Modified Xiaoyao San ameliorates depressive-like behaviors by triggering autophagosome formation to alleviate neuronal apoptosis

Major depressive disorder (MDD) affects ˜16% of the world population. Chronic stressors contribute to reduced hippocampal volumes and increase the risk of developing MDD. Our previous work showed that XYS ameliorates social isolation and chronic unpredictable mild stress (CUMS) induced depressive-like behaviors in rats by regulating hypothalamic-pituitary-adrenal hyperactivation, locus coeruleus -norepinephrine activity and kynurenine/5-hydroxytryptamin balance. Here, we report that CUMS & isolation-treated mice exhibit depressive-like behaviors and show a phenotype of mixed apoptosis/autophagy characteristic in mice hippocampus in vivo. Modified Xiaoyao San (MXS) significantly ameliorates CUMS & social isolation-induced anhedonia, loss of interests, psychomotor retardation and behavioral despair. It suppresses the apoptosis by downregulaing condensation of heterochromatin and reducing hippocampal TdT-mediated dUTP Nick-End Labeling (TUNEL)-positive cells. MSX significantly inhibits mitochondrial outer membrane permeabilization (MOMP) reduces the release of cytochrome C and the shift of apoptosis inducing factor (AIF) from mitochondria to nucleus. Further, it stimulates the formation of autophagosomes and activates the expression of Atg5 and LC3II. Combined silencing of Atg5 and Atg7 dampens MOMP and impaired the anti-apoptotic effects of MXS. In conclusion, MXS ameliorates depressive-like behaviors by triggering autophagy to alleviate neuronal apoptosis. MXS is an effective supplement for MDD treatment, and can be harnessed to enhance autophagy and synergize with antidepressant action.