A209 XENOBIOTIC RECEPTOR REGULATION OF CLOSTRIDIUM DIFFICILE-ASSOCIATED TISSUE DAMAGE AND INFLAMMATION. (1st March 2018)

• Record Type: Journal Article
• Authors: Erickson, S L; Flannigan, K L; Alston, L; Hirota, S A
• Is Part Of: Journal of the Canadian Association of Gastroenterology. Volume 1(2018)Supplement 1
• Page Start: 365
• Page End: 366
• Publication Date: 2018-03-01
• Subjects: Gastroenterology -- Periodicals; 616.33005
• DOI: 10.1093/jcag/gwy008.210
• Languages: English
• ISSNs: 2515-2084

Abstract

Abstract: Background: The current treatments available for C. difficile infections (CDI) target the bacteria, however they do nothing to treat the damaging inflammation triggered by the virulence factors, TcdA and TcdB. Indeed, enhanced chemokine/cytokine expression during CDI is associated with poor clinical outcomes. Interestingly, a number of rifamycin antibiotics have been shown to have potent activity against C. difficile, while also exhibiting anti-inflammatory effects through their ability to activate the pregnane X receptor (PXR) and inhibit NFκB signaling. In the current study, we sought to test the hypothesis that targeting the PXR could prove to be an effective strategy to reduce C. difficile toxin-induced inflammation and tissue damage. Aims: 1) To assess the ability of PXR agonists to attenuate TcdB-induced CXCL8/IL-8 production in vitro 2) To test whether PXR activation can attenuate TcdA/B-induced damage and inflammation in an in vivo model of C. difficile toxin exposure 3) Determine the mechanism by which activation of the PXR attenuates TcdA/B-induced damage and inflammation Methods: We first assessed the ability of the PXR to modulate the production of the neutrophil chemokine CXCL8/IL-8 from human colonic intestinal epithelial cells (IECs;Caco-2), a mediator highly expressed during CDI. Caco-2 IECs were treated for 16 hours with purified C. difficile TcdB (2.5μg/mL) in the presence of PXR agonists at various concentrations (rifampicin, SR12813). In addition to culture supernatants, cell lysates were used to evaluate cell death and toxin function by immunoblot for caspase-3 and glucosylated RAC1, respectively. We then assessed whether PXR activation could attenuate toxin-induced inflammation and tissue damage in vivo. Mice were administered TcdA/B (25μg;intrarectal administration) in the presence of PCN(25mg/kg), a rodent specific PXR agonist. After 4 hours of TcdA/B exposure, colonic tissues were harvested and the expression of IL-17A, CXCL1, CXCL2 and CXCL10 were assessed by qPCR and neutrophil infiltration assessed by flow cytometry. Results: Activation of the PXR with known agonists attenuated C. difficile TcdB-induced CXCL8/IL-8 release in Caco-2 IECs. This effect was not due to alterations in IEC survival, nor due to a direct inhibition of TcdB function by PXR agonists. In our in vivo studies, we found that PXR activation with PCN attenuated TcdA/B induced expression of the pro-inflammatory cytokines IL-17A, CXCL1, CXCL2, CXCL10 and significantly reduced neutrophil infiltration in the colon. Conclusions: Although there are many emerging treatments for CDI, drug tolerability, disease recurrence, resistance and dosing remain problematic. Taken together, these data will help us expand our knowledge of the PXR's role in host-pathogen interactions, and its potential to be modulated for the treatment of inflammation and tissue damage in CDI. Funding Agencies: CCCDr. Keith Sharkey's CCFC Chair in IBD Research, The Dr. Lloyd Sutherland Investigator in IBD/GI Research, Canadian Foundation for Innovation, Canada Research Chairs Program