Inflammatory bowel disease. Part I: Nature and pathogenesis

The role of dietary polyphenols in inflammatory bowel disease: A possible clue on the molecular mechanisms involved in the prevention of immune and inflammatory reactions

Inflammatory bowel disease (IBD) is one of the major complications of the gastrointestinal tract, characterized by chronic inflammation, which disturbs the quality of life of the affected individuals. Genetic predisposition, immune, inflammatory, and enzyme-mediated signaling cascades are the primary mechanisms involved in the pathogenesis of the disease. Currently, the treatment strategy involves the maintenance of remission and induction of inflammation by anti-inflammatory agents and immune suppressants. Polyphenol-containing diets, including fruits and vegetables of regular use, possess anti-inflammatory, and antioxidant potential through the inhibition of major contributing pathways to IBD. This review discusses the role of these dietary polyphenols in downregulating the major signaling cascades in IBD. Our review encourages the development of nutritional strategies to improve the efficiency of current therapies for IBD and reduce the risks of side effects associated with conventional therapy. PRACTICAL APPLICATIONS: At present, almost every third person in society is under stress and having chronic disorders like diabetes, arthritis, allergy, cardiovascular disease, IBD, etc. This insists on the direct/indirect role of changes in the lifestyle for such deterioration in society. This review would emphasize the medicinal value of polyphenols present in fruits and vegetables for chronic inflammatory disorders. This concept portrays the food components which have the potential to promote health, improve general well-being, and reduce the risk of IBD. We propose to add fruits with bioactive polyphenols in the regular diet to help in preventing the immune-mediated intestinal chronic inflammatory syndrome and reduce the risks of colorectal cancer development.

Dietary selenium deficiency exacerbates DSS-induced epithelial injury and AOM/DSS-induced tumorigenesis

Selenium (Se) is an essential micronutrient that exerts its functions via selenoproteins. Little is known about the role of Se in inflammatory bowel disease (IBD). Epidemiological studies have inversely correlated nutritional Se status with IBD severity and colon cancer risk. Moreover, molecular studies have revealed that Se deficiency activates WNT signaling, a pathway essential to intestinal stem cell programs and pivotal to injury recovery processes in IBD that is also activated in inflammatory neoplastic transformation. In order to better understand the role of Se in epithelial injury and tumorigenesis resulting from inflammatory stimuli, we examined colonic phenotypes in Se-deficient or -sufficient mice in response to dextran sodium sulfate (DSS)-induced colitis, and azoxymethane (AOM) followed by cyclical administration of DSS, respectively. In response to DSS alone, Se-deficient mice demonstrated increased morbidity, weight loss, stool scores, and colonic injury with a concomitant increase in DNA damage and increases in inflammation-related cytokines. As there was an increase in DNA damage as well as expression of several EGF and TGF-β pathway genes in response to inflammatory injury, we sought to determine if tumorigenesis was altered in the setting of inflammatory carcinogenesis. Se-deficient mice subjected to AOM/DSS treatment to model colitis-associated cancer (CAC) had increased tumor number, though not size, as well as increased incidence of high grade dysplasia. This increase in tumor initiation was likely due to a general increase in colonic DNA damage, as increased 8-OHdG staining was seen in Se-deficient tumors and adjacent, non-tumor mucosa. Taken together, our results indicate that Se deficiency worsens experimental colitis and promotes tumor development and progression in inflammatory carcinogenesis.

Nutritional regulation of porcine bacterial-induced colitis by conjugated linoleic acid

Excessive intake of saturated fatty acids and/or linoleic acid favors the induction of an array of lipid mediators and cytokines enhancing inflammatory responses. Conversely, dietary supplementation with (n-3) fatty acids or vitamin D ameliorates inflammation and autoimmune diseases. Although it was well accepted that conjugated linoleic acid (CLA) prevented diseases with a common inflammatory pathogenesis (i.e., cancer and atherosclerosis), no studies were available on the roles of CLA in mucosal inflammation. The present study was designed to investigate the anti-inflammatory actions and molecular mechanisms underlying the regulation of colonic health by CLA. We hypothesized that colonic inflammation can be ameliorated by dietary CLA supplementation. To test this hypothesis, inflammation of the colonic mucosa was triggered by challenging pigs fed either soybean oil-supplemented or CLA-supplemented diets with an enteric bacterial pathogen (i.e., Brachyspira hyodysenteriae). Immunoregulatory cytokines and peroxisome proliferator-activated receptor-gamma (PPAR-gamma) mRNA expression were assayed in colonic lymph nodes and colon of pigs. Colonic mucosal lesions and lymphocyte subset distribution were evaluated by histology and immunohistochemistry. Supplementation of CLA in the diet before the induction of colitis decreased mucosal damage; maintained cytokine profiles (i.e., interferon-gamma and interleukin-10) and lymphocyte subset distributions (i.e., CD4+ and CD8+), resembling those of noninfected pigs; enhanced colonic expression of PPAR-gamma; and attenuated growth failure. Therefore, CLA fed preventively before the onset of enteric disease attenuated inflammatory lesion development and growth failure.

Immunological basis of inflammatory bowel disease: role of the microcirculation

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the intestine and/or colon of unknown etiology in which patients suffer from severe diarrhea, rectal bleeding, abdominal pain, fever, and weight loss. Active episodes of IBD are characterized by vasodilation, venocongestion, edema, infiltration of large numbers of inflammatory cells, and erosions and ulcerations of the bowel. It is becoming increasingly apparent that chronic gut inflammation may result from a dysregulated immune response toward components of the normal intestinal flora, resulting in a sustained overproduction of proinflammatory cytokines and mediators. Many of these Th1 and macrophage-derived cytokines and lipid metabolites are known to activate microvascular endothelial cells, thereby promoting leukocyte recruitment into the intestinal interstitium. This review discusses the basic immune mechanisms involved in the regulation of inflammatory responses in the gut and describes how a breakdown in this protective response initiates chronic gut inflammation.

The accessory cell populations in ulcerative colitis: a comparison between the colon and appendix in colitis and acute appendicitis

We present an immunohistochemical study of accessory cells in acute appendicitis and ulcerative colitis (UC). By comparing these two diseases, it is possible to distinguish between changes associated with inflammatory bowel disease and those resulting from nonspecific intestinal inflammation. Nine total colectomy specimens from patients with UC, in which the appendix was also involved, were compared with nine cases of acute appendicitis. Accessory cells were stained for CD68 (PGMI), ACPI (acid cysteine proteinase inhibitor), S100 protein, MAC387 (calgranulin), CD1a, factor XIIIa, and WR18 (HLA class II). In ulcerative colitis, but not acute appendicitis, there was extension of a network of S100 positive dendritic cells into the crptal mucosa, and these S100-positive dendritic cells were closely aligned with the epithelium. The epithelium in UC, but not in acute appendicitis, showed intense upregulation of HLA class II, and this was particularly marked at the crypt bases. Dendritic, MAC387-positive cells were seen only in UC. In both diseases there were abundant ACPI-positive accessory cells in the cryptal areas, a population normally restricted to the dome areas. Factor XIIIa- and PGM1-positive cells, although abundant in both conditions, had distributions similar to those that we had previously shown in normal controls. No CD1a-positive cells were identified in either UC or acute appendicitis. We hypothesize that S100 identifies a subpopulation of activated macrophages. The concentration of this subpopulation, in close contact with the epithelium, which also shows altered expression of HLA class II antigens, suggests that a component of the immune response is targeting this area in UC. In addition, we also suggest that the identification of MAC387-positive dendritic cells in UC reflects increased macrophage turnover in inflammatory bowel disease.

Endothelial proliferation in experimental granulomatous colitis. Autoradiography and immunohistochemistry studies

The time sequence and magnitude of endothelial cell proliferation was investigated in an experimental model of granulomatous colitis in rats, induced by intramural inoculations of mycobacterium Bacillus Calmette-Guerin. Colonic tissues were assessed by gross examination, histopathology, autoradiography, and immunohistochemistry. Gross examination of the colonic tissue showed thickening of the colonic wall, erythema, hemorrhage, and scattered ulcers. Histopathological findings were characterized by an acute transmural inflammation, progressing to chronic inflammation accompanied by regenerative changes in the glandular epithelium, goblet cell depletion, mucosal atrophy and fibrosis. Well-developed noncaseating granulomas were first observed at day 5 and were found to be a dominant feature up to day 17. Autoradiographic studies showed increased endothelial cell labeling up to 17% at 48 hr, compared to less than 1% labeling in control animals. Immunostaining for factor VIII-related antibody, an endothelial cell marker, showed increased numbers of microvessels and individual positive cells located in areas of inflammation as early as 24 hr. At day 5 these individual cells along with dilated neocapillaries were found surrounding the granulomas. This model of granulomatous colitis mimics many features of the human disease state. The early increase in endothelial cell proliferation that precedes granuloma formation during the course of the inflammatory response may suggest that the events leading to the expression of granulomatous colitis are dependent on endothelial proliferation.