A protective role for human IL-10-expressing CD4+ T cells in colitis

Comparative Genomic Analysis and Physiological Properties of Limosilactobacillus fermentum SMFM2017-NK2 with Ability to Inflammatory Bowel Disease

The objective of this study was to evaluate the anti-inflammatory effect of Latilactobacillus sakei SMFM2017-NK1 (LS1), L. sakei SMFM2017-NK3 (LS2), and Limosilactobacillus fermentum SMFM2017-NK2 (LF) on colitis using an animal model. DSS (dextran sulfate sodium salt) was orally injected into C57BL/6N mice to induce inflammation in the colon for seven days. Colitis mice models were treated with LS1, LS2, and LF, respectively, and Lacticaseibacillus rhamnosus GG (LGG) was used as a positive control. During oral administration of lactic acid bacteria, the weights of the mice were measured, and the disease activity index (DAI) score was determined by judging the degree of diarrhea and bloody stool. When comparing the differences between the minimum weight after DSS administration and the maximum weight after lactic acid bacteriaadministration were compared, the LF-treated group showed the highest weight gain at 8.91%. The DAI scores of the LF, LS2, and LGG groups were lower than that of the control group. After sacrifice, mRNA expression levels for proinflammatory cytokines (TNF-α, IL-1β, IL-6, and IFN-γ) and mediators (iNOS and COX-2) in the colon were measured. LF was selected as a superior strain for anti-inflammation in the colon. It was further analyzed to determine its biochemical characteristics, cytotoxicity, and thermal stability. Catalase and oxidase activities for LF were negative. In cytotoxicity and heat stability tests, the LF group had higher cell viability than the LGG group. The genome of LF was obtained, and 5682 CDS, 114 tRNA, 2 RNA, and 5 repeat regions were predicted. Especially, LF could be distinguished from the other three L. fermentum strains based on taxonomic profiling, specific orthologous genes of the strain, and genomic variants. The results of this study suggest that L. fermentum SMFM2017-NK2 is a novel strain with an anti-inflammatory effect on colitis.

Glutamine alleviates intestinal injury in a murine burn sepsis model by maintaining intestinal intraepithelial lymphocyte homeostasis

Intestinal intraepithelial lymphocytes (IELs) play a sentinel role in the mucosal immune system because of their unique anatomical location in the epithelial layer. The disruption of IEL homeostasis is implicated in driving the intestinal injury of many typical inflammatory disorders, such as inflammatory bowel disease (IBD) and sepsis. Therefore, it is meaningful to alleviate intestinal injury by restoring IEL homeostasis in disease conditions. This study explores the effects of glutamine on intestinal IEL homeostasis in a murine model of burn sepsis. We report that glutamine inhibits inflammatory response and reduces injury in the small intestine of burn septic mice. This effect is attributed to the maintaining of IEL homeostasis by suppressing apoptosis and restoring the disrupted subpopulation balance induced by burn sepsis. Mechanistically, we show that glutamine does not affect the IL-15 dependent mechanisms that drive the maintenance and differentiation of IELs. Instead, glutamine sustains IEL homeostasis by upregulate aryl hydrocarbon receptor (AHR) and interleukin (IL)-22 transcription and expression. Consistently, the protective roles of glutamine in burn septic mice were repressed by further supplement with an AHR antagonist CH-223191. Collectively, our study reveals a new role of glutamine to maintain IEL homeostasis by activating the AHR signaling pathway, which in turn ameliorates intestinal injury in burn sepsis.

Functions of the aryl hydrocarbon receptor (AHR) beyond the canonical AHR/ARNT signaling pathway

The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor regulating adaptive and maladaptive responses toward exogenous and endogenous signals. Research from various biomedical disciplines has provided compelling evidence that the AHR is critically involved in the pathogenesis of a variety of diseases and disorders, including autoimmunity, inflammatory diseases, endocrine disruption, premature aging and cancer. Accordingly, AHR is considered an attractive target for the development of novel preventive and therapeutic measures. However, the ligand-based targeting of AHR is considerably complicated by the fact that the receptor does not always follow the beaten track, i.e. the canonical AHR/ARNT signaling pathway. Instead, AHR might team up with other transcription factors and signaling molecules to shape gene expression patterns and associated physiological or pathophysiological functions in a ligand-, cell- and micromilieu-dependent manner. Herein, we provide an overview about some of the most important non-canonical functions of AHR, including crosstalk with major signaling pathways involved in controlling cell fate and function, immune responses, adaptation to low oxygen levels and oxidative stress, ubiquitination and proteasomal degradation. Further research on these diverse and exciting yet often ambivalent facets of AHR biology is urgently needed in order to exploit the full potential of AHR modulation for disease prevention and treatment.

The development of colitis in Il10-/- mice is dependent on IL-22

Mice deficient in the IL-10 pathway are the most widely used models of intestinal immunopathology. IL-17A is strongly implicated in gut disease in mice and humans, but conflicting evidence has drawn IL-17's role in the gut into question. IL-22 regulates antimicrobial and repair activities of intestinal epithelial cells (IECs) and is closely associated with IL-17A responses but it's role in chronic disease is uncertain. We report that IL-22, like IL-17A, is aberrantly expressed in colitic Il10-/- mice. While IL-22+ Th17 cells were elevated in the colon, IL-22-producing ILC3s were highly enriched in the small intestines of Il10-/- mice. Remarkably, Il10-/-Il22-/- mice did not develop colitis despite retaining high levels of Th17 cells and remaining colonized with colitogenic Helicobacter spp. Accordant with IL-22-induced IEC proliferation, the epithelia hyperplasia observed in Il10-/- animals was reversed in Il10-/-Il22-/- mice. Also, the high levels of antimicrobial IL-22-target genes, including Reg3g, were normalized in Il10-/-Il22-/- mice. Consistent with a heightened antimicrobial environment, Il10-/- mice had reduced diversity of the fecal microbiome that was reestablished in Il10-/-Il22-/- animals. These data suggest that spontaneous colitis in Il10-/- mice is driven by IL-22 and implicates an underappreciated IL-10/IL-22 axis in regulating intestinal homeostasis.

Protein Phosphatase 1α and Cofilin Regulate Nuclear Translocation of NF-κB and Promote Expression of the Anti-Inflammatory Cytokine Interleukin-10 by T Cells

While several protein serine/threonine kinases control cytokine production by T cells, the roles of serine/threonine phosphatases are largely unexplored. Here, we analyzed the involvement of protein phosphatase 1α (PP1α) in cytokine synthesis following costimulation of primary human T cells. Small interfering RNA (siRNA)-mediated knockdown of PP1α (PP1^KD) or expression of a dominant negative PP1α (D95N-PP1) drastically diminished interleukin-10 (IL-10) production. Focusing on a key transcriptional activator of human IL-10, we demonstrate that nuclear translocation of NF-κB was significantly inhibited in PP1^KD or D95N-PP1 cells. Interestingly, knockdown of cofilin, a known substrate of PP1 containing a nuclear localization signal, also prevented nuclear accumulation of NF-κB. Expression of a constitutively active nonphosphorylatable S3A-cofilin in D95N-PP1 cells restored nuclear translocation of NF-κB and IL-10 expression. Subpopulation analysis revealed that defective nuclear translocation of NF-κB was most prominent in CD4⁺ CD45RA^- CXCR3^- T cells that included IL-10-producing T_H2 cells. Together these findings reveal novel functions for PP1α and its substrate cofilin in T cells namely the regulation of the nuclear translocation of NF-κB and promotion of IL-10 production. These data suggest that stimulation of PP1α could limit the overwhelming immune responses seen in chronic inflammatory diseases.

Cell-Specific Requirements for STAT Proteins and Type I IFN Receptor Signaling Discretely Regulate IL-24 and IL-10 Expression in NK Cells and Macrophages

Il10 forms a cytokine cluster with Il19, Il20, and Il24 in a conserved region of chromosome 1. The latter genes are in the IL-20 subfamily of IL-10-related cytokines and, although they are not as well studied their biologic actions and expression patterns, seem to have little in common with IL-10. IL-24, like IL-10, however, is uniquely expressed in T cells and is a signature gene of the Th2 lineage, which suggests they could be coregulated in certain cell types. Little is known about other cellular sources of IL-24. We investigated IL-24 and IL-10 expression in murine macrophages and NK cells, and found that although they are coexpressed under most stimulation conditions, IL-24 and IL-10 are controlled by distinct, cell type-specific pathways. In bone marrow-derived macrophages, optimal IL-24 expression required LPS+IL-4 costimulation and STAT6 but was independent of type I IFN receptor signaling and STAT4. Conversely, LPS-induced IL-10 was independent of IL-4/STAT6 and STAT4 but, consistent with other reports, required type I IFN receptor signaling for optimal expression. Remarkably, NK-specific IL-24 (but not IL-10) expression was dependent on both type I IFN receptor signaling and STAT4. Induction of IL-24 expression was accompanied by cell-specific recruitment of STAT6 and STAT4 to multiple sites that we identified within Il24, which mediated STAT-dependent histone modifications across the gene. Collectively, our results indicate that despite being coexpressed, IL-10 and IL-24 are independently regulated by different type I IFN receptor signaling pathways in innate immune cells and provide insight into the mechanisms that fine-tune cell type-specific gene expression within the Il10 cluster.

Macrophage-derived IL-10 mediates mucosal repair by epithelial WISP-1 signaling

In response to injury, epithelial cells migrate and proliferate to cover denuded mucosal surfaces and repair the barrier defect. This process is orchestrated by dynamic crosstalk between immune cells and the epithelium; however, the mechanisms involved remain incompletely understood. Here, we report that IL-10 was rapidly induced following intestinal mucosal injury and was required for optimal intestinal mucosal wound closure. Conditional deletion of IL-10 specifically in CD11c-expressing cells in vivo implicated macrophages as a critical innate immune contributor to IL-10-induced wound closure. Consistent with these findings, wound closure in T cell- and B cell-deficient Rag1-/- mice was unimpaired, demonstrating that adaptive immune cells are not absolutely required for this process. Further, following mucosal injury, macrophage-derived IL-10 resulted in epithelial cAMP response element-binding protein (CREB) activation and subsequent synthesis and secretion of the pro-repair WNT1-inducible signaling protein 1 (WISP-1). WISP-1 induced epithelial cell proliferation and wound closure by activating epithelial pro-proliferative pathways. These findings define the involvement of macrophages in regulating an IL-10/CREB/WISP-1 signaling axis, with broad implications in linking innate immune activation to mucosal wound repair.

CD103+ CD11b+ Dendritic Cells Induce Th17 T Cells in Muc2-Deficient Mice with Extensively Spread Colitis

Mucus alterations are a feature of ulcerative colitis (UC) and can drive inflammation by compromising the mucosal barrier to luminal bacteria. The exact pathogenesis of UC remains unclear, but CD4+ T cells reacting to commensal antigens appear to contribute to pathology. Given the unique capacity of dendritic cells (DCs) to activate naive T cells, colon DCs may activate pathogenic T cells and contribute to disease. Using Muc2-/- mice, which lack a functional mucus barrier and develop spontaneous colitis, we show that colitic animals have reduced colon CD103+ CD11b- DCs and increased CD103- CD11b+ phagocytes. Moreover, changes in colonic DC subsets and distinct cytokine patterns distinguish mice with distally localized colitis from mice with colitis spread proximally. Specifically, mice with proximally spread, but not distally contained, colitis have increased IL-1β, IL-6, IL-17, TNFα, and IFNγ combined with decreased IL-10 in the distal colon. These individuals also have increased numbers of CD103+ CD11b+ DCs in the distal colon. CD103+ CD11b+ DCs isolated from colitic but not noncolitic mice induced robust differentiation of Th17 cells but not Th1 cells ex vivo. In contrast, CD103- CD11b+ DCs from colitic Muc2-/- mice induced Th17 as well as Th1 differentiation. Thus, the local environment influences the capacity of intestinal DC subsets to induce T cell proliferation and differentiation, with CD103+ CD11b+ DCs inducing IL-17-producing T cells being a key feature of extensively spread colitis.

Induction of Murine Intestinal Inflammation by Adoptive Transfer of Effector CD4+ CD45RB high T Cells into Immunodeficient Mice

There are many different animal models available for studying the pathogenesis of human inflammatory bowel diseases (IBD), each with its own advantages and disadvantages. We describe here an experimental colitis model that is initiated by adoptive transfer of syngeneic splenic CD4(+)CD45RB(high) T cells into T and B cell deficient recipient mice. The CD4(+)CD45RB(high) T cell population that largely consists of naïve effector cells is capable of inducing chronic intestinal inflammation, closely resembling key aspects of human IBD. This method can be manipulated to study aspects of disease onset and progression. Additionally it can be used to study the function of innate, adaptive, and regulatory immune cell populations, and the role of environmental exposures, i.e., the microbiota, in intestinal inflammation. In this article we illustrate the methodology for inducing colitis with a step-by-step protocol. This includes a video demonstration of key technical aspects required to successfully develop this murine model of experimental colitis for research purposes.

Endometrial regenerative cells as a novel cell therapy attenuate experimental colitis in mice

Background

Endometrial regenerative cells (ERCs) are mesenchymal-like stem cells that can be non-invasively obtained from menstrual blood and are easily grown /generated at a large scale without tumorigenesis. We previously reported that ERCs exhibit unique immunoregulatory properties in vitro, however their immunosuppressive potential in protecting the colon from colitis has not been investigated. The present study was undertaken to determine the efficacy of ERCs in mediating immunomodulatory functions against colitis.

Methods

Colitis was induced by 4% dextran-sulfate-sodium (DSS, in drinking water) in BALB/c mice for 7 days. ERCs were cultured from healthy female menstrual blood, and injected (1 million/mouse/day, i.v.) into mice on days 2, 5, and 8 following colitis induction. Colonic and splenic tissues were collected on day 14 post-DSS-induction. Clinical signs, disease activity index (DAI), pathological and immunohistological changes, cytokine profiles and cell populations were evaluated.

Results

DSS-induced mice in untreated group developed severe colitis, characterized by body-weight loss, bloody stool, diarrhea, mucosal ulceration and colon shortening, as well as pathological changes of intra-colon cell infiltrations of neutrophils and Mac-1 positive cells. Notably, ERCs attenuated colitis with significantly reduced DAI, decreased levels of intra-colon IL-2 and TNF-α, but increased expressions of IL-4 and IL-10. Compared with those of untreated colitis mice, splenic dendritic cells isolated from ERC-treated mice exhibited significantly decreased MHC-II expression. ERC-treated mice also demonstrated much less CD3⁺CD25⁺ active T cell and CD3⁺CD8⁺ T cell population and significantly higher level of CD4⁺CD25⁺Foxp3⁺ Treg cells.

Conclusions

This study demonstrated novel anti-inflammatory and immunosuppressive effects of ERCs in attenuating colitis in mice, and suggested that the unique features of ERCs make them a promising therapeutic tool for the treatment of ulcerative colitis.

Control of intestinal inflammation by interleukin-10

Twenty years ago, the observation that mice genetically deficient in IL-10 spontaneously developed severe intestinal inflammation, revealed an essential role for IL-10 in the maintenance of intestinal homeostasis. In the intervening period much has been learned about the cellular and molecular factors that are involved in IL-10-mediated regulatory pathways. Elegant experiments with conditional cell-type specific knockout strains have illustrated that IL-10 acts on both myeloid cells and T cells within the intestine to suppress innate and adaptive inflammatory responses and enhance regulatory circuits. Although several distinct cellular sources of IL-10 have been identified in the gut, CD4(+) T cells are a crucial non-redundant source of IL-10 for the regulation of intestinal inflammation. Induction of IL-10 may represent an important means through which intestinal microbiota establishes mutually beneficial commensalism with mammalian hosts, but can be exploited by certain pathogens to facilitate infection. Recent genetic studies in humans have confirmed the essential role of IL-10 in preventing deleterious inflammation in the gut. A better understanding of the molecular pathways involved in IL-10 induction and function in the intestine may facilitate the development of novel therapies for inflammatory bowel disease (IBD).

Pathogenic properties of enterohepatic Helicobacter spp. isolated from rhesus macaques with intestinal adenocarcinoma

Considerable progress has been made in understanding the roles of Helicobacter pylori in inflammation and gastric cancer; however, far less is known about the roles of enterohepatic Helicobacter species (EHS) in carcinogenesis and their zoonotic or pathogenic potential. We determined the prevalence of EHS infection in a cohort of geriatric rhesus monkeys in which intestinal adenocarcinoma (IAC) is common and investigated the association between EHS infection and IAC. The cohort consisted of 36 animals, 14 of which (age 26-35 years) had IAC. Of the 36 rhesus, 35 (97%) were positive for EHS using PCR or bacterial isolation from faeces, colonic or tumour tissues. Only a single rhesus, which had IAC, was negative for EHS by all detection methods. The EHS identified by 16S rRNA sequencing in this study were from three Helicobacter taxa: Helicobacter macacae (previously rhesus monkey taxon 1), Helicobacter sp. rhesus monkey taxon 2, previously described from strain MIT 99-5507, and Helicobacter sp. rhesus monkey taxon 4, related to Helicobacter fennelliae. Thirteen of 14 monkeys with IAC were positive for either H. macacae (7/13, 54%), EHS rhesus monkey taxon 4 (4/13, 31%) or a mixture of the two EHS (2/13, 15%). These results indicate that EHS are prevalent among aged rhesus macaques with IAC. Using Helicobacter genus-specific florescent in situ hybridization, EHS were detected on the surface of colonic epithelia of infected monkeys. All Helicobacter isolates, including H. macacae, effectively adhered to, invaded, and significantly induced proinflammatory genes, including IL-8, IL-6, TNF-α and iNOS, while downregulating genes involved in the function of inflammasomes, particularly IL-1β, CASPASE-1, NRLP3, NLRP6 and NLRC4 in the human colonic T84 cell line (P<0.0001). These results suggest that EHS may represent an aetiological agent mediating diarrhoea, chronic inflammation, and possibly intestinal cancer in non-human primates, and may play a role in similar disease syndromes in humans. Downregulation of inflammasome function may represent an EHS strategy for long-term persistence in the host and play a role in inducing pathological changes in the host's lower bowel.

Regulatory cell populations in the intestinal mucosa

PURPOSE OF REVIEW

The purpose of this review is to summarize recent advances in the fields of intestinal T-regulatory cell (Treg) and tolerogenic dendritic cell subsets. Under homeostatic conditions, CD4(+) Tregs and tolerogenic dendritic cells function to maintain mucosal tolerance. Loss of immune homeostasis is the primary cause of intestinal abnormalities, including inflammatory bowel disease. Thus, an improved understanding of cellular mechanisms promoting tolerance will be critical for the development of more efficacious therapies to treat chronic intestinal inflammation.

RECENT FINDINGS

Significant progress has been made in the past year in the study of mucosal Treg and dendritic cell populations. In particular, efforts have focused on the migration and differentiation of these cells in the intestinal mucosa, the functional consequences of cross-talk with the intestinal microbiome, mechanisms by which tolerogenic dendritic cells take up antigen, and regulation of retinoic acid synthesis.

SUMMARY

Recent studies examining tolerogenic cell populations of the intestinal mucosa highlight the progress in understanding the function, regulation, and cross-talk of Treg and dendritic cell populations, and their interactions with the gut microbiota. Scientific advances in these areas will undoubtedly lead to the development of more effective therapeutic strategies for intestinal abnormalities such as inflammatory bowel disease.

Plasmacytoid dendritic cells are crucial in Bifidobacterium adolescentis-mediated inhibition of Yersinia enterocolitica infection

In industrialized countries bacterial intestinal infections are commonly caused by enteropathogenic Enterobacteriaceae. The interaction of the microbiota with the host immune system determines the adequacy of an appropriate response against pathogens. In this study we addressed whether the probiotic Bifidobacterium adolescentis is protective during intestinal Yersinia enterocolitica infection. Female C57BL/6 mice were fed with B. adolescentis, infected with Yersinia enterocolitica, or B. adolescentis fed and subsequently infected with Yersinia enterocolitica. B. adolescentis fed and Yersinia infected mice were protected from Yersinia infection as indicated by a significantly reduced weight loss and splenic Yersinia load when compared to Yersinia infected mice. Moreover, protection from infection was associated with increased intestinal plasmacytoid dendritic cell and regulatory T-cell frequencies. Plasmacytoid dendritic cell function was investigated using depletion experiments by injecting B. adolescentis fed, Yersinia infected C57BL/6 mice with anti-mouse PDCA-1 antibody, to deplete plasmacytoid dendritic cells, or respective isotype control. The B. adolescentis-mediated protection from Yersinia dissemination to the spleen was abrogated after plasmacytoid dendritic cell depletion indicating a crucial function for pDC in control of intestinal Yersinia infection. We suggest that feeding of B. adolescentis modulates the intestinal immune system in terms of increased plasmacytoid dendritic cell and regulatory T-cell frequencies, which might account for the B. adolescentis-mediated protection from Yersinia enterocolitica infection.

Association between interleukin-10-819 promoter polymorphism and susceptibility to Crohn's disease: A meta-analysis

AIM: To explore the association between interleukin-10 (IL-10) 819T/C polymorphism and Crohn's disease susceptibility.

METHODS: A systematic search of electronic databases such as CBM, CNKI, PubMed, Elsevier and EMbase was performed to retrieve relevant studies. Pooled odds ratios (ORs) with 95% confidence intervals (95% CI) were calculated using the RevMan 5.1.4 software, and publication bias was tested by Egger's regression test and Begg's test.

RESULTS: A total of 11 studies involving 1670 patients with Crohn's disease and 3312 healthy controls were identified. The results of meta-analyses showed no significant association between IL-10 819T/C polymorphism and susceptibility to Crohn's disease (for T/T vs C/C: OR = 0.90, 95% CI: 0.70 to 1.17; T/C vs C/C: OR = 0.84, 95% CI: 0.56 to 1.27; for dominant inheritance model: OR = 0.97, 95% CI 0.86 to 1.10; for recessive inheritance model: OR = 0.90, 95% CI: 0.71 to 1.14).

CONCLUSION: Current evidence strongly suggests that there is no significant association between IL-10 819T/C polymorphism and susceptibility to Crohn's disease.