IL-23 plays a key role in Helicobacter hepaticus-induced T cell-dependent colitis

ER stress differentially affects pro-inflammatory changes induced by mitochondrial dysfunction in the human monocytic leukemia cell line, THP-1

The functional and physical interaction between mitochondria and the endoplasmic reticulum (ER) has been the subject of intense study. To test the effect of this interaction on macrophage inflammatory activation, the human macrophage-like monocytic leukemia cell line THP-1 was treated with oligomycin, rotenone, or sodium azide, which induce mitochondrial dysfunction (MD) by blocking the electron transport chain (ETC). MD induced by these agents triggered activation of various sensors and markers of ER stress. This linkage affected macrophage function since LPS-induced expression of IL-23 was enhanced by the MD inducers, and this enhancing effect was abolished by inhibition of pancreatic endoplasmic reticulum kinase (PERK) activity. This MD-mediated ER stress may be universal since it was observed in human embryonic kidney HEK293 cells and colon cancer SW480 cells. On the other hand, MD regulated LPS-induced activation of the AKT/GSK3β/β-catenin pathway in a manner not affected by inhibition of PERK or inositol-requiring enzyme 1α (IRE1α) activities. These results indicate that the occurrence of MD can lead to ER stress and these two events, separately or in combination, can affect various cellular processes.

IL-23 in inflammatory bowel diseases and colon cancer

Studies in recent years have identified a pivotal role of the cytokine IL-23 in the pathogenesis of inflammatory bowel diseases (IBD: Crohn´s disease, ulcerative colitis) and colitis-associated colon cancer. Genetic studies revealed that subgroups of IBD patients have single nucleotide polymorphisms in the IL-23R gene suggesting that IL-23R signaling affects disease susceptibility. Furthermore, increased production of IL-23 by macrophages, dendritic cells or granulocytes has been observed in various mouse models of colitis, colitis-associated cancer and IBD patients. Moreover, in several murine models of colitis, suppression of IL-12/IL-23 p40, IL-23 p19 or IL-23R function led to marked suppression of gut inflammation. This finding was associated with reduced activation of IL-23 target cells such as T helper 17 cells, innate lymphoid cells type 3, granulocytes and natural killer cells as well as with impaired production of proinflammatory cytokines. Based on these findings, targeting of IL-23 emerges as important concept for suppression of gut inflammation and inflammation-associated cancer growth. Consistently, neutralizing antibodies against IL-12/IL-23 p40 and IL-23 p19 have been successfully used in clinical trials for therapy of Crohn´s disease and pilot studies in ulcerative colitis are ongoing. These findings underline the crucial regulatory role of IL-23 in chronic intestinal inflammation and colitis-associated cancer and indicate that therapeutic strategies aiming at IL-23 blockade may be of key relevance for future therapy of IBD patients.

IL-23R Signaling Plays No Role in Myocardial Infarction

Ischemic heart diseases are the most frequent diseases in the western world. Apart from Interleukin (IL-)1, inflammatory therapeutic targets in the clinic are still missing. Interestingly, opposing roles of the pro-inflammatory cytokine IL-23 have been described in cardiac ischemia in mice. IL-23 is a composite cytokine consisting of p19 and p40 which binds to IL-23R and IL-12Rβ1 to initiate signal transduction characterized by activation of the Jak/STAT, PI3K and Ras/Raf/MAPK pathways. Here, we generate IL-23R-Y416FΔICD signaling deficient mice and challenged these mice in close- and open-chest left anterior descending coronary arteria ischemia/reperfusion experiments. Our experiments showed only minimal changes in all assayed parameters in IL-23R signaling deficient mice compared to wild-type mice in ischemia and for up to four weeks of reperfusion, including ejection fraction, endsystolic volume, enddiastolic volume, infarct size, gene regulation and α smooth muscle actin (αSMA) and Hyaluronic acid (HA) protein expression. Moreover, injection of IL-23 in wild-type mice after LAD ischemia/reperfusion had also no influence on the outcome of the healing phase. Our data showed that IL-23R deficiency has no effects in myocardial I/R.

NIK signaling axis regulates dendritic cell function in intestinal immunity and homeostasis

Dendritic cells (DCs) play an integral role in regulating mucosal immunity and homeostasis, but the signaling network mediating this function of DCs is poorly defined. We identified the noncanonical NF-κB-inducing kinase (NIK) as a crucial mediator of mucosal DC function. DC-specific NIK deletion impaired intestinal immunoglobulin A (IgA) secretion and microbiota homeostasis, rendering mice sensitive to an intestinal pathogen, Citrobacter rodentium. DC-specific NIK was required for expression of the IgA transporter polymeric immunoglobulin receptor (pIgR) in intestinal epithelial cells, which in turn relied on the cytokine IL-17 produced by TH17 cells and innate lymphoid cells (ILCs). NIK-activated noncanonical NF-κB induced expression of IL-23 in DCs, contributing to the maintenance of TH17 cells and type 3 ILCs. Consistent with the dual functions of IL-23 and IL-17 in mucosal immunity and inflammation, NIK deficiency also ameliorated colitis induction. Thus, our data suggest a pivotal role for the NIK signaling axis in regulating DC functions in intestinal immunity and homeostasis.

Diet Modifies Colonic Microbiota and CD4+ T-Cell Repertoire to Induce Flares of Colitis in Mice With Myeloid-Cell Expression of Interleukin 23

BACKGROUND & AIMS

Several studies have shown that signaling via the interleukin 23 (IL23) receptor is required for development of colitis. We studied the roles of IL23, dietary factors, alterations to the microbiota, and T cells in the development and progression of colitis in mice.

METHODS

All mice were maintained on laboratory diet 5053, unless otherwise noted. We generated mice that express IL23 in CX3CR1-positive myeloid cells (R23FR mice) upon cyclic administration of tamoxifen dissolved in diet 2019. Diets 2019 and 5053 have minor differences in the overall composition of protein, fat, fiber, minerals, and vitamins. CX3CR1^CreER mice (FR mice) were used as controls. Some mice were given antibiotics, and others were raised in a germ-free environment. Intestinal tissues were collected and analyzed by histology and flow cytometry. Feces were collected and analyzed by 16S rDNA sequencing. Feces from C57/Bl6, R23FR, or FR mice were fed to FR and R23FR germ-free mice in microbiota transplant experiments. We also performed studies with R23FR/Rag^-/-, R23FR/Mu^-/-, and R23FR/Tcrd^-/- mice. R23FR mice were given injections of antibodies against CD4 or CD8 to deplete T cells. Mesenteric lymph nodes and large intestine CD4⁺ cells from R23FR or FR mice in remission from colitis were transferred into Rag^-/- mice. CD4⁺ cells were isolated from donor R23FR mice and recipient Rag^-/- mice, and T-cell receptor sequences were determined.

RESULTS

Expression of IL23 led to development of a relapsing-remitting colitis that was dependent on the microbiota and CD4⁺ T cells. The relapses were caused by switching from the conventional diet used in our facility (diet 5053) to the diet 2019 and were not dependent on tamoxifen after the first cycle. The switch in the diet modified the microbiota but did not alter levels of IL23 in intestinal tissues compared with mice that remained on the conventional diet. Mesenteric lymph nodes and large intestine CD4⁺ cells from R23FR mice in remission, but not from FR mice, induced colitis after transfer into Rag^-/- mice, but only when these mice were placed on the diet 2019. The CD4⁺ T-cell receptor repertoire of Rag^-/- mice with colitis (fed the 2019 diet) was less diverse than that from donor mice and Rag^-/- mice without colitis (fed the 5053 diet) because of expansion of dominant T-cell clones.

CONCLUSIONS

We developed mice that express IL23 in CX3CR1-positive myeloid cells (R23FR mice) and found that they are more susceptible to diet-induced colitis than mice that do not express IL23. The R23FR mice have a population of CD4⁺ T cells that becomes activated in response to dietary changes and alterations to the intestinal microbiota. The results indicate that alterations in the diet, intestinal microbiota, and IL23 signaling can contribute to pathogenesis of inflammatory bowel disease.

Helicobacter pylori infection and inflammatory bowel disease: a crosstalk between upper and lower digestive tract

Helicobacter pylori has coexisted with humans for approximately 60,000 years and greater than 50% of the global population is infected with H. pylori. H. pylori was successfully cultured in vitro in 1983 and studies of H. pylori have achieved substantial advances over the last 35 years. Since then, H. pylori has been characterized as the primary pathogenic factor for chronic gastritis, peptic ulcer, and gastric malignancy. Numerous patients have received H. pylori eradication treatment, but only 1-2% of H. pylori-infected individuals ultimately develop gastric cancer. Recently, numerous epidemiological and basic experimental studies suggested a role for chronic H. pylori infection in protecting against inflammatory bowel disease (IBD) by inducing systematic immune tolerance and suppressing inflammatory responses. Here we summarize the current research progress on the association between H. pylori and IBD, and further describe the detailed molecular mechanism underlying H. pylori-induced dendritic cells (DCs) with the tolerogenic phenotype and immunosuppressive regulatory T cells (Tregs). Based on the potential protective role of H. pylori infection on IBD, we suggest that the interaction between H. pylori and the host is complicated, and H. pylori eradication treatment should be administered with caution, especially for children and young adults.

The JAK inhibitor ruxolitinib reduces inflammation in an ILC3-independent model of innate immune colitis

Innate immunity contributes to the pathogenesis of inflammatory bowel disease (IBD). However, the mechanisms of IBD mediated by innate immunity are incompletely understood and there are limited models of spontaneous innate immune colitis to address this question. Here we describe a new robust model of colitis occurring in the absence of adaptive immunity. RAG1-deficient mice expressing TNFAIP3 in intestinal epithelial cells (TRAG mice) spontaneously developed 100% penetrant, early-onset colitis that was limited to the colon and dependent on intestinal microbes but was not transmissible to co-housed littermates. TRAG colitis was associated with increased mucosal numbers of innate lymphoid cells (ILCs) and depletion of ILC prevented colitis in TRAG mice. ILC depletion also therapeutically reversed established colitis in TRAG mice. The colitis in TRAG mice was not prevented by interbreeding to mice lacking group 3 ILC nor by depletion of TNF. Treatment with the JAK inhibitor ruxolitinib ameliorated colitis in TRAG mice. This new model of colitis, with its predictable onset and colon-specific inflammation, will have direct utility in developing a more complete understanding of innate immune mechanisms that can contribute to colitis and in pre-clinical studies for effects of therapeutic agents on innate immune-mediated IBD.

A Large Polysaccharide Produced by Helicobacter hepaticus Induces an Anti-inflammatory Gene Signature in Macrophages

Interactions between the host and its microbiota are of mutual benefit and promote health. Complex molecular pathways underlie this dialog, but the identity of microbe-derived molecules that mediate the mutualistic state remains elusive. Helicobacter hepaticus is a member of the mouse intestinal microbiota that is tolerated by the host. In the absence of an intact IL-10 signaling, H. hepaticus induces an IL-23-driven inflammatory response in the intestine. Here we investigate the interactions between H. hepaticus and host immune cells that may promote mutualism, and the microbe-derived molecule(s) involved. Our results show that H. hepaticus triggers early IL-10 induction in intestinal macrophages and produces a large soluble polysaccharide that activates a specific MSK/CREB-dependent anti-inflammatory and repair gene signature via the receptor TLR2. These data identify a host-bacterial interaction that promotes mutualistic mechanisms at the intestinal interface. Further understanding of this pathway may provide novel prevention and treatment strategies for inflammatory bowel disease.

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Helicobacter hepaticus (Hh) activates a specific anti-inflammatory program in macrophages

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This activity is driven by an Hh polysaccharide inducing high IL-10/IL-6 ratio in BMDMs

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The polysaccharide-specific response is dependent on the TLR2/MSK/CREB pathway

A Mechanistic Computational Model Reveals That Plasticity of CD4+ T Cell Differentiation Is a Function of Cytokine Composition and Dosage

CD4⁺ T cells provide cell-mediated immunity in response to various antigens. During an immune response, naïve CD4⁺ T cells differentiate into specialized effector T helper (Th1, Th2, and Th17) cells and induced regulatory (iTreg) cells based on a cytokine milieu. In recent studies, complex phenotypes resembling more than one classical T cell lineage have been experimentally observed. Herein, we sought to characterize the capacity of T cell differentiation in response to the complex extracellular environment. We constructed a comprehensive mechanistic (logical) computational model of the signal transduction that regulates T cell differentiation. The model's dynamics were characterized and analyzed under 511 different environmental conditions. Under these conditions, the model predicted the classical as well as the novel complex (mixed) T cell phenotypes that can co-express transcription factors (TFs) related to multiple differentiated T cell lineages. Analyses of the model suggest that the lineage decision is regulated by both compositions and dosage of signals that constitute the extracellular environment. In this regard, we first characterized the specific patterns of extracellular environments that result in novel T cell phenotypes. Next, we predicted the inputs that can regulate the transition between the canonical and complex T cell phenotypes in a dose-dependent manner. Finally, we predicted the optimal levels of inputs that can simultaneously maximize the activity of multiple lineage-specifying TFs and that can drive a phenotype toward one of the co-expressed TFs. In conclusion, our study provides new insights into the plasticity of CD4⁺ T cell differentiation, and also acts as a tool to design testable hypotheses for the generation of complex T cell phenotypes by various input combinations and dosages.

Effects of Anti-Integrin Treatment With Vedolizumab on Immune Pathways and Cytokines in Inflammatory Bowel Diseases

Background and aims

Despite proven clinical efficacy of vedolizumab (VDZ) for inducing and maintaining remission in patients with Crohn’s disease (CD) and ulcerative colitis (UC), subgroups of patients have no therapeutic benefit from anti-α4β7 integrin therapy with VDZ. Within this study, we aimed to identify genetic, cellular, and immunological mechanisms that define response and failure to VDZ treatment.

Methods

Intestinal RNA sequencing was performed in UC and CD patients before and at week 14 of VDZ therapy. α4β7 expression on peripheral and mucosal immune cells was assessed by flow cytometry and immunohistochemistry. Cellular modes of VDZ-mediated action were analyzed ex vivo and in VDZ-treated inflammatory bowel disease patients.

Results

Transcriptome analysis showed an impairment of signaling cascades associated with adhesion, diapedesis, and migration of granulocytes and agranulocytes upon VDZ therapy. In non-remitters to VDZ therapy, a tissue destructive and leukocyte-mediated inflammatory activity with activation of TNF-dependent pathways was present, all of which were inhibited in remitters to VDZ. Clinical remission was associated with a significant reduction of α4β7 expression on Th2 and Th17 polarized mucosal CD4⁺ T cells at week 14 of VDZ therapy and with significantly higher numbers of α4β7-expressing mucosal cells prior to the initiation of VDZ therapy compared with non-remitters.

Conclusion

Intestinal α4β7 expression prior to VDZ therapy might represent a biomarker that predicts therapeutic response to subsequent VDZ treatment. Due to high activation of TNF signaling in VDZ non-remitters, anti-TNF treatment might represent a promising therapeutic strategy in VDZ refractory patients.

Increased Expression of IL-23 Receptor (IL-23R) in Vogt-Koyanagi-Harada (VKH) Disease

OBJECTIVE

Vogt-Koyanagi-Harada (VKH) disease is an autoimmune disease mediated by T cells that target melanocytes. It has been shown that IL-23 receptor (IL-23R) signaling promotes the generation of pathogenic T helper 17 cells. The aim of this study was designed to detect the possible role of IL-23R in VKH disease.

METHODS

Subjects were divided into an active and inactive VKH patient group and a normal control group. The IL-23R level in peripheral blood mononuclear cells (PBMCs) was measured by flow cytometry and real-time polymerase chain reaction. PBMCs were stimulated with serum from patients or controls to detect the influence of serum from VKH patients on IL-23R expression.

RESULTS

The IL-23R mRNA level was markedly increased in PBMCs from the active VKH patient group as compared to normal controls. Flow cytometry analysis showed that there was also an elevated IL-23R protein level in PBMCs in active VKH patients. The IL-23R protein level was higher in PBMCs obtained from healthy controls when they were cultured with serum from active VKH patient as compared to cell cultured with serum from normal controls. After the intraocular inflammation in VKH patients was controlled, the IL-23R gene expression returned back to normal levels.

CONCLUSION

Our study suggests that an elevated IL-23R level may participate in the development of VKH disease.

Development of Reliable, Valid and Responsive Scoring Systems for Endoscopy and Histology in Animal Models for Inflammatory Bowel Disease

BACKGROUND AND AIMS

Although several endoscopic and histopathologic indices are available for evaluating the severity of inflammation in mouse models of colitis, the reliability of these scoring instruments is unknown. Our aim was to evaluate the reliability of the individual items in the existing indices and develop new scoring systems by selection of the most reliable index items.

METHODS

Two observers scored the histological slides [n = 224] and endoscopy videos [n = 201] from treated and untreated Interleukin[IL]-10 knock-out and T-cell transferred SCID mice. Intra-rater and inter-rater reliability for endoscopy and histology scores, and each individual item, were measured using intraclass correlation coefficients [ICCs]. The Mouse Colitis Histology Index [MCHI] and Mouse Colitis Endoscopy Index [MCEI] were developed using the most reliable items. Both were correlated to the colon density and to each other and were evaluated for their ability to detect changes in pathobiology.

RESULTS

The intraclass correlation coefficients (ICCs) for inter-rater agreement (95% CIs) for the total histology and endoscopy scores were 0.90 [0.87-0.92] and 0.80 [0.76-0.84], respectively. The MCHI and MCEI were highly correlated with colon density, with a Spearman Rho = 0.81[0.75-0.85] and 0.73 [0.66-0.79], respectively, and with each other, Spearman Rho = 0.71 [0.63-0.77]. The MCHI and MCEI were able to distinguish between the experimental groups within the models, with pairwise differences between the treated and untreated groups being statistically significant [p < 0.001].

CONCLUSIONS

These histological and endoscopic indices are valid and reliable measures of intestinal inflammation in mice, and they are responsive to treatment effects in pre-clinical studies.

NOD2 up-regulates TLR2-mediated IL-23p19 expression via NF-κB subunit c-Rel in Paneth cell-like cells

IL-23p19 plays important roles in intestinal antimicrobial immunity, while its over-expression can lead to intestinal inflammation. However, the bacterial compounds and the type of pattern recognition receptor involved in the inducible expression of IL-23p19 in Paneth cells remain unclear. Here we show that the mRNA expression of IL-23p19 was increased in Paneth cell (PC)-like cells stimulated by Toll-like receptor 2 (TLR2) ligands, peptidoglycan (PGN) and Pam3CSK4, and was further increased in the presence of nucleotide-binding oligomerization domain 2 (NOD2)-ligand muramyl dipeptide (MDP). However, its mRNA expression was decreased in NOD2-knockdown PC-like cells. Additionally, the c-Rel activation was increased in Pam3CSK4- or PGN-stimulated PC-like cells, but the PGN-induced c-Rel activation was decreased in NOD2-knockdown PC-like cells and had no significant difference compared with Pam3CSK4-induced c-Rel activation. Our results suggest that NOD2 up-regulates TLR2-mediated IL-23p19 expression via increasing c-Rel activation in PC-like cells. This finding might provide us with a novel therapeutic target for inflammatory bowel disease to inhibit IL-23p19 over-expression via the NOD2-c-Rel pathway.

Sweet! Helicobacter Sugar Calms Intestinal Macrophages

In the absence of IL-10, Helicobacter hepaticus (Hh) induces colitis. In this issue of Cell Host & Microbe, Danne et al. (2017) report that Hh produces a polysaccharide that induces an anti-inflammatory response in macrophages, providing a potential clue as to why this bacterium is normally tolerated by the immune system.

Interferon-gamma deficiency protects against aging-related goblet cell loss

Aging is a well-recognized risk factor for dry eye. Interferon-gamma (IFN-γ) has been implicated in conjunctival keratinization and goblet cell loss in dry eye. We investigated the role of IFN-γ in age-related dry eye by evaluating young (8 weeks) and aged (15 months; 15M) C57BL/6 (B6) and IFN-γKO mice. Age effects on the conjunctiva and cornea epithelium were assessed with PAS staining and corneal staining, respectively. Expression of T cell-related cytokines (IL-17A, IFN-γ), chemokines (CXCL10 and CCL20), in the ocular surface epithelium was evaluated by real time PCR. A significant decrease in filled goblet cells was noted in 15M B6 mice and this was significantly lower than age and sex-matched IFN-γKO mice. Aged male B6 had significantly higher IFN-γ, and CXCL10 mRNA in their conjunctiva than female B6 mice. Aged IFN-γKO females had significantly higher IL-17A mRNA in conjunctiva than IFN-γKO males and B6 mice. Corneal barrier dysfunction was observed in 15M female B6 and aged IFN-γKO mice of both sexes; however it was significantly higher in IFN-γKO compared to B6 mice. While there was a significant increase in IL 17A, and CCL20 in corneas of aged female B6 and IFN-γKO mice compared to males, these changes were more evident in aged female IFN-γKO group.

Partial resistance of IFN-γKO mice to aging-induced goblet cell loss indicates IFN-γ is involved in the age-related decline in conjunctival goblet cells. Increased corneal IL-17A expression paralleled corneal barrier disruption in aging female of both strains. IFN-γ appears to suppress IL-17A on the ocular surface.

c-MAF-dependent regulatory T cells mediate immunological tolerance to a gut pathobiont

Both microbial and host genetic factors contribute to the pathogenesis of autoimmune diseases. There is accumulating evidence that microbial species that potentiate chronic inflammation, as in inflammatory bowel disease, often also colonize healthy individuals. These microorganisms, including the Helicobacter species, can induce pathogenic T cells and are collectively referred to as pathobionts. However, how such T cells are constrained in healthy individuals is not yet understood. Here we report that host tolerance to a potentially pathogenic bacterium, Helicobacter hepaticus, is mediated by the induction of RORγt+FOXP3+ regulatory T (iTreg) cells that selectively restrain pro-inflammatory T helper 17 (TH17) cells and whose function is dependent on the transcription factor c-MAF. Whereas colonization of wild-type mice by H. hepaticus promoted differentiation of RORγt-expressing microorganism-specific iTreg cells in the large intestine, in disease-susceptible IL-10-deficient mice, there was instead expansion of colitogenic TH17 cells. Inactivation of c-MAF in the Treg cell compartment impaired differentiation and function, including IL-10 production, of bacteria-specific iTreg cells, and resulted in the accumulation of H. hepaticus-specific inflammatory TH17 cells and spontaneous colitis. By contrast, RORγt inactivation in Treg cells had only a minor effect on the bacteria-specific Treg and TH17 cell balance, and did not result in inflammation. Our results suggest that pathobiont-dependent inflammatory bowel disease is driven by microbiota-reactive T cells that have escaped this c-MAF-dependent mechanism of iTreg-TH17 homeostasis.

Do the Microbiota Influence Vaccines and Protective Immunity to Pathogens? Issues of Sovereignty, Federalism, and Points-Testing in the Prokaryotic and Eukaryotic Spaces of the Host-Microbial Superorganism

In contrast to live attenuated vaccines, which are designed to induce immunity through a time-limited bloom in systemic tissues, the microbiota is a persistent feature of body surfaces, especially the intestine. The immune responses to the microbiota are idiosyncratic depending on the niche intimacy of different taxa and generally adapt the host to avoid overgrowth and maintain mutualism rather than to eliminate the organisms of that taxon. Both the microbiota and the host have so much molecular cross talk controlling each other, that the prokaryotic and the eukaryotic spaces of the host-microbial superorganism are federal rather than sovereign. This molecular cross talk is vital for the immune system to develop its mature form. Nevertheless, the microbiota/host biomass spaces are rather well separated: The microbiota also limits colonization and penetration of pathogens through intense metabolic competition. Immune responses to those members of the microbiota mutually adapted to intimate association at mucosal surfaces have attractive potential durability, but for clinical use as persistent vehicles they would require personalization and engineered reversibility to manage the immune context and complications in individual human subjects.

Intestinal IFN-γ-producing type 1 regulatory T cells coexpress CCR5 and programmed cell death protein 1 and downregulate IL-10 in the inflamed guts of patients with inflammatory bowel disease

BACKGROUND

IL-10 is an anti-inflammatory cytokine required for intestinal immune homeostasis. It mediates suppression of T-cell responses by type 1 regulatory T (T_R1) cells but is also produced by CD25⁺ regulatory T (Treg) cells.

OBJECTIVE

We aimed to identify and characterize human intestinal T_R1 cells and to investigate whether they are a relevant cellular source of IL-10 in patients with inflammatory bowel diseases (IBDs).

METHODS

CD4⁺ T cells isolated from the intestinal lamina propria of human subjects and mice were analyzed for phenotype, cytokine production, and suppressive capacities. Intracellular IL-10 expression by CD4⁺ T-cell subsets in the inflamed guts of patients with IBD (Crohn disease or ulcerative colitis) was compared with that in cells from noninflamed control subjects. Finally, the effects of proinflammatory cytokines on T-cell IL-10 expression were analyzed, and IL-1β and IL-23 responsiveness was assessed.

RESULTS

Intestinal T_R1 cells could be identified by coexpression of CCR5 and programmed cell death protein 1 (PD-1) in human subjects and mice. CCR5⁺PD-1⁺ T_R1 cells expressed IFN-γ and efficiently suppressed T-cell proliferation and transfer colitis. Intestinal IFN-γ⁺ T_R1 cells, but not IL-7 receptor-positive T_H cells or CD25⁺ Treg cells, showed lower IL-10 expression in patients with IBDs. T_R1 cells were responsive to IL-23, and IFN-γ⁺ T_R1 cells downregulated IL-10 with IL-1β and IL-23. Conversely, CD25⁺ Treg cells expressed higher levels of IL-1 receptor but showed stable IL-10 expression.

CONCLUSIONS

We provide the first ex vivo characterization of human intestinal T_R1 cells. Selective downregulation of IL-10 by IFN-γ⁺ T_R1 cells in response to proinflammatory cytokines is likely to drive excessive intestinal inflammation in patients with IBDs.

Proinflammatory Role of Monocyte-Derived CX3CR1int Macrophages in Helicobacter hepaticus-Induced Colitis

Cells of the monocyte/macrophage lineage play important roles in the pathogenesis of inflammatory bowel diseases, but they are also present in the normal healthy intestine, where they are critical for maintaining homeostasis. It has been unclear whether the proinflammatory roles of intestinal macrophages reflect altered behavior of the existing resident cells, or whether they involve recruitment of a distinct cell type. Here, we have explored these ideas using the model of colitis induced by Helicobacter hepaticus in the context of neutralization or deletion of interleukin-10 (IL-10). Granulocytes and monocytes made up most of the inflammatory myeloid infiltrates found in the colon of H. hepaticus-infected colitic mice, rising to a peak within 2 weeks of H. hepaticus inoculation but taking several months to resolve completely. The inflammatory response was dependent on the combined presence of H. hepaticus and absence of IL-10 and was accompanied by increased production of inflammatory mediators such as IL-1β, tumor necrosis factor alpha (TNF-α), IL-6, and IL-23p19 by infiltrating myeloid cells, mostly relatively immature cells of the macrophage lineage that express intermediate levels of CX3CR1. In contrast, the population of mature CX3CR1^hi macrophages did not expand as markedly during colitis, and these cells made little contribution to inflammatory mediator production. Taking into account their numerical dominance in the myeloid compartment, we conclude that newly recruited monocytes are the main source of proinflammatory mediators in colitis induced in the absence of IL-10 signaling and that altered behavior of mature macrophages is not a major component of this pathology.

Intestinal Epithelial Cell Autophagy Is Required to Protect against TNF-Induced Apoptosis during Chronic Colitis in Mice

Genome-wide association studies have linked polymorphisms in the autophagy gene ATG16L1 with susceptibility to inflammatory bowel disease (IBD). However, the cell-type-specific effects of autophagy on the regulation of chronic intestinal inflammation have not been investigated. Here, we assessed the effect of myeloid-specific or intestinal epithelial cell (IEC)-specific deletion of Atg16l1 on chronic colitis triggered by the intestinal opportunistic pathogen Helicobacter hepaticus in mice. Although Atg16l1 deficiency in myeloid cells had little effect on disease, mice selectively lacking Atg16l1 in IECs (Atg16l1^VC) developed severely exacerbated pathology, accompanied by elevated pro-inflammatory cytokine secretion and increased IEC apoptosis. Using ex vivo IEC organoids, we demonstrate that autophagy intrinsically controls TNF-induced apoptosis and in vivo blockade of TNF attenuated the exacerbated pathology in Atg16l1^VC mice. These findings suggest that the IBD susceptibility gene ATG16L1 and the process of autophagy within the epithelium control inflammation-induced apoptosis and barrier integrity to limit chronic intestinal inflammation.

IL-10 control of CD11c+ myeloid cells is essential to maintain immune homeostasis in the small and large intestine

Although IL-10 promotes a regulatory phenotype of CD11c⁺ dendritic cells and macrophages in vitro, the role of IL-10 signaling in CD11c⁺ cells to maintain intestinal tolerance in vivo remains elusive. To this aim, we generated mice with a CD11c-specific deletion of the IL-10 receptor alpha (Cd11c^creIl10ra^fl/fl). In contrast to the colon, the small intestine of Cd11c^creIl10ra^fl/fl mice exhibited spontaneous crypt hyperplasia, increased numbers of intraepithelial lymphocytes and lamina propria T cells, associated with elevated levels of T cell-derived IFNγ and IL-17A. Whereas naive mucosal T-cell priming was not affected and oral tolerance to ovalbumin was intact, augmented T-cell function in the lamina propria was associated with elevated numbers of locally dividing T cells, expression of T-cell attracting chemokines and reduced T-cell apoptosis. Upon stimulation, intestinal IL-10Rα deficient CD11c⁺ cells exhibited increased activation associated with enhanced IL-6 and TNFα production. Following colonization with Helicobacter hepaticus Cd11c^creIl10ra^fl/fl mice developed severe large intestinal inflammation characterized by infiltrating T cells and increased levels of Il17a, Ifng, and Il12p40. Altogether these findings demonstrate a critical role of IL-10 signaling in CD11c⁺ cells to control small intestinal immune homeostasis by limiting reactivation of local memory T cells and to protect against Helicobacter hepaticus-induced colitis.

Recipe for IBD: can we use food to control inflammatory bowel disease?

The mucosal immune system and the microbiota in the intestinal tract have recently been shown to play a key role in the pathogenesis of inflammatory bowel disease (IBD). Both of these can be influenced by food. Thus, we propose dietary intervention as a therapeutic option for IBD. In this review, we discuss the interaction of the intestinal mucosal immune system and the intestinal microbiota in the context of IBD. In addition, we discuss the impact of food components on immune responses in IBD. Finally, we address the current evidence of how this interaction (i.e., immune system-microbiota) can be modulated by food components, pre/probiotics, and fecal microbiota transplantation (FMT) and how these approaches can support intestinal homeostasis. By gathering the vast amount of literature available on the impact of food on IBD, we aim to distinguish between scientifically sound data and theories, which have not been included in this review.

Deciphering interactions between the gut microbiota and the immune system via microbial cultivation and minimal microbiomes

The community of microorganisms in the mammalian gastrointestinal tract, referred to as the gut microbiota, influences host physiology and immunity. The last decade of microbiome research has provided significant advancements for the field and highlighted the importance of gut microbes to states of both health and disease. Novel molecular techniques have unraveled the tremendous diversity of intestinal symbionts that potentially influence the host, many proof-of-concept studies have demonstrated causative roles of gut microbial communities in various pathologies, and microbiome-based approaches are beginning to be implemented in the clinic for diagnostic purposes or for personalized treatments. However, several challenges for the field remain: purely descriptive reports outnumbering mechanistic studies and slow translation of experimental results obtained in animal models into the clinics. Moreover, there is a dearth of knowledge regarding how gut microbes, including novel species that have yet to be identified, impact host immune responses. The sheer complexity of the gut microbial ecosystem makes it difficult, in part, to fully understand the microbiota-host networks that regulate immunity. In the present manuscript, we review key findings on the interactions between gut microbiota members and the immune system. Because culturing microbes allows performing functional studies, we have emphasized the impact of specific taxa or communities thereof. We also highlight underlying molecular mechanisms and discuss opportunities to implement minimal microbiome-based strategies.

Regulation of IL-12p40 by HIF controls Th1/Th17 responses to prevent mucosal inflammation

Intestinal inflammatory lesions are inherently hypoxic, due to increased metabolic demands created by cellular infiltration and proliferation, and reduced oxygen supply due to vascular damage. Hypoxia stabilizes the transcription factor hypoxia-inducible factor-1α (HIF) leading to a coordinated induction of endogenously protective pathways. We identified IL12B as a HIF-regulated gene and aimed to define how the HIF-IL-12p40 axis influenced intestinal inflammation. Intestinal lamina propria lymphocytes (LPL) were characterized in wild-type and IL-12p40^-/- murine colitis treated with vehicle or HIF-stabilizing prolyl-hydroxylase inhibitors (PHDi). IL12B promoter analysis was performed to examine hypoxia-responsive elements. Immunoblot analysis of murine and human LPL supernatants was performed to characterize the HIF/IL-12p40 signaling axis. We observed selective induction of IL-12p40 following PHDi-treatment, concurrent with suppression of Th1 and Th17 responses in murine colitis models. In the absence of IL-12p40, PHDi-treatment was ineffective. Analysis of the IL12B promoter identified canonical HIF-binding sites. HIF stabilization in LPLs resulted in production of IL-12p40 homodimer which was protective against colitis. The selective induction of IL-12p40 by HIF-1α leads to a suppression of mucosal Th1 and Th17 responses. This HIF-IL12p40 axis may represent an endogenously protective mechanism to limit the progression of chronic inflammation, shifting from pro-inflammatory IL-12p70 to an antagonistic IL-12p40 homodimer.

Helicobacter species are potent drivers of colonic T cell responses in homeostasis and inflammation

Specific gut commensal bacteria improve host health by eliciting mutualistic regulatory T (T_reg) cell responses. However, the bacteria that induce effector T (T_eff) cells during inflammation are unclear. We addressed this by analyzing bacterial-reactive T cell receptor (TCR) transgenic cells and TCR repertoires in a murine colitis model. Unexpectedly, we found that mucosal-associated Helicobacter species triggered both T_reg cell responses during homeostasis and T_eff cell responses during colitis, as suggested by an increased overlap between the T_eff/T_reg TCR repertoires with colitis. Four of six T_reg TCRs tested recognized mucosal-associated Helicobacter species in vitro and in vivo. By contrast, the marked expansion of luminal Bacteroides species seen during colitis did not trigger a commensurate T_eff cell response. Unlike other T_reg cell-inducing bacteria, Helicobacter species are known pathobionts and cause disease in immunodeficient mice. Thus, our study suggests a model in which mucosal bacteria elicit context-dependent T_reg or T_eff cell responses to facilitate intestinal tolerance or inflammation.

Aberrant intestinal microbiota due to IL-1 receptor antagonist deficiency promotes IL-17- and TLR4-dependent arthritis

BACKGROUND

Perturbation of commensal intestinal microbiota has been associated with several autoimmune diseases. Mice deficient in interleukin-1 receptor antagonist (Il1rn ^-/- mice) spontaneously develop autoimmune arthritis and are susceptible to other autoimmune diseases such as psoriasis, diabetes, and encephalomyelitis; however, the mechanisms of increased susceptibility to these autoimmune phenotypes are poorly understood. We investigated the role of interleukin-1 receptor antagonist (IL-1Ra) in regulation of commensal intestinal microbiota, and assessed the involvement of microbiota subsets and innate and adaptive mucosal immune responses that underlie the development of spontaneous arthritis in Il1rn ^-/- mice.

RESULTS

Using high-throughput 16S rRNA gene sequencing, we show that IL-1Ra critically maintains the diversity and regulates the composition of intestinal microbiota in mice. IL-1Ra deficiency reduced the intestinal microbial diversity and richness, and caused specific taxonomic alterations characterized by overrepresented Helicobacter and underrepresented Ruminococcus and Prevotella. Notably, the aberrant intestinal microbiota in IL1rn ^-/- mice specifically potentiated IL-17 production by intestinal lamina propria (LP) lymphocytes and skewed the LP T cell balance in favor of T helper 17 (Th17) cells, an effect transferable to WT mice by fecal microbiota. Importantly, LP Th17 cell expansion and the development of spontaneous autoimmune arthritis in IL1rn ^-/- mice were attenuated under germ-free condition. Selective antibiotic treatment revealed that tobramycin-induced alterations of commensal intestinal microbiota, i.e., reduced Helicobacter, Flexispira, Clostridium, and Dehalobacterium, suppressed arthritis in IL1rn ^-/- mice. The arthritis phenotype in IL1rn ^-/- mice was previously shown to depend on Toll-like receptor 4 (TLR4). Using the ablation of both IL-1Ra and TLR4, we here show that the aberrations in the IL1rn ^-/- microbiota are partly TLR4-dependent. We further identify a role for TLR4 activation in the intestinal lamina propria production of IL-17 and cytokines involved in Th17 differentiation preceding the onset of arthritis.

CONCLUSIONS

These findings identify a critical role for IL1Ra in maintaining the natural diversity and composition of intestinal microbiota, and suggest a role for TLR4 in mucosal Th17 cell induction associated with the development of autoimmune disease in mice.

Effect of CXCR3/HO-1 genes modified bone marrow mesenchymal stem cells on small bowel transplant rejection

AIM

To investigate whether bone marrow mesenchymal stem cells (BMMSCs) modified with the HO-1 and CXCR3 genes can augment the inhibitory effect of BMMSCs on small bowel transplant rejection.

METHODS

Lewis rat BMMSCs were cultured in vitro. Third-passage BMMSCs were transduced with the CXCR3/HO-1 genes or the HO-1 gene alone. The rats were divided into six groups and rats in the experimental group were pretreated with BMMSCs 7 d prior to small bowel transplant. Six time points (instant, 1 d, 3 d, 7 d, 10 d, and 14 d) (n = 6) were chosen for each group. Hematoxylin-eosin staining was used to observe pathologic rejection, while immunohistochemistry and Western blot were used to detect protein expression. Flow cytometry was used to detect T lymphocytes and enzyme linked immunosorbent assay was used to detect cytokines.

RESULTS

The median survival time of BMMSCs from the CXCR3/HO-1 modified group (53 d) was significantly longer than that of the HO-1 modified BMMSCs group (39 d), the BMMSCs group (26 d), and the NS group (control group) (16 d) (P < 0.05). Compared with BMMSCs from the HO-1 modified BMMSCs, BMMSCs, and NS groups, rejection of the small bowel in the CXCR3/HO-1 modified group was significantly reduced, while the weight of transplant recipients was also significantly decreased (P < 0.05). Furthermore, IL-2, IL-6, IL-17, IFN-γ, and TNF-α levels were significantly decreased and the levels of IL-10 and TGF-β were significantly increased (P < 0.05).

CONCLUSION

BMMSCs modified with the CXCR3 and HO-1 genes can abrogate the rejection of transplanted small bowel more effectively and significantly increase the survival time of rats that receive a small bowel transplant.

Oncostatin M drives intestinal inflammation and predicts response to tumor necrosis factor-neutralizing therapy in patients with inflammatory bowel disease

Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are complex chronic inflammatory conditions of the gastrointestinal tract that are driven by perturbed cytokine pathways. Anti-tumor necrosis factor-α (TNF) antibodies are mainstay therapies for IBD. However, up to 40% of patients are nonresponsive to anti-TNF agents, which makes the identification of alternative therapeutic targets a priority. Here we show that, relative to healthy controls, inflamed intestinal tissues from patients with IBD express high amounts of the cytokine oncostatin M (OSM) and its receptor (OSMR), which correlate closely with histopathological disease severity. The OSMR is expressed in nonhematopoietic, nonepithelial intestinal stromal cells, which respond to OSM by producing various proinflammatory molecules, including interleukin (IL)-6, the leukocyte adhesion factor ICAM1, and chemokines that attract neutrophils, monocytes, and T cells. In an animal model of anti-TNF-resistant intestinal inflammation, genetic deletion or pharmacological blockade of OSM significantly attenuates colitis. Furthermore, according to an analysis of more than 200 patients with IBD, including two cohorts from phase 3 clinical trials of infliximab and golimumab, high pretreatment expression of OSM is strongly associated with failure of anti-TNF therapy. OSM is thus a potential biomarker and therapeutic target for IBD, and has particular relevance for anti-TNF-resistant patients.

Microbiome-driven carcinogenesis in colorectal cancer: Models and mechanisms

Colorectal cancer (CRC) is a leading cause of cancer death and archetype for cancer as a genetic disease. However, the mechanisms for genetic change and their interactions with environmental risk factors have been difficult to unravel. New hypotheses, models, and methods are being used to investigate a complex web of risk factors that includes the intestinal microbiome. Recent research has clarified how the microbiome can generate genomic change in CRC. Several phenotypes among a small group of selected commensals have helped us better understand how mutations and chromosomal instability (CIN) are induced in CRC (e.g., toxin production, metabolite formation, radical generation, and immune modulation leading to a bystander effect). This review discusses recent hypotheses, models, and mechanisms by which the intestinal microbiome contributes to the initiation and progression of sporadic and colitis-associated forms of CRC. Overall, it appears the microbiome can initiate and/or promote CRC at all stages of tumorigenesis by acting as an inducer of DNA damage and CIN, regulating cell growth and death, generating epigenetic changes, and modulating host immune responses. Understanding how the microbiome interacts with other risk factors to define colorectal carcinogenesis will ultimately lead to more accurate risk prediction. A deeper understanding of CRC etiology will also help identify new targets for prevention and treatment and help accelerate the decline in mortality for this common cancer.

Recent Advances: The Imbalance of Cytokines in the Pathogenesis of Inflammatory Bowel Disease

Cytokines play an important role in the immunopathogenesis of inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, where they drive and regulate multiple aspects of intestinal inflammation. The imbalance between proinflammatory and anti-inflammatory cytokines that occurs in IBD results in disease progression and tissue damage and limits the resolution of inflammation. Targeting cytokines have been novel strategies in the treatment of IBD. Recent studies show the beneficial effects of anticytokine treatments to IBD patients, and multiple novel cytokines are found to be involved in the pathogenesis of IBD. In this review, we will discuss the recent advances of novel biologics in clinics and clinical trials, and novel proinflammatory and anti-inflammatory cytokines found in IBD with focusing on IL-12 family and IL-1 family members as well as their relevance to the potential therapy of IBD.

Helicobacter hepaticus cytolethal distending toxin promotes intestinal carcinogenesis in 129Rag2-deficient mice

Multiple pathogenic Gram-negative bacteria produce the cytolethal distending toxin (CDT) with activity of DNase I; CDT can induce DNA double-strand breaks (DSBs), G2/M cell cycle arrest, and apoptosis in cultured mammalian cells. However, the link of CDT to in vivo tumorigenesis is not fully understood. In this study, 129/SvEv Rag2^-/- mice were gavaged with wild-type Helicobacter hepatics 3B1(Hh) and its isogenic cdtB mutant HhcdtBm7, followed by infection for 10 and 20 weeks (WPI). HhCDT deficiency did not affect cecal colonization levels of HhcdtBm7, but attenuated severity of cecal pathology in HhcdtBm7-infected mice. Of importance, preneoplasic dysplasia was progressed to cancer from 10 to 20 WPI in the Hh-infected mice but not in the HhcdtBm7-infected mice. In addition, the loss of HhCDT significantly dampened transcriptional upregulation of cecal Tnfα and Il-6, but elevated Il-10 mRNA levels when compared to Hh at 10 WPI. Furthermore, the presence of HhCDT increased numbers of lower bowel intestinal γH2AX-positive epithelial cells (a marker of DSBs) at both 10 and 20 WPI and augmented phospho-Stat3 foci⁺ intestinal crypts (activation of Stat3) at 20 WPI. Our findings suggest that CDT promoted Hh carcinogenesis by enhancing DSBs and activation of the Tnfα/Il-6-Stat3 signaling pathway.

Lessons Learned From Trials Targeting Cytokine Pathways in Patients With Inflammatory Bowel Diseases

Insights into the pathogenesis of inflammatory bowel diseases (IBDs) have provided important information for the development of therapeutics. Levels of interleukin 23 (IL23) and T-helper (Th) 17 cell pathway molecules are increased in inflamed intestinal tissues of patients with IBD. Loss-of-function variants of the IL23-receptor gene (IL23R) protect against IBD, and, in animals, blocking IL23 reduces the severity of colitis. These findings indicated that the IL23 and Th17 cell pathways might be promising targets for the treatment of IBD. Clinical trials have investigated the effects of agents designed to target distinct levels of the IL23 and Th17 cell pathways, and the results are providing insights into IBD pathogenesis and additional strategies for modulating these pathways. Strategies to reduce levels of proinflammatory cytokines more broadly and increase anti-inflammatory mechanisms also are emerging for the treatment of IBD. The results from trials targeting these immune system pathways have provided important lessons for future trials. Findings indicate the importance of improving approaches to integrate patient features and biomarkers of response with selection of therapeutics.

Biological therapy targeting the IL-23/IL-17 axis in inflammatory bowel disease

INTRODUCTION

As many inflammatory bowel disease (IBD) patients do not benefit from long-term anti-tumour necrosis factor treatment, new anti-inflammatories are urgently needed. After the discovery of the interleukin (IL) 23/17 axis being pivotal in IBD pathogenesis, many different compounds were developed, targeting different components within this pathway. Areas covered: A literature search to March 2016 was performed to identify the most relevant reports on the role of the IL-23/IL-17 axis in IBD and on the different molecules targeting this pathway. First, the authors briefly summarize the immunology of the IL-23/IL-17 pathway to elucidate the mode of action of all different agents. Second, they describe all different molecules targeting this pathway. Besides discussing efficacy and safety data, they also explore immunogenicity, exposure during pregnancy and pharmacokinetics. Expert opinion: A new era in IBD treatment has recently been initiated: besides immunomodulators and TNF-antagonists, anti-adhesion molecules and monoclonal antibodies targeting the IL-23/IL-17 pathway have been developed. Biomarkers for personalized medicine are urgently needed. This therapeutic (r)evolution will further improve disease-related and patient-reported outcome, though a lot of questions should still be addressed in future years.

Vitamin D Signaling through Induction of Paneth Cell Defensins Maintains Gut Microbiota and Improves Metabolic Disorders and Hepatic Steatosis in Animal Models

Metabolic syndrome (MetS), characterized as obesity, insulin resistance, and non-alcoholic fatty liver diseases (NAFLD), is associated with vitamin D insufficiency/deficiency in epidemiological studies, while the underlying mechanism is poorly addressed. On the other hand, disorder of gut microbiota, namely dysbiosis, is known to cause MetS and NAFLD. It is also known that systemic inflammation blocks insulin signaling pathways, leading to insulin resistance and glucose intolerance, which are the driving force for hepatic steatosis. Vitamin D receptor (VDR) is highly expressed in the ileum of the small intestine, which prompted us to test a hypothesis that vitamin D signaling may determine the enterotype of gut microbiota through regulating the intestinal interface. Here, we demonstrate that high-fat-diet feeding (HFD) is necessary but not sufficient, while additional vitamin D deficiency (VDD) as a second hit is needed, to induce robust insulin resistance and fatty liver. Under the two hits (HFD+VDD), the Paneth cell-specific alpha-defensins including α-defensin 5 (DEFA5), MMP7 which activates the pro-defensins, as well as tight junction genes, and MUC2 are all suppressed in the ileum, resulting in mucosal collapse, increased gut permeability, dysbiosis, endotoxemia, systemic inflammation which underlie insulin resistance and hepatic steatosis. Moreover, under the vitamin D deficient high fat feeding (HFD+VDD), Helicobacter hepaticus, a known murine hepatic-pathogen, is substantially amplified in the ileum, while Akkermansia muciniphila, a beneficial symbiotic, is diminished. Likewise, the VD receptor (VDR) knockout mice exhibit similar phenotypes, showing down regulation of alpha-defensins and MMP7 in the ileum, increased Helicobacter hepaticus and suppressed Akkermansia muciniphila. Remarkably, oral administration of DEFA5 restored eubiosys, showing suppression of Helicobacter hepaticus and increase of Akkermansia muciniphila in association with resolving metabolic disorders and fatty liver in the HFD+VDD mice. An in vitro analysis showed that DEFA5 peptide could directly suppress Helicobacter hepaticus. Thus, the results of this study reveal critical roles of a vitamin D/VDR axis in optimal expression of defensins and tight junction genes in support of intestinal integrity and eubiosis to suppress NAFLD and metabolic disorders.

Tissue-infiltrating neutrophils represent the main source of IL-23 in the colon of patients with IBD

OBJECTIVE

In IBD, interleukin-23 (IL-23) and its receptor (IL-23R) are implicated in disease initiation and progression. Novel insight into which cells produce IL-23 at the site of inflammation at an early stage of IBD will promote the development of new tools for diagnosis, treatment and patient monitoring. We examined the cellular source of IL-23 in colon tissue of untreated newly diagnosed paediatric patients with IBD.

DESIGN

Colon tissues from IBD and non-IBD patients were analysed by quantitative real-time PCR (qPCR), immunofluorescence confocal microscopy and flow cytometry after appropriate sample preparation. Blood samples from IBD and non-IBD patients and healthy controls were analysed using flow cytometry and qPCR.

RESULTS

We discovered that tissue-infiltrating neutrophils were the main source of IL-23 in the colon of paediatric patients with IBD, while IL-23(+) human leucocyte antigen-DR(+) or IL-23(+)CD14(+) cells were scarce or non-detectable, respectively. The colonic IL-23(+) neutrophils expressed C-X-C motif (CXC)R1 and CXCR2, receptors for the CXC ligand 8 (CXCL8) chemokine family, and a corresponding CXCR1(+)CXCR2(+)IL-23(+)subpopulation of neutrophils was also identified in the blood of both patients with IBD and healthy individuals. However, CXCL8-family chemokines were only elevated in colon tissue from patients with IBD.

CONCLUSIONS

This study provides the first evidence of CXCR1(+)CXCR2(+)IL-23-producing neutrophils that infiltrate and accumulate in inflamed colon tissue of patients with IBD. Thus, this novel source of IL-23 may play a key role in disease progression and will be important to take into consideration in the development of future strategies to monitor, treat and prevent IBD.

Viral Infection of the Central Nervous System Exacerbates Interleukin-10 Receptor Deficiency-Mediated Colitis in SJL Mice

Theiler´s murine encephalomyelitis virus (TMEV)-infection is a widely used animal model for studying demyelinating disorders, including multiple sclerosis (MS). The immunosuppressive cytokine Interleukin (IL)-10 counteracts hyperactive immune responses and critically controls immune homeostasis in infectious and autoimmune disorders. In order to investigate the effect of signaling via Interleukin-10 receptor (IL-10R) in infectious neurological diseases, TMEV-infected SJL mice were treated with IL-10R blocking antibody (Ab) in the acute and chronic phase of the disease. The findings demonstrate that (i) Ab-mediated IL-10 neutralization leads to progressive colitis with a reduction in Foxp3+ regulatory T cells and increased numbers of CD8+CD44+ memory T cells as well as activated CD4+CD69+ and CD8+CD69+ T cells in uninfected mice. (ii) Concurrent acute TMEV-infection worsened enteric disease-mediated by IL-10R neutralization. Virus-triggered effects were associated with an enhanced activation of CD4+ T helper cells and CD8+ cytotoxic T lymphocytes and augmented cytokine expression. By contrast, (iii) IL-10R neutralization during chronic TMEV-infection was not associated with enhanced peripheral immunopathology but an increased CD3+ T cell influx in the spinal cord. IL-10R neutralization causes a breakdown in peripheral immune tolerance in genetically predisposed mice, which leads to immune-mediated colitis, resembling inflammatory bowel disease. Hyperactive immune state following IL-10R blockade is enhanced by central nervous system-restricted viral infection in a disease phase-dependent manner.

Carbonic Anhydrate I Epitope Peptide Improves Inflammation in a Murine Model of Inflammatory Bowel Disease

BACKGROUND

Carbonic anhydrase I (CA I), a major cecal bacterial antigen, improves inflammatory bowel disease (IBD) symptoms in a murine model. The aim of this study was to identify the responsible epitope region within the CA I protein and evaluate its effect on inflammation using a murine IBD model.

METHODS

Candidate peptides within the CA I protein sequence that interact with major histocompatibility complex class II were chosen and their immune responses were evaluated using mesentery lymph nodes (MLNs) from a CD4CD25 T-cell transfer murine colitis model. Mice were treated with regulatory dendritic cells (Reg-DCs)-pulsed CA I peptide. We assessed their clinical signs, histopathology, induction of cytokines and transcription factors, and generation of CD103CD11c dendritic cells and regulatory T cells (Tregs).

RESULTS

We identified 4 candidate epitope peptides of CA I. Among these, Reg-DCs pulsed with CA I 58-73 peptide (Reg-DCsCA I 58-73) alone ameliorated colitis. Reg-DCsCA I 58-73-treated mice showed higher mRNA expression levels of forkhead box protein 3, aldehyde dehydrogenase family 1a2, transforming growth factor-β, and interleukin (Il)10, when compared with lower mRNA expression of retinoic acid-related orphan receptor gamma and Il17a in MLNs. Compared with control mice, these mice also showed higher numbers of Foxp3CD4CD25 Tregs and CD103CD11c dendritic cells in MLNs and colon. Administration of Reg-DCsCA I 58-73 induced antigen-specific Tregs in MLNs of colitic mice.

CONCLUSIONS

CA I 58-73 peptide induces antigen-specific therapeutic effect in a murine IBD model using Reg-DCs, indicating that CA I 58-73 is a candidate epitope for IBD immunotherapy.

Helicobacter saguini, a Novel Helicobacter Isolated from Cotton-Top Tamarins with Ulcerative Colitis, Has Proinflammatory Properties and Induces Typhlocolitis and Dysplasia in Gnotobiotic IL-10-/- Mice

A urease-negative, fusiform, novel bacterium named Helicobacter saguini was isolated from the intestines and feces of cotton-top tamarins (CTTs) with chronic colitis. Helicobacter sp. was detected in 69% of feces or intestinal samples from 116 CTTs. The draft genome sequence, obtained by Illumina MiSeq sequencing, for H. saguini isolate MIT 97-6194-5, consisting of ∼2.9 Mb with a G+C content of 35% and 2,704 genes, was annotated using the NCBI Prokaryotic Genomes Automatic Annotation Pipeline. H. saguini contains homologous genes of known virulence factors found in other enterohepatic helicobacter species (EHS) and H. pylori These include flagellin, γ-glutamyl transpeptidase (ggt), collagenase, the secreted serine protease htrA, and components of a type VI secretion system, but the genome does not harbor genes for cytolethal distending toxin (cdt). H. saguini MIT 97-6194-5 induced significant levels of interleukin-8 (IL-8) in HT-29 cell culture supernatants by 4 h, which increased through 24 h. mRNAs for the proinflammatory cytokines IL-1β, tumor necrosis factor alpha (TNF-α), IL-10, and IL-6 and the chemokine CXCL1 were upregulated in cocultured HT-29 cells at 4 h compared to levels in control cells. At 3 months postinfection, all H. saguini-monoassociated gnotobiotic C57BL/129 IL-10(-/-) mice were colonized and had seroconverted to H. saguini antigen with a significant Th1-associated increase in IgG2c (P < 0.0001). H. saguini induced a significant typhlocolitis, associated epithelial defects, mucosa-associated lymphoid tissue (MALT) hyperplasia, and dysplasia. Inflammatory cytokines IL-22, IL-17a, IL-1β, gamma interferon (IFN-γ), and TNF-α, as well as inducible nitric oxide synthase (iNOS) were significantly upregulated in the cecal tissues of infected mice. The expression of the DNA damage response molecule γ-H2AX was significantly higher in the ceca of H. saguini-infected gnotobiotic mice than in the controls. This model using a nonhuman primate Helicobacter sp. can be used to study the pathogenic potential of EHS isolated from primates with naturally occurring inflammatory bowel disease (IBD) and colon cancer.

New insights toward the pathogenesis of ankylosing spondylitis; genetic variations and epigenetic modifications

Ankylosing spondylitis (AS) is a chronic inflammatory autoimmune disease, characterized by typically an axial arthritis. AS is the prototype of a group of disorders called spondyloarthropathies, which is believed to have common clinical manifestations and genetic predisposition. To date, the exact etiology of AS remains unclear. Over the past few years, however, the role of genetic susceptibility and epigenetic modifications caused through environmental factors have been extensively surveyed with respect to the pathogenesis of AS, resulted in important advances. This review article focuses on the recent advances in the field of AS research, including HLA and non-HLA susceptibility genes identified in genome-wide association studies (GWAS), and aberrant epigenetic modifications of gene loci associated with AS. HLA genes most significantly linked with AS susceptibility include HLA-B27 and its subtypes. Numerous non-HLA genes such as those in ubiquitination, aminopeptidases and MHC class I presentation molecules like ERAP-1 were also reported. Moreover, epigenetic modifications occurred in AS has been summarized. Taken together, the findings presented in this review attempt to explain the circumstance by which both genetic variations and epigenetic modifications are involved in triggering and development of AS. Nonetheless, several unanswered dark sides continue to clog our exhaustive understanding of AS. Future researches in the field of epigenetics should be carried out to extend our vision of AS etiopathogenesis.

The Mucosal Immune System and Its Regulation by Autophagy

The gastrointestinal tract presents a unique challenge to the mucosal immune system, which has to constantly monitor the vast surface for the presence of pathogens, while at the same time maintaining tolerance to beneficial or innocuous antigens. In the intestinal mucosa, specialized innate and adaptive immune components participate in directing appropriate immune responses toward these diverse challenges. Recent studies provide compelling evidence that the process of autophagy influences several aspects of mucosal immune responses. Initially described as a “self-eating” survival pathway that enables nutrient recycling during starvation, autophagy has now been connected to multiple cellular responses, including several aspects of immunity. Initial links between autophagy and host immunity came from the observations that autophagy can target intracellular bacteria for degradation. However, subsequent studies indicated that autophagy plays a much broader role in immune responses, as it can impact antigen processing, thymic selection, lymphocyte homeostasis, and the regulation of immunoglobulin and cytokine secretion. In this review, we provide a comprehensive overview of mucosal immune cells and discuss how autophagy influences many aspects of their physiology and function. We focus on cell type-specific roles of autophagy in the gut, with a particular emphasis on the effects of autophagy on the intestinal T cell compartment. We also provide a perspective on how manipulation of autophagy may potentially be used to treat mucosal inflammatory disorders.

T-bet is a key modulator of IL-23-driven pathogenic CD4(+) T cell responses in the intestine

IL-23 is a key driver of pathogenic Th17 cell responses. It has been suggested that the transcription factor T-bet is required to facilitate IL-23-driven pathogenic effector functions; however, the precise role of T-bet in intestinal T cell responses remains elusive. Here, we show that T-bet expression by T cells is not required for the induction of colitis or the differentiation of pathogenic Th17 cells but modifies qualitative features of the IL-23-driven colitogenic response by negatively regulating IL-23R expression. Consequently, absence of T-bet leads to unrestrained Th17 cell differentiation and activation characterized by high amounts of IL-17A and IL-22. The combined increase in IL-17A/IL-22 results in enhanced epithelial cell activation and inhibition of either IL-17A or IL-22 leads to disease amelioration. Our study identifies T-bet as a key modulator of IL-23-driven colitogenic responses in the intestine and has important implications for understanding of heterogeneity among inflammatory bowel disease patients.

Tbet or Continued RORγt Expression Is Not Required for Th17-Associated Immunopathology

The discovery of Th17 cell plasticity, in which CD4⁺ IL-17–producing Th17 cells give rise to IL-17/IFN-γ double-producing cells and Th1-like IFNγ⁺ ex-Th17 lymphocytes, has raised questions regarding which of these cell types contribute to immunopathology during inflammatory diseases. In this study, we show using Helicobacter hepaticus-induced intestinal inflammation that IL-17A^Cre– or Rag1^Cre-mediated deletion of Tbx21 has no effect on the generation of IL-17/IFN-γ double-producing cells, but leads to a marked absence of Th1-like IFNγ⁺ ex-Th17 cells. Despite the lack of Th1-like ex-Th17 cells, the degree of H. hepaticus-triggered intestinal inflammation in mice in which Tbx21 was excised in IL-17–producing or Rag1-expressing cells is indistinguishable from that observed in control mice. In stark contrast, using experimental autoimmune encephalomyelitis, we show that IL-17A^Cre–mediated deletion of Tbx21 prevents the conversion of Th17 cells to IL-17A/IFN-γ double-producing cells as well as Th1-like IFN-γ⁺ ex-Th17 cells. However, IL-17A^Cre–mediated deletion of Tbx21 has only limited effects on disease course in this model and is not compensated by Ag-specific Th1 cells. IL-17A^Cre–mediated deletion of Rorc reveals that RORγt is essential for the maintenance of the Th17 cell lineage, but not immunopathology during experimental autoimmune encephalomyelitis. These results show that neither the single Th17 subset, nor its progeny, is solely responsible for immunopathology or autoimmunity.

CD4 T cells are required for both development and maintenance of disease in a new mouse model of reversible colitis

Current therapies to treat inflammatory bowel diseases have limited efficacy, significant side effects, and often wane over time. Little is known about the cellular and molecular mechanisms operative in the process of mucosal healing from colitis. To study such events, we developed a new model of reversible colitis in which adoptive transfer of CD4(+)CD45RB(hi) T cells into Helicobacter typhlonius-colonized lymphopenic mice resulted in a rapid onset of colonic inflammation that was reversible through depletion of colitogenic T cells. Remission was associated with an improved clinical and histopathological score, reduced immune cell infiltration to the intestinal mucosa, altered intestinal gene expression profiles, regeneration of the colonic mucus layer, and the restoration of epithelial barrier integrity. Notably, colitogenic T cells were not only critical for induction of colitis but also for maintenance of disease. Depletion of colitogenic T cells resulted in a rapid drop in tumor necrosis factor α (TNFα) levels associated with reduced infiltration of inflammatory immune cells to sites of inflammation. Although neutralization of TNFα prevented the onset of colitis, anti-TNFα treatment of mice with established disease failed to resolve colonic inflammation. Collectively, this new model of reversible colitis provides an important research tool to study the dynamics of mucosal healing in chronic intestinal remitting-relapsing disorders.

Cytokine-Induced Modulation of Colorectal Cancer

The emergence of novel immunomodulatory cancer therapies over the last decade, above all immune checkpoint blockade, has significantly advanced tumor treatment. For colorectal cancer (CRC), a novel scoring system based on the immune cell infiltration in tumors has greatly improved disease prognostic evaluation and guidance to more specific therapy. These findings underline the relevance of tumor immunology in the future handling and therapeutic approach of malignant disease. Inflammation can either promote or suppress CRC pathogenesis and inflammatory mediators, mainly cytokines, critically determine the pro- or anti-tumorigenic signals within the tumor environment. Here, we review the current knowledge on the cytokines known to be critically involved in CRC development and illustrate their mechanisms of action. We also highlight similarities and differences between CRC patients and murine models of CRC and point out cytokines with an ambivalent role for intestinal cancer. We also identify some of the future challenges in the field that should be addressed for the development of more effective immunomodulatory therapies.