Modulators of Macrophage Polarization Influence Healing of the Infarcted Myocardium

Comprehensive macro and micro views on immune cells in ischemic heart disease

Ischemic heart disease (IHD) is a prevalent cardiovascular condition that remains the primary cause of death due to its adverse ventricular remodelling and pathological changes in end-stage heart failure. As a complex pathologic condition, it involves intricate regulatory processes at the cellular and molecular levels. The immune system and cardiovascular system are closely interconnected, with immune cells playing a crucial role in maintaining cardiac health and influencing disease progression. Consequently, alterations in the cardiac microenvironment are influenced and controlled by various immune cells, such as macrophages, neutrophils, dendritic cells, eosinophils, and T-lymphocytes, along with the cytokines they produce. Furthermore, studies have revealed that Gata6+ pericardial cavity macrophages play a key role in regulating immune cell migration and subsequent myocardial tissue repair post IHD onset. This review outlines the role of immune cells in orchestrating inflammatory responses and facilitating myocardial repair following IHD, considering both macro and micro views. It also discusses innovative immune cell-based therapeutic strategies, offering new insights for further research on the pathophysiology of ischemic heart disease and immune cell-targeted therapy for IHD.

Exosomes based strategies for cardiovascular diseases: Opportunities and challenges

Exosomes, as nanoscale extracellular vesicles (EVs), are secreted by all types of cells to facilitate intercellular communication in living organisms. After being taken up by neighboring or distant cells, exosomes can alter the expression levels of target genes in recipient cells and thereby affect their pathophysiological outcomes depending on payloads encapsulated therein. The functions and mechanisms of exosomes in cardiovascular diseases have attracted much attention in recent years and are thought to have cardioprotective and regenerative potential. This review summarizes the biogenesis and molecular contents of exosomes and details the roles played by exosomes released from various cells in the progression and recovery of cardiovascular disease. The review also discusses the current status of traditional exosomes in cardiovascular tissue engineering and regenerative medicine, pointing out several limitations in their application. It emphasizes that some of the existing emerging industrial or bioengineering technologies are promising to compensate for these shortcomings, and the combined application of exosomes and biomaterials provides an opportunity for mutual enhancement of their performance. The integration of exosome-based cell-free diagnostic and therapeutic options will contribute to the further development of cardiovascular regenerative medicine.

Modulation of anti-cardiac fibrosis immune responses by changing M2 macrophages into M1 macrophages

BACKGROUND

Macrophages play a crucial role in the development of cardiac fibrosis (CF). Although our previous studies have shown that glycogen metabolism plays an important role in macrophage inflammatory phenotype, the role and mechanism of modifying macrophage phenotype by regulating glycogen metabolism and thereby improving CF have not been reported.

METHODS

Here, we took glycogen synthetase kinase 3β (GSK3β) as the target and used its inhibitor NaW to enhance macrophage glycogen metabolism, transform M2 phenotype into anti-fibrotic M1 phenotype, inhibit fibroblast activation into myofibroblasts, and ultimately achieve the purpose of CF treatment.

RESULTS

NaW increases the pH of macrophage lysosome through transmembrane protein 175 (TMEM175) and caused the release of Ca2+ through the lysosomal Ca2+ channel mucolipin-2 (Mcoln2). At the same time, the released Ca2+ activates TFEB, which promotes glucose uptake by M2 and further enhances glycogen metabolism. NaW transforms the M2 phenotype into the anti-fibrotic M1 phenotype, inhibits fibroblasts from activating myofibroblasts, and ultimately achieves the purpose of treating CF.

CONCLUSION

Our data indicate the possibility of modifying macrophage phenotype by regulating macrophage glycogen metabolism, suggesting a potential macrophage-based immunotherapy against CF.

A simplified herbal decoction attenuates myocardial infarction by regulating macrophage metabolic reprogramming and phenotypic differentiation via modulation of the HIF-1α/PDK1 axis

BACKGROUND

Myocardial infarction (MI) poses a global public health challenge, often associated with elevated mortality rates and a grim prognosis. A crucial aspect of the inflammatory injury and healing process post-MI involves the dynamic differentiation of macrophages. A promising strategy to alleviate myocardial damage after MI is by modulating the inflammatory response and orchestrating the shift from pro-inflammatory (M1) to anti-inflammatory (M2) macrophages, aiming to achieve a reduced M1/M2 ratio. Nuanxinkang (NXK), a simplified herbal decoction, has demonstrated noteworthy cardioprotective, inflammation-regulating, and myocardial energy metabolism-regulating properties.

METHODS

In this study, we constructed an MI model by ligating coronary arteries to investigate the efficacy of NXK in improving ventricular remodeling and cardiac function. Mice were administered NXK (1.65 g/kg/d) or an equivalent volume of regular saline via gavage for 28 consecutive days, commencing the day after surgery. Then, we conducted echocardiography to assess the cardiac function, Masson staining to illustrate the extent of myocardial fibrosis, TUNEL staining to reveal myocardial apoptosis, and flow cytometry to analyze the polarization of M1 and M2 macrophages in the hearts. Besides, a lipopolysaccharide (LPS)-induced pro-inflammatory macrophage (M1) polarization model was implemented in RAW264.7 cells to elucidate the underlying mechanism of NXK in regulating macrophage polarization. RAW264.7 cells were pre-treated with or without NXK-containing serum. Oxidative stress was detected by MitoSox staining, followed by Seahorse energy metabolism assay to evaluate alterations in mitochondrial metabolic patterns and ATP production. Both In vivo and in vitro, HIF-1α and PDK1 were detected by fluorescent quantitative PCR and Western blotting.

RESULTS

In vivo, MI mice exhibited a decline in cardiac function, adverse ventricular remodeling, and an increase in glycolysis, coupled with M1-dominant polarization mediated by the HIF-1α/PDK1 axis. Notably, robust responses were evident with high-dose NXK treatment (1.65 g/kg/day), leading to a significant enhancement in cardiac function, inhibition of cardiac remodeling, and partial suppression of macrophage glycolysis and the inflammatory phenotype in MI mice. This effect was achieved through the modulation of the HIF-1α/PDK1 axis. In vitro, elevated levels of mitochondrial ROS production and glycolysis were observed in LPS-induced macrophages. Conversely, treatment with NXK notably reduced the oxidative stress damage induced by LPS and enhanced oxidative phosphorylation (OXPHOS). Furthermore, NXK demonstrated the ability to modify the energy metabolism and inflammatory characteristics of macrophages by modulating the HIF-1α/PDK1 axis. The influence of NXK on this axis was partially counteracted by the HIF-1α agonist DMOG. And NXK downregulated PDK1 expression, curtailed glycolysis, and reversed LPS-induced M1 polarization in macrophages, similar to the PDK1 inhibitor DCA.

CONCLUSION

In conclusion, NXK protects against MI-induced cardiac remodeling by inducing metabolic reprogramming and phenotypic differentiation of macrophages, achieved through the modulation of the HIF-1α/PDK1 axis. This provides a novel and promising strategy for the treatment of MI.

Platelet Membrane Nanocarriers Cascade Targeting Delivery System to Improve Myocardial Remodeling Post Myocardial Ischemia-Reperfusion Injury

Although treatments for myocardial infarction have advanced significantly, the global mortality due to ischemia and subsequent reperfusion injury remains high. Here, a platelet (PLT) membrane nanocarrier (PL720) that encapsulates L-arginine and FTY720 to facilitate the cascade-targeted delivery of these substances to the myocardial injury site and enable the controlled release of L-arginine and FTY720 is developed. Such an innovative approach shows enhanced cardioprotection through multiple target strategies involved in ischemia-reperfusion injury and late reperfusion inflammation. During the ischemia-reperfusion phase, PL720 targets and accumulates in damaged coronary arteries. PL720 rapidly releases L-arginine, stimulating endothelial cells to produce NO, thereby dilating blood vessels and promoting blood flow recovery, while FTY720's sustained release exerts anti-apoptotic effects. During the late reperfusion inflammatory phase, PL720 is captured by circulating inflammatory monocytes and transported into a deeper ischemic myocardial lesion. PL720 promotes macrophage polarization and accelerates the inflammatory repair. Furthermore, the issue of bradycardia associated with the clinical use of FTY720 is innovatively relieved. Therefore, PL720 is a vascular injury and inflammation dual targeting strategy, exhibiting significant potential for multi-targeted therapy and clinical translation for cardiac injury.

Spatiotemporal development and the regulatory mechanisms of cardiac resident macrophages: Contribution in cardiac development and steady state

Cardiac resident macrophages (CRMs) are integral components of the heart and play significant roles in cardiac development, steady-state, and injury. Advances in sequencing technology have revealed that CRMs are a highly heterogeneous population, with significant differences in phenotype and function at different developmental stages and locations within the heart. In addition to research focused on diseases, recent years have witnessed a heightened interest in elucidating the involvement of CRMs in heart development and the maintenance of cardiac function. In this review, we primarily concentrated on summarizing the developmental trajectories, both spatial and temporal, of CRMs and their impact on cardiac development and steady-state. Moreover, we discuss the possible factors by which the cardiac microenvironment regulates macrophages from the perspectives of migration, proliferation, and differentiation under physiological conditions. Gaining insight into the spatiotemporal heterogeneity and regulatory mechanisms of CRMs is of paramount importance in comprehending the involvement of macrophages in cardiac development, injury, and repair, and also provides new ideas and therapeutic methods for treating heart diseases.

Human Bone Marrow Mesenchymal Stem Cells Promote the M2 Phenotype in Macrophages Derived from STEMI Patients

Acute ST-elevation myocardial infarction (STEMI) leads to myocardial injury or necrosis, and M1 macrophages play an important role in the inflammatory response. Bone marrow mesenchymal stem/stromal cells (BM-MSCs) are capable of modulating macrophage plasticity, principally due to their immunoregulatory capacity. In the present study, we analyzed the capacity of MSCs to modulate macrophages derived from monocytes from patients with STEMI. We analyzed the circulating levels of cytokines associated with M1 and M2 macrophages in patients with STEMI, and the levels of cytokines associated with M1 macrophages were significantly higher in patients with STEMI than in controls. BM-MSCs facilitate the generation of M1 and M2 macrophages. M1 macrophages cocultured with MSCs did not have decreased M1 marker expression, but these macrophages had an increased expression of markers of the M2 macrophage phenotype (CD14, CD163 and CD206) and IL-10 and IL-1Ra signaling-induced regulatory T cells (Tregs). M2 macrophages from patients with STEMI had an increased expression of M2 phenotypic markers in coculture with BM-MSCs, as well as an increased secretion of anti-inflammatory cytokines and an increased generation of Tregs. The findings in this study indicate that BM-MSCs have the ability to modulate the M1 macrophage response, which could improve cardiac tissue damage in patients with STEMI.

Identifying Immune Cell Infiltration and Hub Genes During the Myocardial Remodeling Process After Myocardial Infarction

Purpose

Myocardial remodeling after myocardial infarction (MI) is a complex repair process following myocardial injury, characterized by the infiltration of multiple types of immune cells. However, the underlying molecular mechanism of myocardial remodeling after MI remains obscure. This study aimed to identify the hub differential expression genes (DEGs) of myocardial remodeling after MI and determine the distribution of immune cells infiltrating the pathology.

Methods

We downloaded GSE132143, GSE151834, and GSE176092 data from the GEO database. The GSE132143 dataset was used to identify DEGs, perform functional annotation, and screen hub genes based on protein-protein interaction (PPI) analysis. The GSE151834 dataset was used to validate the expression of hub genes. CIBERSORTx analysis was performed to explore the immune microenvironment in myocardial remodeling after MI. After conducting a literature review, we selected P3H3 to confirm the expression by utilizing immunohistochemistry and qRT-PCR. Finally, the snRNA-seq data in dataset GSE176092 was used for clarifying the expression of these hub genes in various cell clusters.

Results

We found 975 DEGs in myocardial remodeling after MI. Four hub genes (P3H3, COL15A1, COL16A1, COL27A1) were identified and were verified in the GSE151834 dataset. According to immune infiltration analysis, CD4+ naive T cells, regulatory T cells, monocytes, M2 macrophages, and neutrophils were involved in the pathological process of myocardial remodeling after MI. Additionally, in vitro experiments verified that P3h3 expression was significantly elevated in myocardial remodeling after MI. The snRNA-seq data analyzed that P3h3, Col15a1, Col16a1, and Col27a1 were highly expressed in fibroblasts of post-MI.

Conclusion

This study identified four hub genes P3H3, COL15A1, COL16A1, and COL27A1, particularly P3H3, as potential targets for targeted therapy in MI patients.

The comprehensive role of apoptosis inhibitor of macrophage (AIM) in pathological conditions

CD5L/AIM (apoptosis inhibitor of macrophage), as an important component in maintaining tissue homeostasis and inflammation, is mainly produced and secreted by macrophages but partially dissociated and released from blood AIM-IgM. AIM plays a regulatory role in intracellular physiological mechanisms, including lipid metabolism and apoptosis. AIM not only increases in autoimmune diseases, directly targets liver cells in liver cancer and promotes cell clearance in acute kidney injury, but also causes arteriosclerosis and cardiovascular events, and aggravates inflammatory reactions in lung diseases and sepsis. Obviously, AIM plays a pleiotropic role in the body. However, to date, studies have failed to decipher the mechanisms behind its different roles (beneficial or harmful) in inflammatory regulation. The inflammatory response is a "double-edged sword," and maintaining balance is critical for effective host defense while minimizing the adverse side effects of acute inflammation. Enhancing the understanding of AIM function could provide the theoretical basis for new therapies in these pathological settings. In this review, we discuss recent studies on the roles of AIM in lipid metabolism, autoimmune diseases and organic tissues, such as liver cancer, myocardial infarction, and kidney disease.

Naringenin facilitates M2 macrophage polarization after myocardial ischemia-reperfusion by promoting nuclear translocation of transcription factor EB and inhibiting the NLRP3 inflammasome pathway

Myocardial ischemia-reperfusion injury (MIRI) remains an unsolved puzzle in medical circles. Naringenin (NAR) is a flavonoid with cardioprotective potential. The purpose of this article was to discuss the protective mechanism of NAR in MIRI by regulating macrophage polarization. The MIRI mouse model was established and perfused with NAR before surgery. In the in vitro experiment, macrophages RAW264.7 were treated with lipopolysaccharide to induce M1 polarization after pretreatment with NAR. Rescue experiments were carried out to validate the functions of transcription factor EB (TFEB), the NLR pyrin domain containing 3 (NLRP3) inflammasome, and autophagy in macrophage polarization. NAR reduced histopathological injury and infarction of myocardial tissues in MIRI mice, inhibited M1 polarization and promoted M2 polarization of macrophages, diminished levels of pro-inflammatory factors, and augmented levels of anti-inflammatory factors. NAR facilitated TFEB nuclear translocation and inhibited the NLRP3 inflammasome pathway. Silencing TFEB or Nigericin partly nullified the effect of NAR on macrophage polarization. NAR increased autophagosome formation, autophagy flux, and autophagy level. Autophagy inhibitor 3-methyladenine partly invalidated the inhibition of NAR on the NLRP3 inflammasome pathway. In animal experiments, NAR protected MIRI mice through the TFEB-autophagy-NLRP3 inflammasome pathway. Collectively, NAR inhibited NLRP3 inflammasome activation and facilitated M2 macrophage polarization by stimulating TFEB nuclear translocation, thus protecting against MIRI.

Atorvastatin-pretreated mesenchymal stem cell-derived extracellular vesicles promote cardiac repair after myocardial infarction via shifting macrophage polarization by targeting microRNA-139-3p/Stat1 pathway

BACKGROUND

Extracellular vesicles (EVs) derived from bone marrow mesenchymal stem cells (MSCs) pretreated with atorvastatin (ATV) (MSCATV-EV) have a superior cardiac repair effect on acute myocardial infarction (AMI). The mechanisms, however, have not been fully elucidated. This study aims to explore whether inflammation alleviation of infarct region via macrophage polarization plays a key role in the efficacy of MSCATV-EV.

METHODS

MSCATV-EV or MSC-EV were intramyocardially injected 30 min after coronary ligation in AMI rats. Macrophage infiltration and polarization (day 3), cardiac function (days 0, 3, 7, 28), and infarct size (day 28) were measured. EV small RNA sequencing and bioinformatics analysis were conducted for differentially expressed miRNAs between MSCATV-EV and MSC-EV. Macrophages were isolated from rat bone marrow for molecular mechanism analysis. miRNA mimics or inhibitors were transfected into EVs or macrophages to analyze its effects on macrophage polarization and cardiac repair in vitro and in vivo.

RESULTS

MSCATV-EV significantly reduced the amount of CD68+ total macrophages and increased CD206+ M2 macrophages of infarct zone on day 3 after AMI compared with MSC-EV group (P < 0.01-0.0001). On day 28, MSCATV-EV much more significantly improved the cardiac function than MSC-EV with the infarct size markedly reduced (P < 0.05-0.0001). In vitro, MSCATV-EV also significantly reduced the protein and mRNA expressions of M1 markers but increased those of M2 markers in lipopolysaccharide-treated macrophages (P < 0.05-0.0001). EV miR-139-3p was identified as a potential cardiac repair factor mediating macrophage polarization. Knockdown of miR-139-3p in MSCATV-EV significantly attenuated while overexpression of it in MSC-EV enhanced the effect on promoting M2 polarization by suppressing downstream signal transducer and activator of transcription 1 (Stat1). Furthermore, MSCATV-EV loaded with miR-139-3p inhibitors decreased while MSC-EV loaded with miR-139-3p mimics increased the expressions of M2 markers and cardioprotective efficacy.

CONCLUSIONS

We uncovered a novel mechanism that MSCATV-EV remarkably facilitate cardiac repair in AMI by promoting macrophage polarization via miR-139-3p/Stat1 pathway, which has the great potential for clinical translation.

Activating α7nAChR helps post-myocardial infarction healing by regulating macrophage polarization via the STAT3 signaling pathway

BACKGROUND

Monocytes/macrophages play critical roles in inflammation and cardiac remodeling following myocardial infarction (MI). The cholinergic anti-inflammatory pathway (CAP) modulates local and systemic inflammatory responses by activating α7 nicotinic acetylcholine receptors (α7nAChR) in monocytes/macrophages. We investigated the effect of α7nAChR on MI-induced monocyte/macrophage recruitment and polarization and its contribution to cardiac remodeling and dysfunction.

METHODS

Adult male Sprague Dawley rats underwent coronary ligation and were intraperitoneally injected with the α7nAChR-selective agonist PNU282987 or the antagonist methyllycaconitine (MLA). RAW264.7 cells were stimulated with lipopolysaccharide (LPS) + interferon-gamma (IFN-γ) and treated with PNU282987, MLA, and S3I-201 (a STAT3 inhibitor). Cardiac function was evaluated by echocardiography. Masson's trichrome and immunofluorescence were used to detect cardiac fibrosis, myocardial capillary density, and M1/M2 macrophages. Western blotting was used to detect protein expression, and the proportion of monocytes was measured using flow cytometry.

RESULTS

Activating the CAP with PNU282987 significantly improved cardiac function and reduced cardiac fibrosis and 28-day mortality after MI. On days 3 and 7 post-MI, PNU282987 reduced the percentage of peripheral CD172a + CD43low monocytes and the infiltration of M1 macrophages in the infarcted hearts, whereas it increased the recruitment of peripheral CD172a + CD43high monocytes and M2 macrophages. Conversely, MLA exerted the opposite effects. In vitro, PNU282987 inhibited M1 macrophage polarization and promoted M2 macrophage polarization in LPS + IFN-γ-stimulated RAW264.7 cells. These PNU282987-induced changes in LPS + IFN-γ-stimulated RAW264.7 cells were reversed by administering S3I-201.

CONCLUSION

Activating α7nAChR inhibits the early recruitment of pro-inflammatory monocytes/macrophages during MI and improves cardiac function and remodeling. Our findings suggest a promising therapeutic target for regulating monocyte/macrophage phenotypes and promoting healing after MI.

The protective effect of gamma aminobutyric acid B receptor activation on sympathetic nerve remodeling via the regulation of M2 macrophage polarization after myocardial infarction

INTRODUCTION & OBJECTIVES

Acute myocardial infarction (AMI) in coronary heart disease is a leading cause of sudden death primarily due to malignant ventricular arrhythmias (VAs). Inflammatory cell infiltration and inflammation-induced overactivation of sympathetic nerves are the major cause of VAs in AMI pathophysiological processes. Type 2 macrophages play an anti-inflammatory role in AMI. Targeting macrophages may be a therapeutic strategy to prevent VAs post AMI. We found that gamma aminobutyric acid (GABA) promotes macrophages polarized to M2 and hypothesized that GABA might exert anti-inflammatory effects by promoting type 2 macrophage polarization in AMI. We aim to characterized GABA_B receptor distribution, function, and mechanisms in M2 macrophage polarization and explored the functional aspect of GABA_B receptor activation in sympathetic remodeling.

RESULTS

Gamma aminobutyric acid B receptors were expressed on macrophage surface both in vitro and in vivo. GABA_B receptor agonist baclofen, GABA promoted macrophage switch to M2. While GABA_B receptor antagonist CGP52432 blocked a baclofen induced switch to M2 polarization. GABA and baclofen increased M2 macrophage percentage and CGP52432 blocked this process in vivo. Also, IL-10 and TGF-β1 released by M2 were increased in both AMI and baclofen/AMI group; Serum NE levels were decreased by baclofen. All the above effects were reversed by CGP52432 treatment. Baclofen decreased TH and GAP-43 staining while CGP52432 enhanced their expression post AMI indicating GABA_B receptor activation inhibited sympathetic nerve sprouting and activity by reducing NE release.

CONCLUSIONS

Gamma aminobutyric acid B receptor activation promoted M2 polarization and protested AMI heart by regulating sympathetic nerve remodeling.

Propionate alleviated post-infarction cardiac dysfunction by macrophage polarization in a rat model

BACKGROUND

The propionate (C3), the important components of short-chain fatty acids (SCFAs), had the effect of inhibiting pro-inflammatory macrophages. Earlier macrophages phenotypic transition from pro-inflammatory M1 to reparative M2 in early stage was a central juncture of cardiac dysfunction mitigation after myocardial infarction (MI).

METHODS

160 Sprague-Dawley rats were assigned to 4 groups: sham group (n = 40), sham + C3 group (n = 40), MI group (n = 40) and MI + C3 group (n = 40). The rats in sham + C3 and MI + C3 group were treated with oral sodium propionate (200 mM), and equivalent concentration of sodium chloride was administered in sham and MI group as control. After 7 days of propionate adaptive feeding, rats were anesthetized and induced the MI by coronary occlusion. The classification of macrophages, the level of inflammatory factors and inflammatory signaling were estimated at 3rd days after thoracotomy, and the extent of myocardial fibrosis was evaluated at 7th and 28th days after operation. Echocardiography was estimated on 28th day after surgery. RAW264.7 cells, stimulated by LPS + IFN-γ with or without propionate, were harvested for western blot and supernatants were collected for cytokine analysis by ELISA.

RESULTS

Propionate administration reduced the MI-induced myocardial fibrosis in infarcted border and attenuated cardiac function deterioration compared with MI group. In comparison with MI group, propionate promoted macrophages reduction, macrophage M2-like polarization, and inflammatory cytokines decrease in infarcted border zone following MI, which partly depends on the inhibition of JNK/P38/NFκB signaling pathways.

CONCLUSIONS

Oral propionate in early stage, as a nutritional intervention, alleviated post-MI chronic cardiac remodeling and cardiac dysfunction at least in part by modulating macrophages polarization and pro-inflammatory cytokine, which were associated with reduction of JNK/P38/NFκB phosphorylation.

Macrophages in cardiac remodelling after myocardial infarction

Myocardial infarction (MI), as a result of thrombosis or vascular occlusion, is the most prevalent cause of morbidity and mortality among all cardiovascular diseases. The devastating consequences of MI are compounded by the complexities of cellular functions involved in the initiation and resolution of early-onset inflammation and the longer-term effects related to scar formation. The resultant tissue damage can occur as early as 1 h after MI and activates inflammatory signalling pathways to elicit an immune response. Macrophages are one of the most active cell types during all stages after MI, including the cardioprotective, inflammatory and tissue repair phases. In this Review, we describe the phenotypes of cardiac macrophage involved in MI and their cardioprotective functions. A specific subset of macrophages called resident cardiac macrophages (RCMs) are derived from yolk sac progenitor cells and are maintained as a self-renewing population, although their numbers decrease with age. We explore sophisticated sequencing techniques that demonstrate the cardioprotective properties of this cardiac macrophage phenotype. Furthermore, we discuss the interactions between cardiac macrophages and other important cell types involved in the pathology and resolution of inflammation after MI. We summarize new and promising therapeutic approaches that target macrophage-mediated inflammation and the cardioprotective properties of RCMs after MI. Finally, we discuss future directions for the study of RCMs in MI and cardiovascular health in general.

Identification of Hub Genes in the Remodeling of Non-Infarcted Myocardium Following Acute Myocardial Infarction

(1) Background: There are few diagnostic and therapeutic targets for myocardial remodeling in the salvageable non-infarcted myocardium. (2) Methods: Hub genes were identified through comprehensive bioinformatics analysis (GSE775, GSE19322, and GSE110209 from the gene expression omnibus (GEO) database) and the biological functions of hub genes were examined by gene ontology (GO) functional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. Furthermore, the differential expression of hub genes in various cell populations between the acute myocardial infarction (AMI) and sham-operation groups was analyzed by processing scRNA data (E-MTAB-7376 from the ArrayExpress database) and RNA-seq data (GSE183168). (3) Results: Ten strongly interlinked hub genes (Timp1, Sparc, Spp1, Tgfb1, Decr1, Vim, Serpine1, Serpina3n, Thbs2, and Vcan) were identified by the construction of a protein-protein interaction network from 135 differentially expressed genes identified through comprehensive bioinformatics analysis and their reliability was verified using GSE119857. In addition, the 10 hub genes were found to influence the ventricular remodeling of non-infarcted tissue by modulating the extracellular matrix (ECM)-mediated myocardial fibrosis, macrophage-driven inflammation, and fatty acid metabolism. (4) Conclusions: Ten hub genes were identified, which may provide novel potential targets for the improvement and treatment of AMI and its complications.

PCSK9 Modulates Macrophage Polarization-Mediated Ventricular Remodeling after Myocardial Infarction

Background and Aims

An increasing number of high-risk patients with coronary heart disease (similar to acute myocardial infarction (AMI)) are using PCSK9 inhibitors. However, whether PCSK9 affects myocardial repair and the molecular mechanism of PCSK9 modulation of immune inflammation after AMI are not known. The present research investigated the role of PCSK9 in the immunomodulation of macrophages after AMI and provided evidence for the clinical application of PCSK9 inhibitors after AMI to improve cardiac repair.

Methods and Results

Wild-type C57BL6/J (WT) and PCSK9^−/− mouse hearts were subjected to left anterior descending (LAD) coronary artery occlusion to establish an AMI model. Correlation analysis showed that higher PCSK9 expression indicated worse cardiac function after AMI, and PCSK9 knockout reduced infarct size, improved cardiac function, and attenuated inflammatory cell infiltration compared to WT mice. Notably, the curative effects of PCSK9 inhibition were abolished after the systemic depletion of macrophages using clodronate liposomes. PCSK9 showed a regulatory effect on macrophage polarization in vivo and in vitro. Our studies also revealed that activation of the TLR4/MyD88/NF-κB axis was a possible mechanism of PCSK9 regulation of macrophage polarization.

Conclusion

Our data suggested that PCSK9 modulated macrophage polarization-mediated ventricular remodeling after myocardial infarction.

Macrophage polarization in hypoxia and ischemia/reperfusion: Insights into the role of energetic metabolism

Macrophages, the key cells of innate immunity, possess wide phenotypical and functional heterogeneity. In vitro studies showed that microenvironment signals could induce the so-called polarization of macrophages into two phenotypes: classically activated macrophages (M1) or alternatively activated macrophages (M2). Functionally, they are considered as proinflammatory and anti-inflammatory/pro-regenerative, respectively. However, in vivo studies into macrophage states revealed a continuum of phenotypes from M1 to M2 state instead of the clearly distinguished extreme phenotypes. An important role in determining the type of polarization of macrophages is played by energy metabolism, including the activity of oxidative phosphorylation. In this regard, hypoxia and ischemia that affect cellular energetics can modulate macrophage polarization. Here, we overview the data on macrophage polarization during metabolic shift-associated pathologies including ischemia and ischemia/reperfusion in various organs and discuss the role of energy metabolism potentially triggering the macrophage polarization.

SS-31 Modification Inhibits the Proinflammatory Effect on Macrophages Induced by Superparamagnetic Iron Oxide Nanoparticles

Superparamagnetic iron oxide nanoparticles can induce macrophage polarization into the proinflammatory M1-type. This adverse effect is very likely to restrict the applications of superparamagnetic iron oxide nanoparticles in various inflammatory medical conditions. To inhibit the proinflammatory effect, the mitochondrial-targeted antioxidant peptide SS-31 was physically adsorbed on superparamagnetic iron oxide nanoparticles to develop superparamagnetic iron oxide nanoparticles@SS-31. The macrophages (RAW 264.7) were incubated with superparamagnetic iron oxide nanoparticles or superparamagnetic iron oxide nanoparticles@SS-31 at a concentration of 50 μg Fe3O4/mL for 24 hours. Compared to the superparamagnetic iron oxide nanoparticles group, the superparamagnetic iron oxide nanoparticles@SS-31 group demonstrated significantly reduced cell damage, as evidenced by the inhibition of cell viability loss, early cell apoptosis and the production of reactive oxygen species. Moreover, the proinflammatory factor TNF-α and M1-type cell surface markers CD86 and CD80 were significantly downregulated in the superparamagnetic iron oxide nanoparticles@SS-31 group as shown by enzyme-linked immunosorbent assay and flow cytometric analysis. Notably, compared with the superparamagnetic iron oxide nanoparticles group, levels of the anti-inflammatory factors IL-10, TGF-β and the M2-type cell surface marker CD163 were markedly upregulated in the superparamagnetic iron oxide nanoparticles@SS-31 group. In addition, severe disruption of the mitochondrial ultrastructure was observed by transmission electron microscopy in the superparamagnetic iron oxide nanoparticles group, but the superparamagnetic iron oxide nanoparticles@SS-31 group displayed structurally intact mitochondria. All of these results suggest that superparamagnetic iron oxide nanoparticles can promote macrophage M1-type polarization by inducing oxidative stress and mitochondrial damage, while superparamagnetic iron oxide nanoparticles@SS-31 can significantly inhibit superparamagnetic iron oxide nanoparticles-induced toxicity by releasing SS-31 to exert mitochondrial-targeted antioxidant and anti-inflammatory effects, indicating that the strategy of coloading the SS-31 peptide into superparamagnetic iron oxide nanoparticles has the potential to alleviate superparamagnetic iron oxide nanoparticles-induced proinflammatory effects.

Exosomes derived from human placental mesenchymal stem cells ameliorate myocardial infarction via anti-inflammation and restoring gut dysbiosis

BACKGROUND

Myocardial infarction (MI) represents a severe cardiovascular disease with limited therapeutic agents. This study was aimed to elucidate the role of the exosomes derived from human placental mesenchymal stem cells (PMSCs-Exos) in MI.

METHODS

PMSCs were isolated and cultured in vitro, with identification by both transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). To further investigate the effects of PMSC-Exos on MI, C57BL/6 mice were randomly divided into Sham group, MI group, and PMSC-Exos group. After 4 weeks of the intervention, cardiac function was assessed by cardiac echocardiography, electrocardiogram and masson trichrome staining; lipid indicators were determined by automatic biochemical instrument; inflammatory cytokines were measured by cytometric bead array (CBA); gut microbiota, microbial metabolites short chain fatty acids (SCFAs) as well as lipopolysaccharide (LPS) were separately investigated by 16S rRNA high throughput sequencing, gas chromatography mass spectrometry (GC-MS) and tachypleus amebocyte lysate kit; transcriptome analysis was used to test the transcriptional components (mRNA\miRNA\cirRNA\lncRNA) of PMSC-Exos.

RESULTS

We found that human PMSC-Exos were obtained and identified with high purity and uniformity. MI model was successfully established. Compared to MI group, PMSC-Exos treatment ameliorated myocardial fibrosis and left ventricular (LV) remodeling (P < 0.05). Moreover, PMSC-Exos treatment obviously decreased MI molecular markers (AST/BNP/MYO/Tn-I/TC), pro-inflammatory indicators (IL-1β, IL-6, TNF-α, MCP-1), as well as increased HDL in comparison with MI group (all P < 0.05). Intriguingly, PMSC-Exos intervention notably modulated gut microbial community via increasing the relative abundances of Bacteroidetes, Proteobacteria, Verrucomicrobia, Actinobacteria, Akkermansia, Bacteroides, Bifidobacterium, Thauera and Ruminiclostridium, as well as decreasing Firmicutes (all P < 0.05), compared with MI group. Furthermore, PMSC-Exos supplementation increased gut microbiota metabolites SCFAs (butyric acid, isobutyric acid and valeric acid) and decreased LPS in comparison with MI group (all P < 0.05). Correlation analysis indicated close correlations among gut microbiota, microbial SCFAs and inflammation in MI.

CONCLUSIONS

Our study highlighted that PMSC-Exos intervention alleviated MI via modulating gut microbiota and suppressing inflammation.

The effect of immune cell-derived exosomes in the cardiac tissue repair after myocardial infarction: Molecular mechanisms and pre-clinical evidence

After a myocardial infarction (MI), the inflammatory responses are induced and assist to repair ischaemic injury and restore tissue integrity, but excessive inflammatory processes promote abnormal cardiac remodelling and progress towards heart failure. Thus, a timely resolution of inflammation and a firmly regulated balance between regulatory and inflammatory mechanisms can be helpful. Molecular- and cellular-based approaches modulating immune response post-MI have emerged as a promising therapeutic strategy. Exosomes are essential mediators of cell-to-cell communications, which are effective in modulating immune responses and immune cells following MI, improving the repair process of infarcted myocardium and maintaining ventricular function via the crosstalk among immune cells or between immune cells and myocardial cells. The present review aimed to seek the role of immune cell-secreted exosomes in infarcted myocardium post-MI, together with mechanisms behind their repairing impact on the damaged myocardium. The exosomes we focus on are secreted by classic immune cells including macrophages, dendritic cells, regulatory T cells and CD4+ T cells; however, further research is demanded to determine the role of exosomes secreted by other immune cells, such as B cells, neutrophils and mast cells, in infarcted myocardium after MI. This knowledge can assist in the development of future therapeutic strategies, which may benefit MI patients.

Nucleolin Improves Heart Function During Recovery From Myocardial Infarction by Modulating Macrophage Polarization

BACKGROUND

Nucleolin has multiple functions within cell survival and proliferation pathways. Our previous studies have revealed that nucleolin can significantly reduce myocardial ischemia-reperfusion injury by promoting myocardial angiogenesis and reducing myocardial apoptosis. In this study, we attempted to determine the role of nucleolin in myocardial infarction (MI) injury recovery and the underlying mechanism.

METHODS

Male BALB/c mice aged 6-8 weeks were used to set up MI models by ligating the left anterior descending coronary artery. Nucleolin expression in the heart was downregulated by intramyocardial injection of a lentiviral vector expressing nucleolin-specific small interfering RNA. Macrophage infiltration and polarization were measured by real-time polymerase chain reaction, flow cytometry, and immunofluorescence. Cytokines were detected by enzyme-linked immunosorbent assay.

RESULTS

Nucleolin expression in myocardium after MI induction decreased a lot at early phase and elevated at late phase. Nucleolin knockdown impaired heart systolic and diastolic functions and decreased the survival rate after MI. Macrophage infiltration increased in the myocardium after MI. Most macrophages belonged to the M1 phenotype at early phase (2 days) and the M2 phenotype increased greatly at late phase after MI. Nucleolin knockdown in the myocardium led to a decrease in M2 macrophage polarization with no effect on macrophage infiltration after MI. Furthermore, Notch3 and STAT6, key regulators of M2 macrophage polarization, were upregulated by nucleolin in RAW 264.7 macrophages.

CONCLUSIONS

Lack of nucleolin impaired heart function during recovery after MI by reducing M2 macrophage polarization. This finding probably points to a new therapeutic option for ischemic heart disease.

Can N-3 polyunsaturated fatty acids be considered a potential adjuvant therapy for COVID-19-associated cardiovascular complications?

Coronavirus disease 2019 (COVID-19), caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has currently led to a global pandemic with millions of confirmed and increasing cases around the world. The novel SARS-CoV-2 not only affects the lungs causing severe acute respiratory dysfunction but also leads to significant dysfunction in multiple organs and physiological systems including the cardiovascular system. A plethora of studies have shown the viral infection triggers an exaggerated immune response, hypercoagulation and oxidative stress, which contribute significantly to poor cardiovascular outcomes observed in COVID-19 patients. To date, there are no approved vaccines or therapies for COVID-19. Accordingly, cardiovascular protective and supportive therapies are urgent and necessary to the overall prognosis of COVID-19 patients. Accumulating literature has demonstrated the beneficial effects of n-3 polyunsaturated fatty acids (n-3 PUFA) toward the cardiovascular system, which include ameliorating uncontrolled inflammatory reactions, reduced oxidative stress and mitigating coagulopathy. Moreover, it has been demonstrated the n-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are precursors to a group of potent bioactive lipid mediators, generated endogenously, which mediate many of the beneficial effects attributed to their parent compounds. Considering the favorable safety profile for n-3 PUFAs and their metabolites, it is reasonable to consider n-3 PUFAs as potential adjuvant therapies for the clinical management of COVID-19 patients. In this article, we provide an overview of the pathogenesis of cardiovascular complications secondary to COVID-19 and focus on the mechanisms that may contribute to the likely benefits of n-3 PUFAs and their metabolites.

The multi-faceted role of retinoid X receptor in cardiovascular diseases

Retinoid X receptors (RXRs) are members of ligand-dependent transcription factors whose effects on a diversity of cellular processes, including cellular proliferation, the immune response, and lipid and glucose metabolism. Knock out of RXRα causes a hypoplasia of the myocardium which is lethal during fetal life. In addition, the heart maintains a well-orchestrated balances in utilizing fatty acids (FAs) and other substrates to meet the high energy requirements. As the master transcriptional regulators of lipid metabolism, RXRs become particularly important for the energy needs of the heart. Accumulating evidence suggested that RXRs may exert direct beneficial effects in the heart both through heterodimerization with other nuclear receptors (NRs) and homodimerization, thus standing as suitable targets for treating in cardiovascular diseases. Although compounds that target RXRs are promising drugs, their use is limited by toxicity. A better understanding of the structural biology of RXRs in cardiovascular disease should enable the rational design of more selective nuclear receptor modulators to overcome these problems. Here, this review summarizes a brief overview of RXRs structure and versatility of RXR action in the control of cardiovascular diseases. And we also discussed the therapeutic potential of RXR ligand.

Pre- and Post-Conditioning of the Heart: An Overview of Cardioprotective Signaling Pathways

Since the discovery of ischemic pre- and post-conditioning, more than 30 years ago, the knowledge about the mechanisms and signaling pathways involved in these processes has significantly increased. In clinical practice, on the other hand, such advancement has yet to be seen. This article provides an overview of ischemic pre-, post-, remote, and pharmacological conditioning related to the heart. In addition, we reviewed the cardioprotective signaling pathways and therapeutic agents involved in the above-mentioned processes, aiming to provide a comprehensive evaluation of the advancements in the field. The advancements made over the last decades cannot be ignored and with the exponential growth in techniques and applications. The future of pre- and post-conditioning is promising.

Liposomal delivery of azithromycin enhances its immunotherapeutic efficacy and reduces toxicity in myocardial infarction

A growing body of evidence shows that altering the inflammatory response by alternative macrophage polarization is protective against complications related to acute myocardial infarction (MI). We have previously shown that oral azithromycin (AZM), initiated prior to MI, reduces inflammation and its negative sequelae on the myocardium. Here, we investigated the immunomodulatory role of a liposomal AZM formulation (L-AZM) in a clinically relevant model to enhance its therapeutic potency and avoid off-target effects. L-AZM (40 or 10 mg/kg, IV) was administered immediately post-MI and compared to free AZM (F-AZM). L-AZM reduced cardiac toxicity and associated mortality by 50% in mice. We observed a significant shift favoring reparatory/anti-inflammatory macrophages with L-AZM formulation. L-AZM use resulted in a remarkable decrease in cardiac inflammatory neutrophils and the infiltration of inflammatory monocytes. Immune cell modulation was associated with the downregulation of pro-inflammatory genes and the upregulation of anti-inflammatory genes. The immunomodulatory effects of L-AZM were associated with a reduction in cardiac cell death and scar size as well as enhanced angiogenesis. Overall, L-AZM use enhanced cardiac recovery and survival after MI. Importantly, L-AZM was protective from F-AZM cardiac off-target effects. We demonstrate that the liposomal formulation of AZM enhances the drug’s efficacy and safety in an animal model of acute myocardial injury. This is the first study to establish the immunomodulatory properties of liposomal AZM formulations. Our findings strongly support clinical trials using L-AZM as a novel and clinically relevant therapeutic target to improve cardiac recovery and reduce heart failure post-MI in humans.

Impact of BDNF Val66Met Polymorphism on Myocardial Infarction: Exploring the Macrophage Phenotype

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin growth factor family, well known for its role in the homeostasis of the cardiovascular system. Recently, the human BDNF Val66Met single nucleotide polymorphism has been associated with the increased propensity for arterial thrombosis related to acute myocardial infarction (AMI). Using cardiac magnetic resonance imaging and immunohistochemistry analyses, we showed that homozygous mice carrying the human BDNF Val66Met polymorphism (BDNF^Met/Met) undergoing left anterior descending (LAD) coronary artery ligation display an adverse cardiac remodeling compared to wild-type (BDNF^Val/Val). Interestingly, we observed a persistent presence of pro-inflammatory M1-like macrophages and a reduced accumulation of reparative-like phenotype macrophages (M2-like) in the infarcted heart of mutant mice. Further qPCR analyses showed that BDNF^Met/Met peritoneal macrophages are more pro-inflammatory and have a higher migratory ability compared to BDNF^Val/Val ones. Finally, macrophages differentiated from circulating monocytes isolated from BDNF^Met/Met patients with coronary heart disease displayed the same pro-inflammatory characteristics of the murine ones. In conclusion, the BDNF Val66Met polymorphism predisposes to adverse cardiac remodeling after myocardial infarction in a mouse model and affects macrophage phenotype in both humans and mice. These results provide a new cellular mechanism by which this human BDNF genetic variant could influence cardiovascular disease.

M1-like macrophage-derived exosomes suppress angiogenesis and exacerbate cardiac dysfunction in a myocardial infarction microenvironment

The roles and the underlying mechanisms of M1-type macrophages in angiogenesis and postmyocardial infarction (MI) cardiac repair have remained unclear. In this study, we investigated the role of M1-like macrophage-derived exosomes in a MI microenvironment. We found that the proinflammatory M1-like-type macrophages released an extensive array of proinflammatory exosomes (M1-Exos) after MI. M1-Exos exerted an anti-angiogenic effect and accelerated MI injury. They also exhibited highly expressed proinflammatory miRNAs, such as miR-155. miR-155 was transferred to endothelial cells (ECs), leading to the inhibition of angiogenesis and cardiac dysfunction by downregulating its novel target genes, including Rac family small GTPase 1 (RAC1), p21 (RAC1)-activated kinase 2 (PAK2), Sirtuin 1 (Sirt1), and protein kinase AMP-activated catalytic subunit alpha 2 (AMPKα2). M1-Exos depressed Sirt1/AMPKα2-endothelial nitric oxide synthase and RAC1-PAK2 signaling pathways by simultaneously targeting the five molecule nodes (genes), reduced the angiogenic ability of ECs, aggravated myocardial injury, and restrained cardiac healing. The elucidation of this mechanism provides novel insights into the functional significance of M1 macrophages and their derived exosomes on angiogenesis and cardiac repair. This mechanism can be used as a novel potential therapeutic approach for the prevention and treatment of MI.

Ischemia/Reperfusion Injury: Pathophysiology, Current Clinical Management, and Potential Preventive Approaches

Myocardial ischemia reperfusion syndrome is a complex entity where many inflammatory mediators play different roles, both to enhance myocardial infarction-derived damage and to heal injury. In such a setting, the establishment of an effective therapy to treat this condition has been elusive, perhaps because the experimental treatments have been conceived to block just one of the many pathogenic pathways of the disease, or because they thwart the tissue-repairing phase of the syndrome. Either way, we think that a discussion about the pathophysiology of the disease and the mechanisms of action of some drugs may shed some clarity on the topic.

"Bridging the Gap" Everything that Could Have Been Avoided If We Had Applied Gender Medicine, Pharmacogenetics and Personalized Medicine in the Gender-Omics and Sex-Omics Era

Gender medicine is the first step of personalized medicine and patient-centred care, an essential development to achieve the standard goal of a holistic approach to patients and diseases. By addressing the interrelation and integration of biological markers (i.e., sex) with indicators of psychological/cultural behaviour (i.e., gender), gender medicine represents the crucial assumption for achieving the personalized health-care required in the third millennium. However, ‘sex’ and ‘gender’ are often misused as synonyms, leading to frequent misunderstandings in those who are not deeply involved in the field. Overall, we have to face the evidence that biological, genetic, epigenetic, psycho-social, cultural, and environmental factors mutually interact in defining sex/gender differences, and at the same time in establishing potential unwanted sex/gender disparities. Prioritizing the role of sex/gender in physiological and pathological processes is crucial in terms of efficient prevention, clinical signs’ identification, prognosis definition, and therapy optimization. In this regard, the omics-approach has become a powerful tool to identify sex/gender-specific disease markers, with potential benefits also in terms of socio-psychological wellbeing for each individual, and cost-effectiveness for National Healthcare systems. “Being a male or being a female” is indeed important from a health point of view and it is no longer possible to avoid “sex and gender lens” when approaching patients. Accordingly, personalized healthcare must be based on evidence from targeted research studies aimed at understanding how sex and gender influence health across the entire life span. The rapid development of genetic tools in the molecular medicine approaches and their impact in healthcare is an example of highly specialized applications that have moved from specialists to primary care providers (e.g., pharmacogenetic and pharmacogenomic applications in routine medical practice). Gender medicine needs to follow the same path and become an established medical approach. To face the genetic, molecular and pharmacological bases of the existing sex/gender gap by means of omics approaches will pave the way to the discovery and identification of novel drug-targets/therapeutic protocols, personalized laboratory tests and diagnostic procedures (sex/gender-omics). In this scenario, the aim of the present review is not to simply resume the state-of-the-art in the field, rather an opportunity to gain insights into gender medicine, spanning from molecular up to social and psychological stances. The description and critical discussion of some key selected multidisciplinary topics considered as paradigmatic of sex/gender differences and sex/gender inequalities will allow to draft and design strategies useful to fill the existing gap and move forward.

Preservation of Post-Infarction Cardiac Structure and Function via Long-Term Oral Formyl Peptide Receptor Agonist Treatment

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Myocardial infarction leads to recruitment of monocyte/macrophages to the injured myocardium to drive infarct healing.

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Activation of formyl peptide receptors (FPR1 and FPR2) present on macrophages contributes to key cellular activities that can potentiate wound healing.

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Myocardial infarction was induced in rodents to study the effects of long-term treatment with Compound 43, a small molecule agonist of FPR1 and FPR2.

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Main findings: Compound 43 stimulated proresolution macrophage activities, improved left ventricle and infarct structure, and preserved cardiac function post-myocardial infarction.

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The results suggest that stimulation of proresolution activities of FPRs can favorably alter post-myocardial infarction pathophysiology that leads to heart failure.

Dysregulated inflammation following myocardial infarction (MI) promotes left ventricular (LV) remodeling and loss of function. Targeting inflammation resolution by activating formyl peptide receptors (FPRs) may limit adverse remodeling and progression towards heart failure. This study characterized the cellular and signaling properties of Compound 43 (Cmpd43), a dual FPR1/FPR2 agonist, and examined whether Cmpd43 treatment improves LV and infarct remodeling in rodent MI models. Cmpd43 stimulated FPR1/2-mediated signaling, enhanced proresolution cellular function, and modulated cytokines. Cmpd43 increased LV function and reduced chamber remodeling while increasing proresolution macrophage markers. The findings demonstrate that FPR agonism improves cardiac structure and function post-MI.

Resveratrol improves cardiac function by promoting M2-like polarization of macrophages in mice with myocardial infarction

Macrophage polarization determines the transition from the inflammation phase to the inflammation resolution phase after myocardial infarction (MI). The aim of the present study was to investigate whether resveratrol (RSV) could inhibit the inflammatory mediators associated with the regulation of macrophage phenotypes and functions in MI mice. We initially discovered that RSV significantly improved cardiac function and suppressed the expression of fibrosis markers, such as collagen-I, collagen-III, and fibronectin, and pro-inflammatory cytokines, including interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α). RSV inhibited the expression of M1-like macrophage-related biomarkers (e.g., TNF-α and MCP-1) when bone marrow-derived macrophages (BMDMs) were stimulated with lipopolysaccharide (LPS) and interferon-γ (INF-γ). In contrast, it upregulated M2-like macrophage-related biomarkers (e.g., CD163 and Arg-1) when BMDMs were stimulated with interleukin-4 (IL-4) and interleukin-10 (IL-10). In addition, we found that RSV promoted M2-like macrophage polarization under anoxic conditions, which could be related to JAK2-SATA3 phosphorylation. In summary, RSV might promote anti-inflammatory M2-like polarization of macrophages after MI to improve cardiac function via the regulation of JAK2-SATA3 phosphorylation.

Extracellular vesicles from regenerative human cardiac cells act as potent immune modulators by priming monocytes

BACKGROUND

Nano-sized vesicles, so called extracellular vesicles (EVs), from regenerative cardiac cells represent a promising new therapeutic approach to treat cardiovascular diseases. However, it is not yet sufficiently understood how cardiac-derived EVs facilitate their protective effects. Therefore, we investigated the immune modulating capabilities of EVs from human cardiac-derived adherent proliferating (CardAP) cells, which are a unique cell type with proven cardioprotective features.

RESULTS

Differential centrifugation was used to isolate EVs from conditioned medium of unstimulated or cytokine-stimulated (IFNγ, TNFα, IL-1β) CardAP cells. The derived EVs exhibited typical EV-enriched proteins, such as tetraspanins, and diameters mostly of exosomes (< 100 nm). The cytokine stimulation caused CardAP cells to release smaller EVs with a lower integrin ß1 surface expression, while the concentration between both CardAP-EV variants was unaffected. An exposure of either CardAP-EV variant to unstimulated human peripheral blood mononuclear cells (PBMCs) did not induce any T cell proliferation, which indicates a general low immunogenicity. In order to evaluate immune modulating properties, PBMC cultures were stimulated with either Phytohemagglutin or anti-CD3. The treatment of those PBMC cultures with either CardAP-EV variant led to a significant reduction of T cell proliferation, pro-inflammatory cytokine release (IFNγ, TNFα) and increased levels of active TGFβ. Further investigations identified CD14+ cells as major recipient cell subset of CardAP-EVs. This interaction caused a significant lower surface expression of HLA-DR, CD86, and increased expression levels of CD206 and PD-L1. Additionally, EV-primed CD14+ cells released significantly more IL-1RA. Notably, CardAP-EVs failed to modulate anti-CD3 triggered T cell proliferation and pro-inflammatory cytokine release in monocultures of purified CD3+ T cells. Subsequently, the immunosuppressive feature of CardAP-EVs was restored when anti-CD3 stimulated purified CD3+ T cells were co-cultured with EV-primed CD14+ cells. Beside attenuated T cell proliferation, those cultures also exhibited a significant increased proportion of regulatory T cells.

CONCLUSIONS

CardAP-EVs have useful characteristics that could contribute to enhanced regeneration in damaged cardiac tissue by limiting unwanted inflammatory processes. It was shown that the priming of CD14+ immune cells by CardAP-EVs towards a regulatory type is an essential step to attenuate significantly T cell proliferation and pro-inflammatory cytokine release in vitro.

Notch Signaling Regulates Immune Responses in Atherosclerosis

Atherosclerosis is a chronic autoimmune inflammatory disease that can cause coronary artery disease, stroke, peripheral artery disease, depending on which arteries are affected. At the beginning of atherosclerosis plasma lipoproteins accumulate in the sub-endothelial space. In response, monocytes migrate from the circulation through the endothelium into the intima where they differentiate into macrophages. These early events trigger a complex immune response that eventually involves many cellular subtypes of both innate and adaptive immunity. The Notch signaling pathway is an evolutionary conserved cell signaling system that mediates cell-to-cell communication. Recent studies have revealed that Notch modulate atherosclerosis by controlling macrophages polarization into M1 or M2 subtypes. Furthermore, it is known that Notch signaling controls differentiation and activity of T-helper and cytotoxic T-cells in inflammatory diseases. In this review, we will discuss the role of Notch in modulating immunity in the context of atherosclerosis and whether targeting Notch may represent a therapeutic strategy.

The Role of Metabolic Remodeling in Macrophage Polarization and Its Effect on Skeletal Muscle Regeneration

Significance: Macrophages are crucial for tissue homeostasis. Based on their activation, they might display classical/M1 or alternative/M2 phenotypes. M1 macrophages produce pro-inflammatory cytokines, reactive oxygen species (ROS), and nitric oxide (NO). M2 macrophages upregulate arginase-1 and reduce NO and ROS levels; they also release anti-inflammatory cytokines, growth factors, and polyamines, thus promoting angiogenesis and tissue healing. Moreover, M1 and M2 display key metabolic differences; M1 polarization is characterized by an enhancement in glycolysis and in the pentose phosphate pathway (PPP) along with a decreased oxidative phosphorylation (OxPhos), whereas M2 are characterized by an efficient OxPhos and reduced PPP. Recent Advances: The glutamine-related metabolism has been discovered as crucial for M2 polarization. Vice versa, flux discontinuities in the Krebs cycle are considered additional M1 features; they lead to increased levels of immunoresponsive gene 1 and itaconic acid, to isocitrate dehydrogenase 1-downregulation and to succinate, citrate, and isocitrate over-expression. Critical Issues: A macrophage classification problem, particularly in vivo, originating from a gap in the knowledge of the several intermediate polarization statuses between the M1 and M2 extremes, characterizes this field. Moreover, the detailed features of metabolic reprogramming crucial for macrophage polarization are largely unknown; in particular, the role of β-oxidation is highly controversial. Future Directions: Manipulating the metabolism to redirect macrophage polarization might be useful in various pathologies, including an efficient skeletal muscle regeneration. Unraveling the complexity pertaining to metabolic signatures that are specific for the different macrophage subsets is crucial for identifying new compounds that are able to trigger macrophage polarization and that might be used for therapeutical purposes.

Therapeutic role of miR-19a/19b in cardiac regeneration and protection from myocardial infarction

The primary cause of heart failure is the loss of cardiomyocytes in the diseased adult heart. Previously, we reported that the miR-17-92 cluster plays a key role in cardiomyocyte proliferation. Here, we report that expression of miR-19a/19b, members of the miR-17-92 cluster, is induced in heart failure patients. We show that intra-cardiac injection of miR-19a/19b mimics enhances cardiomyocyte proliferation and stimulates cardiac regeneration in response to myocardial infarction (MI) injury. miR-19a/19b protected the adult heart in two distinctive phases: an early phase immediately after MI and long-term protection. Genome-wide transcriptome analysis demonstrates that genes related to the immune response are repressed by miR-19a/19b. Using an adeno-associated virus approach, we validate that miR-19a/19b reduces MI-induced cardiac damage and protects cardiac function. Finally, we confirm the therapeutic potential of miR-19a/19b in protecting cardiac function by systemically delivering miR-19a/19b into mice post-MI. Our study establishes miR-19a/19b as potential therapeutic targets to treat heart failure.

Deletion of Biliverdin Reductase A in Myeloid Cells Promotes Chemokine Expression and Chemotaxis in Part via a Complement C5a--C5aR1 Pathway

Biliverdin reductase (BVR)-A is a pleotropic enzyme converting biliverdin to bilirubin and a signaling molecule that has cytoprotective and immunomodulatory effects. We recently showed that biliverdin inhibits the expression of complement activation fragment 5a receptor one (C5aR1) in RAW 264.7 macrophages. In this study, we investigated the role of BVR-A in determining macrophage inflammatory phenotype and function via regulation of C5aR1. We assessed expression of C5aR1, M1-like macrophage markers, including chemokines (RANTES, IP-10), as well as chemotaxis in response to LPS and C5a in bone marrow-derived macrophages from BVR ^fl/fl and LysM-Cre:BVR ^{fl / fl} mice (conditional deletion of BVR-A in myeloid cells). In response to LPS, macrophages isolated from LysM-Cre:BVR ^fl/fl showed significantly elevated levels of C5aR1 as well as chemokines (RANTES, IP10) but not proinflammatory markers, such as iNOS and TNF. An increase in C5aR1 expression was also observed in peritoneal macrophages and several tissues from LysM-Cre:BVR ^fl/fl mice in a model of endotoxemia. In addition, knockdown of BVR-A resulted in enhanced macrophage chemotaxis toward C5a. Part of the effects of BVR-A deletion on chemotaxis and RANTES expression were blocked in the presence of a C5aR1 neutralizing Ab, confirming the role of C5a-C5aR1 signaling in mediating the effects of BVR. In summary, BVR-A plays an important role in regulating macrophage chemotaxis in response to C5a via modulation of C5aR1 expression. In addition, macrophages lacking BVR-A are characterized by the expression of M1 polarization-associated chemokines, the levels of which depend in part on C5aR1 signaling.

Mechanical stretch induces hair regeneration through the alternative activation of macrophages

Tissues and cells in organism are continuously exposed to complex mechanical cues from the environment. Mechanical stimulations affect cell proliferation, differentiation, and migration, as well as determining tissue homeostasis and repair. By using a specially designed skin-stretching device, we discover that hair stem cells proliferate in response to stretch and hair regeneration occurs only when applying proper strain for an appropriate duration. A counterbalance between WNT and BMP-2 and the subsequent two-step mechanism are identified through molecular and genetic analyses. Macrophages are first recruited by chemokines produced by stretch and polarized to M2 phenotype. Growth factors such as HGF and IGF-1, released by M2 macrophages, then activate stem cells and facilitate hair regeneration. A hierarchical control system is revealed, from mechanical and chemical signals to cell behaviors and tissue responses, elucidating avenues of regenerative medicine and disease control by demonstrating the potential to manipulate cellular processes through simple mechanical stimulation.

Dpep2 Emerging as a Modulator of Macrophage Inflammation Confers Protection Against CVB3-Induced Viral Myocarditis

Overwhelming cardiac inflammation has been reported to be the pathogenic mechanism of Coxsackievirus B3 (CVB3)-induced viral myocarditis (VMC), while the detailed molecular mechanisms remain unknown. Membrane-bound dipeptidases (MBD, also known as Dpep) have been shown to be involved in inflammatory diseases. However, the clear and direct evidence of their impacts on inflammation is still lacking. In this study, our results revealed that Dpep2 expression was remarkably increased during CVB3 infection, and primarily produced by the cardiac tissue-infiltrating macrophages instead of constitutive cardiomyocytes. Macrophages have been reported to play an important pathological role in driving VMC. Interestingly, macrophage-specific Dpep2 deletion robustly aggravated CVB3-induced cardiac inflammation, evidenced by augmented expression of TNF-α, IL-6, and MCP-1 in heart tissue. In addition, Dpep2-deficient bone-marrow derived macrophages (BMDMs) generated more TNF-α, IL-6, and MCP-1 after CVB3 stimulation compared with the control BMDMs. Moreover, this suppressive effect of Dpep2 on macrophages relied on its repression on NF-κB signaling pathway, but not on its conventional hydrolysate LTE4. Taken together, this study revealed that Dpep2 could protect against CVB3-induced VMC by acting as a suppressor of macrophage inflammation. Better understanding how macrophage Dpep2 dampened the cardiac inflammation would provide us with insights for the efficient control of CVB3-induced VMC.

Inhibition of MicroRNA-9-5p Protects Against Cardiac Remodeling Following Myocardial Infarction in Mice

Follistatin-like 1 (Fstl1) protects cardiomyocytes from a broad spectrum of pathologic injuries including myocardial infarction (MI). It is worthy of note that although cardiac Fstl1 is elevated in post-MI microenvironment, its cardioprotective role is still restricted to a limited extent considering the frequency and severity of adverse cardiac remodeling following MI. We therefore propose that intrinsic Fstl1-suppressing microRNA (miRNA) may exist in the heart and its neutralization may further facilitate post-MI recovery. Here, miR-9-5p is predicted as one of the potential Fstl1-targeting miRNAs whose expression is decreased in ischemic myocardium and reversely correlated with Fstl1. Luciferase activity assay further validated Fstl1 as a direct target of miR-9-5p. In addition, forced expression of miR-9-5p in H9c2 cells is concurrent with diminished expression of Fstl1 and vice versa. Importantly, transfection of miR-9-5p mimics in hypoxic H9c2 cells exacerbates cardiac cell death, lactate dehydrogenase release, reactive oxygen species accumulation, and malonyldialdehyde concentration. More importantly, in vivo silencing of miR-9-5p by a specific antagomir in a murine acute MI model effectively preserves post-MI heart function with attenuated fibrosis and inflammatory response. Further studies demonstrated that antagomir treatment stabilizes Fstl1 expression as well as blocks cardiac cell death and reactive oxygen species generation in both ischemia-challenged hearts and hypoxia-treated cardiomyoblasts. Finally, cytoprotection against hypoxic challenge by miR-9-5p inhibitor is partially reversed by knockdown of Fstl1, indicating a novel role of miR-9-5p/Fstl1 axis in survival defense against hypoxic challenge. In summary, these findings identified miR-9-5p as a mediator of hypoxic injury in cardiomyoblasts and miR-9-5p suppression prevents cardiac remodeling after acute MI, providing a potential strategy for early treatment against MI.

The Interplay between MicroRNAs and Cellular Components of Tumour Microenvironment (TME) on Non-Small-Cell Lung Cancer (NSCLC) Progression

Cellular components of the tumour microenvironment (TME) are recognized to regulate the hallmarks of cancers including tumour proliferation, angiogenesis, invasion, and metastasis, as well as chemotherapeutic resistance. The linkage between miRNA, TME, and the development of the hallmarks of cancer makes miRNA-mediated regulation of TME a potential therapeutic strategy to complement current cancer therapies. Despite significant advances in cancer therapy, lung cancer remains the deadliest form of cancer among males in the world and has overtaken breast cancer as the most fatal cancer among females in more developed countries. Therefore, there is an urgent need to develop more effective treatments for NSCLC, which is the most common type of lung cancer. Hence, this review will focus on current literature pertaining to antitumour or protumourigenic effects elicited by nonmalignant stromal cells of TME in NSCLC through miRNA regulation as well as current status and future prospects of miRNAs as therapeutic agents or targets to regulate TME in NSCLC.

Unified nexus of macrophages and maresins in cardiac reparative mechanisms

Macrophages are immune-sensing "big eater" phagocytic cells responsible for an innate, adaptive, and regenerative response. After myocardial infarction, macrophages predominantly clear the deceased cardiomyocyte apoptotic or necrotic neutrophils to develop a regenerative and reparative program with the activation of the lipoxygenase-mediated maresin (MaR) metabolome at the site of ischemic injury. The specialized proresolving molecule and macrophage mediator in resolving inflammation, MaR-1, produced by human macrophages, has potent defining effects that limit polymorphonuclear neutrophil infiltration, enhance uptake of apoptotic PMNs, regulate inflammation resolution and tissue regeneration, and reduce pain. In addition to proresolving and anti-inflammatory actions, MaR-1 displays potent tissue regenerative effects in stroke and is an antinociceptive. Macrophages actively participate in the biosynthesis of bioactive MaR-2, which exhibits anti-inflammatory, proresolving, and atherosclerotic effects. A new class of macrophage-derived molecules, MaR conjugates in tissue regeneration, is identified that regulates phagocytosis and the repair and regeneration of damaged tissue. The presented review provides a current summary of the effect of MaR in resolution pathophysiology, with relevance to a cardiac repair program.-Jadapalli, J. K., Halade, G. V. Unified nexus of macrophages and maresins in cardiac reparative mechanisms.

Inflammation following acute myocardial infarction: Multiple players, dynamic roles, and novel therapeutic opportunities

Acute myocardial infarction (AMI) and the heart failure that often follows, are major causes of death and disability worldwide. As such, new therapies are required to limit myocardial infarct (MI) size, prevent adverse left ventricular (LV) remodeling, and reduce the onset of heart failure following AMI. The inflammatory response to AMI, plays a critical role in determining MI size, and a persistent pro-inflammatory reaction can contribute to adverse post-MI LV remodeling, making inflammation an important therapeutic target for improving outcomes following AMI. In this article, we provide an overview of the multiple players (and their dynamic roles) involved in the complex inflammatory response to AMI and subsequent LV remodeling, and highlight future opportunities for targeting inflammation as a therapeutic strategy for limiting MI size, preventing adverse LV remodeling, and reducing heart failure in AMI patients.

Cardiac macrophage biology in the steady-state heart, the aging heart, and following myocardial infarction

Macrophages play critical roles in homeostatic maintenance of the myocardium under normal conditions and in tissue repair after injury. In the steady-state heart, resident cardiac macrophages remove senescent and dying cells and facilitate electrical conduction. In the aging heart, the shift in macrophage phenotype to a proinflammatory subtype leads to inflammaging. Following myocardial infarction (MI), macrophages recruited to the infarct produce both proinflammatory and anti-inflammatory mediators (cytokines, chemokines, matrix metalloproteinases, and growth factors), phagocytize dead cells, and promote angiogenesis and scar formation. These diverse properties are attributed to distinct macrophage subtypes and polarization status. Infarct macrophages exhibit a proinflammatory M1 phenotype early and become polarized toward an anti-inflammatory M2 phenotype later post-MI. Although this classification system is oversimplified and needs to be refined to accommodate the multiple different macrophage subtypes that have been recently identified, general concepts on macrophage roles are independent of subtype classification. This review summarizes current knowledge about cardiac macrophage origins, roles, and phenotypes in the steady state, with aging, and after MI, as well as highlights outstanding areas of investigation.

Apoptosis inhibitor of macrophage depletion decreased M1 macrophage accumulation and the incidence of cardiac rupture after myocardial infarction in mice

Background

Cardiac rupture is an important cause of death in the acute phase after myocardial infarction (MI). Macrophages play a pivotal role in cardiac remodeling after MI. Apoptosis inhibitor of macrophage (AIM) is secreted specifically by macrophages and contributes to macrophage accumulation in inflamed tissue by maintaining survival and recruiting macrophages. In this study, we evaluated the role of AIM in macrophage accumulation in the infarcted myocardium and cardiac rupture after MI.

Methods and results

Wild-type (WT) and AIM^‒/‒ mice underwent permanent left coronary artery ligation and were followed-up for 7 days. Macrophage accumulation and phenotypes (M1 pro-inflammatory macrophage or M2 anti-inflammatory macrophage) were evaluated by immunohistological analysis and RT-PCR. Matrix metalloproteinase (MMP) activity levels were measured by gelatin zymography. The survival rate was significantly higher (81.1% vs. 48.2%, P<0.05), and the cardiac rupture rate was significantly lower in AIM^‒/‒ mice than in WT mice (10.8% vs. 31.5%, P<0.05). The number of M1 macrophages and the expression levels of M1 markers (iNOS and IL-6) in the infarcted myocardium were significantly lower in AIM^‒/‒ mice than in WT mice. In contrast, there was no difference in the number of M2 macrophages and the expression of M2 markers (Arg-1, CD206 and TGF-β1) between the two groups. The ratio of apoptotic macrophages in the total macrophages was significantly higher in AIM^‒/‒ mice than in WT mice, although MCP-1 expression did not differ between the two groups. MMP-2 and 9 activity levels in the infarcted myocardium were significantly lower in AIM^‒/‒ mice than in WT mice.

Conclusions

These findings suggest that AIM depletion decreases the levels of M1 macrophages, which are a potent source of MMP-2 and 9, in the infarcted myocardium in the acute phase after MI by promoting macrophage apoptosis, and leads to a decrease in the incidence of cardiac rupture and improvements in survival rates.

MicroRNA-93 elevation after myocardial infarction is cardiac protective

Coronary Artery Disease (CAD) is one of the most serious diseases that endangers human health worldwide, myocardial infarction (MI) is an acute form of CAD. Recent developments in MI therapies have resulted in significant reductions in mortality. However, subsequent chronic congestive heart failure and ventricle remodeling plagues an increasing number of MI patients. MicroRNAs (miR) have been reported to be involved in the process of cardiac remodeling, a recent study shows that miR-93 is elevated in the blood of CAD patients. Similar to human CAD, we found miR-93 is elevated both in ventricle tissue and blood in mice MI model, and miR-93 is secreted from cardiomyocytes cultured under hypoxia. Interestingly, miR-93 inhibits apoptosis and protects cardiomyocytes from ischemia/reperfusion injury. In other type of ischemic disease like stoke and peripheral arterial disease, miR-93 shows long term protective effects via enhancing angiogenesis, inducing macrophage M2 polarization and antioxidant effects. These effects are favorable for ventricle remodeling inhibition after MI. In a pilot experiment, we indicated that miR-93 knockdown deteriorate cardiac remodeling in 30days after MI in mice models. Therefore, we hypothesize that miR-93 upregulation and secretion from cardiomyocytes after MI is adaptive, which could inhibit cardiac remodeling and heart failure.