Astaxanthin Protects Ultraviolet B-Induced Oxidative Stress and Apoptosis in Human Keratinocytes via Intrinsic Apoptotic Pathway

Background: Ultraviolet radiation causes skin damage due to increased production of reac-tive oxygen species (ROS) and inflammatory intermediates and direct attack of DNA of skin cells. Astaxanthin is a reddish pigment that belongs to a group of chemicals called carot-enoids and has protective effects as an antioxidant. Objective: To determine the beneficial effects of astaxanthin on damaged human skin after exposure to ultraviolet radiation. Methods: Normal human epidermal keratinocytes (NHEKs) were pre-treated with astax-anthin for 24 hours and exposed to ultraviolet B (UVB) irradiation. After 24 hours, the Cell Counting Kit-8 (CCK-8) assay measured cell viability, ROS assay and flow cytometry analysis assessed apoptosis, and western blotting was performed to determine expression of apoptosis-related proteins. Results: Astaxanthin significantly inhibited UVB-induced NHEKs cytotoxicity. Pretreat-ment of NHEKs with astaxanthin reduced UVB-induced ROS production. Astaxanthin caused significant inhibition of UVB-induced apoptosis, as evidenced by flow cytometry analysis and western blotting. Conclusion: These results suggest that astaxanthine has a beneficial effect of reducing damage caused by UVB by effectively inhibiting cell death and reducing ROS production in keratinocytes.