FSH抑制氧化损伤猪卵巢颗粒细胞自噬的机制研究

Although Follicle-stimulating Hormone (FSH) is identified as a major survival factor for antral follicles, its potential mechanism for inhibiting granulosa cell (GC) death remain to be elucidated. Our previous study has established the prominent function of FSH/PI3K/AKT signaling axis in suppressing Foxo1, a critical mediator of autophagy in GC exposed to oxidative stress. In additon, FSH treatment of GC also displayed a chronic activation of mTOR under oxidative conditions. Furthermore, FSH may protect GC from oxidative damage by inhibiting the autophagic mechanisms. In this project, we plan to select PI3K/AKT pathway as an entry point, try to identifying the key regulatory signaling cascades of autophagy by FSH under oxidative stress conditions, and investigating the role of FSH on regulating the interactions among the downstream effector molecules and autophagic proteins of this pathway in GC. On this basis, we will further explore the protective mechanism of FSH in restraining a lethal form of autophagy in GC by focusing on mTOR and Foxo1, the major effectors of PI3K/AKT signaling pathway. Our findings may bring forward brand new aspects involving autophagy for future researches in follicular atresia, and will provide theoretical basis for reducing oxidative stress induced GC death and follicular atresia, as well as improving animal reproductive performance and developing new technologies for the clinical treatment of ovulation failure related disorders.

FSH是维持有腔卵泡存活的关键因子，但是FSH抑制有腔卵泡颗粒细胞死亡的机制尚未完全阐明。根据项目组先前的研究结果，氧化应激条件下FSH能通过PI3K/AKT信号传导途径抑制自噬关键蛋白Foxo1的功能，并维持自噬核心抑制因子mTOR的活性。此外，FSH还可能通过抑制自噬途径降低氧化应激引起的颗粒细胞死亡。本项目计划以PI3K/AKT通路为切入点，探明氧化应激条件下FSH调控自噬的关键信号通路，深入研究FSH对该通路下游主要效应分子与自噬调控蛋白间互作的影响。在此基础上，进一步揭示以mTOR和Foxo1为核心的信号通路在FSH抑制氧化应激条件下颗粒细胞损伤性自噬过程中的机制。项目研究结果将从自噬的角度为解释卵泡闭锁的调控机制提供新的研究方向和思路，也将为缓解氧化应激造成的颗粒细胞死亡和卵泡闭锁提供新的理论依据，对动物繁殖性能的提高与人类排卵障碍相关疾病的治疗具有重要的理论和实践意义。

卵泡的质量决定了后代的健康状态，卵泡发育异常是造成雌性动物不孕不育与繁殖性能下降的关键因素。前人研究表明，环境应激（饲养环境、生活环境）和动物繁殖过程本身均会产生氧化应激，导致卵巢颗粒细胞氧化损伤，引起卵泡闭锁和排卵障碍相关疾病。FSH是维持有腔卵泡健康和颗粒细胞存活的关键因子，但是FSH抑制有腔卵泡颗粒细胞氧化损伤的机制尚未完全阐明。近年来的研究表明氧化应激可以诱导多种哺乳动物细胞发生自噬性死亡。本报告首次提出并证明FSH通过抑制自噬性死亡相关信号通路参与对颗粒细胞的抗氧化损伤保护。体内外研究结果显示，FSH 能显著抑制氧化剂对颗粒细胞自噬的诱导，并维持氧化应激条件下颗粒细胞活力。阻断自噬和FSH处理均能抑制氧化剂诱导的颗粒细胞死亡，但在阻断自噬的基础上FSH无法继续提高颗粒细胞活力水平。进一步的研究显示，FSH诱导的I型磷脂酰肌醇3激酶（PI3K）-蛋白激酶B（AKT）-雷帕霉素的机械靶标（MTOR）信号通路（PI3K-AKT-MTOR）的激活抑制了氧化应激引起的自噬，进而促进颗粒细胞的存活。此外，FSH-PI3K-AKT信号轴也可通过靶向FOXO1来下调颗粒细胞自噬活性；相反，组成型激活的FOXO1不仅阻断FSH对颗粒细胞的保护作用，而且从包括自噬蛋白到自噬基因表达的各层面恢复了细胞自噬过程。另外，FSH 还能通过抑制FOXO1 乙酰化减弱FOXO1 与ATG 蛋白的结合，进而减少氧化应激条件下颗粒细胞的自噬性死亡。研究结果首次从自噬的角度为解释卵泡闭锁的调控机制提供新的研究方向和思路，对于丰富繁殖理论、提高动物繁殖力、治疗人类生育类疾病都具有重要意义。