Perfluorooctane sulfonate impairs the cardiac development of a marine medaka (Oryzias melastigma)

PFOS and PFOSA induce oxidative stress-mediated cardiac defects in zebrafish via PPARγ and AHR pathways, respectively

Perfluorooctane sulfonate (PFOS) and its precursor, perfluorooctane sulfonamide (PFOSA), are widespread in the environment. Evidence suggests a strong link between maternal exposure to PFOS/PFOSA and congenital heart diseases in the offspring, but the underlying mechanisms remain unclear. We hypothesized that PFOS and PFOSA induce cardiac defects through the peroxisome proliferator-activated receptor gamma (PPARγ) and aryl hydrocarbon receptor (AHR) pathways, respectively. In this study, we demonstrated that exposing zebrafish embryos to either PFOSA or PFOS caused cardiac malformations and dysfunction. Both PFOS and PFOSA induced reactive oxygen species (ROS) overproduction, mitochondrial damage, and apoptosis in zebrafish larvae hearts. Blockade of PPARγ through either pharmaceutical inhibition or genetic knockdown only attenuated the changes caused by PFOS, but not those elicited by PFOSA. Conversely, inhibition of AHR alleviated the adverse effects induced by PFOSA but not by PFOS. Both PFOSA and PFOS exhibited similar binding affinities to AHR using molecular docking techniques. The varying ability of PFOS and PFOSA to induce AHR activity in zebrafish embryonic hearts can be attributed to their different capabilities for activating PPARγ. In summary, our findings indicate that PFOS and PFOSA induce excessive ROS production in zebrafish larvae via the PPARγ and AHR pathways, respectively. This oxidative stress in turn causes mitochondrial damage and apoptosis, leading to cardiac defects.

The effect of tris (1,3-dichloro-2-propyl) phosphate on the early embryonic heart development of Oryzias melastigma

The flame retardant tri (1, 3-dichloro-2-propyl) phosphate (TDCIPP) is widely present in environmental media and organisms. People have paid much attention to the growth and developmental toxicity of TDCIPP, but there is little information about its cardiotoxicity and potential mechanisms. In this study, marine medaka (Oryzias melastigma) embryos were exposed to TDCIPP solutions (0, 0.05, 0.5, 5, and 50 μg/L) for 21 days to investigate the adverse effects of TDCIPP on cardiac development. The results showed that TDCIPP exposure altered the heart rate at different stages of embryonic development. In addition, 50 μg/L TDCIPP resulted in increased sinus venosus (SV)-bulbus arteriosus (BA) distance, pericardial cysts, and cardiac linearization in newly hatched fish. During embryonic development, the expression level of key genes regulating cardiac development is disturbed. The early stage of cardiac development is the sensitive window period for the toxic effects of TDCIPP. Oxidative stress was observed in newly hatched juveniles, but no significant lipid peroxidation damage was observed. In addition, vitellogenin (VTG) levels in juvenile fish were significantly reduced. Our results show that TDCIPP exposure induces cardiotoxicity in marine medaka embryos, which is induced in the early stages and promotes heart defects by amplifying inflammatory responses at a later stage.

Chronic environmental level exposure to perfluorooctane sulfonate overshadows graphene oxide to induce apoptosis through activation of the ROS-p53-caspase pathway in marine medaka Oryzias melastigma

The widespread occurrence of perfluorooctane sulfonate (PFOS) and the mass production and application of graphene oxide (GO) lead to their inevitable release and interaction in the environment, which may enhance associated toxic impacts on aquatic organisms. This study elucidates the induction of apoptosis by 60-day chronic single and mixture exposures to environmentally relevant levels of PFOS (0.5 μg/L and 5 μg/L) and GO (1 mg/L) in adult marine medaka Oryzias melastigma. Results showed a significant increase (p < 0.05) in reactive oxygen species (ROS) levels, the apoptotic positive rate in livers, and activities of caspases 3, 8, and 9 in all treated groups compared to the control. PFOS individual and PFOS-GO combined exposures significantly impacted fish growth, upregulated expressions of six apoptosis-related genes including p53, apaf1, il1b, tnfa, bcl2l1, bax, as well as enriched cell cycle and p53 signaling pathways (transcriptomic analysis) related to apoptosis compared to control group. Besides higher ROS production, GO also had a higher binding affinity to proteins than PFOS, especially to caspase 8 as revealed by molecular docking. Overall, PFOS induced ROS-p53-caspase apoptosis pathway through multi-gene regulation during single or mixture exposure, while GO single exposure induced apoptosis through tissue damage and ROS-caspase pathway activation and direct docking with caspase 8 to activate the caspase cascade. Under co-exposure, the PFOS-induced apoptotic pathway overshadowed the GO-induced pathway, due to competition for limited active sites on caspases. These findings will contribute to a better understanding of the apoptosis mechanism and ecological risks of nanomaterials and per- and polyfluoroalkyl substances in marine ecosystems.

A second hit by PFOS exposure exacerbated developmental defects in medaka embryos with a history of ancestral BPA exposure

Bisphenol-A (BPA), a known endocrine-disrupting chemical (EDC) in plastics and resins, has been found to induce heritable health effects in fish and mammals, affecting directly exposed individuals and indirectly their progenies in subsequent generations. It is not clearly understood if subsequent generations of the BPA-exposed ancestors have increased sensitivity to the second hit by the chemicals of emerging concern. To understand this, the present study examined the effects of developmental exposure to perfluorooctanesulfonic acid (PFOS), which has been a global contaminant recently, in embryos whose ancestors were exposed to BPA. Two lineages of medaka (Oryzias latipes) were established: 1) the BPA lineage in which the F0 generation was exposed to 10 μg/L BPA during early development and 2) the control lineage with no BPA exposure in the F0 generation. These lineages were raised up to the F4 generation without further exposure. The embryos of the F4 generation were exposed to PFOS at 0, 0.002, 0.02, 0.2, 2, and 20 mg/L concentrations. Early developmental defects resulting in mortality, delayed hatching, teratogenic phenotypes, and altered gene expression were examined in both lineages. The expression level of genes encoding DNA methyltransferases and genes responsible for oxidative stress defense were determined. Following environmentally relevant PFOS exposure, organisms with a history of BPA exposure displayed significant changes in all categories of developmental defects mentioned above, including increased expression of genes related to oxidative stress, compared to individuals without BPA exposure. The present study provides initial evidence that a history of ancestral BPA exposure can alter sensitivity to developmental disorders following the second hit by PFOS exposure. The variable of ancestral BPA exposure could be considered in mechanistic, medical, and regulatory toxicology, and can also be applied to holistic environmental equity research.

Neurobehavioral toxicity induced by combined exposure of micro/nanoplastics and triphenyltin in marine medaka (Oryzias melastigma)

Microplastics/nanoplastics (MNPs) inevitably coexist with other pollutants in the natural environment, making it crucial to study the interactions between MNPs and other pollutants as well as their combined toxic effects. In this study, we investigated neurotoxicity in marine medaka (Oryzias melastigma) exposed to polystyrene micro/nanoplastics (PS-MNPs), triphenyltin (TPT), and PS-MNPs + TPT from physiological, behavioral, biochemical, and genetic perspectives. The results showed that marine medaka exposed to 200 ng/L TPT or 200 μg/L PS-NPs alone exhibited some degree of neurodevelopmental deficit, albeit with no significant behavioral abnormalities observed. However, in the PS-MP single exposure group, the average acceleration of short-term behavioral indices was significantly increased by 78.81%, indicating a highly stress-responsive locomotor pattern exhibited by marine medaka. After exposure to PS-MNPs + TPT, the swimming ability of marine medaka significantly decreased. In addition, PS-MNPs + TPT exposure disrupted normal neural excitability as well as activated detoxification processes in marine medaka larvae. Notably, changes in neural-related genes suggested that combined exposure to PS-MNPs and TPT significantly increased the neurotoxic effects observed with exposure to PS-MNPs or TPT alone. Furthermore, compared to the PS-MPs + TPT group, PS-NPs + TPT significantly inhibited swimming behavior and thus exacerbated the neurotoxicity. Interestingly, the neurotoxicity of PS-MPs was more pronounced than that of PS-NPs in the exposure group alone. However, the addition of TPT significantly enhanced the neurotoxicity of PS-NPs compared to PS-MPs + TPT. Overall, the study underscores the combined neurotoxic effects of MNPs and TPT, providing in-depth insights into the ecotoxicological implications of MNPs coexisting with pollutants and furnishing comprehensive data.

Prenatal exposure to poly/perfluoroalkyl substances and risk for congenital heart disease in offspring

Congenital heart disease (CHD) is the most prevalent congenital malformation worldwide, and the association between per- and polyfluoroalkyl substances (PFASs) exposure and CHD in population has only received limited study. Therefore, we conducted a multicenter case-control study to explore the associations between prenatal exposure to individual PFASs, and also a PFAS mixture, and CHD risk, including 185 CHDs and 247 controls in China from 2016 to 2021. Thirteen PFASs in maternal plasma were quantified using liquid chromatography-tandem mass spectrometry. Logistic regression and two multipollutant models (Bayesian kernel machine regression [BKMR] and quantile g-computation [qgcomp]) were used to assess the potential associations between any individual PFAS, and also a PFAS mixture, and CHD risk. After adjusting for potential confounders, logistic regression indicated significant associations between elevated levels of perfluorononanoic acid (odds ratio [OR]= 1.30, 95% confidence intervals [CI]: 1.07-1.58), perfluorodecanoic acid (OR=2.07, 95%CI: 1.32-3.26), and perfluoroundecanoic acid (OR=2.86, 95%CI:1.45-5.65) and CHD risk. The BKMR model and qgcomp approach identified that a significant positive association between the PFAS mixture and risk for CHD. These findings provide essential evidence that there is indeed a health crisis associated with PFASs and that it is linked to CHD.

Perfluorooctanoic acid induces cardiac dysfunction in human induced pluripotent stem cell-derived cardiomyocytes

Perfluorooctanoic acid (PFOA), commonly found in drinking water, leads to widespread exposure through skin contact, inhalation, and ingestion, resulting in detectable levels of PFOA in the bloodstream. In this study, we found that exposure to PFOA disrupts cardiac function in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). We observed reductions in field and action potentials in hiPSC-CMs exposed to PFOA. Furthermore, PFOA demonstrated a dose-dependent inhibitory effect on various ion channels, including the calcium, sodium, and potassium channels. Additionally, we noted dose-dependent inhibition of the expression of these ion channels in hiPSC-CMs following exposure to PFOA. These findings suggest that PFOA exposure can impair cardiac ion channel function and decrease the transcription of genes associated with these channels, potentially contributing to cardiac dysfunction such as arrhythmias. Our study sheds light on the electrophysiological and epigenetic consequences of PFOA-induced cardiac dysfunction, underscoring the importance of further research on the cardiovascular effects of perfluorinated compounds (PFCs).

Exposure to tris (1,3-dichloro-2-propyl) phosphate affects the embryonic cardiac development of Oryzias melastigma

Tris (1,3-dichloro-2-propyl) phosphate (TDCPP) is a growing concern and may be a potential risk to marine environmental health due to its widespread usage and distribution. However, the toxic effects of TDCPP on cardiac development in marine fish have not been reported. In this study, Oryzias melastigma embryos were exposed to TDCPP at doses of 0, 0.04, 0.4, 4 and 40 μg/L from early embryogenesis to 10 days postfertilization (dpf). Then, the heart rate and sinus venosus-bulbus arteriosus (SV-BA) distance of the exposed embryos were measured at 5, 6, 8 and 10 dpf. Furthermore, alterations in the mRNA levels of the genes encoding cyclooxygenase-2 (COX-2), bone morphogenetic protein 4 (BMP4), fibroblast growth factor 8 (FGF8), and GATA-binding protein 4 (GATA4) were evaluated at 5, 6, 8 and 10 dpf. We found that the heart rate significantly increased in all TDCPP exposure groups at 10 dpf. The SV-BA distance significantly decreased in all TDCPP exposure groups at all developmental stages (except for the 0.4 μg/L group at 5 dpf and the 4 μg/L group at 10 dpf). The mRNA expression of COX-2 was downregulated at 5 dpf, BMP4 was downregulated at 5 and 6 dpf, FGF8 was downregulated at 5, 6 and 8 dpf, GATA4 was downregulated at 8 dpf, and GATA4 was upregulated at 10 dpf. These results indicate that the changes in heart rate and SV-BA distance might be accompanied by disturbances in the four genes involved in cardiac development. Our findings will help to illustrate the possible cardiac toxic effects of marine fish exposed to TDCPP.

Micro(nano)plastics in marine medaka: Entry pathways and cardiotoxicity with triphenyltin

The simultaneous presence of micro(nano)plastics (MNPs) and pollutants represents a prevalent environmental challenge that necessitates understanding their combined impact on toxicity. This study examined the distribution of 5 μm (PS-MP5) and 50 nm (PS-NP50) polystyrene plastic particles during the early developmental stages of marine medaka (Oryzias melastigma) and assessed their combined toxicity with triphenyltin (TPT). Results showed that 2 mg/L PS-MP5 and PS-NP50 could adhere to the embryo surface. PS-NP50 can passively enter the larvae and accumulate predominantly in the intestine and head, while PS-MP5 cannot. Nonetheless, both types can be actively ingested by the larvae and distributed in the intestine. 2 mg/L PS-MNPs enhance the acute toxicity of TPT. Interestingly, high concentrations of PS-NP50 (20 mg/L) diminish the acute toxicity of TPT due to their sedimentation properties and interactions with TPT. 200 μg/L PS-MNPs and 200 ng/L TPT affect complement and coagulation cascade pathways and cardiac development of medaka larvae. PS-MNPs exacerbate TPT-induced cardiotoxicity, with PS-NP50 exhibiting stronger effects than PS-MP5, which may be related to the higher adsorption capacity of NPs to TPT and their ability to enter the embryos before hatching. This study elucidates the distribution of MNPs during the early developmental stages of marine medaka and their effects on TPT toxicity, offering a theoretical foundation for the ecological risk assessment of MNPs.

Exposure to manganese (II) chloride induces developmental toxicity, oxidative stress and inflammatory response in Marine medaka (Oryzias melastigma) embryos

Manganese (Mn) is an essential metal for organisms, but high levels can induce serious toxicity. To date, the toxic mechanism of Mn to marine fish is still poorly understood. In the present study, Oryzias melastigma embryos were exposed to different concentrations of MnCl₂ (0-152.00 mg/L) to investigate its effect on early development. The results showed that exposure to MnCl₂ caused developmental toxicity to embryos, including increased heart rate, delayed hatching time, decreased hatching rate and increased malformation rate. MnCl₂ exposure could induce oxidative stress in O. melastigma embryos, as indicated by increased the contents of malondialdehyde (MDA) and the activities of the antioxidant enzymes (superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT)). The heart might be an important target organ for MnCl₂ because of cardiac malformations and disruption in the expression of cardiac development-related genes (ATPase, epo, fg8g, cox1, cox2, bmp4 and gata4). In addition, the expression levels of stress- (omTERT and p53) and inflammation-related genes (TNFα and il1β) were significantly up-regulated, suggesting that MnCl₂ can trigger stress and inflammatory response in O. melastigma embryos. In conclusion, this study demonstrated that MnCl₂ exposure can induce developmental toxicity, oxidative stress and inflammatory response in O. melastigma embryos, providing insights into the toxic mechanism of Mn to the early development of marine fish.

Reduced Transcriptome Analysis of Zebrafish Embryos Prioritizes Environmental Compounds with Adverse Cardiovascular Activities

Cardiovascular diseases are the leading cause of premature death in humans and remain a global public health challenge. While age, sex, family history, and false nutrition make a contribution, our understanding of compounds acting as cardiovascular disruptors is far from complete. Here, we aim to identify cardiovascular disruptors via a reduced transcriptome atlas (RTA) approach, which integrates large-scale transcriptome data sets of zebrafish and compiles a specific gene panel related to cardiovascular diseases. Among 767 gene expression profiles covering 81 environmental compounds, 11 priority compounds are identified with the greatest effects on the cardiovascular system at the transcriptional level. Among them, metals (AgNO₃, Ag nanoparticles, arsenic) and pesticides/biocides (linuron, methylparaben, triclosan, and trimethylchlorotin) are identified with the most significant effects. Distinct transcriptional signatures are further identified by the percentage values, indicating that different physiological endpoints exist among prioritized compounds. In addition, cardiovascular dysregulations are experimentally confirmed for the prioritized compounds via alterations of cardiovascular physiology and lipid profiles of zebrafish. The accuracy rate of experimental verification reaches up to 62.9%. The web-based RTA analysis tool, Cardionet, for rapid cardiovascular disruptor discovery was further provided at http://www.envh.sjtu.edu.cn/cardionet.jsp. Our integrative approach yields an efficient platform to discover novel cardiovascular-disrupting chemicals in the environment.

A review of cardiovascular effects and underlying mechanisms of legacy and emerging per- and polyfluoroalkyl substances (PFAS)

Cardiovascular disease (CVD) poses the leading threats to human health and life, and their occurrence and severity are associated with exposure to environmental pollutants. Per- and polyfluoroalkyl substances (PFAS), a group of widely used industrial chemicals, are characterized by persistence, long-distance migration, bioaccumulation, and toxicity. Some PFAS, particularly perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexanesulfonic acid (PFHxS), have been banned, leaving only legacy exposure to the environment and human body, while a number of novel PFAS alternatives have emerged and raised concerns, such as polyfluoroalkyl ether sulfonic and carboxylic acid (PFESA and PFECA) and sodium p-perfluorous nonenoxybenzene sulfonate (OBS). Overall, this review systematically elucidated the adverse cardiovascular (CV) effects of legacy and emerging PFAS, emphasized the dose/concentration-dependent, time-dependent, carbon chain length-dependent, sex-specific, and coexposure effects, and discussed the underlying mechanisms and possible prevention and treatment. Extensive epidemiological and laboratory evidence suggests that accumulated serum levels of legacy PFAS possibly contribute to an increased risk of CVD and its subclinical course, such as cardiac toxicity, vascular disorder, hypertension, and dyslipidemia. The underlying biological mechanisms may include oxidative stress, signaling pathway disturbance, lipid metabolism disturbance, and so on. Various emerging alternatives to PFAS also play increasingly prominent toxic roles in CV outcomes that are milder, similar to, or more severe than legacy PFAS. Future research is recommended to conduct more in-depth CV toxicity assessments of legacy and emerging PFAS and explore more effective surveillance, prevention, and treatment strategies, accordingly.

Acute and Chronic Effects of Crude Oil Water-Accommodated Fractions on the Early Life Stages of Marine Medaka (Oryzias melastigma, McClelland, 1839)

Oil spill is a major marine environmental pollution issue. Research regarding the long-term effects of oil spills on the early life stage of marine fish is still limited. In this study, the potential adverse impact of crude oil from one oil spill accident which occurred in the Bohai Sea on the early life stages of marine medaka (Oryzias melastigma, McClelland, 1839) was evaluated. A 96-h acute test (larvae) and a 21-d chronic test (embryo-larvae) of water-accommodated fractions (WAFs) from crude oil were conducted, respectively. The results of the acute test showed that only the highest concentration of WAFs (100.00%) significantly affected the mortality of larvae (p < 0.01) and that the 96 h-LC₅₀ was 68.92% (4.11 mg·L^-1 expressed as total petroleum hydrocarbons (TPHs)). Larval heart demonstrated histopathological alterations in all WAF-exposed groups. The chronic test results showed that, except for larval mortality, the total hatching success (%)/hatching time of embryos in WAF treatments was not significantly different from those of the control group (p > 0.05), and no malformation was found in surviving larvae after 21 d of exposure. Nevertheless, the exposed embryos and larvae in the highest concentration of WAFs (60.00%) demonstrated significantly reduced heart rate (p < 0.05) and increased mortality (p < 0.01), respectively. Overall, our results indicated that both acute and chronic WAF exposures had adverse impacts on the survival of marine medaka. In the early life stages, the heart of the marine medaka was the most sensitive organ which showed both structural alteration and cardiac dysfunction.

Toxicity of perfluoroalkyl substances (PFAS) toward embryonic stages of mahi-mahi (Coryphaena hippurus)

Perfluoroalkyl substances (PFAS) are highly persistent organic pollutants that have been detected in a wide array of environmental matrices and, in turn, diverse biota including humans and wildlife wherein they have been associated with a multitude of toxic, and otherwise adverse effects, including ecosystem impacts. In the present study, we developed a toxicity assay for embryonic stages of mahi-mahi (Coryphaena hippurus), as an environmentally relevant pelagic fish species, and applied this assay to the evaluation of the toxicity of "legacy" and "next-generation" PFAS including, respectively, perfluorooctanoic acid (PFOA) and several perfluoroethercarboxylic acids (PFECA). Acute embryotoxicity, in the form of lethality, was measured for all five PFAS toward mahi-mahi embryos with median lethal concentrations (LC₅₀) in the micromolar range. Consistent with studies in other similar model systems, and specifically the zebrafish, embryotoxicity in mahi-mahi generally (1) correlated with fluoroalkyl/fluoroether chain length and hydrophobicity, i.e., log P, of PFAS, and thus, aligned with a role of uptake in the relative toxicity; and (2) increased with continuous exposure, suggesting a possible role of development stage specifically including a contribution of hatching (and loss of protective chorion) and/or differentiation of target systems (e.g., liver). Compared to prior studies in the zebrafish embryo model, mahi-mahi was significantly more sensitive to PFAS which may be related to differences in either exposure conditions (e.g., salinity) and uptake, or possibly differential susceptibility of relevant targets, for the two species. Moreover, when considered in the context of the previously reported concentration of PFAS within upper sea surface layers, and co-localization of buoyant eggs (i.e., embryos) and other early development stages (i.e., larvae, juveniles) of pelagic fish species to the sea surface, the observed toxicity potentially aligns with environmentally relevant concentrations in these marine systems. Thus, impacts on ecosystems including, in particular, population recruitment are a possibility. The present study is the first to demonstrate embryotoxicity of PFAS in a pelagic marine fish species, and suggests that mahi-mahi represents a potentially informative, and moreover, environmentally relevant, ecotoxicological model for PFAS in marine systems.

Perfluorooctane Sulfonamide (PFOSA) Induces Cardiotoxicity via Aryl Hydrocarbon Receptor Activation in Zebrafish

Perfluorooctane sulfonamide (PFOSA), a precursor of perfluorooctanesulfonate (PFOS), is widely used during industrial processes, though little is known about its toxicity, particularly to early life stage organisms that are generally sensitive to xenobiotic exposure. Here, following exposure to concentrations of 0.01, 0.1, 1, 10, and 100 μg/L PFOSA, transcriptional, morphological, physiological, and biochemical assays were used to evaluate the potential effects on aquatic organisms. The top Tox functions in exposed zebrafish were related to cardiac diseases predicted by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and Ingenuity Pathway Analysis (IPA) analysis. Consistent with impacts predicted by transcriptional changes, abnormal cardiac morphology, disordered heartbeat signals, as well as reduced heart rate and cardiac output were observed following the exposure of 0.1, 1, 10, or 100 μg/L PFOSA. Furthermore, these PFOSA-induced cardiac effects were either prevented or alleviated by supplementation with an aryl hydrocarbon receptor (AHR) antagonist or ahr2-morpholino knock-down, uncovering a seminal role of AHR in PFOSA-induced cardiotoxicity. Our results provide the first evidence in fish that PFOSA can impair proper heart development and function and raises concern for PFOSA analogues in the natural environment.

Using comprehensive lipid profiling to study effects of PFHxS during different stages of early zebrafish development

PFHxS (Perfluorohexane sulfonic acid) is one of the short-chain perfluoroalkyl substances (PFASs) which are widely used in many industrial and consumer applications. However, limited information is available on the molecular mechanism of PFHxS toxicity (e.g. lipid metabolism). This study provides in-depth information on the lipid regulation of zebrafish embryos with and without PFHxS exposure. Lipid changes throughout zebrafish development (4 to 120 h post fertilization (hpf)) were closely associated with lipid species and lipid composition (fatty acyl chains). A comprehensive lipid analysis of four different PFHxS exposures (0, 0.3, 1, 3, and 10 μM) at different zebrafish developmental stages (24, 48, 72, and 120 hpf) was performed. Data on exposure concentration, lipids, and developmental stage showed that all PFHxS concentrations dysregulated the lipid metabolism and these were developmental-dependent. The pattern of significantly changed lipids revealed that PFHxS caused effects related to oxidative stress, inflammation, and impaired fatty acid β-oxidation. Oxidative stress and inflammation caused the remodeling of glycerophospholipid (phosphatidylcholine (PC) and phosphatidylethanolamine (PE)), with increased incorporation of omega-3 PUFA and a decreased incorporation of omega-6 PUFA.

Environmental relevant herbicide prometryn induces developmental toxicity in the early life stages of marine medaka (Oryzias melastigma) and its potential mechanism

Triazine herbicides have been widely detected in marine environments because of their extensive usage in agriculture, but their impact on marine organisms is unclear. In this study, marine medaka (Oryzias melastigma) embryos were exposed to 0, 1, 10, 100, and 1000 μg/L prometryn, one of the most detected triazine herbicides, to investigate its potential effects. The results showed that 1, 10, 100, and 1000 µg/L prometryn not only induced yolk sac shrinkage and heart malformations, but also significantly delayed the hatching time and increased the heart rate and hatching failure rate of embryos. Moreover, 1, 10, 100, and 1000 μg/L prometryn caused obvious malformations and decreased the body length of the newly hatched larvae. After 21 d of exposure, increased larval death rate, decreased body length and width, and higher lipid accumulation were observed in the larvae from all prometryn groups. Furthermore, prometryn exposure upregulated the expression levels of cardiac development-related genes GATA, COX, ATPase, SmyD1, EPO, FGF8, NKX2, and BMP4 in the larvae. Transcriptome analysis revealed that 10 μg/L prometryn upregulated 604 genes, and the topmost pathways of differentially expressed genes were the complement and coagulation cascades and AMPK signaling pathways. qPCR results confirmed that prometryn exposure significantly increased the expression levels of the complement and coagulation cascade genes f2, f5, c3, and c5. This study demonstrated that environmentally relevant concentrations of prometryn induced significant toxicity in the early life stages of marine medaka. Therefore, the health risks of herbicides to marine organisms are of great concern.

Perfluorooctane sulfonate induces heart toxicity involving cardiac apoptosis and inflammation in rats

Perfluorooctane sulfonate (PFOS) is a persistent pollutant that exerts toxicity and induces cardiogenesis in humans and animals. Yet, the effect of PFOS exposure on cardiac toxicity in adult rats has, to our knowledge, not been reported and the mechanism still remains unknown. The present study aimed to investigate the toxicity of PFOS on rat hearts and any associated mechanisms. Rats were exposed to 0 (control), 1 and 10 mg/kg PFOS every other day for 14 days. Body weight and heart weight were recorded. The serum levels of lactic dehydrogenase (LDH), creatine kinase (CK), creatine kinase-isoenzyme-MB (CK-MB) and cardiac troponin-T (cTn-T) in heart tissues were measured using biochemical assays. TUNEL staining and western blotting were applied to analyze levels of apoptosis in rat hearts. Pathological assessment and immunohistochemistry analysis of heart tissues were used to evaluate the levels of PFOS-induced cardiotoxicity and inflammatory infiltration. PFOS exposure at the dosage of 10 mg/kg significantly increased the percentage of heart to body weight; however, it did not alter the body weight. At 10 mg/kg, PFOS significantly increased expression levels of myocardial injury markers, such as cTn-T, LDH, CK and CK-MB, while 1 mg/kg PFOS upregulated the expression level of cTn-T in rats. Notably, cardiac fibrosis and myocardiac hypertrophy appeared in the 10 mg/kg PFOS group. In addition, TUNEL-positive cells were significantly increased by exposure to 10 mg/kg PFOS in rat heart tissues. The protein expressions profiles of p53 and Bax were also significantly upregulated in the 10 mg/kg PFOS group. Inflammatory infiltration, detected by anaylzing expression levels of IL-1β and TNF-α, was significantly raised by 10 mg/kg PFOS exposure. In conclusion, these results demonstrated that 10 mg/kg PFOS-induced cardiac toxicity in rats, which was associated with an increase in apoptosis and the expression of proinflammatory cytokines.

Perfluorinated compounds disrupted osmoregulation in Oryzias melastigma during acclimation to hypoosmotic environment

Perfluorinated compounds (PFCs) are a type of ubiquitous contaminants spreading in the estuarine and coastal areas. Anadromous fish should deal with hypoosmotic challenge with PFCs stress during their migration from seawater to estuaries. However, few studies have been carried out to investigate the adverse impact of PFCs on fish osmoregulation and the underlying mechanism. In this study, Oryzias melastigma, an euryhaline fish model, were exposed to four representative PFC congeners including perfluorobutane sulfonate (PFBS), perfluorooctane sulfonates (PFOS), perfluorooctanoic acid (PFOA), and perfluorododecanoic acid (PFDoA) separately under both seawater and freshwater conditions. Histopathological changes in gills, ion homeostasis, Na⁺/K⁺-ATPase (NKA) activity, as well as the expression of related genes was detected upon exposure. Results showed that PFCs induced morphological changes in gills, disturbed the levels of major ions (Na⁺, Ca²⁺, Mg²⁺), and inhibited the NKA activity. Transcriptome analysis in fish gills during the acclimation to freshwater revealed that PFCs influenced the osmoregulation mainly by interfering with the endocrine system, signal transduction, as well as cellular community and motility. Validation with qRT-PCR confirmed that the mRNA expressions of osmoregulatory genes encoding hormones and receptors, as well as ion transmembrane transporters were disturbed by PFCs. Longer chain homolog (PFOS) showed a greater impact on osmoregulation than the shorter chain homolog (PFBS). Within the same carbon chain, sulfonic congener (PFOS) induced more serious injury to gills than carboxylic congener (PFOA). The interaction between PFCs and salinity varied in different adverse outcome. These results help to further understand the mechanism of how PFCs influence osmoregulation and elicit the need to assess the ecological risk of PFCs and other pollutants on anadromous migration.

Bone developmental toxicity of organophosphorus flame retardants TDCIPP and TPhP in marine medaka Oryzias melastigma

The global phase-out has decreased the use of polybrominated diphenyl ethers (PBDEs), thereby, rapidly increasing the production and use of their important surrogates, organophosphorus flame retardants (OPFRs). Currently, OPFRs are often found at higher levels in the environments compared to PBDEs. Although the two typical OPFRs, tris (1,3-dichloroisopropyl) phosphate (TDCIPP) and triphenyl phosphate (TPhP), have been frequently detected in marine environments with significant concentrations, their toxicity to marine organisms remains unknown. We used Oryzias melastigma to investigate and compare their developmental toxicity in marine organisms through two-generational chronic exposure. The results showed that TDCIPP and TPhP exposure shortened the body length and length of the pectoral fin of O. melastigma. Both TDCIPP and TPhP deformed the pectoral fins in the 1st fry and caused spinal curvature in adult fish. Therefore, these two chemicals may pose potential risks to marine fish and marine ecosystems. Further studies suggested that although these two chemicals caused similar developmental bone toxicity, they had different modes of modulating the expression of bone developmental genes such as, bmp4, bmp2 and runx2.

Developmental toxicity in marine medaka (Oryzias melastigma) embryos and larvae exposed to nickel

As an important trace metal, nickel (Ni) has been reported extensively in the studies on freshwater animals. However, the toxic effects of Ni on marine organisms are not clearly understood. Therefore, in order to investigate the toxic effects of Ni on the early development of marine fish, the marine medaka (Oryzias melastigma) embryos and larvae were immersed in 0.13-65.80 mg/L Ni solution. The results showed that Ni exposure changed the egg size and heart rate of the embryos, lowered the hatchability, increased the deformity rate, and shortened the total body length of newly hatched larvae. Besides, it was found that before organogenesis and post-hatching periods were the sensitive periods of embryos to Ni. The 25 d LC₅₀ value of embryos was 49.28 mg/L, and the 5 d LC₅₀ of larvae was 55.92 mg/L, indicating that the embryos were more sensitive to Ni than the larvae. Furthermore, the expressions of the metallothionein (MT) gene, the skeletal development-related gene (Cyp26b1) and the cardiac development-related genes (ATPase, smyd1, cox2 and bmp4) were determined, and the results showed that the expressions of ATPase and smyd1 were up-regulated, while MT, Cyp26b1 and cox2 were significantly down-regulated at 9 days post-fertilization (dpf). Overall, Ni exposure caused a significant toxic effect on the early development of the O. melastigma embryos and larvae. Our findings could provide an important supplement to the toxicity data of tropical Ni and provide a reference for the exploration of the molecular mechanisms of Ni toxicity.

Haemodynamic dependence of mechano-genetic evolution of the cardiovascular system in Japanese medaka

The progression of cardiac gene expression-wall shear stress (WSS) interplay is critical to identifying developmental defects during cardiovascular morphogenesis. However, mechano-genetics from the embryonic to larval stages are poorly understood in vertebrates. We quantified peak WSS in the heart and tail vessels of Japanese medaka from 3 days post fertilization (dpf) to 14 dpf using in vivo micro-particle image velocimetry flow measurements, and in parallel analysed the expression of five cardiac genes (fgf8, hoxb6b, bmp4, nkx2.5, smyd1). Here, we report that WSS in the atrioventricular canal (AVC), ventricular outflow tract (OFT), and the caudal vessels in medaka peak with inflection points at 6 dpf and 10-11 dpf instead of a monotonic trend. Retrograde flows are captured at the AVC and OFT of the medaka heart for the first time. In addition, all genes were upregulated at 3 dpf and 7 dpf, indicating a possible correlation between the two, with the cardiac gene upregulation preceding WSS increase in order to facilitate cardiac wall remodelling.

Developmental exposure to a POPs mixture or PFOS increased body weight and reduced swimming ability but had no effect on reproduction or behavior in zebrafish adults

Complex mixtures of persistent organic pollutants (POPs) are regularly detected in the environment and animal tissues. Often these chemicals are associated with latent effects following early-life exposures, following the developmental origin of health and disease paradigm. We investigated the long-term effects of a human relevant mixture of 29 POPs on adult zebrafish following a developmental exposure, in addition to a single PFOS exposure for comparison, as it was the compound with the highest concentration within the mixture. Zebrafish embryos were exposed from 6 to 96 h post fertilization to x10 and x70 the level of POP mixture or PFOS (0.55 and 3.83 μM) found in human blood before being transferred to clean water. We measured growth, swimming performance, and reproductive output at different life stages. In addition, we assessed anxiety behavior of the adults and their offspring, as well as performing a transcriptomic analysis on the adult zebrafish brain, as the POP mixture and PFOS concentrations used are known to affect larval behavior. Exposure to POP mixture and PFOS reduced swimming performance and increased length and weight, compared to controls. No effect of developmental exposure was observed on reproductive output or anxiety behavior. Additionally, RNA-seq did not reveal pathways related to anxiety although pathways related to synapse biology were affected at the x10 PFOS level. Furthermore, pathway analysis of the brain transcriptome of adults exposed as larvae to the low concentration of PFOS revealed enrichment in pathways such as calcium, MAPK, and GABA signaling, all of which are important for learning and memory. Based on our results we can conclude that some effects on the endpoints measured were apparent, but if these effects lead to adversities at population levels remains elusive.

Size-dependent adverse effects of microplastics on intestinal microbiota and metabolic homeostasis in the marine medaka (Oryzias melastigma)

Microplastic (MP) is an emerging environmental pollutant and exposure to MPs has been associated with numerous adverse health outcomes in both wild and laboratory animals. The toxicity of MPs depends on concentration, exposure time, chemical composition and size distribution, but the impacts of particle size remain inconclusive yet. In this study, adult marine medaka (Oryzias melastigma) were exposed to different size of polystyrene MPs (PS-MPs) with concentration of 10 mg/L for 60 days and the growth performance, lipid metabolism, immune parameters and gut microbiome were determined. Results indicated that particle size is a dominant factor causing lipid metabolism disorders and hepatic toxicity in PS-MPs-exposed fish. The bodyweight, adipocyte size and hepatic lipid contents were significantly increased in 200 μm PS-MPs-exposed fish, while 2 and 10 μm PS-MPs-exposed fish exhibited liver injury principally manifested asthepresence oflittlefibrosis and inflammation. Given that larger particles could not enter the circulatory system, the impacts of PS-MPs on intestinal microbial biota homeostasis were further investigated. The results not only showed the characterization of gut microbial communities in Oryzias melastigma, but also indicated that microbial diversity and composition were altered in gut of fish exposed to PS-MPs, in particular 200 μm PS-MPs. The differentially abundant bacterial taxa in PS-MPs-exposed fish mainly belonged to the phylum Verrucomicrobia, Firmicutes and Fusobacteria. And furthermore, increased abundance of Verrucomicrobia and Firmicutes/Bacteroidetes ratio and decreased Fusobacteria were correlated with the increased bodyweight. Intestinal microbiome should play a critical role in regulating host lipid metabolism in fish exposed to lager size of PS-MPs.

Occurrence and toxicity of perfluoroalkyl acids along the estuarine and coastal regions under varied environmental factors

Due to the significant economic and ecological value, the increasing pollution threat to estuarine and coastal regions is of great concern. Perfluoroalkyl acids (PFAAs) are emerging pollutants which possess adverse ecological risk. In this review, we have compiled the data on the levels of PFAAs in environmental samples, mainly in estuarine and coastal zones. A worldwide map was generated to show the distribution of PFAAs. The experimental results have also been considered, which, together with those of environmental samples, has allowed us to infer about the factors that intervene in the behavior of PFAAs. The presence of PFAAs is determined primarily by the source of pollution. Salinity is as well shown as a significant condition, dependent too on the sampling environment. The analysis of PFAAs from environmental samples constitutes a fundamental tool for the surveillance of these pollutants, but the lack of homogeneity of protocols for sampling, as well as for the results presentation, limits the comparative capacity. Laboratory studies are also an essential tool in the analysis of particular aspects related to PFAAs, but many times the conditions tested are not environmentally significant. In this way, it would not be prudent to establish "paradigms" about the behavior of the PFAAs in certain areas or organisms, instead to suggest the points that can be considered fundamental for each issue addressed. The main variables that appear to intervene in estuarine and coastal regions are mainly the proximity to the source of pollution, salinity, pH, precipitation (rain) as well as types of PFAAs. All these can synergistically lead to different impacts on the ecosystem. Therefore, the particular risks of PFAAs in estuarine and coastal regions is a set of multiple variables, dependent on each sampling condition and according to the previously named parameters.

Toxicity effects of hydrophilic algal lysates from Coolia tropicalis on marine medaka larvae (Oryzias melastigma)

Coolia tropicalis is a species of benthic and epiphytic toxic algae, which can produce phycotoxins that intoxicate marine fauna. In this study, the potential toxic effects of C. tropicalis on fish were investigated using larval marine medaka (Oryzias melastigma) as a model to evaluate fish behavior, physiological performance, and stress-induced molecular responses to exposure to two sublethal concentrations (LC₁₀ and LC₂₀) of hydrophilic algal lysates. Exposure to C. tropicalis lysates inhibited swimming activity, activated spontaneous undirected locomotion, altered nerve length ration, and induced early development abnormalities, such as shorter eye diameter, body as well as axon length. Consistent with these abnormalities, changes in the expression of genes associated with apoptosis (CASPASE-3 and BCL-2), the inflammatory response (IL-1β and COX-2), oxidative stress (SOD), and energy metabolism (ACHE and VHA), were also observed. This study advances our understanding of the mechanisms of C. tropicalis toxicity in marine fish in the early life stages and contributes to future ecological risk assessments of toxic benthic dinoflagellates.

Assessing the human health risks of per- and polyfluoroalkyl substances: A need for greater focus on their interactions as mixtures

Humans are exposed to complex mixtures of per- and polyfluoroalkyl substances (PFAS). However, human health risk assessment of PFAS currently relies on animal toxicity data derived from individual substance exposure, which may not adequately predict the risk from combined exposure due to possible interactions that can influence the overall risk. Long-chain perfluoroalkyl acids (PFAAs), particularly perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are recognised as global emerging contaminants of concern due to their ubiquitous distribution in all environmental media, wildlife, and humans, persistency, bioaccumulative-, toxic-, and human health-risk potentials. This article reviews the current understanding of the human health risks associated with PFAS exposure focusing on more recent toxicological and epidemiological studies from 2010 to 2020. The existing information on PFAA mixtures was also reviewed in an attempt to highlight the need for greater focus on their potential interactions as mixtures within the class of these chemicals. A growing number of toxicological studies have indicated several adverse health outcomes of PFAA exposure, including developmental and reproductive toxicity, neurotoxicity, hepatotoxicity, genotoxicity, immunotoxicity, thyroid disruption, and carcinogenicity. Epidemiological findings further support some of these adverse human health outcomes. However, the mechanisms underlying these adverse effects are not well defined. A few in vitro studies focusing on PFAA mixtures revealed that these compounds may act additively or interact synergistically/antagonistically depending on the species, dose level, dose ratio, and mixture components. Hence, the combined effects or potential interactions of PFAS mixtures should be considered and integrated into toxicity assessment to obtain a realistic and more refined human health risk assessment.

Transgenerational Effects of Hexavalent Chromium on Marine Medaka (Oryzias melastigma) Reveal Complex Transgenerational Adaptation in Offspring

Hexavalent chromium [Cr(VI)] pollution is one of most serious heavy metal pollutants in the coastal area and posed serious threats to marine organisms and human beings. Many studies have been conducted on its toxicological effects on living organisms from morphological to physiological aspects. However, there are few studies about the transgenerational toxicological of Cr(VI). In this study, we exposed adult marine medaka fishes with Cr(VI) and their offspring with Cr(VI) to examine transgenerational effects of Cr(VI). We found that there were mechanisms such as changing reproduction modes in males to compensate for impacts on the reproduction. There were differences and similarities between the parental effect and the environmental effect, with the former one causing more serious adverse effects on the offspring of Cr(VI)-exposed fish. It was noteworthy that there was an interaction between the parental and offspring treatment which leads to the attenuation of the parental effects on offspring when the offspring also underwent the same treatment. In addition, physiological adaptation has also been observed in fish to improve their fitness. Overall, effects of Cr(VI) on fish and their offspring were studied to pave a way to study the of mechanisms of adaptation.

Risk assessment of cardiotoxicity to zebrafish (Danio rerio) by environmental exposure to triclosan and its derivatives

Triclosan (TCS) and its two derivatives (2,4-dichlorophenol and 2,4,6-trichlorophenol) are priority pollutants that coexist in aquatic environments. Joint exposure of TCS, 2,4-dichlorophenol and 2,4,6-trichlorophenol, hereafter referred to as TCS-DT, contributes severe toxicity to aquatic organisms. There is currently a paucity of data regarding TCS-DT molecular toxicity, especially on cardiac diseases. We used zebrafish (Danio rerio) as a model organism, and evaluated the molecular-level cardiotoxicity induced by TCS-DT from embryonic to adult stages. TCS-DT exposure prominently led to phenotypic malformations, such as pericardial cysts, cardiac bleeding, increased SV-BA distance, decreased heart rate and reduced ejection fraction, as well as abnormal swimming behavior. Analyses of the GO and KEGG pathways revealed enrichment pathways related to cardiac development and screened for significantly down-regulated adrenaline signaling in cardiomyocytes. The cardiac marker genes (amhc, cmlc2, vmhc, and nkx2.5) were obtained through protein-protein interaction (PPI) networks, and expressed as down-regulation by WISH. After chronic exposure to TCS-DT from 30 to 90-dpf, both body mass and heart indexes prominently increased, showing myocardial hypertrophy, abnormal heart rate and histopathological injury. Heart tissue damage included disordered and ruptured myocardial fibers, broken and dissolved myofilaments, nuclear pyknosis, mitochondrial injury and inflammatory cell infiltration. Further, abnormal changes in a series of cardiac functions-related biomarkers, including superoxide dismutase, triglyceride, lactate dehydrogenase and creatinine kinase MB, provided evidence for cardiac pathological responses. These results highlight the molecular mechanisms involving TCS-DT induced cardiac toxicity, and provide theoretical data to guide prevention and treatment of pollutant-induced cardiac diseases.

Long-read sequencing and de novo genome assembly of marine medaka (Oryzias melastigma)

BACKGROUND

Marine medaka (Oryzias melastigma) is considered as an important ecotoxicological indicator to study the biochemical, physiological and molecular responses of marine organisms towards increasing amount of pollutants in marine and estuarine waters.

RESULTS

In this study, we reported a high-quality and accurate de novo genome assembly of marine medaka through the integration of single-molecule sequencing, Illumina paired-end sequencing, and 10X Genomics linked-reads. The 844.17 Mb assembly is estimated to cover more than 98% of the genome and is more continuous with fewer gaps and errors than the previous genome assembly. Comparison of O. melastigma with closely related species showed significant expansion of gene families associated with DNA repair and ATP-binding cassette (ABC) transporter pathways. We identified 274 genes that appear to be under significant positive selection and are involved in DNA repair, cellular transportation processes, conservation and stability of the genome. The positive selection of genes and the considerable expansion in gene numbers, especially related to stimulus responses provide strong supports for adaptations of O. melastigma under varying environmental stresses.

CONCLUSIONS

The highly contiguous marine medaka genome and comparative genomic analyses will increase our understanding of the underlying mechanisms related to its extraordinary adaptation capability, leading towards acceleration in the ongoing and future investigations in marine ecotoxicology.

Microplastics negatively impact embryogenesis and modulate the immune response of the marine medaka Oryzias melastigma

Microplastic (MP) pollution is an emerging contaminant in aquatic environments worldwide. Nonetheless, the developmental toxicity of MPs in the early life stages of fish and the mechanisms involved are not yet fully understood. The present study investigated the effects of different concentrations of polystyrene (PS) MPs on the early development of the marine model fish the medaka Oryzias melastigma. Our results showed that waterborne exposure to PS MPs significantly delayed the hatching time, altered the heartbeat and decreased the hatching rate of embryos. Furthermore, the genes involved in cardiac development, encoding for embryo-hatching enzymes, as well as inflammatory responses were significantly upregulated. The transcriptome results showed that mainly the pathways involved in metabolism, immune response, genetic information processing and diseases were significantly enriched. These results demonstrate that PS MPs negatively impact embryogenesis and the immune response of O. melastigma.

Teratogenic effects of environmentally relevant concentrations of phenanthrene on the early development of marine medaka (Oryzia melastigma)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in marine environments and have arouse great concern since they pose adverse effects to marine ecosystem. To determine the potential impacts of environmentally relevant PAHs on early life stages of marine fish, this study exposed embryos of marine medaka (Oryzias melastigma) to 0, 2, 10, 50, and 250 μg/L of phenanthrene (Phe), one of the most abundant PAHs. The results demonstrated that Phe exposure decreased hatching rates, delayed hatching time of embryos, and increased deformity rate of newly-hatched larvae. Exposure to 10 and 50 μg/L Phe decreased the survival rate of marine medaka larvae at 28 days post-fertilization (dpf), and no embryo successfully hatched in 250 μg/L Phe exposure group. Morphology results showed that 10, 50, and 250 μg/L Phe exposure significantly retarded the development of embryos, and 2, 10, and 50 μg/L caused yolk sac edema and pericardial edema in newly-hatched larvae, indicating that low concentrations of Phe could induce developmental cardiac toxicity. Furthermore, the changes in the expression of heart development-related genes were determined, and the results showed that Phe-induced cardiac malformation might be related with fgf8, bmp4, smyd1, ATPase and gata4 genes. Overall, environmentally relevant PAHs could disrupt heart morphogenesis and hatching process of marine medaka, which might have profound consequences for sustainability of fish population.

The role of PFOS on triclosan toxicity to two model freshwater organisms

Surface-active substances may enhance the bioavailability of certain pollutants by modifying the permeability of cell membranes. However, they could also interact in a positive manner by increasing toxicity to aquatic organisms. A comparative effects assessment of waterborne exposure to triclosan (TCS) alone vs. combined with perfluorooctanesulfonic acid (PFOS) was herein investigated in daphnids (Daphnia magna) and medaka (Oryzias latipes) early life stages (ELS) using a battery of non-invasive behavioral, physiological and anatomical endpoints. Additionally, TCS bioaccumulation was evaluated in medaka embryos to help discern differences in effects caused by either, changes in TCS permeability or by a positive interaction with PFOS. The TCS analytical measurements in the medaka ELS exposure media revealed fast dissipation with half-lives < 12 h. The D. magna immobilization and feeding inhibition assays suggested an increased response when TCS (≥200 and 37.50 μg/L, respectively) was co-exposed with PFOS. Concentrations <800 μg TCS/L did not affect medaka ELS. However, exposures to ≥400 μg TCS/L + PFOS had effects on the embryo and eleutheroembryo viability. The morphometric analysis of the embryonic gallbladder area and the oxidative stress, determined in vivo by the manifestation of reactive oxygen species (ROS), revealed a hormetic response in both experimental sets. The TCS + PFOS experimental set generally resulted in increased gallbladder areas and ROS activity levels compared to those quantified in the corresponding TCS set. The bioaccumulation studies in the medaka embryos revealed comparable TCS levels regardless of PFOS presence. Without disregarding any TCS's enhanced bioavailability caused by the surface-active substance, overall results primarily indicate increased biological effects of TCS due to a potentiation action of PFOS as a binary mixture with TCS.

F-53B and PFOS treatments skew human embryonic stem cell in vitro cardiac differentiation towards epicardial cells by partly disrupting the WNT signaling pathway

F-53B and PFOS are two per- and polyfluoroalkyl substances (PFASs) widely utilized in the metal plating industry as mist suppressants. Recent epidemiological studies have linked PFASs to cardiovascular diseases and alterations in heart geometry. However, we still have limited understanding of the effects of F-53B and PFOS on the developing heart. In this study, we employed a human embryonic stem cell (hESC)-based cardiac differentiation system and whole transcriptomics analyses to evaluate the potential developmental cardiac toxicity of F-53B and PFOS. We utilized F-53B and PFOS concentrations of 0.1-60 μM, covering the levels detected in human blood samples. We demonstrated that both F-53B and PFOS inhibited cardiac differentiation and promoted epicardial specification via upregulation of the WNT signaling pathway. Most importantly, the effects of F-53B were more robust than those of PFOS. This was because F-53B treatment disrupted the expression of more genes and led to lower cardiac differentiation efficiency. These findings imply that F-53B may not be a safe replacement for PFOS.

Transcriptome analysis of acute exposure of the Manila clam, Ruditapes philippinarum to perfluorooctane sulfonate (PFOS)

Perfluorooctane sulfonate (PFOS) is an increasingly important environmental pollutant, which has been detected almost everywhere in the environment. Despite the widespread presence of PFOS, much less notice is taken of its toxicology effects on marine bivalves. Thus, the transcriptome response to PFOS treatment (nominal concentration of 20 mg/L) in hepatopancreas of a sentinel organism, Ruditapes philippinarum was examined. Compared with the control group, 32,149 unigenes were up-regulated and 26,958 unigenes down-regulated. Notably, significant gene expression changes were found in carbohydrate metabolism, energy metabolism, amino acid metabolism, lipid metabolism and protein biosynthesis, indicating the metabolic disruptions caused by PFOS in R. philippinarum. Additionally, numerous other differentially expressed genes were involved in immune system, antioxidant defense system and detoxification metabolism. In summary, transcriptome profiling of R. philippinarum after exposure to PFOS provided molecular support for our current understanding of the detrimental toxicity of PFOS on marine bivalves.

Organic contaminants sorbed to microplastics affect marine medaka fish early life stages development

The role of polyethylene microplastics 4-6 μm size (MPs) in the toxicity of environmental compounds to fish early life stages (ELS) was investigated. Marine medaka Oryzias melastigma embryos and larvae were exposed to suspended MPs spiked with three model contaminants: benzo(a)pyrene (MP-BaP), perfluorooctanesulfonic acid (MP-PFOS) and benzophenone-3 (MP-BP3) for 12 days. There was no evidence of MPs ingestion but MPs agglomerated on the surface of the chorion. Fish ELS exposed to virgin MPs did not show toxic effects. Exposure to MP-PFOS decreased embryonic survival and prevented hatching. Larvae exposed to MP-BaP or MP-BP3 exhibited reduced growth, increased developmental anomalies and abnormal behavior. Compared to equivalent waterborne concentrations, BaP and PFOS appeared to be more embryotoxic when spiked on MPs than when alone in seawater. These results suggest a relevant pollutant transfer by direct contact of MPs to fish ELS that should be included in the ecotoxicological risk assessment of MPs.

Adverse effects of perfluoroalkyl acids on fish and other aquatic organisms: A review

Perfluoroalkyl acids (PFAAs) have been widely used in many industrial and consumer products. They have been detected ubiquitously in ambient water along with other environmental matrices, and their adverse effects on aquatic organisms have been a subject of active investigation. Here, we intended to summarize and synthesize the existing body of knowledge on PFAA toxicity through an extensive literature review, and shed light on areas where further research is warranted. PFAA toxicity appears to be influenced by the sex and developmental stages of aquatic organisms, but not significantly by exposure route. PFAA-induced aquatic toxicity could be classified as metabolism disturbance, reproduction disruption, oxidative stress, developmental toxicity, thyroid disruption, etc. At the molecular level, these responses can be initiated by key events, such as nuclear receptor activation, reactive oxygen species induction, or interaction with a membrane, followed by a cascade of downstream responses. PFAA-induced toxicity involves diverse metabolic processes, and therefore elucidating crosstalk or interactions among diverse metabolic pathways is a challenging task. In the presence of other chemicals, PFAAs can function as agonists or antagonists, resulting in different directions of combined toxicity. Therefore, mixture toxicity with other groups of chemicals is another research opportunity. Experimental evidence supports the trans-generational toxicity of PFAAs, suggesting that their long-term consequences for aquatic ecosystems should become of concern. A recent global ban of several PFAAs resulted in an increasing dependence on PFAA alternatives. The lack of sufficient toxicological information on this emerging group of chemicals warrant caution and rigorous toxicological assessments.

PPAR-Mediated Toxicology and Applied Pharmacology

Peroxisome proliferator-activated receptors (PPARs), members of the nuclear hormone receptor family, attract wide attention as promising therapeutic targets for the treatment of multiple diseases, and their target selective ligands were also intensively developed for pharmacological agents such as the approved drugs fibrates and thiazolidinediones (TZDs). Despite their potent pharmacological activities, PPARs are reported to be involved in agent- and pollutant-induced multiple organ toxicity or protective effects against toxicity. A better understanding of the protective and the detrimental role of PPARs will help to preserve efficacy of the PPAR modulators but diminish adverse effects. The present review summarizes and critiques current findings related to PPAR-mediated types of toxicity and protective effects against toxicity for a systematic understanding of PPARs in toxicology and applied pharmacology.

Occurrence of perfluoroalkyl substances in the Bay of Marseille (NW Mediterranean Sea) and the Rhône River

Four perfluoroalkyl substances (PFAS) were analyzed in 62 duplicate surface water samples from the Rhône River and Marseille Bay (France; NW Mediterranean Sea). Perfluorooctane sulfonate (PFOS) was detected in all samples and exceeded the European Environmental Quality Standard (EQS) values in over 80% of the cases. The most contaminated samples were from the Rhône River (up to 200 ng L^-1 ∑₄ PFAS), as well as those collected near a wastewater treatment plant outlet in Marseille Bay (up to 9 ng L^-1 ∑₄ PFAS). While PFOS was the predominant PFAS in Marseille Bay, remarkably high concentrations of perfluorohexanoic acid (PFHxA) were measured in the Rhône River (8-193 ng L^-1). The relative abundances of individual compounds differed thus significantly between the Rhône River and Marseille Bay, indicating different sources. A simulation made with the MARS3D model showed that PFOS inputs from the Rhône River can enter Marseille Bay at levels > EQS.

The PFOS disturbed immunomodulatory functions via nuclear Factor-κB signaling in liver of zebrafish (Danio rerio)

Excessive perfluorooctane sulfonate (PFOS) in natural water ecosystem has the potential to detrimentally affect immune system, but little is known of such effects or underlying mechanisms in fish. In the present study, we evaluated the effects of PFOS on growth performance, organizational microstructure, activities of immune-related enzymes and expressions of immune-related genes in male zebrafish (Danio rerio) exposed to different concentrations of 0, 0.02, 0.04 and 0.08 mg/L of PFOS for 7, 14, and 21 days or cotreatment with PFOS and PDTC to investigate the effects of PFOS on immune system and the potential toxic mechanisms caused by PFOS. The results indicated that PFOS accumulated in livers after exposure, and remarkably elevations were found in three exposure groups compared with the control group at three stages. The growth of the adult zebrafish in the experiments was significantly inhibited, the microstructures of liver were serious damaged. The ROS levels were remarkably increased. The activities of ACP, AKP, and lysozyme were obviously decreased, while the activities of MPO and NF-κB were significantly increased. The expressions of immune-related mRNA were significantly affected. After co-treatment with PFOS and PDTC, the growth inhibition, the morphological damage, the ROS induction, and the expressions of immune-related mRNA were reversed. Taken together, the results indicated that PFOS can significantly inhibit the growth, disturb the immune system by changing the normal structure of liver, the activities of immune-related enzymes, and a series of gene transcriptions involved in immune regulation in liver of male zebrafish. PFOS-induced pro-inflammatory effect of hepatocytes was observed, and the involvement of NF-κB signaling pathway was participated in its action mechanism. These findings provide further evidence that PFOS interferes with the immune regulation of liver of male zebrafish under in vivo conditions.

Assessing the human health risks of perfluorooctane sulfonate by in vivo and in vitro studies

The wide use of perfluorooctane sulfonate (PFOS) has led to increasing concern about its human health risks over the past decade. In vivo and in vitro studies are important and effective means to ascertain the toxic effects of PFOS on humans and its toxic mechanisms. This article systematically reviews the human health risks of PFOS based on the currently known facts found by in vivo and in vitro studies from 2008 to 2018. Exposure to PFOS has caused hepatotoxicity, neurotoxicity, reproductive toxicity, immunotoxicity, thyroid disruption, cardiovascular toxicity, pulmonary toxicity, and renal toxicity in laboratory animals and many in vitro human systems. These results and related epidemiological studies confirmed the human health risks of PFOS, especially for exposure via food and drinking water. Oxidative stress and physiological process disruption based on fatty acid similarity were widely studied mechanisms of PFOS toxicity. Future research for assessing the human health risks of PFOS is recommended in the chronic toxicity and molecular mechanisms, the application of various omics, and the integration of toxicological and epidemiological data.

Developmental Toxicity of Perfluorooctanesulfonate (PFOS) and Its Chlorinated Polyfluoroalkyl Ether Sulfonate Alternative F-53B in the Domestic Chicken

The chlorinated polyfluoroalkyl ether sulfonate F-53B is used as a mist suppressant in the Chinese electroplating industry. Because of the regulations on perfluorooctanesulfonate (PFOS), its use is expected to increase. Until now, F-53B toxicity data have been scarce and are, to our knowledge, lacking for birds. This study therefore investigated the effects of PFOS and F-53B, separately and as mixtures, on the development of the chicken ( Gallus gallus domesticus). Compounds were injected in ovo, before incubation, at 150 and 1500 ng/g egg. At embryonic day 20, a significantly lower heart rate was observed in all treated groups compared to the control group and hatchlings exposed to the high dose of F-53B had a significantly enlarged liver (8%). Embryonic survival was not affected and no significant effects on hatchling body mass or oxidative stress parameters were found. Our results suggest that these compounds likely have different toxicity thresholds for the investigated endpoints, and/or different modes of action. This study thereby underlines the potential developmental toxicity of PFOS and F-53B at environmentally relevant concentrations. Assessment of PFOS alternatives should therefore continue, preferably prior to their large scale use, as they should be ensured to be less harmful than PFOS itself.

The genome of the marine medaka Oryzias melastigma

Marine medaka (Oryzias melastigma) is considered to be a useful fish model for marine and estuarine ecotoxicology studies and has good potential for field-based population genomics because of its geographical distribution in Asian estuarine and coastal areas. In this study, we present the first whole-genome draft of O. melastigma. The genome assembly consists of 8,602 scaffolds (N50 = 23.737 Mb) and a total genome length of 779.4 Mb. A total of 23,528 genes were predicted, and 12,670 gene families shared with three teleost species (Japanese medaka, mangrove killifish and zebrafish) were identified. Genome analyses revealed that the O. melastigma genome is highly heterozygous and contains a large number of repeat sequences. This assembly represents a useful genomic resource for fish scientists.

Assessing the toxicity of triphenyltin to different life stages of the marine medaka Oryzias melastigma through a series of life-cycle based experiments

Toxic effects of triphenyltin (TPT) to different life stages of the marine medaka Oryzias melastigma were investigated through a series of life-cycle based exposure experiments. In embryo stage, TPT exposure could elevate the heartbeat rate at Day 6-8 post-fertilization and increase the expression levels of five heart development related genes (i.e., ATPase, COX2, BMP4, GATA4 and NKX2.5). In larval stage, TPT shortened the body length at ≥10μg/L and suppressed the swimming activity of the fish larvae at Day 1 post-hatching at 50μg/L. In reproductive stage, TPT exposure resulted in a male-biased sex ratio (2μg/L) and reduced the gonadosomatic index (GSI) in females (≥ 0.1μg/L), which might in turn lead to a decline in their population fitness. The reproductive stage of O. melastigma was more sensitive to TPT than other stages, while the GSI of female medaka was the most sensitive endpoint.

Different effects of bisphenol a and its halogenated derivatives on the reproduction and development of Oryzias melastigma under environmentally relevant doses

Bisphenol A (BPA) and its halogenated compounds (H-BPAs) are widely detected in the environmental media and organisms. However, their toxicological effects, especially chronic exposure at low doses, have not been fully compared. In this study, the effects of BPA and H-BPAs on the reproduction and development of Oryzias melastigma were systematically assessed and compared at various developmental stages. BPA and its derivatives tetrabromobisphenol A (TBBPA) and tetrachlorobisphenol A (TCBPA) elicited the acceleration of embryonic heartbeat. BPA did not show any significant impact on the hatching time and rate of embryos. In contrast, both TBBPA and TCBPA led to the delayed hatching and decreased hatching rate. Accordingly, the expressions of hatching enzyme significantly decreased upon exposure and TCBPA was found to be more toxic than TBBPA. The body weight and gonadsomatic index (GSI) of the treated fish were relatively lower than the control fish upon long-term (four months from larvae to adult) exposure to BPA rather than H-BPAs. Slowed oocyte development occurred in the ovary, and the estrogen level decreased after exposure to BPA rather than H-BPAs. In male fish, no significant alteration was observed in the testis for all groups. The concentration of testosterone significantly decreased upon exposure to BPA rather than H-BPAs. The effects of these three chemicals on the estrogen-related gene expressions were different under various developmental stages. Our study indicated the importance of considering both the exposure stages and structure-activity relationship when assessing the eco-toxicological impact of pollutants.

Evaluation of the Cardiotoxicity of Evodiamine In Vitro and In Vivo

Evodiamine is a bioactive alkaloid that is specified as a biomarker for the quality assessment of Evodia rutaecarpa (E. rutaecarpa) and for traditional Chinese medicines containing this plant. We previously reported that quantitative structure–activity modeling indicated that evodiamine may cause cardiotoxicity. However, previous investigations have indicated that evodiamine has beneficial effects in patients with cardiovascular diseases and there are no previous in vitro or in vivo reports of evodiamine-induced cardiotoxicity. The present study investigated the effects of evodiamine on primary cultured neonatal rat cardiomyocytes in vitro, and on zebrafish in vivo. Cell viability was reduced in vitro, where evodiamine had a 24 h 50% inhibitory concentration of 28.44 µg/mL. Cells exposed to evodiamine also showed increased lactate dehydrogenase release and maleic dialdehyde levels, and reduced superoxide dismutase activity. In vivo, evodiamine had a 10% lethal concentration of 354 ng/mL and induced cardiac malfunction, as evidenced by changes in heart rate and circulation, and pericardial malformations. This study indicated that evodiamine could cause cardiovascular side effects involving oxidative stress. These findings suggest that cardiac function should be monitored in patients receiving preparations containing evodiamine.

6:2 Chlorinated polyfluorinated ether sulfonate, a PFOS alternative, induces embryotoxicity and disrupts cardiac development in zebrafish embryos

As an alternative to perfluorooctanesulfonate (PFOS), 6:2 chlorinated polyfluorinated ether sulfonate (commercial name: F-53B) has been used as a mist suppressant in Chinese electroplating industries for over 30 years. It has been found in the environment and fish, and one acute assay indicated F-53B was moderately toxic. However, the toxicological information on this compound was incomplete and insufficient for assessment of their environment impact. The object of this study was to examine the developmental toxicity of F-53B using zebrafish embryos. Zebrafish embryos were incubated in 6-well plates with various concentrations of F-53B (1.5, 3, 6, and 12mg/L) from 6 to 132h post fertilization (hpf). Results showed that F-53B exposure induced developmental toxicity, including delayed hatching, increased occurrence of malformations, and reduced survival. Malformations, including pericardial and yolk sac edemas, abnormal spines, bent tails, and uninflated swim bladders, appeared at 84 hpf, and increased with time course and dose. A decrease in survival percentages was noted in the 6 and 12mg/L F-53B-treated groups at 132 hpf. Continuous exposure to 3mg/L F-53B resulted in high accumulation levels in zebrafish embryos, suggesting an inability for embryos to eliminate this compound and a high cumulative risk to fish. We also examined the cardiac function of embryos at specific developmental stages following exposure to different concentrations, and found that F-53B induced cardiac toxicity and reduced heart rate. Even under low F-53B concentration, o-dianisidine staining results showed significant decrease of relative erythrocyte number at 72 hpf before the appearance of observed effects of F-53B on the heart. To elucidate the underlying molecular changes, genes involved in normal cardiac development were analyzed using real-time qPCR in the whole-body of zebrafish embryos. F-53B inhibited the mRNA expression of β-catenin (ctnnb2) and wnt3a. The mRNA levels of β-catenin targeted genes (nkx2.5 and sox9b), which play critical roles in cardiogenesis, were also reduced after exposure. Thus, exposure to F-53B impaired the development of zebrafish embryos and disrupted cardiac development, which might be mediated by effects on the Wnt signaling pathway and decrease of erythrocyte numbers.

Developmental toxicity and molecular responses of marine medaka (Oryzias melastigma) embryos to ciguatoxin P-CTX-1 exposure

Ciguatoxins are produced by toxic benthic dinoflagellates and cause ciguatera fish poisoning worldwide, but the toxic effects on developing marine fish have not been well investigated. The Pacific ciguatoxin (P-CTX-1), is a potent sodium channel agonist, which is one of the most toxic members among all CTXs. This study evaluated the toxic effects of microinjecting purified Pacific ciguatoxin-1 (P-CTX-1) on embryonic development of marine medaka Oryzias melastigma. A lower 96h-LD₅₀ value was estimated for eleuthero-embryos (1.32ngg^-1) than that for embryos (1.71ngg^-1), indicating that P-CTX-1 is more lethal to newly hatched medaka larvae. P-CTX-1 induced detrimental effects during embryonic development, including hatching failure, abnormalities in physical development (caudal fin malformation and spinal deformities), internal damage (green coloration of the gall bladder and hemorrhaging), immune dysfunction, and altered muscle physiology (bradycardia and hyperkinetic twitching). The results of a transcriptional expression analysis of genes related to the stress/immune responses, cardiac and bone development, and apoptosis supported the observed developmental abnormalities. This study advanced the understanding of P-CTX-1 mediated toxic mechanisms in the development of early life stages of a fish, and thus contributed to the toxicity assessment of CTXs in marine ecosystems.

Mitochondrial toxicity of perfluorooctane sulfonate in mouse embryonic stem cell-derived cardiomyocytes

Perfluorooctane sulfonate (PFOS) is a persistent organic contaminant that may cause cardiotoxicity in animals and humans. However, little is known about the underlying mechanism by which it affects the organelle toxicity in cardiomyocytes during the cardiogenesis. Our previous proteomic study showed that differences of protein expression mainly existed in mitochondria of cardiomyocytes differentiated from embryonic stem (ES) cells after exposure to PFOS. Here, we focused on mitochondrial toxicity of PFOS in ES cell-derived cardiomyocytes. The cardiomyogenesis from ES cells in vitro was inhibited, and the expression of L-type Ca²⁺ channel (LTCC) was decreased to interrupt [Ca²⁺]_c transient amplitude in cardiomyocytes after PFOS treatment. Transmission electron microscope revealed that swollen mitochondrion with vacuole in PFOS-treated cells. Meanwhile, mitochondrial transmembrane potential (ΔΨm) was declined and ATP production was lowered. These changes were related to the increased EGFR phosphorylation, activated Rictor signaling, then mediated HK2 binding to mitochondrial membrane. Furthermore, PFOS reduced the interaction of IP3R-Grp75-VDAC and accumulated intracellular fatty acids by activating Rictor, thereby attenuating PGC-1α and Mfn2 expressions, then destroying mitochondria-associated endoplasmic reticulum membrane (MAM), which resulted in the decrease of [Ca²⁺]_mito transient amplitude triggered by ATP. In conclusion, mitochondrial structure damages and abnormal Ca²⁺ shuttle were the important aspects in PFOS-induced cardiomyocytes toxicity from ES cells by activating Rictor signaling pathway.

Effects of Perfluorooctane sulfonate on immobilization, heartbeat, reproductive and biochemical performance of Daphnia magna

In recent years, Perfluorooctane sulfonate (PFOS) was widely detected in Yellow-Bohai Sea and other areas, causing a series of adverse effects in aquatic organisms. However, present studies of its chronic and acute toxicity on aquatic organisms were far more inadequate. Therefore, in the present study, Daphnia magna was used to investigate PFOS toxicity on their immobilization, heartbeat, reproductive and biochemical performance in acute, subchronic and chronic exposure. The results showed that the 48h-EC₅₀ value for immobilization was 79.35 mg L^-1 and the toxicity was classified as intermediate. Heartbeat was significantly stimulated and reproductive parameters were significantly suppressed by PFOS, which can be used to reflect the toxicological effects on individuals. On the other hand, intrinsic rate of natural increase was more sensitive than reproductive parameters, which indicated negative responses on population dynamics of Daphnia magna. In addition, there were different degrees of inhibition on GST, CAT and ChE activity, which indicated three types of enzyme could become biomarkers to chronic PFOS exposure. Most of selected and evaluated endpoints have significant sensitivity to PFOS at the concentration of 8 mg L^-1 during subchronic and chronic exposure.