Miro1 Mediates the Neuroprotective Effects of Electroacupuncture Against Cerebral Ischemia-Reperfusion Injury in Mice

Cerebral ischemia-reperfusion injury (CIRI) is a severe neurological condition where restoring neuronal mitochondrial function critically impacts prognosis. While electroacupuncture (EA) has demonstrated neuroprotective effects by improving mitochondrial function, the precise underlying mechanisms remain unclear. Emerging evidence suggests that astrocyte-to-neuron mitochondrial transfer, facilitated by mitochondrial Rho-GTPase 1 (Miro1), serves as a vital neuroprotective pathway. Therefore, this study investigates whether astrocytic Miro1 participates in the neuroprotective effects of EA against CIRI in mice by regulating the expression of the mitochondrial marker translocase of the outer mitochondrial membrane 40 (TOM40) and adenosine triphosphate (ATP) levels in damaged neurons.

126 C57BL/6 mice were randomly allocated into seven experimental groups (n = 18 per group): Sham-operated (Sham), middle cerebral artery occlusion (MCAO) model, EA, sham electroacupuncture (SEA), EA combined with astrocyte-specific Miro1 knockdown (GFAP: glial fibrillary acidic protein, EA+AAV-GFAP-shMiro1), astrocyte-specific Miro1 over-expression (AAV-GFAP-hiMiro1), and adenoviral empty vector control (AAV-GFAP-control). The CIRI model was induced using MCAO. Prior to model induction, the EA group received pretreatment with EA at the Baihui (GV20) acupoint. The SEA group underwent identical procedures to the EA group except for electrical stimulation. For the EA+AAV-GFAP-shMiro1, AAV-GFAP-hiMiro1, and AAV-GFAP-control groups, mice received intracerebroventricular injections of AAV-GFAP-shMiro1, AAV-GFAP-hiMiro1, or AAV-GFAP-control, respectively, 48 hours prior to EA treatment, with other procedures matching the EA group. At 24 hours post-reperfusion, neurological deficit scores, cerebral infarct volume, and neuronal survival in the peri-infarct penumbra were assessed. Astrocytes and neurons from the peri-infarct penumbra were isolated to measure ATP levels and expression of the mitochondrial-specific protein TOM40 in neurons, as well as ATP levels, TOM40, and Miro1 protein expression in astrocytes.

Relative to the Sham group, the MCAO group displayed a significant increase in cerebral infarct volume and neurological deficit scores, accompanied by a marked reduction in neuronal viability, TOM40 expression, and ATP levels (p < 0.01). In contrast to the MCAO and SEA groups, the EA and AAV-GFAP-hiMiro1 groups demonstrated improved neurological scores, reduced infarct volume, enhanced neuronal viability, elevated neuronal ATP levels and TOM40 expression, as well as decreased astrocytic ATP and TOM40 levels, but significantly increased Miro1 expression in astrocytes (p < 0.01). When compared to the EA group, the EA+AAV-GFAP-shMiro1 group exhibited a reversal of all the aforementioned improvements (p < 0.01), while the AAV-GFAP-hiMiro1 group showed no significant changes (p > 0.05).

EA exerts neuroprotective effects in MCAO mice by upregulating Miro1 protein expression in astrocytes and upregulating the mitochondrial marker TOM40 alongside ATP levels in neurons. Silencing Miro1 abolished the neuroprotective effects of EA and reduced neuronal TOM40 expression, while Miro1 overexpression increased this mitochondrial marker and mimicked EA-mediated neuroprotection. These findings identify Miro1 as a key effector of EA-induced neuroprotection, although the upstream signaling pathways linking EA to Miro1 upregulation require further investigation.