Effect of calcitonin gene-related peptide on myocardin expression and phenotypic switch in vascular smooth muscle cells

AIM: To investigate the effects of calcitonin gene-related peptide (CGRP) on myocardin expression and phenotypic switch in vascular smooth muscle cells (VSMCs). METHODS: VSMCs were obtained by aortic tissue adherent culture and treated with angiotensin Ⅱ (AngⅡ), AngⅡ + CGRP or AngⅡ + CGRP + CGRP_8-37. The protein expression of myocardin and the phenotypic proteins of the VSMCs was detected by Western blot. RESULTS: The expression of myocardin in cultured VSMCs showed downregulation along with time expansion. The protein level of myocardin was higher at 48 h and 72 h than that at baseline in the cultured VSMCs (P<0.05). However, the myocardin was lower at 48 h and 72 h than that at baseline after treatment with CGRP in cultured VSMCs (P<0.05). Furthermore, at 48 h in cultured VSMCs, the myocardin decreased along with α-smooth muscle actin (α-SMA) (P<0.05), and osteopontin (OPN) increased (P<0.05) in AngⅡ group compared with control group. After treatment with CGRP, the levels of myocardin and α-SMA become higher (P<0.05) but OPN was lower (P<0.05) in CGRP group than those in AngⅡ group. CGRP_8-37 abrogated CGRP-induced increase in myocardin and α-SMA and decrease in OPN in CGRP_8-37 group compared with CGRP group. CONCLUSION: CGRP may regulate the phenotypic switch of the VSMCs and maintain the cells in contractile phenotype through the upregulation of myocardin protein, which may be accomplished by the combination of CGRP and its receptor.