Monocytes and macrophages: Origin, homing, differentiation, and functionality during inflammation

Inflammatory metabolite 7α,25-OHC promotes TIMP1 expression in COVID-19 monocytes through synergy effect of SMARCC1/JUND/H3K27ac

Chromatin remodeling factors are involved in the inflammatory responses, contributing to tissue damage and multi-organ dysfunction in COVID-19 patients. However, the underlying mechanisms remain unclear. In this study, high-dimensional analyses of single-cell RNA sequencing and single-cell ATAC sequencing data revealed increased chromatin accessibility at the promoters or enhancers of the pro-inflammatory cytokine tissue inhibitor of metalloproteinase-1 (TIMP1), as well as altered gene transcription profiles in monocytes from COVID-19 patients. Motif enrichment and positive regulators analyses identified SMARCC1, the core subunit of the chromatin remodeling complex, and the transcription factor JUND as positive regulators to co-modulate TIMP1 expression. In-vitro experiments, co-immunoprecipitation and chromatin immunoprecipitation (ChIP)-qPCR, and others, demonstrated the collaboration of SMARCC1 and JUND. Increased 7α,25-dihydroxycholesterol (7α,25-OHC) enhanced SMARCC1-JUND interactions to co-regulate TIMP1 expression. Further investigation indicated that 7α,25-OHC promoted the expression of SMARCC1 and its co-localization with H3K27ac, which involved in the expression of TIMP1 and inflammatory responses. Our study highlights the critical roles of SMARCC1 and JUND in COVID-19 inflammation, and offers the potential targets for the prevention and treatment of COVID-19.

Novel function of macrophage migration inhibitory factor in regulating post-infarct inflammation and the therapeutic significance

INTRODUCTION

Recent studies indicate that macrophage migration inhibitory factor (MIF) has a dual role in myocardial infarction (MI), with different cellular sources of MIF influencing inflammation and healing differentially.

OBJECTIVES

To investigate the role and underlying mechanism of MIF in MI and interventional efficacy targeting MIF.

METHODS

Wild-type (WT), global MIF gene knockout (KO) and chimeric mice were subjected to coronary artery occlusion. The inflammatory responses and healing processes following MI were studied in both in vivo and in vitro settings. Furthermore, the therapeutic potential of pharmacological MIF inhibition to improve the prognosis of MI was explored.

RESULTS

Globally, MIF enhanced systemic and local inflammatory responses, as well as splenic monocyte mobilization, in mice with MI. MIF promoted monocyte migration through CCR2 and CXCR4 in peripheral blood mononuclear cells (PBMCs) and the infarcted myocardium. Additionally, MIF augmented angiotensin Ⅱ type 1 receptor (AT-1R) expression and interacted with AT-1R to promote the splenic monocyte mobilization following acute MI. MIF derived from bone marrow cells (KOWT mice) had stronger systemic and local inflammatory responses and augmented mobilization of splenic monocytes. In contrast, deficiency of MIF in leukocytes (WTKO mice) increased Ly-6Clow monocyte accumulation, M2 macrophage infiltration, and degree of myocardial fibrosis in infarcted myocardium. In vitro, MIF derived from ischemic heart enhanced M2 but impaired M1 macrophage marker expression in PBMCs. Anti-MIF treatment effectively attenuated splenic monocyte mobilization and both systemic and regional inflammatory responses post-MI without affecting the healing process, thereby improving the long-term prognosis.

CONCLUSION

Deletion of global and inflammatory-cell-derived MIF diminished inflammation following MI by inhibiting monocyte mobilization and downregulating pro-inflammatory mediators, while cardiac-derived MIF exerted anti-inflammatory influence and facilitated healing. Furthermore, MIF antibody therapy protected the heart from severe ischemic injury and improved long-term prognosis.

Anti-tumor necrosis factor therapy in the treatment of systemic autoinflammatory diseases: the responses of innate immune cells

Systemic autoinflammatory diseases are rare conditions resulting from dysregulation of the innate immune system, culminating in repetitive bouts of systemic inflammation without the presence of external or self-antigens. Most systemic autoinflammatory diseases are associated with mutations in genes affecting the innate immune response. Tumor necrosis factor is a central player in the pathogenesis of numerous chronic inflammatory disorders, and anti-tumor necrosis factor therapy is widely used in the clinical management of systemic autoinflammatory diseases. Tumor necrosis factor inhibitors block the interaction of tumor necrosis factor with its 2 receptors, tumor necrosis factor receptor 1 and tumor necrosis factor receptor 2. These inhibitors primarily target soluble tumor necrosis factor, which mainly binds to tumor necrosis factor receptor 1, exerting anti-inflammatory effects. Interestingly, tumor necrosis factor inhibitors also affect transmembrane tumor necrosis factor, which engages tumor necrosis factor receptor 2 to initiate reverse signaling. This reverse signaling can activate innate immune cells, prevent apoptosis, or paradoxically inhibit the production of pro-inflammatory cytokines. Tumor necrosis factor inhibitors also promote the release of soluble tumor necrosis factor receptor 2, which neutralizes circulating tumor necrosis factor. Some agents targeting tumor necrosis factor receptor 2 can even act as agonists, triggering reverse signaling by binding to transmembrane tumor necrosis factor. While effective, prolonged use of tumor necrosis factor inhibitors may cause significant side effects due to the widespread expression and pleiotropic functions of tumor necrosis factor receptors. A more thorough understanding of the mechanisms underlying the action of tumor necrosis factor inhibitors is required to develop a more effective and safer treatment for systemic autoinflammatory diseases. This article reviews current studies on the role of the innate immune system in systemic autoinflammatory disease pathogenesis, the impact of anti-tumor necrosis factor therapy on innate immune cells, and perspectives on developing improved agents targeting tumor necrosis factor or its receptors.

Flammulina velutipes polysaccharide exerts immunomodulatory function involving RSAD2 to regulate the NF-κB/MAPK signaling pathway in RAW264.7 macrophage cells and in mouse spleen cells

There are ongoing efforts to explore the potential of natural bioactive substances including polysaccharides in immunological regulation and understand the mechanisms under their immune-regulating function. In this study, a polysaccharide from Flammulina velutipes (FVP-1) exhibited immunomodulatory in RAW264.7 macrophage cells and mouse spleen cells. FVP-1 increased the secretion of cytokines (like TNF-α, IL-6 and IL-1β) and their mRNA expression, upregulated the transcription and translation expression of COX-2 and iNOS, and enhanced the release of reactive oxygen species the phagocytic activity in macrophages, thereby promoting the maturation and transformation of certain lymphocytes. All these functions of FVP-1 depended to some extent on its concentration. The RSAD2 effector was involved in the immunomodulatory function of FVP-1 towards macrophages and mouse splenocytes, through mediating FVP-1's activation and regulation of the NF-κB/MAPK signaling pathway. These findings indicate the potential of FVP-1 as a natural immunomodulator and approach for improving immune function.

Macrophages of the Heart: Homeostasis and Disease

Cardiac macrophages (CMs) are the most abundant immune cell type in the heart. They are critical for maintaining cardiac homeostasis and in the orchestration of immune responses to ischemic and non-ischemic cardiomyopathies. Their functions are highly heterogeneous and regulated by their tissue microenvironment. CMs have high plasticity, which allows them to perform various functions in the myocardium to bring about homeostasis within the cardiovascular system (CVS). CMs also play critical roles in coronary development and angiogenesis, tissue repair and remodeling, cardiac conduction and in the clearance of necrotic and apoptotic cells. However, there is a paucity of studies on the biology of cardiac macrophages in both steady state and disease, especially, in humans. In this review, we discuss the multifaceted roles of CMs in the heart, focusing on their ontogeny, homeostatic functions and immunological responses during inflammation and reparative processes post-injury. We highlight the heterogeneity of CMs in their ontogeny, phenotypes and functions as well as their roles in the pathogenesis of pathological conditions such as myocarditis, myocardial fibrosis and heart failure. Understanding the unique characteristics of cardiac macrophages in the cardiac milieu is critical for the development of macrophage-specific therapeutic interventions to alleviate the global burden of cardiovascular disease (CVD). Therefore, future studies should focus on further improving the understanding of the biology of cardiac macrophages to harness their potential as therapeutic targets for cardiovascular disorders.

Dietary succinate supplementation alleviates DSS-induced colitis via the IL-4Rα/Hif-1α Axis

Inflammatory bowel disease (IBD) remains a pressing global health challenge, necessitating novel therapeutic strategies. Succinate, a metabolite known for its role in type 2 immunity and tuft cell activation in the small intestine, presents its potential in IBD management. However, its impact on colonic inflammation has not been explored. Here, we demonstrate that succinate administration induces a type 2 immune response, significantly alleviating dextran sulfate sodium (DSS)-induced colonic inflammation. Succinate enhances antibacterial capacity, reduces intestinal permeability, and reshapes the colonic cytokine milieu. Mechanistically, succinate promotes myeloid cell expansion in peripheral blood, mesenteric lymph nodes, and the colonic lamina propria. The protective effects of succinate were abolished in Ccr2-/- mice, confirming the role of monocyte recruitment, but persisted in Rag1-/- mice, indicating independence from adaptive immunity. Adoptive transfer of monocytes from succinate-treated donors mitigated intestinal inflammation in recipient mice. Transcriptomic analysis revealed heightened expression of Il1b and Il6, and higher lactate production in monocytes upon lipopolysaccharide (LPS) stimulation, highlighting a reprogrammed pro-inflammatory trained immunity phenotype. Finally, we identify the IL-4Rα/Hif-1α axis is critical for succinate-mediated protection. These findings reveal the ability of succinate to reprogram monocytes into protective intestinal macrophages via induction of type 2 response, restoring homeostasis through enhanced barrier function and immune modulation. Our study positions thus uncover succinate as a promising therapeutic candidate for IBD.

Protocol for the generation and assessment of functional macrophages from mouse bone marrow cells

Macrophages play essential roles in tissues, wherein they exert beneficial or detrimental functions depending on the signals they encounter during their differentiation. Here, we present a protocol to differentiate mouse bone marrow cells into macrophages under specific cues to evaluate their impact on macrophage phenotypic acquisition. We provide detailed instructions for optimal cell culture conditions, quality controls, and examples of concluding immunological functional assays. This protocol is applicable in short- and long-term drug-based modulation of macrophage functions. For complete details on the use and execution of this protocol, please refer to Scafidi et al.1.

Unraveling the Mystery of Insulin Resistance: From Principle Mechanistic Insights and Consequences to Therapeutic Interventions

Insulin resistance (IR) is a significant factor in the development and progression of metabolic-related diseases like dyslipidemia, T2DM, hypertension, nonalcoholic fatty liver disease, cardiovascular and cerebrovascular disorders, and cancer. The pathogenesis of IR depends on multiple factors, including age, genetic predisposition, obesity, oxidative stress, among others. Abnormalities in the insulin-signaling cascade lead to IR in the host, including insulin receptor abnormalities, internal environment disturbances, and metabolic alterations in the muscle, liver, and cellular organelles. The complex and multifaceted characteristics of insulin signaling and insulin resistance envisage their thorough and comprehensive understanding at the cellular and molecular level. Therapeutic strategies for IR include exercise, dietary interventions, and pharmacotherapy. However, there are still gaps to be addressed, and more precise biomarkers for associated chronic diseases and lifestyle interventions are needed. Understanding these pathways is essential for developing effective treatments for IR, reducing healthcare costs, and improving quality of patient life.

Association between pan-immune-inflammation value and heart failure: Evidence from the NHANES 2011-2020

ObjectiveThis study aimed to explore the association between pan-immune-inflammation value and heart failure outcomes using data from the nationally representative National Health and Nutrition Examination Survey database.MethodsWe conduct a cross-sectional cohort analysis using National Health and Nutrition Examination Survey data, including participants aged ≥20 years with available pan-immune-inflammation value data. We performed smooth curve fitting and threshold analysis, using both linear and non-linear regression models, to assess dose-response relationship and explore the continuous effect of pan-immune-inflammation value on heart failure outcomes.ResultsOur analysis revealed a significant and independent non-linear association between elevated pan-immune-inflammation value levels and an increased risk of heart failure occurrence. After adjustment for multiple covariates, these findings remained consistent and each increment unit in logarithmic pan-immune-inflammation value is associated with 34% increase in the risk of heart failure occurrence. Furthermore, we identified an inflection point of logarithmic pan-immune-inflammation value = 5.98 as a critical threshold. Stratified analyses revealed that the association between pan-immune-inflammation value and heart failure occurrence remains consistent across different subgroups.ConclusionsThis study confirmed the clinical value of pan-immune-inflammation value as a novel inflammatory biomarker in the assessment and monitoring of heart failure.

Features of the monocyte inflammatory response in patients with premature coronary artery disease

The purpose of this study was to examine the secretion of inflammatory cytokines by cultured monocytes/macrophages in patients with premature coronary artery disease (CAD). The study included 38 patients with premature CAD and 35 patients without CAD. A primary culture of CD14+ monocytes was obtained by immunomagnetic separation. The inflammatory response was induced by incubation of a cell culture with lipopolysaccharide (LPS) for 24 hours on Days 1 and 6. Basal and LPS-stimulated secretion of the cytokines, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) was assessed by enzyme immunoassay on Days 2 and 7 of cultivation. The level of basal secretion of TNF-α, IL-1β, IL-6, MCP-1 was higher in patients with CAD compared to patients in the control group. The levels of re-stimulated TNF-α secretion and the levels of LPS-stimulated and re-stimulated IL-1β secretion on the second and sixth days were also higher in patients with CAD. LPS-stimulated MCP-1 secretion on the second day did not differ in patients of both groups, but re-stimulated MCP-1 secretion was higher in patients with CAD. The results of logistic regression analysis showed that the basal secretion levels of IL-1β and IL-6 were independently associated with premature CAD, along with smoking, body mass index and serum HDL-cholesterol levels.

The Relationship Between the Monocyte-to-High-Density Lipoprotein Cholesterol Ratio and Platelet Volume Indices With Diabetic Retinopathy

Aim This study aims to evaluate the roles of monocyte count-to-high-density lipoprotein (HDL) cholesterol ratio (MHR) and platelet volume indices (PVI) in predicting diabetic retinopathy (DR) in patients diagnosed with type 2 diabetes mellitus (DM) and to explore new methods for early prediction of retinopathy. Methods This prospective study included 120 patients aged over 18 years with type 2 DM diagnosed according to the American Diabetes Association criteria, along with a control group of 40 healthy individuals. Patients with type 2 DM were divided into three groups: 40 without retinopathy, 40 with non-proliferative diabetic retinopathy (NPDR), and 40 with proliferative diabetic retinopathy (PDR). Parameters such as complete blood count, PVI (mean platelet volume, platelet distribution width, plateletcrit, platelet large cell ratio), lipid profile, inflammatory markers (sedimentation rate, C-reactive protein), MHR, renal function tests, and glucose metabolism markers were analyzed alongside demographic, clinical, and laboratory data to assess their associations with DR in both patient and control groups. Results This study investigated the relationship between DR and hematological parameters (PVI, MHR). Hypertension, hyperlipidemia, and chronic kidney disease were common comorbidities. NPDR patients more frequently used metformin and dipeptidyl peptidase (DPP)-4 inhibitors, while PDR patients more often used insulin (p<0.05). Diabetic neuropathy and nephropathy were more prevalent in the PDR group. PDR patients had a significantly longer DM duration. Mean platelet volume (MPV) and platelet large cell ratio (PLCR) were higher in the PDR group. ROC analysis identified MHR (>11.9, 65% sensitivity, 35% specificity) and plateletcrit (PCT<0.29%, 61% sensitivity, 80% specificity) cut-offs for DR prediction. MHR's area under the curve (AUC) was greater than PCT's (p<0.05). MPV differed between PDR and NPDR, but MHR did not differ among DR groups or between DR/non-DR individuals. Glycosylated hemoglobin (HbA1c) and DM duration correlated positively with MHR, which also correlated with leukocyte count. HbA1c and glucose correlated with platelet distribution width (PDW). Each unit increase in DM duration increased MHR 1.13-fold, and each unit increase in HbA1c increased MHR 1.9-fold. Conclusions The duration of DM was significantly longer in patients with PDR compared to those with NPDR and those without retinopathy. MPV and PLCR levels were significantly higher in PDR patients than in NPDR patients. In evaluating the relationship between PVI and MHR for predicting diabetic retinopathy, significant cut-off values of MHR and PCT were found to be predictive indicators of diabetic retinopathy.

IgG4-mediated M2 macrophage polarization in tertiary lymphoid structures of esophageal cancer: implications for immunosuppression

Background

Our previous research highlighted the potential role of immunoglobulin G4 (IgG4) in mediating immunosuppression within the tumor microenvironment (TME). Tertiary lymphoid structures (TLS) in the TME have important immune-related functions. This study aims to analyze the distribution characteristics of IgG4-expressing cells, regulatory T cells (Tregs), and M2-type macrophages as well as to elucidate the relationship between IgG4 and the polarization of M2 macrophages within TLS in esophageal cancer.

Object

To elucidate the distribution of IgG4, Treg cells, and M2 macrophages in TLS and to assess the impact of IgG4 on macrophage polarization.

Methods

Esophageal cancer tissue were analyzed with multiplex immunofluorescence to determine the spatial distribution and density of B cells, T cells, and their subtypes. The relationship between IgG4 and CD8+ T cells in TLS, along with interleukin-10 (IL-10) expression and Treg presence, was studied. Serum IgG4 and IL-10 levels were compared between patients and healthy controls. In vitro, the impact of IgG4 on monocyte differentiation into M2 macrophages was observed.

Results

IgG4 density was inversely related with CD8+ T cells in mature TLS indicating a potential immunosuppressive role (P<0.05,*). Serum analysis revealed that both IgG4 (P<0.01, **) and IL-10 (P<0.0001, ****) were significantly elevated and positively correlated in tumor patients compared to controls (P<0.01, **). In vitro experiments confirmed that IgG4 monocyte differentiation into M2 macrophages, potentially enhancing the immunosuppressive phenotype in TLS.

Conclusion

IgG4 and IL-10 may contribute to immunosuppression in esophageal cancer by promoting the polarization of M2 macrophages within TLS, which could be a therapeutic target.

Monocyte and Macrophage Functions in Oncogenic Viral Infections

Monocytes and macrophages are part of innate immunity and constitute the first line of defense against pathogens. Bone marrow-derived monocytes circulate in the bloodstream for one to three days and then typically migrate into tissues, where they differentiate into macrophages. Circulatory monocytes represent 5% of the nucleated cells in normal adult blood. Following differentiation, macrophages are distributed into various tissues and organs to take residence and maintain body homeostasis. Emerging evidence has highlighted the critical role of monocytes/macrophages in oncogenic viral infections, mainly their crucial functions in viral persistence and disease progression. These findings open opportunities to target innate immunity in the context of oncogenic viruses and to explore their potential as immunotherapies.

Chitosan/hesperidin nanoparticles formulation: a promising approach against ethanol-induced gastric ulcers via Sirt1/FOXO1/PGC-1α/HO-1 pathway

Hesperidin (Hes) protects different organs from damage by acting as a potent antioxidant and anti-inflammatory. This study aims to evaluate the gastroprotective effects of free hesperidin and its chitosan nanoparticles (HNPs) against ethanol-induced gastric ulcers in rats, hypothesizing that HNPs will enhance bioavailability and therapeutic efficacy due to improved solubility and targeted delivery. HNPs were synthesized via ion gelation and characterized using TEM, SEM, and zeta potential analyses. Key assessments included gastric acidity, histological analysis, and markers of inflammation, oxidative stress, and apoptosis. HNPs significantly decreased gastric acidity, reduced inflammatory and apoptotic markers, and enhanced antioxidant enzyme activities compared to free hesperidin and esomeprazole. Furthermore, Sirt-1, PGC-1α, HO-1, and FOXO1 gene expression were also evaluated. HNPs raised Sirt-1, PGC-1α, HO-1, and downregulated FOXO1, and they suppressed the activities of NF-κB p65, COX-2, IL-1β, CD86, FOXO1 P53, and caspase-3 and increased Sirt-1 activity. HNPs treatment notably restored antioxidant enzyme activity, reduced oxidative stress and inflammatory markers, and improved histological outcomes more effectively than free hesperidin and esomeprazole. These results indicate that chitosan nanoparticles significantly enhance the gastroprotective effects of hesperidin against ethanol-induced gastric ulcers, potentially offering a more effective therapeutic strategy. Further research should explore the clinical applications of HNPs in human subjects.

Immunometabolism of ferroptosis in the tumor microenvironment

Ferroptosis is an iron-dependent form of cell death that results from excess lipid peroxidation in cellular membranes. Within the last decade, physiological and pathological roles for ferroptosis have been uncovered in autoimmune diseases, inflammatory conditions, infection, and cancer biology. Excitingly, cancer cell metabolism may be targeted to induce death by ferroptosis in cancers that are resistant to other forms of cell death. Ferroptosis sensitivity is regulated by oxidative stress, lipid metabolism, and iron metabolism, which are all influenced by the tumor microenvironment (TME). Whereas some cancer cell types have been shown to adapt to these stressors, it is not clear how immune cells regulate their sensitivities to ferroptosis. In this review, we discuss the mechanisms of ferroptosis sensitivity in different immune cell subsets, how ferroptosis influences which immune cells infiltrate the TME, and how these interactions can determine epithelial-to-mesenchymal transition (EMT) and metastasis. While much focus has been placed on inducing ferroptosis in cancer cells, these are important considerations for how ferroptosis-modulating strategies impact anti-tumor immunity. From this perspective, we also discuss some promising immunotherapies in the field of ferroptosis and the challenges associated with targeting ferroptosis in specific immune cell populations.

Skin Telocytes Could Fundament the Cellular Mechanisms of Wound Healing in Platelet-Rich Plasma Administration

For more than 40 years, autologous platelet concentrates have been used in clinical medicine. Since the first formula used, namely platelet-rich plasma (PRP), other platelet concentrates have been experimented with, including platelet-rich fibrin and concentrated growth factor. Platelet concentrates have three standard characteristics: they act as scaffolds, they serve as a source of growth factors and cytokines, and they contain live cells. PRP has become extensively used in regenerative medicine for the successful treatment of a variety of clinical (non-)dermatological conditions like alopecies, acne scars, skin burns, skin ulcers, muscle, cartilage, and bone repair, and as an adjuvant in post-surgery wound healing, with obvious benefits in terms of functionality and aesthetic recovery of affected tissues/organs. These indications were well documented, and a large amount of evidence has already been published supporting the efficacy of this method. The primordial principle behind minimally invasive PRP treatments is the usage of the patient's own platelets. The benefits of the autologous transplantation of thrombocytes are significant, representing a fast and economic method that requires only basic equipment and training, and it is biocompatible, thus being a low risk for the patient (infection and immunological reactions can be virtually disregarded). Usually, the structural benefits of applying PRP are attributed to fibroblasts only, as they are considered the most numerous cell population within the interstitium. However, this apparent simplistic explanation is still eluding those different types of interstitial cells (distinct from fibroblasts) that are residing within stromal tissue, e.g., telocytes (TCs). Moreover, dermal TCs have an already documented potential in angiogenesis (extra-cutaneous, but also within skin), and their implication in skin recovery in a few dermatological conditions was attested and described ultrastructurally and immunophenotypically. Interestingly, PRP biochemically consists of a series of growth factors, cytokines, and other molecules, to which TCs have also proven to have a positive expression. Thus, it is attractive to hypothesize and to document any tissular collaboration between cutaneous administered PRP and local dermal TCs in skin recovery/repair/regeneration. Therefore, TCs could be perceived as the missing link necessary to provide a solid explanation of the good results achieved by administering PRP in skin-repairing processes.