Objective N-methyl-D-aspartate (NMDA) excitotoxicity has been proposed to mediate apoptosis of retinal ganglion cells (RGCs) in glaucoma. Taurine (TAU) has been shown to have neuroprotective properties, thus we examined anti-apoptotic effect of TAU against retinal damage after NMDA exposure. Methodology. Sprague-Dawley rats were divided into 5 groups of 33 each. Group 1 was administered intravitreally with vehicle and group 2 was similarly injected with NMDA (160 nmol). Groups 3, 4 and 5 were injected with TAU (320 nmol) 24 hours before (pre-treatment), in combination (co-treatment) and 24 hours after (post-treatment) NMDA exposure. Seven days after injection, rats were sacrificed; eyes were enucleated, fixed and processed for morphometric analysis, TUNEL and caspase-3 staining. Optic nerve morphology assessment was done using toluidine blue staining. The estimation of BDNF, pro/anti-apoptotic factors (Bax/Bcl-2) and caspase-3 activity in retina was done using ELISA technique. Results. Severe degenerative changes were observed in retinae after intravitreal NMDA exposure. The retinal morphology in the TAU pre-treated group appeared more similar to the control retinae and demonstrated a higher number of nuclei than the NMDA group both per 100 µm length (by 1.5-fold, p < 0.001) and per 100 µm2 area (by 1.41-fold, p < 0.05) of the GCL. After NMDA exposure, visible axonal swelling was observed in optic nerve sections. In comparison with the changes observed in the NMDA treated group, the TAU treated group showed fewer prominent changes; axonal swelling was less frequent and less marked. Additionally, no marked glial cell changes were observed in the TAU-pretreated group. All TAU treated groups, particularly the pre-treated group, showed a significant decrease in the NMDA-induced optic nerve damage, with a 50% reduction (p < 0.001) in the mean grading compared to NMDA group. For the same, there was 25% decrease in co- and post-treatment groups, as compared with the NMDA group. Pre-treatment with TAU abolished apoptotic response to NMDA as indicated by decrease in the number of TUNEL- and caspase-3-positive cells. TAU pre-treatment also increased the Bcl-2 level (by 2.80-fold, p < 0.001) and decreased the level of Bax (by 34%, p < 0.01), and activity of caspase-3 (by 36%, p < 0.001) compared to NMDA group. In conclusion, our study revealed that pre-treatment with TAU prevents NMDA-induced retinal cell apoptosis more effectively than co- and post-treatment with TAU.
Silencing brain catalase expression reduces ethanol intake in developmentally-lead-exposed rats Neurotoxicology (IF 3.076) Pub Date : 2018-10-30 M.S. Mattalloni, Paula A. Albrecht, C. Salinas-Luypaert, Romina Deza-Ponzio, M.E. Quintanilla, M. Herrera-Marschitz, L.M. Cancela, M. Rivera-Meza, M.B. Virgolini
Exposure to Pesticides and the Prevalence of Diabetes in a Rural Population in Korea Neurotoxicology (IF 3.076) Pub Date : 2018-10-24 Sungjin Park, Sung-Kyung Kim, Jae-Yeop Kim, Kyungsuk Lee, Jung Ran Choi, Sei-Jin Chang, Choon Hee Chung, Kyu-Sang Park, Sung-Soo Oh, Sang-Baek Koh
Background Among the adverse health effects of exposure to pesticides, an association with diabetes has been reported. However, there is a lack of epidemiologic studies on the health effects of exposure to pesticides, particularly investigating the association between occupational pesticide exposure and diabetes prevalence. Purpose The present study examined the association between pesticide exposure and prevalence of diabetes in a rural population in Korea. Methods This cross-sectional study used data from the Korea Farmers Cohort study, and included 2559 participants in the baseline survey between November 2005 and January 2008. We performed a clinical examination including blood sampling and assessed data on diabetes diagnosis, demographics, and pesticide exposure. Logistic regression was performed to evaluate the association between pesticide exposure and diabetes prevalence, adjusting for age, sex, monthly income, and marital status. In addition, a stratified analysis by body mass index (BMI) was conducted, with two categories: normal weight (<25 kg/m2) and overweight or obese (≥25 kg/m2). Results At baseline, the prevalence of diabetes was 9.30%. Pesticide exposure was associated with the risk of diabetes after adjustment for covariates. In the analysis stratified by BMI, all the variables related to pesticide exposure were associated with prevalence of diabetes in the overweight or obese group, whereas no significant association was found in the normal weight group. Conclusion Exposure to pesticides was associated with diabetes, and this association was stronger in overweight or obese individuals than in normal weight individuals. Further longitudinal studies that consider information on BMI are necessary.
6-Hydroxydopamine induces different mitochondrial bioenergetics response in brain regions of rat Neurotoxicology (IF 3.076) Pub Date : 2018-10-22 Débora F. Gonçalves, Aline A. Courtes, Diane D. Hartmann, Pamela C. da Rosa, Débora M. Oliveira, Félix A.A. Soares, Cristiane L. Dalla Corte
Mitochondrial dysfunction has been demonstrated to have a central role in Parkinson Disease (PD) pathophysiology. Some studies have indicated that PD causes an impairment in mitochondrial bioenergetics; however, the effects of PD on brain-region specific bioenergetics was never investigated before. This study aimed to evaluate mitochondrial bioenergetics in different rat brain structures in an in vitro model of PD using 6-OHDA. Rat brain slices of hippocampus, striatum, and cortex were exposed to 6-OHDA (100 µM) for 1 hour and mitochondrial bioenergetic parameters, peroxide production, lactate dehydrogenase (LDH) and citrate synthase (CS) activities were analyzed. Hippocampus slices exposed to 6-OHDA presented increased peroxide production but, no mitochondrial adaptive response against 6-OHDA damage. Cortex slices exposed to 6-OHDA presented increased oxygen flux related to oxidative phosphorylation and energetic pathways exchange demonstrated by the increase in LDH activity, suggesting a mitochondrial compensatory response. Striatum slices exposed to 6-OHDA presented a decrease of oxidative phosphorylation and decrease of oxygen flux related to ATP-synthase indicating an impairment in the respiratory chain. The co-incubation of 6-OHDA with n-acetylcysteine (NAC) abolished the effects of 6-OHDA on mitochondrial function in all brain regions tested, indicating that the increased reactive oxygen species (ROS) production is responsible for the alterations observed in mitochondrial bioenergetics. The present results indicate a brain-region specific response against 6-OHDA, providing new insights into brain mitochondrial bioenergetic function in PD. These findings may contribute to the development of future therapies with a target on energy metabolism.
Corticosterone and pyridostigmine/DEET exposure attenuate peripheral cytokine expression: supporting a dominant role for neuroinflammation in a mouse model of Gulf War Illness Neurotoxicology (IF 3.076) Pub Date : 2018-10-16 Lindsay T. Michalovicz, Alicia R. Locker, Kimberly A. Kelly, Julie V. Miller, Zachary Barnes, Mary Ann Fletcher, Diane B. Miller, Nancy G. Klimas, Mariana Morris, Stephen M. Lasley, James P. O’Callaghan
Gulf War Illness (GWI) is a chronic multi-symptom disorder experienced by as many as a third of the veterans of the 1991 Gulf War; the constellation of “sickness behavior” symptoms observed in ill veterans is suggestive of a neuroimmune involvement. Various chemical exposures and conditions in theater have been implicated in the etiology of the illness. Previously, we found that GW-related organophosphates (OPs), such as the sarin surrogate, DFP, and chlorpyrifos, cause neuroinflammation. The combination of these exposures with exogenous corticosterone (CORT), mimicking high physiological stress, exacerbates the observed neuroinflammation. The potential relationship between the effects of OPs and CORT on the brain versus inflammation in the periphery has not been explored. Here, using our established GWI mouse model, we investigated the effects of CORT and DFP exposure, with or without a chronic application of pyridostigmine bromide (PB) and N,N-diethyl-meta-toluamide (DEET), on cytokines in the liver and serum. While CORT primed DFP-induced neuroinflammation, this effect was largely absent in the periphery. Moreover, the changes found in the peripheral tissues do not correlate with the previously reported neuroinflammation. These results not only support GWI as a neuroimmune disorder, but also highlight the separation between central and peripheral effects of these exposures.
Eurobehavioral and oxidative stress alterations following methylmercury and retinyl palmitate co-administration in pregnant and lactating rats and their offspring Neurotoxicology (IF 3.076) Pub Date : 2018-10-11 Pedro Espitia-Pérez, Suelen Marin Albino, Lyda Espitia-Pérez, Hugo Brango, Helen da Rosa, Alexandre Kleber Silveira, Diogo Pompéu Moraes, Camila Cerveira, Moara Mingori, Camila Tiefensee Ribeiro, Daniel Pens Gelain, Carlos Eduardo Schnorr, José Cláudio Fonseca Moreira
Multiple effects of the herbicide glufosinate-ammonium and its main metabolite on neural stem cells from the subventricular zone of newborn mice Neurotoxicology (IF 3.076) Pub Date : 2018-10-10 Justyne Feat-Vetel, Vanessa Larrigaldie, Géraldine Meyer-Dilhet, Ameziane Herzine, Camille Mougin, Anthony Laugeray, Thierry Gefflaut, Olivier Richard, Valérie Quesniaux, Céline MontécotDubourg, Stéphane Mortaud
Prenatal exposure to organochlorine pesticides and early childhood communication development in British girls Neurotoxicology (IF 3.076) Pub Date : 2018-10-05 Zuha Jeddy, Katarzyna Kordas, Kristen Allen, Ethel V. Taylor, Kate Northstone, W. Dana Flanders, Gonza Namulanda, Andreas Sjodin, Terryl J. Hartman
Background The developing brain is susceptible to exposure to neurodevelopmental toxicants such as pesticides. Aims We explored associations of prenatal serum concentrations of hexachlorobenzene (HCB), beta-Hexachlorocyclohexane (β-HCH), 2,2-Bis(4-chlorophenyl)-1,1-dichloroethene (p,p’-DDE) and 2,2-Bis(4-chlorophenyl-1,1,1-trichloroethane (p,p’-DDT) with maternal-reported measures of verbal and non-verbal communication in young girls. Study Design and Methods We studied a sample of 400 singleton girls and their mothers participating in the Avon Longitudinal Study of Parents and Children (ALSPAC) using multivariable linear regression models adjusting for parity, Home Observation Measurement of the Environment (HOME) score, maternal age and education status, and maternal tobacco use during the first trimester of pregnancy. Exposure and Outcome Measures Maternal serum samples (collected at median 15 wks. gestation [IQR 10, 28]) were assessed for selected organochlorine pesticide levels. Communication was assessed at 15 and 38 months, using adapted versions of the MacArthur Bates Communicative Development Inventories for Infants and Toddlers (MCDI). Results At 15 months, girls born to mothers with prenatal concentrations of HCB in the highest tertile had vocabulary comprehension and production scores approximately 16% (p = 0.007) lower than girls born to mothers with concentrations in the lowest tertile. This association varied by maternal parity in that the evidence was stronger for daughters of nulliparous mothers. At 38 months, girls born to mothers with prenatal concentrations of HCB in the highest tertile had mean adjusted intelligibility scores that were 3% (p = 0.03) lower than those born to mothers with concentrations in the lowest tertile; however, results did not vary significantly by parity. Maternal concentrations of β-HCH and p,p’-DDE were not significantly associated with MCDI scores at 15 or 36 months. p,p’-DDT had an inconsistent pattern of association; a significant positive association was observed between p,p’-DDT with verbal comprehension scores at 15 months; however, at 38 months a significant inverse association was observed for p,p’-DDT with communicative scores. This inverse association for p,p’-DDT among older girls tended to be stronger among daughters of mothers who had lower depression scores. Conclusions Organochlorine pesticide exposure in utero may affect communication development.
The investigation of the pyrethroid insecticide lambda-cyhalothrin (LCT)-affected Ca2+ homeostasis and -activated Ca2+-associated mitochondrial apoptotic pathway in normal human astrocytes: the evaluation of protective effects of BAPTA-AM (a selective Ca2+ chelator) Neurotoxicology (IF 3.076) Pub Date : 2018-10-05 Shu-Shong Hsu, Chung-Ren Jan, Wei-Zhe Liang
Differential copper-induced death and regeneration of olfactory sensory neuron populations and neurobehavioral function in larval zebrafish Neurotoxicology (IF 3.076) Pub Date : 2018-10-04 Eva Y. Ma, Kevin Heffern, Julia Cheresh, Evan P. Gallagher
The Time Course of Blood Brain Barrier Leakage and its implications On the Progression of Methamphetamine-Induced Seizures Neurotoxicology (IF 3.076) Pub Date : 2018-09-30 John F. Bowyer, Karen M. Tranter, Bonnie Robinson, Joseph P. Hanig, Madeline Faubion, Sumit Sarkar
007/s11916-015-0528-Gulf War agents pyridostigmine bromide and permethrin cause hypersensitive nociception that is restored after vagus nerve stimulation Neurotoxicology (IF 3.076) Pub Date : 2018-09-29 Damir Nizamutidinov, Sanjib Mukherjee, Chenghao Deng, Harald M. Stauss, Lee A. Shapiro
Gulf war illness (GWI) is a chronic multi-symptom disease that afflicts 25-33% of troops that were deployed in the 1990-1991 Gulf War. GWI symptoms include cognitive, behavioral and emotional deficits, as well as migraines and pain. It is possible that exposure to Gulf War agents and prophylactics contributed to the reported symptomology. Pyridostigmine bromide (PB) and permethrin (PER) were given to prevent nerve gas attacks and insect vector born disease, respectively. Previous studies have demonstrated that 10 days of exposure to these chemicals can cause symptoms analogous to those observed in GWI, including impairment of long-term memory in mice. Other studies using this model have shown chronic neuroinflammation, and chronic neuroinflammation can lead to altered nociceptive sensitivity. At 10-weeks after the 10-day PB and PER exposure paradigm, we observed lowered nociceptive threshold on the Von Frey test that was no longer evident at 28 weeks and 38 weeks months post-exposure. We further determined that vagus nerve stimulation, initiated at 38 weeks months after exposure, restores the lowered nociceptive sensitivity. Therefore, stimulating the vagus nerve appears to influence nociception. Future studies are need to elucidate possible mechanisms of this effect.
Fluoride activates microglia, secretes inflammatory factors and influences synaptic neuron plasticity in the hippocampus of rats Neurotoxicology (IF 3.076) Pub Date : 2018-09-28 Li Yang, Peiyu Jin, Xiaoyan Wang, Qing Zhou, Xiaoli Lin, Shuhua Xi
Epidemiological studies have reported that highly fluoridated drinking water may significantly decrease the Intelligence Quotient (IQ) of exposed children. It is thought that synaptic plasticity is the basis of learning and memory skills in developing children. However, the effect on synaptic plasticity by activated microglia induced via fluoride treatment is less clear. Our previous research showed that fluoride ions activated microglia which then released pro-inflammatory cytokines. In this study, hippocampal-dependent memory status was evaluated in rat models sub-chronically exposed to fluoride in their drinking water. Microglial activation in the hippocampus was examined using immunofluorescence staining and the expression of synaptophysin (SYP) and postsynaptic density protein 95 (PSD-95), Long-term potentiation(LTP) and the expression of Amino-3-hydroxy-5-methy-4-isoxazole propionate (AMPA) receptor subunit GluR2 as well as N-methyl-D-aspartate (NMDA) receptor subunit NMDAR2β of exposed rats. We found that fluoride exposure activated microglia and increased the expression of DAP12 and TREM2, as well as promoted pro-inflammatory cytokines secretion via ERK/MAPK and P38/MAPK signal pathways. Furthermore fluoride depressed LTP and decreased PSD-95 protein levels as well as expression of ionotropic glutamate receptors GluR2 and NMDAR2β. We concluded that the role of fluoride on synaptic plasticity may be associated with neuroinflammation induced by microglia.
Inhibition of NRF2 signaling and increased reactive oxygen species during embryogenesis in a rat model of retinoic acid-induced neural tube defects Neurotoxicology (IF 3.076) Pub Date : 2018-09-26 Dan Liu, Jia Xue, Yusi Liu, Hui Gu, Xiaowei Wei, Wei Ma, Wenting Luo, Ling Ma, Shanshan Jia, Naixuan Dong, Jieting Huang, Yanfu Wang, Zhengwei Yuan
Exposure to retinoic acid (RA) during pregnancy increases the risk of serious neural tube defects (NTDs) in the developing fetus. The precise molecular mechanism for this process is unclear; however, RA is associated with oxidative stress mediated by reactive oxygen species. Nuclear factor erythroid 2-related factor 2 (NRF2) is a master regulator of oxidative stress that directs the expression of antioxidant genes and detoxifying proteins to maintain redox homeostasis. We established a rat model of NTDs in which pregnant dams were administered all-trans (at)RA on gestational day 10, and oxidative stress levels and the spatiotemporal expression of NRF2 and its downstream targets were examined in the resulting embryos and in maternal blood. In the NTD group, total antioxidative capacity decreased and 8-hydroxy-2'-deoxyguanosine increased in maternal serum and fetal spinal cord tissues. Plasma GSH content, the GSH/GSSG ratio, and glutathione peroxidase activity in fetal spinal cords were lower in the NTD group relative to controls. We detected NRF2 protein reduction and concomitant upregulation of Kelch-like ECH-associated protein 1 (KEAP1) - a cytoplasmic inhibitor of NRF2 - in the NTD group. The mRNA and protein levels of downstream targets of NRF2 were downregulated in the spinal cords of NTD embryos. These data demonstrate substantial oxidative stress and NRF2 signaling pathway disruption in a model of NTDs induced by atRA. The inhibitory effects of atRA on NRF2 signaling may lower cellular defenses against RA-induced oxidative stress and could play important roles in NTD occurrence during embryonic development.
Dexmedetomidine ameliorates lidocaine-induced spinal neurotoxicity via inhibiting glutamate release and the PKC pathway Neurotoxicology (IF 3.076) Pub Date : 2018-09-18 Haiping Xu, Baisong Zhao, Yingjun She, Xingrong Song
Dexmedetomidine, a selective α2 adrenergic agonist, has been shown to have neuroprotective and anti-apoptotic effects. To further investigate the underlying mechanisms, we used a rat model of spinal neurotoxicity induced by intrathecal administration of lidocaine. Four days after intrathecal catheter implantation, rats received an intraperitoneal injection of various doses of dexmedetomidine before an intrathecal injection of 20 µL 10% lidocaine. Dexmedetomidine-pretreated rats were also exposed to a selective α2-adrenergic antagonist (yohimbine) or a specific protein kinase C (PKC) inhibitor (Gö 6983) that selectively inhibits several PKC isoforms. Lidocaine injection significantly damaged the spinal cord: hind limb locomotor function was reduced and tail-flick latency was prolonged; significant spinal cord damage and neuronal apoptosis were identified using histological and TUNEL staining assays; increased glutamate release was detected using high performance liquid chromatography (HPLC) analysis; and increased expression of PKC and PKCβI was detected using Western blotting analysis. Pretreatment with dexmedetomidine ameliorated all of the lidocaine-induced effects; however, this protection was abolished when yohimbine or Gö 6983 was injected together with dexmedetomidine. Our results indicate that dexmedetomidine protects the spinal cord from lidocaine-induced spinal neurotoxicity through regulating PKC expression and glutamate release.
Thymoquinone prevents cisplatin neurotoxicity in primary DRG neurons Neurotoxicology (IF 3.076) Pub Date : 2018-09-15 Ramazan Üstün, Elif Kaval Oğuz, Ayşe Şeker, Hasan Korkaya
Chemotherapy-induced peripheral neuropathy (CIPN) is a substantial, dose-limiting adverse effect that occurs in cancer patients. Cis-dichlorodiamine (II) platinum (CDDP, cisplatin) is a platinum-based chemotherapeutic agent that causes severe acute and chronic peripheral neuropathies in 30% of cancer patients. Thymoquinone (TQ), a leading bioactive constituent of Nigella sativa seeds, has been reported to have antioxidant, anti-inflammatory, anti-neoplastic and neuroprotective properties. Dorsal root ganglia (DRG) include different classes of primary sensory neurons, such as nociceptors, mechanoreceptors, and proprioceptive neurons. Here, we investigated the neuroprotective activity of TQ against cisplatin neurotoxicity in cultured DRG neurons. We prepared neuronal cultures from DRGs of adult mice, pre-treated them with or without varying doses of TQ prior to exposure of cells to cisplatin. The preparations were viewed under the scope before and after the treatment at 24 hr, 48 hr, and 72 hr time points. We analyzed neuronal cell viability and neurite outgrowths, and evaluated morphologic changes of neuronal or non-neuronal cells. TQ significantly increases the ability to extend neurites and neuronal cell viability when compared to the culture conditions which were treated with cisplatin only. Although we provide compelling evidence for the protective activity of TQ against chemotherapy-induced neurotoxicity, further detailed investigations in preclinical settings are warranted for its clinical use.
Changes in VIP-, SP- and CGRP- like immunoreactivity in intramural neurons within the pig stomach following supplementation with low and high doses of acrylamide Neurotoxicology (IF 3.076) Pub Date : 2018-09-14 Katarzyna Palus, Michał Bulc, Jarosław Całka
Acrylamide is one of the food toxins to which the human body is exposed. Although researchers’ interest in acrylamide has been growing in recent years, the knowledge of its effect on the gastrointestinal tract, especially on intramural neurons which form the enteric nervous system is scarce. The aim of this experiment was to determine the influence of acrylamide, administered at doses equivalent to the human tolerable daily intake (TDI, 0.5 µg/kg b.w./day) and ten times higher than the TDI (5 µg/kg b.w./day), on the distribution of vasoactive intestinal peptide (VIP), substance P (SP), and calcitonin gene related peptide (CGRP) expression intramural neurons of the domestic pig stomach. Using double immunofluorescent labelling we revealed that the ENS neurons underwent adaptive changes in response to the supplementation of acrylamide, which manifested themselves as increased expression of VIP, SP and CGRP, both in intramural neurons and by an increase in the nerve density in submucous and muscular layers in the porcine stomach. These substances take part in defensive reactions of neurons and transmission of sensory reactions may play an important role in protecting the stomach against the harmful effect of acrylamide. Moreover, it has been shown that acrylamide induces a significant response of ENS neurons even in TDI dose, which suggests that it is not neutral to the body. These findings may be the basis for further toxicological studies addressing the question if currently permitted minimal content of acrylamide in the food does jeopardize the health of human consumers?
Immunofluorescence/fluorescence assessment of brain-derived neurotrophic factor, c-Fos activation, and apoptosis in the brain of zebrafish (Danio rerio) larvae exposed to glufosinate Neurotoxicology (IF 3.076) Pub Date : 2018-09-14 Selim ÇOMAKLI, Mine KÖKTÜRK, Ahmet TOPAL, Mustafa ÖZKARACA, Saltuk Buğrahan CEYHUN
AMPA-induced extracellular Zn2+ influx into nigral dopaminergic neurons causes movement disorder in rats Neurotoxicology (IF 3.076) Pub Date : 2018-08-31 Haruna Tamano, Hiroki Morioka, Ryusuke Nishio, Azusa Takeuchi, Atsushi Takeda
On the basis of the findings that the rapid influx of extracellular Zn2+ into nigral dopaminergic neurons causes dopaminergic neurodegeneration, here we report that AMPA causes movement disorder in rats. AMPA markedly increased turning behavior in response to apomorphine 1 and 2 weeks after AMPA injection into the substantia nigra pars compacta (SNpc), while AMPA-induced movement disorder was suppressed by co-injection of intracellular Zn2+ chelators, i.e., ZnAF-2DA and TPEN, suggesting that AMPA-induced movement disorder is due to intracellular Zn2+ dysregulation. Furthermore, AMPA markedly induced loss of nigrostriatal dopaminergic neurons 2 weeks after AMPA injection into the SNpc, while AMPA-induced neurodegeneration was also suppressed in the SNpc and the striatum by co-injection of ZnAF-2DA and TPEN. AMPA rapidly increased nigral intracellular Zn2+ after AMPA injection into the SNpc and this increase was blocked by co-injection of TPEN. These results indicate that AMPA receptor activation rapidly increases influx of extracellular Zn2+ into nigral dopaminergic neurons and causes nigrostriatal dopaminergic neurodegeneration, resulting in movement disorder in rats. The evidence that AMPA-induced intracellular Zn2+ dysregulation causes movement disorder via nigrostriatal dopaminergic neurodegeneration suggests that AMPA receptors, probably Ca2+- and Zn2+-permeable GluR2-lacking AMPA receptors are potential targets for overcoming Parkinson's syndrome.
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