Alterations in zebrafish development induced by simvastatin: Comprehensive morphological and physiological study, focusing on muscle

Early statin exposure influences cardiac and skeletal development with implications for ion channel transcriptomes in zebrafish

Statins, widely prescribed for cholesterol management by inhibiting HMG-CoA reductase in the cholesterol biosynthesis pathway, may also influence vertebrate development. In this study, we investigated the developmental effects of two widely used statins, atorvastatin (ATO) and pravastatin (PRA), on zebrafish offspring. For ATO, we administered doses classified as low (1 μM), medium (5 μM), and high (10 μM), while for PRA, the corresponding concentrations were set at low (18 μM), medium (180 μM), and high (270 μM). Our results showed significant reductions in birth and hatching rates, along with decreased body length in offspring at all ATO concentrations and medium to high PRA concentrations. A notable increase in malformation rates, especially in the spine and heart, was observed across all ATO treatments and in medium and high PRA groups. Additionally, we observed reduced heart contraction rates, decreased heart size, lower bone volumes, and diminished expression of mRNA osteogenic markers. Elevated venous sinus-artery bulb (SV-BA) ratios, increased thoracic area, and abnormal cartilage development were also prominent in all ATO-treated groups. Transcriptome analysis revealed alterations in genes predominantly associated with ion channels. These findings provide insights into the potential impacts of specific concentrations of statins on offspring development and highlight potential gene interactions with statins.

EmbryoNet: using deep learning to link embryonic phenotypes to signaling pathways

Evolutionarily conserved signaling pathways are essential for early embryogenesis, and reducing or abolishing their activity leads to characteristic developmental defects. Classification of phenotypic defects can identify the underlying signaling mechanisms, but this requires expert knowledge and the classification schemes have not been standardized. Here we use a machine learning approach for automated phenotyping to train a deep convolutional neural network, EmbryoNet, to accurately identify zebrafish signaling mutants in an unbiased manner. Combined with a model of time-dependent developmental trajectories, this approach identifies and classifies with high precision phenotypic defects caused by loss of function of the seven major signaling pathways relevant for vertebrate development. Our classification algorithms have wide applications in developmental biology and robustly identify signaling defects in evolutionarily distant species. Furthermore, using automated phenotyping in high-throughput drug screens, we show that EmbryoNet can resolve the mechanism of action of pharmaceutical substances. As part of this work, we freely provide more than 2 million images that were used to train and test EmbryoNet.

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

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

Establishment of a lipid metabolism disorder model in ApoEb mutant zebrafish

BACKGROUND AND AIMS

ApoEb is a zebrafish homologous to mammalian ApoE, whose deficiency would lead to lipid metabolism disorders (LMDs) like atherosclerosis. We attempted to knock out the zebrafish ApoEb, then establish a zebrafish model with LMD.

METHODS

ApoEb was knocked out using the CRISPR/Cas9 system, and the accumulation of lipids was confirmed by Oil Red O staining, confocal imaging, and lipid measurements. The lipid-lowering effects of simvastatin (SIM), ezetimibe (EZE) and Xuezhikang (XZK), an extract derived from red yeast rice, were evaluated through in vivo imaging in zebrafish larvae.

RESULTS

In the ApoEb mutant, significant vascular lipid deposition occurred, and lipid measurement performed in the whole-body homogenate of larvae and adult plasma showed significantly increased lipid levels. SIM, EZE and XZK apparently relieved hyperlipidemia in ApoEb mutants, and XZK had a significant inhibitory effect on the recruitment of neutrophils and macrophages.

CONCLUSIONS

In this study, an LMD model has been established in ApoEb mutant zebrafish. We suggest that this versatile model could be applied in studying hypercholesterolemia and related vascular pathology in the context of early atherosclerosis, as well as the physiological function of ApoE.

Systems assessment of statins hazard: Integrating in silico prediction, developmental toxicity profile and transcriptomics in zebrafish

Statins are prescribed widely as lipid-lowering agents. However, statins are associated with an increased harmful risk on public health and the ecosystem. Little is known about statins' toxicity on biological development and the underlying molecular mechanisms. We exposed zebrafish embryos to a series of statins to evaluate their development toxicity. Statins-induced embryonic developmental defects in a concentration-dependent manner. 72 h LC₅₀ values for lovastatin, simvastatin, fluvastatin, atorvastatin, rosuvastatin, and pravastatin were 0.01 μM, 0.04 μM, 1.93 μM, 37.28 μM, 79.29 μM, and 2170 μM, respectively. Moreover, the expression of genes involved in heart contraction, calcium ion binding, transcription factors, nucleus, and G protein-coupled receptor signaling pathway was altered by statins. The early growth response gene (egr4) and transcription factor genes (fosab and fosb) were screened as potential toxicity targets due to their significant upregulation based on protein-protein interaction (PPI) and drug-gene interaction network analysis. Finally, the ecotoxicity profile of statins was predicted by in silico method, and statins were high or moderate risk to aquatic organisms. We provide a systems toxicology strategy to explore the toxicity of statins and illustrate the potential mechanisms of action.

Simvastatin as an emerging pollutant on non-target aquatic invertebrates: effects on antioxidant-related genes in Daphnia magna

Simvastatin (SIM) is one of the most widely used lipid-lowering drugs and consequently has been frequently detected in various waters. However, its potential adverse effects and toxic mechanisms on non-target organisms such as Daphnia magna (D. magna) remain still unclear. In the present study, the expressions of Nrf2 and antioxidant genes including Keap1, HO-1, GCLC, GST, SOD, CAT, GPx5, GPx7, GRx, TRX, TrxR, and Prx1 in D. magna exposed to SIM for 24 h, 48 h, and 96 h were investigated. The changes of SOD, CAT, GST, and GPx enzymatic activities, and the GSH and MDA content under SIM for 48-h exposure were also addressed. Results showed that the expression of Nrf2 was inhibited at 24 h but induced at 96 h, displaying a time- and/or dose-dependent relationship under SIM exposure. In contrast, Keap1 exhibited induction at 24 h. HO-1 showed significant induction under SIM exposure for different time. SOD generally displayed an induction trend under SIM exposure for different periods. GPX5 expression showed significant induction under SIM exposure, particularly at 24 h in 5 µg L^-1 increasing 15 folds of the control. But GPX7 expression generally displayed inhibition except in 5 µg L^-1. Trx and TrxR showed different induction or inhibition, which was depended on the exposure time and concentration. Prx1 displayed significant induction in most SIM groups. In addition, the decreasing GSH and increasing MDA content also indicated oxidative stress of SIM exposure. Overall, SIM exposure affected the expression of Nrf2 and antioxidant-related genes and altered the redox homeostasis of D. magna, even may cause the morphological changes such as shorten spine and abnormal development eye.

Assessment of the Preventive Effect of L-carnitine on Post-statin Muscle Damage in a Zebrafish Model

Statins, such as lovastatin, are lipid-lowering drugs (LLDs) that have been used to treat hypercholesterolaemia, defined as abnormally elevated cholesterol levels in the patient’s blood. Although statins are considered relatively safe and well tolerated, recipients may suffer from adverse effects, including post-statin myopathies. Many studies have shown that supplementation with various compounds may be beneficial for the prevention or treatment of side effects in patients undergoing statin therapy. In our study, we investigated whether L-carnitine administered to zebrafish larvae treated with lovastatin alleviates post-statin muscle damage. We found that exposure of zebrafish larvae to lovastatin caused skeletal muscle disruption observed as a reduction of birefringence, changes in muscle ultrastructure, and an increase in atrogin-1. Lovastatin also affected heart performance and swimming behaviour of larvae. Our data indicated that the muscle-protective effect of L-carnitine is partial. Some observed myotoxic effects, such as disruption of skeletal muscle and increase in atrogin-1 expression, heart contraction could be rescued by the addition of L-carnitine. Others, such as slowed heart rate and reduced locomotion, could not be mitigated by L-carnitine supplementation.

Simvastatin and Muscle: Zebrafish and Chicken Show that the Benefits are not Worth the Damage

Simvastatin is one of the most common medicines prescribed to treat human hypercholesterolemia. Simvastatin acts through the inhibition of cholesterol synthesis. Unfortunately, simvastatin causes unwanted side effects on muscles, such as soreness, tiredness, or weakness. Therefore, to understand the mechanism of action of simvastatin, it is important to study its physiological and structural impacts on muscle in varied animal models. Here we report on the effects of simvastatin on two biological models: zebrafish embryos and chicken muscle culture. In the last years, our group and others showed that simvastatin treatment in zebrafish embryos reduces fish movements and induces major structural alterations in skeletal muscles. We also showed that simvastatin and membrane cholesterol depletion induce major changes in proliferation and differentiation of muscle cells in chick muscle cultures. Here, we review and discuss these observations considering reported data on the use of simvastatin as a potential therapy for Duchenne muscular dystrophy.

Exposure to Deepwater Horizon crude oil increases free cholesterol in larval red drum (Sciaenops ocellatus)

The 2010 Deepwater Horizon oil spill impacted over 2100 km of shoreline along the northern Gulf of Mexico, which coincided with the spawning season of many coastal species, including red drum (Sciaenops ocellatus). Red drum develop rapidly and are sensitive to crude oil exposure during the embryonic and larval periods. This study investigates the predictions from recent transcriptomic studies that cholesterol biosynthetic processes are impacted by oil exposure in fish early life stages. We found that red drum larvae exposed for 72 h to ΣPAH₅₀ 3.55-15.45 µg L^-1 exhibited significantly increased pericardial area, a cardiotoxicity metric, but the expression of several genes targeted in the cholesterol synthesis pathway was not affected. However, whole-mount staining revealed significant increases in free cholesterol throughout the larval body (ΣPAH₅₀ 4.71-16.15 µg L^-1), and total cholesterol followed an increasing trend (ΣPAH₅₀ 3.55-15.45 µg L^-1). Cholesterol plays a critical role in fish embryo development and ion channel function. Therefore, the disruption of cholesterol homeostasis, as observed here, could play a role in the oil toxicity phenotype observed across many fish species.

Developmental toxicity induced by particulate matter (PM2.5) in zebrafish (Danio rerio) model

Contemporary research in epidemiology has found that being exposed to air pollution at an early stage of life has associations with both acute and chronic conditions of the multi-organs. Nevertheless, the reasons for this have yet to be fully explained. Because of this there is a need for a robust investigation into the damaging toxic influence of diesel particulate matter (PM2.5) on living organisms. This study is aimed to investigate the developmental toxicity of PM2.5 by using zebrafish (Danio rerio) embryo/larvae as a disease model and to understand the toxicity effects of PM2.5 on ecological environment more thoroughly. This research demonstrates that being exposed to PM2.5 leads to a significant increase in mortality, effective developmental morphology, reductions in hatching rates and lower heart rates in zebrafish. Additionally, it leads to increases in the length of string heart, area of pericardium, and apoptosis, reduces the number of normal intersegmental vessels (ISVs) and motor neurons in the trunk region and liver formation defects in zebrafish embryos. Investigation employing a scanning electron microscope demonstrates that being exposed to PM2.5 leads to damage in zebrafish larvae skin cell layers. Histological analysis demonstrates that when these larvae are treated with PM2.5 then abnormalities occur in the neurons, liver, heart, gills, brain, and eyes, and remarkable increase in in the cellular/subcellular levels of organelle dissolution. These findings are useful to help us understand the pathophysiological influence of being exposed to PM2.5 on the multi-organ defects of zebrafish. More research into which particular elements that make up diesel pollution contribute to this toxicity is needed so that the dangers to development can be further analysed.

Effects of Phenanthrene Exposure on Cholesterol Homeostasis and Cardiotoxicity in Zebrafish Embryos

Polycyclic aromatic hydrocarbons (PAHs) are pervasive pollutants in aquatic ecosystems, and developing fish embryos are especially sensitive to PAH exposure. Exposure to crude oil or phenanthrene (a reference PAH found in oil) produces an array of gross morphological abnormalities in developing fish embryos, including cardiotoxicity. Recently, studies utilizing transcriptomic analyses in several oil-exposed fish embryos found significant changes in the abundance of transcripts involved in cholesterol biosynthesis. Given the vital role of cholesterol availability in embryonic heart development, we hypothesized that cholesterol dysregulation in early development contributes to phenanthrene-induced cardiotoxicity. We exposed zebrafish embryos to 12 or 15 µM phenanthrene from 6 to 72 h post fertilization (hpf) and demonstrated that, in conjunction with pericardial edema and bradycardia, several genes (fdft1 and hmgcra) in the cholesterol biosynthetic pathway were significantly altered. When embryos were pretreated with a cholesterol solution from 6 to 24 hpf followed by exposure to phenanthrene from 24 to 48 hpf, the effects of phenanthrene on heart rate were partially mitigated. Despite changes in gene expression, whole-mount in situ staining of cholesterol was not significantly affected in embryos exposed to phenanthrene ranging in stage from 24 to 72 hpf. However, the 2-dimensional yolk area was significantly increased with phenanthrene exposure at 72 hpf, suggesting that lipid transport from the yolk to the developing embryo was impaired. Environ Toxicol Chem 2021;40:1586-1595. © 2021 SETAC.

Zebrafish as a Model for the Study of Lipid-Lowering Drug-Induced Myopathies

Drug-induced myopathies are classified as acquired myopathies caused by exogenous factors. These pathological conditions develop in patients without muscle disease and are triggered by a variety of medicaments, including lipid-lowering drugs (LLDs) such as statins, fibrates, and ezetimibe. Here we summarise the current knowledge gained via studies conducted using various models, such as cell lines and mammalian models, and compare them with the results obtained in zebrafish (Danio rerio) studies. Zebrafish have proven to be an excellent research tool for studying dyslipidaemias as a model of these pathological conditions. This system enables in-vivo characterization of drug and gene candidates to further the understanding of disease aetiology and develop new therapeutic strategies. Our review also considers important environmental issues arising from the indiscriminate use of LLDs worldwide. The widespread use and importance of drugs such as statins and fibrates justify the need for the meticulous study of their mechanism of action and the side effects they cause.

REP1 deficiency causes systemic dysfunction of lipid metabolism and oxidative stress in choroideremia

Choroideremia (CHM) is an X-linked recessive chorioretinal dystrophy caused by mutations in CHM, encoding for Rab escort protein 1 (REP1). Loss of functional REP1 leads to the accumulation of unprenylated Rab proteins and defective intracellular protein trafficking, the putative cause for photoreceptor, retinal pigment epithelium (RPE), and choroidal degeneration. CHM is ubiquitously expressed, but adequate prenylation is considered to be achieved, outside the retina, through the isoform REP2. Recently, the possibility of systemic features in CHM has been debated; therefore, in this study, whole metabolomic analysis of plasma samples from 25 CHM patients versus age- and sex-matched controls was performed. Results showed plasma alterations in oxidative stress-related metabolites, coupled with alterations in tryptophan metabolism, leading to significantly raised serotonin levels. Lipid metabolism was disrupted with decreased branched fatty acids and acylcarnitines, suggestive of dysfunctional lipid oxidation, as well as imbalances of several sphingolipids and glycerophospholipids. Targeted lipidomics of the chmru848 zebrafish provided further evidence for dysfunction, with the use of fenofibrate over simvastatin circumventing the prenylation pathway to improve the lipid profile and increase survival. This study provides strong evidence for systemic manifestations of CHM and proposes potentially novel pathomechanisms and targets for therapeutic consideration.

Simvastatin affects Nrf2/MAPK signaling pathway and hepatic histological structure change in Gambusia affinis

Simvastatin (SV) is a typical lipid-lowering agent detected widely in waters, so its latent toxic effects to fish are deserved of concern. The purposes of this study aim at revealing the responses of antioxidant system in mosquitofish (Gambusia affinis) under SV exposure. Transcriptional expressions of oxidative stress-related key transcriptional factor Nrf2 and its downstream genes in mosquitofish were determined under SV exposure for different time. Partly related enzymatic activities, Nrf2 and MAPK protein expressions were also addressed in the same conditions, and histological changes in liver tissues were investigated too. Results showed that Nrf2 mRNA increased with the rising SV concentrations at 3 d and 7 d, displaying typical dose-dependent relationship, and Nrf2 protein by WB showed consistency with transcriptional changes to some degree. Comparatively, responses of gene expressions were more sensitive than enzymatic changes. The histological changes in the mosquitofish liver exposed to SV for 7 d indicated the potential adverse effects of statins. This work demonstrated that SV in aquatic environment could affect the transcriptional expression of antioxidant system, partly related enzymatic activity, and hepatic structure in the mosquitofish, revealing its potential risk on non-target organisms and environmental safety.

Polystyrene Nanoplastics Can Alter the Toxicological Effects of Simvastatin on Danio rerio

Once in the environment, nanoplastics (NPls) may interact with other contaminants, such as pharmaceuticals, potentially acting as carriers and modulating their toxicity. Thus, the main aim of the current study is to investigate how polystyrene (PS) NPls (mean diameter: 60 nm) interact with simvastatin (SIM), an anticholesterolemic drug, and modulate its toxicity to zebrafish (Danio rerio) embryos. PS NPls were carboxyl group functionalized, to promote the interaction/binding of NPls with SIM (worst-case scenarios) and it was fluorescently dyed, allowing to detect the intake. Exposure was 96 h to 0–150 mg/L NPls or 0–150 µg/L SIM, as well as to dual combinations (NPls 0.015 or 1.5 mg/L and SIM 12.5 or 15 µg/L). PS NPls alone did not exert effects whereas SIM (≥12.5 µg/L) significantly delayed the hatching, decreased the heartbeat, induced edemas and mortality. The combination of NPls (1.5 mg/L) and SIM (12.5 or 15 µg/L) had significant effects on the survival of the organisms while the correspondent NPls and SIM single exposures did not have significant effects on this endpoint. Concerning the malformations appearance, SIM alone had similar effects than when in co-exposures (0.015 mg/L NPls plus 12.5 or 15 µg/L SIM). Hatching and heartbeat increased after the co-exposures SIM and NPls comparing with SIM single exposures, showing that 0.015 mg/L NPls plus 12.5 or 15 µg/L SIM did not cause significant effects on these endpoints. This study shows that NPls effects on bioavailability and toxicity of other contaminants cannot be ignored when assessing the environmental behavior and risks of NPls.

Acute and chronic effects of environmental realistic concentrations of simvastatin in danio rerio: evidences of oxidative alterations and endocrine disruptive activity

Due to their wide use, pharmaceuticals can be discarded, metabolized and excreted into the environment, potentially affecting aquatic organisms. Lipid-regulating drugs are among the most prescribed medications around the world, to control human cholesterol levels, in more than 20 million patients. Despite this massive use of lipid-regulating drugs, particularly simvastatin, the role of these drugs is not fully characterized and understood in terms of its potential toxicological effects at the environmental level. This work intended to characterize the toxicity of an acute (120 h post-fertilization) and chronic (60 days) exposure to the antihyperlipidemic drug simvastatin (in concentrations of 92.45, 184.9, 369.8, 739.6 and 1479.2 ng L^-1), in the freshwater species zebrafish (Danio rerio). The concentrations hereby mentioned were implemented in both exposures, and were based on levels found in wastewater treatment plant influents (11.7 ± 3.2 μg L^-1), effluents (2.65 ± 0.8 μg L^-1) and Apies River (1.585 ± 0.3 μg L^-1), located in Pretoria, South Africa and, particularly in the maximum levels found in effluents from wastewater treatment plants in Portugal (369.8 ng L^-1). The acute effects were analysed focusing on behavioural endpoints (erratic and purposeful swimming), total distance travelled and swimming time), biomarkers of oxidative stress (the activities of the enzymes superoxide dismutase, catalase, glutathione peroxidase), biotransformation (the activity of glutathione S-transferases) and lipid peroxidation (levels of thiobarbituric acid reactive substances). Animals chronically exposed were also histologically analysed for sex determination and gonadal developmental stages identification. In terms of acute exposure, significant alterations were reported in terms of behavioural alterations (hyperactivity), followed by a general reduction in all tested biomarkers. Also, the analysis of chronically exposed fish evidenced no alterations in sex ratio and maturation stages. In addition, the analysis of chronically exposed fish evidenced no alterations in terms of sexual characteristics, suggesting that the chronic exposure of Danio rerio to simvastatin does not alter the sex ratio and maturation stages of individuals. This assumption suggests that simvastatin did not act as an endocrine disruptor. Moreover, the metabolism, neuronal interactions and the antioxidant properties of SIM seem to have modulated the hereby-mentioned results of toxicity. Results from this assay allow inferring that simvastatin can have an ecologically relevant impact in living organisms.

A Multi-Model Pipeline for Translational Intracerebral Haemorrhage Research

Apart from acute and chronic blood pressure lowering, we have no specific medications to prevent intracerebral haemorrhage (ICH) or improve outcomes once bleeding has occurred. One reason for this may be related to particular limitations associated with the current pre-clinical models of ICH, leading to a failure to translate into the clinic. It would seem that a breakdown in the 'drug development pipeline' currently exists for translational ICH research which needs to be urgently addressed. Here, we review the most commonly used pre-clinical models of ICH and discuss their advantages and disadvantages in the context of translational studies. We propose that to increase our chances of successfully identifying new therapeutics for ICH, a bi-directional, 2- or 3-pronged approach using more than one model species/system could be useful for confirming key pre-clinical observations. Furthermore, we highlight that post-mortem/ex-vivo ICH patient material is a precious and underused resource which could play an essential role in the verification of experimental results prior to consideration for further clinical investigation. Embracing multidisciplinary collaboration between pre-clinical and clinical ICH research groups will be essential to ensure the success of this type of approach in the future.

An in vivo brain-bacteria interface: the developing brain as a key regulator of innate immunity

Infections have numerous effects on the brain. However, possible roles of the brain in protecting against infection, and the developmental origin and role of brain signaling in immune response, are largely unknown. We exploited a unique Xenopus embryonic model to reveal control of innate immune response to pathogenic E. coli by the developing brain. Using survival assays, morphological analysis of innate immune cells and apoptosis, and RNA-seq, we analyzed combinations of infection, brain removal, and tail-regenerative response. Without a brain, survival of embryos injected with bacteria decreased significantly. The protective effect of the developing brain was mediated by decrease of the infection-induced damage and of apoptosis, and increase of macrophage migration, as well as suppression of the transcriptional consequences of the infection, all of which decrease susceptibility to pathogen. Functional and pharmacological assays implicated dopamine signaling in the bacteria–brain–immune crosstalk. Our data establish a model that reveals the very early brain to be a central player in innate immunity, identify the developmental origins of brain–immune interactions, and suggest several targets for immune therapies.

The glucocorticoid-induced leucine zipper mediates statin-induced muscle damage

Statins, the most prescribed class of drugs for the treatment of hypercholesterolemia, can cause muscle-related adverse effects. It has been shown that the glucocorticoid-induced leucine zipper (GILZ) plays a key role in the anti-myogenic action of dexamethasone. In the present study, we aimed to evaluate the role of GILZ in statin-induced myopathy. Statins induced GILZ expression in C2C12 cells, primary murine myoblasts/myotubes, primary human myoblasts, and in vivo in zebrafish embryos and human quadriceps femoris muscle. Gilz induction was mediated by FOXO3 activation and binding to the Gilz promoter, and could be reversed by the addition of geranylgeranyl, but not farnesyl, pyrophosphate. Atorvastatin decreased Akt phosphorylation and increased cleaved caspase-3 levels in myoblasts. This effect was reversed in myoblasts from GILZ knockout mice. Similarly, myofibers isolated from knockout animals were more resistant toward statin-induced cell death than their wild-type counterparts. Statins also impaired myoblast differentiation, and this effect was accompanied by GILZ induction. The in vivo relevance of our findings was supported by the observation that gilz overexpression in zebrafish embryos led to impaired embryonic muscle development. Taken together, our data point toward GILZ as an essential mediator of the molecular mechanisms leading to statin-induced muscle damage.

Chronic exposure to environmentally relevant levels of simvastatin disrupts zebrafish brain gene signaling involved in energy metabolism

Simvastatin (SIM), a hypocholesterolaemic drug belonging to the statins group, is a widely prescribed pharmaceutical for prevention of cardiovascular diseases. Several studies showed that lipophilic statins, as SIM, cross the blood-brain barrier and interfere with the energy metabolism of the central nervous system in humans and mammalian models. In fish and other aquatic organisms, the effects of SIM on the brain energy metabolism are unknown, particularly following exposure to low environmentally relevant concentrations. Therefore, the present study aimed at investigating the influence of SIM on gene signaling pathways involved in brain energy metabolism of adult zebrafish (Danio rerio) following chronic exposure (90 days) to environmentally relevant SIM concentrations ranging from 8 ng/L to 1000 ng/L. Real-time PCR was used to determine the transcript levels of several genes involved in different pathways of the brain energy metabolism (glut1b, gapdh, acadm, accα, fasn, idh3a, cox4i1, and cox5aa). The findings here reported integrated well with ecological and biochemical responses obtained in a parallel study. Data demonstrated that SIM modulates transcription of key genes involved in the mitochondrial electron transport chain, in glucose transport and metabolism, in fatty acid synthesis and β-oxidation. Further, SIM exposure led to a sex-dependent transcription profile for some of the studied genes. Overall, the present study demonstrated, for the first time, that SIM modulates gene regulation of key pathways involved in the energy metabolism in fish brain at environmentally relevant concentrations.

Indole-3-carbinol inhibits lipid deposition and promotes autophagy in hyperlipidemia zebrafish larvae

Indole-3-carbinol (I3C) is extracted from cruciferous vegetables and is well known for its anti-cancer, antioxidant and anti-inflammatory effects. This study investigated the protective effect of I3C in hyperlipidemia zebrafish larvae and early life stage toxicity of I3C on zebrafish embryos/larvae. Zebrafish larvae were fed with 4% high-cholesterol diet (HCD) and treated with I3C 2.5μmol/L and 5μmol/L for two weeks. Confocal image analysis, oil Red O staining were used to analysis vascular lipid accumulation and western blotting was used to evaluate possible mechanics. In addition, zebrafish embryos were treated with I3C for 96 h to assess the general toxicity and cardiotoxicity. We found that lipid deposition on vasculature was dose-dependently decreased in the I3C treated groups as compared with control group (47%, 23%, p<0.01). Moreover, we demonstrated that I3C inhibited lipid deposition by inducing autophagy, as identified by the enhancement of LC3-II, beclin-1, hVps34 and m-cathepsin D as well as by the reduction of P62, Bcl-2, Akt, p- Akt, mTOR, and p- mTOR in HCD fed zebrafish larvae (p<0.05). In summary, I3C shows protective effects on hyperlipidemia zebrafish larvae and maybe a promising multitarget drug in the prevention and protection against atherosclerotic.

Effects of simvastatin on the PXR signaling pathway and the liver histology in Mugilogobius abei

Simvastatin is one of the most commonly cholesterol-lowering prescribed drugs all over the world. With the increase of consumption of these pharmaceuticals and subsequent their discharge into the aquatic environment in recent years, they are present at detectable levels in most sewage effluents. Unfortunately, limited information is provided about their potential impacts on aquatic organisms, especially on the detoxification-related metabolism in fish. In the present study, one local native benthic fish (Mugilogobius abei) in southern China was employed as test species and exposed to SV (0.5 μg L^-1, 5 μg L^-1, 50 μg L^-1 and 500 μg L^-1) for 72 h. The transcriptional expression of nucleus transcriptional factor pregnane X receptor (PXR) and its downstream targeted genes including multixenobiotics resistance protein or permeability glycoprotein (P-gp), cytochrome 1A (CYP1A), cytochrome P450 3A (CYP3A), glutathione-S-transferase (GST) and the expression of associated microRNA such as miR-27, miR-34 and miR-148 in Mugilogobius abei were investigated. Result showed that the expressions of P-gp, CYP 1A, CYP 3A, GST and PXR were induced to some extend under simvastatin exposure for 72 h. A positive correlation was observed between PXR and CYP1A, CYP3A and P-gp. While for microRNA, a negative relationship was found between miR-34a and CYP3A, CYP1A. The expression of miR-148a was significantly induced under the exposure of SV (50 μg L^-1), which was positive related to the transcriptional expression of PXR. For enzyme activity, erythromycin N-demethylase (ERND) significantly increased at 24 h and the activity of catalase (CAT) and superoxide dismutase (SOD) exhibited different trends. CAT was slightly inhibited at 24 h exposure but SOD was significantly induced in high concentration. Glutathione-S-transferase (GST) activity was significant inhibited after 72 h exposure. The reductive small molecule glutathione (GSH) content showed obvious decrease, while the quantity of malondialdehyde (MDA) increased significantly in high concentrations of SV exposure. GSH and MDA showed a typical negative correlation to some degree. Moreover, simvastatin caused histological changes in the liver tissues of M. abei, especially the size of adipocyte significantly decreased. The present study indicated that environmentally relevant concentration SV may affect the PXR signaling pathway in M. abei and pose potential ecological risks to non-target organisms like fish.

Chronic environmentally relevant levels of simvastatin disrupt embryonic development, biochemical and molecular responses in zebrafish (Danio rerio)

Simvastatin (SIM), a hypocholesterolaemic compound, is among the most prescribed pharmaceuticals for cardiovascular disease prevention worldwide. Several studies have shown that acute exposure to SIM causes multiple adverse effects in aquatic organisms. However, uncertainties still remain regarding the chronic effects of SIM in aquatic ecosystems. Therefore, the present study aimed to investigate the effects of SIM in the model freshwater teleost zebrafish (Danio rerio) following a chronic exposure (90 days) to environmentally relevant concentrations ranging from 8 ng/L to 1000 ng/L. This study used a multi-parameter approach integrating distinct ecologically-relevant endpoints, i.e. survival, growth, reproduction and embryonic development, with biochemical markers (cholesterol and triglycerides). Real Time PCR was used to analyse the transcription levels of key genes involved in the mevalonate pathway (hmgcra, cyp51, and dhcr7). Globally, SIM induced several effects that did not follow a dose-response relationship; embryonic development, biochemical and molecular markers, were significantly impacted in the lower concentrations, 8 ng/L, 40 ng/L and/or 200 ng/L, whereas no effects were recorded for the highest tested SIM levels (1000 ng/L). Taken together, these findings expand our understanding of statin effects in teleosts, demonstrating significant impacts at environmentally relevant concentrations and highlight the importance of addressing the effects of chemicals under chronic low-level concentrations.

Response of PXR signaling pathway to simvastatin exposure in mosquitofish (Gambusia affinis) and its histological changes

As a widely used lipid lowering agent, simvastatin recently has been frequently detected in aquatic environment and the potential adverse effects from simvastatin exposure to non-target organisms such as fish is worthy of more attention. The aim of this study was to reveal the responses of detoxification system in fish to simvastatin exposure. In this investigation a ubiquitous small freshwater fish, mosquito fish (Gambusia affinis), was employed as test organism, and the transcriptional expression of nucleus transcriptional factor pregnane X receptor (PXR) and its downstream genes, including P-glycoprotein (P-gp), cytochrome 3A (CYP3A), multidrug resistance protein 2 (MRP2), UDP-glucuronosyl transferase (UGT) in mosquito fish were investigated by qRT-PCR methods under the exposure of concentrations of simvastatin (0.5 μg L-1, 5 μg L-1, 50 μgL-1, 500 μg L-1) for 24 h, 72 h and 168 h. The related enzyme activity (Erythromycin-N-Demethylase, ERND), the protein expression of PXR and the histological changes of liver tissues in fish were also determined via west blotting and transmission electron microscope approaches in the same conditions. Results showed that the mRNA expression of PXR, CYP3A and P-gp showed significantly changes under simvastatin exposure, exhibiting an obvious time/dose-effect relationship with the prolong of exposure time. ERND activity also showed time-effect at 24 h, and western blotting showed PXR protein displaying a dose-effect relationship to some extent. Hepatocyte cellular of mosquito fish exposed to simvastatin (5 μg L-1, 168 h) exhibited obvious histological changes in form of swelling, incomplete fragmentary structure etc. Overall, simvastatin altered the expression of PXR signaling pathway and subsequently bring about changes in high-levels of mosquito fish.

Coenzyme Q10 protects against statin-induced myotoxicity in zebrafish larvae (Danio rerio)

3-Hydroxy-3-methylglutaryl-CoA reductase (HMGCR) is the rate-limiting enzyme of the mevalonic acid pathway and is required for cholesterol biosynthesis and the synthesis of Coenzyme Q10 (CoQ10). Statins inhibit HMGCR, thus inhibiting the downstream products of this pathway including the biosynthesis of decaprenyl-pyrophosphate that is critical for the synthesis of Coenzyme Q10 (CoQ10). We show that zebrafish (Danio rerio) larvae treated in tank water with Atorvastatin (ATV; Lipitor) exhibited movement alterations and reduced whole body tissue metabolism. The ATV-inhibition of HMGCR function altered transcript abundance of muscle atrophy markers (atrogen-1, murf) and the mitochondrial biogenesis marker (pgc-1α). Furthermore, ATV-induced reduction in larval response to tactile stimuli was reversed with treatment of CoQ10. Together, the implication of our results contributes to the understanding of the mechanisms of action of the statin-induced damage in this model fish species.