| The high incidence of human reproductive problems is a global phenomenon,and the understanding of its pathogenic factors is still limited.Epidemiological data suggest that extensive use of environmental endocrine disruptors may be an important risk factor for infertility.Current studies on endocrine disruptors mainly focus on exposure during development(embryo)period.Our study considers that male germ cells are more susceptible to environmental exposure during meiosis than female after birth,and the frequent unwinding of DNA during meiosis is the most susceptible period for environmental exposure-induced epigenetic change.Therefore,this study explored and compared the effects of two endocrine disruptors,bisphenol A(BPA)and ethinyl estradiol(EE2),which are frequently contacted in daily life,on male reproductive function after birth.The study proceeds from two factors that determine the success of male reproduction: one is spermatogenesis and sperm function(sperm function not only includes the ability to fertilize the egg,but also the ability to carry environmental exposure information),and the second is the sexual behavior.Section 1 Effects and mechanisms of BPA and EE2 exposure on sperm function and the health of their progeny in ratsObjective: To explore the effects of low-dose BPA and EE2 on sperm function and the health of their progeny in rats.Methods: Male rats(PND 26)were randomly divided into control group(group C),BPA exposure group(35 ?g/kg bw/day,BPA group)and EE2 exposure group(2.5?g/kg bw/day,EE2 Group).At PND 182,F0 male rats were mated with unexposed female rats to produce F1 generation,and the fertility and fecundity of F0 generation were detected.At PND 202,rats(F0)were sacrificed and the sperm quality,testicular transcriptome,pathology of testis,the cycle of seminiferous epithelium,testicular androgen levels,and serum hormone levels were detected.Food intake and body weight of the F1 male and female rats were continuously monitored.Rats of F1(male and female rats)were sacrificed at PND 202 and the blood glucose,blood lipids and sperm function,testicular pathology,the cycle of seminiferous epithelium and serum sex hormones were tested.Results: 1)Lower body weight and lower blood lipids(TC and LDL-C)were observed in the EE2 group but not in the BPA group.2)Male rats in BPA group took more time to produce offspring(BPA group:5(4-9);C group: 3(1-4)),while the fertility was decreased in EE2 group(EE2group:33.3%;C group: 100%).Either of them affected the sperm quality and testicular H&E staining structure,but autolysosomes and apoptotic bodies were observed in testicular ultrastructure.3)BPA induces 51 differential expression genes(DEGs)in testis,while DEGs in EE2 group is 269.4)The retinoic acid(RA)metabolic pathway and testosterone synthesis pathway in the testis of the EE2 group were altered,as well as the decreased testosterone level in serum and testis tissue.While percentage of stage VII and stage ? seminiferous epithelial cells did not change significantly under EE2 exposure.5)Parental BPA exposure increases the body weight of their male offspring;paternal EE2 exposure increases the body weight of both male and female offspring,as well as the serum TC in male offspring.6)The sperm function,testicular structure,circulating testosterone and estrogenlevels and percentage of stage VII and stage ? seminiferous epithelial cells were not changed significantly in male offspring of rats exposed to BPA and EE2.Conclusions: 1)Rats exposed to BPA took more time to produce offspring and induced testicular ultrastructural and transcriptome changes,but its fertility and sperm quality were normal.The declined fertility of EE2 exposure was associated with decreased RA metabolic pathway and testosterone synthesis induced by EE2.2)Parental BPA and EE2 exposure increased the body weight of male offspring,and this effect may relate to the induction of high inflammatory signaling pathway changes in the hypothalamus(details in the second section of the results);while the sperm function of male offspring were not obvious changed.Section 2 Effects of BPA and EE2 exposure on male sexual behavior and its mechanismObjective: Further explore the effects of low doses of BPA and EE2 exposure on sexual behavior in male rats.Methods: The experimental design were the same as those in the section 1.The sexual behavior of F0 and F1 male rats during PND 170-PND180 were observed by camera and transcriptome sequencing analysis were performed on the hypothalamus of F0 and F1 male rats.Results: 1)BPA,but not EE2 exposure increased the ejaculation latency of male rats(2.8 folds),and they induced changes in the hypothalamic transcriptome genes of 4and 14 respectively.2)Parental BPA and EE2 exposure did not affect the latency of mount,intromission,ejaculatory and the frequency of mount,intromission and as well as the copulatory efficacy of male offspring rats,but parental BPA exposure induced 164 DEGs in the hypothalamus of the offspring.It mainly involves the alteration of the high-inflammation signaling pathway.While parental EE2 exposure induced 3433 DEGs in the hypothalamic of the offspring,mainly involving changes in inflammation,endocrine and synaptic pathways.Conclusions: Exposure to BPA increased the ejaculation latency in male rats.This increase was not directly related to the regulation of male sexual behavior in the hypothalamus.Parental BPA and EE2 exposure did not affect the sexual behavior of the offspring male rats,but there is a risk of increasing the hypothalamic inflammatory response of its male offspring.Moreover,the male offspring of EE2 exposure rats were at high risk of drug dependence.In summary,this experiment provides transcriptome results of low doses of BPA and EE2 exposure on the two important target organs in the reproductive function-testis and hypothalamus;and more clues were provided to understand the effects of BPA and EE2 on the mRNA level of testicular and hypothalamic tissues. |
PDF Full Text Request