Project Summary Tissue plasminogen activator (tPA) remains the only FDA-approved therapy for acute ischemic stroke. Unfortunately, one-third to half of patients with successful recanalization of large cerebral vessels do not have good clinical outcome. This is in part due to incomplete microvascular reperfusion termed focal “no-reflow”, which is particularly prevalent in diabetic stroke. The current proposal will determine the role of endothelial-pericyte crosstalk, mediated by the action of the endothelial eicosanoids epoxyeicosatrienoates (EETs) on pericytes, in microvascular no-reflow after diabetic stroke in mice. We will test the hypothesis that endothelial-derived EETs preserve capillary perfusion in brain after ischemia, in part by protecting pericytes from ischemic injury, and that diabetes reduces microvascular endothelial EETs; thus, leading to greater pericyte injury and capillary damage after diabetic stroke. We will also determine if EETs protect pericytes by inhibiting G-protein coupled receptor 39 (GPR39). Stroke is induced in mice with and without type 2 diabetic (T2D), and with higher or lower endothelial EETs (due to transgenic overexpression or deletion of EETs-degrading enzyme soluble epoxide hydrolase, sEH, in endothelium) using an intraluminal occlusive filament or in-situ thrombin injection to occlude the middle cerebral artery (MCA). Intra-vital imaging using optical microangiography (OMAG) and two-photon microscopy (2PM) will be used to assess pericyte morphology, BBB integrity, capillary blood flow, and platelet and leukocyte morphology and dynamics within the peri-infarct region in-vivo, in real-time after MCA occlusion. Mice will be survived for 4 days after stroke to assess cellular and tissue damage (H&E, EM, IHC), and for 28 days to assess long-term functional deficit (neurocognitive and somatosensory). We propose that preserving endothelial- pericyte EETs/GPR39 signaling protects pericytes, prevents no-reflow and reduces brain tissue damage and neurobehavioral functional deficit. Enhancing endothelial EETs, either pharmacologically or in transgenic mice with higher endothelial EETs, will also enhance tPA efficacy and reduce tPA-associated hemorrhage after stroke in diabetic mice.