Induction of HLA-DR antigen expression on human colonic epithelium by tumor necrosis factor-alpha and interferon-gamma

Positive Feedback Cycle of TNFα Promotes Staphylococcal Enterotoxin B-Induced THP-1 Cell Apoptosis

Staphylococcal enterotoxin B (SEB) has been demonstrated to be of importance in Staphylococcus aureus related diseases, such as atopic dermatitis (AD). Dysregulated apoptosis in AD is remarkable, and SEB can induce apoptosis of various cell types. However, the mechanisms by which SEB induces apoptosis and influences disease processes remain unclear. In this study, the recombinant SEB-induced THP-1 monocyte apoptosis was demonstrated in the absence of preliminary cell activation in a time- and dose-dependent manner. SEB could up-regulate the expression of tumor necrosis factor alpha (TNFα) in THP-1 cells and induce apoptosis via an extrinsic pathway. TNFα could in turn increase the expression of HLA-DRa, the SEB receptor on the cell surface. As a result, a positive feedback cycle of TNFα was established. TNFα expression and SEB-induced apoptosis were decreased by knocking down the expression of either HLA-DRa or TNFR1. Therefore, the feedback cycle of TNFα is crucial for SEB functions. This work provides insights into the mechanisms of SEB-induced monocyte apoptosis and emphasizes the major role of TNFα in future related studies.

Strong HLA-DR antigen expression on cancer cells relates to better prognosis of colorectal cancer patients: Possible involvement of c-myc suppression by interferon-gamma in situ

Strong HLA-DR antigen expression on cancer cells relates to better prognosis of colorectal cancer patients, although the precise mechanism is controversial. From an immunological point of view, HLA-DR antigen, induced by interferon (IFN)-gamma, is required for tumor-associated antigen recognition by CD4(+) T cells. For instance, as reported previously, the expression of HLA-DR antigen in normal colorectal epithelium immediately adjacent to cancer coincided significantly with the existence of IFN-gamma mRNA in the tissue. From another aspect, IFN-gamma has been revealed to suppress c-myc expression in vivo through a stat1-dependent mechanism, which is important for cell growth, cell cycle and chromosome instability. In the present study, strong HLA-DR-positive expression on cancer cells was significantly related to better prognosis for colorectal cancer patients. High IFN-gamma mRNA expression in situ indicated significantly less activation of c-myc mRNA expression. Further, HLA-DR antigen expression in cancer cells, as well as Dukes stages, was an independent factor for better long-term survival by multivariate analysis. Taken together, IFN-gamma, which induces HLA-DR antigens on the cell surface, also suppresses c-myc expression in situ, and is a possible non-immunological mechanism involved in the better long-term survival of colorectal cancer patients.

Prolonged-release mesalazine: a review of its therapeutic potential in ulcerative colitis and Crohn's disease

Prolonged-release mesalazine (Pentasa) consists of ethylcellulose-coated microgranules from which mesalazine (known in the US as mesalamine) is released in the small and large intestine in a diffusion-dependent manner. Dose-dependent improvements in clinical and endoscopic parameters have been reported with prolonged-release mesalazine 2 and 4 g/day in clinical trials in patients with mild to moderately active ulcerative colitis. Induction of clinical and endoscopic remission was achieved in more patients receiving a daily dosage of 4 g/day than in those receiving placebo. In patients with ulcerative colitis in remission, prolonged-release mesalazine is effective in reducing the rate of relapse. Higher dosages tend to be more effective, and a 12-month remission rate of 64% has been reported for patients treated with a 4 g daily dosage of this formulation. Comparative data indicate that prolonged-release mesalazine has similar efficacy in maintaining remission to molar equivalent doses of sulfasalazine. Data from a study in patients with mild to moderately active Crohn's disease indicates that higher dosages (4 g/day) of prolonged-release mesalazine are more effective than placebo in reducing disease activity. After 16 weeks' treatment, 64% of patients receiving a 4 g/day dosage experienced clinical improvement and 43% attained remission. In studies of patients in remission of Crohn's disease, the formulation appears to be more effective in preventing relapse in patients with isolated small bowel disease than in those with colonic involvement. The tolerability profile of oral prolonged-release mesalazine is similar to that of placebo and the incidence of adverse events does not appear to be dose-related. Nausea/vomiting, diarrhoea, abdominal pain and dyspepsia occur most frequently, although their incidence is low. Reports of nephrotoxicity during prolonged-release mesalazine treatment are rare.

CONCLUSIONS

Oral prolonged-release mesalazine is effective for maintenance and induction of remission of mild to moderately active colitis, both in patients with distal disease and in those with pancolitis. The formulation has similar efficacy to that of equimolar concentrations of sulfasalazine. Prolonged-release mesalazine also appears to be effective in the treatment of Crohn's disease, and maintenance therapy is of particular value in patients with isolated small bowel involvement. Evidence suggests that higher dosages (3 to 4 g/day) of prolonged-release mesalazine have additional therapeutic benefits over lower dosages in patients with inflammatory bowel disease without increasing the incidence of adverse events.

Independent prognostic value of eosinophil and mast cell infiltration in colorectal cancer tissue

Overall peritumoural inflammatory cell infiltration is a prognostic variable in solid tumours, but the survival-related impact of the individual cell types within the infiltrate has still not been fully evaluated and compared with the conventional disease classification. In the present study, the prognostic value of individual white cell counts in the peritumoural inflammatory infiltrate in colorectal cancer was assessed. Intra-operative tumour tissue samples from 584 patients undergoing elective surgery for colorectal cancer were included. None of the patients received pre- or post-operative adjuvant chemotherapy. Tissue blocks were cut from the periphery of the tumours and embedded in paraffin. All blocks included both tumour tissue and normal bowel tissue. Serial sections of 4 microm were analysed for tumour tissue inflammatory cell infiltration using a computer- and video-assisted microscope, which allowed semi-automated quantification of cells within a fixed area. Total white cells and individual counts of eosinophils, neutrophils, mast cells, lymphocytes, and plasma cells were evaluated in every tumour specimen. Stratification into four groups with similar numbers of events was used to dichotomize the cell counts with respect to survival. The median observation period was 61 (49-75) months. In a multivariate analysis including Dukes' stage, gender, age, peri-operative blood transfusion, tumour location, and counts of specific inflammatory cells, only advanced Dukes' stage ( p< 0.0001), high age ( p=0.0003), and tumour location in the rectum predicted poor survival, while high counts of eosinophils ( p=0.006) and mast cells ( p=0.02) predicted good survival. Tumour-associated eosinophilia and mastocytosis appear to be independent prognostic variables in colorectal cancer. Future studies should investigate the potential biological role of tumour tissue eosinophils and mast cells in the modulation of tumour growth.

Microbiology of the intestinal lymph follicle: a clue to elucidate causative microbial agent(s) in Crohn's disease

It has been suggested that microbial agent(s) are involved in the onset of Crohn's disease. None of the candidates, however, has been unequivocally demonstrated to be a causative agent. The macroscopically earliest lesion takes place in the lymph follicle, irrespective of the initial attack or relapse in Crohn's disease. Human leucocyte antigen-DR (HLA-DR) antigens are expressed on the epithelium around the lymph follicle even in areas endoscopically uninvolved in Crohn's disease. These observations make the lymph follicle critical in the onset of Crohn's disease. The lymph follicle is a port of entry of a variety of microbial agent(s), leading to the speculation that microbial agent(s) exist in the lymph follicle. Polymerase chain reaction (PCR) using universal primers designed from conserved regions of bacterial ribosomal RNA or techniques such as representational difference analysis, may well identify microbial agent(s) in the lymph follicle that are specific to Crohn's disease. The existence of bacteria in the lymph follicle is here indicated by preliminary studies.

Effect of gamma-interferon on binding of gliadin and other food peptides to the human intestinal cell line HT-29

gamma-Interferon is one of the main cytokines released during activation of intestinal lymphocytes in coeliac patients. The question has never been addressed whether gamma-interferon influences binding of gliadin and other food peptides to human enterocytes. Therefore, the human intestinal epithelial cell line HT-29 was cultured with gliadin, casein, beta-lactoglobulin and ovalbumin, with or without gamma-interferon, and peptide binding to cells was determined by flow cytometry and fluorescence microscopy. gamma-Interferon stimulated gliadin binding by a factor of 4. Binding was saturable with half maximal binding at 0.15 mg/ml. For maximal binding, an incubation of at least 24 h was necessary. gamma-Interferon increased binding of beta-lactoglobulin and casein, too, but inhibited that of ovalbumin. Binding of gliadin was inhibited by the other peptides. Under the conditions of ongoing mucosal inflammatory reactions and release of gamma-interferon, enhanced binding may trigger intestinal lymphocytes, increase secretion of cytokines and thus induce a vicious circle.

Effect of interferon-gamma on lymphocyte cell subsets in human large bowel: a study using organ culture method

This study was conducted to investigate the effects of interferon (IFN)-gamma on normal colonic lamina propria lymphocyte subsets in humans using organ culture method. Lamina propria lymphocyte subsets in normal colonic biopsy tissues receiving 1 x 10(5) u/ml of IFN-gamma (IFN-gamma-treated group) were investigated in comparison with those cultured in medium only (IFN-gamma-non-treated group) for 24 hr. CD8-positive cells and IgG, IgA1 and IgM-containing cells were elevated in the IFN-gamma-treated group compared with those in the IFN-gamma-non-treated group, which was similar to immunological changes in mucosal lesions of inflammatory bowel disease.

Topographic study of Helicobacter pylori and HLA-DR antigen expression on gastric epithelium

Helicobacter pylori and HLA-DR antigen expression on gastric epithelium, identified by an indirect immunoperoxidase staining method using monoclonal antibodies against H. pylori and HLA-DR antigens, were studied topographically. Fifty-nine biopsy specimens from 41 patients who had neither gastric cancer nor peptic ulcers were examined. H. pylori was observed predominantly over or on the surface epithelium, while HLA-DR antigens were frequently expressed on the epithelium of the isthmus region. These observations led to the conclusion that there was no direct topographic association between H. pylori and epithelial HLA-DR expression. However, the frequency of HLA-DR expression in H. pylori-positive (28/29) specimens was significantly higher than that in H. pylori-negative (18/30) specimens (P < 0.01). Furthermore, a greater number of H. pylori was associated with a stronger expression of HLA-DR antigens (P < 0.001). We conclude that H. pylori is indirectly related to HLA-DR expression on gastric epithelium. H. pylori is the first microbial agent that has been suggested to be associated with epithelial HLA-DR expression in the human gastrointestinal tract.