Electroacupuncture promotes BDNF-dependent neurogenesis via microglial reprogramming in a chronic stress model

BACKGROUND: Aberrant microglial activation and impaired adult hippocampal neurogenesis play critical roles in the pathogenesis of depression. Although electroacupuncture (EA) has demonstrated clinical antidepressant efficacy, the underlying mechanisms by which it modulates microglial activity and promotes neurogenesis remain unclear. METHODS: Male C57BL/6 J mice were subjected to chronic unpredictable mild stress (CUMS) for three weeks. Following this period, the mice were divided into groups receiving either EA at the Yintang (GV29) and Baihui (GV20) acupoints, imipramine (IMI) as a positive control, or no treatment (vehicle control) for an additional 3 weeks. To evaluate depressive-like behaviors, we conducted the sucrose preference test, forced swimming test, and tail suspension test. Anxiety-like behaviors were assessed using the open field test and elevated plus maze. We employed immunofluorescence, Golgi staining, Western blotting, and real-time quantitative PCR (qRT-PCR) to elucidate the effects of EA on microglia-driven hippocampal neurogenesis and BDNF signaling. Notably, loss-of-function experiments utilizing PLX5622 for microglial ablation and ANA-12 for TrkB blockade demonstrated the necessity of both microglia and BDNF signaling for the therapeutic efficacy of EA. RESULTS: EA treatment significantly alleviated CUMS-induced anxiodepressive behaviors. This behavioral recovery was associated with a phenotypic shift in microglia towards a pro-neurogenic state in the hippocampus. Importantly, microglia were essential for the therapeutic effects of EA, as evidenced by their ablation with PLX5622. Furthermore, EA enhanced neurogenesis by orchestrating a multi-step augmentation of BDNF signaling, which involved PKA activation, subsequent release from MeCP2-mediated transcriptional repression, and ultimately increased maturation of BDNF. CONCLUSIONS: Our findings demonstrate that EA exerts antidepressant effects by promoting a pro-neurogenic transformation of microglia. Mechanistically, these microglia enhance BDNF function via the PKA/MeCP2/BDNF pathway, thereby facilitating hippocampal neurogenesis and restoring synaptic plasticity, which collectively alleviate depressive symptoms.