Cardiology Letters 2014, 23(6):397-404

The effect of oxidative stress on acetylcholine-induced relaxation in deendothelized arteries

Berényiová A, Kristek F, Dovinová I, Drobná M, Čačányiová S

Ústav normálnej a patologickej fyziológie SAV, Bratislava, Slovenská republika

Aim: Nitric oxide (NO) participates in the local control of the cardiovascular system, causing dilation of smooth muscle cells in the vascular wall. NO production is realized via endothelial cells in response to vasorelaxants (such as acetylcholine). The endothelial layer was regarded as the primary source of NO: however, it was found that the smooth muscle cells of endothelium-denuded arteries expressed functional NO synthase and are capable of production. We hypothesized that the destruction of the anatomical integrity induced by mechanical denudation of endothelial layer induces an insensibility of vessels to the vasodilators as a consequence of oxidative stress. The aim of this study was to investigate whether the loss of acetylcholine-induced vasorelaxation in endothelium-denuded arteries could be induced by a decrease in a non-endothelial NO, as a consequence of oxidative stress.

Methods: Vasorelaxant responses were followed in arteries (thoracic aorta, pulmonary artery) isolated from male Wistar rats. The production of superoxide radicals was measured using a lucigenin chemiluminescence method in endothelium-preserved and endothelium-denuded arteries.

Results: While an acetylcholine-induced vasorelaxation was observed in all arteries with intact endothelium, this effect was inhibited in deendothelized rings. Acute application of tempol, a free-radical scavenger, refreshed the inhibited acetylcholine vasorelaxation in endothelium-denuded arteries. The following application of 1H-[1,2,4]oxadiazolo[4,3-α]quinoxalín-1-one (ODQ), a guanylate cyclase inhibitor, and/or NG-nitro-L-arginine methylester (L-NAME), an inhibitor of NO-synthase, blocked the benefical effect of tempol. Chemiluminescent assay showed that an injury to the endothelial layer increased the production of superoxide radicals which was decreased after tempol administration.

Conclusions: This study showed that the inhibition of vasorelaxation in deendothelized arteries could be a consequence of oxidative stress which eliminated the non-endothelial source of NO. The findings confirmed that the non-endothelial source of NO represented a reserve source of active NO and challenged the concept of the obligatory role of endothelial cells in vasorelaxation.

Keywords: vasorelaxation; nitric oxide; endothelial denudation; oxidative stress; acetylcholine; superoxid dismutase; NG-nitro-L-arginine methylester

Published: June 1, 2014  Show citation