Recruitment of Dynamic Endothelial Ca2+ Signals by the TRPA1 Channel Activator AITC in Rat Cerebral Arteries

Abstract

Stimulation of endothelial TRP channels, specifically TRPA1, promotes vasodilation of cerebral arteries through activation of Ca2+ -dependent effectors along the myoendothelial interface. However, presumed TRPA1-triggered endothelial Ca2+ signals have not been described. We investigated whether TRPA1 activation induces specific spatial and temporal changes in Ca2+ signals along the intima that correlates with incremental vasodilation. Confocal imaging, immunofluorescence staining, and custom image analysis were employed. We found that endothelial cells of rat cerebral arteries exhibit widespread basal Ca2+ dynamics (44 ± 6 events/minute from 26 ± 3 distinct sites in a 3.6 × 10(4) μm2 field). The TRPA1 activator AITC increased Ca2+ signals in a concentration-dependent manner, soliciting new events at distinct sites. Origination of these new events corresponded spatially with TRPA1 densities in IEL holes, and the events were prevented by the TRPA1 inhibitor HC-030031. Concentration-dependent expansion of Ca2+ events in response to AITC correlated precisely with dilation of pressurized cerebral arteries (p = 0.93 by F-test). Correspondingly, AITC caused rapid endothelium-dependent suppression of asynchronous Ca2+ waves in subintimal smooth muscle. Our findings indicate that factors that stimulate TRPA1 channels expand Ca2+ signal-effector coupling at discrete sites along the endothelium to evoke graded cerebral artery vasodilation.