alexa Downregulation of NF-κB activation in human keratinocytes by melanogenic inhibitors


Fermentation Technology

Author(s): Yeong Shik Kim, Jinseon Lee

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Background: Exposure of skin cells, particularly keratinocytes to various nuclear factor-kappaB (NF-κB) activators (e.g. tumor necrosis factor-α, interleukin-1, lipopolysaccharides, and ultraviolet light) leads to phosphorylation and degradation of the inhibitory protein, IκB. Liberated NF-κB is translocated into the nucleus where it can change or alter expression of target genes, resulting in the secretion of extracellular signaling molecules including melanotrophic factors affecting melanocyte.Objective: In order to demonstrate the possible role of NF-κB activation on the synthesis of melanotrophic factors from the keratinocytes, the activities of NF-κB induced by melanogenic inhibitors (MIs) were determined in human HaCaT keratinocytes transfected with pNF-κB–SEAP–NPT plasmid. Transfectant cells released the secretory alkaline phosphatase (SEAP) as a transcription reporter in response to the NF-κB activity and contain the neomycin phosphotransferase (NPT) gene for the dominant selection marker for geneticin resistance. Methods: MIs such as niacinamide, kojic acid, hydroquinone, resorcinol, arbutin, and glycolic acid were preincubated with transfectant HaCaT cells for 3 h and then ultraviolet B (UVB) was irradiated. NF-κB activation was measured with the SEAP reporter gene assay using a fluorescence detection method. Results: Of the MIs tested, kojic acid (IC50=60 μM) was found to be the most potent inhibitor of UVB-upregulating NF-κB activation in transfectant HaCaT cells, which is followed by niacinamide (IC50=540 μM). Pretreatment of the transfectant HaCaT cells with the MIs, especially kojic acid and niacinamide, effectively lowered NF-κB binding measured by electrophoretic mobility shift assay. Furthermore, these two inhibitors remarkably reduced the secretion level of IL-6, one of melanotrophic factors, triggered by UV-radiation of the HaCaT cells. Conclusion: These observations suggest that MIs working at the in vivo level might act partially through the modulation of the synthesis of melanotrophic factors in keratinocyte.

This article was published in Journal of Dermatological Science and referenced in Fermentation Technology

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