Lactylation-driven microglial GCH1-BH4 axis suppresses neuroinflammation and underlies the preventive effects of treadmill running against CSDS-induced depression-like behaviors in mice.

Exercise is a novel non-pharmacological intervention for depression, yet the molecular mechanisms linking exercise-induced metabolic signals to epigenetic regulation of neuroinflammation remain largely undefined. We hypothesized that treadmill running ameliorates depressive-like behaviors via suppressing neuroinflammation by lactate-mediated histone lactylation and activation of the GCH1-BH4 axis in the microglia. A chronic social defeat stress (CSDS) mouse model, combined with treadmill running, BH4 treatment, and C646 infusion, along with BV2 microglial cell experiments, were used to assess role and mechanism of GCH1-BH4 axis in the antidepressive effects of running exercise. Treadmill running significantly reduces susceptibility to CSDS-induced depressive-like behaviors in mice, inhibited hippocampal microglial activation and pro-inflammatory cytokine expression. Additionally, running elevated systemic lactate levels, increased H3K18la lactylation, and upregulated microglial GCH1 expression with restored BH4 levels in the hippocampus. In BV2 cells, sodium lactate directly upregulated H3K18la and GCH1 in a concentration- and time-dependent manner, effects that were blocked by the glycolysis inhibitor 2-DG and the P300 inhibitor C646. Exogenous BH4 attenuated LPS-induced microglial inflammation in vitro and reversed CSDS-induced behavioral deficits in vivo. Conversely, intraperitoneal C646 infusion reversed the antidepressant effects of running by downregulating GCH1. These findings establish the lactate-GCH1-BH4 axis as a novel epigenetic mechanism by which treadmill exercise suppresses neuroinflammation and ameliorates depressive-like behaviors, offering a potential therapeutic target for stress-related mood disorders.