Raphanus sativus and its isothiocyanates inhibit vascular smooth muscle cells proliferation and induce G₁ cell cycle arrest

Mu (Raphanus sativus, Korean White Radish) crude extract (Mu-CE) has been studied for its anti-proliferative activity on mouse aortic smooth muscle cells. The abnormal growth of vascular smooth muscle cells (VSMC) is a prominent feature of vascular disease, including atherosclerosis, restenosis after angioplasty. We examined the mechanisms of the action of Mu-CE on VSMC proliferation. The viability of VSMC decreased to 35% at 24 h of treatment with Mu-CE. Treatment of Mu-CE showed potent inhibitory effects on the DNA synthesis of cultured VSMC. In addition, Mu-CE induced apoptosis using cell death ELISA assay. These inhibitory effects were associated with G₁ cell cycle arrest. Treatment of Mu-CE, which induced a cell-cycle arrest in G ₁-phase, induced down-regulation of cyclins and CDKs and up-regulation of the CDK inhibitor p21 expression, whereas up-regulation of p27 by Mu-CE was not observed. Then, total isothiocyanates (ITC) including four different 4-(Methylthio)-3-butenyl isothiocyanate (MTBITC), allyl isothiocayanate (AITC), benzyl isothiocyanate (BITC), and phenethyl isothiocyanate (PEITC) was isolated from n-hexane extracts of Mu. When the VSMC were treated with ITC, the cell viability was significantly decreased. These findings indicate the efficacy of Mu-CE in inhibiting cell proliferation, G ₁- to S-phase cell-cycle progress on VSMC.