Introduction: We examined the role circadian clock component of Bmal1 in VSMC activation and intima hyperplasia after vascular injury.
Methods: Bmal1 protein expression was evaluated in ligated mouse carotid arteries from C57BL/6J and cultured VSMCs stimulated by platelet-derived growth factor-BB (PDGF-BB) using western blotting. VSMC proliferation was measured using the MTS assay and the manual cell counting.
Results: The mice exhibited marked intimal hyperplasia after the ligation. Western blotting analyses revealed increased Bmal1 protein expression in the freshly isolated aorta after ligation, with significant increase in VSMCs following PDGF-BB treatment. PDGF-BB-induced Bmal1 expression was inhibited through treatment with a NOX inhibitor, diphenyleneiodonium and the MEK inhibitor, U0126. Furthermore, early growth response protein-1 (EGR-1) knockdown significantly reduced Bmal1 expression induced by PDGF-BB. Moreover, Bmal1 knockdown significantly decreased PDGF-BB-induced ERK phosphorylation and cell proliferation.
Conclusions: These data suggest that Bmal1 plays a crucial role in intima hyperplasia after vascular injury through the regulation of VSMC proliferation.