Dirty Jobs: Macrophages at the Heart of Cardiovascular Disease

Macrophages on the run: Exercise balances macrophage polarization for improved health

OBJECTIVE

Exercise plays a crucial role in maintaining and improving human health. However, the precise molecular mechanisms that govern the body's response to exercise or/compared to periods of inactivity remain elusive. Current evidence appears to suggest that exercise exerts a seemingly dual influence on macrophage polarization states, inducing both pro-immune response M1 activation and cell-repair-focused M2 activation. To reconcile this apparent paradox, we leveraged a comprehensive meta-analysis of 75 diverse exercise and immobilization published datasets (7000+ samples), encompassing various exercise modalities, sampling techniques, and species.

METHODS

75 exercise and immobilization expression datasets were identified and processed for analysis. The data was analyzed using boolean relationships which uses binary gene expression relationships in order to increase the signal to noise achieved from the data, allowing for the use of comparison across such a diverse set of datasets. We utilized a boolean relationship-aided macrophage gene model [1], to model the macrophage polarization state in pre and post exercise samples in both immediate exercise and long term training.

RESULTS

Our modeling uncovered a key temporal dynamic: exercise triggers an immediate M1 surge, while long term training transitions to sustained M2 activation. These patterns were consistent across different species (human vs mouse), sampling methods (blood vs muscle biopsy), and exercise type (resistance vs endurance), and routinely showed statistically significant results. Immobilization was shown to have the opposite effect of exercise by triggering an immediate M2 activation. Individual characteristics like gender, exercise intensity and age were found to impact the degree of polarization without changing the overall patterns. To model macrophages within the specific context of muscle tissue, we identified a focused gene set signature of muscle resident macrophage polarization, allowing for the precise measurement of macrophage activity in response to exercise within the muscle.

CONCLUSIONS

These consistent patterns across all 75 examined studies suggest that the long term health benefits of exercise stem from its ability to orchestrate a balanced and temporally-regulated interplay between pro-immune response (M1) and reparative macrophage activity (M2). Similarly, it suggests that an imbalance between pro-immune and cell repair responses could facilitate disease development. Our findings shed light on the intricate molecular choreography behind exercise-induced health benefits with a particular insight on its effect on the macrophages within the muscle.

MiR-21-3p inhibitor exerts myocardial protective effects by altering macrophage polarization state and reducing excessive mitophagy

Chronic heart failure (CHF) is closely associated with inflammation and mitochondrial dysfunction in cardiomyocytes. This study attempts to investigate the effects of microRNA-21-3p (miR-21-3p) on macrophage polarization and mitophagy in CHF. Here we found miR-21-3p was upregulated in CHF and negatively correlated with carnitine palmitoyl transferase 1A (CPT1A). L-palmitoyl carnitine (L-PC) exacerbated isoproterenol (ISO)-induced myocardial structural disruption and fibrosis in rats, which was exacerbated by miR-21-3p. Mechanistically, miR-21-3p accelerated M1 macrophage polarization. Both miR-21-3p inhibitor and CPT1A overexpression suppressed mitophagy. The inhibition of CPT1A on mitophagy was reversed by miR-21-3p. MiR-21-3p targeted CPT1A mRNA and co-localized with CPT1A protein in cardiomyocytes. In the co-culture system of M1 macrophages and H9c2 cells, miR-21-3p mimics in H9c2 cells promoted M1 polarization, whereas miR-21-3p inhibitor reduced M1 phenotype. M1 macrophages exacerbated H9c2 cell damage. These findings support the potential therapeutic targeting of miR-21-3p to regulate inflammation and mitophagy by inducing CPT1A in CHF.

Genetic association with autoimmune diseases identifies molecular mechanisms of coronary artery disease

Autoimmune patients have a significantly increased risk of developing coronary artery disease (CAD) compared to the general population. However, autoimmune patients often lack traditional risk factors for CAD and there is increasing recognition of inflammation in CAD development. In this study, we leveraged genome-wide association study (GWAS) data to understand whether there is a genetic relationship between CAD and autoimmunity. Statistical genetic comparison methods were used to identify correlated and causal SNPs between various autoimmune diseases and CAD. Pleiotropic SNPs were identified by cross-phenotype association analysis (CPASSOC) and overlap between GWAS. Causal SNPs were identified using Mendelian Randomization (MR) and Colocalization (COLOC). Using SNP-to-gene mapping, we additionally identified pleiotropic and causal genes and pathways associated between autoimmunity and CAD, which were contextualized by documentation of enrichment in individual cell types identified from coronary atherosclerotic plaques by single-cell RNA sequencing. These results provide insight into potential inflammatory therapeutic targets for CAD.

Cardiac resident macrophages: The core of cardiac immune homeostasis

Cardiac resident macrophages (CRMs) are essential in maintaining the balance of the immune homeostasis in the heart. One of the main factors in the progression of cardiovascular diseases, such as myocarditis, myocardial infarction(MI), and heart failure(HF), is the imbalance in the regulatory mechanisms of CRMs. Recent studies have reported novel heterogeneity and spatiotemporal complexity of CRMs, and their role in maintaining cardiac immune homeostasis and treating cardiovascular diseases. In this review, we focus on the functions of CRMs, including immune surveillance, immune phagocytosis, and immune metabolism, and explore the impact of CRM's homeostasis imbalance on cardiac injury and cardiac repair. We also discuss the therapeutic approaches linked to CRMs. The immunomodulatory strategies targeting CRMs may be a therapeutic approach for the treatment of cardiovascular disease.

Crosstalk between Inflammation and Atherosclerosis in Rheumatoid Arthritis and Systemic Lupus Erythematosus: Is There a Common Basis?

Cardiovascular disease is the leading cause of morbidity and mortality in patients with rheumatoid arthritis and systemic lupus erythematosus. Traditional cardiovascular risk factors, although present in lupus and rheumatoid arthritis, do not explain such a high burden of early cardiovascular disease in the context of these systemic connective tissue diseases. Over the past few years, our understanding of the pathophysiology of atherosclerosis has changed from it being a lipid-centric to an inflammation-centric process. In this review, we examine the pathogenesis of atherosclerosis in systemic lupus erythematosus and rheumatoid arthritis, the two most common systemic connective tissue diseases, and consider them as emblematic models of the effect of chronic inflammation on the human body. We explore the roles of the inflammasome, cells of the innate and acquired immune system, neutrophils, macrophages, lymphocytes, chemokines and soluble pro-inflammatory cytokines in rheumatoid arthritis and systemic lupus erythematosus, and the roles of certain autoantigens and autoantibodies, such as oxidized low-density lipoprotein and beta2-glycoprotein, which may play a pathogenetic role in atherosclerosis progression.

Engineering immune response to regulate cardiovascular disease and cancer

Cardiovascular disease (CVD) and cancer are major contributors to global morbidity and mortality. This book chapter delves into the intricate relationship between the immune system and the pathogenesis of both cardiovascular and cancer diseases, exploring the roles of innate and adaptive immunities, immune regulation, and immunotherapy in these complex conditions. The innate immune system acts as the first line of defense against tissue damage and infection, with a significant impact on the initiation and progression of CVD and cancer. Endothelial dysfunction, a hallmark in CVD, shares commonalities with the tumor microenvironment in cancer, emphasizing the parallel involvement of the immune system in both conditions. The adaptive immune system, particularly T cells, contributes to prolonged inflammation in both CVD and cancer. Regulatory T cells and the intricate balance between different T cell subtypes influence disease progression, wound healing, and the outcomes of ischemic injury and cancer immunosurveillance. Dysregulation of immune homeostasis can lead to chronic inflammation, contributing to the development and progression of both CVD and cancer. Thus, immunotherapy emerged as a promising avenue for preventing and managing these diseases, with strategies targeting immune cell modulation, cytokine manipulation, immune checkpoint blockade, and tolerance induction. The impact of gut microbiota on CVD and cancer too is explored in this chapter, highlighting the role of gut leakiness, microbial metabolites, and the potential for microbiome-based interventions in cardiovascular and cancer immunotherapies. In conclusion, immunomodulatory strategies and immunotherapy hold promise in reshaping the landscape of cardiovascular and cancer health. Additionally, harnessing the gut microbiota for immune modulation presents a novel approach to prevent and manage these complex diseases, emphasizing the importance of personalized and precision medicine in healthcare. Ongoing research and clinical trials are expected to further elucidate the complex immunological underpinnings of CVD and cancer thereby refining these innovative approaches.

Excretory/secretory products from Trichinella spiralis adult worms ameliorate myocardial infarction by inducing M2 macrophage polarization in a mouse model

BACKGROUND

Ischemia-induced inflammatory response is the main pathological mechanism of myocardial infarction (MI)-caused heart tissue injury. It has been known that helminths and worm-derived proteins are capable of modulating host immune response to suppress excessive inflammation as a survival strategy. Excretory/secretory products from Trichinella spiralis adult worms (Ts-AES) have been shown to ameliorate inflammation-related diseases. In this study, Ts-AES were used to treat mice with MI to determine its therapeutic effect on reducing MI-induced heart inflammation and the immunological mechanism involved in the treatment.

METHODS

The MI model was established by the ligation of the left anterior descending coronary artery, followed by the treatment of Ts-AES by intraperitoneal injection. The therapeutic effect of Ts-AES on MI was evaluated by measuring the heart/body weight ratio, cardiac systolic and diastolic functions, histopathological change in affected heart tissue and observing the 28-day survival rate. The effect of Ts-AES on mouse macrophage polarization was determined by stimulating mouse bone marrow macrophages in vitro with Ts-AES, and the macrophage phenotype was determined by flow cytometry. The protective effect of Ts-AES-regulated macrophage polarization on hypoxic cardiomyocytes was determined by in vitro co-culturing Ts-AES-induced mouse bone marrow macrophages with hypoxic cardiomyocytes and cardiomyocyte apoptosis determined by flow cytometry.

RESULTS

We observed that treatment with Ts-AES significantly improved cardiac function and ventricular remodeling, reduced pathological damage and mortality in mice with MI, associated with decreased pro-inflammatory cytokine levels, increased regulatory cytokine expression and promoted macrophage polarization from M1 to M2 type in MI mice. Ts-AES-induced M2 macrophage polarization also reduced apoptosis of hypoxic cardiomyocytes in vitro.

CONCLUSIONS

Our results demonstrate that Ts-AES ameliorates MI in mice by promoting the polarization of macrophages toward the M2 type. Ts-AES is a potential pharmaceutical agent for the treatment of MI and other inflammation-related diseases.

Uncovering the molecular mechanisms between heart failure and end-stage renal disease via a bioinformatics study

Background: Heart failure (HF) is not only a common complication in patients with end-stage renal disease (ESRD) but also a major cause of death. Although clinical studies have shown that there is a close relationship between them, the mechanism of its occurrence is unclear. The aim of this study is to explore the molecular mechanisms between HF and ESRD through comprehensive bioinformatics analysis, providing a new perspective on the crosstalk between these two diseases. Methods: The HF and ESRD datasets were downloaded from the Gene Expression Omnibus (GEO) database; we identified and analyzed common differentially expressed genes (DEGs). First, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and gene set variation analyses (GSVA) were applied to explore the potential biological functions and construct protein-protein interaction (PPI) networks. Also, four algorithms, namely, random forest (RF), Boruta algorithm, logical regression of the selection operator (LASSO), and support vector machine-recursive feature elimination (SVM-RFE), were used to identify the candidate genes. Subsequently, the diagnostic efficacy of hub genes for HF and ESRD was evaluated using eXtreme Gradient Boosting (XGBoost) algorithm. CIBERSORT was used to analyze the infiltration of immune cells. Thereafter, we predicted target microRNAs (miRNAs) using databases (miRTarBase, TarBase, and ENOCRI), and transcription factors (TFs) were identified using the ChEA3 database. Cytoscape software was applied to construct mRNA-miRNA-TF regulatory networks. Finally, the Drug Signatures Database (DSigDB) was used to identify potential drug candidates. Results: A total of 68 common DEGs were identified. The enrichment analysis results suggest that immune response and inflammatory factors may be common features of the pathophysiology of HF and ESRD. A total of four hub genes (BCL6, CCL5, CNN1, and PCNT) were validated using RF, LASSO, Boruta, and SVM-RFE algorithms. Their AUC values were all greater than 0.8. Immune infiltration analysis showed that immune cells such as macrophages, neutrophils, and NK cells were altered in HF myocardial tissue, while neutrophils were significantly correlated with all four hub genes. Finally, 11 target miRNAs and 10 TFs were obtained, and miRNA-mRNA-TF regulatory network construction was performed. In addition, 10 gene-targeted drugs were discovered. Conclusion: Our study revealed important crosstalk between HF and ESRD. These common pathways and pivotal genes may provide new ideas for further clinical treatment and experimental studies.