Light-emitting diodes at 830 and 850 nm inhibit melanin synthesis in vitro

Treatment of hyperpigmentation remains a challenge. Because of the positive effects of low-energy Nd:YAG lasers on the treatment of melasma, it is suggested that laser-like light-emitting diodes (LEDs) can potentially ameliorate hyperpigmentation. We evaluated the effect of seven different LED wavelengths on melanogenesis. LED irradiation at 830 nm (dose-dependent, from 1 to 20 J/cm2) and 850 nm (1 J/cm2) significantly reduced melanin production and tyrosinase expression, not only in a normal human melanocyte monoculture both with and without forskolin stimulation but also in a three-dimensional multiple cell type culture. It reduced melanin content via inactivation of the apoptosis signal-regulating kinase and extracellular signal-regulated kinase 1/2 pathways. The level of phosphorylated cyclic AMP response element-binding protein was also decreased by LED irradiation. Moreover, LED irradiation reduced melanogenesis through decreased expression of tyrosinase family genes (tyrosinase-related protein-1 and 2, and microphthalmia-associated transcription factor). These results indicate that LEDs could potentially be used to treat melanin-overproducing skin conditions.