Effects of gemfibrozil on lipid metabolism, steroidogenesis, and reproduction in the fathead minnow (Pimephales promelas)

Lipid metabolism in crocodilians: A field with promising applications in the field of ecotoxicology

In the last years, lipid physiology has become an important research target for systems biology applied to the field of ecotoxicology. Lipids are not only essential components of biological membranes, but also participate in extra and intracellular signaling processes and as signal transducers and amplifiers of regulatory cascades. Particularly in sauropsids, lipids are the main source of energy for reproduction, growth, and embryonic development. In nature, organisms are exposed to different stressors, such as parasites, diseases and environmental contaminants, which interact with lipid signaling and metabolic pathways, disrupting lipid homeostasis. The system biology approach applied to ecotoxicological studies is crucial to evaluate metabolic regulation under environmental stress produced by xenobiotics. In this review, we cover information of molecular mechanisms that contribute to lipid metabolism homeostasis in sauropsids, specifically in crocodilian species. We focus on the role of lipid metabolism as a powerful source of energy and its importance during oocyte maturation, which has been increasingly recognized in many species, but information is still scarce in crocodiles. Finally, we highlight priorities for future research on the influence of environmental stressors on lipid metabolism, their potential effect on the reproductive system and thus on the offspring, and their implications on crocodilians conservation.

Fish as models to study liver and blood lipid-related effects of fibrates and statins and screen new hypolipidemic drugs

Fibrates and statins lead worldwide prescriptions of lipid-lowering drugs, whose consumption is increasing considerably due to the growing incidence of dyslipidemias, particularly in high-income areas. Consequently, these chemicals are frequently found in aquatic environments, usually closer to highly urbanized and populated areas, reaching the water systems primarily through waste-water treatment plant (WWTP) effluents. Despite that, the knowledge regarding the effects caused by fibrates and statins in fish, namely in liver lipid metabolism and blood-related parameters, is still very limited. There is yet no standardized fish model for testing the effects of those drugs. However, experimental evidence suggests that the mechanisms of action (MoA) of fibrates and statins are fairly similar to those observed in humans, which makes these aquatic organisms viable alternatives for toxicological and mechanistic studies. This graphical review serves as a state point regarding the potential use of fish as a model for the study of hypolipidemic compounds, addressing (I) the current state of aquatic pollution caused by statins and fibrates, (II) the experimental designs used in the literature to assess effects on fish, (III) the liver metabolism and blood effects caused by exposure to fibrates and statins, as well as (IV) the MoA of both drugs. It further focuses on the current and future benefits of establishing a standardized fish model(s) for testing hypolipidemic drugs.

Elucidating the Effects of the Lipids Regulators Fibrates and Statins on the Health Status of Finfish Species: A Review

The most documented fibrates are gemfibrozil, clofibrate and bezafibrate, while for statins, the majority of the published literature focuses on atorvastatin and simvastatin. The present work reviews previously published research concerning the effects of these hypocholesterolaemic pharmaceuticals on fish, with a particular focus on commercially important species, commonly produced by the European aquaculture industry, specifically in recirculated aquaculture systems (RAS). Overall, results suggest that both acute and chronic exposures to lipid-lowering compounds may have adverse effects on fish, disrupting their capacity to excrete exogenous substances, as well as both lipid metabolism and homeostasis, causing severe ontogenetic and endocrinological abnormalities, leading to hampered reproductive success (e.g., gametogenesis, fecundity), and skeletal or muscular malformations, having serious repercussions on fish health and welfare. Nonetheless, the available literature focusing on the effects of statins or fibrates on commonly farmed fish is still limited, and further research is required to understand the implications of this matter on aquaculture production, global food security and, ultimately, human health.

The Biological Effects of Pharmaceuticals in the Marine Environment

Environmental pharmaceuticals represent a threat of emerging concern for marine ecosystems. Widely distributed and bioaccumulated, these contaminants could provoke adverse effects on aquatic organisms through modes of action like those reported for target species. In contrast to pharmacological uses, organisms in field conditions are exposed to complex mixtures of compounds with similar, different, or even opposing therapeutic effects. This review summarizes current knowledge of the main cellular pathways modulated by the most common classes of environmental pharmaceuticals occurring in marine ecosystems and accumulated by nontarget species-including nonsteroidal anti-inflammatory drugs, psychiatric drugs, cardiovascular and lipid regulator agents, steroidal hormones, and antibiotics-and describes an intricate network of possible interactions with both synergistic and antagonistic effects on the same cellular targets and metabolic pathways. This complexity reveals the intrinsic limits of the single-chemical approach to predict the long-term consequences and future impact of pharmaceuticals at organismal, population, and community levels.

Morbidity and mortality in Danio rerio and Pimephales promelas exposed to antilipidemic drug mixtures (fibrates and statins) during embryogenesis: Comprehensive assessment via ante and post mortem endpoints

Antilipidemic drugs are routinely detected in effluent and surface waters downstream of wastewater treatment plants. A mixture exposure study with nine environmentally relevant antilipidemic drugs was performed with zebrafish (Danio rerio, ZF) and fathead minnow (Pimephales promelas, FHM) embryos to investigate the effects on sensitive embryologic stages. Zebrafish embryos were exposed nominally to: (a) 0.005 μM, (b) 0.05 μM, or (c) 0.5 μM of each drug in the mixture. Fathead minnow embryos were exposed nominally to: (a) 0.0005 μM, (b) 0.005 μM, or (c) 0.05 μM of each drug in the mixture. Several of the individual drug concentrations were within ranges previously found in the environment. Multiple metrics demonstrate that (a) exposure of ZF and FHM embryos to antilipidemic drugs during embryonic development results in lethal and sublethal effects, (b) ZF were more sensitive than FHM based on median lethal concentration (LC₅₀ 0.02 μM and 0.05 μM, respectively), but FHM exhibited more severe abnormal sublethal morphologies than zebrafish embryos, and (c) the sublethal effects differed between the two species. This model identified novel specific endpoints for assessing sensitive, sublethal effects of pharmaceuticals in the environment. Abnormal myofiber birefringence pattern, hemorrhage, and heart rate are not included in standard evaluations but each of these metrics demonstrated a dose-dependent response in this study. Results demonstrate risk to fish development with potential repercussions at the population level, especially if environmental concentrations increase.

Cardiovascular drugs and lipid regulating agents in surface waters at global scale: Occurrence, ecotoxicity and risk assessment

Cardiovascular drugs and lipid regulating agents have emerged as major groups of environmental contaminants over the past decades. However, knowledge about their occurrence in freshwaters and their ecotoxicity is still limited. Here, we critically summarize the presence of 82 cardiovascular drugs and lipid regulating agents at a global-scale and represent their effects on aquatic organisms. Only about 71% of these pharmaceuticals in use have been analyzed for their residues in aquatic ecosystems and only about 24% for their effects. When detected in surface waters, they occurred at concentrations of dozens to hundreds of ng/L. In wastewaters, they reached up to several μg/L. Effects of cardiovascular drugs and lipid regulating agents have been extensively studied in fish and a few in invertebrates, such as Daphnia magna and mussels. These pharmaceuticals affect cardiac physiology, lipid metabolism, growth and reproduction. Besides, effects on spermatogenesis and neurobehavior are observed. Environmental risks are associated with beta-blockers propranolol, metoprolol, and lipid lowering agents bezafibrate and atorvastatin, where adverse effects (biochemical and transcriptional) occurred partially at surface water concentrations. In some cases, reproductive effects occurred at environmentally relevant concentrations. This review summarizes the state of the art on the occurrence of cardiovascular drugs and lipid regulating agents at a global-scale and highlights their risks to fish. Further research is needed to include more subtle changes on heart function and to explore non-investigated drugs. Their occurrence in freshwaters and impact on a diverse array of aquatic organisms are particularly needed to fully assess their environmental hazards and risks.

Fatty acid metabolism and brain mitochondrial performance of juvenile Nile tilapia (Oreochromis niloticus) exposed to the water-accommodated fraction of Maya crude oil

Crude oil and its derivatives are still the primary source of energy for humankind. However, during its transportation and treatment, spills of this resource can occur in aquatic environments. Nile tilapia is one of the most globally widespread fish species. This species is even found in brackish water due to its tolerance to salinity and pollution. In this study, the performance of brain cells (mitochondrial membrane potential [ΔΨm], calcium [Ca²⁺] and O₂ and H₂O₂ levels) exposed to crude oil was assessed. In addition, fatty acid metabolism (cholesterol concentration and fatty acid synthase [FAS], acyl CoA-oxidase [AOX] and catalase [CAT] activities) in the brain, heart, liver and intestine of Nile tilapia exposed to the water-accommodated fraction (WAF) of 0.01, 0.1 or 1 g/L Maya crude oil (MCO) for 96 h were evaluated. After exposure, in brain cells, there were only increases in ROS and slight reductions in ΔΨm. Exposure to WAF of MCO induced and increased the levels of cholesterol and altered FAS and AOX activities in all examined tissues. The brain is the most susceptible organ to alterations in the activity of fatty acid metabolic enzymes and cholesterol levels relative to the heart, liver and intestine. The correlation between inhibition of the activity of CAT and AOX suggests a possible reduction in the proliferation and size of peroxisomes. Most biomarkers were significantly altered in the brains of Nile tilapia exposed to the WAF containing 1 g/L MCO in comparison to the control.

Passage through a hydropower plant affects the physiological and health status of Atlanstic salmon smolts

Atlantic salmon is an anadromous species migrating from upper-reach nursery areas in rivers to the oceanic feeding areas at smolt stage and inversely at adult stage requiring unimpeded migration routes. However, dams associated with hydroelectric power plants (HPP) disrupt river connectivity and affect fish movement and survival. The objective of the current study was to evaluate the short and mid-term physiological and immune response of Atlantic salmon smolts after passing through Andenne HPP (Meuse River, Belgium). Several parameters were studied after an in situ deliberate passage including direct mortality and external damages, stress and immune biomarkers as plasma cortisol and glucose levels, complement and peroxidase activities, and immune and oxidative stress related gene expression 24 h, 72 h and 120 h after passage. Survival rate was lower and external damages were more important in fish that confronted the HPP compared to the control ones. Moreover, the passage through the turbine affected plasma glucose levels, complement and peroxidase activities and the expression of some immune genes such as lysg, igm and mpo in a timely manner suggesting that this passage can lead to a great energy expenditure and a disruption of innate immunity. Our observations can partially explain the delayed mortality observed in many studies leading to a poor success of restocking programs. HPPs not only have a direct impact in terms of mortalities and injuries but also an indirect one in terms of physiological and immune changes that can compromise Atlantic salmon smolts ability to escape successfully to the ocean.

Impacts of Sex and Exposure Duration on Gene Expression in Zebrafish Following Perfluorooctane Sulfonate Exposure

Perfluorooctane sulfonate (PFOS) is a member of the anthropogenic class of perfluorinated alkyl acids (PFAAs) and one of the most frequently detected PFAAs in water, humans, mammals, and fish around the world. The zebrafish (Danio rerio) is a small freshwater fish considered an appropriate vertebrate model for investigating the toxicity of compounds. Previous investigations showed tissue-specific bioaccumulation and alterations in the expression of fatty acid-binding proteins (fabps) in male and female zebrafish, potentially due to interactions between PFAA and fatty acid transporters. In addition, a number of neurological impacts have been reported as a result of human and animal exposure to PFAAs. Therefore, the present comprehensive study was designed to investigate whether PFOS exposure affects the expression of genes associated with fatty acid metabolism (fabp1a, fabp2, and fabp10a) in zebrafish liver, intestine, heart, and ovary and genes involved in the nervous system (acetylcholinesterase, brain-derived neurotrophic factor, choline acetyltransferase, histone deacetylase 6, and nerve growth factor) in brain and muscle. The results indicate alterations in expression of genes associated with fatty acid metabolism and neural function that vary with both exposure concentration and sex. In addition, our findings highlight that expression of these genes differs according to exposure duration. The present results extend the knowledge base on PFOS effects to other tissues less often studied than the liver. The findings of the present investigation provide a basis for future studies on the potential risks of PFOS as one of the most abundant PFAAs in the environment. Environ Toxicol Chem 2020;39:437-449. © 2019 SETAC.

Parental gemfibrozil exposure impacts zebrafish F1 offspring, but not subsequent generations

Gemfibrozil (GEM) is a fibrate lipid regulator and one of the most commonly occurring fresh water pharmaceuticals. The negative effects of fibrates including GEM on fish reproduction have been frequently reported including effects of F₀ GEM exposure on reproduction of the unexposed F₁ offspring. We predicted that chronic, direct exposure of zebrafish with low concentrations of GEM would adversely affect parental male reproduction and unexposed offspring for multiple generations. Adult zebrafish were exposed to 10 μg/L GEM for 6 weeks and a range of reproductive indices were analyzed. The F₁-F₄ offspring were reared in clean water from 3 distinct lineages where only a single or both parents were exposed and compared to a control lineage where parents were unexposed. Reproductive indices were examined in unexposed F₁-F₄ offspring to test the hypothesis of multi- or trans- generational impacts. Exposure to GEM caused a decline in breeding success and mean embryo production in F₀ parents and a reduction in whole body 11-ketotestosterone (11-KT), altered male courtship, aggression and sperm morphology. Our results indicate that paternal exposure alone is sufficient to result in reproductive effects in unexposed male offspring but that effects are mostly limited to F₁. We suggest that GEM may act as a reproductive endocrine disruptor in fish and that chronic exposure reduced male reproductive fitness but not over multiple generations.

Effects of gemfibrozil on sex hormones and reproduction related performances of Oryzias latipes following long-term (155 d) and short-term (21 d) exposure

Gemfibrozil, a lipid-regulating pharmaceutical, has been widely used for treating dyslipidemia in humans and detected frequently in freshwater environments. Since plasma cholesterol is a precursor of steroid hormones, the use of gemfibrozil may influence the sex hormone balances. However, its endocrine toxicity following long-term exposure is not well understood. The purpose of the present study is to investigate the effects of gemfibrozil on sex hormones and reproductive outcomes in a freshwater fish, following a long-term (155 d) exposure. For this purpose, Japanese medaka embryos (F0) were exposed to a series of gemfibrozil concentrations, i.e., 0, 0.04, 0.4, 3.7, and 40 mg/L for 155 d, and reproductive parameters, sex hormones, and associated gene expressions were assessed. For comparison, a short-term exposure (21 d) was performed separately with adult medaka and measured for sex hormones and related gene expressions. Following the 155 d long-term exposure, the fecundity showed a decreasing pattern. In addition, at 3.7 mg/L gemfibrozil, testosterone (T) level in the female fish was significantly decreased, and the hatchability of F1 fish was significantly decreased. The estrogen receptor (er) or vitellogenin (vtg) genes in gonads and liver were up-regulated. However, plasma cholesterol levels did not show significant changes in both sexes. The observations from the short-term (21 d) exposure were different from those of the long-term exposure. Following the short-term exposure, decreased 17β-estradiol (E2), and 11-ketotestosterone (11-KT) levels along with decrease plasma cholesterol were observed in the male fish. The hormone disruption following the short-term exposure appears to be associated with the hypocholesterolemic activity of gemfibrozil. Our results show that the mechanisms of gemfibrozil toxicity may depend on the exposure duration. Consequences of long-term exposure to other fibrates in the water environment warrant further investigations.

Alterations to the Intestinal Microbiome and Metabolome of Pimephales promelas and Mus musculus Following Exposure to Dietary Methylmercury

Mercury is a global contaminant, which may be microbially transformed into methylmercury (MeHg), which bioaccumulates. This results in potentially toxic body burdens in high trophic level organisms in aquatic ecosystems and maternal transfer to offspring. We previously demonstrated effects on developing fish including hyperactivity, altered time-to-hatch, reduced survival, and dysregulation of the dopaminergic system. A link between gut microbiota and central nervous system function in teleosts has been established with implications for behavior. We sequenced gut microbiomes of fathead minnows exposed to dietary MeHg to determine microbiome effects. Dietary exposures were repeated with adult CD-1 mice. Metabolomics was used to screen for metabolome changes in mouse brain and larval fish, and results indicate effects on lipid metabolism and neurotransmission, supported by microbiome data. Findings suggest environmentally relevant exposure scenarios may cause xenobiotic-mediated dysbiosis of the gut microbiome, contributing to neurotoxicity. Furthermore, small-bodied teleosts may be a useful model species for studying certain types of neurodegenerative diseases, in lieu of higher vertebrates.

A multibiomarker approach highlights effects induced by the human pharmaceutical gemfibrozil to gilthead seabream Sparus aurata

Lipid regulators are among the most prescribed human pharmaceuticals worldwide. Gemfibrozil, which belongs to this class of pharmaceuticals, is one of the most frequently encountered in the aquatic environment. However, there is limited information concerning the mechanisms involved in gemfibrozil effects to aquatic organisms, particularly to marine organisms. Based on this knowledge gap, the current study aimed to assess biochemical and behavioral effects following a sublethal exposure to gemfibrozil (1.5, 15, 150, 1500 and 15,000 μg L^-1) in the estuarine/marine fish Sparus aurata. After the exposure to 1.5 μg L^-1 of gemfibrozil, fish had reduced ability to swim against a water flow and increased lipid peroxidation in the liver. At concentrations between 15-15,000 μg L^-1, the activities of some enzymes involved in antioxidant defense were induced, appearing to be sufficient to prevent oxidative damage. Depending on the organ, different responses to gemfibrozil were displayed, with enzymes like catalase being more stimulated in gills, whereas glutathione peroxidase was more activated in liver. Although there were no obvious concentration-response relationships, the integrated biomarker response version 2 (IBRv2) analysis revealed that the highest concentrations of gemfibrozil (between 150-15,000 μg L^-1) caused more alterations. All the tested concentrations of gemfibrozil induced effects in S. aurata, in terms of behavior and/or oxidative stress responses. Oxidative damage was found at a concentration that is considered environmentally relevant, suggesting a potential of this pharmaceutical to impact fish populations.

Gemfibrozil and carbamazepine decrease steroid production in zebrafish testes (Danio rerio)

Gemfibrozil (GEM) and carbamazepine (CBZ) are two environmentally relevant pharmaceuticals and chronic exposure of fish to these compounds has decreased androgen levels and fish reproduction in laboratory studies. The main focus of this study was to examine the effects of GEM and CBZ on testicular steroid production, using zebrafish as a model species. Chronic water borne exposures of adult zebrafish to 10 μg/L of GEM and CBZ were conducted and the dosing was confirmed by chemical analysis of water as 17.5 ± 1.78 and 11.2 ± 1.08 μg/L respectively. A 67 day exposure led to reduced reproductive output and lowered whole body, plasma, and testicular 11-ketotestosterone (11-KT). Testicular production of 11-KT was examined post exposure (42 days) using ex vivo cultures to determine basal and stimulated steroid production. The goal was to ascertain the step impaired in the steroidogenic pathway by each compound. Ex vivo 11-KT production in testes from males chronically exposed to GEM and CBZ was lower than that from unexposed males. Although hCG, 25-OH cholesterol, and pregnenolone stimulation increased 11-KT production in all treatment groups over basal levels, hCG stimulated 11-KT production remained significantly less in testes from exposed males compared to controls. 25-OH cholesterol and pregnenolone stimulated 11-KT production was similar between GEM and control groups but the CBZ group had lower 11-KT production than controls with both stimulants. We therefore propose that chronic GEM and CBZ exposure can reduce production of 11-KT in testes through direct effects independent of mediation through HPG axis. The biochemical processes for steroid production appear un-impacted by GEM exposure; while CBZ exposure may influence steroidogenic enzyme expression or function.

Place-based screening of mixtures of dominant emerging contaminants measured in Lake Michigan using zebrafish embryo gene expression assay

Determining impacts of emerging contaminants is difficult due to the different concentrations of mixtures of these chemicals over a landscape. Assessment approaches need to account for absorption, distribution, metabolism and excretion of the chemicals in an organism, and potential crosstalk between molecular pathways. The goal of this study was to assess the utility of employing a modified zebrafish embryo toxicity (ZFET) assay that assesses morphological alterations and measurements of estrogen-associated mRNA transcripts, to exposure of a mixtures of chemicals at concentrations measured in several locations in Lake Michigan. The 5 pharmaceuticals in this study were carbamazepine, diltiazem, fluoxetine, gemfibrozil and metformin. Exposures consisted of 4 concentrations of each individual chemical, mixture concentrations measured at seven locations in Lake Michigan, or 17β-estradiol. The relative expression of Estrogen Receptor-alpha, brain aromatase (CYP19A2), and gonadotropin releasing hormone 3 mRNA were measured at the end the 6-d exposure to determine estrogenicity of the individual chemical or mixture. In this study, there was significant induction of CYP19A2 in individual exposures of diltiazem, fluoxetine, gemfibrozil and metformin at concentrations measured in Lake Michigan. Exposure to 5 of the 7 chemical mixtures altered the expression of one of the three biomarkers. Transcripts varied across mixtures, indicating that biological screening of whole water samples for potential estrogenicity may need to include alternative molecular pathways other than just steroid receptor binding. This research demonstrates that pairing chemical measurements with a modified ZFET assay, twhich incorporates molecular biomarkers and morphological endpoints, could provide location and mixture specific toxic profiling.

Effects of gemfibrozil on the growth, reproduction, and energy stores of Daphnia magna in the presence of varying food concentrations

Gemfibrozil, a common lipid regulator, enters aquatic environments through treated municipal wastewater effluent that fails to remove it completely from effluent streams. When exposed to gemfibrozil concentrations of 50, 500, 5,000, and 50,000 ng L^-1, Daphnia magna showed increased lipid reserves by 14-21% (significant at 500 ng L^-1), increased length by 9-13% (significant at 50 ng L^-1), increased mass by 6-13% (significant at 50 ng L^-1) and increased neonate production by 57-74% (significant at 50 ng L^-1). Gemfibrozil-exposed Daphnia held under conditions where food availability was low, grew and reproduced as well as those in the control. Taken together, these results suggest that gemfibrozil exposure within environmentally relevant concentration ranges is not toxic to Daphnia magna but has the potential to be beneficial to the species under these conditions.

Altered expression of metabolites and proteins in wild and caged fish exposed to wastewater effluents in situ

Population growth has led to increased global discharges of wastewater. Contaminants that are not fully removed during wastewater treatment, such as pharmaceuticals and personal care products (PPCPs), may negatively affect aquatic ecosystems. PPCPs can bioaccumulate causing adverse health effects and behavioural changes in exposed fish. To assess the impact of PPCPs on wild fish, and to assess whether caged fish could be used as a surrogate for resident wild fish in future monitoring, we caged goldfish in a marsh affected by discharges of wastewater effluents (Cootes Paradise, Lake Ontario, Canada). We collected plasma from resident wild goldfish, and from goldfish that we caged in the marsh for three weeks. We analyzed the plasma proteome and metabolome of both wild and caged fish. We also compared proteomic and metabolic responses in caged and wild fish from the marsh to fish caged at a reference site (Jordan Harbour Conservation Area). We identified significant changes in expression of over 250 molecules that were related to liver necrosis, accumulation and synthesis of lipids, synthesis of cyclic AMP, and the quantity of intracellular calcium in fish from the wastewater affected marsh. Our results suggest that PPCPs could be affecting the health of wild fish populations.

Evaluation of gemfibrozil effects on a marine fish (Sparus aurata) combining gene expression with conventional endocrine and biochemical endpoints

The information on the potential hazardous effects of gemfibrozil (GEM) on marine fish is extremely scarce. In the current study, molecular, endocrine and biochemical parameters were assessed in Sparus aurata after 96h waterborne exposure to a GEM concentration range. Hepatic mRNA levels of target genes known to be regulated via peroxisome proliferator-activated receptor α (pparα) in mammals, such as apolipoprotein AI (apoa1) and lipoprotein (lpl) were significantly increased, without a concomitant activation of the ppar pathways. GEM (15μgL(-1)) induced an upregulation in mRNA levels of interleukin 1β (il1β), tumour necrosis factor-α (tnfα) and caspase 3 (casp3), suggesting an activation of proinflammatory processes in S. aurata liver. However, mRNA levels of genes related with the antioxidant defence system and cell-tissue repair were unaltered under the tested experimental conditions. Higher levels of GEM induced a cortisol rise, an indication that it is recognized as a stressor by S. aurata. Cortisol levels and the mRNA levels of il1β, tnfα and casp3 may be suggested as potential biomarkers of GEM effects in marine fish.

Fatty acid metabolism in fish species as a biomarker for environmental monitoring

Pollution by Organic Contaminants (OC) in aquatic environments is a relevant issue at the global scale. Lipids comprised of Fatty Acids (FA) play many important roles in the physiology and life history of fishes. Toxic effects of OC are partly dependent on its bioaccumulation in the lipids of aquatic organisms due its physicochemical properties. Therefore, there is an increasing interest to investigate the gene expression as well as the presence and activity of proteins involved in FA metabolism. The attention on Peroxisome Proliferation Activate Receptors (PPARs) also prevails in fish species exposed to OC and in the transport, biosynthesis and β-oxidation of FA. Several studies have been conducted under controlled conditions to evaluate these biological aspects of fish species exposed to OC, as fibrates, endocrine disrupting compounds, perfluoroalkyl acids, flame retardants, metals and mixtures of organic compounds associated with a polluted area. However, only fibrates, which are agonists of PPARs, induce biological responses suitable to be considered as biomarkers of exposure to these pollutants. According to the documented findings on this topic, it is unlikely that these physiological aspects are suitable to be employed as biomarkers with some noticeable exceptions, which depend on experimental design. This emphasises the need to investigate the responses in fish treated with mixtures of OC and in wild fish species from polluted areas to validate or refute the suitability of these biomarkers for environmental or fish health monitoring.

Photodegradation of gemfibrozil in aqueous solution under UV irradiation: kinetics, mechanism, toxicity, and degradation pathways

The lipid regulator gemfibrozil (GEM) has been reported to be persistent in conventional wastewater treatment plants. This study investigated the photolytic behavior, toxicity of intermediate products, and degradation pathways of GEM in aqueous solutions under UV irradiation. The results demonstrated that the photodegradation of GEM followed pseudo-first-order kinetics, and the pseudo-first-order rate constant was decreased markedly with increasing initial concentrations of GEM and initial pH. The photodegradation of GEM included direct photolysis via (3)GEM(*) and self-sensitization via ROS, where the contribution rates of degradation were 0.52, 90.05, and 8.38 % for ·OH, (1)O2, and (3)GEM(*), respectively. Singlet oxygen ((1)O2) was evidenced by the molecular probe compound, furfuryl alcohol (FFA), and was identified as the primary reactive species in the photolytic process. The steady-state concentrations of (1)O2 increased from (0.324 ± 0.014) × 10(-12) to (1.021 ± 0.040) × 10(-12) mol L(-1), as the initial concentrations of GEM were increased from 5 to 20 mg L(-1). The second-order rate constant for the reaction of GEM with (1)O2 was calculated to be 2.55 × 10(6) M(-1) s(-1). The primary transformation products were identified using HPLC-MS/MS, and possible photodegradation pathways were proposed by hydroxylation, aldehydes reactions, as well as the cleavage of ether side chains. The toxicity of phototransformation product evaluation revealed that photolysis potentially provides a critical pathway for GEM toxicity reduction in potable water and wastewater treatment facilities.

Oxidative stress, energy storage, and swimming performance of Limnodynastes peronii tadpoles exposed to a sub-lethal pharmaceutical mixture throughout development

Pharmaceutical contaminants represent emerging threats to aquatic animals and ecosystem health, and research exploring toxicological outcomes associated with these compounds in non-target wildlife has been flagged for prioritization. Amphibians represent particularly vulnerable organisms and many populations around the world are currently at risk of extinction. However, to date, relatively few studies have explored the consequences of exposures to common non-steroidal pharmaceuticals during sensitive amphibian life-stages. To address existing knowledge gaps, tadpoles of the Australian striped-marsh frog (Limnodynastes peronii) were exposed to control water and a mixture of the common pharmaceutical contaminants diclofenac, naproxen, atenolol and gemfibrozil at 0.1, 1, 10, 100 and 1000 μg/L throughout the developmental period. Effects on detoxification pathways, energy storage, growth and development, and swimming performance were assessed following exposure. Developmental rates and liver-somatic index (LSI) were significantly reduced in the highest exposure concentration, and condition factor (K) was increased at concentrations as low as 10 μg/L. Morphological endpoints were associated with significantly altered levels of hepatic triglycerides, which in turn were correlated with increased peroxidase activity in animals exposed to the highest concentration (1000 μg/L). The mixture had no significant effect on swimming performance, but a trend of decreased swimming velocity (average and maximum) was observed with increasing concentration, and this was correlated with effects on LSI. Results demonstrate that mixtures of common non-steroidal pharmaceuticals can elicit a range of physiological, metabolic and morphological responses in larval amphibians, and more research is therefore warranted to explore possible relationships between endpoints at different levels of organization.

Effects of the lipid regulator drug gemfibrozil: A toxicological and behavioral perspective

Pharmaceuticals are emerging contaminants as their worldwide consumption increases. Fibrates such as gemfibrozil (GEM) are used in human medicine to reduce blood concentrations of cholesterol and triacylglycerol and also are some of the most frequently reported pharmaceuticals in waste waters and surface waters. Despite some studies have already demonstrated the negative impact in physiological and/or reproductive endpoints in adult fish, data on survival and behavioral effects in fish larvae are lacking. This study aimed to assess the effects of GEM on zebrafish eleutheroembryo development and locomotor behavior. A fish embryo toxicity (FET) test was undertaken to evaluate GEM acute toxicity by exposing embryos to 0, 6.58, 9.87, 14.81, 22.22, 33.33 and 50mg/L. Developmental endpoints such as hatching success, edemas and malformations were recorded. A second test was undertaken by exposing embryos to 0, 1.5, 3 and 6mg/L in order to evaluate the effects of GEM on 120 and 144h post fertilization (hpf) larvae locomotor activity by video tracking, using a Zebrabox(®) (Viewpoint, France) device. From the data recorded, several parameters such as total swimming distance (TSD) and total swimming time (TST) in each 120s integration time were calculated. Data showed that this compound has a moderate toxic effect on fish embryo development, affecting both survival and hatching success with a calculated 96h LC50 of 11.01mg/L and no effects at the developmental level at 6mg/L. GEM seems to impair locomotor activity, even at concentrations where developmental abnormalities were unperceived, at concentrations as low as 1.5mg/L. Both TSD and TST were sensitive to GEM exposure. These effects do not seem to be independent of the developmental stage as 120hpf larvae seem to present a development bias with repercussions in locomotor behavior. This study highlights the need to include behavioral endpoints in ecotoxicological assays as this seems to be a more sensitive endpoint often disregarded.

Leveraging existing data for prioritization of the ecological risks of human and veterinary pharmaceuticals to aquatic organisms

Medicinal innovation has led to the discovery and use of thousands of human and veterinary drugs. With this comes the potential for unintended effects on non-target organisms exposed to pharmaceuticals inevitably entering the environment. The impracticality of generating whole-organism chronic toxicity data representative of all species in the environment has necessitated prioritization of drugs for focused empirical testing as well as field monitoring. Current prioritization strategies typically emphasize likelihood for exposure (i.e. predicted/measured environmental concentrations), while incorporating only rather limited consideration of potential effects of the drug to non-target organisms. However, substantial mammalian pharmacokinetic and mechanism/mode of action (MOA) data are produced during drug development to understand drug target specificity and efficacy for intended consumers. An integrated prioritization strategy for assessing risks of human and veterinary drugs would leverage available pharmacokinetic and toxicokinetic data for evaluation of the potential for adverse effects to non-target organisms. In this reiview, we demonstrate the utility of read-across approaches to leverage mammalian absorption, distribution, metabolism and elimination data; analyse cross-species molecular target conservation and translate therapeutic MOA to an adverse outcome pathway(s) relevant to aquatic organisms as a means to inform prioritization of drugs for focused toxicity testing and environmental monitoring.

Effects of pharmaceuticals present in aquatic environment on Phase I metabolism in fish

The fate of pharmaceuticals in aquatic environments is an issue of concern. Current evidence indicates that the risks to fish greatly depend on the nature and concentrations of the pharmaceuticals and might be species-specific. Assessment of risks associated with the presence of pharmaceuticals in water is hindered by an incomplete understanding of the metabolism of these pharmaceuticals in aquatic species. In mammals and fish, pharmaceuticals are primarily metabolized by cytochrome P450 enzymes (CYP450). Thus, CYP450 activity is a crucial factor determining the detoxification abilities of organisms. Massive numbers of toxicological studies have investigated the interactions of human pharmaceuticals with detoxification systems in various fish species. In this paper, we review the effects of pharmaceuticals found in aquatic environments on fish hepatic CYP450. Moreover, we discuss the roles of nuclear receptors in cellular regulation and the effects of various groups of chemicals on fish, presented in the recent literature.

Pharmaceuticals and personal care products: A critical review of the impacts on fish reproduction

Research in environmental toxicology involving pharmaceuticals and personal care products (PPCPs) has increased greatly over the last 10-15 years. Much research has been focused on the endocrine-disrupting potential of PPCPs, as they relate to negative population impacts of aquatic organisms. This review assesses the current data on the reported effects of PPCPs on fish reproduction with an emphasis on fecundity, a predictor of population effects. Studies of both individual PPCPs and PPCP mixtures are presented. As the majority of individual PPCP studies reviewed demonstrate negative effects on fish fecundity, we relate these findings to detected surface water concentrations of these compounds. Very few studies involving PPCP mixtures have been conducted; however, the need for these types of studies is warranted as fish are most likely exposed to mixtures of PPCPs in the wild. In addition, laboratory and field assessments of wastewater treatment plant (WWTP) effluents, a major source of PPCPs, are reviewed. Much of the data provided from these assessments are variable and do not generally demonstrate negative impacts on reproduction, or the studies are unable to directly associate observed effects with WWTP effluents. Finally, future research considerations are outlined to provide an avenue into understanding how wild populations of fish are affected by PPCPs. These considerations are aimed at determining the adaptation potential of fish exposed to mixtures of PPCPs over multiple generations. As global use of PPCPs continually rises, the need to discern the effects of chronic exposure to PPCPs is greatly increased.

Effects of lipid-lowering pharmaceutical clofibrate on lipid and lipoprotein metabolism of grass carp (Ctenopharyngodon idellal Val.) fed with the high non-protein energy diets

This study investigated the effects of clofibrate treatment on blood lipids, hepatic enzyme activities and relative expression of genes involved in lipid metabolism of grass carp fed with high non-protein energy diets. For that purpose, five diets were formulated: a commercial-like diet (Control), a high-carbohydrate diet (HC), a high-fat diet (HF) and two diets identical to the HC and HF diets, but supplemented with 1.25 g kg(-1) clofibrate (HC + Clo and HF + Clo diets). Grass carp fed the HC and HF diet exhibited increases in blood lipids and body fat compared with the control group after 4 weeks. In the clofibrate treatment groups, there was a marked decrease in triacylglycerol and cholesterol concentrations of plasma, and total lipids of the whole body, mesentery adipose tissue and liver tissue. Fish treated with clofibrate exhibited increased hepatic acyl-CoA oxidase activity, but did not show any changes in carnitine palmitoyltransferase (CPT) I activity compared with HC and HF diets without clofibrate. Clofibrate treatment had no effect on peroxisome proliferator-activated receptor alpha and CPT I mRNA expression. However, there was an increase in lipoprotein lipase expression in the clofibrate-treated groups. In addition, the relative mRNA expression levels of hepatic de novo lipogenic enzymes (fatty acid synthetase and acetyl coenzyme-A carboxylase) were significantly higher in the fish fed the HC diet than those of other groups, and clofibrate inhibited this increase. These results suggest that clofibrate has the hypolipidaemic effects and affects lipid metabolism in grass carp.

Metformin exposure at environmentally relevant concentrations causes potential endocrine disruption in adult male fish

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants that have been found ubiquitously in wastewater and surface waters around the world. A major source of these compounds is incomplete metabolism in humans and subsequent excretion in human waste, resulting in discharge into surface waters by wastewater treatment plant (WWTP) effluent. One pharmaceutical found in particularly high abundance in recent WWTP effluent and surface water studies is metformin, one of the world's most widely prescribed antidiabetic drugs. Interactions between insulin signaling and steroidogenesis suggest potential endocrine-disrupting effects of metformin found in the aquatic environment. Adult fathead minnows (Pimephales promelas) were chronically exposed to metformin for 4 wk, at 40 µg/L, a level similar to the average found in WWTP effluent in Milwaukee, Wisconsin, USA. Genetic endpoints related to metabolism and endocrine function as well as reproduction-related endpoints were examined. Metformin treatment induced significant up-regulation of messenger ribonucleic acid (mRNA) encoding the egg-protein vitellogenin in male fish, an indication of endocrine disruption. The present study, the first to study the effects of environmentally relevant metformin exposure in fathead minnows, demonstrates the need for further study of the endocrine-disrupting effects of metformin in aquatic organisms.

Development of mediator-type biosensor to wirelessly monitor whole cholesterol concentration in fish

We developed a wireless monitoring system to monitor fish condition by tracking the change in whole cholesterol concentration. The whole cholesterol concentration of fish is a source of steroid hormones or indicator of immunity level, which makes its detection important for tracking physiological condition of fish. Wireless monitoring system comprises of mediator-type biosensor and wireless transmission device. Biosensor is implantable to fish body, and transmission device is so light, in that fish is allowed to swim freely during monitoring. Cholesterol esterase and oxidase were fixated on to the detection site of biosensor and used to detect the whole cholesterol concentration. However, cholesterol oxidase incorporates oxidation-reduction reaction of oxygen for detection, which concentration fluctuates easily due to change in environmental condition. Meanwhile, mediator-type biosensor enables monitoring of whole cholesterol concentration by using mediator to substitute that oxidation-reduction reaction of oxygen. Characteristic of fabricated mediator-type biosensor was tested. The sensor output current of mediator-type biosensor remained stable compared to output current of non-mediator-type biosensor under fluctuating oxygen concentration of 0-8 ppm, which implied that this sensor is less affected by change in dissolved oxygen concentration. That biosensor was then implanted into fish for wireless monitoring. As a result, approximately 48 h of real-time monitoring was successful.

Effects of triclocarban, N,N-diethyl-meta-toluamide, and a mixture of pharmaceuticals and personal care products on fathead minnows (Pimephales promelas)

Pharmaceuticals and personal care products (PPCPs) have been detected widely in aquatic ecosystems, but little is known about their mechanisms of toxicity. We exposed adult fathead minnows (Pimephales promelas) for 48 h to triclocarban (1.4 µg/L), N,N-diethyl-meta-toluamide (DEET; 0.6 µg/L), or a mixture of PPCPs consisting of atenolol (1.5 µg/L), caffeine (0.25 µg/L), diphenhydramine (0.1 µg/L), gemfibrozil (1.5 µg/L), ibuprofen (0.4 µg/L), naproxen (1.6 µg/L), triclosan (2.3 µg/L), progesterone (0.2 µg/L), triclocarban (1.4 µg/L), and DEET (0.6 µg/L). Quantitative real-time polymerase chain reaction revealed an upregulation in vitellogenin (vtg) in livers of females and males exposed to triclocarban. Also, an upregulation of hepatic lipoprotein lipase (lpl) and a downregulation of androgen receptor (ar) and steroidogenic acute regulatory protein (star) were observed in testes. The group treated with DEET only showed a significant decrease in ar in females. In contrast, the PPCP mixture downregulated vtg in females and males and expression of estrogen receptor alpha (erα), star, and thyroid hormone receptor alpha 1 (thra1) in testes. The authors' results show that the molecular estrogenic effects of triclocarban are eliminated (males) or reversed (females) when dosed in conjunction with several other PPCP, once again demonstrating that results from single exposures could be vastly different from those observed with mixtures. Environ Toxicol Chem 2014;33:910-919. © 2013 SETAC.

Gemfibrozil modulates cytochrome P450 and peroxisome proliferation-inducible enzymes in the liver of the yellow European eel (Anguilla anguilla)

The human lipid regulator gemfibrozil (GEM) has been shown to induce peroxisome proliferation in rodents leading to hepatocarcinogenesis. Since GEM is found at biological active concentrations in the aquatic environment, the present study investigates the effects of this drug on the yellow European eel (Anguilla anguilla). Eels were injected with different concentrations of GEM (0.1 to 200 μg/g) and sampled 24- and 96-h post-injection. GEM was shown to inhibit CYP1A, CYP3A and CYP2K-like catalytic activities 24-h post-injection, but at 96-h post-injection, only CYP1A was significantly altered in fish injected with the highest GEM dose. On the contrary, GEM had little effect on the phase II enzymes examined (UDP-glucuronyltransferase and glutathione-S-transferase). Peroxisome proliferation inducible enzymes (liver peroxisomal acyl-CoA oxidase and catalase) were very weakly induced. No evidence of a significant effect on the endocrine system of eels was observed in terms of plasmatic steroid levels or testosterone esterification in the liver.

A new approach for the laboratory culture of the fathead minnow, Pimephales promelas

Fathead minnows are routinely cultured for use in aquatic toxicology studies. A new mass culture system described in the present study consisted of 6 stainless steel tanks, each containing 68 fish and 20 spawning substrates. Spawning results are compared with a previous system of 22 individual glass aquaria, which contained 16 fish and 4 spawning substrates per tank. During a 19-mo period, the new system produced an average of 4105 eggs/d, compared with an average of 2465 eggs/d with the previous system. Labor and maintenance were reduced with the new system. The stainless steel tanks eliminated aquaria glass breakage, and daily water use was reduced by 45%. Analysis of reference toxicant data from fish cultured using both systems indicated no change in the sensitivity of the test animals. Analyses of 2009 egg production data determined that a 6:1 to 7:1 female to male ratio had a significantly positive impact on egg production levels and that 6-mo-old breeding stock should be introduced to the spawning tanks in mid-spring for optimal egg production during the rest of the year. Implementing a stainless steel mass culture system significantly increased efficiency of egg production; reduced turnaround delay of mature animal availability for toxicity and molecular testing; and reduced labor time, costs, and inherent safety hazards, compared with glass aquaria systems.

The read-across hypothesis and environmental risk assessment of pharmaceuticals

Pharmaceuticals in the environment have received increased attention over the past decade, as they are ubiquitous in rivers and waterways. Concentrations are in sub-ng to low μg/L, well below acute toxic levels, but there are uncertainties regarding the effects of chronic exposures and there is a need to prioritise which pharmaceuticals may be of concern. The read-across hypothesis stipulates that a drug will have an effect in non-target organisms only if the molecular targets such as receptors and enzymes have been conserved, resulting in a (specific) pharmacological effect only if plasma concentrations are similar to human therapeutic concentrations. If this holds true for different classes of pharmaceuticals, it should be possible to predict the potential environmental impact from information obtained during the drug development process. This paper critically reviews the evidence for read-across, and finds that few studies include plasma concentrations and mode of action based effects. Thus, despite a large number of apparently relevant papers and a general acceptance of the hypothesis, there is an absence of documented evidence. There is a need for large-scale studies to generate robust data for testing the read-across hypothesis and developing predictive models, the only feasible approach to protecting the environment.

Gene expression of fathead minnows (Pimephales promelas) exposed to two types of treated municipal wastewater effluents

Contaminants of emerging concern (CECs) in treated municipal effluents have the potential to adversely impact exposed organisms prompting elevated public concern. Using transcriptomic tools, we investigated changes in gene expression and cellular pathways in the liver of male fathead minnows (Pimephales promelas) exposed to 5% concentrations of full secondary-treated (HTP) or advanced primary-treated (PL) municipal wastewater effluents containing CECs. Gene expression changes were associated with apical end points (plasma vitellogenin and changes in secondary sexual characteristics). Of 32 effluent CECs analyzed, 28 were detected including pharmaceuticals, personal care products, hormones, and industrial compounds. Exposure to both effluents produced significantly higher levels of plasma VTG and changes in secondary sexual characteristics (e.g., ovipositor development). Transcript patterns differed between effluents, with <10% agreement in the detected response (e.g., altered production of transcripts involved in xenobiotic detoxification, oxidative stress, and apoptosis were observed following exposure to both effluents). Exposure to PL effluent caused changes in transcription of genes involved in metabolic pathways (e.g., lipid transport and steroid metabolism). Exposure to HTP effluent affected transcripts involved in signaling pathways (e.g., focal adhesion assembly and extracellular matrix). The results suggest a potential association between some transcriptomic changes and physiological responses following effluent exposure. This study identified responses in pathways not previously implicated in exposure to complex chemical mixtures containing CECs, which are consistent with effluent exposure (e.g., oxidative stress) in addition to other pathway responses specific to the effluent type.

Propiconazole inhibits steroidogenesis and reproduction in the fathead minnow (Pimephales promelas)

Conazoles are designed to inhibit cytochrome P450 (CYP) 14α-demethylase, an enzyme key to fungal cell wall formation. In vertebrates, conazoles may inhibit other CYPs, potentially disrupting processes like sex steroid synthesis. Propiconazole is a current-use pesticide that is among the first chemicals being tested in the U.S. Environmental Protection Agency endocrine disruptor screening program. Fathead minnows (Pimephales promelas) were exposed to 0, 5, 50, 500, or 1000 µg propiconazole/l in a 21-day study that evaluated apical reproductive endpoints (fecundity, fertility, hatch); measures of endocrine function and steroid synthesis, such as cholesterol, vitellogenin (VTG), and sex steroid (testosterone [T], 17β-estradiol [E2]) concentrations in the plasma; and changes in gonadal expression of steroidogenic genes. Plasma E2 and VTG concentrations in females were reduced by exposure to propiconazole, and egg production was decreased in the 500 and 1000 µg/l treatment groups. These in vivo effects coincided with inhibition of E2 synthesis by ovary explants exposed to propiconazole in vitro. We also observed a compensatory response in females exposed to propiconazole, manifested as increased gonad weight and upregulation of genes coding for key steriodogenic proteins, including CYP19 (aromatase), CYP17 (hydroxylase/lyase), CYP11A (cholesterol side-chain-cleavage), and steroidogenic acute regulatory protein. Other than an increase in relative testis weight, effects on endocrine function in males were less pronounced than in females. This study provides important data relative to the potential endocrine activity of propiconazole in fish and, more generally, to the further delineation of pathways for the reproductive effects of steroid synthesis inhibitors in fish.