Interplay of Peroxisome Proliferator-Activated Receptor-γ and Colonic Integrity during Clostridium difficile Infection

  • 吳 岱潔

Student thesis: Master's Thesis


Clostridium difficile infection (CDI) causes severe colitis with watery diarrhea in long-term antibiotic treatment patients. Previous studies have showed that peroxisome proliferator-activated receptor γ (PPARγ), owing to its function in immune regulation, is a potential therapy target for colitis. However, the role of PPARγ in pathogenesis of CDI remains unclear. In our CDI mouse model, we found that levels of PPARγ and tight junction protein were decreased in colonic tissue. To further investigate the relationship between PPARγ and colonic integrity, we used PPARγ deficient mice and found there was no difference in colonic tissue in these two genotype mice. However, after infected with C. difficile, the colonic permeability and gut bacteria dissemination were significantly increased in PPARγ deficient mice than that in WT mice. To dissect the role of PPARγ on the regulation of tight junction protein, occludin, we demonstrated the levels of occludin and PPARγ were also decreased parallel in colonic epithelial cells. Simultaneously, disruption of tight junction functionality was revealed by real time cell analyzer. We demonstrated that the decreased PPARγ during CDI was proteasome dependent by treatment with proteasome inhibitors. However, proteasome inhibitors couldn’t prevent the decrease of occludin. When activation of PPARγ by treated with PPARγ agonist, pioglitazone, the mRNA and protein levels of occludin were reversed after CDI. To directly interpret the interaction of PPARγ and the occludin regulation, we predicted the possible peroxisome proliferator binding elements (PPRE) in silico. It showed that PPARγ bound at occludin promoter region by ChIP assay, but released after treated with pioglitazone. Further, we treated mice with pioglitazone, and the mice showed improvement of inflammation and intestinal integrity in the intestinal tract. Taken together, our results suggest that decrease of PPARγ might contribute to exacerbated barrier loss through down-regulation of occludin.
Date of Award2014
Original languageEnglish
SupervisorPei-Jane Tsai (Supervisor)

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