Mucin secretion in inflammatory bowel disease: comparison of a macrophage-derived mucin secretagogue (MMS-68) to conventional secretagogues

The role of arachidonic acid regulatory enzymes in colorectal disease

PURPOSE

Nonsteroidal anti-inflammatory drugs have a wide ranging effect on diseases of the colon and rectum. Interestingly, nonsteroidal anti-inflammatory drugs seem to play a beneficial role in colorectal cancer chemoprevention and adenoma regression, but may have a deleterious effect in inflammatory bowel disease. Prostaglandin inhibition is central to both the beneficial and toxic effects of this class of drugs. Arachidonic acid metabolism is essential to prostaglandin synthesis.

METHODS

A Medline search using "nonsteroidal anti-inflammatory drugs," "colon cancer," "inflammatory bowel disease," "colitis," "COX inhibitors," "arachidonic acid," and "chemoprevention" as key words was performed for English-language articles. Further references were obtained through cross-referencing the bibliography cited in each work.

RESULTS

Based on numerous studies, nonsteroidal anti-inflammatory drugs have a beneficial role in colon cancer and colonic adenomas. However, they have been reported to have a deleterious effect on the colon in inflammatory bowel disease and have been shown to cause colitis. Nonsteroidal anti-inflammatory drugs work via multiple pathways, some well defined, and others unknown.

CONCLUSIONS

In the new millennium, nonsteroidal anti-inflammatory drugs may be used for chemoprevention of colorectal and other cancers. In addition, they may be used in combination with surgery and chemotherapy to primarily treat colorectal carcinoma. Undoubtedly, the use of novel cyclooxygenase inhibitors with less of a toxicity profile will allow more widespread use of nonsteroidal anti-inflammatory drugs for a variety of diseases. The future of this class of drugs is promising.

Platelet-activating factor receptor deficiency delays elimination of adult worms but reduces fecundity in Strongyloides venezuelensis-infected mice

We describe the parasitological kinetics and histopathological and immunological alterations in platelet-activating factor receptor-deficient (PAFR(-/-)) and wild-type mice after a single Strongyloides venezuelensis infection (subcutaneous inoculation of 500 L3 larvae). There was no difference in the numbers of worms that reached and became established in the small intestines of PAFR(-/-) and wild-type mice. However, at 12 days after infection, significantly more worms were recovered from PAFR(-/-) mice. Although PAFR(-/-) infected mice showed a delay in elimination of adult worms, worms established in the small intestine of these mice produced a significantly lower number of eggs due to a reduction in worm fecundity. There were also significant reductions in the number of circulating and tissue eosinophils and tumor necrosis factor levels in the small intestines of PAFR(-/-) mice infected for 7 days compared to the number and level in wild-type mice. Histological analysis confirmed the reduced inflammatory process and revealed that the PAFR(-/-) mice had a smaller number of goblet cells. The concentrations of the type 2 cytokines interleukin-4 (IL-4), IL-5, and IL-10 were lower in small intestine homogenates and in supernatants of antigen-stimulated lymphocytes from spleens or mesenteric lymph nodes of PAFR(-/-) mice than in the corresponding preparations from wild-type mice. Thus, in S. venezuelensis-infected PAFR(-/-) mice, decreased intestinal inflammation is associated with enhanced worm survival but decreased fecundity. We suggest that although a Th2-predominant inflammatory response decreases worm survival, the worm may use factors produced during this response to facilitate egg output and reproduction. PAFR-mediated responses appear to modulate these host-derived signals that are important for worm fecundity.

Platelet-activating factor activates mitogen-activated protein kinases, inhibits proliferation, induces differentiation and suppresses the malignant phenotype of human colon carcinoma cells

Recent studies suggest that the action of platelet-activating factor (PAF), a potent phospholipid modulator of allergic and inflammatory reactions, is diverse and functions as a modulator of a variety of physiological and pathological events in many cell types and tissues. Its role (if any) in modulating the proliferation, transformation and/or differentiation of epithelial colonic cells, however, is not known. In this study, we showed that PAF is biologically active in epithelial-derived human colon carcinoma cells with different phenotypic properties. These cells expressed the PAF receptor. PAF activated three prominent mitogen-activated protein kinase modules (ERK, p38MAPK and Jun N-terminal kinases) in these cells, inhibited proliferation and induced differentiation (measured by the induction of Waf1/p21 and the induction of the differentiation-related marker CEA). The net effect of PAF treatment was the suppression of malignant cell behavior (measured by anchorage-independent growth and cellular invasion). It is concluded that PAF is a modulator of proliferation and differentiation in human epithelial-derived colon carcinoma cells.

CXCR2 regulates respiratory syncytial virus-induced airway hyperreactivity and mucus overproduction

Severe inflammation and mucus overproduction are partially responsible for respiratory syncytial virus (RSV)-induced disease in infants. Using a murine model, we characterized the virally induced chemokine receptors responsible for mediating the pathophysiological response to RSV infection, we found that CXCR2 mRNA was induced at 4 days after RSV infection. Immunohistochemical staining demonstrated that CXCR2 protein was expressed on alveolar macrophages. Immunoneutralization of CXCR2 resulted in decreased airway hyperreactivity relative to the RSV-infected controls. In addition, there was decreased mucus in the bronchoalveolar lavage fluid, decreased periodic-acid Schiff staining, and significantly less mucus-associated gob-5 mRNA and protein in anti-CXCR2-treated mice. The effects of anti-CXCR2 treatment were not a result of differences in viral clearance or neutrophil influx, as these parameters were comparable in both groups of animals. To confirm our immunoneutralization studies, we performed experiments in CXCR2(-/-) mice. Results in CXCR2(-/-) mice recapitulated results from our immunoneutralization studies. However, CXCR2(-/-) mice also showed a statistically significant decrease in muc5ac, relative to RSV-infected wild-type animals. Thus, CXCR2 may be a relevant target in the pathogenesis of RSV bronchiolitis, since it contributes to mucus production and airway hyperreactivity in our model of RSV infection.

Chronically HIV-1-Infected Monocytic Cells Induce Apoptosis in Cocultured T Cells

We have previously developed a human macrophage hybridoma model system to study the effect of HIV-1 infection on monocytic function. Upon coculture of one chronically (35 days postinfection) HIV-1-infected human macrophage hybridoma cell line, 43HIV, there was a dose-dependent decrease in the viability of cocultured Ag-stimulated T cells associated with an increase in DNA strand breaks. Enhanced apoptosis was determined by labeling with biotinylated dUTP and propidium iodide, increased staining with annexin V, increased side light scatter and expression of CD95, and decreased forward light scatter and expression of Bcl-2. There was also increased DNA strand breaks as determined by propidium iodide staining in unstimulated T cells cocultured with 43HIV and in T cells stimulated with anti-CD3 mAb and PHA. Pretreatment with 5145, a human polyclonal anti-gp120 Ab that recognizes the CD4 binding region, as well as with an anti-Fas ligand mAb blocked apoptosis in CD4+ T cells but not in CD8+ T cells. A soluble factor with a Mr below 10,000 Da was defined that induced apoptosis in CD4+ and CD8+ T cells and B cells. SDS-PAGE analysis of the active fractions revealed a band of 6000 Da that, after electroelution, had proapoptotic activity. The pI of the activity was estimated to be between 6.5 and 7.0. In conclusion, chronically HIV-1-infected monocytic cells induce apoptosis in bystander-, Ag-, anti-CD3-, and mitogen-stimulated T cells by multiple factors, which may contribute to the depletion of lymphocytes induced by HIV-1.