Protective mechanism of FSH against oxidative damage in mouse ovarian granulosa cells by repressing autophagy
Oxidative stress-induced granulosa cell (GCs) death represents a common reason for follicular atresia. Follicle-stimulating hormone (FSH) has been shown to prevent GCs from oxidative injury, although the underlying mechanism remains to be elucidated. Here we first report that the suppression of autophagic cell death via some novel signaling effectors is engaged in FSH-mediated GCs protection against oxidative damage. The decline in GCs viability caused by oxidant injury was remarkably reduced following FSH treatment, along with impaired macroautophagic/autophagic flux under conditions of oxidative stress both in vivo and in vitro. Blocking of autophagy displayed similar levels of suppression in oxidant-induced cell death compared with FSH treatment, but FSH did not further improve survival of GCs pretreated with autophagy inhibitors. Further investigations revealed that activation of the phosphoinositide 3-kinase (PI3K)-AKT-MTOR (mechanistic target of rapamycin [serine/threonine kinase]) signaling pathway was required for FSH-mediated GCs survival from oxidative stress-induced autophagy. Additionally, the FSH-PI3K-AKT axis also downregulated the autophagic response by targeting FOXO1, whereas constitutive activation of FOXO1 in GCs not only abolished the protection from FSH, but also emancipated the autophagic process, from the protein level of MAP1LC3B-II to autophagic gene expression. Furthermore, FSH inhibited the production of acetylated FOXO1 and its interaction with Atg proteins, followed by a decreased level of autophagic cell death upon oxidative stress. Taken together, our findings suggest a new mechanism involving FSH-FOXO1 signaling in defense against oxidative damage to GCs by restraining autophagy, which may be a potential avenue for the clinical treatment of anovulatory disorders.