Project Summary/Abstract Like all mammalian vascular beds, the central nervous system relies on a functional vascular system (the neurovascular system) to maintain the developmental and metabolic activities of its resident cells. Neurovascular compromise thus imparts direct and indirect consequences to parenchymal tissue, and those consequences impair central nervous system function. Brain arteriovenous malformation (AVM) is a human neurovascular disease characterized by abnormal blood vessel morphology and organization – these abnormalities lead to feed-forward changes in hemodynamics that increase the risk of hemorrhagic stroke, chronic disability, and death. Currently, there are no Food & Drug Administration-approved pharmacological treatments for brain AVM; thus, understanding the mechanistic underpinnings of this disease will inform on molecular-based therapies. Through the Funded Parent Project, we are using in vivo and in vitro approaches to examine whether Adrenomedullin signaling is required for vascular abnormalities associated with Rbpj-deficient brain AVM in mice and for cellular perturbations caused by RBPJ deficiency in cultured human brain endothelial cells. The experimental aims in this Diversity Supplement will use our in vitro human brain endothelial cell system to determine whether cytoskeleton dynamics are affected in RBPJ-deficient endothelial cells and whether small- molecule inhibition of Adrenomedullin signaling can prevent cytoskeleton dysfunction. We will test the hypothesis that inhibition of Adrenomedullin signaling, in the context of endothelial RBPJ- deficiency, will normalize cytoskeletal organization and function, and thereby prevent those abnormalities from promoting endothelial cell dysfunction. This hypothesis will be addressed in two supplemental aims that will determine whether inhibition of Adrenomedullin signaling, via administration of the small-molecule inhibitor NSC16311, prevents dysregulation of F-actin polymerization dynamics (Supplemental Aim 1) and prevents dysregulation of F-actin turnover rate (Supplemental Aim 2) in cultured, RBPJ-deficient human brain endothelial cells. These studies will advance our long-term research objectives, which are to understand how loss of RBPJ leads to brain endothelial cell dysfunction and how such dysfunction contributes to neurovascular pathologies like brain AVM. Our work will also inform on the efficacy of pharmacological inhibition to normalize aberrant cell signaling, to prevent endothelial cell dysfunction, and thereby to promote neurovascular health.