Role of PKC in the novel synergistic action of urotensin II and angiotensin II and in urotensin II-induced vasoconstriction

1 Department of Physiology and Pathophysiology, Shanghai Medical College, and 2 Department of Pharmacology, School of Pharmacy, Fudan University, Shanghai, People's Republic of China; and 3 Department of Pharmacology, National University of Singapore, Singapore Submitted 19 May 2006 ; accepted in final form 25 August 2006 The intracellular signaling of human urotensin II (hU-II) and its interaction with other vasoconstrictors such as ANG II are poorly understood. In endothelium-denuded rat aorta, coadministration of hU-II (1 nM) and ANG II (2 nM) exerted a significant contractile effect that was associated with increased protein kinase C (PKC) activity and phosphorylation of PKC- / II and myosin light chain, whereas either hU-II or ANG II administered alone at these concentrations had no statistically significant effect. This synergistic effect was abrogated by the PKC inhibitor chelerythrine (10 and 30 µM), the selective PKC- / II inhibitor Gö-6976 (0.1 and 1 µM), the hU-II receptor ligand urantide (30 nM and 1 µM), or the ANG II antagonist losartan (1 µM). Moreover, in endothelium-intact rat aorta, the synergistic effect of hU-II and ANG II was not exerted any longer, and this synergistic effect was unmasked by pretreatment of the nitric oxide synthase inhibitor N G -nitro- L -arginine methyl ester. hU-II (10 nM) alone caused a long-lasting increase in phospho-PKC- , phospho-myosin light chain, and PKC activity, which was associated with long-lasting vasoconstriction. These changes were prevented by chelerythrine. Methoxyverapamil-thapsigargin treatment reduced the hU-II-induced vasoconstriction by 50%. The methoxyverapamil-thapsigargin-resistant component of hU-II-induced vasoconstriction was dose-dependently inhibited by chelerythrine. In conclusion, hU-II induces a novel PKC-dependent synergistic action with ANG II in inducing vasoconstriction. PKC- / II is probably the PKC isoform involved in this synergistic action. Nitric oxide produced in the endothelium probably masks this synergistic action. The long-lasting vasoconstriction induced by hU-II alone is PKC dependent and associated with PKC- phosphorylation. protein kinase C; vascular smooth muscle cells Address for reprint requests and other correspondence: Y.-C. Zhu, Dept. of Physiology and Pathophysiology, Fudan Univ. Shanghai Medical College, 138 Yi Xue Yuan Road, Shanghai 200032, People's Republic of China (e-mail: yczhu{at}shmu.edu.cn )