Baicalein prevents skin damage, tumorigenesis and tumor growth in chronic ultraviolet B-irradiated hairless mice

Non-melanoma skin cancer accounted for over one million new cases, according to the Global Cancer Statistics 2020 report. Moreover, UV radiation causes photodamage (skin inflammation and angiogenesis), photoaging (increases in skin wrinkle and reduction in skin elasticity). This study investigated the preventive effects of baicalein against skin damage, aging, tumorigenesis and tumor growth in long-term UVB irradiated hairless mice. Five-week-old male mice were divided into the following groups: a non-UVB group (control), vehicle-treated UVB group (UVB control), and UVB groups treated with two different doses of baicalein (10 and 30 mg/kg, twice daily). The mice were exposed to UVB irradiation (36-192 mJ/cm2) three times per week for 23 weeks. Baicalein was orally administered at the specified doses for the same duration. Skin cytokine, chemokine, and vascular endothelial growth factor (VEGF) levels were measured using ELISA kits. Baicalein (at doses of 10 and 30 mg/kg) suppressed UVB-induced increases in skin thickness, improved skin elasticity, and reduced the number and growth of skin tumors. Additionally, baicalein inhibited UVB-induced increases in IL-1 beta, IL-6, MCP-1, MIF, VEGF, p53, COX-2, total/phospho-NF-kappa B expression levels in the skin. Immunohistochemical analysis revealed that baicalein attenuated UVB-induced increases in the number of Ki-67-, and HIF-1 alpha-positive cells. The preventive effects of baicalein on skin damage and skin tumor growth in chronically UVB-irradiated mice were associated with reduced skin cytokine levels through the down-regulation of COX-2, phosphorylated NF-kappa B p65, and HIF-1 alpha expression.