Alanyl-glutamine administration suppresses Th17 and reduces inflammatory reaction in dextran sulfate sodium-induced acute colitis

Abstract

T helper (Th) cells play a major role in the pathogenesis of inflammatory bowel disease (IBD). Glutamine (Gln) is known to have immunomodulatory effects in metabolic stressed conditions. This study investigated the effects of post-treatment of alanyl-glutamine (Ala-Gln) on Th cell-associated cytokine expressions and inflammatory reaction in dextran sulfate sodium (DSS)-induced colitis. C57BL/6 mice received distilled water containing 3% DSS for 5 days to induce colitis, whereas the normal control (NC) group received distilled water. After induction of colitis, one of the colitis groups (DG) was intraperitoneally injected with an Ala-Gln solution (0.5 g Gln/kg/d), and the saline DSS group (DS) received an identical volume of saline. After treatment for 3 days, mice were sacrificed, and the blood and tissue samples were collected for further analysis. DSS colitis resulted in higher percentages of blood interleukin (IL)-17-secreting Th cells and greater expression of Th cell-associated cytokine messenger RNA (mRNA) in the mesenteric lymph nodes (MLN). Also, luminal immunoglobin (Ig) G, keratinocyte-derived chemokine, and macrophage chemoattractant protein-1 levels were higher in the DS group than the NC group, whereas these parameters did not differ between the DG and NC groups. The DG group had lower blood IL-17A, 17F, MLN IL-17 mRNA and macrophage percentage in the peritoneal lavage fluid than those of the DS group. These results suggest that post-treatment with Ala-Gln suppressed Th17-associated cytokine expressions, reduced macrophage infiltration into the peritoneal cavity and decreased pro-inflammatory cytokine production in the colon, thus may have attenuated inflammatory response in DSS-induced colitis.