Browsing by Author "Beck, Paul L."
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Item Open Access Clostridium difficile toxin-induced intestinal injury is mediated by the inflammasome(2009) Ng, Jeffrey; Beck, Paul L.; Muruve, Daniel A.Item Open Access The EGF Receptor and HER2 Participate in TNF-α-Dependent MAPK Activation and IL-8 Secretion in Intestinal Epithelial Cells(Hindawi Publishing Corporation, 2012-07-24) Jijon, Humberto B.; Buret, Andre; Hirota, Christina L.; Hollenberg, Morley D.; Beck, Paul L.Item Open Access Exaggerated IL-15 and Altered Expression of foxp3+ Cell-Derived Cytokines Contribute to Enhanced Colitis in Nlrp3−/− Mice(2016-08-17) Hirota, Simon A.; Ueno, Aito; Tulk, Sarah E.; Becker, Helen M.; Schenck, L. Patrick; Potentier, Mireille S.; Li, Yan; Ghosh, Subrata; Muruve, Daniel A.; MacDonald, Justin A.; Beck, Paul L.The pathogenesis of Crohn’s disease (CD) involves defects in the innate immune system, impairing responses to microbes. Studies have revealed that mutations NLRP3 are associated with CD. We reported previously that Nlrp3−/− mice were more susceptible to colitis and exhibited reduced colonic IL-10 expression. In the current study, we sought to determine how the loss of NLRP3 might be altering the function of regulatory T cells, a major source of IL-10. Colitis was induced in wild-type (WT) and Nlrp3−/− mice by treatment with dextran sulphate sodium (DSS). Lamina propria (LP) cells were assessed by flow cytometry and cytokine expression was assessed. DSS-treated Nlrp3−/− mice exhibited increased numbers of colonic foxp3+ T cells that expressed significantly lower levels of IL-10 but increased IL-17. This was associated with increased expression of colonic IL-15 and increased surface expression of IL-15 on LP dendritic cells. Neutralizing IL-15 in Nlrp3−/− mice attenuated the severity of colitis, decreased the number of colonic foxp3+ cells, and reduced the colonic expression of IL-12p40 and IL-17. These data suggest that the NLRP3 inflammasome can regulate intestinal inflammation through noncanonical mechanisms, providing additional insight as to how NLRP3 variants may contribute to the pathogenesis of CD.Item Open Access Examining the Role of NLRP3 in Intestinal Homeostasis and Fibrosis(2018-07-24) Tjong, Jessica Ria; Beck, Paul L.; Muruve, Daniel A.; Hirota, Simon AndrewFibrosis is the most common cause of surgery in Crohn’s disease (CD) and the mechanisms of fibrosis in CD are not well understood. Nucleotide-binding oligomerization domain (NOD)-like receptors, including NLRP3, are cytosolic protein sensors involved in inflammatory pathways and implicated in CD pathogenesis. NLRP3 has been shown to drive fibrosis in various tissues, including the heart, kidney, lungs, liver and pancreas; however, its role in intestinal fibrosis is currently unknown. The main hypothesis of this project is that NLRP3 mediates intestinal fibrosis. Primary intestinal myofibroblasts isolated from Nlrp3-/- mice had reduced response to pro-fibrogenic cytokine TGFβ compared to wildtype (WT), with lower phosphorylation of downstream signalling protein Smad2, and decreased induction of connective tissue growth factor (CTGF), as well as decreased migration. Loss of NLRP3 in intestinal myofibroblasts also led to increased resistance to cell death during serum deprivation. In an in vivo model of chronic colitis, Nlrp3-/- mice had significantly worse disease and susceptibility compared to WT. However, both Nlrp3-/- and WT mice had similar levels of intestinal fibrosis. Relevance to the human disease was further highlighted by the finding that NLRP3 transcript levels in mucosal colonic biopsies from patients with CD were significantly increased, and increased expression correlated with inflammation. Overall, our data suggest that loss of NLRP3 leads to reduced response to TGFβ in colonic myofibroblasts, and that NLRP3 may potentiate TGFβ beta signalling in the gut. Further insights into the mechanisms of intestinal fibrosis will significantly impact the development of new tools that will help with assessing and treating patients with CD complications.Item Open Access The EGF Receptor and HER2 Participate in TNF-α-Dependent MAPK Activation and IL-8 Secretion in Intestinal Epithelial Cells(2012-09-05) Jijon, Humberto B.; Buret, Andre; Hirota, Christina L.; Hollenberg, Morley D.; Beck, Paul L.TNF-alpha activates multiple mitogen-activated protein kinase (MAPK) cascades in intestinal epithelial cells (IECs) leading to the secretion of interleukin 8 (IL-8), a neutrophil chemoattractant and an angiogenic factor with tumor promoting properties. As the epidermal growth factor receptor (EGFR) is a known transducer of proliferative signals and a potent activator of MAPKs, we hypothesized that the EGFR participates in TNF-dependent MAPK activation and IL-8 secretion by intestinal epithelial cells (IECs). We show that the EGFR is tyrosine-phosphorylated following treatment of IECs (HT-29 and IEC-6) with TNF-alpha. This requires EGFR autophosphorylation as it was blocked by the EGFR kinase inhibitor AG1478. Autophosphorylation was also inhibited by both a Src-kinase inhibitor and the metalloproteinase inhibitor batimastat. TNF treatment of IECs resulted in the accumulation of soluble TGF-alpha; treatment of IECs with batimastat suppressed TGF-alpha release and immunoneutralization of TGF-alpha resulted in decreased EGFR and ERK phosphorylations. TNF-alpha treatment of IECs resulted in an association between EGFR and HER2 and inhibition of HER2 using a specific inhibitor AG879 in combination with AG1478-suppressed TNF-alpha-dependent ERK phosphorylation and IL-8 release. Downregulation of HER2 via siRNA resulted in a significant decrease in ERK phosphorylation and a 50% reduction in IL-8 secretion.Item Open Access The role of PAR-1 & PAR-2 in the modulation of intestinal epithelial wound repair in vitro(2005) Swaminathan, Sunita; Beck, Paul L.Item Metadata only The role of PAR-1 and PAR-2 in the modulation of intestinal epithelial wound repair in vitro(2005) Swaminathan, Sunita; Beck, Paul L.