P2Y6 receptor inhibition aggravates ischemic brain injury by reducing microglial phagocytosis

Abstract

Introduction Clearance of damaged cells and debris is beneficial for the functional recovery after ischemic brain injury. However, the specific phagocytic receptor that mediates microglial phagocytosis after ischemic stroke is unknown. Aim To investigate whether P2Y6 receptor‐mediated microglial phagocytosis is beneficial for the debris clearance and functional recovery after ischemic stroke. Results The expression of the P2Y6 receptor in microglia increased within 3 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, subsequently aggravated neurological function as measured 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. Finally, we found that the expression of myosin light chain kinase decreased after microglial phagocytosis inhibition in the ischemic mouse brain, which suggested that myosin light chain kinase was involved in P2Y6 receptor‐mediated phagocytosis. Conclusion Our results indicate that P2Y6 receptor‐mediated microglial phagocytosis plays a beneficial role during the acute stage of ischemic stroke, which can be a therapeutic target for ischemic stroke.

DHA modulates MANF and TREM2 abundance, enhances neurogenesis, reduces infarct size, and improves neurological function after experimental ischemic stroke

“…9 Ischemic stroke perturbs endogenous inhibitory signaling and triggers microglial activation 10 that either aggravates ischemic injury or induces repair and regeneration, depending on the different signals received by microglial receptors. 10,11 TREM2 abundance on the microglia cell surface is 300 times higher than on astrocytes. 12 TREM2, coupled with the transmembrane signaling adaptor DAP12, is involved in physiological processes, including proinflammatory responses and phagocytosis of cell debris from damaged neurons and Aβ protein.…”

Microglia Purinoceptor P2Y6: An Emerging Therapeutic Target in CNS Diseases

“…On the contrary, Wen and colleagues observed that inflammatory cytokine mRNA expression of IL-1α, IL-1β, IL-6, IL-10, TNF-α and transforming growth factor-beta (TGF-β), both in the in vivo model of stroke and in vitro, did not change with MRS2578, which is a selective P2Y6R antagonist [ 47 ]. This indicates that P2Y6R inhibition only decreased the phagocytic function of microglia, without affecting the inflammatory response [ 47 ].…”

“…P2Y6R-mediated microglial phagocytosis has been reported to be beneficial for debris clearance and functional recovery after an ischemic stroke [ 47 ]. Briefly, the P2Y6R levels increased significantly in ischemic mice after transient middle cerebral artery occlusion (tMCAO), and the P2Y6R seems to be expressed exclusively in microglia [ 47 ]. Moreover, inhibition of P2Y6R activity exacerbated neurological function deficit and brain injury after tMCAO.…”

“…For instance, the P2Y6R activity was blocked by the intraperitoneal injection of the selective P2Y6R antagonist MRS2578 (3 mg/kg) for three consecutive days, after 90 min of tMCAO [ 47 ]. TUNEL cells (apoptotic cells) engulfed by Iba1+ microglia are decreased after the P2Y6R antagonist in the peri-infarct region in the MRS2578 group compared to the control group [ 47 ], suggesting that the MRS2578 significantly inhibited microglial phagocytosis in the brain after tMCAO [ 47 ]. Inhibiting the P2Y6R activity did not affect the expression of inflammatory cytokines and neutrophil infiltration.…”

“…Inhibiting the P2Y6R activity did not affect the expression of inflammatory cytokines and neutrophil infiltration. The results showed that the mRNA levels of IL-1α, IL-1β, IL-6, IL-10, TNF-α, and TGF-β are up-regulated after three days of tMCAO, except IL-10 [ 47 ]. However, the expression of these aforementioned cytokines remained similar in the MRS2578 and control groups [ 47 ].…”