The Effect And Mechanism Of Electroacupuncture Modulation Of Microglia Polarization On Neuroinflammation In Rats With Cerebral Ischemia

OBJECTIVECerebral ischemia/reperfusion injury(CIRI)is a major cause of poor prognosis in ischemic stroke.Neuroinflammation is an important factor affecting CIRI and is mainly regulated by microglia polarization.Microglia activated by ischemia and developed into M1 and M2 phenotypes,M1 phenotype inhibits brain damage repair by releasing pro-inflammatory factors and M2 phenotype releases anti-inflammatory factors to promote brain function recovery.STAT6/PPARγ(signal transduction and activator of transcription 6/peroxisome proliferator-activated receptor γ,STAT6/PPARγ)has been found to be a key factor in regulating microglia polarization,results of RNA sequencing predict a central role for STAT6/PPARy in the regulation of microglia function.Our previous study found that electroacupuncture(EA)can alleviate neuroinflammation and reduce CIRI by downregulating microglia levels,but it is unclear exactly how EA regulates microglia function and whether this process is influenced by the STAT6/PPARγpathway.METHODSRats received middle cerebral artery occlusion(MCAO)procedure and were divided into sham-operated group(Sham group),MCAO group,EA group and EA+STAT6 phosphorylation inhibitor AS 1517499 group(EA+AS group)(n=20/group).After MCAO procedure,the EA and EA+AS group received EA intervention with Hegu(LI4),Chize(LU 5),Zusanli(ST 36)and Sanyinjiao(SP 6)(parameters:dilatational wave,5 Hz frequency and 2 mA intensity,once a day for 20 min),and the EA+AS group received intraperitoneal injection of AS1517499(10 mg/kg)before EA intervention.TTC,HE and TUNEL staining were used to observe the brain infarct volume,and the changes of histomorphology and cells apoptosis in ischemic penumbra cortex in each group.The degree of neurological damage in each group after 3 and 7 d of intervention was observed using behavioral assessment,STAT6/PPARγ pathway and NF-κB activity was detected by western blotting and quantitative real-time fluorescent PCR(qPCR),M1 and M2 microglia polarization was observed by immunofluorescence,and neuroinflammation levels were detected by enzyme-linked immunosorbent assay(ELISA)and qPCR.RESULTSEA intervention significantly alleviated neural injury in subacute stage in MCAO rats,reduced brain infarct volume and cells apoptosis in ischemic penumbra cortex,enhanced STAT6/PPARy pathway activity,inhibited NF-κB activity,increased the number of M2 microglia and the release of anti-inflammatory cytokines,and inhibited M1-type polarization of microglia and expression of pro-inflammatory factors.In contrast,when STAT6 phosphorylation inhibitor was added followed by EA treatment,STAT6/PPARγ pathway activity in ischemic penumbra cortex was inhibited,nerve injury recovery was not significant,microglia were mainly polarized towards M1 type,and neuroinflammation was increased,which impaired the benign modulatory effect of EA intervention on microglia-associated neuroinflammation in MCAO rats.CONCLUSIONSTAT6 may be one of the potential targets for EA intervention to alleviate CIHI EA intervention could inhibit microglia M1 polarization and promote microglia M2 polarization by enhancing the activity of STAT6/PPARγ pathway in ischemic penumbra cortex,thus reducing the level of neuroinflammation and alleviating CIRI in MCAO rats.