Recruitment of dynamic cerebral artery endothelial Ca2+ signals by the TRPA1 channel activator AITC

Abstract

Real‐time regulation of vascular tone by endothelial Ca2+ signals is a crucial determinant of blood flow. Recent findings suggest that transient receptor potential (TRP) channels, particularly TRPA1, may play a key role in activating endothelial Ca2+‐dependent effectors in cerebral arteries to promote acute vasodilation. In the current study, we employed high‐speed confocal imaging and a novel analysis algorithm to evaluate the impact of TRPA1 channel activation on Ca2+ signals in the endothelium of rat cerebral arteries and assess its relationship to vasodilation. We found that endothelial cells of rat cerebral arteries exhibit widespread basal Ca2+ dynamics (44 ± 6 events at 26 ± 3 distinct sites per minute in a 3.6×104 μm2 field). The TRPA1 activator allyl isothiocyanate (AITC) increased Ca2+ signals in a concentration dependent manner, primarily by soliciting new events at distinct sites along the intima (56 ± 5% and 52 ± 4% increase in events and sites, respectively, at 60 μM). These stimulated events corresponded spatially with TRPA1 channel densities within holes in the internal elastic lamina (IEL) and were blocked by the TRPA1‐specific inhibitor HC‐030031. The concentration‐dependent expansion of Ca2+ events in response to AITC correlated precisely with the dilation of pressurized cerebral arteries (p = 0.93 by F‐test comparison of nonlinear regression curve fits). Correspondingly, AITC caused rapid endothelium‐dependent suppression of pro‐contractile asynchronous Ca2+ waves in subintimal smooth muscle cells. The current findings suggest that factors evoking stimulation of TRPA1 channels trigger and expand discrete Ca2+ signal‐effector coupling sites along the endothelium to evoke graded cerebral artery vasodilation. Supported by NIH R01 HL085887 and R01 HL091905.

TRPA1 channels in the vasculature

“…The role of KCa2.3 channels is not completely clear, but these channels may play a secondary role to KCa3.1 channels, or may be important for setting the resting membrane potential of the endothelium (Taylor et al, 2003). This proposed mechanism is supported by recent preliminary results demonstrating increased dynamic Ca 2+ signalling activity in the endothelium of intact cerebral arteries in response to AITC (Taylor et al, 2012).…”