Phytochemicals as modulators of ultraviolet-b radiation induced cellular and molecular events: A review

Abstract

Ultraviolet (UV) radiation is a very prominent environmental toxic agent. Particularly, UVB (280–320 nm – short wave) wavelength penetrates the epidermis and is completely absorbed in the upper dermis, whereas UVA (320–400 nm - long wave) penetrates to the deeper dermis. UVA is a relatively weak carcinogen than UVB because of its weak strength as a tumor initiating agent. UVB exposure elicits adverse effect which includes sunburn, basal and squamous cell carcinoma, melanoma, cataracts, photoaging of the skin and immunosuppression. Increased ozone depletion and modern lifestyle has increased the amount of UV exposure, and this consequently led to a surge in the incidence of skin cancer. UVB-irradiation acts as both tumor initiator and tumor promoter in animal models. UVB-initiated signal transduction pathways are believed to be responsible for tumor promotion effects. Variety of cellular changes, which includes activation of transcription factors and protein kinases were altered during acute and chronic UVB-exposure. All these events leads to skin cancer development involving DNA damage, inflammation, immunosuppression, epidermal hyperplasia, cell cycle dysregulation, depletion of antioxidant–defenses, and reactive oxygen species generation. An epidemiological study shows that human beings consuming varieties of vegetables and fruits are protected from UVB induced carcinogenesis. In the recent years, number of experimental evidences showed that natural nutraceuticals and phytoceuticals are vital targets for UVB-mediated cellular and molecular events and prevents cellular milieu from UVB mediated health effects. In this review, we have discussed the current progress in the study on UVB-mediated signaling that can be exploited as targets for phytochemicals.