Treatment with IL-27 attenuates experimental colitis through the suppression of the development of IL-17-producing T helper cells

Inflammatory bowel disease (IBD) represents a group of chronic inflammatory diseases characterized by inflammation and relapsing gastrointestinal disorders. Recent studies have shown that Th17 cells, which are well known as key mediators of chronic inflammation, have a pivotal role in onset and development of IBD in humans and mice, alike. In recent years, it has been reported that IL-27, which is an IL-12-related heterodimeric cytokine consisting of EBI3 and p28 subunits, act directly on naive T cells to suppress the differentiation of Th17 cells. However, effects of exogenous IL-27 on the IBD are not well elucidated. To clarify the suppressive effect of IL-27 treatment on IBD, we applied the flexible linking method to EBI3 and p28 subunits and generated a single-chain human IL-27 (scIL-27). scIL-27 inhibited xenogenic mouse Th17 cell differentiation in vitro, indicating that scIL-27 also acts in mouse immune systems. In a 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced mouse acute colitis model, subcutaneous scIL-27 treatment significantly improved the colon length, extent of necrosis, and ulceration and thickened epithelium and several pathological scores in a dose-dependent manner. scIL-27 clearly suppressed several inflammatory cytokines, including IL-17, in inflamed colon, except for anti-inflammatory cytokine IL-10. The mesenteric lymph node cells from scIL-27-treated mice also exhibited a reduced inflammatory response and, furthermore, a lower population of Th17 cells than those of PBS-treated mice. Finally, we showed the therapeutic efficacy of scIL-27 on TNBS-induced colitis even after active colitis was established. These results suggest new possible therapeutic approaches for IBD, including disorders such as Crohn's disease and ulcerative colitis.     

Heme Oxygenase-1 Ameliorates Dextran Sulfate Sodium-induced Acute Murine Colitis by Regulating Th17/Treg Cell Balance

Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn''s disease, is a group of autoimmune diseases characterized by nonspecific inflammation in the gastrointestinal tract. Recent investigations suggest that activation of Th17 cells and/or deficiency of regulatory T cells (Treg) is involved in the pathogenesis of IBD. Heme oxygenase (HO)-1 is a protein with a wide range of anti-inflammatory and immune regulatory function, which exerts significantly protective roles in various T cell-mediated diseases. In this study, we aim to explore the immunological regulation of HO-1 in the dextran sulfate sodium-induced model of experimental murine colitis. BALB/c mice were administered 4% dextran sulfate sodium orally; some mice were intraperitoneally pretreated with HO-1 inducer hemin or HO-1 inhibitor stannum protoporphyrin IX. The results show that hemin enhances the colonic expression of HO-1 and significantly ameliorates the symptoms of colitis with improved histological changes, accompanied by a decreased proportion of Th17 cells and increased number of Tregs in mesenteric lymph node and spleen. Moreover, induction of HO-1 down-regulates retinoic acid-related orphan receptor γt expression and IL-17A levels, while promoting Treg-related forkhead box p3 (Foxp3) expression and IL-10 levels in colon. Further study in vitro revealed that up-regulated HO-1 switched the naive T cells to Tregs when cultured under a Th17-inducing environment, which involved in IL-6R blockade. Therefore, HO-1 may exhibit anti-inflammatory activity in the murine model of acute experimental colitis via regulating the balance between Th17 and Treg cells, thus providing a possible novel therapeutic target in IBD.     

Mathematical Model of the Roles of T Cells in Inflammatory Bowel Disease

Gut mucosal homeostasis depends on complex interactions among the microbiota, the intestinal epithelium, and the gut associated immune system. A breakdown in some of these interactions may precipitate inflammation. Inflammatory bowel diseases, Crohn’s disease, and ulcerative colitis are chronic inflammatory disorders of the gastrointestinal tract. The initial stages of disease are marked by an abnormally high level of pro-inflammatory helper T cells, Th1. In later stages, Th2 helper cells may dominate while the Th1 response may dampen. The interaction among the T cells includes the regulatory T cells (Treg). The present paper develops a mathematical model by a system of differential equations with terms nonlocal in the space spanned by the concentrations of cytokines that represents the interaction among T cells through a cytokine signaling network. The model demonstrates how the abnormal levels of T cells observed in inflammatory bowel diseases can arise from abnormal regulation of Th1 and Th2 cells by Treg cells.     

Synergy of IL-23 and Th17 Cytokines: New Light on Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs), including Crohn’s disease and ulcerative colitis, involve an interplay between host genetics and environmental factors including intestinal microbiota. Animal models of IBD have indicated that chronic inflammation can result from over-production of inflammatory responses or deficiencies in key negative regulatory pathways. Recent research advances in both T-helper 1 (Th1) and T-helper 17 (Th17) effect responses have offered new insights on the induction and regulation of mucosal immunity which is linked to the development of IBD. Th17 cytokines, such as IL-17 and IL-22, in combination with IL-23, play crucial roles in intestinal protection and homeostasis. IL-23 is expressed in gut mucosa and tends to orchestrate T-cell-independent pathways of intestinal inflammation as well as T cell dependent pathways mediated by cytokines produced by Th1 and Th17 cells. Th17 cells, generally found to be proinflammatory, have specific functions in host defense against infection by recruiting neutrophils and macrophages to infected tissues. Here we will review emerging data on those cytokines and their related regulatory networks that appear to govern the complex development of chronic intestinal inflammation; we will focus on how IL-23 and Th17 cytokines act coordinately to influence the balance between tolerance and immunity in the intestine.     

Inflammatory bowel disease requires the interplay between innate and adaptive immune signals

Inflammatory bowl disease （IBD） is a type 1 T helper cell （Th1）-mediated autoimmune disease. Various studies have revealed that environmental pathogens also play a significant role in the initiation and progression of this disease. Interestingly, the pathogenesis of IBD has been shown to be related to nitric oxide （NO） released from innate immune cells. Although NO is known to be highly toxic to the gut epithelia, there is very little information about the regulation of NO production, One major question in the etiology of IBD is how Thl cells and pathogens interact in the induction of IBD. In present study, we focused on the regulation of NO. We show that macrophages require both interferon-γ, （IFN-γ）-mediated and TLR4-mediated signals for the production of NO, which causes inflammation in the intestine and subsequently IBD. Thus, IBD is the result of concerted actions of innate immune signals, such as the binding of LPS to TLR-4, and adaptive immune signals, such as IFN-γ produced by Thl cells.     

Th17-related cytokines in inflammatory bowel diseases: friends or foes?

T helper (Th)17 cells and other interleukin (IL)-17-producing cells are supposed to play critical roles in several human immune-mediated diseases, including Crohn's disease (CD) and ulcerative colitis (UC), the main forms of inflammatory bowel diseases (IBD) in man. Th17 cells infiltrate massively the inflamed intestine of IBD patients and in vitro and in vivo studies have shown that Th17-type cytokines may trigger and amplify multiple inflammatory pathways. Nonetheless, some Th17-related cytokines, such as interleukin (IL)-17A and IL-22, may target gut epithelial cells and promote the activation of counter-regulatory mechanisms. This observation together with the demonstration that Th17 cells are not stable and can be converted into either regulatory T cells or Th1 cells if stimulated by immune-suppressive (e.g. TGF-β1) or inflammatory (e.g. IL-12, IL-23) cytokines have contributed to advance our understanding of mechanisms that regulate mucosal homeostasis and inflammation in the gut.     

Alteration of V beta usage and cytokine production of CD4+ TCR beta beta homodimer T cells by elimination of Bacteroides vulgatus prevents colitis in TCR alpha-chain-deficient mice

A major pathogenic factor for the development of inflammatory bowel disease (IBD) is the breakdown of the intestinal homeostasis between the host immune system and the luminal microenvironment. To assess the potential influence of luminal Ags on the development of IBD, we fed TCR alpha(-/-) mice an elemental diet (ED). ED-fed TCR alpha(-/-) mice showed no pathologic features of IBD, and their aberrant mucosal B cell responses were suppressed. Similar numbers of CD4(+), TCR betabeta homodimer T cells (betabeta T cells) were developed in the colonic mucosa of ED-fed mice; however, Th2-type cytokine productions were lower than those seen in diseased regular diet (RD)-fed mice. The higher cytokine production in diseased RD-fed mice could be attributed to the high incidence of Bacteroides vulgatus (recovered in 80% of these mice), which can induce Th2-type responses of colonic CD4(+), betabeta T cells. In contrast, ED-fed TCR alpha(-/-) mice exhibited a diversification of Vbeta usage of betabetaT cell populations from the dominant Vbeta8 one associated with B. vulgatus in cecal flora to Vbeta6, Vbeta11, and Vbeta14. Rectal administration of disease-free ED-fed mice with B. vulgatus resulted in the development of Th2-type CD4(+), betabeta T cell-induced colitis. These findings suggest that the ED-induced alteration of intestinal microenvironments such as the enteric flora prevented the development of IBD in TCR alpha(-/-) mice via the immunologic quiescence of CD4(+), betabeta T cells.     

L-cysteine supplementation attenuates local inflammation and restores gut homeostasis in a porcine model of colitis

Background

Inflammatory bowel disease (IBD), a chronic inflammation of the gastrointestinal tract, is characterized by a deregulation of the mucosal immune system and resistance of activated T cells to apoptosis. Current therapeutics show limited efficacy and potential toxicity; therefore there is a need for novel approaches for the treatment of IBD. L-cysteine was examined for its ability to reduce colitis symptoms and modulate local gene expression in a DSS-induced porcine model of colitis.

Methods

Colitis was induced via intra-gastric infusion of dextran sodium sulfate (DSS), followed by the administration of L-cysteine or saline. Clinical signs, morphological measurements, histology and gut permeability were assessed for the prognosis of colitis. Local tissue production of cytokines and gene expression in the colon were analyzed by ELISA and real-time RT-PCR.

Results

L-cysteine supplementation attenuated DSS-induced weight loss and intestinal permeability, reduced local chemokine expression and neutrophil influx, and markedly improved colon histology. Furthermore, cysteine significantly reduced the expression of pro-inflammatory cytokines, including TNF-α, IL-6, IL-12p40, IL-1β, and resulted in increased expression of the apoptosis initiator caspase-8 and decreased expression of the pro-survival genes cFLIP and Bcl-xL.

Conclusions and general significance

These results suggest that L-cysteine administration aids in restoring gut immune homeostasis by attenuating inflammatory responses and restoring susceptibility of activated immune cells to apoptosis, and that cysteine supplementation may be a novel therapeutic strategy for the treatment of IBD.     

Reduced Epithelial Na+/H+ Exchange Drives Gut Microbial Dysbiosis and Promotes Inflammatory Response in T Cell-Mediated Murine Colitis

Inflammatory bowel diseases (IBD) are associated with functional inhibition of epithelial Na⁺/H⁺ exchange. In mice, a selective disruption of NHE3 (Slc9a3), a major apical Na⁺/H⁺ exchanger, also promotes IBD-like symptoms and gut microbial dysbiosis. We hypothesized that disruption of Na⁺/H⁺ exchange is necessary for the development of dysbiosis, which promotes an exacerbated mucosal inflammatory response. Therefore, we performed a temporal analysis of gut microbiota composition, and mucosal immune response to adoptive T cell transfer was evaluated in Rag2^-/- and NHE3^-/-/Rag2^-/- (DKO) mice with and without broad-spectrum antibiotics. Microbiome (16S profiling), colonic histology, T cell and neutrophil infiltration, mucosal inflammatory tone, and epithelial permeability were analyzed. In adoptive T cell transfer colitis model, Slc9a3 status was the most significant determinant of gut microbial community. In DKO mice, NHE3-deficiency and dysbiosis were associated with dramatically accelerated and exacerbated disease, with rapid body weight loss, increased mucosal T cell and neutrophil influx, increased mucosal cytokine expression, increased permeability, and expansion of CD25^-FoxP3⁺ Tregs; this enhanced susceptibility was alleviated by oral broad-spectrum antibiotics. Based on these results and our previous work, we postulate that epithelial electrolyte homeostasis is an important modulator in the progression of colitis, acting through remodeling of the gut microbial community.     

B cell developmental requirement for the G alpha i2 gene

Null mutation of the Galphai2 trimeric G protein results in a discrete and profound mucosal disorder, including inflammatory bowel disease (IBD), attenuation of IL-10 expression, and immune function polarized to Th1 activity. Genetic and adoptive transfer experiments have established a role for B cells and IL-10 in mucosal immunologic homeostasis and IBD resistance. In this study, we addressed the hypothesis that Galphai2 is required for the development of IL-10-producing B cells. Galphai2(-/-) mice were reduced in the relative abundance of marginal zone (MZ), transitional type 2 (T2), and B-1a B cells and significantly increased in follicular mature and B-1b B cells. Reconstitution of RAG2(-/-) mice with Galphai2(-/-) bone marrow induced an IBD-like colitis and a deficiency in absolute numbers of MZ, T2, and B-1 B cells. Thus, the Galphai2(-/-) genotype in colitis susceptibility and B cell development involved a cis effect within the hemopoietic compartment. In vitro, the B cell population of Galphai2(-/-) mice was functionally deficient in LPS-induced proliferation and IL-10 production, consistent with the exclusive capacity of T2 and MZ cell subpopulations for LPS responsiveness. In vivo, Galphai2(-/-) mice were selectively impaired for the IgM response to T-independent type II, consistent with the relative depletion of MZ and peritoneal B-1 subpopulations. Collectively, these results reveal a selective role for Galphai2 in MZ and B-1 B cell development. Disorders of this Galphai2-dependent process in B cell development may represent a mechanism for IBD susceptibility.     

CD4CD8αα Lymphocytes,A Novel Human Regulatory T Cell Subset Induced by Colonic Bacteria and Deficient in Patients with Inflammatory Bowel Disease

How the microbiota affects health and disease is a crucial question. In mice, gut Clostridium bacteria are potent inducers of colonic interleukin (IL)-10-producing Foxp3 regulatory T cells (Treg), which play key roles in the prevention of colitis and in systemic immunity. In humans, although gut microbiota dysbiosis is associated with immune disorders, the underlying mechanism remains unknown. In contrast with mice, the contribution of Foxp3 Treg in colitis prevention has been questioned, suggesting that other compensatory regulatory cells or mechanisms may exist. Here we addressed the regulatory role of the CD4CD8 T cells whose presence had been reported in the intestinal mucosa and blood. Using colonic lamina propria lymphocytes (LPL) and peripheral blood lymphocytes (PBL) from healthy individuals, and those with colon cancer and irritable bowel disease (IBD), we demonstrated that CD4CD8αα (DP8α) T lymphocytes expressed most of the regulatory markers and functions of Foxp3 Treg and secreted IL-10. Strikingly, DP8α LPL and PBL exhibited a highly skewed repertoire toward the recognition of Faecalibacterium prausnitzii, a major Clostridium species of the human gut microbiota, which is decreased in patients with IBD. Furthermore, the frequencies of DP8α PBL and colonic LPL were lower in patients with IBD than in healthy donors and in the healthy mucosa of patients with colon cancer, respectively. Moreover, PBL and LPL from most patients with active IBD failed to respond to F. prausnitzii in contrast to PBL and LPL from patients in remission and/or healthy donors. These data (i) uncover a Clostridium-specific IL-10-secreting Treg subset present in the human colonic LP and blood, (ii) identify F. prausnitzii as a major inducer of these Treg, (iii) argue that these cells contribute to the control or prevention of colitis, opening new diagnostic and therapeutic strategies for IBD, and (iv) provide new tools to address the systemic impact of both these Treg and the intestinal microbiota on the human immune homeostasis.     

肠道微生物群落与炎症性肠病关系研究进展

目的炎症性肠病（IBD）包括克罗恩病（CD）和溃疡性结肠炎（UC）,以持续性肠道非特异性炎症为特征,通常反复发作、迁延不愈,临床上仍无特效性的治疗手段。IBD确切的发病机制尚不清楚,涉及免疫、环境及遗传等因素,这些因素共同诱导肠道炎症、黏膜损伤和修复。肠道微生物群落及其代谢产物、宿主基因易感性及肠道黏膜免疫三方面共同参与了IBD的发病机制。本文从消化道微生态角度出发,对目前IBD相关的肠道微生物群落研究现状、宿主-微生物间免疫应答及益生菌治疗等内容进行探讨。     

HVEM signalling promotes colitis

Background

Tumor necrosis factor super family (TNFSF) members regulate important processes involved in cell proliferation, survival and differentiation and are therefore crucial for the balance between homeostasis and inflammatory responses. Several members of the TNFSF are closely associated with inflammatory bowel disease (IBD). Thus, they represent interesting new targets for therapeutic treatment of IBD.

Methodology/Principal Findings

We have used mice deficient in TNFSF member HVEM in experimental models of IBD to investigate its role in the disease process. Two models of IBD were employed: i) chemical-induced colitis primarily mediated by innate immune cells; and ii) colitis initiated by CD4⁺CD45RB^high T cells following their transfer into immuno-deficient RAG1^-/- hosts. In both models of disease the absence of HVEM resulted in a significant reduction in colitis and inflammatory cytokine production.

Conclusions

These data show that HVEM stimulatory signals promote experimental colitis driven by innate or adaptive immune cells.     

A crucial role for the vitamin D receptor in experimental inflammatory bowel diseases

The active form of vitamin D (1,25D3) suppressed the development of animal models of human autoimmune diseases including experimental inflammatory bowel disease (IBD). The vitamin D receptor (VDR) is required for all known biologic effects of vitamin D. Here we show that VDR deficiency (knockout, KO) resulted in severe inflammation of the gastrointestinal tract in two different experimental models of IBD. In the CD45RB transfer model of IBD, CD4+/CD45RBhigh T cells from VDR KO mice induced more severe colitis than wild-type CD4+/CD45RBhigh T cells. The second model of IBD used was the spontaneous colitis that develops in IL-10 KO mice. VDR/IL-10 double KO mice developed accelerated IBD and 100% mortality by 8 wk of age. At 8 wk of age, all of the VDR and IL-10 single KO mice were healthy. Rectal bleeding was observed in every VDR/IL-10 KO mouse. Splenocytes from the VDR/IL-10 double KO mice cells transferred IBD symptoms. The severe IBD in VDR/IL-10 double KO mice is a result of the immune system and not a result of altered calcium homeostasis, or gastrointestinal tract function. The data establishes an essential role for VDR signaling in the regulation of inflammation in the gastrointestinal tract.     

过表达白细胞介素10的间充质干细胞对炎症性肠病的治疗作用

炎症性肠病(inflammatory bowel disease,IBD)是一种以T细胞浸润至结肠为特征的难治性炎性自身免疫疾病。间充质干细胞 (mesenchymal stem cells,MSCs) 具有免疫抑制能力,在IBD的治疗中具有一定的潜力。但是由于MSCs在体内的免疫调节能力不稳定,所以其治疗效果会受到影响。本研究构建了过表达白细胞介素10(interleukin 10,IL-10)的工程化MSCs,并对其在IBD小鼠模型中的治疗潜力进行评估。MSCs经编码IL-10的慢病毒(lentivirus,LV)转染后,其表型和细胞增殖率均不发生变化。免疫细胞和 MSCs体外共培养的结果表明,与未修饰的MSCs相比,同过表达IL-10的MSCs共培养的免疫细胞中辅助T细胞1(T helper 1 cells,Th1)和辅助T细胞17(T helper 17 cells,Th17)数量显著性降低(P<0.05),同过表达IL-10的MSCs共培养的巨噬细胞细胞培养上清液,TNF-α含量显著性降低(P<0.0001)。右旋糖酐硫酸钠(dextran sodium sulfate,DSS)诱导IBD小鼠模型中,尾静脉注射过表达IL-10的MSCs与注射未修饰MSCs相比,过表达IL-10的MSCs具有更好的治疗效果,结肠长度、疾病活动指数(disease activity index,DAI)和结肠炎性细胞因子表达共同证明这一差异。实验结果均具有统计学差异(P<0.05)。总体而言,经LV转染过表达IL-10的MSCs可能是IBD的一种有希望的替代治疗选择。     

Heligmosomoides polygyrus bakeri Induces Tolerogenic Dendritic Cells that Block Colitis and Prevent Antigen-Specific Gut T Cell Responses

Immunological diseases such as inflammatory bowel disease (IBD) are infrequent in less developed countries, possibly because helminths provide protection by modulating host immunity. In IBD murine models, the helminth Heligmosomoides polygyrus bakeri prevents colitis. It was determined whether H. polygyrus bakeri mediated IBD protection by altering dendritic cell (DC) function. We used a Rag IBD model where animals were reconstituted with IL10(-/-) T cells, making them susceptible to IBD and with OVA Ag-responsive OT2 T cells, allowing study of a gut antigenic response. Intestinal DC from H. polygyrus bakeri-infected Rag mice added to lamina propria mononuclear cells (LPMC) isolated from colitic animals blocked OVA IFN-γ/IL-17 responses in vitro through direct contact with the inflammatory LPMC. DC from uninfected Rag mice displayed no regulatory activity. Transfer of DC from H. polygyrus bakeri-infected mice into Rag mice reconstituted with IL10(-/-) T cells protected animals from IBD, and LPMC from these mice lost OVA responsiveness. After DC transfer, OT2 T cells populated the intestines normally. However, the OT2 T cells were rendered Ag nonresponsive through regulatory action of LPMC non-T cells. The process of regulation appeared to be regulatory T cell independent. Thus, H. polygyrus bakeri modulates intestinal DC function, rendering them tolerogenic. This appears to be an important mechanism through which H. polygyrus bakeri suppresses colitis. IFN-γ and IL-17 are colitogenic. The capacity of these DC to block a gut Ag-specific IFN-γ/IL-17 T cell response also is significant.     

A novel murine model of inflammatory bowel disease and inflammation-associated colon cancer with ulcerative colitis-like features

Mutations that increase susceptibility to inflammatory bowel disease (IBD) have been identified in a number of genes in both humans and mice, but the factors that govern how these mutations contribute to IBD pathogenesis and result in phenotypic presentation as ulcerative colitis (UC) or Crohn disease (CD) are not well understood. In this study, mice deficient in both TNF and IL-10 (T/I mice) were found to spontaneously develop severe colitis soon after weaning, without the need for exogenous triggers. Colitis in T/I mice had clinical and histologic features similar to human UC, including a markedly increased risk of developing inflammation-associated colon cancer. Importantly, development of spontaneous colitis in these mice was prevented by antibiotic treatment. Consistent with the known role of Th17-driven inflammation in response to bacteria, T/I mice had elevated serumTh17-type cytokines when they developed spontaneous colitis and after systemic bacterial challenge via NSAID-induced degradation of the mucosal barrier. Although TNF production has been widely considered to be be pathogenic in IBD, these data indicate that the ability to produce normal levels of TNF actually protects against the spontaneous development of colitis in response to intestinal colonization by bacteria. The T/I mouse model will be useful for developing new rationally-based therapies to prevent and/or treat IBD and inflammation-associated colon cancer and may further provide important insights into the pathogenesis of UC in humans.     

Regulatory dendritic cells pulsed with carbonic anhydrase I protect mice from colitis induced by CD4+CD25- T cells

Inflammatory bowel disease (IBD), which is characterized by a dysregulated intestinal immune response, is postulated to be controlled by intestinal self-antigens and bacterial Ags. Fecal extracts called cecal bacterial Ag (CBA) have been implicated in the pathogenesis of IBD. In this study, we identified a major protein of CBA related to the pathogenesis of IBD and established a therapeutic approach using Ag-pulsed regulatory dendritic cells (Reg-DCs). Using two-dimensional gel electrophoresis and MALDI-TOF mass spectrometry, carbonic anhydrase I (CA I) was identified as a major protein of CBA. Next, we induced colitis by transfer of CD4(+)CD25(-) T cells obtained from BALB/c mice into SCID mice. Mice were treated with CBA- or CA I-pulsed Reg-DCs (Reg-DCs(CBA) or Reg-DCs(CA1)), which expressed CD200 receptor 3 and produced high levels of IL-10. Treatment with Reg-DCs(CBA) and Reg-DCs(CA1) ameliorated colitis. This effect was shown to be Ag-specific based on no clinical response of irrelevant Ag (keyhole limpet hemocyanin)-pulsed Reg-DCs. Foxp3 mRNA expression was higher but RORγt mRNA expression was lower in the mesenteric lymph nodes (MLNs) of the Reg-DCs(CA1)-treated mice compared with those in the MLNs of control mice. In the MLNs, Reg-DCs(CA1)-treated mice had higher mRNA expression of IL-10 and TGF-β1 and lower IL-17 mRNA expression and protein production compared with those of control mice. In addition, Reg-DCs(CBA)-treated mice had higher Foxp3(+)CD4(+)CD25(+) and IL-10-producing regulatory T cell frequencies in MLNs. In conclusion, Reg-DCs(CA1) protected progression of colitis induced by CD4(+)CD25(-) T cell transfer in an Ag-specific manner by inducing the differentiation of regulatory T cells.     

Probiotic bacteria produce conjugated linoleic acid locally in the gut that targets macrophage PPAR γ to suppress colitis

Background

Inflammatory bowel disease (IBD) therapies are modestly successful and associated with significant side effects. Thus, the investigation of novel approaches to prevent colitis is important. Probiotic bacteria can produce immunoregulatory metabolites in vitro such as conjugated linoleic acid (CLA), a polyunsaturated fatty acid with potent anti-inflammatory effects. This study aimed to investigate the cellular and molecular mechanisms underlying the anti-inflammatory efficacy of probiotic bacteria using a mouse model of colitis.

Methodology/Principal Findings

The immune modulatory mechanisms of VSL#3 probiotic bacteria and CLA were investigated in a mouse model of DSS colitis. Colonic specimens were collected for histopathology, gene expression and flow cytometry analyses. Immune cell subsets in the mesenteric lymph nodes (MLN), spleen, blood and colonic lamina propria cells were phenotypically and functionally characterized. Fecal samples and colonic contents were collected to determine the effect of VSL#3 and CLA on gut microbial diversity and CLA production. CLA and VSL#3 treatment ameliorated colitis and decreased colonic bacterial diversity, a finding that correlated with decreased gut pathology. Colonic CLA concentrations were increased in response to probiotic bacterial treatment, but without systemic distribution in blood. VSL#3 and CLA decreased macrophage accumulation in the MLN of mice with DSS colitis. The loss of PPAR γ in myeloid cells abrogated the protective effect of probiotic bacteria and CLA in mice with DSS colitis.

Conclusions/Significance

Probiotic bacteria modulate gut microbial diversity and favor local production of CLA in the colon that targets myeloid cell PPAR γ to suppress colitis.     

Sequestering HMGB1 via DNA-Conjugated Beads Ameliorates Murine Colitis

Inflammatory bowel disease (IBD) is chronic inflammation of the gastrointestinal tract that affects millions of people worldwide. Although the etiology of IBD is not clear, it is known that products from stressed cells and enteric microbes promote intestinal inflammation. High mobility group box 1 (HMGB1), originally identified as a nuclear DNA binding protein, is a cytokine-like protein mediator implicated in infection, sterile injury, autoimmune disease, and IBD. Elevated levels of HMGB1 have been detected in inflamed human intestinal tissues and in feces of IBD patients and mouse models of colitis. Neutralizing HMGB1 activity by administration of anti-HMGB1 antibodies or HMGB1-specific antagonist improves clinical outcomes in animal models of colitis. Since HMGB1 binds to DNA with high affinity, here we developed a novel strategy to sequester HMGB1 using DNA immobilized on sepharose beads. Screening of DNA-bead constructs revealed that B2 beads, one linear form of DNA conjugated beads, bind HMGB1 with high affinity, capture HMGB1 ex vivo from endotoxin-stimulated RAW 264.7 cell supernatant and from feces of mice with colitis. Oral administration of B2 DNA beads significantly improved body weight, reduced colon injury, and suppressed colonic and circulating cytokine levels in mice with spontaneous colitis (IL-10 knockout) and with dextran sulfate sodium-induced colitis. Thus, DNA beads reduce inflammation by sequestering HMGB1 and may have therapeutic potential for the treatment of IBD.