Background & aims: A dysregulated response of CD4(+) T cells against the microbiota contributes to the development of inflammatory bowel disease. Effector CD4(+) T cells, generated in response to microbe-derived antigens, can reduce somatic inflammatory pain through the local release of opioids. We investigated whether colitogenic CD4(+) T cells that accumulate in the inflamed colon also produce opioids and are able to counteract inflammation-induced visceral pain in mice.
Methods: Colitis was induced via transfer of naive CD4(+)CD45RB(high) T cells to immune-deficient mice or by administration of dextran sulfate sodium. Mice without colitis were used as controls. Samples of colon tissue were collected, and production of opioids by immune cells from inflamed intestine was assessed by quantitative polymerase chain reaction and cytofluorometry analyses. The role of intestinal opioid tone in inflammation-induced visceral hypersensitivity was assessed by colorectal distention.
Results: In mice with T cell- or dextran sulfate sodium-induced colitis, colitogenic CD4(+) T cells (T-helper 1 and Th17 cells) accumulated in the inflamed intestine and expressed a high level of endogenous opioids. In contrast, macrophages and epithelial cells did not express opioids; opioid synthesis in the myenteric plexus was not altered on induction of inflammation. In mice with colitis, the local release of opioids by colitogenic CD4(+) T cells led to significant reduction of inflammation-associated visceral hypersensitivity.
Conclusions: In mice, colitogenic Th1 and Th17 cells promote intestinal inflammation and colonic tissue damage but have simultaneous opioid-mediated analgesic activity, thereby reducing abdominal pain.
Keywords: 4′,6-diamidino-2-phenylindole; CBA; Cytometric Bead Array; DAPI; DSS; FCS; HPRT; IBD; IFN; IL; Ig; Mouse Model; Mucosal Immunity; OVA; PBS; PDYN; PENK; POMC; T-helper; Th; UC; Visceral Sensitivity; dextran sulfate sodium; fetal calf serum; hypoxanthine phosphoribosyltransferase; immunoglobulin; inflammatory bowel disease; interferon; interleukin; mAb; mRNA; messenger RNA; monoclonal antibody; ovalbumin; phosphate-buffered saline; prodynorphin; proenkephalin; proopiomelanocortin.
Copyright © 2014 AGA Institute. Published by Elsevier Inc. All rights reserved.