Abstract
Ultraviolet B (UVB) radiation induces DNA damage, oxidative stress and inflammation, and suppresses the immune system in the skin, which collectively contribute to skin aging and carcinogenesis. The DNA damage response, including DNA repair, can be regulated by the circadian clock and microRNA (miRNA) expression. The aim of the present study was to evaluate the reparative action of Trichosanthes kirilowii extract (TKE) against UVB irradiation‑induced DNA damage in human keratinocytes. TKE demonstrated low cytotoxicity in normal HaCaT keratinocytes at low doses (up to 100 µg/ml). The results of a comet assay revealed that TKE enhanced the repair of UVB‑induced DNA damage. TKE significantly upregulated the expression of the core clock protein, brain and muscle aryl hydrocarbon receptor nuclear translocator‑like protein‑1 (BMAL1), and downregulated the expression of miRNA (miR)‑142‑3p, as demonstrated using western blotting and the reverse transcription‑quantitative polymerase chain reaction. Furthermore, the suppression of miR‑142‑3p by a specific inhibitor positively correlated with the repair activity. Overall, the data obtained demonstrated that TKE enhanced the repair of UVB‑induced DNA damage by regulating the expression of BMAL1 and miR‑142‑3p. Consequently, TKE can be considered a potential candidate for the treatment of skin diseases associated with UVB‑induced damage.