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ABSTRACTNotch and Wnt/ß-catenin signals play essential roles in intestinal development and homeostasis. Citrobacter rodentiuminduces transmissible murine colonic hyperplasia (TMCH) and various degrees of inflammation, depending upon the genetic background. We aimed at delineating the role of the Notch and Wnt/ß-catenin pathways in the regulation of colonic crypt hyperplasia and/or colitis following C. rodentiuminfection. During TMCH, relative levels of the Notch intracellular domain (NICD) increased significantly, along with increases in Jagged-1 and Hes-1 coinciding with the progression and regression phases of hyperplasia. Blocking of Notch signaling with dibenzazepine (DBZ) for 5 days before the onset of hyperplasia also blocked Wnt/ß-catenin signaling. Targeting the Notch pathway for 5 days after the onset of hyperplasia failed to inhibit Wnt/ß-catenin-regulated crypt hyperplasia. Chronic DBZ administration for 10 days blocked both Notch and Wnt signaling, disrupted the intestinal barrier, and induced colitis. Core-3-/-mice, which are defective in mucin secretion and are susceptible to experimental triggers of colitis, also exhibited significant colitis in response to C. rodentiumplus DBZ. Chronic DBZ administration in these mice did not result in depletion of the putative stem cell marker doublecortin-like kinase-1 (DCLK1) in the crypts. Dietary bael (Aegle marmelos) extract (4%) and curcumin (4%) restored signaling via the Notch and Wnt/ß-catenin pathways, thereby promoting crypt regeneration, and also replenished the mucus layer, leading to amelioration of C. rodentium- and DBZ-induced colitis in NIH:Swiss mice. Thus, the balancing act between cell proliferation and mucus production to restore barrier integrity seems to depend upon the interplay between the Wnt/ß-catenin and Notch pathways in the TMCH model.

Citrobacter rodentium induces transmissible murine colonic hyperplasia (TMCH) and variable degrees of inflammation and necrosis depending upon the genetic background. Utilizing C. rodentium-induced TMCH in C3H/HeNHsd inbred mice, we observed significant crypt hyperplasia on days 3 and 7 preceding active colitis. NF-κB activity in the crypt-denuded lamina propria (CLP) increased within 24 h postinfection, followed by its activation in the crypts at day 3, which peaked by day 7. Increases in interleukin-α1 (IL-1α), IL-12(p40), and macrophage inflammatory protein 1α (MIP-1α) paralleled NF-κB activation, while increases in IL-1α/β, IL-6/IL-12(p40)/granulocyte colony-stimulating factor (G-CSF)/keratinocyte-derived chemokine (KC)/monocyte chemotactic protein 1 (MCP-1), and MIP-1α followed NF-κB activation leading to significant recruitment of neutrophils to the colonic mucosa and increased colonic myeloperoxidase (MPO) activity. Phosphorylation of the crypt cellular and nuclear p65 subunit at serines 276 and 536 led to functional NF-κB activation that facilitated expression of its downstream target, CXCL-1/KC, during TMCH. Distinct compartmentalization of phosphorylated extracellular signal-regulated kinase 1 and 2 ([ERK1/2] Thr180/Tyr182) and p38 (Thr202/Tyr204) in the CLP preceded increases in the crypts. Inhibition of ERK1/2 and p38 suppressed NF-κB activity in both crypts and the CLP. Dietary administration of 6% pectin or 4% curcumin in C. rodentium-infected mice also inhibited NF-κB activity and blocked CD3, F4/80, IL-1α/β, G-CSF/MCP-1/KC, and MPO activity in the CLP while not affecting NF-κB activity in the crypts. Thus, distinct compartmentalization of NF-κB activity in the crypts and the CLP regulates crypt hyperplasia and/or colitis, and dietary intervention may be a novel strategy to modulate NF-κB-dependent protective immunity to facilitate crypt regeneration following C. rodentium-induced pathogenesis.

ABSTRACTCitrobacter rodentiuminduces transmissible murine colonic hyperplasia (TMCH) and variable degrees of inflammation and necrosis depending upon the genetic background. Utilizing C. rodentium-induced TMCH in C3H/HeNHsd inbred mice, we observed significant crypt hyperplasia on days 3 and 7 preceding active colitis. NF-?B activity in the crypt-denuded lamina propria (CLP) increased within 24 h postinfection, followed by its activation in the crypts at day 3, which peaked by day 7. Increases in interleukin-a1 (IL-1a), IL-12(p40), and macrophage inflammatory protein 1a (MIP-1a) paralleled NF-?B activation, while increases in IL-1a/ß, IL-6/IL-12(p40)/granulocyte colony-stimulating factor (G-CSF)/keratinocyte-derived chemokine (KC)/monocyte chemotactic protein 1 (MCP-1), and MIP-1a followed NF-?B activation leading to significant recruitment of neutrophils to the colonic mucosa and increased colonic myeloperoxidase (MPO) activity. Phosphorylation of the crypt cellular and nuclear p65 subunit at serines 276 and 536 led to functional NF-?B activation that facilitated expression of its downstream target, CXCL-1/KC, during TMCH. Distinct compartmentalization of phosphorylated extracellular signal-regulated kinase 1 and 2 ([ERK1/2] Thr180/Tyr182) and p38 (Thr202/Tyr204) in the CLP preceded increases in the crypts. Inhibition of ERK1/2 and p38 suppressed NF-?B activity in both crypts and the CLP. Dietary administration of 6% pectin or 4% curcumin in C. rodentium-infected mice also inhibited NF-?B activity and blocked CD3, F4/80, IL-1a/ß, G-CSF/MCP-1/KC, and MPO activity in the CLP while not affecting NF-?B activity in the crypts. Thus, distinct compartmentalization of NF-?B activity in the crypts and the CLP regulates crypt hyperplasia and/or colitis, and dietary intervention may be a novel strategy to modulate NF-?B-dependent protective immunity to facilitate crypt regeneration following C. rodentium-induced pathogenesis.