Downregulation of nuclear factor-kappaB activation in human keratinocytes by melanogenesis inhibitors

The study investigated the effect of melanogenesis inhibitors on the activation of nuclear factor-kappaB (NF-kB) in human keratinocytes. Researchers used human HaCaT keratinocytes transfected with a plasmid containing a NF-kB responsive element to measure the activity of NF-kB through the release of secretory alkaline phosphatase (SEAP) as a transcription reporter. Melanogenesis inhibitors such as niacinamide, kojic acid, hydroquinone, resorcinol, arbutin, and glycolic acid were pre-incubated with the cells for 3 hours before UVB irradiation. Kojic acid (IC50 60 μM) was the most potent inhibitor of UVB-induced NF-kB activation, followed by niacinamide (IC50 540 μM). Both kojic acid and niacinamide significantly reduced NF-kB binding and the secretion of interleukin-6 (IL-6), a melanotrophic factor, after UV radiation. The results suggest that melanogenesis inhibitors may act by modulating the synthesis of melanotrophic factors in keratinocytes.