Gene-expression profiles and transcriptional regulatory pathways that underlie the identity and diversity of mouse tissue macrophages

The impact of gut microbial short-chain fatty acids on colorectal cancer development and prevention

Cancer is a long-term illness that involves an imbalance in cellular and immune functions. It can be caused by a range of factors, including exposure to environmental carcinogens, poor diet, infections, and genetic alterations. Maintaining a healthy gut microbiome is crucial for overall health, and short-chain fatty acids (SCFAs) produced by gut microbiota play a vital role in this process. Recent research has established that alterations in the gut microbiome led to decreased production of SCFA's in lumen of the colon, which associated with changes in the intestinal epithelial barrier function, and immunity, are closely linked to colorectal cancer (CRC) development and its progression. SCFAs influence cancer progression by modifying epigenetic mechanisms such as DNA methylation, histone modifications, and non-coding RNA functions thereby affecting tumor initiation and metastasis. This suggests that restoring SCFA levels in colon through microbiota modulation could serve as an innovative strategy for CRC prevention and treatment. This review highlights the critical relationship between gut microbiota and CRC, emphasizing the potential of targeting SCFAs to enhance gut health and reduce CRC risk.

CKN reduces TLR4-mediated inflammation and cerebral I/R injury by activating the LXRα/ABCA1 pathway in microglia

AIMS

CKN is a self-developed LXRα agonist capable of up-regulating the expression of ABCA1, diminishing intracellular lipid deposition, and attenuating the inflammatory response. Nevertheless, the protective effect and mechanism of ischemic stroke remain indistinct. The aim of this study is to investigate the therapeutic effects and the underlying mechanisms of CKN in ischemic stroke.

MATERIALS AND METHODS

In this study, the tMCAO model was utilized to induce cerebral artery occlusion in mice, and cholesterol-induced BV2 and primary microglia models were adopted. Neuronal damage and the effect of CKN on ABCA1 expression, lipid deposition, and TLR4 signaling in penumbra microglia were assessed.

KEY FINDINGS

The results demonstrated that: (1) CKN treatment markedly ameliorated the neurological deficit score of the tMCAO model, contracted the infarct size, and mitigated the damage of the cerebral cortex. (2) CKN has the capacity to up-regulate the expression of ABCA1 in microglia within the ischemic penumbra by activating the LXRα/ABCA1 signaling pathway, and minimize lipid deposition and inflammatory responses. (3) The activation of the LXRα/ABCA1 signaling pathway is profoundly implicated in the inflammatory response triggered by CKN inhibition of the TLR4 signaling pathway in microglia.

SIGNIFICANCE

The present study demonstrated for the first time that the activation of the LXRα/ABCA1 signaling possessed the ability to attenuate reperfusion injury in ischemic stroke by means of reducing lipid droplet formation and TLR4-mediated inflammatory signaling within microglia in the ischemic penumbra.

New insights into therapeutic strategies for targeting hepatic macrophages to alleviate liver fibrosis

Liver fibrosis is a wound-healing response induced by persistent liver damage, resulting from complex multicellular interactions and multifactorial networks. Without intervention, it can progress to cirrhosis and even liver cancer. Current understanding suggests that liver fibrosis is reversible, making it crucial to explore effective therapeutic strategies for its alleviation. Chronic inflammation serves as the primary driver of liver fibrosis, with hepatic macrophages playing a dual role depending on their polarization state. This review summarizes various prevention and therapeutic strategies targeting hepatic macrophages in the context of liver fibrosis. These strategies include inhibition of macrophage recruitment, modulation of macrophage activation and polarization, regulation of macrophage metabolism, and induction of phagocytosis and autophagy in hepatic macrophages. Additionally, we discuss the communication between hepatic macrophages, hepatocytes, and hepatic stellate cells (HSCs), as well as the current clinical application of anti-fibrotic drugs targeting macrophages. The goal is to identify effective therapeutic targets at each stage of macrophage participation in liver fibrosis development, with the aim of using hepatic macrophages as a target for liver fibrosis treatment.

Direct microglia replacement reveals pathologic and therapeutic contributions of brain macrophages to a monogenic neurological disease

Krabbe disease, also named globoid cell (GC) leukodystrophy (GLD) for its distinct lipid-laden macrophages, is a severe leukodystrophy caused by galactosylceramidase (GALC) mutations. Hematopoietic stem cell transplant (HSCT) ameliorates disease and is associated with central nervous system (CNS) engraftment of GALC+ donor macrophages. Yet, the role of macrophages in GLD pathophysiology and HSCT remains unclear. Using single-cell sequencing, we revealed early interferon response signatures that preceded progressively severe macrophage dyshomeostasis and identified a molecular signature of GCs, which we validated in human brain specimens. Genetic depletion and direct microglia replacement by CNS monocyte injection rapidly replaced >80% of endogenous microglia with healthy macrophages in the twitcher (GalcW355∗) mouse model of GLD. Perinatal microglia replacement completely normalized transcriptional signatures, rescued histopathology, and doubled average survival. Overall, we uncovered distinct forms of microglial dysfunction and evidence that direct, CNS-limited microglia replacement improves a monogenic neurodegenerative disease, identifying a promising therapeutic target.

Border-associated macrophages as gatekeepers of brain homeostasis and immunity

The brain's border tissues serve as essential hubs for neuroimmune regulation and the trafficking of biomaterials to and from the brain. These complex tissues-including the meninges, perivascular spaces, choroid plexus, and circumventricular organs-balance the brain's need for immune privilege with immune surveillance and blood-brain communication. Macrophages are integral components of these tissues, taking up key strategic positions within the brain's circulatory system. These border-associated macrophages, or "BAMs," are therefore emerging as pivotal for brain homeostasis and disease. BAMs perform trophic functions that help to support border homeostasis but also act as immune sentinels essential for border defense. In this review, we integrate recent findings on BAM origins, cell states, and functions, aiming to provide global insights and perspectives on the complex relationship between these macrophages and their border niche.

KLF family members control expression of genes required for tissue macrophage identities

Tissue-resident macrophages adopt distinct gene expression profiles and exhibit functional specialization based on their tissue of residence. Recent studies have begun to define the signals and transcription factors that induce these identities. Here we describe an unexpected and specific role for the broadly expressed transcription factor Krüppel-like factor 2 (KLF2) in the development of embryonically derived large cavity macrophages (LCMs) in the serous cavities. KLF2 not only directly regulates the transcription of genes previously shown to specify LCM identity, such as retinoic acid receptors and GATA6, but also is required for induction of many other transcripts that define the identity of these cells. Our results suggest that KLF4 may similarly regulate the identity of alveolar macrophages in the lung. These data demonstrate that broadly expressed transcription factors, such as group 2 KLFs, can play important roles in the specification of distinct identities of tissue-resident macrophages.

Cardiomyocyte proliferation: Advances and insights in macrophage-targeted therapy for myocardial injury

In the mammalian heart, cardiomyocytes undergo a transient window of proliferation that leads to regenerative impairment, limiting cardiomyocyte proliferation and myocardial repair capacity. Cardiac developmental patterns exacerbate the progression of heart disease characterized by myocardial cell loss, ultimately leading to cardiac dysfunction and heart failure. Myocardial infarction causes the death of partial cardiomyocytes, which triggers an immune response to remove debris and restore tissue integrity. Interestingly, when transient myocardial injury triggers irreversible loss of cardiomyocytes, the subsequent macrophages responsible for proliferation and regeneration have a unique immune phenotype that promotes the formation of pre-existing new cardiomyocytes. During mammalian regeneration, mononuclear-derived macrophages and self-renewing resident cardiac macrophages provide multiple cytokines and molecular signals that create a regenerative environment and cellular plasticity capacity in postnatal cardiomyocytes, a pivotal strategy for achieving myocardial repair. Consistent with other human tissues, cardiac macrophages originating from the embryonic endothelium produce a hierarchy of contributions to monocyte recruitment and fate specification. In this review, we discuss the novel functions of macrophages in triggering cardiac regeneration and repair after myocardial infarction and provide recent advances and prospective insights into the phenotypic transformation and heterogeneous features involving cardiac macrophages. In conclusion, macrophages contribute critically to regeneration, repair, and remodeling, and are challenging targets for cardiovascular therapeutic interventions.

Effects of glutamine supplementation on the growth performance, antioxidant capacity, immunity and intestinal morphology of cold-stressed prestarter broiler chicks

BACKGROUND

Cold stress has important effects on the growth and production of broiler chickens. Glutamine (Gln) is a conditionally essential amino acid that plays an important role in promoting intestinal development and enhancing immune function. The aim of this study was to investigate the effects of Gln supplementation on the growth performance and health of cold-stressed prestarter broiler chicks.

METHODS AND RESULTS

A total of 375 1-day-old male SZ901 broilers were randomly divided into five groups (CON, CS, GLN1, GLN2, GLN3). Birds in the CON and CS groups were provided with normal drinking water, while the GLN1, GLN2 and GLN3 groups were provided with water supplemented with 0.4%, 0.8% and 1.2% Gln, respectively. At d7, birds in groups CS, GLN1, GLN2, and GLN3 were stressed at 12 ± 1 ℃ for 12 h. The results showed that cold stress significantly decreased the growth performance, serum antioxidant capacity and antibody concentrations, small intestine villus structure, and increased the gene expression of intestinal inflammatory factors of broiler chicks compared with the CON group (P < 0.05). Compared with the CS group, Gln supplementation exhibited increased growth performance, serum antioxidant capacity and antibody concentrations, gene expression levels of intestinal tight junction protein, villus height and villus height to crypt depth ratio (V/C) of small intestine, and decreased mRNA expression level of intestinal inflammatory factors (P < 0.05).

CONCLUSIONS

Gln supplementation ameliorated the impact of cold stress to a large extent as it promoted the development of the intestine and immune system and enhanced the antioxidant enzyme system in cold-stressed prestarter chicks.

Splenic CD169+Tim4+ Marginal Metallophilic Macrophages Are Essential for Wound Healing After Myocardial Infarction

BACKGROUND

Fidelity of wound healing after myocardial infarction (MI) is an important determinant of subsequent adverse cardiac remodeling and failure. Macrophages derived from infiltrating Ly6Chi (lymphocyte antigen 6 complex, locus C) blood monocytes are a key component of this healing response; however, the importance of other macrophage populations is unclear.

METHODS

We used a variety of in vivo murine models and orthogonal approaches, including surgical MI, flow cytometry and single-cell RNA sequencing, lineage tracing and cell tracking, splenectomy, parabiosis, cell adoptive transfer, and functional characterization, to establish an essential role for splenic CD169+Tim4+ (cluster of differentiation 169+; T cell immunoglobulin- and mucin-domain-containing molecule 4) marginal metallophilic macrophages (MMMs) in post-MI wound healing in mice. Flow cytometry was used to measure circulating CD169+Tim4+ monocytes in humans with ST-segment-elevation MI and control participants with stable coronary artery disease undergoing elective percutaneous coronary intervention.

RESULTS

Splenic CD169+Tim4+ MMMs circulate in blood as Ly6Clow monocytes expressing macrophage markers and help populate CD169+Tim4+CCR2-LYVE1low macrophages in the naive heart. After acute MI, splenic MMMs augment phagocytosis and CCR (C-C motif chemokine receptor) 3 and CCR4 expression, and robustly mobilize to the heart, resulting in marked expansion of cardiac CD169+Tim4+LYVE1low macrophages with an immunomodulatory and proresolving gene signature. These macrophages are obligatory for apoptotic neutrophil clearance, suppression of inflammation, and induction of a reparative macrophage phenotype in the infarcted heart. Splenic MMMs are both necessary and sufficient for post-MI wound healing, and limit late pathological remodeling. Liver X receptor-α agonist-induced expansion of the splenic marginal zone and MMMs during acute MI alleviates inflammation and improves short- and long-term cardiac remodeling. Humans with acute ST-segment-elevation MI also exhibit expansion of circulating CD169+Tim4+ cells, primarily within the intermediate (CD14+CD16+) monocyte population.

CONCLUSIONS

Splenic CD169+Tim4+ MMMs are required for proresolving and reparative responses after MI and can be manipulated for therapeutic benefit to limit long-term heart failure.

IRF4-regulated transcriptional and functional heterogeneity of lung-resident CD11b+ cDC2 subsets during influenza virus infection

Lung-resident conventional dendritic cells (cDCs) coordinate immune responses to respiratory viruses in the respiratory tract or after migration to mediastinal lymph nodes (mLN). Migratory DCs include cDC1s (CD103+XCR1+CD24hi) expressing IRF8 or cDC2s (CD11b+SIRPα+CD24+) expressing IRF4. IRF4+ cDC2s are divided into a CD24hi subset that requires IRF4 for differentiation and a CD24int subset that is present in the absence of IRF4. During influenza A virus (IAV) infection of mice, we characterized the kinetics of cDC2 subset accumulation in the lung and mLN and their differences in IRF4-dependent gene expression and function. We found that the 2 IRF4-expressing cDC2 subsets upregulated CD86 to high levels, produced IL-12p40 and the chemokines CCL17 and CCL22, and were capable of acquiring antigen in vivo and activating antigen-specific CD8+ T cells. Notably, the CD11b+CD24int cDC2 subset expressed canonical cDC markers and transcription factors and expanded to high numbers in the lung and mLN by d 6 postinfection. Transcriptome analyses on d 5 postinfection revealed that the CD11b+CD24int cDC2 subset expressed both IRF4 and IRF8 and harbored an elevated IFN response signature compared to the CD11b+CD24hi subset. Analyses of mice lacking Irf4 in CD11c+ cells showed that IRF4 promoted the function of CD11b+CD24int cDC2s, including the capacity to migrate to mLN and to produce CCL17 and CCL22, consistent with their altered gene expression profile in the absence of IRF4. In sum, our data show that the 2 lung-resident CD11b+ cDC2 subsets present in naïve mice elaborated distinct and common functional responses regulated by IRF4 during IAV infection.

Dynamics of compartment-specific proteomic landscapes of hepatotoxic and cholestatic models of liver fibrosis

Accumulation of extracellular matrix (ECM) in liver fibrosis is associated with changes in protein abundance and composition depending upon etiology of the underlying liver disease. Current efforts to unravel etiology-specific mechanisms and pharmacological targets rely on several models of experimental fibrosis. Here, we characterize and compare dynamics of hepatic proteome remodeling during fibrosis development and spontaneous healing in experimental mouse models of hepatotoxic (carbon tetrachloride [CCl4] intoxication) and cholestatic (3,5-diethoxycarbonyl-1,4-dihydrocollidine [DDC] feeding) injury. Using detergent-based tissue extraction and mass spectrometry, we identified compartment-specific changes in the liver proteome with detailed attention to ECM composition and changes in protein solubility. Our analysis revealed distinct time-resolved CCl4 and DDC signatures, with identified signaling pathways suggesting limited healing and a potential for carcinogenesis associated with cholestasis. Correlation of protein abundance profiles with fibrous deposits revealed extracellular chaperone clusterin with implicated role in fibrosis resolution. Dynamics of clusterin expression was validated in the context of human liver fibrosis. Atomic force microscopy of fibrotic livers complemented proteomics with profiles of disease-associated changes in local liver tissue mechanics. This study determined compartment-specific proteomic landscapes of liver fibrosis and delineated etiology-specific ECM components, providing thus a foundation for future antifibrotic therapies.

Metallophilic marginal zone macrophages cross-prime CD8+ T cell-mediated protective immunity against blood-borne tumors

Splenic metallophilic marginal zone macrophages (MMMs) are positioned to control the dissemination of blood-borne threats. We developed a purification protocol to enable characterization of MMMs phenotypically and transcriptionally. MMM gene expression profile was enriched for pathways associated with CD8+ T cell activation and major histocompatibility complex class I (MHC class I) cross-presentation. In vitro, purified MMMs equaled conventional dendritic cells type 1 (cDC1s) in cross-priming CD8+ T cells to soluble and particulate antigens, yet MMMs employed a distinct vacuolar processing pathway. In vivo biphoton and ex vivo light-sheet imaging showed long-standing contacts with cognate T cells differentiating to effectors. MMMs cross-primed protective CD8+ T cell antitumor responses both by capturing blood-borne tumor antigens and by internalizing tumor cells seeding the spleen. This cross-priming required expression of the transcription factor Batf3 by MMMs but was independent of cDC1-mediated capture of tumor material for cross-presentation or MHC class I-dressing. Thus, MMMs combine control of the dissemination of blood-borne pathogens and tumor materials with the initiation of innate and adaptive responses.

Shared pathway of WDFY4-dependent cross-presentation of immune complexes by cDC1 and cDC2

Priming CD8+ T cells against tumors or viral pathogens results largely from cross-presentation of exogenous antigens by type 1 conventional dendritic cells (cDC1s). Although monocyte-derived DCs and cDC2s can cross-present in vitro, their physiological relevance remains unclear. Here, we used genetic models to evaluate the role of cDC subsets in presentation of cell-associated and immune complex antigens to CD4+ and CD8+ T cells in vivo. For cell-associated antigens, cDC1s were necessary and sufficient to prime both CD4+ and CD8+ T cells. In contrast, for immune complex antigens, either cDC1 or cDC2, but not monocyte-derived DCs, could carry out cross-presentation to CD8+ T cells. Mice lacking cDC1 and vaccinated with immune complexes could cross-prime CD8+ T cells that were sufficient to mediate tumor rejection. Notably, this cross-presentation mediated by cDC2 was also WDFY4 dependent, similar to cross-presentation of cell-associated antigens by cDC1. These results demonstrate a previously unrecognized activity of WDFY4 in cDC2s and suggest a cross-presentation pathway shared by cDC subsets.

HIF-1 regulates mitochondrial function in bone marrow-derived macrophages but not in tissue-resident alveolar macrophages

HIF-1α plays a critical role in shaping macrophage phenotype and effector function. We have previously shown that tissue-resident alveolar macrophages (TR-AMs) have extremely low glycolytic capacity at steady-state but can shift toward glycolysis under hypoxic conditions. Here, we generated mice with tamoxifen-inducible myeloid lineage cell specific deletion of Hif1a (Hif1afl/fl:LysM-CreERT2+/-) and from these mice, we isolated TR-AMs and bone marrow-derived macrophages (BMDMs) in which Hif1a is deleted. We show that TR-AM HIF-1α is required for the glycolytic shift under prolyl hydroxylase inhibition but is dispensable at steady-state for inflammatory effector function. In contrast, HIF-1α deletion in BMDMs led to diminished glycolytic capacity at steady-state and reduced inflammatory capacity, but higher mitochondrial function. Gene set enrichment analysis revealed enhanced c-Myc transcriptional activity in Hif1a-/- BMDMs, and upregulation of gene pathways related to ribosomal biogenesis and cellular proliferation. We conclude that HIF-1α regulates mitochondrial function in BMDMs but not in TR-AMs. The findings highlight the heterogeneity of HIF-1α function in distinct macrophage populations and provide new insight into how HIF-1α regulates gene expression, inflammation, and metabolism in different types of macrophages.

Establishment of a Reverse Genetics System for the Study of Human Immune Functions in Mice

Reverse genetics approaches in mice are widely utilized to understand gene functions and their aberrations in diseases. However, limitations exist in translating findings from animal models to human physiology. Humanized mice provide a powerful bridge to understanding human physiology and mechanisms of diseases pathogenesis while maintaining the feasibility of working with small animals. Methods for generating humanized mouse models that allow scientists to probe contributions of particular genes have been rudimentary. Here, we established an efficient method for generating genetically modified human cord blood derived CD34 + cells for transplantation, resulting in humanized mice with near-complete loss of specific gene expression by the human immune system. Mice transplanted with Cas9-edited human CD34 + cells recapitulate functional consequences of specific gene losses in the human immune system. This advancement enables the development of humanized mouse models with targeted gene knockouts, offering a valuable research tool for human gene function studies in vivo .

An aging bone marrow exacerbates lung fibrosis by fueling profibrotic macrophage persistence

Pulmonary fibrosis is an incurable disease that manifests with advanced age. Yet, how hematopoietic aging influences immune responses and fibrosis progression remains unclear. Using heterochronic bone marrow transplant mouse models, we found that an aged bone marrow exacerbates lung fibrosis irrespective of lung tissue age. Upon lung injury, there was an increased accumulation of monocyte-derived alveolar macrophages (Mo-AMs) driven by cell-intrinsic hematopoietic aging. These Mo-AMs exhibited an enhanced profibrotic profile and stalled maturation into a homeostatic, tissue-resident phenotype. This delay was shaped by cell-extrinsic environmental signals such as reduced pulmonary interleukin-10 (IL-10), perpetuating a profibrotic macrophage state. We identified regulatory T cells (Tregs) as critical providers of IL-10 upon lung injury that promote Mo-AM maturation and attenuate fibrosis progression. Our study highlights the impact of an aging bone marrow on lung immune regulation and identifies Treg-mediated IL-10 signaling as a promising target to mitigate fibrosis and promote tissue repair.

Tracing LYVE1+ peritoneal fluid macrophages unveils two paths to resident macrophage repopulation with differing reliance on monocytes

Mouse resident peritoneal macrophages, called large cavity macrophages (LCM), arise from embryonic progenitors that proliferate as mature, CD73+Gata6+ tissue-specialized macrophages. After injury from irradiation or inflammation, monocytes are thought to replenish CD73+Gata6+ LCMs through a CD73-LYVE1+ LCM intermediate. Here, we show that CD73-LYVE1+ LCMs indeed yield Gata6+CD73+ LCMs through integrin-mediated interactions with mesothelial surfaces. CD73-LYVE1+ LCM repopulation of the peritoneum was reliant upon and quantitatively proportional to recruited monocytes. Unexpectedly, fate mapping indicated that only ~10% of Gata6-dependent LCMs that repopulated the peritoneum after injury depended on the LYVE1+ LCM stage. Further supporting nonoverlapping lifecycles of CD73-LYVE1+ and CD73+Gata6+ LCMs, in mice bearing a paucity of monocytes, Gata6+CD73+ LCMs rebounded after ablative irradiation substantially more efficiently than their presumed LYVE1+ or CD73- LCM upstream precursors. Thus, after inflammatory insult, two temporally parallel pathways, each generating distinct differentiation intermediates with varying dependencies on monocytes, contribute to the replenish hment of Gata6+ resident peritoneal macrophages.

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.

Unraveling the spatial and signaling dynamics and splicing kinetics of immune infiltration in osteoarthritis synovium

Introduction

Osteoarthritis (OA), a debilitating joint disorder characterized by synovial inflammation and immune myeloid cell infiltration, currently lacks a comprehensive spatial and transcriptional atlas. This study investigates the spatial dynamics, splicing kinetics, and signaling pathways that drive immune infiltration in OA synovium.

Methods

We integrated single-cell RNA sequencing (scRNA-seq) data from 8 OA and 4 healthy synovial samples with spatial transcriptomics using Spatrio. Spatial transition tensor (STT) analysis decoded multistable spatial homeostasis, while splicing kinetics and non-negative matrix factorization (NMF) identified gene modules. CellPhoneDB and pyLIGER mapped ligand-receptor interactions and transcriptional networks.

Results

Re-annotation of scRNA-seq data resolved synovial cells into 27 subclasses. Spatial analysis revealed OA-specific attractors (8 in OA vs. 6 in healthy samples), including immune myeloid (Attractor3) and lymphoid infiltration (Attractor4). Key genes OLR1 (myeloid homeostasis) and CD69 (T-cell activation) exhibited dysregulated splicing kinetics, driving inflammatory pathways. Myeloid-specific transcription factors (SPI1, MAF, NFKB1) and lymphoid-associated BCL11B were identified as regulators. Computational drug prediction nominated ZILEUTON as a potential inhibitor of ALXN5 to mitigate myeloid infiltration.

Discussion

This study delineates the spatial and transcriptional landscape of OA synovium, linking immune cell dynamics to localized inflammation. The identification of OLR1 and CD69 as spatial homeostasis drivers, alongside dysregulated signaling networks, offers novel therapeutic targets. These findings advance strategies to modulate immune infiltration and restore synovial homeostasis in OA.

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.

Single cell transcriptomic analysis reveals tumor immune infiltration by macrophage cells gene signature in lung adenocarcinoma

BACKGROUND

Tumor-associated macrophages (TAMs) play pivotal roles in innate immunity and contribute to the advancement of lung cancer. We aimed to identify novel TAM-related biomarkers and significance of macrophage infiltration in lung adenocarcinoma (LUAD) through an integrative analysis of single-cell RNA-sequencing (scRNA-seq) data. To describe the cell atlas and construct a novel prognostic signature in LUAD.

METHODS

The gene signature linked to TAMs was identified utilizing Scanpy from the scRNA-seq dataset GSE131907. Subsequent analysis involved evaluating the expression levels of these genes, their potential molecular mechanisms, and prognostic significance in LUAD using data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. We also constructed a risk score models through LASSO Cox regression for these genes. The underlying mechanism was further elucidated through the application of GSEA, ESTIMATE, TIDE, and other bioinformatic algorithms.

RESULTS

Single-cell atlas was described by analyze 29 scRNA-seq samples from 19 LUAD patients. The TAMs-related gene signature (TGS) was identified as an independent prognostic factor by LASSO Cox regression analysis using differential expression genes (DEGs) derived from pro- and anti-inflammatory macrophage cells. Risk score model including nine TAMs-related genes (FOSL1, ZNF697, ADM, UBE2S, TICAM1, S100P, BIRC3, TLE1, and DEFB1) were obtained for prognosis construction. Moreover, the risk model underwent additional validation in four external GEO cohorts: GSE31210, GSE72094, GSE26939, and GSE30219. Interestingly, TGS-high tumors revealed enrichments in TGF-β signaling and hypoxia pathways, which shown low immune infiltration and immunosuppression by ESTIMATE and TIDE algorithm. The TGS-high risk group exhibited lower richness and diversity in the T-cell receptor (TCR) repertoire.

CONCLUSION

This study introduces a novel TGS score developed through LASSO Cox regression analysis, utilizing DEGs in pro- and anti-inflammatory macrophage cells. High TGS tumors exhibited enrichment in TGF-β signaling and hypoxia pathways, suggesting their potential utility in predicting prognosis and immune responses in patients with LUAD. These results offer promising implications for the development of therapeutic strategies for LUAD.

The Multifaceted Roles of BACH1 in Disease: Implications for Biological Functions and Therapeutic Applications

BTB domain and CNC homolog 1 (BACH1) belongs to the family of basic leucine zipper proteins and is expressed in most mammalian tissues. It can regulate its own expression and play a role in transcriptionally activating or inhibiting downstream target genes. It has a crucial role in various biological processes, such as oxidative stress, cell cycle, heme homeostasis, and immune regulation. Recent research highlights BACH1's significant regulatory roles in a series of conditions, including stem cell pluripotency maintenance and differentiation, growth, senescence, and apoptosis. BACH1 is closely associated with cardiovascular diseases and contributes to angiogenesis, atherosclerosis, restenosis, pathological cardiac hypertrophy, myocardial infarction, and ischemia/reperfusion (I/R) injury. BACH1 promotes tumor cell proliferation and metastasis by altering tumor metabolism and the epithelial-mesenchymal transition phenotype. Moreover, BACH1 appears to show an adverse role in diseases such as neurodegenerative diseases, gastrointestinal disorders, leukemia, pulmonary fibrosis, and skin diseases. Inhibiting BACH1 may be beneficial for treating these diseases. This review summarizes the role of BACH1 and its regulatory mechanism in different cell types and diseases, proposing that precise targeted intervention of BACH1 may provide new strategies for human disease prevention and treatment.

Tumor-infiltrating myeloid cells; mechanisms, functional significance, and targeting in cancer therapy

Tumor-infiltrating myeloid cells (TIMs), which encompass tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), myeloid-derived suppressor cells (MDSCs), and tumor-associated dendritic cells (TADCs), are of great importance in tumor microenvironment (TME) and are integral to both pro- and anti-tumor immunity. Nevertheless, the phenotypic heterogeneity and functional plasticity of TIMs have posed challenges in fully understanding their complexity roles within the TME. Emerging evidence suggested that the presence of TIMs is frequently linked to prevention of cancer treatment and improvement of patient outcomes and survival. Given their pivotal function in the TME, TIMs have recently been recognized as critical targets for therapeutic approaches aimed at augmenting immunostimulatory myeloid cell populations while depleting or modifying those that are immunosuppressive. This review will explore the important properties of TIMs related to immunity, angiogenesis, and metastasis. We will also document the latest therapeutic strategies targeting TIMs in preclinical and clinical settings. Our objective is to illustrate the potential of TIMs as immunological targets that may improve the outcomes of existing cancer treatments.

Unraveling the role of macrophages in diabetes: Impaired phagocytic function and therapeutic prospects

The rising aging population and changing lifestyles have led to a global increase in diabetes and its complications, making it one of the most prevalent diseases worldwide. Chronic inflammation is a key pathogenic feature of diabetes and its complications, yet the precise mechanisms remain unclear, impeding the development of targeted therapies. Recent studies have highlighted the β cell-macrophage crosstalk pathway as a crucial factor in chronic low-grade inflammation and glucose homeostasis imbalance in both type 1 and type 2 diabetes. Furthermore, impaired macrophage phagocytic functions, including pathogen phagocytosis, efferocytosis, and autophagy, play a significant role in diabetes complications. Given their high plasticity, macrophages represent a promising research target. This review summarizes recent findings on macrophage phagocytic dysfunction in diabetes and its complications, and explores emerging therapies targeting macrophage phagocytic function. We also discuss the current challenges in translating basic research to clinical practice, aiming to guide researchers in developing targeted treatments to regulate macrophage status and phagocytic function, thus preventing and treating metabolic inflammatory diseases.

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.

Exploring the microbiota-gut-brain axis: impact on brain structure and function

The microbiota-gut-brain axis (MGBA) plays a significant role in the maintenance of brain structure and function. The MGBA serves as a conduit between the CNS and the ENS, facilitating communication between the emotional and cognitive centers of the brain via diverse pathways. In the initial stages of this review, we will examine the way how MGBA affects neurogenesis, neuronal dendritic morphology, axonal myelination, microglia structure, brain blood barrier (BBB) structure and permeability, and synaptic structure. Furthermore, we will review the potential mechanistic pathways of neuroplasticity through MGBA influence. The short-chain fatty acids (SCFAs) play a pivotal role in the MGBA, where they can modify the BBB. We will therefore discuss how SCFAs can influence microglia, neuronal, and astrocyte function, as well as their role in brain disorders such as Alzheimer's disease (AD), and Parkinson's disease (PD). Subsequently, we will examine the technical strategies employed to study MGBA interactions, including using germ-free (GF) animals, probiotics, fecal microbiota transplantation (FMT), and antibiotics-induced dysbiosis. Finally, we will examine how particular bacterial strains can affect brain structure and function. By gaining a deeper understanding of the MGBA, it may be possible to facilitate research into microbial-based pharmacological interventions and therapeutic strategies for neurological diseases.

Inhibition of tumour necrosis factor alpha by Etanercept attenuates Shiga toxin-induced brain pathology

Infection with enterohemorrhagic E. coli (EHEC) causes severe changes in the brain leading to angiopathy, encephalopathy and microglial activation. In this study, we investigated the role of tumour necrosis factor alpha (TNF-α) for microglial activation and brain pathology using a preclinical mouse model of EHEC infection. LC-MS/MS proteomics of mice injected with a combination of Shiga toxin (Stx) and lipopolysaccharide (LPS) revealed extensive alterations of the brain proteome, in particular enrichment of pathways involved in complement activation and coagulation cascades. Inhibition of TNF-α by the drug Etanercept strongly mitigated these changes, particularly within the complement pathway, suggesting TNF-α-dependent vasodilation and endothelial injury. Analysis of microglial populations using a novel human-in-the-loop deep learning algorithm for the segmentation of microscopic imaging data indicated specific morphological changes, which were reduced to healthy condition after inhibition of TNF-α. Moreover, the Stx/LPS-mediated angiopathy was significantly attenuated by inhibition of TNF-α. Overall, our findings elucidate the critical role of TNF-α in EHEC-induced brain pathology and highlight a potential therapeutic target for mitigating neuroinflammation, microglial activation and injury associated with EHEC infection.

Induced pluripotent stem cell-derived macrophages as a platform for modelling human disease

Macrophages are innate immune cells that are present in essentially all tissues, where they have vital roles in tissue development, homeostasis and pathogenesis. The importance of macrophages in tissue function is reflected by their association with various human diseases, and studying macrophage functions in both homeostasis and pathological tissue settings is a promising avenue for new targeted therapies that will improve human health. The ability to generate macrophages from induced pluripotent stem (iPS) cells has revolutionized macrophage biology, with the generation of iPS cell-derived macrophages (iMacs) providing unlimited access to genotype-specific cells that can be used to model various human diseases involving macrophage dysregulation. Such disease modelling is achieved by generating iPS cells from patient-derived cells carrying disease-related mutations or by introducing mutations into iPS cells from healthy donors using CRISPR-Cas9 technology. These iMacs that carry disease-related mutations can be used to study the aetiology of the particular disease in vitro. To achieve more physiological relevance, iMacs can be co-cultured in 2D systems with iPS cell-derived cells or in 3D systems with iPS cell-derived organoids. Here, we discuss the studies that have attempted to model various human diseases using iMacs, highlighting how these have advanced our knowledge about the role of macrophages in health and disease.

Origin, Function, and Implications of Intestinal and Hepatic Macrophages in the Pathogenesis of Alcohol-Associated Liver Disease

Macrophages are members of the human innate immune system, and the majority reside in the liver. In recent years, they have been recognized as essential players in the maintenance of liver and intestinal homeostasis as well as key guardians of their respective immune systems, and they are increasingly being recognized as such. Paradoxically, they are also likely involved in chronic pathologies of the gastrointestinal tract and potentially in the alteration of the gut-liver axis in alcohol use disorder (AUD) and alcohol-associated liver disease (ALD). To date, the causal relationship between macrophages, the pathogenesis of ALD, and the immune dysregulation of the gut remains unclear. In this review, we will discuss our current understanding of the heterogeneity of intestinal and hepatic macrophages, their ontogeny, the potential factors that regulate their origin, and the evidence of how they are associated with the manifestation of chronic inflammation. We will also illustrate how the micro-environment of the intestine shapes the phenotypes and functionality of the macrophage compartment in both the intestines and liver and how they change during chronic alcohol abuse. Finally, we highlight the obstacles to current research and the prospects for this field.

The Emerging Role of Pleural Macrophages in Influenza Defense

The pleural cavity is gaining recognition as an important player in lung infections. Our recent research revealed that pleural macrophages (PMs) migrate from the pleural cavity into the lung during influenza virus infection, contributing to improved disease outcomes. This summary highlights key findings on the role of PMs in influencing viral lung infection outcomes and explores the potential directions for advancing this emerging field of study.

Genetic variation in IL-4 activated tissue resident macrophages determines strain-specific synergistic responses to LPS epigenetically

How macrophages in the tissue environment integrate multiple stimuli depends on the genetic background of the host, but this is still poorly understood. We investigate IL-4 activation of male C57BL/6 and BALB/c strain specific in vivo tissue-resident macrophages (TRMs) from the peritoneal cavity. C57BL/6 TRMs are more transcriptionally responsive to IL-4 stimulation, with induced genes associated with more super enhancers, induced enhancers, and topologically associating domains (TAD) boundaries. IL-4-directed epigenomic remodeling reveals C57BL/6 specific enrichment of NF-κB, IRF, and STAT motifs. Additionally, IL-4-activated C57BL/6 TRMs demonstrate an augmented synergistic response upon in vitro lipopolysaccharide (LPS) exposure, despite naïve BALB/c TRMs displaying a more robust transcriptional response to LPS. Single-cell RNA sequencing (scRNA-seq) analysis of mixed bone marrow chimeras indicates that transcriptional differences and synergy are cell intrinsic within the same tissue environment. Hence, genetic variation alters IL-4-induced cell intrinsic epigenetic reprogramming resulting in strain specific synergistic responses to LPS exposure.

Intestinal E. coli-produced yersiniabactin promotes profibrotic macrophages in Crohn's disease

Inflammatory bowel disease (IBD)-associated fibrosis causes significant morbidity. Mechanisms are poorly understood but implicate the microbiota, especially adherent-invasive Escherichia coli (AIEC). We previously demonstrated that AIEC producing the metallophore yersiniabactin (Ybt) promotes intestinal fibrosis in an IBD mouse model. Since macrophages interpret microbial signals and influence inflammation/tissue remodeling, we hypothesized that Ybt metal sequestration disrupts this process. Here, we show that macrophages are abundant in human IBD-fibrosis tissue and mouse fibrotic lesions, where they co-localize with AIEC. Ybt induces profibrotic gene expression in macrophages via stabilization and nuclear translocation of hypoxia-inducible factor 1-alpha (HIF-1α), a metal-dependent immune regulator. Importantly, Ybt-producing AIEC deplete macrophage intracellular zinc and stabilize HIF-1α through inhibition of zinc-dependent HIF-1α hydroxylation. HIF-1α+ macrophages localize to sites of disease activity in human IBD-fibrosis strictures and mouse fibrotic lesions, highlighting their physiological relevance. Our findings reveal microbiota-mediated metal sequestration as a profibrotic trigger targeting macrophages in the inflamed intestine.

Alveolar Macrophages in Viral Respiratory Infections: Sentinels and Saboteurs of Lung Defense

Respiratory viral infections continue to cause pandemic and epidemic outbreaks in humans and animals. Under steady-state conditions, alveolar macrophages (AlvMϕ) fulfill a multitude of tasks in order to maintain tissue homeostasis. Due to their anatomic localization within the deep lung, AlvMϕ are prone to detect and react to inhaled viruses and thus play a role in the early pathogenesis of several respiratory viral infections. Here, detection of viral pathogens causes diverse antiviral and proinflammatory reactions. This fact not only makes them promising research targets, but also suggests them as potential targets for therapeutic and prophylactic approaches. This review aims to give a comprehensive overview of the current knowledge about the role of AlvMϕ in respiratory viral infections of humans and animals.

Exploring CAR-macrophages in non-tumor diseases: Therapeutic potential beyond cancer

BACKGROUND

After significant advancements in tumor treatment, personalized cell therapy based on chimeric antigen receptors (CAR) holds promise for transforming the management of various diseases. CAR-T therapy, the first approved CAR cell therapy product, has demonstrated therapeutic potential in treating infectious diseases, autoimmune disorders, and fibrosis. CAR-macrophages (CAR-Ms) are emerging as a promising approach in CAR immune cell therapy, particularly for solid tumor treatment, highlighting the feasibility of using macrophages to eliminate pathogens and abnormal cells.

AIM OF REVIEW

This review summarizes the progress of CAR-M therapy in non-tumor diseases and discusses various CAR intracellular activation domain designs and their potential to optimize therapeutic effects by modulating interactions between cellular components in the tissue microenvironment and CAR-M. Additionally, we discuss the characteristics and advantages of CAR-M therapy compared to traditional medicine and CAR-T/NK therapy, as well as the challenges and prospects for the clinical translation of CAR-M.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review provides a comprehensive understanding of CAR-M for the treatment of non-tumor diseases, analyzes the advantages and characteristics of CAR-M therapy, and highlights the important impact of CAR intracellular domain design on therapeutic efficacy. In addition, the challenges and clinical translation prospects of developing CAR-M as a new cell therapy are discussed.

Baseline gene expression in BALB/c and C57BL/6 peritoneal macrophages influences but does not dictate their functional phenotypes

Macrophages are effector cells of the immune system and essential modulators of immune responses. Different functional phenotypes of macrophages with specific roles in the response to stimuli have been described. The C57BL/6 and BALB/c mouse strains tend to selectively display distinct macrophage activation states in response to pathogens, namely, the M1 and M2 phenotypes, respectively. Herein we used RNA-Seq and differential expression analysis to characterize the baseline gene expression pattern of unstimulated resident peritoneal macrophages from C57BL/6 and BALB/c mice. Our aim is to determine if there is a possible predisposition of these mouse strains to any activation phenotype and how this may affect the interpretation of results in studies concerning their interaction with pathogens. We found differences in basal gene expression patterns of BALB/c and C57BL/6 mice, which were further confirmed using RT-PCR for a subset of relevant genes. Despite these differences, our data suggest that baseline gene expression patterns of both mouse strains do not appear to determine by itself a specific macrophage phenotype.

Harnessing the power of probiotics to enhance neuroplasticity for neurodevelopment and cognitive function in stunting: a comprehensive review

BACKGROUND

Stunting become a global concern because it's not only affecting physical stature, but also affecting on neurodevelopment and cognitive function. These impacts are resulting in long-term consequences especially for human resources, such as poor-quality labor, decreased productivity due to decreasing of health quality, including immunity and cognitive aspect.

DISCUSSION

This comprehensive review found that based on many studies, there is an altered gut microbiota, or dysbiosis, in stunted children, causing the impairment of brain development through Microbiota-Gut Brain Axis (MGB Axis) mechanism. The administration of probiotics has been known affect MGBA by improving the physical and chemical gut barrier integrity, producing antimicrobial substance to inhibit pathogen, and recovering the healthy gut microbiota. Probiotics, along with healthy gut microbiota, produce SCFAs which have various positive impact on CNS, such as increase neurogenesis, support the development and function of microglia, reduce inflammatory signaling, improve the Blood Brain Barrier's (BBB's) integrity, produce neurotropic factors (e.g. BDNF, GDNF), and promote the formation of new synapse. Probiotics also could induce the production of IGF-1 by intestinal epithelial cells, which functioned as growth factor of multiple body tissues and resulted in improvement of linear growth as well as brain development.

CONCLUSION

These properties of probiotics made it become the promising and feasible new treatment approach for stunting. But since most of the studies in this field are conducted in animal models, it is necessary to translate animal data into human models and do additional study to identify the numerous components in the MGB axis and the effect of probiotics on human.

Integrated proteomics and scRNA-seq analyses of ovarian cancer reveal molecular subtype-associated cell landscapes and immunotherapy targets

BACKGROUND

Epithelial ovarian cancer (EOC) represents the most lethal gynaecological malignancy, yet understanding the connections between its molecular subtypes and their therapeutic implications remains incomplete.

METHODS

We conducted mass spectrometry-based proteomics analyses of 154 EOC tumour samples and 29 normal fallopian tubes, and single-cell RNA sequencing (scRNA-seq) analyses of an additional eight EOC tumours to classify proteomic subtypes and assess their cellular ecosystems and clinical significance. The efficacy of identified therapeutic targets was evaluated in patient-derived xenograft (PDX) and orthotopic mouse models.

RESULTS

We identified four proteomic subtypes with distinct clinical relevance: malignant proliferative (C1), immune infiltrating (C2), Fallopian-like (C3) and differentiated (C4) subtypes. C2 subtype was characterized by lymphocyte infiltration, notably an increased presence of GZMK CD8+ T cells and phagocytosis-like MRC+ macrophages. Additionally, we identified CD40 as a specific prognostic factor for C2 subtype. The interaction between CD40+ phagocytosis-like macrophages and CD40RL+ IL17R CD4+ T cells was correlated with a favourable prognosis. Finally, we established a druggable landscape for non-immune EOC patients and verified a TYMP inhibitor as a promising therapeutic strategy.

CONCLUSIONS

Our study refines the current immune subtype for EOC, highlighting CD40 agonists as promising therapies for C2 subtype patients and targeting TYMP for non-immune patients.

Guided monocyte fate to FRβ/CD163+ S1 macrophage antagonises atopic dermatitis via fibroblastic matrices in mouse hypodermis

Macrophages are versatile myeloid leukocytes with flexible cellular states to perform diverse tissue functions beyond immunity. This plasticity is however often hijacked by diseases to promote pathology. Scanning kinetics of macrophage states by single-cell transcriptomics and flow cytometry, we observed atopic dermatitis drastically exhausted a resident subtype S1. Characterized by FRβ/CD163 expression, S1 exhibited strong efferocytosis and chemoattracted monocytes and eosinophils. Here we have delineated mechanisms regulating monocyte decision to acquire S1 identity in skin. During M-CSF driven macrophage differentiation in healthy skin, FRβ was expressed via intrinsic control of STAT6 and ALK5 activities, and did not require heterotypic cellular crosstalk. In contrast, CD163 expression required exposure to fibroblastic secretion. This process depended on SHP1 activity and involved STAT5 inactivation. Suppressed STAT5 activity caused CD163 expression and rendered macrophage insensitive to further induction by fibroblasts. Parsing coculture experiments with in silico ligand expression, we identified laminin-α2 and type-V collagen secreted by hypodermal fibroblasts as CD163-driving factors. S1 identity loss in AD followed a stepwise cascade: reduced laminins availability first dampened CD163 expression, IL4 and TGFβ subsequently acted on CD163lo/- cells to downregulate FRβ. In AD skin, we showed that imitating this fibroblast-macrophage crosstalk with exogenous laminin-211 encouraged monocyte differentiation to S1 macrophages, fostered homeostatic commitment of extravasated eosinophils, and alleviated dermatitis. Hence, we demonstrated that reinforcing a steady-state cue from hypodermal fibroblasts could override maladaptive pressure on macrophage and restored tissue homeostasis.

Polyphenols: From Classification to Therapeutic Potential and Bioavailability

Though ubiquitous in nature, polyphenols gained scientific prominence only after the pioneering work of researchers like E. Fischer and K. Freudenberg, who demonstrated their potential beyond traditional applications, such as in the leather industry. Today, these bioactive compounds are recognized for their diverse therapeutic roles, including their use as adjuvants in cancer treatment, cancer prevention, and their anti-inflammatory and antioxidant properties. Additionally, polyphenols have demonstrated benefits in managing obesity, cardiovascular diseases, and neuromodulation. Their synthesis is influenced by environmental and genetic factors, with their concentrations varying based on the intensity of these variables, as well as the stage of ripening. This review provides a comprehensive overview of polyphenols, covering their classification, chemical structures, and bioavailability. The mechanisms influencing bioavailability, bioaccessibility, and bioactivity are explored in detail, alongside an introduction to their bioactive effects and associated metabolic pathways. Specific examples, such as the bioavailability of polyphenols in coffee and various types of onions, are analyzed. Despite their promising biological activities, a significant limitation of polyphenols lies in their inherently low oral bioavailability. However, their systemic circulation and the bioactive by-products formed during digestion present exciting opportunities for further research and application.

Facing stress and inflammation: From the cell to the planet

As identified in 1936 by Hans Selye, stress is shaping diseases through the induction of inflammation. But inflammation display some yin yang properties. On one hand inflammation is merging with the innate immune response aimed to fight infectious or sterile insults, on the other hand inflammation favors chronic physical or psychological disorders. Nature has equipped the cells, the organs, and the individuals with mediators and mechanisms that allow them to deal with stress, and even a good stress (eustress) has been associated with homeostasis. Likewise, societies and the planet are exposed to stressful settings, but wars and global warming suggest that the regulatory mechanisms are poorly efficient. In this review we list some inducers of the physiological stress, psychologic stress, societal stress, and planetary stress, and mention some of the great number of parameters which affect and modulate the response to stress and render it different from an individual to another, from the cellular level to the societal one. The cell, the organ, the individual, the society, and the planet share many stressors of which the consequences are extremely interconnected ending in the domino effect and the butterfly effect.

A pan-family screen of nuclear receptors in immunocytes reveals ligand-dependent inflammasome control

Ligand-dependent transcription factors of the nuclear receptor (NR) family regulate diverse aspects of metazoan biology, enabling communications between distant organs via small lipophilic molecules. Here, we examined the impact of each of 35 NRs on differentiation and homeostatic maintenance of all major immunological cell types in vivo through a "Rainbow-CRISPR" screen. Receptors for retinoic acid exerted the most frequent cell-specific roles. NR requirements varied for resident macrophages of different tissues. Deletion of either Rxra or Rarg reduced frequencies of GATA6+ large peritoneal macrophages (LPMs). Retinoid X receptor alpha (RXRα) functioned conventionally by orchestrating LPM differentiation through chromatin and transcriptional regulation, whereas retinoic acid receptor gamma (RARγ) controlled LPM survival by regulating pyroptosis via association with the inflammasome adaptor ASC. RARγ antagonists activated caspases, and RARγ agonists inhibited cell death induced by several inflammasome activators. Our findings provide a broad view of NR function in the immune system and reveal a noncanonical role for a retinoid receptor in modulating inflammasome pathways.

CD226 + adipose tissue macrophages arise from MDP-derived monocytes and regulate lipid metabolism

Macrophages are innate immune cells present in all tissues, in which they participate in immune responses and maintenance of tissue homeostasis. They develop either from embryonic precursors or from circulating monocytes, and their functions are in part dictated by their origin. We previously observed robust monocyte recruitment and contribution to the macrophage pool in brown adipose tissue. In particular, monocytes were predicted to give rise to two phenotypically distinct macrophage subsets identifiable by CD206 or CD226 expression. In the present study, we investigated monocyte differentiation pathways in brown adipose tissue and the function of monocyte-derived macrophages. We found that bone marrow monocytes highly contributed to the CD226 + macrophage population while the CD206 + population contained mainly yolk sac-derived cells. Fate mapping analysis revealed a low contribution of GMP- and a high contribution of MDP-derived monocytes to the CD226 + macrophage subset. Importantly, adoptive transfer experiments demonstrate that MDP- but not GMP-derived monocytes are pre-conditioned to give rise to CD226 + macrophages. Using meta-analysis of single cell RNA-sequencing data, we found that MDP-derived CD226 + macrophages were present in several tissues including peritoneal cavity, adrenal glands and all adipose depots, with a particular enrichment in beige and brown fat. A similar macrophage subset was identified in humans. Functionally, while depletion of CD206 + macrophages using anti-CD115 blocking antibodies led to decreased adipose triglyceride content, genetic depletion of CD226 + macrophages caused the opposite phenotype. We thus identify CD226 + MDP-derived macrophages as a new myeloid cell type conserved across tissues and tied to lipid metabolism homeostasis.

A microparticle delivery system for extended release of all-trans retinoic acid and its impact on macrophage insulin-like growth factor 1 release and myotube formation

Muscle atrophy secondary to disuse, aging, or illness increases the risk of injury, prolonged recovery, and permanent disability. The recovery process involves macrophages and their secretions, such as insulin-like growth factor 1 (IGF-1), which direct muscle to regenerate and grow. Retinoic acid receptor (RAR) activation in macrophages increases IGF-1 expression and can be achieved with all-trans retinoic acid (ATRA). However, poor bioavailability limits its clinical application. Thus, we encapsulated ATRA into poly(lactide-co-glycolide) microparticles (ATRA-PLG) to maintain bioactivity and achieve extended release. ATRA-PLG induces IGF-1 release by RAW 264.7 macrophages, and conditioned media from these cells enhances C2C12 myotube formation through IGF-1. Additionally, ATRA released from ATRA-PLG enhances myotube formation in the absence of macrophages. Toward clinical translation, we envision that ATRA-PLG will be injected in the vicinity of debilitated muscle where it can be taken up by macrophages and induce IGF-1 release over a predetermined therapeutic window. Along these lines, we demonstrate that ATRA-PLG microparticles are readily taken up by bone marrow-derived macrophages and reside within the cytosol for at least 12 days with no toxicity. Interestingly, ATRA-PLG induced IGF-1 secretion by thioglycolate-elicited macrophages, but not bone marrow derived macrophages. We found that the RAR isoforms present in lysate differed between the macrophages studied, which could explain the different IGF-1 responses to ATRA. Given that ATRA-PLG enhances myotube formation directly (through ATRA) and indirectly (through macrophage IGF-1) this study supports the further testing of this promising pharmaceutical using rodent models of muscle regeneration and growth.

Cryoablation of primary breast cancer tumors induces a systemic abscopal effect altering TIME (Tumor Immune Microenvironment) in distant tumors

Introduction

Despite recent advances, triple-negative breast cancer (TNBC) patients remain at high risk for recurrence and metastasis, which creates the need for innovative therapeutic approaches to improve patient outcomes. Cryoablation is a promising, less invasive alternative to surgical resection, capable of inducing tumor necrosis via freeze/thaw cycles. Necrotic cell death results in increased inflammatory signals and release of preserved tumor antigens, which have the potential to boost the local and systemic anti-tumor immune response. Thus, compared to surgery, cryoablation enhances the activation of T cells leading to an improved abscopal effect, defined as the occurrence of a systemic response after local treatment. We previously showed with a bilateral-tumor mouse model of TNBC that cryoablation of the primary tumor leads to increased infiltration of distant (abscopal) tumors by tumor infiltrating lymphocytes (TILs) and decreased rates of recurrence and metastasis. However, the early drivers of the cryoablation generated abscopal effect are still unknown and knowledge of the mechanism could provide insight into improving the anti-tumor immune response through pharmacologic immune modulation in addition to cryoablation.

Methods

One million 4T1-12B-luciferase expressing cells were transplanted into the mammary fat pad of BALB/c mice. Two weeks later, left (primary) tumors were either resected or cryoablated. A week after the procedure, right (abscopal) and left tumors, along with spleen, tumor-draining lymph node and blood were collected and processed for flow cytometry and/or RNA-sequencing and immunofluorescence.

Results

Here we show that cryoablation of mouse mammary carcinomas results in smaller abscopal tumors that harbor increased frequencies of anti-tumor cells [such as natural killer (NK) cells], accompanied by a systemic increase in the frequency of migratory conventional type 1 dendritic cells (cDC1; CD103+ XCR1+), compared to resection. The changes in cell frequencies are mirrored by the immune gene signature of the abscopal tumors, with cryoablation inducing genes involved with NK cell activation and leukocyte-mediated toxicity, including IL11ra1 and Pfr1.

Conclusions

These results better define the early mechanisms through which cryoablation improves tumor elimination, which is mediated by enhanced frequencies of anti-tumoral cells such as NK and cDC1s at the abscopal tumor and in the spleen of mice treated with cryoablation, respectively.

Mouse and human macrophages and their roles in cardiovascular health and disease

The past 15 years have witnessed a leap in understanding the life cycle, gene expression profiles, origins and functions of mouse macrophages in many tissues, including macrophages of the artery wall and heart that have critical roles in cardiovascular health. Here, we review the phenotypical and functional diversity of macrophage populations in multiple organs and discuss the roles that proliferation, survival, and recruitment and replenishment from monocytes have in maintaining macrophages in homeostasis and inflammatory states such as atherosclerosis and myocardial infarction. We also introduce emerging data that better characterize the life cycle and phenotypic profiles of human macrophages. We discuss the similarities and differences between murine and human macrophages, raising the possibility that tissue-resident macrophages in humans may rely more on bone marrow-derived monocytes than in mouse.

Microglia and macrophages in glioblastoma: landscapes and treatment directions

Glioblastoma is the most common primary malignant tumour of the central nervous system and remains uniformly and rapidly fatal. The tumour-associated macrophage (TAM) compartment comprises brain-resident microglia and bone marrow-derived macrophages (BMDMs) recruited from the periphery. Immune-suppressive and tumour-supportive TAM cell states predominate in glioblastoma, and immunotherapies, which have achieved striking success in other solid tumours have consistently failed to improve survival in this 'immune-cold' niche context. Hypoxic and necrotic regions in the tumour core are found to enrich, especially in anti-inflammatory and immune-suppressive TAM cell states. Microglia predominate at the invasive tumour margin and express pro-inflammatory and interferon TAM cell signatures. Depletion of TAMs, or repolarisation towards a pro-inflammatory state, are appealing therapeutic strategies and will depend on effective understanding and classification of TAM cell ontogeny and state based on new single-cell and spatial multi-omic in situ profiling. Here, we explore the application of these datasets to expand and refine TAM characterisation, to inform improved modelling approaches, and ultimately underpin the effective manipulation of function.

Dexmedetomidine directly binds to and inhibits Toll-like receptor 4

BACKGROUND

While a number of anesthetics has been shown potentially associated with neurotoxicity in the developing brain, dexmedetomidine, a drug that was rather recently introduced into the perioperative setting, is considered beneficial from neurological wellbeing. However, the underlying mechanism of how dexmedetomidine affects brain health remains to be determined. Based on our recent study, we hypothesized that dexmedetomidine would directly bind to and inhibit Toll-like receptor 4 (TLR4), a critical receptor largely expressed in microglia and responsible for neurological insult.

METHODS

We used TLR4 reporter assays to test if dexmedetomidine attenuates TLR4 activation. Furthermore, a direct binding of dexmedetomidine on TLR4 was tested using photoactivatable medetomidine. Lastly, the effect of dexmedetomidine on ketamine (anesthetic)-induced neurotoxicity was tested in rat pups (P7).

RESULTS

We showed that dexmedetomidine attenuated TLR4 activation using reporter assay (IC50 = 5.8 µg/mL). Photoactivatable dexmedetomidine delineated its direct binding sites on TLR4. We also showed that dexmedetomidine attenuated microglia activation both in vitro and in vivo.

DISCUSSION

We proposed a novel mechanism of dexmedetomidine-mediated neuroprotection.

The role of macrophage migratory behavior in development, homeostasis and tumor invasion

Tumor-associated macrophages (TAMs) recapitulate the developmental and homeostatic behaviors of tissue resident macrophages (TRMs) to promote tumor growth, invasion and metastasis. TRMs arise in the embryo and colonize developing tissues, initially to guide tissue morphogenesis and then to form complex networks in adult tissues to constantly search for threats to homeostasis. The macrophage growth factor, colony-stimulating factor-1 (CSF-1), which is essential for TRM survival and differentiation, is also responsible for the development of the unique motility machinery of mature macrophages that underpins their ramified morphologies, migratory capacity and ability to degrade matrix. Two CSF-1-activated kinases, hematopoietic cell kinase and the p110δ catalytic isoform of phosphatidylinositol 3-kinase, regulate this machinery and selective inhibitors of these proteins completely block macrophage invasion. Considering tumors co-opt the invasive capacity of TAMs to promote their own invasion, these proteins are attractive targets for drug development to inhibit tumor progression to invasion and metastasis.

Single-cell, spatial, and fate-mapping analyses uncover niche dependent diversity of cochlear myeloid cells

Recent advances in fate mapping and single-cell technologies have revealed how the dynamics and function of tissue-resident macrophages are shaped by their environment. However, macrophages in sensory organs such as the cochlea where the central nervous system and peripheral nervous system meet remain understudied. Combining single-cell transcriptomics, fate mapping, and parabiosis experiments, we show that five types of myeloid cells including three tissue-resident macrophage subpopulations, coexist in the mouse cochlea. The three macrophage subsets showed different potential functions in relationship with their specific topography across cochlear compartments. Further analysis revealed that they were partially derived from yolk sac progenitors during development, while in adulthood, most cochlear macrophages were long-term resident. Finally, we showed that cochlear macrophage morphology and density changed during aging. Our findings show that cochlea is a microenvironment with a unique heterogeneity of macrophages in terms of gene expression, spatial distribution, ontogeny, and function.

Myeloid cannabinoid CB1 receptor deletion confers atheroprotection in male mice by reducing macrophage proliferation in a sex-dependent manner

AIMS

Although the cannabinoid CB1 receptor has been implicated in atherosclerosis, its cell-specific effects in this disease are not well understood. To address this, we generated a transgenic mouse model to study the role of myeloid CB1 signalling in atherosclerosis.

METHODS AND RESULTS

Here, we report that male mice with myeloid-specific Cnr1 deficiency on atherogenic background developed smaller lesions and necrotic cores than controls, while only minor genotype differences were observed in females. Male Cnr1-deficient mice showed reduced arterial monocyte recruitment and macrophage proliferation with less inflammatory phenotype. The sex-specific differences in proliferation were dependent on oestrogen receptor (ER)α-oestradiol signalling. Kinase activity profiling identified a CB1-dependent regulation of p53 and cyclin-dependent kinases. Transcriptomic profiling further revealed chromatin modifications, mRNA processing, and mitochondrial respiration among the key processes affected by CB1 signalling, which was supported by metabolic flux assays. Chronic administration of the peripherally restricted CB1 antagonist JD5037 inhibited plaque progression and macrophage proliferation, but only in male mice. Finally, CNR1 expression was detectable in human carotid endarterectomy plaques and inversely correlated with proliferation, oxidative metabolism, and inflammatory markers, suggesting a possible implication of CB1-dependent regulation in human pathophysiology.

CONCLUSION

Impaired macrophage CB1 signalling is atheroprotective by limiting their arterial recruitment, proliferation, and inflammatory reprogramming in male mice. The importance of macrophage CB1 signalling appears to be sex-dependent.