Abstract 2833: Functional cross-talk between the Wnt and Notch pathways regulate hyperplasia and/or colitis in response to bacterial infection
Authors: Ahmed Ishfaq , Chandrakesan Parthasarathy , Mccoy Sandra , Xia Lijun , Umar Shahid 
Published: June 2012

Notch and Wnt/β-catenin pathways play essential roles in intestinal development, homeostasis and neoplasia. Citrobacter rodentium (CR) induces transmissible murine colonic hyperplasia (TMCH) and variable degrees of inflammation and necrosis depending upon the genetic background. In the current study, we investigated functional cross-talk between the Notch and Wnt pathways and how they regulate colonic crypt hyperplasia and/or colitis in response to CR infection. Infection of NIH:Swiss outbred mice with CR induced gross thickening and rigidity of the distal colon and crypt hyperplasia which peaked by day 12, persisted until day 27 before declining by day 34. Nuclear staining for Notch target Hes-1 increased at days 6-27 before declining at day 34. Acute (5 days) treatment with Notch blocker dibenzazepine (DBZ; @10μmol/Kg) beginning on the 1st day of CR infection followed by euthanasia at day 6 blocked both Notch and Wnt signaling and induced goblet cells hyperplasia; acute DBZ treatment beginning on the 7th day of CR infection followed by euthanasia at day 12 inhibited Notch signaling without blocking the components of the Wnt pathway: both β-catenin and its downstream target Jagged-1, a Notch ligand, increased significantly at day 12 leading to crypt hyperplasia. Chronic (10 days) DBZ treatment beginning on the 1st day of CR infection followed by euthanasia at day 12 blocked both Notch and Wnt signaling, increased epithelial permeability and induced colitis. To directly establish that the disruption of mucus gel layer overlying the gut epithelium by DBZ may be the cause of colitis in CR infected animals, we utilized mice lacking Core 3 beta1,3-N-acetylglucosaminyltransferase, an enzyme important in synthesis of Core 3-derived O-glycans, the primary component of the intestinal mucins. The Core-3−/− mice are susceptible to experimental triggers of colitis. Infection of Core-3−/− mice with CR destroyed the intestinal barrier and induced colitis which was exacerbated following DBZ treatment. The changes accrued were not due to loss of colonic stemness as DBZ did not alter putative stem cell marker DCAMKL-1 expression in either strain. Dietary bael extract (4%) and curcumin (4%) restored the Notch/Wnt cross-talk and promoted crypt regeneration/hyperplasia in CR-infected/DBZ-treated SW mice. Thus, 1. TMCH exhibits active Notch and Wnt signaling. 2. Blocking Notch signaling early induces goblet cells hyperplasia but no colitis. 3. Acute but late stage blocking of Notch signaling does not abrogate Wnt/β-catenin-induced crypt hyperplasia. 4. Chronic defect in Notch signaling also blocks Wnt pathway and induces colitis in response to CR infection due to loss of barrier function and lack of crypt regeneration despite lack of alterations in colonic stemness. Thus, both Wnt and Notch cross-talk and epithelial barrier regulate hyperplasia and/or colitis in response to CR infection.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2833. doi:10.1158/1538-7445.AM2011-2833