Endothelial Piezo1 channel and cerebral blood flow control

Project Summary/Abstract: Cerebral blood flow (CBF) is precisely controlled to satisfy neuronal metabolic demands. Active neurons signal to the vasculature via multiple neurovascular coupling mechanisms to increase regional blood flow in a phenomenon known as functional hyperemia (FH). The hyperemic response increases the frictional forces imposed by blood flow onto endothelial cells (ECs) of arterioles and capillaries. We have recently demonstrated that the Piezo1 channel is a crucial mechanosensor in brain capillary ECs, and that it mediates Ca2+ signals in response to mechanical stimuli. However, the impact of Piezo1 signaling on CBF control remains unknown. In response to the NIH Notice of Special Interest (NOT-AT-21-002) “Promoting Research on Interoception and Its Impact on Health and Disease,” we provide compelling preliminary evidence that Piezo1-mediated interoception is crucial in CBF regulation, and that this mechanism is compromised during hypertension. Building on our preliminary data, we aim to test the overarching hypothesis that cerebrovascular Piezo1 regulates CBF at the local capillary level and at the large-scale level in extended brain regions. Aim 1 will employ EC-specific genetically encoded Ca2+ indicator mice, widefield and two-photon fluorescence imaging to determine the spatial, temporal, and spread characteristics of Piezo1-mediated Ca2+ transients in brain capillaries. Moreover, we will use genetic and pharmacological approaches to determine if Ca2+ signaling mediated by Piezo1 is coupled to the production of the potent vasodilator nitric oxide to increase local capillary blood flow. In Aim 2, we will determine how large-scale Piezo1 activation during FH triggers a cationic conductance, which dampens hyperpolarization-mediated FH, much like a built-in brake system. To achieve this goal, we will use genetically engineered mice with reduced Piezo1 activity in all ECs or brain ECs, along with near infrared laser imaging, and laser doppler flowmetry. In Aim 3, we will determine if cerebrovascular Piezo1 signaling is compromised in hypertension and whether a Piezo1 channelopathy-like effect leads ultimately to CBF deficits. We will directly measure Piezo1 channel activity and CBF in two mouse models of hypertension and in genetically engineered transgenic mice that harbor a human Piezo1 mutation. Use of this mutation is clinically relevant, in that PIEZO1 mutations are prevalent in African Americans, a population with the highest prevalence of hypertension worldwide. Completion of this project will support the concept that Piezo1 is crucial in CBF regulation, and that alteration of its activity is a novel risk factor for CBF decline. This work will further provide new therapeutic targets for improving CBF in cardiovascular disease.