Pharmacodynamic activity of drugs and ecotoxicology--can the two be connected?

Towards Precision Ecotoxicology: Leveraging Evolutionary Conservation of Pharmaceutical and Personal Care Product Targets to Understand Adverse Outcomes Across Species and Life Stages

Translation of environmental science to the practice aims to protect biodiversity and ecosystem services, and our future ability to do so relies on the development of a precision ecotoxicology approach wherein we leverage the genetics and informatics of species to better understand and manage the risks of global pollution. A little over a decade ago, a workshop focusing on the risks of pharmaceuticals and personal care products (PPCPs) in the environment identified a priority research question, "What can be learned about the evolutionary conservation of PPCP targets across species and life stages in the context of potential adverse outcomes and effects?" We review the activities in this area over the past decade, consider prospects of more recent developments, and identify future research needs to develop next-generation approaches for PPCPs and other global chemicals and waste challenges. Environ Toxicol Chem 2024;43:526-536. © 2023 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Evidence for Specific Receptor-Mediated Toxicity of Pharmaceuticals in Aquatic Organisms Derived from Acute and Chronic Standard Endpoints

The toxicity of 17 active pharmaceutical ingredients (APIs) was investigated using standardized acute and chronic tests with Daphnia magna and 2 algae species. Chronic toxicity was generally greater for Daphnia than for algae. Compilation of additional data resulted in 100 APIs for which the acute-to-chronic ratio (ACR) was determined for Daphnia. The frequency of high ACRs (~20% with ACRs > 100) indicates that specific receptor-mediated toxicity toward D. magna is rather common among APIs. The 11 APIs with ACRs > 1000 included lipid-modifying agents, immunosuppressants, antibiotics, antineoplastics, antiobesics, antivirals, and antihistamines. There was no consistent association between ACR and chronic toxicity, ionization status, or lipophilicity. High ACRs were not exclusively associated with the presence of orthologs of the pharmacological target in Daphnia. Statins, acetylcholinesterase inhibitors, and antihistamines are discussed in more detail regarding the link between targets and toxic mode of action. For acetylcholinesterase inhibitors, receptor-mediated toxicity was already apparent after acute exposure, whereas the high ACR and chronic toxicity of some antihistamines probably related to interaction with a secondary rather than the primary pharmacological target. Acute or modeled chronic toxicity estimates have often been used for prioritizing pharmaceuticals. This may be seriously misleading because chronic effects are currently not predictable for APIs with specific receptor-mediated toxicity. However, it is exactly these APIs that are the most relevant in terms of environmental risks. Environ Toxicol Chem 2022;41:601-613. © 2021 SETAC.

Lethal and Sub-Lethal Effects and Modulation of Gene Expression Induced by T Kinase Inhibitors in Zebrafish (Danio Rerio) Embryos

Tyrosine kinase inhibitors (TKIs) are designed for targeted cancer therapy. The consumption of these drugs during the last 20 years has been constantly rising. In the zebrafish (Danio rerio) embryo toxicity test, we assessed the toxicity of six TKIs: imatinib mesylate, erlotinib, nilotinib, dasatinib, sorafenib and regorafenib. Imatinib mesylate and dasatinib induced lethal effects, while regorafenib, sorfenib and dasatinib caused a significant increase of sub-lethal effects, predominantly oedema, no blood circulation and formation of blood aggregates. The analyses of the changes in the expression of selected genes associated with the hormone system after the exposure to imatinib mesylate, dasatinib and regorafenib demonstrated that all three tested TKIs deregulated the expression of oestrogen receptor esr1, cytochrome P450 aromatase (cypa19b) and hydroxysteroid-dehydrogenase (hsd3b), regorafenib, and also thyroglobulin (tg). The expression of genes involved in the DNA damage response (gadd45 and mcm6) and apoptosis (bcl2) was deregulated only by exposure to regorafenib. The data indicate that common mechanisms, namely antiangiogenic activity and interference with steroidogenesis are involved in the TKI induced sub-lethal effects and potential hormone disrupting activity, respectively. The residues of TKIs may represent an environmental hazard; therefore, further ecotoxicological studies focusing also on the effects of their mixtures are warranted.

Performance Comparison between the Specific and Baseline Prediction Models of Ecotoxicity for Pharmaceuticals: Is a Specific QSAR Model Inevitable?

Assessing the ecotoxicity of pharmaceuticals is of urgent need due to the recognition of their possible adverse effects on nontarget organisms in the aquatic environment. The reality of ecotoxicity data scarcity promotes the development and application of quantitative structure activity relationship (QSAR) models. In the present study, we aimed to clarify whether a QSAR model of ecotoxicity specifically for pharmaceuticals is needed considering that pharmaceuticals are a class of chemicals with complex structures, multiple functional groups, and reactive properties. To this end, we conducted a performance comparison of two previously developed and validated QSAR models specifically for pharmaceuticals with the commonly used narcosis toxicity prediction model, i.e., Ecological Structure Activity Relationship (ECOSAR), using a subset of pharmaceuticals produced in China that had not been included in the training datasets of QSAR models under consideration. A variety of statistical measures demonstrated that the pharmaceutical specific model outperformed ECOSAR, indicating the necessity of developing a specific QSAR model of ecotoxicity for the active pharmaceutical contaminants. ECOSAR, which was generally used to predict the baseline or the minimum toxicity of a compound, generally underestimated the ecotoxicity of the analyzed pharmaceuticals. This could possibly be because some pharmaceuticals can react through specific modes of action. Nonetheless, it should be noted that 95% prediction intervals spread over approximately four orders of magnitude for both tested QSAR models specifically for pharmaceuticals.

Environmental risk assessment of psychoactive drugs in the aquatic environment

The consumption of psychoactive pharmaceuticals has increased worldwide, and wastewater treatment plants are not able to eliminate them from the effluent. An extensive review was carried out to assess the environmental risk (ERA model) based on secondary data about potential impacts on non-target organisms of seven psychoactive drugs consumed worldwide (alprazolam, bromazepam, citalopram, clonazepam, diazepam, lorazepam, and oxazepam). Risk quotients (RQs) were calculated according to the European Medicines Agency (EMA) on ERA of Medicinal Products For Human Use based on (i) the predicted and measured environmental concentrations (PEC and MEC, respectively) of the psychoactive drug in surface water, groundwater, and wastewater effluent and (ii) the predicted no-effect concentration (PNEC) derived from ecotoxicological assays or ECOSAR software. Furthermore, this study reviews and discusses non-standardized ecotoxicity assays, such as sublethal and behavioral effects on different organisms. In total, 903 MEC entries of psychoactive drugs and 162 data on ecotoxicological assays were gathered from the literature survey addressing behavioral effects (115), acute/chronic effects (35), and sublethal effects (12). Citalopram and diazepam were the only substances that are likely to pose an environmental risk (RQ > 1) to surface waters. Even though there is considerable amount of data on behavioral effects of psychoactive drugs to aquatic species, results are currently not integrated into the EMA risk assessment framework. The large amount of data on psychoactive drug concentrations and effects on non-target organisms collected, interpreted, and discussed in the present study should be used as a baseline for future improvement of ERA strategies.

Bioaccumulation and tissue distribution of antibiotics in wild marine fish from Laizhou Bay, North China

Information about bioaccumulation and tissue distribution of antibiotics in wild marine fish is still limited. In the present study, tissue levels, bioaccumulation and distribution patterns of 9 sulfonamide (SA), trimethoprim (TMP), 5 fluoroquinolone (FQ), and 4 macrolide (ML) antibiotics were investigated in gill, muscle, kidney, and liver tissues of seven wild fish species collected from Laizhou Bay, North China in 2016. All the 19 antibiotics were detected in these fish tissues with the total concentrations ranging from 22ng/g dry weight (dw) to 500ng/g dw. The mean values of logarithm bioaccumulation factors (BAFs) in the gills, muscles, kidneys, and livers ranged from 2.2 to 4.8, 1.9 to 4.0, 2.5 to 4.9, and 2.5 to 5.4, respectively. Log BAFs of antibiotics in these tissues significantly increased (r=0.61-0.77, p<0.001) with their logarithm values of liposome-water distribution coefficient (D_lipw) except in the muscles, suggesting that D_lipw can well assess the bioaccumulation potentials of antibiotics in phospholipid-rich tissues. In general, the SAs, TMP, and FQs were primarily accumulated in the muscles and the MLs were primarily in the livers, which may be related to their toxicokinetic processes of these marine fish. The present study for the first time reported the tissue distribution patterns of antibiotics in wild marine fish.

Differential sensitivity to the antifouling chemical medetomidine between wood frog and American toad tadpoles with evidence for low-dose stimulation and high-dose inhibition of metamorphosis

Antifouling chemicals are legacy contaminants in aquatic ecosystems. Previous experiments have shown that a 14-day exposure to the antifouling chemical medetomidine delays metamorphosis and reduces body mass in wood frog tadpoles. In the present study, we exposed wood frog tadpoles to medetomidine for 3, 7, and 10 days at 100 nM, 1 μM, and 10 μM. We also exposed American toad tadpoles to medetomidine for 3 days at four concentrations (10 nM, 100 nM, 1 μM, and 10 μM) in static renewal experiments. In each experiment, we measured growth, frequency and time to metamorphosis, and mass at metamorphosis. In both species, medetomidine significantly slowed development as measured by the Gosner stage. After 34 days in culture, wood frog tadpoles exposed to 1 and 10 μM medetomidine for as few as 3 days were significantly less developed compared to controls. Toads exposed to 1 μM medetomidine for 3 days were also significantly less developed on day 27, but by day 34, there was no difference from controls. For wood frogs, medetomidine significantly affected time to metamorphosis with a trend for tadpoles at lower concentrations metamorphosing sooner than those at higher concentrations. While medetomidine affected time to metamorphosis in wood frogs, it did not affect fresh mass, dry mass, or mortality compared to controls. Wood frog tadpoles that did not metamorphose after over 90 days in culture were more frequent in high-concentration groups than in the control. In toads, 10 μM medetomidine was 100% lethal within 23 days, but at the same concentration and duration, no wood frog tadpoles died. Lower concentrations were also significantly lethal to toads compared to controls, but tadpoles that survived in 10 and 100 nM metamorphosed sooner than those in 1 μM. Fresh mass of toad tadpoles exposed to 1 μm was significantly smaller at metamorphosis compared to that of controls. Medetomidine also affected the behavior of tadpoles. In toads, medetomidine significantly reduced both percent activity and startle response. In wood frogs, medetomidine significantly reduced percent activity, but increased startle response. We discuss our finding of low-dose stimulation and high-dose inhibition of different life history endpoints in terms of hormetic mechanisms. The differential sensitivity between species in terms of mortality, frequency of metamorphosis, and behavior highlights the potential negative environmental effects of medetomidine to amphibians.

Spatial patterns of pharmaceuticals and wastewater tracers in the Hudson River Estuary

The widespread use of pharmaceuticals by human populations results in their sustained discharge to surface waters via wastewater treatment plants (WWTPs). In this study, 16 highly prescribed pharmaceuticals were quantified along a 250 km transect of the Hudson River Estuary and New York Harbor to describe their sources and spatial patterns. Sampling was conducted over two dry weather periods in May and July 2016, at 72 sites which included mid-channel and nearshore sites, as well as locations influenced by tributaries and WWTP outfalls. The detection frequency of the study pharmaceuticals was almost identical between the May and July sampling periods at 55% and 52%, respectively. Six pharmaceuticals were measurable at 92% or more of the sites during both sampling periods, illustrating their ubiquitous presence throughout the study area. Individual pharmaceutical concentrations were highly variable spatially, ranging from non-detect to 3810 ng/L during the study. Major factors controlling concentrations were proximity and magnitude of WWTP discharges, inputs from tributaries and tidal mixing. Two compounds, sucralose and caffeine, were evaluated as tracers to identify wastewater sources and assess pharmaceutical behavior. Sucralose was useful in identifying wastewater inputs to the river and concentrations showed excellent correlations with numerous pharmaceuticals in the study. Caffeine-sucralose ratios showed potential in identifying discharges of untreated wastewater occurring during a combined sewage overflow event. Many of the study pharmaceuticals were present throughout the Hudson River Estuary as a consequence of sustained wastewater discharge. Whereas some concentrations were above published effects levels, a more complete risk assessment is needed to understand the potential for ecological impacts due to pharmaceuticals in the Hudson River Estuary.

Derivation of aquatic predicted no-effect concentration (PNEC) for ibuprofen and sulfamethoxazole based on various toxicity endpoints and the associated risks

For pharmaceuticals, the ecological risk assessment based on traditional endpoints of toxicity could not be properly protective in the long run since the mode of action could vary because they are intended for different therapeutic uses. In this study, the predicted no-effect concentrations (PNECs) of two selected pharmaceuticals, ibuprofen (IBU) and sulfamethoxazole (SMX), were derived based on either traditional endpoints of survival and growth data or some nonlethal endpoints such as reproduction, biochemical and molecular data. The PNECs of IBU based on biochemical-cellular and reproduction data were 0.018 and 0.026 μg L^-1 that were significantly lower than those derived from other endpoints, while the lowest PNEC for SMX derived from growth data with the concentration of 0.89 μg L^-1. Ecological risk assessment was performed for IBU and SMX to the aquatic environment by applying hazard quotient and probabilistic distribution based quotient (DBQs) methods. The results showed that the probability of DBQs of IBU exceeding 0.1 was 11.2%, while for SMX the probability was 0.9% that could be neglected.

Urbanization, environment and pharmaceuticals: advancing comparative physiology, pharmacology and toxicology

Pharmaceuticals are routinely reported in the environment, which indicates an increasingly urban water cycle and highlights a global megatrend. Physicochemical properties and intrinsic biological activity of medicines routinely differ from conventional organic contaminants; thus, diverging applicability domains often challenge environmental chemistry and toxicology computational tools and biological assays originally developed to address historical chemical stressors. Because pharmacology and toxicology information is more readily available for these contaminants of emerging concern than other chemicals in the environment, and many drug targets are conserved across species, leveraging mammalian drug discovery, safety testing and clinical pharmacology information appears useful to define environmental risks and to design less hazardous industrial chemicals. Research is needed to advance biological read across, which promises to reduce uncertainties during chemical assessment aimed at protecting public health and the environment. Whereas such comparative information has been critical to advance an understanding of pharmaceutical hazards and risks in urban ecosystems, studies of medicines with fish and other ecotoxicological models are reciprocally benefiting basic and translational efforts, advancing comparative mechanistic toxicology, and providing robust comparative bridges for integrating conservation and toxicology.

Impact of Pharmaceuticals on the Environment: Risk Assessment Using QSAR Modeling Approach

An extensive use of pharmaceuticals and the widespread practices of their erroneous disposal measures have made these products contaminants of emerging concern (CEC). Especially, active pharmaceutical ingredients (APIs) are ubiquitously detected in surface water and soil, mainly in the aquatic compartment, where they do affect the living systems. Unfortunately, there is a huge gap in the availability of ecotoxicological data on pharmaceuticals' environmental behavior and ecotoxicity which force EMEA (European Medicines Agency) to release guidelines for their risk assessment. In silico modeling approaches are vital tools to exploit the existing information to rapidly emphasize the potentially most hazardous and toxic pharmaceuticals and prioritize the most environmentally hazardous ones for focusing further on their experimental studies. The quantitative structure-activity relationship (QSAR) models are capable of predicting missing properties for toxic end-points required to prioritize existing, or newly synthesized chemicals for their potential hazard. This chapter reviews the information regarding occurrence and impact of pharmaceuticals and their metabolites in the environment along with their persistence, environmental fate, risk assessment, and risk management. A bird's eye view about the necessity of in silico methods for fate prediction of pharmaceuticals in the environment as well as existing successful models regarding ecotoxicity of pharmaceuticals are discussed. Available toxicity endpoints, ecotoxicity databases, and expert systems frequently used for ecotoxicity predictions of pharmaceuticals are also reported. The overall discussion justifies the requirement to build up additional in silico models for quick prediction of ecotoxicity of pharmaceuticals economically, without or involving only limited animal testing.

Prozac in the water: Chronic fluoxetine exposure and predation risk interact to shape behaviors in an estuarine crab

Predators exert considerable top-down pressure on ecosystems by directly consuming prey or indirectly influencing their foraging behaviors and habitat use. Prey is, therefore, forced to balance predation risk with resource reward. A growing list of anthropogenic stressors such as rising temperatures and ocean acidification has been shown to influence prey risk behaviors and subsequently alter important ecosystem processes. Yet, limited attention has been paid to the effects of chronic pharmaceutical exposure on risk behavior or as an ecological stressor, despite widespread detection and persistence of these contaminants in aquatic environments. In the laboratory, we simulated estuarine conditions of the shore crab, Hemigrapsus oregonensis, and investigated whether chronic exposure (60 days) to field-detected concentrations (0, 3, and 30 ng/L) of the antidepressant fluoxetine affected diurnal and nocturnal risk behaviors in the presence of a predator, Cancer productus. We found that exposure to fluoxetine influenced both diurnal and nocturnal prey risk behaviors by increasing foraging and locomotor activity in the presence of predators, particularly during the day when these crabs normally stay hidden. Crabs exposed to fluoxetine were also more aggressive, with a higher frequency of agonistic interactions and increased mortality due to conflicts with conspecifics. These results suggest that exposure to field-detected concentrations of fluoxetine may alter the trade-off between resource acquisition and predation risk among crabs in estuaries. This fills an important data gap, highlighting how intra- and interspecific behaviors are altered by exposure to field concentrations of pharmaceuticals; such data more explicitly identify potential ecological impacts of emerging contaminants on aquatic ecosystems and can aid water quality management.

Occurrence of enrofloxacin in overflows from animal lot and residential sewage lagoons and a receiving-stream

Enrofloxacin (ENRO), a fluoroquinolone, was quantified in overflows from an animal lot and residential sewage lagoons and in a receiving-stream (Gans Creek). The concentrations of ENRO in samples was determined by high-performance liquid chromatography - tandem mass spectrometry. In total, ninety samples including duplicates were analyzed during several monthly sampling campaigns. The samples collected represented the residential sewage lagoon overflow (RLO), animal lot lagoon overflow (ALLO), the combined overflows (RLO and ALLO), and Gans Creek (upstream, midstream and downstream positions). The frequency of detection of ENRO was 90% for RLO and 100% for both ALLO and Gans Creek. The highest concentration of ENRO (0.44 μg/L) was found in ALLO sample collected during high precipitation. ENRO levels found in RLO samples ranged from < LOQ to 259 ng/L and the highest value observed also coincided with high flow. The levels of ENRO found in Gans Creek ranged from 17-216 ng/L. A preliminary ecotoxicological assessment was conducted through calculation of the risk quotients (RQs) for organisms based on the ratio of the measured environmental concentrations in this study to the predicted-no-effect-concentrations (acute and chronic effect) data. From the RQs, high risks were observed for Microcystis aeruginosa (cyanobacteria; RQ = 4.4); Anabaena flosaquae (cyanobacteria; RQ = 1.3); and Lemna minor (aquatic vascular plant; RQ = 2.0). The long-term effects of mixtures of PHCs on Gans Creek watershed are probable.

Effects of trimethoprim on life history parameters, oxidative stress, and the expression of cytochrome P450 genes in the copepod Tigriopus japonicus

Trimethoprim (TMP) is an antibiotic that has been detected in various environments including marine habitats; however, the toxic effects of TMP are poorly understood in non-target marine organisms. In this study, the effects of TMP on mortality, development, reproduction, intracellular reactive oxygen species (ROS) levels, and transcription levels of antioxidant and xenobiotic detoxification-related enzyme genes were investigated in the copepod Tigriopus japonicus. The TMP half lethal dose at 48 h (LC50-48 h) in nauplius and TMP LC50-96 h in adult T. japonicus copepods was determined as 156 mg/L and 200 mg/L, respectively. In TMP-exposed T. japonicus, delayed developmental time and impaired reproduction were observed as harmful effects on the life history parameters. Increased ROS levels were also shown in response to TMP exposure at the highest concentration (100 mg/L TMP) and the expression of antioxidant- (e.g. GST-kappa, GST-sigma) and xenobiotic detoxification (e.g. CYPs)-related genes were upregulated in a time and/or dose-dependent manner in response to TMP. Particularly, significant upregulation of three CYP genes (Tj-CYP3024A2, Tj-CYP3024A3 and Tj-CYP3027C2) were examined, suggesting that these CYP genes are likely playing an important role in the TMP detoxification metabolism in T. japonicus. In summary, we found that TMP induced oxidative stress via the transcriptional regulation of antioxidant- and xenobiotic detoxification-related genes, leading to changes in life history parameters such as developmental delay and reproduction impairment. Three Tj-CYP genes (Tj-CYP3024A2, Tj-CYP3024A3 and Tj-CYP3027C2) could be useful as potential T. japonicus biomarkers in response to antibiotics.

Metabolomics Analysis Reveals the Participation of Efflux Pumps and Ornithine in the Response of Pseudomonas putida DOT-T1E Cells to Challenge with Propranolol

Efflux pumps are critically important membrane components that play a crucial role in strain tolerance in Pseudomonas putida to antibiotics and aromatic hydrocarbons that result in these toxicants being expelled from the bacteria. Here, the effect of propranolol on P. putida was examined by sudden addition of 0.2, 0.4 and 0.6 mg mL^-1 of this β-blocker to several strains of P. putida, including the wild type DOT-T1E and the efflux pump knockout mutants DOT-T1E-PS28 and DOT-T1E-18. Bacterial viability measurements reveal that the efflux pump TtgABC plays a more important role than the TtgGHI pump in strain tolerance to propranolol. Mid-infrared (MIR) spectroscopy was then used as a rapid, high-throughput screening tool to investigate any phenotypic changes resulting from exposure to varying levels of propranolol. Multivariate statistical analysis of these MIR data revealed gradient trends in resultant ordination scores plots, which were related to the concentration of propranolol. MIR illustrated phenotypic changes associated with the presence of this drug within the cell that could be assigned to significant changes that occurred within the bacterial protein components. To complement this phenotypic fingerprinting approach metabolic profiling was performed using gas chromatography mass spectrometry (GC-MS) to identify metabolites of interest during the growth of bacteria following toxic perturbation with the same concentration levels of propranolol. Metabolic profiling revealed that ornithine, which was only produced by P. putida cells in the presence of propranolol, presents itself as a major metabolic feature that has important functions in propranolol stress tolerance mechanisms within this highly significant and environmentally relevant species of bacteria.

Mediated effect of ultrasound treated Diclofenac on mussel hemocytes: First evidence for the involvement of respiratory burst enzymes in the induction of DCF-mediated unspecific mode of action

The present study investigates the toxic behavior of diclofenac (DCF) before and after its ultrasound (US) treatment, as well as the involvement of intracellular target molecules, such as NADPH oxidase and NO synthase, in the DCF-induced adverse effects on hemocytes of mussel Mytilus galloprovincialis. In this context, appropriate volumes (350 and 500mL) of DCF solutions (at concentrations of 2, 2.5, 5 and 10mgL(-1)) were treated under different ultrasound operating conditions (frequency at 582 and 862kHz, electric power density at 133 and 167W) for assessing US method efficiency. In parallel, DCF and US DCF-mediated cytotoxic (in terms of cell viability measured with the use of neutral red uptake/NRU method), oxidative (in terms of superoxide anions/(.)O2(-), nitric oxides such as NO2(-) and lipid peroxidation products, such as malondialdehyde/MDA content) and genotoxic (DNA damage measured by the use of Comet assay method) effects were investigated in hemocytes exposed for 1h to 5, 10 and 100ngL(-1) and 1, 10 and 20μgL(-1) of DCF. The involvement of NADPH oxidase and NO synthase to the DCF-induced toxicity was further investigated by the use of 10μΜ L-NAME, a NO synthase inhibitor and 10μΜ DPI, a NADPH oxidase inhibitor. According to the results, 350mL of 2mgL(-1) DCF showed higher degradation (>50%) under 167W electric power density and frequency at 862kHz for 120min, compared to degradation in all other cases, followed by a significant elimination of its toxicity. Specifically, US DCF-treated hemocytes showed a significant attenuation of DCF-mediated cytotoxic, oxidative and genotoxic effects, which appeared to be caused by NADPH oxidase and NO synthase activation, since their inhibition was followed by a significant elimination of (.)O2(-) and NO2(-) generation and the concomitant oxidative damage within cells. The results of the present study showed for the first time that unspecific mode of action of DCF, associated with the induction of NADPH oxidase and NO synthase in mussel hemocytes, could be significantly diminished after partial US degradation of DCF, at least under optimized operating conditions currently tested.

Neuronal in vitro activity is more sensitive to valproate than intracellular ATP: Considerations on conversion problems of IC50 in vitro data for animal replacement

We investigated the effects of acute valproate (VPA) on mouse embryonic primary cortex cells (MEPCs). Intracellular ATP concentrations were compared with changes in the mean action potential (AP) frequencies of MEPC networks growing on microelectrode arrays. Our data implies biphasic reactions towards increasing VPA concentrations for both parameters. Intracellular ATP and mean AP frequencies increased around characteristic concentrations of 0.15 and 0.07mM to hormetic plateaus of approx. 120% and 160% of their controls, before fading around 17 and 1.7 mM, respectively. The biphasic in vitro behavior of the two parameters hinders a simple extraction of IC50 and Hillslope values. Different ways of data-fitting with single and double logistic functions are discussed. For a typical hormetic increase of 60% above control, IC50 and Hillslope were decreased by 37% and 15%, respectively. Despite these marginal effects at a logarithmic concentration scale, the hormetic and double logistic behavior of parameters may provide information on the mode of action of toxic compounds. Comparison of our values with the LD50 of mice, recalculated by normalization to body mass, suggests that a neurotoxic rather than a cytotoxic mechanism is killing the animals. The future use of cellular microsystems to replace animal experiments will motivate the development of new microsensors, as well as the consideration of newly accessible parameters in systems biology models.

Prioritization of pharmaceuticals for potential environmental hazard through leveraging a large-scale mammalian pharmacological dataset

The potential for pharmaceuticals in the environment to cause adverse ecological effects is of increasing concern. Given the thousands of active pharmaceutical ingredients (APIs) that can enter the aquatic environment through human and/or animal (e.g., livestock) waste, a current challenge in aquatic toxicology is identifying those that pose the greatest risk. Because empirical toxicity information for aquatic species is generally lacking for pharmaceuticals, an important data source for prioritization is that generated during the mammalian drug development process. Applying concepts of species read-across, mammalian pharmacokinetic data were used to systematically prioritize APIs by estimating their potential to cause adverse biological consequences to aquatic organisms, using fish as an example. Mammalian absorption, distribution, metabolism, and excretion (ADME) data (e.g., peak plasma concentration, apparent volume of distribution, clearance rate, and half-life) were collected and curated, creating the Mammalian Pharmacokinetic Prioritization For Aquatic Species Targeting (MaPPFAST) database representing 1070 APIs. From these data, a probabilistic model and scoring system were developed and evaluated. Individual APIs and therapeutic classes were ranked based on clearly defined read-across assumptions for translating mammalian-derived ADME parameters to estimate potential hazard in fish (i.e., greatest predicted hazard associated with lowest mammalian peak plasma concentrations, total clearance and highest volume of distribution, half-life). It is anticipated that the MaPPFAST database and the associated API prioritization approach will help guide research and/or inform ecological risk assessment.

Long-term exposure to fluoxetine reduces growth and reproductive potential in the dominant rocky intertidal mussel, Mytilus californianus

Environmental stressors shape community composition and ecosystem functioning. Contaminants such as pharmaceuticals are of increasing concern as an environmental stressor due to their persistence in surface waters worldwide. Limited attention has been paid to the effects of pharmaceuticals on marine life, despite widespread detection of these contaminants in the marine environment. Of the existing studies, the majority assess the negative effects of pharmaceuticals over an exposure period of 30 days or less and focus on cellular and subcellular biomarkers. Longer studies are required to determine if chronic contaminant exposure poses risks to marine life at environmentally relevant concentrations; and examination of whole organism effects are necessary to identify potential community-level consequences in estuarine and marine ecosystems. We conducted a long-term exposure study (107 days) with the anti-depressant pharmaceutical, fluoxetine (the active constituent in Prozac®) to determine whether minimal concentrations affected whole organism metrics in the California mussel, Mytilus californianus. We measured algal clearance rates, mussel growth, and the gonadosomatic index, a measure of reproductive health. We found that fluoxetine negatively affects all measured characteristics, however many effects were mediated by length of exposure. Our results fill an important data gap, highlighting organism-level effects of chronic exposure periods; such data more explicitly identify the overall impacts of pharmaceuticals and other contaminants on marine communities and ecosystems.

In Silico Models for Ecotoxicity of Pharmaceuticals

Pharmaceuticals and their active metabolites are one of the significantly emerging environmental toxicants. The major routes of entry of pharmaceuticals into the environment are industries, hospitals, or direct disposal of unwanted or expired drugs made by the patient. The most important and distinct features of pharmaceuticals are that they are deliberately designed to have an explicit mode of action and designed to exert an effect on humans and other living systems. This distinctive feature makes pharmaceuticals and their metabolites different from other chemicals, and this necessitates the evaluation of the direct effects of pharmaceuticals in various environmental compartments as well as to living systems. In this background, the alarming situation of ecotoxicity of diverse pharmaceuticals have forced government and nongovernment regulatory authorities to recommend the application of in silico methods to provide quick information about the risk assessment and fate properties of pharmaceuticals as well as their ecological and indirect human health effects. This chapter aims to offer information regarding occurrence of pharmaceuticals in the environment, their persistence, environmental fate, and toxicity as well as application of in silico methods to provide information about the basic risk management and fate prediction of pharmaceuticals in the environment. Brief ideas about toxicity endpoints, available ecotoxicity databases, and expert systems employed for rapid toxicity predictions of ecotoxicity of pharmaceuticals are also discussed.

Pharmaceutical Residues in Sewage Treatment Works and their Fate in the Receiving Environment

Pharmaceuticals are increasingly used in large amounts in human (and veterinary) medicine around the world. They reach the aquatic environment mainly through sewage treatment systems and can reach μg l−1 levels. The continual input of pharmaceuticals to the aquatic environment, via sewage, can also impart a persistent quality to compounds that otherwise possess no inherent environmental stability. While the literature contains increasing numbers of studies detailing fate, effects and behaviour in the environment, the subject is still not fully understood for all the different therapeutic classes. The toxicological significance for non-target (especially aquatic) organisms is poorly understood. The use/release of antibiotics and natural/synthetic steroids to the environment has generated most of the concern to date, but a plethora of other drugs are increasingly attracting attention, as their biological activity alone may support ecotoxicity assessments of those compounds with high production volumes (or toxicity), especially in view of the increasing importance of freshwater resources. Pharmaceuticals display a variety of removal efficiencies during wastewater treatment and their fate and behaviour are not determined by their physicochemical properties alone. Despite the fact that many drugs have high sorption potentials, partitioning to the solid phase was determined to be an unlikely removal pathway for the majority of compounds. The partitioning behaviour of these compounds both in sewage treatment and the aquatic environment is likely to be dictated by a number of physicochemical parameters. Findings also indicate that the costs of using tertiary treatment options (mainly based on drinking water treatment) to remove drugs from wastewater effluent are likely to be prohibitively expensive, and potentially undesirable, due sustainability implications. While adjusting existing treatment parameters may increase the removal efficiencies of pharmaceuticals, any changes to sewage treatment parameters would need to be offset against the economic and environmental costs. Likewise, any regulations on drug use must be balanced against health benefits. If receiving waters are used for potable supplies, the presence of these compounds may (although it is unlikely) represent a potential hazard to human health, especially in areas without advanced water treatment. The focus for future research should therefore be on proper and sufficient science for establishing the occurrence, exposure and effects of pharmaceuticals in the environment, so that sound decisions can be made regarding human and ecological health.

Ecotoxicology, Environmental Risk Assessment and Potential Impact on Human Health

This chapter examines potential risks posed by active pharmaceutical ingredients (APIs) present in the aquatic environment to humans and aquatic life. We begin by describing the mechanisms by which pharmaceuticals enter the vertebrate body, produce effects and leave the body. Then we describe theoretical and practical issues limiting the certainty which can be expected from risk estimates. This is followed by a description of particular considerations applicable to evaluation of human risks, along with a summary of methods and conclusions from some important studies examining those risks. A similar discussion of theoretical issues and selected data relevant for estimating risks to aquatic life is then presented. We finish by discussing potential contributions of antibiotics present in the environment to the development and spread of antibiotic resistance. We conclude that there are too few data to definitively address every concern, particularly risks to aquatic life and contributions to development of antibiotic resistance. On the other hand, available data suggest risks to humans are very low for all active pharmaceutical ingredients (APIs) and risks to aquatic life are very low for most APIs. Although aquatic risks cannot be as confidently ruled out for a few APIs, potential risks are probably limited to particularly contaminated regions in close vicinity to concentrated pollution sources, such as wastewater treatment plant outfalls.

Observed and modeled effects of pH on bioconcentration of diphenhydramine, a weakly basic pharmaceutical, in fathead minnows

A need exists to better understand the influence of pH on the uptake and accumulation of ionizable pharmaceuticals in fish. In the present study, fathead minnows were exposed to diphenhydramine (DPH; disassociation constant = 9.1) in water for up to 96 h at 3 nominal pH levels: 6.7, 7.7, and 8.7. In each case, an apparent steady state was reached by 24 h, allowing for direct determination of the bioconcentration factor (BCF), blood-water partitioning (PBW,TOT), and apparent volume of distribution (approximated from the whole-body-plasma concentration ratio). The BCFs and measured PBW,TOT values increased in a nonlinear manner with pH, whereas the volume of distribution remained constant, averaging 3.0 L/kg. The data were then simulated using a model that accounts for acidification of the gill surface caused by elimination of metabolically produced acid. Good agreement between model simulations and measured data was obtained for all tests by assuming that plasma binding of ionized DPH is 16% that of the neutral form. A simpler model, which ignores elimination of metabolically produced acid, performed less well. These findings suggest that pH effects on accumulation of ionizable compounds in fish are best described using a model that accounts for acidification of the gill surface. Moreover, measured plasma binding and volume of distribution data for humans, determined during drug development, may have considerable value for predicting chemical binding behavior in fish.

Comparative pharmacology and toxicology of pharmaceuticals in the environment: diphenhydramine protection of diazinon toxicity in Danio rerio but not Daphnia magna

Pharmaceuticals and other contaminants of emerging concern present unique challenges to environmental risk assessment and management. Fortunately, mammalian pharmacology and toxicology safety data are more readily available for pharmaceuticals than other environmental contaminants. Identifying approaches to read-across such pharmaceutical safety information to non-target species represents a major research need to assess environmental hazards. Here, we tested a biological read-across hypothesis from emergency medicine with common aquatic invertebrate and vertebrate models. In mammals, the antihistamine diphenhydramine (DPH) confers protection from poisoning by acetylcholinesterase inhibition because DPH blocks the acetylcholine receptor. We employed standardized toxicity methods to examine individual and mixture toxicity of DPH and the acetylcholinesterase inhibitor diazinon (DZN) in Daphnia magna (an invertebrate) and Danio rerio (zebrafish, a vertebrate). Though the standardized Fish Embryo Toxicity method evaluates early life stage toxicity of zebrafish (0-3 days post fertilization, dpf), we further evaluated DPH, DZN, and their equipotent mixture during three development stages (0-3, 3-6, 7-10 dpf) in zebrafish embryos. Independent action and concentration addition mixture models and fish plasma modeling were used to assist interpretation of mixture toxicity experiments. Though our primary hypothesis was not confirmed in acute studies with Daphnia magna, DPH conferred a protective effect for acute DZN toxicity to zebrafish when DPH plasma levels were expected to be greater than mammalian therapeutic, but lower than acutely lethal, internal doses. We further observed that timing of developmental exposure influenced the magnitude of DZN and DPH toxicity to zebrafish, which suggests that future zebrafish toxicity studies with pharmaceuticals and pesticides should examine exposure during developmental stages.

An integrated approach for prioritizing pharmaceuticals found in the environment for risk assessment, monitoring and advanced research

Numerous active pharmaceutical ingredients (APIs), approved prior to enactment of detailed environmental risk assessment (ERA) guidance in the EU in 2006, have been detected in surface waters as a result of advancements in analytical technologies. Without adequate knowledge of the potential hazards these APIs may pose, assessing their environmental risk is challenging. As it would be impractical to commence hazard characterization and ERA en masse, several approaches to prioritizing substances for further attention have been published. Here, through the combination of three presentations given at a recent conference, "Pharmaceuticals in the Environment, Is there a problem?" (Nîmes, France, June 2013) we review several of these approaches, identify salient components, and present available techniques and tools that could facilitate a pragmatic, scientifically sound approach to prioritizing APIs for advanced study or ERA and, where warranted, fill critical data gaps through targeted, intelligent testing. We further present a modest proposal to facilitate future prioritization efforts and advanced research studies that incorporates mammalian pharmacology data (e.g., adverse outcomes pathways and the fish plasma model) and modeled exposure data based on pharmaceutical use.

Quantitative cross-species extrapolation between humans and fish: the case of the anti-depressant fluoxetine

Fish are an important model for the pharmacological and toxicological characterization of human pharmaceuticals in drug discovery, drug safety assessment and environmental toxicology. However, do fish respond to pharmaceuticals as humans do? To address this question, we provide a novel quantitative cross-species extrapolation approach (qCSE) based on the hypothesis that similar plasma concentrations of pharmaceuticals cause comparable target-mediated effects in both humans and fish at similar level of biological organization (Read-Across Hypothesis). To validate this hypothesis, the behavioural effects of the anti-depressant drug fluoxetine on the fish model fathead minnow (Pimephales promelas) were used as test case. Fish were exposed for 28 days to a range of measured water concentrations of fluoxetine (0.1, 1.0, 8.0, 16, 32, 64 µg/L) to produce plasma concentrations below, equal and above the range of Human Therapeutic Plasma Concentrations (H_TPCs). Fluoxetine and its metabolite, norfluoxetine, were quantified in the plasma of individual fish and linked to behavioural anxiety-related endpoints. The minimum drug plasma concentrations that elicited anxiolytic responses in fish were above the upper value of the H_TPC range, whereas no effects were observed at plasma concentrations below the H_TPCs. In vivo metabolism of fluoxetine in humans and fish was similar, and displayed bi-phasic concentration-dependent kinetics driven by the auto-inhibitory dynamics and saturation of the enzymes that convert fluoxetine into norfluoxetine. The sensitivity of fish to fluoxetine was not so dissimilar from that of patients affected by general anxiety disorders. These results represent the first direct evidence of measured internal dose response effect of a pharmaceutical in fish, hence validating the Read-Across hypothesis applied to fluoxetine. Overall, this study demonstrates that the qCSE approach, anchored to internal drug concentrations, is a powerful tool to guide the assessment of the sensitivity of fish to pharmaceuticals, and strengthens the translational power of the cross-species extrapolation.

Are pharmaceuticals with evolutionary conserved molecular drug targets more potent to cause toxic effects in non-target organisms?

The ubiquitous use of pharmaceuticals has resulted in a continuous discharge into wastewater and pharmaceuticals and their metabolites are found in the environment. Due to their design towards specific drug targets, pharmaceuticals may be therapeutically active already at low environmental concentrations. Several human drug targets are evolutionary conserved in aquatic organisms, raising concerns about effects of these pharmaceuticals in non-target organisms. In this study, we hypothesized that the toxicity of a pharmaceutical towards a non-target invertebrate depends on the presence of the human drug target orthologs in this species. This was tested by assessing toxicity of pharmaceuticals with (miconazole and promethazine) and without (levonorgestrel) identified drug target orthologs in the cladoceran Daphnia magna. The toxicity was evaluated using general toxicity endpoints at individual (immobility, reproduction and development), biochemical (RNA and DNA content) and molecular (gene expression) levels. The results provide evidence for higher toxicity of miconazole and promethazine, i.e. the drugs with identified drug target orthologs. At the individual level, miconazole had the lowest effect concentrations for immobility and reproduction (0.3 and 0.022 mg L-1, respectively) followed by promethazine (1.6 and 0.18 mg L-1, respectively). At the biochemical level, individual RNA content was affected by miconazole and promethazine already at 0.0023 and 0.059 mg L-1, respectively. At the molecular level, gene expression for cuticle protein was significantly suppressed by exposure to both miconazole and promethazine; moreover, daphnids exposed to miconazole had significantly lower vitellogenin expression. Levonorgestrel did not have any effects on any endpoints in the concentrations tested. These results highlight the importance of considering drug target conservation in environmental risk assessments of pharmaceuticals.

An exploratory investigation of various modes of action and potential adverse outcomes of fluoxetine in marine mussels

The present study investigated possible adverse outcome pathways (AOPs) of the antidepressant fluoxetine (FX) in the marine mussel Mytilus galloprovincialis. An evaluation of molecular endpoints involved in modes of action (MOAs) of FX and biomarkers for sub-lethal toxicity were explored in mussels after a 7-day administration of nominal FX concentrations encompassing a range of environmentally relevant values (0.03-300ng/L). FX bioaccumulated in mussel tissues after treatment with 30 and 300ng/L FX, resulting in bioconcentration factor (BCF) values ranging from 200 to 800, which were higher than expected based solely on hydrophobic partitioning models. Because FX acts as a selective serotonin (5-HT) re-uptake inhibitor increasing serotonergic neurotransmission at mammalian synapses, cell signaling alterations triggered by 5-HT receptor occupations were assessed. cAMP levels and PKA activities were decreased in digestive gland and mantle/gonads of FX-treated mussels, consistent with an increased occupation of 5-HT1 receptors negatively coupled to the cAMP/PKA pathway. mRNA levels of a ABCB gene encoding the P-glycoprotein were also significantly down-regulated. This membrane transporter acts in detoxification towards xenobiotics and in altering pharmacokinetics of antidepressants; moreover, it is under a cAMP/PKA transcriptional regulation in mussels. Potential stress effects of FX were investigated using a battery of biomarkers for mussel health status that included lysosomal parameters, antioxidant enzyme activities, lipid peroxidation, and acetylcholinesterase activity. FX reduced the health status of mussels and induced lysosomal alterations, as suggested by reduction of lysosomal membrane stability in haemocytes and by lysosomal accumulation of neutral lipids in digestive gland. No clear antioxidant responses to FX were detected in digestive gland, while gills displayed significant increases of catalase and glutathione-s-transferase activities and a significant decrease of acetylcholinesterase activity. Though AOPs associated with mammalian therapeutic MOAs remain important during assessments of pharmaceutical hazards in the environment, this study highlights the importance of considering additional MOAs and AOPs for FX, particularly in marine mussels.

The biological effects of antidepressants on the molluscs and crustaceans: a review

Antidepressants are among the most commonly detected human pharmaceuticals in the aquatic environment. Since their mode of action is by modulating the neurotransmitters serotonin, dopamine, and norepinephrine, aquatic invertebrates who possess transporters and receptors sensitive to activation by these pharmaceuticals are potentially affected by them. We review the various types of antidepressants, their occurrence and concentrations in aquatic environments, and the actions of neurohormones modulated by antidepressants in molluscs and crustaceans. Recent studies on the effects of antidepressants on these two important groups show that molluscan reproductive and locomotory systems are affected by antidepressants at environmentally relevant concentrations. In particular, antidepressants affect spawning and larval release in bivalves and disrupt locomotion and reduce fecundity in snails. In crustaceans, antidepressants affect freshwater amphipod activity patterns, marine amphipod photo- and geotactic behavior, crayfish aggression, and daphnid reproduction and development. We note with interest the occurrence of non-monotonic dose responses curves in many studies on effects of antidepressants on aquatic animals, often with effects at low concentrations, but not at higher concentrations, and we suggest future experiments consider testing a broader range of concentrations. Furthermore, we consider invertebrate immune responses, genomic and transcriptomic sequencing of invertebrate genes, and the ever-present and overwhelming question of how contaminant mixtures could affect the action of neurohormones as topics for future study. In addressing the question, if antidepressants affect aquatic invertebrates at concentrations currently found in the environment, there is strong evidence to suggest the answer is yes. Furthermore, the examples highlighted in this review provide compelling evidence that the effects could be quite multifaceted across a variety of biological systems.

Fish on Prozac (and Zoloft): ten years later

A decade has now passed since our research group initially reported several adverse effects of fluoxetine to aquatic organisms commonly employed for developing environmental quality criteria, evaluating whole effluent toxicity, and monitoring ambient toxicity of surface waters and sediments. Our subsequent observation of fluoxetine, sertraline and their active metabolites (norfluoxetine and desmethylsertraline, respectively) accumulating in muscle, liver and brain tissues of three different fish species from an effluent-dominated stream was termed "Fish on Prozac." Here I briefly review some scientific lessons learned from our study of antidepressants and the environment, including opportunities for research, management, environmental education and public outreach. Intrinsic chemical properties of antidepressants and other pharmaceuticals have afforded research in areas ranging from analytical chemistry and comparative pharmacology, to influences of ionization, chirality and adverse outcome pathways on hazard and risk assessment, and further promises to support sustainable molecular design of less hazardous chemicals. Using probabilistic hazard assessment and fish plasma modeling approaches, selective serotonin reuptake inhibitors and tricyclic antidepressants are predicted to result in therapeutic hazard to fish (internal fish plasma level equaling mammalian therapeutic dose) when exposed to water (inhalational) at or below 1μg/L, a common trigger value for environmental assessments. Though many questions remain unanswered, studies of antidepressants in urbanizing aquatic systems have provided, and will continue to develop, an advanced understanding of environmental hazards and risks from pharmaceuticals and other contaminants.

Toxicities of four anti-neoplastic drugs and their binary mixtures tested on the green alga Pseudokirchneriella subcapitata and the cyanobacterium Synechococcus leopoliensis

The residues of anti-neoplastic drugs are new and emerging pollutants in aquatic environments. This is not only because of their increasing use, but also because due to their mechanisms of action, they belong to a group of particularly dangerous compounds. However, information on their ecotoxicological properties is very limited. We tested the toxicities of four anti-neoplastic drugs with different mechanisms of action (5-fluorouracil [5-FU], cisplatin [CDDP], etoposide [ET], and imatinib mesylate [IM]), and some of their binary mixtures, against two phytoplankton species: the alga Pseudokirchneriella subcapitata, and the cyanobacterium Synechococcus leopoliensis. These four drugs showed different toxic potential, and the two species examined also showed differences in their susceptibilities towards the tested drugs and their mixtures. With P. subcapitata, the most toxic of these drugs was 5-FU (EC50, 0.13 mg/L), followed by CDDP (EC50, 1.52 mg/L), IM (EC50, 2.29 mg/L), and the least toxic, ET (EC50, 30.43 mg/L). With S. leopoliensis, the most toxic was CDDP (EC50, 0.67 mg/L), followed by 5-FU (EC50, 1.20 mg/L) and IM (EC50, 5.36 mg/L), while ET was not toxic up to 351 mg/L. The toxicities of the binary mixtures tested (5-FU + CDDP, 5-FU + IM, CDDP + ET) were predicted by the concepts of 'concentration addition' and 'independent action', and are compared to the experimentally determined toxicities. The measured toxicity of 5-FU + CDDP with P. subcapitata and S. leopoliensis was higher than that predicted, while the measured toxicity of CDDP + ET with both species was lower than that predicted. The measured toxicity of 5-FU + IM with P. subcapitata was higher, and with S. leopoliensis was lower, than that predicted. These data show that these mixtures can have compound-specific and species-specific synergistic or antagonistic effects, and they suggest that single compound toxicity data are not sufficient for the prediction of the aquatic toxicities of such anticancer drug mixtures.

Molecular docking: a potential tool to aid ecotoxicity testing in environmental risk assessment of pharmaceuticals

A cocktail of human pharmaceuticals pollute aquatic environments and there is considerable scientific uncertainty about the effects that this may have on aquatic organisms. Human drug target proteins can be highly conserved in non target species suggesting that similar modes of action (MoA) may occur. The aim of this work was to explore whether molecular docking offers a potential tool to predict the effects of pharmaceutical compounds on non target organisms. Three highly prescribed drugs, diclofenac, ibuprofen and levonorgestrel which regularly pollute freshwater environments were used as examples. Their primary drug targets are cyclooxygenase 2 (COX2) and progesterone receptor (PR). Molecular docking experiments were performed using these drugs and their primary drug target homologues for Danio rerio, Salmo salar, Oncorhynchus mykiss, Xenopus tropicalis, Xenopus laevis and Daphnia pulex. The results show that fish and frog COX2 enzymes are likely to bind diclofenac and ibuprofen in the same way as humans but that D. pulex would not. Binding will probably lead to inhibition of COX function and reduced prostaglandin production. Levonorgestrel was found to bind in the same binding pocket of the progesterone receptor in frogs and fish as the human form. This suggests implications for the fecundity of fish and frogs which are exposed to levonorgestrel. Chronic ecotoxicological effects of these drugs reported in the literature support these findings. Molecular docking may provide a valuable tool for ecotoxicity tests by guiding selection of test species and incorporating the MoA of drugs for relevant chronic test end points in environmental risk assessments.

Early responses measured in the brachyuran crab Carcinus maenas exposed to carbamazepine and novobiocin: application of a 2-tier approach

One of the main consequences of the constant input of pharmaceuticals to the aquatic environment is that biota might develop unknown chronic effects, thus affecting their health even at low concentrations. The aim of this study is to evaluate the health status of Carcinus maenas employing a 2-tier approach, after 28 days of exposure to carbamazepine (CBZ) and novobiocin (NOV) at 0.1, 1, 10 and 50µgL(-1). Lysosomal membrane stability (LMS) is employed in tier 1. In tier 2 was applied a battery of biomarkers of exposure and effect (ethoxyresorufin O-deethylase (EROD), dibenzyl flourescein dealkylase (DBF), glutathione S-transferase (GST), glutathione peroxidase (GPx), lipid peroxidation (LPO) and DNA adducts) measured in gill, hepatopancreas, muscle and gonad tissues. Results show a dose-dependent effect. LMS in crabs exposed to environmental concentrations of pharmaceuticals was significantly lower compared to controls (p<0.05), indicating their stressed status. EROD activity was induced significantly (p<0.05) in all tissues by NOV (10-50µgL(-1)). DBF activity was induced significantly (p<0.05) in gill and hepatopancreas tissues by CBZ (10-50µgL(-1)). GST activity was activated in all tissues of crabs exposed to the highest concentrations tested (p<0.05). All tissues showed induction of GPX activity after exposure to selected drugs (p<0.05). LPO was activated in gill and hepatopancreas tissues by the pharmaceuticals at 50µgL(-1) (p<0.05). Crabs exposed to NOV (50µgL(-1)) presented DNA damage in gill and hepatopancreas tissues (p<0.05). Environmental concentrations of these pharmaceuticals have a measurable effect on the biomarkers studied. The 2-tier approach applied might be a suitable tool for the assessment of sublethal responses in crabs exposed to pharmaceuticals in the marine environment.

Mode of action of human pharmaceuticals in fish: the effects of the 5-alpha-reductase inhibitor, dutasteride, on reproduction as a case study

In recent years, a growing number of human pharmaceuticals have been detected in the aquatic environment, generally at low concentrations (sub-ng/L-low μg/L). In most cases, these compounds are characterised by highly specific modes of action, and the evolutionary conservation of drug targets in wildlife species suggests the possibility that pharmaceuticals present in the environment may cause toxicological effects by acting through the same targets as they do in humans. Our research addressed the question of whether or not dutasteride, a pharmaceutical used to treat benign prostatic hyperplasia, may cause adverse effects in a teleost fish, the fathead minnow (Pimephales promelas), by inhibiting the activity of both isoforms of 5α-reductase (5αR), the enzyme that converts testosterone into dihydrotestosterone (DHT). Mammalian pharmacological and toxicological information were used to guide the experimental design and the selection of relevant endpoints, according to the so-called "read-across approach", suggesting that dutasteride may affect male fertility and steroid hormone dynamics. Therefore, a 21-day reproduction study was conducted to determine the effects of dutasteride (10, 32 and 100 μg/L) on fish reproduction. Exposure to dutasteride significantly reduced fecundity of fish and affected several aspects of reproductive endocrine functions in both males and females. However, none of the observed adverse effects occurred at concentrations of exposure lower than 32 μg/L; this, together with the low volume of drug prescribed every year (10.34 kg in the UK in 2011), and the extremely low predicted environmental concentration (0.03 ng/L), suggest that, at present, the potential presence of dutasteride in the environment does not represent a threat to wild fish populations.

Preliminary studies on model development for rodent toxicity and its interspecies correlation with aquatic toxicities of pharmaceuticals

Environmental toxicity due to pharmaceuticals has been an issue of serious concern for long time. Development of chemometric models with reliable predictive power has been considered as an effective tool for the design of new drug agents with reduced or without ecotoxic potential. Considering a higher degree of similarity in genetic homology towards drug receptor with mammals, we have used a dataset of 194 compounds with reported rodent, fish, daphnia and algae toxicity data for extrapolation of their toxicity towards humans. Allowing for rodents as the most surrogate to human physiology, attempts have also been made to develop interspecies correlation models keeping rodent toxicity as dependent variable so that any drug without reported rodent toxicity can be predicted using fish, daphnia or algae toxicity data which can be consequently extrapolated to human toxicity. The developed models have been subjected to multiple validation strategies. Acceptable results have been obtained in both cases of direct and interspecies extrapolation quantitative structure-activity relationship models.

Antidepressants cause foot detachment from substrate in five species of marine snail

Active Pharmaceutical Ingredients (APIs) are released into aquatic ecosystems through discharged sewage wastewater. Antidepressants are among those APIs often detected in wastewater effluent and have been recently reported to cause foot detachment from the substrate in freshwater snails. We tested the effects of four commonly prescribed antidepressants {fluoxetine ("Prozac"), fluvoxamine ("Luvox"), venlafaxine ("Effexor"), and citalopram ("Celexa") on adhesion to the substrate in five species of marine snails, three from the Pacific coast (Chlorostoma funebralis, Nucella ostrina, Urosalpinx cinerea) and two species from the Atlantic coast (Tegula fasciatus and Lithopoma americanum) of North America representing three different gastropod families. All antidepressants tested induced foot detachment from the substrate in all snail species in a mainly dose-dependent manner (p < 0.04-0.00000001). The lowest LOECs (lowest observed effect concentration) for antidepressants and snails were recorded for Lithopoma in 43.4 μg/L (100 nM) fluvoxamine and Chlorostoma in 157 μg/L (500 nM) venlafaxine and 217 μg/L (500 nM) fluvoxamine. The trochids and turbinids were 2-10× more sensitive to the antidepressants than the muricids. Latency to detachment was also dose dependent, with the fastest average times to detach seen in Chlorostoma and Lithopoma (7.33 and 13.16 min respectively in 3.13 mg/L venlafaxine). The possible physiological mechanisms regulating antidepressant-induced foot detachment in marine snails and the possible ecological consequences are discussed.

Pharmaceuticals and personal care products in the environment: what are the big questions?

BACKGROUND

Over the past 10-15 years, a substantial amount of work has been done by the scientific, regulatory, and business communities to elucidate the effects and risks of pharmaceuticals and personal care products (PPCPs) in the environment.

OBJECTIVE

This review was undertaken to identify key outstanding issues regarding the effects of PPCPs on human and ecological health in order to ensure that future resources will be focused on the most important areas.

DATA SOURCES

To better understand and manage the risks of PPCPs in the environment, we used the "key question" approach to identify the principle issues that need to be addressed. Initially, questions were solicited from academic, government, and business communities around the world. A list of 101 questions was then discussed at an international expert workshop, and a top-20 list was developed. Following the workshop, workshop attendees ranked the 20 questions by importance.

DATA SYNTHESIS

The top 20 priority questions fell into seven categories: a) prioritization of substances for assessment, b) pathways of exposure, c) bioavailability and uptake, d) effects characterization, e) risk and relative risk, f ) antibiotic resistance, and g) risk management.

CONCLUSIONS

A large body of information is now available on PPCPs in the environment. This exercise prioritized the most critical questions to aid in development of future research programs on the topic.

Identification and prioritization of bioaccumulable pharmaceutical substances discharged in hospital effluents

The consumption of pharmaceuticals and their excretion in wastewater is a continuous source of pollution for aquatic ecosystems. In certain cases these compounds are found in the environment at concentrations high enough to cause disturbance in aquatic organisms. Aware of this problem hospitals are giving increasing attention to the nature of their effluents and their impact on the environment, by implementing more efficient effluent management policies. This concern is justified in view of the large volumes of toxic products consumed (detergents, disinfectants, pharmaceuticals, chemical reagents, radioactive elements, etc.). Moreover, these effluents usually do not undergo any specific treatment before being discharged into urban sewage networks. In this article, we present a method for selecting the pharmaceuticals discharged in hospital effluents that have the worst impact on the aquatic ecosystem, primarily based on their bioaccumulation potential. This study focused on the pharmaceuticals consumed at the Hospices Civils de Lyon (HCL), the second largest hospital structure in France (5200 hospital beds). Of the 960 substances consumed in HCL hospitals, a shortlist of 70 substances considered as being potentially bioaccumulable was established. The use of aggravating factors of risk has then led to the final selection of 14 priority compounds. They include 4 compounds consumed in large quantities in HCL hospitals, 6 endocrine disruptors and 4 potentially ecotoxic compounds. For all these compounds, it is now advisable to verify their bioaccumulation potential experimentally and confirm their presence in the environment. In addition, in order to monitor the risk relating to possible contamination of the food chain, it will be necessary to measure accumulated dose levels in species of different trophic levels. Lastly, chronic ecotoxicity tests will permit evaluating the danger and risk that some of these substances may represent for aquatic ecosystems.

Risk assessment for ecotoxicity of pharmaceuticals--an emerging issue

INTRODUCTION

Existence of a large amount of pharmaceuticals and their active metabolites in the environment has recently been considered as one of the most serious concerns in environmental sciences. Large diversity of pharmaceuticals has been found in the environmental domain in considerable amounts that are not only destructive to environment but also fatal for human and animal fraternity.

AREAS COVERED

There is a considerable lack of knowledge about the environmental fate and quantification of a large number of pharmaceuticals. This communication aims to review the literature information regarding occurrence of pharmaceuticals and their metabolites in the environment, their persistence, environmental fate and toxicity as well as application of theoretical, non-experimental, non-animal, alternative and, in particular, in silico methods to provide information about the basic physicochemical and fate properties of pharmaceuticals to the environment. The reader will gain an overview of risk assessment strategies for ecotoxicity of pharmaceuticals and advances in application of quantitative structure-toxicity relationship (QSTR) in this field.

EXPERT OPINION

This review justifies the need to develop more QSTR models for prediction of ecotoxicity of pharmaceuticals in order to reduce time and cost involvement in such exercise.

The toxicity potential of pharmaceuticals found in the Douro River estuary (Portugal): assessing impacts on gonadal maturation with a histopathological and stereological study of zebrafish ovary and testis after sub-acute exposures

Concerns associated with pharmaceuticals in aquatic systems demand the establishment of links between xenobiotics and their respective concentrations and impacts on aquatic organisms. Herein, effects of non-steroidal pharmaceuticals in the gonadal maturation of zebrafish (Danio rerio) were evaluated by histopathological and stereological analyses after 21 days of exposure. Carbamazepine, fenofibric acid, propranolol, sulfamethoxazole and trimethoprim were selected, considering their detection in the Douro estuary (Portugal). Exposures were performed with single compounds and mixtures, the exposure concentrations including environmental levels. Overall, quantitative analyses showed a decreasing trend for late maturation stages in male and female gametogenesis with parallel increases in immature gametes. In females, and at the highest concentration mixture, a significant switch between the volume densities of late/mature oocytes versus primary oocytes was observed. On the verge of statistical significance, oocyte atresia was higher in both mixtures (5.75 ± 4.02% for MXA and 5.65 ± 5.27% for MXB) versus control (2.21 ± 1.88%), in accordance with the histological identification of large atretic areas in some fish. Unlike females, males showed significant effects with single exposures. Spermatozoa in controls totalled 53.25 ± 7.13% of the testis volume, decreasing with carbamazepine (47.19 ± 5.30%), fenofibric acid (46.36 ± 4.30%), propranolol (37.22 ± 2.38%) and sulfametoxazole (39.37 ± 5.15%). An increase in spermatocyte percentage was noted with propranolol (40.13 ± 7.36%) and sulfametoxazole (40.84 ± 1.66%) versus control (30.93 ± 6.53%). The changes in maturation dynamics did not impact the gonadosomatic index. The results show that pharmaceuticals from various therapeutic classes can disrupt the maturation dynamics of fish ovaries and testes. Further studies are justified to tackle the underlying mechanisms and to gauge the full extent of effects/risks.

Using the fish plasma model for comparative hazard identification for pharmaceuticals in the environment by extrapolation from human therapeutic data

Thousands of drugs are currently in use, but only for a few of them experimental chronic fish data exist. Therefore, Huggett et al. (Human Ecol Risk Assess 2003; 9:1789-1799) proposed the fish plasma model (FPM) to extrapolate the potential of unintended long-term effects in fish. The FPM compares human therapeutic plasma concentrations (HPC(T)) with estimated fish steady-state concentrations (FPC(ss)), under the assumption that biological drug targets may be conserved across the species. In this study, the influence of using different input parameters on the model result was characterised for 42 drugs. The existence of structurally and functionally conserved protein targets in zebrafish could not be refuted. Thus, the FPM model application was not in contradiction to its basic assumption. Further, dissociation of drugs was shown to be important in determining the output and model robustness. As the proposed model for FPC(ss) estimation was considered to predict accurate values for neutral and lipophilic chemicals only, a modified bioconcentration model was used with D(OW) as predictor. Using reasonable worst case assumptions, a hazard was indicated for one third of the selected drugs. Our results support the notion that this approach might help to prioritise among in use drugs to identify compounds where follow up evidence should be considered.

Bioremediation of pharmaceuticals, pesticides, and petrochemicals with gomeya/cow dung

Use and misuse of pharmaceuticals, pesticides, and petrochemicals by man is causing havoc with nature, as they persist as such or as their toxic metabolites. These pollutants bioaccumulate in environment, and they ultimately reach man through various means. They are hazardous because of potential toxicity, mutagenicity, carcinogenicity, and genotoxicity. To rejuvenate nature, remediation methods currently available are usually expensive and might convert one toxic pollutant to another. Bioremediation methods use naturally occurring microorganisms to detoxify man-made pollutants so that they change pollutants to innocuous products that make soil fertile in the process. Taking cue from Ayurveda, Gomeya/cow dung is used as an excellent bioremediation method. Thus, utilizing freely available cow dung as slurry or after composting in rural areas, is a cheap and effective measure to bioremediate the harmful pollutants. Yet, more research in this direction is warranted to bioremediate nonbiodegradable, potentially toxic pollutants.

First report on interspecies quantitative correlation of ecotoxicity of pharmaceuticals

Pharmaceuticals being extensively and progressively used in human and veterinary medicine are emerging as significant environmental contaminants. Pharmaceuticals are designed to have a specific mode of action and many of them are persistent in the body. These features among others make pharmaceuticals to be evaluated for potential effects on aquatic flora and fauna. Low levels of pharmaceuticals have been detected in many countries in sewage treatment plant effluents, surface waters, groundwater and drinking waters. In contrast, there is a general scarcity of publicly available ecotoxicological data concerning pharmaceuticals. Interspecies toxicity correlations provide a tool for estimating contaminant sensitivity with known levels of uncertainty for a diversity of wildlife species. In this context, we have developed interspecies toxicity correlation between Daphnia magna (zooplankton) and fish (species according to OECD guidelines) assessing the ecotoxicological hazard potential of diverse 77 pharmaceuticals. The developed models are validated and consensus models are presented to predict toxicity of the individual compounds for any one species when the data for the other species are available. Informative illustrations of the contributing structural fragments which are responsible for the greater toxicity of the diverse pharmaceuticals are identified by the developed models. Developed models are also used to predict fish toxicities of 59 pharmaceuticals (for which Daphnia toxicities are present) and Daphnia toxicities of 30 pharmaceuticals (for which fish toxicities are present). This study will allow a better and comprehensive risk assessment of pharmaceuticals for which toxicity data is missing for a particular endpoint.

Physiological effects of diclofenac, ibuprofen and propranolol on Baltic Sea blue mussels

Pharmaceuticals are constantly dispersed into the environment and little is known of the effects on non-target organisms. This is an issue of growing concern. In this study, Baltic Sea blue mussels, Mytilus edulis trossulus, were exposed to diclofenac, ibuprofen and propranolol, three pharmaceuticals that are produced and sold in large quantities and have a widespread occurrence in aquatic environments. The mussels were exposed to pharmaceuticals in concentrations ranging from 1 to 10,000 microg l(-1). The pharmaceuticals were added both separately and in combination. Mussels exposed to high concentrations of pharmaceuticals showed a clear response compared to controls. Firstly, they had a significantly lower scope for growth, which indicates that the organisms had a smaller part of their energy available for normal metabolism, and secondly, they had lower byssus strength and lower abundance of byssus threads, resulting in reduced ability to attach to the underlying substrate. Mussels exposed to lower concentrations showed tendencies of the same results. The concentration of diclofenac and propranolol was quantified in the mussels using both liquid chromatography coupled to mass spectrometry (LC-MS). The measurements showed a significantly higher concentration in the organisms as compared to the water the mussels were exposed to; the uptake reached concentrations two orders of magnitudes higher than found in sewage treatment plant effluents. This study showed that common pharmaceuticals are taken up and negatively affect the physiology of a non-target species at levels of two to three orders of magnitudes higher than found in sewage treatment plant effluents.

Monitoring the effects of chiral pharmaceuticals on aquatic microorganisms by metabolic fingerprinting

The effects of the chiral pharmaceuticals atenolol and propranolol on Pseudomonas putida, Pseudomonas aeruginosa, Micrococcus luteus, and Blastomonas natatoria were investigated. The growth dynamics of exposed cultures were monitored using a Bioscreen instrument. In addition, Fourier-transform infrared (FT-IR) spectroscopy with appropriate chemometrics and high-performance liquid chromatography (HPLC) were employed in order to investigate the phenotypic changes and possible degradation of the drugs in exposed cultures. For the majority of the bacteria studied there was not a statistically significant difference in the organism's phenotype when it was exposed to the different enantiomers or mixtures of enantiomers. In contrast, the pseudomonads appeared to respond differently to propranolol, and the two enantiomers had different effects on the cellular phenotype. This implies that there were different metabolic responses in the organisms when they were exposed to the different enantiomers. We suggest that our findings may indicate that there are widespread effects on aquatic communities in which active pharmaceutical ingredients are present.