Defining the role of endothelial Piezo1, a mechanosensitive ion channel, in providing resilience to vascular contributions to cognitive impairment and dementia (VCID)

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Cerebrovascular dysfunction is a contributing factor to the development of cognitive impairment and dementia in both Alzheimer’s disease (AD) and in non-AD pathologies. Vascular contributions to cognitive impairment and dementia (VCID) is an evolving field of study which covers the overlap and interrelationship between vascular disorders and disorders leading to dementia. More basic science research investigating the impact of aging, AD pathology, and cerebrovascular function is currently needed. Piezo1 is a recently identified mechanosensitive ion channel that gates calcium influx in response to membrane stretch or increased shear forces. It is expressed in multiple tissues, but plays a critical role in cardiovascular health and disease. In the peripheral vasculature, activation of this ion channel by luminal shear or by a selective agonist promotes increased endothelial intracellular calcium and vasodilation. Our significant preliminary data provide the first demonstration that endothelial Piezo1 plays an important role in regulating cerebral blood flow (CBF) and contributes to microvascular stability. We also demonstrate that CBF can be enhanced by delivery of a selective Piezo1 agonist (Yoda1) at doses that do not alter systemic blood pressure. An intriguing recent study showed that shear-mediated Ca2+ influx in cells exogenously expressing human PIEZO1 was potently inhibited by amyloid beta (Ab) monomers (Ab40>Ab42). If these findings are similarly valid with endogenously-expressed Piezo1 within the cerebral vasculature, it would suggest a new mechanism by which elevated Ab contributes to impaired CBF regulation and the eventual development of VCID. We tested this possibility with mouse brain microvascular endothelial cells (BMVECs). We found that exposure to human Ab40 indeed abolished the flow-mediated Ca2+ response, but that responsiveness to direct pharmacological Piezo1 activation remained intact. We further demonstrated that the in vivo CBF response to Yoda1 was also intact in TgSwDI mice which express elevated levels of soluble Ab40 and Ab42. These provocative findings suggest that while flow/shear-dependent function of cerebral endothelium may indeed be impaired by elevated Ab peptides, this dysfunction may be “bypassed” by direct pharmacological activation of Piezo1. In this proposal, we will test the overall hypothesis that loss of endothelial Piezo1 function (such as in conditions of chronically reduced flow or elevated soluble Ab) leads to cerebrovascular dysregulation and the development of VCID. In addition, we seek to establish proof-of-concept for a strategy to provide resilience to VCID by pharmacologically “mimicking” flow-mediated endothelial activation with selective Piezo1 agonists. Completion of these studies will establish a vital role of EC Piezo1 in the regulation of cerebral blood flow and the pathological consequences of its functional loss in the development of VCID. These studies will further establish the scientific justification for new therapeutic strategies aimed at restoring endothelial Piezo1 function in the context of amyloid pathology.