CpG motifs of bacterial DNA exert protective effects in mouse models of IBD by antigen-independent tolerance induction

Engaging natural antibody responses for the treatment of inflammatory bowel disease via phosphorylcholine-presenting nanofibres

Inflammatory bowel disease lacks a long-lasting and broadly effective therapy. Here, by taking advantage of the anti-infection and anti-inflammatory properties of natural antibodies against the small-molecule epitope phosphorylcholine (PC), we show in multiple mouse models of colitis that immunization of the animals with self-assembling supramolecular peptide nanofibres bearing PC epitopes induced sustained levels of anti-PC antibodies that were both protective and therapeutic. The strength and type of immune responses elicited by the nanofibres could be controlled through the relative valency of PC epitopes and exogenous T-cell epitopes on the nanofibres and via the addition of the adjuvant CpG. The nanomaterial-assisted induction of the production of therapeutic antibodies may represent a durable therapy for inflammatory bowel disease.

Circular and Circulating DNA in Inflammatory Bowel Disease: From Pathogenesis to Potential Molecular Therapies

Inflammatory bowel diseases (IBD), including Crohn's Disease (CD) and Ulcerative Colitis (UC) are chronic multifactorial disorders which affect the gastrointestinal tract with variable extent. Despite extensive research, their etiology and exact pathogenesis are still unknown. Cell-free DNAs (cfDNAs) are defined as any DNA fragments which are free from the origin cell and able to circulate into the bloodstream with or without microvescicles. CfDNAs are now being increasingly studied in different human diseases, like cancer or inflammatory diseases. However, to date it is unclear how IBD etiology is linked to cfDNAs in plasma. Extrachromosomal circular DNA (eccDNA) are non-plasmidic, nuclear, circular and closed DNA molecules found in all eukaryotes tested. CfDNAs appear to play an important role in autoimmune diseases, inflammatory processes, and cancer; recently, interest has also grown in IBD, and their role in the pathogenesis of IBD has been suggested. We now suggest that eccDNAs also play a role in IBD. In this review, we have comprehensively collected available knowledge in literature regarding cfDNA, eccDNA, and structures involving them such as neutrophil extracellular traps and exosomes, and their role in IBD. Finally, we focused on old and novel potential molecular therapies and drug delivery systems, such as nanoparticles, for IBD treatment.

CpG Adjuvant in Allergen-Specific Immunotherapy: Finding the Sweet Spot for the Induction of Immune Tolerance

Prevalence and incidence of IgE-mediated allergic diseases have increased over the past years in developed and developing countries. Allergen-specific immunotherapy (AIT) is currently the only curative treatment available for allergic diseases that has long-term efficacy. Although AIT has been proven successful as an immunomodulatory therapy since its beginnings, it still faces several unmet needs and challenges today. For instance, some patients can experience severe side effects, others are non-responders, and prolonged treatment schedules can lead to lack of patient adherence and therapy discontinuation. A common strategy to improve AIT relies on the use of adjuvants and immune modulators to boost its effects and improve its safety. Among the adjuvants tested for their clinical efficacy, CpG oligodeoxynucleotide (CpG-ODN) was investigated with limited success and without reaching phase III trials for clinical allergy treatment. However, recently discovered immune tolerance-promoting properties of CpG-ODN place this adjuvant again in a prominent position as an immune modulator for the treatment of allergic diseases. Indeed, it has been shown that the CpG-ODN dose and concentration are crucial in promoting immune regulation through the recruitment of pDCs. While low doses induce an inflammatory response, high doses of CpG-ODN trigger a tolerogenic response that can reverse a pre-established allergic milieu. Consistently, CpG-ODN has also been found to stimulate IL-10 producing B cells, so-called B regulatory cells (Bregs). Accordingly, CpG-ODN has shown its capacity to prevent and revert allergic reactions in several animal models showing its potential as both preventive and active treatment for IgE-mediated allergy. In this review, we describe how CpG-ODN-based therapies for allergic diseases, despite having shown limited success in the past, can still be exploited further as an adjuvant or immune modulator in the context of AIT and deserves additional attention. Here, we discuss the past and current knowledge, which highlights CpG-ODN as a potential adjuvant to be reevaluated for the enhancement of AIT when used in appropriate conditions and formulations.

Tolerizing Strategies for the Treatment of Autoimmune Diseases: From ex vivo to in vivo Strategies

Autoimmune diseases such as multiple sclerosis (MS), type I diabetes (T1D), inflammatory bowel diseases (IBD), and rheumatoid arthritis (RA) are chronic, incurable, incapacitating and at times even lethal conditions. Worldwide, millions of people are affected, predominantly women, and their number is steadily increasing. Currently, autoimmune patients require lifelong immunosuppressive therapy, often accompanied by severe adverse side effects and risks. Targeting the fundamental cause of autoimmunity, which is the loss of tolerance to self- or innocuous antigens, may be achieved via various mechanisms. Recently, tolerance-inducing cellular therapies, such as tolerogenic dendritic cells (tolDCs) and regulatory T cells (Tregs), have gained considerable interest. Their safety has already been evaluated in patients with MS, arthritis, T1D, and Crohn’s disease, and clinical trials are underway to confirm their safety and therapeutic potential. Cell-based therapies are inevitably expensive and time-consuming, requiring laborious ex vivo manufacturing. Therefore, direct in vivo targeting of tolerogenic cell types offers an attractive alternative, and several strategies are being explored. Type I IFN was the first disease-modifying therapy approved for MS patients, and approaches to endogenously induce IFN in autoimmune diseases are being pursued vigorously. We here review and discuss tolerogenic cellular therapies and targeted in vivo tolerance approaches and propose a novel strategy for cell-specific delivery of type I IFN signaling to a cell type of choice.

Lactobacillus rhamnosus GG components, SLP, gDNA and CpG, exert protective effects on mouse macrophages upon lipopolysaccharide challenge

The aim of this study was to determine whether Lactobacillus rhamnosus GG (LGG) components (surface layer protein, SLP; genomic DNA, gDNA; unmethylated cytosine-phosphate-guanine-containing oligodeoxynucleotide, CpG-ODN), alone or in combination, could affect immunomodulation, and evaluate the signalling mechanism in mouse macrophage RAW264.7 cells challenged with lipopolysaccharide (LPS). LGG components were used to treat cells before LPS stimulation. Cytokine and Toll-like receptor (TLR) expression were assessed using real-time quantitative PCR (RT-qPCR). Mitogen-activated protein kinase (MAPK), extracellular regulated protein kinase (ERK) and nuclear factor-kappa B (NF-κB) signalling pathways were evaluated using immunoblots and immunofluorescence. SLP or SLP + gDNA pre-treatment significantly reduced the LPS-induced mRNA expression of tumour necrosis factor alpha (TNF-α). Pre-treatment with LGG single components (SLP, gDNA or CpG) or their combinations (SLP + gDNA or SLP + CpG) significantly decreased the LPS-induced interleukin-6 (IL-6) mRNA level (P < 0·05). Pre-treatment with SLP or gDNA, alone or in combination, significantly suppressed LPS-induced TLR2 and TLR4 mRNA levels (P < 0·05). SLP pre-treatment also significantly decreased the LPS-induced expression of TLR9 (P < 0·05). Pre-treatment with LGG single components or combinations significantly suppressed the LPS-induced phosphorylation levels of ERK (P > 0·05). In conclusion, pre-incubation with LGG components, singly or in combination, generally inhibited the activation of TLR, MAPK and NF-κB signalling pathways in LPS-stimulated cells, leading to attenuated inflammatory cytokine TNF-α and IL-6 production. These results indicate that nonviable probiotic LGG components exert an anti-inflammation effect on epithelial cells. SIGNIFICANCE AND IMPACT OF THE STUDY: Lactobacillus rhamnosus GG (LGG) is widely used as probiotics. However, its main components are not well known for affecting immunomodulation. This study investigated the effects of pre-treatments with different components such as surface layer protein, genomic DNA and unmethylated cytosine-phosphate-guanine-containing oligodeoxynucleotides, alone or in combination on immunomodulation, and evaluated the signalling mechanism in mouse macrophage RAW264.7 cells challenged with lipopolysaccharide. Pre-incubation with components alone or in combination generally inhibited the activation of Toll-like receptor, mitogen-activated protein kinases, extracellular regulated protein kinases and nuclear factor-kappa B signalling pathways in lipopolysaccharide-stimulated cells, which generally leads to attenuated inflammatory cytokine interleukin-6 and tumour necrosis factor alpha production. These results indicate that nonviable probiotic LGG components exert an anti-inflammation effect on epithelial cells.

Composition and immuno-stimulatory properties of extracellular DNA from mouse gut flora

AIM

To demonstrate that specific bacteria might release bacterial extracellular DNA (eDNA) to exert immunomodulatory functions in the mouse small intestine.

METHODS

Extracellular DNA was extracted using phosphate buffered saline with 0.5 mmol/L dithiothreitol combined with two phenol extractions. TOTO-1 iodide, a cell-impermeant and high-affinity nucleic acid stain, was used to confirm the existence of eDNA in the mucus layers of the small intestine and colon in healthy Male C57BL/6 mice. Composition difference of eDNA and intracellular DNA (iDNA) of the small intestinal mucus was studied by Illumina sequencing and terminal restriction fragment length polymorphism (T-RFLP). Stimulation of cytokine production by eDNA was studied in RAW264.7 cells in vitro.

RESULTS

TOTO-1 iodide staining confirmed existence of eDNA in loose mucus layer of the mouse colon and thin surface mucus layer of the small intestine. Illumina sequencing analysis and T-RFLP revealed that the composition of the eDNA in the small intestinal mucus was significantly different from that of the iDNA of the small intestinal mucus bacteria. Illumina Miseq sequencing showed that the eDNA sequences came mainly from Gram-negative bacteria of Bacteroidales S24-7. By contrast, predominant bacteria of the small intestinal flora comprised Gram-positive bacteria. Both eDNA and iDNA were added to native or lipopolysaccharide-stimulated Raw267.4 macrophages, respectively. The eDNA induced significantly lower tumor necrosis factor-α/interleukin-10 (IL-10) and IL-6/IL-10 ratios than iDNA, suggesting the predominance for maintaining immune homeostasis of the gut.

CONCLUSION

Our results indicated that degraded bacterial genomic DNA was mainly released by Gram-negative bacteria, especially Bacteroidales-S24-7 and Stenotrophomonas genus in gut mucus of mice. They decreased pro-inflammatory activity compared to total gut flora genomic DNA.

DNA Transfer and Toll-like Receptor Modulation by Helicobacter pylori

Helicobacter pylori is the most common bacterial infection worldwide, and virtually all infected persons develop co-existing gastritis. H. pylori is able to send and receive signals from the gastric mucosa, which enables both host and microbe to engage in a dynamic equilibrium. In order to persist within the human host, H. pylori has adopted dichotomous strategies to both induce inflammation as a means of liberating nutrients while simultaneously tempering the immune response to augment its survival. Toll-like receptors (TLRs) and Nod proteins are innate immune receptors that are present in epithelial cells and represent the first line of defense against pathogens. To ensure persistence, H. pylori manipulates TLR-mediated defenses using strategies that include rendering its LPS and flagellin to be non-stimulatory to TLR4 and TLR5, respectively; translocating peptidoglycan into host cells to induce NOD1-mediated anti-inflammatory responses; and translocating DNA into host cells to induce TLR9 activation.

The Protective Role of Type I Interferons in the Gastrointestinal Tract

The immune system of the gastrointestinal (GI) tract manages the significant task of recognizing and eliminating pathogens while maintaining tolerance of commensal bacteria. Dysregulation of this delicate balance can be detrimental, resulting in severe inflammation, intestinal injury, and cancer. Therefore, mechanisms to relay important signals regulating cell growth and immune reactivity must be in place to support GI homeostasis. Type I interferons (IFN-I) are a family of pleiotropic cytokines, which exert a wide range of biological effects including promotion of both pro- and anti-inflammatory activities. Using animal models of colitis, investigations into the regulation of intestinal epithelium inflammation highlight the role of IFN-I signaling during fine modulation of the immune system. The intestinal epithelium of the gut guides the immune system to differentiate between commensal and pathogenic microbiota, which relies on intimate links with the IFN-I signal-transduction pathway. The current paradigm depicts an IFN-I-induced antiproliferative state in the intestinal epithelium enabling cell differentiation, cell maturation, and proper intestinal barrier function, strongly supporting its role in maintaining baseline immune activity and clearance of damaged epithelia or pathogens. In this review, we will highlight the importance of IFN-I in intestinal homeostasis by discussing its function in inflammation, immunity, and cancer.

Type 1 Interferon in the Human Intestine-A Co-ordinator of the Immune Response to the Microbiota

The human gut is in constant complex interaction with the external environment. Although much is understood about the composition and function of the microbiota, much remains to be learnt about the mechanisms by which these organisms interact with the immune system in health and disease. Type 1 interferon (T1IFN), a ubiquitous and pleiotropic family of cytokines, is a critical mediator of the response to viral, bacterial, and other antigens sampled in the intestine. Although inflammation is enhanced in mouse model of colitis when T1IFN signaling is lost, the action of T1IFN is context specific and can be pro- or anti-inflammatory. In humans, T1IFN has been used to treat inflammatory diseases, including multiple sclerosis and inflammatory bowel disease but intestinal inflammation can also develop after the administration of T1IFN. Recent findings indicate that "tonic" or "endogenous" T1IFN, induced by signals from the commensal microbiota, modulates the local signaling environment to prime the intestinal mucosal immune system to determine later responses to pathogens and commensal organisms. This review will summarize the complex immunological effects of T1IFN and recent the role of T1IFN as a mediator between the microbiota and the mucosal immune system, highlighting human data wherever possible. It will discuss what we can learn from clinical experiences with T1IFN and how the T1IFN pathway may be manipulated in the future to maintain mucosal homeostasis.

Regulation of human intestinal T-cell responses by type 1 interferon-STAT1 signaling is disrupted in inflammatory bowel disease

Type 1 interferon (IFN-1) promotes regulatory T-cell function to suppress inflammation in the mouse intestine, but little is known about IFN-1 in the human gut. We therefore assessed the influence of IFN-1 on CD4+ T-cells isolated from human colon tissue obtained from healthy controls or patients with inflammatory bowel disease (IBD). Immunofluorescent imaging revealed constitutive expression of IFNβ in human intestinal tissue, and colonic T-cells were responsive to exogenous IFN-1 as assessed by phosphorylation of signal transduction and activator of transcription 1 (pSTAT1) and induction of interferon stimulated genes (ISGs). Unlike their blood counterparts, intestinal T-cells from non-inflamed regions of IBD colon displayed enhanced responsiveness to IFN-1, increased frequency of pSTAT1+ cells, and greater induction of ISGs upon IFN-1 exposure in vitro. In healthy tissue, antibody neutralization of IFNβ selectively reduced T-cell production of the pro-regulatory cytokine interleukin-10 (IL-10) and increased IFNγ synthesis. In contrast, neutralization of IFNβ in IBD tissue cultures increased the frequency of T-cells producing inflammatory cytokines but did not alter IL-10 expression. These data support a role for endogenous IFN-1 as a context-dependent modulator of T-cell function that promotes regulatory activity in healthy human intestine, but indicate that the IFN-1/STAT1 pathway is dysregulated in inflammatory bowel disease.

Ameliorating Active Ulcerative Colitis via an Orally Available Toll-Like Receptor-9 Modifier: A Prospective Open-Label, Multicenter Phase II Trial

BACKGROUND

Treatment of active ulcerative colitis is associated with incomplete efficacy, adverse events, and loss of response. Toll-like receptor-9 mediates innate and adaptive immune response toward intestinal microorganisms. The oral synthetic oligonucleotide toll-like receptor-9 modulator has demonstrated anti-inflammatory properties in colitis murine models and a satisfactory safety profile in humans.

AIM

To evaluate the efficacy and safety of BL-7040 (a Toll-like receptor-9 modulator) in patients with moderately active ulcerative colitis.

METHODS

Moderately active ulcerative colitis patients were included in this multicenter, open-label phase IIa trial. Concomitant mesalamine and steroids at a stable dose were allowed. Clinical outcome was evaluated using the Mayo score, histology, and mucosal cytokine levels. Side effects were registered.

RESULTS

Sixteen out of 22 patients completed a 5-week treatment course and 2-week follow-up. Six patients discontinued the study, three of them due to adverse events. Clinical remission was observed in two patients (12.5 %), and clinical response as well as mucosal healing were achieved in half (50 %) of the patients, while all others remained stable. Furthermore, mucosal neutrophil (p = 0.002) and mucosal interleukin-6 levels (p = 0.046) were significantly reduced in responders compared to non-responders. Toll-like receptor-9 was well tolerated with only one unrelated to study drug serious adverse event (hemoglobin decrease) and 29 mild-to-moderate adverse events.

CONCLUSIONS

Oral administration of the Toll-like receptor-9 agonist BL-7040 appeared efficacious, safe and well tolerated in patients with moderately active ulcerative colitis.

A Multihit Model: Colitis Lessons from the Interleukin-10-deficient Mouse

Complex mechanisms are pulling the strings to initiate the development of inflammatory bowel disease. Current evidence indicates that an interaction of genetic susceptibilities (polymorphisms), environmental factors, and the host microbiota leads to a dysregulation of the mucosal immune system. In the past decades, the interleukin-10-deficient mouse has served as an excellent model to mirror the multifactorial nature of this disease. Here, we want to review in detail the interplay of the genetic factors, immune aspects, and especially summarize and discuss the role of the microbiota contributing to colitis development in the interleukin-10-deficient mouse model of inflammatory bowel disease as a multihit model.

The role of type I interferons in intestinal infection, homeostasis, and inflammation

Type I interferons are a widely expressed family of effector cytokines that promote innate antiviral and antibacterial immunity. Paradoxically, they can also suppress immune responses by driving production of anti-inflammatory cytokines, and dysregulation of these cytokines can contribute to host-mediated immunopathology and disease progression. Recent studies describe their anti-inflammatory role in intestinal inflammation and the locus containing IFNAR, a heterodimeric receptor for the type I interferons has been identified as a susceptibility region for human inflammatory bowel disease. This review focuses on the role of type I IFNs in the intestine in health and disease and their emerging role as immune modulators. Clear understanding of type I IFN-mediated immune responses may provide avenues for fine-tuning existing IFN treatment for infection and intestinal inflammation.

Norovirus triggered microbiota-driven mucosal inflammation in interleukin 10-deficient mice

BACKGROUND

Infection may trigger clinically overt mucosal inflammation in patients with predisposition for inflammatory bowel disease. However, the impact of particular enteropathogenic microorganisms is ill-defined. In this study, the influence of murine norovirus (MNV) infection on clinical, histopathological, and immunological features of mucosal inflammation in the IL10-deficient (Il10) mouse model of inflammatory bowel disease was examined.

METHODS

C57BL/6J and C3H/HeJBir wild-type and Il10 mice kept under special pathogen-free conditions and devoid of clinical and histopathological signs of mucosal inflammation were monitored after MNV infection for structural and functional intestinal barrier changes by in situ MNV reverse transcription PCR, transgene reporter gene technology, histology, flux measurements, quantitative real-time PCR, immunohistology, and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay. In addition, the influence of the enteric microbiota was analyzed in MNV-infected germfree Il10 mice.

RESULTS

Although MNV-infected wild-type mice remained asymptomatic, mucosal inflammation was noted in previously healthy Il10 mice 2 to 4 weeks after infection. MNV-induced changes in Il10 mice included increased paracellular permeability indicated by increased mucosal mannitol flux, reduced gene expression of tight junction molecules, and an enhanced rate of epithelial apoptosis. MNV-induced reduction of tight junction protein expression and inflammatory lesions were absent in germfree Il10 mice, whereas epithelial apoptosis was still observed.

CONCLUSIONS

Despite its subclinical course in wild-type animals, MNV causes epithelial barrier disruption in Il10 animals representing a potent colitogenic stimulus that largely depends on the presence of the enteric microbiota. MNV might thus trigger overt clinical disease in individuals with a nonsymptomatic predisposition for inflammatory bowel disease by impairment of the intestinal mucosa.

Protective role for Toll-like receptor-9 in the development of atherosclerosis in apolipoprotein E-deficient mice

OBJECTIVE

Atherosclerosis is driven by inflammatory reactions that are shared with the innate immune system. Toll-like receptor-9 (TLR9) is an intracellular pattern recognition receptor of the innate immune system that is currently under clinical investigation as a therapeutic target in inflammatory diseases. Here, we investigated whether TLR9 has a role in the development of atherosclerosis in apolipoprotein E-deficient (ApoE(-/-)) mice.

APPROACH AND RESULTS

Newly generated double-knockout ApoE(-/-):TLR9(-/-) mice and control ApoE(-/-) mice were fed a high-fat diet from 8 weeks and effects on lesion size, cellular composition, inflammatory status, and plasma lipids were assessed after 8, 12, 15, and 20 weeks. All 4 time points demonstrated exacerbated atherosclerotic lesion severity in ApoE(-/-):TLR9(-/-) mice, with a corresponding increase in lipid deposition and accumulation of macrophages, dendritic cells, and CD4(+) T cells. Although ApoE(-/-):TLR9(-/-) mice exhibited an increase in plasma very low-density lipoprotein/low-density-lipoprotein cholesterol, the very low-density lipoprotein/low-density lipoprotein:high-density lipoprotein ratio was unaltered because of a parallel increase in plasma high-density lipoprotein cholesterol. As a potential mechanism accounting for plaque progression in ApoE(-/-):TLR9(-/-) mice, CD4(+) T-cell accumulation was further investigated and depletion of these cells in ApoE(-/-):TLR9(-/-) mice significantly reduced lesion severity. As a final translational approach, administration of a TLR9 agonist (type B CpG oligodeoxynucleotide 1668) to ApoE(-/-) mice resulted in a reduction of lesion severity.

CONCLUSIONS

Genetic deletion of the innate immune receptor TLR9 exacerbated atherosclerosis in ApoE(-/-) mice fed a high-fat diet. CD4(+) T cells were identified as potential mediators of this effect. A type B CpG oligodeoxynucleotide TLR9 agonist reduced lesion severity, thus identifying a novel therapeutic approach in atherosclerosis.

Physiologic TLR9-CpG-DNA interaction is essential for the homeostasis of the intestinal immune system

BACKGROUND

Cytosine-guanosine dinucleotide (CpG) motifs are immunostimulatory components of bacterial DNA and activators of innate immunity through Toll-like receptor 9 (TLR9). Administration of CpG oligodeoxynucleotides before the onset of experimental colitis prevents intestinal inflammation by enforcement of regulatory mechanisms. It was investigated whether physiologic CpG/TLR9 interactions are critical for the homeostasis of the intestinal immune system.

METHODS

Mesenteric lymph node cell and lamina propria mononuclear cell (LPMC) populations from BALB/c wild-type (wt) or TLR9 mice were assessed by flow cytometry and proteome profiling. Cytokine secretion was determined and nuclear extracts were analyzed for nuclear factor kappa B (NF-κB) and cAMP response-element binding protein activity. To assess the colitogenic potential of intestinal T cells, CD4-enriched cells from LPMC of wt or TLR9 donor mice were injected intraperitoneally in recipient CB-17 SCID mice.

RESULTS

TLR9 deficiency was accompanied by slight changes in cellular composition and phosphorylation of signaling proteins of mesenteric lymph node cell and LPMC. LPMC from TLR9 mice displayed an increased proinflammatory phenotype compared with wt LPMC. NF-κB activity in cells from TLR9 mice was enhanced, whereas cAMP response-element binding activity was reduced compared with wt. Transfer of lamina propria CD4-enriched T cells from TLR9 mice induced severe colitis, whereas wt lamina propria CD4-enriched T cells displayed an attenuated phenotype.

CONCLUSIONS

Lack of physiologic CpG/TLR9 interaction impairs the function of the intestinal immune system indicated by enhanced proinflammatory properties. Thus, physiologic CpG/TLR interaction is essential for homeostasis of the intestinal immune system as it is required for the induction of counterregulating anti-inflammatory mechanisms.

Influence of donor microbiota on the severity of experimental graft-versus-host-disease

The link between microbial flora and the shaping of immune responses is being increasingly appreciated, and recent data have uncovered a role for recipient microbiota in the severity of graft-versus-host disease (GVHD). The impact of donor microbiota on T cell-mediated alloresponses and GVHD is not known, however. Using multiple clinically relevant murine models, we analyzed the effect of donor microbiota on the severity of GVHD induced by T cells from specific pathogen-free and germ-free donors, and found that donor microbiota does not alter the expansion or differentiation of alloreactive T cells or the severity of GVHD.

Strain-specific colitis susceptibility in IL10-deficient mice depends on complex gut microbiota-host interactions

BACKGROUND

Colitis susceptibility in Il10(-/-) mice depends on genetic background and microbiota composition. A major genetic locus mediating colitis susceptibility, Cdcs1, was transferred from susceptible C3Bir-Il10(-/-) to resistant B6-Il10(-/-) mice, resulting in susceptible congenic BC-R3-Il10(-/-) mice. The aim of this study was to determine the impact of microbiota on this differential colitis susceptibility using a Helicobacter hepaticus infection model.

METHODS

Parental C3Bir-Il10(-/-) , B6-Il10(-/-) , and congenic BC-R3-Il10(-/-) mice were inoculated with H. hepaticus and analyzed for inflammation. In parental Il10(-/-) mice, microbiota composition was determined by terminal restriction fragment length polymorphism (T-RFLP) and quantitative polymerase chain reaction (qPCR).

RESULTS

Most severe inflammation was observed in C3Bir-Il10(-/-) in the cecum, in BC-R3-Il10(-/-) in cecum and colon, and, unexpectedly, in B6-Il10(-/-) in the colon. C3Bir-Il10(-/-) and BC-R3-Il10(-/-) secreted significantly more interferon-gamma (IFNγ) and interleukin (IL)17 than B6-Il10(-/-) . T-RFLP analyses in C3Bir-Il10(-/-) and B6-Il10(-/-) mice revealed 1) a significant impact of H. hepaticus infection on species richness and diversity, and 2) strain differences in microbiota composition only after H. hepaticus infection. qPCR revealed higher numbers of Clostridia leptum and Bacteroides spp. in the cecum of infected C3Bir-Il10(-/-) mice, and Lactobacillus spp. in B6-Il10(-/-) mice.

CONCLUSIONS

Cdcs1 modifies the response to H. hepaticus infection. However, this infection alone does not reflect the original response to a complex colitogenic biota. H. hepaticus-induced inflammation altered intestinal microbiota in a mouse strain-specific manner. Bacteroides spp. became more abundant in susceptible C3Bir-Il10(-/-) , lactobacilli in B6-Il10(-/-) mice. Therefore, both host immune response and differential compositional changes of microbiota play a role in strain-specific colitis susceptibility in Il10(-/-) mice.

Influence of dietary components on regulatory T cells

Common dietary components including vitamins A and D, omega-3 and probiotics are now widely accepted to be essential to protect against many diseases with an inflammatory nature. On the other hand, high-fat diets are documented to exert multiple deleterious effects, including fatty liver diseases. Here we discuss the effect of dietary components on regulatory T cell (Treg) homeostasis, a central element of the immune system to prevent chronic tissue inflammation. Accordingly, evidence on the impact of dietary components on diseases in which Tregs play an influential role will be discussed. We will review chronic tissue-specific autoimmune and inflammatory conditions such as inflammatory bowel disease, type 1 diabetes mellitus, multiple sclerosis, rheumatoid arthritis and allergies among chronic diseases where dietary factors could have a direct influence via modulation of Tregs homeostasis and functions.

Campylobacter jejuni disrupts protective Toll-like receptor 9 signaling in colonic epithelial cells and increases the severity of dextran sulfate sodium-induced colitis in mice

Inflammatory bowel disease (IBD) is characterized by chronic intestinal inflammation associated with a dysregulated immune response to commensal bacteria in susceptible individuals. The relapse of IBD may occur following an infection with Campylobacter jejuni. Apical epithelial Toll-like receptor 9 (TLR9) activation by bacterial DNA is reported to maintain colonic homeostasis. We investigated whether a prior C. jejuni infection disrupts epithelial TLR9 signaling and increases the severity of disease in a model of mild dextran sulfate sodium (DSS) colitis in mice. In a further attempt to identify mechanisms, T84 monolayers were treated with C. jejuni followed by a TLR9 agonist. Transepithelial resistance (TER) and dextran flux across confluent monolayers were monitored. Immunohistochemistry, Western blotting, and flow cytometry were used to examine TLR9 expression. Mice colonized by C. jejuni lacked any detectable pathology; however, in response to low levels of DSS, mice previously exposed to C. jejuni exhibited significantly reduced weight gain and increased occult blood and histological damage scores. Infected mice treated with DSS also demonstrated a significant reduction in levels of the anti-inflammatory cytokine interleukin-25. In vitro studies indicated that apical application of a TLR9 agonist enhances intestinal epithelial barrier function and that this response is lost in C. jejuni-infected monolayers. Furthermore, infected cells secreted significantly more CXCL8 following the basolateral application of a TLR9 agonist. Surface TLR9 expression was reduced in C. jejuni-infected monolayers subsequently exposed to a TLR9 agonist. In conclusion, infection by C. jejuni disrupts TLR9-induced reinforcement of the intestinal epithelial barrier, and colonization by C. jejuni increases the severity of mild DSS colitis.

Campylobacter jejuni disrupts protective Toll-like receptor 9 signaling in colonic epithelial cells and increases the severity of dextran sulfate sodium-induced colitis in mice

Inflammatory bowel disease (IBD) is characterized by chronic intestinal inflammation associated with a dysregulated immune response to commensal bacteria in susceptible individuals. The relapse of IBD may occur following an infection with Campylobacter jejuni. Apical epithelial Toll-like receptor 9 (TLR9) activation by bacterial DNA is reported to maintain colonic homeostasis. We investigated whether a prior C. jejuni infection disrupts epithelial TLR9 signaling and increases the severity of disease in a model of mild dextran sulfate sodium (DSS) colitis in mice. In a further attempt to identify mechanisms, T84 monolayers were treated with C. jejuni followed by a TLR9 agonist. Transepithelial resistance (TER) and dextran flux across confluent monolayers were monitored. Immunohistochemistry, Western blotting, and flow cytometry were used to examine TLR9 expression. Mice colonized by C. jejuni lacked any detectable pathology; however, in response to low levels of DSS, mice previously exposed to C. jejuni exhibited significantly reduced weight gain and increased occult blood and histological damage scores. Infected mice treated with DSS also demonstrated a significant reduction in levels of the anti-inflammatory cytokine interleukin-25. In vitro studies indicated that apical application of a TLR9 agonist enhances intestinal epithelial barrier function and that this response is lost in C. jejuni-infected monolayers. Furthermore, infected cells secreted significantly more CXCL8 following the basolateral application of a TLR9 agonist. Surface TLR9 expression was reduced in C. jejuni-infected monolayers subsequently exposed to a TLR9 agonist. In conclusion, infection by C. jejuni disrupts TLR9-induced reinforcement of the intestinal epithelial barrier, and colonization by C. jejuni increases the severity of mild DSS colitis.

Time to include the gut microbiota in the hygienic standardisation of laboratory rodents

The gut microbiota (GM) composition and its impact on animal experiments has become currently dramatically relevant in our days: (1) recent progress in metagenomic technologies, (2) the availability of large scale quantitative analyses to characterize even subtle phenotypes, (3) the limited diversity of laboratory rodent GM due to strict barriers at laboratory animal vendors, and (4) the availability of up to 300.000 different transgenic mouse strains from different sources displaying a huge variety in their GM composition. In this review the GM is described as a variable in animal experiments which need to be reduced for scientific as well as ethical reasons, and strategies how to implement this in routine diagnostic procedures are proposed. We conclude that we have both enough information available to state that the GM has an essential impact on animal models, as well as the methods available to start dealing with these impacts.

Immunomodulatory functions of type I interferons

Interferon-α (IFNα) and IFNβ, collectively known as type I IFNs, are the major effector cytokines of the host immune response against viral infections. However, the production of type I IFNs is also induced in response to bacterial ligands of innate immune receptors and/or bacterial infections, indicating a broader physiological role for these cytokines in host defence and homeostasis than was originally assumed. The main focus of this Review is the underappreciated immunomodulatory functions of type I IFNs in health and disease. We discuss their function in the regulation of innate and adaptive immune responses, the response to bacterial ligands, inflammasome activation, intestinal homeostasis and inflammatory and autoimmune diseases.

DSS induced colitis increases portal LPS levels and enhances hepatic inflammation and fibrogenesis in experimental NASH

BACKGROUND & AIMS

Intestinal bacterial overgrowth and increased permeability are features of non alcoholic steatohepatitis (NASH). Bacterial endotoxin has been shown to promote NASH progression. Application of dextran sulfate sodium (DSS) is a colitis model in mice characterized by damage of the intestinal barrier. This study was designed to investigate if application of DSS aggravates experimental NASH.

METHODS

Male C57bl/6 mice were allocated into four experimental groups receiving either (I) standard chow (SC), (II) a high fat (HF) diet, (III) SC+DSS (1% in the drinking water), and (IV) HF+DSS for 12 weeks.

RESULTS

DSS treatment caused inflammation and proinflammatory gene expression (IL-1β, IL-17, TNF) in the colon. Expression of colonic antimicrobial peptide Cramp was significantly induced in SC+DSS mice, whereas expression was blocked in the HF+DSS group. Endotoxin levels were elevated in SC+DSS and HF mice but further augmented in the HF+DSS group. In line with this, increased hepatic TLR4 and TLR9 mRNA levels were detected in HF+DSS mice. The histological analysis revealed hepatic steatosis in both HF groups. Hepatic inflammation was more severe in HF+DSS mice, reflected by histology and analysis of proinflammatory gene expression (TNF and MCP-1). HF+DSS mice showed increased hepatic fibrosis by sirius red staining, hepatic collagen I expression, and α-SMA positive cells accompanied by higher p47(phox), TIMP-1, TGF-β, Pai-1, and α-SMA mRNA expression.

CONCLUSIONS

Induction of an intestinal inflammation in experimental NASH promotes LPS translocation, hepatic inflammation, and fibrogenesis probably due to inhibition of intestinal antimicrobial peptides. These findings underscore the pathophysiological role of the gut-liver axis in the progression of NASH.

Type I IFN protects against antigen-induced arthritis

Autoimmune diseases including rheumatoid arthritis (RA) involve immune reactions against specific antigens. The type I IFN system is suspected to promote autoimmunity in systemic lupus erythematosus, but may also dampen immune reactions in e.g. inflammatory bowel disease. This prompted us to investigate the role of type I IFN in antigen-induced arthritis (AIA). The importance of type I IFN in methylated (m) BSA-induced arthritis was studied by using mice deficient for the type I IFN receptor (IFNAR) and by administration of the IFN-α activator viral double-stranded (ds) RNA or recombinant IFN-α at antigen sensitization. In IFNAR knock-out mice, arthritis severity was significantly higher than in WT mice. Administration of dsRNA at antigen sensitization protected WT but not IFNAR KO mice from arthritis. Also, addition of recombinant IFN-α during the immunization, but not the induction phase of arthritis, almost abolished arthritis. Protection mediated by IFN-α was accompanied by delayed and decreased antigen-specific proliferative responses, including impaired lymph node recall responses after intra-articular antigenic challenge. In conclusion, we demonstrate that type I IFN can prevent joint inflammation by downregulating antigen-specific cellular immunity.

Glycogen synthase kinase 3-β: a master regulator of toll-like receptor-mediated chronic intestinal inflammation

BACKGROUND

A disturbed regulation of Toll-like receptor (TLR) signal transduction resulting in the exclusive activation of proinflammatory signaling pathways may be critical for the perpetuation of established chronic colitis. Glycogen synthase kinase 3-β (GSK3-β) was recently identified as an important regulator of TLR signaling mediating excessive inflammatory responses. The aim of this study was to assess the role of GSK3-β activity in chronic intestinal inflammation.

METHODS

Chronic colitis was induced by dextran sodium sulfate (DSS) treatment. Mice were treated intraperitoneally with phosphate-buffered saline (PBS), CpG-ODN, or GSK3-β inhibitors (SB216763, LiCl). Intestinal inflammation was evaluated by histologic analysis and cytokine secretion of mesenteric lymph node cells (MLC). Nuclear extracts of MLC and lamina propria mononuclear cells (LPMC) were analyzed for nuclear factor kappaB (NF-κB) and CREB activity. Murine and human intestinal immune cells were stimulated in vitro with CpG-ODN, lipopolysaccharide (LPS), or anti-CD3 with or without LiCl.

RESULTS

GSK3-β blockade significantly reduced chronic intestinal inflammation and even abolished the colitis-intensifying effects of CpG-ODN treatment. In vitro inhibition of GSK3-β reduced the proinflammatory phenotype of both murine and human intestinal immune cells from chronic inflamed tissue. In vivo blockade of GSK3-β resulted in a shift from NF-κB activity toward CREB activity in murine MLC and LPMC.

CONCLUSIONS

Blockade of GSK3-β attenuates excessive proinflammatory TLR-mediated immune responses. GSK3-β inhibition therefore constitutes a promising therapeutic option for selectively reducing exaggerated intestinal immune reactions toward the luminal flora in inflammatory bowel disease.

Toll-like receptors in inflammatory bowel diseases: a decade later

Differential alteration of Toll-like receptor (TLR) expression in inflammatory bowel disease (IBD) was first described 10 years ago. Since then, studies from many groups have led to the current concept that TLRs represent key mediators of innate host defense in the intestine, involved in maintaining mucosal as well as commensal homeostasis. Recent findings in diverse murine models of colitis have helped to reveal the mechanistic importance of TLR dysfunction in IBD pathogenesis. It has become evident that environment, genetics, and host immunity form a multidimensional and highly interactive regulatory triad that controls TLR function in the intestinal mucosa. Imbalanced relationships within this triad may promote aberrant TLR signaling, critically contributing to acute and chronic intestinal inflammatory processes in IBD colitis and associated cancer.

Clinical significance of serum chemerin levels in patients with Crohn's disease

AIM: To analyze the clinical significance of serum chemerin levels in patients with Crohn's disease (CD) by evaluating the correlation of serum chemerin with gender, age and CD activity index (CDAI).

METHODS: Serum samples were collected from 50 CD patients and 50 healthy controls to determine chemerin levels by enzyme-linked immunosorbent assay (ELISA). The t-test was used to compare the statistic difference in serum chemerin levels between the two groups. The correlation of serum chemerin with gender, age and CDAI were analyzed by the t test, one-way analysis of variance, and Pearson's correlation.

RESULTS: Serum chemerin level was significantly higher in CD patients than in healthy controls (124.18 μg/L ± 21.32 μg/L vs 95.38 μg/L ± 11.22 μg/L, P < 0.01). There was a significant positive correlation between serum chemerin level and CDAI (r = 0.438, P < 0.05) though no correlation was noted between serum chemerin level and gender or age in CD patients (both P > 0.05).

CONCLUSION: These findings indicate that the potential regulatory function of chemerin in intestinal inflammation may be associated with the immunopathogenesis of CD.

Inflammatory bowel diseases: when natural friends turn into enemies-the importance of CpG motifs of bacterial DNA in intestinal homeostasis and chronic intestinal inflammation

From numerous studies during the last years it became evident that bacteria and bacterial constituents play a decisive role both in the maintenance of intestinal immune homeostasis as well as in the development and perpetuation of chronic intestinal inflammation. In this review we focus on the role of bacterial DNA which is a potent immunomodulatory component of the bacterial flora. Bacterial DNA has been shown to be protective against experimental colitis. In contrast bacterial DNA essentially contributes to the perpetuation of an already established chronic intestinal inflammation in a Toll-like receptor (TLR)9-dependent manner. This dichotomic action may be explained by a different activation status of essential regulators of TLR signaling like Glycogen synthase kinase 3-β (GSK3-β) depending on the pre-activation status of the intestinal immune system. In this review we suggest that regulators of TLR signaling may be interesting therapeutic targets in IBD aiming at the restoration of intestinal immune homeostasis.

Circulating levels of chemerin and adiponectin are higher in ulcerative colitis and chemerin is elevated in Crohn's disease

BACKGROUND

Chemerin is an adipokine that stimulates chemotaxis of cells of the innate immune system. Inflammatory bowel disease (IBD) is linked to an impaired immune response and, therefore, we hypothesized that systemic chemerin may be altered in IBD patients.

METHODS

Serum was collected from patients with Crohn's disease (CD, 230 patients), ulcerative colitis (UC, 80 patients), and healthy controls (HC, 80 probands). Chemerin and adiponectin, which has already been measured in the serum of similar cohorts by others, were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Chemerin was elevated in IBD compared to HC and was higher in male CD than UC patients. Female and male CD patients had lower adiponectin levels compared to UC, and adiponectin was lower in female CD patients compared to female HC. Adiponectin tended to be higher in female and male UC patients compared to HC and this difference became significant in the whole study group. Correlations with disease activity were only found in males. Here, chemerin was higher in CD patients on remission but was reduced in UC with nonactive disease. Adiponectin was higher in UC with inactive disease. Treatment with corticosteroids was linked to elevated adiponectin in male CD patients and higher chemerin in female UC patients. Unlike adiponectin, which was elevated in female serum in all cohorts, chemerin was only higher in female UC patients.

CONCLUSIONS

These findings further indicate potential regulatory functions of adipokines in intestinal inflammation that are partly gender-dependent and that may even be associated with the distinct immunopathogenesis of UC and CD.

Effect of natural commensal-origin DNA on toll-like receptor 9 (TLR9) signaling cascade, chemokine IL-8 expression, and barrier integritiy of polarized intestinal epithelial cells

BACKGROUND AND AIM

The intestinal epithelium is constantly exposed to high levels of genetic material like bacterial DNA. Under normal physiological conditions, the intestinal epithelial monolayer as a formidable dynamic barrier with a high-polarity structure facilitates only a controlled and selective flux on components between the lumen and the underlining mucosa and even is able to facilitate structure-based macromolecules movement. The aim of this study was to test the effect of natural commensal-origin DNA on the TLR9 signaling cascade and the barrier integrity of polarized intestinal epithelial cells (IECs).

METHODS

: Polarized HT-29 and T84 cells were treated with TNF-alpha in the presence or absence of DNA from Lactobacillus rhamnosus GG (LGG) and Bifidobacterium longum. TLR9 and interleukin-8 (IL-8) mRNA expression was assessed by semiquantitative and TaqMan real-time reverse-transcription polymerase chain reaction. Expression of TLR9 protein, degradation of inhibitor of kappa B alpha (IkappaBalpha), and p38 mitogen-activated protein kinase (p38 MAP) phosphorylation were assessed by Western blotting. To further reveal the role of TLR9 signaling, the TLR9 gene was silenced by siRNA. IL-8 secretion was measured by an enzyme-linked immunosorbent assay. Nuclear factor-kappa B (NF-kappaB) activity was assessed by the electrophoretic mobility shift assay (EMSA) and NF-kappaB-dependent luciferase reporter gene assays. As an indicator of tight junction formation and monolayer integrity of epithelial cell monolayers, transepithelial electrical resistance (TER) was repetitively monitored. Transmonolayer movement of natural commensal-origin DNA across monolayers was monitored using qRT-PCR and nested PCR based on bacterial 16S rRNA genes.

RESULTS

In response to apically applied natural commensal-origin DNA, polarized HT-29 and T84 cells enhanced expression of TLR9 in a specific manner, which was subsequently associated with attenuation of TNF-alpha-induced NF-kappaB activation and NF-kappaB-mediated IL-8 expression. TLR9 silencing abolished this inhibitory effect. Apically applied LGG DNA attenuated TNF-alpha-enhanced NF-kappaB activity by reducing IkappaBalpha degradation and p38 phosphorylation. LGG DNA did not decrease the TER but rather diminished the TNF-alpha-induced TER reduction. Translocation of natural commensal-origin DNA into basolateral compartments did not occur under tested conditions.

CONCLUSIONS

Our study indicates that TLR9 signaling mediates, at least in part, the anti-inflammatory effects of natural commensal-origin DNA on the gut because TLR9 silencing abolished the inhibitory effect of natural commensal-origin DNA on TNF-alpha-induced IL-8 secretion in polarized IECs. The nature of the TLR9 agonist, the polarity of cells, and the tight junction integrity of IECs has to be taken into account in order to predict the outcome of TLR9 signaling. (Inflamm Bowel Dis 2010).

Analysis of Cd14 as a genetic modifier of experimental inflammatory bowel disease (IBD) in mice

BACKGROUND AND AIM

By combining QTL and gene expression analyses, we have previously identified Cd14 as a potential candidate gene contributing to the differential IBD susceptibility of C3H/HeJBir (C3/J)-Il10(-/-) mice [carrying IBD-resistance alleles at this QTL (Cdcs6)] and C57BL/6J (B6)-Il10(-/-) mice, corroborating studies that showed an association of a CD14-promoter polymorphism with Crohn's disease and ulcerative colitis. The aim of the present study was to analyze the molecular mechanisms leading to differential intestinal expression of Cd14 and its contribution to IBD development.

METHODS

Intestinal CD14 expression was assessed by FACS, immunohistochemistry, and ELISA on supernatants of primary epithelial cell and tissue cultures. RAW264.7 cells were stimulated with LPS and PGN in the presence or absence of CD14. Cd14 alleles were sequenced and promoters cloned for luciferase assays in transfected RAW264.7 cells. The severity of typhlocolitis between Cd14(-/-) and wild-type mice was compared in 2 distinct mouse models of IBD (acute DSS and Il10(-/-) ).

RESULTS

In the gut, CD14 was detected mainly in its soluble form (sCD14), with higher expression in C3/J-Il10(-/-) mice. Polymorphisms in C3/J mice caused higher activity of the Cd14 promoter (luciferase assays). Intestinal sCD14 concentrations influenced the LPS and PGN responses of RAW264.7 cells. In vivo, genetic deletion of Cd14 aggravated colitis in both mouse models of IBD.

CONCLUSIONS

Our study shows that Cd14-promoter polymorphisms affect CD14 expression and confirms the protective effect of CD14 against experimental IBD, potentially mediated by TLR2- and TLR4-dependent effects on intestinal barrier function. These findings support the concept that human CD14-promoter polymorphisms contribute to disease development.

GM-CSF-induced CD11c+CD8a--dendritic cells facilitate Foxp3+ and IL-10+ regulatory T cell expansion resulting in suppression of autoimmune thyroiditis

GM-CSF plays an essential role in the differentiation of dendritic cells (DCs). Our studies have shown that GM-CSF treatment can induce semi-mature DCs and CD4+CD25+ regulatory T cells (Tregs) and suppress ongoing autoimmunity in mouse models. In this study, we examined the differences in the potential of GM-CSF to exert tolerogenic function on CD8a+ and CD8a- sub-populations of DCs in vivo. We show that GM-CSF modulates CD8a-, but not CD8a+ DCs in vivo, by inhibiting the surface expression of activation markers MHC II and CD80 and production of inflammatory cytokines such as IL-12 and IL-1beta. Self-antigen [mouse thyroglobulin (mTg)] presentation by GM-CSF-exposed CD8a- DCs to T cells from mTg-primed mice induced a profound increase in the frequency of forkhead box P3 (FoxP3)-expressing T cells compared with antigen presentation by GM-CSF-exposed CD8a+ DCs and control CD8a+ and CD8a- DCs. This tolerogenic property of GM-CD8a- DCs was abrogated when IL-12 was added. GM-CSF-exposed CD8a- DCs could also induce secretion of significantly higher amounts of IL-10 by T cells from mTg-primed mice. Importantly, adoptive transfer of CD8a- DCs from GM-CSF-treated SCID mice, but not untreated mice, into wild-type CBA/J mice prevented the development of experimental autoimmune thyroiditis (EAT) in the recipient animals upon immunization with mTg. Collectively, our results show that GM-CSF renders CD8a- DCs tolerogenic, and these DCs induce Foxp3+ and IL-10+ Tregs.