GPNMB regulates M2 polarization of microglia thereby alleviating nerve injury after cerebral ischemic stroke through PI3K/Akt pathway / 中国免疫学杂志

ABSTRACT

Objective:To investigate the mechanism by which glycoprotein non-transferable melanin B(GPNMB)regulates microglia M2 polarization to reduce nerve damage after cerebral ischemic stroke(CIS).Methods:SD rats were used for establishment of middle cerebral artery occlusion(MCAO)model.Neurons,astrocytes and microglia were cultured under oxygen and glucose depri-vation(OGD)conditions,and the expression of GPNMB in tissues and cells were measured by Western blot.Gpnmb wrapped with adeno-associated virus(AAV)or shRNA-Gpnmb were injected into rat brain tissues for overexpression or inhibition of GPNMB,modified neurological deficit score(mNSS),Rotarod fatigue test and tape removal test were used to evaluate rat nerve function,the proportion of cerebral infarction was determined by TTC staining,microglia M1/M2 polarization markers were detected by immunofluorescence and RT-PCR,and the expression of Phosphatidylinositol 3-kinase(PI3K)/Serine/threonine kinase(Akt)pathway was determined by Western blot.Microglia was cultured under OGD conditions in vitro,Gpnmb was overexpressed and PI3K expression were inhibited by LY294002,and M1/M2 polarization markers were measured.Results:Compared with normal rats or normal cultured cells,the expres-sion of GPNMB in MCAO model or OGD-intervened microglia was up-regulated(P<0.05);when Gpnmb was overexpressed in the brain tissue of MCAO rats,the mNSS score decreased,the Rotarod time of latency to fall lengthened,the contact time and removal time shortened in the tape removal test,the proportion of cerebral infarction decreased,the M1 polarization level of microglia decreased while the M2 polarization level increased,PI3K/Akt pathway activated,and these difference were statistically significant(P<0.05);inhibition of PI3K reversed the effect of overexpression of Gpnmb on promoting M2 polarization of microglia in vitro(P<0.05).Conclusion:GPNMB promotes M2 polarization of microglia by activating the PI3K/Akt pathway,thereby reducing nerve damage after CIS.