Abstract
The abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) is a crucial event in the development of atherosclerosis, and tumor necrosis factor-α (TNF-α) is actively involved in this process by enhancing the proliferation and migration of VSMCs. 2-Methoxycinnamaldehyde (MCA) is a natural compound of Cinnamomum cassia. Although 2-hydroxycinnamaldehyde (HCA), another compound from Cinnamomum cassia, has been widely studied with regard to its antitumor activity, MCA has not attracted researchers' interest due to its mild toxic effects on cancer cells and its mechanisms of action remain unknown. In this study, we examined the effects of MCA on the TNF-α-induced proliferation and migration of human aortic smooth muscle cells (HASMCs). As shown by our results, MCA inhibited TNF-α-induced cell proliferation by reducing the levels of cyclin D1, cyclin D3, CDK4 and CDK6, and increasing the levels of the cyclin-dependent kinase inhibitors, p21 and p27, without resulting in cellular cytotoxicity. Furthermore, MCA decreased the level of secreted matrix metalloproteinase (MMP)-9 by inhibiting MMP-9 transcription. Unexpectedly, MCA did not affect the TNF-α-induced levels of mitogen-activated protein kinases (MAPKs). However, by showing that MCA potently inhibited the degradation of IκBα and the subsequent nuclear translocation of nuclear factor-κB (NF-κB), we demonstrated that MCA exerts its effects through the NF-κB signaling pathway. MCA also effectively inhibited platelet-derived growth factor (PDGF)-induced HASMC migration. Taken together, these observations suggest that MCA has the potential for use as an anti-atherosclerotic agent.