Urotensin II (UII) is a potent vasoactive peptide and mitogenic agent to induce proliferation of various cells including vascular smooth muscle cells (VSMCs). In this study, we examined the effects of a novel UII receptor (UT) antagonist, KR-36676, on vasoconstriction of aorta and proliferation of aortic SMCs. In rat aorta, UII-induced vasoconstriction was significantly inhibited by KR-36676 in a concentration-dependent manner. In primary human aortic SMCs (hAoSMCs), UII-induced cell proliferation was significantly inhibited by KR-36676 in a concentration-dependent manner. In addition, KR-36676 decreased UII-induced phosphorylation of ERK, and UII-induced cell proliferation was also significantly inhibited by a known ERK inhibitor U0126. In mouse carotid ligation model, intimal thickening of carotid artery was dramatically suppressed by oral treatment with KR-36676 (30 mg/ kg/day) for 4 weeks compared to vehicle-treated group. From these results, it is indicated that KR-36676 suppress UII-induced proliferation of VSMCs at least partially through inhibition of ERK activation, and that it also attenuates UII-induced vasoconstriction and vascular neointima formation. Our study suggest that KR-36676 may be an attractive candidate for the pharmacological management of vascular dysfunction.
Keywords: ERK; KR-36676; Proliferation; Smooth muscle; Urotensin II; Urotensin II receptor antagonist.