Insights in immunomodulatory therapies for ulcerative colitis and Crohn's disease

Repeated enemas with hepatocyte growth factor selectively stimulate epithelial cell proliferation of injured mucosa in rats with experimental colitis

AIMS

Hepatocyte growth factor (HGF) modulates intestinal epithelial cell proliferation and migration. We previously reported that systemic administration of recombinant human HGF (rh-HGF) ameliorated experimental colitis. However, an increase in serum HGF concentrations may induce undesired systemic effects, limiting the use of rh-HGF. To avoid possible side effects, we investigated the safety and efficacy of rectally administered rh-HGF as a treatment for experimental colitis.

MAIN METHODS

We measured serum human HGF concentration following a single rectal enema of rh-HGF. Rats with 2,4,6-trinitrobenzene sulfonic acid (TNBS)- or dextran sulfate sodium (DSS)-induced colitis were treated with rectal enemas of rh-HGF once a day for seven days. The degree of mucosal injuries and the proliferative activity of the colon epithelium were examined.

KEY FINDINGS

Rats administered a rectal enema of rh-HGF at a dose of 0.1 mg/ml or less had no detectable rh-HGF in the serum. Repeated enemas of rh-HGF at this dose significantly reduced mucosal injuries, both with respect to lesion size and inflammatory cell infiltration. This regimen also stimulated proliferation of epithelial cells surrounding injured mucosa; however, the cell proliferation of uninjured mucosa was not affected by this local treatment.

SIGNIFICANCE

Rectally administered rh-HGF selectively accelerates the repair of injured mucosa in rat experimental colitis without systemic exposure to HGF. Rectal enemas of HGF are thus a potential novel and safe therapy for IBD.

Stem cells as potential therapeutic targets for inflammatory bowel disease

The incidence and prevalence of Crohn's disease and ulcerative colitis, the two major forms of inflammatory bowel disease (IBD), are rising. According to some estimates >1 million new cases of IBD arise in the United States annually. The conventional therapies available for IBD range from anti-inflammatory drugs to immunosuppressive agents, but these therapies generally fail to achieve satisfactory results due to their side effects. Interest in a new therapeutic option, that is, biological therapy, has gained much momentum recently due to its focus on different stages of the inflammatory process. Stem cell (SC) research has become a new direction for IBD therapy due to our recent understanding of cell populations involved in the pathogenic process. To this end, hematopoietic and mesenchymal stem cells are receiving more attention from IBD investigators. The intestinal environment, with its crypts and niches, supports incoming embryonic and hematopoietic stem cells and allows them to engraft and differentiate. The above findings suggest that, in the future, SC-based therapy will be a promising alternative to conventional therapy for IBD. In this review, we discuss SCs as potential therapeutic targets for future treatment of IBD.

Qingdai Granules up-regulate MUC2 mRNA expression but down-regulate iNOS mRNA expression in the colonic mucosa of rats with ulcerative colitis

AIM: To investigate the effects of Qingdai Granules (QDG) on the expression of mucin 2 (MUC2) and inducible nitric oxide synthase (iNOS) mRNAs in the colonic mucosa of rats with ulcerative colitis.

METHODS: Ulcerative colitis was induced in rats by giving an enema of trinitrobenzene sulphonic acid (TNBS) and ethanol. The experimental animals were randomly divided into six groups: normal group, model group, sulfasalazine (SASP) group (500 mg/kg), and low-, medium- and high-dose QDG groups (600, 900 and 1 200 mg/kg). Except the normal group, the other groups were given intragastrically normal saline, SASP, and different concentrations of QDG, respectively, from day 3 after model establishment for 10 d. On day 14, rats were killed to evaluate disease activity index (DAI) and colon mucosa damage index (CMDI). The expression of MUC2 and iNOS mRNAs in the colonic mucosa of rats was detected by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: Compared with the model group, the DAI and CMDI in the medium- and high-dose QDG groups significantly decreased, the expression of MUC2 mRNA in the colon of rats in the medium- and high-dose QDG groups was significantly up-regulated (2.06 ± 0.70 vs 1.24 ± 0.47 and 2.34 ± 0.86 vs 1.24 ± 0.47; both P < 0.01), and the expression of iNOS mRNA in the high-dose QDG group was significantly down-regulated (0.35 ± 0.12 vs 0.62 ± 0.31, P < 0.05).

CONCLUSION: QDG can exert protective effects against rat ulcerative colitis perhaps by up-regulating MUC2 mRNA expression and down-regulating iNOS mRNA expression.

Pediatric inflammatory bowel diseases and the risk of lymphoma: should we revise our treatment strategies?

Inflammatory bowel diseases (IBDs) are lifelong inflammatory gastrointestinal diseases starting in about one third of patients during childhood. Treatment strategies aim to control this chronic inflammatory process. Owing to recent advances in the understanding of IBD, immunosuppressive agents (mainly against TNFalpha directed) as well as biological drugs are more and more often used. This therapeutic approach clearly improved the clinical condition of the majority of patients with IBD. However, with this more aggressive treatment strategy, safety concerns clearly arise. Recently, the description of a series of a particularly severe form of T cell lymphoma in pediatric and young adult patients with IBD under immunomodulator and biological combination therapy raised the question of the risks of treatment-induced side effects or complications. As reviewed in the present article, there is a slightly increased risk of not only lymphoma development in IBD patients, potentially related to the inflammatory process, but also to the use of immunosuppressive therapies. On the basis of the literature data, were analyzed current treatment strategies for children with moderate-to-severe IBD, who are candidates to receive immunomodulator and/or biological agents potentially accelerating the risk of lymphoma development. Comparative clinical studies in IBD are still missing; however, it is prudent to think about adapting immunosuppressive therapies to the inflammatory process of the underlying disorder and if possible to reduce them to monotherapy. Alternative treatment strategies for heavy immunosuppression exist (eg, enteral nutrition in Crohn disease or colectomy in patients with ulcerative colitis) and should be considered whenever appropriate. There is a major need for comparative studies before evidence-based guidelines can be established for safest and best treatment strategies of pediatric patients with IBD.

Therapeutic effects of selective cyclooxygenase-2 inhibitor PC407 on 2,4,6-trinitrobenzene sulfonic acid-induced ulcerative colitis in rats

AIM: To explore the therapeutic effects of a new selective cyclooxygenase-2 (COX-2) inhibitor PC407 on rat ulcerative colitis induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS) and its possible mechanism.

METHODS: A rat colitis model was induced by TNBS and ethonal enema. The rats were randomly divided into 5 groups: normal group, model control group, celecoxib group (18 mg/kg) and PC407 groups (9, 18mg/kg). Celecoxib and PC407 were administered intragastrically once per day for 6 days and the loose stool were recorded. All the rats were anesthetized to separate colon, thymus gland and spleen on the 7th day. The body weights of experimental rats before anesthesia were documented and the macroscopic and histological changes of the colon were observed. The effects in treatment groups were evaluated by loose stool rate, colon index, ulcer ratio, thymus index and spleen index. The protein products of COX-2, tumor necrosis factor-α (TNF-α) in mucosa were analyzed by immunohistochemistry.

RESULTS: In comparison with that in model control group, the body weight was increased significantly in 18 mg/kg-PC407 group (258.9 g vs 223.6 g, P < 0.05), but the loose stool rate was decreased markedly (30% vs 80 %, P < 0.01); moreover, 18 mg/kg PC407 significantly ameliorated the lesions and pathological changes in colon caused by TNBS, improved the indexes such as colon index (5.03 ± 1.26 mg/g vs 7.60 ± 2.07 mg/g, P < 0.01), ulcer ratio (24.69% ± 2.83% vs 36.13% ± 9.64%, P < 0.01), thymus index (1.96 ± 0.48 mg/g vs 1.08 ± 0.32 mg/g, P < 0.01) and spleen index (2.85 ± 0.33 mg/g vs 3.87 ± 0.96 mg/g, P < 0.01), and down-regulated the colonic mucosal expression of COX-2 (30.6% ± 7.0% vs 67.4% ± 1.2%, P < 0.01) and TNF-α (19.5% ± 3.0% vs 52% ± 4.7%, P < 0.01). PC407 at a dose of 9 mg/kg also could improve the above indexes, but the effects were less than PC407 at 18 mg/kg.

CONCLUSION: PC407 has significant therapeutic effects on TNBS-induced colitis in rats, and the mechanism may relate to its regulation on COX-2 and TNF-α expression.

Basal lymphoid aggregates in ulcerative colitis colon: a site for regulatory T cell action

Regulatory T cells seem to play a central role in maintaining immune tolerance in the gut mucosa. Previously we have shown that interleukin (IL)-10 is produced at high levels in the inflamed colonic tissue of ulcerative colitis (UC) patients. The cellular source was CD4+ T cells, suggesting local activation of regulatory T cells. The present study was performed to determine whether the frequency of regulatory T cells is increased in UC colon and whether they are present in the basal lymphoid aggregates, the prominent microanatomical structure in UC colon. Colonic tissue specimens from UC and control patients were analysed for frequencies of lamina propria lymphocytes expressing the regulatory T cell markers forkhead box protein 3 (FoxP3), CD25 and glucocorticoid-induced tumour necrosis factor receptor family-related gene (GITR) as well as CD28, CD4 and CD3 by using marker specific reagents in immunomorphometry. Two-colour immunohistochemistry was used for detection of CD25/IL-10, FoxP3/IL-10 and CD25/FoxP3 double-positive cells. GITR+ and FoxP3+ cells were present in normal colon mucosa, although at a relatively low frequency, and were located preferentially within the solitary follicles. UC was associated with significantly increased frequencies of CD25+, GITR+ and FoxP3+ lamina propria lymphocytes both within the basal lymphoid aggregates and in the lamina propria outside. Many of the CD25+ cells co-expressed FoxP3 as well as IL-10, suggesting that these are indeed IL-10 secreting regulatory T cells, activated in an attempt to counteract the inflammation. Increased frequency of regulatory T cell subtypes seems insufficient to control the disease activity in UC.

Azathioprine in inflammatory bowel disease: improved molecular insights and resulting clinical implications

Azathioprine and 6-mercaptopurine represent important first-line immunosuppressive drugs in the treatment of inflammatory bowel disease. Owing to 45 years of clinical experience with thiopurines in inflammatory bowel disease, there currently exist strong data from numerous clinical trials and meta-analyses, which clearly document the therapeutic efficacy of azathioprine and 6-mercaptopurine in the treatment of inflammatory bowel disease. However, the exact molecular mechanism of action of these drugs was insufficiently understood for a long time. During the last few years, important new insights into the intracellular effects of azathioprine have been gained and thiopurines have been identified as strong inducers of T-cell apoptosis. This article aims to summarize traditional and current concepts of azathioprine-mediated effects and endeavors to discuss the resulting clinical implications.