title: Constitutive expression of MC1R in HaCaT keratinocytes inhibits basal and UVB-induced TNF-alpha production.
abstract: Alpha-melanocyte stimulating hormone (alpha-MSH) binds to melanocortin-1 receptor (MC1R) on melanocytes to stimulate pigmentation and modulate various cutaneous inflammatory responses. MC1R expression is not restricted to melanocytic cells and may be induced in keratinocytes after UVB exposure. We hypothesized that MC1R signaling in keratinocytes, wherein basal conditions are barely expressed, may modulate mediators of inflammation, such as nuclear factor-kappa B (NF-kappaB) and tumor necrosis factor-alpha (TNF-alpha). Therefore, we generated HaCaT cells that stably express human MC1R or the Arg151Cys (R151C) nonfunctional variant. We demonstrate that: (1) the constitutive activity of MC1R results in elevated intracellular cAMP level, reduced NF-kappaB activity and decreased TNF-alpha transcription; (2) binding of alpha-MSH to MC1R and the subsequent increase in cAMP production do not inhibit TNFalpha-mediated NF-kappaB activation; (3) MC1R signaling is sufficient to strongly inhibit UVB-induced TNF-alpha expression and this inhibitory effect is further enhanced by alpha-MSH stimulation. Our findings suggest that the constitutive activity of the G-protein-coupled MC1R in keratinocytes may contribute to the modulation of inflammatory events and immune response induced by UV light.
authors: CNRS, UMR 5247 (IBMM), Faculté de Pharmacie, Université Montpellier I, Montpellier, France.
authors: Geneviève
authors: G
authors: Garcin
authors: Lionel
authors: L
authors: Le Gallic
authors: Pierre-Emmanuel
authors: PE
authors: Stoebner
authors: Anne
authors: A
authors: Guezennec
authors: Joelle
authors: J
authors: Guesnet
authors: Thierry
authors: T
authors: Lavabre-Bertrand
authors: Jean
authors: J
authors: Martinez
authors: Laurent
authors: L
authors: Meunier
mesh_terms: D002460:Cell Line; D005786:Gene Expression Regulation / Q000528:radiation effects; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism*; D044102:Receptor, Melanocortin, Type 1 / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D014466:Ultraviolet Rays; D000521:alpha-MSH / Q000494:pharmacology
chemical_list: D044102:Receptor, Melanocortin, Type 1; D014409:Tumor Necrosis Factor-alpha; D000521:alpha-MSH