Inhibitory effects of [6]-gingerol on PMA-induced COX-2 expression and activation of NF-kappaB and p38 MAPK in mouse skin

[6]-Gingerol, a major pungent ingredient of ginger (Zingiber officinale Roscoe, Zingiberaceae), has a wide array of pharmacologic effects. Previous studies have demonstrated that [6]-gingerol inhibits mouse skin tumor promotion and anchorage-independent growth of cultured mouse epidermal cells stimulated with epidermal growth factor. Cyclooxygenase-2 (COX-2), a key enzyme in the prostaglandin biosynthesis, has been recognized as a molecular target for many anti-inflammatory as well as chemopreventive agents. Topical application of [6]-gingerol inhibited phorbol 12-myristate 13-acetate -induced COX-2 expression. One of the essential transcription factors responsible for COX-2 induction is NF-kappaB. [6]-Gingerol suppressed NF-kappaB DNA binding activity in mouse skin. In addition, [6]-gingerol inhibited the phoshorylation of p38 mitogen-activated protein kinase which may account for its inactivation of NF-kappaB and suppression of COX-2 expression.