Testicular transcript responses in rare minnow Gobiocypris rarus following different concentrations bisphenol A exposure

Lufenuron treatment temporarily represses gene expression and affects the SUMO pathway in liver of Atlantic salmon

Lufenuron is a benzoylurea insecticide currently in use to combat sea lice infestation in salmon aquaculture in Chile. With pending approval in Norway, the aim of this work was to study the uptake and toxicity of lufenuron in liver tissue of Atlantic salmon. Juvenile salmon weighing 40 g were given a standard 7-day oral dose, and bioaccumulation and transcriptional responses in the liver were examined 1 day after the end-of-treatment (day 8) and after 1 week of elimination (day 14). Bioaccumulation levels of lufenuron were 29 ± 3 mg/kg at day 8 and 14 ± 1 mg/kg at day 14, indicating relatively rapid clearance. However, residues of lufenuron were still present in the liver after 513 days of depuration. The exposure gave a transient inhibition of transcription in the liver at day 8 (2437 significant DEGs, p-adj < .05), followed by a weaker compensatory response at day 14 (169 significant DEGs). Pathways associated with RNA metabolism such as the sumoylation pathway were most strongly affected at day 8, while the apelin pathway was most profoundly affected at day 14. In conclusion, this study shows that lufenuron easily bioaccumulates and that a standard 7-day oral dose induces a transient inhibition of transcription in liver of salmon.

Study on reproductive endocrine disturbance and DNA damage mechanism of female Ruditapes philippinarum under Benzo[a]pyrene stress

The reproductive toxicity of polycyclic aromatic hydrocarbons (PAHs) in aquatic organisms has attracted increasing attention from scholars. Currently, research in this field primarily focuses on vertebrates such as zebrafish and other model species. However, there is still a significant knowledge gap in the toxicity of PAHs to invertebrates and its potential mechanisms. Benzo[a]pyrene (B[a]P) is one of the most representative PAHs. In this study, female Ruditapes philippinarum (R. philippinarum) was treated with B[a]P concentrations of 0, 0.8, 4, and 20 μg/L to investigate reproductive indicators in the proliferative, growth, mature, and spawn stages. Transcriptomics was used to investigate the expression of genes associated with the reproductive endocrine system, DNA repair, autophagy, apoptosis, and ovarian development at different reproductive stages. Our results suggested that B[a]P disrupted the endocrine system by interfering with the production of steroid hormones and the transmission of estrogen signals in female R. philippinarum. The structure of the ovarian DNA duplex is severely damaged under the stress of B[a]P, and a series of cellular responses caused by DNA damage are also interfered. Additionally, we observed a reduction in the gonadosomatic index (GSI) and mature oocytes numbers after B[a]P exposed. Tissue section indicated that severe damage to the ovarian structure at mature and spawn stages. In conclusion, this study combined transcriptomic and toxicological to explore the negative effects on ovarian development induced by B[a]P, focusing on reproductive endocrine disturbance and DNA damage.

Histology study and transcriptome analysis of the testis of Loach(Misgurnus anguillicaudatus) in response to phenanthrene exposure

Phenanthrene (PHE) is one of the most abundant polycyclic aromatic hydrocarbon compounds (PAHs) in the aquatic environment. The loaches were exposed at concentrations of 0.30、1.00、3.00 mg L^-1 for 60 days. The effects of PHE on the testis development were evaluated by calculating the survival rate, observing the structure of testis and analyzing transcriptome. Firstly, PHE markedly decreased the survival rate in a dose-dependent manner. Then, the number and density of spermatogonia, primary spermatocytes, secondary spermatocytes and spermatids were substantially reduced under PHE exposure. The space in the seminiferous tubule obviously increased in the high PHE concentration group. Meanwhile, transcriptome comparative analysis identified 5329 differentially expressed genes (DEGs) including 2928 up-regulated and 2401 down-regulated in the testis of loach exposed PHE for 60 days. Meiotic cell cycle, arganelle fission, ATPase activity and adenylate nucleotide binding were significantly differences by GO (Gene Ontology) enrichment. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis revealed that TNF (Tumor Necrosis Factor) signaling pathway, CAMs (Cell Adhesion Molecules), cytochrome P450 and lipid metabolism were markedly regulated. In addition, eight DEGs were randomly selected from the testis transcriptomics results for qPCR verification, the results were consistent with RNA-Seq. Finally, related genes (piwil2, dmc1, vasa, ubr2, dnd, rnf17, plcb2, c-fos, gpx4) of testis development were further confirmed and they were differentially regulated after PHE exposure. In summary, a survey of the mechanism of loach testis response to PHE was performed, and a large number of gene expression levels regarding metabolism, spermatogenesis and immunity genes were acquired from RNA-seq. This study provide informations for elucidating the molecular mechanism of PHE affected the testis development of loach.

Bisphenol A disrupts apolipoprotein E expression through estrogen-related receptor gamma and DNA methlylation in the liver of male rare minnow Gobiocypris rarus

An increasing number of studies show that bisphenol A (BPA) can cause lipid metabolism disorder. However, few studies focused on the effect of BPA on lipid transport. Apolipoprotein E (ApoE) plays important roles in triglyceride (TG) transportation. Our previous study found that ApoE was a sensitive gene in response to BPA exposure in male rare minnow. To investigate the effect and mechanism of BPA on hepatic ApoE, adult male rare minnow Gobiocypris rarus were exposed to environmentally relevant concentrations of BPA (15 μg/L) for 1, 3 and 5 weeks. Results showed that BPA inhibited ApoE expression at week 1 and 5, while induced its expression at week 3. A positive estrogen-related receptor gamma (Esrrg) response element was identified in the promoter region of ApoE. The change of the Esrrg recruitment was consistent with ApoE mRNA expression. Moreover, the methylation status of the CpG sites near and on the Esrrg binding sites changed opposite to the ApoE mRNA level, which may be the main cause for the change in Esrrg recruitment. The expression of ApoE protein was significantly enhanced following long-term BPA exposure. Consistently, the TG accumulation was significantly increased in the plasma. The present study demonstrates that BPA could affect rare minnow ApoE expression, which is probably one of the ways for BPA disturbing fish lipid metabolism.

Bisphenol A regulates apolipoprotein A1 expression through estrogen receptors and DNA methlylation and leads to cholesterol disorder in rare minnow testis

Bisphenol A (BPA) is a well-known plasticizer that widely distributed in the aquatic environment. BPA has many adverse effects on reproduction. However, few studies have investigated the mechanism of BPA affecting reproduction from the perspective of lipid metabolism. Apolipoprotein A1 (ApoA1) is the major component of high-density lipoprotein (HDL), and plays critical roles in reverse cholesterol transport (RCT). In this study, in order to investigate the effect and molecular mechanism of BPA on testicular ApoA1 and the role of ApoA1 in BPA induced abnormal spermatogenesis, adult male rare minnow Gobiocypris rarus were exposed to 15 μg/L of BPA for 1, 3 and 5 weeks. Results showed that BPA could significantly affect testicular ApoA1 mRNA and protein levels, testicular cholesterol levels, plasmatic sex hormone levels and the integrity of sperm head membrane. The main mechanism of BPA regulating ApoA1 expression is to alter Esr recruitment and CpG sites DNA methylation in ApoA1 promoter. The induced ApoA1 up-regulated high density lipoprotein cholesterol levels and enhanced RCT, and finally decreased the testicular free cholesterol levels. This is likely a key mechanism by which BPA induces sex hormone disorder and sperm head membrane damage. The present study reveals the mechanism by which BPA interferes with spermatogenesis from the perspective of cholesterol transport.

Ventricular Fibrosis and Coronary Remodeling Following Short-Term Exposure of Healthy and Malnourished Mice to Bisphenol A

Bisphenol-A (BPA) is an endocrine disruptor associated with higher risk of insulin resistance, type 2 diabetes, and cardiovascular diseases especially in susceptible populations. Because malnutrition is a nutritional disorder associated with high cardiovascular risk, we sought to compare the effects of short-term BPA exposure on cardiovascular parameters of healthy and protein-malnourished mice. Postweaned male mice were fed a normo- (control) or low-protein (LP) diet for 8 weeks and then exposed or not to BPA (50 μg kg⁻¹ day⁻¹) for the last 9 days. Systolic blood pressure was higher in BPA or LP groups compared with the control group. However, diastolic blood pressure was enhanced by BPA only in malnourished mice. Left ventricle (LV) end diastolic pressure (EDP), collagen deposition, and CTGF mRNA expression were higher in the control or malnourished mice exposed to BPA than in the respective nonexposed groups. Nevertheless, mice fed LP diet exposed to BPA exhibited higher angiotensinogen and cardiac TGF-β1 mRNA expression than mice treated with LP or BPA alone. Wall:lumen ratio and cross-sectional area of intramyocardial arteries were higher either in the LP or BPA group compared with the control mice. Taken together, our data suggest that short-term BPA exposure results in LV diastolic dysfunction and fibrosis, and intramyocardial arteries inward remodeling, besides potentiate protein malnutrition-induced hypertension and cardiovascular risk.

Is There a Link between Bisphenol A (BPA), a Key Endocrine Disruptor, and the Risk for SARS-CoV-2 Infection and Severe COVID-19?

Infection by the severe acute respiratory syndrome (SARS) coronavirus-2 (SARS-CoV-2) is the causative agent of a new disease (COVID-19). The risk of severe COVID-19 is increased by certain underlying comorbidities, including asthma, cancer, cardiovascular disease, hypertension, diabetes, and obesity. Notably, exposure to hormonally active chemicals called endocrine-disrupting chemicals (EDCs) can promote such cardio-metabolic diseases, endocrine-related cancers, and immune system dysregulation and thus, may also be linked to higher risk of severe COVID-19. Bisphenol A (BPA) is among the most common EDCs and exerts its effects via receptors which are widely distributed in human tissues, including nuclear oestrogen receptors (ERα and ERβ), membrane-bound oestrogen receptor (G protein-coupled receptor 30; GPR30), and human nuclear receptor oestrogen-related receptor gamma. As such, this paper focuses on the potential role of BPA in promoting comorbidities associated with severe COVID-19, as well as on potential BPA-induced effects on key SARS-CoV-2 infection mediators, such as angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2). Interestingly, GPR30 appears to exhibit greater co-localisation with TMPRSS2 in key tissues like lung and prostate, suggesting that BPA exposure may impact on the local expression of these SARS-CoV-2 infection mediators. Overall, the potential role of BPA on the risk and severity of COVID-19 merits further investigation.

Acute BPA exposure-induced oxidative stress, depressed immune genes expression and damage of hepatopancreas in red swamp crayfish Procambarus clarkii

Bisphenol A is a typical endocrine disrupting chemicals (EDCs) and produce various toxic effects on animals due to its potential endocrine disruption, oxidative damage effect, mutagenic effect and hypomethylation. To study its effect on the immune system of crustaceans, the Procambarus clarkii were utilized to detect the immune related indicators after 225 μg/L BPA exposure for 1 week. Hepatopancreatic histology and ultrastructure analysis showed that the brush border disappeared, the lumen increased, and the connection between the hepatic tubules fade away in BPA treated group. BPA could significantly increase the level of ROS, inhibit the activities of antioxidant-related enzymes (SOD, POD, and CAT), and thereby cause the oxidative stress. The enzyme activities of AKP, ACP and lysozyme in hepatopancreas after BPA exposure were also depressed even after Aeromonas hydrophila infections. The relative expression profiles of immune-related genes after BPA exposure and bacterial infection showed suppressed trends of most selected genes. Under A. hydrophila infections, the cumulative mortality of 225 μg/L BPA-treated crayfish was significantly higher than other groups. All these results indicated that BPA exposure had adverse effects on the immune ability of P. clarkii. The present study will provide an important foundation for further understanding the effects of EDCs on crustacean immune functions.

Bisphenol A-Induced Epigenetic Changes and Its Effects on the Male Reproductive System

Bisphenol A (BPA) is a widespread chemical agent which can exert detrimental effects on the male reproductive system. Exposure to BPA has been shown to induce several epigenetic modifications in both animal and human cells. Specifically, BPA could not only modify the methylation pattern of multiple genes encoding proteins related to reproductive physiology but also directly influence the genes responsible for DNA methylation. BPA effects include hormonal alterations, microscopic and macroscopic alteration of male reproductive organs, and inheritable epigenetic changes involving human reproduction. BPA exposure was also linked to prostate cancer. This review aims to show the current scenario of BPA-induced epigenetic changes and its effects on the male reproductive system. Possible strategies to counter the toxic effect of BPA were also addressed.

Effects of Dietary Bisphenol A on the Reproductive Function of Gilthead Sea Bream (Sparus aurata) Testes

Bisphenol A (BPA), a known endocrine disrupting chemical (EDC), was administered by diet to gilthead sea bream (Sparus aurata) in order to study its effects on the endocannabinoid system (ECS) and gonadal steroidogenesis. 2-year-old male gilthead sea bream were fed with two different concentrations of BPA (LOW at 4 and HIGH at 4000 µg/kg body weight for 21 days during the reproductive season. Exposure to 4000 µg BPA/kg bw/day (BPA HIGH) reduced sperm motility and altered the straight-line velocity (VSL) and linearity (LIN). Effects on steroidogenesis were evident, with testosterone (T) being up-regulated by both treatments and 11-ketotestosterone (11-KT) down-regulated by BPA HIGH. Plasma levels of 17β-estradiol (E₂) were not affected. The Gonadosomatic Index (GSI) increased in the BPA HIGH group. Interestingly, the levels of endocannabinoids and endocannabinoid-like compounds were significantly reduced after both treatments. Unpredictably, a few changes were noticed in the expression of genes coding for ECS enzymes, while the receptors were up-regulated depending on the BPA dose. Reproductive markers in testis (leptin receptor (lepr), estrogen receptors (era, erb), progesterone receptors (pr) and the gonadotropin releasing hormone receptor (gnrhr)) were up-regulated. BPA induced the up-regulation of the hepatic genes involved in oogenesis (vitellogenin (vtg) and zona pellucida 1 (zp1)).

An epigenome-wide analysis of cord blood DNA methylation reveals sex-specific effect of exposure to bisphenol A

Exposure to bisphenol A (BPA) in utero is associated with adverse health outcome of the offspring. Differential DNA methylation at specific CpG sites may link BPA exposure to health impacts. We examined the association of prenatal BPA exposure with genome-wide DNA methylation changes in cord blood in 277 mother-child pairs in the Hokkaido Study on Environment and Children’s Health, using the Illumina HumanMethylation 450 BeadChip. We observed that a large portion of BPA-associated differentially methylated CpGs with p-value < 0.0001 was hypomethylated among all newborns (91%) and female infants (98%), as opposed to being hypermethylated (88%) among males. We found 27 and 16 CpGs with a false discovery rate (FDR) < 0.05 in the analyses for males and females, respectively. Genes annotated to FDR-corrected CpGs clustered into an interconnected genetic network among males, while they rarely exhibited any interactions in females. In contrast, none of the enrichment for gene ontology (GO) terms with FDR < 0.05 was observed for genes annotated to the male-specific CpGs with p < 0.0001, whereas the female-specific genes were significantly enriched for GO terms related to cell adhesion. Our epigenome-wide analysis of cord blood DNA methylation implies potential sex-specific epigenome responses to BPA exposure.

Microcystin-LR disturbs testicular development of giant freshwater prawn Macrobrachium rosenbergii

Microcystins (MCs) are produced by cyanobacterial blooms and known for their hepatotoxicity. They could cause serious damage to the reproduction of higher vertebrate mice and fish. However, few studies have focused on the reproductive toxicity of MCs to invertebrates. Giant freshwater prawn Macrobrachium rosenbergii are highly cultivated in China. During their breeding process, M. rosenbergii are often infested by cyanobacteria blooms. In the present study, to investigate the toxic effect of MCs on the testicular development of M. rosenbergii. Male M. rosenbergii were exposed to environmental relevant concentration of MC-LR for 1, 2 and 3 weeks. Results showed that MC-LR entered M. rosenbergii testis, down-regulated hemolymph testosterone (T) levels, and damaged testicular germ cells, mitochondria and cell junctions, and inhibited testicular development. Moreover, MC-LR could significantly induce the expression of gonadal development related genes in testis and eyestalk). The present results indicate that MC-LR can disrupt the testicular development of M. rosenbergii by affecting T levels and gonadal development related genes in the testis and eyestalk.

Adverse effects of bisphenol A on Sertoli cell blood-testis barrier in rare minnow Gobiocypris rarus

Bisphenol A (BPA), an environmental contaminant, has been shown to disturb the dynamics of Sertoli cell blood-testis barrier (BTB) in mammal testis. However, the effects of BPA on Sertoli cell barrier (SC barrier) were little known in fish to date. To evaluate the potential mechanism of reproductive toxicity of BPA, we studied the damage of SC barrier using in vivo models. In this study, male adult rare minnow Gobiocypris rarus were exposed to 15 μg/L BPA for 7-35 days. Gonadal histology and the integrity of SC barrier were analyzed. Meanwhile, the expressions of SC barrier -associated proteins, tumor necrosis factor (TNFα) content, and the mRNA expressions of genes in the mitogen activated protein kinase (MAPK) pathway were detected. Histological analysis demonstrated 15 μg/L BPA promoted the infiltration of inflammatory cells in fish testes after 7-days exposure. The biotin tracer assay showed that 7-days BPA exposure increased permeability for spermatid cysts. In addition, the BPA treatment caused increased TNFα in testis, which was reportedly related to SC barrier impairment. The expressions of Occludin and β-Catenin protein were significantly decreased in the testes after 7- and 21-days exposure. BPA also altered the mRNA expressions of occludin, β-catenin, p38 MAPK and JNK. Therefore, the detrimental effects of BPA on reproduction of male fish may attribute to the disturbed expressions of SC junction proteins.

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.

Testicular transcriptome alterations in zebrafish (Danio rerio) exposure to 17β-estradiol

The hormone 17β-estradiol (E₂) can be found in rivers, effluents, and even drinking water. Researches have demonstrated that E₂ affects various metabolic pathways through gene activation and may cause reproductive toxicity in fish. Therefore, the aim of this study was to evaluate E₂-induced toxicity via testicular transcriptome of zebrafish (Danio rerio) exposed to different concentrations (10 ng L^-1, and 100 ng L^-1) of E₂. A total of >600 significant differentially expressed genes (DEGs) were enriched among the three treatments. Short time-series expression miner analysis revealed five KEGG pathways including drug metabolism, other enzymes, calcium signaling pathway, ECM-receptor interaction, gap junction, and cell adhesion molecules. Twenty genes were selected to verify the accuracy of RNA-Seq. Other reported genes related to sex differentiation, development, energy metabolism, and other processes were found. One set of genes significantly increased/decreased/fluctuated over time, especially 12 h after E₂ exposure. Genes associated with ovaries (zp3c), and development (bmp15, gdf9, and sycp2l) were significantly upregulated with increasing E₂ concentration. E₂ and testosterone was significantly decreased by 10 (except for T) and 100 ng L^-1 E₂ exposure at 12 h. The current study demonstrated that sex differentiation, development, energy metabolism, immunity, and ribosome biogenesis in male zebrafish were all significantly affected by 17β-estradiol exposure through transcriptional alterations.

Bisphenol A regulates rare minnow testicular vitellogenin expression via reducing its promoter Er recruitment

Vitellogenins (Vtgs) are major precursor of the egg-yolk proteins. They are synthesized in liver of adult female ovipara, but normally silent in males. For their sensitive response to estrogen, Vtgs are usually used as biomarkers for environmental estrogenic compounds. In the present study, three vtg subtypes (vtg1, vtg2 and vtg3) were proved to present in the testis of rare minnow Gobiocypris rarus for the first time. Immunohistochemistry result showed that Vtg proteins mainly deposit in spermatogonium and spermatocytes. Following 225μg/L bisphenol A (BPA) exposure 1, 3 and 9 weeks, testicular vtg mRNAs were mostly significantly decreased. The further chromatin immunoprecipitation showed that BPA could decrease estrogen receptor (Er) recruitment in vtg promoter, which possibly reduced Er's transcription activation effect on vtgs. However, different from the continuously decreased vtg mRNA levels, testicular Vtg protein levels were recovered at week 9. Considering the induced hepatic Vtg expression, testicular Vtgs may be replenished by the induced hepatic Vtgs under BPA exposure.

Estrogenic effects associated with bisphenol a exposure in male zebrafish (Danio rerio) is associated with changes of endogenous 17β-estradiol and gene specific DNA methylation levels

The binding affinity of bisphenol A (BPA) to estrogen receptors (ERs) is much lower than that of 17β-estradiol (E₂), and whether there are other molecular mechanisms responsible for the estrogenic action of BPA in vivo currently remains unknown. The objective of this study was to explore the potential association between the estrogenic effect induced by bisphenol A in vivo and changes of endogenous E₂ and gene specific DNA methylation levels. After a waterborne exposure of male zebrafish to 500, 1000, or 1500μg/L of BPA for 21d, vitellogenin (VTG) concentration in whole body homogenate, plasma E₂ and testosterone levels, hepatic ERs mRNA expressions, gonadal cyp19a1a and cyp17a1 mRNA expressions, and methylation levels of hepatic esr1 and gonadal cyp19a1a's promoters were determined. Our results indicated that for the 500 and 1500μg/L treatment groups, VTG might be induced mainly by the elevated E₂ levels; increases of E₂ levels could be partly explained by the up-regulated expression of gonadal aromatase, mRNA levels of which were found to be negatively related to the methylation levels of both its promoter and one CpG site. In addition, upon BPA exposure, hepatic esr1 mRNA levels were also negatively related to the methylation levels of both its promoter and one CpG site. These observations provide evidence for the non-ERs mediated mechanisms underlying the estrogenic action of BPA on male zebrafish.

Bisphenol A induces spermatocyte apoptosis in rare minnow Gobiocypris rarus

Bisphenol A (BPA) is an endocrine disruptor, and could induce germ cells apoptosis in the testis of mammals. But whether it could affect fish in the same mechanism has not' been studied till now. In the present study, to investigate the influence of BPA on testis germ cells in fish, adult male rare minnow Gobiocypris rarus were exposed to 225μgL(-1) (0.99μM) BPA for 1, 3 and 9 weeks. Through TdT-mediated dUTP nick end labeling (TUNEL) and transmission electron microscope (TEM) analysis, we found that the amount of apoptotic spermatocytes significantly increased in a time dependent manner following BPA exposure. Western Blot results showed that the ratio of Bcl2/Bax, the important apoptosis regulators in intrinsic mitochondrial apoptotic pathway, was significantly decreased. qPCR showed that mRNA expression of several genes in mitochondrial apoptotic pathway including bcl2, bax, casp9, cytc and mcl1b were significantly changed following BPA exposure. In addition, mRNA expression of meiosis regulation genes (kpna7 and wee2), and genes involved in both apoptosis and meiosis (birc5, ccna1, and gsa1a) were also affected by BPA. Taken together, the present study demonstrated that BPA could induce spermatocytes apoptosis in rare minnow testis, and the apoptosis was probably under regulation of intrinsic mitochondrial apoptotic pathway. Moreover, the spermatocyte apoptosis was likely initiated by BPA induced meiosis arrest.