The Xanthophyll Carotenoid Astaxanthin has Distinct Biological Effects to Prevent the Photoaging of the Skin Even by its Postirradiation Treatment.

Exposure of human skin to ultraviolet (UV) radiation causes significant damage to that tissue. The effects of UV on the skin mainly include acute inflammation (erythema/edema) and abnormal keratinization wherein prostaglandin E2 (produced by cyclooxygenase-2), interleukin-8 and transglutaminase 1 (a major regulatory factor of keratinization) play pivotal roles. Later phases of UV-induced skin reactions include hyperpigmentation, wrinkle formation and carcinogenesis, the former two being associated with the UVB-induced production and/or secretion of endothelin-1, stem cell factor and granulocyte-macrophage colony-stimulating factor by keratinocytes in the epidermis. Those paracrine factors then stimulate expression of the critical melanogenic enzyme tyrosinase by melanocytes in the epidermis and increase expression of neprilysin, an enzyme that degrades elastin, by fibroblasts in the dermis. This review summarizes the biological effects of the xanthophyll carotenoid astaxanthin, which prevents UV-induced cutaneous inflammation, abnormal keratinization and wrinkling as well as pigmentation of the skin even by its postirradiation treatment.