Outcome in ulcerative colitis after switch from adalimumab/golimumab to infliximab: A multicenter retrospective study

BACKGROUND

Anti-TNF therapies infliximab (IFX), adalimumab (ADA), and golimumab (GOL) are approved for treating moderate to severe ulcerative colitis (UC). In UC, only the switch from IFX to ADA has been investigated, reaching no more than 10-43% remission rates at 12 months.

AIM

Of the present study was to investigate disease outcome after a switch from subcutaneous (SC) agents to the intravenous (IV) agent (IFX).

METHODS

In this retrospective multicentre study, we analysed the charts of UC patients unresponsive/intolerant or with secondary loss of response (LOR) to ADA or GOL who were switched to IFX. We evaluated clinical response and remission together with adverse events at 3, 6, and 12 months follow-up.

RESULTS

Seventy-six patients were included; 38 patients started ADA and 38 started GOL for a mean therapy duration of 6 ± 6 months. Indications for switch were adverse events in 3%, primary failure in 79%, and LOR in 18% of patients. Clinical remission was reached by 47%, 50%, and 77% of patients, respectively. Patients that switched for LOR did numerically, but not statistically, better than patients who switched for primary failure.

CONCLUSIONS

Our data show a superior remission rate in SC to IV anti-TNF switch in UC compared to the IV to SC switch reported in literature.

Mucosa-associated microbiota drives pathogenic functions in IBD-derived intestinal iNKT cells

Inflammatory bowel disease (IBD) pathogenesis has been linked to the aberrant activation of the Gut-associated lymphoid tissues against components of the intestinal microbiota. Although the contribution of CD4⁺ T helper cells to inflammatory processes is being increasingly acknowledged, the functional engagement of human invariant natural killer T (iNKT) cells is still poorly defined. Here, we evaluated the functional characteristics of intestinal iNKT cells during IBD pathogenesis and to exploit the role of mucosa-associated microbiota recognition in triggering iNKT cells' pro-inflammatory responses in vivo. Lamina propria iNKT cells, isolated from surgical specimens of active ulcerative colitis and Crohn's disease patients and non-IBD donors, were phenotypically and functionally analyzed ex vivo, and stable cell lines and clones were generated for in vitro functional assays. iNKT cells expressing a pro-inflammatory cytokine profile were enriched in the lamina propria of IBD patients, and their exposure to the mucosa-associated microbiota drives pro-inflammatory activation, inducing direct pathogenic activities against the epithelial barrier integrity. These observations suggest that iNKT cell pro-inflammatory functions may contribute to the fuelling of intestinal inflammation in IBD patients.

Unmet needs of Italian physicians managing patients with inflammatory bowel disease

BACKGROUND

Little is known about the unmet needs of physicians caring for patients with inflammatory bowel disease (IBD).

AIMS

This study explored the practical difficulties and needs for professional updating of Italian IBD physicians.

METHODS

A questionnaire was distributed to 600 physicians attending IG-IBD meetings.

RESULTS

280 physicians completed the questionnaire (46.7%). On a 5-point Likert scale (from 1, strongly disagree to 5, strongly agree), they identified the most problematic issues in managing IBD patients as increasing bureaucracy (3.9), lack of extra-gastroenterological IBD expertise (3.4), lack of diagnostic techniques (3.1) and budget limitations (2.9). The most lacking techniques, ranked from 1 (greatest need) to 9 (lowest need), were: anti-drug antibody and trough level assays (2.7), device-assisted enteroscopy (3.1), exploration under anaesthesia (3.2), MR enterography (3.2), and bowel ultrasonography (3.3). About professional updating, respondents indicated (on a 5-point Likert scale) that helpful topics were practical medicine (4.3), managing difficult patients (4.1), and guidelines (4.0). The most desired modality for updating was residential courses on clinical practice (4.3).

CONCLUSION

Several factors potentially limit the best management of IBD patients in Italy. Satisfying these unmet needs could improve care for IBD patients.

Using Robotic Systems to Process and Embed Colonic Murine Samples for Histological Analyses

The understanding of human diseases has been greatly expanded thanks to the study of animal models. Nonetheless, histopathological evaluation of experimental models needs to be as rigorous as that applied for human samples. Indeed, drawing reliable and accurate conclusions is critically influenced by the quality of tissue section preparation. Here, we describe a protocol for histopathological analysis of murine tissues that implements several automated steps during the procedure, from the initial preparation to the paraffin embedding of the murine samples. The reduction of methodological variables through rigorous protocol standardization from automated procedures contributes to increased overall reliability of murine pathological analysis. Specifically, this protocol describes the utilization of automated processing and embedding robotic systems, routinely used for the tissue processing and paraffin embedding of human samples, to process murine specimens of intestinal inflammation. We conclude that the reliability of histopathological examination of murine tissues is significantly increased upon introduction of standardized and automated techniques.

Therapeutic faecal microbiota transplantation controls intestinal inflammation through IL10 secretion by immune cells

Alteration of the gut microbiota has been associated with different gastrointestinal disorders. Normobiosis restoration by faecal microbiota transplantation (FMT) is considered a promising therapeutic approach, even if the mechanisms underlying its efficacy are at present largely unknown. Here we sought to elucidate the functional effects of therapeutic FMT administration during experimental colitis on innate and adaptive immune responses in the intestinal mucosa. We show that therapeutic FMT reduces colonic inflammation and initiates the restoration of intestinal homeostasis through the simultaneous activation of different immune-mediated pathways, ultimately leading to IL-10 production by innate and adaptive immune cells, including CD4⁺ T cells, iNKT cells and Antigen Presenting Cells (APC), and reduces the ability of dendritic cells, monocytes and macrophages to present MHCII-dependent bacterial antigens to colonic T cells. These results demonstrate the capability of FMT to therapeutically control intestinal experimental colitis and poses FMT as a valuable therapeutic option in immune-related pathologies.

Pathogenicity of In Vivo Generated Intestinal Th17 Lymphocytes is IFNγ Dependent

BACKGROUND AND AIMS

T helper 17 [Th17] cells are crucially involved in the immunopathogenesis of inflammatory bowel diseases in humans. Nevertheless, pharmacological blockade of interleukin 17A [IL17A], the Th17 signature cytokine, yielded negative results in patients with Crohn's disease [CD], and attempts to elucidate the determinants of Th17 cells' pathogenicity in the gut have so far proved unsuccessful. Here, we aimed to identify and functionally validate the pathogenic determinants of intestinal IL-17-producing T cells.

METHODS

In vivo-generated murine intestinal IL-17-producing T cells were adoptively transferred into immunodeficient Rag1-/- recipients to test their pathogenicity. Human IL-17, IFNγ/IL-17, and IFNγ actively secreting T cell clones were generated from lamina propria lymphocytes of CD patients. The pathogenic activity of intestinal IL-17-producing T cells against the intestinal epithelium was evaluated.

RESULTS

IL-17-producing cells with variable colitogenic activity can be generated in vivo using different experimental colitis models. The pathogenicity of IL-17-secreting cells was directly dependent on their IFNγ secretion capacity, as demonstrated by the reduced colitogenic activity of IL-17-secreting cells isolated from IFNγ-/- mice. Moreover, IFNγ production is a distinguished attribute of CD-derived lamina propria Th17 cells. IFNγ secretion by CD-derived IL-17-producing intestinal clones is directly implicated in the epithelial barrier disruption through the modulation of tight junction proteins.

CONCLUSIONS

Intestinal Th17 cell pathogenicity is associated with IFNγ production, which directly affects intestinal permeability through the disruption of epithelial tight junctions.

Follistatin-like protein 1 sustains colon cancer cell growth and survival

Follistatin-like protein 1 (FSTL1) is a secreted glycoprotein, which controls several physiological and pathological events. FSTL1 expression is deregulated in many tumors, but its contribution to colon carcinogenesis is not fully understood. Here, we investigated the expression and functional role of FSTL1 in colorectal cancer (CRC). A significant increase of FSTL1 was seen in human CRC as compared to the surrounding non-tumor tissues and this occurred at both RNA and protein level. Knockdown of FSTL1 in CRC cells with a specific antisense oligonucleotide (AS) reduced expression of regulators of the late G1 phase, such as phosphorylated retinoblastoma protein, E2F-1, cyclin E and phospho-cyclin-dependent kinase-2, and promoted accumulation of cells in the G1 phase of the cell cycle thus resulting in diminished cell proliferation. Consistently, recombinant FSTL1 induced proliferation of normal intestinal epithelial cells through an ERK1/2-dependent mechanism. Cell cycle arrest driven by FSTL1 AS in CRC cells was accompanied by activation of caspases and subsequent induction of apoptosis. Moreover, FSTL1 knockdown made CRC cells more susceptible to oxaliplatin and irinotecan-induced death. Data indicate that FSTL1 is over-expressed in human CRC and suggest a role for this protein in favouring intestinal tumorigenesis.

Long-Term Safety of In Utero Exposure to Anti-TNFα Drugs for the Treatment of Inflammatory Bowel Disease: Results from the Multicenter European TEDDY Study

OBJECTIVES

The long-term safety of exposure to anti-tumor necrosis factor (anti-TNFα) drugs during pregnancy has received little attention. We aimed to compare the relative risk of severe infections in children of mothers with inflammatory bowel disease (IBD) who were exposed to anti-TNFα drugs in utero with that of children who were not exposed to the drugs.

METHODS

Retrospective multicenter cohort study. Exposed cohort: children from mothers with IBD receiving anti-TNFα medication (with or without thiopurines) at any time during pregnancy or during the 3 months before conception. Non-exposed cohort: children from mothers with IBD not treated with anti-TNFα agents or thiopurines at any time during pregnancy or the 3 months before conception. The cumulative incidence of severe infections after birth was estimated using Kaplan-Meier curves, which were compared using the log-rank test. Cox-regression analysis was performed to identify potential predictive factors for severe infections in the offspring.

RESULTS

The study population comprised 841 children, of whom 388 (46%) had been exposed to anti-TNFα agents. Median follow-up after delivery was 47 months in the exposed group and 68 months in the non-exposed group. Both univariate and multivariate analysis showed the incidence rate of severe infections to be similar in non-exposed and exposed children (1.6% vs. 2.8% per person-year, hazard ratio 1.2 (95% confidence interval 0.8-1.8)). In the multivariate analysis, preterm delivery was the only variable associated with a higher risk of severe infection (2.5% (1.5-4.3)).

CONCLUSIONS

In utero exposure to anti-TNFα drugs does not seem to be associated with increased short-term or long-term risk of severe infections in children.

Short-term Oral Antibiotics Treatment Promotes Inflammatory Activation of Colonic Invariant Natural Killer T and Conventional CD4+ T Cells

The gut mucosa is continuously exposed to a vast community of microorganisms, collectively defined as microbiota, establishing a mutualistic relationship with the host and contributing to shape the immune system. Gut microbiota is acquired at birth, and its composition is relatively stable during the entire adult life. Intestinal dysbiosis, defined as a microbial imbalance of gut bacterial communities, can be caused by several factors, including bacterial infections and antibiotic use, and has been associated with an increased risk to develop or exacerbate immune-mediated pathologies, such as allergic reactions, asthma, and inflammatory bowel diseases. Still, the mechanisms by which antibiotic-induced gut dysbiosis may lead to development of mucosal inflammation are still matter of debate. To this end, we aimed to evaluate the impact of antibiotic treatment on phenotype and functions of intestinal immune cell populations, including invariant natural killer T (iNKT) cells, a subset of lipid-specific T cells profoundly influenced by alterations on the commensal microbiota. To this aim, a cocktail of broad-spectrum antibiotics was administered for 2 weeks to otherwise healthy mice before re-colonization of the intestinal microbial community with oral gavage of eubiotic or dysbiotic mucosa-associated bacteria and luminal colonic content, followed or not by intestinal inflammation induction. Here. we showed that short-term antibiotic treatment alters frequency and functions of intestinal iNKT cells, even in the absence of intestinal inflammation. The presence of a dysbiotic microbiota after antibiotic treatment imprints colonic iNKT and CD4⁺ T cells toward a pro-inflammatory phenotype that collectively contributes to aggravate intestinal inflammation. Nonetheless, the inflammatory potential of the dysbiotic microbiota decreases over time opening the possibility to temporally intervene on the microbial composition to re-equilibrate dysbiosis, thus controlling concomitantly mucosal immune T cell activations.

Ultrasound Elasticity Imaging Predicts Therapeutic Outcomes of Patients With Crohn's Disease Treated With Anti-Tumour Necrosis Factor Antibodies

BACKGROUND AND AIMS

Ultrasound elasticity imaging is a non-invasive technique developed to evaluate fibrosis. Measuring tissue strain by ultrasound elasticity imaging can reliably detect severe ileal fibrosis in patients with Crohn's disease [CD]. We have hypothesised that a more severe range of fibrosis might influence the therapeutic response to anti-tumour necrosis factor [TNF] treatment. The aim of this study was to assess the ability of ultrasound elasticity imaging to predict the therapeutic outcome for CD patients.

METHODS

Consecutive patients with ileal/ileocolonic CD, starting anti-TNF treatment, were enrolled for the study. These patients underwent bowel ultrasound and ultrasound elasticity imaging at baseline and at 14 and 52 weeks after anti-TNF treatment. Bowel wall stiffness was quantified by calculating the strain ratio between the mesenteric tissue and the bowel wall. Strain ratio ≥ 2 was used to identify severe ileal fibrosis. Transmural healing at 14 and 52 weeks was defined as bowel wall thickness ≤ 3 mm.

RESULTS

Thirty patients with CD were enrolled. Five patients underwent surgery for bowel obstruction. The frequency of surgeries was significantly greater in patients with a strain ratio ≥ 2 at baseline [p = 0.003]. A significant reduction of the bowel thickness was observed after 14 and 52 weeks of anti-TNF treatment [p < 0.005]. A significant inverse correlation was observed between the strain ratio values at baseline and the thickness variations following anti-TNF therapy [p = 0.007]; 27% of patients achieved transmural healing at 14 weeks. The baseline strain ratio was significantly lower in patients with transmural healing [p < 0.05].

CONCLUSIONS

This study shows that ultrasound elasticity imaging predicts therapeutic outcomes for CD patients treated with anti-TNF.

Implementation of an automated inclusion system for the histological analysis of murine tissue samples: A feasibility study in DSS-induced chronic colitis

Animal models are powerful tools to expand our understanding of human diseases. Histopathological evaluation of murine experimental models is often required to support further research; thus, a more rigorous evaluation of murine histological samples is strongly advocated. Indeed, the overall quality of tissue sections is critical to draw reliable and accurate conclusions. As several methodological variables may reduce the reliability of the pathological analysis, a standardization of the procedural steps required for the processing of histological murine tissues is advisable. Here, we describe a method to standardize the technical procedure from the initial preparation to the paraffin embedding of murine samples. Specifically, we have implemented an automated inclusion system, that is, the SAKURA Tissue-Tek inclusion instrument, which is routinely used for paraffin inclusion of human samples, to process murine specimens of intestinal inflammation. Colitis severity was assessed in chronically Dextran Sodium Sulphate (DSS)–treated mice by cytofluorimetric analysis of colonic cellular infiltrates, expression of inflammatory genes and histopathological analysis of tissue samples, comparing manual and automated tissue preparation systems. We here conclude that implementation of this technique can significantly increase the quality and the reliability of histopathological examination of murine tissues.

Interleukin-34 sustains pro-tumorigenic signals in colon cancer tissue

Interleukin-34 (IL-34), a cytokine produced by a wide range of cells, binds to the macrophage colony-stimulating factor receptor (M-CSFR-1) and receptor-type protein-tyrosine phosphatase zeta (PTP-z) and controls myeloid cell differentiation, proliferation and survival. various types of cancers over-express IL-34 but the role of the cytokine in colorectal cancer (CRC) remains unknown. We here investigated the expression and functional role of IL-34 in CRC. A more pronounced expression of IL-34 was seen in CRC samples as compared to matched normal/benign colonic samples and this occurred at both RNA and protein level. Immunohistochemical analysis of CRC tissue samples showed that both cancer cells and lamina propria mononuclear cells over-expressed IL-34. Additionally, CRC cells expressed both M-CSFR-1 and PTP-z, thus suggesting that CRC cells can be responsive to IL-34. Indeed, stimulation of DLD-1 cancer cells with IL-34, but not with MSCF1, enhanced the cell proliferation and cell invasion without affecting cell survival. Analysis of intracellular signals underlying the mitogenic effect of IL-34 revealed that the cytokine enhanced activation of ERK1/2 and pharmacologic inhibition of ERK1/2 abrogated IL-34-driven cell proliferation. Consistently, IL-34 knockdown in HT-29 cells with a specific IL-34 antisense oligonucleotide reduced ERK1/2 activation, cell proliferation and enhanced the susceptibility of cells to Oxaliplatin-induced death. This is the first study showing up-regulation of IL-34 in CRC and suggesting a role for this cytokine in colon tumorigenesis.

Non-invasive evaluation of intestinal disorders: The role of elastographic techniques

Over the recent years the non-invasive techniques for the evaluation of the small bowel have been playing a major role in the management of chronic intestinal diseases, such as inflammatory bowel diseases (IBD). The diagnostic performances of magnetic resonance imaging, computed tomography and ultrasound in the field of small bowel disorders, have been assessed and established for more than two decades. Newer sonographic techniques, such as strain elastography and shear wave elastography, have been put forward for the assessment of disease activity and characterization of IBD-related damage in the setting of Crohn's disease and other gastrointestinal disorders. The data from the preliminary research and clinical studies have shown promising results as regards the ability of elastographic techniques to differentiate inflammatory from fibrotic tissue. The distinction between IBD activity (inflammation) and IBD-related damage (fibrosis) is currently considered crucial for the assessment and management of patients. Moreover, all the elastographic techniques are currently being considered in the setting of other intestinal disorders (e.g., rectal tumors, appendicitis). The aim of this paper is to offer both a comprehensive narrative review of the non-invasive techniques available for the assessment of small-bowel disorders, with particular emphasis on inflammatory bowel diseases, and a summary of the current evidence on the use of elastographic techniques in this setting.

Safety of treatments for inflammatory bowel disease: Clinical practice guidelines of the Italian Group for the Study of Inflammatory Bowel Disease (IG-IBD)

Inflammatory bowel diseases are chronic conditions of unknown etiology, showing a growing incidence and prevalence in several countries, including Italy. Although the etiology of Crohn's disease and ulcerative colitis is unknown, due to the current knowledge regarding their pathogenesis, effective treatment strategies have been developed. Several guidelines are available regarding the efficacy and safety of available drug treatments for inflammatory bowel diseases. Nevertheless, national guidelines provide additional information adapted to local feasibility, costs and legal issues related to the use of the same drugs. These observations prompted the Italian Group for the Study of Inflammatory Bowel Disease (IG-IBD) to establish Italian guidelines on the safety of currently available treatments for Crohn's disease and ulcerative colitis. These guidelines discuss the use of aminosalicylates, systemic and low bioavailability corticosteroids, antibiotics (metronidazole, ciprofloxacin, rifaximin), thiopurines, methotrexate, cyclosporine A, TNFα antagonists, vedolizumab, and combination therapies. These guidelines are based on current knowledge derived from evidence-based medicine coupled with clinical experience of a national working group.

Disease patterns in late-onset ulcerative colitis: Results from the IG-IBD "AGED study"

BACKGROUND

Late-onset UC represents an important issue for the near future, but its outcomes and relative therapeutic strategies are yet poorly studied.

AIM

To better define the natural history of late-onset ulcerative colitis.

METHODS

In a multicenter retrospective study, we investigated the disease presentation and course in the first 3 years in 1091 UC patients divided into 3 age-groups: diagnosis ≥65years, 40-64 years, and <40years. Disease patterns, medical and surgical therapies, and risk factors for disease outcomes were analyzed.

RESULTS

Chronic active or relapsing disease accounts for 44% of patients with late-onset UC. Across all age-groups, these disease patterns require 3-6 times more steroids than remitting disease, but immunomodulators and, to a lesser extent, biologics are less frequently prescribed in the elderly. Advanced age, concomitant diseases and related therapies were found to be inversely associated with the use of immunomodulators or biologics, but not with surgery.

CONCLUSIONS

The conclusion that late-onset UC follows a mild course may apply only to a subset of patients. an important percentage of elderly patients present with more aggressive disease. Since steroid use and surgery rates did not differ in this subgroup, lower use of immunosuppressive therapy and biologics may reflect concerns in prescribing these therapies in the elderly.

Challenges in treating patients with inflammatory bowel disease and concurrent viral hepatitis infection

Inflammatory bowel diseases (IBD) require long-term administration of immunomodulatory treatments to maintain disease remission. Due to the high worldwide prevalence of hepatitis B (HBV) or C (HCV) virus infections, presence of concurrent hepatitis can be a relevant clinical issue to manage when treating IBD. Areas covered: The paper summarizes epidemiological data about IBD and HBV/HCV infection and reviews current knowledge about the natural history of HBV and HCV in the IBD setting, concentrating on risk of hepatitis reactivation during immunosuppressive treatment. Most updated recommendations for management of HBV and HCV infections in IBD patients are discussed. Expert commentary: The development of new drugs for IBD with different molecular targets and the availability of potent and efficacious antiviral drugs for HBV and HCV will simplify management of hepatitis infection in IBD patients in the near future.

Predicting Outcomes to Optimize Disease Management in Inflammatory Bowel Diseases

BACKGROUND AND AIMS

Efforts to slow or prevent the progressive course of inflammatory bowel diseases [IBD] include early and intensive monitoring and treatment of patients at higher risk for complications. It is therefore essential to identify high-risk patients - both at diagnosis and throughout disease course.

METHODS

As a part of an IBD Ahead initiative, we conducted a comprehensive literature review to identify predictors of long-term IBD prognosis and generate draft expert summary statements. Statements were refined at national meetings of IBD experts in 32 countries and were finalized at an international meeting in November 2014.

RESULTS

Patients with Crohn's disease presenting at a young age or with extensive anatomical involvement, deep ulcerations, ileal/ileocolonic involvement, perianal and/or severe rectal disease or penetrating/stenosing behaviour should be regarded as high risk for complications. Patients with ulcerative colitis presenting at young age, with extensive colitis and frequent flare-ups needing steroids or hospitalization present increased risk for colectomy or future hospitalization. Smoking status, concurrent primary sclerosing cholangitis and concurrent infections may impact the course of disease. Current genetic and serological markers lack accuracy for clinical use.

CONCLUSIONS

Simple demographic and clinical features can guide the clinician in identifying patients at higher risk for disease complications at diagnosis and throughout disease course. However, many of these risk factors have been identified retrospectively and lack validation. Appropriately powered prospective studies are required to inform algorithms that can truly predict the risk for disease progression in the individual patient.

IL-10 promotes homeostatic proliferation of human CD8(+) memory T cells and, when produced by CD1c(+) DCs, shapes naive CD8(+) T-cell priming

IL-10 is an anti-inflammatory cytokine that inhibits maturation and cytokine production of dendritic cells (DCs). Although mature DCs have the unique capacity to prime CD8(+) CTL, IL-10 can promote CTL responses. To understand these paradoxic findings, we analyzed the role of IL-10 produced by human APC subsets in T-cell responses. IL-10 production was restricted to CD1c(+) DCs and CD14(+) monocytes. Interestingly, it was differentially regulated, since R848 induced IL-10 in DCs, but inhibited IL-10 in monocytes. Autocrine IL-10 had only a weak inhibitory effect on DC maturation, cytokine production, and CTL priming with high-affinity peptides. Nevertheless, it completely blocked cross-priming and priming with low-affinity peptides of a self/tumor-antigen. IL-10 also inhibited CD1c(+) DC-induced CD4(+) T-cell priming and enhanced Foxp3 induction, but was insufficient to induce T-cell IL-10 production. CD1c(+) DC-derived IL-10 had also no effect on DC-induced secondary expansions of memory CTL. However, IL-15-driven, TCR-independent proliferation of memory CTL was enhanced by IL-10. We conclude that DC-derived IL-10 selects high-affinity CTL upon priming. Moreover, IL-10 preserves established CTL memory by enhancing IL-15-dependent homeostatic proliferation. These combined effects on CTL priming and memory maintenance provide a plausible mechanism how IL-10 promotes CTL responses in humans.

Interleukin-34 Induces Cc-chemokine Ligand 20 in Gut Epithelial Cells

BACKGROUND AND AIM

Production of chemokines by intestinal epithelial cells is a key step in the amplification of the destructive immune-inflammatory response in patients with inflammatory bowel diseases [IBD]. In this study, we examined whether intestinal epithelial cells express macrophage colony-stimulating factor receptor 1 [M-CSFR-1], the functional receptor of interleukin-34 [IL-34], a cytokine that is over-produced in IBD and supposed to sustain inflammatory pathways.

METHODS

M-CSFR-1 expression was evaluated in intestinal samples of IBD patients, controls, and colon epithelial cell lines by real-time polymerase chain reaction [PCR], immunohistochemistry, and western blotting. DLD-1 cells were stimulated with IL-34 in the presence or absence of MAP kinase inhibitors, chemokine induction was assessed by real-time PCR and enzyme-linked immunosorbent assay [ELISA], and mitogen-activated protein (MAP) kinase activation was monitored by western blotting. The effect of a neutralising IL-34 antibody on CC chemokine ligand (CCL) 20 synthesis was tested in ex vivo organ cultures of IBD mucosal explants.

RESULTS

Enhanced expression of M-CSFR-1 RNA transcripts was seen in inflamed mucosa of IBD patients as compared with controls. Immunohistochemical analysis confirmed up-regulation of M-CSFR-1 in IBD and showed that both epithelial and lamina propria mononuclear cells expressed this receptor. Stimulation of DLD-1 with IL-34 increased CCL20 production through an ERK1/2-dependent mechanism. Consistently, treatment of IBD explants with anti-IL-34 reduced CCL20 production.

CONCLUSIONS

These data show that intestinal epithelial cells are a target of IL-34 and suggest that this cytokine contributes to mediating the cross-talk between epithelial cells and immune cells in IBD.

A gut-vascular barrier controls the systemic dissemination of bacteria

In healthy individuals, the intestinal microbiota cannot access the liver, spleen, or other peripheral tissues. Some pathogenic bacteria can reach these sites, however, and can induce a systemic immune response. How such compartmentalization is achieved is unknown. We identify a gut-vascular barrier (GVB) in mice and humans that controls the translocation of antigens into the blood stream and prohibits entry of the microbiota. Salmonella typhimurium can penetrate the GVB in a manner dependent on its pathogenicity island (Spi) 2-encoded type III secretion system and on decreased β-catenin-dependent signaling in gut endothelial cells. The GVB is modified in celiac disease patients with elevated serum transaminases, which indicates that GVB dismantling may be responsible for liver damage in these patients. Understanding the GVB may provide new insights into the regulation of the gut-liver axis.

Dichotomy of short and long thymic stromal lymphopoietin isoforms in inflammatory disorders of the bowel and skin

Background

Thymic stromal lymphopoietin (TSLP) is a cytokine with pleiotropic functions in the immune system. It has been associated with allergic reactions in the skin and lungs but also homeostatic tolerogenic responses in the thymus and gut.

Objective

In human subjects TSLP is present in 2 isoforms, short and long. Here we wanted to investigate the differential expression of the TSLP isoforms and discern their biological implications under homeostatic or inflammatory conditions.

Methods

We evaluated the expression of TSLPs in tissues from healthy subjects, patients with ulcerative colitis, patients with celiac disease, and patients with atopic dermatitis and on epithelial cells and keratinocytes under steady-state conditions or after stimulation. We then tested the immune activity of TSLP isoforms both in vitro and in vivo.

Results

We showed that TSLP isoforms are responsible for 2 opposite immune functions. The short isoform is expressed under steady-state conditions and exerts anti-inflammatory activities by affecting the capacity of PBMCs and dendritic cells to produce inflammatory cytokines. Moreover, the short isoform TSLP ameliorates experimental colitis in mice and prevents endotoxin shock. The long isoform of TSLP is proinflammatory and is only expressed during inflammation. The isoforms are differentially regulated by pathogenic bacteria, such as Salmonella species and adhesive-invasive Escherichia coli.

Conclusions

We have solved the dilemma of TSLP being both homeostatic and inflammatory. The TSLP isoform ratio is altered during several inflammatory disorders, with strong implications in disease treatment and prevention. Indeed, targeting of the long isoform of TSLP at the C-terminal portion, which is common to both isoforms, might lead to unwanted side effects caused by neutralization of the homeostatic short isoform.