Abstract P3002: EndothelialTrpm2 Deletion Attenuates Ischemic Stroke By Preventing Blood-brain Barrier Disruption

IntroductionEndothelial hyperpermeability is a hallmark of brain damage at the early stage of ischemic stroke. The subsequent blood-brain barrier (BBB) disruption drives the initial pathological changes and aggregates neuronal death. Ca2+ overload is an important cause of endothelial dysfunction. TRPM2 is a Ca2+-permeable ion channel activated by oxidative stress, and oxidative stress is a critical contributor for endothelial hyperpermeability during ischemic stroke. HypothesisWe hypothesized that TRPM2-mediated Ca2+ influx plays a key role in causing endothelial hyperpermeability during ischemic stroke. MethodsSpecific deletion of Trpm2 in endothelial cells was achieved by crossing Cdh5-cre mice with Trpm2 fl/fl mice. Middle cerebral artery occlusion (MCAO) was performed to simulate ischemic stroke. Tetrazolium chloride and Evans blue assays were used to evaluate infarct size and BBB leakage. Occludin and F4-80 / myeloperoxidase staining were used to detect tight junction degradation and immune cell invasion. Cerebral endothelial cells (CECs) were isolated and cultured. Oxygen-glucose deprivation (OGD) was used to simulate in vitro ischemic conditions. In vitro endothelial leakage assays were used to examine CEC permeability. Rhodamine-123 imaging and Ca2+ imaging were used to evaluate oxidative stress and Ca2+ overload in CECs. WB was used to examine CD36 signaling activation and whole-cell current recording was used to detect TRPM2 activation. ResultsSpecific deletion of Trpm2 in endothelial cells protects mice against MCAO-induced brain injury, which is characterized by reduced infarct size, mitigated plasma extravasation, reduced neutrophil / macrophage invasion and inhibited oxidative stress in the brain. In vitro experiments demonstrated that Trpm2 deletion alleviates ROS production, Ca2+ overload and endothelial hyperpermeability induced by OGD and CD36 ligand thrombospondin-1 (TSP1). In CECs, activation of CD36 signaling induced by OGD and TSP1 was impaired by TRPM2 knockout. In transfected HEK293T cells, OGD and TSP1 induce the activation of TRPM2 currents in a CD36-dependent manner. ConclusionEndothelial specific TRPM2 knockout attenuates ischemic stroke by preserving BBB integrity.