Bisphenol S induces obesogenic effects through deregulating lipid metabolism in zebrafish (Danio rerio) larvae

Long-term exposure to prometryn damages the visual system and changes color preference of female zebrafish (Danio rerio)

Color vision, initiated from the cone photoreceptors, is essential for fish to obtain environmental information. Although the visual impairment of triazine herbicide prometryn has been reported, data on the effect of herbicide such as prometryn on natural color sensitivity of fish is scarce. Here, zebrafish were exposed to prometryn (0, 1, 10, and 100 μg/L) from 2 h post-fertilization to 160 days post-fertilization, to explore the effect and underlying mechanism of prometryn on color perception. The results indicated that 10 and 100 μg/L prometryn shortened the height of red-green cone cells, and down-regulated expression of genes involved in light transduction pathways (arr3a, pde6h) and visual cycle (lrata, rpe65a); meanwhile, 1 μg/L prometryn increased all-trans-retinoic acid levels in zebrafish eyes, and up-regulated the expression of genes involved in retinoid metabolism (rdh10b, aldh1a2, cyp26a1), finally leading to weakened red and green color perception of female zebrafish. This study first clarified how herbicide such as prometryn affected color vision of a freshwater fish after a long-term exposure from both morphological and functional disruption, and its hazard on color vision mediated-ecologically relevant tasks should not be ignored.

Bisphenol S exposure induces cardiac remodeling and aggravates high-fat diet-induced cardiac hypertrophy in mice

Bisphenol S (BPS) is widely used in the manufacture products and increase the risk of cardiovascular diseases. The effect of the association between obesity and BPS on cardiac outcomes is still unknown. Male C57BL/6 mice were divided into standard chow diet (SC; 15 kJ/g), standard chow diet + BPS (SCB), high-fat diet (HF; 21 kJ/g), and high-fat diet + BPS (HFB). Over 12 weeks, the groups were exposed to BPS through drinking water (dose: 25 μg/Kg/day) and/or a HF diet. We evaluated: body mass (BM), total cholesterol, systolic blood pressure (SBP), left ventricle (LV) mass, and cardiac remodeling. In the SCB group, BM, total cholesterol, and SBP increase were augmented in relation to the SC group. In the HF and HFB groups, these parameters were higher than in the SC and SCB groups. Cardiac hypertrophy was evidenced by augmented LV mass and wall thickness, and ANP protein expression in all groups in comparison to the SC group. Only the HFB group had a thicker LV wall than SCB and HF groups, and increased cardiomyocyte area when compared with SC and SCB groups. Concerning cardiac fibrosis, SCB, HF, and HFB groups presented higher interstitial collagen area, TGFβ, and α-SMA protein expression than the SC group. Perivascular collagen area was increased only in the HF and HFB groups than SC group. Higher IL-6, TNFα, and CD11c protein expression in all groups than the SC group evidenced inflammation. All groups had elevated CD36 and PPARα protein expression in relation to the SC group, but only HF and HFB groups promoted cardiac steatosis with increased perilipin 5 protein expression than the SC group. BPS exposure alone promoted cardiac remodeling with pathological concentric hypertrophy, fibrosis, and inflammation. Diet-induced remodeling is aggravated when associated with BPS, with marked hypertrophy, alongside fibrosis, inflammation, and lipid accumulation.

β-Sitosterol Reduces the Content of Triglyceride and Cholesterol in a High-Fat Diet-Induced Non-Alcoholic Fatty Liver Disease Zebrafish (Danio rerio) Model

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with hyperlipidemia, which is closely related to high levels of sugar and fat. β-sitosterol is a natural product with significant hypolipidemic and cholesterol-lowering effects. However, the underlying mechanism of its action on aquatic products is not completely understood.

METHODS

A high-fat diet (HFD)-induced NAFLD zebrafish model was successfully established, and the anti-hyperlipidemic effect and potential mechanism of β-sitosterol were studied using oil red O staining, filipin staining, and lipid metabolomics.

RESULTS

β-sitosterol significantly reduced the accumulation of triglyceride, glucose, and cholesterol in the zebrafish model. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that differential lipid molecules in β-sitosterol mainly regulated the lipid metabolism and signal transduction function of the zebrafish model. β-sitosterol mainly affected steroid biosynthesis and steroid hormone biosynthesis in the zebrafish model. Compared with the HFD group, the addition of 500 mg/100 g of β-sitosterol significantly inhibited the expression of Ppar-γ and Rxr-α in the zebrafish model by at least 50% and 25%, respectively.

CONCLUSIONS

β-sitosterol can reduce lipid accumulation in the zebrafish model of NAFLD by regulating lipid metabolism and signal transduction and inhibiting adipogenesis and lipid storage.

Trophic transfer of micro- and nanoplastics and toxicity induced by long-term exposure of nanoplastics along the rotifer (Brachionus plicatilis)-marine medaka (Oryzias melastigma) food chain

Microplastics (MPs) and nanoplastics (NPs) are emerging pollutants in the ocean, but their transfer and toxicity along the food chains are unclear. In this study, a marine rotifer (Brachionus plicatilis)-marine medaka (Oryzias melastigma) food chain was constructed to evaluate the transfer of polystyrene MPs and NPs (70 nm, 500 nm, and 2 μm, 2000 μg/L) and toxicity of 70 nm PS-NPs (0, 20, 200, and 2000 μg/L) on marine medaka after long-term food chain exposure. The results showed that the amount of 70 nm NPs accumulated in marine medaka was 1.24 μg/mg, which was significantly higher than that of 500 nm NPs (0.87 μg/mg) and 2 μm MP (0.69 μg/mg). Long-term food chain exposure to NPs caused microflora dysbiosis, resulting in activation of toll-like receptor 4 (TLR4) pathway, which induced liver inflammation. Moreover, NPs food chain exposure increased liver and muscle tissue triglyceride and lactate content, but decreased the protein, sugar, and glycogen content. NPs food chain exposure impaired reproductive function and inhibited offspring early development, which might pose a threat to the sustainability of marine medaka population. Overall, the study revealed the transfer of MPs and NPs and the effects of NPs on marine medaka along the food chain.

Bisphenol S, bisphenol F, bisphenol a exposure and body composition in US adults

Bisphenol S (BPS) and bisphenol F (BPF) are increasingly used to replace bisphenol A (BPA), an endocrine-disrupting chemical with putative obesogenic properties; whether and how BPS and BPF affect adiposity in humans remains to be determined. Therefore, we examined the association of BPA, BPS， and BPF with body composition among US adults. We included 1787 participants aged 20-59 years old in the National Health and Nutrition Examination Survey 2013-2016 who had information on urinary BPA, BPS, and BPF concentrations, and body composition measured using dual-energy x-ray absorptiometry. After full adjustment for potential confounders in linear regression models, BPA was significantly associated with the % body fat of the whole body, arm, and leg, with the β (95% CI) for the highest quartile vs. the lowest quartile of 1.34 (95%CI [0.11, 2.58], P = 0.03), 1.60 (95%CI [0.20, 3.00], P = 0.03), and 1.63 (95%CI [0.24, 3.02], P = 0.02), respectively. No association between BPA and lean mass was found. For BPS, significant associations were found for % body fat of the whole body (β [95% CI] = 1.42 [0.49, 2.36], P = 0.004), trunk (β[95% CI] = 1.92 [0.86, 2.97], P = 0.001), and arm (β [95% CI] = 1.60 [0.49, 2.70], P = 0.01), as well as lean mass of the whole body (β [95% CI] = 2610.6 [1324.3, 3896.8], P < 0.001), trunk (β [95% CI] = 1467.0 [745.3, 2188.7], P < 0.001), arm (β [95% CI] = 113.4 [10.3, 216.5], P = 0.03), and leg (β [95% CI] = 431.5 [219.6, 643.4], P < 0.001), comparing the third quartile vs. the lowest quartile. No significant association was observed between BPF and % body fat and lean mass. Results suggest that higher BPA levels were significantly associated with greater % body fat of the whole body and limbs, and there was suggestive evidence that BPS levels were associated with both % body fat and lean mass of the whole body and body parts in a nonmonotonic relationship.

Sex-specific associations of bisphenol A and its substitutes with body fat distribution among US adults: NHANES 2011-2016

Bisphenol A (BPA) and its structural analogs (bisphenol S (BPS) and bisphenol F (BPF)) are widely consumed endocrine disrupting chemicals that may contribute to the etiology of obesity. To date, few studies have directly investigated the sex-related associations between bisphenols and body fat distribution in adults. In this study, we included 2669 participants from the National Health and Nutrition Examination Survey (NHANES) 2011-2016 to evaluate and compare sex-specific differences of the associations of BPA, BPS, and BPF with body fat distribution. We found that there were significant positive correlations between BPS and body fat indices (STFAT [adjustedβ=1.94, 95% CI: (0.24, 3.64)], TAF [0.18 (0.04, 0.32)], SAT [0.15 (0.03, 0.27)], android fat mass [0.20 (0.004, 0.40)], BMI [1.63 (0.61, 2.65)], and WC [3.19 (0.64, 5.73)] in the highest quartiles of BPS), but not in BPA and BPF. Stratified analyses suggested that the significant associations of BPS with body fat indices were stronger in women than men (STFAT [adjustedβ=3.75, 95% CI: (1.04, 6.45) vs. adjustedβ=-0.06, 95% CI: (-2.23, 2.11), P for interaction < 0.001], TAF [ 0.32 (0.09, 0.54) vs. 0.01 (-0.17, 0.19), P for interaction < 0.001], SAT [0.27 (0.09, 0.45) vs. 0.01 (-0.14, 0.16), P for interaction < 0.001], android fat mass [0.41 (0.12, 0.71) vs. -0.02 (-0.28, 0.24), P for interaction < 0.001], gynoid fat mass [0.56 (0.11, 1.01) vs. -0.05 (-0.41, 0.31), P for interaction = 0.002], BMI [2.76 (1.08, 4.44) vs. 0.47 (-0.80, 1.74), P for interaction < 0.001], and WC [5.51 (1.44, 9.58) vs. 0.61 (-2.67, 3.88), P for interaction < 0.001]), and positive associations between BPS with fat distribution were also observed in non-smoking women. Our study indicated that in women, higher concentration of urinary BPS was associated with increased body fat accumulation, except for visceral adipose tissue mass. These findings emphasize the role of environmental BPS exposure in the increasing fat deposits, and confirm the need for more prospective cohort studies on a sex-specific manner.

PPARα Senses Bisphenol S to Trigger EP300-Mediated Autophagy Blockage and Hepatic Steatosis

The internal exposure dose of bisphenol S (BPS) is increasing since its use as a substitute for BPA. The relationship between BPS and nonalcoholic liver disease (NAFLD) and the underlying mechanism remain unclarified. In this study, we evaluated the correlation of BPS with NAFLD in populations from the Jiangsu Survey and the 2013-2016 National Health Nutrition Examination Survey and unraveled the molecular pathway by which BPS blocked hepatic autophagy, contributing to lipid accumulation. The study found that serum and urine BPS were associated with NAFLD risks in both the Chinese and US populations. For each additional unit of the BPS level, the NAFLD risk increased by 3.163-fold (serum) and 3.979-fold (urine) in the Chinese population. In addition, after BPS exposure at a dose equivalent to human exposure for 20 weeks, mice developed liver lipid accumulation. BPS could trigger PPARα-mediated transcriptional activation of EP300 expression. BPS promoted the translocation of EP300 from the nucleus to the cytoplasm to regulate the acetylation of Raptor and the activation of mTORC1, which in turn induced autophagy blockage and interfered with lipid degradation in hepatocytes. Conversely, knockdown of EP300 reduced Raptor acetylation and ameliorated autophagy blockage. This study demonstrated that EP300 was a key enzyme for the development of BPS-related NAFLD and provided novel evidence that BPS causes NAFLD.

Continuous exposure to bisphenol S increases the accumulation of endogenous metabolic toxicants by obstructing the glucuronic acid pathway

Uridine diphosphate glucuronic acid (UDPGA) is an essential substrate in the glucuronidation of exogenous and endogenous lipophilic compounds via the liver glucuronic acid pathway, and its synthesis depends on glucose and energy in the body. Bisphenol S (BPS), as a lipophilic environmental pollutant, has been widely utilized in the manufacturing of daily necessities. The biological effect of BPS in interference with liver energy metabolism might affect UDPGA synthesis and the excretion of lipophilic compounds, but this was not clearly revealed. Here, female zebrafish that were exposed to BPS for 35 days exhibited a significant decrease in UDPGA in the liver with significant accumulation of exogenous BPS and endogenous bilirubin in the body. One vital reason may be that the exposure to BPS for 35 days promoted the lipid formation through PPARg signaling and reduced energy levels in the liver, resulting in the decreased raw materials for UDPGA production in glucuronic acid pathway. Meanwhile, transcriptome analysis showed that BPS inhibited the mRNA expression levels of genes related to the glucuronic acid pathway. The accumulation of endogenous and exogenous lipophilic compounds can trigger a variety of toxicological effect. Thus, weakened liver detoxification might be the primary cause of the toxicological effects of lipophilic pollutants.

Association of urinary bisphenols with oxidative stress and inflammatory markers and their role in obesity

Bisphenol A (BPA) and its substitutes are widely used in daily life. Animal and cell line experiments have confirmed the effects of bisphenols on oxidative stress and inflammation. However, current population evidence for the effects of BPA alternatives, such as bisphenol F (BPF) and bisphenol S (BPS), on oxidative stress and inflammation is still sparse. Based on the National Health and Nutrition Examination Survey 2013-2016 data, our study used linear regression, weighted quantile sum model, and Bayesian kernel machine regression model to evaluate the effects of BPA, BPS, and BPF alone and in combination on oxidative stress (serum total bilirubin, and iron) and inflammation (alkaline phosphatase, C-reactive protein, γ-glutamyl transferase ferritin, neutrophil count, lymphocyte count, and neutrophil-to-lymphocyte ratio) markers. On this basis, the possible roles of oxidative stress and inflammation in obesity, which is associated with exposure to bisphenols (BPs), were initially explored. Based on the different covariates selected, a total of 3039 and 2258 participants were included in our study for models 1 and 2, respectively; the median age of participants was 48 years, and 48.7 % were male. Based on all models, our results showed that exposure to BPs alone or in combination was associated with downregulation of serum total bilirubin. Urinary BPF concentration was specifically associated with the neutrophil-to-lymphocyte ratio. Serum total bilirubin may play a role in the association between obesity and BP mixture exposure. Upregulation of the neutrophil-to-lymphocyte ratio was not associated with obesity. In conclusion, our study found that single or combined exposure to BPs, as measured in urine, may be associated with changes in oxidative stress and inflammatory markers, and a decrease in serum total bilirubin may play a mediating role in BP-induced obesity.

Recent Advances in Sources, Migration, Public Health, and Surveillance of Bisphenol A and Its Structural Analogs in Canned Foods

The occurrence of bisphenol A (BPA) and its structural analogs, known as endocrine disruptors is widely reported. Consumers could be exposed to these chemicals through canned foods, leading to health risks. Considerable advances have occurred in the pathogenic mechanism, migration law, and analytical methodologies for these compounds in canned foods. However, the confusion and controversies on sources, migration, and health impacts have plagued researchers. This review aimed to provide insights and perspectives on sources, migration, effects on human health, and surveillance of these chemicals in canned food products. Current trends in the determination of BPA and its structural analogs have focused on mass spectroscopy and electrochemical sensor techniques. Several factors, including pH, time, temperature, and volume of the headspace in canned foods, could affect the migration of the chemicals. Moreover, it is necessary to quantify the proportion of them originating from the can material used in canned product manufacturing. In addition, adverse reaction research about exposure to low doses and combined exposure with other food contaminants will be required. We strongly believe that the information presented in this paper will assist in highlighting the research needs on these chemicals in canned foods for future risk evaluations.

Comparative pharyngeal cartilage developmental toxicity of bisphenol A, bisphenol S and bisphenol AF to zebrafish (Danio rerio) larvae: A combination of morphometry and global transcriptome analyses

Exposure to BPA is recently shown to affect cartilage development in teleost fishes; whether BPS and BPAF, its two most frequently used phenolic analogues have similar effect, however, remains unclear. Here, we utilize zebrafish (Danio rerio) as an in-vivo larval model for systematic comparison of the pharyngeal arch-derived cartilage developmental toxicity of BPA, BPS and BPAF. Zebrafish are continuously exposed to three bisphenol analogues (3-BPs) at a range of concentrations since the embryonic stage (0.5 hpf), and identified cartilage malformations of the mandibular and hyoid pharyngeal arches at larval stage (120 hpf). BPA and BPAF prolong length and broaden cartilage angles; however, BPS shortens length and narrows the angles of skull cartilages. The results of the comparative transcriptome show that FoxO and MAPK signaling pathways are closely associated with the toxicity of BPA and BPAF, while BPS exposure affects energy metabolism-related pathways. Moreover, exposure to 3-BPs have an impact on the oxidative stress status. Our data collectively indicate that BPS and BPAF may not be safer than BPA regarding the impact on pharyngeal cartilage development in fish model, the mechanisms still need explorations, and that these two analogues should be applied with caution.

Cetyl Alcohol Polyethoxylates Disrupt Metabolic Health in Developmentally Exposed Zebrafish

Alcohol polyethoxylates (AEOs), such as cetyl alcohol ethoxylates (CetAEOs), are high-production-volume surfactants used in laundry detergents, hard-surface cleaners, pesticide formulations, textile production, oils, paints, and other products. AEOs have been suggested as lower toxicity replacements for alkylphenol polyethoxylates (APEOs), such as the nonylphenol and octylphenol polyethoxylates. We previously demonstrated that nonylphenol polyethoxylates induced triglyceride accumulation in several in vitro adipogenesis models and promoted adiposity and increased body weights in developmentally exposed zebrafish. We also demonstrated that diverse APEOs and AEOs were able to increase triglyceride accumulation and/or pre-adipocyte proliferation in a murine pre-adipocyte model. As such, the goals of this study were to assess the potential of CetAEOs to promote adiposity and alter growth and/or development (toxicity, length, weight, behavior, energy expenditure) of developmentally exposed zebrafish (Danio rerio). We also sought to expand our understanding of ethoxylate chain-length dependent effects through interrogation of varying chain-length CetAEOs. We demonstrated consistent adipogenic effects in two separate human bone-marrow-derived mesenchymal stem cell models as well as murine pre-adipocytes. Immediately following chemical exposures in zebrafish, we reported disrupted neurodevelopment and aberrant behavior in light/dark activity testing, with medium chain-length CetAEO-exposed fish exhibiting hyperactivity across both light and dark phases. By day 30, we demonstrated that cetyl alcohol and CetAEOs disrupted adipose deposition in developmentally exposed zebrafish, despite no apparent impacts on standard length or gross body weight. This research suggests metabolic health concerns for these common environmental contaminants, suggesting further need to assess molecular mechanisms and better characterize environmental concentrations for human health risk assessments.

A New In Vivo Zebrafish Bioassay Evaluating Liver Steatosis Identifies DDE as a Steatogenic Endocrine Disruptor, Partly through SCD1 Regulation

Non-alcoholic fatty liver disease (NAFLD), which starts with liver steatosis, is a growing worldwide epidemic responsible for chronic liver diseases. Among its risk factors, exposure to environmental contaminants, such as endocrine disrupting compounds (EDC), has been recently emphasized. Given this important public health concern, regulation agencies need novel simple and fast biological tests to evaluate chemical risks. In this context, we developed a new in vivo bioassay called StAZ (Steatogenic Assay on Zebrafish) using an alternative model to animal experimentation, the zebrafish larva, to screen EDCs for their steatogenic properties. Taking advantage of the transparency of zebrafish larvae, we established a method based on fluorescent staining with Nile red to estimate liver lipid content. Following testing of known steatogenic molecules, 10 EDCs suspected to induce metabolic disorders were screened and DDE, the main metabolite of the insecticide DDT, was identified as a potent inducer of steatosis. To confirm this and optimize the assay, we used it in a transgenic zebrafish line expressing a blue fluorescent liver protein reporter. To obtain insight into DDE's effect, the expression of several genes related to steatosis was analyzed; an up-regulation of scd1 expression, probably relying on PXR activation, was found, partly responsible for both membrane remodeling and steatosis.

Bisphenol S disrupts opsins gene expression and impairs the light-sensing function via antagonizing TH-TRβ signaling pathway in zebrafish larvae

Bisphenol S (BPS) is extensively used in "bisphenol A-free" products such as baby bottles. Although the visual toxicity of BPS has been reported, the underlying mechanism was largely unknown. In the present study, zebrafish were exposed to 0, 4 and 400 nM BPS from 2 h post-fertilization (hpf) to 120 hpf to further explore the thyroid disruption mechanism underlying the BPS induced impairment of visual function. The results showed that BPS decreased T3 levels in larval eyes, induced retinal expression of thyroid hormone receptor β (TRβ), and thereby down-regulated the expression of TH-mediated opsin genes (opn1lw1, opn1lw2, opn1mw1, opn1mw2, opn1mw3, and opn1sw2) and impaired subsequent phototransduction pathways, leading to decreased visually mediated phototactic response and body color adaptation but stimulated visual motor response (VMR). Combining exposure of exogenous T3 or 1-850 (antagonist for TRβ) with BPS could partly compensate the inhibited expression of opsin genes (opn1mw2, opn1lw1, and opn1lw2) and alleviate the hyperactivity of larval VMR caused by BPS alone, suggesting that BPS disrupted the opsins expression and also light-sensing function via antagonizing TH-TRβ signaling pathway. This study underlined the importance of TH signaling in regulating the proper vision and proposed a novel mechanism for the visual toxicity of BPS.

Bisphenol S Impairs Behaviors through Disturbing Endoplasmic Reticulum Function and Reducing Lipid Levels in the Brain of Zebrafish

The number of neurotoxic pollutants is increasing, but their mechanism of action is unclear. Here, zebrafish were exposed to 0, 1, 10, and 100 μg/L bisphenol S (BPS) for different durations beginning at 2 h postfertilization (hpf) to explore the neurotoxic mechanisms of BPS. Zebrafish larvae exposed to BPS displayed abnormal neurobehaviors. At 48 and 120 hpf, BPS inhibited yolk lipid consumption and reduced the lipid distribution in the zebrafish brain. Moreover, BPS downregulated the mRNA levels of genes involved in fatty acid elongation in the endoplasmic reticulum (ER) and activated ER stress pathways at 48 and 120 hpf, and KEGG analysis after RNA-seq showed that the protein processing pathway in the ER was significantly enriched after BPS exposure. Exposure to ER toxicants (thapsigargin and tunicamycin), two positive controls, induced neurotoxic effects on zebrafish embryos and larvae similar to those of BPS exposure. These data suggested that BPS and ER toxicants disturbed ER function and reduced brain lipid levels. Continued exposure to BPS into adulthood not only inhibited brain fatty acid elongation and ER function but also caused abnormal swelling of the ER in zebrafish. Our data provide new insights into the neurotoxic mechanism of BPS.

Bisphenols induce cardiotoxicity in zebrafish embryos: Role of the thyroid hormone receptor pathway

Bisphenols are frequently found in the environment and have been of emerging concern because of their adverse effects on aquatic animals and humans. In this study, we demonstrated that bisphenol A, S, and F (BPA, BPS, BPF) at environmental concentrations induced cardiotoxicity in zebrafish embryos. BPA decreased heart rate at 96 hpf (hours post fertilization) and increased the distance between the sinus venosus (SV) and bulbus arteriosus (BA), in zebrafish. BPF promoted heart pumping and stroke volume, shortened the SV-BAdistance, and increased body weight. Furthermore, we found that BPA increased the expression of the dio3b, thrβ, and myh7 genes but decreased the transcription of dio2. In contrast, BPF downregulated the expression of myh7 but upregulated that of thrβ. Molecular docking results showed that both BPA and BPF are predicted to bind tightly to the active pockets of zebrafish THRβ with affinities of -4.7 and -4.77 kcal/mol, respectively. However, BPS did not significantly affect dio3b, thrβ, and myh7 transcription and had a higher affinity for zebrafish THRβ (-2.13 kcal/mol). These findings suggest that although BPA, BPS, and BPF have similar structures, they may induce cardiotoxicity through different molecular mechanisms involving thyroid hormone systems. This investigation provides novel insights into the potential mechanism of cardiotoxicity from the perspective of thyroid disruption and offer a cautionary role for the use of BPA substitution.

Bromuconazole exposure induces cardiotoxicity and lipid transport disorder in larval zebrafish

Bromuconazole (BRO), as one of the typical triazole fungicides, has not been reported on its effects on aquatic organisms. In this study, zebrafish embryos were used as experimental objects to evaluate the toxicity of BRO. In the acute embryo toxicity test, it was observed that the heart rate and growing development were affected by BRO in a concentration-dependent manner, and the half-lethal concentration (LC50) of BRO at 96 h post-fertilization (hpf) was about 11.83 mg/L. Then, low concentrations of BRO (50 ng/L, 0.075 mg/L, 0.3 mg/L, 1.2 mg/L), which were set according to the LC50 and environmental related concentrations, were used to analyze the toxic effects on the different endpoints in larval zebrafish. Interestingly, the transcriptomic analysis found that most different expressed genes (DEGs) could be focused on the pathways of lipid metabolism, myocardial function, glycometabolism, indicating that heart function and lipid metabolism in larval zebrafish were disrupted by BRO. For supporting this idea, we re-exposed the transgenic zebrafish and WT zebrafish embryos, proved that BRO caused damage to heart development and lipid transport on morphological and genetic level, which was consistent with transcriptomic results. In addition, BRO exposure caused oxidative damage in the larvae. Taken together, BRO exposure could affect the myocardial contraction function and lipid transport in larval zebrafish, accompanied by disturbances in the level of oxidative stress, which was of great significance for improving the biotoxicological information of BRO.

Effects of bisphenol AF on growth, behavior, histology and gene expression in marine medaka (Oryzias melastigma)

Bisphenol AF (BPAF) is one of the substitutes for bisphenol A (BPA), which has endocrine-disrupting, reproductive and neurological toxicity. BPAF has frequently been detected in the aquatic environment, which has been a long-term threat to the health of aquatic organisms. In this study, female marine medaka (Oryzias melastigma) were exposed to 6.7 μg/L, 73.4 μg/L, and 367.0 μg/L BPAF for 120 d. The effects of BPAF on behavior, growth, liver and ovarian histology, gene transcriptional profiles, and reproduction of marine medaka were determined. The results showed that with the increase of BPAF concentration, the swimming speed of female marine medaka showed an increasing trend and then decreasing trend. BPAF (367.0 μg/L) significantly increased body weight and condition factors in females. BPAF (73.4 μg/L and 367.0 μg/L) significantly delayed oocyte maturation. Exposure to 367.0 μg/L BPAF showed an increasing trend in the transcript levels of lipid synthesis and transport-related genes such as fatty acid synthase (fasn), sterol regulatory element binding protein (srebf), diacylglycerol acyltransferase (dgat), solute carrier family 27 member 4 (slc27a4), fatty acid-binding protein (fabp), and peroxisome proliferator-activated receptor gamma (pparγ) in the liver. In addition, 6.7 μg/L BPAF significantly down-regulated the expression levels of antioxidant-related genes [superoxide dismutase (sod), glutathione peroxidase (gpx), and catalase (cat)], and complement system-related genes [complement component 5 (c5), complement component 7a (c7a), mannan-binding lectin serine peptidase 1 (masp1), and tumor necrosis factor (tnf)] were significantly up-regulated in the 73.4 and 367.0 μg/L groups, which implies the effect of BPAF on the immune system in the liver. In the hypothalamic-pituitary-ovarian axis (HPG) results, the transcription levels of estrogen receptor α (erα), estrogen receptor β (erβ), androgen receptor (arα), gonadotropin-releasing hormone 2 (gnrh2), cytochrome P450 19b (cyp19b), aromatase (cyp19a), and luteinizing hormone receptor (lhr) in the brain and ovary, and vitellogenin (vtg) and choriogenin (chg) in the liver of 367.0 μg/L BPAF group showed a downward trend. In addition, exposure to 367.0 μg/L BPAF for 120 d inhibited the spawning behavior of marine medaka. Our results showed that long-term BPAF treatment influenced growth (body weight and condition factors), lipid metabolism, and ovarian maturation, and significantly altered the immune response and the transcriptional expression levels of HPG axis-related genes.

Exposure to Bisphenol A Substitutes, Bisphenol S and Bisphenol F, and Its Association with Developing Obesity and Diabetes Mellitus: A Narrative Review

Bisphenol A, a well-known endocrine-disrupting chemical, has been replaced with its analogs bisphenol S (BPS) and bisphenol F (BPF) over the last decade due to health concerns. BPS and BPF are present in relatively high concentrations in different products, such as food products, personal care products, and sales receipts. Both BPS and BPF have similar structural and chemical properties to BPA; therefore, considerable scientific efforts have investigated the safety of their exposure. In this review, we summarize the findings of relevant epidemiological studies investigating the association between urinary concentrations of BPS and/or BPF with the incidence of obesity or diabetes. The results showed that BPS and BPF were detected in many urinary samples at median concentrations ranging from 0.03 to 0.4 µg·L^-1. At this exposure level, BPS median urinary concentrations (0.4 µg·L^-1) were associated with the development of obesity. At a lower exposure level (0.1-0.03 µg·L^-1), two studies showed an association with developing diabetes. For BPF exposure, only one study showed an association with obesity. However, most of the reported studies only assessed BPS exposure levels. Furthermore, we also summarize the findings of experimental studies in vivo and in vitro regarding our aim; results support the possible obesogenic effects/metabolic disorders mediated by BPS and/or BPF exposure. Unexpectedly, BPS may promote worse obesogenic effects than BPA. In addition, the possible mode of action underlying the obesogenic effects of BPS might be attributed to various pathophysiological mechanisms, including estrogenic or androgenic activities, alterations in the gene expression of critical adipogenesis-related markers, and induction of oxidative stress and an inflammatory state. Furthermore, susceptibility to the adverse effects of BPS may be altered by sex differences according to the results of both epidemiological and experimental studies. However, the possible mode of action underlying these sex differences is still unclear. In conclusion, exposure to BPS or BPF may promote the development of obesity and diabetes. Future approaches are highly needed to assess the safety of BPS and BPF regarding their potential effects in promoting metabolic disturbances. Other studies in different populations and settings are highly suggested.

Long-term BPA exposure leads to bone malformation and abnormal expression of MAPK/Wnt/FoxO signaling pathway genes in zebrafish offspring

Bisphenol A (BPA) is one of the world's most widely used plasticizer, and its hazardous impacts have been well studied. However, few studies focused on the effects of parental long-term BPA exposure on the bone development of offspring. In the present study, the bone development of offspring was studied following long-term exposure of parental zebrafish to environmentally relevant 15 and 225 µg/L BPA. The results showed that BPA increased the mortality and deformity rate of offspring and caused craniofacial deformities characterized by changes in various cartilage angles and lengths. The alizarin red and calcein staining showed that BPA could delay bone mineralization and reduce bone mass accumulation. The results of acridine orange staining indicated that BPA induced apoptosis of the skull. The degree of harm of BPA presented a dose-dependent pattern. The results of the comparative transcriptome showed that there were 380 different expression genes (DEGs) in the 15 µg/L BPA group, and 645 DEGs in the 225 µg/L BPA group. MAPK/Wnt/FoxO signaling pathway-related genes were significantly down-regulated in the BPA-exposed groups. The present study demonstrates that long-term parental BPA exposure would severely affect cartilage development and bone mineralization of fish offspring, and MAPK/Wnt/FoxO signaling pathways may be involved in this process.

Transgenerational effects of parental bisphenol S exposure on zebrafish (Danio rerio) reproduction

Bisphenol S (BPS) is extensively used for production of polycarbonates and other commodities, and is often detected in environment and biota. Parental BPS exposure has been reported to interfere with reproductive development of offspring, but limited information is available on its multigenerational reproductive toxicity. In our present study, zebrafish (Danio rerio) were exposed to BPS (1 and 100 μg/L) from 3 hpf to 120 dpf, and the effects on reproduction, sex steroid hormones, DNA methylation levels and gene transcription involved in steroidogenesis and DNA methylation were investigated in unexposed F1-2 offspring. The results showed that 100 μg/L BPS exposure increased DNA methylation in F1 testes, and 1 μg/L BPS led to DNA methylation in F2 ovaries. The increased DNA methylation levels led to decreased expression of steroidogenic enzymes, including cyp11a, cyp17 and 3βhsd, which might be a main reason for the elevated plasma 17β-estradiol and decreased testosterone levels. In addition, sex ratio indicated a female dominance trend, and reproductive capacity of male fish was severely impaired. Overall, these findings suggest that parental BPS exposure impairs reproductive development of unexposed offspring via DNA methylation and BPS-induced epigenetic modification inheritance has a long-term effect on the fitness and sustainability of fish populations.

Obesity II: Establishing causal links between chemical exposures and obesity

Obesity is a multifactorial disease with both genetic and environmental components. The prevailing view is that obesity results from an imbalance between energy intake and expenditure caused by overeating and insufficient exercise. We describe another environmental element that can alter the balance between energy intake and energy expenditure: obesogens. Obesogens are a subset of environmental chemicals that act as endocrine disruptors affecting metabolic endpoints. The obesogen hypothesis posits that exposure to endocrine disruptors and other chemicals can alter the development and function of the adipose tissue, liver, pancreas, gastrointestinal tract, and brain, thus changing the set point for control of metabolism. Obesogens can determine how much food is needed to maintain homeostasis and thereby increase the susceptibility to obesity. The most sensitive time for obesogen action is in utero and early childhood, in part via epigenetic programming that can be transmitted to future generations. This review explores the evidence supporting the obesogen hypothesis and highlights knowledge gaps that have prevented widespread acceptance as a contributor to the obesity pandemic. Critically, the obesogen hypothesis changes the narrative from curing obesity to preventing obesity.

Obesity III: Obesogen assays: Limitations, strengths, and new directions

There is increasing evidence of a role for environmental contaminants in disrupting metabolic health in both humans and animals. Despite a growing need for well-understood models for evaluating adipogenic and potential obesogenic contaminants, there has been a reliance on decades-old in vitro models that have not been appropriately managed by cell line providers. There has been a quick rise in available in vitro models in the last ten years, including commercial availability of human mesenchymal stem cell and preadipocyte models; these models require more comprehensive validation but demonstrate real promise in improved translation to human metabolic health. There is also progress in developing three-dimensional and co-culture techniques that allow for the interrogation of a more physiologically relevant state. While diverse rodent models exist for evaluating putative obesogenic and/or adipogenic chemicals in a physiologically relevant context, increasing capabilities have been identified for alternative model organisms such as Drosophila, C. elegans, zebrafish, and medaka in metabolic health testing. These models have several appreciable advantages, including most notably their size, rapid development, large brood sizes, and ease of high-resolution lipid accumulation imaging throughout the organisms. They are anticipated to expand the capabilities of metabolic health research, particularly when coupled with emerging obesogen evaluation techniques as described herein.

Bisphenol S exposure accelerates the progression of atherosclerosis in zebrafish embryo-larvae

Bisphenol S (BPS), widely utilized in manufacturing of daily necessities, is a toxicant with potential to induce atherosclerotic cardiovascular disease (ASCVD). However, the mode of action by which BPS exposure induces ASCVD remains unknown. Here, macrophages that were exposed to BPS in combination with oxidized low-density lipoprotein (oxLDL) exhibited enhanced formation of foam cells, a hallmark of ASCVD. Furthermore, zebrafish embryo-larvae were exposed to BPS (0, 1, 10 and 100 μg/L) for 15 days (d) and the characteristic symptoms of ASCVD including an inflammatory response, macrophage recruitment around blood vessels, and accumulation of oxLDL on vascular endothelium, were induced in 15-d larvae. After zebrafish were exposed to BPS for 45 d, BPS mobilized fatty acid metabolism and activated peroxisome proliferator-activated receptor signaling in larval liver, the hub of endogenous lipid metabolism, causing an increase in plasma LDL. Driven by high plasma LDL levels, the caudal artery of zebrafish larvae exhibited lipid accumulation and a thickened area with a large number of collagen fibers, accompanied by characteristic lesions, as well as hyperlipidemia, erythrocyte aggregation, thinner blood vessel walls and increased levels of leukocytes and thromboocytes in plasma. Our data demonstrate that BPS accelerates the progression of ASCVD using zebrafish embryo-larvae as a model.

Metabolic Consequences of Developmental Exposure to Polystyrene Nanoplastics, the Flame Retardant BDE-47 and Their Combination in Zebrafish

Single-use plastic production is higher now than ever before. Much of this plastic is released into aquatic environments, where it is eventually weathered into smaller nanoscale plastics. In addition to potential direct biological effects, nanoplastics may also modulate the biological effects of hydrophobic persistent organic legacy contaminants (POPs) that absorb to their surfaces. In this study, we test the hypothesis that developmental exposure (0–7 dpf) of zebrafish to the emerging contaminant polystyrene (PS) nanoplastics (⌀100 nm; 2.5 or 25 ppb), or to environmental levels of the legacy contaminant and flame retardant 2,2′,4,4′-Tetrabromodiphenyl ether (BDE-47; 10 ppt), disrupt organismal energy metabolism. We also test the hypothesis that co-exposure leads to increased metabolic disruption. The uptake of nanoplastics in developing zebrafish was validated using fluorescence microscopy. To address metabolic consequences at the organismal and molecular level, metabolic phenotyping assays and metabolic gene expression analysis were used. Both PS and BDE-47 affected organismal metabolism alone and in combination. Individually, PS and BDE-47 exposure increased feeding and oxygen consumption rates. PS exposure also elicited complex effects on locomotor behaviour with increased long-distance and decreased short-distance movements. Co-exposure of PS and BDE-47 significantly increased feeding and oxygen consumption rates compared to control and individual compounds alone, suggesting additive or synergistic effects on energy balance, which was further supported by reduced neutral lipid reserves. Conversely, molecular gene expression data pointed to a negative interaction, as co-exposure of high PS generally abolished the induction of gene expression in response to BDE-47. Our results demonstrate that co-exposure to emerging nanoplastic contaminants and legacy contaminants results in cumulative metabolic disruption in early development in a fish model relevant to eco- and human toxicology.

Nonylphenol Polyethoxylates Enhance Adipose Deposition in Developmentally Exposed Zebrafish

Alkylphenol polyethoxylates (APEOs), such as nonylphenol ethoxylates (NPEOs), are high-production-volume surfactants used in laundry detergents, hard-surface cleaners, pesticide formulations, textile production, oils, paints, and other products. NPEOs comprise -80% of the total production of APEOs and are widely reported across diverse environmental matrices. Despite a growing push for replacement products, APEOs continue to be released into the environment through wastewater at significant levels. Research into related nonionic surfactants from varying sources has reported metabolic health impacts, and we have previously demonstrated that diverse APEOs and alcohol polyethoxylates promote adipogenesis in the murine 3T3-L1 pre-adipocyte model. These effects appeared to be independent of the base alkylphenol and related to the ethoxylate chain length, though limited research has evaluated NPEO exposures in animal models. The goals of this study were to assess the potential of NPEOs to promote adiposity (Nile red fluorescence quantification) and alter growth and/or development (toxicity, length, weight, and energy expenditure) of developmentally exposed zebrafish (Danio rerio). We also sought to expand our understanding of the ability to promote adiposity through evaluation in human mesenchymal stem cells. Herein, we demonstrated consistent adipogenic effects in two separate human bone-marrow-derived mesenchymal stem cell models, and that nonylphenol and its ethoxylates promoted weight gain and increased adipose deposition in developmentally exposed zebrafish. Notably, across both cell and zebrafish models we report increasing adipogenic/obesogenic activity with increasing ethoxylate chain lengths up to maximums around NPEO-6 and then decreasing activity with the longest ethoxylate chain lengths. This research suggests metabolic health concerns for these common obesogens, suggesting further need to assess molecular mechanisms and better characterize environmental concentrations for human health risk assessments.

Microplastics increase the accumulation of phenanthrene in the ovaries of marine medaka (Oryzias melastigma) and its transgenerational toxicity

Microplastics (MPs) are considered to exacerbate the impacts of hydrophobic organic pollutants on aquatic organisms through the carrier function, but whether MPs affect the transgenerational toxicity of pollutants is unclear. This study exposed adult female marine medaka to phenanthrene (Phe)-adsorbed MPs for 60 days to investigate the effects of MPs on the bioaccumulation, reproductive and transgenerational toxicity of Phe. Compared to Phe alone, co-exposure to Phe and 200 μg/L MPs significantly increased Phe bioaccumulation in the intestines and ovaries. Phe alone and Phe combined with MPs disrupted the regulation of the hypothalamus-pituitary-gonadal axis, and reduced vitellogenin levels and reproductive capacity of female fish. In particular, co-exposure to 200 μg/L MPs and Phe increased the rate of follicular atresia, inhibited ovarian maturity, and aggravated reproductive toxicity. Notably, maternal uptake of Phe could be transferred to the offspring, and embryonic accumulation increased with the concentrations of MPs. Moreover, MPs aggravated Phe-induced bradycardia in embryos, suggesting that MPs exacerbated the transgenerational toxicity of Phe. These findings reveal that the growing number of MPs in the ocean might amplify the adverse effects of organic pollutants on the health and population stability of marine fishes, and this problem merits more attention.

Urinary bisphenol concentrations and its association with metabolic disorders in the US and Korean populations

Bisphenol A (BPA) is a representative endocrine disrupting compound used in a vast array of consumer products, and are being frequently substituted by its analogues, bisphenol S (BPS) and bisphenol F (BPF). We aimed to examine the association between urinary bisphenol levels with obesity and lipid profiles in the general population to comprehensively evaluate its potential of metabolic disturbance. A representative sample of 1046 US adults from the National Health and Nutrition Examination Survey (2013-2016) and 3268 Korean adults from the Korean National Environmental Health Survey (2015-2017) was analyzed. We examined the exposure levels of bisphenols and determined their associations with obesity, high-density lipoprotein cholesterol (HDL-C) and triglyceride (TG) levels, and hypercholesterolemia prevalence through multiple linear, and binary/ordinal logistic regression models. In both populations, high BPA levels (lowest tertile vs. 2nd, 3rd tertiles) showed corresponding associations with lipid profile and obesity. BPA levels were associated with decreased HDL-C levels (Q3: β = -0.053, p = 0.08 (US); Q2: β = -0.030, p-0.03), increased TG levels (Q3: β = 0.121, p = 0.029 (US); Q3: β = 0.089, p = 0.021, and higher odds for obesity (Q3: OR = 1.58, 95% CI: 1.06, 2.35 (US); Q3: OR = 1.41, 95% CI: 1.11, 1.78). Higher BPS levels were positively associated with obesity status, especially in US men (Q2: OR = 1.84, 95% CI: 1.15, 2.96) and Korean women (Q3: OR = 1.27, 95% CI: 0.99, 1.64). A significant decrease in HDL-C (Q3: β = -0.088, p = 0.01) and elevated odds for obesity at higher BPF levels (Q3: OR = 1.60, 95% CI: 1.00, 2.56) was observed in US women. The findings of our study indicate that BPA and its analogues, BPS and BPF, are associated with lipid metabolism disorders in addition to obesity in adults. Given the increase in exposure to BPA alternatives, continuous biomonitoring, and further investigation of their health effects through prospective cohort studies are warranted.

17β-Trenbolone binds to androgen receptor, decreases number of primordial germ cells, modulates expression of genes related to sexual differentiation, and affects sexual differentiation in zebrafish (Danio rerio)

Exposure to 17β-trenbolone caused a skewed sex ratio in fish. However, the molecular initiating event and key molecular event(s) remain unknown. In this study, zebrafish were exposed to 17β-trenbolone at nominal concentrations of 2 ng/L, 20 ng/L, 200 ng/L, and 2000 ng/L from fertilization to 60 days post fertilization (dpf). First, the sex ratio at 60 dpf was calculated to evaluate adverse outcomes on sexual differentiation. 17β-Trenbolone caused a skewed sex ratio toward males, with intersex individuals observed in the 20 ng/L group and all-male populations found in the 200 ng/L and 2000 ng/L groups. Then, the distribution and number of primordial germ cells, the expression of sex differentiation-related genes, and plasma vitellogenin concentrations were detected in wild-type zebrafish and the EGFP-nanos-3'UTR transgenic line using whole-mount in situ hybridization, real-time PCR, EGFP fluorescence quantification, and enzyme-linked immunosorbent assay. The results indicated that 17β-trenbolone exposure decreased the number of primordial germ cells at 1 dpf and 3 dpf, decreased expression of ovarian differentiation-related genes foxl2 and cyp19a1a at 60 dpf, increased expression of testis differentiation-related genes dmrt1, sox9a, and amh at 60 dpf, and decreased plasma vitellogenin levels at 60 dpf, revealing the key molecular events at different time points involved in affected sexual differentiation by 17β-trenbolone. Finally, molecular docking showed that 17β-trenbolone docked into ligand-binding domain of zebrafish androgen receptor with high binding energy (-3.72 kcal/mol), suggesting that binding to androgen receptor is the molecular initiating event affecting sexual differentiation by 17β-trenbolone. We found that 17β-trenbolone can bind to the zebrafish androgen receptor, decrease the number of primordial germ cells during the early embryonic stage, modulate the expression of genes related to sexual differentiation during gonadal differentiation, and eventually cause a skewed sex ratio toward males in adults.

Disrupted metabolic pathways and potential human diseases induced by bisphenol S

Although the toxicity of bisphenol S has been studied in some species, the global metabolic network disrupted by bisphenol S remains unclear. To this end, published datasets related to the genes, proteins, and metabolites disturbed by bisphenol S were investigated through omics methods. The dataset revealed that bisphenol S at high concentrations tended to downregulate biomolecules, while low concentrations of bisphenol S tended to enhance metabolic reactions. The results showed that exposure to bisphenol S upregulated estrogen and downregulated androgen metabolism in humans, mice, rats, and zebrafish. Fatty acid metabolism and phospholipid metabolism in mice were upregulated. Reactions in amino acid metabolism were upregulated, with the exception of the suppressive conversion of arginine to ornithine. In zebrafish, fatty acid synthesis was promoted, while nucleotide metabolism was primarily depressed through the downregulation of pyruvate 2-o-phosphotransferase. The interference in amino acid metabolism by bisphenol S could trigger Alzheimer's disease, while its disturbance of glucose metabolism was associated with type II diabetes. Disturbed glycolipid metabolism and vitamin metabolism could induce Alzheimer's disease and diabetes. These findings based on omics data provide scientific insight into the metabolic network regulated by bisphenol S and the diseases triggered by its metabolic disruption.

Alternatives for the worse: Molecular insights into adverse effects of bisphenol a and substitutes during human adipocyte differentiation

Bisphenol A (BPA), which is used in a variety of consumer-related plastic products, was reported to cause adverse effects, including disruption of adipocyte differentiation, interference with obesity mechanisms, and impairment of insulin- and glucose homeostasis. Substitute compounds are increasingly emerging but are not sufficiently investigated.We aimed to investigate the mode of action of BPA and four of its substitutes during the differentiation of human preadipocytes to adipocytes and their molecular interaction with peroxisome proliferator-activated receptor γ (PPARγ), a pivotal regulator of adipogenesis.Binding and effective biological activation of PPARγ were investigated by surface plasmon resonance and reporter gene assay, respectively. Human preadipocytes were continuously exposed to BPA, BPS, BPB, BPF, BPAF, and the PPARγ-antagonist GW9662. After 12 days of differentiation, lipid production was quantified via Oil Red O staining, and global protein profiles were assessed using LC-MS/MS-based proteomics. All tested bisphenols bound to human PPARγ with similar efficacy as the natural ligand 15d-PGJ2in vitroand provoked an antagonistic effect on PPARγ in the reporter gene assay at non-cytotoxic concentrations. During the differentiation of human preadipocytes, all bisphenols decreased lipid production. Global proteomics displayed a down-regulation of adipogenesis and metabolic pathways, similar to GW9662. Interestingly, pro-inflammatory pathways were up-regulated, MCP1 release was increased, and adiponectin decreased. pAKT/AKT ratios revealed significantly reduced insulin sensitivity by BPA, BPB, and BPS upon insulin stimulation.Thus, our results show that not only BPA but also its substitutes disrupt crucial metabolic functions and insulin signaling in adipocytes under low, environmentally relevant concentrations. This effect, mediated through inhibition of PPARγ, may promote hypertrophy of adipose tissue and increase the risk of developing metabolic syndrome, including insulin resistance.

Unraveling the mechanism of long-term bisphenol S exposure disrupted ovarian lipids metabolism, oocytes maturation, and offspring development of zebrafish

Bisphenol S (BPS) acts as a xenoestrogen and disturbs the female reproductive system; however, the underlying mechanism has not been elucidated. In this study, the effect of chronic BPS exposure (1 μg/L and 100 μg/L) on ovarian lipid metabolism in zebrafish was investigated to determine its influence on adult reproductive capacity and offspring development. The results showed that long-term (240 days) exposure to BPS induced lipid accumulation in the ovaries by promoting the transport of more lipids from the circulation to the ovaries and by upregulating triacylglycerol synthesis-related genes. Significantly increased expression of cpt2, acadm, acadl, and pparα, which are involved in β-oxidation in the ovarian mitochondria, indicated that more energy was provided for oocyte maturation in exposed zebrafish ovaries. Thus, the proportion of full-grown stage oocytes in ovaries and egg reproduction were elevated at an accelerated rate, which earlier than normal reproductive cycle (8-10 days posts pawning). Moreover, the maternally BPS-exposed F1 embryos (2 h post-spawning, hpf) showed higher neutral lipid levels, impaired hatching capacity, and increased occurrence of larval deformities. All these findings demonstrated that stimulated lipid synthesis and β-oxidation in zebrafish ovaries significantly contribute to BPS-induced oocyte precociousness with subsequent effects on the development of unexposed offspring. This study provides new insight into the impact of xenoestrogens on oviparous reproduction in females and offspring development from the perspective of ovarian lipid metabolism.

Monobutyl phthalate can induce autophagy and metabolic disorders by activating the ire1a-xbp1 pathway in zebrafish liver

Monobutyl phthalate (MBP) can exist in biological organisms for a long time because of its excellent fat solubility, and it has been found to have certain toxic effects. In this study, the acute effects of MBP on endoplasmic reticulum (ER) stress and metabolism in the zebrafish liver were studied. After continuous exposure to MBP (5 and 10 mg / L) for 96 h, ER damage and the appearance of apoptotic bodies and autophagosomes were found in liver. This is because MBP stimulated the ire-xbp1 pathway of ER stress, thus leading to apoptosis and autophagy. Also, through analysis of metabolic enzymes and genes, it was found that the activated ire-xbp1 pathway could promote lipid synthesis and cause the accumulation of lipid droplets. The gene pparγ related to lipid storage affected the level of insulin, which can also further affect the glucose metabolism process, that is, glycolysis and aerobic respiration were inhibited. And the pentose phosphate pathway (PPP) was activated as a compensation mechanism to alleviate glycogen accumulation. The abnormal supply of energy and the death of excessive cells will eventually severely damage the zebrafish liver. This study will enrich the knowledge about the toxic effects of MBP.

Metabolic pathways, alterations in miRNAs expression and effects of genetic polymorphisms of bisphenol a analogues: A systematic review

Bisphenol A (BPA) is one of the most common endocrine disruptors found in the environment and its harmful health effects in humans and wildlife have been extensively reported One of the main aims of this review was to examine the metabolic pathways of BPA and BPA substitutes and the endocrine disrupting properties of their metabolites. According to the available literature, phase I and phase II metabolic reactions play an important role in the detoxification process of bisphenols (BPs), but their metabolism can also lead to the formation of highly reactive metabolites. The second part of this work addresses the associations between exposure to BPA and its analogues with the alterations in miRNAs expression and the effects of single nucleotide polymorphisms (SNPs). Available scientific evidence shows that BPs can dysregulate the expression of several miRNAs, and in turn, these miRNAs could be considered as epigenetic biomarkers to prevent the development of a variety of BP-mediated diseases. Interestingly, genetic polymorphisms are able to modify the relationship of BPA exposure with the risk of adverse health effects, suggesting that interindividual genetic differences modulate the susceptibility to the effects of environmental contaminants.

Detrimental Effects of Bisphenol Compounds on Physiology and Reproduction in Fish: A Literature Review

Bisphenol-A is one of the most studied endocrine-chemicals, which is widely used all over the world in plastic manufacture. Because of its extensive use, it has become one of the most abundant chemical environmental pollutants, especially in aquatic environments. BPA is known to affect fish reproduction via estrogen receptors but many studies advocate that BPA affects almost all aspects of fish physiology. The possible modes of action include genomic, as well as and non-genomic mechanisms, estrogen, androgen, and thyroid receptor-mediated effects. Due to the high detrimental effects of BPA, various analogs of BPA are being used as alternatives. Recent evidence suggests that the analogs of BPA have similar modes of action, with accompanying effects on fish physiology and reproduction. In this review, a detailed comparison of effects produced by BPA and analogs and their mode of action is discussed.

Multi- and transgenerational effects following early-life exposure of zebrafish to permethrin and coumarin 47: Impact on growth, fertility, behavior and lipid metabolism

Transgenerational effects induced by environmental stressors are a threat to ecosystems and human health. However, there is still limited observation and understanding of the potential of chemicals to influence life outcomes over several generations. In the present study, we investigated the effects of two environmental contaminants, coumarin 47 and permethrin, on exposed zebrafish (F0) and their progeny (F1-F3). Coumarin 47 is commonly found in personal care products and dyes, whereas permethrin is used as a domestic and agricultural pyrethroid insecticide/insect repellent. Zebrafish (F0) were exposed during early development until 28 days post-fertilization and their progeny (F1-F3) were bred unexposed. On one hand, the effects induced by coumarin 47 suggest no multigenerational toxicity. On the other hand, we found that behavior of zebrafish larvae was significantly affected by exposure to permethrin in F1 to F3 generations with some differences depending on the concentration. This suggests persistent alteration of the neural or neuromuscular function. In addition, lipidomic analyses showed that permethrin treatment was partially correlated with lysophosphatidylcholine levels in zebrafish, an important lipid for neurodevelopment. Overall, these results stress out one of the most widely used pyrethroids can trigger long-term, multi- and possibly transgenerational changes in the nervous system of zebrafish. These neurobehavioral changes echo the effects observed under direct exposure to high concentrations of permethrin and therefore call for more research on mechanisms underlying effect inheritance.

Bisphenol S exposure alters behavioral parameters in adult zebrafish and offspring

The environmental emission of bisphenol S (BPS), which is globally utilized in the manufacturing of polycarbonates, epoxy resin and thermal paper, has affected the aquatic ecosystem. Thus, effects of BPS exposure on the fitness of aquatic animals have been noted. Here, adult male and female zebrafish were used as aquatic model organisms and separately exposed to environmentally relevant doses of BPS (0, 1, 10 and 100 μg/L) for 14 days. The results showed that BPS changed the body pigment of zebrafish and slowed the maturation of oocytes in the ovary, resulting in a significant decrease in the shoaling behavior of adult zebrafish and the attraction of BPS-treated females during the mating process. Furthermore, in the subgeneration of adult zebrafish exposed to BPS for 7 days, survival behaviors, such as locomotor, phototaxis and feeding behaviors, deviated from normal behaviors. After exposing the adult zebrafish to BPS for an additional 7 days, the above described survival behaviors and light adaptation were disrupted in offspring. Our data, based on intergenerational behavioral studies, demonstrate that BPS affects the behaviors of aquatic animals and the ability of offspring to feed and avoid predators, possibly jeopardizing the survival of aquatic animals.

In vitro evaluation of the hepatic lipid accumulation of bisphenol analogs: A high-content screening assay

Bisphenol A (BPA) has a variety of adverse effects on human health; therefore, BPA analogs are increasingly used as replacements. Notably, recent studies have revealed that BPA exposure induced hepatic lipid accumulation, but few studies are available regarding the similar effects of other bisphenol analogues (BPs). Thus, in the present study, a high-content screening (HCS) assay was performed to simultaneously evaluate the hepatic lipid accumulation of 13 BPs in vitro. The BPs induced lipid deposition in HepG2 cells ranking as below: 4,4'-thiodiphenol (TDP) < bisphenol S (BPS) < 4,4'-dihydroxybenzophenone (DHBP) < tetrabromobisphenol A (TBBPA) < tetrachlorobisphenol A (TCBPA) < bisphenol E (BPE) < bisphenol F (BPF) < bisphenol B (BPB) < bisphenol AF (BPAF) < bisphenol A (BPA) < bisphenol C (BPC) < tetramethylbisphenol A (TMBPA) < bisphenol AP (BPAP). Meanwhile, Oil Red O staining and triacylglycerol detection further validated the lipid accumulation elicited by the latter 8 BPs, which exhibited the more significant effects on lipid deposition. Mechanistically, significantly increased expressions of genes involved in fatty acid synthesis and nuclear receptors and decreased levels of genes associated with fatty acid β-oxidation were observed under BPs treatment. Therefore, the present work is the first to systematically provide direct evidence for BPs-induced hepatic lipid accumulation in vitro via HCS, which can be helpful for safety assessments of BPs.

Long-term bisphenol S exposure aggravates non-alcoholic fatty liver by regulating lipid metabolism and inducing endoplasmic reticulum stress response with activation of unfolded protein response in male zebrafish

Environmental chemical exposures have been implicated as risk factors for the development of non-alcoholic fatty liver (NAFLD). Bisphenol S (BPS), widely used in multitudinous consumer products, could disrupt lipid metabolism in the liver. This study aimed at examining the hypothesis that long-term exposure to BPS promotes the development of liver fibrosis and inflammation by means of the application of a semi-static exposure experiment that exposed zebrafish to 1, 10, and 100 μg/L BPS from 3 h post fertilization to 120 day post fertilization. Results showed that the 120-d BPS exposure elevated plasma aspartate aminotransferase and alanine aminotransferase activities, increased triacylglycerol (TAG) and total cholesterol levels in male liver, and even induced hepatic apoptosis and fibrosis. Hepatic lipid accumulation observed in the 30-d BPS-exposed zebrafish was recovered after a 90-d depuration phase, thereby indicating that long-term BPS exposure promotes the progression of simple steatosis to non-alcoholic steatohepatitis. Furthermore, BPS exposure for 120-d promoted the synthesis of TAG and lipotoxic free fatty acids by elevating the transcription of srebp1, acc, fasn, and elovl6, induced endoplasmic reticulum (ER) stress with increasing expression levels of unfolded protein response (UPR) genes (perk, hsp5, atf4a, and ddit3), and then stimulated the expression of two key autophagy genes (atg3 and lc3) and inflammatory genes (il1b and tnfα). It is indicated that BPS can induce the development of steatohepatitis via the activation of the PERK-ATF4a pathway of the UPR. Data gathered suggest that environmental pollutants-induced ER stress with the activation of UPR can potentially trigger the NAFLD development in males. Overall, our study provided new sights into understanding of the adverse health effects of metabolism disrupting chemicals.

Road impact in a protected area with rich biodiversity: the case of the Sebitoli road in Kibale National Park, Uganda

While road network expansion is crucial for economic development, it can cause a notable disturbance of fauna, especially in protected area in terms of habitat fragmentation, risk of collision, and also indirect threat such as pollution. In this study, we monitored the 4.6-km long tarmac road crossing the Kibale National Park in Uganda, home to a rich variety of wild species including the endangered chimpanzees. We evaluated the effects of collisions and pollution, as well as the impact of the renovation process in terms of disturbance and the mitigation measures deployed. This survey reports the death of 24 wild animals killed by cars, including two chimpanzees. The atmospheric concentrations of O₃, NO₂, SO₂, and BTEX did not exceed recommended limits. More than 5000 plastic bottles were collected along the road within 4 months, and for the first time, the presence of BPA and BPS was detected in the hairs of wild chimpanzees. The road bisecting the Kibale National Park poses a high danger in terms of traffic and an underestimated risk related to plastic pollution. Measures (signpost, speed bumps) should be urgently deployed to decrease the risk posed by the renovated road for emblematic species such as chimpanzees, which are crucial for tourism and economy in Uganda.

Bisphenol S Induces Ectopic Angiogenesis in Embryos via VEGFR2 Signaling, Leading to Lipid Deposition in Blood Vessels of Larval Zebrafish

Bisphenol S (BPS), used as a bisphenol A substitute, has been detected in various environments. However, the safety of BPS is still unclear. Here, zebrafish embryos were exposed to BPS (0, 1, 10, and 100 μg/L) for 24, 48, 72, 96 h, and 15 days. BPS induced ectopic sprouting of budding blood vessels in embryos, but the blood flow velocity within these lesions was unchanged at 48 h. At 72 h postfertilization (hpf), by observing the subintestinal venous plexus responsible for yolk absorption, we found that VEGFR2 transduced an angiogenic signal and that the subsequent reduction in blood flow velocity inhibited yolk absorption. At 96 hpf, yolk consumption was still delayed because of the disturbed transportation route, resulting in transient extensive lipid retention in the blood vessels. After feeding, obvious atherogenic lipids were discovered in the blood vessels, especially in bends, bifurcations, and stenoses. This dynamic visualization of the pathogenesis demonstrates a plausible mechanistic link between BPS exposure-induced embryonic vessel overgrowth and an increased atherosclerosis risk.

The mixture effects of bisphenol derivatives on estrogen receptor and androgen receptor

Bisphenol A (BPA) is a well-known for endocrine-disrupting chemical (EDC) and is one of the highest amounts of chemicals produced worldwide. Some countries restrict the use of BPA, which is widely used in the production of a variety products. Considering the toxicity and limitations on use of BPA, efforts are needed to find safer alternatives. Increasingly, bisphenol F (BPF) and bisphenol S (BPS) are alternatives of BPA, which is increasing their exposure levels in various environments. There are many ways to assess whether a chemical is an EDC. Here, we evaluated the endocrine-disrupting risks of the bisphenols by investigating their agonist and antagonist activities with the estrogen (ER), androgen (AR), and aryl hydrocarbon (AhR) receptors. Our results showed that BPA, BPS, and BPF (BPs) have estrogen agonist and androgen antagonist activities and decrease the ERα protein level. Interestingly, a mixture of the BPs had ER and anti-AR activity at lower concentrations than BPs alone. The activation of AhR was not a concentration-dependent effect of BPs, although it was increased significantly. In conclusion, BPs have estrogen agonist and androgen antagonist activities, and the effect of exposure to a BPs mixture differs from that of BPs alone.

Global liver proteomic analysis of Wistar rats chronically exposed to low-levels of bisphenol A and S

Exposure to bisphenol A (BPA) and bisphenol S (BPS) has been associated with the development of metabolic disorders, such as obesity, dyslipidemias, and nonalcoholic fatty liver disease. Nonetheless, the associated mechanisms are still not fully understood. BPS is being used with no restrictions to replace BPA, which increases the concern regarding its safety and claims for further investigation on its potential mechanisms of toxicity. The present study aims to access liver molecular disturbances which could be associated with systemic metabolic disorders following exposure to BPA or BPS. Therefore, body weight gain and serum biochemical parameters were measured in male Wistar rats chronically exposed to 50 or 500 µg/kg/day of BPA or BPS, while an extensive evaluation of liver protein expression changes was conducted after exposure to 50 µg/kg/day of both compounds. Exposure to the lowest dose of BPA led to the development of hyperglycemia and hypercholesterolemia, while the BPS lowest dose led to the development of hypertriglyceridemia. Besides, exposure to 500 µg/kg/day of BPS significantly increased body weight gain and LDL-cholesterol levels. Hepatic proteins differentially expressed in BPA and BPS-exposed groups compared to the control group were mostly related to lipid metabolism and synthesis, with upregulation of glucokinase activity-related sequence 1 (1.8-fold in BPA and 2.4-fold in BPS), which is involved in glycerol triglycerides synthesis, and hydroxymethylglutaryl-CoA synthase cytoplasmic (2-fold in BPS), an enzyme involved in mevalonate biosynthesis. Essential mitochondrial proteins of the electron transport chain were upregulated after exposure to both contaminants. Also, BPA and BPS dysregulated expression of liver antioxidant enzymes, which are involved in cellular reactive oxygen species detoxification. Altogether, the results of the present study contribute to expand the scientific understanding of how BPA and BPS lead to the development of metabolic disorders and reinforce the risks associated with exposure to these contaminants.

Cu accumulation, detoxification and tolerance in the red swamp crayfish Procambarus clarkii

Copper is an essential metal but potentially toxic to aquatic animals at high levels. The present study investigated physiologically adaptive responses to waterborne Cu²⁺ exposure (0, 0.03, 0.30, 3.00 mg/L) in a representative species of crustaceans, the red swamp crayfish (Procambarus clarkii) for 7 d, followed by a 7-d depuration period. The tissue-specific distribution of Cu showed that crayfish hepatopancreas was the primary accumulating site among internal tissues. During Cu²⁺ exposure, crayfish repressed the expression level of Cu homeostasis genes (Ctr1, Atox1, copper-transporting ATPase 2, MTF-1/2, and MT) in hepatopancreas to inhibit intracellular Cu transporting. Cu²⁺-exposed crayfish increased activities of GPx and GST, GSH contents, and mRNA expression of antioxidative enzyme genes (Cu/Zn-sod, cat, gpx, gst) to cope with the Cu²⁺-induced oxidative stress which accompanied by an increased MDA content. Additionally, after a 7-d depuration, crayfish effectively eliminated excess Cu from hepatopancreas by up-regulating expression level of Cu homeostasis genes, and recovered from oxidative damage by enhancing antioxidative enzyme gene expression (Cu/Zn-sod, cat, gpx, gst) and consuming more GSH, which thereby caused a return of the MDA level to the control value. Overall, our study provided new insights into the regulatory mechanisms of cellular Cu homeostasis system and antioxidative system, contributing to Cu detoxification and tolerance ability exhibited by crayfish under Cu²⁺ stress and after withdrawal of Cu²⁺ stress.

Short and long-term effects of bisphenol S (BPS) exposure during pregnancy and lactation on plasma lipids, hormones, and behavior in rats

Bisphenol S (BPS) has replaced bisphenol A (BPA), a known non-persistent endocrine disrupting chemical, in several products. Considering that little is known regarding BPS effects, especially during critical windows of ontogenetic development, and that BPA, which is quite similar to BPS, is know to be transferred to the offspring via the placenta and milk, in the present study we investigated the behavioral, biochemical and endocrine profiles of Wistar rats born from dams that were BPS-exposed [groups: BPS10 (10 μg/kg/day), BPS50 (50 μg/kg/day)] during pregnancy and lactation. Due to the non-monotonic dose-response effect of bisphenol, the data of both BPS groups were directly compared with those of the controls, not to each other. Males and females were analyzed separately. At weaning, male BPS50 offspring had hypotriglyceridemia and hyperthyroxinemia, whereas BPS50 females showed higher 25(OH)D levels. At adulthood, BPS offspring of both sexes had lower food intake. BPS males showed lower visceral adiposity. BPS50 females had smaller fat droplets in brown adipocytes. BPS males showed higher anxiety and higher locomotor activity, while BPS10 females showed lower exploration. During a food challenge test at adulthood, BPS males consumed more high-fat diet at 30 min. BPS10 females initially (at 30 min) consumed more high-fat diet but, after 12 h, less of this diet was consumed. BPS50 males had hypertriglyceridemia and lower plasma T3, while BPS females showed lower plasma T4. BPS10 females had lower progesterone, whereas BPS50 females had higher plasma 25(OH)D. Maternal BPS exposure has adverse effects on the triacylglycerol, hormones levels and behavior of the progeny. Furthermore, the increased preference for the fat-enriched diet suggests an increased risk for obesity and its health consequences in the long term.

Perinatal exposure to Bisphenol S (BPS) promotes obesity development by interfering with lipid and glucose metabolism in male mouse offspring

Bisphenol S (BPS), a substitute of bisphenol A (BPA), is widely used for manufacturing different polymers. Due to its wide range of applications, BPS has been frequently detected in the foodstuffs, environment and human blood and excreta. In this study, we examined the effects of the perinatal exposure to BPS on obesity development using ¹H NMR based on metabolomics strategy combined with gene expression analysis in male mouse offspring at a dosage of 100 ng/g bw/day. We found that perinatal exposure to BPS significantly increased the body weight, the weights of liver and epididymal white adipose tissue (epiWAT), serum alanine aminotransferase (ALT) activity, and the contents of triglyceride (TG) and cholesterol (T-Cho) in the liver. Histopathological analysis showed that lipids were accumulated significantly in liver tissues and epiWAT with BPS exposure. Furthermore, expressions of genes involved in the inflammatory pathways were significantly increased in liver tissues and epiWAT. Meanwhile, serum metabolomics study showed significant changes in the contents of metabolites associated with lipid and glucose metabolism. Correspondingly, the relative expression levels of genes involved in lipid and glucose metabolism were significantly changed in the liver tissue and epiWAT of male mouse offspring. In conclusion, these results showed that perinatal exposure to BPS may increase the risk of obesity by interfering with lipid and glucose metabolism in male mouse offspring. The potential health risks of BPS in the human required further detailed studies evaluating.

Effect of Propiconazole on the Lipid Metabolism of Zebrafish Embryos ( Danio rerio)

Propiconazole is a triazole fungicide that has been widely used in agriculture and has been detected in the aquatic environment. This study aimed to investigate the effects of propiconazole exposure on lipid metabolism in the early life stages of zebrafish for 120 h postfertilization (hpf). Using the early life stages of zebrafish to address scientific questions is lower in cost, more efficient, and suitable to meeting current legislation than those in other traditional fish species. Exposure to propiconazole significantly inhibited the development of zebrafish embryos and larvae. This exposure also caused reduced locomotor activities in zebrafish. Furthermore, total cholesterol levels, lipoprotein lipase, and fatty acid synthase activities were significantly decreased. The expression levels of genes involved in lipid metabolism were significantly up-regulated in response to propiconazole exposure. GC-MS/MS analysis revealed that fatty acids were significantly decreased. Together, the findings indicate the potential environmental risks of propiconazole exposure in the aquatic ecosystem.

Long-term bisphenol S exposure induces fat accumulation in liver of adult male zebrafish (Danio rerio) and slows yolk lipid consumption in F1 offspring

Bisphenol S (BPS), as a substitute for bisphenol A, was frequently detected in human urine and blood. It has been reported that BPS could disrupt fat metabolism in vivo and vitro although mechanisms remain unclear. Additionally, there is no study that the disruptive effect of BPS on parental fat metabolism indirectly interferes with the lipid metabolism of offspring. Here, after 120-d exposure to 1, 10, 100, and 1000 μg/L BPS, the transcription level of genes involved in lipid metabolism in liver and feeding regulation of brain-gut axis, as well as the hepatic triacylglycerol (TAG) and plasma lipid levels were investigated in both male and female zebrafish. Results showed that in male liver, fatty acid synthesis and degradation were inhibited by reducing transcription levels of srebp1 and pparα, and the synthesis of TAG was significantly increased using fatty acid as a precursor by elevating agpat4 and dgat2 mRNA expression levels. As a consequence, fat accumulation and the increased TAG levels were observed in male liver, and lipid levels were also elevated in male plasma. In female liver, there was no excessive fat accumulation and BPS exposure had a non-monotonic effect on the gene expression of fasn, dagt2, and pparα. Notably, the unexposed offspring showed a large amount of yolk lipid remain at 5 days post fertilization. This study obviously demonstrated that long-term BPS exposure increases the risk of non-alcoholic fatty liver disease in male zebrafish and life-cycle exposure hazard on offspring is noteworthy.

Sex-specific alterations of lipid metabolism in zebrafish exposed to polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) mixtures exerting environmental health risk. In mammals, PCBs have been shown to disrupt metabolic state, especially lipid metabolism, and energy balance, but their effects on lipid metabolism in fish are largely unknown. The zebrafish were selected as model and both male and female adult zebrafish were exposed to different concentrations of PCBs at gradient concentrations of 0.2, 2.0 and 20.0 μg/L for 6 weeks. PCB exposure did not affect survival, but a significant inhibition of growth was observed in the males after exposure to 20.0 μg/L. The lower concentrations of 0.2 and 2.0 μg/L increased hepatic lipid accumulation to a greater extent in male fish, but the higher concentration of 20.0 μg/L did not cause significant fat accumulation in either male or female fish. In males, the expression of genes related to lipogenesis and lipid catabolism was upregulated in a concentration-dependent manner in the liver and visceral mass without liver and gonad; the effects of exposure on lipid metabolism-related genes in female fish were less pronounced. PCB exposure did not induce significant oxidative stress, but did upregulate the expression of stress- and apoptosis-related genes, mostly in male fish. The low concentrations of PCBs (0.2 μg/L and 2.0 μg/L) exerted sex-specific effects on zebrafish lipid metabolism, and male fish were more sensitive to the exposure. This study provides new mechanistic insights into the complex interactions between PCBs, lipid metabolism, and sex in zebrafish, and may contribute to a future systematic assessment of the effects of PCBs on aquatic ecosystems.

Oxidative damage induced by copper in testis of the red swamp crayfish Procambarus clarkii and its underlying mechanisms

Copper (Cu) is one of the most widespread environmental pollutants and is known to exert multiple toxic effects including reproductive toxicity. In this study, we investigated the toxic effect of Cu on reproduction of the red swamp crayfish (Procambarus clarkii), an economic crustacean species, by exposing adult male crayfish to 0.03 and 3.00 mg/L Cu²⁺ for 7 days. The results showed that Cu²⁺ exposure induced oxidative stress accompanied by elevated reactive oxygen species (ROS) and malondialdehyde (MDA) levels in testes, and resulted in decreased sperm quality and abnormal testicular structures with apoptotic germ cells and vacuolisation in Sertoli cells. To reveal the molecular mechanism of Cu²⁺-induced oxidative damage in crayfish testes, we sequenced, assembled and annotated the transcriptome for crayfish testes, using the Illumina sequencing approach. After the 3.00 mg/L Cu²⁺ treatment, 6745 genes with differentially expressed profile were identified, of which many genes were involved in cellular response to ROS based on Gene Ontology enrichment analysis. Further, KEGG analysis demonstrated that genes with up-regulated expression levels significantly enriched in mitochondria oxidative phosphorylation pathway, suggesting disturbed mitochondrial electron transport chain was probably a main source of Cu²⁺-induced ROS production in testes. This study represented the first use of transcriptome to investigate the toxic effect of Cu²⁺ on male crayfish reproduction, and the pathways identified underlying Cu²⁺ toxicity at molecular level provide a novel insight into the reproductive toxicity of Cu in crustaceans.