Identification of splenic reservoir monocytes and their deployment to inflammatory sites

Distribution, metabolism, and excretion of [14C] purinostat mesylate, a novel selective HDAC I/IIb inhibitor, in rats analyzed by high-performance liquid chromatography coupled with LTQ orbitrap mass spectrometry/radioactivity monitoring

Purinostat Mesylate (PM) is a novel and highly efficient selective histone deacetylase (HDAC) I/IIb inhibitor for hematologic tumor treatment that was granted Investigational New Drug (IND) approval for clinical investigation by the National Medical Products Administration and is currently in phase IIb clinical trials for relapsed/refractory diffuse large B-cell lymphoma. In this paper, the excretion, distribution, and metabolism properties of this IND were researched by High-Performance Liquid Chromatography coupled with LTQ Orbitrap Mass Spectrometry/Radioactivity Monitoring (HPLC-LTQ-Orbitrap-MS/RAM) and liquid scintillation counting. Following a single intravenous dose of [14C] PM to rats, a total of 98.49 % of the dose was recovered from intact rats within 0-168 h post-dose, with 14.16 % in urine and 83.15 % in feces, most of which was recovered within the first 24 h post-dose. For bile duct cannulated rats, a total of 95.54 % of the dose was recovered, with 62.37 % in bile, 23.37 % in urine and 8.58 % in feces within 0-72 h post-dose, suggesting that [14C] PM was excreted mainly into feces via biliary excretion. [14C] PM was distributed widely and eliminated rapidly throughout the body, with the lung, liver, kidney and intestine as the main organs. Interestingly, slow elimination was observed in the spleen, which could benefit the functional restoration of the spleen in hematological tumors. In terms of metabolism, [14C] PM underwent an extensive metabolic transformation in rats. Fourteen metabolites were tentatively identified, with major phase I metabolic pathways encompassing reduction, N-dealkylation, and oxidative deamination. Concomitantly, the primary phase II metabolic routes involved acetylation and glucuronic acid conjugation. This study was the first comprehensive PM pharmacokinetic study utilizing [14C] isotope labeling technology.

Specialized Pro-Resolving Mediators as Emerging Players in Cardioprotection: From Inflammation Resolution to Therapeutic Potential

AIM

Timely myocardial reperfusion is essential for restoring blood flow to post-ischemic tissue, thereby reducing cardiac injury and limiting infarct size. However, this process can paradoxically result in additional, irreversible myocardial damage, known as myocardial ischemia-reperfusion injury (MIRI). The goal of this review is to explore the role of specialized pro-resolving mediators (SPMs) in atherosclerosis and MIRI, and to assess the therapeutic potential of targeting inflammation resolution in these cardiovascular conditions.

METHODS

This review summarizes current preclinical and clinical evidence on the involvement of SPMs in the pathogenesis of atherosclerosis and MIRI, acknowledging that several cellular and molecular aspects of their mechanisms of action remain to be fully elucidated.

RESULTS

MIRI is a complex phenomenon in which inflammation, initially triggered during ischemia and further amplified upon reperfusion, plays a central role in its pathogenesis. Various cellular and molecular players mediate the initial pro-inflammatory response and the subsequent anti-inflammatory reparative phase following acute myocardial infarction (AMI), contributing both to ischemia- and reperfusion-induced damage as well as to the healing process. SPMs have emerged as key endogenous immunoresolvents with potent anti-inflammatory, antioxidant, and pro-resolving properties that contribute to limit excessive acute inflammation and promote tissue repair. While dysregulated SPM-related signaling has been linked to various cardiovascular diseases (CVD), their precise role in AMI and MIRI remains incompletely understood.

CONCLUSION

Targeting inflammation resolution may represent a promising therapeutic strategy for mitigating atheroprogression and addressing a complex condition such as MIRI.

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.

Suppression of the Prostaglandin I2-Type 1 Interferon Axis Induces Extramedullary Hematopoiesis to Promote Cardiac Repair After Myocardial Infarction

BACKGROUND

Immune cells are closely associated with all processes of cardiac repair after myocardial infarction (MI), including the initiation, development, and resolution of inflammation. Spleen extramedullary hematopoiesis (EMH) serves as a crucial source of emergency mature blood cells that are generated through the self-renewal and differentiation of hematopoietic stem/progenitor cells (HSPCs). However, how EMH responds to MI and the role of EMH in cardiac repair after MI remains unclear.

METHODS

To assess the role of spleen EMH in MI, a Tcf21CreER Scfflox/flox MI mouse model with inhibited EMH was constructed. GFP+ (green fluorescent protein) hematopoietic stem cells were sorted from eGFP (enhanced GFP) mouse spleen by flow cytometry and injected into Tcf21CreER Scfflox/flox mice to test the sources of local inflammatory cells during MI. Using highly specific liquid chromatography-tandem mass spectrometry and single-cell RNA sequencing, we analyzed the lipidomic profile of arachidonic acid metabolites and the transcriptomes of HSPCs in the spleen after MI.

RESULTS

We found that MI enhanced EMH, as reflected by the increase in spleen weight and volume and the number of HSPCs in the spleen. The lack of EMH in Scf-deficient mice exacerbated tissue injury after MI. Analysis of the transcriptome of spleen HSPCs after MI revealed that the type 1 interferon pathway was substantially inhibited in hematopoietic stem cell /multipotent progenitor subclusters, and the absence of type 1 interferon signaling enhanced the MI-induced spleen EMH. Lipidomics analysis revealed that prostaglandin I2 (PGI2) was markedly reduced in the spleen. PGI2 suppressed MI-induced EMH through a PGI2 receptor (IP)-cyclic adenosine monophosphate-453p-SP1 cascade in spleen HSPCs. Hematopoietic cell-specific IP-deficient mice exhibited enhanced EMH and improved cardiac recovery after MI.

CONCLUSIONS

Together, our findings revealed that a PGI2-IFN axis was involved in spleen EMH after MI, providing new mechanistic insights into spleen EMH after MI and offering a new therapeutic target for treating ischemic cardiac injury.

Impact of the spleen size on short-term prognosis in patients with cardiogenic shock receiving Impella-incorporated temporary mechanical circulatory support

The spleen size may be associated with mortality and morbidity in patients with heart failure, whereas its clinical implication in patients with cardiogenic shock receiving Impella-incorporated temporary mechanical circulatory support (MCS) remains unknown. Patients who received Impella-incorporated temporary MCS in our institute between March 2018 and August 2023 were eligible. The splenic volume index (SVI) was retrospectively calculated in all participants by measuring spleen size on the computed tomography obtained at the time of Impella placement. The impact of baseline SVI/central venous pressure (CVP) ratio on the 30-day mortality after Impella placement was evaluated. A total of 74 patients (70 years old, 62% men) were included. Median baseline SVI was 71.6 (50.3, 92.1) mL/m2. A lower SVI was associated with more decreased cardiac output and a higher SVI was associated with more elevated CVP (p < 0.05 for both). A lower SVI/CVP ratio was associated with higher 30-day mortality with an adjusted hazard ratio of 3.734 (95% confidence interval 1.397-9.981, p = 0.009). A baseline lower SVI/CVP ratio was associated with short-term mortality in patients receiving Impella-incorporated temporary MCS.

The efficacy and safety of stem cell therapy for ischemic stroke: a systematic review and network meta-analysis study

BACKGROUND AND AIM

Using a network meta-analysis, this study evaluates the clinical efficacy and safety of different types of stem cell therapy in regard to the recovery of neurological function, motor function, and daily living ability in ischemic stroke patients.

METHODS

A computerized search of the Cochrane Library, PubMed, Web of Science, Google Scholar, CNKI, and Wanfang Database was performed to collect randomized controlled clinical studies published from the time of library construction to December 2024, on the use of stem cells to improve function in patients with ischemic stroke.

RESULTS

A total of 19 studies and 1055 patients were included, comprising five stem cell types: bone marrow mononuclear cells (BMMNC), bone marrow mesenchymal stem cells (BMSC), progenitor cells (PC), peripheral blood stem cells (PBSC), and umbilical cord blood mesenchymal stem cells (UBMSC). A network meta-analysis showed that, in terms of National Institute of Health Stroke Scale (NIHSS) scores, the ranked results of different stem cell transplants were: UBMSC [69.4%] > PBSC 29.2%] > BMSC [0.8%] > PC [0.6%] > BMMNC [0.0%] > CRT [0.0%]. In terms of Modified Rankin Scale (mRS) scores, the ranked results of different stem cell transplants were: BMMNC [66.8%] > PBSC [31.7%] > PC [1.3%] > BMSC [0.2%] > CRT [0%]. In terms of Modified Barthel Index (MBI) scores, the ranked results of different stem cell transplants were: BMMNC [56.3%] > PC [34.2%] > BMSC [9.5%] > CRT [0%]. In terms of Fugl-Meyer Assessment (FMA) scores, the results of the ranking of different stem cell transplants were: BMMNC [79.3%] > BMSC [17.3%] > UBMSC [3.4%] > CRT [0%].

CONCLUSION

UBMSC had the best efficacy in repairing neurological function in patients with ischemic stroke. BMMNC had the best efficacy in improving motor function and daily living ability in patients with ischemic stroke. BMMNC had a superior overall effect.

Multiorgan Imaging for Interorgan Crosstalk in Cardiometabolic Diseases

Cardiometabolic diseases encompass a group of conditions characterized by metabolic and inflammatory abnormalities that increase the risk of diabetes and cardiovascular disease. These syndromes involve multiple organs, including the heart, arterial system, brain, skeletal muscle, adipose tissue, hematopoietic system, liver, kidneys, and pancreas. The crosstalk between these organs contributes to the development of disease. Advances in imaging techniques, such as magnetic resonance imaging, magnetic resonance spectroscopy, computed tomography, and positron emission tomography, have revolutionized the evaluation of these conditions. Hybrid imaging modalities, such as positron emission tomography/computed tomography and positron emission tomography/magnetic resonance imaging, provide unique insights into the anatomy and metabolic alterations occurring in response to cardiometabolic risk factors. These methods are particularly valuable for assessing multisystemic involvement and interorgan crosstalk, revealing critical interactions such as the brain-heart axis, the heart-liver axis, and the fat-muscle-heart dynamics. This review discusses the role of state-of-the-art imaging techniques in evaluating the pathophysiological mechanisms underlying these complex syndromes and the clinical applications of the different imaging techniques in the assessment of cardiometabolic diseases.

Contributions of Noncardiac Organ-Heart Immune Crosstalk and Somatic Mosaicism to Heart Failure: Current Knowledge and Perspectives

Heart failure is the final outcome of most cardiovascular diseases and shares risk factors with other cardiovascular pathologies. Among these, inflammation plays a central role in disease progression and myocardial remodeling. Over the past 2 decades, numerous studies have explored immune-related mechanisms in cardiovascular disease, highlighting the importance of immune cross-talk between the heart and extra-cardiac organs, including bone marrow, spleen, liver, gut, and adipose tissue. This review examines how immune interactions among these organs contribute to heart failure pathogenesis, with a focus on clonal hematopoiesis, an age-related alteration of hematopoietic stem cells that fosters pathological bone marrow-heart communication. Additionally, we explore recent advances in the understanding of clonal hematopoiesis and its role in heart failure, emphasizing its implications for prognosis and potential therapeutic interventions. By integrating insights from immunology, metabolism, and aging, we provide a comprehensive perspective on the immunologic determinants of heart failure, paving the way for precision medicine approaches aimed at mitigating cardiovascular risk.

Neural Mechanisms in Cardiovascular Health and Disease

Although the neurocardiac axis is central to cardiovascular homeostasis, its dysregulation drives heart failure and cardiometabolic diseases. This review examines the bidirectional interplay between the autonomic nervous system and the heart, highlighting the role of this interplay in disease progression and its therapeutic potential. The autonomic nervous system modulates cardiac function and vascular tone through its sympathetic and parasympathetic branches. However, in heart failure, chronic sympathetic overdrive and parasympathetic withdrawal exacerbate myocardial remodeling and metabolic dysfunction, both of which are exacerbated by cardiometabolic conditions such as obesity and diabetes. These conditions are increasingly recognized to impair neurocardiac regulation, thereby promoting inflammation and adverse outcomes. An important emerging area concerns neuroimmune control, in which the brain orchestrates systemic inflammation through circuits involving the bone marrow, spleen, and other organs, thereby amplifying cardiovascular damage. This neuroimmune axis integrates peripheral signals to influence immune responses that contribute to disease progression. Lifestyle factors, such as stress, sleep, exercise, and diet, affect autonomic and immune balance and, thus, cardiovascular disease. Therapeutically, targeting neurocardiac and neuroimmune pathways pharmacologically or via neuromodulation (eg, vagal or splenic nerve stimulation) offers promise although the clinical translation of the latter remains challenging. In this review, we synthesize preclinical and clinical data to highlight the neurocardiac axis as a critical nexus in heart failure and cardiometabolic disease. Harnessing neuroimmune and neurocardiac interactions may inform precision approaches to reduce the burden of these conditions.

Myeloid Fatty Acid Metabolism Activates Neighboring Hematopoietic Stem Cells to Promote Heart Failure With Preserved Ejection Fraction

BACKGROUND

Despite the high morbidity and mortality of heart failure with preserved ejection fraction (HFpEF), treatment options remain limited. The HFpEF syndrome is associated with a high comorbidity burden, including high prevalence of obesity and hypertension. Although inflammation is implicated to play a key role in HFpEF pathophysiology, underlying causal mechanisms remain unclear.

METHODS

Comparing patient samples and animal models, we defined the innate immune response during HFpEF in situ and through flow cytometry and single-cell RNA sequencing. After identifying transcriptional and cell signatures, we implemented a high-fat diet and hypertensive model of HFpEF and tested roles for myeloid and hematopoietic stem cells during HFpEF. Contributions of macrophage metabolism were also evaluated, including through mass spectrometry and carbon labeling. Primary macrophages were studied ex vivo to gain insight into complementary cell-intrinsic mechanisms.

RESULTS

Here we report evidence that patients with cardiometabolic HFpEF exhibit elevated peripheral blood hematopoietic stem cells. This phenotype was conserved across species in a murine mode of high-fat diet and hypertension. Hematopoietic stem cell proliferation was coupled to striking remodeling of the peripheral hematopoietic stem cell niche and expression of the macrophage adhesion molecule Vcam1. This could be partially inhibited by sodium-glucose cotransporter-2 inhibitors and explained by elevated fatty acid metabolism in macrophage mitochondria, which in turn remodeled the Vcam1 promoter to enhance its expression.

CONCLUSIONS

These findings identify a significant new stem cell signature of cardiometabolic HFpEF and support a role for myeloid maladaptive fatty acid metabolism in the promotion of systemic inflammation and cardiac diastolic dysfunction.

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.

CD163 + M2-like monocytes increase in pregnant women with first-attempted frozen embryo transfer

Macrophages play a vital role in endometrial receptivity and embryo implantation. However, it remains unclear if macrophages in peripheral blood is associated with pregnancy outcomes of frozen embryo transfer during implantation window. 50 patients preparing for the first time of frozen embryo transfer (FET) and 17 patients with recurrent implantation failure (RIF) from December 2022 to March 2023 were included in our present study. The percentages of peripheral macrophages and other immune cells (B-cell, T-cell, NK cell) were evaluated by flow cytometry. The concentrations of cytokines were verified with an IMMULITE 1000 Immunoassay System. FET patients were categorized into pregnant and nonpregnant groups according to clinical outcomes, respectively. The proportion of peripheral CD68+CD163+ M2 macrophages was increased in pregnant women than in nonpregnant women among the first time of FET patients. CD4+ T helper cells were positively correlated with M2-like macrophages in these women. The pregnancy rate of women with higher peripheral CD163 + M2-like monocytes increased compared with women with lower peripheral CD163 + M2-like monocytes in an independent cohort according to the cutoff value of CD163 + M2-like monocytes in ROC curve. Our findings revealed that peripheral CD163+ M2 macrophages in implantation window were associated with pregnancy outcomes. This indicated that the importance of peripheral M2 macrophages at the implantation site for pregnancy success.

Immune Evasion in Cancer Metastasis: An Unappreciated Role of Monocytes

Metastasis is the leading cause of cancer-related deaths. During the metastatic cascade, cancer cells tightly interact with immune cells influencing each other in the tumor microenvironment and systemically. Monocytes are important components of immune evasion and critical regulators of cancer progression. They circulate through the bloodstream and contribute to the formation of a pro-tumor microenvironment both in the tumor and pre-metastatic niche. Whereas monocyte participation in cancer development and response to therapy has been described extensively, its impact on metastasis remains a completely uncovered area. This review first summarizes data concerning the influence of monocytes on metastasis formation during their presence in the circulation, primary tumor, and pre-metastatic niche. We also highlight the latest examinations into the clinical relevance of targeting monocytes to prevent metastasis.

Cardiosplenic axis-targeted immunomodulatory liposome for myocardial ischemia-reperfusion injury treatment

Monocyte/macrophage (Mo/Mϕ) infiltration is critical in myocardial ischemia-reperfusion injury (MIRI). However, the complex composition of the myocardium severely hinders drug accumulation and makes it challenging to modulate the Mo/Mϕ immune response at the MIRI site. The spleen, acting as a Mo/Mϕ reservoir, plays a crucial role in the development of MIRI along the cardiosplenic axis. Compared to directly delivering medications to the MIRI site, targeting the spleen for Mo/Mϕ immunomodulation provides an alternative strategy to modulate the immunological phenotype on-site. Therefore, we developed a melatonin-loaded liposome (ST-MT@lipo2) that specifically targets the spleen and can effectively regulate the immunological response of splenic monocytes and macrophages, consequently enhancing their immune response at the site of MIRI. Additionally, the splenectomy mouse model revealed that ST-MT@lipo2 regulated MIRI's immune response through the cardiosplenic axis by regulating the MCP-1/CCR2 pathway to reduce circulating inflammatory monocyte migration from the spleen to the MIRI site. Moreover, pathological staining and echocardiography showed that ST-MT@lipo2 reduced myocardial damage and improved cardiac function in MIRI mice. This study demonstrates the crucial importance of modulating the immune response in the cardiosplenic axis for treating MIRI, which also inspired the treatments for inflammatory diseases by controlling the spleen immunological milieu.

Cellular effects of splenectomy on liver regeneration after 70% resection

Introduction

Mammalian liver regeneration is a complex process, the regulation of which involves many mechanisms. The immune system has a pronounced influence on the course of reparative processes in mammals. The hepatic portal vein system provides a direct anatomical connection between the liver and the spleen - the largest lymphoid organ in mammals. Accordingly, the spleen may have a direct effect on liver regeneration as a source of biologically active substances and migrating leukocytes. Specific mechanisms of such influence remain understudied. This study aimed to assess the effect of splenectomy on liver regeneration after 70% resection in mouse model.

Methods

Murine model of liver regeneration after 70% resection was reproduced in C57BL/6 male mice, some of them splenectomized 7 days before the liver resection. Proliferation marker Ki67 in the liver was assessed by immunohistochemistry and the protein content for cyclin D1, cyclin A2 and p53 in the liver was assessed by Western blotting. Using TUNEL assay, an increase in the number of apoptotic cells was detected. The highest number of TUNEL+ cells was detected 1 day after liver resection, while the number of apoptotic cells in animals with prior splenectomy was significantly lower compared to animals with preserved spleen. The dynamics of Ly6C+ monocytes and Ly6G+ leukocytes were studied by flow cytometry. Macrophages were isolated from the regenerating liver using magnetic sorting for F4/80 and their gene expression profiles were analyzed using Clariom™ S Assay, mouse. Peripheral blood and splenic monocytes were isolated by magnetic sorting for CD115 and analyzed by Illumina HiSeq 2500 platform RNA sequencing. Migration of peripheral blood and splenic leukocytes to the regenerating liver was studied using allogeneic transplantation of cells derived from B10-GFP mice.

Results and discussion

Animals splenectomized prior to the liver resection showed higher rates of cell proliferation along with higher content of р53 protein in the remnant organ. Splenectomy also correlated with decreased rates of Ly6C+ monocyte and Ly6G+ leukocyte migration. Macrophages in the regenerating liver were transcriptomically enriched for signaling pathways associated with monocyte migration, cell adhesion and cell death. As shown by the GFP+ leukocyte transplantation experiment, the leukocytes migrating to the regenerating liver are mainly of splenic origin. According to high-throughput sequencing data, these cells express high levels of cell adhesion molecules. The spleen has a significant effect on liver regeneration through secretion of biologically active substances and migrating leukocytes. Pre-splenectomy leads to a more pronounced liver damage response after 70% resection, as indicated by higher rates of cell proliferation, higher p53 protein content and cell death-associated signaling pathway activation.

Regulatory T cells suppress GM-CSF-producing T helper cells via IL-2 modulation to restrain immunopathology

Regulatory T (Treg) cells are critical for maintaining peripheral tolerance and preventing autoimmunity. Treg cell depletion or dysfunction results in fatal multiorgan inflammation linked to unrestrained effector T cell expansion. Here, we combine in vivo gene targeting and fate-mapping with high-dimensional cytometry to identify Treg cells' steady-state function and suppressive mechanisms that prevent autoimmune inflammation and dissect the T helper (TH) cell-derived cytokines and responding cells executing tissue damage upon global loss of peripheral tolerance. We unveil that type 1 cytokines, granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon (IFN)γ, but not interleukin (IL)-17A, direct the ensuing immunopathology and mortality. GM-CSF orchestrates tissue invasion by monocytes and granulocytes and enhances their reactive oxygen species production and phagocytic capability. IL-2 modulation by Treg cells is crucial in restraining pathogenic GM-CSF-producing TH cells. Our study highlights the critical role of Treg cells and IL-2 signaling in controlling GM-CSF-producing TH cells and type 1 responses to curb phagocyte-mediated tissue destruction.

Targeting Splenic Myeloid Cells with Nanobiologics to Prevent Postablative Pancreatic Cancer Recurrence via Inducing Antitumor Peripheral Trained Immunity

Minimally invasive irreversible electroporation ablation shows promise for pancreatic cancer (PCa), but the high recurrence and metastasis rates pose a therapeutic challenge for loco-regional ablation treatment. Immunotherapy holds promise for preventing tumor recurrence, however, its efficacy against PCa remains limited. Here, using a preclinical model of PCa, it is identified that tumor development dramatically restructures the splenic immune landscape characterized by increased frequency of myeloid cells. Further, nanobiologics with high affinity for splenic myeloid cells using erythrocyte membrane fused with apoA1-modified liposomes are presented. Biocompatible CaCO3 nanoparticles are incorporated to serve as a release reservoir of immunomodulatory therapeutics (muramyl dipeptide, MDP). The nanobiologics, MDCa@RBC-Alipo, induce antitumor-trained immunity by epigenetically and metabolically rewiring splenic myeloid cells, thereby overcoming the immunosuppressive tumor microenvironment in residual PCa following irreversible electroporation ablation. This approach enhances the therapeutic efficacy of aPD-L1 and significantly inhibits tumor recurrence and hemorrhagic ascites development. The trafficking of MDP directly to the spleen highlights a previously uncharacterized pathway for inducing peripheral trained immunity, thereby presenting a novel therapeutic approach for locally advanced PCa treatment.

RAS-p110α signalling in macrophages is required for effective inflammatory response and resolution of inflammation

Macrophages are crucial in the body's inflammatory response, with tightly regulated functions for optimal immune system performance. Our study reveals that the RAS-p110α signalling pathway, known for its involvement in various biological processes and tumourigenesis, regulates two vital aspects of the inflammatory response in macrophages: the initial monocyte movement and later-stage lysosomal function. Disrupting this pathway, either in a mouse model or through drug intervention, hampers the inflammatory response, leading to delayed resolution and the development of more severe acute inflammatory reactions in live models. This discovery uncovers a previously unknown role of the p110α isoform in immune regulation within macrophages, offering insight into the complex mechanisms governing their function during inflammation and opening new avenues for modulating inflammatory responses.

Unraveling the significance of innate inflammation in vascular disease

Atheroma formation is initiated by the activation of endothelial and smooth muscle cells, as well as immune cells, including neutrophils, lymphocytes, monocytes, macrophages, and dendritic cells. Monocytes, macrophages, and neutrophils are the innate immune cells that provide a rapid initial line of defence against vascular disease. These cells have a short lifespan and cannot retain memories, making them potential therapeutic targets for the inflammatory process associated with atherosclerosis. In addition, macrophages comprise the majority of vessel wall infiltrates and are, therefore, implicated in all stages of atherosclerosis progression. Neutrophils are the most common type of leukocyte found in circulation, and their high levels of matrix-degrading protease explain their significance in fibrous cap destabilization. However, the activation of immune cells becomes more complex by various microenvironmental stimuli and cytokines, which ultimately transform immune cells into their pro-inflammatory state. Different types of macrophage subsets with distinct functions in inflammation, such as M1 macrophages, cause an increase in pro-inflammatory cytokines and produce reactive oxygen species and nitric oxide, further worsening the disease. This review aims to shed light on immune-mediated inflammation in cardiovascular disease by focusing on the role of macrophage subsets in vascular inflammation and plaque stability, as well as the interaction between neutrophils and monocyte-macrophages.

Myelopoiesis is temporally dynamic and is regulated by lifestyle to modify multiple sclerosis

Monocytes and neutrophils from the myeloid lineage contribute to multiple sclerosis (MS), but the dynamics of myelopoiesis during MS are unclear. Here we uncover a disease stage-specific relationship between lifestyle, myelopoiesis and neuroinflammation. In mice with relapsing-remitting experimental autoimmune encephalomyelitis (RR-EAE), myelopoiesis in the femur, vertebrae and spleen is elevated prior to disease onset and during remission, preceding the peaks of clinical disability and neuroinflammation. In progressive EAE (P-EAE), vertebral myelopoiesis rises steadily throughout disease, while femur and splenic myelopoiesis is elevated early before waning later during disease height. In parallel, sleep disruption or hyperlipidemia and cardiometabolic syndrome augment M-CSF generation and multi-organ myelopoiesis to worsen P-EAE clinical symptoms, neuroinflammation, and spinal cord demyelination, with M-CSF blockade abrogating these symptoms. Lastly, results from a previous trial show that Mediterranean diet restrains myelopoietic activity and myeloid lineage progenitor skewing and improves clinical symptomology of MS. Together, our data suggest that myelopoiesis in MS is dynamic and dependent on disease stage and location, and that lifestyle factors modulate disease by influencing M-CSF-mediated myelopoiesis.

The nonlinear correlation of neutrophil-lymphocyte ratio on 1-year mortality risk in patients with severe acute heart failure

BACKGROUND

This retrospective cohort study was designed to examine the relationship between the neutrophil-lymphocyte ratio (NLR) and the 1-year risk of death in patients with acute heart failure (AHF) in the intensive care unit (ICU).

METHODS

We retrospectively analyzed 1,176 patients with AHF from the MIMIC-IV database. Cox regression was used to evaluate the relationship between NLR and 1-year mortality risk after adjusting for covariates. Nonlinear associations and optimal NLR cutoff values were determined using restricted cubic splines. Propensity score matching was used to eliminate imbalances in the baseline confounders. Kaplan-Meier survival analysis further confirmed the correctness of the threshold. The ROC was used to evaluate the diagnostic accuracy of the NLR for long-term outcomes. Subgroup analyses were performed to assess the generality of NLR in specific populations.

RESULTS

The mortality rate was lowest in the lower tertile NLR group (< 5.43) and highest in the upper tertile group (> 13.53, P for trend < 0.001). NLR showed a nonlinear correlation with mortality (P for Non-linearity = 0.0075), with the risk increasing significantly when NLR exceeded 11.11. The AUC of NLR for predicting 1-year mortality was 0.579 (95%CI 0.542-0.617). The NLR was not significantly different from long-term outcomes in most groups, but the association was stronger in patients with AHF who did not have sepsis.

CONCLUSION

Elevated NLR, a marker of heightened systemic inflammation, was associated with a higher risk of 1-year mortality in ICU patients with AHF.

CLINICAL TRIAL NUMBER

Not applicable.

Cardiac resident macrophages in cardiovascular disease: from physiology to pathology

Cardiovascular disease (CVD) is the leading cause of death and disease burden worldwide. Macrophages are important components of the internal immune cells, which profoundly affects the internal environmental homeostasis and repair after injury. Cardiac resident macrophages have been shown to regulate a variety of myocardial physiology and pathological activities. Homeostatic resident macrophages in the heart promote angiogenesis, remove ageing and dying cells and participate in cardiac electrical conduction. However, the role of cardiac resident macrophages is still not fully understood despite the growing attention they have received. This review provides an overview of macrophage biology and highlights prominent and emerging interrelationships and functions between cardiac resident macrophages and CVD, aiming to prove a description of the functional diversity of cardiac resident macrophages in different CVD to explore potential options to regulate them. This may provide opportunities for successful therapeutic interventions to improve the prognosis of patients with CVD.

Neuroimmune circuits in the plaque and bone marrow regulate atherosclerosis

Atherosclerosis remains the leading cause of death globally. Although its focal pathology is atheroma that develops in arterial walls, atherosclerosis is a systemic disease involving contributions by many organs and tissues. It is now established that the immune system causally contributes to all phases of atherosclerosis. Recent and emerging evidence positions the nervous system as a key modulator of inflammatory processes that underlie atherosclerosis. This neuroimmune cross-talk, we are learning, is bidirectional, and immune-regulated afferent signalling is becoming increasingly recognized in atherosclerosis. Here, we summarize data and concepts that link the immune and nervous systems in atherosclerosis by focusing on two important sites, the arterial vessel and the bone marrow.

Redefining Macrophage Heterogeneity in Atherosclerosis: A Focus on Possible Therapeutic Implications

Atherosclerosis is a lipid disorder where modified lipids (especially oxidized LDL) induce macrophage foam cell formation in the aorta. Its pathogenesis involves a continuum of persistent inflammation accompanied by dysregulated anti-inflammatory responses. Changes in the immune cell status due to differences in the lesional microenvironment are crucial in terms of plaque development, its progression, and plaque rupture. Ly6Chi monocytes generated through both medullary and extramedullary cascades act as one of the major sources of plaque macrophages and thereby foam cells. Both monocytes and monocyte-derived macrophages also participate in pathological events in atherosclerosis-associated multiple organ systems through inter-organ communications. For years, macrophage phenotypes M1 and M2 have been shown to perpetuate inflammatory and resolution responses; nevertheless, such a dualistic classification is too simplistic and contains severe drawbacks. As the lesion microenvironment is enriched with multiple mediators that possess the ability to activate macrophages to diverse phenotypes, it is obvious that such cells should demonstrate substantial heterogeneity. Considerable research in this regard has indicated the presence of additional macrophage phenotypes that are exclusive to atherosclerotic plaques, namely Mox, M4, Mhem, and M(Hb) type. Furthermore, although the concept of macrophage clusters has come to the fore in recent years with the evolution of high-dimensional techniques, classifications based on such 'OMICS' approaches require extensive functional validation as well as metabolic phenotyping. Bearing this in mind, the current review provides an overview of the status of different macrophage populations and their role during atherosclerosis and also outlines possible therapeutic implications.

A Spleen-Targeted Tolerogenic mRNA-LNPs Vaccine for the Treatment of Experimental Asthma

Lipid nanoparticles (LNPs)-based mRNA vaccines have witnessed their great advantages in the fight against infectious diseases. However, the pro-inflammatory properties of mRNA-LNPs vaccines may hinder the induction of antigen-specific tolerogenic immune responses. Here, it is demonstrated that stearic acid-doped LNPs co-loaded with nucleoside-modified mRNA and celastrol selectively target spleen, convert their adjuvanticity and promote a tolerogenic rather than immunogenic DCs phenotype. Furthermore, the tolerogenic mRNA vaccine also invokes the generation of antigen-specific regulatory T cells (Tregs) in the spleen and migration of the induced Tregs to the lung. In a mouse model of allergic asthma, immunization with the tolerogenic mRNA vaccine significantly alleviated symptom induction, reducing eosinophilic granulocyte accumulation and mucus secretion. In conclusion, this spleen-targeted mRNA-LNPs vaccine platform induces tolerogenic immune responses, offering promise for the development of therapeutics against allergic asthma and other conditions requiring immune tolerance modulation.

Myocarditis and Inflammatory Cardiomyopathy in Dilated Heart Failure

Inflammatory cardiomyopathy is a condition that is characterised by the presence of inflammatory cells in the myocardium, which can lead to a significant deterioration in cardiac function. The etiology of this condition involves multiple factors, both infectious and non-infectious causes. While it is primarily associated with viral infections, other potential causes include bacterial, protozoal, or fungal infections, as well as a wide variety of toxic substances and drugs, and systemic immune-mediated pathological conditions. In spite of comprehensive investigation, the presence of inflammatory cardiomyopathy accompanied by left ventricular dysfunction, heart failure or arrhythmia is indicative of an unfavourable outcome. The reasons for the occurrence of either favourable outcomes, characterised by the absence of residual myocardial injury, or unfavourable outcomes, marked by the development of dilated cardiomyopathy, in patients afflicted by the condition remain to be elucidated. The relative contributions of pathogenic agents, genomic profiles of the host, and environmental factors in disease progression and resolution remain subjects of ongoing discourse. This includes the determination of which viruses function as active inducers and which merely play a bystander role. It remains unknown which changes in the host immune profile are critical in determining the outcome of myocarditis caused by various viruses, including coxsackievirus B3 (CVB3), adenoviruses, parvoviruses B19 and SARS-CoV-2. The objective of this review is unambiguous: to provide a concise summary and comprehensive assessment of the extant evidence on the pathogenesis, diagnosis and treatment of myocarditis and inflammatory cardiomyopathy. Its focus is exclusively on virus-induced and virus-associated myocarditis. In addition, the extant lacunae of knowledge in this field are identified and the extant experimental models are evaluated, with the aim of proposing future directions for the research domain. This includes differential gene expression that regulates iron and lipid and metabolic remodelling. Furthermore, the current state of knowledge regarding the cardiovascular implications of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is also discussed, along with the open questions that remain to be addressed.

Targeted spleen modulation: a novel strategy for next-generation disease immunotherapy

The spleen, the largest lymphatic organ, comprises a diverse array of immunocytes in approximately one quarter of the body, including T cells, B cells, natural killer cells, and myeloid cells (such as dendritic cells, neutrophils, myeloid-derived suppressor cells, and macrophages). These immune cells undergo dynamic transitions and mobilization, enabling the spleen to execute a wide range of immunological functions. The spleen's structural organization and multicellular composition, along with its reservoir of lymphocytes, facilitate the capture and clearance of blood-borne antigens while also orchestrating both innate and adaptive immune responses. Additionally, the spleen plays critical roles in hematopoiesis and the removal of aged or damaged red blood cells. Despite being innervated by sympathetic (catecholaminergic) nerve fibers, the spleen lacks parasympathetic (vagal or cholinergic) innervation. The neuroimmune axis, particularly the interplay between sympathetic and parasympathetic nervous system immune circuits, significantly influences disease onset and progression. Extensive research employing physical, genetic, and pharmacological approaches has sought to directly modulate splenic immunocytes and activate neuroimmune interactions to restore immune homeostasis and counteract disease. Two primary mechanisms underlie these immunomodulatory interventions: (1) the cholinergic anti-inflammatory pathway, wherein norepinephrine released by splenic catecholaminergic fibers binds to β2-adrenergic receptors on CD4⁺ T cells, triggering acetylcholine secretion, which in turn suppresses inflammatory cytokine production in macrophages via α7 nicotinic acetylcholine receptor signaling, and (2) direct immunomodulation of splenic immunocytes, which regulates key genes and signaling pathways, alters cytokine secretion, and modulates ion flux to influence cellular functions. Among various therapeutic strategies, physical methods, particularly electrical stimulation and splenic ultrasound stimulation, have demonstrated the greatest promise for clinical applications in splenic immunomodulation and disease management.

New insights on extramedullary granulopoiesis and neutrophil heterogeneity in the spleen and its importance in disease

Neutrophils are traditionally viewed as uncomplicated exterminators that arrive quickly at sites of infection, kill pathogens, and then expire. However, recent studies employing modern transcriptomics coupled with novel imaging modalities have discovered that neutrophils exhibit significant heterogeneity within organs and have complex functional roles ranging from tissue homeostasis to cancer and chronic pathologies. This has revised the view that neutrophils are simplistic butchers, and there has been a resurgent interest in neutrophils. The spleen was described as a granulopoietic organ more than 4 decades ago, and studies indicate that neutrophils are briefly retained in the spleen before returning to circulation after proliferation. Transcriptomic studies have discovered that splenic neutrophils are heterogeneous and distinct compared with those in blood. This suggests that a unique hematopoietic niche exists in the splenic microenvironment, i.e., capable of programming neutrophils in the spleen. During severe systemic inflammation with an increased need of neutrophils, the spleen can adapt by producing neutrophils through emergency granulopoiesis. In this review, we describe the structure and microanatomy of the spleen and examine how cells within the splenic microenvironment help to regulate splenic granulopoiesis. A focus is placed on exploring the increase in splenic granulopoiesis to meet host needs during infection and inflammation. Emerging technologies such as single-cell RNA sequencing, which provide valuable insight into splenic neutrophil development and heterogeneity, are also discussed. Finally, we examine how tumors subvert this natural pathway in the spleen to generate granulocytic suppressor cells to promote tumor growth.

Splenic red pulp macrophages eliminate the liver-resistant Streptococcus pneumoniae from the blood circulation of mice

Invasive infections by encapsulated bacteria are the major cause of human morbidity and mortality. The liver resident macrophages, Kupffer cells, form the hepatic firewall to clear many encapsulated bacteria in the blood circulation but fail to control certain high-virulence capsule types. Here we report that the spleen is the backup immune organ to clear the liver-resistant serotypes of Streptococcus pneumoniae (pneumococcus), a leading human pathogen. Asplenic mice failed to control the growth of the liver-resistant pneumococci in the blood circulation. Immunologic and genetic analyses identified splenic red pulp (RP) macrophages as the major phagocytes for bacterial clearance. Furthermore, the plasma natural antibodies against the cell wall phosphocholine and the complement system were necessary for RP macrophage-mediated immunity. These findings have provided a conceptual framework for the innate defense against blood bacterial infections, a mechanistic explanation for the hyper-susceptibility of asplenic individuals to S. pneumoniae, and a proof of concept for developing vaccines and therapeutic antibodies against encapsulated pathogens.

Role of macrophages in cardiac arrhythmias: Pathogenesis and therapeutic perspectives

The pathophysiology of arrhythmias is complex, involving changes in cardiac contractile and conduction systems, electrical conduction heterogeneity, and structural alterations. Recent studies indicate that cardiac macrophages can induce arrhythmias by interacting with cardiomyocytes or altering tissue composition. Due to the heterogeneity and diversity, macrophages develop different cellular functions during pathological processes. This review identifies various macrophage subpopulations and focuses on their pathological mechanisms in arrhythmogenesis. Furthermore, we explore the interactions of macrophages with other immune cells and summarize the promising approaches for targeting macrophages in arrhythmias treatment. Macrophages directly or indirectly influence arrhythmogenesis through multiple systemic effects. Preclinical studies suggest that modifying macrophages' phenotype or regulating their activity may directly affect cardiac conduction. This review provides a theoretical basis for developing immunotherapies for patients with cardiac arrhythmias.

Infiltration by monocytes of the central nervous system and its role in multiple sclerosis: reflections on therapeutic strategies

Mononuclear macrophage infiltration in the central nervous system is a prominent feature of neuroinflammation. Recent studies on the pathogenesis and progression of multiple sclerosis have highlighted the multiple roles of mononuclear macrophages in the neuroinflammatory process. Monocytes play a significant role in neuroinflammation, and managing neuroinflammation by manipulating peripheral monocytes stands out as an effective strategy for the treatment of multiple sclerosis, leading to improved patient outcomes. This review outlines the steps involved in the entry of myeloid monocytes into the central nervous system that are targets for effective intervention: the activation of bone marrow hematopoiesis, migration of monocytes in the blood, and penetration of the blood-brain barrier by monocytes. Finally, we summarize the different monocyte subpopulations and their effects on the central nervous system based on phenotypic differences. As activated microglia resemble monocyte-derived macrophages, it is important to accurately identify the role of monocyte-derived macrophages in disease. Depending on the roles played by monocyte-derived macrophages at different stages of the disease, several of these processes can be interrupted to limit neuroinflammation and improve patient prognosis. Here, we discuss possible strategies to target monocytes in neurological diseases, focusing on three key aspects of monocyte infiltration into the central nervous system, to provide new ideas for the treatment of neurodegenerative diseases.

Monocyte-derived macrophages act as reinforcements when microglia fall short in Alzheimer's disease

The central nervous system (CNS) is endowed with its own resident innate immune cells, the microglia. They constitute approximately 10% of the total cells within the CNS parenchyma and act as 'sentinels', sensing and mitigating any deviation from homeostasis. Nevertheless, under severe acute or chronic neurological injury or disease, microglia are unable to contain the damage, and the reparative activity of monocyte-derived macrophages (MDMs) is required. The failure of the microglia under such conditions could be an outcome of their prolonged exposure to hostile stimuli, leading to their exhaustion or senescence. Here, we describe the conditions under which the microglia fall short, focusing mainly on the context of Alzheimer's disease, and shed light on the functions performed by MDMs. We discuss whether and how MDMs engage in cross-talk with the microglia, why their recruitment is often inadequate, and potential ways to augment their homing to the brain in a well-controlled manner.

Emerging mechanisms of organ crosstalk: The role of oxylipins

There is growing interest in the role of oxylipins in the pathophysiology of several diseases. This is accompanied by a limited but evolving evidence base describing augmented oxylipin concentrations in a range of complications including cardiovascular disease, obesity, liver disease and neurological disorders. Despite this, literature describing oxylipin profiles in blood and multiple organs is inconsistent and the mechanisms by which these profiles are altered, and the relationships between localised tissue and circulating oxylipins are poorly understood. Inflammation and immune response associated with disease requires communication across organs and physiological systems. For example, inflammation and comorbidities associated with obesity extend beyond the adipose tissue and affect the vascular, hepatobiliary and digestive systems amongst others. Communication between organs and physiological systems is implicated in the progression of disease as well as the maintenance of homeostasis. There is emerging evidence for the role of oxylipins as a mechanism of communication in organ crosstalk but the role of these in orchestrating multiple organ and system responses is poorly understood. Herein, we review evidence to support and describe the role of oxylipins in organ crosstalk via the cardiosplenic and gut-link axis. In addition, we review emerging mechanisms of oxylipin regulation, the gut microbiome and modification using nutritional intervention. Finally, we describe future perspectives for addressing challenges in measurement and interpretation of oxylipin research with focus on the host genome as a modifier of oxylipin profiles and response to dietary lipid intervention.

Monocytes across life span in HIV infection: lights and shadows

PURPOSE OF REVIEW

This review highlights the role of monocytes in the pathogenesis of HIV-1 infection, focusing on their involvement in the inflammatory response and their function as viral targets and long-term reservoirs.

RECENT FINDINGS

Monocytes have been categorized into three subsets: classical, intermediate, and nonclassical, each with distinct functional characteristics. Advances in genetic sequencing technologies have enabled a more in-depth exploration of the phenotypic and functional variations among these subsets, particularly in the context of HIV. These findings underscore their role as crucial components of the immune response and as reservoirs for the virus.

SUMMARY

Previous studies on the role of monocytes have demonstrated their contribution to persistent infection and chronic immune activation, especially in adults living with HIV. The lessons learned from these studies should now be harnessed to design studies focused on newborns and children with vertically acquired HIV.

The microbiota-gut-brain axis in Huntington's disease: pathogenic mechanisms and therapeutic targets

Huntington's disease (HD) is a currently incurable neurogenerative disorder and is typically characterized by progressive movement disorder (including chorea), cognitive deficits (culminating in dementia), psychiatric abnormalities (the most common of which is depression), and peripheral symptoms (including gastrointestinal dysfunction). There are currently no approved disease-modifying therapies available for HD, with death usually occurring approximately 10-25 years after onset, but some therapies hold promising potential. HD subjects are often burdened by chronic diarrhea, constipation, esophageal and gastric inflammation, and a susceptibility to diabetes. Our understanding of the microbiota-gut-brain axis in HD is in its infancy and growing evidence from preclinical and clinical studies suggests a role of gut microbial population imbalance (gut dysbiosis) in HD pathophysiology. The gut and the brain can communicate through the enteric nervous system, immune system, vagus nerve, and microbiota-derived-metabolites including short-chain fatty acids, bile acids, and branched-chain amino acids. This review summarizes supporting evidence demonstrating the alterations in bacterial and fungal composition that may be associated with HD. We focus on mechanisms through which gut dysbiosis may compromise brain and gut health, thus triggering neuroinflammatory responses, and further highlight outcomes of attempts to modulate the gut microbiota as promising therapeutic strategies for HD. Ultimately, we discuss the dearth of data and the need for more longitudinal and translational studies in this nascent field. We suggest future directions to improve our understanding of the association between gut microbes and the pathogenesis of HD, and other 'brain and body disorders'.

Novel carbon dots with dual Modulatory effects on the bone marrow and spleen as a potential therapeutic candidate for treating spinal cord injury

Spinal cord injury triggers leukocyte mobilization from the peripheral circulation to the injury site, exacerbating spinal cord damage. Simultaneously, bone marrow hematopoietic stem cells (HSCs) and splenic leukocytes rapidly mobilize to replenish the depleted peripheral blood leukocyte pool. However, current treatments for spinal cord injuries overlook interventions targeting peripheral immune organs and tissues, highlighting the need to develop novel drugs capable of effectively regulating peripheral immunity and treating spinal cord injuries. In this study, we designed, synthesized, and characterized novel Ejiao carbon dots (EJCDs) that inhibit myeloid cell proliferation and peripheral migration by promoting HSC self-renewal, and distinct differentiation into erythroid progenitors in vitro and in vivo. Additionally, EJCDs attenuate the immune response in the spleen, leukocytes' reservoir, following spinal cord injury by diminishing the local infiltration of monocytes and macrophages while promoting motor function recovery. These effects are mediated through the downregulation of CCAAT enhancer binding protein-β expression in the spleen and the upregulation of FZD4 protein expression in Lin- Sca-1+ c-kit+ cells (LSKs) within the bone marrow. Our findings demonstrate that EJCDs effectively reduce myeloid cell infiltration post-spinal cord injury and promote neurological recovery, making them promising therapeutic candidates for treating spinal cord injuries.

Identification of splenic IRF7 as a nanotherapy target for tele-conditioning myocardial reperfusion injury

The sequestration of nanoparticles by mononuclear phagocyte system is a challenge for the use of nanotherapy for treating cardiovascular diseases due to the conventionally perceived loss of therapeutic potency. Here, we revitalize cardiovascular nanotherapy by unlocking an alternative route in which nanomedicines are redirected to the spleen, leveraging its potential as a highly efficient and targeted site for remote conditioning, or tele-conditioning myocardial reperfusion injury. The theoretical foundation underpinning is the splenogenic nature of recruited monocytes upon myocardial reperfusion in the acute stage, which is confirmed through murine heterotopic spleen transplantation. Single-cell RNA-seq analysis identifies IRF7 as a pivotal mediator in the spleen-heart communication network that is initially induced in the spleen and orchestrates functional changes in myocardial macrophages. Spleen-related induction of IRF7 is also valid in human myocardial reperfusion scenarios. In addition, in a murine preclinical model of male mice, temporal inhibition of splenic IRF7 through the designed spleen-targeting erythrosome engineered with the targeting peptide RP182, termed as STEER nanoparticles, mitigates the acute-stage innate immune responses and improves the cardiac function in the long term. In contrast, systemic inhibition, genetic knockout of IRF7 or absolute depletion of splenic monocytes does not have therapeutic benefits, indicating the superiority of nanoparticle-based targeted treatment. These findings establish the spleen as a naturally favored site for nanoparticle-based treatments, offering promising avenues for managing myocardial reperfusion injury.

IL-27 producers in a neonatal BCG vaccination model are a heterogenous population of myeloid cells that are diverse in phenotype and function

Tuberculosis (TB) is a serious public health concern in many regions of the world and the only approved vaccine to prevent TB is the live-attenuated BCG vaccine. Despite being widely used, the BCG vaccine fails to prevent pulmonary TB in adults. The BCG vaccine is administered during the neonatal period when levels of the immunosuppressive cytokine interleukin (IL)-27 are elevated, and previous studies have demonstrated that the source of IL-27 can impact downstream immune responses. We therefore sought to characterize the specific subpopulations of myeloid cells that produce IL-27 following BCG vaccination. To investigate this, we administered the BCG vaccine to neonatal IL-27p28eGFP mice that report IL-27 production. Our studies demonstrated that BCG vaccination steadily increased IL-27 production throughout the weeks post-vaccination. We also showed that a predominantly CD11b+ F4/80+ population of IL-27 producers increased MHC class II expression following BCG vaccination in both the spleen and the lung. However, producers of IL-27 in these tissues differ, with a population of CD11c+ MHC II+ cells emerging in the spleen and a subset of Ly6G/C+ MHC II+ emerging in the lung. 10x scMultiome analysis further validated the increase in MHC class II expression and demonstrated improved antigen presentation functionality following vaccination. The sequencing analysis also revealed subpopulations of IL-27 producers with immunosuppressive functions such as a population of macrophages with increased Mrc1 expression post-vaccination. Our findings suggest that IL-27 producers are a heterogenous population of myeloid cells that impact the development of protective immune responses induced by the BCG vaccine.

Effects of injury size on local and systemic immune cell dynamics in volumetric muscle loss

We took a systems approach to the analysis of macrophage phenotype in regenerative and fibrotic volumetric muscle loss outcomes in mice together with analysis of systemic inflammation and of other leukocytes in the muscle, spleen, and bone marrow. Differences in expression of macrophage phenotype markers occurred as early as day 1, persisted to at least day 28, and were associated with increased numbers of leukocytes in the muscle and bone marrow, increased pro-inflammatory marker expression in splenic macrophages, and changes in the levels of pro-inflammatory cytokines in the blood. The most prominent differences were in muscle neutrophils, which were much more abundant in fibrotic outcomes compared to regenerative outcomes at day 1 after injury. However, neutrophil depletion had little to no effect on macrophage phenotype or on muscle repair outcomes. Together, these results suggest that the entire system of immune cell interactions must be considered to improve muscle repair outcomes.

Focusing on Formyl Peptide Receptors after Traumatic Spinal Cord Injury: from Immune Response to Neurogenesis

The intricate pathophysiological cascades following spinal cord injury (SCI), encompassing cellular demise, axonal degeneration, and the formation of glial scars, pose formidable barriers to neural regeneration and restoration. Notably, neuroinflammation and glial scars emerge as pivotal barrier to post-SCI repair. Formyl peptide receptors (FPRs) emerge as critical regulators of immune responses, exerting significant influence over inflammatory modulation and nerve regeneration subsequent to SCI. Beyond their classical expression in myeloid cells, FPRs demonstrate a pronounced presence within the central nervous system (CNS) with roles in the progression of neurodegenerative disorders and neurological malignancies. Post-SCI, the equilibrium of the inflammatory microenvironment is recalibrated through the strategic modulation of FPRs, including facilitating a balance in microglial polarization, stimulating neural stem cells (NSCs) migration, and promoting neural axon elongation. These observations enlighten the potential of FPRs as innovative targets for neuronal regenerations bolstering SCI repair. This review endeavors to delineate the distribution and function of FPRs in the aftermath of SCI, with a special attention to their roles in inflammatory regulation, NSCs mobilization, and synaptic growth. By elucidating these mechanisms, we aspire to contribute novel insights and strategies for SCI therapy.

Rebalancing Immune Interactions within the Brain-Spleen Axis Mitigates Neuroinflammation in an Aging Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia worldwide, characterized by accumulation of amyloid-β protein and hyperphosphorylated tau protein in the brain. Neuroinflammation, resulting from chronic activation of brain-resident innate immune cells as well as enhanced peripheral leukocyte access across the blood-brain barrier, crucially affects AD progression. In this context, TNFSF10, a cytokine substantially expressed in the AD brain, has been shown to modulate both the innate and the adaptive branches of the immune response in AD-related neuroinflammation. In this study, we explored whether a TNFSF10-neutralizing treatment could represent a tool to re-balance the overall overshooting inflammatory response in a mouse model of AD. Specifically, 3xTg-AD mice were treated sub-chronically with an anti-TNFSF10 monoclonal antibody for three months, and were then sacrificed at 15 months. TNFSF10 neutralization reduced the expression of the inflammatory marker CD86, inversely related to levels of the anti-inflammatory marker CD206 in the brain of 3xTg-AD mice, suggesting a switch of microglia towards a neuroprotective phenotype. Similar results were observed in the splenic macrophage population. Moreover, flow cytometry revealed a significant decrease of CD4+CD25+FOXP3+ T regulatory cells as well as reduced number of CD11b+LY6Chigh proinflammatory monocytes in both the brain and the spleen of 3xTg-AD mice treated with anti-TNFSF10 monoclonal antibody. Finally, the treatment resulted in lower count of splenic CD4+ and CD8+ T cells expressing PD1. The data suggest that TNFSF10 system-targeted treatment effectively restrain overshooting central and peripheral inflammation by rebalancing the overall immune response, mitigating the progression of AD pathology.

Immune Alterations and Viral Reservoir Atlas in SIV-Infected Chinese Rhesus Macaques

BACKGROUND/OBJECTIVES

Over the last decades, our projects have been dedicated to clarifying immunopathological and virological events associated with Human Immunodeficiency Virus (HIV) infection.

METHODS

By using non-human primate models of pathogenic and non-pathogenic lentiviral infections, we aimed at identifying the cells and tissues in which the virus persists, despite antiretroviral therapy (ART). Indeed, the eradication of viral reservoirs is a major challenge for HIV cure.

RESULTS

We present a series of results performed in rhesus macaques of Chinese origin deciphering the virological and immunological events associated with ART that can be of interest for people living with HIV.

CONCLUSIONS

This model could be of interest for understanding in whole body the clinical alteration that persist despite ART.

Testosterone exacerbates neutrophilia and cardiac injury in myocardial infarction via actions in bone marrow

Men develop larger infarct sizes than women after a myocardial infarction (MI), but the mechanism underlying this sex difference is unknown. Here, we demonstrated that blood neutrophil counts post-MI were higher in male than female mice. Castration-induced testosterone deficiency reduced blood neutrophil counts to the level in females and increased survival post-MI. These effects were mimicked by Osterix-directed ablation of the androgen receptor in bone marrow (BM). Mechanistically, androgens downregulated the leukocyte retention factor CXCL12 in BM stromal cells. Post-hoc analysis of clinical trial data showed that neutrophilia was greater in men than women after reperfusion of first-time ST-elevation MI, and tocilizumab, an interleukin-6 receptor inhibitor, reduced blood neutrophil counts and infarct size to a greater extent in men than women. Our work reveals a previously unknown mechanism connecting testosterone with neutrophilia and MI injury via BM and identifies the importance of considering sex when developing anti-inflammatory strategies to treat MI.

Mechanical Force-Induced cGAS Activation in Carcinoma Cells Facilitates Splenocytes into Liver to Drive Metastasis

Liver metastasis is the main cause of cancer-related mortality. During the metastasis process, circulating carcinoma cells hardly pass through narrow capillaries, leading to nuclear deformation. However, the effects of nuclear deformation and its underlying mechanisms on metastasis need further study. Here, it is shown that mechanical force-induced nuclear deformation exacerbates liver metastasis by activating the cGAS-STING pathway, which promotes splenocyte infiltration in the liver. Mechanical force results in nuclear deformation and rupture of the nuclear envelope with inevitable DNA leakage. Cytoplasmic DNA triggers the activation of cGAS-STING pathway, enhancing the production of IL6, TNFα, and CCL2. Additionally, splenocyte recruitment by the proinflammatory cytokines support carcinoma cell survival and colonization in the liver. Importantly, both intervening activity of cGAS and blocking of splenocyte migration to the liver efficiently ameliorate liver metastasis. Overall, these findings reveal a mechanism by which mechanical force-induced nuclear deformation exacerbates liver metastasis by regulating splenocyte infiltration into the liver and support targeting cGAS and blocking splenocyte recruitment as candidate therapeutic approaches for liver metastasis.

Bone Marrow Niche in Cardiometabolic Disease: Mechanisms and Therapeutic Potential

Cardiovascular and cardiometabolic diseases are leading causes of morbidity and mortality worldwide, driven in part by chronic inflammation. Emerging research suggests that the bone marrow microenvironment, or marrow niche, plays a critical role in both immune system regulation and disease progression. The bone marrow niche is essential for maintaining hematopoietic stem cells (HSCs) and orchestrating hematopoiesis. Under normal conditions, this niche ensures a return to immune homeostasis after acute stress. However, in the setting of inflammatory conditions such as those seen in cardiometabolic diseases, it becomes dysregulated, leading to enhanced myelopoiesis and immune activation. This review explores the reciprocal relationship between the bone marrow niche and cardiometabolic diseases, highlighting how alterations in the niche contribute to disease development and progression. The niche regulates HSCs through complex interactions with stromal cells, endothelial cells, and signaling molecules. However, in the setting of chronic diseases such as hypertension, atherosclerosis, and diabetes, inflammatory signals disrupt the balance between HSC self-renewal and differentiation, promoting the excessive production of proinflammatory myeloid cells that exacerbate the disease. Key mechanisms discussed include the effects of hyperlipidemia, hyperglycemia, and sympathetic nervous system activation on HSC proliferation and differentiation. Furthermore, the review emphasizes the role of epigenetic modifications and metabolic reprogramming in creating trained immunity, a phenomenon whereby HSCs acquire long-term proinflammatory characteristics that sustain disease states. Finally, we explore therapeutic strategies aimed at targeting the bone marrow niche to mitigate chronic inflammation and its sequelae. Novel interventions that modulate hematopoiesis and restore niche homeostasis hold promise for the treatment of cardiometabolic diseases. By interrupting the vicious cycle of inflammation and marrow dysregulation, such therapies may offer new avenues for reducing cardiovascular risk and improving patient outcomes.

Epigenetic Regulation of Innate and Adaptive Immune Cells in Salt-Sensitive Hypertension

Access to excess dietary sodium has heightened the risk of cardiovascular diseases, particularly affecting individuals with salt sensitivity of blood pressure. Our research indicates that innate antigen-presenting immune cells contribute to rapid blood pressure increases in response to excess sodium intake. Emerging evidence suggests that epigenetic reprogramming, with subsequent transcriptional and metabolic changes, of innate immune cells allows these cells to have a sustained response to repetitive stimuli. Epigenetic mechanisms also steer T-cell differentiation in response to innate immune signaling. Immune cells respond to environmental and nutritional cues, such as salt, promoting epigenetic regulation changes. This article aims to identify and discuss the role of epigenetic mechanisms in the immune system contributing to salt-sensitive hypertension.

Role of Trained Immunity in Heath and Disease

PURPOSE OF REVIEW

This review aims to explore the role of immune memory and trained immunity, focusing on how innate immune cells like monocytes, macrophages, and natural killer cells undergo long-term epigenetic and metabolic rewiring. Specifically, it examines the mechanisms by which trained immunity, often triggered by infection or vaccination, could impact cardiac processes and contribute to both protective and pathological responses within the cardiovascular system.

RECENT FINDINGS

Recent research demonstrates that vaccination and infection not only activate immune responses in circulating monocytes and tissue macrophages but also affect immune progenitor cells within the bone marrow environment, conferring lasting protection against heterologous infections. These protective effects are attributed to epigenetic and metabolic reprogramming, which enable a heightened immune response upon subsequent encounters with pathogens. However, while trained immunity is beneficial in combating infections, it has been linked to exacerbated inflammation, which may increase susceptibility to cardiovascular diseases, including atherosclerosis and heart failure. Our review highlights the dual nature of trained immunity: while it offers protective advantages against infections, it also poses potential risks for cardiovascular health by promoting chronic inflammation. Understanding the molecular mechanisms underlying immune memory's impact on cardiac processes could lead to new therapeutic strategies to mitigate cardiovascular diseases, such as atherosclerosis, heart failure, and diabetes. These insights build the grounds for future research to balance the benefits of trained immunity with its potential risks in cardiovascular disease management.

The role of M1/M2 macrophage polarization in the pathogenesis of obesity-related kidney disease and related pathologies

Obesity is a rapidly growing health problem worldwide, affecting both adults and children and increasing the risk of chronic diseases such as type 2 diabetes, hypertension and cardiovascular disease (CVD). In addition, obesity is closely linked to chronic kidney disease (CKD) by either exacerbating diabetic complications or directly causing kidney damage. Obesity-related CKD is characterized by proteinuria, lipid accumulation, fibrosis and glomerulosclerosis, which can gradually impair kidney function. Among the immune cells of the innate and adaptive immune response involved in the pathogenesis of obesity-related diseases, macrophages play a crucial role in the inflammation associated with CKD. In obese individuals, macrophages enter a pro-inflammatory state known as M1 polarization, which contributes to chronic inflammation. This polarization promotes tissue damage, inflammation and fibrosis, leading to progressive loss of kidney function. In addition, macrophage-induced oxidative stress is a key feature of CKD as it also promotes cell damage and inflammation. Macrophages also contribute to insulin resistance in type 2 diabetes by releasing inflammatory molecules that impair glucose metabolism, complicating the management of diabetes in obese patients. Hypertension and atherosclerosis, which are often associated with obesity, also contribute to the progression of CKD via immune and inflammatory pathways. Macrophages influence blood pressure regulation and contribute to vascular inflammation, particularly via the renin-angiotensin system. In atherosclerosis, macrophages accumulate in arterial plaques, leading to chronic inflammation and plaque instability, which may increase the risk of CVD in CKD patients. This review focuses on the involvement of macrophages in CKD and highlights their role as a critical link between CKD and other pathologies. Targeting macrophage polarization and the ensuing macrophage-induced inflammation could be an effective therapeutic strategy for CKD and related diseases and improve outcomes for patients with obesity-related kidney disease.