Importantly, this synergistic response was also seen in macrophages from a donor wild type for NOD2 but was absent in macrophages from patients with Crohn disease homozygous for non-functional NOD2 variants. These studies provide strong molecular links between vitamin D deficiency and the genetics of Crohn disease, a chronic incurable inflammatory bowel condition, as Crohn's pathogenesis is associated with attenuated NOD2 or DEFB2/HBD2 function.

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Butyrate exerts potent anti-tumor effects by inhibiting cancer cell growth and inducing apoptosis. However, the molecular mechanisms mediating these effects remain largely unknown. Using the Caco-2 cell line, a well established model of colon cancer cells, our data show that butyrate induced apoptosis (maximum 79%) is mediated via activation of the caspasecascade. A key event was the proteolytic activation of caspase-3, triggering degradation of poly-(ADP-ribose) polymerase (PARP). Inactivation of caspase-3 with the tetrapeptide zDEVD-FMK completely inhibited the apoptotic response to butyrate. In parallel, butyrate potently upregulated the expression of the pro-apoptotic protein bak, without changing Caco-2 cell bcl-2 expression. Butyrateinduced Caco-2 cell apoptosis was completely blocked by the addition of cycloheximide, indicating the necessity of protein synthesis. However, when this inhibitor was added at a time point where bak expression was already enhanced (12 ± 16 h after butyrate stimulation), it failed to protect Caco-2 cells against apoptosis. Taken together, these data provide evidence that the molecular events involved in butyrate induced colon cancer cell apoptosis include the caspasecascade and the mitochondrial bcl-pathway.

The structure and function of enterocyte membranes are particularly sensitive to the degree of fatty acid saturation. The objective of the present study was to assess intestinal fat transport in essential fatty acid (EFA)-deficient animal models. Both the digestive and absorptive phases leading to the formation and the secretion of triglyceride (TG)-rich lipoproteins were investigated. After an intraduodenal fat infusion, the percentage increase of plasma TG over fasting values was examined over a period of 4 h in two groups of control and EFA-deficient rats. Lower values at 1 and 2 h (P less than 0.05) were observed in EFA-deficient rats, suggesting fat malabsorption. Likewise, postprandial chylomicronemia was diminished. In a separate group of rats, EFA deficiency was associated with reduced TG and chylomicron-TG transport into lymph. Although pancreatic lipase activity did not change (47.1 vs. 46.2 mumol free fatty acids.mg protein-1.h-1), bile flow was decreased over the 8-h period of collection. Concomitantly, a significant decline (nmol.min-1.g liver-1, P less than 0.05) was discernible in the biliary secretory rate of bile salts (14.09 +/- 2.13 vs. 35.09 +/- 3.73), phospholipids (7.01 +/- 0.61 vs. 11.79 +/- 1.65) and cholesterol (0.19 +/- 0.01 vs. 0.83 +/- 0.06). In vitro studies, utilizing everted sacs incubated with mixed micelles, revealed that EFA-deficient jejunal segments of rats incorporated and esterified less [14C]oleic acid (21 and 32%, respectively). Moreover, the synthesis and secretion of TG-rich lipoproteins were found markedly reduced in mouse jejunal explant cultures. We conclude that EFA deficiency modifies both the intraluminal and intracellular phases of fat absorption.

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Caco-2 cells were incubated with iron/ascorbate for 1-24 h, they exhibited increased malondialdehyde levels and decreased polyunsaturated fatty acid proportion in favor of saturated fatty acids. These modifications were accompanied with alterations in membrane fluidity and permeability. The oxidative stress did not induce changes in the antioxidant enzyme activity of superoxide dismutase, catalase, glutathione peroxidase, and glutathione transferase, or in cellular glutathione content. However, iron/ascorbate-mediated lipid peroxidation promoted inhibitor-B degradation and NF-B activation, as well as gave rise to IL-8, cyclooxygenase-2, and ICAM-1. These results support the importance of oxidant/ antioxidant balance in the epithelial cell inflammatory response. oxidative stress; membrane transport; nuclear factor-B; cyclooxygenase-2; intercellular adhesion molecule-1.

Objective.Inflammatory bowel disease (IBD) is generally reported to be associated with spondylarthropathies (SpA) in 5%–15% of cases. Systematic colonoscopic assessment by protocol demonstrated mucosal inflammation characteristic of Crohn disease (CD) in up to one-third of patients with SpA. Video capsule endoscopy (CE) is a superior diagnostic tool to detect small bowel mucosal disease. Our study compared the accuracy of CE to standard colonoscopy for detection of inflammatory bowel lesions in patients with SpA, and to describe predictors of small bowel inflammation (SBI) in this cohort.Methods.Prospective cross-sectional study of adult patients followed for SpA. Patients were evaluated by CE and standard colonoscopy with biopsies. SBI was quantified using the Lewis Score. Additional screening tests included fecal calprotectin (FCP), C-reactive protein (CRP), and a diagnostic panel of serologic, inflammatory and genetic tests (SGI).Results.There were 64 patients recruited (53% female, mean age 42 ± 13 yrs). Chronic gastrointestinal (GI) symptoms were present in 57%. CE revealed significant SBI in 27/64 (42.2%), compared to 7/64 (10.9%) by standard colonoscopy (p = 0.035). Elevated FCP was associated with small bowel CD (OR 4.5, 95% CI 1.01–19.9; p = 0.042). No correlation was observed with presence of GI symptoms, CRP, or SGI results. Finding CD led to a change in management in 65.2% of cases.Conclusion.CE uncovered SBI consistent with CD in 42.2% of patients with SpA, with a significant incremental yield over colonoscopy of 31%. FCP levels were significantly correlated with CE results, while GI symptoms and SGI results were poor predictors of SBI.

FAS-FAS ligand interaction has been implicated in increased enterocyte apoptosis seen in immune-mediated bowel injury. However, scant information exists on the role of FAS in physiological enterocyte turnover. In the present study, the regulation of enterocyte FAS and FAS ligand expression by cytokines and its functional role in human intestinal epithelial cell apoptosis and proliferation were analyzed with two different models: a nontransformed human intestinal epithelial cell line (HIEC) and normal colonic explant cultures. HIEC constitutively expressed FAS, as analyzed by flow cytometry. However, stimulation with agonistic anti-FAS antibody (1-500 ng/ml) did not induce HIEC apoptosis. In contrast, in the presence of tumor necrosis factor alpha (TNFalpha) and/or interferon gamma (IFNgamma), HIEC became highly susceptible to FAS-induced apoptosis. The sensitizing effect to FAS-induced apoptosis was mediated via TNFalpha- and IFNgamma-induced upregulation of FAS expression (maximally 348%). Receptor studies showed that the effect of TNFalpha on FAS was mediated via the p55 TNF receptor. In colonic organ cultures, IFNgamma and TNFalpha also enhanced colonocyte FAS expression, resulting in a markedly increased apoptotic response to stimulation of this receptor, as shown by in situ terminal deosyuridine triphosphate nick-end staining. Neither FAS ligand expression nor its induction by cytokines was observed in HIEC or colonic explants. Proliferation studies showed that FAS is not implicated in regulating HIEC growth. These findings suggest that, despite the fact that normal human enterocytes express FAS, costimulatory factors, such as TNFalpha or IFNgamma, abundantly secreted under inflammatory conditions, are necessary to sensitize intestinal epithelial cells to FAS-induced apoptosis by upregulating this receptor.