Abstract
In this study, the effects of combining ursolic acid + resveratrol, for possible combined inhibitory effects on skin tumor promotion, were evaluated. Ursolic acid, resveratrol, and the combination of ursolic acid + resveratrol were applied topically prior to 12-O-tetracanoylphorbol-13-acetate (TPA) treatment on mouse skin to examine their effect on TPA-induced signaling pathways, epidermal hyperproliferation, skin inflammation, inflammatory gene expression, and skin tumor promotion. The combination of ursolic acid + resveratrol produced a greater inhibition of TPA-induced epidermal hyperproliferation. The combination of ursolic acid + resveratrol inhibited TPA-induced signaling pathways, including EGFR, STAT3, Src, Akt, Cox-2, Fas, NF-κB, p38 MAPK, c-Jun, and JNK1/2 while increasing levels of tumor suppressors, such as p21 and PDCD4, to a greater extent compared with the groups treated with the individual compounds. Ursolic acid + resveratrol also induced a dramatic increase of p-AMPK-α(Thr172). Combined treatment with ursolic acid + resveratrol resulted in a greater inhibition of expression of proinflammatory cytokines, including Il1a, Il1b, and Il22. Furthermore, NF-κB, Egr-1, and AP-1 DNA binding activities after TPA treatment were dramatically decreased by the combination of ursolic acid + resveratrol. Treatment with ursolic acid + resveratrol during skin tumor promotion with TPA produced greater inhibition of tumor multiplicity and tumor size than with either agent alone. Collectively, the greater ability of the combination of ursolic acid + resveratrol to inhibit skin tumor promotion was due to the greater inhibitory effects on growth factor and inflammatory signaling, skin inflammation, and epidermal hyperproliferation induced by TPA treatment.