Electroacupuncture Improves Learning and Memory Impairment in Rats with Cerebral Ischemia/Reperfusion Injury by Promoting Microglia/Macrophage M2 Polarization Through Nrf2/HO-1 Pathway

Objective: While electroacupuncture (EA) has shown effectiveness in treating learning and memory deficits associated with ischemic stroke (IS), the specific mechanisms involved remain unclear. The goal of this study was to investigate whether EA improves learning and memory deficits in MCAO rats by regulating microglia/macrophage polarization through the nuclear factor red lineage 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway. Methods: Sprague-Dawley rats were subjected to MCAO modeling and treated with EA 24 hours post-MCAO for a period of two weeks. To investigate the involvement of Nrf2/HO-1 in the effects of EA, tin protoporphyrin (SnPPIX), an inhibitor of HO-1, was injected into the left ventricle of rats before initiating EA treatment. Neurological function in MCAO rats was evaluated using a neurological deficit score. The effects of EA on learning and memory deficits were assessed using the Morris water maze (MWM) and open field test (OFT). Hematoxylin-Eosin (HE) staining was used to observe hippocampal structural morphology, and 2,3,5-Triphenyltetrazolium Chloride (TTC) staining was used to assess the infarct volume. Protein expression levels of the Nrf2/ HO-1 signaling pathway and microglial/macrophage polarization were determined using ELISA, immunofluorescence double-labeling, Western blotting (WB), and real-time quantitative polymerase chain reaction PCR (qRT-PCR). Results: EA significantly enhanced learning and memory function in rats by upregulating NRF2/HO-1 expression and promoting M2 polarization of microglia/macrophages. However, administration of SnPPIX, an HO-1 inhibitor, counteracted the beneficial effects of EA on memory improvement in MCAO rats, while also worsening cerebral infarct volume and inflammatory response. Conclusion: EA effectively improved learning and memory impairments in MCAO rats by activating the Nrf2/HO-1 signaling pathway, leading to the promotion of M2 polarization in microglia/macrophages.