Tissue-resident macrophages. Nat Immunol. 2013;14:986-995. [PMID: 24048120 DOI: 10.1038/ni.2705]

Tn antigen suppresses lipopolysaccharide-induced dermatitis via Clec10a

C-type lectin domain family 10 member A (Clec10a), also called macrophage galactose-type lectin 1 (MGL1) or CD301a, is expressed on myeloid cells, including macrophages in the skin. Several pieces of evidence suggest that Clec10a physically binds to O-linked mucin-like molecules, but the functional ligand that mediates signaling in macrophages remains undetermined. We previously reported that house dust mite (HDM) treatment on the skin produced a greater amount of Toll-like receptor 4 (TLR4)-mediated inflammatory cytokines from macrophage in Clec10a-deficient mice than in wild-type (WT) mice, suggesting that a functional ligand for Clec10a contained in HDM inhibited TLR4-mediated skin macrophage activation. In this study, we investigated the glycan structure of a functional Clec10a ligand (Clec10a-L) contained in HDM. We showed that Clec10a bound to O-linked mucin-like molecules such as polyacrylamide (PAA)-conjugated Tn antigen (Tn antigen-PAA), Core1-PAA, LacNAc-PAA, Lewis A-PAA, and Lewis X-PAA. Among them, plate-coated Tn antigen-PAA, Lewis A-PAA, and Lewis X-PAA activated Clec10a expressed on the reporter cells. However, intradermal injection of only Tn antigen-PAA, but not Lewis A-PAA and Lewis X-PAA, ameliorated LPS-induced dermatitis in WT but not Clec10a-deficient mice. Moreover, Tn antigen-PAA suppressed LPS-induced production of inflammatory cytokines IL-6 and TNF-α by bone marrow-derived cultured macrophage in vitro. These results indicate that Tn antigen is a functional Clec10a-L in HDM that suppresses TLR4-induced macrophage activation in the skin.

Pediatric early-onset neuropsychiatric obsessive compulsive disorders

At the time of this writing, most pediatricians or child psychiatrists will probably have treated a child with early acute-onset obsessive compulsive disorder (OCD) behaviors due to the pediatric autoimmune neuropsychiatric disorder associated with Group A beta-hemolytic streptococcus, abbreviated PANDAS, described more than two decades ago; or Tourette syndrome, incorporating motor and vocal tics, described more than a century ago. One typically self-limited post-infectious OCD resulting from exposure to other putative microbial disease triggers defines PANS, abbreviating pediatric autoimmune neuropsychiatric syndrome. Tourette syndrome, PANDAS and PANS share overlapping neuroimaging features of hypometabolism of the medial temporal lobe and hippocampus on brain 18Fluorodeoxyglucose positron emission tomography fused to magnetic resonance imaging (PET/MRI) consistent with involvement of common central nervous system (CNS) pathways for the shared clinical expression of OCD. The field of pediatric neuropsychiatric disorders manifesting OCD behaviors is at a crossroads commensurate with recent advances in the neurobiology of the medial temporal area, with its wide-ranging connectivity and cortical cross-talk, and CNS immune responsiveness through resident microglia. This review advances the field of pediatric neuropsychiatric disorders and in particular PANS, by providing insights through clinical vignettes and descriptive clinical and neuroimaging correlations from the author's file. Neuroscience collaborations with child psychiatry and infectious disease practitioners are needed to design clinical trials with the necessary rigor to provide meaningful insights into the rational clinical management of PANS with the aim of developing evidence-based guidelines for the clinical management of early, abrupt-onset childhood OCD to avert potentially life-long neuropsychological struggles.

Macrophages in the premetastatic and metastatic niche: key functions and therapeutic directions

Metastasis plays a significant role in the high mortality rates associated with cancer and is usually the endpoint of a series of sequential and dynamic events. A crucial step in metastasis development and progression is the formation of a premetastatic niche (PMN), which provides a conducive microenvironment for the settlement and colonization of disseminated tumor cells at distant metastatic sites. Extensive research has demonstrated the significance of macrophage populations within primary tumors in promoting metastatic progression. Nevertheless, the contribution of macrophages at secondary sites to the regulation of PMN formation is frequently overlooked. This review systematically explores the role of macrophages in priming the PMN to facilitate cancer metastasis. Additionally, we provide a compendium of existing strategies to target macrophages in cancer therapy.

The immune system in cardiovascular diseases: from basic mechanisms to therapeutic implications

Immune system plays a crucial role in the physiological and pathological regulation of the cardiovascular system. The exploration history and milestones of immune system in cardiovascular diseases (CVDs) have evolved from the initial discovery of chronic inflammation in atherosclerosis to large-scale clinical studies confirming the importance of anti-inflammatory therapy in treating CVDs. This progress has been facilitated by advancements in various technological approaches, including multi-omics analysis (single-cell sequencing, spatial transcriptome et al.) and significant improvements in immunotherapy techniques such as chimeric antigen receptor (CAR)-T cell therapy. Both innate and adaptive immunity holds a pivotal role in CVDs, involving Toll-like receptor (TLR) signaling pathway, nucleotide-binding oligomerization domain-containing proteins 1 and 2 (NOD1/2) signaling pathway, inflammasome signaling pathway, RNA and DNA sensing signaling pathway, as well as antibody-mediated and complement-dependent systems. Meanwhile, immune responses are simultaneously regulated by multi-level regulations in CVDs, including epigenetics (DNA, RNA, protein) and other key signaling pathways in CVDs, interactions among immune cells, and interactions between immune and cardiac or vascular cells. Remarkably, based on the progress in basic research on immune responses in the cardiovascular system, significant advancements have also been made in pre-clinical and clinical studies of immunotherapy. This review provides an overview of the role of immune system in the cardiovascular system, providing in-depth insights into the physiological and pathological regulation of immune responses in various CVDs, highlighting the impact of multi-level regulation of immune responses in CVDs. Finally, we also discuss pre-clinical and clinical strategies targeting the immune system and translational implications in CVDs.

CD80 Antibody and MTX Co-Engineered Extracellular Vesicles Targets CD80+ Macrophages to Suppress Inflammation and Alleviate Chronic Inflammatory Diseases

Introduction

Aberrant interaction between innate immune and adaptive immune cells can disrupt tissue homeostasis, consequently triggering chronic inflammatory diseases such as rheumatoid arthritis (RA) and periodontitis (PD). Pro-inflammatory macrophages serve as critical mediators in the early immune response, constituting a major population of CD80+ cells, while anti-inflammatory macrophages modulating inflammatory processes through the secretion of transforming growth factor-beta (TGF-β). This cytokine facilitates the differentiation of peripheral regulatory T cells (Tregs) and contributes to the establishment of immune tolerance. However, there are no definitive therapies to reshape the tissue homeostasis between innate immune and adaptive immune cells.

Methods

(1) anti-CD80-MTX-EVs was obtained by gradient centrifugation, which were characterized by TEM and DLS, and the associated membrane proteins were identified by Western Blot. (2) The mouse bone marrow-derived macrophages were co-cultured separately with EVs, anti-CD80-EVs, and anti-CD80-MTX-EVs in vitro, and the expression of CD80 on the macrophages surface as well as the proportion of Treg cell generation were detected. (3) EVs, anti-CD80-EVs and anti-CD80-MTX-EVs were injected into mice models of arthritis and periodontitis for treatment, the therapeutic effect was evaluated by the expressions of related cytokines, staining of HE, the proportion of CD80+ macrophages and the phenotypic differentiation of T cells in the tissues.

Results

We successfully constructed engineered EVs (anti-CD80-MTX-EVs) targeting inflammatory macrophages for intracellular MTX delivering, which inducing the anti-inflammatory transformation while upregulating the expression of TGF-β of macrophages. Furthermore, our findings demonstrate that anti-CD80-MTX-EVs effectively reduce CD80+ macrophage levels, promote Treg cell generation, and inhibit Th1 cell production in vivo.

Conclusion

In this study, the anti-CD80-MTX-Evs demonstrated significant therapeutic effects in both rheumatoid arthritis and periodontitis models through a triple mechanism: reducing CD80+ macrophage population, enhancing Treg cell differentiation, and suppressing Th1 cell development. Overall, this study presents an innovative strategy for resolving inflammation within chronic inflammatory diseases.

A Single-Cell Atlas-Inspired Hitchhiking Therapeutic Strategy for Acute Pancreatitis by Restricting ROS in Neutrophils

Neutrophils can undergo transcriptional and epigenetic reprogramming in disease, thus causing inflammation or modulating tissue repair and fibrosis. A thorough understanding of the neutrophil subpopulation composition and their polarization processes in acute pancreatitis (AP) is essential to open up design of treatments tailored to individual patients. Herein, this study distinct subgroups and two differentiation pathways associated with N1 and N2 polarization during AP by single-cell sequencing. Inspired by this, a hollow manganese dioxide (HMnO2)-based nanoreactor (Pyp@APHM) conjugated with neutrophil-binding Ly-6G antibody and loaded with porphyrin is developed for targeted and in situ modulation of neutrophil polarization. Pyp@APHM can enrich the AP site by hitchhiking on neutrophils and then degrade in response to a weakly acidic environment to simultaneously release manganese ions and porphyrin ligands, enabling in situ synthesis of manganese porphyrin antioxidants. Leveraging this strategy, Pyp@APHM can effectively eliminate reactive oxygen species (ROS) and broadly inhibit both N1 and N2 polarization, as well as enhance tissue oxygenation by generating O2, thereby further mitigating pancreatic inflammation. This study provides a comprehensive single-cell atlas of neutrophils in AP and proposes an innovative hitchhiking therapeutic strategy for AP by restricting ROS in neutrophils.

Histone methyltransferase ASH1L primes metastases and metabolic reprogramming of macrophages in the bone niche

Bone metastasis is a major cause of cancer death; however, the epigenetic determinants driving this process remain elusive. Here, we report that histone methyltransferase ASH1L is genetically amplified and is required for bone metastasis in men with prostate cancer. ASH1L rewires histone methylations and cooperates with HIF-1α to induce pro-metastatic transcriptome in invading cancer cells, resulting in monocyte differentiation into lipid-associated macrophage (LA-TAM) and enhancing their pro-tumoral phenotype in the metastatic bone niche. We identified IGF-2 as a direct target of ASH1L/HIF-1α and mediates LA-TAMs' differentiation and phenotypic changes by reprogramming oxidative phosphorylation. Pharmacologic inhibition of the ASH1L-HIF-1α-macrophages axis elicits robust anti-metastasis responses in preclinical models. Our study demonstrates epigenetic alterations in cancer cells reprogram metabolism and features of myeloid components, facilitating metastatic outgrowth. It establishes ASH1L as an epigenetic driver priming metastasis and macrophage plasticity in the bone niche, providing a bona fide therapeutic target in metastatic malignancies.

Inhibition of Dectin-1 alleviates inflammation in early diabetic retinopathy by regulating microglia phenotype

BACKGROUND

Diabetic retinopathy (DR) is a major factor in vision loss in diabetic patients, triggering a series of pathological changes. At present, the treatment methods for diabetic retinopathy are limited. There is an urgent need to further explore its mechanism to bring more treatment options to patients.There is increasing evidence that microglia activation plays a crucial role in inflammatory DR. The C type lectin receptor Dectin-1 is known to play an important role in the inflammatory regulation of microglia, however, its role and mechanism in DR remains unclear. This study aims to elucidate the possible mechanisms through which Dectin-1 influences the inflammatory response in high glucose(HG) stimulated microglia and its impact on retinal inflammation during the early stages of DR.

METHODS

Human microglial cells (HMC3) were stimulated with HG (25 mmol/L), and a streptozotocin (STZ)induced C57BL/6J mouse model was established to simulate DR. To investigate the role of Dectin-1 in HMC3 cells and its underlying molecular mechanisms, we employed western blotting, quantitative realtime PCR (qRT-PCR), hematoxylineosin (H&E) staining, and immunofluorescence analysis.

RESULTS

Our findings revealed that Dectin-1 levels were elevated in microglia stimulated by HG, playing a pivotal role in cell polarization and the induction of inflammatory factors in vitro. In vivo experiments conducted on STZ induced diabetic mice demonstrated an increased expression of Dectin-1 in retinal tissues. This elevation further promoted the expression of pro inflammatory factors, such as TNF-α, IL-1β, and iNOS, triggering an inflammatory response and causing damage to the retina. Notably, inhibiting Dectin-1 reversed these detrimental effects, ultimately contributing to the delay in the progression of DR. Our investigation also uncovered a significant interaction between Dectin-1 and the downstream pro-inflammatory pathway NF-κB. This interaction occurred through the activation of spleen tyrosine kinase (Syk), both in vitro and in vivo.

CONCLUSIONS

In summary, our research strongly suggests that Dectin-1 plays a crucial pro-inflammatory role in early DR. This mechanismis, at least in part, mediated through the Syk/NF-κB pathway. Consequently, inhibition of Dectin-1 is expected to become a potential therapeutic target for delaying DR.

Progress of ursolic acid on the regulation of macrophage: summary and prospect

Ursolic acid (UA), a prevalent pentacyclic triterpenoid found in numerous fruits and herbs, has garnered significant attention for its vital role in anti-inflammatory processes and immune regulation. The study of immune cells has consistently been a focal point, particularly regarding macrophages, which play crucial roles in antigen presentation, immunomodulation, the inflammatory response, and pathogen phagocytosis. This paper reveals the underlying regulatory effects of UA on the function of macrophages and the specific therapeutic effects of UA on a variety of diseases. Owing to the superior effect of UA on macrophages, different types of macrophages in different tissues have been described. Through the multifaceted regulation of macrophage function, UA may provide new ideas for the development of novel anti-inflammatory and immunomodulatory drugs. However, to facilitate its translation into actual medical means, the specific mechanism of UA in macrophages and its clinical application still need to be further studied.

Cellular crosstalk in fibrosis: insights into macrophage and fibroblast dynamics

Pathological fibrosis, the excessive deposition of extracellular matrix and tissue stiffening that causes progressive organ dysfunction, underlies diverse chronic diseases. The fibrotic microenvironment is driven by the dynamic microenvironmental interaction between various cell types; macrophages and fibroblasts play central roles in fibrotic disease initiation, maintenance, and progression. Macrophage functional plasticity to microenvironmental stimuli modulates fibroblast functionality by releasing pro-inflammatory cytokines, growth factors, and matrix remodeling enzymes that promote fibroblast proliferation, activation, and differentiation into myofibroblasts. Activated fibroblasts and myofibroblasts serve as the fibrotic effector cells, secreting extracellular matrix components and initiating microenvironmental contracture. Fibroblasts also modulate macrophage function through the release of their own pro-inflammatory cytokines and growth factors, creating bidirectional crosstalk that reinforces the chronic fibrotic cycle. The intricate interplay between macrophages and fibroblasts, including their secretomes and signaling interactions, leads to tissue damage and pathological loss of tissue function. In this review, we examine macrophage-fibroblast reciprocal dynamic interactions in pathological fibrotic conditions. We discuss the specific lineages and functionality of macrophages and fibroblasts implicated in fibrotic progression, with focus on their signal transduction pathways and secretory signalling that enables their pro-fibrotic behaviour. We then finish with a set of recommendations for future experimentation with the goal of developing a set of potential targets for anti-fibrotic therapeutic candidates. Understanding the cellular interactions between macrophages and fibroblasts provides valuable insights into potential therapeutic strategies to mitigate fibrotic disease progression.

Cell type-specific efferocytosis determines functional plasticity of alveolar macrophages

Resolution of lung injuries is vital to maintain gas exchange, but there is an increased risk of secondary bacterial infections during this stage. Alveolar macrophages (AMs) are crucial to clear bacteria and control the resolution of inflammation, but environmental cues that switch functional phenotypes of AMs remain incompletely understood. Here, we found that AMs lack the capacity to mount an effective immune response against bacteria during resolution of inflammation. Neutrophil (PMN)-derived myeloperoxidase (MPO) fueled canonical glutaminolysis via the mitochondrial membrane transporter uncoupling protein-2 (UCP2), resulting in decreased mtROS-dependent killing of bacteria and secretion of pro-inflammatory cytokines. MPO-enhanced UCP2 expression inhibited mitochondrial hyperpolarization and boosted efferocytosis irrespective of the presence of bacterial pathogens. Conversely, efferocytosis of other cell types resulted in a distinct anti-inflammatory AM phenotype while maintaining antibacterial phenotypic plasticity. Overall, our findings indicate that the uptake of apoptotic PMNs or MPO switches AMs to prioritize resolution of inflammation over antibacterial responses, a feature that is conserved in murine extrapulmonary macrophages and human AMs.

GM-CSF drives IL-6 production by macrophages in polymyalgia rheumatica

OBJECTIVES

Insight into the immunopathology of polymyalgia rheumatica (PMR) is scarce and mainly derived from peripheral blood studies. The limited data available point towards macrophages as potential key players in PMR. This study aimed to identify the factors driving proinflammatory macrophage development and their functions in the immunopathology of PMR.

METHODS

Monocyte phenotypes were investigated by flow cytometry in peripheral blood (PMR, n = 22; healthy controls, n = 20) and paired subacromial-subdeltoid (SASD) bursal fluid (PMR, n = 9). Macrophages in SASD bursa were characterised by immunohistochemistry and immunofluorescence (PMR, n = 12; controls undergoing shoulder replacement surgery, n = 10). The functions of cytokines expressed in PMR-affected tissue were examined using macrophage differentiation cultures (PMR, n = 7; healthy controls, n = 7).

RESULTS

Monocytes (CD14highCD16- and CD14highCD16+) were increased in blood of PMR patients and activated in bursal fluid. Macrophages dominated immune infiltrates in PMR-affected tissue, expressing various proinflammatory cytokines. While interleukin (IL)-6 and interferon-gamma (IFN-γ) expression was abundant in both PMR and control tissue, granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF) were significantly increased in PMR tissue. Macrophages in PMR-affected tissue showed an elevated CD206/folate receptor β ratio, reflecting a GM-CSF skewed signature. A combination of GM-CSF/M-CSF/IFN-γ significantly boosted IL-6 production in vitro, while limited IL-6 production was observed without GM-CSF.

CONCLUSIONS

The monocyte compartment is expanded and activated in PMR. Macrophages in PMR-affected tissue produce abundant proinflammatory cytokines such as IL-6. A network of locally expressed cytokines, including GM-CSF, M-CSF, and IFN-γ, may drive the proinflammatory functions of these macrophages. Overall, macrophages may constitute key therapeutic targets for PMR.

Macrophage biology in the pathogenesis of Helicobacter pylori infection

Infection with H. pylori induces chronic gastric inflammation, progressing to peptic ulcer and stomach adenocarcinoma. Macrophages function as innate immune cells and play a vital role in host immune defense against bacterial infection. However, the distinctive mechanism by which H. pylori evades phagocytosis allows it to colonize the stomach and further aggravate gastric preneoplastic pathology. H. pylori exacerbates gastric inflammation by promoting oxidative stress, resisting macrophage phagocytosis, and inducing M1 macrophage polarization. M2 macrophages facilitate the proliferation, invasion, and migration of gastric cancer cells. Various molecular mechanisms governing macrophage function in the pathogenesis of H. pylori infection have been identified. In this review, we summarize recent findings of macrophage interactions with H. pylori infection, with an emphasis on the regulatory mechanisms that determine the clinical outcome of bacterial infection.

Immune-mediated cardiac development and regeneration

The complex interplay between the immune and cardiovascular systems during development, homeostasis and regeneration represents a rapidly evolving field in cardiac biology. Single cell technologies, spatial mapping and computational analysis have revolutionised our understanding of the diversity and functional specialisation of immune cells within the heart. From the earliest stages of cardiogenesis, where primitive macrophages guide heart tube formation, to the complex choreography of inflammation and its resolution during regeneration, immune cells emerge as central orchestrators of cardiac fate. Translating these fundamental insights into clinical applications represents a major challenge and opportunity for the field. In this Review, we decode the immunological blueprint of heart development and regeneration to transform cardiovascular disease treatment and unlock the regenerative capacity of the human heart.

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.

rFIP-nha activates macrophages towards a pro-inflammatory phenotype via AIM2 inflammasome modulation

Fungal immunomodulatory proteins (FIPs) are small proteins from fungi with considerable immunomodulatory activity. FIP-nha (Nectria haematococca) contains two glycosylation sites at positions N5 and N39, and displays a high thermostability and notable anti-tumour activity. However, FIP-nha's immunomodulatory activity on macrophages and the associated mechanism remain unclear. In this study, three rFIP-nha glycan mutants (N5A, N39A, N5+39A) were recombinantly expressed in Pichia pastoris. To test the impact on FIP-nha's immunomodulatory activity, the phagocytotic activity, cytokine secretion, and gene expression of THP-1 macrophages were investigated. rFIP-nha and its mutants reduced macrophage phagocytosis, and induced IL-1β, IL-12 and IL-10 cytokine secretion significantly, indicating that the protein confers a pro-inflammatory behaviour on THP-1 macrophages. However, there were no obvious differences among the different glycan mutants, indicating that the observed activation mechanisms are likely glycosylation-independent. Furthermore, to study the immunomodulatory mechanism, four kinds of inflammasomes (NLRP1, NLRP3, NLRC4 and AIM2) were tested at transcriptional level. AIM2 was found to be 10-fold upregulated. Then, THP1-KO-ASC cells and AIM2 related inhibitors showed that IL-1β release induced by rFIP-nha is ASC signalling pathway dependent. Taken together, these findings suggest that rFIP-nha activates THP-1 macrophages in a pro-inflammatory way by activating the AIM2 inflammasome.

The immune mechanisms of the urinary tract against infections

Urinary tract infection (UTI), a common clinical infectious disease, is marked by high incidence and frequent recurrence. Recurrent UTIs can cause severe complications, negatively affecting health. The emergence and spread of drug-resistant bacteria present significant challenges to UTI treatment. This article systematically reviews the key immune mechanisms in the body's defense against UTI pathogens. It discusses various immune response components, such as the urinary tract mucosal epithelium, neutrophils, macrophages, dendritic cells, mast cells, innate lymphocytes, T cells, and B cells, with the aim of providing insights for future UTI research.

Mass cytometry analysis reveals a cross-tissue immune landscape in Actinobacillus pleuropneumoniae-induced pneumonia

Porcine contagious pleuropneumonia caused by Actinobacillus pleuropneumoniae (APP) is a fatal respiratory disease that threatens the worldwide farming industry's health. The immune responses of extrapulmonary tissues play an important role in developing porcine contagious pleuropneumonia; however, the immune responses of extrapulmonary tissues induced by APP are rarely uncovered. Here, we used high-dimensional mass cytometry to investigate the immune cell response in the spleen and peripheral blood during APP infection in mice. We found that the immune response triggered by APP was highly tissue-specific. Numerous infection time- or tissue-specific immune cell clusters, including previously unrecognized ones, were also identified in the spleen and peripheral blood. Integrative analysis of splenic lymphoid and myeloid cell clusters maps the dynamic immune response cellular network during APP infection. Surprisingly, during the early stages of APP infection, the majority of the top 6 cell clusters contributing to the infection time-specificity in the spleen were adaptive immune cell clusters rather than innate immune cell clusters, among which CD24hiMHCII+CD8+TEM cells exhibited a stronger expression of IFN-γ, IL-17A, and IL-10 compared to the CD24lo compartment. In peripheral blood, there was unprecedented heterogeneity in the immune cell composition. Also, peripheral immune cell clusters closely related to the severity of APP infection were identified. In summary, our data provide a systemic and comprehensive overview of the immune responses to APP infection in the spleen and peripheral blood. This provides a foundation for understanding the immune pathogenesis of APP and identifying potential diagnostic biomarkers and therapeutic targets.

IMPORTANCE

This study explored the cross-tissue immune dynamic landscape in the APP-induced pneumonia model by utilizing high-dimensional mass cytometry. We discovered that APP-induced immune responses are tissue-specific. Key infection-specific clusters in the spleen and peripheral blood were identified, some of which were previously unrecognized. Meanwhile, the specific functions of APP infection-related immune subsets were explored. The research systematically outlined an overview of immune responses in these tissues, deepening the understanding of APP pathogenesis and laying the foundation for the search for diagnostic and therapeutic targets.

Bibliometric and visual analysis in the field of macrophages in Traditional Chinese Medicine from 2003 to 2023

Objective

Macrophages are increasingly recognized as crucial therapeutic targets in the treatment of diverse pathological conditions. While considerable research has focused on macrophage-related mechanisms within Traditional Chinese Medicine (TCM), there remains a notable absence of comprehensive quantitative analyses in this field. This study aims to examine the evolutionary trajectory of macrophage-related research in TCM from 2003 to 2023, providing insights to guide future investigative directions.

Methods

We searched for articles published between 2003 and 2023 from the Web of Science Core Collection (WoSCC) database and analyzed them using R software, VOSviewer and CiteSpace.

Results

A total of 1,823 documents were obtained through the search. The results indicated that the number of publications between 2003 and 2023 exhibited an upward trend, with the majority of these documents originating from Chinese academic institutions and authored by Chinese scholars. This observation suggests a potential correlation with the growing prominence of Chinese medicine within China. Macrophage polarizations, a prominent focus in the study of macrophages, has also assumed an increasingly significant role in the domain of macrophages in TCM-related disciplines. The publication of these results also suggests that targeting macrophages in TCM for the treatment of some diseases is very promising, especially in ulcerative colitis, tumor-related diseases, and some liver diseases. This study provides a more comprehensive analysis of the current status and significant areas of research in the field of macrophage research in TCM, offering valuable insights for prospective research endeavors.

Conclusion

Macrophage-related studies in TCM have garnered increasing attention from global scholars from researchers worldwide, and are expected to become a hotspot for targeting macrophages to develop new drugs to treat diseases in the future. This study comprehensively analyzes the current status and hotspots of macrophages in Chinese medicine, which can provide valuable references for future research.

Signaling lymphocytic activation molecule family 8 disrupts epithelial barrier in chronic rhinosinusitis with nasal polyps through M1 macrophage polarization

BACKGROUND

Recent studies reveal that M1 macrophages accumulate predominantly in noneosinophilic chronic rhinosinusitis with nasal polyps (neCRSwNP). However, the precise mechanisms regulating M1 macrophages and their impact on the epithelial barrier remain unclear.

OBJECTIVE

To investigate the expression and regulatory role of signaling lymphocytic activation molecule family (SLAMF)8, a molecule exclusively expressed in myeloid cells, in M1 macrophage polarization and its potential contribution to neCRSwNP development.

METHODS

We evaluated SLAMF8 expression and its correlation with clinical variables using real-time quantitative polymerase chain reaction and Western blot in sinonasal mucosa samples from CRSwNP and control subjects. Immunofluorescence staining confirmed the co-expression of SLAMF8 with macrophages. After SLAMF8 knockdown, we explored the influence on macrophage M1 polarization and the effect on epithelial-mesenchymal transition (EMT) process and tight junction integrity in epithelial cells through an indirect co-culture system of M1 macrophages with human nasal epithelial cells.

RESULTS

SLAMF8 was highly expressed on M1 macrophages in polyp tissues, notably in neCRSwNP, and correlated with disease severity indices only in neCRSwNP. SLAMF8 knockdown in THP-1 cells reduced M1 macrophage markers (CD86, iNOS, and NLRP3) and decreased secretion of inflammatory cytokines (interleukin-1 beta, interleukin-6, and tumor necrosis factor alpha). Co-culture with M1 macrophage supernatant after SLAMF8 knockdown enhanced epithelial viability, reduced EMT and apoptosis, and up-regulated tight junction markers, occludin and claudin-4, in nasal epithelial cells.

CONCLUSION

SLAMF8 elevation correlates with the EMT, epithelial tight junction, and disease severity in neCRSwNP. SLAMF8 up-regulation promotes M1 macrophage polarization, which facilitates EMT and impairs nasal epithelial barrier function. SLAMF8 may represent a novel therapeutic target for neCRSwNP.

ErTao decoction alleviates liver fibrosis by suppressing STING-mediated macrophages and NLRP3 inflammasome activation

BACKGROUND

Liver fibrosis (LF) is a common pathological process in the progression of multiple chronic liver diseases to cirrhosis, affecting millions of people worldwide annually. The incomplete understanding of its mechanisms has led to a lack of clinically effective therapeutic options. ErTao decoction (ETD, ), a derivative combining the components of Erchen Decoction and Taohong Siwu Decoction, is rooted in the traditional Chinese medicine theory of "phlegm-dampness-blood stasis". However, the precise mechanism by which ETD exerts its therapeutic effects in LF remains unclear.

PURPOSE

The purpose of study was to investigate the protective effect of ETD and elucidate its underlying molecular mechanism on LF.

METHODS

In this study, we employed a multifaceted approach to evaluate the effects of ETD on LF. We used H&E staining, Sirius red staining, immunofluorescence, immunohistochemical analysis, and Western blotting to assess the protective effects of ETD in a CCl4-induced fibrosis mouse model. In vitro validation was conducted using macrophages and hepatic stellate cells to further elucidate the mechanisms involved. STING-deficient mice were used to assess its regulatory effects on liver injury, inflammatory and activation through immunohistochemical staining and Western blotting. Furthermore, UHPLCHRMS detection and computer-aided drug analysis were employed to identify and validate potential effective components of ETD for responsible for its therapeutic effects in treating LF.

RESULTS

In our in vivo and in vitro experiments, we found that ETD effectively reduced collagen fiber deposition and alleviated LF pathological changes by inhibiting macrophage inflammatory activation and suppressing NLRP3 and STING signaling. Notably, STING deficiency exhibited a protective effect against liver tissue injury and inhibited inflammatory activation of hepatic macrophages in LF model mice. Additionally, comprehensive analysis of the active ingredients in ETD strongly suggested that Naringin served as a pivotal bioactive constituent within ETD responsible for modulating STING signaling.

CONCLUSIONS

Our study highlighted the protective effects of ETD on LF by inhibiting STING-mediated macrophage activation and NLRP3 inflammasome signaling. Notably, Naringin might serve as a promising novel STING inhibitor to effectively counteract the progression of LF. These findings represented significant advances in LF research and paved the way for the development of novel therapeutic strategies.

Tissue-resident macrophages and renal diseases: landscapes and treatment directions

Tissue-resident macrophage (TRM) is a specialized subset of macrophage that resides within specific tissues and organs. TRMs play crucial roles in resisting pathogen invasion, maintaining the homeostasis of the immune microenvironment, and promoting tissue repair and regeneration. The development and function of TRMs exhibit significant heterogeneity across different tissues. Kidney TRMs (KTRMs) originate from both embryonic yolk sac erythro-myeloid progenitors and the fetal liver, demonstrating the capacity for self-renewal independent of bone marrow hematopoiesis. KTRMs are not only essential for the maintenance of renal homeostasis and the monitoring of microvascular environment, but contribute to renal injury due to inflammation, fibrosis and immune dysfunction in kidneys. In this review, we summarize currently available studies on the regulatory role of KTRMs in processes of renal injury and repair. The altering effects and underlying mechanisms of KTRMs in regulating local tissue cells and immune cells in different renal diseases are reviewed, primarily including lupus nephritis, diabetic nephropathy, renal fibrosis, and renal carcinoma. Understanding the plasticity and immune regulatory functions of KTRMs may offer new insights into the pathogenesis and the exploration of therapeutic strategies of kidney diseases.

Modulating Neutrophil Extracellular Trap Formation In Vivo with Locoregional Precision Using Differently Charged Self-Assembled Hydrogels

Neutrophil extracellular traps (NETs) are DNA networks released by neutrophils, first described as a defense response against pathogens but have since been associated with numerous inflammatory diseases. Diverse physical material properties have been shown to promote NET formation. Herein, we report the discovery that the charge of self-assembled peptide hydrogels predictably modulates the formation of NETs in vivo within the implanted material. Positively charged gels induce rapid NET release, whereas negatively charged gels do not. This differential immune response to our self-assembled peptide gels enabled the development of a material platform that allows rheostat-like modulation over the degree of NET formation with anatomical and locoregional control.

Characterizing macrophage diversity in colorectal malignancies through single-cell genomics

Colorectal cancer (CRC) is one of the most common malignant tumors of the digestive tract, with increasing incidence and mortality rates, posing a significant burden on human health. Its progression relies on various mechanisms, among which the tumor microenvironment and tumor-associated macrophages (TAMs) have garnered increasing attention. Macrophage infiltration in various solid tumors is associated with poor prognosis and is linked to chemotherapy resistance in many cancers. These significant biological behaviors depend on the heterogeneity of macrophages. Tumor-promoting TAMs comprise subpopulations characterized by distinct markers and unique transcriptional profiles, rendering them potential targets for anticancer therapies through either depletion or reprogramming from a pro-tumoral to an anti-tumoral state. Single-cell RNA sequencing technology has significantly enhanced our research resolution, breaking the traditional simplistic definitions of macrophage subtypes and deepening our understanding of the diversity within TAMs. However, a unified elucidation of the nomenclature and molecular characteristics associated with this diversity remains lacking. In this review, we assess the application of conventional macrophage polarization subtypes in colorectal malignancies and explore several unique subtypes defined from a single-cell omics perspective in recent years, categorizing them based on their potential functions.

Mass Spectrometry Imaging Reveals the In Situ Distribution and Metabolic Effects of Fullerenes

Fullerene-based nanoparticles have been extensively developed and applied in biological immunotherapy due to their unique immunomodulatory properties. However, current methods for investigating their biodistribution predominantly rely on fluorescent labeling, which limits our understanding of the true biodistribution of fullerenes at both organ and suborgan levels, as well as their impact on organ-specific metabolism. In this study, we utilized laser desorption ionization and matrix-assisted laser desorption/ionization mass spectrometry imaging to achieve simultaneous in vivo mapping of fullerenes and their associated metabolites. Following tail-vein injection into mice, fullerenes were primarily localized in the liver and spleen with significant enrichment in the red pulp of the spleen. Notably, fullerene accumulation in normal tissues resulted in substantial alterations in endogenous metabolic pathways, particularly those related to pyrimidine, purine, and energy metabolism. This approach provides valuable insights into the metabolic effects of fullerenes in vivo, offering a foundation for further investigation into their biological and therapeutic implications.

Engineered extracellular vesicles promote the repair of acute kidney injury by modulating regulatory T cells and the immune microenvironment

BACKGROUND

Acute kidney injury (AKI) is a common and severe clinical condition. However, the underlying mechanisms of AKI have not been fully elucidated, and effective treatment options remain limited. Studies have shown that immune cells play a critical role in AKI, with regulatory T cells (Tregs) being one of the most important immunosuppressive lymphocytes. Tregs proliferation can attenuate AKI, whereas depletion exacerbates kidney injury. Given that endothelial cells (ECs) are the initial cells that interact with immune cells when they invade the tissue parenchyma, ECs are closely associated with immune reactions.

METHODS AND RESULTS

In this study, P-selectin binding peptide-extracellular vesicles (PBP-EVs) that target and repair ECs are engineered. Transcriptome sequencing reveals that PBP-EVs reduce the expression of inflammatory genes in AKI mice. Using high-resolution intravital two-photon microscopy (TPM), an increased recruitment of Tregs in the kidneys of AKI Foxp3-EGFP transgenic mice following PBP-EVs treatment is observed, as well as significant Lgr5+ renal stem cell proliferation in AKI Lgr5-CreERT2; R26mTmG mice. Additionally, PBP-EVs treatment result in reduced infiltration of inflammatory cells, pathological damage and fibrosis of AKI mice. Upon depletion of Tregs in Foxp3-DTR transgenic mice, we observe diminished therapeutic effect of PBP-EVs on AKI.

CONCLUSIONS

The experimental results indicate that PBP-EVs can promote the repair and regeneration of AKI by mitigating endothelial cell damage and subsequently modulating Tregs and the immune microenvironment. These findings provide novel insights and strategies for the treatment of AKI.

Innate Immunity and Asthma Exacerbations: Insights From Human Models

Asthma is a common chronic respiratory disease characterized by the presence of airway inflammation, airway hyperresponsiveness, and mucus hypersecretion. Repeated asthma exacerbations can lead to progressive airway remodeling and irreversible airflow obstruction. Thus, understanding and preventing asthma exacerbations are of paramount importance. Although multiple endotypes exist, asthma is most often driven by type 2 airway inflammation. New therapies that target specific type 2 mediators have been shown to reduce the frequency of asthma exacerbations but are incompletely effective in a significant number of asthmatics. Furthermore, it remains unknown whether current treatments lead to sustained changes in the airway or if targeting additional pathways may be necessary to achieve asthma remission. Activation of innate immunity is the initial event in the inflammatory sequence that occurs during an asthma exacerbation. However, there continue to be critical gaps in our understanding of the innate immune response to asthma exacerbating factors. In this review, we summarize the current understanding of the role of innate immunity in asthma exacerbations and the methods used to study them. We also identify potential novel therapeutic targets for asthma and future areas for investigation.

The multifaceted roles of macrophages in the transition from hepatitis to hepatocellular carcinoma: From mechanisms to therapeutic strategies

Macrophages are central to the progression from hepatitis to hepatocellular carcinoma (HCC), with their remarkable plasticity and ability to adapt to the changing liver microenvironment. Chronic inflammation, fibrosis, and ultimately tumorigenesis are driven by macrophage activation, making them key regulators of liver disease progression. This review explores the diverse roles of macrophages in the transition from hepatitis to HCC. In the early stages of hepatitis, macrophages are essential for pathogen clearance and tissue repair. However, chronic activation leads to prolonged inflammation, which exacerbates liver damage and promotes fibrosis. As the disease progresses to liver fibrosis, macrophages interact with hepatic stellate cells, fostering a pro-tumorigenic microenvironment that supports HCC development. In hepatocarcinogenesis, macrophages contribute to tumor initiation, growth, metastasis, immune evasion, cancer stem cell maintenance, and angiogenesis. Their functional plasticity enables them to adapt to the tumor microenvironment, thereby promoting tumor progression and resistance to therapy. Targeting macrophages represents a promising strategy for preventing and treating HCC. Therapeutic approaches, including reprogramming macrophage phenotypes to enhance anti-tumor immunity, blocking macrophage recruitment and activation, and utilizing nanoparticle-based drug delivery systems, may provide new avenues for combating HCC by modulating macrophage functions and tumor microenvironment dynamics.

The Regenerative Marriage Between High-Density Platelet-Rich Plasma and Adipose Tissue

The use of autologous biological preparations (ABPs) and their combinations fills the void in healthcare treatment options that exists between surgical procedures, like plastic reconstructive, cosmetic, and orthopedic surgeries; non-surgical musculoskeletal biological procedures; and current pharmaceutical treatments. ABPs, including high-density platelet-rich plasma (HD-PRP), bone marrow aspirate concentrates (BMACs), and adipose tissue preparations, with their unique stromal vascular fractions (SVFs), can play important roles in tissue regeneration and repair processes. They can be easily and safely prepared at the point of care. Healthcare professionals can employ ABPs to mimic the classical wound healing cascade, initiate the angiogenesis cascade, and induce tissue regenerative pathways, aiming to restore the integrity and function of damaged tissues. In this review, we will address combining autologous HD-PRP with adipose tissue, in particular the tissue stromal vascular fraction (t-SVF), as we believe that this biocellular combination demonstrates a synergistic effect, where the HD-PRP constituents enhance the regenerative potential of t-SVF and its adipose-derived mesenchymal stem cells (AD-MSCs) and pericytes, leading to improved functional tissue repair, tissue regeneration, and wound healing in variety of clinical applications. We will address some relevant platelet bio-physiological aspects, since these properties contribute to the synergistic effects of combining HD-PRP with t-SVF, promoting overall better outcomes in chronic inflammatory conditions, soft tissue repair, and tissue rejuvenation.

A functional cardiac patch promotes cardiac repair by modulating the CCR2- cardiac-resident macrophage niche and their cell crosstalk

C-C chemokine receptor type 2 (CCR2-) cardiac-resident macrophages (CCR2- cRMs) are known to promote cardiac repair after myocardial infarction (MI). However, the substantial depletion and slow recovery of CCR2- cRMs pose significant barriers in cardiac recovery. Here, we construct a functional conductive cardiac patch (CCP) that can provide exogenously elastic conductive microenvironment and induce endogenously reparative microenvironment mediated by CCR2- cRMs for MI repair. This CCP exhibits suitable mechanical properties, conductivity, and high water retention, reminiscent of natural myocardium, which can actively engage in modulating CCR2- cRM renewal and their cell crosstalk. The functional CCP can promote the expression of Connexin43 between CCR2- cRMs and cardiomyocytes (CMs) and regulate paracrine signaling to activate epicardial cell epithelial-to-mesenchymal transition (EMT) toward endothelial cells using rat and Wt1CreERT2 transgenic lineage tracing mice. Overall, this study provides a promising strategy to construct a synergistic reparative microenvironment for MI repair.

Microporous annealed particle hydrogels in cell culture, tissue regeneration, and emerging application in cancer immunotherapy

Microporous annealed particle (MAP) hydrogels consist of densely crosslinked and annealed hydrogel particles. Compared to common hydrogels, the inherent porosity within and among these hydrogel particles offers interconnected channels for substance exchange in addition to sufficient growth space for cells, thereby forming a three-dimensional culture system that highly mimics the in vivo microenvironment. Such characteristics enable MAP hydrogels to adapt to various requirements of biomedical applications, along with their excellent injectability and mechanical properties. This review initially provides a comprehensive summary of the fabrication methods and material types of MAP hydrogels, alongside an assessment of their mechanical properties and porosity. In vitro studies are evaluated based on the impact of MAP hydrogels on cellular behaviors, focusing on cell proliferation, differentiation, migration, activity, and phenotype. In vivo research highlights the promising applications of MAP hydrogels in tissue regeneration, as well as their innovative use in cancer immunotherapy. Current challenges and future research directions are outlined, underscoring the potential of MAP hydrogels to significantly improve clinical outcomes in cancer treatment and regenerative medicine.

Staphylococcus aureus in Inflammation and Pain: Update on Pathologic Mechanisms

Staphylococcus aureus (S. aureus) is a Gram-positive bacterium of significant clinical importance, known for its versatility and ability to cause a wide array of infections, such as osteoarticular, pulmonary, cardiovascular, device-related, and hospital-acquired infections. This review describes the most recent evidence of the pathogenic potential of S. aureus, which is commonly part of the human microbiota but can lead to severe infections. The prevalence of pathogenic S. aureus in hospital and community settings contributes to substantial morbidity and mortality, particularly in individuals with compromised immune systems. The immunopathogenesis of S. aureus infections involves intricate interactions with the host immune and non-immune cells, characterized by various virulence factors that facilitate adherence, invasion, and evasion of the host's defenses. This review highlights the complexity of S. aureus infections, ranging from mild to life-threatening conditions, and underscores the growing public health concern posed by multidrug-resistant strains, including methicillin-resistant S. aureus (MRSA). This article aims to provide an updated perspective on S. aureus-related infections, highlighting the main diseases linked to this pathogen, how the different cell types, virulence factors, and signaling molecules are involved in the immunopathogenesis, and the future perspectives to overcome the current challenges to treat the affected individuals.

Functional Nanosheet Immunoswitches Reprogramming Innate Macrophages for Immunotherapy of Colorectal Cancer and Sepsis

Macrophages are involved in the immunopathogenesis of cancer and inflammatory diseases and are a primary target for immunotherapy to reprogram the M1 and M2 phenotypes in tumor and inflammatory microenvironments. Herein, functional nanosheet immunoswitches that can bidirectionally polarize macrophages in tumor and inflammatory microenvironments are designed for effective immunotherapy of colorectal cancer and sepsis. WSe2 nanosheets are functionalized with palmitic acid to obtain an M1 immunoswitch (PA-WSe2) that promotes the polarization of macrophages toward the M1 phenotype in the tumor microenvironment by activating the STAT1 signaling pathway. WS2 nanosheets bearing linoleic acid are synthesized as an M2 immunoswitch (LA-WS2) that effectively polarizes macrophages to the M2 phenotype in the septic microenvironment by activating the STAT3 signaling pathway. The PA-WSe2 M1 immunoswitch upregulates the secretion of pro-inflammatory cytokines and reactive oxygen and nitrogen species (ROS and RNS) via M1 polarization, leading to the effective immunotherapy for colorectal cancer in vivo. In contrast, the LA-WS2 M2 immunoswitch induces the elevated production of anti-inflammatory cytokines and scavenging of ROS and RNS through M2 polarization, resulting in superior immunotherapy for severe sepsis in mice. These nanosheet immunoswitches can provide a route to immunotherapy for various cancers and inflammatory diseases.

CAF-macrophage crosstalk in tumour microenvironments governs the response to immune checkpoint blockade in gastric cancer peritoneal metastases

BACKGROUND

Peritoneal metastasis is the most common metastasis pattern of gastric cancer. Patients with gastric cancer peritoneal metastasis (GCPM) have a poor prognosis and respond poorly to conventional treatments. Recently, immune checkpoint blockade (ICB) has demonstrated favourable efficacy in the treatment of GCPM. Stratification of best responders and elucidation of resistance mechanisms of ICB therapies are highly important and remain major clinical challenges.

DESIGN

We performed a phase II trial involving patients with GCPM treated with ICB (sintilimab) combined with chemotherapy. The samples of primary tumours, GCPMs and peripheral blood from patients were collected for single-cell sequencing to comprehensively interpret the tumour microenvironment of GCPM and its impacts on immunotherapy efficacy.

RESULTS

The GCPM ecosystem coordinates a unique immunosuppressive pattern distinct from that of primary GC, which is dominated by a stroma-myeloid niche composed of SPP1+tumour-associated macrophages (TAMs) and Thrombospondin 2 (THBS2)+matrix cancer-associated fibroblasts (mCAFs). Consequently, this stroma-myeloid crosstalk is the major mediator of ICB resistance in patients with GCPM. Mechanistically, the accumulated THBS2+mCAFs facilitate the recruitment of peritoneum-specific tissue-resident macrophages and their transformation into SPP1+TAMs via the complement C3 and its receptor C3a receptor 1 (C3AR1), thereby forming a protumoral stroma-myeloid niche. Blocking the C3-C3AR1 axis disrupts the stroma-myeloid crosstalk and thereby significantly improves the benefits of ICB in in vivo models.

CONCLUSION

Our findings provide a new molecular portrait of cell compositions associated with ICB resistance in patients with GCPM and aid in the prioritisation of therapeutic candidates to potentiate immunotherapy.

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.

Sestrin2 balances mitophagy and apoptosis through the PINK1-Parkin pathway to attenuate severe acute pancreatitis

Mitophagy serves as a mitochondrial quality control mechanism to maintain the homeostasis of mitochondria and the intracellular environment. Studies have shown that there is a close relationship between mitophagy and apoptosis. Sestrin2 (Sesn2) is a highly conserved class of stress-inducible proteins that play important roles in reducing oxidative stress damage, inflammation, and apoptosis. However, the potential mechanism of how Sesn2 regulates mitophagy and apoptosis in severe acute pancreatitis (SAP) remains unclear. In the study, RAW264.7 (macrophage cell Line) cellular inflammation model established by lipopolysaccharide (LPS) treatment as well as LPS and CAE-induced SAP mouse model (wild-type and Sen2 Knockout mouse) were used. Our study showed that LPS stimulation significantly increased the level of Sesn2 in RAW264.7 cells, Sesn2 increased mitochondrial membrane potential, decreased inflammation levels, mitochondrial superoxide levels and apoptosis, and also promoted monocyte macrophages toward the M2 anti-inflammatory phenotype, suggesting a protective effect of Sesn2 on mitochondria. Further, Sesn2 increased mitophagy and decreased apoptosis via modulating the PINK1-Parkin signaling. Meanwhile, knockout of Sesn2 exacerbated pancreatic, mitochondrial damage and inflammation in a mouse model of SAP. In addition, the protective effect of Sesn2 against SAP was shown to be associated with mitophagy conducted by the PINK1-Parkin pathway via inhibiting apoptosis. These findings reveal that Sesn2 in balancing mitochondrial autophagy and apoptosis by modulating the PINK1-Parkin signaling may present a new therapeutic strategy for the treatment of SAP.

Advanced Immunomodulatory Biomaterials for Therapeutic Applications

The multifaceted biological defense system modulating complex immune responses against pathogens and foreign materials plays a critical role in tissue homeostasis and disease progression. Recently developed biomaterials that can specifically regulate immune responses, nanoparticles, graphene, and functional hydrogels have contributed to the advancement of tissue engineering as well as disease treatment. The interaction between innate and adaptive immunity, collectively determining immune responses, can be regulated by mechanobiological recognition and adaptation of immune cells to the extracellular microenvironment. Therefore, applying immunomodulation to tissue regeneration and cancer therapy involves manipulating the properties of biomaterials by tailoring their composition in the context of the immune system. This review provides a comprehensive overview of how the physicochemical attributes of biomaterials determine immune responses, focusing on the physical properties that influence innate and adaptive immunity. This review also underscores the critical aspect of biomaterial-based immune engineering for the development of novel therapeutics and emphasizes the importance of understanding the biomaterials-mediated immunological mechanisms and their role in modulating the immune system.

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.

Diverse Functions of Macrophages in Obesity and Metabolic Dysfunction-Associated Steatotic Liver Disease: Bridging Inflammation and Metabolism

Macrophages play crucial roles in immune response and tissue homeostasis, with their functions becoming increasingly complex in obesity-mediated metabolic disorders. This review explores the extensive range of macrophage activities within adipose and liver tissues, emphasizing their contribution to the pathogenesis and progression of obesity and its related metabolic dysfunction-associated steatotic liver disease (MASLD). In the context of obesity, macrophages respond adaptively to lipid overloads and inflammatory cues in adipose tissue, profoundly influencing insulin resistance and metabolic homeostasis. Concurrently, their role in the liver extends to moderating inflammation and orchestrating fibrotic responses, integral to the development of MASLD. Highlighting the spectrum of macrophage phenotypes across these metabolic landscapes, we summarize their diverse roles in linking inflammatory processes with metabolic functions. This review advocates for a deeper understanding of macrophage subsets in metabolic tissues, proposing targeted research to harness their therapeutic potential in mitigating MASLD and other metabolic disorders.

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.

Integrating multiomics sequencing analyses uncover the key mechanisms related to oxidative stress, mitochondria, and immune cells in keloid

BACKGROUND

This study aimed to investigate the key molecular mechanisms underlying keloid pathogenesis by integrating oxidative stress, mitochondria, and immune cells.

METHODS

Transcriptome sequencing (mRNA, lncRNA, and circRNA expression data), proteomic sequencing, and small RNA sequencing analyses of lesional and non-lesional skin of patients with keloids and healthy control (normal) skin were conducted. By integrating mRNA and publicly available gene expression data (GSE158395), differentially expressed genes related to oxidative stress and mitochondrial function in keloids were identified. Hub genes were identified using various bioinformatics analyses such as immune infiltration analysis, weighted gene co-expression network analysis, machine learning, and expression validation using proteomics sequencing data. Moreover, a competing endogenous RNA (ceRNA) network of hub genes was constructed by combining miRNA, lncRNA, and circRNA expression data. Five hub genes were identified: MGST1, DHCR24, ALDH3A2, ADH1B, and FKBP5.

RESULTS

These hub genes had a high diagnostic value for keloids, with an AUC value > 0.8 each. In addition, five hub genes were associated with the infiltration of multiple immune cells. The immune cells with the strongest positive and negative correlations with hub genes were M0 and M1 macrophages. A ceRNA network was constructed, and several ceRNAs, such as AC005062.1/miR-134-5p/FKBP5 and BASP1-AS1/miR-503-5p/ADH1B, were identified. These five hub genes may contribute to keloid pathogenesis.

CONCLUSION

These genes and their related ceRNAs may serve as diagnostic biomarkers and therapeutic targets for keloids.

Effectively alleviate rheumatoid arthritis via maintaining redox balance, inducing macrophage repolarization and restoring homeostasis of fibroblast-like synoviocytes by metformin-derived carbon dots

Overproduction of reactive oxygen species (ROS), elevated synovial inflammation, synovial hyperplasia and fibrosis are the main characteristic of microenvironment in rheumatoid arthritis (RA). Macrophages and fibroblast-like synoviocytes (FLSs) play crucial roles in the progression of RA. Hence, synergistic combination of ROS scavenging, macrophage polarization from pro-inflammatory M1 phenotype towards M2 anti-inflammatory phenotype, and restoring homeostasis of FLSs will provide a promising therapeutic strategy for RA. In this study, we successfully synthesized metformin-derived carbon dots (MCDs), and investigated the antirheumatic effect in vivo and in vitro. Designed MCDs could target inflamed cells and accumulate at the inflammatory joints of collagen-induced arthritis (CIA) rats. In vivo therapeutic investigation suggested that MCDs reduced synovial inflammation and hyperplasia, ultimately prevented cartilage destruction, bone erosion, and synovial fibrosis in CIA rats. In addition, MCDs eliminated the cellular ROS in M1 phenotype macrophages in RA microenvironment through the enzyme-like catalytic activity as well as inhibiting NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome signaling pathway, effectively polarizing them into the M2 phenotype to realize the anti-inflammatory effect. Furthermore, MCDs could inhibit the proliferation, migration, and fibrosis of inflamed FLSs. Mechanistically, MCDs restored the homeostasis of FLSs while reducing the level of synovial inflammation by blocking IL-6/gp130 signaling pathway. Combined with preferable biocompatibility, MCDs offer a prospective treatment approach for RA.

Epithelial and immune transcriptomic characteristics and possible regulatory mechanisms in asthma exacerbation: insights from integrated studies

Background

Asthma exacerbation significantly contribute to disease mortality and result in heightened health care expenditures. This study was aimed at gaining important new insights into the heterogeneity of epithelial and immune cells and elucidating key regulatory genes involved in the pathogenesis of asthma exacerbation.

Methods

Functional enrichment, pseudotime, metabolism and cell-cell communication analyses of epithelial cells and immune cells in single-cell RNA sequencing (scRNA-seq) dataset were applied. Immune infiltration analysis was performed in bulk RNA sequencing (bulk RNA-seq) dataset. Key regulatory genes were obtained by taking the intersection of the differentially expressed genes (DEGs) between control and asthma group in epithelial cells, immune cells and bulk RNA-seq data. Asthma animal and in vitro cell line models were established to verify the key regulatory genes expression by employing quantitative reverse transcription polymerase chain reaction (qRT-PCR).

Results

ScRNA-seq analysis identified 7 epithelial subpopulations and 14 distinct immune cell types based on gene expression profiles. Further analysis demonstrated that these cells manifested high heterogeneity at the levels of functional variations, dynamics, communication patterns and metabolic changes. Notably, TMPRSS11A, TUBA1A, SCEL, ICAM4, TMPRSS11B, IGFBP2, CLC, NFAM1 and F13A1 were identified as key regulatory genes of asthma. The results of the qRT-PCR demonstrated that the 9 key regulatory genes were involved in asthma.

Conclusions

We systematically explored epithelial and immune characteristics in asthma exacerbation and identified 9 key regulatory genes underlying asthma occurrence and progression, which may be valuable for providing new insights into the cellular and molecular mechanisms driving asthma exacerbations.

From acute lung injury to cerebral ischemia: a unified concept involving intercellular communication through extracellular vesicle-associated miRNAs released by macrophages/microglia

Ischemic stroke and acute lung injury are prevalent life-threatening conditions marked by intricate molecular mechanisms and elevated mortality rates. Despite evident pathophysiological distinctions, a notable similarity exists in the gene responses to tissue injury observed in both pathologies. This similarity extends to both protein-encoding RNAs and non-coding RNAs. Extracellular vesicles (EVs) are nano-scale vesicles derived through cell secretion, possessing unique advantages such as high biocompatibility, low immunogenicity, intrinsic cell targeting, and facile chemical and genetic manipulation. Importantly, miRNAs, the most prevalent non-coding RNAs, are selectively concentrated within EVs. Macrophages/microglia serve as immune defense and homeostatic cells, deriving from progenitor cells in the bone marrow. They can be classified into two contrasting types: classical proinflammatory M1 phenotype or alternative anti-inflammatory M2 phenotype. However, there exists a continuum of various intermediate phenotypes between M1 and M2, and macrophages/microglia can transition from one phenotype to another. This review will investigate recent discoveries concerning the impact of EVs derived from macrophages/microglia under various states on the progression of ischemic stroke and acute lung injury. The focus will be on the involvement of miRNAs within these vesicles. The concluding remarks of this review will underscore the clinical possibilities linked to EV-miRNAs, accentuating their potential as both biomarkers and therapeutic targets.

Human Monocyte-Derived Macrophages Demonstrate Distinct Responses to Ambient Particulate Matter in a Polarization State- and Particle Seasonality-Specific Manner

Macrophages are professional phagocytic immune cells that, following activation, polarize on a spectrum between the proinflammatory M1 and the proresolution M2 states. Macrophages have further been demonstrated to retain plasticity, allowing for the reprogramming of their polarization states following exposure to new stimuli. Particulate matter (PM) has been repeatedly shown to modify macrophage function and polarization while also inducing worsening respiratory infection morbidity and mortality. However, limited work has considered the impact of the initial macrophage polarization state on subsequent responses to PM exposure. PM composition can demonstrate seasonality-specific compositional changes based on differences in seasonal weather patterns and energy needs, introducing the need to consider the seasonality-specific effects of airborne PM when investigating its impact on human health. This study sought to determine the impact of airborne PM collected during different seasons of the year in Xinxiang, China, on macrophage function in a polarization state-dependent manner. Macrophages were differentiated using the macrophage colony-stimulating factor (M-CSF) on CD14+CD16- monocytes isolated from the blood of healthy human volunteers. The resulting macrophages were polarized into indicated states using well-characterized polarization methods and assessed for phagocytic function, bioenergetic properties, and secretory profile following exposure to PM collected during a single day during each season of the year. Macrophages demonstrated clear polarization state-dependent phagocytic, bioenergetic, and secretory properties at the baseline and following PM exposure. Specific PM seasonality had a minimal impact on phagocytic function and a minor effect on bioenergetic properties but had clear impacts on the secretory profile as demonstrated by the enriched secretion of well-characterized mediator clusters by particle season. Together, these data suggest that both particle seasonality and macrophage polarization state must be considered when investigating the impact of PM on macrophage function. These factors may contribute to the negative outcomes linked to PM exposure during respiratory infections.

Macrophage-derived extracellular vesicles as new players in chronic non-communicable diseases

Macrophages are innate immune cells present in all tissues and play an important role in almost all aspects of the biology of living organisms. Extracellular vesicles (EVs) are released by cells and transport their contents (micro RNAs, mRNA, proteins, and long noncoding RNAs) to nearby or distant cells for cell-to-cell communication. Numerous studies have shown that macrophage-derived extracellular vesicles (M-EVs) and their contents play an important role in a variety of diseases and show great potential as biomarkers, therapeutics, and drug delivery vehicles for diseases. This article reviews the biological functions and mechanisms of M-EVs and their contents in chronic non-communicable diseases such as cardiovascular diseases, metabolic diseases, cancer, inflammatory diseases and bone-related diseases. In addition, the potential application of M-EVs as drug delivery systems for various diseases have been summarized.

Tissue-resident immune cells: from defining characteristics to roles in diseases

Tissue-resident immune cells (TRICs) are a highly heterogeneous and plastic subpopulation of immune cells that reside in lymphoid or peripheral tissues without recirculation. These cells are endowed with notably distinct capabilities, setting them apart from their circulating leukocyte counterparts. Many studies demonstrate their complex roles in both health and disease, involving the regulation of homeostasis, protection, and destruction. The advancement of tissue-resolution technologies, such as single-cell sequencing and spatiotemporal omics, provides deeper insights into the cell morphology, characteristic markers, and dynamic transcriptional profiles of TRICs. Currently, the reported TRIC population includes tissue-resident T cells, tissue-resident memory B (BRM) cells, tissue-resident innate lymphocytes, tissue-resident macrophages, tissue-resident neutrophils (TRNs), and tissue-resident mast cells, but unignorably the existence of TRNs is controversial. Previous studies focus on one of them in specific tissues or diseases, however, the origins, developmental trajectories, and intercellular cross-talks of every TRIC type are not fully summarized. In addition, a systemic overview of TRICs in disease progression and the development of parallel therapeutic strategies is lacking. Here, we describe the development and function characteristics of all TRIC types and their major roles in health and diseases. We shed light on how to harness TRICs to offer new therapeutic targets and present burning questions in this field.

An Integrative analysis of single-cell RNA-seq, transcriptome and Mendelian randomization for the Identification and validation of NAD+ Metabolism-Related biomarkers in ulcerative colitis

Ulcerative colitis (UC) is a chronic and refractory inflammatory disease of the colon and rectum. This study utilized bioinformatics methods to explore the potential of Nicotinamide adenine dinucleotide (NAD+) metabolism-related genes (NMRGs) as key genes in UC. Using the GSE87466 dataset, differentially expressed NMRGs were identified through differential expression analysis, weighted gene co-expression network analysis (WGCNA), and NMRG scoring. These NMRGs were used as exposure factors, with UC as the outcome, to identify causal candidate genes through Mendelian randomization (MR) analysis. Key genes were further validated as biomarkers using machine learning and expression validation in external datasets (GSE75214, GSE224758). A nomogram based on the expression levels of these biomarkers was constructed to predict UC risk, and the biomarkers' expression was validated through real-time quantitative polymerase chain reaction (RT-qPCR). Subsequently, signaling pathway analysis, enrichment analysis, immune infiltration analysis, and drug prediction were conducted to comprehensively understand the biological roles of the key genes in the human body. Single-cell (GSE116222) and spatial transcriptomic analyses (GSE189184) revealed the expression patterns of these key genes in specific cell types. NCF2, IL1B, S100A8, and SLC26A2 were identified as biomarkers, with NCF2 and IL1B serving as protective factors and S100A8 and SLC26A2 as risk factors for UC. The nomogram based on these biomarkers demonstrated strong predictive value. Functional analysis revealed significant IL1B, NCF2, and S100A8 enrichment in pathways such as IL-4 and IL-13 signaling, while SLC26A2 was strongly associated with respiratory electron transport. Significant differences in immune cells, such as macrophages and neutrophils, were also observed. Single-cell analysis showed high expression of NCF2, IL1B, and S100A8 in monocytes, while SLC26A2 was primarily expressed in epithelial cells, intestinal epithelial cells, and mast cells. Overall, these findings reveal the roles of NMRGs, providing valuable insights into the diagnosis and treatment of UC patients.

The Roles of Myeloid Cells in Breast Cancer Progression

This chapter reviews tumor-associated myeloid cells, including macrophages, neutrophils, and other innate immune cells, and their multifaceted roles in supporting breast cancer progression and metastasis. In primary tumors, myeloid cells play key roles in promoting tumor epithelial-mesenchymal transition (EMT) and invasion. They can facilitate intravasation (entry into the bloodstream) and colonization, disrupting the endothelial cell layer and reshaping the extracellular matrix. They can also stimulate angiogenesis, suppress immune cell responses, and enhance cancer cell adaptability. In the bloodstream, circulating myeloid cells enable the survival of disseminated tumor cells via immunosuppressive effects and physical shielding. At the metastatic sites, they prime the premetastatic niche, facilitate tumor cell extravasation, and support successful colonization and outgrowth. Mechanistically, myeloid cells enhance cancer cell survival, dormancy escape, proliferation, and mesenchymal-epithelial transition (MET). Nonetheless, substantial gaps in our understanding persist regarding the functional and spatiotemporal diversity, as well as the evolutionary patterns, of myeloid cells during metastatic progression. Myeloid cell plasticity and differential responses to therapies present key barriers to successful treatments. Identifying specific pro-tumoral myeloid cell subpopulations and disrupting their interactions with cancer cells represent promising therapeutic opportunities. Emerging evidence suggests combining immunomodulators or stromal normalizers with conventional therapies could help overcome therapy-induced immunosuppression and improve patient outcomes. Overall, further elucidating myeloid cell heterogeneity and function throughout the process of breast cancer progression and metastasis will enable more effective therapeutic targeting of these critical stromal cells.