AT1R-TRPC3 signaling cascade in pressure-induced constriction of brain pericytes

About This Grant

PROJECT SUMMARY Small Vessel Disease (SVD), characterized by dysfunctional microvessels in the brain, is a leading contributor to stroke and dementia worldwide, with up to 40% of dementias developing with a vascular component. While microvascular deficits often arise years prior to neuronal damage, treatments targeting microvascular function to preserve brain health are limited. Hypertension is the leading modifiable risk factor for vascular or mixed dementias and affects nearly half of the adult population in the United States, according to the American Heart Association. As little is known of how capillaries sense and respond to changes in luminal pressure, treatments to protect capillary blood flow to preserve cognitive health are not available. Pericytes are a heterogenous population of contractile cells that wrap around the basement membrane of capillaries. Due to their fast on/off contractile kinetics, pericytes in the arteriole-capillary transition (ACT) zone have emerged as integral regulators of capillary blood flow. However, the signaling processes that trigger pericyte contraction are largely unknown. My preliminary work has identified the TRPC3 channel as a key regulator of pericyte membrane depolarization in response to increased capillary luminal pressure. My next inquiry, at the core of this proposal, is then to investigate the upstream signaling activates the TRPC3 channel. G-Protein Coupled Receptors, including the Angiotensin Type 1 Receptor (AT1R), have garnered substantial attention in pressure-induced signaling as potential mechanosensitive receptors. My preliminary work demonstrates that ligand activation of AT1R also contracts ACT pericytes, and interestingly, in a TRPC3 channel dependent manner. To investigate this AT1R to TRPC3 channel signaling cascade, Aim 1 focuses on AT1R- generated ligand activation of the TRPC3 channel in native capillary pericytes using a whole cell patch clamp electrophysiology approach. Aim 2 investigates the mechanosensitivity and engagement of AT1R in pericyte pressure-induced constriction through a multimodal approach, including whole cell patch clamp electrophysiology, ex-vivo pressure myography diameter measurements, sharp microelectrode electrophysiology, and in vivo vessel network interrogation with two photon scanning laser microscopy. Completion of this proposal will fill a significant knowledge gap in mechanistic signaling processes in pericyte contractility. With a greater understanding of pericyte reactivity, the pericyte control of capillary blood flow can be more specifically targeted to prevent hypoperfusion of cerebral tissue. Focusing on preserving capillary blood flow in diseases such hypertension can provide a novel approach to preserve cognitive health in an effort to delay the devastating and irreversible effects of dementia.