Polyphenolic antioxidant (-)-epigallocatechin-3-gallate from green tea reduces UVB-induced inflammatory responses and infiltration of leukocytes in human skin

Identification of natural products capable of affording protection against UVB radiation-induced inflammatory responses and generation of oxidative st ress may have important human health implications. The UVB exposure-induced skin injury and oxidative stress has been associated with a variety of ski n disease conditions including photoaging, inflammation and cancer. Tea is a popular beverage consumed worldwide. In several mouse skill models, topic al application as well as oral consumption of green tea has been shown to a fford protection against chemical and UVB-induced carcinogenesis and inflam matory responses. In the present study, we investigated in human skin, whet her topical application of (-)-epigallocatechin-3-gallate (EGCG), the major polyphenolic constituent in green tea, inhibits UVB-induced infiltration o f leukocytes (macrophage/neutrophils), a potential source of generation of reactive oxygen species (ROS), and generation of prostaglandin (PG) metabol ites, Human subjects were UVB irradiated on sun-protected skin to four time s their minimal erythema dosage (MED) and skin biopsies or keratomes were o btained either 24 h or 48 h later. We found that topical application of EGC G (3 mg/2,5 cm(2)) before UVB (4 MED) exposure to human skin significantly blocked UVB-induced infiltration of leukocytes and reduced myeloperoxidase activity. These infiltrating leukocytes are considered to be the major sour ce of generation of ROS, In the same set of experiments we found that topic al application of EGCG before UVB exposure decreased UVB-induced erythema, In additional experiments, we found that microsomes from EGCG pretreated hu man skin and exposed to UVB, compared to UVB exposure alone, produced signi ficantly reduced PG metabolites, particularly PGE,, The PG metabolites play a critical role in free radical generation and skin tumor promotion in mul tistage skin carcinogenesis. Careful microscopic examination of skin sectio ns, stained with hematoxylin and eosin, under higher magnification (x400) a lso revealed that EGCG pretreated and UVB-exposed human skin contained fewe r dead cells in the epidermis with comparison to nonpretreated UVB-exposed skin. Taken together, our data demonstrate that EGCG has the potential to b lock the UVB-induced infiltration of leukocytes and the subsequent generati on of ROS in human skin. This may explain the possible mechanism involved i n anti-inflammatory effects of green tea. We suggest that EGCG may be usefu l as a topical agent for protection against UVB-induced ROS-associated infl ammatory dermatoses, photoaging and photocarcinogenesis. Further studies ar e warranted in this direction.