Orange peel extract, containing high levels of polymethoxyflavonoid, suppressed UVB-induced COX-2 expression and PGE2 production in HaCaT cells through PPAR-γ activation

Ultraviolet light (UV) induces an inflammatory response in the skin by cyclooxygenase (COX)-2 expression and prostaglandin (PG) E-2 production. Citrus peel has been used as a natural medicine. It contains polymethoxyflavonoids (PMFs) as a major ingredient, which have anti-inflammatory activity. We obtained orange peel extract containing high levels of PMFs. The extract suppressed UVB-induced COX-2 expression and PGE(2) production in HaCaT cells. Furthermore, it was found that this extract acted as a peroxisome proliferator-activated receptor (PPAR)- agonist. The suppression of UVB-induced COX-2 expression by this extract was inhibited by GW 9662 and T0070907, which are both PPAR- antagonists. It is therefore suggested that orange peel extract, containing high levels of PMFs, suppresses UVB-induced COX-2 expression and PGE(2) production through PPAR-. Hence, these extracts could provide useful protection against or alleviation of UV damage.