Essential Role of Store-Operated Calcium Entry in Urotensin-Ii Induced Vascular Smooth Muscle Cells Proliferation

Urotensin-II (U-II) is a vasoactive peptide with many effects in the cardiovascular system. It has been described that U-II promotes vascular smooth muscle cell (SMC) proliferation and migration. However, its signalling pathway remains unclear. The aim of this study is to determine the role of store-operated Ca2+ entry (SOCE) and the activation of cAMP response element-binding (CREB) transcription factor in U-II evoked SMC proliferation. We used 5-bromo-2-deoxyuridine (Brdu), and immunofluorescence assays to determine SMC proliferation. Ca2+ imaging experiments were performed to study Ca2+ entry in cultured SMC isolated from thoracic rat aorta.Our results show that U-II (100 nM) evokes Ca2+ and Mn2+ entry that was significantly reduced by SOCE inhibitors Gadolinium (10 µM) and 2-aminoethyl diphenylborinate (2APB, 75 µM). Moreover, U-II promotes dose dependent SMC proliferation, reaching maximum effect with 100 nM concentration. This event was significantly abolished by SOCE inhibition with 2APB (75 µM). Furthermore, RNA silencing of the new players of SOCE, Stim1 and Orai1, inhibited Ca2+ entry induced by UII in SMC, and effectively prevented SMC proliferation. On the other hand, we have determined that U-II promotes the phosphorylation of CREB and its translocation into cell nucleus. P-CREB activation was also sensitive to SOCE inhibitors.In conclusion, our data demonstrate an essential role of Ca2+ entry through Stim1 and Orai1 dependent SOCE pathway and CREB activation in U-II induced vascular SMC proliferation.Acknowledgements: This study was supported by Red Cardiovascular RECAVA and Instituto Carlos III (RD06-0014-0020; PS09-02287) and from the Government of Andalucia by Consejeria de Innovacion, Ciencia y Empresa de la Junta de Andalucia (P08-CVI-3913; P09-CTS-4715).