Inhibition of α2A-Adrenoceptors Ameliorates Dextran Sulfate Sodium-Induced Acute Intestinal Inflammation in Mice

Abstract

It has been hypothesized that α2- Adrenoceptors (a2-ARs) may be involved in the pathomechanismof colitis; however, the results are conflicting because both aggravation and amelioration of colonic inflammation have been described in response to a2-AR agonists. Therefore, we aimed to analyze the role of α2A-ARs in acute murine colitis. The experiments were carried out in wild- Type, α2A-, α2B-, and α2C-AR knockout (KO) C57BL/6 mice. Colitis was induced by dextran sulfate sodium (DSS, 2%); α2-AR ligands were injected i.p. The severity of colitis was determined both macroscopically and histologically. Colonicmyeloperoxidase (MPO) and cytokine levels weremeasured by enzyme-linked immunosorbent assay and proteome profiler array, respectively. The nonselective α2-AR agonist clonidine induced a modest aggravation of DSSinduced colitis. It accelerated the disease development and markedly enhanced the weight loss of animals, but did not influence the colon shortening, tissue MPO levels, or histologic score. Clonidine induced similar changes in α2B- And α2C-AR KO mice, whereas it failed to affect the disease activity index scores and caused only minor weight loss in α2A-AR KO animals. In contrast, selective inhibition of α2A-ARs by BRL 44408 significantly delayed the development of colitis; reduced the colonic levels of MPO and chemokine (C-C motif) ligand 3, chemokine (C-X-C motif) ligand 2 (CXCL2), CXCL13, and granulocytecolony stimulating factor; and elevated that of tissue inhibitor of metalloproteinases-1. In this work, we report that activation of α2-ARs aggravates murine colitis, an effect mediated by the α2A-AR subtype, and selective inhibition of these receptors reduces the severity of gut inflammation.