Bisphenol A (BPA), a ubiquitous endocrine disruptor that is present in many household products, has been linked to obesity, cancer, and, most relevant here, childhood neurological disorders such as ...anxiety and hyperactivity. However, how BPA exposure translates into these neurodevelopmental disorders remains poorly understood. Here, we used zebrafish to link BPA mechanistically to disease etiology. Strikingly, treatment of embryonic zebrafish with very low-dose BPA (0.0068 μM, 1,000-fold lower than the accepted human daily exposure) and bisphenol S (BPS), a common analog used in BPA-free products, resulted in 180% and 240% increases, respectively, in neuronal birth (neurogenesis) within the hypothalamus, a highly conserved brain region involved in hyperactivity. Furthermore, restricted BPA/BPS exposure specifically during the neurogenic window caused later hyperactive behaviors in zebrafish larvae. Unexpectedly, we show that BPA-mediated precocious neurogenesis and the concomitant behavioral phenotype were not dependent on predicted estrogen receptors but relied on androgen receptor-mediated up-regulation of aromatase. Although human epidemiological results are still emerging, an association between high maternal urinary BPA during gestation and hyperactivity and other behavioral disturbances in the child has been suggested. Our studies here provide mechanistic support that the neurogenic period indeed may be a window of vulnerability and uncovers previously unexplored avenues of research into how endocrine disruptors might perturb early brain development. Furthermore, our results show that BPA-free products are not necessarily safer and support the removal of all bisphenols from consumer merchandise.
Significance Here we demonstrate that bisphenol A (BPA) exposure during a time point analogous to the second trimester in humans has real and measurable effects on brain development and behavior. Furthermore, our study is the first, to our knowledge, to show that bisphenol S, a replacement used in BPA-free products, equally affects neurodevelopment. These findings suggest that BPA-free products are not necessarily safe and support a societal push to remove all structurally similar bisphenol analogues and other compounds with endocrine-disruptive activity from consumer goods. Our data here, combined with over a dozen physiological and behavioral human studies that begin to point to the prenatal period as a BPA window of vulnerability, suggest that pregnant mothers limit exposure to plastics and receipts.
In the present study, we evaluated the zearalenone induced adverse effects in zebrafish embryos using various endpoints like embryo toxicity, heart rate, oxidative stress indicators (reactive oxygen ...species (ROS), lipid peroxidation (LPO), Nitric oxide (NO)), antioxidant responses (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase enzyme (GST) and reduced glutathione (GSH), metabolic biomarkers (lactate dehydrogenase (LDH) and Nitric oxide (NO)), neurotoxicity (acetylcholinesterase (AChE)), genotoxicity (comet assay and acridine orange staining (AO)) and histological analysis. In this study, four concentrations 350, 550, 750 and 950 μg/L of ZEA were chosen based on LC10 and LC50 values of the previous report. The results shows that ZEA induces developmental defects like pericardial edema, hyperemia, yolk sac edema, spine curvature and reduction in heart rate from above 550 μg/L exposure and the severity was increased with concentration and time dependent manner. Significant induction in oxidative stress indices (ROS, LPO and NO), reduction in antioxidant defence system (SOD, CAT, GPx, GST and GSH) and changes in metabolic biomarkers (LDH and AP) were observed at higher ZEA exposed concentration. Neurotoxic effects of ZEA were observed with significant inhibition of AChE activity at higher exposure groups (750 and 950 μg/L). Moreover, we also noticed DNA damage, apoptosis and histological changes in the higher ZEA treatments at 96 h post fertilization (hpf) embryos. Hence, in the present study we concluded that oxidative stress is the main culprit in ZEA induced developmental, genotoxicity and neurotoxicity in zebrafish embryos.
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•The effect of ZEA on zebrafish during early embryonic development was studied.•Dosages higher than 550 μg/L ZEA exposure resulted in developmental defects.•ZEA induced oxidative stress, DNA damage and apoptosis was reported.•ZEA could alter histopathology and inhibits AChE activity in zebrafish embryos.
Bisphenol A (BPA) is an abundant environmental contaminant and studies have shown the presence of BPA in the urine of over 90% of population tested in Canada and USA. In addition to its reported ...harmful effects, there is concern for its transgenerational effects. For a compound to induce transgenerational effect, an epigenetic mark should be mitotically and meiotically stable without reprogramming in primordial germ cells and post fertilization embryos. In the present study, female zebrafish were treated with an environmental dose (20 μg/L) of BPA and then crossed with untreated males. To assess epigenetic effects, transcript levels of several genes involved in female reproduction were measured in adult and in 24 hpf embryos up to F3 generation. Exposure to BPA affected adult female fertility up to F2 generation. In F0, F1 and F2 ovaries transcript levels for several genes involved in reproduction, including esr, star, lhcgr and fshr were affected. To investigate epigenetic mechanisms of gene expression modulation, we studied promoter DNA methylation. Among genes involved in gonadal differentiation, amh transcript level was reduced in 24 hpf embryos, up to the F3 generation. Variation in amh transcript level was associated with hyper-methylation of its promoter and changes in H3K4me3/H3K27me3 enrichment, coherent with gene silencing. The findings provide evidence for transgenerational effects of BPA in zebrafish and demonstrate that amh is susceptible to stable epigenetic alterations.
Transgenerational effects of BPA on female reproductive physiology.
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•BPA's effects show a transgenerational transmission via maternal route.•Transgenerational transmission involves both histone modification and DNA methylation.•Amh hypermethylation shows a stable transmission throughout generations.
Glyphosate is a component of commonly used herbicides for controlling weeds in crops, gardens and municipal parks. There is increasing awareness that glyphosate-based herbicides, in addition to ...acting on plants, may also exert toxicity in wildlife and humans. In this study, male and female adult zebrafish were exposed to 700 µg/L of glyphosate (GLY), for 28 days. We used the metabolomic approach and UHPLC-ESI-MS to analyze liver samples to investigate the adverse effects of glyphosate on hepatic metabolism. The impact of GLY was found to be sex-specific. In female, GLY exposure affected purine metabolism by decreasing the levels of AMP, GMP and inosinic acid, consequently increasing uric acid levels with respect to the control (CTRL). Exposure to GLY also caused a decrease of UMP levels in the pyrimidine metabolism pathway. In male, GLY exposure decreased the aminoadipic acid within the lysine degradation pathway. Transcript analysis of genes involved in stress response, oxidative stress and the immune system were also performed. Results demonstrated an increased stress response in both sexes, as suggested by higher
expression. However, the
transcript level was increased in female but decreased in male. The results demonstrated reduced
,
, and
in male following exposure to GLY, indicating an impaired oxidative stress response. At the same time, an increase in the
transcript level in female was observed. mRNA levels of the pro-inflammatory interleukins
and
were increased in female. Taken together, the results provide evidence of disrupted nucleotide hepatic metabolism, increased stress inflammatory response in female and disruption of oxidative stress response in male.
The neuropeptide vasopressin is known for its regulation of osmotic balance in mammals. Arginine vasotocin (AVT) is a non-mammalian homolog of this neuropeptide that is present in fish. Limited ...information suggested that vasopressin and its homologs may also influence reproductive function. In the present study, we investigated the direct effect of AVT on spermatogenesis, using zebrafish as a model organism. Results demonstrate that AVT and its receptors (avpr1aa, avpr2aa, avpr1ab, avpr2ab, and avpr2l) are expressed in the zebrafish brain and testes. The direct action of AVT on spermatogenesis was investigated using an ex vivo culture of mature zebrafish testes for 7 days. Using histological, morphometric, and biochemical approaches, we observed direct actions of AVT on zebrafish testicular function. AVT treatment directly increased the number of spermatozoa in an androgen-dependent manner, while reducing mitotic cells and the proliferation activity of type B spermatogonia. The observed stimulatory action of AVT on spermiogenesis was blocked by flutamide, an androgen receptor antagonist. The present results support the novel hypothesis that AVT stimulates short-term androgen-dependent spermiogenesis. However, its prolonged presence may lead to diminished spermatogenesis by reducing the proliferation of spermatogonia B, resulting in a diminished turnover of spermatogonia, spermatids, and spermatozoa. The overall findings offer an insight into the physiological significance of vasopressin and its homologs in vertebrates as a contributing factor in the multifactorial regulation of male reproduction.
•GnRH & GnIH are expressed in the ovarian follicles of zebrafish at different stages of development.•Both GnRH & GnIH stimulate GVBD in the late-vitellogenic follicle enclosed oocytes, in vitro.•GnRH ...increases caspase-3 activity, whereas GnIH reduces it in late-vitellogenic follicles.•GnRH & GnIH stimulate GVBD, but have opposite effect on caspase-3 activity in late-vitellogenic follicles•Presence of both GnRH3 & GnIH are necessary for the normal LH-induced resumption of oocyte meiosis.
The control of oocyte growth and its final maturation is multifactorial and involves a number of hypothalamic, hypophyseal, and peripheral hormones. In this study, we investigated the direct actions of the gonadotropin-releasing hormone (GnRH) and the gonadotropin-inhibitory hormone (GnIH), which are expressed in the ovarian follicles, on final oocyte maturation in zebrafish, in vitro. Our study demonstrates the expression of GnRH and GnIH in the ovarian follicles of zebrafish (Danio rerio) at different stages of development and provides information on the direct action of these hormones on final oocyte maturation. Treatment with both GnRH and GnIH peptides stimulated the germinal vesicle breakdown (GVBD) of the late-vitellogenic oocyte. Both the GnRH and GnIH treatments showed no significant change in the caspase-3 activity of pre-vitellogenic and mid-vitellogenic oocytes, while they displayed different responses in the late-vitellogenic follicles. The GnRH treatment increased caspase-3 activity, whereas the GnIH reduced caspase-3 activity in the late-vitellogenic follicles. We also investigated the effects of GnRH and GnIH on the hCG-induced resumption of meiosis and caspase activity in vitro. GnRH and GnIH were found to have a similar effect on the hCG-induced resumption of meiosis, while they showed the opposite effect on caspase-3 activity. Furthermore, we investigated the effects of concomitant treatment of GnRH and GnIH peptides with hCG. The results demonstrated that the presence of both GnRH3 and GnIH are necessary for the normal induction of final oocyte maturation by gonadotropins. The findings support the hypothesis that GnIH and GnRH peptides produced in the ovary are part of a complex multifactorial regulatory system that controls zebrafish final oocyte maturation in paracrine/autocrine manner working in concert with gonadotropin hormones.
Reproduction and growth follow a seasonal pattern in many fish species involving changes in gonadal development, growth, and metabolism. Significant metabolic energy is needed during gametogenesis in ...both female and male to produce hundreds of eggs and billions of sperms. Seasonal variations are controlled by the hormones of brain-pituitary-peripheral axis and are accompanied by significant metabolic changes. There is evidence that GnRH and GnIH are among the key neurohormones that regulate the reciprocal control of growth and reproduction. The objective of this study was to investigate changes in metabolic profile and energy allocation patterns at different stages of reproduction, using goldfish as a model organism and LC-MS as analytical platform for metabolic analysis. Goldfish undergoes a clear seasonal cycle of growth and reproduction. In vivo experiments were conducted at three different time point of the annual cycle: regressed gonadal phase (peak growth phase), mid gametogenesis and late gametogenesis. Emphasis is placed on changes in liver metabolic pathways to energetically sustain the physiological processes related to growth and reproduction. Moreover, we tested the hypothesis that GnRH and GnIH may play a role in the regulation of metabolism by investigating acute effects of these peptides at different stages of reproductive cycle.
The findings in this paper provide novel information on the seasonal changes in basal metabolism during different stages of reproductive cycle, and evidence for differential allocation of energy during reciprocal control of reproduction and growth in goldfish. Chemometrics combined with pathway-driven bioinformatics elucidated a shift in the metabolic profile, indicating distinct patterns of energy allocation in the reproductive and growth seasons. Furthermore, to our knowledge this is the first study to provide evidence for a possible regulatory role of GnRH and GnIH in liver metabolism and energy allocation patterns associated with growth and reproductive processes. Together our findings present a framework for better understanding of the hormonally induced changes in metabolism to energetically sustain growth and reproduction in fish and other oviparous species undergoing seasonal cycle.
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•Results demonstrate significant changes in metabolome during different stages of reproduction and growth.•Energy allocation favours anabolic processes during regressed gonadal phase that corresponds to maximum growth phase.•The metabolic profile of fish during mid gametogenesis is characterized by high phospholipid biosynthesis•During late gametogenesis, there is enhanced ketone bodies metabolism compared to other reproductive seasons•GnRH and GnIH are contributing factors in regulating energy allocation during growth and reproductive phases.
Highlights • Discussion of estrogen receptor subtypes and structure. • Discussion of estrogen receptor mechanism(s) of action. • Estrogen receptor function in fish. • Summary of Estrogen receptor ...autoregulation in fish. • Providing context to estrogen receptor regulation and function in fish.
Although the use of bisphenol A (BPA) has been banned in a number of countries, its presence in the environment still creates health issues both for humans and wildlife. So far, BPA toxicity has been ...largely investigated on different biological processes, from reproduction to development, immune system, and metabolism. In zebrafish, Danio rerio, previous studies revealed the ability of environmentally relevant concentrations of this contaminant to significantly impair fertility via epigenetic modification. In addition, several studies demonstrated the ability of different probiotic strains to improve organism health. This study provides information on the role of the probiotic mixture SLAb51 to counteract adverse BPA effects on reproduction. A 28-day trial was set up with different experimental groups: BPA, exposed to 10 µg/L BPA; P, receiving a dietary supplementation of SLAb51 at a final concentration of 109 CFU/g; BPA+P exposed to 10 µg/L BPA and receiving SLAb51 at a final concentration of 109 CFU/g and a C group. Since oocyte growth and maturation represent key aspects for fertility in females, studies were performed on isolated class III (vitellogenic) and IV (in maturation) follicles and liver, with emphasis on the modulation of the different vitellogenin isoforms. In males, key signals regulating spermatogenesis were investigated. Results demonstrated that in fish exposed to the combination of BPA and probiotic, most of the transcripts were closer to C or P levels, supporting the hypothesis of SLAb51 to antagonize BPA toxicity. This study represents the first evidence related to the use of SLAb51 to improve reproduction and open new fields of investigation regarding its use to reduce endocrine disrupting compound impacts on health.
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