Effects of ginsenoside Rg2 on the ultraviolet B-induced DNA damage responses in HaCaT cells

Abstract

Our previous study demonstrated the increase in the repair of UVB damage by mRg2, a mixture of ginsenosides containing 60% Rg2 in NIH3T3 cells. In the present study, the effects of purified Rg2 on the repair and apoptosis in ultraviolet B (UVB)-exposed HaCaT cells were investigated on gene expression levels. When cells were exposed to UVB and post-incubated in normal medium for 24 h, the cell viability decreased to about 50% of that in nontreated control. When Rg2 was post-incubated, however, the UVB-induced cytotoxicity was significantly prevented in an Rg2 concentration- and time-dependent manner. The apoptotic nuclear fragmentation resulting from UVB exposure was also significantly protected by the Rg2 post-incubation. Microarray analysis showed that the genes stimulated by the Rg2-alone treatment include those involved in p53 signaling pathway such as GADD45alpha, GADD45beta, and cell communication genes. RT-PCR analysis showed that the Rg2-alone treatment slightly upregulated the p53 and GADD45 transcript and protein levels by about 1.5-fold as compared with the nontreated control. The mRNA levels of p53 and GADD45 in cells exposed to UVB and post-incubated with Rg2 for 24 h decreased in an Rg2 concentration-dependent manner as compared with that post-incubated in normal medium. However, the mRNA level of the UVB-exposed cells post-incubated with 5 microM retinol was essentially the same as that post-incubated in normal medium. Time course experiment showed that the mRNA levels of p53 and GADD45 in UVB-exposed cells were upregulated by post-incubation with 50 microM Rg2 until 6 and 9 h, respectively, and then gradually decreased until 24 h. By Western blot analysis, it was also revealed that the Rg2 post-incubation decreases the expression of p53, phospho-p53, GADD45, and ATM in UVB-exposed cells. Time course analysis also indicated that these decreased expressions were due to the earlier upregulation of p53 and GADD45 proteins. When UVB-exposed cells were post-incubated with Rg2 for 24 h after UVB exposure, the level of remaining cyclobutane pyrimidine dimers decreased in both Rg2 concentration- and time-dependent manner. All these results suggest that Rg2 protects cells against UVB-induced genotoxicity by increasing DNA repair, in possible association with modulation of protein levels involved in p53 signaling pathway.

Protective effects of Rg2 against UVB-induced DNA damage in HaCaT cells is dependent on p53 expression

“…Our previous studies have suggested that these decreases are associated with the repair of the UVB-induced DNA damage accompanied by the accelerated p53 and GADD45 expression at earlier time periods (Jeong et al 2007;Ha et al 2010). In the present study, we also observed the Rg2-mediated protection from UVB damage in control siRNA-transfected cells, but not in p53 knockdown cells (Figures 2-5).…”

Effect of Korean Red Ginseng Extract on Cell Death Responses in Peroxynitrite-Treated Keratinocytes

“…The up-regulation of p53 signalling intermediates, including GADD45, has been reported in human promyelocytic leukemia cells exposed to volatile organic compounds, such as benzene and toluene, suggesting that the responses of p53 pathways to genotoxic and non-genotoxic agents are disparate and complex [33]. A number of small molecules that act upstream of p53 or target the p53 protein itself to rescue p53 function have been identified recently [34].…”

Ginsenoside Rb1, Rg1 and three extracts of traditional Chinese medicine attenuate ultraviolet B‐induced G1 growth arrest in HaCaT cells and dermal fibroblasts involve down‐regulating the expression of p16, p21 and p53

“…Postincubation of the UVB-exposed cells in a medium containing ginsenoside Rg2 significantly reduced UVB-induced DNA damage responses in HaCaT cells (34). Obvious protective effects of ginsenoside Rg1 and Rb1 can be observed against UVB radiation-induced HaCaT cells' nucleolus damage (14).…”