Photochemoprotective effect of green tea polyphenols against ultraviolet B irradiation induced skin damage in albino rats

ABSTRACT

Exposure of skin to solar ultraviolet radiation [UVR] is a major environmental factor that has serious adverse effects on the structure and function of the skin. UVR-induced free radicals contribute to inflammation and are implicated in photocarcinogenesis. The epidermal antioxidant defense system combats reactive oxygen species [ROS] induced oxidative damage; however, antioxidant levels decline following UVR exposure. An interesting strategy to improve photoprotection is to support the skin's endogenous antioxidant system with exogenous supplementation. Green tea polyphenols [GTP] have attracted considerable attention because of their skin photoprotective capability. The aim of this study was to investigate the Photochemoprotecive effects of systemic and topical green tea polyphenols [GTP] against UVR induced cutaneous oxidative stress, alteration of immune function and skin damage in albino rats. This study was carried out on one hundred ten adult albino rats divided into eight groups, 10 animals each, except group II which comprised 40 rats that was subdivided into 4 subgroups, each of 10 rats. Group I negative control. Group II positive control. Group III UVR, low dose [180 mJ/cm 2]. Group IV UVR high dose [280 mJ/cm 2]. Group V UVR 180 mJ/cm 2 for animals received GTP orally. Group VI UVR 180 mJ/cm 2 for animals received GTP topically. Group VII UVR 280 mJ/cm 2 for animals received GTP orally. Group VIII UVR 280 mJ/cm 2 for animals received GTP topically. Bifold- skin thickness was measured to assess cutaneous edema 24 h after the last UVR exposure, then rats were sacrificed and dorsal skin was obtained for antioxidant enzyme assay; Superoxide dismutase [SOD], Catalase [CAT], Lipid peroxidase [LPO], Glutathione[GSH] and Glutathione peroxidase [GPx]. Hematologic and immunologic studies included WBC count, neutrophils, eosinonphils, lymphocytes, CD4 T cells and CD8 T cells. histolopathological and ultra structural study of the skin was done. All these biochemical parameters showed evidence of UVR toxicity more with the high dose in the form of modulating the activities of antioxidant enzymes and inflammation, skin photoallergy and cutaneous edema. Furthermore, histopathological and ultra structural studies showed that UVR induced skin damage and mitotic changes. The data presented in this study demonstrate that whether systemically administered or topically applied GTP inhibited UVR - induced oxidative stress, cutaneous edema and contact hypersensitivity and offered favorable protective effects against ultraviolet radiation-induced skin phototoxicity in the rat model. Further studies on GTP oral consumption or topical applications to patients and people exposed to UVB irradiation are recommended