Reproductive endocrine disruption effect and mechanism in male zebrafish after life cycle exposure to environmental relevant triclosan

Dual cyp17a1/a2 knockout unveils paralog-specific steroid pathways in fish reproduction

Cyp17a is a key enzyme in steroidogenesis and reproduction in vertebrates. In teleosts, two paralogous genes, cyp17a1 and cyp17a2, have been identified, and while the potential impact of mutations in these genes have been studied, a comprehensive comparative analysis of their regulatory mechanisms in teleost reproduction remains lacking. In this study, we established a double mutant (dko) of cyp17a1 and cyp17a2 and conducted a transcriptome analysis of their gonads to systematically investigate the differences in steroidogenesis and gene expression between the two genes. Phenotypic analysis revealed that both cyp17a1-/- and dko mutants exhibited a reduced gonadosomatic index, abnormal Leydig cell proliferation, and male infertility. RNA sequencing of the testes identified 2688 differentially expressed genes (DEGs), with significant variations between the mutants and wild-type males. KEGG enrichment analysis indicated that DEGs were enriched in pathways related to steroid biosynthesis, HIF-1, PPAR, and Hippo signaling. Furtherly, steroid profiling confirmed cyp17a1-/--specific androgen and estrogen deficiency (T, 11-KT, E1, and E2), while revealing dko-specific deficiencies in DHP, cortisol, and cortisone, alongside an overaccumulation of corticosterone, highlighting paralog-specific substrate preferences. These findings underscore the Cyp17a paralogs as critical regulators of testicular metabolic-transport networks, thereby offering insights into male infertility linked to steroid biosynthesis defects.

Multigenerational immunotoxicity assessment: A three-generation study in Drosophila melanogaster upon developmental exposure to triclosan

Triclosan (TCS) is widely used as an antibacterial agent, nevertheless, its presence in different environmental matrices and its persistent environmental nature pose a significant threat to the organism, including humans. Numerous studies showed that TCS exposure could lead to multiple toxicities, including immune dysfunction. However, whether parental TCS exposure could impair the offspring's immune response remains limited. Maintaining the immune homeostasis is imperative to neutralize the pathogen and crucial for tissue repair and the organism's survival. Thus, this study aimed to assess the multigenerational immune response of TCS using Drosophila melanogaster. TCS was administered to organisms (1.0, 10, and 100.0 μg/mL) over three generations during their developing phases, and its effect on the immunological response of the unexposed progeny was evaluated. Total circulatory hemocyte (immune cells) count, crystal cell count, phagocytic activity, clotting time, gene expression related to immune response and epigenetics, ROS generation, and cell death were assessed in the offspring. A concentration-dependent decline in total hemocytes, crystal cells, phagocytic activity, and increased clotting time in the subsequent generations was observed. Furthermore, parental TCS exposure enhanced the ROS levels, induced cell death, and altered the expression of antimicrobial peptides drosomycin, diptericin, and inflammatory genes upd1, upd2, and upd3, in the offspring's hemocytes across successive generations. The upregulation of reaper hid, and grim suggests that TCS promotes apoptotic death in the offspring's hemocytes. Notably, the increased mRNA expression of epigenetic regulators dnmt2 and g9a in the hemocytes of the offspring indicates epigenetic modifications. Further, we also observed that the antioxidant N-acetylcysteine (NAC) supplementation to the parents alleviated TCS toxicity and improved immunological functions in the progeny, indicating the role of ROS in the TCS-induced multigenerational immune toxicity. This finding provides valuable insights into the potential immune risk of prenatal TCS exposure to their offspring in the higher organism.

Reproductive toxicity of perfluorobutane sulfonate in zebrafish (Danio rerio): Impacts on oxidative stress, hormone disruption and HPGL axis dysregulation

Per and polyfluoroalkyl substances (PFAS) are anthropogenic chemicals extensively used in consumer products. Perfluorobutane sulfonate (PFBS), a short-chain PFAS, has been introduced as an alternative to long-chain PFAS, but limited studies have investigated its reproductive toxicity in fish. In this study, adult zebrafish were exposed to PFBS at concentrations of 0.14, 1.4, and 14 μM for 28 days. PFBS accumulation in male and female gonads was confirmed by specific mass spectrum peaks detected in exposed samples. PFBS exposure at 14 μM significantly reduced egg production and hatching rates. The gonadosomatic index (GSI) was decreased by 73 % in males and 50 % in females compared to the control. PFBS impaired antioxidant enzyme activity, with superoxide dismutase (SOD) 4.73 U/mg protein in testes and 3.46 U/mg protein in ovaries, leading to elevated lipid peroxidation and nitric oxide levels in males (0.053 μmol/mg/ml and 5.65 μM) and females (0.047 μmol/mg/ml and 4.01 μM), respectively. PFBS exposure induced endocrine disruption through the hypothalamic-pituitary-gonadal-liver (HPGL) axis, showing increased estrogen (50 pg/g) in males and testosterone (181.6 pg/g) in females. Gene expression analysis revealed significant alteration in the HPGL axis, including cyp19b, er2b, fshb, lhb, 17βhsd, lhr, cyp19a, and vtg, indicating PFBS influence on sex hormone synthesis. Histopathological analysis of PFBS exposure groups revealed a reduction of spermatozoa in the testes and late vitellogenic oocytes in the ovaries. Overall, the result of the present study indicates that PFBS exposure induces oxidative stress, disrupts hormone synthesis, dysregulates HPGL axis gene expression, and causes reproductive toxicity in both male and female zebrafish.

Effects of environmentally relevant concentrations of glyphosate and aminomethylphosphonic acid on biotransformation and stress response proteins in the liver of zebrafish (Danio rerio)

Herbicides pose a threat to various non-target organisms, including fish. A widely used herbicide, glyphosate, and its main breakdown product, aminomethylphosphonic acid (AMPA), are quite ubiquitous in freshwater systems. The aim of this work was to analyze changes in the relative abundance of hepatic proteins participating in the biotransformation and response to chemical stress in adult zebrafish Danio rerio exposed to environmentally relevant concentrations of glyphosate (100 μg/L), AMPA (100 μg/L), and their mixture (50 μg/L + 50 μg/L) for two weeks. Proteomic analysis showed that the tested concentrations caused dysregulation of various biotransformation proteins, the most upregulated of which in all treatment groups was the Phase I enzyme cyp27a7. While glyphosate had a more pronounced impact on the biotransformation pathways, AMPA showed stronger interference with redox homeostasis. When acting together, the parent compound and its metabolite were more potent to disturb fish metabolic processes, including nucleotide metabolism and proteasome pathway, and to downregulate proteins known for their roles in protection from oxidative modifications of cellular constituents and disruption of redox signaling.

Possible mechanisms for adverse effects on zebrafish sperm and testes associated with low-level chronic PFOA exposure

Perfluorooctanoic acid (PFOA), which is widely used during the manufacturing of fluoropolymer coatings and polytetrafluoroethylene, is now a widespread pollutant in the environment and within the human body. This study used zebrafish, an aquatic model species, to investigate how low levels of chronic PFOA exposure affect the reproductive system. The results of the experiments in which zebrafish were exposed to 414 ng/L or 4140 ng/L for 60 days showed a variety of adverse effects on testicular tissue and sperm, including dose-dependent changes in plasma estradiol and testosterone levels, various sperm malformations, decreased sperm motility and concentration, and PFOA-induced oxidative stress and testicular damage with increased rates of apoptosis. In addition, offspring of the zebrafish that had been exposed to PFOA were characterized by increased malformation and mortality. Subsequent transcriptional analyses of the male gonads revealed the significant activation of oxidative stress bioprocesses and immuno-inflammatory signaling pathways, along with the dysregulation of reproductive bioprocesses. In conclusion, low-level chronic exposure to PFOA affects both the reproductive performance of adults and the development of offspring; the mechanisms for these adverse effects involve alterations in several molecular pathways that may be involved in PFOA-induced oxidative stress and reproductive abnormalities. The presented data can be used to assess the ecotoxicity of PFOA to the male reproductive system at environmentally-relevant concentrations.

Triclosan impairs spermatocyte cell proliferation and induces autophagy by regulating microRNA-20a-5 P by pargeting PTEN

BACKGROUND

Triclosan (TCS), as an endocrine disrupter, has been found to affect male fertility. However, the potential molecular mechanism is still unknown. We aimed to investigate whether the toxic effects of TCS on spermatocyte cells was mediated by the regulation of microRNA-20a-5 P on PTEN.

METHODS

GC-2 and TM4 cells were treated with TCS (0.5-80 μM) for 24 or 48 hours. Effect of TCS on proliferation of GC-2 and TM4 cells was detected using a cell counting kit-8 (CCK8) assay. Expression of miR-17 family and autophagy genes were detected. The interaction between miR-20a-5 P and PTEN was determined by a dual-luciferase reporter assay.

RESULTS

TCS decreased cell proliferation of GC-2 and TM4 cells. Expression of autophagy-related genes and miR-17 family was altered by TCS. PTEN expression was significantly increased, whereas the expression of miR-20a-5 P was significantly decreased in GC-2 and TM4 cells. As predicted in relevant databases, there is a binding site of miR-20a-5 P in PTEN. The expression of PTEN was significantly down-regulated by the miR-20a-5 P mimic.

CONCLUSION

As a downstream target of miR-20a-5 P, PTEN functioned in the autophagy process of which TCS inhibited the proliferation of spermatocyte cells. Our results provided new ideas for revealing the molecular mechanism and protective strategy on male infertility.