Exposure to tricyclic antidepressant nortriptyline affects early-life stages of zebrafish (Danio rerio)

Synthesis and Structure of Novel Phenothiazine Derivatives, and Compound Prioritization via In Silico Target Search and Screening for Cytotoxic and Cholinesterase Modulatory Activities in Liver Cancer Cells and In Vivo in Zebrafish

Phenothiazines (PTZ) are antipsychotics known to modulate a variety of neurotransmitter activities that include dopaminergic and cholinergic signaling and have been identified as potential anticancer agents in vitro. However, it is important to also test whether a highly cytotoxic, repurposed, or novel PTZ has low toxicity and neuromodulatory activity in vivo using vertebrate model organisms, such as zebrafish. In this study, we synthesized novel phenothiazines and screened them in vitro in liver cancer and in vivo in zebrafish embryos/larvae. The syntheses of several intermediate PTZ 10-yl acyl chlorides were followed by elemental analysis and determination of 1H NMR and 13C NMR mass (ESI+) spectra of a large number of novel PTZ 10-carboxamides. Cytotoxicities of 28 PTZ derivatives (1-28) screened against Hep3B and SkHep1 liver cancer cell lines revealed five intermediate and five novel leads along with trifluoperazine (TFP), prochlorperazine (PCP), and perphenazine, which are relatively more cytotoxic than the basic PTZ core. Overall, the derivatives were more cytotoxic to Hep3B than SkHep1 cells. Moreover, in silico target screening identified cholinesterases as some of the commonest targets of the screened phenothiazines. Interestingly, molecular docking studies with acetylcholinesterase (AChE) and butyrylcholinesterase proteins showed that the most cytotoxic compounds 1, 3, PCP, and TFP behaved similar to Huprin W in their amino acid interactions with the AChE protein. The highly cytotoxic intermediate PTZ derivative 1 exhibited a relatively lower toxicity profile than those of 2 and 3 during the zebrafish development. It also modulated in vivo the cholinesterase activity in a dose-dependent manner while significantly increasing the total cholinesterase activity and/or ACHE mRNA levels, independent of the liver cancer cell type. Our screen also identified novel phenothiazines, i.e., 8 and 10, with significant cytotoxic and cholinesterase modulatory effects in liver cancer cells; yet both compounds had low levels of toxicity in zebrafish. Moreover, they modulated the cholinesterase activity or expression of ACHE in a cancer cell line-specific manner, and compound 10 significantly inhibited the cholinesterase activity in zebrafish. Accordingly, using a successful combination of in silico, in vitro, and in vivo approaches, we identified several lead anticancer and cholinesterase modulatory PTZ derivatives for future research.

Multi-level toxicity assessment of the antidepressant venlafaxine in embryos/larvae and adults of zebrafish (Danio rerio)

The toxic effects of venlafaxine (VLX) on aquatic organisms have already been verified and therefore are a proven matter of concern. Herein, we evaluated zebrafish embryos/adults after acute exposure to VLX. Embryos/larvae were exposed to different concentrations of VLX (100-1000 mg/L; 1.33 as a dilution factor), to evaluate mortality/developmental changos and to analyze biomarkers (0.002-100 mg/L). For adults, mortality, genotoxicity, and biomarkers were assessed in five different concentrations of VLX (1-100 mg/L). The median lethal concentration (LC50-168h) was 274.1 mg/L for embryos/larvae, and >100 mg/L for adults (LC50-96h). VLX decreased the heart rate frequency and caused premature hatching and lack of equilibrium in embryos/larvae exposed to different concentrations ranging from 100 to 562.5 mg/L. The activity of acetylcholinesterase (AChE) was inhibited in larvae exposed to 1, 25 and 100 mg/L. Glutathione-S-transferase (GST) activity was reduced in both larvae and adults after exposure to different concentrations, mainly at 25 mg/L. For both larvae and adults, lactate dehydrogenase (LDH) activity increased after 100 mg/L of VLX exposure. No DNA damage was observed in peripheral erythrocytes. Exposure to VLX may cause adverse effects on zebrafish in their early and adult life stages, interfering with embryo-larval development, and can induce physiological disturbances in adults.

Impacts of cetylpyridinium chloride on the behavior and brain neurotransmitter levels of juvenile and adult zebrafish (Danio rerio)

Cetylpyridinium chloride (CPC) is a cationic surfactant that has been widely used as an antibacterial ingredient in pharmaceutical and personal care products. Due to its high residue in surface waters, there is increasing concern over the potential risk of CPC to aquatic ecosystems. However, knowledge of its impacts on fish is still limited. Therefore, this study exposed juvenile and adult zebrafish to CPC (0, 10, and 40 μg/L) for four days. Subsequently, changes in their behavioral traits and brain levels of several neurotransmitters were investigated. The behavioral assay showed that CPC exposure significantly decreased the locomotor activity and social interaction of zebrafish at both life stages, and juveniles were more sensitive to CPC exposure than adults. In the control groups, the brain neurotransmitters concentrations increased with age in zebrafish. However, CPC exposure tended to increase the brain neurotransmitter levels of juveniles but decreased their levels in adults. Correlation analysis revealed that the brain monoamine neurotransmitters and their turnover might play important roles in the life stage-dependent behavioral response to CPC. In particular, the DOPAC/DA ratio was significantly associated with CPC-induced hypoactivity and reduced social interactions in juveniles but not adults. Our findings demonstrated that CPC exposure could cause abnormal behavior in juvenile and adult zebrafish and disturb their brain neurotransmitters, even at environmentally relevant concentrations, and thus highlighted the necessity for further assessing its potential risks to aquatic ecosystems.

Toxicity of waterborne vortioxetine, a new antidepressant, in non-target aquatic organisms: From wonder to concern drugs?

Vortioxetine is increasing in popularity as a treatment for major depressive disorder and has been detected in wastewater effluent. However, information on the toxicity and environmental risk of vortioxetine in non-target organisms is scarce. Here, embryonic and juvenile zebrafish (Danio rerio) were used to assess the toxicity of vortioxetine (0, 1, 10, 30, 100, 300, and 1000 μg/L) after 120 h and 7 d of exposure, respectively. Vortioxetine induced significant toxicity during embryonic development, including effects on survival, hatching, basal heart rate, spontaneous tail coiling and developmental abnormalities, and inhibited larval locomotor activity at concentrations higher than 30 μg/L. Additionally, vortioxetine evoked anxiolytic-like behavior and caused histopathological changes to multiple organs (gills, heart, liver and intestine) in juvenile zebrafish. Significant increase in 5-HT content was observed in whole zebrafish larvae and juvenile brain tissues from animals treated with 1 or 100 μg/L vortioxetine. Notably, the lowest effective concentrations of vortioxetine for zebrafish were mainly in the range of 10-30 μg/L, which were slightly lower than the vortioxetine therapeutic concentrations. Risk quotients assuming conservative exposure assessments were above one in European countries indicating moderate risk for the behavioral endpoints assessed. We believe that these results highlight the adverse effects of vortioxetine on non-target organisms and that further investigations will be required to provide a higher confidence.

Persistent impact of amitriptyline on the behavior, brain neurotransmitter, and transcriptional profile of zebrafish (Danio rerio)

Discontinuation of amitriptyline (AMI) has been demonstrated to induce long-term withdrawal syndromes in mammals. However, no studies have focused on the persistent impacts of short-term AMI exposure on teleosts. Here, following exposure to AMI (2.5 and 40 μg/L) for 7 days (E7), zebrafish were transferred into AMI-free water to recover for 21 days (R21). The behavior, brain neurotransmitters, and brain transcriptional profiles were investigated on E7 and R21. AMI exposure induced persistent hypoactivity (2.5 and 40 μg/L) and abnormal schooling behavior (40 μg/L). AMI also induced long-term impacts on the brain serotonin (5-HT), 5-hydroxyindoleacetic acid, norepinephrine, and acetylcholine levels, several of which showed significant correlations with the locomotor activity or schooling behavior. Transcriptional analysis revealed persistent dysregulation in the pathways involved in the circadian rhythm, glycan biosynthesis and metabolism, and axon guidance in brain samples. Twelve genes were predicted as key driver genes in response to AMI exposure, and their significantly differential expression may direct changes across the related molecular networks. Moreover, upregulated brain 5-HT may serve as the central modulator of the persistent AMI pathogenesis in zebrafish. Considering AMI residues in natural waters may temporarily exceed μg/L, corresponding persistent adverse effects on teleosts should not be ignored.

Effects of different pharmaceutical residues on embryos of fish species native to Central Europe

Environmental concentrations of pharmacologically active substances are increasing dramatically throughout the world, to the point where they are now considered a serious threat to the aquatic environment. This high occurrence of pharmaceutical residues in the aquatic environment is due to an increase in i) the prescription and consumption of drugs, and ii) their subsequent discharge into wastewater and its imperfect purification in wastewater treatment plants. Recent surveys have clearly shown that such substances can have serious negative effects on non-target organisms. In the present study, we tested the effects of several commonly used pharmaceuticals, such as antidepressants, analgesics and antibiotics, on the embryonic stages of different fishes. Specifically, we applied concentration ranges of tramadol, enrofloxacin and nortriptylined on a common toxicological model organism, the zebrafish (Danio rerio), and other species native to Central European freshwaters, i.e. common carp (Cyprinus carpio), catfish (Silurus glanis) and tench (Tinca tinca). Our results show that, though malformation and negative impacts on hatching and mortality were only observed at the highest test concentrations, gene expression indicated that even low environmentally relevant concentrations (0.1 μg/L) can cause significant changes in early development of embryo.

Embryotoxicity of Selective Serotonin Reuptake Inhibitors—Comparative Sensitivity of Zebrafish (Danio rerio) and African Clawed Frog (Xenopus laevis) Embryos

Over the past twenty years, the prescription of antidepressant drugs has increased all over the world. After their application, antidepressants, like other pharmaceuticals, are excreted and enter the aquatic environment. They are dispersed among surface waters mainly through waste water sources, typically at very low concentrations— from a tenth up to hundreds of ng/L. Frequently detected antidepressants include fluoxetine and citalopram—both selective serotonin reuptake inhibitors. The aim of our study was to assess the embryotoxicity of fluoxetine hydrochloride and citalopram hydrochloride on the early life stages of zebrafish (Danio rerio) and the African clawed frog (Xenopus laevis). The embryos were exposed to various concentrations of the individual antidepressants and of their mixtures for 96 h. The tested levels included both environmentally relevant and higher concentrations for the evaluation of dose-dependent effects. Our study demonstrated that even environmentally relevant concentrations of these psychiatric drugs influenced zebrafish embryos, which was proven by a significant increase (p < 0.01) in the embryos’ heart rates after fluoxetine hydrochloride exposure and in their hatching rate after exposure to a combination of both antidepressants, and thus revealed a potential risk to aquatic life. Despite these results, we can conclude that the African clawed frog is more sensitive, since exposure to the highest concentrations of fluoxetine hydrochloride (10,000 μg/L) and citalopram hydrochloride (100,000 μg/L) resulted in total mortality of the frog embryos.

Environmental impacts of COVID-19 treatment: Toxicological evaluation of azithromycin and hydroxychloroquine in adult zebrafish

One of the most impact issues in recent years refers to the COVID-19 pandemic, the consequences of which thousands of deaths recorded worldwide, are still inferior understood. Its impacts on the environment and aquatic biota constitute a fertile field of investigation. Thus, to predict the impact of the indiscriminate use of azithromycin (AZT) and hydroxychloroquine (HCQ) in this pandemic context, we aim to assess their toxicological risks when isolated or in combination, using zebrafish (Danio rerio) as a model system. In summary, we observed that 72 h of exposure to AZT and HCQ (alone or in binary combination, both at 2.5 μg/L) induced the reduction of total protein levels, accompanied by increased levels of thiobarbituric acid reactive substances, hydrogen peroxide, reactive oxygen species and nitrite, suggesting a REDOX imbalance and possible oxidative stress. Molecular docking analysis further supported this data by demonstrating a strong affinity of AZT and HCQ with their potential antioxidant targets (catalase and superoxide dismutase). In the protein-protein interaction network analysis, AZT showed a putative interaction with different cytochrome P450 molecules, while HCQ demonstrated interaction with caspase-3. The functional enrichment analysis also demonstrated diverse biological processes and molecular mechanisms related to the maintenance of REDOX homeostasis. Moreover, we also demonstrated an increase in the AChE activity followed by a reduction in the neuromasts of the head when zebrafish were exposed to the mixture AZT + HCQ. These data suggest a neurotoxic effect of the drugs. Altogether, our study demonstrated that short exposure to AZT, HCQ or their mixture induced physiological alterations in adult zebrafish. These effects can compromise the health of these animals, suggesting that the increase of AZT and HCQ due to COVID-19 pandemic can negatively impact freshwater ecosystems.