A new monocyte chemotactic protein-1/chemokine CC motif ligand-2 competitor limiting neointima formation and myocardial ischemia/reperfusion injury in mice

An injectable polyacrylamide/chitosan-based hydrogel with highly adhesive, stretchable and electroconductive properties loaded with irbesartan for treatment of myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MIRI) significantly contributes to the high incidence of complications and mortality associated with acute myocardial infarction. Recently, injectable electroconductive hydrogels (IECHs) have emerged as promising tools for replicating the mechanical, electroconductive, and physiological characteristics of cardiac tissue. Herein, we aimed to develop a novel IECH by incorporating irbesartan as a drug delivery system (DDS) for cardiac repair. Our approach involved merging a conductive poly-thiophene derivative (PEDOT: PSS) with an injectable dual-network adhesive hydrogel (DNAH) comprising a catechol-branched polyacrylamide network and a chitosan-hyaluronic acid covalent network. The resulting P-DNAH hydrogel, benefitting from a high conducting polymer content, a chemically crosslinked network, a robust dissipative matrix, and dynamic oxidation of catechol to quinone exhibited superior mechanical strength, desirable conductivity, and robust wet-adhesiveness. In vitro experiments with the P-DNAH hydrogel carrying irbesartan (P-DNAH-I) demonstrated excellent biocompatibility by cck-8 kit on H9C2 cells and a rapid initial release of irbesartan. Upon injection into the infarcted hearts of MIRI mouse models, the P-DNAH-I hydrogel effectively inhibited the inflammatory response and reduced the infarct size. In conclusion, our results suggest that the P-DNAH hydrogel, possessing suitable mechanical properties and electroconductivity, serves as an ideal IECH for DDS, delivering irbesartan to promote heart repair.

Targeting inflammation to reduce recurrent stroke

BACKGROUND

Approximately one in four stroke patients suffer from recurrent vascular events, underlying the necessity to improve secondary stroke prevention strategies. Immune mechanisms are causally associated with coronary atherosclerosis. However, stroke is a heterogeneous disease and the relative contribution of inflammation across stroke mechanisms is not well understood. The optimal design of future randomized control trials (RCTs) of anti-inflammatory therapies to prevent recurrence after stroke must be informed by a clear understanding of the prognostic role of inflammation according to stroke subtype and individual patient factors.

AIM

In this narrative review, we discuss (1) inflammatory pathways in the etiology of ischemic stroke subtypes; (2) the evidence on inflammatory markers and vascular recurrence after stroke; and (3) review RCT evidence of anti-inflammatory agents for vascular prevention.

SUMMARY OF REVIEW

Experimental work, genetic epidemiological data, and plaque-imaging studies all implicate inflammation in atherosclerotic stroke. However, emerging evidence also suggests that inflammatory mechanisms are also important in other stroke mechanisms. Advanced neuroimaging techniques support the role of neuroinflammation in blood-brain barrier dysfunction in cerebral small vessel disease (cSVD). Systemic inflammatory processes also promote atrial cardiopathy, incident and recurrent atrial fibrillation (AF). Although several inflammatory markers have been associated with recurrence after stroke, interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hsCRP) are presently the most promising markers to identify patients at increased vascular risk. Several RCTs have shown that anti-inflammatory therapies reduce vascular risk, including stroke, in coronary artery disease (CAD). Some, but not all of these trials, selected patients on the basis of elevated hsCRP. Although unproven after stroke, targeting inflammation to reduce recurrence is a compelling strategy and several RCTs are ongoing.

CONCLUSION

Evidence points toward the importance of inflammation across multiple stroke etiologies and potential benefit of anti-inflammatory targets in secondary stroke prevention. Taking the heterogeneous stroke etiologies into account, the use of serum biomarkers could be useful to identify patients with residual inflammatory risk and perform biomarker-led patient selection for future RCTs.

Application of locally responsive design of biomaterials based on microenvironmental changes in myocardial infarction

Morbidity and mortality caused by acute myocardial infarction (AMI) are on the rise, posing a grave threat to the health of the general population. Up to now, interventional, surgical, and pharmaceutical therapies have been the main treatment methods for AMI. Effective and timely reperfusion therapy decreases mortality, but it cannot stimulate myocardial cell regeneration or reverse ventricular remodeling. Cell therapy, gene therapy, immunotherapy, anti-inflammatory therapy, and several other techniques are utilized by researchers to improve patients' prognosis. In recent years, biomaterials for AMI therapy have become a hot spot in medical care. Biomaterials furnish a microenvironment conducive to cell growth and deliver therapeutic factors that stimulate cell regeneration and differentiation. Biomaterials adapt to the complex microenvironment and respond to changes in local physical and biochemical conditions. Therefore, environmental factors and material properties must be taken into account when designing biomaterials for the treatment of AMI. This article will review the factors that need to be fully considered in the design of biological materials.

Role of inflammation and immune response in atherosclerosis: Mechanisms, modulations, and therapeutic targets

Cardiovascular diseases (CVDs) have emerged as the leading cause of mortality globally, with atherosclerosis being a prominent focus of investigation among medical researchers worldwide. Atherosclerosis is characterized as a disease of the large and medium-sized arteries that is multifocal, accumulative, and immunoinflammatory in nature, resulting from the deposition of lipids. Accumulating evidence suggests that inflammatory responses and immunoregulation play a vital role in the occurrence and development of atherosclerosis. While existing treatments for atherosclerosis can assist in symptom management and slowing disease progression, a complete cure remains elusive. Consequently, there is significant interest in research and development of potential new drugs for this condition. Therefore, this review aims to consolidate the current understanding of the pathogenesis of atherosclerosis with an emphasis on inflammation, immune response and infection. Besides, it examines the effects and mechanisms of immunological modulations in atherosclerosis, and the potential therapeutic targets and drugs for intervening in the inflammatory responses and immunoregulation associated with atherosclerosis. Additionally, novel drug options for treating atherosclerosis are explored within the context of this review.

Preservation solution Custodiol containing human alpha-1-antitrypsin improves graft recovery after prolonged cold ischemic storage in a rat model of heart transplantation

Introduction

The shortage of available donor hearts and the risk of ischemia/reperfusion injury restrict heart transplantation (HTX). Alpha-1-antitrypsin (AAT), a well-characterized inhibitor of neutrophil serine protease, is used in augmentation therapy to treat emphysema due to severe AAT deficiency. Evidence demonstrates its additional anti-inflammatory and tissue-protective effects. We hypothesized that adding human AAT in a preservation solution reduces graft dysfunction in a rat model of HTX following extended cold ischemic storage.

Methods

The hearts from isogenic Lewis donor rats were explanted, stored for either 1h or 5h in cold Custodiol supplemented with either vehicle (1h ischemia, n=7 or 5h ischemia, n=7 groups) or 1 mg/ml AAT (1h ischemia+AAT, n=7 or 5h ischemia+AAT, n=9 groups) before heterotopic HTX. Left-ventricular (LV) graft function was evaluated in vivo 1.5h after HTX. Immunohistochemical detection of myeloperoxydase (MPO) was performed in myocardial tissue and expression of 88 gene quantified with PCR was analyzed both statistical and with machine-learning methods.

Results

After HTX, LV systolic function (dP/dt_max 1h ischemia+AAT 4197 ± 256 vs 1h ischemia 3123 ± 110; 5h ischemia+AAT 2858 ± 154 vs 5h ischemia 1843 ± 104mmHg/s, p<0.05) and diastolic function (dP/dt_min 5h ischemia+AAT 1516 ± 68 vs 5h ischemia 1095 ± 67mmHg/s, p<0.05) at an intraventricular volume of 90µl were improved in the AAT groups compared with the corresponding vehicle groups. In addition, the rate pressure product (1h ischemia+AAT 53 ± 4 vs 1h ischemia 26 ± 1; 5h ischemia+AAT 37 ± 3 vs 5h ischemia 21 ± 1mmHg*beats/min at an intraventricular volume of 90µl; p<0.05) was increased in the AAT groups compared with the corresponding vehicle groups. Moreover, the 5h ischemia+AAT hearts exhibited a significant reduction in MPO-positive cell infiltration in comparison to the 5h ischemia group. Our computational analysis shows that ischemia+AAT network displays higher homogeneity, more positive and fewer negative gene correlations than the ischemia+placebo network.

Discussion

We provided experimental evidence that AAT protects cardiac grafts from prolonged cold ischemia during HTX in rats.

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.

Alterations of long noncoding RNAs and mRNAs in extracellular vesicles derived from the murine heart post-ischemia-reperfusion injury

Extracellular vesicles (EVs) play important roles in cardiovascular diseases by delivering their RNA cargos. However, the features and possible role of the lncRNAs and mRNAs in cardiac EVs during ischemia-reperfusion (IR) remain unclear. Therefore, we performed RNA sequencing analysis to profile the features of lncRNAs and mRNAs and predicted their potential functions. Here, we demonstrated that the severity of IR injury was significantly correlated with cardiac EV production. RNA sequencing identified 73 significantly differentially expressed (DE) lncRNAs (39 upregulated and 34 downregulated) and 720 DE-mRNAs (317 upregulated and 403 downregulated). Gene Ontology (GO) and pathway analysis were performed to predict the potential functions of the DE-lncRNAs and mRNAs. The lncRNA-miRNA-mRNA ceRNA network showed the possible functions of DE-lncRNAs with DE-mRNAs which are enriched in the pathways of T cell receptor signalling pathway and cell adhesion molecules. Moreover, the expressions of ENSMUST00000146010 and ENSMUST00000180630 were negatively correlated with the severity of IR injury. A significant positive correlation was revealed between TCONS_00010866 expression and the severity of the cardiac injury. These findings revealed the lncRNA and mRNA profiles in the heart derived EVs and provided potential targets and pathways involved in cardiac IR injury.

Cytokine storm: behind the scenes of the collateral circulation after acute myocardial infarction

At least 17 million people die from acute myocardial infarction (AMI) every year, ranking it first among causes of death of human beings, and its incidence is gradually increasing. Typical characteristics of AMI include acute onset and poor prognosis. At present, there is no satisfactory treatment, but development of coronary collateral circulation (CCC) can be key to improving prognosis. Recent research indicates that the levels of cytokines, including those related to promoting inflammatory responses and angiogenesis, increase after the onset of AMI. In the early phase of AMI, cytokines play a vital role in inducing development of collateral circulation. However, when myocardial infarction is decompensated, cytokine secretion increases greatly, which may induce a cytokine storm and worsen prognosis. Cytokines can regulate the activation of a variety of signal pathways and form a complex network, which may promote or inhibit the establishment of collateral circulation. We searched for published articles in PubMed and Google Scholar, employing the keyword "acute myocardial infarction", "coronary collateral circulation" and "cytokine storm", to clarify the relationship between AMI and a cytokine storm, and how a cytokine storm affects the growth of collateral circulation after AMI, so as to explore treatment methods based on cytokine agents or inhibitors used to improve prognosis of AMI.

Macrophages in myocardial infarction

The heart contains a population of resident macrophages that markedly expands following injury through recruitment of monocytes and through proliferation of macrophages. In myocardial infarction, macrophages have been implicated in both injurious and reparative responses. In coronary atherosclerotic lesions, macrophages have been implicated in disease progression and in the pathogenesis of plaque rupture. Following myocardial infarction, resident macrophages contribute to initiation and regulation of the inflammatory response. Phagocytosis and efferocytosis are major functions of macrophages during the inflammatory phase of infarct healing, and mediate phenotypic changes, leading to acquisition of an anti-inflammatory macrophage phenotype. Infarct macrophages respond to changes in the cytokine content and extracellular matrix composition of their environment and secrete fibrogenic and angiogenic mediators, playing a central role in repair of the infarcted heart. Macrophages may also play a role in scar maturation and may contribute to chronic adverse remodeling of noninfarcted segments. Single cell studies have revealed a remarkable heterogeneity of macrophage populations in infarcted hearts; however, the relations between transcriptomic profiles and functional properties remain poorly defined. This review manuscript discusses the fate, mechanisms of expansion and activation, and role of macrophages in the infarcted heart. Considering their critical role in injury, repair, and remodeling, macrophages are important, but challenging, targets for therapeutic interventions in myocardial infarction.

FMF Kliniğine Alternatif Bir Bakış Açısı: MCP-1 (A-2518G) ve CCR2 (G190A) Polimorfizmleri ve MCP1 Ekspresyonu

Amaç: Ailevi Akdeniz Ateşi (AAA) otoinflamatuar bir hastalıktır ve çeşitli klinik bulgular olarak kendini gösterebilir. Kemokinler, inflamatuar sürecin önemli unsurlarıdır. MCP-1 ve onun reseptörü CCR2, FMF'de kritik roller oynayabilen monositler/makrofajlar için ana kemokinlerdir. Bundan dolayı MEFV gen fonksiyonunu etkileyebilecek MCP-1 (A-2518G) ve CCR2 (G190A) polimorfizmlerinin ve MCP-1 ekspresyon düzeyinin araştırılması amaçlanmıştır. Gereç ve Yöntem: FMF'li hastalar Tel-Hashomer kriterlerine göre belirlendi. Elde edilen kan örneklerinden DNA ve RNA izole edildi. Genotipleme analizi, PCR-RFLP tekniği ile yapıldı. Ayrıca Real-time PCR yöntemi ile ekspresyon analizleri yapıldı. Elde edilen sonuçlar istatistiksel olarak değerlendirildi. Bulgular: Çalışmaya toplam 229 birey (125 erkek ve 104 kadın) dahil edildi. Bunlardan 120 kişide FMF kliniği bulunurken, 107 kişide yoktu. Kalan iki kişi şüpheli klinik duruma sahipti. Çalışmaya alınan bireyler MEFV genotiplemesine göre değerlendirildiğinde ise 75 birey homozigot mutant, 77 birey Heterozigot saptanırken 77 birey ise MEFV geninde mutasyon taşımıyordu. Yapılan analizde Hem FMF kliniği hem de MEFV genotipleri ile MCP-1 (A-2518G) ve CCR2 (G190A) genotipleri arasında anlamlı bir ilişki bulunmadı. Ekspresyon analizinde, FMF kliniği olan hastalarda olmayanlara göre MCP-1 ekspresyonu artmış olarak saptandı. Ayrıca heterozigot MEFV grubunda mutasyonu olmayanlara göre MCP-1 ekspresyonu artmış olarak saptandı, Dahası homozigot MEFV grubunda MCP-1 ekspresyonu en yüksek düzeydeydi. Ek olarak, MCP-1 (A-2518G) genotiplendirmesine göre, MCP-1 ekspresyonu, Wild type gruba kıyasla hem homozigot hem de heterozigot gruplarda yükselmiştir. Sonuç: FMF hastalığında MCP-1 ekspresyonu artmış olup, bu durum FMF hastaları arasındaki klinik farklılıkları açıklayabilir. MEFV mutasyonları, MCP-1 transkripsiyonunu artırarak inflamasyonu şiddetlendirebilir. MCP-1(A-2518G) mutasyonlu hastalarda MCP-1 ekspresyonu artar, bu da FMF kliniğini ağırlaştırır. Anahtar Kelimeler: Ailevi Akdeniz Ateşi, MCP-1, CCR2, Expresyon analizi

Role of the CCL2-CCR2 axis in cardiovascular disease: Pathogenesis and clinical implications

The CCL2-CCR2 axis is one of the major chemokine signaling pathways that has received special attention because of its function in the development and progression of cardiovascular disease. Numerous investigations have been performed over the past decades to explore the function of the CCL2-CCR2 signaling axis in cardiovascular disease. Laboratory data on the CCL2-CCR2 axis for cardiovascular disease have shown satisfactory outcomes, yet its clinical translation remains challenging. In this article, we describe the mechanisms of action of the CCL2-CCR2 axis in the development and evolution of cardiovascular diseases including heart failure, atherosclerosis and coronary atherosclerotic heart disease, hypertension and myocardial disease. Laboratory and clinical data on the use of the CCL2-CCR2 pathway as a targeted therapy for cardiovascular diseases are summarized. The potential of the CCL2-CCR2 axis in the treatment of cardiovascular diseases is explored.

Sinapic Acid Attenuated Cardiac Remodeling After Myocardial Infarction by Promoting Macrophage M2 Polarization Through the PPARγ Pathway

Background

Macrophage polarization is an important regulatory mechanism of ventricular remodeling. Studies have shown that sinapic acid (SA) exerts an anti-inflammatory effect. However, the effect of SA on macrophages is still unclear.

Objectives

The purpose of the study was to investigate the role of SA in macrophage polarization and ventricular remodeling after myocardial infarction (MI).

Methods

An MI model was established by ligating the left coronary artery. The rats with MI were treated with SA for 1 or 4 weeks after MI. The effect of SA on bone marrow-derived macrophages (BMDMs) was also observed in vitro.

Results

Cardiac systolic dysfunction was significantly improved after SA treatment. SA reduced MCP-1 and CCR2 expression and macrophage infiltration. SA decreased the levels of the inflammatory factors TNF-α, IL-1α, IL-1β, and iNOS and increased the levels of the M2 macrophage markers CD206, Arg-1, IL-10, Ym-1, Fizz-1, and TGF-β at 1 week after MI. SA significantly increased CD68⁺/CD206⁺ macrophage infiltration. Myocardial interstitial fibrosis and MMP-2 and MMP-9 levels were decreased, and the sympathetic nerve marker TH and nerve sprouting marker GAP43 were suppressed after SA treatment at 4 weeks after MI. The PPARγ level was notably upregulated after SA treatment. In vitro, SA also increased the expression of PPARγ mRNA in BMDMs and IL-4-treated BMDMs in a concentration-dependent manner. SA enhanced Arg1 and IL-10 expression in BMDMs, and the PPARγ antagonist GW9662 attenuated M2 macrophage marker expression.

Conclusions

Our results demonstrated that SA attenuated structural and neural remodeling by promoting macrophage M2 polarization via PPARγ activation after MI.

Inflammatory Mediators in Atherosclerotic Vascular Remodeling

Atherosclerotic vascular disease remains the most common cause of ischemia, myocardial infarction, and stroke. Vascular function is determined by structural and functional properties of the arterial vessel wall, which consists of three layers, namely the adventitia, media, and intima. Key cells in shaping the vascular wall architecture and warranting proper vessel function are vascular smooth muscle cells in the arterial media and endothelial cells lining the intima. Pathological alterations of this vessel wall architecture called vascular remodeling can lead to insufficient vascular function and subsequent ischemia and organ damage. One major pathomechanism driving this detrimental vascular remodeling is atherosclerosis, which is initiated by endothelial dysfunction allowing the accumulation of intimal lipids and leukocytes. Inflammatory mediators such as cytokines, chemokines, and modified lipids further drive vascular remodeling ultimately leading to thrombus formation and/or vessel occlusion which can cause major cardiovascular events. Although it is clear that vascular wall remodeling is an elementary mechanism of atherosclerotic vascular disease, the diverse underlying pathomechanisms and its consequences are still insufficiently understood.

Pharmacological Targeting of the CCL2/CCR2 Axis for Atheroprotection: A Meta-Analysis of Preclinical Studies

BACKGROUND

The CCL2 (CC-chemokine ligand 2)/CCR2 (CC-chemokine receptor 2) axis governs monocyte recruitment to atherosclerotic lesions. Genetic and epidemiological studies show strong associations of CCL2 levels with atherosclerotic disease. Still, experimental studies testing pharmacological inhibition of CCL2 or CCR2 in atheroprone mice apply widely different approaches and report variable results, thus halting clinical translation.

METHODS

We systematically searched the literature for studies employing pharmacological CCL2/CCR2 blockade in atheroprone mice and meta-analyzed their effects on lesion size and morphology.

RESULTS

In a meta-analysis of 14 studies testing 11 different agents, CCL2/CCR2 blockade attenuated atherosclerotic lesion size in the aortic root or arch (g=-0.75 [-1.17 to -0.32], P=6×10^-4; N=171/171 mice in experimental/control group), the carotid (g=-2.39 [-4.23 to -0.55], P=0.01; N=24/25), and the femoral artery (g=-2.38 [-3.50 to -1.26], P=3×10^-5; N=10/10). Furthermore, CCL2/CCR2 inhibition reduced intralesional macrophage accumulation and increased smooth muscle cell content and collagen deposition. The effects of CCL2/CCR2 inhibition on lesion size correlated with reductions in plaque macrophage accumulation, in accord with a prominent role of CCL2/CCR2 signaling in monocyte recruitment. Subgroup analyses showed comparable efficacy of different CCL2- and CCR2-inhibitors in reducing lesion size and intralesional macrophages. The quality assessment revealed high risk of detection bias due to lack of blinding during outcome assessment, as well as evidence of attrition and reporting bias.

CONCLUSIONS

Preclinical evidence suggests that pharmacological targeting of CCL2 or CCR2 might lower atherosclerotic lesion burden, but the majority of existing studies suffer major quality issues that highlight the need for additional high-quality research.

The transcription factor interferon regulatory factor-1 is an endogenous mediator of myocardial ischemia reperfusion injury

Myocardial ischemia reperfusion (MIR) injury negatively affects the prognosis of acute myocardial infarction (AMI), while effective suppression of MIR injury remains a largely unmet clinical need. Interferon regulatory factors (IRF) are key players in chronic cardiac disorders such as cardiac remodeling. However, their roles in acute MIR injury remain largely unknown. In the current study, microarray data indicated that IRF1 expression was consistently changed in the human ischemic heart and ischemic reperfused mouse heart. Western blot analysis confirmed the expression alterations of IRF1 in ischemic reperfused mouse heart. Cardiac-specific IRF1 knockdown significantly decreased infarct size, improved cardiac function, and suppressed myocardial apoptosis after MIR injury. Conversely, cardiac-specific IRF1 overexpression significantly promoted MIR injury. Further investigation revealed that IRF1 transcriptionally regulated the expression of inducible nitric oxide synthase (iNOS), and augmented oxidative stress. Taken together, we presented the first direct evidence that IRF1 served as a mediator of MIR injury, and IRF1 may represent a potential therapeutic target for alleviating MIR injury.

Particulate Matter-Induced Acute Coronary Syndrome: MicroRNAs as Microregulators for Inflammatory Factors

The most prevalent cause of mortality and morbidity worldwide is acute coronary syndrome (ACS) and its consequences. Exposure to particulate matter (PM) from air pollution has been shown to impair both. Various plausible pathogenic mechanisms have been identified, including microRNAs (miRNAs), an epigenetic regulator for gene expression. Endogenous miRNAs, average 22-nucleotide RNAs (ribonucleic acid), regulate gene expression through mRNA cleavage or translation repression and can influence proinflammatory gene expression posttranscriptionally. However, little is known about miRNA responses to fine PM (PM_2.5, PM₁₀, ultrafine particles, black carbon, and polycyclic aromatic hydrocarbon) from air pollution and their potential contribution to cardiovascular consequences, including systemic inflammation regulation. For the past decades, microRNAs (miRNAs) have emerged as novel, prospective diagnostic and prognostic biomarkers in various illnesses, including ACS. We wanted to outline some of the most important studies in the field and address the possible utility of miRNAs in regulating particulate matter-induced ACS (PMIA) on inflammatory factors in this review.

Mendelian Randomization Studies in Stroke: Exploration of Risk Factors and Drug Targets With Human Genetic Data

Elucidating the causes of stroke is key to developing effective preventive strategies. The Mendelian randomization approach leverages genetic variants related to an exposure of interest to investigate the effects of varying that exposure on disease risk. The random allocation of genetic variants at conception reduces confounding from environmental factors and thus strengthens causal inference, analogous to treatment allocation in a randomized controlled trial. With the recent explosion in the availability of human genetic data, Mendelian randomization has proven a valuable tool for studying risk factors for stroke. In this review, we provide an overview of recent developments in the application of Mendelian randomization to unravel the pathophysiology of stroke subtypes and identify therapeutic targets for clinical translation. The approach has offered novel insight into the differential effects of risk factors and antihypertensive, lipid-lowering, and anticoagulant drug classes on risk of stroke subtypes. Analyses have further facilitated the prioritization of novel drug targets, such as for inflammatory pathways underlying large artery atherosclerotic stroke and for the coagulation cascade that contributes to cardioembolic stroke. With continued methodological advances coupled with the rapidly increasing availability of genetic data related to a broad range of stroke phenotypes, the potential for Mendelian randomization in this context is expanding exponentially.

Immunotherapy and cardiovascular diseases (CVD): novel avenues for immunotherapeutic approaches

As current therapies for cardiovascular disease (CVD), predominantly based on lipid lowering, still face an unacceptable residual risk, novel treatment strategies are being explored. Besides lipids, inflammatory processes play a major role in the pathogenesis of atherosclerosis, the underlying cause of the majority of CVD. The first clinical trials targeting the interleukin-1β-inflammasome axis have shown that targeting this pathway is successful in reducing cardiovascular events but did not decrease overall CVD mortality. Hence, novel and improved immunotherapeutics to treat CVD are being awaited. In this review we highlight novel immunotherapeutic approaches in CVD as well as future challenges ahead.

The Entry and Egress of Monocytes in Atherosclerosis: A Biochemical and Biomechanical Driven Process

In accordance with “the response to injury” theory, the entry of monocytes into the intima guided by inflammation signals, taking up cholesterol and transforming into foam cells, and egress from plaques determines the progression of atherosclerosis. Multiple cytokines and receptors have been reported to be involved in monocyte recruitment such as CCL2/CCR2, CCL5/CCR5, and CX3CL1/CX3CR1, and the egress of macrophages from the plaque like CCR7/CCL19/CCL21. Interestingly, some neural guidance molecules such as Netrin-1 and Semaphorin 3E have been demonstrated to show an inhibitory effect on monocyte migration. During the processes of monocytes recruitment and migration, factors affecting the biomechanical properties (e.g., the membrane fluidity, the deformability, and stiffness) of the monocytes, like cholesterol, amyloid-β peptide (Aβ), and lipopolysaccharides (LPS), as well as the biomechanical environment that the monocytes are exposed, like the extracellular matrix stiffness, mechanical stretch, blood flow, and hypertension, were discussed in the latter section. Till now, several small interfering RNAs (siRNAs), monoclonal antibodies, and antagonists for CCR2 have been designed and shown promising efficiency on atherosclerosis therapy. Seeking more possible biochemical factors that are chemotactic or can affect the biomechanical properties of monocytes, and uncovering the underlying mechanism, will be helpful in future studies.

Inflammation during Percutaneous Coronary Intervention-Prognostic Value, Mechanisms and Therapeutic Targets

Periprocedural myocardial injury and myocardial infarction (MI) are not infrequent complications of percutaneous coronary intervention (PCI) and are associated with greater short- and long-term mortality. There is an abundance of preclinical and observational data demonstrating that high levels of pre-, intra- and post-procedural inflammation are associated with a higher incidence of periprocedural myonecrosis as well as future ischaemic events, heart failure hospitalisations and cardiac-related mortality. Beyond inflammation associated with the underlying coronary pathology, PCI itself elicits an acute inflammatory response. PCI-induced inflammation is driven by a combination of direct endothelial damage, liberation of intra-plaque proinflammatory debris and reperfusion injury. Therefore, anti-inflammatory medications, such as colchicine, may provide a novel means of improving PCI outcomes in both the short- and long-term. This review summarises periprocedural MI epidemiology and pathophysiology, evaluates the prognostic value of pre-, intra- and post-procedural inflammation, dissects the mechanisms involved in the acute inflammatory response to PCI and discusses the potential for periprocedural anti-inflammatory treatment.

Post-ischemic Myocardial Inflammatory Response: A Complex and Dynamic Process Susceptible to Immunomodulatory Therapies

Following acute occlusion of a coronary artery causing myocardial ischemia and implementing first-line treatment involving rapid reperfusion, a dynamic and balanced inflammatory response is initiated to repair and remove damaged cells. Paradoxically, restoration of myocardial blood flow exacerbates cell damage as a result of myocardial ischemia-reperfusion (MI-R) injury, which eventually provokes accelerated apoptosis. In the end, the infarct size still corresponds to the subsequent risk of developing heart failure. Therefore, true understanding of the mechanisms regarding MI-R injury, and its contribution to cell damage and cell death, are of the utmost importance in the search for successful therapeutic interventions to finally prevent the onset of heart failure. This review focuses on the role of innate immunity, chemokines, cytokines, and inflammatory cells in all three overlapping phases following experimental, mainly murine, MI-R injury known as the inflammatory, reparative, and maturation phase. It provides a complete state-of-the-art overview including most current research of all post-ischemic processes and phases and additionally summarizes the use of immunomodulatory therapies translated into clinical practice.

Monocyte-Chemoattractant Protein-1 Levels in Human Atherosclerotic Lesions Associate With Plaque Vulnerability

[Figure: see text].

Targeting inflammation in atherosclerosis - from experimental insights to the clinic

Atherosclerosis, a dominant and growing cause of death and disability worldwide, involves inflammation from its inception to the emergence of complications. Targeting inflammatory pathways could therefore provide a promising new avenue to prevent and treat atherosclerosis. Indeed, clinical studies have now demonstrated unequivocally that modulation of inflammation can forestall the clinical complications of atherosclerosis. This progress pinpoints the need for preclinical investigations to refine strategies for combatting inflammation in the human disease. In this Review, we consider a gamut of attractive possibilities for modifying inflammation in atherosclerosis, including targeting pivotal inflammatory pathways such as the inflammasomes, inhibiting cytokines, manipulating adaptive immunity and promoting pro-resolution mechanisms. Along with lifestyle measures, pharmacological interventions to mute inflammation could complement traditional targets, such as lipids and hypertension, to make new inroads into the management of atherosclerotic risk.

The Regulatory Role of Histone Modification on Gene Expression in the Early Stage of Myocardial Infarction

Myocardial infarction (MI) is a fatal heart disease with high morbidity and mortality. Various studies have demonstrated that a series of relatively specific biological events occur within 24 h of MI. However, the roles of histone modifications in this pathological process are still poorly understood. To investigate the regulation of histone modifications on gene expression in early MI, we performed RNA sequencing (RNA-seq) and chromatin immunoprecipitation sequencing (ChIP-seq) on myocardial tissues 24 h after the onset of MI. The genome-wide profiles of five histone marks (H3K27ac, H3K9ac, H3K4me3, H3K9me3, and H3K27me3) were explored through ChIP-seq. RNA-seq identified 1,032 differentially expressed genes (DEGs) between the MI and sham groups. ChIP-seq analysis found that 195 upregulated DEGs were modified by change of at least one of the three active histone marks (H3K27ac, H3K9ac, and H3K4me3), and the biological processes and pathways analysis showed that these DEGs were significantly enriched in cardiomyocyte differentiation and development, inflammation, angiogenesis, and metabolism. In the transcriptional regulatory network, Ets1, Etv1, and Etv2 were predicted to be involved in gene expression regulation. In addition, by integrating super-enhancers (SEs) with RNA-seq data, 76 DEGs were associated with H3K27ac-enriched SEs in the MI group, and the functions of these SE-associated DEGs were mainly related to angiogenesis. Our results suggest that histone modifications may play important roles in the regulation of gene expression in the early stage of MI, and the early angiogenesis response may be initiated by SEs.

Immunotherapy for cardiovascular disease

The outcomes of the Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) trial have unequivocally proven that inflammation is a key driver of atherosclerosis and that targeting inflammation, in this case by using an anti-interleukin-1β antibody, improves cardiovascular disease (CVD) outcomes. This is especially true for CVD patients with a pro-inflammatory constitution. Although CANTOS has epitomized the importance of targeting inflammation in atherosclerosis, treatment with canakinumab did not improve CVD mortality, and caused an increase in infections. Therefore, the identification of novel drug targets and development of novel therapeutics that block atherosclerosis-specific inflammatory pathways and exhibit limited immune-suppressive side effects, as pursued in our collaborative research centre, are required to optimize immunotherapy for CVD. In this review, we will highlight the potential of novel immunotherapeutic targets that are currently considered to become a future treatment for CVD.

Chemokines in Myocardial Infarction

In the infarcted myocardium, cardiomyocyte necrosis triggers an intense inflammatory reaction that not only is critical for cardiac repair, but also contributes to adverse remodeling and to the pathogenesis of heart failure. Both CC and CXC chemokines are markedly induced in the infarcted heart, bind to endothelial glycosaminoglycans, and regulate leukocyte trafficking and function. ELR+ CXC chemokines (such as CXCL8) control neutrophil infiltration, whereas CC chemokines (such as CCL2) mediate recruitment of mononuclear cells. Moreover, some members of the chemokine family (such as CXCL10 and CXCL12) may mediate leukocyte-independent actions, directly modulating fibroblast and vascular cell function. This review manuscript discusses our understanding of the role of the chemokines in regulation of injury, repair, and remodeling following myocardial infarction. Although several chemokines may be promising therapeutic targets in patients with myocardial infarction, clinical implementation of chemokine-based therapeutics is hampered by the broad effects of the chemokines in both injury and repair.

The effector cells and cellular mediators of immune system involved in cardiac inflammation and fibrosis after myocardial infarction

The cardiac repair after myocardial infarction (MI) involves two phases, namely, inflammatory response and proliferative response. The former is an inflammatory reaction, evoked by different kinds of pro-inflammatory leukocytes and molecules stimulated by myocardial necrosis, while the latter is a repair process, predominated by a magnitude of anti-inflammatory cells and cytokines, as well as fibroblasts. Cardiac remodeling post-MI is dependent on the balance of individualized intensity of the post-MI inflammation and subsequent cardiac fibrosis. During the past 30 years, enormous studies have focused on investigating immune cells and mediators involved in cardiac inflammation and fibrosis, which are two interacting processes of post-MI cardiac repair. These results contribute to revealing the mechanism of adverse cardiac remodeling after MI and alleviating the impairment of cardiac function. In this study, we will broadly discuss the role of immune cell subpopulation and the involved cytokines and chemokines during cardiac repair post-MI, particular in cardiac inflammation and fibrosis.

Targeting Chemokine-Glycosaminoglycan Interactions to Inhibit Inflammation

Leukocyte migration into tissues depends on the activity of chemokines that form concentration gradients to guide leukocytes to a specific site. Interaction of chemokines with their specific G protein-coupled receptors (GPCRs) on leukocytes induces leukocyte adhesion to the endothelial cells, followed by extravasation of the leukocytes and subsequent directed migration along the chemotactic gradient. Interaction of chemokines with glycosaminoglycans (GAGs) is crucial for extravasation in vivo. Chemokines need to interact with GAGs on endothelial cells and in the extracellular matrix in tissues in order to be presented on the endothelium of blood vessels and to create a concentration gradient. Local chemokine retention establishes a chemokine gradient and prevents diffusion and degradation. During the last two decades, research aiming at reducing chemokine activity mainly focused on the identification of inhibitors of the interaction between chemokines and their cognate GPCRs. This approach only resulted in limited success. However, an alternative strategy, targeting chemokine-GAG interactions, may be a promising approach to inhibit chemokine activity and inflammation. On this line, proteins derived from viruses and parasites that bind chemokines or GAGs may have the potential to interfere with chemokine-GAG interactions. Alternatively, chemokine mimetics, including truncated chemokines and mutant chemokines, can compete with chemokines for binding to GAGs. Such truncated or mutated chemokines are characterized by a strong binding affinity for GAGs and abrogated binding to their chemokine receptors. Finally, Spiegelmers that mask the GAG-binding site on chemokines, thereby preventing chemokine-GAG interactions, were developed. In this review, the importance of GAGs for chemokine activity in vivo and strategies that could be employed to target chemokine-GAG interactions will be discussed in the context of inflammation.

Peroxisome proliferator-activated receptor-gamma targeting nanomedicine promotes cardiac healing after acute myocardial infarction by skewing monocyte/macrophage polarization in preclinical animal models

Aims

Monocyte-mediated inflammation is a major mechanism underlying myocardial ischaemia-reperfusion (IR) injury and the healing process after acute myocardial infarction (AMI). However, no definitive anti-inflammatory therapies have been developed for clinical use. Pioglitazone, a peroxisome proliferator-activated receptor-gamma (PPARγ) agonist, has unique anti-inflammatory effects on monocytes/macrophages. Here, we tested the hypothesis that nanoparticle (NP)-mediated targeting of pioglitazone to monocytes/macrophages ameliorates IR injury and cardiac remodelling in preclinical animal models.

Methods and results

We formulated poly (lactic acid/glycolic acid) NPs containing pioglitazone (pioglitazone-NPs). In a mouse IR model, these NPs were delivered predominantly to circulating monocytes and macrophages in the IR heart. Intravenous treatment with pioglitazone-NPs at the time of reperfusion attenuated IR injury. This effect was abrogated by pre-treatment with the PPARγ antagonist GW9662. In contrast, treatment with a pioglitazone solution had no therapeutic effects on IR injury. Pioglitazone-NPs inhibited Ly6Chigh inflammatory monocyte recruitment as well as inflammatory gene expression in the IR hearts. In a mouse myocardial infarction model, intravenous treatment with pioglitazone-NPs for three consecutive days, starting 6 h after left anterior descending artery ligation, attenuated cardiac remodelling by reducing macrophage recruitment and polarizing macrophages towards the pro-healing M2 phenotype. Furthermore, pioglitazone-NPs significantly decreased mortality after MI. Finally, in a conscious porcine model of myocardial IR, pioglitazone-NPs induced cardioprotection from reperfused infarction, thus providing pre-clinical proof of concept.

Conclusion

NP-mediated targeting of pioglitazone to inflammatory monocytes protected the heart from IR injury and cardiac remodelling by antagonizing monocyte/macrophage-mediated acute inflammation and promoting cardiac healing after AMI.

Monocytes prime autoreactive T cells after myocardial infarction

In humans, loss of central tolerance for the cardiac self-antigen α-myosin heavy chain (α-MHC) leads to circulation of cardiac autoreactive T cells and renders the heart susceptible to autoimmune attack after acute myocardial infarction (MI). MI triggers profound tissue damage, releasing danger signals and self-antigen by necrotic cardiomyocytes, which lead to recruitment of inflammatory monocytes. We hypothesized that excessive inflammation by monocytes contributes to the initiation of adaptive immune responses to cardiac self-antigen. Using an experimental model of MI in α-MHC-mCherry reporter mice, which specifically express mCherry in cardiomyocytes, we detected α-MHC antigen in myeloid cells in the heart-draining mediastinal lymph node (MLN) 7 days after MI. To test whether monocytes were required for cardiac self-antigen trafficking to the MLN, we blocked monocyte recruitment with a C-C motif chemokine receptor type 2 (CCR2) antagonist or immune modifying nanoparticles (IMP). Blockade of monocyte recruitment reduced α-MHC antigen detection in the MLN after MI. Intramyocardial injection of the model antigen ovalbumin into OT-II transgenic mice demonstrated the requirement for monocytes in antigen trafficking and T-cell activation in the MLN. Finally, in nonobese diabetic mice, which are prone to postinfarction autoimmunity, blockade of monocyte recruitment reduced α-MHC-specific responses leading to improved tissue repair and ventricular function 28 days after MI. Taken together, these data support a role for monocytes in the onset of pathological cardiac autoimmunity following MI and suggest that therapeutic targeting of monocytes may mitigate postinfarction autoimmunity in humans.NEW & NOTEWORTHY Our study newly identifies a role for inflammatory monocytes in priming an autoimmune T-cell response after myocardial infarction. Select inhibition of monocyte recruitment to the infarct prevents trafficking of cardiac self-antigen and activation of cardiac myosin reactive T cells in the heart-draining lymph node. Therapeutic targeting of inflammatory monocytes may limit autoimmune responses to improve cardiac remodeling and preserve left ventricular function after myocardial infarction.

MCP-1 mediates ischemia-reperfusion-induced cardiomyocyte apoptosis via MCPIP1 and CaSR

Monocyte chemotactic protein-1 (MCP-1) plays a crucial role in ischemia-reperfusion (I/R) injury; however, the detailed mechanism of MCP-1 in I/R injury-induced cardiomyocyte apoptosis remains unclear. In this study, we explored the cascade downstream of I/R-induced MCP-1 that modulates cell apoptosis and determined whether Ca²⁺-sensing receptors (CaSRs) are involved in the process. Protein levels were detected in a cardiac muscle cell line (HL-1) and primary cultured neonatal mouse ventricular cardiomyocytes using Western blotting and immunocytochemistry. Released MCP-1 was detected using ELISA. Both Hoechst staining and flow cytometry methods were used to measure cell apoptosis. Specific pharmacological inhibitors of CC chemokine receptor 2 (RS-102895) and CaSR (NPS-2143) as well as a CaSR activator (evocalcet) were applied to confirm the roles of these factors in I/R-induced cell apoptosis. I/R inhibited cell viability and upregulated cell apoptosis. Moreover, I/R induced the release of MCP-1 from both HL-1 cells and primary cardiomyocytes. Further research confirmed that CaSR acted as an upstream effector of monocyte chemotactic protein-1-induced protein-1 (MCPIP1) and coordinately regulated cell apoptosis, which was verified by addition of an inhibitor or activator of CaSR. Moreover, MCPIP1 induced cell apoptosis through endoplasmic reticulum (ER) stress but not autophagy induced by I/R. Based on these findings, I/R-induced MCP-1 release regulates cardiomyocyte apoptosis via the MCPIP1 and CaSR pathways, suggesting a new therapeutic strategy for I/R injury.NEW & NOTEWORTHY Ischemia-reperfusion (I/R)-induced monocyte chemotactic protein-1 release regulates cardiomyocyte apoptosis via the monocyte chemotactic protein-1-induced protein-1 (MCPIP1) and Ca²⁺-sensing receptor pathway. The functional changes mediated by MCPIP1 involve the activation of endoplasmic reticulum stress, but not the autophagy pathway, after I/R injury.

Tissue Resident CCR2- and CCR2+ Cardiac Macrophages Differentially Orchestrate Monocyte Recruitment and Fate Specification Following Myocardial Injury

RATIONALE

Recent advancements have brought to light the origins, complexity, and functions of tissue-resident macrophages. However, in the context of tissue injury or disease, large numbers of monocytes infiltrate the heart and are thought to contribute to adverse remodeling and heart failure pathogenesis. Little is understood about the diversity of monocytes and monocyte-derived macrophages recruited to the heart after myocardial injury, including the mechanisms that regulate monocyte recruitment and fate specification.

OBJECTIVE

We sought to test the hypothesis that distinct subsets of tissue-resident CCR2- (C-C chemokine receptor 2) and CCR2+ macrophages orchestrate monocyte recruitment and fate specification after myocardial injury.

METHODS AND RESULTS

We reveal that in numerous mouse models of cardiomyocyte cell death (permanent myocardial infarction, reperfused myocardial infarction, and diphtheria toxin cardiomyocyte ablation), there is a shift in macrophage ontogeny whereby tissue-resident macrophages are predominately replaced by infiltrating monocytes and monocyte-derived macrophages. Using syngeneic cardiac transplantation to model ischemia-reperfusion injury and distinguish tissue-resident from recruited cell populations in combination with intravital 2-photon microscopy, we demonstrate that monocyte recruitment is differentially orchestrated by distinct subsets of tissue-resident cardiac macrophages. Tissue-resident CCR2+ macrophages promote monocyte recruitment through an MYD88 (myeloid differentiation primary response 88)-dependent mechanism that results in release of MCPs (monocyte chemoattractant proteins) and monocyte mobilization. In contrast, tissue-resident CCR2- macrophages inhibit monocyte recruitment. Using CD (cluster of differentiation) 169-DTR (diphtheria toxin receptor) and CCR2-DTR mice, we further show that selective depletion of either tissue-resident CCR2- or CCR2+ macrophages before myocardial infarction results in divergent effects on left ventricular function, myocardial remodeling, and monocyte recruitment. Finally, using single-cell RNA sequencing, we show that tissue-resident cardiac macrophages differentially instruct monocyte fate specification.

CONCLUSIONS

Collectively, these observations establish the mechanistic basis by which monocytes are initially recruited to the injured heart and provide new insights into the heterogeneity of monocyte-derived macrophages.

Biomechanical assessment of remote and postinfarction scar remodeling following myocardial infarction

The importance of collagen remodeling following myocardial infarction (MI) is extensively investigated, but little is known on the biomechanical impact of fibrillar collagen on left ventricle post-MI. We aim to identify the significant effects of the biomechanics of types I, III, and V collagen on physio-pathological changes of murine hearts leading to heart failure. Immediately post-MI, heart reduces its function (EF = 40.94 ± 2.12%) while sarcomeres' dimensions are unchanged. Strikingly, as determined by immunohistochemistry staining, type V collagen fraction significantly grows in remote and scar for sustaining de novo-types I and III collagen fibers' assembly while hindering their enzymatic degradation. Thereafter, the compensatory heart function (EF = 63.04 ± 3.16%) associates with steady development of types I and III collagen in a stiff remote (12.79 ± 1.09 MPa) and scar (22.40 ± 1.08 MPa). In remote, the soft de novo-type III collagen uncoils preventing further expansion of elongated sarcomeres (2.7 ± 0.3 mm). Once the compensatory mechanisms are surpassed, the increased turnover of stiff type I collagen (>50%) lead to a pseudo-stable biomechanical regime of the heart (≅9 MPa) with reduced EF (50.55 ± 3.25%). These end-characteristics represent the common scenario evidenced in patients suffering from heart failure after MI. Our pre-clinical data advances the understanding of the cause of heart failure induced in patients with extended MI.

Genetically Determined Levels of Circulating Cytokines and Risk of Stroke

BACKGROUND

Cytokines and growth factors have been implicated in the initiation and propagation of vascular disease. Observational studies have shown associations of their circulating levels with stroke. Our objective was to explore whether genetically determined circulating levels of cytokines and growth factors are associated with stroke and its etiologic subtypes by conducting a 2-sample Mendelian randomization (MR) study.

METHODS

Genetic instruments for 41 cytokines and growth factors were obtained from a genome-wide association study of 8293 healthy adults. Their associations with stroke and stroke subtypes were evaluated in the MEGASTROKE genome-wide association study data set (67 162 cases; 454 450 controls) applying inverse variance-weighted meta-analysis, weighted-median analysis, Mendelian randomization-Egger regression, and multivariable Mendelian randomization. The UK Biobank cohort was used as an independent validation sample (4985 cases; 364 434 controls). Genetic instruments for monocyte chemoattractant protein-1 (MCP-1/CCL2) were further tested for association with etiologically related vascular traits by using publicly available genome-wide association study data.

RESULTS

Genetic predisposition to higher MCP-1 levels was associated with higher risk of any stroke (odds ratio [OR] per 1 SD increase, 1.06; 95% CI, 1.02-1.09; P=0.0009), any ischemic stroke (OR, 1.06; 95% CI, 1.02-1.10; P=0.002), large-artery stroke (OR, 1.19; 95% CI, 1.09-1.30; P=0.0002), and cardioembolic stroke (OR, 1.14; 95% CI, 1.06-1.23; P=0.0004), but not with small-vessel stroke or intracerebral hemorrhage. The results were stable in sensitivity analyses and remained significant after adjustment for cardiovascular risk factors. Analyses in the UK Biobank showed similar associations for available phenotypes (any stroke: OR, 1.08; 95% CI, 0.99-1.17; P=0.09; any ischemic stroke: OR, 1.07; 95% CI, 0.97-1.18; P=0.17). Genetically determined higher MCP-1 levels were further associated with coronary artery disease (OR, 1.04; 95% CI, 1.00-1.08; P=0.04) and myocardial infarction (OR, 1.05; 95% CI, 1.01-1.09; P=0.02), but not with atrial fibrillation. A meta-analysis of observational studies showed higher circulating MCP-1 levels in patients with stroke in comparison with controls.

CONCLUSIONS

Genetic predisposition to elevated circulating levels of MCP-1 is associated with higher risk of stroke, in particular with large-artery stroke and cardioembolic stroke. Whether targeting MCP-1 or its receptors can lower stroke incidence requires further study.

Circulating Monocyte Chemoattractant Protein-1 and Risk of Stroke: Meta-Analysis of Population-Based Studies Involving 17 180 Individuals

Rationale: Proinflammatory cytokines have been identified as potential targets for lowering vascular risk. Experimental evidence and Mendelian randomization suggest a role of MCP-1 (monocyte chemoattractant protein-1) in atherosclerosis and stroke. However, data from large-scale observational studies are lacking. Objective: To determine whether circulating levels of MCP-1 are associated with risk of incident stroke in the general population. Methods and Results: We used previously unpublished data on 17 180 stroke-free individuals (mean age, 56.7±8.1 years; 48.8% men) from 6 population-based prospective cohort studies and explored associations between baseline circulating MCP-1 levels and risk of any stroke, ischemic stroke, and hemorrhagic stroke during a mean follow-up interval of 16.3 years (280 522 person-years at risk; 1435 incident stroke events). We applied Cox proportional-hazards models and pooled hazard ratios (HRs) using random-effects meta-analyses. After adjustments for age, sex, race, and vascular risk factors, higher MCP-1 levels were associated with increased risk of any stroke (HR per 1-SD increment in ln-transformed MCP-1, 1.07; 95% CI, 1.01-1.14). Focusing on stroke subtypes, we found a significant association between baseline MCP-1 levels and higher risk of ischemic stroke (HR, 1.11 [1.02-1.21]) but not hemorrhagic stroke (HR, 1.02 [0.82-1.29]). The results followed a dose-response pattern with a higher risk of ischemic stroke among individuals in the upper quartiles of MCP-1 levels as compared with the first quartile (HRs, second quartile: 1.19 [1.00-1.42]; third quartile: 1.35 [1.14-1.59]; fourth quartile: 1.38 [1.07-1.77]). There was no indication for heterogeneity across studies, and in a subsample of 4 studies (12 516 individuals), the risk estimates were stable after additional adjustments for circulating levels of IL (interleukin)-6 and high-sensitivity CRP (C-reactive protein). Conclusions: Higher circulating levels of MCP-1 are associated with increased long-term risk of stroke. Our findings along with genetic and experimental evidence suggest that MCP-1 signaling might represent a therapeutic target to lower stroke risk.Visual Overview: An online visual overview is available for this article.

Heparin Binding Proteins as Therapeutic Target: An Historical Account and Current Trends

The polyanionic nature and the ability to interact with proteins with different affinities are properties of sulfated glycosaminoglycans (GAGs) that determine their biological function. In designing drugs affecting the interaction of proteins with GAGs the challenge has been to generate agents with high binding specificity. The example to emulated has been a heparin-derived pentasaccharide that binds to antithrombin-III with high affinity. However, the portability of this model to other biological situations is questioned on several accounts. Because of their structural flexibility, oligosaccharides with different sulfation and uronic acid conformation can display the same binding proficiency to different proteins and produce comparable biological effects. This circumstance represents a formidable obstacle to the design of drugs based on the heparin scaffold. The conceptual framework discussed in this article is that through a direct intervention on the heparin-binding functionality of proteins is possible to achieve a high degree of action specificity. This objective is currently pursued through two strategies. The first makes use of small molecules for which in the text we provide examples from past and present literature concerning angiogenic factors and enzymes. The second approach entails the mutagenesis of the GAG-binding site of proteins as a means to generate a new class of biologics of therapeutic interest.

G-Protein Coupled Receptor Targeting on Myeloid Cells in Atherosclerosis

Atherosclerosis, the underlying cause of the majority of cardiovascular diseases (CVDs), is a lipid-driven, inflammatory disease of the large arteries. Gold standard therapy with statins and the more recently developed proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have improved health conditions among CVD patients by lowering low density lipoprotein (LDL) cholesterol. Nevertheless, a substantial part of these patients is still suffering and it seems that 'just' lipid lowering is insufficient. The results of the Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) have now proven that inflammation is a key driver of atherosclerosis and that targeting inflammation improves CVD outcomes. Therefore, the identification of novel drug targets and development of novel therapeutics that block atherosclerosis-specific inflammatory pathways have to be promoted. The inflammatory processes in atherosclerosis are facilitated by a network of immune cells and their subsequent responses. Cell networking is orchestrated by various (inflammatory) mediators which interact, bind and induce signaling. Over the last years, G-protein coupled receptors (GPCRs) emerged as important players in recognizing these mediators, because of their diverse functions in steady state but also and specifically during chronic inflammatory processes - such as atherosclerosis. In this review, we will therefore highlight a selection of these receptors or receptor sub-families mainly expressed on myeloid cells and their role in atherosclerosis. More specifically, we will focus on chemokine receptors, both classical and atypical, formyl-peptide receptors, the chemerin receptor 23 and the calcium-sensing receptor. When information is available, we will also describe the consequences of their targeting which may hold promising options for future treatment of CVD.

Cardiac FGF23: new insights into the role and function of FGF23 after acute myocardial infarction

OBJECTIVE

We aimed to elucidate the local role of FGF23 after myocardial infarction in a mouse model induced by left anterior descending artery (LAD) ligation. APPROACH AND RESULTS: (C57BL/6 N) mice underwent MI via LAD ligation and were sacrificed at different time-points post MI. The expression and influence of FGF23 on fibroblast and macrophages was also analyzed using isolated murine cells. We identified enhanced cardiac FGF23 mRNA expression in a time-dependent manner with an early increase, already on the first day after MI. FGF23 protein expression was abundantly detected in the infarcted area during the inflammatory phase. While described to be primarily produced in bone or macrophages, we identified cardiac fibroblasts as the only source of local FGF23 production after MI. Inflammatory mediators, such as IL-1β, IL-6 and TNF-α, were able to induce FGF23 expression in these cardiac fibroblasts. Interestingly, we were not able to detect FGF23 at later time points after MI in mature scar tissue or remote myocardium, most likely due to TGF-β1, which we have shown to inhibit the expression of FGF23. We identified FGFR1c to be the most abundant receptor for FGF23 in infarcted myocardium and cardiac macrophages and fibroblasts. FGF23 increased migration of cardiac fibroblast, as well as expression of Collagen 1, Periostin, Fibronectin and MMP8. FGF23 also increased expression of TGF-β1 in M2 polarized macrophages.

CONCLUSION

In conclusion, cardiac fibroblasts in the infarcted myocardium produce and express FGF23 as well as its respective receptors in a time-dependent manner, thus potentially influencing resident cell migration. The transitory local expression of FGF23 after MI points towards a complex role of FGF23 in myocardial ischemia and warrants further exploration, considering its role in ventricular remodeling.

Blocking CCL5-CXCL4 heteromerization preserves heart function after myocardial infarction by attenuating leukocyte recruitment and NETosis

Myocardial infarction (MI) is a major cause of death in Western countries and finding new strategies for its prevention and treatment is thus of high priority. In a previous study, we have demonstrated a pathophysiologic relevance for the heterophilic interaction of CCL5 and CXCL4 in the progression of atherosclerosis. A specifically designed compound (MKEY) to block this CCL5-CXCR4 interaction is investigated as a potential therapeutic in a model of myocardial ischemia/reperfusion (I/R) damage. 8 week-old male C57BL/6 mice were intravenously treated with MKEY or scrambled control (sMKEY) from 1 day before, until up to 7 days after I/R. By using echocardiography and intraventricular pressure measurements, MKEY treatment resulted in a significant decrease in infarction size and preserved heart function as compared to sMKEY-treated animals. Moreover, MKEY treatment significantly reduced the inflammatory reaction following I/R, as revealed by specific staining for neutrophils and monocyte/macrophages. Interestingly, MKEY treatment led to a significant reduction of citrullinated histone 3 in the infarcted tissue, showing that MKEY can prevent neutrophil extracellular trap formation in vivo. Disrupting chemokine heterodimers during myocardial I/R might have clinical benefits, preserving the therapeutic benefit of blocking specific chemokines, and in addition, reducing the inflammatory side effects maintaining normal immune defence.

Synthetic CpG oligonucleotides induce a genetic profile ameliorating murine myocardial I/R injury

We previously demonstrated that pre‐conditioning with CpG oligonucleotide (ODN) 1668 induces quick up‐regulation of gene expression 3 hours post‐murine myocardial ischaemia/reperfusion (I/R) injury, terminating inflammatory processes that sustain I/R injury. Now, performing comprehensive microarray and biocomputational analyses, we sought to further enlighten the “black box” beyond these first 3 hours. C57BL/6 mice were pretreated with either CpG 1668 or with control ODN 1612, respectively. Sixteen hours later, myocardial ischaemia was induced for 1 hour in a closed‐chest model, followed by reperfusion for 24 hours. RNA was extracted from hearts, and labelled cDNA was hybridized to gene microarrays. Data analysis was performed with BRB ArrayTools and Ingenuity Pathway Analysis. Functional groups mediating restoration of cellular integrity were among the top up‐regulated categories. Genes known to influence cardiomyocyte survival were strongly induced 24 hours post‐I/R. In contrast, proinflammatory pathways were down‐regulated. Interleukin‐10, an upstream regulator, suppressed specifically selected proinflammatory target genes at 24 hours compared to 3 hours post‐I/R. The IL1 complex is supposed to be one regulator of a network increasing cardiovascular angiogenesis. The up‐regulation of numerous protective pathways and the suppression of proinflammatory activity are supposed to be the genetic correlate of the cardioprotective effects of CpG 1668 pre‐conditioning.

PCSK9 induces a pro-inflammatory response in macrophages

Intraplaque release of inflammatory cytokines from macrophages is implicated in atherogenesis by inducing the proliferation and migration of media smooth muscle cells (SMCs). PCSK9 is present and released by SMCs within the atherosclerotic plaque but its function is still unknown. In the present study, we tested the hypothesis that PCSK9 could elicit a pro-inflammatory effect on macrophages. THP-1-derived macrophages and human primary macrophages were exposed to different concentrations (0.250 ÷ 2.5 µg/ml) of human recombinant PCSK9 (hPCSK9). After 24 h incubation with 2.5 µg/ml PCSK9, a significant induction of IL-1β, IL-6, TNF-α, CXCL2, and MCP1 mRNA, were observed in both cell types. Co-culture of THP-1 macrophages with HepG2 overexpressing hPCSK9 also showed the induction of TNF-α (2.4 ± 0.5 fold) and IL-1β (8.6 ± 1.8 fold) mRNA in macrophages. The effect of hPCSK9 on TNF-α mRNA in murine LDLR^-/- bone marrow macrophages (BMM) was significantly impaired as compared to wild-type BMM (4.3 ± 1.6 fold vs 31.1 ± 6.1 fold for LDLR^-/- and LDLR^+/+, respectively). Finally, a positive correlation between PCSK9 and TNF-α plasma levels of healthy adult subjects (males 533, females 537) was observed (B = 8.73, 95%CI 7.54 ÷ 9.93, p < 0.001). Taken together, the present study provides evidence of a pro-inflammatory action of PCSK9 on macrophages, mainly dependent by the LDLR.

PCSK9 induces a pro-inflammatory response in macrophages

Intraplaque release of inflammatory cytokines from macrophages is implicated in atherogenesis by inducing the proliferation and migration of media smooth muscle cells (SMCs). PCSK9 is present and released by SMCs within the atherosclerotic plaque but its function is still unknown. In the present study, we tested the hypothesis that PCSK9 could elicit a pro-inflammatory effect on macrophages. THP-1-derived macrophages and human primary macrophages were exposed to different concentrations (0.250 ÷ 2.5 µg/ml) of human recombinant PCSK9 (hPCSK9). After 24 h incubation with 2.5 µg/ml PCSK9, a significant induction of IL-1β, IL-6, TNF-α, CXCL2, and MCP1 mRNA, were observed in both cell types. Co-culture of THP-1 macrophages with HepG2 overexpressing hPCSK9 also showed the induction of TNF-α (2.4 ± 0.5 fold) and IL-1β (8.6 ± 1.8 fold) mRNA in macrophages. The effect of hPCSK9 on TNF-α mRNA in murine LDLR^−/− bone marrow macrophages (BMM) was significantly impaired as compared to wild-type BMM (4.3 ± 1.6 fold vs 31.1 ± 6.1 fold for LDLR^−/− and LDLR^+/+, respectively). Finally, a positive correlation between PCSK9 and TNF-α plasma levels of healthy adult subjects (males 533, females 537) was observed (B = 8.73, 95%CI 7.54 ÷ 9.93, p < 0.001). Taken together, the present study provides evidence of a pro-inflammatory action of PCSK9 on macrophages, mainly dependent by the LDLR.

Deficiency of MAPK-activated protein kinase 2 (MK2) prevents adverse remodelling and promotes endothelial healing after arterial injury

Maladaptive remodelling of the arterial wall after mechanical injury (e. g. angioplasty) is characterised by inflammation, neointima formation and media hypertrophy, resulting in narrowing of the affected artery. Moreover, mechanical injury of the arterial wall causes loss of the vessel protecting endothelial cell monolayer. Mitogen-activated protein kinase (MAPK)-activated protein kinase 2 (MK2), a major downstream target of p38 MAPK, regulates inflammation, cell migration and proliferation, essential processes for vascular remodelling and reendothelialisation. Therefore, we investigated the role of MK2 in remodelling and reendothelialisation after arterial injury in genetically modified mice in vivo. Hypercholesterolaemic low-densitylipoprotein- receptor-deficient mice (ldlr-/- ) were subjected to wire injury of the common carotid artery. MK2-deficiency (ldlr-/-/mk2-/- ) nearly completely prevented neointima formation, media hypertrophy, and lumen loss after injury. This was accompanied by reduced proliferation and migration of MK2-deficient smooth muscle cells. In addition, MK2-deficiency severely reduced monocyte adhesion to the arterial wall (day 3 after injury, intravital microscopy), which may be attributed to reduced expression of the chemokine ligands CCL2 and CCL5. In line, MK2-deficiency significantly reduced the content of monocytes, neutrophiles and lymphocytes of the arterial wall (day 7 after injury, flow cytometry). In conclusion, in a model of endothelial injury (electric injury), MK2-deficiency strongly increased proliferation of endothelial cells and improved reendothelialisation of the arterial wall after injury. Deficiency of MK2 prevents adverse remodelling and promotes endothelial healing of the arterial wall after injury, suggesting that MK2-inhibition is a very attractive intervention to prevent restenosis after percutaneous therapeutic angioplasty.

Human Cardiac-Derived Stem/Progenitor Cells Fine-Tune Monocyte-Derived Descendants Activities toward Cardiac Repair

Cardiac repair following MI relies on a finely regulated immune response involving sequential recruitment of monocytes to the injured tissue. Monocyte-derived cells are also critical for tissue homeostasis and healing process. Our previous findings demonstrated the interaction of T and natural killer cells with allogeneic human cardiac-derived stem/progenitor cells (hCPC) and suggested their beneficial effect in the context of cardiac repair. Therefore, we investigated here whether monocytes and their descendants could be also modulated by allogeneic hCPC toward a repair/anti-inflammatory phenotype. Through experimental in vitro assays, we assessed the impact of allogeneic hCPC on the recruitment, functions and differentiation of monocytes. We found that allogeneic hCPC at steady state or under inflammatory conditions can incite CCL-2/CCR2-dependent recruitment of circulating CD14⁺CD16⁻ monocytes and fine-tune their activation toward an anti-inflammatory profile. Allogeneic hCPC also promoted CD14⁺CD16⁻ monocyte polarization into anti-inflammatory/immune-regulatory macrophages with high phagocytic capacity and IL10 secretion. Moreover, hCPC bended the differentiation of CD14⁺CD16⁻ monocytes to dendritic cells (DCs) toward anti-inflammatory macrophage-like features and impaired their antigen-presenting function in favor of immune-modulation. Collectively, our results demonstrate that allogeneic hCPC could reshape monocytes, macrophages as well as DCs responses by favoring their anti-inflammatory/tolerogenic activation/polarization. Thereby, therapeutic allogeneic hCPC might also contribute to post-infarct myocardial healing by modeling the activities of monocytes and their derived descendants.

MerTK Cleavage on Resident Cardiac Macrophages Compromises Repair After Myocardial Ischemia Reperfusion Injury

RATIONALE

Clinical benefits of reperfusion after myocardial infarction are offset by maladaptive innate immune cell function, and therapeutic interventions are lacking.

OBJECTIVE

We sought to test the significance of phagocytic clearance by resident and recruited phagocytes after myocardial ischemia reperfusion.

METHODS AND RESULTS

In humans, we discovered that clinical reperfusion after myocardial infarction led to significant elevation of the soluble form of MerTK (myeloid-epithelial-reproductive tyrosine kinase; ie, soluble MER), a critical biomarker of compromised phagocytosis by innate macrophages. In reperfused mice, macrophage Mertk deficiency led to decreased cardiac wound debridement, increased infarct size, and depressed cardiac function, newly implicating MerTK in cardiac repair after myocardial ischemia reperfusion. More notably, Mertk(CR) mice, which are resistant to cleavage, showed significantly reduced infarct sizes and improved systolic function. In contrast to other cardiac phagocyte subsets, resident cardiac MHCII^LOCCR2^- (major histocompatibility complex II/C-C motif chemokine receptor type 2) macrophages expressed higher levels of MerTK and, when exposed to apoptotic cells, secreted proreparative cytokines, including transforming growth factor-β. Mertk deficiency compromised the accumulation of MHCII^LO phagocytes, and this was rescued in Mertk(CR) mice. Interestingly, blockade of CCR2-dependent monocyte infiltration into the heart reduced soluble MER levels post-ischemia reperfusion.

CONCLUSIONS

Our data implicate monocyte-induced MerTK cleavage on proreparative MHCII^LO cardiac macrophages as a novel contributor and therapeutic target of reperfusion injury.

Monocyte subtypes and the CCR2 chemokine receptor in cardiovascular disease

Monocytes circulate in the blood and migrate to inflammatory tissues, but their functions can be either detrimental or beneficial, depending on their phenotypes. In humans, classical monocytes are inflammatory cluster of differentiation (CD)14++CD16−CCR2++ cells originated from the bone marrow or spleen reservoirs and comprise ≥92% of monocytes. Intermediate monocytes (CD14++CD16+CCR2+) are involved in the production of anti-inflammatory cytokines [such as interleukin (IL)-10], reactive oxygen species (ROS), and proinflammatory mediators [such as tumor necrosis factor-α (TNF-α) and IL-1β). Nonclassical monocytes (CD14+CD16++CCR2−) are patrolling cells involved in tissue repair and debris removal from the vasculature. Many studies in both humans and animals have shown the importance of monocyte chemoattractant protein-1 (MCP-1) and its receptor [chemokine receptor of MCP-1 (CCR2)] in pathologies, such as atherosclerosis and myocardial infarction (MI). This review presents the importance of these monocyte subsets in cardiovascular diseases (CVDs), and sheds light on new strategies for the blocking of the MCP-1/CCR2 axis as a therapeutic goal for treating vascular disorders.

Quantifying the area-at-risk of myocardial infarction in-vivo using arterial spin labeling cardiac magnetic resonance

T₂-weighted cardiovascular magnetic resonance (T2-CMR) of myocardial edema can quantify the area-at-risk (AAR) following acute myocardial infarction (AMI), and has been used to assess myocardial salvage by new cardioprotective therapies. However, some of these therapies may reduce edema, leading to an underestimation of the AAR by T2-CMR. Here, we investigated arterial spin labeling (ASL) perfusion CMR as a novel approach to quantify the AAR following AMI. Adult B6sv129-mice were subjected to in vivo left coronary artery ligation for 30 minutes followed by 72 hours reperfusion. T₂-mapping was used to quantify the edema-based AAR (% of left ventricle) following ischemic preconditioning (IPC) or cyclosporin-A (CsA) treatment. In control animals, the AAR by T2-mapping corresponded to that delineated by histology. As expected, both IPC and CsA reduced MI size. However, IPC, but not CsA, also reduced myocardial edema leading to an underestimation of the AAR by T₂-mapping. In contrast, regions of reduced myocardial perfusion delineated by cardiac ASL were able to delineate the AAR when compared to both T2-mapping and histology in control animals, and were not affected by either IPC or CsA. Therefore, ASL perfusion CMR may be an alternative method for quantifying the AAR following AMI, which unlike T2-mapping, is not affected by IPC.

The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis

In adult mammals, massive sudden loss of cardiomyocytes after infarction overwhelms the limited regenerative capacity of the myocardium, resulting in the formation of a collagen-based scar. Necrotic cells release danger signals, activating innate immune pathways and triggering an intense inflammatory response. Stimulation of toll-like receptor signaling and complement activation induces expression of proinflammatory cytokines (such as interleukin-1 and tumor necrosis factor-α) and chemokines (such as monocyte chemoattractant protein-1/ chemokine (C-C motif) ligand 2 [CCL2]). Inflammatory signals promote adhesive interactions between leukocytes and endothelial cells, leading to extravasation of neutrophils and monocytes. As infiltrating leukocytes clear the infarct from dead cells, mediators repressing inflammation are released, and anti-inflammatory mononuclear cell subsets predominate. Suppression of the inflammatory response is associated with activation of reparative cells. Fibroblasts proliferate, undergo myofibroblast transdifferentiation, and deposit large amounts of extracellular matrix proteins maintaining the structural integrity of the infarcted ventricle. The renin-angiotensin-aldosterone system and members of the transforming growth factor-β family play an important role in activation of infarct myofibroblasts. Maturation of the scar follows, as a network of cross-linked collagenous matrix is formed and granulation tissue cells become apoptotic. This review discusses the cellular effectors and molecular signals regulating the inflammatory and reparative response after myocardial infarction. Dysregulation of immune pathways, impaired suppression of postinfarction inflammation, perturbed spatial containment of the inflammatory response, and overactive fibrosis may cause adverse remodeling in patients with infarction contributing to the pathogenesis of heart failure. Therapeutic modulation of the inflammatory and reparative response may hold promise for the prevention of postinfarction heart failure.