Protective Effect Of Gynura Bicolor On Ultraviolet B Induced Acute Pohotodamage And The Possible Mechanism

Objective To explore the protective effect and possible mechanism of Gynura bicolor(GB)alcohol extract on acute photodamaged human Ha Cat cells and Sprague-Dawley(SD)rat from ultraviolet B(UVB).Methods The antioxidant activities of Gynura bicolor(GB)alcohol extract was detected by DPPH(1,1-diphenyl-2-picrylhydrazyl)method.The cellular activity of Ha Cat cells which were irradiated with different dosages(0m J/cm2、30m J/cm2、 60m J/cm2、90m J/cm2、200m J/cm2)of UVB or were treated with different concentration of GB(0.3125mg/ml、0.625mg/ml、1.25mg/ml、2.5mg/ml、5mg/ml)or were pre-treated with different concentrations of GB(0.3125mg/ml、0.625mg/ml、1.25mg/ml)before irradiating UVB were detected by MTT method.The apoptosis rate of Ha Cat cells which were pre-treated with different concentrations of GB(0.3125mg/ml、0.625mg/ml、1.25mg/ml)before irradiating UVB were determined with flow cytometry.Ha Cat cells were pretreated with different concentrations of GB(0.3125mg/ml、0.625mg/ml、1.25mg/ml)before UVB radiation,the m RNA level of p53,caspase-3,Bax and Bcl-2 in Ha Cat cells were evaluated with RT-PCR method,and protein level of p53,caspase-3,Bax and Bcl-2 in Ha Cat cells were evaluated with Western blot(WB).In vivo,model of photodamaged SD rat were constructed according to the minimum erythema dose(UVB)of SD rats,and the dorsal skin of SD rats were smeared with aqueous solution of GB.The changes of tissue structure in SD rats by HE staining,the expression and distribution of P53 and caspase-3in the skin of SD rats were detected by immunohistochemical method.Statistical analysis was carried out by using factorial design analysis of variance(ANOVA),one-way ANOVA and least significant difference(LSD)test.Results In vitro,DPPH assay showed GB had prominant antioxidant capacity(SC50=19.6mg/ml).UVB irradiation can inhibit Ha Cat cell viability,the degree of inhibition was dose dependent(P <0.01),30 m J / cm2 was the best UVB dose with cell survival rate of 80%.GB concentration greater than 1.25mg/ml would reduce cell activity of Ha Cat.The pretreatment of Ha Cat cells by GB could obviously improve the cell viability after UVB irradiation and increased with the dose of GB.After UVB irradiation,the apoptosis rate of GB treatment group(31.69% ± 5.3%)was significantly increased compared with the normal group(5.67% ± 0.8%)(P <0.01),GB can reduce the apoptosis rate after UVB irradiation,and this reduction was dose dependent of GB.After 30 m J/cm2 UVB irradiation,the m RNA and protein expression of p53、Bax、caspase-3 were increased while Bcl-2 was decreased(P <0.01),and this effect can be reversed by GB with the concentration dependence.In vivo experiments showed that the external application of GB could alleviate the skin injury on the back of SD rats and improve the superficial inflammation of the dermis as well as inhibit the expression of p53(P <0.05)and caspase-3(P<0.05)induced by UVB irradiation.Conclusion Gynura bicolor could protect the acute photodamage of human Ha Cat cells and SD rats from UVB radiation and the possible mechanism may by inhibit p53 mediated Bcl-2 / Bax/casaspe-3apoptosis pathway.