The Roles Of Akt/mTOR And Mitochondria Signaling Pathway In Male Rat Reproduction Toxicity Induced By BPA

Bisphenol A (BPA; 4,4'-isopropylidenediphenol) is an important industrial material for producing polycarbonate (PC) plastics and epoxy resins. Over 2.7 million tons of BPA are produced annually, and the growth in demand is predicted to be 6-10% per year. Because of the high production, the widespread use of PC plastics and epoxy resins, and the easy exposure and migration, BPA almost exists in all spheres of our life. For the above reasons, despite its short half-life in environment mediums and biological organisms, the exposure risk of BPA is substantial. Many researches have indicated that the detection rate of BPA in human urine is greater than 80%.BPA is a typical endocrine disrupting chemical (EDCs), which possesses weak estrogenic effects and strong anti-androgenic properties. What's more, BPA can induce oxidative stress in organisms. Rodent studies and human researches have shown the correlation between BPA exposure and male reproductive dysfunction, although some other studies have yielded conflicting results. However, since spermatogenesis is a sophisticated process that needs optimized microenvironment and multifaceted regulations, and any exogenous disturbance may break the balance, the harm of BPA should not to be neglected.Akt/mTOR signal transduction pathway is very important in organisms, which is involved in cell survival, differentiation, proliferation, metabolism, and motility in response to extracellular cues. Some studies have shown that when this pathway was inhibited, problems in spermatogenesis could be observed. In spermatogenesis, the role of cell apoptosis is indispensable, it can eliminate overmuch or abnormal spermatogenic cells. And, the role of mitochondria apoptosis pathway has been confirmed. However, excessive apoptosis will also harm spermatogenesis.Since BPA can induce oxidative stress in reproductive system, and then activate mitochondria apoptosis pathway, and because of the close relationship between Akt/mTOR pathway and mitochondria apoptosis pathway, the present study takes the oxidative stress induced by BPA exposure as point of cut-in, and animals at different ages as research subjects, using diverse biochemistry and molecular biology methods to explore the role of Akt/mTOR pathway and mitochondria apoptosis pathway in male reproductive toxicity induced BPA.Part I Study of the mechanism involved in BPA induced reproductive toxicity in pubertal male SD ratBisphenol A (BPA), a ubiquitous pollutant in the environment, has long been suspected of causing male reproductive toxicity. However, the precise mechanisms of this effect are still unknown. In this research, rats were exposed to 0,2,10,50 mg/kg body weight BPA, then the levels of sex hormones, oxidative stress, and semen quality were detected; HE staining, TUNEL assay, and transmission electron microscopy were used to investigate the morphological changes, apoptosis, and autophagy in rats testes respectively; expressions of relevant genes and proteins were measured using RT-PCR, western blotting, and immunohistochemical staining. The conclusion is that BPA exposure can lead to oxidative stress and endocrine disorders in pubertal male SD rats, cause apoptosis and autophagy in testes, then harm spermatogenesis ultimately. In the process, Akt pathway was activated and mTOR pathway was inhibited, mitochondria apoptosis pathway and autophagy pathway were both activated.Part II Study of the mechanism involved in BPA induced reproductive toxicity in adult male SD ratBisphenol A (BPA) is an ubiquitous chemical in the environment where we live, as an endocrine disrupting chemical, the exposure risk and negative effects of BPA have gained more and more attentions from many countries and researchers. The aim of this study was to observe the reproductive toxicity effects induced by BPA in pubertal male SD rats, and try to elucidate the underlying mechanism involved in the process. The results indicate that oxidative stress, endocrine disorders, and Raf-ERK/Akt-mTOR signaling pathway are involved in the reproductive toxicity cause by BPA.Part III Study of the mechanism involved in prenatal BPA induced reproductive toxicity in offspring prepubertal male SD ratBisphenol A (BPA) exposure is ubiquitous, and in laboratory animals and humans, the exposure has been associated with male spermatogenesis dysfunction. However, it is largely unknown if this association has a fetal origin. The aim of this research is to explore the mechanism that how prenatal BPA exposure exerts its reproductive toxic effects on male offspring spermatogenesis. We fed pregnant SD rat BPA at doses ranging from 1 to 100 mg/kg body weight during gestation day 14?21, the male offspring at prepuberty and adult were euthanized separately, the levels of sex hormones and reactive oxygen species (ROS), semen quality, proteins and genes on Akt/mTOR and mitochondrial apoptosis pathway were detected. Besides, some close-linked autophagy indexes were measured incidentally. The results revealed that in utero BPA exposure can cause endocrine disruption and oxidative stress in male offspring, lead to inhibition of spermatogenesis by suppressing Akt/mTOR pathway and activating mitochondrial apoptosis pathway. Autophagy pathway in offspring testes was suppressed constantly. Although indexes above fluctuated with age, reproductive hazard eventually happened. These preliminary results indicate that the profound effect and the low dose effect of BPA on male offspring reproductive system via Akt/mTOR/mitochondrial apoptosis pathway are noteworthy.