Abstract
Ochnaflavone (c‐3 of apigenin‐0‐c‐4 of apigenin; OC), a biflavonoid present in the human diet, is known to inhibit angiotensin II‐induced hypertrophy and serum‐induced smooth muscle cell proliferation. OC is known to have anti‐fungal and anti‐inflammatory activities. However, it is not known whether OC exerts similar cardioprotective effects in cells treated with tumor necrosis factor (TNF)‐α. In this study, we isolated OC from Lonicera japonica and studied its effect on matrix metalloproteinase‐9 (MMP‐9) gene expression in human aortic smooth muscle cells (HASMC). Furthermore, we investigated whether OC exerts the multiple suppressive effects on cytokine TNF‐α‐induced HASMC. Treatment of OC showed its potent inhibitory effects on DNA synthesis of cultured HASMC in the presence of TNF‐α. These inhibitory effects were associated with reduced extracellular signal‐regulated kinase 1/2 (ERK1/2) activity and G1 cell cycle arrest. Treatment of OC, which induced a cell cycle block in G1‐phase, induced downregulation of cyclins and CDKs and upregulation of the CDK inhibitor p21^waf1^ expression, whereas upregulation of p27 or p53 by OC was not observed. Because anti‐atherogenic effects need not be limited to anti‐proliferation, we decided to examine whether OC exerts inhibitory effects on MMP‐9 activity in TNF‐α‐induced HASMC. OC inhibited TNF‐α‐induced MMP‐9 secretion on HASMC in a dose‐dependent manner. This inhibition was characterized by downregulation of MMP‐9, which was transcriptionally regulated at nuclear factor (NF)‐κB site and activation protein (AP)‐1 site in the MMP‐9 promoter. These findings indicate the efficacy of OC in inhibiting cell proliferation, G1 to S‐phase cell cycle progress, and MMP‐9 expression through the transcription factors NF‐κB and AP‐1 on TNF‐α‐induced HASMC. The findings of the present study may provide a potential mechanism that explains the anti‐atherogenic activity of OC. J. Cell. Biochem. 99: 1298–1307, 2006. © 2006 Wiley‐Liss, Inc.