α-melanocyte-stimulating hormone protects against mesenteric ischemia-reperfusion injury

Mesenteric ischemia-reperfusion (I/R) injury to the intestine is a common and often devastating clinical occurrence for which there are few therapeutic options. α-Melanocyte-stimulating hormone (α-MSH) is a tridecapeptide released by the pituitary gland and immunocompetent cells that exerts antiinflammatory actions and abrogates postischemic injury to the kidneys and brainstem of rodents. To test the hypothesis that α-MSH would afford similar protection in the postischemic small intestine, we analyzed the effects of this peptide on intestinal transit, histology, myeloperoxidase activity, and nuclear factor-κB (NF-κB) activation after 45 min of superior mesenteric artery occlusion and ≤6 h of reperfusion. Rats subjected to I/R exhibited markedly depressed intestinal transit, histological evidence of severe injury to the ileum, increased myeloperoxidase activity in ileal cytoplasmic extracts, and biphasic activation of NF-κB in ileal nuclear extracts. In contrast, rats treated with α-MSH before I/R exhibited intestinal transit and histological injury scores comparable to those of sham-operated controls. In addition, the α-MSH-treated rats demonstrated less I/R-induced activation of intestinal NF-κB and myeloperoxidase activity after prolonged (6 h) reperfusion. We conclude that α-MSH significantly limits postischemic injury to the rat small intestine.