Enhancing endothelial cell signaling in resistance arteries to reverse vasospasm

抄録

Endothelial cell dysfunction is a ubiquitous feature of cardiovascular disease, associated with enhanced vasoreactivity, or vasospasm. This increased vasoreactivity is due to loss of ability to generate nitric oxide (NO) and endothelial cell hyperpolarization (EDH). The possibility that altering endothelial function may prevent the development of vasospasm was studied here.

The vasoreactivity of rat small mesenteric resistance arteries was assessed with wire myography and analyzed with a bespoke MATLAB script, to quantify vasoconstriction/vasodilation using Fourier transform with power spectra analysis. Arterial vasomotion, reflecting normal vasoreactivity, was evoked by vasoconstriction to the a1- adrenoceptor agonist phenylephrine. Vasomotion presented as symmetrical cycles of vasoconstriction/vasorelaxation (0.2Hz, signal to noise (S/N) ratio=0.87, n=18). Rat coronary arteries were utilized to study spontaneous myogenic tone development.

Vasomotion was disrupted by the NO synthase inhibitor, 100uM L-NAME (0.07Hz/0.55, n=13), the sGC inhibitor 10uM ODQ (0.08Hz/0.50, n=11) or by endothelial cell removal (0.02Hz/0.37, n=5). Loss of vasomotion with L-NAME could be reversed by the NO donor, 2uM SNOG (0.2Hz/0.80, n=11) or the direct sGC stimulator, 1uM BAY 41-2272 (0.2Hz/0.84, n=5). SNOG failed to re-establish vasomotion in the presence of ODQ/after endothelium removal. Spontaneous myogenic tone in coronary arteries (22% +/- 3 of maximum constriction) was augmented upon addition of L-NAME (78% +/- 6 of maximum constriction). This increase was reversed with NNC 55-0396, a T-type Ca2+ channel inhibitor, to 23% +/- 4 of maximum constriction. Further addition of nifedipine fully relaxed the arteries.

These data indicate endothelium-derived NO facilitates vasomotion via cGMP-dependent mechanisms. Waveform analysis highlighted differences between chemical block of NO synthesis and removal of the endothelium. The former was associated with vasospasm interspersed by vasodilation, probably due to intercellular feedback via endothelial potassium channels and EDH. Sustained vasospasm was observed in denuded arteries, which lack this signaling circuit. These data show a physiological profile of vasoreactivity can be re-established by enhancing cGMP-signaling. Data collected from myogenically active vessels suggests that T-type channels are responsible for enhanced vasoreactivity but not myogenic tone. Defining the cellular pathways responsible for the loss of vasomotion and increased vasoreactivity may suggest potential targets to address the vasospasm associated with endothelial dysfunction.