Treatment of inflammatory bowel disease (IBD)

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract, which includes Crohn's disease (CD) and ulcerative colitis (UC). These diseases have become important health problems. Medical therapy for IBD has advanced dramatically in the last decade with the introduction of targeted biologic therapies, the optimization of older therapies, including rugs such as immunomodulators and 5-aminosalicylic acid (5-ASA), and a better understanding of the mucosal immune system and the genetics involved in the pathogenesis of IBD. The goal of IBD therapy is to induce and maintain remission. The current treatment paradigm involves a step-up approach, moving to aggressive, powerful therapies only when milder therapies with fewer potential side effects fail or when patients declare themselves to have an aggressive disease. This review focuses on the current treatments for inflammatory bowel disease.     

肠道菌群在炎症性肠病发病机制与治疗中的作用研究进展

炎症性肠病是一种以肠道炎症和黏膜损伤为特征的慢性疾病,主要包括克罗恩病和溃疡性结肠炎,其发病原因尚不明确。现有研究表明炎症性肠病的发病机制与宿主的遗传易感性、肠道菌群紊乱、肠黏膜屏障破坏和肠黏膜免疫异常等密切相关。总结目前炎症性肠病发病机制、患者肠道菌群结构及治疗方法等相关的研究进展,旨在对今后炎症性肠病的治疗和药物研发有所裨益。     

Emerging immunological targets in inflammatory bowel disease

Crohn's disease (CD) and ulcerative colitis (UC) are the major forms of inflammatory bowel diseases (IBD) in man. They are caused by damage to the lining of the intestine and deeper layers, due to an excessive immune response directed against components of the gut microflora and poorly controlled by counter-regulatory mechanisms. CD and UC are however immunologically distinct. CD-related inflammation is characterized by a marked mucosal infiltration of T lymphocytes secreting T helper type (Th) 1 and Th17 cytokines. In UC, the local immune response is less polarized but may show enhanced production of IL-5, IL-13 and Th17 cytokines. Downstream however CD and UC share important end-stage effector pathways of intestinal injury, mediated by an active cross-talk between immune and non-immune cells. The clarification of the complex networks of immune-inflammatory mediators operating in the gut of IBD patients has led to the identification of new targets that should facilitate the development of novel biological therapies.     

Evolving knowledge and therapy of inflammatory bowel disease

With recent advances in the understanding of its pathophysiology, inflammatory bowel disease has become a very active area for the development of novel therapeutic agents. New targets for biologics include cytokines involved in T-cell activation, with antibodies directed against IL-12 and interferon-gamma. Selective adhesion molecule blockade has produced promising, though mixed, results. Recombinant human granulocyte-macrophage colony-stimulating factor might be effective in active Crohn's disease, presumably through stimulation of intestinal innate immune responses. With increasing evidence for a crucial role for luminal flora in maintaining the health of the bowel, strategies to manipulate intestinal bacteria using probiotics and prebiotics are being actively investigated as well.     

Interleukin-1beta converting enzyme (caspase-1) in intestinal inflammation

An imbalance of T helper cell type 1 (Th1) versus type 2 (Th2) polarization in favor of Th1 cell subsets appears to be a key pathogenic mechanism in chronic inflammatory bowel disease (IBD), in particular in Crohn's disease. The interferon gamma-inducing factor interleukin (IL)-18 acts in strong synergism with the Th1 polarizing cytokine IL-12. Recent studies provide evidence for the participation of IL-18 in the pathogenesis of IBD: IL-18 expression is increased in inflamed lesions of Crohn's disease patients and neutralization of IL-18 in different models of experimental colitis resulted in a dramatic amelioration of disease severity. IL-18 and IL-1beta are cleaved and thereby activated by the interleukin-1beta converting enzyme (ICE). Activation of ICE also occurs during different types of infectious colitis, and ICE expression and subsequent release of IL-1beta and IL-18 significantly contribute to intestinal inflammation. ICE knockout mice as well as mice treated with the ICE inhibitor pralnacasan are protected against experimental mucosal inflammation. Thus, inhibition of ICE represents an intriguing new target that requires further investigation in animal models.     

Emerging drugs to treat Crohn's disease

The advent of the anti-TNF agent infliximab has dramatically changed our concept of treating refractory inflammatory bowel disease, particularly Crohn's disease. Although infliximab has proven to induce clinical response and remission with rapid onset of mucosal healing, to spare steroids, to improve perianal disease and to increase quality of life, there is an ongoing debate about optimizing infliximab therapy and a clear unmet medical need for patients losing their response to this agent. Novel anti-TNF agents, mostly more humanized monoclonal antibodies, with subcutaneous administration, have shown efficacy and are in advanced stages of clinical development. Compounds targeted at alternative pathways in the immune cascade are not expected to enter the market soon. Promising novel therapeutic classes include the anti-IL-12/23 and anti-IFN-gamma agents and the selective adhesion molecule inhibitors. Most of the biologic therapies, including anti-TNF agents, are aimed at crucial pathways in the immune system on the crossroads between immune pathology and host defense. Therefore, long-term benefit to risk profiles need to be established for all novel drugs.     

Review article: a critical approach to new forms of treatment of Crohn's disease and ulcerative colitis

Most patients with inflammatory bowel disease can be managed with conventional immunosuppressive therapy. The choice of agents to prevent relapses of inflammatory bowel disease must be based on efficacy, toxicity and cost. Studies in animal models of inflammatory bowel disease indicate that chronic intestinal inflammation results from enhanced immune responses to bacteria that are present normally in the lumen. Loss of tolerance, an abnormal function or defective healing of the mucosal barrier may all give raise to chronic intestinal inflammation. This hypothesis is the basis of new therapies aimed at either decreasing the levels of luminal bacterial antigens and/or selectively blocking detrimental mucosal immune responses. Anti-TNF is an example of this novel approach that is very effective in Crohn's disease. The use of biological therapy is costly, however, and the long-term complications are not yet known. The recent increase of tuberculosis in patients treated with anti-TNF indicates that careful monitoring is necessary. It is clear that the new forms of treatment may play an important role in tailoring the appropriate drug to a specific group of patients. However, for the time being, fine-tuning in the use of conventional immunosuppression is necessary. New knowledge in the pharmacogenetics of these compounds allows improvements to be made in their use. It is to be hoped that a critical approach in the use of current and future drugs, taking into account the advances in the aetiopathogenesis of inflammatory bowel disease, will contribute to the quality of life of patients with inflammatory bowel disease.     

Soluble mediators and the interaction of drugs in IBD

The chronic idiopathic bowel diseases (IBD) - Crohn's disease and ulcerative colitis - are considered to be the result of an unrestrained inflammatory reaction. Although an explanation for the etiopathogenesis has still not emerged, the explosion of information on the inflammatory process is expected to yield a multitude of drugs targeted at particular elements of the inflammatory process. The final common pathway of immune activation in IBD is the local influx of monocytes, macrophages and polymorphonuclear neutrophils (PMNs). The processes which account for the recruitment of these cells include cytokine generation, complement activation and eicosanoid biosynthesis. Once the influx of PMNs and macrophages occurs, an increased production of platelet-activating factor (PAF) and leukotrienes (LTs), in particular LTB(4), results in the secondary amplification of the inflammatory response, which provides the clinical manifestations of IBD. Other important soluble mediators of inflammation include complement-derived and chemotactic peptides, specific adhesion molecules, neuropeptides and reactive metabolites of oxygen and nitrogen. Current established therapies, such as glucocorticoids and 5-aminosalicylic acid (5-ASA), inhibit raised concentrations of these interdependent soluble mediators of inflammation, which may amplify one another or have parallel effects. Future medical options for treatment of IBD aim at removing perpetuating antigens or inhibiting the entry of inflammatory cells by manipulating adhesion molecules, by blocking the proinflammatory molecules, or by preserving endogenous suppressive molecules or correcting genetic defects. However, it remains to be defined whether targeting multiinflammatory actions or a single key pivotal process is the better therapeutic strategy and whether subgroups of IBD with different clinical courses will require different treatment approaches.     

A critical approach to new forms of treatment of Crohn's disease and ulcerative colitis

Most patients with inflammatory bowel disease can be managed with conventional immunosuppressive therapy. The choice of agents to prevent relapses of inflammatory bowel disease must be based on efficacy, toxicity and cost. Studies in animal models of inflammatory bowel disease indicate that chronic intestinal inflammation results from enhanced immune responses to bacteria that are present normally in the lumen. Loss of tolerance, an abnormal function or defective healing of the mucosal barrier may all give raise to chronic intestinal inflammation. This hypothesis is the basis of new therapies aimed at either decreasing the levels of luminal bacterial antigens and/or selectively blocking detrimental mucosal immune responses. Anti-TNF is an example of this novel approach that is very effective in Crohn's disease. The use of biological therapy is costly, however, and the long-term complications are not yet known. The recent increase of tuberculosis in patients treated with anti-TNF indicates that careful monitoring is necessary. It is clear that the new forms of treatment may play an important role in tailoring the appropriate drug to a specific group of patients. However, for the time being, fine-tuning in the use of conventional immunosuppression is necessary. New knowledge in the pharmacogenetics of these compounds allows improvements to be made in their use. It is to be hoped that a critical approach in the use of current and future drugs, taking into account the advances in the aetiopathogenesis of inflammatory bowel disease, will contribute to the quality of life of patients with inflammatory bowel disease.     

Recent advances in the medical therapy of Crohn's disease in childhood

Crohn's disease (CrD) is characterised by an ongoing inflammatory response in the gut, in the absence of an obvious trigger. The treatment of CrD in children, during relapse and remission, requires special consideration of growth and development. This review addresses the use of present medical management strategies, including enteral nutrition, corticosteroids, immunosuppression and anti-TNF-alpha therapies. Anti-inflammatory IL-11 and leukocyte adhesion inhibitors have shown only moderate clinical efficacy in adults. Emerging treatments directed against the inflammatory cascade under investigation include inhibitors of IL-6 and -12, IFN-gamma and MAPKs. Probiotics and colony stimulating factors aim to stimulate the innate immune system. Research data from clinical trials are reviewed and summarised in respect of their potential within paediatric practice.     

维多珠单抗治疗炎症性肠病的机制与临床应用研究进展

炎症性肠病（IBD）是一类病因未明的肠道慢性复发性炎症性疾病,其治疗仍以传统药物为主。由于传统药物不良反应较明显,近年来衍生出多种生物制剂,如抗肿瘤坏死因子（TNF）制剂、整合素拮抗剂等。作为一种人源化的抗 α4β7 整合素单克隆抗体,维多珠单抗（Vedolizumab）通过抑制 α4β7 整合素与黏膜地址素细胞黏附分子-1（MAdCAM-1）相互作用,选择性阻断记忆 T细胞向炎症肠道组织转运,减轻肠道炎症反应,因而主要用于对抗 TNF生物制剂失效的 IBD患者。本文对维多珠单抗治疗 IBD的机制、临床疗效及安全性进行综述。     

New insights into inflammatory bowel disease pathophysiology: paving the way for novel therapeutic targets

The etiopathogenesis of Crohn's disease (CD) and ulcerative Colitis (UC), the two major forms of inflammatory bowel disease (IBD), is still unknown. Although the exact cause and mechanisms of both IBD have yet to be completely understood, it is widely accepted that both CD and UC result from an inappropriate immune response that occurs in genetically susceptible individuals as the result of a complex interaction among environmental factors, microbial factors, and the intestinal immune system. In the last few years a tremendous advance in knowledge of the mechanisms underlying intestinal inflammation in IBD has been achieved, leading to new therapeutic targets and novel drugs. These new therapeutic weapons have been specifically designed to selective shut down intestinal inflammation at different levels. Aim of this review is to summarize the recent advances in IBD pathophysiology and the new therapeutic targets and drugs that are changing the IBD clinical management.     

白细胞吸附疗法在重症炎症性肠病中的应用进展

炎症性肠病(IBD)是一种以反复发作的、多种免疫因子参与的慢性肠道炎症,其发病率在逐年增加。其发病机制可能与机体免疫反应、肠道炎性活动、肠道功能紊乱、精神状态、遗传等因素有关。目前主要的治疗方式以营养疗法、药物治疗、单克隆抗体相关的生物治疗、免疫抑制剂疗法为主,因发病机制仍不十分明确,这些疗法都不能完全有效地控制炎症的发展。近年来研究发现,血液中的白细胞(中性白细胞和单核细胞)的激活在IBD的发生与发展中起着至关重要的作用,因此,有效地清除血液中激活的白细胞,中断炎症反应链,可以达到控制疾病进展的目的。许多研究者将白细胞免疫吸附疗法应用于对重症炎症性肠病(SIBD)病人的治疗,并取得了一定的效果。这是对目前IBD治疗的补充,也是一种研究思路,但其吸附效果、疗效、不良反应等还有待进一步研究。     

Mucosal T cell proliferation and apoptosis in inflammatory bowel disease

Both forms of inflammatory bowel disease (IBD), Crohn's disease (CD) and ulcerative colitis (UC), represent prototypical conditions whose most salient features are the presence of chronic inflammation involving various parts of the intestinal tract and an increased risk of cancer, which is a complication directly related to the duration and activity of gut inflammation. Several factors have been implicated in the unrelenting mucosal inflammation of IBD, prominent among them being the presence of a persistently elevated number of activated T cells in the mucosa of CD and UC patients. These T cells display various defects of proliferation and apoptosis, and these abnormalities are credited with directly contributing to the pathogenesis of IBD and possibly the progression to colon cancer. This notion is supported by the observation that T cells are also prominently found infiltrating most tumors and are functionally impaired compared to T cells in the circulation. This establishes a parallel that may constitute a link between chronic intestinal inflammation and the development of malignancies in the inflamed intestine. This article will review some of the basic features of human intestinal mucosal T cells, examine the mechanisms underlying the processes of cell cycling and cell death, describe the defective proliferative and apoptotic function detected in CD and UC, and discuss the implications of modulating T cell apoptosis in IBD for therapeutic purposes and eventually decreasing the risk of cancer development.     

Intestinal flora and Crohn's disease

The pathogenesis of inflammatory bowel diseases (IBD) proceeds through stages of initiation, amplification and healing. Abundant clinical and experimental data incriminate luminal bacteria or bacterial products in both the initiation and perpetuation of chronic intestinal inflammation. Macrophage and T-cell activation with accompanying inflammatory cytokine production appears to be an early event. Studies of lymphocyte responsiveness to autologous and heterologous intestinal bacteria have suggested that this activation may result from a breakdown in tolerance to the enteric flora in IBD. This lack of tolerance might be due to an imbalance between protective and aggressive commensal luminal bacterial species (dysbiosis), a decreased barrier function and/or an impaired mucosal clearance allowing the access of bacteria to the mucosal immune system and lack of regulatory mediators or cells. There is still controversy over whether the virulence traits of bacteria are expressed broadly or just in a small subset of bacteria. Individual bacterial species within the indigenous flora vary in their capacity to drive intestinal inflammation. In experimental models, some bacteria such as Bacteroides vulgatus can cause colitis alone when monoassociated in the HLA-B27 transgenic rat model. Others, including Lactobacillus and Bifidobacterium species have no proinflammatory capacity and have been used as probiotics. In patients with IBD, systematic approach to this issue is hampered by the limited knowledge of intestinal flora. Adherent-invasive Escherichia coli are a possible candidate for the onset and/or persistence of intestinal inflammation in patients with Crohn's disease, since they possess all the virulence factors that allow the bacteria to cross the intestinal barrier, to move to deep tissues, and to continuously activate macrophages. The recent identification of NOD2/CARD15 as a susceptibility gene for Crohn's disease has provided another link between the immune response to enteric bacteria and the development of mucosal inflammation. NOD2/CARD15 is composed of two caspase recruitment domain (CARD), a nucleotide-binding domain (NBD) and a leucin-rich-repeat (LRR) region. The LRR domain of NOD2/CARD15 has binding activity for bacterial peptidoglycans and its deletion stimulates the NF-kappaB pathway. The most frequent variants of NOD2/CARD15 observed in Crohn's disease tend to cluster in the LRR and its adjacent regions. This suggests that the LRR domain of CD-associated variants is likely to be impaired in its recognition of microbial components. Continuing studies are investigating the pathophysiological mechanisms induced by NOD2/CARD15 variants in the intestinal mucosa.     

Development and validation of a novel IL-10 deficient cell transfer model for colitis

A number of rodent models for inflammatory bowel disease (IBD) have been developed, but most cannot be used to develop and validate new therapies for IBD. From the models developed, the IL-10 deficient mouse model is the one that results in a disease similar to human IBD; however, in this model, colitis occurs with variable incidence taking 3-4 months to develop. These are serious problems with the model when evaluating a new therapy because of the large-scale experiments required and the difficulty in performing an accurate pharmacological analysis. In this study, the IL-10 deficient mouse model was modified by transferring whole spleen and mesenteric lymph node cells from IL-10 deficient mice to CB-17 SCID mice. In this IL-10 deficient cell transfer model, chronic intestinal inflammation developed in all recipients within 2-3 weeks, which was far earlier than in donor IL-10 deficient mice. The pathological phenotypes were similar to those of IL-10 deficient mice and CD45RBhi T cell-transfer models. In addition, we assessed several agents for inflammatory bowel disease to validate the general utility of this cell transfer model. It is worth noting that TNFR-Ig or prednisolone, which is effective for treatment of patients with severe-fulminant Crohn's disease, markedly attenuated pathological clinical indices in this colitis model, whereas the immunosuppressive agents, azathioprine, tacrolimus, and cyclosporine A produced no significant effect. These results suggest that the IL-10 deficient cell transfer model is a good experimental model to use for developing new and effective therapies for active IBD.     

Promising new agents for the treatment of inflammatory bowel disorders

A groundswell of therapeutic modalities is presently sweeping through the field of inflammatory bowel disease (IBD), revolutionising the treatment and management of these disorders. At the forefront of newer agents are biological therapies, also referred to as 'biologics'. These include infliximab (cA2), CDP 571, rhIL-10, ICAM-1 antisense oligonucleotide (ISIS 2302) and opreleukin (rhIL-11). Among these, infliximab and CDP 571 are perhaps the most promising, particularly in Crohn's disease. Both are anti-TNF alpha monoclonal antibody formulations with proven efficacy at doses of 5 mg/kg for inducing remission in patients with moderate to severe refractory Crohn's disease. Infliximab is beneficial in the treatment of fistulous Crohn's disease as well. Anti-inflammatory cytokines such as rhIL-10 and opreleukin (rhIL-11) in early reports appear efficacious in Crohn's disease but not in ulcerative colitis. Budesonide, a second generation glucocorticoid, in an oral controlled ileal release capsule, is an attractive alternative to prednisone for treating active Crohn's disease of the distal ileum and proximal colon. Also available as an enema, budesonide's efficacy approximates that of prednisolone for inducing remission in active distal ulcerative colitis. Postoperative recurrences of Crohn's disease are a common clinical scenario. Recently, mesalazine, metronidazole and mercaptopurine have been re-evaluated in the postoperative setting. In the largest postoperative prophylaxis trial, mercaptopurine was superior to both placebo and mesalazine in preventing clinical, endoscopic and radiographic relapses. Finally, miscellaneous therapies such as transdermal nicotine, nicotine tartrate enemas and topical lidocaine used in pilot studies for ulcerative colitis have shown promise. Case reports of thalidomide and tacrolimus (FK 506) have reported beneficial effects in treating complicated, refractory Crohn's disease.     

Novel approaches to inflammatory bowel disease

Ulcerative colitis and Crohn's disease, collectively known as inflammatory bowel disease (IBD), are chronic, spontaneously relapsing disorders of unknown cause. These diseases appear to be immunologically mediated and have genetic and environmental influences. Although the cause of these diseases remains obscure, the pathogenesis of chronic intestinal inflammation is becoming clearer, due to improved animal models of enterocolitis and important advances in immunological techniques. Traditional therapy for IBD, although helping to induce and maintain disease remission, does little to alter the underlying fundamental disease process. New IBD therapy has not developed significantly over the past twenty years and includes 5-aminosalicylic acid preparations, corticosteroids and immunomodulatory agents, such as azathioprine, 6-mercaptopurine and methotrexate. There is, therefore, a need for new, specific disease-modifying therapy and the development of such therapy has been hastened by a greater understanding of the pathophysiology of IBD. This review examines the most recent novel therapies for IBD, with specific emphasis on immunomodulatory and novel anti-inflammatory therapies. Recent clinical trials are reviewed, and the potential advances and clinical impact that these novel agents may provide are discussed.     

Cytokine and anti-cytokine therapies for inflammatory bowel disease

Although the pathogenesis of inflammatory bowel disease (IBD) remains elusive, it appears that there is chronic activation of the immune and inflammatory cascade in genetically susceptible individuals. Current disease management guidelines have therefore focused on the use of anti-inflammatory agents, aminosalicylates and corticosteroids. These conventional therapies continue to be a first choice in the management of IBD. Immunomodulators, such as azathioprine, 6-mercaptopurine, methotrexate or cyclosporin, are demonstrating increasing importance against steroid-resistant and steroid-dependent patients. However, some patients are still refractory to these therapies. Recent advances in the understanding of the pathophysiological conditions of IBD have provided new immune system modulators as therapeutic tools. Other immunosuppressive agents including FK506 and thalidomide have expanded the choice of medical therapies available for certain subgroups of patients. Furthermore, biological therapies have begun to assume a prominent role. Studies with chimeric monoclonal anti-TNF-alpha antibody treatment have been reported with dramatic successes. However, observations in larger numbers of treated patients are needed to explicate fully the safety of or risks posed by this agent such as developing lymphoma, or other malignancies. Another anti-inflammatory cytokine-therapy includes anti anti-IL-6R, anti-IL-12 or toxin-conjugated anti IL-7R, recombinant cytokines (IL-10 or IL-11). Given the diversity of proinflammatory products under its control, NF-kappaB may be viewed as a master switch in lymphocytes and macrophages, regulating inflammation and immunity. Although some of them still need more confirmatory studies, those immune therapies will provide new insights into cell-based and gene-based treatment against IBD in near future.