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Objective:The plant polyphenol resveratrol(3,4',5-trihydroxystilbene)(RSV)has been proposed for use because of its protective effect on ultraviolet(UV)-induced skin disorders.In UVB-induced skin damage,cell autophagy and apoptosis have been approved to prevent the damage and to contribute to the cytoprotective role of RSV;however,the detailed mechanism remains unknown.So,we conducted this study to investigate the cytoprotective effects of RSV on UVB-irradiated human epidermal keratinocytes(HEKs)and its undergoing mechanisms.Methods:Secretion of thirty-six inflammatory cytokines of HEKs induced by 50mJ/cm2 UVB at 0,12,24,and 48 hours were detected by a human cytokine assay and the interleukin(IL)-8 protein level in the culture media were determined by ELISA.Next,HEKs were treated with or without 100 μmol/L RSV in the presence or absence of 50 mJ/cm2 UVB,and activator protein 1 and NF-κB-related proteins were measured by Western blot.Furthermore,cells exposed to UVB radiation were treated with apoptosis activators procaspase-activating compound 1(PAC-1),apoptosis activator 2(AA2)or RSV to investigate the effect of RSV on the percentage of apoptotic cells by flow cytometry.Then cells were treated with autophagy inhibitors LY294002,3-methyladenine(3-MA)or RSV in the presence of UVB and chloroquine(CQ)to investigate the effect of RSV on autophagy through detecting microtubule-associated protein 1 light chain 3(LC3)expression by western blot.Finally,the effect of LY294002,3-MA,ATG5 siRNA,PAC-1,and AA2 on RSV-mediated reduction of IL-8 expression was determined by ELISA assay.Results:RSV treatment decreased the secretion of IL-8(UVB vs.UVB+RSV:[1454.05pg/mL±52.95pg/mL]vs.[553.68 pg/mL±206.03 pg/mL],P＜0.001),and downregulated the protein level of c-Fos in UVB-irradiated HEKs(UVB vs.UVB+RSV:[0.103±0.009]vs.[0.048±0.015],P＜0.01).In UVB-irradiated HEKs,the result of western blot showed that LY294002 and 3-MA inhibited RSV-induced LC3 Ⅱ accumulation(UVB+CQ+RSV vs.UVB+CQ+3-MA+RSV vs.UVB+CQ+LY294002+RSV:[1.15±0.03]vs.[0.77±0.13]vs.[0.67±0.13],P＜0.01),and the result of flow cytometry showed that PAC-1 and AA2 prevented RSV from reducing cell apoptosis(UVB+RSV vs.UVB+PAC-1+RSV vs.UVB+AA2+RSV:[19.56％±0.62％]vs.[94.33％±0.15％]vs.[94.97％±1.91％],P＜0.001).The data of ELSA assay showed that LY294002,3-MA,and ATG5 siRNA reversed the RSV-mediated inhibition of IL-8 protein secretion by UVB-irradiated HEKs(UVB+LY294002 vs.UVB+LY294002+RSV:[3283.00pg/mL±444.05 pg/mL]vs.[1608.58pg/mL±128.42pg/mL],P＜0.05;UVB+3-MA vs.UVB+3-MA+RSV:[2941.88pg/mL±103.80pg/mL]vs.[1867.51 pg/mL±153.84pg/mL],P＜0.01;UVB+sATG5 vs.UVB+siATG5+RSV:[2530.11 pg/mL±685.34pg/mL]vs.[3011.42pg/mL±435.69pg/mL],P＞0.05),whereas neither PAC-1 nor AA2 exerted similar effects.Conclusion:RSV may regulate autophagic flux to inhibit IL-8 expression in UVB-challenged keratinocytes.