Localized TRPA1 channel Ca ²⁺ signals stimulated by reactive oxygen species promote cerebral artery dilation

Abstract

Reactive oxygen species (ROS) can have divergent effects in cerebral and peripheral circulations. We found that Ca2+-permeable transient receptor potential ankyrin 1 (TRPA1) channels were present and colocalized with NADPH (reduced form of nicotinamide adenine dinucleotide phosphate) oxidase 2 (NOX2), a major source of ROS, in the endothelium of cerebral arteries but not in other vascular beds. We recorded and characterized ROS-triggered Ca2+ signals representing Ca2+ influx through single TRPA1 channels, which we called “TRPA1 sparklets.” TRPA1 sparklet activity was low under basal conditions but was stimulated by NOX-generated ROS. Ca2+ entry during a single TRPA1 sparklet was twice that of a TRPV4 sparklet and ~200 times that of an L-type Ca2+ channel sparklet. TRPA1 sparklets representing the simultaneous opening of two TRPA1 channels were more common in endothelial cells than in human embryonic kidney (HEK) 293 cells expressing TRPA1. The NOX-induced TRPA1 sparklets activated intermediate-conductance, Ca2+-sensitive K+ channels, resulting in smooth muscle hyperpolarization and vasodilation. NOX-induced activation of TRPA1 sparklets and vasodilation required generation of hydrogen peroxide and lipid-peroxidizing hydroxyl radicals as intermediates. 4-Hydroxy-nonenal, a metabolite of lipid peroxidation, also increased TRPA1 sparklet frequency and dilated cerebral arteries. These data suggest that in the cerebral circulation, lipid peroxidation metabolites generated by ROS activate Ca2+ influx through TRPA1 channels in the endothelium of cerebral arteries to cause dilation.

Nitric Oxide–Dependent Feedback Loop Regulates Transient Receptor Potential Vanilloid 4 (TRPV4) Channel Cooperativity and Endothelial Function in Small Pulmonary Arteries

“…Previous studies of endothelial Ca 2+ signals have demonstrated that localized Ca 2+ signals predominantly activate IK and SK channels to cause vasodilation in small systemic arteries including mesenteric, cremaster, and cerebral arteries 1, 2, 3, 4, 56. In small PAs, TRPV4 sparklets preferentially activated eNOS to cause vasodilation.…”

Lipids as central modulators of sensory TRP channels

“…It has been shown that oxidative degradation of membrane lipids is increased in the vascular wall during hypertension and TRPA1 activity is enhanced. This augmented activity is protective against hemorrhagic stroke associated with hypertension [176]. TRPA1 is also activated by ω-3 PUFAs such as DHA which could partially explain the important role of dietary assumption of these fatty acid in cardio-and cerebrovascular disease management.…”

CaMKII regulates intracellular Ca2+ dynamics in native endothelial cells

“…Similar to Ca 2+ pulsars, Ca 2+ wavelets have been reported in skeletal muscle arteries [16]. More recently, a spatially restricted Ca 2+ influx through plasma membrane ion channels, TRPV4-and TRPA1-sparklets, has been reported with an elegant demonstration of the requirement of intracellular scaffolding for cellular function [12,14,16]. These investigations emphasize the need for a better understanding of the regulatory mechanisms of confined Ca 2+ dynamics.…”

“…Thus, localized Ca 2+ events such as Ca 2+ pulsars, Ca 2+ wavelets, TRPV4-and TRPA1-sparklets have recently been characterized and are suggested to regulate vascular tone [12][13][14][15][16]. Early work on Ca 2+ pulsars reported a spontaneous Ca 2+ release from IP 3 -sensitive stores within myoendothelial projections (MEP) in mesenteric resistance arteries [15].…”

“…Although endothelial functions governed by Ca 2+ have been extensively studied, endothelial Ca 2+ homeostasis has mainly been investigated from a global cytoplasmic perspective [8][9][10][11]. Interestingly, an increasing body of evidence suggests that localized Ca 2+ dynamics might actually be a critical player in the modulation of endothelial functions [12][13][14].…”