The Effects Of Urotensin â…¡ On Migration, Proliferation, Phenotypic Conversion And Its Mechanism Of Adventitial Fibroblasts

Background: Urotensin II (UII) is a cyclic somatostatin-like neuropeptide originally isolated from fish urophysis, Its potency of vasoconstriction is of a greater magnitude than that of endothelin 1 (ET-1), making UII the most potent mammalian vasoconstrictor. UII isopeptides are widely distributed in a diverse spectrum of evolutionary level from gastropod to human. The specific receptor of UII, GPR14, now known as UTreceptor (UT), has been identified from human being.UII exhibits many physiological actions, such as stimulating proliferation of human endothelial cells, VSMCs and cardiac fibroblasts, increasing production of collagen I and III, and fibronectin in cardiac fibroblasts, as well as inducing hypertrophic responses in cardiomyocytes from neonatal rat in vitro. It suggests that UII may bring into full play in vascular remodeling. However, little is known about its effect on adventitial fibroblasts (AFs) activation.Objective: To explore the UII effects on phenotypic differentiation, migration and collagen I synthesis of rat aortic AFs.Methods: Growth-arrested AFs were incubated in serum-free medium with UII and some inhibitors of signal transduction pathways. Theα-SM-actin (α-SMA) expression, collagen I synthesis and migration of AFs induced by UII were evaluated by Western blotting, ELISA, and transwell technique, respectively.Results: UII induced theα-SMA expression in a dose- and time-dependent manner, with a maximal effect at a concentration of 10-8M at 24 h (79.9%); it also caused a dose- dependent increase of collagen I synthesis with a maximal effect at a concentration of 10-7M (42.6%). The Ca2+ channel blocker nicardipine (10-5M), protein kinase C (PKC) inhibitor H7 (10-5M), Rho protein kinase inhibitor Y-27632 (10-5M), calcineurin inhibitor cyclosporine A (CSA, 10-5M) and mitogen-activated protein kinase (MAPK) inhibitor PD98059 (10-5M), could inhibit UII-induced increases ofα-SMA expression and collagen synthesis. Meanwhile, UII stimulated the AFs migration dose-dependently with a maximal effect at a concentration of 10-8M by 4.7 times over the control. This effect could also be inhibited by PD98059, H7, CSA and Y-27632 but nicardipine.Conclusion: UII may stimulate AFs phenotypic conversion, migration, and collagen I synthesis via the PKC, MAPK, calcineurin, Rho kinase and /or Ca²⁺ signal transduction pathways, contributing to the development of vascular remodeling through AFs activation.