Macrophages in the gut: Masters in multitasking

Gut microbiota in hepatocellular carcinoma immunotherapy: immune microenvironment remodeling and gut microbiota modification

Hepatocellular carcinoma (HCC) remains a leading cause of cancer-related mortality, with limited treatment options at advanced stages. The gut microbiota, a diverse community of microorganisms residing in the gastrointestinal tract, plays a pivotal role in regulating immune responses through the gut-liver axis. Emerging evidence underscores its impact on HCC progression and the efficacy of immunotherapy. This review explores the intricate interactions between gut microbiota and the immune system in HCC, with a focus on key immune cells and pathways involved in tumor immunity. Additionally, it highlights strategies for modulating the gut microbiota - such as fecal microbiota transplantation, dietary interventions, and probiotics - as potential approaches to enhancing immunotherapy outcomes. A deeper understanding of these mechanisms could pave the way for novel therapeutic strategies aimed at improving patient prognosis.

Digging deeper into necrotizing enterocolitis: bridging clinical, microbial, and molecular perspectives

Necrotizing Enterocolitis (NEC) is a severe, life-threatening inflammatory condition of the gastrointestinal tract, especially affecting preterm infants. This review consolidates evidence from various biomedical disciplines to elucidate the complex pathogenesis of NEC, integrating insights from clinical, microbial, and molecular perspectives. It emphasizes the modulation of NEC-associated inflammatory pathways by probiotics and novel biologics, highlighting their therapeutic potential. We further critically examine dysbiotic alterations within the gut microbiota, with a particular focus on imbalances in bacterial and viral communities, which may contribute to the onset of NEC. The intricate interactions among toll-like receptor 4 (TLR4), microvascular integrity, immune activation, and the inflammatory milieu are meticulously summarized, offering a sophisticated understanding of NEC pathophysiology. This academic review aims to enhance the etiological comprehension of NEC, promote the development of targeted therapeutic interventions, and impart the significant impact of perinatal factors on the formulation of preventive and curative strategies for the disease.

Salt pan brine water sulphated polysaccharides retrieved at pilot scale: ability to stimulate in vitro human macrophages and salmon head kidney cells

Marine environments are the warehouse of a variety of novel bioactive compounds prone to be explored by food and feed industry. The growing interest in sulphated polysaccharides has led to the search for new sustainable sources, such as seawater. These compounds are naturally concentrated in salt pan brine water due to their evaporation by wind and sunlight. To take advantage of these sources, sulphated polysaccharides were concentrated from salt pan brine water using a scalable membrane ultrafiltration system with 30 and 100 kDa cut-off. This process allowed to concentrate ten times the polymeric material of brine water into 1.9 g/L, rendering a fluffy polysaccharide rich material after drying. It was mainly composed of 23 % (w/w) of uronic acids, 19 % of sulphate esters, and 34 % (w/w) of neutral sugars. This polymeric material has shown to stimulate in vitro both human macrophages and Atlantic salmon head kidney SHK-1 cells in a range of 6.25-50 μg/mL without toxicity, showing potential to be used in both human food and aquaculture feeding.

Glutamine limits NLRP3 inflammasome activation and pyroptosis in macrophages by sustaining the IRG1/itaconate axis

Aberrant activation of NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome increases the release of mature pro-inflammatory cytokines interleukin (IL)-1β and IL-18, and enhances pyroptosis; thereby necessitating tight regulation of the NLRP3 inflammasome. Dysfunctional glutamine metabolism contributes to the pathogenesis of multiple inflammatory disorders, and the precise mechanism remains to be elucidated. Here, we provide evidence that glutamine deprivation enhances NLRP3 inflammasome activation in macrophages. Indeed, the absence of exogenous glutamine specifically enhanced NLRP3 inflammasome assembly, thereby accelerating pyroptosis and promoting the maturation of IL-1β and IL-18. Inhibition of glutaminolysis exhibited a similar effect to glutamine deprivation, whereas this effect was reversed by α-ketoglutarate (α-KG), a tricarboxylic acid (TCA)-cycle intermediate that can be replenished by glutamine supply. We further observed reduced generation of endogenous itaconate by glutamine deprivation and verified that both exogenous supplementation of itaconate derivative and increased endogenous itaconate production by overexpressing immune-responsive gene 1 [IRG1; also known as aconitate decarboxylase 1 (ACOD1)] could replace glutamine to inhibit the NLRP3 inflammasome. Mechanistically, glutamine deprivation decreased the source of substrate and inhibited transcription factor EB (TFEB)-dependent transcriptional upregulation of IRG1, thereby impairing the IRG1/itaconate axis that suppresses the NLRP3 inflammasome. Furthermore, glutamine deficiency was detected in a murine sepsis model, whereas extrinsic glutamine supplementation conferred protection against intestinal inflammation and tissue damage in septic mice. Taken together, our findings provide a novel insight into the link between glutamine metabolism and NLRP3 inflammasome activation, highlighting the target of glutamine metabolism, which holds as a potential therapeutic strategy for inflammatory diseases.

Relevance of mouse and human IBD patient-derived colon organoids to investigate intestinal macrophage differentiation

The gastrointestinal tract is a remarkable example of complex biology, with a constant dialogue between the intestinal epithelium, in close contact with the microbiota, and the immune cells that protect the gut from infection. Organoids have revolutionized our approach to modeling the intestinal cellular compartment and have opened new avenues for unraveling the mechanisms involved in intestinal homeostasis and chronic pathogenesis, such as inflammatory bowel disease. To date, few models have been established to explore the role of the colon, which is, however, the main site of inflammation in ulcerative colitis. Here, we used conditioned media produced by colon organoids from mice or humans (control patients and patients with ulcerative colitis) to investigate the relationship between macrophages and the colon epithelium. We addressed transcriptomic profiles of organoid conditioned media-stimulated bone marrow-derived macrophages and found that these cells exhibited a unique anti-inflammatory signature distinct from that of conventional in vitro IL-4/IL-13 M2-differentiated macrophages. In addition, organoid conditioned media induced a clear CD5 antigen-like-mediated immunoregulatory effect characterized by a significant reduction in lipopolysaccharide-induced inducible nitric oxide synthase expression. In line, organoid conditioned media from human colons inhibited lipopolysaccharide-dependent inflammatory cytokine expression in human monocyte-derived macrophages. Interestingly, the inflammatory marker CD68 was reduced by organoid conditioned media from control patients but not from patients with ulcerative colitis, suggesting epithelial dysfunction in patients with ulcerative colitis. Our results report new regulatory mechanisms in the colon and highlight the importance of developing new in vitro models to better characterize the relationship between the intestinal epithelium and immune mucosal cells.

Multifunctional Double-Loaded Oral Nanoplatform for Computed Tomography Imaging-Guided and Integrated Treatment of Inflammatory Bowel Disease

Excessive reactive oxygen species, disruption of the epithelial barrier, immune dysregulation, and gut microbiota imbalance are key factors driving the onset of inflammatory bowel disease (IBD) and complicating its treatment. Prompt diagnosis of diseases and precise delivery of therapeutic agents to inflamed intestinal sites offer promising targeted strategies for effectively treating IBD. Here, a barium sulfate-based nanoplatform (BaSO4@PDA@CeO2/DSP, BPCD) for synergistic delivery of nanozymes and drugs was developed. With enhanced colonic retention after oral drug delivery, this nanoplatform enables precise and effective targeting of inflammatory sites and CT imaging guidance to address multiple factors contributing to IBD. A comprehensive therapeutic effect was achieved through the synergistic action of cerium oxide with the optimized Ce3+/Ce4+ ratio and sustained release of dexamethasone sodium phosphate. Benefiting from superior gastrointestinal stability, the nanoplatform is highly effective in treating IBD by alleviating oxidative stress, modulating macrophage polarization balance, gut flora composition, and repairing the epithelial barrier. BPCD inhibits the development of IBD through multiple mechanisms and has superior biocompatibility, emerging as a practical alternative to traditional IBD therapies.

Triple-Functional Probiotics with Intracellularly Synthesized Selenium Nanoparticles for Colitis Therapy by Regulating the Macrophage Phenotype and Modulating Gut Microbiota

The dysregulated macrophage phenotype, as the main cause of colitis, not only enhanced oxidative stress to exacerbate inflammatory responses but was closely related with gut microbial dysbiosis. It was needed to simultaneously address the three issues for the effective treatment of colitis, but it was not satisfied. Here, we developed "three-birds-one-stone" probiotics, named Se@EcN-C2/A2, for colitis treatment. Escherichia coli Nissle 1917 (EcN), a clinically approved probiotic, was used to intracellularly synthesize selenium (Se) nanoparticles by biomineralization, giving Se@EcN. Coating glycol chitosan and sodium alginate on the surface of Se@EcN (Se@EcN-C2/A2) endowed probiotics with high resistance to the harsh gastrointestinal tract environment and strong adhesion and targeting ability to the inflamed site of the colon to facilitate the uptake by M1 macrophages. Se@EcN-C2/A2 was metabolized to SeCys2 and MetSeCys to be involved in the synthesis of GPX2 and TXNRD1, which led to reaction oxygen species clearance to inhibit Toll-like receptor and nuclear factor κB signaling pathways to suppress inflammatory response and polarize M1 macrophages to M2 phenotypes by activating PI3K/AKT signaling pathways. In DSS-induced colitis mice, Se@EcN-C2/A2 exerted satisfactory therapeutic and prophylactic effects, including scavenging oxidative stress and regulating macrophage phenotypes to suppress inflammatory response and restore gut barrier functions. Moreover, the living probiotic EcN in the colon effectively regulated microbial dysbiosis by decreasing the abundance of Escherichia-Shigella and increasing the abundance of Lactobacillus and Bifidobacterium.

Cross one single body 49 tissues single-cell transcriptome reveals detailed macrophage heterogeneity during pig pregnancy

Introduction

Pregnancy involves complex physiological adaptations across maternal organs and the immune system to support fetal development. Macrophages play a dual role during pregnancy: defending against pathogens and supporting tissue adaptation. However, comprehensive and in-depth studies of cross-tissue transcriptional heterogeneity of macrophages during healthy pregnancy at the single-cell level remain elusive.

Methods

We performed single-cell RNA sequencing (scRNA-seq) to profile macrophages from a healthy pregnant pig across 49 tissues. Immunofluorescence was performed to verify the specific expression of transcription factors.

Results

In this study, we generated a macrophage atlas containing 114,881 macrophages from 49 tissues/organs within one single healthy pregnant pig, identified 33 subtypes, and revealed extensive tissue-specific diversity. We observed significant heterogeneity of macrophage subtypes across five different anatomical sites of adipose tissue. Notably, the Mφ MARCO+ subtype, primarily derived from mesenteric adipose tissue, showed higher activity in pattern recognition receptor signaling pathways compared to subtypes in other tissues, including different fat depots. Cross-tissue analysis revealed distinct expression patterns of transcription factors, cytokines, and cell surface receptors, including the transcription factor PLSCR1, specifically expressed in lung macrophages and verified by immunofluorescence. Cross-species analysis unveiled conservation and heterogeneity among macrophages in pigs, humans, and mice.

Conclusion

We constructed a multiple-tissue single-cell transcriptome atlas of macrophages in one single healthy pregnant pig, revealing their molecular differences and commonalities across tissues and species. Our study provides a valuable resource for understanding macrophage diversity and tissue-specific macrophage adaptations during pregnancy in pigs.

Glial-immune interactions in barrier organs

Neuro-immune interactions within barrier organs, such as lung, gut, and skin, are crucial in regulating tissue homeostasis, inflammatory responses, and host defence. Our rapidly advancing understanding of peripheral neuroimmunology is transforming the field of barrier tissue immunology, offering a fresh perspective for developing therapies for complex chronic inflammatory disorders affecting barrier organs. However, most studies have primarily examined interactions between the peripheral nervous system and the immune system from a neuron-focused perspective, while glial cells, the nonneuronal cells of the nervous system, have received less attention. Glial cells were long considered as mere bystanders, only supporting their neuronal neighbours, but recent discoveries mainly on enteric glial cells in the intestine have implicated these cells in immune-regulation and inflammatory disease pathogenesis. In this review, we will highlight the bi-directional interactions between peripheral glial cells and the immune system and discuss the emerging immune regulatory functions of glial cells in barrier organs.

The Intestinal Macrophage-Intestinal Stem Cell Axis in Inflammatory Bowel Diseases: From Pathogenesis to Therapy

The gut plays a crucial role in digestion and immunity, so its balance is essential to overall health. This balance relies on dynamic interactions between intestinal epithelial cells, immune cells, and crypt stem cells. Inflammatory bowel disease (IBD), which consists of ulcerative colitis and Crohn's disease, is a chronic relapsing inflammatory disease of the gastrointestinal tract closely related to immune dysfunction. Stem cells, known for their ability to self-renew and differentiate, play an important role in repairing damaged intestinal epithelium and maintaining homeostasis in vivo. Macrophages are key gatekeepers of intestinal immune homeostasis and have a significant impact on IBD. Current research has focused on the link between epithelial cells and stem cells, but interactions with macrophages, which have been recognized as attractive targets for the development of new therapeutic approaches to disease, have been less explored. Recently, the developing field of immunometabolism has reinforced that metabolic reprogramming is a key determinant of macrophage function and subsequent disease progression. The aim of this review is to explore the role of the macrophage-stem cell axis in the maintenance of intestinal homeostasis and to summarize potential approaches to treating IBD by manipulating the cellular metabolism of macrophages, as well as the main opportunities and challenges faced. In summary, our overview provides a framework for understanding the critical role of macrophage immunometabolism in maintaining gut health and potential therapeutic targets.

Modulation of Macrophages TLR4-Mediated Transcriptional Response by Lacticaseibacillus rhamnosus CRL1505 and Lactiplantibacillus plantarum CRL1506

Lacticaseibacillus rhamnosus CRL1505 and Lactiplantibacillus plantarum CRL1506 increase the resistance of mice to Gram-negative pathogens infections. In this work, we advanced the characterization of the CRL1505 and CRL1506 immunomodulatory properties by evaluating their effect on the Toll-like receptor 4 (TLR4)-triggered immune response in macrophages. We performed experiments in murine RAW 264.7 macrophages stimulated with lipopolysaccharide (LPS) to evaluate the transcriptomic changes induced by lactobacilli. These in vitro experiments were complemented with in vivo studies in mice to determine the effect of CRL1505 and CRL1506 strains on Peyer's patches and peritoneal macrophages. Microarray transcriptomic studies and qPCR confirmation showed that the CRL1505 and CRL1506 strains modulated the expression of inflammatory cytokines and chemokines as well as adhesion molecules in LPS-challenged RAW macrophages, making the effect of L. rhamnosus CRL1505 more remarkable. Lactobacilli also modulate regulatory factors in macrophages. L. plantarum CRL1506 increased il10 and socs2 while L. rhamnosus CRL1505 upregulated il27, socs1, and socs3 in RAW cells, indicating a strain-specific effect. However, in vivo, both strains induced similar effects. Peyer's patches and peritoneal macrophages from mice treated with lactobacilli produced higher levels of tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-6, and colony stimulating factor (CSF)-3 after LPS stimulation. This effect would allow improved protection against pathogens. In addition, both lactobacilli equally modulated socs1 and socs2 expressions and IL-10 and IL-27 production in Peyer's patches macrophages and socs3 and IL-10 in peritoneal cells. Furthermore, lactobacilli reduced the production of IL-1β, IL-12, CSF2, C-C motif chemokine ligand (CCL)-2, and CCL8 in LPS-challenged macrophages. This differential modulation of regulatory and inflammatory factors would allow minimal inflammatory-mediated tissue damage during the generation of the innate immune response. This work provides evidence that L. rhamnosus CRL1505 and L. plantarum CRL1506 modulate macrophages' TLR4-mediated immunotranscriptomic response, helping to improve protection against Gram-negative bacterial infections.

Mucosal Macrophages Govern Intestinal Regeneration in Response to Injury

BACKGROUND & AIMS

Radiation-induced enteritis develops in cancer patients treated with radiotherapy in the abdominal and pelvic cavity, a condition that impairs their quality of life. Radiation injury depletes proliferative intestinal stem cells; in response to this, the epithelium activates a regenerative program that facilitates the healing of the intestine. However, the mechanisms that induce the activation of the intestinal regenerative program are poorly characterized.

METHODS

In this study, we induced radiation-induced enteritis in mice through abdominal irradiation, mimicking clinical scenarios. Through imaging and flow cytometric analysis, we investigated the recruitment of macrophages to the small intestine during injury and healing. Additionally, we developed a coculture system for mouse and human intestinal organoids and macrophages to explore the cross talk between these cells. Then by combining in vivo ablation of macrophages, fluorescent lineage tracing, imaging, bulk RNA-sequencing (RNA-seq), single-cell RNA-seq, human intestinal organoids, and cell trajectory analysis, we studied the macrophage induction of intestinal regeneration at the cellular and molecular level.

RESULTS

Our findings revealed that macrophages are recruited around the intestinal stem cell compartment upon radiation injury, promoting a fetal-like reprogramming and proliferation of epithelial cells that drives the regeneration process. In contrast, macrophage ablation led to compromised regeneration. Moreover, our single-cell RNA-seq analysis identified key secreted molecules, neuregulin 1 and osteopontin, as pivotal players in regulating this process. Additionally, characterization of human macrophage/organoid cocultures and cell trajectory inference confirmed the conservation of macrophages' role in triggering the regenerative program in primary human cells.

CONCLUSIONS

This study identifies macrophages as essential contributors to intestinal regeneration beyond their innate immune response. Targeting macrophages therapeutically may hold promise in enhancing regeneration and improving the quality of life for cancer survivors.

Tissue macrophages: origin, heterogenity, biological functions, diseases and therapeutic targets

Macrophages are immune cells belonging to the mononuclear phagocyte system. They play crucial roles in immune defense, surveillance, and homeostasis. This review systematically discusses the types of hematopoietic progenitors that give rise to macrophages, including primitive hematopoietic progenitors, erythro-myeloid progenitors, and hematopoietic stem cells. These progenitors have distinct genetic backgrounds and developmental processes. Accordingly, macrophages exhibit complex and diverse functions in the body, including phagocytosis and clearance of cellular debris, antigen presentation, and immune response, regulation of inflammation and cytokine production, tissue remodeling and repair, and multi-level regulatory signaling pathways/crosstalk involved in homeostasis and physiology. Besides, tumor-associated macrophages are a key component of the TME, exhibiting both anti-tumor and pro-tumor properties. Furthermore, the functional status of macrophages is closely linked to the development of various diseases, including cancer, autoimmune disorders, cardiovascular disease, neurodegenerative diseases, metabolic conditions, and trauma. Targeting macrophages has emerged as a promising therapeutic strategy in these contexts. Clinical trials of macrophage-based targeted drugs, macrophage-based immunotherapies, and nanoparticle-based therapy were comprehensively summarized. Potential challenges and future directions in targeting macrophages have also been discussed. Overall, our review highlights the significance of this versatile immune cell in human health and disease, which is expected to inform future research and clinical practice.

Orally-administrable supramolecular probiotic capsules enable cooperative colon-targeted inflammation inhibition for ameliorating ulcerative colitis

Ulcerative colitis (UC) is a prevalent gastrointestinal disease characterized by the chronical and refractory inflammation of colorectal mucosa and walls, which severely impairs overall well-being of individuals. Probiotics has shown tremendous promise for UC therapy due to its multifaceted mucosal barrier restoration and immunomodulation capabilities. Nevertheless, the successful administration of probiotics remains a clinical obstacle. Herein, we report a multifunctional supramolecular probiotic capsule based on clinically-tested biopolymers for UC therapy, which not only allow colon-targeted probiotic delivery via oral route but also enable concurrent delivery of hemostatic and anti-inflammatory drugs. Specifically, Clostridium butyricum (CB) was first engineered with protective norepinephrine (NE) coating and then encapsulated by self-assembled gelatin-based nanocomplexes modified with balsalazide and matrix metalloproteinase 2/9 (MMP2-/9)-responsive fibronectin peptides. The released balsalazide and fibronectin could induce rapid hemostasis and anti-inflammation actions to alleviate inflammation damage of the UC-affected colons in the short term, while CB could restore gut microbiota homeostasis to remodel intestinal immunocomposition and repair mucosal barrier for reducing UC risk in the long term. Overall, this study provides a promising option for UC treatment with good efficacy and minimal invasiveness. STATEMENT OF SIGNIFICANCE: This study reports a supramolecular probiotic capsule with nanointegrative hemostatic and anti-inflammatory capacities for ulcerative colitis (UC) therapy, which could be orally administrated and activated in the inflamed colorectal sites. The probiotic capsules enable immediate UC symptom relief while also accelerating mucosal repair and preventing UC relapse in the long-term, offering an approach for UC treatment in the clinic.

Closed-loop theranostic microgels for immune microenvironment modulation and microbiota remodeling in ulcerative colitis

Inflammatory bowel disease (IBD) is characterized by the upregulation of reactive oxygen species (ROS) and dysfunction of gut immune system, and microbiota. The conventional treatments mainly focus on symptom control with medication by overuse of drugs. There is an urgent need to develop a closed-loop strategy that combines in situ monitoring and precise treatment. Herein, we innovatively designed the 'cluster munition structure' theranostic microgels to realize the monitoring and therapy for ulcerative colitis (a subtype of IBD). The superoxide anion specific probe (tetraphenylethylene-coelenterazine, TPC) and ROS-responsive nanogels consisting of postbiotics urolithin A (UA) were loaded into alginate and ion-crosslinked to obtain the theranostic microgels. The theranostic microgels could be delivered to the inflammatory site, where the environment-triggered breakup of the microgels and release of the nanogels were achieved in sequence. The TPC-UA group had optimal results in reducing inflammation, repairing colonic epithelial tissue, and remodeling microbiota, leading to inflammation amelioration and recovery of tight junction between the colonic epithelium, and maintenance of gut microbiota. During the recovery process, the local chemiluminescence intensity, which is proportional to the degree of inflammation, was gradually inhibited. The cluster munition of theranostic microgels displayed promising outcomes in monitoring inflammation and precise therapy, and demonstrated the potential for inflammatory disease management.

A Multicellular In Vitro Model of the Human Intestine with Immunocompetent Features Highlights Host-Pathogen Interactions During Early Salmonella Typhimurium Infection

Studying the molecular basis of intestinal infections caused by enteric pathogens at the tissue level is challenging, because most human intestinal infection models have limitations, and results obtained from animals may not reflect the human situation. Infections with Salmonella enterica serovar Typhimurium (STm) have different outcomes between organisms. 3D tissue modeling of primary human material provides alternatives to animal experimentation, but epithelial co-culture with immune cells remains difficult. Macrophages, for instance, contribute to the immunocompetence of native tissue, yet their incorporation into human epithelial tissue models is challenging. A 3D immunocompetent tissue model of the human small intestine based on decellularized submucosa enriched with monocyte-derived macrophages (MDM) is established. The multicellular model recapitulated in vivo-like cellular diversity, especially the induction of GP2 positive microfold (M) cells. Infection studies with STm reveal that the pathogen physically interacts with these M-like cells. MDMs show trans-epithelial migration and phagocytosed STm within the model and the levels of inflammatory cytokines are induced upon STm infection. Infected epithelial cells are shed into the supernatant, potentially reflecting an intracellular reservoir of invasion-primed STm. Together, the 3D model of the human intestinal epithelium bears potential as an alternative to animals to identify human-specific processes underlying enteric bacterial infections.

News from the old: Aging features in the intracardiac, musculoskeletal, and enteric nervous systems

Aging strongly affects the peripheral nervous system (PNS), triggering alterations that vary depending on the innervated tissue. The most frequent alteration in peripheral nerve aging is reduced nerve fiber and glial density which can lead to abnormal nerve functionality. Interestingly, the activation of a destructive phenotype takes place in macrophages across the PNS while a reduced number of neuronal bodies is a unique feature of some enteric ganglia. Single cell/nucleus RNA-sequencing has unveiled a striking complexity of cell populations in the peripheral nerves, and these refined cell type annotations could facilitate a better understanding of PNS aging. While the effects of senescence on individual PNS cell types requires further characterization, the use of senolytics appears to improve general PNS function in models of aging. Here, we review the current understanding of age-related changes of the intracardiac, musculoskeletal, and enteric nervous system sub-sections of the PNS, highlighting their commonalities and differences.

A review of gut failure as a cause and consequence of critical illness

In critical illness, all elements of gut function are perturbed. Dysbiosis develops as the gut microbial community loses taxonomic diversity and new virulence factors appear. Intestinal permeability increases, allowing for translocation of bacteria and/or bacterial products. Epithelial function is altered at a cellular level and homeostasis of the epithelial monolayer is compromised by increased intestinal epithelial cell death and decreased proliferation. Gut immunity is impaired with simultaneous activation of maladaptive pro- and anti-inflammatory signals leading to both tissue damage and susceptibility to infections. Additionally, splanchnic vasoconstriction leads to decreased blood flow with local ischemic changes. Together, these interrelated elements of gastrointestinal dysfunction drive and then perpetuate multi-organ dysfunction syndrome. Despite the clear importance of maintaining gut homeostasis, there are very few reliable measures of gut function in critical illness. Further, while multiple therapeutic strategies have been proposed, most have not been shown to conclusively demonstrate benefit, and care is still largely supportive. The key role of the gut in critical illness was the subject of the tenth Perioperative Quality Initiative meeting, a conference to summarize the current state of the literature and identify key knowledge gaps for future study. This review is the product of that conference.

Immunostimulatory effects of isomalto/malto-polysaccharides via TLR2 and TLR4 in preventing doxycycline-induced cytokine loss

Isomalto/malto-polysaccharides (IMMPs) are α-glucans with prebiotic potential used as food ingredients. However, their ability to exert direct cellular effects remains unknown. IMMPs may enhance immunity by activating toll-like receptors (TLRs), key for defense against pathogens. Doxycycline is an antibiotic that requires an effective immune function but paradoxically has immune-attenuating effects by reducing TLR2 activity, potentially increasing antibiotic needs. We hypothesize that IMMPs are recognized by various cell surface TLRs, leading to the activation of the NF-κB signaling pathway. Furthermore, IMMPs' immune-stimulating effect could prevent the doxycycline-induced reduction of TLR2 activity in immune cells. IMMPs activated TLR2, increasing NF-κB signaling by 3.42- and 6.37-fold at 1 and 2 mg/mL, respectively. TLR4 activation increased 5.47-, 7.39-, and 8.34-fold at 0.5, 1, and 2 mg/mL. IMMPs enhanced IL-8, TNFα, and IL1-RA production in THP-1 monocytes. Additionally, preincubation of macrophages with IMMPs enhanced cytokine production and partially prevented doxycycline-induced cytokine reduction in response to TLR2 activation. Molecular docking analyses support IMMPs and doxycycline binding to these TLRs. These findings suggest that IMMPs stimulate immunity via TLR2 and TLR4, partially mitigating doxycycline's adverse effects. This provides a dietary strategy to enhance pathogen clearance, reduce antibiotic needs, and support immune health.

Intestinal epithelium-derived IL-34 reprograms macrophages to mitigate gastrointestinal tract graft-versus-host disease

Gastrointestinal (GI) tract graft-versus-host disease (GVHD) is a major complication after allogeneic hematopoietic stem cell transplantation and is attributable to dysregulation that occurs between the effector and regulatory arms of the immune system. Whereas regulatory T cells have a primary role in counterbalancing GVHD-induced inflammation, identifying and harnessing other pathways that promote immune tolerance remain major goals in this disease. Herein, we identified interleukin-34 (IL-34) as an intestinal epithelium-derived cytokine that was able to mitigate the severity of GVHD within the GI tract. Specifically, we observed that the absence of recipient IL-34 production exacerbated GVHD lethality, promoted intestinal epithelial cell death, and compromised barrier integrity. Mechanistically, the absence of host IL-34 skewed donor macrophages toward a proinflammatory phenotype and augmented the accumulation of pathogenic CD4+ granulocyte-macrophage colony-stimulating factor (GM-CSF)+ T cells within the colon. Conversely, the administration of recombinant IL-34 substantially reduced GVHD mortality and inflammation, which was dependent on the expression of apolipoprotein E in donor macrophages. Complementary genetic and imaging approaches in mice demonstrated that intestinal epithelial cells were the relevant source of IL-34. These results were supported by colonic biopsies from patients with GVHD, which displayed IL-34 expression in intestinal epithelial cells and apolipoprotein E in lamina propria macrophages, validating similar cellular localization in humans. These studies indicate that IL-34 acts as a tissue-intrinsic cytokine that regulates GVHD severity in the GI tract and could serve as a potential therapeutic target for amelioration of this disease.

The tryptophan metabolite kynurenic acid ameliorates septic colonic injury through activation of the PPARγ signaling pathway

Sepsis is the leading cause of death among critically ill patients in clinical practice, making it urgent to reduce its incidence and mortality rates. In sepsis, macrophage dysfunction often worsens and complicates the condition. M1 and M2 macrophages, two distinct types, contribute to pro-inflammatory and anti-inflammatory effects, respectively. An imbalance between them is a major cause of sepsis. The aim of this study was to explore the potential of a differential metabolite between M1 and M2 macrophages in mitigating septic colonic injury via multiomics in combination with clinical data and animal experiments. Using nontargeted metabolomics analysis, we found that Kynurenic acid (KYNA), a metabolite of tryptophan metabolism, was significantly upregulated in the supernatant of M2 macrophages. Furthermore, we discovered that the level of KYNA was significantly decreased in sepsis in both human and mouse serum and was negatively correlated with inflammatory factor levels. In vivo experiments demonstrated that KYNA can effectively alleviate septic colon injury and reduce inflammatory factor levels in mice, indicating that KYNA plays a very important protective role in sepsis. Mechanistically, KYNA promotes the transition of M1 macrophages to M2 macrophages by inhibiting the NF-κB signaling pathway and alleviates septic colonic injury through the PPARγ/NF-κB axis. This article reveals that KYNA, a differentially abundant metabolite between M1 and M2 macrophages, can become a new strategy for alleviating septic colon injury.

The role of macrophage polarization in ulcerative colitis and its treatment

Macrophages have great plasticity. Typically, there are two of activated macrophages: M1 macrophages and M2 macrophages. Of them, M1 macrophages play a major role in responses that are pro-inflammatory, while M2 macrophages play an important part in responses that are anti-inflammatory. Ulcerative colitis (UC) is a chronic, non-specific inflammatory disease of the intestine. The pathophysiology and course of UC are significantly influenced by the inflammatory response triggered by macrophage activation. M1 is a possible cause of increased inflammation in UC whereas M2 has a significant function in the healing of inflammation. The polarization imbalance of intestinal M1/M2 macrophages is closely linked to UC. Thus, by suppressing M1 polarization, encouraging M2 polarization, and reestablishing macrophage polarization balance, the treatment of UC based on macrophage polarization is beneficial for UC. Not only chemical drugs, but also traditional Chinese medicine compounds and herbal extracts have been shown to restore the balance of macrophage polarization, providing a new idea in the treatment of UC.

Lewy body diseases and the gut

Gastrointestinal (GI) involvement in Lewy body diseases (LBDs) has been observed since the initial descriptions of patients by James Parkinson. Recent experimental and human observational studies raise the possibility that pathogenic alpha-synuclein (⍺-syn) might develop in the GI tract and subsequently spread to susceptible brain regions. The cellular and mechanistic origins of ⍺-syn propagation in disease are under intense investigation. Experimental LBD models have implicated important contributions from the intrinsic gut microbiome, the intestinal immune system, and environmental toxicants, acting as triggers and modifiers to GI pathologies. Here, we review the primary clinical observations that link GI dysfunctions to LBDs. We first provide an overview of GI anatomy and the cellular repertoire relevant for disease, with a focus on luminal-sensing cells of the intestinal epithelium including enteroendocrine cells that express ⍺-syn and make direct contact with nerves. We describe interactions within the GI tract with resident microbes and exogenous toxicants, and how these may directly contribute to ⍺-syn pathology along with related metabolic and immunological responses. Finally, critical knowledge gaps in the field are highlighted, focusing on pivotal questions that remain some 200 years after the first descriptions of GI tract dysfunction in LBDs. We predict that a better understanding of how pathophysiologies in the gut influence disease risk and progression will accelerate discoveries that will lead to a deeper overall mechanistic understanding of disease and potential therapeutic strategies targeting the gut-brain axis to delay, arrest, or prevent disease progression.

Resolving Resident Colonic Muscularis Macrophage Diversity and Plasticity During Colitis

BACKGROUND

Immune cell populations in the intestinal muscularis propria during colitis are poorly resolved. Maintaining homeostasis in this niche is critical, highlighted by the poorer prognosis of inflammatory bowel disease associated with muscularis propria inflammation.

METHODS

This study utilizes single-cell RNA sequencing to survey the immune cell populations within the muscularis propria of normal colon and dextran sodium sulfate-induced colitis. Findings are validated by immunohistochemistry, flow cytometry and cell-lineage tracing in vivo, and in vitro assays with muscularis macrophages (MMφ).

RESULTS

In naïve conditions, transcriptional duality is observed in MMφs with 2 major subpopulations: conventional resident Cx3cr1+ MMφs and Lyve1+ MMφs. The Lyve1+ population is phagocytic and expresses several known MMφ markers in mouse and human, confirming their identity as a bona fide MMφ subset. Single-cell transcriptomics indicate that resident MMφs are retained during colitis and exhibit plasticity toward an inflammatory profile. Lyve1+ MMφs, which express anti-inflammatory marker CD163, are absent during colitis, as confirmed by flow cytometry. In contrast, lineage tracing finds that resident Cx3cr1+ MMφs remain during colitis and are not completely replaced by the inflammatory infiltrating monocytes. In vitro studies provide biological evidence of the plasticity of resident Cx3cr1+ MMφs in response to lipopolysaccharide (LPS), mirroring transcriptional observations in vivo of their inflammatory plasticity. Potential markers for colitic MMφs, validated in animal models and in individuals with ulcerative colitis, are identified.

CONCLUSIONS

Our findings contribute to the understanding of the immune system in the muscularis propria niche during colitis by resolving the heterogeneity and origins of colitic MMφs.

Akkermansia muciniphila exacerbates acute radiation-induced intestinal injury by depleting mucin and enhancing inflammation

Dysbiosis of gut microbiota plays a crucial role in acute radiation-induced intestinal injury. However, studies on the influence of gut microbiota on acute radiation-induced intestinal injury are inconsistent. In this study, we established an acute radiation-induced intestinal injury mouse model and performed fecal microbiota transplantation to explore the role of the gut microbiota in acute radiation-induced intestinal injury. We observed a significant increase in Akkermansia muciniphila following irradiation, whereas fecal microbiota transplantation effectively reduced A. muciniphila levels. Contrary to expectations, A. muciniphila supplementation increased acute radiation-induced intestinal injury and mortality. Mechanistically, postradiation A. muciniphila upregulates mucin metabolism genes and consumes mucin, thinning the mucosal barrier and promoting the adhesion and translocation of potential pathogens to epithelial cells, thus exacerbating acute radiation-induced intestinal injury. This enables A. muciniphila to use mucin as an energy source. Additionally, A. muciniphila increases the inflammatory macrophage changes and secretion of inflammatory cytokines, leading to a decrease in epithelial stem cell density and inhibition of goblet cell differentiation, further exacerbating acute radiation-induced intestinal injury. Our findings suggest that in certain intestinal environments, the addition of A. muciniphila may worsen radiation-induced intestinal damage; thus, alternative approaches to reverse the dysbiosis associated with radiotherapy should be explored.

Hydrolysates exhibited differential modulatory effects on macrophage compared to the raw polysaccharide (xyloglucomannan) isolated from Atractylodes macrocephala Koidz

It has been claimed that Atractylodes macrocephala applied as a traditional Chinese medicinal herb for centuries, owing to its excellent immunomodulatory and hepatic protective properties. This study aims to explore the immunomodulation of oligosaccharides obtained by gastrointestinal digestion after oral administration of A. macrocephala polysaccharide (xyloglucomannan, XGM). The analysis of chemistry showed that XGM consisted of D-glucose, D-mannose, and D-xylose in a molar ratio of 6.8:3.0:1.0, and the molecular weight was 5465 Da. Furthermore, HCl and pancreatic amylase were used to simulate digestive tract hydrolysis of polysaccharides, obtaining two XGM hydrolysates (XGM-AH and -EH). Oligosaccharide identification results indicated that both XGM-AH and XGM-EH contained glucans (degree of polymerization, DP = 2 ∼ 5). XGM-AH had a wider variety of oligosaccharides than XGM-EH, mainly glucomannans. In vitro immunostimulatory assay indicated that XGM could effectively stimulate the activation and enhance the phagocytosis of RAW264.7 cells. In contrast, XGM-AH and -EH exhibited anti-inflammatory effects, inhibited lipopolysaccharide (LPS)-induced aberrant activation of macrophages, reduced the release of cytokines of macrophages. Flow cytometry assay suggested that XGM-AH and -EH inhibited LPS-induced M1-type polarization of macrophages. In conclusion, XGM-derived oligosaccharides possess anti-inflammatory bioactivities and exhibit differential macrophage regulatory behaviors in contrast to the immune-activating effects exhibited by the prototype polysaccharides.

The role of RNA modifications in disease-associated macrophages

In recent years, the field of epitranscriptomics has witnessed significant breakthroughs with the identification of more than 150 different chemical modifications in different RNA species. It has become increasingly clear that these chemical modifications play an important role in the regulation of fundamental processes linked to cell fate and development. Further interest was sparked by the ability of the epitranscriptome to regulate pathogenesis. However, despite the involvement of macrophages in a multitude of diseases, a clear knowledge gap exists in the understanding of how RNA modifications regulate the phenotype of these cells. Here, we provide a comprehensive overview of the known roles of macrophage RNA modifications in the context of different diseases.

Immunomodulatory Effects of Lactiplantibacillus plantarum Strain RW1 During Salmonella Infection in Murine Intestinal Epithelial Cells and Dextran Sulfate Sodium-Induced Murine Colitis

Inflammatory diseases resulting from bacterial infections or inflammatory bowel disease pose significant threats to the health of both animals and humans. Although probiotics have emerged as a crucial preventive and adjunctive therapy for these conditions, the precise mechanisms through which probiotics regulate inflammatory diseases remain incompletely understood. In our previous study, animal-derived Lactiplantibacillus plantarum strain RW1 (L. plantarum RW1) with probiotic potential was isolated and characterized. In this study, the signaling pathway of L. plantarum RW1 inhibiting the inflammatory response of mouse intestinal epithelial cells caused by Salmonella infection was studied. Our results revealed that infection of Salmonella enterica subsp. enterica serovar Typhimurium strain ATCC14028 (S. Typhimurium ATCC14028) and Salmonella enterica subsp. enterica serovar Typhimurium strain SL1344 (S. Typhimurium SL1344) significantly increased NF-κB/p65 and TLR4 mRNA levels while decreasing IκB and TLR2 mRNA levels. Whereas L. plantarum RW1 treatment significantly reversed these changes. Western blotting confirmed these findings. Additionally, we explored the protective effects of L. plantarum RW1 in a murine colitis model induced by dextran sulfate sodium (DSS). Treatment with L. plantarum RW1 significantly increased both intestinal length and body weight compared to DSS-treated mice. 16S rRNA sequencing analysis demonstrated that L. plantarum RW1 restored the dysbiosis caused by DSS. Flow cytometry analyses further revealed that L. plantarum RW1 specifically increased regulatory T-cell proportions in Peyer's patches while reducing macrophage and neutrophil proportions, indicating the modulatory effects of L. plantarum RW1 on immune responses in gut-associated lymphatic tissue in the context of colitis. This study sheds light on the intricate interaction between probiotics and hosts, offering valuable insights into their potential application for treating inflammatory diseases in animals and humans.

Immunomodulation of exopolysaccharide produced by Lacticaseibacillus rhamnosus ZFM216 in cyclophosphamide-induced immunosuppressed mice by modulating gut microbiota

This study investigated the immunoregulatory activity of exopolysaccharides (EPS) produced by Lacticaseibacillus rhamnosus ZFM216 in immunosuppressed mice induced by cyclophosphamide (CTX). The results showed that EPS treatment effectively improved the body weight, immune organ index and splenic lymphocyte proliferation. EPS also mitigated the damage of immune organs, restored intestinal morphology, and regulated the levels of serum hemolysin and cytokines (e.g. TNF-α, INF-γ and IL-10). EPS promoted the release of NO, TNF-α, IL-1β, and IL-6 in RAW 264.7 cells, however, such effect was inhibited in the presence of inhibitors of TLR4 and MAPKs signaling pathways-related proteins, confirming that EPS achieved the immunomodulation by activating these two signaling pathways. Additionally, EPS, as a prebiotic, effectively improved the diversity of microbial communities, regulated the relative abundance of dominant microbial communities, restored CTX-induced gut microbiota dysbiosis, and promoted the production of short chain fatty acids (SCFAs) in the gut of mice. Thus, immunoregulatory effect of EPS could be attributed to its good ability to modulate the gut microbiota. EPS produced by L. rhamnosus ZFM216 has promising application as an ingredient of functional foods due to its potent probiotic effect.

Controlling functional homeostasis of ileal resident macrophages by vitamin B12 during steady state and Salmonella infection in mice

Dietary micronutrients, particularly vitamin B12 (VB12), profoundly influence the physiological maintenance and function of intestinal cells. However, it is still unclear whether VB12 modulates the transcriptional and metabolic programming of ileal macrophages (iMacs), thereby contributing to intestinal homeostasis. Using multiomic approaches, we demonstrated that VB12 primarily supports the cell cycle activity and mitochondrial metabolism of iMacs, resulting in increased cell frequency compared to VB12 deficiency. VB12 also retained the ability to promote maintenance and metabolic regulation of iMacs during intestinal infection with Salmonella Typhimurium (STm). On the contrary, depletion of iMacs by inhibiting CSF1R signaling significantly increased host susceptibility to STm and prevented VB12-mediated pathogen reduction. These results thus suggest that regulation of VB12-dependent iMacs critically controls STm expansion, which may be of new relevance to advance our understanding of this vitamin and to strategically formulate sustainable therapeutic nutritional regimens that improve human gut health.

Innate immunity champions: The diverse functions of macrophages

Macrophages are instrumental in maintaining tissue homeostasis, modulating inflammation, and driving regeneration. The advent of omics techniques has led to the identification of numerous tissue-specific macrophage subtypes, thereby introducing the concept of the "macrophage niche". This paradigm underscores the ability of macrophages to adapt their functions based on environmental cues, such as tissue-specific signals. This adaptability is closely linked to their metabolic states, which are crucial for their function and role in health and disease. Macrophage metabolism is central to their ability to switch between proinflammatory and anti-inflammatory states. In this regard, environmental factors, including the extracellular matrix, cellular interactions, and microbial metabolites, profoundly influence macrophage behavior. Moreover, diet and gut microbiota significantly impact macrophage function, with nutrients and microbial metabolites influencing their activity and contributing to conditions like inflammatory bowel disease. Targeting specific macrophage functions and their metabolic processes is leading to the development of novel treatments for a range of chronic inflammatory conditions. The exploration of macrophage biology enriches our understanding of immune regulation and holds the promise of innovative approaches to managing diseases marked by inflammation and immune dysfunction, offering a frontier for scientific and clinical advancement.

Lactobacillus paracasei JY062 and its exopolysaccharide enhance the intestinal barrier through macrophage polarization and Th17/Treg cell balance

Ulcerative colitis (UC) is an immune-mediated intestinal disease without a comprehensive cure, and the alleviation of UC has become an urgent problem. The results showed that JY062 with its EPS group (JEC) alleviated the intestinal barrier damage caused by LPS. After JEC intervention on Caco-2 cells, resulted in upregulation of ZO-1, Claudin-1, Occludin and MUC2 transcript levels and decreased mRNA expression of Claudin-2 (p < 0.05). JEC effectively attenuated the inflammatory response in UC mice and restoration of immunoglobulin levels (IgG, IgM and IgA), which resulted in shortening and swelling of the colon, disappearance of goblet cells, infiltration of inflammatory cells and mucosal damage were alleviated in mice. Similarly, changes in the expression of MUC2 and tight junction proteins after JEC intervention also occurred in UC mice. Administration of JEC significantly inhibited the differentiation of pro-inflammatory Th17 cells in the thymus and peripheral blood, promoted the differentiation of CD4+ T cells to Treg cells, and effectively regulated DSS-induced macrophage imbalance, which was manifested by the polarization of pro-inflammatory M1 macrophages to anti-inflammatory M2 macrophages. This study clearly demonstrates that JEC could significantly prevent intestinal barrier on DSS-induced experimental colitis and could be applied as a potential symbiotic strategy to assist in the alleviation of UC.

Aspartame enhances the scavenging activity of mice to low-dose Escherichia coli infection via strengthening macrophage phagocytosis caused by sweet taste receptor activation

Aspartame is the most common artificial sweetener and a famous sweet-taste receptor agonist. Macrophages are essential in the antibacterial system to maintain the stability of the intestinal environment. Recently, the sweet taste receptor has been found in macrophages. However, the effects of aspartame on macrophage phagocytosis in the gastrointestinal tract are little known. The current study sought to assess the influence of aspartame intake on the scavenging activity of mice to low-dose Escherichia coli infection and related mechanisms. Firstly, no inflammatory response or pathological injury was observed in the intestines of mice after oral administration of aspartame (25-100 mg/kg, i.g.) for 2 weeks. Subsequently, aspartame intake was found to enhance the scavenging activity of mice to low-dose E. coli infection. Similarly, aspartame dose-dependent strengthened the ability of RAW264.7 cells to phagocytose GFP-E.coli J96. Further mechanism evaluation reflected that aspartame could enhance macrophage phagocytosis, migration, and rearrangement via PLCβ-2/Ca2+/PKCβ/Rho A/ROCK1 pathway caused by sweet taste receptor activation. In conclusion, the present study, for the first time, demonstrated that aspartame could enhance the scavenging activity of mice to low-dose E. coli infection via strengthening macrophage phagocytic function through activating sweet taste receptor. It is then suggested that aspartame may affect the antibacterial activity of human gastrointestinal macrophages, and further studies need to validate these effects.

Dissecting Innate and Adaptive Immunity in Inflammatory Bowel Disease: Immune Compartmentalization, Microbiota Crosstalk, and Emerging Therapies

The intestinal immune system is the largest immune organ in the human body. Excessive immune response to intestinal cavity induced by harmful stimuli including pathogens, foreign substances and food antigens is an important cause of inflammatory diseases such as celiac disease and inflammatory bowel disease (IBD). Although great progress has been made in the treatment of IBD by some immune-related biotherapeutic products, yet a considerable proportion of IBD patients remain unresponsive or immune tolerant to immunotherapeutic strategy. Therefore, it is necessary to further understand the mechanism of immune cell populations involved in enteritis, including dendritic cells, macrophages and natural lymphocytes, in the steady-state immune tolerance of IBD, in order to find effective IBD therapy. In this review, we discussed the important role of innate and adaptive immunity in the development of IBD. And the relationship between intestinal immune system disorders and microflora crosstalk were also presented. We also focus on the new findings in the field of T cell immunity, which might identify novel cytokines, chemokines or anti-cytokine antibodies as new approaches for the treatment of IBD.

Enhanced therapeutic efficacy of granulocyte/monocyte adsorption in rats with drug-induced colitis : Insights from a downsized bead column and newly formed B cells

INTRODUCTION

Granulocyte/monocyte adsorption therapy can manage mild-to-moderate inflammatory bowel disease by removing activated granulocytes and monocytes. We evaluated granulocyte/monocyte adsorption using new columns with reduced bead size and theoretically enhanced adsorption.

METHODS

We assessed granulocyte/monocyte adsorption in rats with colitis by analyzing cell changes and cytokine production.

RESULTS

Granulocyte/monocyte adsorption with the new columns improved histology in rats with colitis. Contrary to expectations, the adsorption rate of granulocytes/monocytes into the blood did not show a significant improvement. However, flow cytometry showed increased B cells in peripheral blood mononuclear cells and newly formed B cells in the bone marrow, which produced more interleukin-10 than peripheral blood B cells. Newly formed B cells adoptively transferred into colitis rats accumulated at the inflammation site and tended to inhibit intestinal shortening.

CONCLUSIONS

Newly formed B cells with strong interleukin-10 production may alleviate inflammation. The new columns suggest potential for controlling colitis.

Short-chain fatty acids reverses gut microbiota dysbiosis-promoted progression of glioblastoma by up-regulating M1 polarization in the tumor microenvironment

Glioblastoma (GBM), known as the most malignant and common primary brain tumor of the central nervous system, has finite therapeutic options and a poor prognosis. Studies have shown that host intestinal microorganisms play a role in the immune regulation of parenteral tumors in a number of different ways, either directly or indirectly. However, the potential impact of gut microbiota on tumor microenvironment, particularly glioma immunological milieu, has not been clarified exactly. In this study, by using an orthotopic GBM model, we found gut microbiota dysbiosis caused by antibiotic cocktail treatment boosted the tumor process in vivo. An obvious change that followed gut microbiota dysbiosis was the enhanced percentage of M2-like macrophages in the TME, in parallel with a decrease in the levels of gut microbial metabolite, short-chain fatty acids (SCFAs) in the blood and tumor tissues. Oral supplementation with SCFAs can increase the proportion of M1-like macrophages in the TME, which improves the outcomes of glioma. In terms of mechanism, SCFAs-activated glycolysis in the tumor-associated macrophages may be responsible for the elevated M1 polarization in the TME. This study will enable us to better comprehend the "gut-brain" axis and be meaningful for the development of TAM-targeting immunotherapeutic strategies for GBM patients.

Tarm1 may affect colitis by regulating macrophage M1 polarization in a mouse colitis model

BACKGROUND

In this study, we aimed to explore the role of Tarm1 in juvenile mice with dextran sulfate sodium (DSS)-induced colitis and elucidate the mechanisms that affect intestinal barrier function.

METHODS

A DSS-induced pediatric inflammatory bowel disease mouse model was established using 4-week-old juvenile mice. Disease activity index and histopathological damage scores were determined using hematoxylin and eosin (H&E) staining. Tarm1, F4/80, CD68, and CD86 levels were detected using qPCR, western blotting, and immunofluorescence. Trans epithelial electric resistance (TEER) was detected using the transwell assay.

RESULTS

Results revealed that juvenile colitis mice fed 4% DSS drinking water had increased Tarm1 expression in the colon tissue, increased macrophage M1 polarization, higher expression of pro-inflammatory cytokines, and an impaired intestinal mucosal barrier, compared with the control group. Tarm1-knockdown RAW264.7 cells inhibited lipopolysaccharide (LPS)-induced M1 polarization and attenuated barrier damage in co-cultured intestinal epithelial cells.

CONCLUSION

Tarm1 expression was increased in colonic tissues of juvenile mice with colitis, and LPS-induced M1 polarization and intestinal barrier damage were attenuated in Tarm1-knockdown RAW264.7 cells. This suggests that attenuation of Tarm1 expression is a potential target for pediatric inflammatory bowel disease therapy.

Gut microbiota-driven metabolic alterations reveal the distinct pathogenicity of chemotherapy-induced cachexia in gastric cancer

Cachexia affects approximately 50-80 % of advanced cancer patients, particularly those with gastric cancer (GC). Therefore, early detection of cachexia is essential to prevent its progression. Targeting the gut microbiota may be a promising approach for preventing and treating cachexia in patients with GC. Chemotherapy significantly reduced gut microbiota diversity in GC patients. Specifically, the abundance of bacterial genera such as Bacteroides, Streptococcus, and Prevotella was increased in the gut of patients postchemotherapy, which was closely associated with the development of cachexia. Serum metabolic analysis revealed a strong link between specific microbes and metabolite in patients with chemotherapy-induced GC cachexia. We further constructed a random forest model based on the top 6 genera in terms of abundance for the prediction of chemotherapy-related GC cachexia development; this model had an area under the receiver operating characteristic curve (AUC) of 93.5 % [95 % confidence interval (CI), 86.6 %-100 %], with a specificity and accuracy above 75 %. Additionally, we identified Enterotoxin Bacteroides fragilis (ETBF) as a key factor in chemotherapy-induced GC cachexia. In an in vivo GC model, the colonization of ETBF in the intestines of mice significantly accelerated the muscle and adipose tissue consumption induced by chemotherapy, resulting in cachexia symptoms. Furthermore, ETBF damaged the intestinal mucosal barrier by disrupting cell connections and attracting M1 macrophages, which advances GC cachexia. In conclusion, our findings indicate that gut microbiota imbalance is crucial in GC cachexia development, suggesting potential biomarkers for early diagnosis. Clinical trial registration: http://www.chictr.org.cn, Identification No: ChiCTR2200064547.

Progesterone promotes CXCl2-dependent vaginal neutrophil killing by activating cervical resident macrophage-neutrophil crosstalk

Vaginal infections in women of reproductive age represent a clinical dilemma with significant socioeconomic implications. The current understanding of mucosal immunity failure during early pathogenic invasions that allows the pathogen to grow and thrive is far from complete. Neutrophils infiltrate most tissues following circadian patterns as part of normal repair, regulation of microbiota, or immune surveillance and become more numerous after infection. Neutrophils are responsible for maintaining vaginal immunity. Specific to the vagina, neutrophils continuously infiltrate at high levels, although during ovulation, they retreat to avoid sperm damage and permit reproduction. Here we show that, after ovulation, progesterone promotes resident vaginal macrophage-neutrophil crosstalk by upregulating Yolk sac early fetal organs (FOLR2+) macrophage CXCl2 expression, in a TNFA-patrolling monocyte-derived macrophage-mediated (CX3CR1hiMHCIIhi-mediated) manner, to activate the neutrophils' capacity to eliminate sex-transmitted and opportunistic microorganisms. Indeed, progesterone plays an essential role in conciliating the balance between the commensal microbiota, sperm, and the threat of pathogens because progesterone not only promotes a flurry of neutrophils but also increases neutrophilic fury to restore immunity after ovulation to thwart pathogenic invasion after intercourse. Therefore, modest progesterone dysregulations could lead to a suboptimal neutrophilic response, resulting in insufficient mucosal defense and recurrent unresolved infections.

The role of reactive enteric glia-macrophage interactions in acute and chronic inflammation

Enteric glia are a heterogeneous population of peripheral glia within the enteric nervous system and play pivotal roles in gut homeostasis, tissue integrity, coordination of motility, and intestinal immune responses. Under physiological conditions, they communicate with enteric neurons to control intestinal motility. In contrast, enteric glia undergo reactive changes in response to inflammatory signals during enteric neuroinflammation and participate in immune control. In this state, these glia are called reactive enteric glia, which promote cytokine and chemokine secretion and perpetuate immune cell recruitment, thereby affecting disease progression. Interestingly, reactive glia exhibit a huge plasticity and adapt to or shape the immune environment towards a resolving phenotype during inflammation and neuropathies. Recent studies revealed a bidirectional communication between enteric glia and resident and infiltrating immune cells under healthy conditions and in the context of inflammation-based intestinal disorders and neuropathies. While recent reviews give a superb general overview of enteric glial reactivity, we herein discuss the latest evidence on enteric glial reactivity in two prominent inflammatory conditions: acute postoperative inflammation, resulting in postoperative ileus, and chronic inflammation in inflammatory bowel diseases. We define their plasticity during inflammation and the interplay between reactive enteric glia and intestinal macrophages. Finally, we sketch important questions that should be addressed to clarify further the impact of enteric glial reactivity on intestinal inflammation.

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

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

A metabolic switch orchestrated by IL-18 and the cyclic dinucleotide cGAMP programs intestinal tolerance

Tissues are exposed to diverse inflammatory challenges that shape future inflammatory responses. While cellular metabolism regulates immune function, how metabolism programs and stabilizes immune states within tissues and tunes susceptibility to inflammation is poorly understood. Here, we describe an innate immune metabolic switch that programs long-term intestinal tolerance. Intestinal interleukin-18 (IL-18) stimulation elicited tolerogenic macrophages by preventing their proinflammatory glycolytic polarization via metabolic reprogramming to fatty acid oxidation (FAO). FAO reprogramming was triggered by IL-18 activation of SLC12A3 (NCC), leading to sodium influx, release of mitochondrial DNA, and activation of stimulator of interferon genes (STING). FAO was maintained in macrophages by a bistable switch that encoded memory of IL-18 stimulation and by intercellular positive feedback that sustained the production of macrophage-derived 2'3'-cyclic GMP-AMP (cGAMP) and epithelial-derived IL-18. Thus, a tissue-reinforced metabolic switch encodes durable immune tolerance in the gut and may enable reconstructing compromised immune tolerance in chronic inflammation.

β-Glucan-A promising immunocyte-targeting drug delivery vehicle: Superiority, applications and future prospects

Drug delivery technologies that could convert promising therapeutics into successful therapies have been under broad research for many years. Recently, β-glucans, natural-occurring polysaccharides extracted from many organism species such as yeast, fungi and bacteria, have attracted increasing attention to serve as drug delivery carriers. With their unique structure and innate immunocompetence, β-glucans are considered as promising carriers for targeting delivery especially when applied in the vaccine construction and oral administration of therapeutic agents. In this review, we focus on three types of β-glucans applied in the drug delivery system including yeast β-glucan, Schizophyllan and curdlan, highlighting the benefits of β-glucan based delivery system. We summarize how β-glucans as delivery vehicles have aided various therapeutics ranging from macromolecules including proteins, peptides and nucleic acids to small molecular drugs to reach desired cells or organs in terms of loading strategies. We also outline the challenges and future directions for developing the next generation of β-glucan based delivery systems.

The communication mechanism of the gut-brain axis and its effect on central nervous system diseases: A systematic review

Gut microbiota is involved in intricate and active metabolic processes the host's brain function, especially its role in immune responses, secondary metabolism, and symbiotic connections with the host. Gut microbiota can promote the production of essential metabolites, neurotransmitters, and other neuroactive chemicals that affect the development and treatment of central nervous system diseases. This article introduces the relevant pathways and manners of the communication between the brain and gut, summarizes a comprehensive overview of the current research status of key gut microbiota metabolites that affect the functions of the nervous system, revealing those adverse factors that affect typical communication between the brain-gut axis, and outlining the efforts made by researchers to alleviate these neurological diseases through targeted microbial interventions. The relevant pathways and manners of communication between the brain and gut contribute to the experimental design of new treatment plans and drug development. The factors that may cause changes in gut microbiota and affect metabolites, as well as current intervention methods are summarized, which helps improve gut microbiota brain dialogue, prevent adverse triggering factors from interfering with the gut microbiota system, and minimize neuropathological changes.

Navigating commensal dysbiosis: Gastrointestinal host-pathogen interplay orchestrating opportunistic infections

The gut commensals, which are usually symbiotic or non-harmful bacteria that live in the gastrointestinal tract, have a positive impact on the health of the host. This review, however, specifically discuss distinct conditions where commensals aid in the development of pathogenic opportunistic infections. We discuss that the categorization of gut bacteria as either pathogens or non-pathogens depends on certain circumstances, which are significantly affected by the tissue microenvironment and the dynamic host-microbe interaction. Under favorable circumstances, commensals have the ability to transform into opportunistic pathobionts by undergoing overgrowth. These conditions include changes in the host's physiology, simultaneous infection with other pathogens, effective utilization of nutrients, interactions between different species of bacteria, the formation of protective biofilms, genetic mutations that enhance pathogenicity, acquisition of genes associated with virulence, and the ability to avoid the host's immune response. These processes allow commensals to both initiate infections themselves and aid other pathogens in populating the host. This review highlights the need of having a detailed and sophisticated knowledge of the two-sided nature of gut commensals. Although commensals mostly promote health, they may also become harmful in certain changes in the environment or the body's functioning. This highlights the need of acknowledging the intricate equilibrium in interactions between hosts and microbes, which is crucial for preserving intestinal homeostasis and averting diseases. Finally, we also emphasize the further need of research to better understand and anticipate the behavior of gut commensals in different situations, since they play a crucial and varied role in human health and disease.

The Role of Mucosal Immunity: What Can We Learn From Animal and Human Studies?

Immunoglobulin A (IgA) is a key actor in the mucosal immune system, which moderates interactions between the host and environmental factors such as food antigens and commensal microorganisms. The pathogenesis of IgA nephropathy (IgAN) involves a multistep process starting with deglycosylation of mucosally derived, polymeric IgA1 (dg-IgA1) that reaches the circulation. Modified O-glycans on dg-IgA1 are targeted by IgG-autoantibodies, leading to the formation of circulating immune complexes that deposit in the glomerular mesangium. Infections of mucosal surfaces trigger flares of primary IgAN, while inflammatory bowel disease and liver cirrhosis are important causes of secondary IgAN, supporting a mucosal source of nephritogenic IgA1. In the presence of microbial pathogens or food antigens, activated dendritic cells in the gut mucosa induce T-cell-dependent or T-cell-independent B-cell differentiation into IgA-secreting plasma cells. Herein we review the literature concerning mucosal immune function and how it is altered in this disease. We discuss recent evidence supporting a causal role of gut microbiota dysbiosis in IgAN pathogenesis.

Echinococcus multilocularis serpin regulates macrophage polarization and reduces gut dysbiosis in colitis

Helminths serve as principal regulators in modulating host immune responses, and their excretory-secretory proteins are recognized as potential therapeutic agents for inflammatory bowel disease. Nevertheless, our comprehension of the mechanisms underlying immunoregulation remains restricted. This investigation delves into the immunomodulatory role of a secretory protein serpin (Emu-serpin), within the larval stage of Echinococcus multilocularis. Our observations indicate that Emu-serpin effectively alleviates dextran sulfate sodium-induced colitis, yielding a substantial reduction in immunopathology and an augmentation of anti-inflammatory cytokines. Furthermore, this suppressive regulatory effect is concomitant with the reduction of gut microbiota dysbiosis linked to colitis, as evidenced by a marked impediment to the expansion of the pathobiont taxa Enterobacteriaceae. In vivo experiments demonstrate that Emu-serpin facilitates the expansion of M2 phenotype macrophages while concurrently diminishing M1 phenotype macrophages, alongside an elevation in anti-inflammatory cytokine levels. Subsequent in vitro investigations involving RAW264.7 and bone marrow macrophages reveal that Emu-serpin induces a conversion of M2 macrophage populations from a pro-inflammatory to an anti-inflammatory phenotype through direct inhibition. Adoptive transfer experiments reveal the peritoneal macrophages induced by Emu-serpin alleviate colitis and gut microbiota dysbiosis. In summary, these findings propose that Emu-serpin holds the potential to regulate macrophage polarization and maintain gut microbiota homeostasis in colitis, establishing it as a promising candidate for developing helminth therapy for preventing inflammatory diseases.

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.

Macrophage plasticity: signaling pathways, tissue repair, and regeneration

Macrophages are versatile immune cells with remarkable plasticity, enabling them to adapt to diverse tissue microenvironments and perform various functions. Traditionally categorized into classically activated (M1) and alternatively activated (M2) phenotypes, recent advances have revealed a spectrum of macrophage activation states that extend beyond this dichotomy. The complex interplay of signaling pathways, transcriptional regulators, and epigenetic modifications orchestrates macrophage polarization, allowing them to respond to various stimuli dynamically. Here, we provide a comprehensive overview of the signaling cascades governing macrophage plasticity, focusing on the roles of Toll-like receptors, signal transducer and activator of transcription proteins, nuclear receptors, and microRNAs. We also discuss the emerging concepts of macrophage metabolic reprogramming and trained immunity, contributing to their functional adaptability. Macrophage plasticity plays a pivotal role in tissue repair and regeneration, with macrophages coordinating inflammation, angiogenesis, and matrix remodeling to restore tissue homeostasis. By harnessing the potential of macrophage plasticity, novel therapeutic strategies targeting macrophage polarization could be developed for various diseases, including chronic wounds, fibrotic disorders, and inflammatory conditions. Ultimately, a deeper understanding of the molecular mechanisms underpinning macrophage plasticity will pave the way for innovative regenerative medicine and tissue engineering approaches.