Increased Susceptibility to Dextran Sulfate Sodium Induced Colitis in the T Cell Protein Tyrosine Phosphatase Heterozygous Mouse

T cell protein tyrosine phosphatase (TC-PTP/PTPN2) is an enzyme that is essential for the proper functioning of the immune system and that participates in the control of cell proliferation, and inflammation. We previously observed that TC-PTP(-/-) mice display various immunodeficiencies, hypersensitivity to LPS and die within three weeks of birth due to anemia and widespread inflammation. A recent analysis of the Wellcome Trust Case Control Consortium (WTCC) genome wide scan data, reported in 2007, indicated a potential role for TC-PTP in inflammatory bowel disease (IBD). To further investigate the potential role of TC-PTP in IBD, we studied heterozygous TC-PTP mutant mice challenged with dextran sulfate sodium (DSS) in their drinking water. In comparison to control animals, we observed significant changes in the colon mucosa of DSS-treated TC-PTP(+/-) mice, in the ratio of colon to body weight, as well as an up-regulation of mRNA transcripts for IL-6, IL-23, 1L-12beta, IFN-gamma, TNF-alpha. Moreover, up-regulation of serum IL-6 levels in DSS-treated TC-PTP(+/-) mice confirms that mice with a single copy of the TC-PTP gene display increased susceptibility to systemic inflammation due to bowel epithelial erosion resulting from DSS challenge. Our findings support the lack of modulation of Janus kinases 1 and 3 (Jak1, Jak3), and the downstream signal transducer and activator of transcription 1,3 and 5 (Stat1, Stat3, Stat 5) by PTPN2 in the development of IBD like condition. Pathological and molecular analysis reveal that the deficiency of TC-PTP results in pro-inflammatory condition in the bowel of heterozygous TC-PTP(+/-) mice. These novel findings in TC-PTP hemi-deficiency support the hypothesis that TC-PTP is an important regulator of inflammatory cytokine signaling and that it may be implicated in the pathophysiology of IBD.