Green tea polyphenol (-)-epigallocatechin-3-gallate treatment of human skin inhibits ultraviolet radiation-induced oxidative stress

The use of naturally occurring botanicals with substantial antioxidant acti vity to afford protection to human skin against UV damage is receiving incr easing attention, The green tea constituent (-)-epigallocatechin-3-gallate (EGCG) is a potent antioxidant and has shown remarkable preventive effects against photocarcinogenesis and phototoxicity in mouse models, In this stud y we have investigated the effects of topical application of EGCG, the majo r polyphenol present in green tea, to human skin before UV irradiation on U V-induced markers of oxidative stress and antioxidant enzymes, Using immuno histochemistry and analytical enzyme assays, we found that application of E GCG (similar to1 mg/cm(2) skin) before a single UV exposure of 4x minimal e rythema dose (MED) markedly decreases UV-induced production of hydrogen per oxide (68-90%, P < 0.025-0.005) and nitric oxide (30-100%, P < 0.025-0.005) in both epidermis and dermis in a time-dependent manner. EGCG pretreatment also inhibits UV-induced infiltration of inflammatory leukocytes, particul arly CD11b(+) cells (a surface marker of monocytes/macrophages and neutroph ils), into the skin, which are considered to be the major producers of reac tive oxygen species. EGCG treatment was also found to inhibit UV-induced ep idermal lipid peroxidation at each time point studied (41-84%, P < 0.05). A single UV exposure of 4x MED to human skin was found to increase catalase activity (109-145%) and decrease glutathione peroxidase (GPx) activity (36- 54%) and total glutathione (GSH) level (13-36%) at different time points st udied. Pretreatment with EGCG was found to restore the UV-induced decrease in GSH level and afforded protection to the antioxidant enzyme GPx. Further studies are warranted to study the preventive effects of EGCG against mult iple exposures to UV light of human skin.