Diversity of Intestinal Macrophages in Inflammatory Bowel Diseases

The intestinal epithelial-macrophage-crypt stem cell axis plays a crucial role in regulating and maintaining intestinal homeostasis

The intestinal tract plays a vital role in both digestion and immunity, making its equilibrium crucial for overall health. This equilibrium relies on the dynamic interplay among intestinal epithelial cells, macrophages, and crypt stem cells. Intestinal epithelial cells play a pivotal role in protecting and regulating the gut. They form vital barriers, modulate immune responses, and engage in pathogen defense and cytokine secretion. Moreover, they supervise the regulation of intestinal stem cells. Macrophages, serving as immune cells, actively influence the immune response through the phagocytosis of pathogens and the release of cytokines. They also contribute to regulating intestinal stem cells. Stem cells, known for their self-renewal and differentiation abilities, play a vital role in repairing damaged intestinal epithelium and maintaining homeostasis. Although research has primarily concentrated on the connections between epithelial and stem cells, interactions with macrophages have been less explored. This review aims to fill this gap by exploring the roles of the intestinal epithelial-macrophage-crypt stem cell axis in maintaining intestinal balance. It seeks to unravel the intricate dynamics and regulatory mechanisms among these essential players. A comprehensive understanding of these cell types' functions and interactions promises insights into intestinal homeostasis regulation. Moreover, it holds potential for innovative approaches to manage conditions like radiation-induced intestinal injury, inflammatory bowel disease, and related diseases.

Pharmacological effects of ginseng and ginsenosides on intestinal inflammation and the immune system

Intestinal inflammatory imbalance and immune dysfunction may lead to a spectrum of intestinal diseases, such as inflammatory bowel disease (IBD) and gastrointestinal tumors. As the king of herbs, ginseng has exerted a wide range of pharmacological effects in various diseases. Especially, it has been shown that ginseng and ginsenosides have strong immunomodulatory and anti-inflammatory abilities in intestinal system. In this review, we summarized how ginseng and various extracts influence intestinal inflammation and immune function, including regulating the immune balance, modulating the expression of inflammatory mediators and cytokines, promoting intestinal mucosal wound healing, preventing colitis-associated colorectal cancer, recovering gut microbiota and metabolism imbalance, alleviating antibiotic-induced diarrhea, and relieving the symptoms of irritable bowel syndrome. In addition, the specific experimental methods and key control mechanisms are also briefly described.

STING-Pathway Inhibiting Nanoparticles (SPINs) as a Platform for Treatment of Inflammatory Diseases

Aberrant activation of the cyclic GMP-AMP synthase (cGAS)/Stimulator of Interferon Genes (STING) pathway has been implicated in the development and progression of a myriad of inflammatory diseases including colitis, nonalcoholic steatohepatitis, amyotrophic lateral sclerosis (ALS), and age-related macular degeneration. Thus, STING pathway inhibitors could have therapeutic application in many of these inflammatory conditions. The cGAS inhibitor RU.521 and the STING inhibitor H-151 have shown promise as therapeutics in mouse models of colitis, ALS, and more. However, these agents require frequent high-dose intraperitoneal injections, which may limit translatability. Furthermore, long-term use of systemically administered cGAS/STING inhibitors may leave patients vulnerable to viral infections and cancer. Thus, localized or targeted inhibition of the cGAS/STING pathway may be an attractive, broadly applicable treatment for a variety of STING pathway-driven ailments. Here we describe STING-Pathway Inhibiting Nanoparticles (SPINS)-poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with RU.521 and H-151-as a platform for enhanced and sustained inhibition of cGAS/STING signaling. We demonstrate that SPINs are equally or more effective at inhibiting type-I interferon responses induced by cytosolic DNA than free H-151 or RU.521. Additionally, we describe a SPIN formulation in which PLGA is coemulsified with poly(benzoyloxypropyl methacrylamide) (P(HPMA-Bz)), which significantly improves drug loading and allows for tunable release of H-151 over a period of days to over a week by varying P(HPMA-Bz) content. Finally, we find that all SPIN formulations were as potent or more potent in inhibiting cGAS/STING signaling in primary murine macrophages, resulting in decreased expression of inflammatory M1-like macrophage markers. Therefore, our study provides an in vitro proof-of-concept for nanoparticle delivery of STING pathway inhibitors and positions SPINs as a potential platform for slowing or reversing the onset or progression of cGAS/STING-driven inflammatory conditions.

M2 Macrophage Prominently Distributed in the Rat's Colon of DMH-Induced Inflammation Associated Colorectal Cancer

OBJECTIVE

The aim of this study is to examine the M1 and M2 macrophages distribution in the rat's colon of DMH-induced inflammation associated colorectal cancer.

METHODS

Colon tissue of three groups of 4 rats that induced using 1,2 dimethylhydrazine (DMH) at 30 mg/kg bw every week for 9, 11, and 13 weeks were used. The M1 and M2 distribution was examined by using antibody anti iNOS for M1 and anti-CD163 for M2 with immunohistochemistry method. The data was presents in figure and table in the form of percentage.

RESULT

M1 macrophage was found in all groups in the low distribution level (25% - 50%), while M2 macrophage was observed in all groups with 100% distribution. In the longer period of DMH induction, M2 macrophages was distributed more abundant.

CONCLUSION

All of the rat's colon showing chronic inflammation that led to the tumorigenesis.

HSPA9 reduction exacerbates symptoms and cell death in DSS-Induced inflammatory colitis

Inflammatory bowel disease (IBD) is a chronic inflammatory condition that is influenced by various factors, including environmental factors, immune responses, and genetic elements. Among the factors that influence IBD progression, macrophages play a significant role in generating inflammatory mediators, and an increase in the number of activated macrophages contributes to cellular damage, thereby exacerbating the overall inflammatory conditions. HSPA9, a member of the heat shock protein 70 family, plays a crucial role in regulating mitochondrial processes and responding to oxidative stress. HSPA9 deficiency disrupts mitochondrial dynamics, increasing mitochondrial fission and the production of reactive oxygen species. Based on the known functions of HSPA9, we considered the possibility that HSPA9 reduction may contribute to the exacerbation of colitis and investigated its relevance. In a dextran sodium sulfate-induced colitis mouse model, the downregulated HSPA9 exacerbates colitis symptoms, including increased immune cell infiltration, elevated proinflammatory cytokines, decreased tight junctions, and altered macrophage polarization. Moreover, along with the increased mitochondrial fission, we found that the reduction in HSPA9 significantly affected the superoxide dismutase 1 levels and contributed to cellular death. These findings enhance our understanding of the intricate mechanisms underlying colitis and contribute to the development of novel therapeutic approaches for this challenging condition.

FAM76B regulates PI3K/Akt/NF-κB-mediated M1 macrophage polarization by influencing the stability of PIK3CD mRNA

Macrophage polarization is closely related to inflammation development, yet how macrophages are polarized remains unclear. In our study, the number of M1 macrophages was markedly increased in Fam76b knockout U937 cells vs. wild-type U937 cells, and FAM76B expression was decreased in M1 macrophages induced from different sources of macrophages. Moreover, Fam76b knockout enhanced the mRNA and protein levels of M1 macrophage-associated marker genes. These results suggest that FAM76B inhibits M1 macrophage polarization. We then further explored the mechanism by which FAM76B regulates macrophage polarization. We found that FAM76B can regulate PI3K/Akt/NF-κB pathway-mediated M1 macrophage polarization by stabilizing PIK3CD mRNA. Finally, FAM76B was proven to protect against inflammatory bowel disease (IBD) by inhibiting M1 macrophage polarization through the PI3K/Akt/NF-κB pathway in vivo. In summary, FAM76B regulates M1 macrophage polarization through the PI3K/Akt/NF-κB pathway in vitro and in vivo, which may inform the development of future therapeutic strategies for IBD and other inflammatory diseases.

Identification of cuproptosis-related molecular classification and characteristic genes in ulcerative colitis

Ulcerative colitis (UC) is a refractory inflammatory disease with imbalances in intestinal mucosal homeostasis. Cuproptosis serves as newly identified programmed cell death (PCD) form involved in UC. In the study, UC-related datasets were extracted from the Gene Expression Omnibus (GEO) database. A comparison of UC patients and healthy controls identified 11 differentially expressed cuproptosis-related genes (DE-CRGs), where FDX1, LIAS, and DLAT were differentially expressed in UC groups from the mouse models and clinical samples, with their expression correlating with disease severity. By comprehending weighted gene co-expression network analysis (WGCNA) and differential expression analysis, the key genes common to the module genes relevant to different cuproptosis-related clusters and differentially expressed genes (DEGs) both in different clusters and patients with and without UC were identified using several bioinformatic analysis. Furthermore, the mRNA levels of four characteristic genes with diagnostic potential demonstrated significant decrease in both mouse models and clinical UC samples. Our discoveries offer a theoretical foundation for cuproptosis effect in UC.

The progression of inorganic nanoparticles and natural products for inflammatory bowel disease

There is a growing body of evidence indicating a close association between inflammatory bowel disease (IBD) and disrupted intestinal homeostasis. Excessive production of reactive oxygen species (ROS) and reactive nitrogen species (RNS), along with an increase in M1 proinflammatory macrophage infiltration during the activation of intestinal inflammation, plays a pivotal role in disrupting intestinal homeostasis in IBD. The overabundance of ROS/RNS can cause intestinal tissue damage and the disruption of crucial gut proteins, which ultimately compromises the integrity of the intestinal barrier. The proliferation of M1 macrophages contributes to an exaggerated immune response, further compromising the intestinal immune barrier. Currently, intestinal nanomaterials have gained widespread attention in the context of IBD due to their notable characteristics, including the ability to specifically target regions of interest, clear excess ROS/RNS, and mimic biological enzymes. In this review, we initially elucidated the gut microenvironment in IBD. Subsequently, we delineate therapeutic strategies involving two distinct types of nanomedicine, namely inorganic nanoparticles and natural product nanomaterials. Finally, we present a comprehensive overview of the promising prospects associated with the application of nanomedicine in future clinical settings for the treatment of IBD (graphic abstract). Different classes of nanomedicine are used to treat IBD. This review primarily elucidates the current etiology of inflammatory bowel disease and explores two prominent nanomaterial-based therapeutic approaches. First, it aims to eliminate excessive reactive oxygen species and reactive nitrogen species. Second, they focus on modulating the polarization of inflammatory macrophages and reducing the proportion of pro-inflammatory macrophages. Additionally, this article delves into the treatment of inflammatory bowel disease using inorganic metal nanomaterials and natural product nanomaterials.

The latest perspectives of small molecules FMS kinase inhibitors

FMS kinase is a type III tyrosine kinase receptor that plays a central role in the pathophysiology and management of several diseases, including a range of cancer types, inflammatory disorders, neurodegenerative disorders, and bone disorders among others. In this review, the pathophysiological pathways of FMS kinase in different diseases and the recent developments of its monoclonal antibodies and inhibitors during the last five years are discussed. The biological and biochemical features of these inhibitors, including binding interactions, structure-activity relationships (SAR), selectivity, and potencies are discussed. The focus of this article is on the compounds that are promising leads and undergoing advanced clinical investigations, as well as on those that received FDA approval. In this article, we attempt to classify the reviewed FMS inhibitors according to their core chemical structure including pyridine, pyrrolopyridine, pyrazolopyridine, quinoline, and pyrimidine derivatives.

Aucubin alleviates methotrexate-induced enteritis in rats by inducing autophagy

One of the toxic side effects of methotrexate (MTX) is enteritis. Aucubin, an iridoid glycoside derived from traditional medicinal herbs, has been proven to have anti-inflammation, anti-apoptosis and anti-oxidation properties. This work explored the effect and mechanism of aucubin in treating MTX-induced enteritis in a rat model. Two doses of aucubin (5 and 10 mg/kg) were adopted for the assessment of its pharmacological activity. We observed that in rats with MTX-induced enteritis, the body weight and small intestinal weight decreased. The intestine barrier was injured, as reflected by pathological examinations and an increase in D-lactate and diamine oxidase concentration in serum. Intestinal inflammation was shown by the observation of macrophages in the intestine and the concentrations of inflammatory cytokines tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in serum. The NLR family pyrin domain containing 3 (NLRP3) inflammasome was shown to be activated by the enhancement of NLRP3, cleaved-caspase 1, IL-18 and IL-1β. Moreover, autophagy was reflected by transmission electron microscopy as slightly induced, along with changes in autophagy-related markers microtubule-associated protein 1 light chain 3 (LC3) and Beclin1. Remarkably, aucubin treatment attenuated the MTX-induced disease activity index increase, intestinal damage, inflammatory response and NLRP3 inflammasome activation, but provoked autophagy. Rapamycin, an autophagy activator, showed similar therapeutic effects to aucubin on MTX-induced enteritis. However, 3-methyladenine, an autophagy inhibitor, reversed the protective effects of aucubin. These findings prompted the hypothesis that aucubin alleviates MTX-induced enteritis by aggravating autophagy. This study might provide evidence for further investigation on the therapeutic role of aucubin in MTX-resulted enteritis.

Unraveling the Link between Periodontitis and Inflammatory Bowel Disease: Challenges and Outlook

Periodontitis and Inflammatory Bowel Disease (IBD) are chronic inflammatory conditions, characterized by microbial dysbiosis and hyper-immunoinflammatory responses. Growing evidence suggest an interconnection between periodontitis and IBD, implying a shift from the traditional concept of independent diseases to a complex, reciprocal cycle. This review outlines the evidence supporting an "Oral-Gut" axis, marked by a higher prevalence of periodontitis in IBD patients and vice versa. The specific mechanisms linking periodontitis and IBD remain to be fully elucidated, but emerging evidence points to the ectopic colonization of the gut by oral bacteria, which promote intestinal inflammation by activating host immune responses. This review presents an in-depth examination of the interconnection between periodontitis and IBD, highlighting the shared microbiological and immunological pathways, and proposing a "multi-hit" hypothesis in the pathogenesis of periodontitis-mediated intestinal inflammation. Furthermore, the review underscores the critical need for a collaborative approach between dentists and gastroenterologists to provide holistic oral-systemic healthcare.

The role of sphingosine-1-phosphate in the gut mucosal microenvironment and inflammatory bowel diseases

Sphingosine-1-phosphate (S1P), a type of bioactive sphingolipid, can regulate various cellular functions of distinct cell types in the human body. S1P is generated intracellularly by the catalysis of sphingosine kinase 1/2 (SphK1/2). S1P is transferred to the extracellular environment via the S1P transporter, binds to cellular S1P receptors (S1PRs) and subsequently activates S1P-S1PR downstream signaling. Dysbiosis of the intestinal microbiota, immune dysregulation and damage to epithelial barriers are associated with inflammatory bowel disease (IBD). Generally, S1P mainly exerts a proinflammatory effect by binding to S1PR1 on lymphocytes to facilitate lymphocyte migration to inflamed tissues, and increased S1P was found in the intestinal mucosa of IBD patients. Notably, there is an interaction between the distribution of gut bacteria and SphK-S1P signaling in the intestinal epithelium. S1P-S1PR signaling can also regulate the functions of intestinal epithelial cells (IECs) in mucosa, including cell proliferation and apoptosis. Additionally, increased S1P in immune cells of the lamina propria aggravates the inflammatory response by increasing the production of proinflammatory cytokines. Several novel drugs targeted at S1PRs have recently been used for IBD treatment. This review provides an overview of the S1P-S1PR signaling pathway and, in particular, summarizes the various roles of S1P in the gut mucosal microenvironment to deeply explore the function of S1P-S1PR signaling during intestinal inflammation and, more importantly, to identify potential therapeutic targets for IBD in the SphK-S1P-S1PR axis.

Berberine induces SOCS1 pathway to reprogram the M1 polarization of macrophages via miR-155-5p in colitis-associated colorectal cancer

Berberine is approved for the treatment of intestinal infections and diarrhea and has been shown to have anti-inflammatory and anti-tumor effects in pathological intestinal tissues. However, it is unclear whether the anti-inflammatory effect of berberine contributes to its anti-tumor effect on colitis-associated colorectal cancer (CAC). In this study, we found that berberine effectively inhibited tumorigenesis and protected against colon shortening in CAC mouse model. Immunohistochemistry results showed a reduction in the number of macrophage infiltrations in the colon following berberine treatment. Further analysis revealed that most of the infiltrated macrophages were pro-inflammatory M1 type, which berberine effectively limited. However, in another CRC model without chronic colitis, berberine had no significant effect on tumor number or colon length. In vitro studies demonstrated that berberine treatment significantly reduced the percentage of M1 type and levels of Interleukin-1β (IL-1β), Interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Additionally, miR-155-5p level was down-regulated, and suppressor of cytokine signaling 1 (SOCS1) expression was up-regulated in berberine-treated cells. Notably, the miR-155-5p inhibitor attenuated the regulatory effects of berberine on SOCS1 signaling and macrophage polarization. Altogether, our findings suggest that the inhibitory effect of berberine on CAC development is dependent on its anti-inflammatory activity. Moreover, miR-155-5p may be involved in the pathogenesis of CAC by regulating M1 macrophage polarization, and berberine could be a promising protective agent against miR-155-5p-mediated CAC. This study provides new insights into pharmacologic mechanisms of berberine and supports the possibility that other anti-miR-155-5p drugs may be beneficial in the treatment of CAC.

Isochlorogenic acid A alleviates dextran sulfate sodium-induced ulcerative colitis in mice through STAT3/NF-кB pathway

Isochlorogenic acid A (ICGA-A) is a dicaffeoylquinic acid widely found in various medicinal plants or vegetables, such as Lonicerae japonicae Flos and chicory, and multiple properties of ICGA-A have been reported. However, the therapeutic effect of ICGA-A on colitis is not clear, and thus were investigated in our present study, as well as the underlying mechanisms. Here we found that ICGA-A alleviated clinical symptoms of dextran sodium sulfate (DSS) induced colitis model mice, including disease activity index (DAI) and histological damage. In addition, DSS-induced inflammation was significantly attenuated in mice given ICGA-A supplementation. ICGA-A reduced the fraction of neutrophils in peripheral blood and the infiltration of neutrophils and macrophages in colon tissue, and reduced pro-inflammatory cytokine production and tight junctions in mouse models. Furthermore, ICGA-A down-regulated expression of STAT3 and up-regulated the protein level of IκBα. Our in vitro studies confirmed that ICGA-A inhibited the mRNA expression of pro-inflammatory cytokines. ICGA-A blocked the phosphorylation of STAT3, p65, and IκBα, suppressed the expression STAT3 and p65. In addition, the present study also demonstrated that ICGA-A had no obvious toxicity on normal cells and organs. Taken together, we conclude that ICGA-A mitigates experimental ulcerative colitis (UC) at least in part by inhibiting the STAT3/NF-кB signaling pathways. Hence, ICGA-A may be a promising and effective drug for treating UC.

Intestinal Absorption and Anti-Inflammatory Effects of Siphonein, a Siphonaxanthin Fatty Acid Ester from Green Algae

Siphonein is a C19 acylated siphonaxanthin found in some edible green algae (e.g., Codium fragile and Caulerpa lentillifera). Although the content of siphonein in these green algae is similar to or higher than that of siphonaxanthin, studies of health-related biological activity of siphonein are much less than those of siphonaxanthin. Given the difference in the position of the acyl chain, one cannot infer intestinal absorption of siphonein from other general carotenoid fatty acid esters. In this study, we first investigated the intestinal absorption of siphonein using mouse and cell culture models. A small amount of siphonein was detected in the plasma of treated mice, and its concentration was higher than that of siphonaxanthin (i.e., the hydrolyzed product of ingested siphonein) from 1 to 6 h after administration. Pharmacological inhibition tests with differentiated Caco-2 cells showed that Nieman-Pick C1-like 1-mediated facilitated diffusion was involved in the cellular uptake of siphonein. These results indicate that, unlike general carotenoid fatty acid esters, siphonein can be absorbed without hydrolysis. We also evaluated the anti-inflammatory effect of siphonein in differentiated Caco-2 cells. Siphonein pretreatment modulated lipopolysaccharide-induced cellular lipidome alterations and suppressed mRNA expression of proinflammatory chemokines, CXCL8 protein release, and activation of NF-κB. This study provides new insights into the absorption processes of carotenoids and shows the anti-inflammatory effect of siphonein for the first time.

Macrophages as determinants and regulators of fibrosis in systemic sclerosis

SSc is a multiphase autoimmune disease with a well-known triad of clinical manifestations including vasculopathy, inflammation and fibrosis. Although a plethora of drugs has been suggested as potential candidates to halt SSc progression, nothing has proven clinically efficient. In SSc, both innate and adaptive immune systems are abnormally activated fuelling fibrosis of the skin and other vital organs. Macrophages have been implicated in the pathogenesis of SSc and are thought to be a major source of immune dysregulation. Due to their plasticity, macrophages can initiate and sustain chronic inflammation when classically activated while, simultaneously or parallelly, when alternatively activated they are also capable of secreting fibrotic factors. Here, we briefly explain the polarization process of macrophages. Subsequently, we link the activation of macrophages and monocytes to the molecular pathology of SSc, and illustrate the interplay between macrophages and fibroblasts. Finally, we present recent/near-future clinical trials and discuss novel targets related to macrophages/monocytes activation in SSc.

NF-κB p65 and SETDB1 expedite lipopolysaccharide-induced intestinal inflammation in mice by inducing IRF7/NLR-dependent macrophage M1 polarization

Macrophages exhibit distinct phenotypes that are pro-inflammatory (M1) or anti-inflammatory (M2) in response to inflammation. In this study, we tried to identify the roles and mechanisms of interferon regulatory factor 7 (IRF7) in modulating the phenotypes of macrophages in lipopolysaccharide (LPS)-induced intestinal inflammation. The mouse model of intestinal inflammation was induced by lipopolysaccharide (LPS), and mouse bone marrow-derived macrophages (BMDMs) and mouse intestinal epithelial cells were selected for experimental verification in vitro. Results demonstrated that IRF7 was highly expressed in the mouse model of intestinal inflammation, while IRF7 deficiency repressed macrophage M1 polarization and attenuated intestinal inflammation in mice. p65 and SET domain bifurcated 1 (SETDB1) synergistically promoted histone 3 lysine 4 trimethylation (H3K4me3) methylation to elevate IRF7 expression, which activated the Nod-like receptor (NLR) pathway to induce macrophage M1 polarization. Through this mechanism, IRF7 in BMDMs functioned to accelerate intestinal epithelial cell apoptosis and their release of pro-inflammatory proteins. Furthermore, the promoting effect of p65 and SETDB1 on LPS-induced intestinal inflammation was validated in vivo. To sum up, NF-κB p65 and SETDB1 facilitated IRF7-mediated macrophage M1 polarization, thereby aggravating the LPS-induced intestinal inflammation. Hence, this study highlights the appealing value of these factors as anti-inflammatory targets.

Targeting macrophage autophagy for inflammation resolution and tissue repair in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, non-specific, recurrent inflammatory disease, majorly affecting the gastrointestinal tract. Due to its unclear pathogenesis, the current therapeutic strategy for IBD is focused on symptoms alleviation. Autophagy is a lysosome-mediated catabolic process for maintaining cellular homeostasis. Genome-wide association studies and subsequent functional studies have highlighted the critical role of autophagy in IBD via a number of mechanisms, including modulating macrophage function. Macrophages are the gatekeepers of intestinal immune homeostasis, especially involved in regulating inflammation remission and tissue repair. Interestingly, many autophagic proteins and IBD-related genes have been revealed to regulate macrophage function, suggesting that macrophage autophagy is a potentially important process implicated in IBD regulation. Here, we have summarized current understanding of macrophage autophagy function in pathogen and apoptotic cell clearance, inflammation remission and tissue repair regulation in IBD, and discuss how this knowledge can be used as a strategy for IBD treatment.

A potential therapeutic approach for ulcerative colitis: targeted regulation of macrophage polarization through phytochemicals

Ulcerative colitis (UC), a type of inflammatory bowel disease characterized by recurring and incurable symptoms, causes immense suffering and economic burden for patients due to the limited treatment options available. Therefore, it is imperative to develop novel and promising strategies, as well as safe and effective drugs, for the clinical management of UC. Macrophages play a critical role as the initial line of defense in maintaining intestinal immune homeostasis, and their phenotypic transformation significantly influences the progression of UC. Scientific studies have demonstrated that directing macrophage polarization toward the M2 phenotype is an effective strategy for the prevention and treatment of UC. Phytochemicals derived from botanical sources have garnered the interest of the scientific community owing to their distinct bioactivity and nutritional value, which have been shown to confer beneficial protective effects against colonic inflammation. In this review, we explicated the influence of macrophage polarization on the development of UC and collated data on the significant potential of natural substances that can target the macrophage phenotype and elucidate the possible mechanism of action for its treatment. These findings may provide novel directions and references for the clinical management of UC.

Neuroimmune regulation in Hirschsprung's disease associated enterocolitis

Neuroimmune pathways are important part of the regulation of inflammatory response. Nerve cells regulate the functions of various immune cells through neurotransmitters, and then participate in the inflammatory immune response. Hirschsprung's disease (HD) is a congenital abnormal development of intestinal neurons, and Hirschsprung-associated enterocolitis (HAEC) is a common complication, which seriously affects the quality of life and even endangers the lives of children. Neuroimmune regulation mediates the occurrence and development of enteritis, which is an important mechanism. However, there is a lack of review on the role of Neuroimmune regulation in enterocolitis associated with Hirschsprung's disease. Therefore, this paper summarizes the characteristics of the interaction between intestinal nerve cells and immune cells, reviews the neuroimmune regulation mechanism of Hirschsprung's disease associated enterocolitis (HAEC), and looks forward to the potential clinical application value.

Identification of Critical Modules and Biomarkers of Ulcerative Colitis by Using WGCNA

Background

Ulcerative colitis (UC) is a chronic inflammatory disease of the colon and rectum that has no exact cause and is characterized by relapsing and remitting episodes. We aimed to find biomarkers of UC and its causes.

Methods

We got GSE73661 from the GEO database and used WGCNA to find DEGs that were expressed in the same way in both normal and UC samples. To identify the co-expression modules, we used Weighted Gene Co-Expression Network Analysis. Next, we selected genes that were both DEGs and parts of main modules. Later, three datasets were used to find the hub genes, and qRT-PCR was utilized to confirm the in-silico findings. Additionally, we analyzed the connection between the hub genes and the filtration of immune cells in UC. Using the databases, we made predictions about the miRNAs and lncRNAs that regulate the hub genes and predicted possible therapeutic drugs.

Results

We found 822 DEGs and three main modules related to immunity, endoplasmic reticulum, and metabolism. Using another three datasets and human samples to confirm the mRNA expression of these genes in UC patients, XBP1 and PLPP1 were selected as hub genes, and had excellent diagnostic potential. According to the findings of the immune infiltration, patients with UC exhibited a larger proportion of immune cells. And hub genes, particularly XBP1, were closely linked to a number of immune cell infiltrations. Based on the databases and hub genes, a lncRNA-miRNA-mRNA network, including two miRNAs (miR-214-3p and miR-93-5p), two hub genes, and 124 lncRNAs, and potential therapeutic medicine were identified.

Conclusion

We found two new genes, XBP1 and PLPP1, that are involved in UC and can help diagnose and measure the disease. XBP1 also relates to clinical scores and immune cells. We suggested a gene network and possible drugs based on them.

Insights into diet-associated oxidative pathomechanisms in inflammatory bowel disease and protective effects of functional amino acids

There has been a substantial rise in the incidence and prevalence of clinical patients presenting with inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis. Accumulating evidence has corroborated the view that dietary factors (particularly diets with high levels of saturated fat or sugar) are involved in the development and progression of IBD, which is predominately associated with changes in the composition of the gut microbiota and an increase in the generation of reactive oxygen species. Notably, the ecological imbalance of the gut microbiome exacerbates oxidative stress and inflammatory responses, leading to perturbations of the intestinal redox balance and immunity, as well as mucosal integrity. Recent findings have revealed that functional amino acids, including L-glutamine, glycine, L-arginine, L-histidine, L-tryptophan, and hydroxyproline, are effectively implicated in the maintenance of intestinal redox and immune homeostasis. These amino acids and their metabolites have oxygen free-radical scavenging and inflammation-relieving properties, and they participate in modulation of the microbial community and the metabolites in the gut. The principal focus of this article is a review of recent advances in the oxidative pathomechanisms of IBD development and progression in relation to dietary factors, with a particular emphasis on the redox and signal transduction mechanisms of host cells in response to unbalanced diets and enterobacteria. In addition, an update on current understanding of the protective effects of functional amino acids against IBD, together with the underlying mechanisms for this protection, have been provided.

A Novel Mechanism of Immunoproteasome Regulation via miR-369-3p in Intestinal Inflammatory Response

The immunoproteasome is a multi-catalytic protein complex expressed in hematopoietic cells. Increased expression of immuno-subunits followed by increased proteasome activities is associated with the pathogenesis of IBD. Therefore, the identification of molecules that could inhibit the activities of this complex has been widely studied. microRNAs are small molecules of non-coding RNA that regulate the expression of target genes. Our purpose was to demonstrate that miR-369-3p is able to reduce the expression of the PSMB9 subunit and consequently modulate the catalytic activities of immunoproteasome. After bioinformatics prediction of the gene target of miR-369-3p, we validated its modulation on PSMB9 expression in the RAW264.7 cell line in vitro. We also found that miR-369-3p indirectly reduced the expression of other immunoproteasome subunits and that this regulation reduced the catalytic functions of the immunoproteasome. Increased levels of PSMB9 were observed in colon samples of acute IBD patients compared to the remission IBD group and control group. Our data suggest that miR-369-3p may be a future alternative therapeutic approach to several compounds currently used for the treatment of inflammatory disorders including IBD.

Probiotic Consortia and Their Metabolites Ameliorate the Symptoms of Inflammatory Bowel Diseases in a Colitis Mouse Model

Inflammatory bowel disease (IBD) has become a global public health problem. Although the pathogenesis of the disease is unknown, a potential association between the gut microbiota and inflammatory signatures has been established. Probiotics, especially Lactobacillus or Bifidobacterium, are orally taken as food supplements or microbial drugs by patients with IBD or gastrointestinal disorders due to their safety, efficacy, and power to restore the gut microenvironment. In the current study, we investigated the comprehensive effects of probiotic bacterial consortia consisting of Lactobacillus reuteri, Lactobacillus gasseri, Lactobacillus acidophilus (Lactobacillus spp.), and Bifidobacterium lactis (Bifidobacterium spp.) or their metabolites in a dextran sodium sulfate (DSS)-induced colitis mouse model. Our data demonstrate that probiotic consortia not only ameliorate the disease phenotype but also restore the composition and structure of the gut microbiota. Moreover, the effect of probiotic consortia is better than that of any single probiotic strain. The results also demonstrate that mixed fermentation metabolites are capable of ameliorating the symptoms of gut inflammation. However, the administration of metabolites is not as effective as probiotic consortia with respect to phenotypic characteristics, such as body weight, disease activity index (DAI), and histological score. In addition, mixed metabolites led only to changes in intestinal flora composition. In summary, probiotic consortia and metabolites could exert protective roles in the DSS-induced colitis mouse model by reducing inflammation and regulating microbial dysbiosis. These findings from the current study provide support for the development of probiotic-based microbial products as an alternative therapeutic strategy for IBD. IMPORTANCE IBD is a chronic nonspecific inflammatory disease. IBD is characterized by a wide range of lesions, often involving the entire colon, and is characterized mainly by ulcers and erosions of the colonic mucosa. In the present study, we investigated the efficacy of probiotics on the recovery of gut inflammation and the restoration of gut microecology. We demonstrate that probiotic consortia have a superior effect in inhibiting inflammation and accelerating recovery compared with the effects observed in the control group or groups administered with a single strain. These results support the utilization of probiotic consortia as an alternative therapeutic approach to treat IBD.

Expression of CD44 in Leukocyte Subpopulations in Patients with Inflammatory Bowel Diseases

CD44 expressed in monocytes and lymphocytes seems to play a crucial role in gastrointestinal inflammation, such as the one occurring in the context of inflammatory bowel diseases. Differentially methylated genes are distinctly expressed across monocyte subpopulations related to the state of Crohn’s disease. Hence, the aim of this study was to detect CD44 expression in leukocyte subpopulations in relation to the type of IBD, therapy, and disease duration. Monocyte subpopulations CD14++CD16−, CD14++CD16++, and CD14+CD16+ as well as other leukocytes were analyzed for their CD44 expression using flow cytometry in 46 patients with IBD and 48 healthy controls. Patients with Crohn’s disease treated with non-biological therapy (NBT) exhibited a lower percentage of anti-inflammatory CD14+CD16++ monocytes, whereas NBT-treated patients with ulcerative colitis had lower expression of CD44 on CD14+CD44+ lymphocytes in comparison to controls, respectively. Conversely, patients with Crohn’s disease treated with biological therapy had a higher percentage of CD44+ granulocytes but lower expression of CD44 on anti-inflammatory monocytes compared to controls. Median fluorescence intensity (MFI) of CD44 on CD44+CD14+ lymphocytes was higher in ulcerative colitis patients treated with biological therapy compared to NBT. The percentage of classical CD14++CD16− monocytes was lower in the <9 years of IBD duration subgroup compared with the longer disease duration subgroup. The present study addresses the putative role of differentiation and regulation of leukocytes in tailoring IBD therapeutic regimes.

GPR84 signaling promotes intestinal mucosal inflammation via enhancing NLRP3 inflammasome activation in macrophages

The putative medium-chain free fatty acid receptor GPR84 is a G protein-coupled receptor primarily expressed in myeloid cells that constitute the innate immune system, including neutrophils, monocytes, and macrophages in the periphery and microglia in the brain. The fact that GPR84 expression in leukocytes is remarkably increased under acute inflammatory stimuli such as lipopolysaccharide (LPS) and TNFα suggests that it may play a role in the development of inflammatory and fibrotic diseases. Here we demonstrate that GPR84 is highly upregulated in inflamed colon tissues of active ulcerative colitis (UC) patients and dextran sulfate sodium (DSS)-induced colitis mice. Infiltrating GPR84⁺ macrophages are significantly increased in the colonic mucosa of both the UC patients and the mice with colitis. Consistently, GPR84^-/- mice are resistant to the development of colitis induced by DSS. GPR84 activation imposes pro-inflammatory properties in colonic macrophages through enhancing NLRP3 inflammasome activation, while the loss of GPR84 prevents the M1 polarization and properties of proinflammatory macrophages. CLH536, a novel GPR84 antagonist discovered by us, suppresses colitis by reducing the polarization and function of pro-inflammatory macrophages. These results define a unique role of GPR84 in innate immune cells and intestinal inflammation, and suggest that GPR84 may serve as a potential drug target for the treatment of UC.

The Role of Tissue-Resident Macrophages in the Development and Treatment of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), comprising Crohn’s disease and ulcerative colitis, is a refractory disease with many immune abnormalities and pathologies in the gastrointestinal tract. Because macrophages can distinguish innocuous antigens from potential pathogens to maintain mucosa barrier functions, they are essential cells in the intestinal immune system. With numerous numbers in the intestinal tract, tissue-resident macrophages have a significant effect on the constant regeneration of intestinal epithelial cells and maintaining the immune homeostasis of the intestinal mucosa. They also have a significant influence on IBD through regulating pro-(M1) or anti-inflammatory (M2) phenotype polarization according to different environmental cues. The disequilibrium of the phenotypes and functions of macrophages, disturbed by intracellular or extracellular stimuli, influences the progression of disease. Further investigation of macrophages’ role in the progression of IBD will facilitate deciphering the pathogenesis of disease and exploring novel targets to develop novel medications. In this review, we shed light on the origin and maintenance of intestinal macrophages, as well as the role of macrophages in the occurrence and development of IBD. In addition, we summarize the interaction between gut microbiota and intestinal macrophages, and the role of the macrophage-derived exosome. Furthermore, we discuss the molecular and cellular mechanisms participating in the polarization and functions of gut macrophages, the potential targeted strategies, and current clinical trials for IBD.

Targeting tumor-associated macrophages for cancer immunotherapy

Tumor-associated macrophages (TAMs) are one of the most abundant immune components in the tumor microenvironment and play a plethora of roles in regulating tumorigenesis. Therefore, the therapeutic targeting of TAMs has emerged as a new paradigm for immunotherapy of cancer. Herein, the review summarizes the origin, polarization, and function of TAMs in the progression of malignant diseases. The understanding of such knowledge leads to several distinct therapeutic strategies to manipulate TAMs to battle cancer, which include those to reduce TAM abundance, such as depleting TAMs or inhibiting their recruitment and differentiation, and those to harness or boost the anti-tumor activities of TAMs such as blocking phagocytosis checkpoints, inducing antibody-dependent cellular phagocytosis, and reprogramming TAM polarization. In addition, modulation of TAMs may reshape the tumor microenvironment and therefore synergize with other cancer therapeutics. Therefore, the rational combination of TAM-targeting therapeutics with conventional therapies including radiotherapy, chemotherapy, and other immunotherapies is also reviewed. Overall, targeting TAMs presents itself as a promising strategy to add to the growing repertoire of treatment approaches in the fight against cancer, and it is hopeful that these approaches currently being pioneered will serve to vastly improve patient outcomes and quality of life.

FOXO3 Expression in Macrophages Is Lowered by a High-Fat Diet and Regulates Colonic Inflammation and Tumorigenesis

Obesity, characterized by augmented inflammation and tumorigenesis, is linked to genetic predispositions, such as FOXO3 polymorphisms. As obesity is associated with aberrant macrophages infiltrating different tissues, including the colon, we aimed to identify FOXO3-dependent transcriptomic changes in macrophages that drive obesity-mediated colonic inflammation and tumorigenesis. We found that in mouse colon, high-fat-diet-(HFD)-related obesity led to diminished FOXO3 levels and increased macrophages. Transcriptomic analysis of mouse peritoneal FOXO3-deficient macrophages showed significant differentially expressed genes (DEGs; FDR < 0.05) similar to HFD obese colons. These DEG-related pathways, linked to mouse colonic inflammation and tumorigenesis, were similar to those in inflammatory bowel disease (IBD) and human colon cancer. Additionally, we identified a specific transcriptional signature for the macrophage-FOXO3 axis (MAC-FOXO382), which separated the transcriptome of affected tissue from control in both IBD (p = 5.2 × 10−8 and colon cancer (p = 1.9 × 10−11), revealing its significance in human colonic pathobiologies. Further, we identified (heatmap) and validated (qPCR) DEGs specific to FOXO3-deficient macrophages with established roles both in IBD and colon cancer (IL-1B, CXCR2, S100A8, S100A9, and TREM1) and those with unexamined roles in these colonic pathobiologies (STRA6, SERPINH1, LAMB1, NFE2L3, OLR1, DNAJC28 and VSIG10). These findings establish an important understanding of how HFD obesity and related metabolites promote colonic pathobiologies.

Gut Microbiota, Macrophages and Diet: An Intriguing New Triangle in Intestinal Fibrosis

Intestinal fibrosis is a common complication in inflammatory bowel disease (IBD) without specific treatment. As macrophages are the key actors in inflammatory responses and the wound healing process, they have been extensively studied in chronic diseases these past decades. By their exceptional ability to integrate diverse stimuli in their surrounding environment, macrophages display a multitude of phenotypes to underpin a broad spectrum of functions, from the initiation to the resolution of inflammation following injury. The hypothesis that distinct macrophage subtypes could be involved in fibrogenesis and wound healing is emerging and could open up new therapeutic perspectives in the treatment of intestinal fibrosis. Gut microbiota and diet are two key factors capable of modifying intestinal macrophage profiles, shaping their specific function. Defects in macrophage polarisation, inadequate dietary habits, and alteration of microbiota composition may contribute to the development of intestinal fibrosis. In this review, we describe the intriguing triangle between intestinal macrophages, diet, and gut microbiota in homeostasis and how the perturbation of this discreet balance may lead to a pro-fibrotic environment and influence fibrogenesis in the gut.

Bioactive fish collagen peptides weaken intestinal inflammation by orienting colonic macrophages phenotype through mannose receptor activation

PURPOSE

Particular interest is now given to the potential of dietary supplements as alternative non-pharmacological approaches in intestinal inflammation handling. In this aim, this study evaluates the efficiency of fish collagen peptides, Naticol^®Gut, on colonic inflammation.

METHODS

Wild type and Mannose receptor-deficient in the myeloid lineage C57BL/6 mice were administered with Dextran Sodium Sulfate (DSS), Naticol^®Gut, DSS, and Naticol^®Gut or only water for 4 or 8 days. Inflammatory status was evaluated by establishing macroscopic and microscopic scores, by measuring cytokine and calprotectin production by ELISA and the myeloperoxidase activity by chemiluminescence. Colonic macrophages were phenotyped by measuring mRNA levels of specific markers of inflammation and oxidative status. Colonic immune populations and T-cell activation profiles were determined by flow cytometry. Mucosa-associated gut microbiota assessment was undertaken by qPCR. The phenotype of human blood monocytes from inflammatory bowel disease (IBD) subjects was characterized by RT-qPCR and flow cytometry and their oxidative activity by chemiluminescence.

RESULTS

Naticol^®Gut-treated DSS mice showed attenuated colonic inflammation compared to mice that were only exposed to DSS. Naticol^®Gut activity was displayed through its ability to orient the polarization of colonic macrophage towards an anti-inflammatory and anti-oxidant phenotype after its recognition by the mannose receptor. Subsequently, Naticol^®Gut delivery modulated CD4 T cells in favor of a Th2 response and dampened CD8 T-cell activation. This immunomodulation resulted in an intestinal eubiosis. In human monocytes from IBD subjects, the treatment with Naticol^®Gut also restored an anti-inflammatory and anti-oxidant phenotype.

CONCLUSION

Naticol^®Gut acts as a protective agent against colitis appearing as a new functional food and an innovative and complementary approach in gut health.

Ginsenoside Rg1 ameliorated experimental colitis by regulating the balance of M1/M2 macrophage polarization and the homeostasis of intestinal flora

Aberrant M1/M2 macrophage polarization and dysbiosis are involved in the pathogenesis of ulcerative colitis (UC). Ginsenoside Rg1 exhibits optimal immunomodulatory and anti-inflammatory effects in treating UC of humans and animals, but the action mechanism through the regulation of M1/M2 macrophage polarization and intestinal flora composition remain unclear. Here, experimental colitis was induced in BALB/c mice using dextran sulfate sodium, and Rock1 inhibitor Y27632 was used to explore the action mechanism of ginsenoside Rg1. Following treatment with ginsenoside Rg1 (200 mg/kg/day) and Y27632 (10 mg/kg/day) for 14 consecutive days, the rate of change in mouse body weight, mouse final weight, colonic weight, colonic length, colonic weight index and pathological damage scores of colitis mice were effectively improved, accompanied by less ulcer formation and inflammatory cell infiltration, lower levels of interleukin (IL)-6, IL-33, chemokine (C-C motif) ligand 2 (CCL-2), tumor necrosis factor alpha (TNF-α), and higher IL-4 and IL-10. Importantly, ginsenoside Rg1 and Y27632 significantly down-regulated CD11b⁺F4/80⁺, CD11b⁺F4/80⁺Tim-1⁺ and CD11b⁺F4/80⁺TLR4⁺ macrophages, and CD11b⁺F4/80⁺iNOS⁺ M1 macrophages, and significantly up-regulated CD11b⁺F4/80⁺CD206⁺ and CD11b⁺F4/80⁺CD163⁺ M2 macrophages in colitis mice; concomitantly, ginsenoside Rg1 improved the diversity of colonic microbiota and regulated Lachnospiraceae, Staphylococcus, Bacteroide and Ruminococcaceae_UCG_014 at genus level in colitis mice, but the flora regulated by Y27632 was not identical to it. Moreover, ginsenoside Rg1 and Y27632 down-regulated the protein levels of Rock1, RhoA and Nogo-B in colitis mice. These results suggested that ginsenoside Rg1 and Y27632 ameliorated colitis by regulating M1/M2 macrophage polarization and microbiota composition, associated with inhibition of the Nogo-B/RhoA signaling pathway.

Cells and mediators of inflammation as effectors of epithelial repair in the inflamed intestine

Mucosal and histological healing have become the gold standards for assessing the efficacy of therapy in patients living with inflammatory bowel diseases (IBD). Despite these being the accepted goals in therapy, the mechanisms that underlie the healing of the mucosa after an inflammatory insult are not well understood, and many patients fail to meet this therapeutic endpoint. Here we review the emerging evidence that mediators (e.g., prostaglandins, cytokines, proteases, reactive oxygen, and nitrogen species) and innate immune cells (e.g., neutrophils and monocytes/macrophages), that are involved in the initiation of the inflammatory response, are also key players in the mechanisms underlying mucosal healing to resolve chronic inflammation in the colon. The dual function mediators comprise an inflammation/repair program that returns damaged tissue to homeostasis. Understanding details of the dual mechanisms of these mediators and cells may provide the basis for the development of drugs that can help to stimulate epithelial repair in patients affected by IBD.

Netrin-1: A Modulator of Macrophage Driven Acute and Chronic Inflammation

Netrins belong to the family of laminin-like secreted proteins, which guide axonal migration and neuronal growth in the developing central nervous system. Over the last 20 years, it has been established that netrin-1 acts as a chemoattractive or chemorepulsive cue in diverse biological processes far beyond neuronal development. Netrin-1 has been shown to play a central role in cell adhesion, cell migration, proliferation, and cell survival in neuronal and non-neuronal tissue. In this context, netrin-1 was found to orchestrate organogenesis, angiogenesis, tumorigenesis, and inflammation. In inflammation, as in neuronal development, netrin-1 plays a dichotomous role directing the migration of leukocytes, especially monocytes in the inflamed tissue. Monocyte-derived macrophages have long been known for a similar dual role in inflammation. In response to pathogen-induced acute injury, monocytes are rapidly recruited to damaged tissue as the first line of immune defense to phagocyte pathogens, present antigens to initiate the adaptive immune response, and promote wound healing in the resolution phase. On the other hand, dysregulated macrophages with impaired phagocytosis and egress capacity accumulate in chronic inflammation sites and foster the maintenance-and even the progression-of chronic inflammation. In this review article, we will highlight the dichotomous roles of netrin-1 and its impact on acute and chronic inflammation.

CP-25 exerts therapeutic effects in mice with dextran sodium sulfate-induced colitis by inhibiting GRK2 translocation to downregulate the TLR4-NF-κB-NLRP3 inflammasome signaling pathway in macrophages

Deficiency of G protein-coupled receptor kinase 2 (GRK2) was found to protect mice from dextran sulfate sodium (DSS)-induced colitis. Paeoniflorin-6'-O-benzene sulfonate (CP-25) has been shown to exert anti-inflammatory immune regulatory effects in animal models of inflammatory autoimmune disease. This study aimed to investigate the of GRK2 in the pathogenesis of ulcerative colitis (UC) and its effects on macrophage polarization, macrophage subtype regulation of intestinal barrier function, and therapeutic effects of CP-25 in mice with DSS-induced colitis. We found imbalanced macrophage polarization, intestinal barrier dysfunction, and abnormal activation of GRK2 and TLR4-NF-κB-NLRP3 inflammasome signaling pathway in the colonic mucosa of patients with UC. CP-25, restored the damaged intestinal barrier function by inhibiting the transmembrane region of GRK2 in macrophages stimulated by lipopolysaccharides. CP-25 exerted therapeutic effects by ameliorating clinical manifestation, regulating macrophage polarization, and restoring abnormally activated TLR4-NF-κB-NLRP3 inflammasome signaling pathway by inhibiting GRK2. These data suggest the pathogenesis of UC may be related to the imbalance of macrophage polarization, which leads to abnormal activation of TLR4-NF-κB-NLRP3 inflammasome signaling pathway mediated by GRK2 and destruction of the intestinal mucosal barrier. CP-25 confers therapeutic effects on colitis by inhibiting GRK2 translocation to induce the downregulation of TLR4-NF-κB-NLRP3 inflammasome signaling in macrophages.

Caveolin-1 Deficiency Protects Mice Against Carbon Tetrachloride-Induced Acute Liver Injury Through Regulating Polarization of Hepatic Macrophages

Polarization of hepatic macrophages plays a crucial role in the injury and repair processes of acute and chronic liver diseases. However, the underlying molecular mechanisms remain elusive. Caveolin-1 (Cav1) is the structural protein of caveolae, the invaginations of the plasma membrane. It has distinct functions in regulating hepatitis, cirrhosis, and hepatocarcinogenesis. Given the increasing number of cases of liver cancer, nonalcoholic steatohepatitis, and non-alcoholic fatty liver disease worldwide, investigations on the role of Cav1 in liver diseases are warranted. In this study, we aimed to investigate the role of Cav1 in the pathogenesis of acute liver injury. Wild-type (WT) and Cav1 knockout (KO) mice (Cav1^tm1Mls) were injected with carbon tetrachloride (CCl₄). Cav1 KO mice showed significantly reduced degeneration, necrosis, and apoptosis of hepatocytes and decreased level of alanine transaminase (ALT) compared to WT mice. Moreover, Cav1 was required for the recruitment of hepatic macrophages. The analysis of the mRNA levels of CD86, tumor necrosis factor (TNF), and interleukin (IL)-6, as well as the protein expression of inducible nitric oxide synthase (iNOS), indicated that Cav1 deficiency inhibited the polarization of hepatic macrophages towards the M1 phenotype in the injured liver. Consistent with in vivo results, the expressions of CD86, TNF, IL-6, and iNOS were significantly downregulated in Cav1 KO macrophages. Also, fluorescence-activated cell sorting (FACS) analysis showed that the proportion of M1 macrophages was significantly decreased in the liver tissues obtained from Cav1 KO mice following CCl₄ treatment. In summary, our results showed that Cav1 deficiency protected mice against CCl₄-induced acute liver injury by regulating polarization of hepatic macrophages. We provided direct genetic evidence that Cav1 expressed in hepatic macrophages contributed to the pathogenesis of acute liver injury by regulating the polarization of hepatic macrophages towards the M1 phenotype. These findings suggest that Cav1 expressed in macrophages may represent a potential therapeutic target for acute liver injury.

How Early-Life Gut Microbiota Alteration Sets Trajectories for Health and Inflammatory Bowel Disease?

Inflammatory bowel disease (IBD) is a recurrent chronic inflammatory condition of the intestine without any efficient therapeutic regimens. Gut microbiota, which plays an instrumental role in the development and maturation of the immune system, has been implicated in the pathogenesis of IBD. Emerging evidence has established that early-life events particularly maternal influences and antibiotic treatment are strongly correlated with the health or susceptibility to disease of an individual in later life. Thus, it is proposed that there is a critical period in infancy, during which the environmental exposures bestow a long-term pathophysiological imprint. This notion sheds new light on the development of novel approaches for the treatment, i.e., early interventions, more precisely, the prevention of many uncurable chronic inflammatory diseases like IBD. In this review, we have integrated current evidence to describe the feasibility of the “able-to-be-regulated microbiota,” summarized the underlying mechanisms of the “microbiota-driven immune system education,” explored the optimal intervention time window, and discussed the potential of designing early-probiotic treatment as a new prevention strategy for IBD.

Konjac Glucomannan Oligosaccharides Prevent Intestinal Inflammation Through SIGNR1-Mediated Regulation of Alternatively Activated Macrophages

SCOPE

Konjac glucomannan oligosaccharides (KMOS) are prebiotics and may improve intestinal immunity through modulation of macrophage function. However, the underlying molecular mechanisms were unclear.

METHODS AND RESULTS

Using a mouse model of dextran sulfated sodium (DSS)-induced acute colitis, the study demonstrates here that KMOS (400 mg^-1 kg^-1 d^-1 ) can ameliorate intestinal inflammation in a macrophage dependent manner. Oral exposure to KMOS prevents DSS-induced intestinal pathology, improves epithelial integrity, and decreases accumulation of colonic inflammatory leukocytes and cytokines. The therapeutic effects of KMOS are dependent on the function of macrophages, as depletion of macrophages abolished the effects. In colonic lamina propria of DSS-treated mice, as well as in vitro culture of bone marrow derived macrophages (BMDMs), KMOS skews reprogramming of classically activated macrophages (CAM/M1) into alternatively activated macrophages (AAM/M2). The study further determines that the activation of SIGNR1/phospho-c-Raf (S338)/phospho-p65 (S276)/acetyl-p65 (K310) pathway is responsible for KMOS-induced AAM/M2 polarization. Blockage of SIGNR1 abolishes KMOS-induced AAM/M2 polarization of activated macrophages, expression of phospho-p65 (S276) in colonic macrophages, and alleviation of DSS-induced colitis in mice, suggesting that SIGNR1 is critical for macrophage responses to KMOS.

CONCLUSIONS

This study reveals a SIGNR1-mediated macrophage-dependent pathway that supports regulatory function of KMOS in host immunity and intestinal homeostasis.

DA-DRD5 signaling controls colitis by regulating colonic M1/M2 macrophage polarization

The decrease of neurotransmitter dopamine (DA) levels in the intestine is closely related to the development of inflammatory bowel disease (IBD). However, the functional relevance and underlying mechanistic basis of the effects of DA signaling on IBD remains unclear. Here, we observed that the DRD5 receptor is highly expressed in colonic macrophages, and the deficiency of DA-DRD5 signaling exacerbated experimental colitis. Moreover, DA-DRD5 signaling can inhibit M1 by negatively regulating NF-κB signaling but promote M2 macrophage polarization through activation of the CREB pathway, respectively. The deficiency of DRD5 signaling increased colonic M1 macrophages but reduced M2 cells during colitis. Additionally, the administration of a D1-like agonist that has a higher affinity to DRD5 can attenuate the colitogenic phenotype of mice. Collectively, these findings provide the first demonstration of DA-DRD5 signaling in colonic macrophages controlling the development of colitis by regulating M1/M2 macrophage polarization.

PI3KC3 complex subunit NRBF2 is required for apoptotic cell clearance to restrict intestinal inflammation

NRBF2, a regulatory subunit of the ATG14-BECN1/Beclin 1-PIK3C3/VPS34 complex, positively regulates macroautophagy/autophagy. In this study, we report that NRBF2 is required for the clearance of apoptotic cells and alleviation of inflammation during colitis in mice. NRBF2-deficient mice displayed much more severe colitis symptoms after the administration of ulcerative colitis inducer, dextran sulfate sodium salt (DSS), accompanied by prominent intestinal inflammation and apoptotic cell accumulation. Interestingly, we found that nrbf2-/- mice and macrophages displayed impaired apoptotic cell clearance capability, while adoptive transfer of nrbf2+/+ macrophages to nrbf2-/- mice alleviated DSS-induced colitis lesions. Mechanistically, NRBF2 is required for the generation of the active form of RAB7 to promote the fusion between phagosomes containing engulfed apoptotic cells and lysosomes via interacting with the MON1-CCZ1 complex and regulating the guanine nucleotide exchange factor (GEF) activity of the complex. Evidence from clinical samples further reveals the physiological role of NRBF2 in maintaining intestinal homeostasis. In biopsies of UC patient colon, we observed upregulated NRBF2 in the colon macrophages and the engulfment of apoptotic cells by NRBF2-positive cells, suggesting a potential protective role for NRBF2 in UC. To confirm the relationship between apoptotic cell clearance and IBD development, we compared TUNEL-stained cell counts in the UC with UC severity (Mayo Score) and observed a strong correlation between the two indexes, indicating that apoptotic cell population in colon tissue correlates with UC severity. The findings of our study reveal a novel role for NRBF2 in regulating apoptotic cell clearance to restrict intestinal inflammation.Abbreviation: ANOVA: analysis of variance; ATG14: autophagy related 14; ATG16L1: autophagy related 16-like 1 (S. cerevisiae); BMDM: bone marrow-derived macrophage; BSA: bovine serum albumin; CD: Crohn disease; CD68: CD68 molecule; CFP: cyan fluorescent protein; CMFDA: 5-chloromethylfluorescein diacetate; Co-IP, co-immunoprecipitation; CPR: C-reactive protein; Cy7: cyanine 7 maleimide; DAB: diaminobezidine 3; DAI: disease activity indexes; DAPI: 4'6-diamidino-2-phenylindole; DMEM: dulbecco's modified eagle's medium; DMSO: dimethyl sulfoxide; DOC: sodium deoxycholate; DSS: dextran sulfate sodium; EDTA: ethylenediaminetetraacetic acid; EGTA: ethylenebis (oxyethylenenitrilo) tetraacetic acid; FBS: fetal bovine serum; FITC: fluorescein isothiocyanate; FRET: Förster resonance energy transfer; GDP: guanine dinucleotide phosphate; GEF: guanine nucleotide exchange factor; GFP: green fluorescent protein; GTP: guanine trinucleotide phosphate; GWAS: genome-wide association studies; HEK293: human embryonic kidney 293 cells; HRP: horseradish peroxidase; IBD: inflammatory bowel disease; IgG: immunoglobin G; IL1B/IL-1β: interleukin 1 beta; IL6: interleukin 6; IRGM: immunity related GTPase M; ITGAM/CD11b: integrin subunit alpha M; KO: knockout; LRRK2: leucine rich repeat kinase 2; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MOI: multiplicity of infection; MPO: myeloperoxidase; NaCl: sodium chloride; NEU: neutrophil; NOD2: nucleotide binding oligomerization domain containing 2; NP40: nonidet-P40; NRBF2: nuclear receptor binding factor 2; PBS: phosphate buffer saline; PCR: polymerase chain reaction; PE: P-phycoerythrin; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PtdIns3P: phosphatidylinositol-3-phosphate; PTPRC/CD45: protein tyrosine phosphatase receptor type C; SDS-PAGE: sodium dodecylsulphate-polyacrylamide gel electrophoresis; TBST: tris-buffered saline Tween-20; Tris-HCl: trihydroxymethyl aminomethane hydrochloride; TUNEL: TdT-mediated dUTP nick-end labeling; UC: ulcerative colitis; ULK1: unc-51 like autophagy activating kinase 1; WB: western blotting; WT: wild type; YFP: yellow fluorescent protein.

Divergent Roles for Macrophage C-type Lectin Receptors, Dectin-1 and Mannose Receptors, in the Intestinal Inflammatory Response

Colonic macrophages are considered to be major effectors of inflammatory bowel diseases (IBDs) and the control of gut inflammation through C-type lectin receptors is an emerging concept. We show that during colitis, the loss of dectin-1 on myeloid cells prevents intestinal inflammation, while the lack of mannose receptor (MR) exacerbates it. A marked increase in dectin-1 expression in dextran sulfate sodium (DSS)-exposed MR-deficient mice supports the critical contribution of dectin-1 to colitis outcome. Dectin-1 is crucial for Ly6C^highCCR2^high monocyte population enrichment in the blood and their recruitment to inflamed colon as precursors of inflammatory macrophages. Dectin-1 also promotes inflammasome-dependent interleukin-1β (IL-1β) secretion through leukotriene B4 production. Interestingly, colonic inflammation is associated with a concomitant overexpression of dectin-1/CCL2/LTA4H and downregulation of MR on macrophages from IBD patients. Thus, MR and dectin-1 on macrophages are important mucosal inflammatory regulators that contribute to the intestinal inflammation.

Macrophage polarization: an effective approach to targeted therapy of inflammatory bowel disease

Introduction: Inflammatory bowel disease (IBD) is a systemic disease with immune abnormalities that can affect the entire digestive tract. A high percentage of patients with IBD are unresponsive to current pharmacological agents, hence the need exists for novel therapeutic approaches. There is compelling evidence that macrophage polarization plays a key role in the remission of IBD patients and that it could open up future treatment options for patients.Areas covered: This paper highlights the crucial role of macrophage polarization in IBD. The authors shed light on the phenotype and function of macrophages and potential drug targets for polarization regulation. Existing approaches for regulating macrophage polarization are discussed and potential solutions for safety concerns are considered. We performed a literature search on the IBD and macrophage polarization mainly published in PubMed January 2010-July 2020.Expert opinion: Evidence indicates that there are fewer M2 macrophages and a high proportion of M1 macrophages in the intestinal tissues of individuals who are non- responsive to treatment. Regulating macrophage polarization is a potential novel targeted option for IBD treatment. Improved mechanistic insights are required to uncover more precise and effective targets for skewing macrophages into a proper phenotype.

Lack of Mucosal Cholinergic Innervation Is Associated With Increased Risk of Enterocolitis in Hirschsprung's Disease

BACKGROUND & AIMS

Hirschsprung's disease (HSCR) is a congenital intestinal motility disorder defined by the absence of enteric neuronal cells (ganglia) in the distal gut. The development of HSCR-associated enterocolitis remains a life-threatening complication. Absence of enteric ganglia implicates innervation of acetylcholine-secreting (cholinergic) nerve fibers. Cholinergic signals have been reported to control excessive inflammation, but the impact on HSCR-associated enterocolitis is unknown.

METHODS

We enrolled 44 HSCR patients in a prospective multicenter study and grouped them according to their degree of colonic mucosal acetylcholinesterase-positive innervation into low-fiber and high-fiber patient groups. The fiber phenotype was correlated with the tissue cytokine profile as well as immune cell frequencies using Luminex analysis and fluorescence-activated cell sorting analysis of colonic tissue and immune cells. Using confocal immunofluorescence microscopy, macrophages were identified in close proximity to nerve fibers and characterized by RNA-seq analysis. Microbial dysbiosis was analyzed in colonic tissue using 16S-rDNA gene sequencing. Finally, the fiber phenotype was correlated with postoperative enterocolitis manifestation.

RESULTS

The presence of mucosal nerve fiber innervation correlated with reduced T-helper 17 cytokines and cell frequencies. In high-fiber tissue, macrophages co-localized with nerve fibers and expressed significantly less interleukin 23 than macrophages from low-fiber tissue. HSCR patients lacking mucosal nerve fibers showed microbial dysbiosis and had a higher incidence of postoperative enterocolitis.

CONCLUSIONS

The mucosal fiber phenotype might serve as a prognostic marker for enterocolitis development in HSCR patients and may offer an approach to personalized patient care and new therapeutic options.

Extracellular Vesicles from Thapsigargin-Treated Mesenchymal Stem Cells Ameliorated Experimental Colitis via Enhanced Immunomodulatory Properties

Therapeutic applications of extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) have attracted considerable attention because of their immunomodulatory properties against immune-mediated, inflammatory diseases. Here, we demonstrated enhanced immunomodulatory properties of EVs secreted from endoplasmic reticulum (ER) stress inducer thapsigargin (TSG)-primed human Wharton's jelly-derived MSCs (WJ-MSCs). EVs from TSG-primed WJ-MSCs (TSG-EV) showed increased yield and expression of immunomodulatory factors, such as transforming growth factor-β1 (TGFβ), cyclooxygenase-2 (COX2), and especially indoleamine 2,3-dioxygenase (IDO), compared to control EVs. TSG-EV showed a significantly enhanced immunosuppressive effect on human peripheral blood-derived T cell proliferation and Th1 and Th17 differentiation, whereas Treg and M2-type macrophage were enriched compared to a control EV-treated group. Furthermore, TSG-EV substantially mitigated mouse experimental colitis by reducing the inflammatory response and maintaining intestinal barrier integrity. A significant increase of Tregs and M2-type macrophages in colitic colons of a TSG-EV-treated mouse suggests an anti-inflammatory effect of TSG-EV in colitis model, possibly mediated by Treg and macrophage polarization. These data indicate that TSG treatment promoted immunomodulatory properties of EVs from WJ-MSCs, and TSG-EV may provide a new therapeutic approach for treatment of colitis.

15-Deoxy-△12,14-Prostaglandin J2 Promotes Resolution of Experimentally Induced Colitis

Uncontrolled macrophage functions cause failure to resolve gut inflammation and has been implicated in the pathogenesis of inflammatory bowel disease (IBD). 15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂), one of endogenous lipid mediators formed from arachidonic acid during the inflammatory process, has been reported to terminate inflammation. However, the pro-resolving effect of 15d-PGJ₂ on intestinal inflammation and underlying molecular mechanisms remain largely unknown. In the present study, we examined the effects of 15d-PGJ₂ on the resolution of dextran sulfate sodium (DSS)-induced murine colitis that mimics human IBD. Pharmacologic inhibition of prostaglandin D synthase (PGDS) responsible for the synthesis of 15d-PGJ₂ hampered resolution of inflammation in the colonic mucosa of mice treated with DSS. Notably, intraperitoneal injection of 15d-PGJ₂ accelerated the resolution of experimentally induced colitis. 15d-PGJ₂ treatment reduced the number of neutrophils and M1 macrophages, while it increased the proportion of M2 macrophages. Moreover, 15d-PGJ₂ treated mice exhibited the significantly reduced proportion of macrophages expressing the pro-inflammatory cytokine, IL-6 with concomitant suppression of STAT3 phosphorylation in the colonic mucosa of mice administered 2.5% DSS in drinking water. Taken together, these findings clearly indicate that 15d-PGJ₂, endogenously generated from arachidonic acid by cyclooxygenase-2 and PGDS activities in inflamed tissue, promotes resolution of intestinal colitis.

Oral Administration of Lactobacillus helveticus LA401 and Lactobacillus gasseri LA806 Combination Attenuates Oesophageal and Gastrointestinal Candidiasis and Consequent Gut Inflammation in Mice

Candida albicans is an opportunistic pathogen that causes mucosal gastrointestinal (GI) candidiasis tightly associated with gut inflammatory status. The emergence of drug resistance, the side effects of currently available antifungals and the high frequency of recurrent candidiasis indicate that new and improved therapeutics are needed. Probiotics have been suggested as a useful alternative for the management of candidiasis. We demonstrated that oral administration of Lactobacillus gasseri LA806 alone or combined with Lactobacillus helveticus LA401 in Candida albicans-infected mice decrease the Candida colonization of the oesophageal and GI tract, highlighting a protective role for these strains in C. albicans colonization. Interestingly, the probiotic combination significantly modulates the composition of gut microbiota towards a protective profile and consequently dampens inflammatory and oxidative status in the colon. Moreover, we showed that L. helveticus LA401 and/or L. gasseri LA806 orient macrophages towards a fungicidal phenotype characterized by a C-type lectin receptors signature composed of Dectin-1 and Mannose receptor. Our findings suggest that the use of the LA401 and LA806 combination might be a promising strategy to manage GI candidiasis and the inflammation it causes by inducing the intrinsic antifungal activities of macrophages. Thus, the probiotic combination is a good candidate for managing GI candidiasis by inducing fungicidal functions in macrophages while preserving the GI integrity by modulating the microbiota and inflammation.