Diol- and triol-type ginseng saponins potentiate the apoptosis of NIH3T3 cells exposed to methyl methanesulfonate.

In this study we investigated the effect of ginseng saponins on the p53-dependent apoptosis in NIH3T3 cells exposed to methyl methanesulfonate (MMS), an alkylating agent. Trypan blue exclusion assay, cell morphology studies, and apoptotic index determined by acridine orange staining showed that the postincubation of MMS-exposed cells in medium containing diol- (PD) or triol-type (PT) ginseng saponins potentiate the apoptotic cell death. FACS analysis indicated that the increased apoptotic cell population in the saponin-postincubation group was accompanied by the accumulation of cells in G0/G1 phase. By Western blot analyses it was demonstrated that postincubation of saponins increases the expression of p53 and p21 in MMS-exposed cells but decreased that of CDK2, cyclin E and D1, and PCNA. The upregulation of p53 and p21 and downregulation of CDK2 was shown to be p53-dependent in experiments using the p53 antisense oligonucleotide. These results suggest that ginseng saponins contain components potentiating the apoptosis of MMS-exposed NIH3T3 cells via p53 and p21 activation, accompanied with by downregulation of cell cycle-related protein expression.