Cyclooxygenase-dependent vasoconstricting factor(s) in remodelled rat femoral arteries

Aims: Denudation and regeneration of the vascular endothelium are important in the pathogenesis of atherosclerosis. The aim of this study is to clarify the mechanisms of functional alterations in remodelled arteries following endothelial injury. Methods and results: Non-mechanical endothelial injury was induced by 540-nm light irradiation of rose Bengal in femoral arteries of Wistar rats. Endothelium-dependent vasodilation was assessed by the response to acetylcholine (ACh) 1, 2, and 4 weeks after the injury. In control arteries, ACh-induced relaxation was mainly nitric oxide-dependent at all study time points. In injured arteries, this response was completely restored at 1 week, but was more dependent on KCl-sensitive endothelium-derived hyperpolarizing factor production during the first 2 weeks. Cyclooxygenase (COX) isoforms 1 and 2 were detected in the endothelium of injured arteries, and inhibition of prostanoids production with the non-specific COX inhibitor indomethacin substantially enhanced the ACh-induced vasorelaxation response in injured arteries, but did not affect control arteries. Similar effects were observed with the COX-1 inhibitor SC-560, the COX-2 inhibitor NS-398, the thromboxane (TX) A₂/prostaglandin (PG) H₂ receptor antagonist SQ29548 and the PGF_2α receptor antagonist AL-8810. However, the TX synthetase inhibitor OKY-046 had no effect on ACh-induced relaxation in injured arteries. Conclusion: In remodelled arteries following photochemical endothelial injury, the vasoconstrictive prostanoids PGH₂ and PGF _2α, but not TXA₂, contribute to changes in endothelium-dependent vascular response via COX-1- and 2-dependent pathways.