Treatment of ulcerative colitis in the cottontop tamarin using antibody to tumour necrosis factor alpha

Infliximab in the treatment of severe, steroid-refractory ulcerative colitis: a pilot study

We report the experience of 11 patients (of 60 planned patients) enrolled in a double-blind, placebo-controlled clinical trial of infliximab in patients with severe, active steroid-refractory ulcerative colitis. The study was terminated prematurely because of slow enrollment. Patients having active disease for at least 2 weeks and receiving at least 5 days of intravenous corticosteroids were eligible to receive a single intravenous infusion of infliximab at 5, 10, or 20 mg/kg body weight. The primary endpoint used in this study was treatment failure at 2 weeks after infusion. Treatment failure was defined as 1) unachieved clinical response as defined by a modified Truelove and Witts severity score, 2) increase in corticosteroid dosage, 3) addition of immunosuppressants, 4) colectomy, or 5) death. Safety evaluations included physical examination, clinical chemistry and hematology laboratory tests, and occurrence of adverse experiences. Four of 8 patients (50%) who received infliximab were considered treatment successes at 2 weeks, compared with none of 3 patients who received placebo. Improvement in erythrocyte sedimentation rates and serum concentrations of C-reactive protein and interleukin-6 correlated with the clinical response observed in patients receiving infliximab. Infusion with infliximab produced no significant adverse events. Infliximab was well tolerated and may provide clinical benefit for some patients with steroid-refractory ulcerative colitis.

PLD pathway involved in carbachol-induced Cl- secretion: possible role of TNF-alpha

In a previous study, it was found that exposure to tumor necrosis factor-alpha (TNF-alpha) potentiated the electrophysiological response to carbachol in a time-dependent and cycloheximide-sensitive manner. It was deduced that the potentiation could be due to protein kinase C activity because of increased 1,2-diacylglycerol. It was also observed that propranolol could decrease the electrophysiological response to carbachol (Oprins JC, Meijer HP, and Groot JA. Am J Physiol Cell Physiol 278: C463-C472, 2000). The aim of the present study was to investigate whether the phospholipase D (PLD) pathway plays a role in the carbachol response and the potentiating effect of TNF-alpha. The transphosphatidylation reaction in the presence of the primary alcohol 1-butanol [leading to stable phosphatidylbutanol (Pbut) formation] was used to measure activity of PLD. The phosphatidic acid (PA) levels were also measured. Muscarinic stimulation resulted in an increased formation of Pbut and PA. TNF-alpha decreased levels of PA.

Transcription factor NF-kappaB participates in regulation of epithelial cell turnover in the colon

The transcription factor nuclear factor (NF)-kappaB regulates the expression of genes that can influence cell proliferation and death. Here we analyze the contribution of NF-kappaB to the regulation of epithelial cell turnover in the colon. Immunohistochemical, immunoblot, and DNA binding analyses indicate that NF-kappaB complexes change as colonocytes mature: p65-p50 complexes predominate in proliferating epithelial cells of the colon, whereas the p50-p50 dimer is prevalent in mature epithelial cells. NF-kappaB1 (p50) knockout mice were used to study the role of NF-kappaB in regulating epithelial cell turnover. Knockout animals lacked detectable NF-kappaB DNA binding activity in isolated epithelial cells and had significantly longer crypts with a more extensive proliferative zone than their wild-type counterparts (as determined by proliferating cell nuclear antigen staining and in vivo bromodeoxyuridine labeling). Gene expression profiling reveals that the NF-kappaB1 knockout mice express the potentially growth-enhancing tumor necrosis factor (TNF)-alpha and nerve growth factor-alpha genes at elevated levels, with in situ hybridization localizing some of the TNF-alpha expression to epithelial cells. TNF-alpha is NF-kappaB regulated, and its upregulation in NF-kappaB1 knockouts may result from an alleviation of p50-p50 repression. NF-kappaB complexes may therefore influence cell proliferation in the colon through their ability to selectively activate and/or repress gene expression.

New immunologic treatments for inflammatory bowel disease

After many years with little progress in new treatments for patients with inflammatory bowel disease, there is now rapid expansion of a new class of immunologic agents. These agents are designed to disrupt proinflammatory pathways at specific sites. Monoclonal antibodies to tumor necrosis factor-alpha (TNF-alpha) are already transforming the lives of some patients with previously intractable Crohn disease, and further TNF-alpha directed therapies are being developed. Clinical trials are now underway on agents that inhibit adhesion molecules and antiinflammatory cytokines, while attempts are being made to actively immunize against TNF-alpha. Promising data continue to be reported, although long-term safety data are still mostly unavailable. Although these agents are proving to be very effective in the treatment of patients with Crohn disease, their use should continue to be restricted while indications and dose regimens are defined.

TNF-alpha potentiates the ion secretion induced by muscarinic receptor activation in HT29cl.19A cells

Chronic gastrointestinal diseases such as ulcerative colitis and Crohn's disease are characterized by severe diarrhea. Mucosal biopsies of these patients show enhanced levels of cytokines, secreted by infiltrated inflammatory cells. In this study, we investigated the effect of the cytokine tumor necrosis factor-alpha (TNF-alpha) on ion secretion in human intestinal epithelial cells. The conventional microelectrode technique in the cell line HT29cl. 19A was used, which allows for simultaneous measurements of transepithelial potential difference and intracellular potential difference across the apical membrane. Preincubation (2-78 h) with 10 ng/ml TNF-alpha did not change basal secretory activity. However, the secretory response to the muscarinic receptor agonist carbachol was strongly increased after exposure to TNF-alpha. Application of the protein kinase C (PKC) inhibitor GF 109203X (bisindolylmaleimide I) inhibited the response to carbachol as well as the TNF-alpha-potentiated response, indicating that PKC mediates the effect of carbachol in this cell line. Propranolol, a substance that inhibits the phospholipase D (PLD) pathway, strongly reduced the response to muscarinic stimulation and its potentiation by TNF-alpha. The results indicate that activation of PLD is involved in ion secretion induced by muscarinic receptor activation and that TNF-alpha can potentiate this pathway.

The function of tumour necrosis factor and receptors in models of multi-organ inflammation, rheumatoid arthritis, multiple sclerosis and inflammatory bowel disease

There is now good evidence to demonstrate that aberrations in tumour necrosis factor (TNF) production in vivo may be either pathogenic or protective and several plausible mechanisms may explain these contrasting activities. According to the classic pro-inflammatory scenario, failure to regulate the production of TNF at a site of immunological injury may lead to chronic activation of innate immune cells and to chronic inflammatory responses, which may consequently lead to organ specific inflammatory pathology and tissue damage. However, more cryptic functions of this molecule may be considered to play a significant part in the development of TNF mediated pathologies. Direct interference of TNF with the differentiation, proliferation or death of specific pathogenic cell targets may be an alternative mechanism for disease initiation or progression. In addition to these activities, there is now considerable evidence to suggest that TNF may also directly promote or down regulate the adaptive immune response. A more complete understanding of the temporal and spatial context of TNF/TNF receptor (TNF-R) function and of the molecular and cellular pathways leading to the development of TNF/TNF-R mediated pathologies is necessary to fully comprehend relevant mechanisms of disease induction and progression in humans. In this paper, the potential pathogenic mechanisms exerted by TNF and receptors in models of multi-organ inflammation, rheumatoid arthritis, multiple sclerosis and inflammatory bowel disease are discussed. Elucidating the nature and level of contribution of these mechanisms in chronic inflammation and autoimmunity may lead to better regulatory and therapeutic applications.

Therapeutic potential of infliximab in inflammatory bowel disease

Traditional treatment approaches for patients with inflammatory bowel disease involve 1) pharmacologic management with aminosalicylates, corticosteroids, immunomodulatory agents, and antibiotics; and 2) nonpharmacologic management by surgical and dietary means. Complications and inadequate responses to current treatment modalities have resulted in the development of new and more specific biologic therapies. The proinflammatory cytokine tumor necrosis factor alpha (TNF alpha) is present in elevated concentrations in patients with inflammatory bowel disease; therefore, it has been targeted for treatment approaches. Infliximab is a chimeric, monoclonal antibody to TNF alpha developed to inhibit the interaction of TNF alpha with its receptor, to result in amelioration of inflammation. This biologic agent has received the most attention and is the most studied of those for the treatment of patients with Crohn's disease. This article reviews the symptoms of inflammatory bowel disease, the traditional treatment approaches used, the role of TNF alpha in disease pathogenesis, and the value of infliximab in treatment.

Review article: efficacy of infliximab in Crohn's disease--induction and maintenance of remission

The primary goals of treating patients with Crohn's disease are to induce a clinical remission, maintain the remission, and prevent associated complications. Various treatment regimens for patients with Crohn's disease induce a response and remission; however, most prove ineffective for maintenance of the clinical effect. A therapeutic agent that can induce and maintain remission, while promoting the restoration of intestinal mucosa, would prove to be most beneficial in such a patient population. Several studies with infliximab have clinically demonstrated that the antitumour necrosis factor-alpha therapy rapidly reduced the signs and symptoms in patients with moderate-to-severe Crohn's disease. In acute studies with the chimeric monoclonal antibody, clinical benefit was associated with healing and reduction of inflammation in the bowel mucosal tissue. In a maintenance study, retreatment with infliximab maintained remission of the active disease. Additionally, treatment with the lowest infusion dose of infliximab (5 mg/kg) provided a high degree of clinical benefit with a long-term outcome.

Novel therapies for inflammatory bowel disease

Looking back at successes and failures in newer approaches to treating IBD, it is tempting--although still difficult--to draw conclusions about pathogenesis. When a therapy proves effective, do clinicians truly know how it works? Even with a therapy as specific as anti-TNF antibody, it is not clear if the benefit is attributable to simple binding and clearance of TNF-alpha or to binding on the cell surface and subsequent deletion of the activated macrophage. When a drug appears to be less effective than preclinical models suggest, can failures in effectiveness from delivery or dosing be differentiated? The disappointing results of clinical trials with IL-10--so at odds with the prediction of benefit from animal models--bring into question the validity of those models as well as the soundness of design of the clinical trials on which efficacy of IL-10 is judged. The variability of response even to the most narrowly targeted agents suggests that these diseases are far more heterogeneous in humans than in their murine counterparts. Clinicians are only just beginning to recognize subclinical markers of response, and it may soon be possible to predict response on the basis of genetic composition. For the moment, however, the field of pharmacogenetics is embryonic. Challenges in developing new therapeutic strategies include not only identifying novel agents, but also improving the definitions of clinical endpoints and defining efficacy at the biologic level. Only through considered evaluation of clinical evidence may clinicians determine which therapies should remain novelties and which should become an accepted part of the armamentarium.

On the role of tumor necrosis factor and receptors in models of multiorgan failure, rheumatoid arthritis, multiple sclerosis and inflammatory bowel disease

The specific role of the tumor necrosis factor (TNF)/TNF receptor (TNFR) system in disease pathogenesis still remains an unresolved puzzle. Recent studies in transgenic and knockout animals, where the pathogenic influence of genetically perturbed TNF expression has been evaluated, indicate that several pathways of TNF/TNFR action may contribute independently or in concert to initiate, promote or downregulate disease pathogenesis. Evidently, organ-specific inflammatory or autoimmune pathology may ensue due to sustained activation by TNF of innate immune cells and inflammatory responses, which may consequently lead to tissue damage and to organ-specific chronic pathology. However, more cryptic functions of this molecule may be considered to play a significant part in the development of TNF-mediated pathologies. Direct interference of TNF with the differentiation, proliferation or death of specific pathogenic cell targets may be an alternative mechanism for disease initiation or progression. In addition to these activities, there is now considerable evidence to suggest that TNF may also directly promote or downregulate the adaptive immune response. It is therefore evident that no general scenario may adequately describe the role of TNF in disease pathogenesis. In this article, we aim to place these diverse functions of TNF/TNFRs into context with the development of specific pathology in murine models of multiorgan failure, rheumatoid arthritis, multiple sclerosis and inflammatory bowel disease.

Antitumor necrosis factor therapy for inflammatory bowel disease: a review of agents, pharmacology, clinical results, and safety

Tumor necrosis factor-alpha (TNFalpha), a proinflammatory cytokine, plays an important role in the pathogenesis of inflammatory bowel disease (IBD). Biotechnology agents including a chimeric monoclonal anti-TNF antibody (infliximab), a humanized monoclonal anti-TNF antibody (CDP571), and a recombinant TNF receptor fusion protein (etanercept) have been used to inhibit TNFalpha activity. Controlled trials have demonstrated efficacy for infliximab in moderately to severely active Crohn's disease (CD) and fistulizing CD sufficient to justify recent U.S. Food and Drug Administration (FDA) approval. Additional trials have been completed in rheumatoid arthritis (RA). Similarly, preliminary controlled trials have suggested efficacy for CDP571 in active CD and RA. Larger controlled trials have demonstrated efficacy for etanercept in RA patients who have failed disease modifying antirheumatic drug (DMARD) therapy leading to FDA approval for RA. Toxicities observed with anti-TNF therapies have included formation of human antichimeric antibodies (HACA) with associated acute and delayed hypersensitivity infusion reactions, human antihuman antibodies (HAHAs), and formation of autoantibodies with rare instances of drug-induced lupus. Several cases of non-Hodgkin's lymphoma also has been described. Future studies should evaluate optimal timing and duration of anti-TNF therapy, the utility of adjuvant medical treatments during anti-TNF therapy, and evaluate long-term safety and efficacy of the various anti-TNF agents.

Combination therapy of pentoxifylline and TNFalpha monoclonal antibody in dextran sulphate-induced mouse colitis

BACKGROUND

Tumour necrosis factor-alpha (TNFalpha) has been suspected of playing an important role in the pathogenesis of inflammatory bowel diseases, and has become a target for the treatment of these diseases. Open-label, placebo controlled studies have shown that engineered CDP571 and chimeric anti-TNF antibody (cA2) provide a significant benefit in Crohn's disease. Since these antibodies have to be used repeatedly to maintain remission in inflammatory bowel disease, there is a concern that their use may compromise host defence and produce toxic side-effects.

METHODS

We evaluated the combined use of mouse specific TNFalpha mab (25 microg/mouse, Endogen) and pentoxifylline (PF, 100 mg/kg/day, p.o., TNFalpha release inhibitor) in the DSS (3% dextran sulphate solution) model of mouse colitis. Colitis was induced by the feeding of 3% DSS for three cycles. The study groups were: Group I: single injection of rat anti-mouse IgG, Group II: single injection of TNFalpha mab, Group III: daily PF for three cycles, Group IV: single injection of TNFalpha mab + PF for three cycles, Group V: TNFalpha mab at the beginning of each cycle (three injections) and Group VI: TNFalpha mab (three injections) + daily PF for three cycles. Daily disease activity (DAI) was measured throughout the study. At the end of each cycle, colon tissue was processed for histology, myeloperoxidase (MPO) and plasma TNFalpha.

RESULTS

Mice treated with a single injection of TNFalpha alone or TNFalpha mab + PF showed significantly lower DAI, inflammation scores and ulcer index compared with the IgG treated group. Mice treated with TNFalpha mab + PF had no ulcers. Multiple injections of TNFalpha mab or TNFalpha mab + PF showed greater inhibition in DAI and cytokines in the first two cycles. However, in the third cycle, multiple injections of TNFalpha mab showed adverse proinflammatory effects.

CONCLUSION

The simultaneous administration of pentoxifylline and TNFalpha mab may enhance therapeutic outcomes in inflammatory bowel disease and reduce the side-effects associated with the repeated use of TNFalpha mab.

NSAIDs and butyrate sensitize a human colorectal cancer cell line to TNF-alpha and Fas ligation: the role of reactive oxygen species

The nonsteroidal antiinflammatory drugs (NSAIDs) indomethacin and salicylic acid and the short chain fatty acid butyrate are effective colon cancer chemopreventive agents that increase reactive oxygen species (ROS) generation in colon cancer cells. Here we demonstrate that these agents sensitize the normally resistant human HT-29 colon cancer cell line to apoptosis induced by TNF-alpha or a Fas ligating antibody. The role of ROS in this sensitization is supported by the finding that direct exposure of the cells to H2O2 is sufficient for sensitization. Neither TNF-alpha nor Fas ligation alter basal or chemopreventive agent-activated ROS generation, suggesting that the death ligands and chemopreventive agents act in a complementary fashion. The dual chemopreventive agent/death ligand treatments do not increase Fas, TNF receptor 1, Bak or c-myc expression (although salicylic acid moderately induces of Fas expression). Cell death does correlate with alterations in NF-kappa B activity: the NSAIDs, butyrate and H2O2 enhance c-Rel complex formation by TNF-alpha and provide an overall enhancement of NF-kappa B activation by Fas. The antioxidant N-acetylcysteine (NAC) blocks cell death and NF-kappa B activation induced by Fas ligation, suggesting a potential role for NF-kappa B in Fas-induced apoptosis in these cells. The effects of NAC on TNF-alpha-induced cell death are more complex, with NAC being marginally protective and itself enhancing the formation of c-Rel containing complexes at higher concentrations (25 mM). The influence of NSAIDs and butyrate on ROS generation and death ligand sensitivity may be relevant to their ability to suppress colon carcinogenesis.

Novel intestinal Helicobacter species isolated from cotton-top tamarins (Saguinus oedipus) with chronic colitis

A disease similar to ulcerative colitis in humans has been identified in cotton-top tamarins (CTTs) in captivity. The clinical signs include weight loss, diarrhea, and rectal bleeding with the pathological features and biochemical abnormalities of ulcerative colitis. Approximately 25 to 40% of these animals develop colon cancer after 2 to 5 years of captivity. An infectious etiology has been proposed; however, no microbial agent to date has been identified. Helicobacter spp. have been associated with enterocolitis and inflammatory bowel disease (IBD) in humans and animals. Infection with Helicobacter pylori or Helicobacter mustelae is associated with an increased risk of gastric adenocarcinoma and lymphoma of the mucosa-associated lymphoid tissue. Helicobacter hepaticus causes hepatitis, hepatic adenomas, and hepatocellular carcinomas in susceptible strains of mice. The aim of this study was to assess a colony of CTTs with a high incidence of IBD and colon cancer for the presence of colonic Helicobacter spp. A fusiform, gram-negative bacterium with bipolar flagella and periplasmic fibers was isolated from the feces of CTTs. The bacterium grew under microaerobic conditions at 37 and 42 degrees C but not at 25 degrees C, did not hydrolyze urea, was positive for catalase and oxidase, did not reduce nitrate to nitrite, did not hydrolyze indoxyl acetate or alkaline phosphatase, and was resistant to nalidixic acid, cephalothin, and trimethoprim-sulfamethoxazole. On the basis of 16S rRNA gene sequence analysis, the organism was classified as a novel Helicobacter species. This is the first Helicobacter isolated from CTTs. Further studies are needed to elucidate the role of this novel Helicobacter sp. in the pathogenesis of ulcerative colitis and colonic adenocarcinoma in CTTs.

Mechanisms of intestinal epithelial cell injury and colitis in interleukin 2 (IL2)-deficient mice

Epithelial cell (EC) injury is a feature of all inflammatory bowel disorders (IBD). Although the mechanisms of EC injury are incompletely understood, it has been proposed that T-cell-mediated cytotoxicity and production of inflammatory cytokines are involved. This hypothesis was tested using the interleukin 2-deficient (IL2-/-) mouse model of IBD and cultures of primary colonic EC to determine if abnormal cytokine production or cytotoxicity by colonic T cells cause EC injury. Although capable of cell-mediated killing of allogeneic target cells, IL2-/- colonic T cells were unable to lyse syngeneic colonic EC. During disease progression, large numbers of IL4, TNF-alpha, and IFN-gamma-producing CD4+ and CD8+ cells accumulated within the intraepithelial spaces and lamina propria of the colon of IL2-/- mice. Although colonic EC expressed receptors for IFN-gamma and TNF-alpha, these cytokines did not adversely affect EC viability or growth in vitro consistent with these cytokines not being the primary mediators of EC injury in IBD. Our novel colonic EC culture system provides an in vitro accessible system in which to investigate further the nature of EC-lymphocyte interactions.