Abstract:

Objective To study to the effect of 1064-nm Q-switched Nd:YAG laser irradiation on the melanogenesis in a human epidermal melanocyte line PIG. Methods Cultured PIG cells were irradiated with 1064-nm Q-switched Nd:YAG laser （Medlite C6） at different energy densities for 10 times. After additional culture for various durations, cell viability was detected by MTT assay, tyrosinase activity by dopa oxidation assay, mRNA and protein expressions of tyrosinase, tyrosinase related protein （TRP）-1 and TRP-2 by real-time quantitative fluorescent RT-PCR and Westen blotting respectively. Results The irradiation with Q-switched Nd:YAG laser at energy densities from 1 to 3 J/cm2 had no obvious effect on the viability of PIG cells. After irradiation with Nd:YAG laser at 1 J/cm2, PIG cells showed a significant increase in the tyrosinase activity, mRNA expressions of tyrosinase and TRP-1 compared with unirradiated cells （0.563 ± 0.014 vs 0.501 ± 0.019, 1.40 ± 0.11 vs 1.0, 1.28 ± 0.03 vs 1.0, all P < 0.05）, but both the mRNA （0.91 ± 0.17 vs 1.0, P > 0.05） and protein expressions of TRP-2 experienced no significant changes before and after the irradiation. However, a significant decrease was noted in PIG cells irradiated with Nd:YAG laser at 3 J/cm2 in tyrosinase activity, mRNA and protein expressions of tyrosinase （0.70 ± 0.02 vs 1.0, 0.64 ± 0.05 vs 1.0, both P < 0.05）, TRP-1 （0.73 ± 0.04 vs 1.0, 0.86 ± 0.17 vs 1.0, both P < 0.05) and TRP-2 （0.68 ± 0.04 vs 1.0, 0.69 ± 0.11 vs 1.0, both P < 0.05） in comparison with unirradiated PIG cells. Conclusions The 1064-nm Q-switched Nd:YAG laser irradiation may affect the melanogenesis in PIG cells. With no influence on cell viability, the 1064-nm Q-switched Nd:YAG laser at 1 J/cm2 could enhance melanogenesis, while that at 3 J/cm2 could suppress melanogenesis, in PIG cells.

Key words: [Key words] Q-switched Nd:YAG laser, Tyr, TRPs, melanogenesis