Ibuprofen as an emerging pollutant on non-target aquatic invertebrates: Effects on Chironomus riparius

Highlights

• Ibuprofen provoked severe impact on C. riparius survival with an LC10_48h = 0.024 μg/L.

• Hormonal genes EcR, Met, Dronc, were downregulated in response to ibuprofen.

• Three HSPs (hsp70, hsp24, and hsp27) were altered by ibuprofen.

• Immune response was activated after short and medium-term exposure to ibuprofen.

• Oxidative damage could be the mechanism for the ibuprofen toxicity on C. riparius.

Abstract

The concern about pharmaceuticals has been increased over the last decade due to their burgeoning consumption. Ibuprofen has an extensive presence in surface water with risks for the aquatic biota. This study focuses on the effects of ibuprofen at environmental concentrations on the survival, transcriptional level, and enzymatic activity for 24, 96 h on Chironomus riparius. Ibuprofen developed a substantial effect on survival by all the conditions. mRNA levels of EcR, Dronc, and Met (endocrine system), hsp70, hsp24, and hsp27 (stress response), and Proph and Def (immune system) were modified, joined to increased GST and PO activity. The results confirmed alterations on the development of C. riparius, as well as two essential mechanisms, involved in protection against external toxicological challenge. Ibuprofen poses an incipient risk to C. riparius and could at an organismal level by compromising their survival, development, and ability to respond to adverse conditions on the future populations.

Introduction

The impact of anthropogenic activity on aquatic ecosystems has become more evident in recent years. This has led to the presence of multiple xenobiotic compounds from diverse sources in surface waters. Pharmaceutical compounds, with antibiotics and anti-inflammatories being the most representative since their consumption has increased significantly around the world.(Groot and van’t Hooft, 2016). Pharmaceuticals and personal care products (PPCPs) are now classified as emergent contaminants (ECs), which have caused increasing concern due to their high presence in surface water around the world (Nantaba et al., 2020; Ebele et al., 2017) and their toxicity to the aquatic biota (Bickley et al., 2017; Piedade et al., 2020). Ibuprofen is a pharmaceutical compound belonging to nonsteroidal anti-inflammatory drugs (NSAIDs) used in the treatment of rheumatoid arthritis and musculoskeletal disorders in adults and children (Motov et al., 2019). Ibuprofen inhibits cyclooxygenase enzymes, mainly COX-1 and COX-2, blocking prostaglandin synthesis. Prostaglandins are lipids acting as mediators in the inflammatory response and endocrine, nervous, reproductive, and digestive systems, among others in humans (Manku et al., 2019). In insects, prostaglandins are distributed throughout the whole body and engaged with physiological, immunity, and reproductive functions (Barletta et al., 2019). Ibuprofen consumption has become widespread in recent years and is the most frequently sold over the counter (OTC) medication in the world (Thorpe et al., 2013). These medicines are ingested by humans or animals and released through urine, either in the pure form or in one of their metabolites. Therefore, a more significant presence has been detected in residual water, hence increasing the water volumes to be processed in the wastewater treatment plants (WWTPs) (Jia et al., 2020). Although WWTPs have a high elimination efficiency, around 90 % of ibuprofen and metabolites are removed from wastewater (Kermia et al., 2016). Due to its chemical properties, lipophilicity, and ubiquity, ibuprofen is maintained in the environment being present in diverse compartments, including sediments, surface waters, and drinking water (Chander et al., 2016; Pusceddu et al., 2018; Teijon et al., 2010). Multiple studies quantified ibuprofen in effluents from WWTPs around the world at concentrations ranging from non-detected to 140 μg/L (Teijon et al., 2010; Kermia et al., 2016)). Similarly, it was detected in surface waters such as in Uganda and South Korea, with concentrations ranging 6–780 ng/L (Kim et al., 2009; Nantaba et al., 2020), as well as in tap water (Kermia et al., 2016).

Ibuprofen can also affect the life and/or development of organisms living in aquatic environments. Various authors have evaluated the effects of ibuprofen at different levels on vertebrates, such as different species of fish (Gutiérrez-Noya et al., 2020; Mathias et al., 2018; Zhang et al., 2020), and on invertebrates, primarily molluscs (André and Gagné, 2017; Milan et al., 2013) and crustaceans (Grzesiuk et al., 2020; Wang et al., 2016). Even, one work on Daphnia magna detected effects at transcriptional level on Cytochromes (CYPs) and Glutathione-S-transferases (GSTs) genes (Wang et al., 2016). Nonetheless, there is a lack of knowledge on the effect of this compound on insects, an important group of invertebrates. Chironomus riparius has proven to be an excellent organism for toxicological evaluation due to its short life cycle, easy maintenance in the laboratory, and availability of various testing guidelines, such as Test 218 and 233 (OECD, 2004, 2010). Although some studies have assessed the effects of pharmaceuticals on Chironomus riparius, they have focused mostly on ecological parameters, such as emergence, sex ratio, and reproduction (Nentwig, 2007; Sánchez-Argüello et al., 2009). In addition, behavioral effects were caused by exposure to different ECs, like ibuprofen, on another Chironomid Diamesa zernyi (Villa et al., 2018). However, only Xie et al. (2019 a, b) investigated the effect of pharmaceuticals at the molecular level on this organism. . It is remarkable the sparse information on alterations of this pharmaceutical at the molecular level. Usually, the toxicity guides defined by regulatory agencies as Organisation for Economic Co-operation and Development (OCED), focus the tests on the assessment of ecologically relevant parameters, ignoring the effects at the sub-organismal level. Therefore, some compounds can be classified as harmless because they do not affect survival or reproduction, but still be modifying short, mid, and long-term metabolic pathways.

To reduce the information gap on the effects of ibuprofen toxicity on insects and to emphasize the importance of molecular studies in toxicology as early alarm signals. C. riparius was selected as a model organism in this study. For the experimental approach, fourth instar larvae were exposed to environmentally relevant concentrations of ibuprofen and survival, gene transcriptional activity, and enzyme activities were employed as endpoints. For molecular analysis, genes comprising four crucial processes involved in the viability of the population (hormonal system, detoxification mechanisms, stress response, and the immune system) were selected. Additionally, it was quantified the activity of two enzymes used as biochemical biomarkers, GST and Phenoloxidase (PO).