Macrophage dysfunction initiates colitis during weaning of infant mice lacking the interleukin-10 receptor

MyD88-mediated signaling in intestinal fibroblasts regulates macrophage antimicrobial defense and prevents dysbiosis in the gut

Fibroblasts that reside in the gut mucosa are among the key regulators of innate immune cells, but their role in the regulation of the defense functions of macrophages remains unknown. MyD88 is suggested to shape fibroblast responses in the intestinal microenvironment. We found that mice lacking MyD88 in fibroblasts showed a decrease in the colonic antimicrobial defense, developing dysbiosis and aggravated dextran sulfate sodium (DSS)-induced colitis. These pathological changes were associated with the accumulation of Arginase 1+ macrophages with low antimicrobial defense capability. Mechanistically, the production of interleukin (IL)-6 and CCL2 downstream of MyD88 was critically involved in fibroblast-mediated support of macrophage antimicrobial function, and IL-6/CCL2 neutralization resulted in the generation of macrophages with decreased production of the antimicrobial peptide cathelicidin and impaired bacterial clearance. Collectively, these findings revealed a critical role of fibroblast-intrinsic MyD88 signaling in regulating macrophage antimicrobial defense under colonic homeostasis, and its disruption results in dysbiosis, predisposing the host to the development of intestinal inflammation.

Phage cocktail inhibits inflammation and protects the integrity of the intestinal barrier in dextran sulfate sodium-induced colitis mice model

Ulcerative colitis (UC) is an inflammatory bowel disease characterized by abdominal pain, diarrhea, and rectal bleeding. This study aims to explore the protective effects of a phage cocktail (108 PFU/mL of Clostridium perfringens phage, 108 PFU/mL of Escherichia coli phage, and 108 PFU/mL of Salmonella phage) on a mouse colitis model induced by dextran sulfate sodium (DSS) and its potential toxic effects on normal mice. The results demonstrate that the phage cocktail significantly alleviates clinical symptoms in mice, reduces colon shortening, weight loss, and colonic pathological damage. Furthermore, the phage cocktail markedly suppresses the inflammatory response and safeguards intestinal barrier integrity in the colonic tissues of the mouse colitis model. Preliminary investigation of the toxic effects of the phage cocktail in mice indicates that continuous administration for 14 days does not yield statistically significant differences in hematological and blood biochemical parameters, and specific pathological changes are absent in histopathological examination results. The aforementioned findings suggest that the phage cocktail exhibits anti-inflammatory and intestinal barrier protective effects in the mouse colitis model, and it does not exert significant toxic side effects on mice.

Oral administration of Sophora Flavescens-derived exosomes-like nanovesicles carrying CX5461 ameliorates DSS-induced colitis in mice

Ulcerative colitis (UC) belongs to chronic inflammatory disease with a relapsing characterization. Conventional oral drugs of UC are restricted in clinical by premature degradation in the gastrointestinal tract, modest efficacy, and adverse effects. CX5461 can treat autoimmune disease, immunological rejection, and vascular inflammation. However, low solubility, intravenous administration, and non-inflammatory targeting limited its clinical application. Herein, this work aims to develop Sophora Flavescens-derived exosomes-like nanovesicles carrying CX5461 (SFELNVs@CX5461) for efficient CX5461 oral delivery for UC therapy. We identified SFELNVs as nano-diameter (80 nm) with negative zeta potential (-32mV). Cellular uptake has shown that SFELNVs were targeted uptake by macrophages, thus increasing drug concentration. Additionally, oral SFELNVs@CX5461 exhibited good safety and stability, as well as inflammation-targeting ability in the gastrointestinal tract of dextran sodium sulfate (DSS)-induced colitis mice. In vivo, oral administration of SFELNVs and CX5461 could relieve mice colitis. More importantly, combined SFELNVs and CX5461 alleviated mice colitis by inhibiting pro-inflammatory factors (TNF-α, IL-1β, and IL-6) expression and promoting M2 macrophage polarization. Furthermore, SFELNVs promoted M2 polarization by miR4371c using miRNA sequencing. Our results suggest that SFELNVs@CX5461 represents a novel orally therapeutic drug that can ameliorate colitis, and a promising targeting strategy for safe UC therapy.

Extracellular vesicles of Bacteroides uniformis induce M1 macrophage polarization and aggravate gut inflammation during weaning

Weaning process is commonly associated with gastrointestinal inflammation and dysbiosis of the intestinal microbes. In particular, the impact of gut bacteria and extracellular vesicles on the etiology of intestinal inflammation during weaning is not well understood. We have uncovered a potential link between gut inflammation and the corresponding variation of macrophage bacterial sensing and pro-inflammatory polarization during the weaning process of piglets through single-cell transcriptomic analyses. We conducted a comprehensive analysis of bacterial distribution across the gastrointestinal tract and pinpointed Bacteroides uniformis enriching in piglets undergoing weaning. Next, we found out that exposure to B. uniformis-derived extracellular vesicles (BEVs) exacerbated gut inflammation in a murine colitis model while recruiting and polarizing intestinal macrophages toward a pro-inflammatory phenotype. BEVs modulated the function of macrophages cultured in vitro by suppressing the granulocyte-macrophage colony-stimulating factor/signal transducer and activator of transcription 5/arginase 1 pathway, thereby affecting polarization toward an M1-like state. The effects of BEVs were verified both in the macrophage clearance murine model and by using an adoptive transfer assay. Our findings highlight the involvement of BEVs in facilitating the polarization of pro-inflammatory macrophages and promoting gut inflammation during weaning.

Huang Lian Jie Du decoction attenuated colitis via suppressing the macrophage Csf1r/Src pathway and modulating gut microbiota

Introduction

Ulcerative colitis, a subtype of chronic inflammatory bowel disease (IBD), is characterized by relapsing colonic inflammation and ulcers. The traditional Chinese herbal formulation Huang Lian Jie Du (HLJD) decoction is used clinically to treat diarrhea and colitis. However, the mechanisms associated with the effects of treatment remain unclear. This study aims to elucidate the molecular mechanistic effects of HLJD formulation on colitis.

Methods

Chronic colitis in mice was induced by adding 1% dextran sulfate sodium (DSS) to their drinking water continuously for 8 weeks, and HLJD decoction at the doses of 2 and 4 g/kg was administered orally to mice daily from the second week until experimental endpoint. Stool consistency scores, blood stool scores, and body weights were recorded weekly. Disease activity index (DAI) was determined before necropsy, where colon tissues were collected for biochemical analyses. In addition, the fecal microbiome of treated mice was characterized using 16S rRNA amplicon sequencing.

Results

HLJD decoction at doses of 2 and 4 g/kg relieved DSS-induced chronic colitis in mice by suppressing inflammation through compromised macrophage activity in colonic tissues associated with the colony-stimulating factor 1 receptor (Csf1r)/Src pathway. Furthermore, the HLJD formula could modify the gut microbiota profile by decreasing the abundance of Bacteroides, Odoribacter, Clostridium_sensu_stricto_1, and Parasutterella. In addition, close correlations between DAI, colon length, spleen weight, and gut microbiota were identified.

Discussion

Our findings revealed that the HLJD formula attenuated DSS-induced chronic colitis by reducing inflammation via Csf1r/Src-mediated macrophage infiltration, as well as modulating the gut microbiota profile.

Cytokine Profile in Predicting the Effectiveness of Advanced Therapy for Ulcerative Colitis: A Narrative Review

Cytokine-targeted therapies have shown efficacy in treating patients with ulcerative colitis (UC), but responses to these advanced therapies can vary. This variability may be due to differences in cytokine profiles among patients with UC. While the etiology of UC is not fully understood, abnormalities of the cytokine profiles are deeply involved in its pathophysiology. Therefore, an approach focused on the cytokine profile of individual patients with UC is ideal. Recent studies have demonstrated that molecular analysis of cytokine profiles in UC can predict response to each advanced therapy. This narrative review summarizes the molecules involved in the efficacy of various advanced therapies for UC. Understanding these associations may be helpful in selecting optimal therapeutic agents.

Akkermansia muciniphila-induced trained immune phenotype increases bacterial intracellular survival and attenuates inflammation

The initial exposure to pathogens and commensals confers innate immune cells the capacity to respond distinctively upon a second stimulus. This training capacity might play key functions in developing an adequate innate immune response to the continuous exposure to bacteria. However, the mechanisms involved in induction of trained immunity by commensals remain mostly unexplored. A. muciniphila represents an attractive candidate to study the promotion of these long-term responses. Here, we show that priming of macrophages with live A. muciniphila enhances bacterial intracellular survival and decreases the release of pro- and anti-inflammatory signals, lowering the production of TNF and IL-10. Global transcriptional analysis of macrophages after a secondary exposure to the bacteria showed the transcriptional rearrangement underpinning the phenotype observed compared to acutely exposed cells, with the increased expression of genes related to phagocytic capacity and those involved in the metabolic adjustment conducing to innate immune training. Accordingly, key genes related to bacterial killing and pro-inflammatory pathways were downregulated. These data demonstrate the importance of specific bacterial members in the modulation of local long-term innate immune responses, broadening our knowledge of the association between gut microbiome commensals and trained immunity as well as the anti-inflammatory probiotic potential of A. muciniphila.

Macrophage Development and Function

Macrophages were first described over a hundred years ago. Throughout the years, they were shown to be essential players in their tissue-specific environment, performing various functions during homeostatic and disease conditions. Recent reports shed more light on their ontogeny as long-lived, self-maintained cells with embryonic origin in most tissues. They populate the different tissues early during development, where they help to establish and maintain homeostasis. In this chapter, the history of macrophages is discussed. Furthermore, macrophage ontogeny and core functions in the different tissues are described.

OGR1 (GPR68) and TDAG8 (GPR65) Have Antagonistic Effects in Models of Colonic Inflammation

G-protein-coupled receptors (GPRs), including pro-inflammatory ovarian cancer GPR1 (OGR1/GPR68) and anti-inflammatory T cell death-associated gene 8 (TDAG8/GPR65), are involved in pH sensing and linked to inflammatory bowel disease (IBD). OGR1 and TDAG8 show opposite effects. To determine which effect is predominant or physiologically more relevant, we deleted both receptors in models of intestinal inflammation. Combined Ogr1 and Tdag8 deficiency was assessed in spontaneous and acute murine colitis models. Disease severity was assessed using clinical scores. Colon samples were analyzed using quantitative polymerase chain reaction (qPCR) and flow cytometry (FACS). In acute colitis, Ogr1-deficient mice showed significantly decreased clinical scores compared with wildtype (WT) mice, while Tdag8-deficient mice and double knockout (KO) mice presented similar scores to WT. In Il-10-spontaneous colitis, Ogr1-deficient mice presented significantly decreased, and Tdag8-deficient mice had increased inflammation. In the Il10-/- × Ogr1-/- × Tdag8-/- triple KO mice, inflammation was significantly decreased compared with Tdag8-/-. Absence of Ogr1 reduced pro-inflammatory cytokines in Tdag8-deficient mice. Tdag8-/- had significantly more IFNγ+ T-lymphocytes and IL-23 T-helper cells in the colon compared with WT. The absence of OGR1 significantly alleviates the intestinal damage mediated by the lack of functional TDAG8. Both OGR1 and TDAG8 represent potential new targets for therapeutic intervention.

The IL-10 receptor inhibits cell extrinsic signals necessary for STAT1-dependent macrophage accumulation during colitis

The loss of IL-10R function leads to severe early onset colitis and, in murine models, is associated with the accumulation of immature inflammatory colonic macrophages. We have shown that IL-10R-deficient colonic macrophages exhibit increased STAT1-dependent gene expression, suggesting that IL-10R-mediated inhibition of STAT1 signaling in newly recruited colonic macrophages might interfere with the development of an inflammatory phenotype. Indeed, STAT1-/- mice exhibit defects in colonic macrophage accumulation after Helicobacter hepaticus infection and IL-10R blockade, and this was phenocopied in mice lacking IFNγR, an inducer of STAT1 activation. Radiation chimeras demonstrated that reduced accumulation of STAT1-deficient macrophages was based on a cell-intrinsic defect. Unexpectedly, mixed radiation chimeras generated with both wild-type and IL-10R-deficient bone marrow indicated that rather than directly interfering with STAT1 function, IL-10R inhibits the generation of cell extrinsic signals that promote the accumulation of immature macrophages. These results define the essential mechanisms controlling the inflammatory macrophage accumulation in inflammatory bowel diseases.

IL-10 constrains sphingolipid metabolism via fatty acid desaturation to limit inflammation

Unchecked chronic inflammation is the underlying cause of many diseases, ranging from inflammatory bowel disease to obesity and neurodegeneration. Given the deleterious nature of unregulated inflammation, it is not surprising that cells have acquired a diverse arsenal of tactics to limit inflammation. IL-10 is a key anti-inflammatory cytokine that can limit immune cell activation and cytokine production in innate immune cell types; however, the exact mechanism by which IL-10 signaling subdues inflammation remains unclear. Here, we find that IL-10 signaling constrains sphingolipid metabolism. Specifically, we find increased saturated very long chain (VLC) ceramides are critical for the heightened inflammatory gene expression that is a hallmark of IL-10-deficient macrophages. Genetic deletion of CerS2, the enzyme responsible for VLC ceramide production, limited exacerbated inflammatory gene expression associated with IL-10 deficiency both in vitro and in vivo , indicating that "metabolic correction" is able to reduce inflammation in the absence of IL-10. Surprisingly, accumulation of saturated VLC ceramides was regulated by flux through the de novo mono-unsaturated fatty acid (MUFA) synthesis pathway, where addition of exogenous MUFAs could limit both saturated VLC ceramide production and inflammatory gene expression in the absence of IL-10 signaling. Together, these studies mechanistically define how IL-10 signaling manipulates fatty acid metabolism as part of its molecular anti-inflammatory strategy and could lead to novel and inexpensive approaches to regulate aberrant inflammation.

Cell-penetrating TLR inhibitor peptide alleviates ulcerative colitis by the functional modulation of macrophages

Toll-like receptors (TLRs) have a crucial role not only in triggering innate responses against microbes but in orchestrating an appropriate adaptive immunity. However, deregulated activation of TLR signaling leads to chronic inflammatory conditions such as inflammatory bowel disease (IBD). In this study, we evaluated the immunomodulatory potential of a TLR inhibitor in the form of a cell-penetrating peptide using an ulcerative colitis animal model. A peptide derived from the TIR domain of the TLR adaptor molecule TIRAP that was conjugated with a cell-penetrating sequence (cpTLR-i) suppressed the induction of pro-inflammatory cytokines such as TNF-α and IL-1β in macrophages. In DSS-induced colitis mice, cpTLR-i treatment ameliorated colitis symptoms, colonic tissue damage, and mucosal inflammation. Intriguingly, cpTLR-i attenuated the induction of TNF-α-expressing proinflammatory macrophages while promoting that of regulatory macrophages expressing arginase-1 and reduced type 17 helper T cell (Th17) responses in the inflamed colonic lamina propria. An in vitro study validated that cpTLR-i enhanced the differentiation of monocyte-driven macrophages into mature macrophages with a regulatory phenotype in a microbial TLR ligand-independent manner. Furthermore, the cocultivation of CD4 T cells with macrophages revealed that cpTLR-i suppressed the activation of Th17 cells through the functional modulation of macrophages. Taken together, our data show the immunomodulatory potential of the TLR inhibitor peptide and suggest cpTLR-i as a novel therapeutic candidate for the treatment of IBD.

The Wu-Shi-Cha formula protects against ulcerative colitis by orchestrating immunity and microbiota homeostasis

ETHNOPHARMACOLOGICAL RELEVANCE

Ulcerative colitis (UC) has become a healthy burden worldwide due to its insidious onset and repetitive relapse, with a rather complex etiology, including inappropriate immune response, dysbiosis, genetic susceptibility, and unhealthy diets. The Wu-Shi-Cha (WSC) formula is a widely utilized drug to protect against gastrointestinal disorders.

AIM OF THE STUDY

The study aspired to dissect the pertinent mechanisms of the WSC to treat UC.

MATERIALS AND METHODS

Network pharmacology and weighted gene co-expression network analysis (WGCNA) were performed to predict the targets of WSC in the context of UC and colorectal cancer. Dextran sodium sulfate (DSS) was used to construct murine models of experimental colitis, and the WSC was given to colitis mice for 14 days. Feces and colon samples were subjected to 16S rRNA gene sequencing combined with liquid chromatography-mass spectrometry (LC-MS) and biochemical experiments, respectively.

RESULTS

Network pharmacology analysis predicted that the WSC formula could orchestrate inflammation, infection, and tumorigenesis, and WGCNA based on The Cancer Genome Atlas (TCGA) database showed a potent anti-neoplastic effect of the WSC therapy for colorectal cancer. The WSC therapy rescued bursts of pro-inflammatory cytokines and colonic epithelial collapse in DSS-induced colitis mice. Moreover, the high dose of WSC treatment facilitated the alternative activation of peritoneal macrophages (Mφs) and these Mφs were conducive to the survival of intestinal stem cells (ISCs), and the disturbed homeostasis of gut microbiota was re-established after WSC treatment, as evidenced by the decreased colonization of pathological taxa in the fecal samples.

CONCLUSION

The WSC formula suppresses inflammation and re-establishes the homeostasis of gut microbiota, thereby ameliorating colitis progression.

Pathophysiology of Inflammatory Bowel Disease: Innate Immune System

Inflammatory bowel disease (IBD), comprising Crohn's disease (CD) and ulcerative colitis (UC), is a heterogeneous state of chronic intestinal inflammation with no exact known cause. Intestinal innate immunity is enacted by neutrophils, monocytes, macrophages, and dendritic cells (DCs), and innate lymphoid cells and NK cells, characterized by their capacity to produce a rapid and nonspecific reaction as a first-line response. Innate immune cells (IIC) defend against pathogens and excessive entry of intestinal microorganisms, while preserving immune tolerance to resident intestinal microbiota. Changes to this equilibrium are linked to intestinal inflammation in the gut and IBD. IICs mediate host defense responses, inflammation, and tissue healing by producing cytokines and chemokines, activating the complement cascade and phagocytosis, or presenting antigens to activate the adaptive immune response. IICs exert important functions that promote or ameliorate the cellular and molecular mechanisms that underlie and sustain IBD. A comprehensive understanding of the mechanisms underlying these clinical manifestations will be important for developing therapies targeting the innate immune system in IBD patients. This review examines the complex roles of and interactions among IICs, and their interactions with other immune and non-immune cells in homeostasis and pathological conditions.

Interleukin-10 Deficiency Impacts on TNF-Induced NFκB Regulated Responses In Vivo

Interleukin-10 (IL-10) is an anti-inflammatory cytokine that has a major protective role against intestinal inflammation. We recently revealed that intestinal epithelial cells in vitro regulate NFκB-driven transcriptional responses to TNF via an autocrine mechanism dependent on IL-10 secretion. Here in this study, we investigated the impact of IL-10 deficiency on the NFκB pathway and its downstream targets in the small intestinal mucosa in vivo. We observed dysregulation of TNF, IκBα, and A20 gene and protein expression in the small intestine of steady-state or TNF-injected Il10-/- mice, compared to wild-type C57BL6/J counterparts. Upon TNF injection, tissue from the small intestine showed upregulation of NFκB p65[RelA] activity, which was totally diminished in Il10-/- mice and correlated with reduced levels of TNF, IκBα, and A20 expression. In serum, whilst IgA levels were noted to be markedly downregulated in IL-10-deficient- mice, normal levels of mucosal IgA were seen in intestine mucosa. Importantly, dysregulated cytokine/chemokine levels were observed in both serum and intestinal tissue lysates from naïve, as well as TNF-injected Il10-/- mice. These data further support the importance of the IL-10-canonical NFκB signaling pathway axis in regulating intestinal mucosa homeostasis and response to inflammatory triggers in vivo.

CCR2 promotes monocyte recruitment and intestinal inflammation in mice lacking the interleukin-10 receptor

Macrophages are a heterogeneous population of mononuclear phagocytes abundantly distributed throughout the intestinal compartments that adapt to microenvironmental specific cues. In adult mice, the majority of intestinal macrophages exhibit a mature phenotype and are derived from blood monocytes. In the steady-state, replenishment of these cells is reduced in the absence of the chemokine receptor CCR2. Within the intestine of mice with colitis, there is a marked increase in the accumulation of immature macrophages that demonstrate an inflammatory phenotype. Here, we asked whether CCR2 is necessary for the development of colitis in mice lacking the receptor for IL10. We compared the development of intestinal inflammation in mice lacking IL10RA or both IL10RA and CCR2. The absence of CCR2 interfered with the accumulation of immature macrophages in IL10R-deficient mice, including a novel population of rounded submucosal Iba1+ cells, and reduced the severity of colitis in these mice. In contrast, the absence of CCR2 did not reduce the augmented inflammatory gene expression observed in mature intestinal macrophages isolated from mice lacking IL10RA. These data suggest that both newly recruited CCR2-dependent immature macrophages and CCR2-independent residual mature macrophages contribute to the development of intestinal inflammation observed in IL10R-deficient mice.

Colonizing Microbes, IL-10 and IL-22: Keeping the Peace at the Mucosal Surface

Our world is filled with microbes. Each multicellular organism has developed ways to interact with this microbial environment. Microbes do not always pose a threat; they can contribute to many processes that benefit the host. Upon colonization both host and microbes adapt resulting in dynamic ecosystems in different host niches. Regulatory processes develop within the host to prevent overt inflammation to beneficial microbes, yet keeping the possibility to respond when pathogens attempt to adhere and invade tissues. This review will focus on microbial colonization and the early (innate) host immune response, with special emphasis on the microbiota-modifying roles of IL-10 and IL-22 in the intestine. IL-10 knock out mice show an altered microbial composition, and spontaneously develop enterocolitis over time. IL-22 knock out mice, although not developing enterocolitis spontaneously, also have an altered microbial composition and increase of epithelial-adherent bacteria, mainly caused by a decrease in mucin and anti-microbial peptide production. Recently interesting links have been found between the IL-10 and IL-22 pathways. While IL-22 can function as a regulatory cytokine at the mucosal surface, it also has inflammatory roles depending on the context. For example, lack of IL-22 in the IL-10–/– mice model prevents spontaneous colitis development. Additionally, the reduced microbial diversity observed in IL-10–/– mice was also reversed in IL-10/IL-22 double mutant mice (Gunasekera et al., 2020). Since in early life, host immunity develops in parallel and in interaction with colonizing microbes, there is a need for future studies that focus on the effect of the timing of colonization in relation to the developmental phase of the host. To illustrate this, examples from zebrafish research will be compared with studies performed in mammals. Since zebrafish develop from eggs and are directly exposed to the outside microbial world, timing of the development of host immunity and subsequent control of microbial composition, is different from mammals that develop in utero and only get exposed after birth. Likewise, colonization studies using adult germfree mice might yield different results from those using neonatal germfree mice. Lastly, special emphasis will be given to the need for host genotype and environmental (co-housing) control of experiments.

A Pilot Gene Expression and Histopathologic Analysis of Tracheal Resections in Tracheobronchomalacia

BACKGROUND

The airway structures and mRNA expression of genes that regulate airway inflammation and remodeling may be altered in the trachea of patients with tracheobronchomalacia (TBM).

METHODS

Fourteen tracheal specimens from 2005-to-2018 were used in this study. Surgical resection specimens from patients with TBM and tracheal stenosis (TS) were compared to control tracheal specimens obtained from autopsy cases. We investigated the mRNA expression of genes encoding fibroblast growth factor (FGF), binding protein 2 (FGFBP2), FGF receptor R3 (FGFR3), interleukin-1 beta (IL1β), tumor growth factor-beta 1 (TGFβ1), tissue inhibitor of metalloproteinases 1 (TIMP1), and intercellular adhesion molecule 1 (ICAM1), as well as established markers of airway inflammation including interferon-gamma (IFNγ) and tumor necrosis factor (TNF). The relative expression of target transcripts was assessed by qRT-PCR. A histological examination of the same resected airway specimens was performed on formalin-fixed paraffin embedded tissue sections.

RESULTS

FGFBP2 and FGFR3 showed higher expression in TBM compared to TS and control groups (p<0.05, p<0.01, respectively). Furthermore, both TGFβ1 and TIMP1 were elevated in TBM compared to controls (p<0.05). Conversely, ICAM1 was downregulated in TBM versus TS and controls (p<0.05). IL1β, IFNγ, and TNF were increased in TBM although did not achieve statistical significance. Histologically, compared to control airways, both TBM and TS demonstrated submucosal fibrotic changes, with TBM additionally demonstrating alterations in elastin fiber quality and density in the posterior membrane.

CONCLUSIONS

Significant changes in gene expression are observed in the tracheal walls of patients with TBM and TS compared to controls.

Microcystin-LR (MC-LR) Triggers Inflammatory Responses in Macrophages

We were the first to previously report that microcystin-LR (MC-LR) has limited effects within the colons of healthy mice but has toxic effects within colons of mice with pre-existing inflammatory bowel disease. In the current investigation, we aimed to elucidate the mechanism by which MC-LR exacerbates colitis and to identify effective therapeutic targets. Through our current investigation, we report that there is a significantly greater recruitment of macrophages into colonic tissue with pre-existing colitis in the presence of MC-LR than in the absence of MC-LR. This is seen quantitatively through IHC staining and the enumeration of F4/80-positive macrophages and through gene expression analysis for Cd68, Cd11b, and Cd163. Exposure of isolated macrophages to MC-LR was found to directly upregulate macrophage activation markers Tnf and Il1b. Through a high-throughput, unbiased kinase activity profiling strategy, MC-LR-induced phosphorylation events were compared with potential inhibitors, and doramapimod was found to effectively prevent MC-LR-induced inflammatory responses in macrophages.

Impact of Interleukin 10 Deficiency on Intestinal Epithelium Responses to Inflammatory Signals

Interleukin 10 (IL-10) is a pleiotropic, anti-inflammatory cytokine that has a major protective role in the intestine. Although its production by cells of the innate and adaptive immune system has been extensively studied, its intrinsic role in intestinal epithelial cells is poorly understood. In this study, we utilised both ATAC sequencing and RNA sequencing to define the transcriptional response of murine enteroids to tumour necrosis factor (TNF). We identified that the key early phase drivers of the transcriptional response to TNF within intestinal epithelium were NFκB transcription factor dependent. Using wild-type and Il10-/- enteroid cultures, we showed an intrinsic, intestinal epithelium specific effect of IL-10 deficiency on TNF-induced gene transcription, with significant downregulation of identified NFκB target genes Tnf, Ccl20, and Cxcl10, and delayed overexpression of NFκB inhibitor encoding genes, Nfkbia and Tnfaip3. IL-10 deficiency, or immunoblockade of IL-10 receptor, impacted on TNF-induced endogenous NFκB activity and downstream NFκB target gene transcription. Intestinal epithelium-derived IL-10 appears to play a crucial role as a positive regulator of the canonical NFκB pathway, contributing to maintenance of intestinal homeostasis. This is particularly important in the context of an inflammatory environment and highlights the potential for future tissue-targeted IL-10 therapeutic intervention.

Restored Macrophage Function Ameliorates Disease Pathophysiology in a Mouse Model for IL10 Receptor-deficient Very Early Onset Inflammatory Bowel Disease

BACKGROUND AND AIMS

Mutations in IL10 or the IL10 receptor lead to very early onset [VEO] inflammatory bowel disease [IBD], a life-threatening disease which is often unresponsive to conventional medication. Recent studies have demonstrated that defective IL-10 receptor signalling in innate immune cells is a key driver of severe intestinal inflammation in VEO-IBD. Specifically, IL10 unresponsiveness of macrophages, which govern the tight balance between pro- and anti-inflammatory responses in the intestinal system, plays a central role in the events leading to excessive inflammatory responses and the development of IBD.

METHODS AND RESULTS

We here evaluated haematopoietic stem cell gene therapy in a VEO-IBD mouse model and demonstrated that the therapeutic response closely correlates with gene correction of the IL10 signalling pathway in intestinal macrophages. This finding prompted us to evaluate the therapeutic efficacy of macrophage transplantation in the Il10rb-/- VEO-IBD mouse model. A 6-week regimen employing a combination of depletion of endogenous hyperinflammatory macrophages followed by intraperitoneal administration of wild-type [WT] macrophages significantly reduced colitis symptoms.

CONCLUSIONS

In summary, we show that the correction of the IL10 receptor defect in macrophages, either by genetic therapy or transfer of WT macrophages to the peritoneum, can ameliorate disease-related symptoms and potentially represent novel treatment approaches for VEO-IBD patients.

Temporal Dynamics of Chronic Inflammation on the Cecal Microbiota in IL-10-/- Mice

The intestinal microbiota is a critical component of mucosal health as evidenced by the fact that alterations in the taxonomic composition of the gastrointestinal microbiota are associated with inflammatory bowel diseases. To better understand how the progression of inflammation impacts the composition of the gastrointestinal microbiota, we used culture independent taxonomic profiling to identify temporal changes in the cecal microbiota of C3Bir IL-10^-/- mice concomitantly with the onset and progression of colitis. This analysis revealed that IL-10^-/- mice displayed a biphasic progression in disease severity, as evidenced by histopathological scores and cytokine production. Beginning at 4 weeks of age, pro-inflammatory cytokines including TNF-α, IFN-γ, IL-6, G-CSF, and IL-1α as well as chemokines including RANTES and MIP-1α were elevated in the serum of IL-10^-/- mice. By 19 weeks of age, the mice developed clinical signs of disease as evidenced by weight loss, which was accompanied by a significant increase in serum levels of KC and IL-17. While the overall diversity of the microbiota of both wild type and IL-10^-/- were similar in young mice, the latter failed to increase in complexity as the mice matured and experienced changes in abundance of specific bacterial taxa that are associated with inflammatory bowel disease in humans. Collectively, these results reveal that there is a critical time in young mice between four to six weeks of age when inflammation and the associated immune responses adversely affect maturation of the microbiota.

Gut-resident CX3CR1hi macrophages induce tertiary lymphoid structures and IgA response in situ

Intestinal mononuclear phagocytes (MPs) are composed of heterogeneous dendritic cell (DC) and macrophage subsets necessary for the initiation of immune response and control of inflammation. Although MPs in the normal intestine have been extensively studied, the heterogeneity and function of inflammatory MPs remain poorly defined. We performed phenotypical, transcriptional, and functional analyses of inflammatory MPs in infectious Salmonella colitis and identified CX3CR1⁺ MPs as the most prevalent inflammatory cell type. CX3CR1⁺ MPs were further divided into three distinct populations, namely, Nos2 ⁺CX3CR1^lo, Ccr7 ⁺CX3CR1^int (lymph migratory), and Cxcl13 ⁺CX3CR1^hi (mucosa resident), all of which were transcriptionally aligned with macrophages and derived from monocytes. In follow-up experiments in vivo, intestinal CX3CR1⁺ macrophages were superior to conventional DC1 (cDC1) and cDC2 in inducing Salmonella-specific mucosal IgA. We next examined spatial organization of the immune response induced by CX3CR1⁺ macrophage subsets and identified mucosa-resident Cxcl13 ⁺CX3CR1^hi macrophages as the antigen-presenting cells responsible for recruitment and activation of CD4⁺ T and B cells to the sites of Salmonella invasion, followed by tertiary lymphoid structure formation and the local pathogen-specific IgA response. Using mice we developed with a floxed Ccr7 allele, we showed that this local IgA response developed independently of migration of the Ccr7 ⁺CX3CR1^int population to the mesenteric lymph nodes and contributed to the total mucosal IgA response to infection. The differential activity of intestinal macrophage subsets in promoting mucosal IgA responses should be considered in the development of vaccines to prevent Salmonella infection and in the design of anti-inflammatory therapies aimed at modulating macrophage function in inflammatory bowel disease.

S100A8 and S100A9 Are Important for Postnatal Development of Gut Microbiota and Immune System in Mice and Infants

BACKGROUND & AIMS

After birth, the immune system matures via interactions with microbes in the gut. The S100 calcium binding proteins S100A8 and S100A9, and their extracellular complex form, S100A8-A9, are found in high amounts in human breast milk. We studied levels of S100A8-A9 in fecal samples (also called fecal calprotectin) from newborns and during infancy, and their effects on development of the intestinal microbiota and mucosal immune system.

METHODS

We collected stool samples (n = 517) from full-term (n = 72) and preterm infants (n = 49) at different timepoints over the first year of life (days 1, 3, 10, 30, 90, 180, and 360). We measured levels of S100A8-A9 by enzyme-linked immunosorbent assay and analyzed fecal microbiomes by 16S sRNA gene sequencing. We also obtained small and large intestine biopsies from 8 adults and 10 newborn infants without inflammatory bowel diseases (controls) and 8 infants with necrotizing enterocolitis and measured levels of S100A8 by immunofluorescence microscopy. Children were followed for 2.5 years and anthropometric data and medical information on infections were collected. We performed studies with newborn C57BL/6J wild-type and S100a9^-/- mice (which also lack S100A8). Some mice were fed or given intraperitoneal injections of S100A8 or subcutaneous injections of Staphylococcus aureus. Blood and intestine, mesenterial and celiac lymph nodes were collected; cells and cytokines were measured by flow cytometry and studied in cell culture assays. Colon contents from mice were analyzed by culture-based microbiology assays.

RESULTS

Loss of S100A8 and S100A9 in mice altered the phenotypes of colonic lamina propria macrophages, compared with wild-type mice. Intestinal tissues from neonatal S100-knockout mice had reduced levels of CX3CR1 protein, and Il10 and Tgfb1 mRNAs, compared with wild-type mice, and fewer T-regulatory cells. S100-knockout mice weighed 21% more than wild-type mice at age 8 weeks and a higher proportion developed fatal sepsis during the neonatal period. S100-knockout mice had alterations in their fecal microbiomes, with higher abundance of Enterobacteriaceae. Feeding mice S100 at birth prevented the expansion of Enterobacteriaceae, increased numbers of T-regulatory cells and levels of CX3CR1 protein and Il10 mRNA in intestine tissues, and reduced body weight and death from neonatal sepsis. Fecal samples from term infants, but not preterm infants, had significantly higher levels of S100A8-A9 during the first 3 months of life than fecal samples from adults; levels decreased to adult levels after weaning. Fecal samples from infants born by cesarean delivery had lower levels of S100A8-A9 than from infants born by vaginal delivery. S100 proteins were expressed by lamina propria macrophages in intestinal tissues from infants, at higher levels than in intestinal tissues from adults. High fecal levels of S100 proteins, from 30 days to 1 year of age, were associated with higher abundance of Actinobacteria and Bifidobacteriaceae, and lower abundance of Gammaproteobacteria-particularly opportunistic Enterobacteriaceae. A low level of S100 proteins in infants' fecal samples associated with development of sepsis and obesity by age 2 years.

CONCLUSION

S100A8 and S100A9 regulate development of the intestinal microbiota and immune system in neonates. Nutritional supplementation with these proteins might aide in development of preterm infants and prevent microbiota-associated disorders in later years.

TNF Receptor 1 Promotes Early-Life Immunity and Protects against Colitis in Mice

Neutralization of tumor necrosis factor (TNF) represents a widely used therapeutic strategy for autoimmune diseases including inflammatory bowel disease (IBD). However, the fact that many patients with IBD are non-responsive to anti-TNF therapies suggests the need for a better understanding of TNF signaling in IBD. Here, we show that co-deletion of TNF receptor 1 (TNFR1, Tnfrsf1a) in the Il10^-/- spontaneous colitis model exacerbates disease, resulting in very-early-onset inflammation after weaning. The disease can be interrupted by treatment with antibiotics. The single deletion of TNFR1 induces subclinical colonic epithelial dysfunction and mucosal immune abnormalities, including accumulation of neutrophils and depletion of B cells. During the pre-disease period (before weaning), both Tnfr1^-/- and Il10^-/-Tnfr1^-/- animals exhibit impaired expression of pro-inflammatory cytokines compared with wild-type and Il10^-/- controls, respectively. Collectively, these results demonstrate the net anti-inflammatory functions of TNF/TNFR1 signaling through the regulation of colonic immune homeostasis in early life.

Loss of IL-10 signaling in macrophages limits bacterial killing driven by prostaglandin E2

Cytokines and lipid mediators are key regulators of inflammation; but how they are mechanistically linked is poorly understood. Here, Mukhopadhyay et al. show a novel regulation between cytokine IL-10 and lipid mediator PGE2 that functionally connects them to intestinal inflammation.

Loss of IL-10 signaling in macrophages (Mφs) leads to inflammatory bowel disease (IBD). Induced pluripotent stem cells (iPSCs) were generated from an infantile-onset IBD patient lacking a functional IL10RB gene. Mφs differentiated from IL-10RB^−/− iPSCs lacked IL-10RB mRNA expression, were unable to phosphorylate STAT3, and failed to reduce LPS induced inflammatory cytokines in the presence of exogenous IL-10. IL-10RB^−/− Mφs exhibited a striking defect in their ability to kill Salmonella enterica serovar Typhimurium, which was rescuable after experimentally introducing functional copies of the IL10RB gene. Genes involved in synthesis and receptor pathways for eicosanoid prostaglandin E2 (PGE2) were more highly induced in IL-10RB^−/− Mφs, and these Mφs produced higher amounts of PGE2 after LPS stimulation compared with controls. Furthermore, pharmacological inhibition of PGE2 synthesis and PGE2 receptor blockade enhanced bacterial killing in Mφs. These results identify a regulatory interaction between IL-10 and PGE2, dysregulation of which may drive aberrant Mφ activation and impaired host defense contributing to IBD pathogenesis.

Runx3 prevents spontaneous colitis by directing the differentiation of anti-inflammatory mononuclear phagocytes

Mice deficient in the transcription factor Runx3 develop a multitude of immune system defects, including early onset colitis. This paper demonstrates that Runx3 is expressed in colonic mononuclear phagocytes (MNP), including resident macrophages (RM) and dendritic cell subsets (cDC2). Runx3 deletion in MNP causes early onset colitis due to their impaired maturation. Mechanistically, the resulting MNP subset imbalance leads to up-regulation of pro-inflammatory genes as occurs in IL10R-deficient RM. In addition, RM and cDC2 display a marked decrease in expression of anti-inflammatory/TGF β-regulated genes and β-catenin signaling associated genes, respectively. MNP transcriptome and ChIP-seq data analysis suggest that a significant fraction of genes affected by Runx3 loss are direct Runx3 targets. Collectively, Runx3 imposes intestinal immune tolerance by regulating maturation of colonic anti-inflammatory MNP, befitting the identification of RUNX3 as a genome-wide associated risk gene for various immune-related diseases in humans, including gastrointestinal tract diseases such as Crohn’s disease and celiac.

Commensal Bacteroidetes protect against Klebsiella pneumoniae colonization and transmission through IL-36 signalling

The microbiota primes immune defences but the identity of specific commensal microorganisms that protect against infection is unclear. Conversely, how pathogens compete with the microbiota to establish their host niche is also poorly understood. In the present study, we investigate the antagonism between the microbiota and Klebsiella pneumoniae during colonization and transmission. We discover that maturation of the microbiota drives the development of distinct immune defence programmes in the upper airways and intestine to limit K. pneumoniae colonization within these niches. Immune protection in the intestine depends on the development of Bacteroidetes, interleukin (IL)-36 signalling and macrophages. This effect of Bacteroidetes requires the polysaccharide utilization locus of their conserved commensal colonization factor. Conversely, in the upper airways, Proteobacteria prime immunity through IL-17A, but K. pneumoniae overcomes these defences through encapsulation to effectively colonize this site. Ultimately, we find that host-to-host spread of K. pneumoniae occurs principally from its intestinal reservoir, and that commensal-colonization-factor-producing Bacteroidetes are sufficient to prevent transmission between hosts through IL-36. Thus, our study provides mechanistic insight into when, where and how commensal Bacteroidetes protect against K. pneumoniae colonization and contagion, providing insight into how these protective microorganisms could be harnessed to confer population-level protection against K. pneumoniae infection.

Generation of protective pneumococcal-specific nasal resident memory CD4+ T cells via parenteral immunization

The generation of tissue-resident memory T cells (T_RM) is an essential aspect of immunity at mucosal surfaces, and it has been suggested that preferential generation of T_RM is one of the principal advantages of mucosally administered vaccines. We have previously shown that antigen-specific, IL-17-producing CD4⁺ T cells can provide capsular antibody-independent protection against nasal carriage of Streptococcus pneumoniae; but whether pneumococcus-responsive T_RM are localized within the nasal mucosa and are sufficient for protection from carriage has not been determined. Here, we show that intranasal administration of live or killed pneumococci to mice generates pneumococcus-responsive IL-17A-producing CD4⁺ mucosal T_RM. Furthermore, we show that these cells are sufficient to mediate long-lived, neutrophil-dependent protection against subsequent pneumococcal nasal challenge. Unexpectedly, and in contrast with the prevailing paradigm, we found that parenteral administration of killed pneumococci also generates protective IL-17A⁺CD4⁺ T_RM in the nasal mucosa. These results demonstrate a critical and sufficient role of T_RM in prevention of pneumococcal colonization, and further that these cells can be generated by parenteral immunization. Our findings therefore have important implications regarding the generation of immune protection at mucosal surfaces by vaccination.

IL-10 Family Cytokines IL-10 and IL-22: from Basic Science to Clinical Translation

Cytokines are among the most important effector and messenger molecules in the immune system. They profoundly participate in immune responses during infection and inflammation, protecting against or contributing to diseases such as allergy, autoimmunity, and cancer. Manipulating cytokine pathways, therefore, is one of the most effective strategies to treat various diseases. IL-10 family cytokines exert essential functions to maintain tissue homeostasis during infection and inflammation through restriction of excessive inflammatory responses, upregulation of innate immunity, and promotion of tissue repairing mechanisms. Their important functions in diseases are supported by data from many preclinical models, human genetic studies, and clinical interventions. Despite significant efforts, however, there is still no clinically approved therapy through manipulating IL-10 family cytokines. Here, we summarize the recent progress in understanding the biology of this family of cytokines, suggesting more specific strategies to maneuver these cytokines for the effective treatment of inflammatory diseases and cancers.

Salivary Gland Extract of Kissing Bug, Triatoma lecticularia, Reduces the Severity of Intestinal Inflammation through the Modulation of the Local IL-6/IL-10 Axis

Triatomines are known for their role as vectors of the causative agent of Chagas disease. The occurrence of an arsenal of molecules in their saliva is able to suppress vertebrate immune responses. Thus, it is reasonable to assume that the presence of molecules with therapeutic potential in their saliva is able to constrain inflammation in immune-mediated diseases. Thus, mice were exposed to dextran sulfate sodium (DSS) in drinking water uninterruptedly during 6 consecutive days and treated with T. lecticularia salivary gland extract (SGE) (3, 10, or 30 μg) or vehicle (saline) (n = 6/group). At the highest dose (30 μg), an improvement in clinical outcome and macroscopic aspects of the intestine were observed. This observation was followed by amelioration in histopathological aspects in the colon especially when the doses of 10 and 30 μg were used. Regardless of the concentration used, treatment with T. lecticularia SGE significantly reduced the levels of the inflammatory cytokine IL-6 in the intestine. The production of the anti-inflammatory cytokine IL-10 was positively impacted by the concentrations of 3 and 30 μg. Our results suggest that the presence of molecules in the T. lecticularia SGE is able to attenuate clinical outcome and colon shortening and improve intestinal architecture besides reducing the production of IL-6 and inducing a local production of IL-10 in the intestine.