Profiling of MicroRNAs and IL-10 expression in intestinal CD4+ T cells following infection with Helicobacter hepaticus

In the Helicobacter hepaticus (Hh) colitis model, Hh infection of either wild-type mice treated with a blocking antibody to the IL-10 receptor (anti-IL-10R) or IL-10 KO mice results in intestinal inflammation associated with inflammatory Th1 and Th17 responses. Recent findings suggest that altered expression of the post-transcriptional gene regulators microRNAs contribute to pathogenic immune responses during intestinal inflammation. Here, examination of microRNA expression during Hh colitis showed that microRNAs are differentially expressed in the inflamed large intestine of Hh+ IL-10 KO mice compared to uninfected controls, both at the tissue-level and the CD4+ T-cell level. Kinetic examination of the cecal and colonic levels of miR-155, miR-326 and miR-132 (microRNAs previously shown to augment Th1 and/or Th17 responses) demonstrated that miR-155 was up-regulated and miR-326 and miR-132 were down-regulated at different time points post Hh infection. Furthermore, the change in expression of these microRNAs coincided with inflammation development. Microarray profiling of large intestine LP CD4+ T cells revealed that two microRNAs were significantly up-regulated (miR-21a and miR-31) and seven microRNAs were significantly down-regulated (miR-125a, miR-125b, miR-139, miR-181a, miR-192, miR-30a and miR-467c) in colitic IL-10 KO mice compared to uninfected controls.
The anti-inflammatory cytokine IL-10 is necessary for protection against intestinal inflammation. Here, the phenotype of IL-10-producing LP CD4+ T cells was examined in a non-inflammatory immune response (Hh+ WT mice) and in an inflammatory immune response (Hh+/anti-IL-10R-treated WT mice). Compared to uninfected controls, the Hh+ mice showed a slight expansion in IL-10+ IL-17A+FoxP3+/- cells whereas the Hh+/anti-IL-10R-treated mice showed a significant expansion in all the IL-10+ LP CD4+ T cells co-expressed both inflammatory cytokines IL-17A and/or IFN-γ and/or the Treg transcription factor FoxP3.
The experiments carried out in this thesis demonstrate that the profile of two important regulatory factors, microRNAs and IL-10, is markedly different in LP CD4+ T cells from the colitic setting compared to uninfected controls.