Inhibition of Tumor Necrosis Factor-α Stimulated NFκB/p65 in Human Keratinocytes by α-Melanocyte Stimulating Hormone and Adrenocorticotropic Hormone Peptides

α-Melanocyte stimulating hormone (α-MSH) has pigmentary, anti-inflammatory, antipyretic, and general immunomodulatory roles. It can oppose several cytokines including tumor necrosis factor-α in a number of tissues, including skin. We have previously shown that α-MSH can inhibit tumor necrosis factor-α stimulated intercellular adhesion molecule 1 upregulation and nuclear factor κB (NFκB) transcription factor activation in melanocyte and melanoma cells. It is thought, however, that this MSH biology may also extend to other cells of the skin and in this study we extend our work to keratinocytes. We have investigated in detail the ability of three α-MSH peptides to inhibit tumor necrosis factor α stimulated NFκB activation in nonpigmentary HaCaT keratinocytes (α-MSH, L-Lys-L-Pro-L-Val, and L-Lys-L-Pro-D-Val) and two adrenocorticotropic hormone (ACTH) peptides (1–17 and 1–39), reported to be present in skin tissue. NFκB/p65 activation was analyzed by electrophoretic mobility shift assay and immunofluorescent microscopy. α-MSH, L-Lys-L-Pro-L-Val, and L-Lys-L-Pro-D-Val all significantly inhibited tumor necrosis factor α stimulated NFκB activation, whereas ACTH 1–17 and 1–39 did not, in the HaCaT keratinocytes. MSH peptides and ACTH 1–39 were effective, however, at inhibiting NFκB activation in normal human keratinocytes. Immunolabeling of inhibitor κBα of NFκB (IκBα) revealed an abnormal localization to the nucleus of HaCaT cells, which was unaffected by MSH/ACTH peptides. In contrast, normal human keratinocytes showed a normal IκBα distribution that responded to MSH/ACTH with nuclear translocation. Our data support previous work on the role of MSH/ACTH peptides as immunomodulatory/anti-inflammatory regulators, and extend this work to keratinocytes identifying a novel IκBα mechanism and extends findings to ACTH peptides, identifying an abnormal IκBα mechanism in the immortal HaCaT versus normal keratinocyte