Distinct profiles of effector cytokines mark the different phases of Crohn's disease

Advances in understanding the role of cytokines in inflammatory bowel disease

Cytokines represent the key pathophysiologic elements that govern the initiation, progression, and, in some circumstances, the resolution of the inflammation occurring in inflammatory bowel disease (IBD). Areas covered: In this review, we will focus on the main effector and anti-inflammatory cytokines produced in IBD and discuss the results of recent trials in which cytokine-based therapy has been used for treating IBD patients. Expert commentary: The possibility to sample mucosal biopsies from IBD patients and analyze which molecular pathways are prominent during the active phases of the disease and the easy access to various models of experimental colitis has largely advanced our understanding about the role of cytokines in IBD. These progresses have facilitated the development of several therapeutic compounds, which either target inflammatory cytokines or enhance the regulatory function of immunosuppressive cytokines. While some of such drugs are effective in the induction and maintenance of remission of the disease, other compounds are not useful for attenuating the ongoing mucosal inflammation, thus establishing a hierarchical scale of the relevance of cytokines in IBD. Further work is needed to identify biomarkers, which could help personalize cytokine-targeted therapy and minimize potential side effects.

How to predict response to anti-tumour necrosis factor agents in inflammatory bowel disease

Anti-tumor necrosis factor (TNF) agents have changed the therapeutic approach to inflammatory bowel disease (IBD). However, a considerable proportion of patients either do not primarily respond or lose response to treatment. Despite the long-standing experience in the use of these drugs, still there is the need of identifying the possible predictors of efficacy. Areas covered: We critically review the current knowledge on predictors of response to anti-TNF therapy - both those available in clinical practice and those still under investigation. Multiple factors are involved in treatment success, including disease phenotype and severity, adherence to medications, and pharmacogenomic, pharmacokinetic, and immunologic factors. Literature search was conducted in PubMed using keywords 'inflammatory bowel disease,' 'Crohn's disease,' and 'ulcerative colitis,' matched with 'antitumor necrosis factor,' 'biologic therapy,' 'clinical response,' 'predictors,' and 'efficacy,' Relevant articles were selected for review. Expert commentary: While the role of several factors in clinical practice is clearly established, other investigational markers have been proposed, mostly in small studies, yet for many of them little external validation exists. Therapeutic drug monitoring is emerging as a pivotal strategy to guide decisions in clinical practice. In the near future, novel markers could improve our ability to direct treatment and personalize therapy.

Old and New Lymphocyte Players in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing Crohn's disease and ulcerative colitis, is a chronic intestinal inflammatory disorder characterized by diffuse accumulation of lymphocytes in the gut mucosa as a consequence of over-expression of endothelial adhesion molecules. The infiltrating lymphocytes have been identified as subsets of T cells, including T helper (Th)1 cells, Th17 cells, and regulatory T cells. The function of these lymphocyte subpopulations in the development of IBD is well-known, since they produce a number of pro-inflammatory cytokines, such as interferon-γ and interleukin-17A, which in turn activate mucosal proteases, thus leading to the development of intestinal lesions, i.e., ulcers, fistulas, abscesses, and strictures. However, the immune mechanisms underlying IBD are not yet fully understood, and knowledge about the function of newly discovered lymphocytes, including Th9 cells, innate lymphoid cells, mucosal-associated invariant T cells, and natural killer T cells, might add new pieces to the complex puzzle of IBD pathogenesis. This review summarizes the recent advances in the understanding of the role of mucosal lymphocytes in chronic intestinal inflammation and deals with the therapeutic potential of lymphocyte-targeting drugs in IBD patients.

Impact of Cigarette Smoking on the Gastrointestinal Tract Inflammation: Opposing Effects in Crohn's Disease and Ulcerative Colitis

Cigarette smoking is a major risk factor for gastrointestinal disorders, such as peptic ulcer, Crohn’s disease (CD), and several cancers. The mechanisms proposed to explain the role of smoking in these disorders include mucosal damage, changes in gut irrigation, and impaired mucosal immune response. Paradoxically, cigarette smoking is a protective factor for the development and progression of ulcerative colitis (UC). UC and CD represent the two most important conditions of inflammatory bowel diseases, and share several clinical features. The opposite effects of smoking on these two conditions have been a topic of great interest in the last 30 years, and has not yet been clarified. In this review, we summarize the most important and well-understood effects of smoking in the gastrointestinal tract; and particularly, in intestinal inflammation, discussing available studies that have addressed the causes that would explain the opposite effects of smoking in CD and UC.

Inflammatory bowel disease following anti-interleukin-1-treatment in systemic juvenile idiopathic arthritis

BACKGROUND

Inflammatory bowel disease can develop in the context of some rheumatic diseases in childhood, including juvenile idiopathic arthritis (JIA). Inflammatory bowel disease (IBD) is frequently associated with other immune-mediated diseases; however, systemic onset JIA (sJIA) has not previously been connected to IBD. Treatment of sJIA has significantly changed in recent years, possibly causing changes in inflammatory patterns. Therefore, data from the German Center for Pediatric and Adolescent Rheumtology from 2010 until 2015 were analyzed by retrospective chart review.

FINDINGS

Eighty-two patients with confirmed diagosis of sJIA were found. Of these, three were identified with a diagnosis of IBD confirmed by colonoscopy (two cases of Crohn's disease, one case of ulcerative colitis) 0.8 - 4.3 years after diagnosis. All three were treated with IL-1 antagonists (anakinra in two cases, canakinumab in one case) and were well controlled for sJIA symptoms at time of diagnosis of IBD CONCLUSIONS: IBD seems to be a rare, but possible complication of sJIA. Treatment with IL-1 antagonists might be a relevant factor for a switch in the clinical phenotype of the underlying inflammatory process.

Previous Exposure to Multiple Anti-TNF Is Associated with Decreased Efficiency in Preventing Postoperative Crohn's Disease Recurrence

BACKGROUND AND AIMS

Infliximab and adalimumab are increasingly used to prevent postoperative recurrence in Crohn's disease patients. The impact of previous exposure to one or more anti-tumour necrosis factor [TNF] agents before surgery on the efficacy of anti-TNF therapy on postoperative recurrence is unknown.

METHODS

We performed a retrospective analysis of Crohn's disease patients who underwent surgical bowel resection with anastomosis and prophylactic treatment with anti-TNF therapy between January 2005 and June 2013.

RESULTS

A total of 57 consecutive Crohn's disease patients with bowel resection and anastomosis followed by prophylactic treatment with anti-TNF were included; 21 [37%] and 24 [42%] patients had a previous exposure to one and more than one anti-TNF agents, respectively; 39 patients [68%] had a surveillance colonoscopy. Cumulative rates of postoperative endoscopic recurrence at 2 years were 45.5% [26.6-69.6%] in patients exposed to two or more anti-TNFα as compared with 29.1% [11.5-48.1%] in patients exposed to one or to zero anti-TNFα before surgery [p = 0.07]. Cumulative rates of clinical recurrence at 1 year were 21.6% [9.6-44.4%] in patients exposed to two or more anti-TNFα as compared with 6.9% [1.8-25.1%] in patients exposed to zero or one anti-TNFα before surgery [p = 0.02]. Multivariable analysis identified smoking and previous exposure to two or more anti-TNFα as risk factors for Crohn's disease clinical or endoscopic postoperative recurrence (hazard ratio [HR] = 3.17; 95% confidence interval [CI]: 1.3-7.8, p = 0.01 and HR = 4.2; 95% CI: 1.8-10.2, p = 0.001, respectively).

CONCLUSIONS

Previous exposure to two or more anti-TNF agents was associated with a higher risk of postoperative recurrence in Crohn's disease patients.

IgA-coated E. coli enriched in Crohn's disease spondyloarthritis promote TH17-dependent inflammation

Peripheral spondyloarthritis (SpA) is a common extraintestinal manifestation in patients with active inflammatory bowel disease (IBD) characterized by inflammatory enthesitis, dactylitis, or synovitis of nonaxial joints. However, a mechanistic understanding of the link between intestinal inflammation and SpA has yet to emerge. We evaluated and functionally characterized the fecal microbiome of IBD patients with or without peripheral SpA. Coupling the sorting of immunoglobulin A (IgA)-coated microbiota with 16S ribosomal RNA-based analysis (IgA-seq) revealed a selective enrichment in IgA-coated Escherichia coli in patients with Crohn's disease-associated SpA (CD-SpA) compared to CD alone. E. coli isolates from CD-SpA-derived IgA-coated bacteria were similar in genotype and phenotype to an adherent-invasive E. coli (AIEC) pathotype. In comparison to non-AIEC E. coli, colonization of germ-free mice with CD-SpA E. coli isolates induced T helper 17 cell (TH17) mucosal immunity, which required the virulence-associated metabolic enzyme propanediol dehydratase (pduC). Modeling the increase in mucosal and systemic TH17 immunity we observed in CD-SpA patients, colonization of interleukin-10-deficient or K/BxN mice with CD-SpA-derived E. coli lead to more severe colitis or inflammatory arthritis, respectively. Collectively, these data reveal the power of IgA-seq to identify immunoreactive resident pathosymbionts that link mucosal and systemic TH17-dependent inflammation and offer microbial and immunophenotype stratification of CD-SpA that may guide medical and biologic therapy.

Neuroimmune Modulation of Gut Function

Neuroimmune communications are facilitated by the production of neurotransmitters by immune cells and the generation of immune mediators by immune cells, which form a functional entity called the "neuroimmune synapse." There are several mechanisms that further facilitate neuroimmune interactions including the anatomic proximity between immune cells and nerves, the expression of receptors for neurotransmitters on immune cells and for immune mediators on nerves, and the receptor-mediated activation of intracellular signaling pathways that modulate nerve and immune phenotype and function. The bidirectional communication between nerves and immune cells is implicated in allostasis, a process that describes the continuous adaptation to an ever-changing environment. Neuroimmune interactions are amplified during inflammation by the influx of activated immune cells that significantly alter the microenvironment. In this context, the types of neurotransmitters released by activated neurons or immune cells can exert pro- or anti-inflammatory effects. Dysregulation of the enteric nervous system control of gastrointestinal functions, such as epithelial permeability and secretion as well as smooth muscle contractility, also contribute to the chronicity of inflammation. Persistent active inflammation in the gut leads to neuroimmune plasticity, which is a structural and functional remodeling in both the neural and immune systems. The importance of neuroimmune interactions has made them an emerging target in the development of novel therapies for GI pathologies.

The relationship between the immune system and oral manifestations of inflammatory bowel disease: a review

Inflammatory bowel diseases (IBDs) are chronic, relapsing inflammatory diseases characterized by exacerbations and remissions of the gastrointestinal tract, clinically manifested as Crohn's disease and ulcerative colitis. The etiology of IBDs is considered to be multi factorial, comprising environmental, immune, microbial and genetic factors. Clinical signs may include abdominal pain, frequent bloody diarrheas, mucorrhea, vomiting, fever, fatigue or weight loss. Changes in the oral cavity often precede intestinal symptoms. Inflammatory bowel disease leads to a significant deterioration of oral health, which indicates that cooperation between the dentist and the gastroenterologist is necessary when considering patients' welfare. Patients with IBD have an altered immune response, but microorganisms of the oral cavity may also be responsible for its modification. This review paper discusses the correlation between the immune system and inflammatory bowel disease manifestations in the oral cavity.

Making sense of the cause of Crohn's - a new look at an old disease

The cause of Crohn’s disease (CD) has posed a conundrum for at least a century. A large body of work coupled with recent technological advances in genome research have at last started to provide some of the answers. Initially this review seeks to explain and to differentiate between bowel inflammation in the primary immunodeficiencies that generally lead to very early onset diffuse bowel inflammation in humans and in animal models, and the real syndrome of CD. In the latter, a trigger, almost certainly enteric infection by one of a multitude of organisms, allows the faeces access to the tissues, at which stage the response of individuals predisposed to CD is abnormal. Direct investigation of patients’ inflammatory response together with genome-wide association studies (GWAS) and DNA sequencing indicate that in CD the failure of acute inflammation and the clearance of bacteria from the tissues, and from within cells, is defective. The retained faecal products result in the characteristic chronic granulomatous inflammation and adaptive immune response. In this review I will examine the contemporary evidence that has led to this understanding, and look for explanations for the recent dramatic increase in the incidence of this disease.

Making sense of the cause of Crohn's - a new look at an old disease

The cause of Crohn's disease (CD) has posed a conundrum for at least a century. A large body of work coupled with recent technological advances in genome research have at last started to provide some of the answers. Initially this review seeks to explain and to differentiate between bowel inflammation in the primary immunodeficiencies that generally lead to very early onset diffuse bowel inflammation in humans and in animal models, and the real syndrome of CD. In the latter, a trigger, almost certainly enteric infection by one of a multitude of organisms, allows the faeces access to the tissues, at which stage the response of individuals predisposed to CD is abnormal. Direct investigation of patients' inflammatory response together with genome-wide association studies (GWAS) and DNA sequencing indicate that in CD the failure of acute inflammation and the clearance of bacteria from the tissues, and from within cells, is defective. The retained faecal products result in the characteristic chronic granulomatous inflammation and adaptive immune response. In this review I will examine the contemporary evidence that has led to this understanding, and look for explanations for the recent dramatic increase in the incidence of this disease.

Insight into the role of TSLP in inflammatory bowel diseases

Proinflammatory cytokines are thought to modulate pathogeneses of various inflammatory bowel diseases (IBDs). Thymic stromal lymphopoietin (TSLP), which has been studied in various allergic diseases such as asthma, atopic dermatitis (AD) and eosinophilic esophagitis (EoE), has been less considered to be involved in IBDs. However, mucosal dendritic cells (DCs) induced by various cytokines including TSLP were reported to cause polarization of T cell toward Th2 response, the differentiation of regulatory T-cell (Treg), and secretion of IgA by B cells. In this review, we discuss the concept that decreased TSLP has the potential to accelerate the development of Th1 response dominant diseases such as the Crohn's disease (CD) while increased TSLP has the potential to lead to a development of Th2 cell dominant diseases such the ulcerative colitis (UC). To examine TSLP's role as a potential determining factor for differentiating UC and CD, we analyzed the effects of other genes regulated by TSLP in regards to the UC and CD pathogeneses using data from online open access resources such as NetPath, GeneMania, and the String database. Our findings indicate that TSLP is a key mediator in the pathogenesis of IBDs and that further studies are needed to evaluate its role.

Intestinal APCs of the endogenous nanomineral pathway fail to express PD-L1 in Crohn's disease

Crohn’s disease is a chronic inflammatory condition most commonly affecting the ileum and colon. The aetiology of Crohn’s disease is complex and may include defects in peptidoglycan recognition, and/or failures in the establishment of intestinal tolerance. We have recently described a novel constitutive endogenous delivery system for the translocation of nanomineral-antigen-peptidoglycan (NAP) conjugates to antigen presenting cells (APCs) in intestinal lymphoid patches. In mice NAP conjugate delivery to APCs results in high surface expression of the immuno-modulatory molecule programmed death receptor ligand 1 (PD-L1). Here we report that NAP conjugate positive APCs in human ileal tissues from individuals with ulcerative colitis and intestinal carcinomas, also have high expression of PD-L1. However, NAP-conjugate positive APCs in intestinal tissue from patients with Crohn’s disease show selective failure in PD-L1 expression. Therefore, in Crohn’s disease intestinal antigen taken up by lymphoid patch APCs will be presented without PD-L1 induced tolerogenic signalling, perhaps initiating disease.

Progress with anti-tumor necrosis factor therapeutics for the treatment of inflammatory bowel disease

Anti-tumor necrosis factor (TNF) therapy is a valid, effective and increasingly used option in inflammatory bowel disease management. Nevertheless, further knowledge and therapeutic indications regarding these drugs are still evolving. Anti-TNF therapy may be essential to achieve recently proposed end points, namely mucosal healing, prevention of bowel damage and prevention of patient's disability. Anti-TNF drugs are also suggested to be more effective in early disease, particularly in early Crohn's disease. Moreover, its efficacy for prevention of postoperative recurrence in Crohn's disease is still debated. Costs and adverse effects, the relevance of drug monitoring and the possibility of anti-TNF therapy withdrawal in selected patients are still debated issues. This review aimed to describe and discuss the most relevant data about the progress with anti-TNF therapy for the management of inflammatory bowel disease.

Granulocyte Macrophage Colony-Stimulating Factor-Activated Eosinophils Promote Interleukin-23 Driven Chronic Colitis

The role of intestinal eosinophils in immune homeostasis is enigmatic and the molecular signals that drive them from protective to tissue damaging are unknown. Most commonly associated with Th2 cell-mediated diseases, we describe a role for eosinophils as crucial effectors of the interleukin-23 (IL-23)-granulocyte macrophage colony-stimulating factor (GM-CSF) axis in colitis. Chronic intestinal inflammation was characterized by increased bone marrow eosinopoiesis and accumulation of activated intestinal eosinophils. IL-5 blockade or eosinophil depletion ameliorated colitis, implicating eosinophils in disease pathogenesis. GM-CSF was a potent activator of eosinophil effector functions and intestinal accumulation, and GM-CSF blockade inhibited chronic colitis. By contrast neutrophil accumulation was GM-CSF independent and dispensable for colitis. In addition to TNF secretion, release of eosinophil peroxidase promoted colitis identifying direct tissue-toxic mechanisms. Thus, eosinophils are key perpetrators of chronic inflammation and tissue damage in IL-23-mediated immune diseases and it suggests the GM-CSF-eosinophil axis as an attractive therapeutic target.

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GM-CSF synergizes with IL-5 to exacerbate eosinopoiesis during chronic colitis

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GM-CSF-activated eosinophils promote IL-23 driven colitis

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Depletion of eosinophils, but not of neutrophils, dampens colitis

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GM-CSF increases eosinophil production of inflammatory cytokines TNF and IL-13

Monocyte-derived macrophages from Crohn's disease patients are impaired in the ability to control intracellular adherent-invasive Escherichia coli and exhibit disordered cytokine secretion profile

BACKGROUND

Ileal lesions of Crohn's disease [CD] patients are colonised by adherent-invasive Escherichia coli [AIEC] able to survive in macrophage cell lines. We analysed the ability of monocyte-derived macrophages [MDM] from CD patients to control AIEC intracellular replication and the pro-inflammatory cytokine response of the infected-MDM.

METHODS

Peripheral blood MDM were obtained from 24 CD genotyped for NOD2 and ATG16L1 mutations, 5 ulcerative colitis [UC] patients and 12 healthy controls [HC]. The numbers of intracellular bacteria were determined using gentamicin assay. Cytokine secretion was quantified by ELISA assay.

RESULTS

We observed that higher levels of bacteria were internalised within MDM from CD patients than MDM from HC or UC patients. MDM from CD patients were unable to restrict AIEC intracellular replication. Infection of MDM from CD patients with AIEC resulted in significantly increased secretion of IL-6 and tumour necrosis factor alpha [TNF α] than did infection with non-pathogenic E. coli. AIEC-infected MDM from CD patients exhibited a disordered cytokines secretion compared with MDM from UC patients and HC. AIEC-infected MDM from patients with quiescent CD released significantly higher amounts of IL-6 and TNF-alpha than those with active disease or those from HC. The level of secreted TNF-alpha was correlated to the number of intracellular AIEC in MDM from CD patients. Treatment of MDM with infliximab did not change the MDM behaviour.

CONCLUSIONS

MDM from CD patients are unable to restrict intracellular AIEC replication, leading to disordered inflammatory response influenced by disease activity.

Claudin-2 as a mediator of leaky gut barrier during intestinal inflammation

The epithelial tight junction determines the paracellular water and ion movement in the intestine and also prevents uptake of larger molecules, including antigens, in an uncontrolled manner. Claudin-2, one of the 27 mammalian claudins regulating that barrier function, forms a paracellular channel for small cations and water. It is typically expressed in leaky epithelia like proximal nephron and small intestine and provides a major pathway for the paracellular transport of sodium, potassium, and fluid. In intestinal inflammation (Crohn's disease, ulcerative colitis), immune-mediated diseases (celiac disease), and infections (HIV enteropathy), claudin-2 is upregulated in small and large intestine and contributes to diarrhea via a leak flux mechanism. In parallel to that upregulation, other epithelial and tight junctional features are altered and the luminal uptake of antigenic macromolecules is enhanced, for which claudin-2 may be partially responsible through induction of tight junction strand discontinuities.

Role of immunosuppressives in special situations: perianal disease and postoperative period

Complex perianal disease is associated with poor outcome and requires early effective therapy. Corticosteroids are not effective in perianal fistulising Crohn's disease, and antibiotics, immunosuppressants and anti-TNF therapy are required. It is important to consider combined medical surgical therapy after accurate imaging using an MRI scan of the pelvis. Drainage of any abscess at examination under anaesthesia and seton insertion are important before introduction of immunosuppressants and anti-TNF therapy. Long-term follow up of patients in a single centre reported responders to azathioprine having a reduced risk of perianal surgery (OR = 0.36; 95% CI: 0.27-0.46), but complex perianal fistulising Crohn's disease generally requires combination therapy with anti-TNF and azathioprine. Patients with recent perianal disease without fistulae and aged 40 years or older respond better to azathioprine monotherapy. Response to monotherapy with azathioprine is often slow and incomplete. In the recent GETAID study of early administration of azathioprine versus conventional management in patients at high risk of disabling disease, a higher cumulative proportion of patients in the azathioprine group were free of perianal surgery. In patients not responding to anti-TNF therapy, thalidomide or tacrolimus may be considered. Hyperbaric oxygen may be used as adjunctive therapy where available. The role of adipose-derived stem cell injection requires further long-term studies. In prevention of post-operative recurrence of Crohn's disease, azathioprine or 6-mercaptopurine had a favourable incremental cost-effectiveness ratio compared with no prophylactic therapy up to 1 year. In a Cochrane systematic review, azathioprine/6-mercaptopurine was associated with a significantly reduced risk of clinical recurrence [RR = 0.59, 95% CI: 0.38-0.92, number needed to treat (NNT) = 7] and severe endoscopic recurrence (RR = 0.6, 95% CI: 0.44-0.92, NNT = 4). Individual studies of prevention of post-operative recurrence using azathioprine/6-mercaptopurine have shown only modest benefit. In patients at high risk of relapse after surgical resection, anti-TNF therapy may be beneficial, but more data is required from ongoing studies. Strategies to prevent post-operative recurrence in Crohn's disease are evolving but need further refinement.

Pro- and anti-inflammatory cytokine gene single-nucleotide polymorphisms in inflammatory bowel disease

Anti-inflammatory cytokines have an important role in disease, tumour and transplant processes. Alterations in the regulation of several cytokines have been implicated in a variety of inflammatory disorders, including IBD (inflammatory bowel disease) [Crohn's disease (CD) and ulcerative colitis (UC)]. Cytokine polymorphisms are also known to affect the level of gene expression. Thus, the aim of this study was to determine the relationship between cytokine polymorphisms and the IBD pathologies in a Spanish population. Polymorphisms analysis was performed using PCR-SSOP using a microbeads luminex assay. The following polymorphisms were determined: TNFα [-238G/A (rs361525) and -308G/A (rs1800629)], IFNγ [+874A/T (rs62559044)], TGFβ [+869C/T (rs1982073) and +915G/C (rs1800471)], IL10 [-1082A/A (rs1800896), -592A/C (rs1800872), -819C/T (rs1800871)], IL6 [-174C/G (rs1800795)], IL12p40 [3'UTR -1188A/C (rs3212227)], IL1α [-889C/T (rs1800587)], IL1β [-511C/T (rs1143634) and +3962C/T (rs1143633)], IL1R [Pst-1 1970C/T] and IL1RA [Mspa-1 11100C/T]. No statistical differences in TNFα, IFNγ, TGFβ, IL10, IL6, IL1α, IL1β, IL1R and IL1Ra genotypes and allele distributions between the IBD groups and healthy controls were found. However, we observed significant differences in the 3'UTR -1188A/C polymorphism of IL12p40. So -1188A allele was increased in patients with UC and the -1188C allele (high IL12p40 production) was increased in patients with CD with respect to controls. These data are in concordance with the fact that CD has been shown to be associated with a Th1 T-cell-mediated inflammation model and high IL12/IFNγ production at histological affected sites. These data suggest that cytokine polymorphisms in TNFα, IFNγ, TGFβ, IL10, IL6 and IL1α, IL1β, IL1R and IL1Ra cytokine gene do not seem to be relevant in IBD susceptibility and IL12p40 3'UTR -1188A/C polymorphism seems to be associated with a differential IBD development.

Endogenous regulation of inflammatory pain by T-cell-derived opioids: when friend turns to foe

Painful sensation is a hallmark of microbe-induced inflammation. This inflammatory pain is downregulated a few days after infection by opioids locally released by effector T lymphocytes generated in response to microbe-derived antigens. This review focuses on the endogenous regulation of inflammatory pain associated with adaptive T-cell response and puts in perspective the clinical consequences of the opioid-mediated analgesic activity of colitogenic T lymphocytes in inflammatory bowel disease.

Colonic phenotype of the ileum in Crohn's disease: a prospective study before and after ileocolonic resection

BACKGROUND

Colonic metaplasia has been described in pouchitis. In a prospective study, we investigated whether colonic phenotype may develop in Crohn's disease (CD) ileum. The expression of sulfomucins (colonic mucin), sialomucins, and CD10 (small intestine mucin and phenotype) was evaluated before and after ileocolonic resection for CD.

METHODS

From February 2007 to March 2010, 22 patients with CD undergoing surgery were enrolled. Clinical (Crohn's Disease Activity Index >150) and endoscopic recurrence (Rutgeerts score ≥1) rates were assessed at 6 and 12 months. Ileal samples were taken at surgery (T0), at 6 (T1), and 12 months (T2) for histology, histochemistry (High Iron Diamine-Alcian Blue), and immunohistochemistry (anti-CD10).

RESULTS

In 22 patients, recurrence was assessed at 6 and 12 months (clinical recurrence 9% and 18%; endoscopic recurrence 73% and 77%). In all 22 patients, ileal samples were taken at 6 and 12 months (involved area in patients with recurrence). In 19 of 22 (86.3%) patients, the involved ileum was also studied at surgery. At T0, T1, and T2, the expression of sialomucins and CD10 (small intestine mucin and phenotype) was comparable and higher (P < 0.0001) than the expression of sulfomucins (colonic mucin) (mean [range], T0:82 [35-100] versus 75 [0-100] versus 16 [0-50]; T1:96 [60-100] versus 94.7 [50-100] versus 3.89 [0-40]; T2:93.3 [60-100] versus 88.1 [25-100] versus 6.6 [0-40]). The expression of small-intestine mucin and phenotype was higher at T1 (P = 0.025) versus T0 (P = 0.026). Differently, the expression of colonic mucin was lower at T1 versus T0 (P = 0.027).

CONCLUSIONS

In CD, the ileum involved by severe/established lesions develops a "metaplastic" colonic mucosa phenotype. Differently, CD ileum with no lesions or with early recurrence maintains the "native" small intestine type mucin secretion and phenotype.

Domino effect of hypomagnesemia on the innate immunity of Crohn’s disease patients

Digestive diseases play major role in development and complications of other disorders including diabetes. For example, Crohn’s disease (CD) is an inflammatory bowel disease associated with Mycobacterium avium subspecies paratuberculosis. The inflammation is a complex process that involves the activity of both innate and adaptive immune responses. CD lesions are primarily due to T cell response, however; innate immune response has a significant role in initiating its pathogenesis. Toll-like receptors and NOD-like receptors promote the activity of nuclear factor (NF)-κB pathway for cytokines production. This results in the production of high levels of tumor necrosis factor-α, interleukin (IL)-1β and IL-6. Moreover, intestinal inflammation of CD is related to increased activity of NMDA receptors and the release of substance P. Imbalanced magnesium homeostasis in CD is a frequent finding in CD, Diabetes and others. The loss of such a major mineral affects many physiological processes in the body including its role as an immunomodulator. This review aims to (1) describe the significance of hypomagnesemia in the release of pro-inflammatory mediators in CD; (2) demonstrate effects of magnesium on pathways like NF-κB; (3) address the role of hypomagnesemia in the activity of CD; and (4) examine possible future research to establish a standard magnesium supplementation strategy; helping patients with CD or other disorders to maintain a sustained remission.

Cytokines in inflammatory bowel disease

Cytokines have a crucial role in the pathogenesis of inflammatory bowel diseases (IBDs), such as Crohn's disease and ulcerative colitis, where they control multiple aspects of the inflammatory response. In particular, the imbalance between pro-inflammatory and anti-inflammatory cytokines that occurs in IBD impedes the resolution of inflammation and instead leads to disease perpetuation and tissue destruction. Recent studies suggest the existence of a network of regulatory cytokines that has important implications for disease progression. In this Review, we discuss the role of cytokines produced by innate and adaptive immune cells, as well as their relevance to the future therapy of IBD.

Giardia duodenalis cathepsin B proteases degrade intestinal epithelial interleukin-8 and attenuate interleukin-8-induced neutrophil chemotaxis

Giardia duodenalis (syn. G. intestinalis, G. lamblia) infections are a leading cause of waterborne diarrheal disease that can also result in the development of postinfectious functional gastrointestinal disorders via mechanisms that remain unclear. Parasite numbers exceed 10(6) trophozoites per centimeter of gut at the height of an infection. Yet the intestinal mucosa of G. duodenalis-infected individuals is devoid of signs of overt inflammation. G. duodenalis infections can also occur concurrently with infections with other proinflammatory gastrointestinal pathogens. Little is known of whether and how this parasite can attenuate host inflammatory responses induced by other proinflammatory stimuli, such as a gastrointestinal pathogen. Identifying hitherto-unrecognized parasitic immunomodulatory pathways, the present studies demonstrated that G. duodenalis trophozoites attenuate secretion of the potent neutrophil chemoattractant interleukin-8 (CXCL8); these effects were observed in human small intestinal mucosal tissues and from intestinal epithelial monolayers, activated through administration of proinflammatory interleukin-1β or Salmonella enterica serovar Typhimurium. This attenuation is caused by the secretion of G. duodenalis cathepsin B cysteine proteases that degrade CXCL8 posttranscriptionally. Furthermore, the degradation of CXCL8 via G. duodenalis cathepsin B cysteine proteases attenuates CXCL8-induced chemotaxis of human neutrophils. Taken together, these data demonstrate for the first time that G. duodenalis trophozoite cathepsins are capable of attenuating a component of their host's proinflammatory response induced by a separate proinflammatory stimulus.

Pro-inflammatory human Th17 cells selectively express P-glycoprotein and are refractory to glucocorticoids

Inflammatory T helper 17 cells in humans are distinguished by selective expression of MDR1 and are enriched in the gut of patients with Crohn’s disease.

IL-17A–expressing CD4⁺ T cells (Th17 cells) are generally regarded as key effectors of autoimmune inflammation. However, not all Th17 cells are pro-inflammatory. Pathogenic Th17 cells that induce autoimmunity in mice are distinguished from nonpathogenic Th17 cells by a unique transcriptional signature, including high Il23r expression, and these cells require Il23r for their inflammatory function. In contrast, defining features of human pro-inflammatory Th17 cells are unknown. We show that pro-inflammatory human Th17 cells are restricted to a subset of CCR6⁺CXCR3^hiCCR4^loCCR10⁻CD161⁺ cells that transiently express c-Kit and stably express P-glycoprotein (P-gp)/multi-drug resistance type 1 (MDR1). In contrast to MDR1⁻ Th1 or Th17 cells, MDR1⁺ Th17 cells produce both Th17 (IL-17A, IL-17F, and IL-22) and Th1 (IFN-γ) cytokines upon TCR stimulation and do not express IL-10 or other anti-inflammatory molecules. These cells also display a transcriptional signature akin to pathogenic mouse Th17 cells and show heightened functional responses to IL-23 stimulation. In vivo, MDR1⁺ Th17 cells are enriched and activated in the gut of Crohn’s disease patients. Furthermore, MDR1⁺ Th17 cells are refractory to several glucocorticoids used to treat clinical autoimmune disease. Thus, MDR1⁺ Th17 cells may be important mediators of chronic inflammation, particularly in clinical settings of steroid resistant inflammatory disease.

Intestinal epithelium and autophagy: partners in gut homeostasis

One of the most significant challenges of cell biology is to understand how each type of cell copes with its specific workload without suffering damage. Among the most intriguing questions concerns intestinal epithelial cells in mammals; these cells act as a barrier between the internally protected region and the external environment that is exposed constantly to food and microbes. A major process involved in the processing of microbes is autophagy. In the intestine, through multiple, complex signaling pathways, autophagy including macroautophagy and xenophagy is pivotal in mounting appropriate intestinal immune responses and anti-microbial protection. Dysfunctional autophagy mechanism leads to chronic intestinal inflammation, such as inflammatory bowel disease (IBD). Studies involving a number of in vitro and in vivo mouse models in addition to human clinical studies have revealed a detailed role for autophagy in the generation of chronic intestinal inflammation. A number of genome-wide association studies identified roles for numerous autophagy genes in IBD, especially in Crohn’s disease. In this review, we will explore in detail the latest research linking autophagy to intestinal homeostasis and how alterations in autophagy pathways lead to intestinal inflammation.

Th17 cytokines in inflammatory bowel diseases: discerning the good from the bad

T helper (Th) 17 cells are a branch of the CD4+ T cell compartment involved in host protection against bacterial and fungal infections as well as in orchestration of chronic inflammation and autoimmunity in many organs. Th17 cells produce interleukin (IL)-17A and variable amounts of IL-17F, IL-21, IL-22 and IL-26, under the regulation of retinoic-acid-related orphan receptors (ROR)-γt and ROR-α. Accumulating evidence supports the involvement of Th17 cells in the tissue-damaging immune response occurring in patients with Crohn's disease and patients with ulcerative colitis, the two major forms of inflammatory bowel disease (IBD) in human beings. However in the gut, Th17 cells can also have tissue-protective effects, mostly depending on their ability to enhance epithelial barrier function and counter-regulatory mechanisms. In this article, we summarize the available data on the dual role of Th17 cells in gut homeostasis and inflammation and discuss whether and how Th17 cytokine blockers can enter into the therapeutic armamentarium of IBD.

The challenges of stratifying patients for trials in inflammatory bowel disease

Immunotherapy with biological agents or small molecules is revolutionising the treatment of chronic inflammatory disease in humans; however, a significant proportion of patients fail to respond or lose responsiveness. This is particularly evident in inflammatory bowel disease (IBD), a group of chronic, immune-mediated disorders of the gastrointestinal tract. Different responsiveness to treatment in IBD can be explained by substantial disease heterogeneity, which is being increasingly recognised by genetic and immunological studies. The current enthusiasm for stratified medicine suggests that it may become possible to identify clinical, immunological, biochemical or genetic biomarkers to target immunotherapy to patients more likely to respond. Here, we identify and highlight the opportunities and the challenges of this strategy in the context of IBD.

The role of interleukin 17 in Crohn's disease-associated intestinal fibrosis

Background

Interleukin (IL)-17A and IL-17E (also known as IL-25) have been implicated in fibrosis in various tissues. However, the role of these cytokines in the development of intestinal strictures in Crohn’s disease (CD) has not been explored. We investigated the levels of IL-17A and IL-17E and their receptors in CD strictured and non-strictured gut, and the effects of IL-17A and IL-17E on CD myofibroblasts.

Results

IL-17A was significantly overexpressed in strictured compared with non-strictured CD tissues, whereas no significant difference was found in the expression of IL-17E or IL-17A and IL-17E receptors (IL-17RC and IL-17RB, respectively) in strictured and non-strictured CD areas. Strictured CD explants released significantly higher amounts of IL-17A than non-strictured explants, whereas no difference was found as for IL-17E, IL-6, or tumor necrosis factor-α production. IL-17A, but not IL-17E, significantly inhibited myofibroblast migration, and also significantly upregulated matrix metalloproteinase (MMP)-3, MMP-12, tissue inhibitor of metalloproteinase-1 and collagen production by myofibroblasts from strictured CD tissues.

Conclusions

Our results suggest that IL-17A, but not IL-17E, is pro-fibrotic in CD. Further studies are needed to clarify whether the therapeutic blockade of IL-17A through the anti-IL-17A monoclonal antibody secukinumab is able to counteract the fibrogenic process in CD.

Investigational cytokine-targeted therapies for ulcerative colitis

INTRODUCTION

Up to one-third of patients with ulcerative colitis (UC) do not respond to standard medications, including mesalamine, steroids and thiopurines. The recognition that UC-related pathological process is the result of an altered balance between inflammatory and counter-regulatory signals, mostly mediated by cytokines, has led to the development of novel compounds, which are now ready to move into clinical practice. This article summarizes the recent data on the development and use of compounds either inhibiting inflammatory cytokines or enhancing the activity of counter-regulatory cytokines in patients with UC and murine models of UC.

AREAS COVERED

A PubMed search was performed using the following keywords: 'ulcerative colitis', 'therapy', 'treatment' and 'cytokine'. In addition, ongoing clinical trials were checked and compounds were searched on the website of pharmaceutical companies.

EXPERT OPINION

Several investigational cytokine-based therapies have provided promising results in attenuating clinical activity in patients with UC and mice with experimental colitis. However, clinical and immunological heterogeneity of UC patients, therapy-related side effects and redundant biological functions of cytokines represent potential pitfalls and should be considered in optimizing therapeutic strategies.