308-nm excimer laser combined with piperine promotes melanin synthesis through PTEN/PDK1/GSK3b regulation of keratinocyte paracrine

Abstract

Vitiligo is a common skin disorder involving depigmentation. A 308-nm excimer laser and piperine were shown to be useful for the treatment of vitiligo. The aim of this study was to investigate the effect of a 308-nm excimer laser combined with piperine in the treatment of vitiligo and the molecular mechanism by which this treatment promotes melanin synthesis through regulation of the paracrine activity of keratinocytes (KCs). In this study, cells and animals were treated with a 308-nm excimer laser and piperine. ELISA, Western blot analysis, immunofluorescence and RT‒qPCR were used to measure the levels of proteins and genes, and EdU, Transwell, and flow cytometric assays were used to assess cell proliferation and apoptosis. Treatment with the 308-nm excimer laser combined with piperine promoted KCs secretion of cytokines related to melanin production, restrained the secretion of proinflammatory cytokines, elevated the level of PTEN, decreased the level of PDK1, inhibited the phosphorylation of Akt, and facilitated the phosphorylation of GSK3b. After coculture of melanocytes (MCs) with KCs supernatant, the proliferation and migration of MCs increased, the apoptosis of MCs decreased, and the expression of melanin synthesis-related genes increased. Moreover, compared with the 308-nm excimer laser or piperine alone, the combined treatment had a more significant effect. Moreover, inhibiting PTEN weakened the effect of the combined treatment. Animal experiments revealed that a 308-nm excimer laser combined with piperine had a therapeutic effect on vitiligo. After combined treatment, the number of CD8 + T cells decreased, and the PTEN/PDK1/GSK3b pathway was activated, which increased melanin synthesis and alleviated the progression of vitiligo. In conclusion, a 308-nm excimer laser combined with piperine regulates KCs paracrine activity through the PTEN/PDK1/GSK3b molecular axis, promotes MCs proliferation and melanin synthesis, and alleviates the progression of vitiligo, which provides new targets for the clinical treatment of vitiligo.