IL-9 regulates intestinal barrier function in experimental T cell-mediated colitis

Abstract

As previous studies suggested that IL-9 may control intestinal barrier function, we tested the role of IL-9 in experimental T cell-mediated colitis induced by the hapten reagent 2,4,6-trinitrobenzenesulfonic acid (TNBS). The deficiency of IL-9 suppressed TNBS-induced colitis and led to lower numbers of PU.1 expressing T cells in the lamia propria, suggesting a regulatory role for Th9 cells in the experimental TNBS colitis model. Since IL-9 is known to functionally alter intestinal barrier function in colonic inflammation, we assessed the expression of tight junction molecules in intestinal epithelial cells of TNBS-inflamed mice. Therefore we made real-time PCR analyses for tight junction molecules in the inflamed colon from wild-type and IL-9 KO mice, immunofluorescent stainings and investigated the expression of junctional proteins directly in intestinal epithelial cells of TNBS-inflamed mice by Western blot studies. The results demonstrated that sealing proteins like occludin were up regulated in the colon of inflamed IL-9 KO mice. In contrast, the tight junction protein Claudin1 showed lower expression levels when IL-9 is absent. Surprisingly, the pore-forming molecule Claudin2 revealed equal expression in TNBS-treated wild-type and IL-9-deficient animals. These results illustrate the pleiotropic functions of IL-9 in changing intestinal permeability in experimental colitis. Thus, modulation of IL-9 function emerges as a new approach for regulating barrier function in intestinal inflammation.

Keywords:

• IL-9
• TNBS colitis
• Th9 cells
• intestinal epithelial cells
• tight junctions
• claudins

Abbreviations:

• CD, Crohn´s disease; IBD, Inflammatory bowel disease; IL-9, Interleukin-9; KO, knockout; Th9, T-helper cell type 9; TNBS, 2,4,6-trinitrobenzenesulfonic acid; RT-PCR, reverse transcription-polymerase chain reaction; UC, ulcerative colitis; WT, wild-type

Disclosure of Potential Conflicts of Interest

There were no potential conflicts of interest.

Acknowledgments

The authors thank Ludmilla Sologub for excellent technical assistance.

Additional information

Funding

The research of B.W. and M.F.N. was supported by the Clinical Research Group KFO 257 CEDER of the DFG and UK Medical Research Council, the Wellcome Trust (100963) to A.N.J.M.