Brian K. Reuter

Exacerbation of Inflammation-associated Colonic Injury in Rat through Inhibition of Cyclooxygenase-2

Cyclooxygenase type 1 is constitutively expressed and accounts for synthesis of prostaglandins in the normal gastrointestinal tract. Cyclooxygenase-2 is expressed at sites of inflammation. Selective inhibitors of cyclooxygenase-2 have been suggested to spare gastrointestinal prostaglandin synthesis, and therefore lack the ulcerogenic effects associated with standard nonsteroidal antiinflammatory drugs. However, the effects of cyclooxygenase-2 inhibitors on inflamed gastrointestinal mucosa have not been examined. We examined cyclooxygenase-2 mRNA and protein expression before and after induction of colitis in the rat, the contribution of cyclooxygenase-2 to colonic prostaglandin synthesis during colitis and the effects of selective inhibitors of cyclooxygenase-2 on colonic injury in this model. Cyclooxygenase-2 mRNA expression increased three to sixfold during the period 24 h to 1 wk after induction of colitis, with marked increases in cyclooxygenase-2 protein expression in the lamina propria and muscularis of the colon during colitis. Cyclooxygenase-1 expression (mRNA and protein) was not affected by the induction of colitis. The prostaglandins produced during colitis were largely derived from cyclooxygenase-2. Treatment with selective cyclooxygenase-2 inhibitors resulted in exacerbation of colitis, with perforation occurring when the compounds were administered for a week. These studies demonstrate that suppression of cyclooxygenase-2 can result in exacerbation of inflammation-associated colonic injury.

The primary defect in experimental ileitis originates from a nonhematopoietic source

The initiating etiologic factor in Crohns disease (CD) remains unclear. SAMP1/YitFc (SAMP) mice develop chronic ileitis similar to human CD. We used bone marrow chimeras to determine if SAMP ileitis results from a primary immunological defect or from dysregulated mucosal immunity secondary to intrinsic, nonhematopoietic (e.g., epithelial) dysfunction. SAMP mice receiving wild-type (AKR) BM developed severe ileitis, whereas SAMP BM did not confer ileitis to WT recipients. WT lymphocytes from reconstituted SAMP mice resembled native SAMP populations in regard to surface phenotype and cytokine production. Ilea from native SAMP mice and SAMP recipients of wild-type BM displayed decreased epithelial barrier resistance ex vivo and increased epithelial permeability in vivo compared to native WT mice and AKR recipients of SAMP BM. This permeability defect preceded the development of ileal inflammation, was present in the absence of commensal bacteria, and was accompanied by altered ileal mRNA expression of the tight junction proteins claudin-2 and occludin. Our results provide evidence that the primary defect conferring ileitis in SAMP mice originates from a nonhematopoietic source. Generation of pathogenic lymphocytes is a consequence of this defect and does not reflect intrinsic proinflammatory leukocyte properties. Decreased barrier function suggests that defects in the epithelium may represent the primary source of SAMP ileitis susceptibility.

Markedly reduced intestinal toxicity of a diclofenac derivative.

Addition of a nitroxybutyl moiety to diclofenac greatly reduces its damaging effects on the gastric mucosa without altering its ability to suppress prostaglandin synthesis and exert anti-inflammatory actions. The present study was performed in order to determine if this derivative of diclofenac, called nitrofenac, would also have less toxicity in the small and large intestine when administered repeatedly over a 1-2 week period. Healthy rats were given equimolar doses of diclofenac (10 mg/kg) or nitrofenac (15 mg/kg) twice daily for up to two weeks. All 10 rats receiving diclofenac died prior to completion of the study, exhibiting massive small intestinal ulceration and perforation. No deaths were observed in the rats treated with nitrofenac, and the only small intestinal abnormality observed was diffuse hyperemia. As nonsteroidal anti-inflammatory drugs have been shown to exacerbate colitis, we compared the effects of twice daily treatment with diclofenac (1-10 mg/kg) or nitrofenac (1.5-15 mg/kg) for 1 week in rats in which colitis had been induced with trinitrobenzene sulfonic acid. Diclofenac administration resulted in mortality which increased dose-dependently (e.g. 86% at 5 mg/kg) and was associated with perforation of the colon. Mortality was not observed with nitrofenac at doses of 1.5 or 7.5 mg/kg, while at 15 mg/kg the mortality rate was 33%. None of the doses of nitrofenac significantly augmented colonic injury or granulocyte infiltration (measured by myeloperoxidase activity). Suppression of colonic prostaglandin E2 synthesis was comparable with equimolar doses of diclofenac and nitrofenace. These studies demonstrate that nitrofenac has markedly reduced intestinal toxicity in healthy and colitic rats when compared to diclofenac.

Mechanisms of Tight Junction Dysregulation in the SAMP1/YitFc Model of Crohn's Disease–like Ileitis

To date, the precise etiology of inflammatory bowel disease (IBD) remains largely unknown; however, it is well accepted that IBD results from a dysregulated mucosal immune response to environmental factors in genetically susceptible hosts. The primary defect, in at least a subpopulation of IBD patients, may be due to abnormal intestinal epithelial barrier function. The SAMP1/YitFc (SAMP) mouse strain is a spontaneous model of IBD, closely resembling Crohns disease for its histologic features and localization to the terminal ileum. Dysregulated epithelial barrier function that precedes histologic evidence of ileitis has been reported to be the primary defect in SAMP mice. Data suggest that barrier dysfunction occurs in the absence of commensal bacteria and is accompanied by aberrant expression of the tight junction proteins claudin‐2 and occludin. Further investigation is needed to define the precise role of the intestinal epithelium, as well as the apical junctional complex and its associated proteins, in the pathogenesis of IBD in order to determine the etiology and aid in the development of novel treatment modalities for these devastating diseases.

Altered epithelial cell lineage allocation and global expansion of the crypt epithelial stem cell population are associated with ileitis in SAMP1/YitFc mice.

Crohns disease is characterized by cycles of mucosal injury and ulceration followed by epithelial regeneration and restoration of normal epithelial function. In this study, we examined whether ileitis in SAMP1/YitFc mice, a recombinant-inbred line that spontaneously develops ileitis resembling human Crohns disease, was associated with alterations in normal patterns of epithelial differentiation or changes in epithelial regeneration after experimental injury. Increased numbers of Paneth, goblet, and intermediate cells were present focally in the ileum of SAMP1/YitFc mice by 4 weeks of age, before any histological evidence of acute or chronic inflammation. This increase in secretory cells became more pronounced at sites of ileitis with increasing age and inflammation. Additionally, there was mispositioning of Paneth and intermediate cells along the crypt-to-villus unit. A concomitant reduction in the number of absorptive enterocytes was observed. In contrast to the ileal-specific changes in lineage allocation, crypt stem cell numbers began to increase in both the ileum and proximal jejunum at the onset of inflammation in SAMP1/YitFc mice. These data suggest that the alterations in epithelial cell differentiation and increases in the size of the crypt stem cell population observed in SAMP1/YitFc mice are regulated by distinct mechanisms. We speculate that these epithelial alterations may play a role in the pathogenesis of ileitis in this murine model of Crohns disease.

A unique therapeutic approach to emesis and itch with a proanthocyanidin-rich genonutrient

BackgroundWe examined the therapeutic potential of a proprietary Croton palanostigma extract (Zangrado®) in the management of emesis and itch.MethodsEmesis was induced in ferrets with morphine-6-glucuronide (0.05 mg/kg sc) in the presence of Zangrado (3 mg/kg, ip) and the cannabinoid receptor 1 antagonist, AM 251 (5 mg/kg, ip). Topical Zangrado (1%) was assessed for anti-pruretic actions in the 5-HT-induced scratching model in rats and evaluated in capsaicin-induced gastric hyperemia as measured by laser doppler flow. In the ApcMinmouse model of precancerous adenomatosis polyposis, mice received Zangrado (100 μg/ml in drinking water) from the age of 6 – 16 weeks for effects on polyp number. In RAW 264.7 cells Zangrado was examined for effects on lipopolysaccharide-induced nitrite production.ResultsZangrado was a highly effective anti-emetic, reducing morphine-induced vomiting and retching by 77%. These benefits were not associated with sedation or hypothermia and were not reversed by cannabinoid receptor antagonism. Itch responses were blocked in both the morphine and 5-HT models. Zangrado did not exacerbate the ApcMincondition rather health was improved. Capsaicin-induced hyperemia was blocked by Zangrado, which also attenuated the production of nitric oxide by activated macrophages.ConclusionZangrado is an effective anti-emetic and anti-itch therapy that is devoid of common side-effects, cannabinoid-independent and broadly suppresses sensory afferent nerve activation. This complementary medicine represents a promising new approach to the management of nausea, itch and irritable bowel syndrome.