Erythropoietin (EPO) Alleviates Chronic Stress-Induced Depression by Modulating SIRT1-Mediated Mitochondrial Function

Mitochondrial dysfunction is a hallmark of many psychiatric disorders, and SIRT1 signaling plays a critical role in regulating mitochondrial dynamics, function, and autophagy. This study investigated the interplays between erythropoietin (EPO), mitochondrial protection, and SIRT1 signaling in depression. Chronic restraint stress (CRS)- induced depression mouse model and CORT-treated HT22 cells were employed, which were subsequently treated with EPO. CRS mice exhibited depressive-like behaviors, which were alleviated by EPO treatment, as evidenced by decreased immobility and increased sucrose preference. EPO also enhanced mitochondrial function by stimulating mitophagy and improving mitochondrial homeostasis, as indicated by elevated ATP levels, reduced nitric oxide, and restored expression of mitochondrial-related genes in both the hippocampus of CRS mice and CORT-treated HT22 cells. Additionally, EPO restored suppressed SIRT1 expression, promoted dendritic spine density and synaptic gene expression in the hippocampus, increased p-STAT5 phosphorylation, and increased NAMPT expression and NAD + levels. Notably, pharmacological inhibition of SIRT1 via EX-527 counteracted EPO effects, exacerbating depressive symptoms and mitochondrial homeostasis. Furthermore, EX-527 treatment decreased ATP levels and mitochondrial DNA copy numbers in CRS + EPO-treated mice and reduced ATG5 expression. However, EX-527 did not significantly impact BNIP3, Parkin, PINK1, LC3B-II, Ace-FOXO1, or FOXO1 expression. EX-527 exposure significantly increased Ac-LC3B precipitation in the hippocampus of CRS + EPO-treated mice and the COXIV/LAMP1 ratio in the HT22 cells. In summary, these results suggested that EPO antidepressant effects were mediated through SIRT1 regulation, which influenced LC3B deacetylation, improving CRS-induced mitochondrial dysfunction and autophagy impairment.