Abstract
FoxO3a, a forkhead family member of transcription factors, is involved in the regulation of cell metabolism, proliferation, differentiation and apoptosis. However, whether FoxO3a participates in the regulation of glucocorticoids induced-hypothalamic-pituitary-adrenal (HPA) dysfunction is still unknown. Our present results indicate that dexamethasone(DEX) increased FoxO3a expression in PC12 and hypothalamic neuronal cultures in correlation to reduced expression of NPW, a process that could be blocked by GR2 antagonist. DEX restrained the phosphorylation of Akt and FoxO3a, but not ERK1/2 phosphorylation, resulting with FoxO3a nuclear localization. Overexpression of FoxO3a inhibited NPW expression, while FoxO3a knockdown by siRNA had the opposite effect. The regulatory region of NPW promoter contains multiple FoxO3a binding sites, and FoxO3a bonding to these sites inhibited its transcriptional activity. In a rat model, chronic administration of corticosterone reduced animals' body weight and sucrose consumption and caused stress- depression like behavior. Corticosterone treatment induced a marked increase in FoxO3a levels, while decreased the expression of NPW protein in the hypothalamus. Immunofluorescent double labeling demonstrated that FoxO3a and NPW were collocated in the hypothalamus. Taken together, these data indicate that NPW is a new direct downstream target gene of FoxO3a. FoxO3a suppressed the transcription of NPW and modulated glucocorticoids-induced HPA dysfunction by directly regulating the expression of NPW. Thus, present findings suggest that FoxO3a and NPW may be potential therapeutic targets for endocrine and psychiatric disorders.