Alpha-melanocyte stimulating hormone (
alpha-MSH) has pigmentary, anti-inflammatory,
antipyretic, and general immunomodulatory roles. It can oppose several
cytokines including
tumor necrosis factor-alpha in a number of tissues, including skin. We have previously shown that
alpha-MSH can inhibit
tumor necrosis factor-alpha stimulated
intercellular adhesion molecule 1 upregulation and
nuclear factor kappaB (NFkappaB)
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
alpha-MSH peptides to inhibit
tumor necrosis factor alpha stimulated NFkappaB activation in nonpigmentary HaCaT keratinocytes (
alpha-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. NFkappaB/p65 activation was analyzed by electrophoretic mobility shift assay and immunofluorescent microscopy.
alpha-MSH, L-Lys-L-Pro-L-Val, and L-Lys-L-Pro-D-Val all significantly inhibited
tumor necrosis factor alpha stimulated NFkappaB 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 NFkappaB activation in normal human keratinocytes. Immunolabeling of inhibitor kappaBalpha of NFkappaB (
IkappaBalpha) 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
IkappaBalpha 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
IkappaBalpha mechanism and extends findings to
ACTH peptides, identifying an abnormal
IkappaBalpha mechanism in the immortal HaCaT versus normal keratinocyte.