P2Y6 Receptor Inhibition Aggravates Ischemic Brain Injury By Reducing Microglial Phagocytosis

Clearance of damaged cells is beneficial for the functional recovery after brain injury.Phagocytosis of tissue and cell debris is an important function of microglia during the development and pathological diseases.However,which specific phagocytic receptor mediates microglial phagocytosis after ischemic stroke is obscure.ICR mice underwent 90 minutes transient middle cerebral artery occlusion.P2Y6 R,Iba1,GFAP and Tuj-1 double immunostainings were performed to determine P2Y6 receptor location.MRS2578 was injected into mice to inhibit P2Y6 receptor activity.Iba1 and TUNEL staining were performed to examine microglia phagocytosis.Modified neurological severity scores and Grid walking test were used to evaluate the neurological function after ischemic stroke.The expression of IL-1 α,IL-1 β,IL-6,IL-10,TNF-α,TGF-β and MPO were used to examine the inflammation response in the brain.The expression of P2Y6 receptor in microglia increased within three days after transient middle cerebral artery occlusion.Inhibition of microglial phagocytosis by the selective inhibitor MRS2578 enlarged the brain atrophy and edema volume after ischemic stroke,and aggravated neurological function by modified neurological severity scores and Grid walking test.MRS2578 treatment had no effect on the expression of IL-1α,IL-1β,IL-6,IL-10,TNF-α,TGF-β and MPO after ischemic stroke,which suggested that it had no effect on the inflammation in the brain.Finally,we found that the expression of myosin light chain kinase decreased after microglial phagocytosis inhibition in ischemic mice,which suggested that myosin light chain kinase was involved in P2Y6 receptor mediated phagocytosis.Our results indicated that the P2Y6 receptor mediated microglial phagocytosis played an important role during the acute stage of ischemic stroke,which was a potential target for the ischemic stroke treatment.