The effects of NOD2/CARD15 mutations on the function of the intestinal barrier

Intestinal barrier in inflammatory bowel disease: A bibliometric and knowledge-map analysis

BACKGROUND

Barrier surfaces composed of specialized epithelial cells separate the host body from the external environment, and are essential for maintaining proper intestinal physiologic and immune homeostasis.

AIM

To explore the development trends and research hotspots of intestinal barrier research in inflammatory bowel disease (IBD).

METHODS

The publications related to the intestinal barrier in IBD were obtained from the Web of Science Core Collection database. Bibliometric analysis and visualization were conducted using VOSviewer, CiteSpace and R software.

RESULTS

A total of 4482 articles published between 2002 and 2022 were identified. The United States is dominant in intestinal barrier research, whereas the University of Chicago is the most active institution. Jerrold from Harvard Medical School was the most productive authors with the most citations. The journals Inflammatory Bowel Disease and Gastroenterology have made significant contributions in this field. The keywords appearing at high frequency related to the intestinal barrier in IBD were detected, including nuclear factor kappa B, tumor necrosis factor-α, apoptosis, oxidative stress and probiotics. Among them, antioxidants, Akkermansia muciniphila, nanoparticles, short-chain fatty acids and extracellular vesicles have received growing interest in recent research.

CONCLUSION

The intestinal barrier field is developing rapidly with extensive cooperation. Targeting the gut microbiota and dietary metabolism to regulate the intestinal barrier has shown promising prospective applications and has generated broad interest. The importance of the intestinal barrier in IBD is gradually being fully recognized, providing a new therapeutic perspective for improving inflammation and prognosis.

Gut Microbiome and Its Interaction with Immune System in Spondyloarthritis

Emerging evidence suggests there is a gut-joint axis in spondyloarthritis (SpA). In a study, subclinical gut inflammation occurred in nearly 50% of SpA. Chronic gut inflammation also correlated with disease activity in SpA. Trillions of microorganisms reside in the human gut and interact with the human immune system. Dysbiosis affects gut immune homeostasis and triggers different autoimmune diseases including SpA. The absence of arthritis in HLA-B27 germ-free mice and the development of arthritis after the introduction of commensal bacteria to HLA-B27 germ-free mice proved to be the important role of gut bacteria in shaping SpA, other than the genetic factor. The recent advance in gene sequencing technology promotes the identification of microorganisms. In this review, we highlighted current evidence supporting the link between gut and axial SpA (axSpA). We also summarized available findings of gut microbiota and its interaction with the immune system in axSpA. Future research may explore the way to modulate gut microorganisms in axSpA and bring gut microbiome discoveries towards application.

Links Between Inflammatory Bowel Disease and Chronic Obstructive Pulmonary Disease

Inflammatory bowel disease (IBD) and chronic obstructive pulmonary disease (COPD) are chronic inflammatory diseases of the gastrointestinal and respiratory tracts, respectively. These mucosal tissues bear commonalities in embryology, structure and physiology. Inherent similarities in immune responses at the two sites, as well as overlapping environmental risk factors, help to explain the increase in prevalence of IBD amongst COPD patients. Over the past decade, a tremendous amount of research has been conducted to define the microbiological makeup of the intestine, known as the intestinal microbiota, and determine its contribution to health and disease. Intestinal microbial dysbiosis is now known to be associated with IBD where it impacts upon intestinal epithelial barrier integrity and leads to augmented immune responses and the perpetuation of chronic inflammation. While much less is known about the lung microbiota, like the intestine, it has its own distinct, diverse microflora, with dysbiosis being reported in respiratory disease settings such as COPD. Recent research has begun to delineate the interaction or crosstalk between the lung and the intestine and how this may influence, or be influenced by, the microbiota. It is now known that microbial products and metabolites can be transferred from the intestine to the lung via the bloodstream, providing a mechanism for communication. While recent studies indicate that intestinal microbiota can influence respiratory health, intestinal dysbiosis in COPD has not yet been described although it is anticipated since factors that lead to dysbiosis are similarly associated with COPD. This review will focus on the gut-lung axis in the context of IBD and COPD, highlighting the role of environmental and genetic factors and the impact of microbial dysbiosis on chronic inflammation in the intestinal tract and lung.

T-cell Composition in Ileal and Colonic Creeping Fat - Separating Ileal from Colonic Crohn's Disease

BACKGROUND AND AIMS

Creeping fat [CF] is a hyperplasia of adipose tissue adjacent to inflamed intestine in Crohn's disease [CD]. Data from genome-wide association studies [GWAS] distinguished Crohn's colitis from ileal CD and ulcerative colitis [UC]. This study analysed the T-cell compartments of ileal and colonic mesenteric fat and corresponding mucosa to provide cellular proof for the suggested GWAS classification.

METHODS

Samples were obtained from 34 CD or UC patients. Cells were analysed by immunohistochemistry and flow cytometry, and tissue cytokine release was assessed by cytometric bead array.

RESULTS

Only ileal CF revealed the distinct adipocyte hyperplasia combined with dense T-cell infiltration and fibrosis; colonic fat from CD and UC patients lacked these findings. T-cell subpopulations differed between mesenteric fat in ileal CD, colonic CD and UC: ileal CF had nearly 10 times more T-cells than colonic fat. The proportions of regulatory and central memory T-cells were significantly higher in ileal CF compared with colonic fat in CD and UC. In all groups, the mucosal T-cell compartment was distinct from the mesenteric fat. Remarkably, correlation between disease activity and proportion of pro- and anti-inflammatory T-cell subpopulations was inverse, comparing ileal and colonic fat in CD.

CONCLUSIONS

This first in-depth analysis of the T-cell compartment in ileal and colonic mesenteric adipose tissue in CD and UC identifies a unique T-cell niche in the ileal mesenteric fat tissue in CD. From a clinical point of view, our findings underscore the novel concept of colonic and ileal CD as distinct IBD entities.

Microbiome and colorectal cancer: Unraveling host-microbiota interactions in colitis-associated colorectal cancer development

Dysbiosis of gut microbiota occurs in many human chronic immune-mediated diseases, such as inflammatory bowel disease (IBD) and colitis-associated colorectal cancer (CAC). Reciprocally, uncontrolled immune responses, that may or may not be induced by dysbiosis, are central to the development of IBD and CAC. There has been a surge of interest in investigating the relationship between microbiota, inflammation and CAC. In this review, we discuss recent findings related to gut microbiota and chronic immune-mediated diseases, such as IBD and CAC. Moreover, the molecular mechanisms underlying the roles of chronic inflammation in CAC are examined. Finally, we discuss the development of novel microbiota-based therapeutics for IBD and colorectal cancer.

Mechanisms of Intestinal Epithelial Barrier Dysfunction by Adherent-Invasive Escherichia coli

Pathobiont expansion, such as that of adherent-invasive Escherichia coli (AIEC), is an emerging factor associated with inflammatory bowel disease. The intestinal epithelial barrier is the first line of defense against these pathogens. Inflammation plays a critical role in altering the epithelial barrier and is a major factor involved in promoting the expansion and pathogenesis of AIEC. AIEC in turn can exacerbate intestinal epithelial barrier dysfunction by targeting multiple elements of the barrier. One critical element of the epithelial barrier is the tight junction. Increasing evidence suggests that AIEC may selectively target protein components of tight junctions, leading to increased barrier permeability. This may represent one mechanism by which AIEC could contribute to the development of inflammatory bowel disease. This review article discusses potential mechanisms by which AIEC can disrupt epithelial tight junction function and intestinal barrier function.

Emerging significance of NLRs in inflammatory bowel disease

Pattern recognition receptors are essential mediators of host defense and inflammation in the gastrointestinal system. Recent data have revealed that toll-like receptors and nucleotide-binding domain and leucine-rich repeat-containing proteins (NLRs) function to maintain homeostasis between the host microbiome and mucosal immunity. The NLR proteins are a diverse class of cytoplasmic pattern recognition receptors. In humans, only about half of the identified NLRs have been adequately characterized. The majority of well-characterized NLRs participate in the formation of a multiprotein complex, termed the inflammasome, which is responsible for the maturation of interleukin-1β and interleukin-18. However, recent observations have also uncovered the presence of a novel subgroup of NLRs that function as positive or negative regulators of inflammation through modulating critical signaling pathways, including NF-κB. Dysregulation of specific NLRs from both proinflammatory and inhibitory subgroups have been associated with the development of inflammatory bowel disease (IBD) in genetically susceptible human populations. Our own preliminary retrospective data mining efforts have identified a diverse range of NLRs that are significantly altered at the messenger RNA level in colons from patients with IBD. Likewise, studies using genetically modified mouse strains have revealed that multiple NLR family members have the potential to dramatically modulate the immune response during IBD. Targeting NLR signaling represents a promising and novel therapeutic strategy. However, significant effort is necessary to translate the current understanding of NLR biology into effective therapies.

Is rifaximin effective in maintaining remission in Crohn's disease?

BACKGROUND

Recent studies indicate that persistent intestinal inflammation in patients with Crohn's disease (CD) might be caused by abnormal intestinal microbiota. This hypothesis may suggest a beneficial effect of antibiotics in CD therapy. So far, guidelines do not recommend antibiotics except in the treatment of complicated CD, and there are few studies on the effects of rifaximin in these patients.

METHODS

Between December 2011 and December 2012, we performed a blinded randomized trial in 168 patients with a previous history of moderately active CD concerning the efficacy of rifaximin. All the patients had previously achieved remission with standard therapy (prednisone/budesonide). Data from patients receiving 800 mg of rifaximin (83 patients) twice a day for 12 weeks were compared with those from patients who received placebo (83 patients). The primary endpoint was maintaining remission during the follow-up.

RESULTS

All the patients (100%; 83/83) on 800 mg of rifaximin were in remission after 12 weeks of treatment in comparison with 84% (70/83) of the placebo group. This significant difference was also persistent at the 24-week follow-up [78% (65/83) vs. 41% (34/83), respectively]. The last evaluation performed at 48 weeks revealed disease activity in 45% (38/83) of the patients of the rifaximin group, i.e. a significant decrease compared with the placebo group [75% (63 of 83)].

CONCLUSIONS

Remission previously obtained with standard treatment can be sustained in patients with moderately active CD after the administration of 800 mg of rifaximin.

Low mannose-binding lectin (MBL) is associated with paediatric inflammatory bowel diseases and ileal involvement in patients with Crohn disease

BACKGROUND

Mannose-binding lectin (MBL) is a pattern-recognition molecule of the innate immune system and may be involved in the pathogenesis of inflammatory bowel disease (IBD). Our aim was to assess the prevalence of MBL deficiency in a cohort of patients with paediatric-onset IBD and study whether it is associated with the clinical manifestations, serum antibody formation, or genetic factors.

METHODS

This prospective study included 159 paediatric patients (mean age: 14.0 years) with IBD [107 patients with Crohn disease (CD) and 52 patients with ulcerative colitis (UC)]. Furthermore, 95 controls were investigated. Serum samples were determined for MBL by enzyme-linked immunosorbent assay (ELISA) and for serologic markers [autoantibodies against Saccharomyces cerevisiae (ASCA) and perinuclear components of neutrophils (pANCA)] by indirect immunofluorescent assay. NOD2/CARD15 variants were tested by polymerase chain reaction/restriction fragment length polymorphism.

RESULTS

The MBL serum concentration was significantly lower in IBD patients(both with CD and UC) compared to controls (IBD, p=0.007, CD, p=0.04, UC p=0.004). Prevalence of low MBL level (<500 ng/mL) was significantly higher in both CD and UC groups compared to controls (p=0.002 and p=0.006). Furthermore, low MBL level was associated with isolated ileal involvement (p=0.01) and MBL deficiency (<100 ng/mL) with male gender (p=0.004) in patients with CD. We failed to confirm any correlation between MBL deficiency and serum autoantibodies or NOD2/CARD15 variants.

CONCLUSIONS

Our results suggest that low MBL associated with paediatric-onset IBD and ileal CD may be considered an additional marker of the IBD pathogenesis.

Use of antibiotics in the treatment of Crohn’s disease

Many data coming from animal models and clinical observations support an involvement of intestinal microbiota in the pathogenesis of Crohn’s disease (CD). It is hypothesized in fact, that the development of chronic intestinal inflammation is caused by an abnormal immune response to normal flora in genetically susceptible hosts. The involvement of bacteria in CD inflammation has provided the rationale for including antibiotics in the therapeutic armamentarium. However, randomized controlled trials have failed to demonstrate an efficacy of these drugs in patients with active uncomplicated CD, even if a subgroup of patients with colonic location seems to get benefit from antibiotics. Nitroimidazole compounds have been shown to be efficacious in decreasing CD recurrence rates in operated patients, and the use of metronidazole and ciprofloxacin is recommended in perianal disease. However, the appearance of systemic side effects limits antibiotic long-term employment necessary for treating a chronic relapsing disease. Rifaximin, characterized by an excellent safety profile, has provided promising results in inducing remission of CD.

Rifaximin-extended intestinal release induces remission in patients with moderately active Crohn's disease

BACKGROUND & AIMS

Bacteria might be involved in the development and persistence of inflammation in patients with Crohn's disease (CD), and antibiotics could be used in therapy. We performed a clinical phase 2 trial to determine whether a gastroresistant formulation of rifaximin (extended intestinal release [EIR]) induced remission in patients with moderately active CD.

METHODS

We performed a multicenter, randomized, double-blind trial of the efficacy and safety of 400, 800, and 1200 mg rifaximin-EIR, given twice daily to 402 patients with moderately active CD for 12 weeks. Data from patients given rifaximin-EIR were compared with those from individuals given placebo, and collected during a 12-week follow-up period. The primary end point was remission (Crohn's Disease Activity Index <150) at the end of the treatment period.

RESULTS

At the end of the 12-week treatment period, 62% of patients who received the 800-mg dosage of rifaximin-EIR (61 of 98) were in remission, compared with 43% of patients who received placebo (43 of 101) (P = .005). A difference was maintained throughout the 12-week follow-up period (45% [40 of 89] vs 29% [28 of 98]; P = .02). Remission was achieved by 54% (56 of 104) and 47% (47 of 99) of the patients given the 400-mg and 1200-mg dosages of rifaximin-EIR, respectively; these rates did not differ from those of placebo. Patients given the 400-mg and 800-mg dosages of rifaximin-EIR had low rates of withdrawal from the study because of adverse events; rates were significantly higher among patients given the 1200-mg dosage (16% [16 of 99]).

CONCLUSIONS

Administration of 800 mg rifaximin-EIR twice daily for 12 weeks induced remission with few adverse events in patients with moderately active CD.