GM-CSF Calibrates Macrophage Defense and Wound Healing Programs during Intestinal Infection and Inflammation

Dual role for microbial short-chain fatty acids in modifying SIV disease trajectory following anti-α4β7 antibody administration

BACKGROUND

Human Immunodeficiency Virus (HIV)/Simian Immunodeficiency Virus (SIV) infection is associated with significant gut damage, similar to that observed in patients with inflammatory bowel disease (IBD). This pathology includes loss of epithelial integrity, microbial translocation, dysbiosis, and resultant chronic immune activation. Additionally, the levels of all-trans-retinoic acid (atRA) are dramatically attenuated. Data on the therapeutic use of anti-α4β7 antibodies has shown promise in patients with ulcerative colitis and Crohn's disease. Recent evidence has suggested that the microbiome and short-chain fatty acid (SCFA) metabolites it generates may be critical for anti-α4β7 efficacy and maintaining intestinal homeostasis.

MATERIALS AND METHODS

To determine whether the microbiome contributes to gut homeostasis after anti-α4β7 antibody administered to SIV-infected rhesus macaques, faecal SCFA concentrations were determined, 16S rRNA sequencing was performed, plasma viral loads were determined, plasma retinoids were measured longitudinally, and gut retinoid synthesis/response gene expression was quantified.

RESULTS

Our results suggest that anti-α4β7 antibody facilitates the return of retinoid metabolism to baseline levels after SIV infection. Furthermore, faecal SCFAs were shown to be associated with retinoid synthesis gene expression and rebound viral loads after therapy interruption.

CONCLUSIONS

Taken together, these data demonstrate the therapeutic advantages of anti-α4β7 antibody administration during HIV/SIV infection and that the efficacy of anti-α4β7 antibody may depend on microbiome composition and SCFA generation.

Glutaryl-CoA dehydrogenase suppresses tumor progression and shapes an anti-tumor microenvironment in hepatocellular carcinoma

BACKGROUND & AIMS

Crotonylation, a crotonyl-CoA-based non-enzymatic protein translational modification, affects diverse biological processes, such as spermatogenesis, tissue injury, inflammation, and neuropsychiatric diseases. Crotonylation is decreased in hepatocellular carcinomas (HCCs), but the mechanism remains unknown. In this study, we aim to describe the role of glutaryl-CoA dehydrogenase (GCDH) in tumor suppression.

METHODS

Three cohorts containing 40, 248 and 17 pairs of samples were used to evaluate the link between GCDH expression levels and clinical characteristics of HCC, as well as responses to anti-programmed cell death protein 1 (PD-1) treatment. Subcutaneous xenograft, orthotopic xenograft, Trp53Δhep/Δhep; MYC- and Ctnnboe; METoe-driven mouse models were adopted to validate the effects of GCDH on HCC suppression.

RESULTS

GCDH depletion promoted HCC growth and metastasis, whereas its overexpression reversed these processes. As GCDH converts glutaryl-CoA to crotonyl-CoA to increase crotonylation levels, we performed lysine crotonylome analysis and identified the pentose phosphate pathway (PPP) and glycolysis-related proteins PGD, TKT, and ALDOC as GCDH-induced crotonylation targets. Crotonyl-bound targets showed allosteric effects that controlled their enzymatic activities, leading to decreases in ribose 5-phosphate and lactate production, further limiting the Warburg effect. PPP blockade also stimulated peroxidation, synergizing with senescent modulators to induce senescence in GCDHhigh cells. These cells induced the infiltration of immune cells by the SASP (senescence-associated secretory cell phenotype) to shape an anti-tumor immune microenvironment. Meanwhile, the GCDHlow population was sensitized to anti-PD-1 therapy.

CONCLUSION

GCDH inhibits HCC progression via crotonylation-induced suppression of the PPP and glycolysis, resulting in HCC cell senescence. The senescent cell further shapes an anti-tumor microenvironment via the SASP. The GCDHlow population is responsive to anti-PD-1 therapy because of the increased presence of PD-1+CD8+ T cells.

IMPACT AND IMPLICATIONS

Glutaryl-CoA dehydrogenase (GCDH) is a favorable prognostic indicator in liver, lung, and renal cancers. In addition, most GCDH depletion-induced toxic metabolites originate from the liver, accumulate locally, and cannot cross the blood-brain barrier. Herein, we show that GCDH inhibits hepatocellular carcinoma (HCC) progression via crotonylation-induced suppression of the pentose phosphate pathway and glycolysis, resulting in HCC cell senescence. We also found that more PD-1+CD8+ T cells are present in the GCDHlow population, who are thus more responsive to anti-PD-1 therapy. Given that the GCDHlow and GCDHhigh HCC population can be distinguished based on serum glucose and ammonia levels, it will be worthwhile to evaluate the curative effects of pro-senescent and immune-therapeutic strategies based on the expression levels of GCDH.

Unraveling the intricacies of neutrophil extracellular traps in inflammatory bowel disease: Pathways, biomarkers, and promising therapies

The development of inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, involves various factors and is characterized by persistent inflammation of the mucosal lining. However, the role of neutrophils in this process remains controversial. Neutrophil extracellular traps (NETs), which consist of chromatin, antimicrobial proteins, and oxidative enzymes, are released by neutrophils to trap pathogens. They are also involved in various immune-mediated and vascular diseases. NETs act as a vital defense mechanisms at the gut-mucosal interface and are frequently exposed to bacterial, viral, and fungal threats. However, they can also contribute to inflammation and worsen imbalances in the gut bacteria. Recent studies have suggested that NETs have a significant impact on IBD development. Previous studies have shown increased levels of NETs in tissue and blood samples from patients with IBD, as well as in experimental colitis mouse models. Therefore, this review discusses how NETs are formed and their role in the pathophysiology of IBD. It discusses how NETs may lead to tissue damage and contribute to IBD-associated complications. Moreover, non-invasive biomarkers are needed to replace invasive procedures such as endoscopy to better evaluate the disease status. Given the crucial role of NETs in IBD progression, this review focuses on potential NET biomarkers that can help predict the evolution of IBD. Furthermore, this review identifies potential therapeutic targets for regulating NET production, which could expand the range of available treatment options for IBD.

Innate lymphoid cells and infectious diseases

Innate lymphoid cells (ILCs) are the main resident lymphocytes that mostly reside in tissues owing to the lack of adaptive antigen receptors. These cells are involved in early anti-infective immunity, antitumour immunity, regulation of tissue inflammation, and maintenance of homeostasis in the internal environment of tissues and have been referred to as the "first armies stationed in the human body". ILCs are widely distributed in the lungs, colon, lymph nodes, oral mucosa and even embryonic tissues. Due to the advantage of their distribution location, they are often among the first cells to come into contact with pathogens.Relevant studies have demonstrated that ILCs play an early role in the defence against a variety of pathogenic microorganisms, including bacteria, viruses, fungi and helminths, before they intervene in the adaptive immune system. ILCs can initiate a rapid, nonspecific response against pathogens prior to the initiation of an adaptive immune response and can generate a protective immune response against specific pathogens, secreting different effectors to play a role.There is growing evidence that ILCs play an important role in host control of infectious diseases. In this paper, we summarize and discuss the current known infectious diseases in which ILCs are involved and ILC contribution to the defence against infectious diseases. Further insights into the mechanisms of ILCs action in different infectious diseases will be useful in facilitating the development of therapeutic strategies for early control of infections.

Amplification of autoimmune organ damage by NKp46-activated ILC1s

In systemic lupus erythematosus, loss of immune tolerance, autoantibody production and immune complex deposition are required but not sufficient for organ damage1. How inflammatory signals are initiated and amplified in the setting of autoimmunity remains elusive. Here we set out to dissect layers and hierarchies of autoimmune kidney inflammation to identify tissue-specific cellular hubs that amplify autoinflammatory responses. Using high-resolution single-cell profiling of kidney immune and parenchymal cells, in combination with antibody blockade and genetic deficiency, we show that tissue-resident NKp46+ innate lymphoid cells (ILCs) are crucial signal amplifiers of disease-associated macrophage expansion and epithelial cell injury in lupus nephritis, downstream of autoantibody production. NKp46 signalling in a distinct subset of group 1 ILCs (ILC1s) instructed an unconventional immune-regulatory transcriptional program, which included the expression of the myeloid cell growth factor CSF2. CSF2 production by NKp46+ ILCs promoted the population expansion of monocyte-derived macrophages. Blockade of the NKp46 receptor (using the antibody clone mNCR1.15; ref. 2) or genetic deficiency of NKp46 abrogated epithelial cell injury. The same cellular and molecular patterns were operative in human lupus nephritis. Our data provide support for the idea that NKp46+ ILC1s promote parenchymal cell injury by granting monocyte-derived macrophages access to epithelial cell niches. NKp46 activation in ILC1s therefore constitutes a previously unrecognized, crucial tissue rheostat that amplifies organ damage in autoimmune hosts, with broad implications for inflammatory pathologies and therapies.

Renal denervation achieves its antiarrhythmic effect through attenuating macrophage activation and neuroinflammation in stellate ganglia in chronic heart failure

AIMS

Renal denervation (RDN) is widely investigated in multiple studies of sympathetically driven cardiovascular diseases. While the therapeutic potential of RDN for ventricular arrhythmia has been reported, the mechanisms responsible for its antiarrhythmic effect are poorly understood. Our recent study showed that macrophage expansion-induced neuroinflammation in the stellate ganglion (SG) was a critical factor for cardiac sympathetic overactivation and ventricular arrhythmogenesis in chronic heart failure (CHF). This study investigates if and how RDN decreases ventricular arrhythmias by attenuating neuroinflammation in cardiac sympathetic postganglionic (CSP) neurons in CHF.

METHODS AND RESULTS

Rat CHF was induced by surgical ligation of the left anterior descending coronary artery (LAD). At 12 weeks after LAD ligation, completed bilateral RDN was achieved by surgically cutting all the visible renal nerves around the renal artery and vein, followed by applying of 70% ethanol around the vessels. Immunofluorescence staining and Western blot data showed that expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) and its receptor-α subunit (GM-CSFRα) in SGs was increased in CHF rats. RDN not only reduced CHF-elevated GM-CSF levels in kidney, serum and SGs, but also attenuated macrophage expansion and neuroinflammation in SGs from CHF rats. Using flow cytometry, we confirmed that RDN reduced the percentage of macrophages in SGs, which is pathologically increased in CHF. RDN also decreased CHF-enhanced N-type Ca2+ currents in CSP neurons and attenuated CHF-elevated cardiac sympathetic nerve activity. ECG data from 24-hour continuous telemetry recording in conscious rats revealed that RDN improved CHF-induced heterogeneity of ventricular electrical activities and reduced the duration of spontaneous ventricular tachyarrhythmias in CHF rats.

CONCLUSIONS

RDN alleviates cardiac sympathetic overactivation and ventricular arrhythmogenesis through attenuating GM-CSF-induced macrophage activation and neuroinflammation within SGs in CHF. This suggests that manipulation of the GM-CSF signaling pathway could be a novel strategy for achieving the antiarrhythmic effect of RDN in CHF.

Macrophage fate: to kill or not to kill?

Macrophages are dynamic innate immune cells that either reside in tissue, serving as sentinels, or recruited as monocytes from bone marrow into inflamed and infected tissue. In response to cues in the tissue microenvironment (TME), macrophages polarize on a continuum toward M1 or M2 with diverse roles in progression and resolution of disease. M1-like macrophages exhibit proinflammatory functions with antimicrobial and anti-tumorigenic activities, while M2-like macrophages have anti-inflammatory functions that generally resolve inflammatory responses and orchestrate a tissue healing process. Given these opposite phenotypes, proper spatiotemporal coordination of macrophage polarization in response to cues within the TME is critical to effectively resolve infectious disease and regulate wound healing. However, if this spatiotemporal coordination becomes disrupted due to persistent infection or dysregulated coagulation, macrophages' inappropriate response to these cues will result in the development of diseases with clinically unfavorable outcomes. Since plasticity and heterogeneity are hallmarks of macrophages, they are attractive targets for therapies to reprogram toward specific phenotypes that could resolve disease and favor clinical prognosis. In this review, we discuss how basic science studies have elucidated macrophage polarization mechanisms in TMEs during infections and inflammation, particularly coagulation. Therefore, understanding the dynamics of macrophage polarization within TMEs in diseases is important in further development of targeted therapies.

Bridging Chronic Inflammation and Digestive Cancer: The Critical Role of Innate Lymphoid Cells in Tumor Microenvironments

The incidence and mortality of digestive system-related cancers have always been high and attributed to the heterogeneity and complexity of the immune microenvironment of the digestive system. Furthermore, several studies have shown that chronic inflammation in the digestive system is responsible for cancer incidence; therefore, controlling inflammation is a potential strategy to stop the development of cancer. Innate Lymphoid Cells (ILC) represent a heterogeneous group of lymphocytes that exist in contrast to T cells. They function by interacting with cytokines and immune cells in an antigen-independent manner. In the digestive system cancer, from the inflammatory phase to the development, migration, and metastasis of tumors, ILC have been found to interact with the immune microenvironment and either control or promote these processes. The conventional treatments for digestive tumors have limited efficacy, therefore, ILC-associated immunotherapies are promising strategies. This study reviews the characterization of different ILC subpopulations, how they interact with and influence the immune microenvironment as well as chronic inflammation, and their promotional or inhibitory role in four common digestive system tumors, including pancreatic, colorectal, gastric, and hepatocellular cancers. In particular, the review emphasizes the role of ILC in associating chronic inflammation with cancer and the potential for enhanced immunotherapy with cytokine therapy and adoptive immune cell therapy.

MOF-818 Nanozyme Suppresses Calcium Oxalate Kidney Stones by Alleviating Oxidative Stress and Inflammatory Injury

There remains a lack of effective drugs to alleviate the kidney stones caused by oxidative stress and inflammatory damage. The MOF-818 nanozyme is utilized to lessen the generation of reactive oxygen species (ROS) effectively, restore the membrane potential of mitochondria, regulate the cell cycle, decrease cell death, hinder the recruitment of macrophages, and mitigate the release of inflammatory factors in macrophages. These effects are attributed to the nanozyme's ability to mimic the enzyme properties of catalase (CAT) and superoxide dismutase (SOD). It is demonstrated that this nanozyme can reduce kidney calcium oxalate crystal deposition by reducing the renal injury caused by high concentration oxalate, upregulate the expression levels of SOD and CAT in tissues, downregulate adhesion proteins and inflammatory factor IL-6 and TNF-α, and promote the polarization of macrophages from M1 to M2 phenotype in the rat model induced by ethylene glycol. Overall, MOF-818 has the potential to effectively suppress oxidative stress and inflammatory harm caused by high levels of oxalate, hence lowering the likelihood of stone formation. MOF-818 nanozyme is also expected to be used as an alternative drug for the treatment of calcium oxalate kidney stones and provide an experimental theoretical basis for the development of new nanomedicines.

Monocyte-macrophages modulate intestinal homeostasis in inflammatory bowel disease

BACKGROUND

Monocytes and macrophages play an indispensable role in maintaining intestinal homeostasis and modulating mucosal immune responses in inflammatory bowel disease (IBD). Although numerous studies have described macrophage properties in IBD, the underlying mechanisms whereby the monocyte-macrophage lineage modulates intestinal homeostasis during gut inflammation remain elusive.

MAIN BODY

In this review, we decipher the cellular and molecular mechanisms governing the generation of intestinal mucosal macrophages and fill the knowledge gap in understanding the origin, maturation, classification, and functions of mucosal macrophages in intestinal niches, particularly the phagocytosis and bactericidal effects involved in the elimination of cell debris and pathogens. We delineate macrophage-mediated immunoregulation in the context of producing pro-inflammatory and anti-inflammatory cytokines, chemokines, toxic mediators, and macrophage extracellular traps (METs), and participating in the modulation of epithelial cell proliferation, angiogenesis, and fibrosis in the intestine and its accessory tissues. Moreover, we emphasize that the maturation of intestinal macrophages is arrested at immature stage during IBD, and the deficiency of MCPIP1 involves in the process via ATF3-AP1S2 signature. In addition, we confirmed the origin potential of IL-1B+ macrophages and defined C1QB+ macrophages as mature macrophages. The interaction crosstalk between the intestine and the mesentery has been described in this review, and the expression of mesentery-derived SAA2 is upregulated during IBD, which contributes to immunoregulation of macrophage. Moreover, we also highlight IBD-related susceptibility genes (e.g., RUNX3, IL21R, GTF2I, and LILRB3) associated with the maturation and functions of macrophage, which provide promising therapeutic opportunities for treating human IBD.

CONCLUSION

In summary, this review provides a comprehensive, comprehensive, in-depth and novel description of the characteristics and functions of macrophages in IBD, and highlights the important role of macrophages in the molecular and cellular process during IBD.

Focal Adhesion Kinase and Colony Stimulating Factors: Intestinal Homeostasis and Innate Immunity Crosstalk

Thousands struggle with acute and chronic intestinal injury due to various causes. Epithelial intestinal healing is dependent on phenotypic transitions to a mobile phenotype. Focal adhesion kinase (FAK) is a ubiquitous protein that is essential for cell mobility. This phenotype change is mediated by FAK activation and proves to be a promising target for pharmaceutical intervention. While FAK is crucial for intestinal healing, new evidence connects FAK with innate immunity and the importance it plays in macrophage/monocyte chemotaxis, as well as other intracellular signaling cascades. These cascades play a part in macrophage/monocyte polarization, maturation, and inflammation that is associated with intestinal injury. Colony stimulating factors (CSFs) such as macrophage colony stimulating factor (M-CSF/CSF-1) and granulocyte macrophage colony stimulating factor (GM-CSF/CSF-2) play a critical role in maintaining homeostasis within intestinal mucosa by crosstalk capabilities between macrophages and epithelial cells. The communication between these cells is imperative in orchestrating healing upon injury. Diving deeper into these connections may allow us a greater insight into the role that our immune system plays in healing, as well as a better comprehension of inflammatory diseases of the gut.

Cryptococcosis Associated With Biologic Therapy: A Narrative Review

Cryptococcus is an opportunistic fungal pathogen that can cause disseminated infection with predominant central nervous system involvement in patients with compromised immunity. Biologics are increasingly used in the treatment of neoplasms and autoimmune/inflammatory conditions and the prevention of transplant rejection, which may affect human defense mechanisms against cryptococcosis. In this review, we comprehensively investigate the association between cryptococcosis and various biologics, highlighting their risks of infection, clinical manifestations, and clinical outcomes. Clinicians should remain vigilant for the risk of cryptococcosis in patients receiving biologics that affect the Th1/macrophage activation pathways, such as tumor necrosis factor α antagonists, Bruton tyrosine kinase inhibitors, fingolimod, JAK/STAT inhibitors (Janus kinase/signal transducer and activator of transcription), and monoclonal antibody against CD52. Other risk factors-such as age, underlying condition, and concurrent immunosuppressants, especially corticosteroids-should also be taken into account during risk stratification.

Group 3 innate lymphoid cells in intestinal health and disease

The gastrointestinal tract is an immunologically rich organ, containing complex cell networks and dense lymphoid structures that safeguard this large absorptive barrier from pathogens, contribute to tissue physiology and support mucosal healing. Simultaneously, the immune system must remain tolerant to innocuous dietary antigens and trillions of normally beneficial microorganisms colonizing the intestine. Indeed, a dysfunctional immune response in the intestine underlies the pathogenesis of numerous local and systemic diseases, including inflammatory bowel disease, food allergy, chronic enteric infections or cancers. Here, we discuss group 3 innate lymphoid cells (ILC3s), which have emerged as orchestrators of tissue physiology, immunity, inflammation, tolerance and malignancy in the gastrointestinal tract. ILC3s are abundant in the developing and healthy intestine but their numbers or function are altered during chronic disease and cancer. The latest studies provide new insights into the mechanisms by which ILC3s fundamentally shape intestinal homeostasis or disease pathophysiology, and often this functional dichotomy depends on context and complex interactions with other cell types or microorganisms. Finally, we consider how this knowledge could be harnessed to improve current treatments or provoke new opportunities for therapeutic intervention to promote gut health.

Hyphal Als proteins act as CR3 ligands to promote immune responses against Candida albicans

Patients with decreased levels of CD18 (β2 integrins) suffer from life-threatening bacterial and fungal infections. CD11b, the α subunit of integrin CR3 (CD11b/CD18, αMβ2), is essential for mice to fight against systemic Candida albicans infections. Live elongating C. albicans activates CR3 in immune cells. However, the hyphal ligands that activate CR3 are not well defined. Here, we discovered that the C. albicans Als family proteins are recognized by the I domain of CD11b in macrophages. This recognition synergizes with the β-glucan-bound lectin-like domain to activate CR3, thereby promoting Syk signaling and inflammasome activation. Dectin-2 activation serves as the "outside-in signaling" for CR3 activation at the entry site of incompletely sealed phagosomes, where a thick cuff of F-actin forms to strengthen the local interaction. In vitro, CD18 partially contributes to IL-1β release from dendritic cells induced by purified hyphal Als3. In vivo, Als3 is vital for C. albicans clearance in mouse kidneys. These findings uncover a novel family of ligands for the CR3 I domain that promotes fungal clearance.

Group 3 innate lymphoid cells: A trained Gutkeeper

Group 3 innate lymphoid cells (ILC3s) are tissue-resident immune lymphocytes that critically regulate intestinal homeostasis, organogenesis, and immunity. ILC3s possess the capacity to "sense" the inflammatory environment within tissues, especially in the context of pathogen challenges that imprints durable non-antigen-specific changes in ILC3 function. As such, ILC3s become a new actor in the emerging field of trained innate immunity. Here, we summarize recent discoveries regarding ILC3 responses to bacterial challenges and the role these encounters play in triggering trained innate immunity. We further discuss how signaling events throughout ILC3 ontogeny potentially control the development and function of trained ILC3s. Finally, we highlight the open questions surrounding ILC3 "training" the answers to which may reveal new insights into innate immunity. Understanding the fundamental concepts behind trained innate immunity could potentially lead to the development of new strategies for improving immunity-based modulation therapies for inflammation, infectious diseases, and cancer.

Tumor-derived extracellular vesicles regulate macrophage polarization: role and therapeutic perspectives

Extracellular vesicles (EVs) are important cell-to-cell communication mediators. This paper focuses on the regulatory role of tumor-derived EVs on macrophages. It aims to investigate the causes of tumor progression and therapeutic directions. Tumor-derived EVs can cause macrophages to shift to M1 or M2 phenotypes. This indicates they can alter the M1/M2 cell ratio and have pro-tumor and anti-inflammatory effects. This paper discusses several key points: first, the factors that stimulate macrophage polarization and the cytokines released as a result; second, an overview of EVs and the methods used to isolate them; third, how EVs from various cancer cell sources, such as hepatocellular carcinoma, colorectal carcinoma, lung carcinoma, breast carcinoma, and glioblastoma cell sources carcinoma, promote tumor development by inducing M2 polarization in macrophages; and fourth, how EVs from breast carcinoma, pancreatic carcinoma, lungs carcinoma, and glioblastoma cell sources carcinoma also contribute to tumor development by promoting M2 polarization in macrophages. Modified or sourced EVs from breast, pancreatic, and colorectal cancer can repolarize M2 to M1 macrophages. This exhibits anti-tumor activities and offers novel approaches for tumor treatment. Therefore, we discovered that macrophage polarization to either M1 or M2 phenotypes can regulate tumor development. This is based on the description of altering macrophage phenotypes by vesicle contents.

GM-CSF, G-CSF or no cytokine therapy with anti-GD2 immunotherapy for high-risk neuroblastoma

Colony-stimulating factors have been shown to improve anti-disialoganglioside 2 (anti-GD2) monoclonal antibody response in high-risk neuroblastoma by enhancing antibody-dependent cell-mediated cytotoxicity (ADCC). A substantial amount of research has focused on recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) as an adjuvant to anti-GD2 monoclonal antibodies. There may be a disparity in care among patients as access to GM-CSF therapy and anti-GD2 monoclonal antibodies is not uniform. Only select countries have approved these agents for use, and even with regulatory approvals, access to these agents can be complex and cost prohibitive. This comprehensive review summarizes clinical data regarding efficacy and safety of GM-CSF, recombinant human granulocyte colony-stimulating factor (G-CSF) or no cytokine in combination with anti-GD2 monoclonal antibodies (ie, dinutuximab, dinutuximab beta or naxitamab) for immunotherapy of patients with high-risk neuroblastoma. A substantial body of clinical data support the immunotherapy combination of anti-GD2 monoclonal antibodies and GM-CSF. In contrast, clinical data supporting the use of G-CSF are limited. No formal comparison between GM-CSF, G-CSF and no cytokine has been identified. The treatment of high-risk neuroblastoma with anti-GD2 therapy plus GM-CSF is well established. Suboptimal efficacy outcomes with G-CSF raise concerns about its suitability as an alternative to GM-CSF as an adjuvant in immunotherapy for patients with high-risk neuroblastoma. While programs exist to facilitate obtaining GM-CSF and anti-GD2 monoclonal antibodies in regions where they are not commercially available, continued work is needed to ensure equitable therapeutic options are available globally.

Sexual dimorphism in skin immunity is mediated by an androgen-ILC2-dendritic cell axis

Males and females exhibit profound differences in immune responses and disease susceptibility. However, the factors responsible for sex differences in tissue immunity remain poorly understood. Here, we uncovered a dominant role for type 2 innate lymphoid cells (ILC2s) in shaping sexual immune dimorphism within the skin. Mechanistically, negative regulation of ILC2s by androgens leads to a reduction in dendritic cell accumulation and activation in males, along with reduced tissue immunity. Collectively, our results reveal a role for the androgen-ILC2-dendritic cell axis in controlling sexual immune dimorphism. Moreover, this work proposes that tissue immune set points are defined by the dual action of sex hormones and the microbiota, with sex hormones controlling the strength of local immunity and microbiota calibrating its tone.

Granulocyte-Macrophage Colony-Stimulating Factor in Allogenic Hematopoietic Stem Cell Transplantation: From Graft-versus-Host Disease to the Graft-versus-Tumor Effect

Allogenic hematopoietic stem cell transplantation (allo-HSCT) is a widely used treatment for a broad range of hematologic malignancies because of its graft-versus-tumor (GVT) effect. Unfortunately, allo-HSCT is still associated with morbidity and mortality related to relapse and transplantation complications, namely graft-versus-host-disease (GVHD). In an era of therapies specifically targeting molecular pathways, transcription factors, and cytokines, a better understanding of GVHD physiopathology is essential for the development of new therapeutic approaches. In this review, we outline the current knowledge of the role of granulocyte- macrophage colony-stimulating factor (GM-CSF) in allo-HSCT. We first discuss the biology of GM-CSF and its signaling pathways, with a focus on the main producing cells, T cells. We discuss recent preclinical studies pointing to a pivotal role of GM-CSF in GVHD, in particular gastrointestinal GVHD. We then summarize the potential role of GM-CSF in the GVT effect, discussing some potential strategies for exploiting GM-CSF in the context of allo-HSCT.

Intestinal macrophages in pathogenesis and treatment of gut leakage: current strategies and future perspectives

Macrophages play key roles in tissue homeostasis, defense, disease, and repair. Macrophages are highly plastic and exhibit distinct functional phenotypes based on micro-environmental stimuli. In spite of several advancements in understanding macrophage biology and their different functional phenotypes in various physiological and pathological conditions, currently available treatment strategies targeting macrophages are limited. Macrophages' high plasticity and diverse functional roles-including tissue injury and wound healing mechanisms-mark them as potential targets to mine for efficient therapeutics to treat diseases. Despite mounting evidence on association of gut leakage with several extraintestinal diseases, there is no targeted standard therapy to treat gut leakage. Therefore, there is an urgent need to develop therapeutic strategies to treat this condition. Macrophages are the cells that play the largest role in interacting with the gut microbiota in the intestinal compartment and exert their intended functions in injury and repair mechanisms. In this review, we have summarized the current knowledge on the origins and phenotypes of macrophages. The specific role of macrophages in intestinal barrier function, their role in tissue repair mechanisms, and their association with gut microbiota are discussed. In addition, currently available therapies and the putative tissue repair mediators of macrophages for treating microbiota dysbiosis induced gut leakage are also discussed. The overall aim of this review is to convey the intense need to screen for microbiota induced macrophage-released prorepair mediators, which could lead to the identification of potential candidates that could be developed for treating the leaky gut and associated diseases.

Modulatory effects of fermented Polygonatum cyrtonema Hua on immune homeostasis and gut integrity in a dextran-sulfate-sodium-induced colitis model

The gut health-promoting properties of saponin-rich Polygonatum cyrtonema Hua (FP) fermented with Lactobacillus plantarum P9 were explored in a dextran sulfate sodium (DSS)-induced colitis mouse model. FP supplementation effectively inhibited DSS-induced physiological alteration and impaired immune responses by reducing the disease activity index (DAI) score and restoring the T helper (Th) 1/Th2 and regulatory T (Treg)/Th17 ratios. In addition, FP supplementation protected the gut barrier function against DSS-induced damage via upregulation of zonula occludens (ZO)-1 and occludin and downregulation of pro-inflammatory cytokines, including interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), IL-18, and the granulocyte-macrophage colony-stimulating factor (GM-CSF). This study further elucidated the potential mechanisms underlying the FP-mediated suppression of the plasticity of type 3 innate lymphoid cells (ILC3) and subsequent macrophage polarization. Therefore, the FP supplementation effectively restored mucosal immune homeostasis and enhanced gut integrity. In addition, it suppressed the growth of Escherichia-Shigella and Enterococcus and promoted the enrichment of probiotics and short-chain fatty acid-producing microbes, such as Romboutsia, Faecalibaculum, and Blautia. In conclusion, P. cyrtonema Hua fermented with L. plantarum P9 might be a promising dietary intervention to improve gut health by sustaining overall gut homeostasis and related gut integrity.

Nanotechnology-enabled M2 macrophage polarization and ferroptosis inhibition for targeted inflammatory bowel disease treatment

Transforming macrophages into the anti-inflammatory M2 phenotype could markedly strengthen inflammatory bowel disease (IBD) treatment, which is considered as a promising strategy. However, the high ferroptosis sensitivity of M2 macrophages, which decreases their activity, is a major stumbling block to this strategy. Therefore, promoting M2 polarization while simultaneously inhibiting ferroptosis to tackle this challenge is indispensable. Herein, a calcium‑carbonate (CaCO3) mineralized liposome encapsulating a ferroptosis inhibitor (Fer-1) was developed (CaCO3@Lipo@Fer-1, CLF). The CaCO3 mineralized coating shields the liposomes to prevent the release of Fer-1 in circulation, while releasing Ca2+ in the acidic-inflammatory environment. This released Ca2+ promotes M2 polarization through the CaSR/AKT/β-catenin pathway. The subsequently released Fer-1 effectively upregulates GSH and GPX4, scavenges reactive oxygen species, and inhibits ferroptosis in M2 macrophages. In vivo, CLF improved the targeting efficiency of IBD lesions (about 4.17-fold) through the epithelial enhanced permeability and retention (eEPR) effect and enhanced IBD therapy by increasing the M2/M1 macrophage ratio and inhibiting ferroptosis. We demonstrate that the synergistic regulation of macrophage polarization and ferroptosis sensitivity by this mineralized nanoinhibitor is a viable strategy for IBD therapy.

Farnesoid X receptor mediates macrophage-intrinsic responses to suppress colitis-induced colon cancer progression

Bile acids (BAs) affect the intestinal environment by ensuring barrier integrity, maintaining microbiota balance, regulating epithelium turnover, and modulating the immune system. As a master regulator of BA homeostasis, farnesoid X receptor (FXR) is severely compromised in patients with inflammatory bowel disease (IBD) and colitis-associated colorectal cancer (CAC). At the front line, gut macrophages react to the microbiota and metabolites that breach the epithelium. We aim to study the role of the BA/FXR axis in macrophages. This study demonstrates that inflammation-induced epithelial abnormalities compromised FXR signaling and altered BAs' profile in a mouse CAC model. Further, gut macrophage-intrinsic FXR sensed aberrant BAs, leading to pro-inflammatory cytokines' secretion, which promoted intestinal stem cell proliferation. Mechanistically, activation of FXR ameliorated intestinal inflammation and inhibited colitis-associated tumor growth, by regulating gut macrophages' recruitment, polarization, and crosstalk with Th17 cells. However, deletion of FXR in bone marrow or gut macrophages escalated the intestinal inflammation. In summary, our study reveals a distinctive regulatory role of FXR in gut macrophages, suggesting its potential as a therapeutic target for addressing IBD and CAC.

Involvement of Embryo-Derived and Monocyte-Derived Intestinal Macrophages in the Pathogenesis of Inflammatory Bowel Disease and Their Prospects as Therapeutic Targets

Inflammatory bowel disease (IBD) is a group of intestinal inflammatory diseases characterized by chronic, recurrent, remitting, or progressive inflammation, which causes the disturbance of the homeostasis between immune cells, such as macrophages, epithelial cells, and microorganisms. Intestinal macrophages (IMs) are the largest population of macrophages in the body, and the abnormal function of IMs is an important cause of IBD. Most IMs come from the replenishment of blood monocytes, while a small part come from embryos and can self-renew. Stimulated by the intestinal inflammatory microenvironment, monocyte-derived IMs can interact with intestinal epithelial cells, intestinal fibroblasts, and intestinal flora, resulting in the increased differentiation of proinflammatory phenotypes and the decreased differentiation of anti-inflammatory phenotypes, releasing a large number of proinflammatory factors and aggravating intestinal inflammation. Based on this mechanism, inhibiting the secretion of IMs' proinflammatory factors and enhancing the differentiation of anti-inflammatory phenotypes can help alleviate intestinal inflammation and promote tissue repair. At present, the clinical medication of IBD mainly includes 5-aminosalicylic acids (5-ASAs), glucocorticoid, immunosuppressants, and TNF-α inhibitors. The general principle of treatment is to control acute attacks, alleviate the condition, reduce recurrence, and prevent complications. Most classical IBD therapies affecting IMs function in a variety of ways, such as inhibiting the inflammatory signaling pathways and inducing IM2-type macrophage differentiation. This review explores the current understanding of the involvement of IMs in the pathogenesis of IBD and their prospects as therapeutic targets.

The crosstalk between enteric nervous system and immune system in intestinal development, homeostasis and diseases

The gut is the largest digestive and absorptive organ, which is essential for induction of mucosal and systemic immune responses, and maintenance of metabolic-immune homeostasis. The intestinal components contain the epithelium, stromal cells, immune cells, and enteric nervous system (ENS), as well as the outers, such as gut microbiota, metabolites, and nutrients. The dyshomeostasis of intestinal microenvironment induces abnormal intestinal development and functions, even colon diseases including dysplasia, inflammation and tumor. Several recent studies have identified that ENS plays a crucial role in maintaining the immune homeostasis of gastrointestinal (GI) microenvironment. The crosstalk between ENS and immune cells, mainly macrophages, T cells, and innate lymphoid cells (ILCs), has been found to exert important regulatory roles in intestinal tissue programming, homeostasis, function, and inflammation. In this review, we mainly summarize the critical roles of the interactions between ENS and immune cells in intestinal homeostasis during intestinal development and diseases progression, to provide theoretical bases and ideas for the exploration of immunotherapy for gastrointestinal diseases with the ENS as potential novel targets.

Macrophage polarization in inflammatory bowel disease

The growing prevalence of inflammatory bowel disease (IBD) has encouraged research efforts, which have contributed to gradual improvements in our understanding of IBD diagnosis and therapeutic approaches. The pathogenesis of IBD has not been fully elucidated; however, the combined actions of environmental, genetic, immune factors, and microbial organisms are believed to cause IBD. In the innate immune system, macrophages play important roles in maintaining intestinal health and in the development of IBD. Macrophages can be polarized from M0 into several phenotypes, among which M1 and M2 play critical roles in IBD development and the repair of intestinal homeostasis and damage. Certain macrophage-related IBD studies already exist; however, the functions of each phenotype have not been fully elucidated. As technology develops, understanding the link between macrophages and IBD has increased, including the growing knowledge of the developmental origins of intestinal macrophages and their performance of comprehensive functions. This review describes macrophage polarization in IBD from the perspectives of macrophage development and polarization, macrophage changes in homeostasis and IBD, metabolic changes, and the mechanisms of macrophage polarization in IBD. The discussion of these topics provides new insights into immunotherapy strategies for IBD. Video Abstract.

Exosome-mediated macrophage regulation for inflammatory bowel disease repair: a potential target of gut inflammation

Inflammatory bowel disease (IBD), which includes Crohn's disease (CD) and ulcerative colitis (UC), is a complex condition without a definite cause. During IBD, immune cells such as macrophages release proinflammatory cytokines and chemokines, contributing to intestinal barrier integrity dysfunction. IBD is largely influenced by macrophages, which are classified into subtypes M1 and M2. M1 macrophages have been found to contribute to the development of IBD, whereas M2 macrophages alleviate IBD. Hence, agents that cause increased polarization of the M2 phenotype could help repair IBD. Exosomes, as ubiquitous conveyors of intercellular messages, are involved in immune responses and immune-mediated disease processes. Exosomes and their microRNA (miRNA) from healthy cells have been found to polarize macrophages to M2 to repair IBD due to their anti-inflammatory properties; however, those from inflammatory-driven cells and disease cells promote M1 macrophages to perpetuate IBD. Here, we review the biogenesis, biochemical composition, and sources of exosomes, as well as the roles of exosomes as extracellular vesicles in regulation of macrophages to repair IBD.

Artemether Attenuates Gut Barrier Dysfunction and Intestinal Flora Imbalance in High-Fat and High-Fructose Diet-Fed Mice

Intestinal inflammation is a key determinant of intestinal and systemic health, and when our intestines are damaged, there is disruption of the intestinal barrier, which in turn induces a systemic inflammatory response. However, the etiology and pathogenesis of inflammatory diseases of the intestine are still not fully understood. Artemether (ART), one of the artemisinin derivatives, has been widely used to treat malaria. Nevertheless, the effect of ART on intestinal inflammation remains unclear. The present study intended to elucidate the potential mechanism of ART in diet-induced intestinal injury. A high-fat and high-fructose (HFHF) diet-induced mouse model of intestinal injury was constructed, and the mice were treated with ART to examine their role in intestinal injury. RT-qPCR, Western blotting, immunohistochemical staining, and 16S rRNA gene sequencing were used to investigate the anti-intestinal inflammation effect and mechanism of ART. The results indicated that ART intervention may significantly ameliorate the intestinal flora imbalance caused by the HFHF diet and alleviate intestinal barrier function disorders and inflammatory responses by raising the expression of tight junction proteins ZO-1 and occludin and decreasing the expression of pro-inflammatory factors TNF-α and IL-1β. Moreover, ART intervention restrained HFHF-induced activation of the TLR4/NF-κB p65 pathway in colon tissue, which may be concerned with the potential protective effect of ART on intestinal inflammation. ART might provide new insights into further explaining the mechanism of action of other metabolic diseases caused by intestinal disorders.

Inactivation of Group 1B Phospholipase A2 Enhances Disease Recovery and Reduces Experimental Colitis in Mice

Phospholipase A2 (PLA2) enzymes influence inflammatory bowel disease in both positive and negative manners depending on the type of PLA2 that is expressed. This study explored the influence of the abundantly expressed Group 1B PLA2 (PLA2G1B) on ulcerative colitis. Wild-type C57BL/6J mice and Pla2g1b-/- mice were treated with dextran sulfate sodium (DSS) for 5 days to induce epithelial injury, followed by another 5 days without DSS for recovery. The Pla2g1b-/- mice displayed significantly less body weight loss, colitis pathology, and disease activity indexes compared to the wild-type mice. The differences in colitis were not due to differences in the colonic lysophospholipid levels, but higher numbers of stem and progenitor cells were found in the intestines of Pla2g1b-/- mice compared to the wild-type mice. The DSS-treated Pla2g1b-/- mice also showed higher expressions of genes that are responsible for epithelial repair and lower expressions of proinflammatory cytokine genes in the colon, as well as reduced inflammatory cytokine levels in the plasma. In vitro experiments revealed the PLA2G1B stimulation of inflammatory cytokine expression by myeloid cells. PLA2G1B inactivation protects against DSS-induced colitis in mice by increasing the intestinal stem cell reservoir for epithelial repair and reducing myeloid cell inflammation in the diseased colon. Thus, PLA2G1B may be a target for colitis management.

mTORC2 acts as a gatekeeper for mTORC1 deficiency-mediated impairments in ILC3 development

Group 3 innate lymphoid cells (ILC3s) are mediators of intestinal immunity and barrier function. Recent studies have investigated the role of the mammalian target of rapamycin complex (mTOR) in ILC3s, whereas the mTORC1-related mechanisms and crosstalk between mTORC1 and mTORC2 involved in regulating ILC3 homeostasis remain unknown. In this study, we found that mTORC1 but not mTORC2 was critical in ILC3 development, IL-22 production, and ILC3-mediated intestinal homeostasis. Single-cell RNA sequencing revealed that mTORC1 deficiency led to disruption of ILC3 heterogeneity, showing an increase in differentiation into ILC1-like phenotypes. Mechanistically, mTORC1 deficiency decreased the expression of NFIL3, which is a critical transcription factor responsible for ILC3 development. The activities of both mTORC1 and mTORC2 were increased in wild-type ILC3s after activation by IL-23, whereas inhibition of mTORC1 by Raptor deletion or rapamycin treatment resulted in increased mTORC2 activity. Previous studies have demonstrated that S6K, the main downstream target of mTORC1, can directly phosphorylate Rictor to dampen mTORC2 activity. Our data found that inhibition of mTORC1 activity by rapamycin reduced Rictor phosphorylation in ILC3s. Reversing the increased mTORC2 activity via heterozygous or homozygous knockout of Rictor in Raptor-deleted ILC3s resulted in severe ILC3 loss and complete susceptibility to intestinal infection in mice with mTORC1 deficiency (100% mortality). Thus, mTORC1 acts as a rheostat of ILC3 heterogeneity, and mTORC2 protects ILC3s from severe loss of cells and immune activity against intestinal infection when mTORC1 activity is diminished.

ILC3: a case of conflicted identity

Innate lymphoid cells type 3 (ILC3s) are the first line sentinels at the mucous tissues, where they contribute to the homeostatic immune response in a major way. Also, they have been increasingly appreciated as important modulators of chronic inflammatory and autoimmune responses, both locally and systemically. The proper identification of ILC3 is of utmost importance for meaningful studies on their role in immunity. Flow cytometry is the method of choice for the detection and characterization of ILC3. However, the analysis of ILC3-related papers shows inconsistency in ILC3 phenotypic definition, as different inclusion and exclusion markers are used for their identification. Here, we present these discrepancies in the phenotypic characterization of human and mouse ILC3s. We discuss the pros and cons of using various markers for ILC3 identification. Furthermore, we consider the possibilities for the efficient isolation and propagation of ILC3 from different organs and tissues for in-vitro and in-vivo studies. This paper calls upon uniformity in ILC3 definition, isolation, and propagation for the increased possibility of confluent interpretation of ILC3's role in immunity.

Bioinspired nanovesicles released from injectable hydrogels facilitate diabetic wound healing by regulating macrophage polarization and endothelial cell dysfunction

Wound healing is one of the major global health concerns in diabetic patients. Overactivation of proinflammatory M1 macrophages could lead to delayed wound healing in diabetes. 4-octyl itaconate (4OI), a derivative of the metabolite itaconate, has aroused growing interest recently on account of its excellent anti-inflammatory properties. Cell membrane coating is widely regarded as a novel biomimetic strategy to deliver drugs and inherit properties derived from source cells for biomedical applications. Herein, we fused induced pluripotent stem cell-derived endothelial cell (iEC) membrane together with M1 type macrophage membrane to construct a hybrid membrane (iEC-M) camouflaged 4OI nanovesicles (4OI@iEC-M). Furthermore, bioinspired nanovesicles 4OI@iEC-M are incorporated into the injectable, multifunctional gelatin methacryloyl hydrogels for diabetic wound repair and regeneration. In our study, bioinspired nanovesicles could achieve dual-targeted deliver of 4OI into both M1 macrophages and endothelial cells, thereby promoting macrophage polarization and protecting endothelial cells. With the synergistically anti-inflammatory and immunoregulative effects, the bioinspired nanovesicles-loaded hydrogels could facilitate neovascularization and exhibit superior diabetic wound repair and regeneration. Taken together, this study might provide a novel strategy to facilitate diabetic wound healing, thereby reducing limb amputation and mortality of diabetes.

Macrophage colony-stimulating factor ameliorates myocardial injury in mice after myocardial infarction by regulating cardiac macrophages through the P2X7R/NLRP3/IL-1β signal pathway

Aims

To investigate the effects of M-CSF on myocardial injury in mice after MI by regulating different types of cardiac macrophages through the P2X7R/NLRP3/IL-1β signal pathway.

Methods

A total of 60 C57BL/6J WT mice were used, with the Sham Group subjected to ligation without ligation through the LAD, the MI model was prepared by ligation of the LAD in the MC Group and MM Group, with the M-CSF reagent (500 μg/kg/d) being given an intraperitoneal injection for the first 5 days after surgery in the MM Group. All mice were fed in a barrier environment for 1 week. After the study, myocardial tissues were collected and IL-4, IL-6, IL-10, TNF-α, MCP-1, IFN-α, ANP, BNP, β-MHC, Collage I, Collage III, P2X7R, NLRP3, IL-1β, Bax, Caspase 3, C-Casp 3, Bcl-2, M1/2 macrophage, the apoptosis of cardiomyocytes, and the collagen deposition were detected.

Results

The inflammatory response was significantly lower in the MM Group, the cardiomyocyte apoptosis, fibrosis, and hypertrophy were inhibited compared to the MC Group, and the levels of P2X7R, NLRP3, and IL-1β were also statistically lower in the MM Group. Additionally, the expression of M2 macrophages increased in the MM Group while the M1 macrophages statistically decreased compared to the MC Group.

Conclusion

M-CSF can significantly increase the expression of M2 macrophage and reduce the level of M1 macrophage by inhibiting the levels of NLRP3/IL-1β-related proteins, thereby inhibiting inflammation, ameliorating reducing myocardial hypertrophy, apoptosis, and fibrosis, improve myocardial injury in mice after MI.

Emerging aspects of cytokine storm in COVID-19: The role of proinflammatory cytokines and therapeutic prospects

COVID-19 has claimed millions of lives during the last 3 years since initial cases were reported in Wuhan, China, in 2019. Patients with COVID-19 suffer from severe pneumonia, high fever, acute respiratory distress syndrome (ARDS), and multiple-organ dysfunction, which may also result in fatality in extreme cases. Cytokine storm (CS) is hyperactivation of the immune system, wherein the dysregulated production of proinflammatory cytokines could result in excessive immune cell infiltrations in the pulmonary tissues, resulting in tissue damage. The immune cell infiltration could also occur in other tissues and organs and result in multiple organs' dysfunction. The key cytokines implicated in the onset of disease severity include TNF-α, IFN-γ, IL-6, IL-1β, GM-CSF, and G-CSF. Controlling the CS is critical in treating COVID-19 disease. Therefore, different strategies are employed to mitigate the effects of CS. These include using monoclonal antibodies directed against soluble cytokines or the cytokine receptors, combination therapies, mesenchymal stem cell therapy, therapeutic plasma exchange, and some non-conventional treatment methods to improve patient immunity. The current review describes the role/s of critical cytokines in COVID-19-mediated CS and the respective treatment modalities.

Metabolic rewiring tunes dermal macrophages in staphylococcal skin infection

The skin needs to balance tolerance of colonizing microflora with rapid detection of potential pathogens. Flexible response mechanisms would seem most suitable to accommodate the dynamic challenges of effective antimicrobial defense and restoration of tissue homeostasis. Here, we dissected macrophage-intrinsic mechanisms and microenvironmental cues that tune macrophage signaling in localized skin infection with the colonizing and opportunistic pathogen Staphylococcus aureus. Early in skin infection, the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) produced by γδ T cells and hypoxic conditions within the dermal microenvironment diverted macrophages away from a homeostatic M-CSF- and hypoxia-inducible factor 1α (HIF-1α)-dependent program. This allowed macrophages to be metabolically rewired for maximal inflammatory activity, which requires expression of Irg1 and generation of itaconate, but not HIF-1α. This multifactorial macrophage rewiring program was required for both the timely clearance of bacteria and for the provision of local immune memory. These findings indicate that immunometabolic conditioning allows dermal macrophages to cycle between antimicrobial activity and protection against secondary infections.

Microbial energy metabolism fuels an intestinal macrophage niche in solitary isolated lymphoid tissues through purinergic signaling

Maintaining macrophage (MΦ) heterogeneity is critical to ensure intestinal tissue homeostasis and host defense. The gut microbiota and host factors are thought to synergistically guide intestinal MΦ development, although the exact nature, regulation, and location of such collaboration remain unclear. Here, we report that microbial biochemical energy metabolism promotes colony-stimulating factor 2 (CSF2) production by group 3 innate lymphoid cells (ILC3s) within solitary isolated lymphoid tissues (SILTs) in a cell-extrinsic, NLRP3/P2X7R-dependent fashion in the steady state. Tissue-infiltrating monocytes accumulating around SILTs followed a spatially constrained, distinct developmental trajectory into SILT-associated MΦs (SAMs). CSF2 regulated the mitochondrial membrane potential and reactive oxygen species production of SAMs and contributed to the antimicrobial defense against enteric bacterial infections. Collectively, these findings identify SILTs and CSF2-producing ILC3s as a microanatomic niche for intestinal MΦ development and functional programming fueled by the integration of commensal microbial energy metabolism.

Soybean (Glycine max) INFOGEST Colonic Digests Attenuated Inflammatory Responses Based on Protein Profiles of Different Varieties

Soybean compounds have been established to modulate inflammation, but less is known about how whole soybean compositions work together after digestion. The objective was to evaluate and compare the anti-inflammatory responses of different soybean varieties under simulated gastrointestinal digestion, with additional consideration of the glycinin:β-conglycinin ratio (GBR). Soybean colonic digests (SCD) inhibited cyclooxygenase (COX)-2 (25-82%), 5-lipoxidase (LOX) (18-35%), and inducible nitric oxide (iNOS) (8-61%). Varieties 88, GN3, and 93 were the most effective inhibitors. SCD (1 mg/mL) of varieties 81 and GN1 significantly (p < 0.05) reduced nitrite production by 44 and 47%, respectively, compared to lipopolysaccharide (LPS)-stimulated macrophages. SCD effectively reduced pro-inflammatory cytokine interleukin (IL)-6 (50 and 80% for 96 and GN1, respectively). Western blot results showed a decrease in the expression of iNOS, p65, and p50. The GBR was in the range of 0.05-1.57. Higher ratio correlated with higher production of IL-1β (r = 0.44) and tumor necrosis factor-alpha (TNF-α, r = 0.56). Inflammatory microarray results showed a significant decrease in expression of markers granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-6 in cells treated with GN1 SCD compared to LPS. The results suggested that SCD exerted its anti-inflammatory potential through nuclear factor kappa B (NF-κΒ) pathway inhibition by decreasing the levels of NF-κB-dependent cytokines and subunits, and inhibition of pro-inflammatory enzyme activity.

A vascularized crypt-patterned colon model for high-throughput drug screening and disease modelling

The colon serves as a primary target for pharmaceutical compound screening and disease modelling. To better study colon diseases and develop treatments, engineered in vitro models with colon-specific physiological features are required. Existing colon models lack integration of colonic crypt structures with underlying perfusable vasculature, where vascular-epithelial crosstalk is affected by disease progression. We present a colon epithelium barrier model with vascularized crypts that recapitulates relevant cytokine gradients in both healthy and inflammatory conditions. Using our previously published IFlowPlate384 platform, we initially imprinted crypt topography and populated the patterned scaffold with colon cells. Proliferative colon cells spontaneously localized to the crypt niche and differentiated into epithelial barriers with a tight brush border. Toxicity of the colon cancer drug, capecitabine, was tested and showed a dose-dependent response and recovery from crypt-patterned colon epithelium exclusively. Perfusable microvasculature was then incorporated around the colon crypts followed by treatment with pro-inflammatory TNFα and IFNγ cytokines to simulate inflammatory bowel disease (IBD)-like conditions. We observed in vivo-like stromal basal-to-apical cytokine gradients in tissues with vascularized crypts and gradient reversals upon inflammation. Taken together, we demonstrated crypt topography integrated with underlying perfusable microvasculature has significant value for emulating colon physiology and in advanced disease modelling.

T helper 2 cells control monocyte to tissue-resident macrophage differentiation during nematode infection of the pleural cavity

The recent revolution in tissue-resident macrophage biology has resulted largely from murine studies performed in C57BL/6 mice. Here, using both C57BL/6 and BALB/c mice, we analyze immune cells in the pleural cavity. Unlike C57BL/6 mice, naive tissue-resident large-cavity macrophages (LCMs) of BALB/c mice failed to fully implement the tissue-residency program. Following infection with a pleural-dwelling nematode, these pre-existing differences were accentuated with LCM expansion occurring in C57BL/6, but not in BALB/c mice. While infection drove monocyte recruitment in both strains, only in C57BL/6 mice were monocytes able to efficiently integrate into the resident pool. Monocyte-to-macrophage conversion required both T cells and interleukin-4 receptor alpha (IL-4Rα) signaling. The transition to tissue residency altered macrophage function, and GATA6+ tissue-resident macrophages were required for host resistance to nematode infection. Therefore, during tissue nematode infection, T helper 2 (Th2) cells control the differentiation pathway of resident macrophages, which determines infection outcome.

Tetramerization of STAT5 regulates monocyte differentiation and the dextran sulfate sodium-induced colitis in mice

In response to external stimuli during immune responses, monocytes can have multifaceted roles such as pathogen clearance and tissue repair. However, aberrant control of monocyte activation can result in chronic inflammation and subsequent tissue damage. Granulocyte-macrophage colony-stimulating factor (GM-CSF) induces monocyte differentiation into a heterogenous population of monocyte-derived dendritic cells (moDCs) and macrophages. However, the downstream molecular signals that dictate the differentiation of monocytes under pathological conditions is incompletely understood. We report here that the GM-CSF-induced STAT5 tetramerization is a critical determinate of monocyte fate and function. Monocytes require STAT5 tetramers to differentiate into moDCs. Conversely, the absence of STAT5 tetramers results in a switch to a functionally distinct monocyte-derived macrophage population. In the dextran sulfate sodium (DSS) model of colitis, STAT5 tetramer-deficient monocytes exacerbate disease severity. Mechanistically, GM-CSF signaling in STAT5 tetramer-deficient monocytes results in the overexpression of arginase I and a reduction in nitric oxide synthesis following stimulation with lipopolysaccharide. Correspondingly, the inhibition of arginase I activity and sustained supplementation of nitric oxide ameliorates the worsened colitis in STAT5 tetramer-deficient mice. This study suggests that STAT5 tetramers protect against severe intestinal inflammation through the regulation of arginine metabolism.

Macrophages in intestinal homeostasis and inflammatory bowel disease

Macrophages are essential for the maintenance of intestinal homeostasis, yet appear to be drivers of inflammation in the context of inflammatory bowel disease (IBD). How these peacekeepers become powerful aggressors in IBD is still unclear, but technological advances have revolutionized our understanding of many facets of their biology. In this Review, we discuss the progress made in understanding the heterogeneity of intestinal macrophages, the functions they perform in gut health and how the environment and origin can control the differentiation and longevity of these cells. We describe how these processes might change in the context of chronic inflammation and how aberrant macrophage behaviour contributes to IBD pathology, and discuss how therapeutic approaches might target dysregulated macrophages to dampen inflammation and promote mucosal healing. Finally, we set out key areas in the field of intestinal macrophage biology for which further investigation is warranted.

CD90 is not constitutively expressed in functional innate lymphoid cells

Huge progress has been made in understanding the biology of innate lymphoid cells (ILC) by adopting several well-known concepts in T cell biology. As such, flow cytometry gating strategies and markers, such as CD90, have been applied to indentify ILC. Here, we report that most non-NK intestinal ILC have a high expression of CD90 as expected, but surprisingly a sub-population of cells exhibit low or even no expression of this marker. CD90-negative and CD90-low CD127+ ILC were present amongst all ILC subsets in the gut. The frequency of CD90-negative and CD90-low CD127+ ILC was dependent on stimulatory cues in vitro and enhanced by dysbiosis in vivo. CD90-negative and CD90-low CD127+ ILC were a potential source of IL-13, IFNγ and IL-17A at steady state and upon dysbiosis- and dextran sulphate sodium-elicited colitis. Hence, this study reveals that, contrary to expectations, CD90 is not constitutively expressed by functional ILC in the gut.

Th1 promotes M1 polarization of intestinal macrophages to regulate colitis-related mucosal barrier damage

This work aimed to investigate the role of helper T cell 1 (Th1) in chronic colitis and its immunoregulatory mechanism. The proportions of Th1 and Th2, and the levels of related cytokines in tissues from patients with inflammatory bowel disease (IBD; ulcerative colitis+Crohn's disease, UC+CD) were detected. DSS was used to induce the mouse model of IBD; thereafter, Th1 cells were induced in vitro and amplified before they were injected intraperitoneally. Later, the changes in life state and body weight of mice were observed, the proportion of M1 macrophages in mucosal tissues and mucosal barrier damage were detected. After treatment with macrophage scavenging agent (Clodronate Liposomes, CLL), the influence of Th1 on IBD mice was observed. Then, the intestinal macrophages were co-cultured with Th1 in vitro to observe the influence of Th1 on the polarization of intestinal macrophages. Besides, cells were treated with the STAT3 inhibitor to further detect the macrophage polarization level. Intestinal macrophages were later co-cultured with intestinal epithelial cells to observe the degree of epithelial cell injury. The Th1 proportions in intestinal tissues of UC and CD patients were higher than those in healthy subjects, but the difference in Th2 proportion was not significant. In the IBD mouse model, Th1 induced the M1 polarization of macrophages, aggravated the intestinal inflammatory response, and resulted in the increased mucosal barrier permeability. Pretreatment with CLL antagonized the effect of Th1 cells, reduced the intestinal tissue inflammatory response and mucosal barrier permeability.

Microcirculation and neutrophil-related cytokine concentrations are not altered around narrow diameter implants in T2DM patients during wound healing

OBJECTIVES

The aim of this study was to assess the microcirculation and the expression patterns of wound-healing-related cytokines around narrow-diameter implants in type 2 diabetes mellitus (T2DM) and normo-glycemic patients.

MATERIALS AND METHODS

A total of 31 patients, 16 of which diagnosed with T2DM (HbA1c > 6.5) and 15 normo-glycemic patients, received narrow diameter implants in the posterior mandible or maxilla. During the 3-month healing period, soft-tissue perfusion was monitored via laser Doppler flowmetry. Peri-implant fluid (PICF) was harvested and analyzed for concentrations of interleukin-1ß (IL-1ß), interleukin-23 (IL-23), interleukin-17 (IL-17), and granulocyte colony-stimulating factor (G-CSF) by a multiplex, bead-based immunoassay.

RESULTS

Microcirculatory perfusion patterns during wound healing exhibited no significant differences throughout the observation period. IL-1ß concentrations were expectedly elevated during the early phases of wound healing. At the first visit after surgery, IL-23 concentrations were significantly higher in implants of diabetic patients. This difference was diminished over the course of the observation period. For the other tested analytes, no differences were observable between both groups.

CONCLUSION

Wound healing after implant surgery was similar in T2DM and healthy patients. Hydrophilic-surface titanium-zirconium implants with reduced diameter may be considered for implant therapy of diabetes mellitus type II patients.

REGISTRATION NUMBER

NCT04630691 (clinicaltrials.gov).

Innate Lymphoid Cell Plasticity in Mucosal Infections

Mucosal tissue homeostasis is a dynamic process that involves multiple mechanisms including regulation of innate lymphoid cells (ILCs). ILCs are mostly tissue-resident cells which are critical for tissue homeostasis and immune response against pathogens. ILCs can sense environmental changes and rapidly respond by producing effector cytokines to limit pathogen spread and initiate tissue recovery. However, dysregulation of ILCs can also lead to immunopathology. Accumulating evidence suggests that ILCs are dynamic population that can change their phenotype and functions under rapidly changing tissue microenvironment. However, the significance of ILC plasticity in response to pathogens remains poorly understood. Therefore, in this review, we discuss recent advances in understanding the mechanisms regulating ILC plasticity in response to intestinal, respiratory and genital tract pathogens. Key transcription factors and lineage-guiding cytokines regulate this plasticity. Additionally, we discuss the emerging data on the role of tissue microenvironment, gut microbiota, and hypoxia in ILC plasticity in response to mucosal pathogens. The identification of new pathways and molecular mechanisms that control functions and plasticity of ILCs could uncover more specific and effective therapeutic targets for infectious and autoimmune diseases where ILCs become dysregulated.

Blood-Based Immune Protein Markers of Disease Progression in Murine Models of Acute and Chronic Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic ailment afflicting millions of people worldwide, with the majority of recognized cases within industrialized countries. The impacts of IBD at the individual level are long-lasting with few effective treatments available, resulting in a large burden on the health care system. A number of existing animal models are utilized to evaluate novel treatment strategies. Two commonly used models are (1) acute colitis mediated by dextran sulphate sodium (DSS) treatment of wild-type mice and (2) chronic colitis mediated by the transfer of proinflammatory T cells into immunodeficient mice. Despite the wide use of these particular systems to evaluate IBD therapeutics, the typical readouts of clinical disease progression vary depending on the model used, which may be reflective of mechanistic differences of disease induction. The most reliable indicator of disease in both models remains intestinal damage which is typically evaluated upon experimental endpoint. Herein, we evaluated the expression profile of a panel of cytokines and chemokines in both DSS and T cell transfer models in an effort to identify a number of inflammatory markers in the blood that could serve as reliable indicators of the relative disease state. Out of the panel of 25 markers tested, 6 showed statistically significant shifts with the DSS model, compared to 11 in the T cell transfer model with IL-6, IL-13, IL-22, TNF-α and IFN-γ being common markers of disease in both models. Our data highlights biological differences between animal models of IBD and helps to guide future studies when selecting efficacy readouts during the evaluation of experimental IBD therapeutics.

The role of group 3 innate lymphoid cell in intestinal disease

Group 3 innate lymphoid cells (ILC3s), a novel subpopulation of lymphocytes enriched in the intestinal mucosa, are currently considered as key sentinels in maintaining intestinal immune homeostasis. ILC3s can secrete a series of cytokines such as IL-22 to eliminate intestinal luminal antigens, promote epithelial tissue repair and mucosal barrier integrity, and regulate intestinal immunity by integrating multiple signals from the environment and the host. However, ILC3 dysfunction may be associated with the development and progression of various diseases in the gut. Therefore, in this review, we will discuss the role of ILC3 in intestinal diseases such as enteric infectious diseases, intestinal inflammation, and tumors, with a focus on recent research advances and discoveries to explore potential therapeutic targets.

Mass-cytometry-based quantitation of global histone post-translational modifications at single-cell resolution across peripheral immune cells in IBD

BACKGROUND AND AIMS

Current understanding of histone post-translational modifications (histone modifications) across immune cell types in patients with inflammatory bowel disease (IBD) during remission and flare is limited. The study aimed to quantify histone modifications at a single-cell resolution in IBD patients during remission and flare and how they differ compared to healthy controls.

METHODS

We performed a case-control study of 94 subjects (83 IBD patients and 11 healthy controls). IBD patients had either UC (n=38) or CD (n=45) in clinical remission or flare. We used epigenetic profiling by time-of-flight (EpiTOF) to investigate changes in histone modifications within peripheral blood mononuclear cells from IBD patients.

RESULTS

We discovered substantial heterogeneity in histone modifications across multiple immune cell types in IBD patients. They had a higher proportion of less differentiated CD34 + hematopoietic progenitors, and a subset of CD56 bright NK cells and γδ T cells characterized by distinct histone modifications associated with the gene transcription. The subset of CD56 bright NK cells had increased several histone acetylations. An epigenetically defined subset of NK was associated with higher levels of CRP in peripheral blood. CD14+ monocytes from IBD patients had significantly decreased cleaved H3T22, suggesting they were epigenetically primed for macrophage differentiation.

CONCLUSION

We describe the first systems-level quantification of histone modifications across immune cells from IBD patients at a single-cell resolution revealing the increased epigenetic heterogeneity that is not possible with traditional ChIP-seq profiling. Our data open new directions in investigating the association between histone modifications and IBD pathology using other epigenomic tools.

Small extracellular vesicles from Ptpn1-deficient macrophages alleviate intestinal inflammation by reprogramming macrophage polarization via lactadherin enrichment

Tyrosine-protein phosphatase non-receptor type 1 (Ptpn1) is known to be involved in macrophage polarization. However, whether and how Ptpn1 regulates macrophage phenotype to affect intestinal epithelial barrier function remains largely unexplored. Herein, we investigated the impact of Ptpn1 and macrophage-derived small extracellular vesicles (sEVs) on macrophage-intestinal epithelial cell (IEC) interactions in the context of intestinal inflammation. We found that Ptpn1 knockdown shifts macrophages toward the anti-inflammatory M2 phenotype, thereby promoting intestinal barrier integrity and suppressing inflammatory response in the macrophage-IEC co-culture model. We further revealed that conditioned medium or sEVs isolated from Ptp1b knockdown macrophages are the primary factor driving the beneficial outcomes. Consistently, administration of the sEVs from Ptpn1-knockdown macrophages reduced disease severity and ameliorated intestinal inflammation in LPS-challenged mice. Furthermore, depletion of macrophages in mice abrogated the protective effect of Ptpn1-knockdown macrophage sEVs against Salmonella Typhimurium infection. Importantly, we found lactadherin to be highly enriched in the sEVs of Ptpn1-knockdown macrophages. Administration of recombinant lactadherin alleviated intestinal inflammation and barrier dysfunction by inducing macrophage M2 polarization. Interestingly, sEVs lactadherin was also internalized by macrophages and IECs, leading to macrophage M2 polarization and enhanced intestinal barrier integrity. Mechanistically, the anti-inflammatory and barrier-enhancing effect of lactadherin was achieved by reducing TNF-α and NF-κB activation. Thus, we demonstrated that sEVs from Ptpn1-knockdown macrophages mediate the communication between IECs and macrophages through enrichment of lactadherin. The outcome could potentially lead to the development of novel therapies for intestinal inflammatory disorders.

Nestin+ Peyer's patch resident MSCs enhance healing of inflammatory bowel disease through IL-22-mediated intestinal epithelial repair

Inflammatory bowel disease (IBD) is a chronic condition characterized by gastrointestinal tract inflammation and still lacks satisfactory treatments. Mesenchymal stromal cells (MSCs) show promising potential for treating IBD, but their therapeutic efficacy varies depending on the tissue of origin. We aim to investigate whether intestine Peyer's patch (PP)-derived MSCs have superior immunomodulatory effects on T cells and better therapeutic effects on IBD compared with bone marrow-derived MSCs. We isolated PPs-derived Nestin+ MSCs (MSCs^PP ) and bone marrow-derived Nestin+ MSCs (MSCs^BM ) from Nestin-GFP transgenic mice to explore their curative effects on murine IBD model. Moreover, we tested the effects of IL-22 knockdown and IL-22 overexpression on the therapeutic efficacy of MSCs^PP and MSCs^BM in murine IBD, respectively. We demonstrated that Nestin+ cells derived from murine PPs exhibit MSC-like biological characteristics. Compared with MSCs^BM , MSCs^PP possess enhanced immunoregulatory ability to suppress T cell proliferation and inflammatory cytokine production. Moreover, we observed that MSCs^PP exhibited greater therapeutic efficacy than MSCs^BM in murine IBD models. Interestingly, IL-22, which was highly expressed in MSCs^PP , could alleviate the severity of the intestinal inflammation, while knockdown IL-22 of MSCs^PP remarkably weakened the therapeutic effects. More importantly, IL-22 overexpressing MSCs^BM could significantly improve the symptoms of murine IBD models. This study systemically demonstrated that murine MSCs^PP have a prominent advantage in murine IBD treatment, partly through IL-22.