Abstract: Objective: To study the effects of NB-UVB irradiation on the melanocytes viability, melanin synthesis, and melanin synthesis-related gene expression. Methods: The melanocyte cell line PIG1 was cultured. The cell proliferation after different doses of UVB irradiation (400, 800, 1200, 1600, 2000 mJ/cm²) was detected by MTT method. The melanin content was detected by NaOH lysis method. The expression of melanin synthesis-related genes, Tyr, Tyrp1, Tyrp2, OA1, MART-1, Pmel17, VAT-1, OCSP, syntenin, CHCHD3, flotillin-1, GPNMB after UVB irradiation were detected by RT-PCR and Western blot. Results: The cell viability decreased significantly after irradiated by NB-UVB radiation at dose of 1600 and 2000 mJ/cm². There was no significant change of cell viability after irradiated by NB-UVB radiation at dose of 400, 800 and 1200 mJ/cm², and melanin synthesis increased with increasing radiation dose. After ultraviolet irradiation, of the 12 melanin synthesis-related genes, 5 of Tyr, Tyrp2, GPNMB, Syntenin, MART-1 mRNA and protein were significantly increased. Conclusion: NB-UVB irradiation significantly increased the melanin synthesis and the expression of related genes.

Key words: NB-UVB, melanocytes, melanin synthesis related genes