Systemically administered alpha-melanocyte-stimulating peptides inhibit NF-kappaB activation in experimental brain...

The neuropeptide alpha-melanocyte-stimulating hormone (alpha-MSH) and its C-terminal tripeptide alpha-MSH11-13 modulate production of proinflammatory cytokines and inhibit inflammation. We examined whether systemic alpha-MSH and alpha-MSH11-13 inhibit activation of the nuclear transcription factor, nuclear factor kappa B (NF-kappaB), a factor that is essential to expression of proinflammatory cytokines, in experimental murine brain inflammation induced by lipopolysaccharide. Electrophoretic mobility shift assays of nuclear extracts demonstrated that parenteral alpha-MSH inhibited NF-kappaB activation. Western blot analysis revealed that this inhibition was linked to alpha-MSH-induced preservation of expression of IkappaBalpha protein in the brain. The effects of alpha-MSH on NF-kappaB and IkappaBalpha were paralleled by pretreatment with alpha-MSH11-13. Similar effects of the two peptides were observed in mice with nonfunctional melanocortin 1 receptors (MC1R), ruling out the possibility that this receptor subtype is essential to the influence on NF-kappaB. These findings indicate that alpha-MSH peptides given systemically can inhibit NF-kappaB activation induced in acute brain inflammation even in the absence of MC1R.