Neutralization of interleukin-1beta in the acute phase of myocardial infarction promotes the progression of left ventricular remodeling

Macrophages in cardiovascular diseases: molecular mechanisms and therapeutic targets

The immune response holds a pivotal role in cardiovascular disease development. As multifunctional cells of the innate immune system, macrophages play an essential role in initial inflammatory response that occurs following cardiovascular injury, thereby inducing subsequent damage while also facilitating recovery. Meanwhile, the diverse phenotypes and phenotypic alterations of macrophages strongly associate with distinct types and severity of cardiovascular diseases, including coronary heart disease, valvular disease, myocarditis, cardiomyopathy, heart failure, atherosclerosis and aneurysm, which underscores the importance of investigating macrophage regulatory mechanisms within the context of specific diseases. Besides, recent strides in single-cell sequencing technologies have revealed macrophage heterogeneity, cell-cell interactions, and downstream mechanisms of therapeutic targets at a higher resolution, which brings new perspectives into macrophage-mediated mechanisms and potential therapeutic targets in cardiovascular diseases. Remarkably, myocardial fibrosis, a prevalent characteristic in most cardiac diseases, remains a formidable clinical challenge, necessitating a profound investigation into the impact of macrophages on myocardial fibrosis within the context of cardiac diseases. In this review, we systematically summarize the diverse phenotypic and functional plasticity of macrophages in regulatory mechanisms of cardiovascular diseases and unprecedented insights introduced by single-cell sequencing technologies, with a focus on different causes and characteristics of diseases, especially the relationship between inflammation and fibrosis in cardiac diseases (myocardial infarction, pressure overload, myocarditis, dilated cardiomyopathy, diabetic cardiomyopathy and cardiac aging) and the relationship between inflammation and vascular injury in vascular diseases (atherosclerosis and aneurysm). Finally, we also highlight the preclinical/clinical macrophage targeting strategies and translational implications.

Novel diagnostic biomarkers related to necroptosis and immune infiltration landscape in acute myocardial infarction

Background

Acute myocardial infarction (AMI) can occur suddenly, which may induce deadly outcomes, and the population suffering from AMI presents a younger trend. Necroptosis, the new cell necrosis type, is associated with the pathogenic mechanisms of diverse cardiovascular diseases (CVDs). Its diagnostic value and molecular mechanisms in AMI are still unclear. Objective: This study focused on determining key necroptosis-related genes as well as immune infiltration in AMI.

Methods

We first examined the GSE66360 dataset for identifying necroptosis-related differentially expressed genes (NRDEGs). Thereafter, GO and functional annotation were performed, then a PPI network was built. In addition, "CIBERSORT" in R was applied in comparing different immune infiltration degrees in AMI compared with control groups. The receiver operating characteristic (ROC) curve was plotted to evaluate whether hub NRDEGs could be used in AMI diagnosis. Associations of immune cells with candidate NRDEGs biomarkers were examined by Spearman analysis. Finally, hub NRDEGs were validated by cell qPCR assays and another two datasets.

Results

A total of 15 NRDEGs were identified and multiple enrichment terms associated with necroptosis were discovered through GO and KEGG analysis. Upon module analysis, 10 hub NRDEGs were filtered out, and the top six hub NRDEGs were identified after ROC analysis. These top six NRDEGs might have a certain effect on modulating immune infiltrating cells, especially for mast cells activated, NK cells activated and neutrophils. Finally, two AMI datasets and qPCR assay came to identical findings.

Conclusion

Our results offer the reliable molecular biomarkers and new perspectives for necroptosis in AMI, which lay a certain foundation for developing novel anti-AMI therapeutic targets.

Blockade of Inflammatory Markers Attenuates Cardiac Remodeling and Fibrosis in Rats with Supravalvular Aortic Stenosis

Since cardiac inflammation has been considered an important mechanism involved in heart failure, an anti-inflammatory treatment could control cardiac inflammation and mitigate the worsening of cardiac remodeling. This study evaluated the effects of dexamethasone (DEX) and ramipril treatment on inflammation and cardiac fibrosis in an experimental model of heart failure induced by supravalvular aortic stenosis. Wistar rats (21d) were submitted to an aortic stenosis (AS) protocol. After 21 weeks, an echocardiogram and a maximal exercise test were performed, and after 24 weeks, rats were treated with DEX, ramipril or saline for 14d. The left ventricle (LV) was removed for histological and inflammatory marker analyses. The AS group showed exercise intolerance (-32% vs. Sham), higher relative wall thickness (+63%), collagen deposition and capillary rarefaction, followed by cardiac disfunction. Both treatments were effective in reducing cardiac inflammation, but only DEX attenuated the increased relative wall thickness (-17%) and only ramipril reduced LV fibrosis. In conclusion, both DEX and ramipril decreased cardiac inflammatory markers, which probably contributed to the reduced cardiac fibrosis and relative wall thickness; however, treated AS rats did not show any improvement in cardiac function. Despite the complex pharmacological treatment of heart failure, treatment with an anti-inflammatory could delay the patient's poor prognosis.

The Immunomodulatory Effects of a 6-Month Extra Virgin Olive Oil Intervention on Monocyte Cytokine Secretion and Plasma Cytokine Levels in Dyslipidemic and Post-Infarct Patients: A Clinical Pilot Study

Atherosclerosis is an immuno-inflammatory process underlying cardiovascular diseases. One of the main actors of this inflammation is monocytes, with the switch in their phenotypes and irregularities in their cytokine production.

OBJECTIVE

This study was aimed to investigate the nutraceutical potential of extra virgin olive oil (EVOO) on the inflammatory status of monocytes in participants showing different levels of cardiovascular risk.

METHODS

43 participants 65-85 years old were recruited including 14 healthy, 12 dyslipidemic patients with hypercholesterolemia recently diagnosed, and 17 post-infarct patients. Participants from all groups were supplemented with EVOO (25 mL/day) for 6 months. IL-1β, IL-6, IL-10, TNF-α cytokine production, and monocyte phenotypes were investigated both at quiescent and at stimulated state by flow cytometry.

RESULTS

At the baseline (pre-intervention), dyslipidemic patients, compared to healthy and post-infarct participants, showed monocytes in an inflammatory state characterized by a significantly weaker IL-10 production. Our results do not show a significant modulation of the phenotype or IL-10, IL-6, and TNF-α production following a 6-month EVOO intake whether at quiescence or under stimulation. However, IL-1β is significantly increased by the intervention of EVOO in post-infarct patients. Paradoxically after the 6-month intervention, monocytes from dyslipidemic patients showed a significantly decreased secretion of IL-1β under LPS stimulation despite the increase observed at basal state.

CONCLUSION

Our results show that 6-month EVOO intervention did not induce a monocyte phenotypic change or that this intervention significantly modifies cytokine production.

Plausible Role of NLRP3 Inflammasome and Associated Cytokines in Pathogenesis of Rheumatic Heart Disease

Rheumatic heart disease (RHD) is a post-streptococcal sequela caused by Streptococcus pyogenes. The global burden of disease is high among people with low socio-economic status, with significant cases emerging every year despite global eradication efforts. The current treatment includes antibiotic therapies to target strep throat and rheumatic fever and valve replacement strategies as a corrective measure for chronic RHD patients. Valvular damage and valve calcification are considered to be the end-stage processes of the disease resulting from impairment of the endothelial arrangement due to immune infiltration. This immune infiltration is mediated by a cascade of events involving NLRP3 inflammasome activation. NLRP3 inflammasome is activated by wide range of stimuli including bacterial cell wall components like M proteins and leukocidal toxins like nicotinamide dehydrogenase (NADase) and streptolysin O (SLO) and these play a major role in sustaining the virulence of Streptococcus pyogenes and progression of RHD. In this review, we are discussing NLRP3 inflammasome and its plausible role in the pathogenesis of RHD by exploiting the host-pathogen interaction mainly focusing on the NLRP3 inflammasome-mediated cytokines IL-1β and IL-18. Different therapeutic approaches involving NLRP3 inflammasome inactivation, caspase-1 inhibition, and blockade of IL-1β and IL-18 are discussed in this review and may be promising for treating RHD patients.

P2X7R-NEK7-NLRP3 Inflammasome Activation: A Novel Therapeutic Pathway of Qishen Granule in the Treatment of Acute Myocardial Ischemia

Background

Acute myocardial ischemia (AMI) is a common heart disease with increasing morbidity and mortality year by year. Persistent and sterile inflammatory infiltration of myocardial tissue is an important factor triggering of acute myocardial ischemia secondary to acute myocardial infarction, and NLRP3 inflammasome activation is an important part of sterile inflammatory response after acute myocardial ischemia. Previous studies have shown that Qishen granule (QSG) can significantly inhibit the inflammatory injury of myocardial tissue caused by ischemia, but its effect and specific mechanism of inhibiting the activation of NLRP3 inflammasome have not been reported. This study was to investigate the specific mechanism of QSG inhibiting inflammation after AMI, and to validate the possible targets.

Methods

The myocardial ischemia model in mice was established by ligation of the left anterior descending coronary artery. Echocardiography was used to evaluate the cardiac function of the mice. Plasma CK-MB and cTnl were detected by ELISA to evaluate the degree of myocardial injury. The extent of myocardial tissue inflammation in mice was assessed by HE staining and immunohistochemistry of IL-18, IL-1β. The expressions of NLRP3, ASC, Caspase-1, and CD86 were detected by immunofluorescence; detection of key pathway proteins P2X7R, NEK7, NLRP3, ASC, Caspase-1, and effector proteins IL-18, IL-1β by Western blot. In vitro experiments, ATP+LPS was used to construct a RAW264.7 macrophage NLRP3 inflammasome activation model. Immunofluorescence and Western blot analysis were performed to detect the expression of NLRP3 pathway activator and effector proteins. Plasmid-transfected P2X7R overexpression and immunoprecipitation assays were used to evaluate the QSG-regulated NLRP3 inflammasome activation pathway.

Results

QSG rescued cardiac function and further reduced inflammatory effects in mice by inhibiting NLRP3 inflammasome activation. In vitro, QSG inhibited LPS combined with ATP-induced NLRP3 inflammasome activation in RAW264.7 macrophages by downregulating the expression of NLRP3 inflammasome key pathway proteins. In addition, inhibition or overexpression of P2X7R in RAW264.7 macrophages and immunoprecipitated protein interactions further confirmed that QSG reduces macrophages inflammasome activation via the P2X7R-NEK7-NLRP3 pathway.

Conclusion

P2X7R-NEK7-NLRP3 inflammasome activation is a novel therapeutic mechanism of QSG in the treatment of acute myocardial ischemia.

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.

An Overview of the Molecular Mechanisms Associated with Myocardial Ischemic Injury: State of the Art and Translational Perspectives

Cardiovascular disease is the leading cause of death in western countries. Among cardiovascular diseases, myocardial infarction represents a life-threatening condition predisposing to the development of heart failure. In recent decades, much effort has been invested in studying the molecular mechanisms underlying the development and progression of ischemia/reperfusion (I/R) injury and post-ischemic cardiac remodeling. These mechanisms include metabolic alterations, ROS overproduction, inflammation, autophagy deregulation and mitochondrial dysfunction. This review article discusses the most recent evidence regarding the molecular basis of myocardial ischemic injury and the new potential therapeutic interventions for boosting cardioprotection and attenuating cardiac remodeling.

IL-1β Impacts Vascular Integrity and Lymphatic Function in the Embryonic Omentum

BACKGROUND

The chromatin-remodeling enzyme BRG1 (brahma-related gene 1) regulates gene expression in a variety of rapidly differentiating cells during embryonic development. However, the critical genes that BRG1 regulates during lymphatic vascular development are unknown.

METHODS

We used genetic and imaging techniques to define the role of BRG1 in murine embryonic lymphatic development, although this approach inadvertently expanded our study to multiple interacting cell types.

RESULTS

We found that omental macrophages fine-tune an unexpected developmental process by which erythrocytes escaping from naturally discontinuous omental blood vessels are collected by nearby lymphatic vessels. Our data indicate that circulating fibrin(ogen) leaking from gaps in omental blood vessels can trigger inflammasome-mediated IL-1β (interleukin-1β) production and secretion from nearby macrophages. IL-1β destabilizes adherens junctions in omental blood and lymphatic vessels, contributing to both extravasation of erythrocytes and their uptake by lymphatics. BRG1 regulates IL-1β production in omental macrophages by transcriptionally suppressing the inflammasome trigger RIPK3 (receptor interacting protein kinase 3).

CONCLUSIONS

Genetic deletion of Brg1 in embryonic macrophages leads to excessive IL-1β production, erythrocyte leakage from blood vessels, and blood-filled lymphatics in the developing omentum. Altogether, these results highlight a novel context for epigenetically regulated crosstalk between macrophages, blood vessels, and lymphatics.

Modulation of the Immune System Promotes Tissue Regeneration

The immune system plays an essential role in the angiogenesis, repair, and regeneration of damaged tissues. Therefore, the design of scaffolds that manipulate immune cells and factors in such a way that could accelerate the repair of damaged tissues, following implantation, is one of the main goals of regenerative medicine. However, before manipulating the immune system, the function of the various components of the immune system during the repair process should be well understood and the fabrication conditions of the manipulated scaffolds should be brought closer to the physiological state of the body. In this article, we first review the studies aimed at the role of distinct immune cell populations in angiogenesis and support of damaged tissue repair. In the second part, we discuss the use of strategies that promote tissue regeneration by modulating the immune system. Given that various studies have shown an increase in tissue repair rate with the addition of stem cells and growth factors to the scaffolds, and regarding the limited resources of stem cells, we suggest the design of scaffolds that are capable to develop repair of damaged tissue by manipulating the immune system and create an alternative for repair strategies that use stem cells or growth factors.

Therapies to prevent post-infarction remodelling: From repair to regeneration

Myocardial infarction is the first cause of worldwide mortality, with an increasing incidence also reported in developing countries. Over the past decades, preclinical research and clinical trials continually tested the efficacy of cellular and acellular-based treatments. However, none of them resulted in a drug or device currently used in combination with either percutaneous coronary intervention or coronary artery bypass graft. Inflammatory, proliferation and remodelling phases follow the ischaemic event in the myocardial tissue. Only recently, single-cell sequencing analyses provided insights into the specific cell populations which determine the final fibrotic deposition in the affected region. In this review, ischaemia, inflammation, fibrosis, angiogenesis, cellular stress and fundamental cellular and molecular components are evaluated as therapeutic targets. Given the emerging evidence of biomaterial-based systems, the increasing use of injectable hydrogels/scaffolds and epicardial patches is reported both as acellular and cellularised/functionalised treatments. Since several variables influence the outcome of any experimented treatment, we return to the pathological basis with an unbiased view towards any specific process or cellular component. Thus, by evaluating the benefits and limitations of the approaches based on these targets, the reader can weigh the rationale of each of the strategies that reached the clinical trials stage. As recent studies focused on the relevance of the extracellular matrix in modulating ischaemic remodelling and enhancing myocardial regeneration, we aim to portray current trends in the field with this review. Finally, approaches towards feasible translational studies that are as yet unexplored are also suggested.

Age and Interleukin-15 Levels Are Independently Associated With Intima-Media Thickness in Obesity-Related NAFLD Patients

Common carotid intima-media thickness (IMT) represents a functional and structural marker of early, precocious, and subclinical atherosclerosis, independently from the carotid plaque. Macrophage cells, which have been detected in adipose tissue and atherosclerotic plaques, are regulated by interleukin-15 (IL-15). At the light of the conflicting results concerning the role of IL-15 in atherosclerosis, the aim of the study was to retrospectively evaluate in a population of 80 obese patients, with median age of 46 years (IQR 34–53 years), with a low rate of comorbidities but with non-alcoholic fatty liver disease (NAFLD) or hepatic steatosis (HS), the relationship between IMT and serum concentrations of IL-15. Anthropometric measures, metabolic profile, and serum inflammatory markers, as well as the levels of IL-15, MCP-1, b FGF, and GM-CSF, were analyzed by a bead-based assay. IMT, HS, subcutaneous, and visceral adipose tissues were detected by ultrasonography. The IL-15 levels of the obese patients were increased with respect to those of 44 young healthy subjects, i.e., 2.77 (1.21–4.8) vs. 1.55 (1–2.4) pg/mL (P = 0.002). In the univariate analysis, IL-15 levels were associated to IMT and to those of MCP-1, b FGF, and GM-CSF, without any relation to other inflammatory markers such as CRP and ferritin, except fibrinogen. In the multivariate analysis, after adjusting the HS severity for the extent of visceral adiposity, a dramatic change in prediction of IMT by HS was shown (β from 0.29 to 0.10, P from 0.008 to 0.37). When the visceral adipose tissue was combined with IL-15, on the one hand, and the well-known coronary artery disease (CAD) risk factors—i.e., age, gender, smoking status, HDL-cholesterol concentrations, triglycerides levels, and HOMA—on the other, only age and IL-15 remained the predictors of IMT (β = 0.60, P = 0.0001 and β = 0.25, P = 0.024, respectively). There was no association of IL-15 with various anthropometric parameters nor with body fat distribution and severity of HS, also after adjusting for age. Age is resulted to be the main factor in the prediction of IMT and thus of early atherosclerosis. The prediction of IMT by IL-15 coupled with the lack of prediction by the well-known CAD risks is in agreement with recent data, which emphasizes the main role of the immune system in the onset/worsening of atherosclerosis, even though the role of visceral adiposity should be further deepened. Age and IL-15 levels were both predictors of early atherosclerosis in this population of obese patients with NAFLD, suggesting a possible role of this cytokine in the atherosclerosis process.

Echocardiographic Molecular Imaging of the Effect of Anticytokine Therapy for Atherosclerosis

BACKGROUND

Echocardiographic molecular imaging techniques are beginning to be applied to evaluate preclinical efficacy of new drugs. In a large clinical trial, anti-interleukin-1β (IL-1β) immunotherapy reduced atherosclerotic events, yet treatment effects were modest, and the mechanisms of action were not fully elucidated. We tested the hypothesis that echocardiographic molecular imaging can assess changes in vascular thromboinflammatory status in response to anti-IL-1β therapy.

METHODS

In wild-type and atherosclerotic mice deficient for the low-density lipoprotein-receptor and Apobec-1, closed-chest myocardial infarction (MI) was performed to mimic high-risk clinical cohorts. Control animals had sham surgery. Post-MI animals were randomized to either no therapy or anti-IL-1β immunotherapy, which was continued weekly. At post-MI day 3 or 21, in vivo ultrasound molecular imaging of aortic VCAM-1, P-selectin, von Willebrand factor A1-domain, and platelet GPIbα in the thoracic aorta was performed. Aortic histology and NF-κB activity were assessed in atherosclerotic mice.

RESULTS

In both atherosclerotic and wild-type mice, MI produced a several-fold increase (P < .05) in aortic molecular signals for P-selectin, VCAM-1, von Willebrand factor, and GPIbα. In atherosclerotic mice, signal remained elevated at day 21. Anti-IL-1β therapy completely abolished the post-MI increase in signal for all endothelial targets (P < .05 vs nontreated) at day 3 and 21. In atherosclerotic mice, MI triggered an increase in aortic plaque growth and macrophage content, a decrease in plaque collagen, and elevated aortic NF-κB (P < .05 for all changes). All of these remote plaque adverse changes were inhibited by anti-IL-1β therapy.

CONCLUSIONS

Echocardiographic molecular imaging of the vascular endothelium can quantify the beneficial effects of therapies designed to suppress the proatherosclerotic arterial thromboinflammatory effects of alarmins such as IL-1β. This approach could potentially be used to evaluate the biologic variables that influence response in preclinical studies, and possibly to select patients most likely to benefit from therapy.

Cytokines as therapeutic targets for cardio- and cerebrovascular diseases

Despite major advances in prevention and treatment, cardiac and cerebral atherothrombotic complications still account for substantial morbidity and mortality worldwide. In this context, inflammation is involved in the chronic process leading atherosclerotic plaque formation and its complications, as well as in the maladaptive response to acute ischemic events. For this reason, modulation of inflammation is nowadays seen as a promising therapeutic strategy to counteract the burden of cardio- and cerebrovascular disease. Being produced and recognized by both inflammatory and vascular cells, the complex network of cytokines holds key functions in the crosstalk of these two systems and orchestrates the progression of atherothrombosis. By binding to membrane receptors, these soluble mediators trigger specific intracellular signaling pathways eventually leading to the activation of transcription factors and a deep modulation of cell function. Both stimulatory and inhibitory cytokines have been described and progressively reported as markers of disease or interesting therapeutic targets in the cardiovascular field. Nevertheless, cytokine inhibition is burdened by harmful side effects that will most likely prevent its chronic use in favor of acute administrations in well-selected subjects at high risk. Here, we summarize the current state of knowledge regarding the modulatory role of cytokines on atherosclerosis, myocardial infarction, and stroke. Then, we discuss evidence from clinical trials specifically targeting cytokines and the potential implication of these advances into daily clinical practice.

Immunotherapy for Infarcts: In Vivo Postinfarction Macrophage Modulation Using Intramyocardial Microparticle Delivery of Map4k4 Small Interfering RNA

The myeloid cells infiltrating the heart early after acute myocardial infarction elaborate a secretome that largely orchestrates subsequent ventricular wall repair. Regulating this innate immune response could be a means to improve infarct healing. To pilot this concept, we utilized (β1,3-d-) glucan-encapsulated small interfering RNA (siRNA)-containing particles (GeRPs), targeting mononuclear phagocytes, delivered to mice as a one-time intramyocardial injection immediately after acute infarction. Findings demonstrated that cardiac macrophages phagocytosed GeRPs in vivo and had little systemic dissemination, thus providing a means to deliver local therapeutics. Acute infarcts were then injected in vivo with phosphate-buffered saline (PBS; vehicle) or GeRPs loaded with siRNA to Map4k4, and excised hearts were examined at 3 and 7 days by quantitative polymerase chain reaction, flow cytometry, and histology. Compared with infarcted PBS-treated hearts, hearts with intrainfarct injections of siRNA-loaded GeRPs exhibited 69–89% reductions in transcripts for Map4k4 (mitogen-activated protein kinase kinase kinase kinase 4), interleukin (IL)-1β, and tumor necrosis factor α at 3 days. Expression of other factors relevant to matrix remodeling—monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinases, hyaluronan synthases, matricellular proteins, and profibrotic factors transforming growth factor beta (TGF-β), and connective tissue growth factor (CTGF)—were also decreased. Most effects peaked at 3 days, but, in some instances (Map4k4, IL-1β, TGF-β, CTGF, versican, and periostin), suppression persisted to 7 days. Thus, direct intramyocardial GeRP injection could serve as a novel and clinically translatable platform for in vivo RNA delivery to intracardiac macrophages for local and selective immunomodulation of the infarct microenvironment.

Glycogen synthase kinase-3β inhibition alleviates activation of the NLRP3 inflammasome in myocardial infarction

Inflammasome-promoted sterile inflammation following cardiac damage is critically implicated in heart dysfunction after myocardial infarction (MI). Glycogen synthase kinase-3 (GSK-3β) is a prominent mediator of the inflammatory response, and high GSK-3 activity is associated with various heart diseases. We investigated the regulatory mechanisms of GSK-3β in activation of the nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome in a rat model with successful induction of MI on days 2-28. An in vitro investigation was performed using newborn rat/human cardiomyocytes and fibroblast cultures under typical inflammasome stimulation and hypoxia treatment. GSK-3β inhibition markedly improved myocardial dysfunction and prevented remodeling, with parallel reduction in the parameters of NLRP3 inflammasome activation after MI. GSK-3β inhibition reduced NLRP3 inflammasome activation in cardiac fibroblasts, but not in cardiomyocytes. GSK-3β's interaction with activating signal cointegrator (ASC) as well as GSK-3β inhibition reduced ASC phosphorylation and oligomerization at the tissues and cellular levels. Taken together, these data show that GSK-3β directly mediates NLRP3 inflammasome activation, causing cardiac dysfunction in MI.

The Dynamic Interplay Between Cardiac Inflammation and Fibrosis

Heart failure is a leading cause of death worldwide. While there are multiple etiologies contributing to the development of heart failure, all cause result in impairments in cardiac function that is characterized by changes in cardiac remodeling and compliance. Fibrosis is associated with nearly all forms of heart failure and is an important contributor to disease pathogenesis. Inflammation also plays a critical role in the heart and there is a large degree of interconnectedness between the inflammatory and fibrotic response. This review discusses the cellular and molecular mechanisms contributing to inflammation and fibrosis and the interplay between the two.

Computational model predicts paracrine and intracellular drivers of fibroblast phenotype after myocardial infarction

The fibroblast is a key mediator of wound healing in the heart and other organs, yet how it integrates multiple time-dependent paracrine signals to control extracellular matrix synthesis has been difficult to study in vivo. Here, we extended a computational model to simulate the dynamics of fibroblast signaling and fibrosis after myocardial infarction (MI) in response to time-dependent data for nine paracrine stimuli. This computational model was validated against dynamic collagen expression and collagen area fraction data from post-infarction rat hearts. The model predicted that while many features of the fibroblast phenotype at inflammatory or maturation phases of healing could be recapitulated by single static paracrine stimuli (interleukin-1 and angiotensin-II, respectively), mimicking the reparative phase required paired stimuli (e.g. TGFβ and endothelin-1). Virtual overexpression screens simulated with either static cytokine pairs or post-MI paracrine dynamic predicted phase-specific regulators of collagen expression. Several regulators increased (Smad3) or decreased (Smad7, protein kinase G) collagen expression specifically in the reparative phase. NADPH oxidase (NOX) overexpression sustained collagen expression from reparative to maturation phases, driven by TGFβ and endothelin positive feedback loops. Interleukin-1 overexpression had mixed effects, both enhancing collagen via the TGFβ positive feedback loop and suppressing collagen via NFκB and BAMBI (BMP and activin membrane-bound inhibitor) incoherent feed-forward loops. These model-based predictions reveal network mechanisms by which the dynamics of paracrine stimuli and interacting signaling pathways drive the progression of fibroblast phenotypes and fibrosis after myocardial infarction.

Imbalance Between Interleukin-1β and Interleukin-1 Receptor Antagonist in Epicardial Adipose Tissue Is Associated With Non ST-Segment Elevation Acute Coronary Syndrome

Introduction

Interleukin-1beta (IL-1β) is crucially involved in the pathogenesis of coronary atherosclerotic diseases (CAD) and its inhibition has proven cardiovascular benefits. Epicardial adipose tissue (EAT) is a local source of inflammatory mediators which may negatively affect the surrounding coronary arteries. In the present study, we explored the relationship between serum and EAT levels of IL-1β and IL-1 receptor antagonist (IL-1ra) in patients with chronic coronary syndrome (CCS) and recent acute coronary syndrome (ACS).

Methods

We obtained EAT biopsies in 54 CCS (Group 1) and 33 ACS (Group 2) patients undergoing coronary artery bypass grafting. Serum and EAT levels of IL-1β and IL-1ra were measured in all patients. An immunophenotypic study was carried out on EAT biopsies and the CD86 events were studied as markers of M1 macrophages.

Results

Circulating levels of IL-1β were significantly higher in the overall CAD population compared to a control group [7.64 pg/ml (6.86; 8.57) vs. 1.89 pg/ml (1.81; 2.29); p < 0.001]. In contrast, no differences were observed for serum IL-1ra levels between CAD and controls. Comparable levels of serum IL-1β were found between Groups 1 and 2 [7.6 pg/ml (6.9; 8.7) vs. 7.9 pg/ml (7.2; 8.6); p = 0.618]. In contrast, significantly lower levels of serum IL-1ra were found in Group 2 compared to Group 1 [274 pg/ml (220; 577) vs. 603 pg/ml (334; 1022); p = 0.035]. No differences of EAT levels of IL-1β were found between Group 2 and Group 1 [3.4 pg/ml (2.3; 8.4) vs. 2.4 pg/ml (1.9; 8.0); p = 0.176]. In contrast, significantly lower EAT levels of IL-1ra were found in Group 2 compared to Group 1 [101 pg/ml (40; 577) vs. 1344 pg/ml (155; 5327); p = 0.002]. No correlation was found between EAT levels of IL-1β and CD86 and CD64 events.

Conclusion

The present study explores the levels of IL-1β and IL-1ra in the serum and in EAT of CCS and ACS patients. ACS seems to be associated to a loss of the counter-regulatory activity of IL-1ra against the pro-inflammatory effects related to IL-1β activation.

Targeted anti-IL-1β platelet microparticles for cardiac detoxing and repair

An acute myocardial infarction (AMI) induces a sterile inflammatory response that facilitates further heart injury and promotes adverse cardiac remodeling. Interleukin-1β (IL-1β) plays a central role in the sterile inflammatory response that results from AMI. Thus, IL-1β blockage is a promising strategy for treatment of AMI. However, conventional IL-1β blockers lack targeting specificity. This increases the risk of serious side effects. To address this problem herein, we fabricated platelet microparticles (PMs) armed with anti-IL-1β antibodies to neutralize IL-1β after AMI and to prevent adverse cardiac remodeling. Our results indicate that the infarct-targeting PMs could bind to the injured heart, increasing the number of anti-IL-1β antibodies therein. The anti-IL-1β platelet PMs (IL1-PMs) protect the cardiomyocytes from apoptosis by neutralizing IL-1β and decreasing IL-1β-driven caspase-3 activity. Our findings indicate that IL1-PM is a promising cardiac detoxification agent that removes cytotoxic IL-1β during AMI and induces therapeutic cardiac repair.

SNO-MLP (S-Nitrosylation of Muscle LIM Protein) Facilitates Myocardial Hypertrophy Through TLR3 (Toll-Like Receptor 3)-Mediated RIP3 (Receptor-Interacting Protein Kinase 3) and NLRP3 (NOD-Like Receptor Pyrin Domain Containing 3) Inflammasome Activation

BACKGROUND

S-nitrosylation (SNO), a prototypic redox-based posttranslational modification, is involved in the pathogenesis of cardiovascular disease. The aim of this study was to determine the role of SNO of MLP (muscle LIM protein) in myocardial hypertrophy, as well as the mechanism by which SNO-MLP modulates hypertrophic growth in response to pressure overload.

METHODS

Myocardial samples from patients and animal models exhibiting myocardial hypertrophy were examined for SNO-MLP level using biotin-switch methods. SNO sites were further identified through liquid chromatography-tandem mass spectrometry. Denitrosylation of MLP by the mutation of nitrosylation sites or overexpression of S-nitrosoglutathione reductase was used to analyze the contribution of SNO-MLP in myocardial hypertrophy. Downstream effectors of SNO-MLP were screened through mass spectrometry and confirmed by coimmunoprecipitation. Recruitment of TLR3 (Toll-like receptor 3) by SNO-MLP in myocardial hypertrophy was examined in TLR3 small interfering RNA-transfected neonatal rat cardiomyocytes and in a TLR3 knockout mouse model.

RESULTS

SNO-MLP level was significantly higher in hypertrophic myocardium from patients and in spontaneously hypertensive rats and mice subjected to transverse aortic constriction. The level of SNO-MLP also increased in angiotensin II- or phenylephrine-treated neonatal rat cardiomyocytes. S-nitrosylated site of MLP at cysteine 79 was identified by liquid chromatography-tandem mass spectrometry and confirmed in neonatal rat cardiomyocytes. Mutation of cysteine 79 significantly reduced hypertrophic growth in angiotensin II- or phenylephrine-treated neonatal rat cardiomyocytes and transverse aortic constriction mice. Reducing SNO-MLP level by overexpression of S-nitrosoglutathione reductase greatly attenuated myocardial hypertrophy. Mechanistically, SNO-MLP stimulated TLR3 binding to MLP in response to hypertrophic stimuli, and disrupted this interaction by downregulating TLR3-attenuated myocardial hypertrophy. SNO-MLP also increased the complex formation between TLR3 and RIP3 (receptor-interacting protein kinase 3). This interaction in turn induced NLRP3 (nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3) inflammasome activation, thereby promoting the development of myocardial hypertrophy.

CONCLUSIONS

Our findings revealed a key role of SNO-MLP in myocardial hypertrophy and demonstrated TLR3-mediated RIP3 and NLRP3 inflammasome activation as the downstream signaling pathway, which may represent a therapeutic target for myocardial hypertrophy and heart failure.

Residual inflammatory risk in coronary heart disease: incidence of elevated high-sensitive CRP in a real-world cohort

Background

Inflammation drives atherosclerosis and its complications. Anti-inflammatory therapy with interleukin 1 beta (IL-1β) antibody reduces cardiovascular events in patients with elevated high-sensitive C-reactive protein (hsCRP). This study aims to identify the share of patients with coronary heart disease (CHD) and residual inflammation who may benefit from anti-inflammatory therapy.

Methods

hsCRP and low-density lipoprotein (LDL) levels were determined in 2741 all-comers admitted to the cardiological ward of our tertiary referral hospital between June 2016 and June 2018. Patients without CHD, with acute coronary syndrome, chronic or recurrent systemic infection, use of immunosuppressant or anti-inflammatory agents, chronic inflammatory diseases, chemotherapy, terminal organ failure, traumatic injury and pregnancy were excluded.

Results

856 patients with stable CHD were included. 42.7% of those had elevated hsCRP ≥ 2 mg/l. Within the group of patients with LDL-cholesterol < 70 mg/dl, 30.9% shared increased hsCRP indicating residual inflammation. After multivariate adjusted backward selection elevated Lipoprotein (a) (OR 1.61, p = 0.048), elevated proBNP (OR 2.57, p < 0.0001), smoking (OR 1.70, p = 0.022), and obesity (OR 2.28, p = 0.007) were associated with elevated hsCRP. In contrast, the use of ezetimibe was associated with normal hsCRP (OR 0.51, p = 0.014). In the subgroup of patients with on-target LDL-cholesterol < 70 mg/dl, backward selection identified elevated proBNP (OR 3.49, p = 0.007) as independent predictor of elevated hsCRP in patients with LDL-cholesterol < 70 mg/dl.

Conclusion

One-third of all-comers patients with CHD showed increased levels of hsCRP despite a LDL-cholesterol < 70 mg/dl potentially qualifying for an anti-inflammatory therapy. Elevated proBNP is an independent risk factor for hsCRP elevation.

Graphic abstract

Electronic supplementary material

The online version of this article (10.1007/s00392-019-01511-0) contains supplementary material, which is available to authorized users.

Recombinant human interleukin-1 receptor antagonist treatment protects rats from myocardial ischemia-reperfusion injury

The interleukin-1 (IL-1) signaling pathway plays a vital role in multiple mechanisms associated with myocardial ischemia-reperfusion (I/R) injury, including inflammation and apoptosis. An IL-1 receptor antagonist (IL-1Ra) can block IL-1 by competitive binding to the IL-1 receptor type I (IL-1RI) and thus may provide a cardioprotective effect. In the present investigation, we determined whether exogenous administration of recombinant human IL-1Ra (rhIL-1Ra) provides a protective role against myocardial I/R injury. Sprague-Dawley rats underwent surgical coronary artery ligation (or sham operation) by occlusion of the left anterior descending artery (LAD) for 30 min followed by reperfusion. After 30 min of reperfusion, a 2 mg/kg dose of rhIL-1Ra was injected subcutaneously. This was followed up with once daily injections for seven days. Echocardiography revealed that ejection fraction (EF) values were significantly greater in the rhIL-1Ra-treated animals. RhIL-1Ra was found to reduce the severity of myocardial injury and increase the viability of the cardiac tissue. There was found to be less IL-1β expression in rhIL-1Ra-treated animals than in controls. These results provide compelling data to suggest administration of IL-1Ra could have a significant cardioprotective effect against myocardial I/R injury and thus IL-1Ra could emerge as a potential clinical drug for the treatment of myocardial I/R injury.

Role of complement C5a and histones in septic cardiomyopathy

Polymicrobial sepsis (after cecal ligation and puncture, CLP) causes robust complement activation with release of C5a. Many adverse events develop thereafter and will be discussed in this review article. Activation of complement system results in generation of C5a which interacts with its receptors (C5aR1, C5aR2). This leads to a series of harmful events, some of which are connected to the cardiomyopathy of sepsis, resulting in defective action potentials in cardiomyocytes (CMs), activation of the NLRP3 inflammasome in CMs and the appearance of extracellular histones, likely arising from activated neutrophils which form neutrophil extracellular traps (NETs). These events are associated with activation of mitogen-activated protein kinases (MAPKs) in CMs. The ensuing release of histones results in defective action potentials in CMs and reduced levels of [Ca²⁺]i-regulatory enzymes including sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA2) and Na⁺/Ca²⁺ exchanger (NCX) as well as Na⁺/K⁺-ATPase in CMs. There is also evidence that CLP causes release of IL-1β via activation of the NLRP3 inflammasome in CMs of septic hearts or in CMs incubated in vitro with C5a. Many of these events occur after in vivo or in vitro contact of CMs with histones. Together, these data emphasize the role of complement (C5a) and C5a receptors (C5aR1, C5aR2), as well as extracellular histones in events that lead to cardiac dysfunction of sepsis (septic cardiomyopathy).

Translational overview of cytokine inhibition in acute myocardial infarction and chronic heart failure

Many cytokines are currently under investigation as potential target to improve cardiac function and outcome in the setting of acute myocardial infarction (MI) or chronic heart failure (HF). Here we aim to provide a translational overview of cytokine inhibiting therapies tested in experimental models and clinical studies. In various experimental studies, inhibition of interleukin-1 (IL-1), -6 (IL-6), -8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), CC- and CXC chemokines, and tumor necrosis factor-α (TNF-α) had beneficial effects on cardiac function and outcome. On the other hand, neutral or even detrimental results have been reported for some (IL-1, IL-6, IL-8, and MCP-1). Ambivalence of cytokine function, differences in study designs, treatment regimens and chosen endpoints hamper the translation of experimental research into clinical practice. Human studies are currently limited to IL-1β inhibition, IL-1 receptor antagonists (IL-1RA), IL-6 receptor antagonists (IL-6RA) or TNF inhibition. Despite favorable effects on cardiovascular events observed in retrospective cohort studies of rheumatoid arthritis patients treated with TNF inhibition or IL-1RA, most prospective studies reported disappointing and inconsistent results. Smaller studies (n < 100) generally reported favorable results of anticytokine therapy on cardiac function, but only one of the larger studies (n > 100) evaluating IL-1β inhibition presented positive results on outcome. In conclusion, of the 10 anticytokine therapies tested in animals models beneficial effects have been reported in at least one setting. In larger clinical studies, findings were unsatisfactory in all but one. Many anticytokine therapies with promising animal experimental data continue to require further evaluation in humans.

Cytosolic DNA Sensing Promotes Macrophage Transformation and Governs Myocardial Ischemic Injury

BACKGROUND

Myocardium irreversibly injured by ischemic stress must be efficiently repaired to maintain tissue integrity and contractile performance. Macrophages play critical roles in this process. These cells transform across a spectrum of phenotypes to accomplish diverse functions ranging from mediating the initial inflammatory responses that clear damaged tissue to subsequent reparative functions that help rebuild replacement tissue. Although macrophage transformation is crucial to myocardial repair, events governing this transformation are poorly understood.

METHODS

Here, we set out to determine whether innate immune responses triggered by cytoplasmic DNA play a role.

RESULTS

We report that ischemic myocardial injury, along with the resulting release of nucleic acids, activates the recently described cyclic GMP-AMP synthase-stimulator of interferon genes pathway. Animals lacking cyclic GMP-AMP synthase display significantly improved early survival after myocardial infarction and diminished pathological remodeling, including ventricular rupture, enhanced angiogenesis, and preserved ventricular contractile function. Furthermore, cyclic GMP-AMP synthase loss of function abolishes the induction of key inflammatory programs such as inducible nitric oxide synthase and promotes the transformation of macrophages to a reparative phenotype, which results in enhanced repair and improved hemodynamic performance.

CONCLUSIONS

These results reveal, for the first time, that the cytosolic DNA receptor cyclic GMP-AMP synthase functions during cardiac ischemia as a pattern recognition receptor in the sterile immune response. Furthermore, we report that this pathway governs macrophage transformation, thereby regulating postinjury cardiac repair. Because modulators of this pathway are currently in clinical use, our findings raise the prospect of new treatment options to combat ischemic heart disease and its progression to heart failure.

The Inflammasomes in Cardiovascular Disease

Cardiovascular disease (CVD) is the number one cause of death worldwide. The pathogenesis of various disease entities that comprise the area of CVD is complex and multifactorial. Inflammation serves a central role in these complex aetiologies. The inflammasomes are intracellular protein complexes activated by danger-associated molecular patterns (DAMPs) present in CVD such as atherosclerosis and myocardial infarction (MI). After a two-step process of priming and activation, inflammasomes are responsible for the formation of pro-inflammatory cytokines interleukin-1β and interleukin-18, inducing a signal transduction cascade resulting in a strong immune response that culminates in disease progression. In the past few years, increased interest has been raised regarding the inflammasomes in CVD. Inflammasome activation is thought to be involved in the pathogenesis of various disease entities such as atherosclerosis, MI and heart failure (HF). Interference with inflammasome-mediated signalling could reduce inflammation and attenuate the severity of disease. In this chapter we provide an overview of the current literature available on the role of inflammasome inhibition as a therapeutic intervention and the possible clinical implications for CVD.

Dual inhibition of cathepsin G and chymase reduces myocyte death and improves cardiac remodeling after myocardial ischemia reperfusion injury

Early reperfusion of ischemic cardiac tissue increases inflammatory cell infiltration which contributes to cardiomyocyte death and loss of cardiac function, referred to as ischemia/reperfusion (IR) injury. Neutrophil- and mast cell-derived proteases, cathepsin G (Cat.G) and chymase, are released early after IR, but their function is complicated by potentially redundant actions and targets. This study investigated whether a dual inhibition of Cat.G and chymase influences cardiomyocyte injury and wound healing after experimental IR in mice. Treatment with a dual Cat.G and chymase inhibitor (DCCI) immediately after reperfusion blocked cardiac Cat.G and chymase activity induced after IR, which resulted in decreased immune response in the infarcted heart. Mice treated with DCCI had less myocardial collagen deposition and showed preserved ventricular function at 1 and 7 days post-IR compared with vehicle-treated mice. DCCI treatment also significantly attenuated focal adhesion (FA) complex disruption and myocyte degeneration after IR. Treatment of isolated cardiomyocytes with Cat.G or chymase significantly promoted FA signaling downregulation, myofibril degeneration and myocyte apoptosis. Conversely, treatment of cardiac fibroblasts with Cat.G or chymase induced FA signaling activation and increased their migration and differentiation to myofibroblasts. These opposite responses in cardiomyocytes and fibroblasts were blocked by treatment with DCCI. These findings show that Cat.G and chymase are key mediators of myocyte apoptosis and fibroblast migration and differentiation that play a role in adverse cardiac remodeling and function post-IR. Thus, dual targeting of neutrophil- and mast cell-derived proteases could be used as a novel therapeutic strategy to reduce post-IR inflammation and improve cardiac remodeling.

The IL-1β Antibody Gevokizumab Limits Cardiac Remodeling and Coronary Dysfunction in Rats With Heart Failure

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Immediate IL-1β antibody gevokizumab administration reduces ischemia/reperfusion related infarct size.

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Immediate and late IL-1β antibody gevokizumab administration improves heart failure related left ventricular remodeling.

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IL-1β antibody gevokizumab improves heart failure related coronary dysfunction.

This study reports preclinical data showing that the interleukin (IL)-1β modulation is a new promising target in the pathophysiological context of heart failure. Indeed, in nondiabetic Wistar and diabetic Goto-Kakizaki rats with chronic heart failure induced by myocardial infarction, administration of the IL-1β antibody gevokizumab improves ‘surrogate’ markers of survival (i.e., left ventricular remodeling, hemodynamics, and function as well as coronary function). However, whether IL-1β modulation per se or in combination with standard treatments of heart failure improves long-term outcome in human heart failure remains to be determined.

Progresses in understanding trauma-induced coagulopathy and the underlying mechanism

Trauma-induced coagulopathy (TIC) is a clinical syndrome caused by imbalance between clotting, anti-coagulation and fibrinolysis resulting from multiple pathological factors such as hemorrhage and tissue injury in the early stage of trauma, and is closely related to the outcome of trauma patients. It is proved in growing evidence that the endogenous coagulation disturbance in trauma itself is the activating factor of TIC, rather than dilution or other acquired coagulopathy. Therefore, a thorough understanding of the molecular mechanisms in the pathogenesis and progression is crucial for effective prevention and treatment in patients with TIC. This review focuses on transitions in the concept of TIC and mechanical progress.

Persistent Microvascular Obstruction After Myocardial Infarction Culminates in the Confluence of Ferric Iron Oxide Crystals, Proinflammatory Burden, and Adverse Remodeling

BACKGROUND

Emerging evidence indicates that persistent microvascular obstruction (PMO) is more predictive of major adverse cardiovascular events than myocardial infarct (MI) size. But it remains unclear how PMO, a phenomenon limited to the acute/subacute period of MI, drives adverse remodeling in chronic MI setting. We hypothesized that PMO resolves into chronic iron crystals within MI territories, which in turn are proinflammatory and favor adverse remodeling post-MI.

METHODS AND RESULTS

Canines (n=40) were studied with cardiac magnetic resonance imaging to characterize the spatiotemporal relationships among PMO, iron deposition, infarct resorption, and left ventricular remodeling between day 7 (acute) and week 8 (chronic) post-MI. Histology was used to assess iron deposition and to examine relationships between iron content with macrophage infiltration, proinflammatory cytokine synthesis, and matrix metalloproteinase activation. Atomic resolution transmission electron microscopy was used to determine iron crystallinity, and energy-dispersive X-ray spectroscopy was used to identify the chemical composition of the iron composite. PMO with or without reperfusion hemorrhage led to chronic iron deposition, and the extent of this deposition was strongly related to PMO volume (r>0.8). Iron deposits were found within macrophages as aggregates of nanocrystals (≈2.5 nm diameter) in the ferric state. Extent of iron deposits was strongly correlated with proinflammatory burden, collagen-degrading enzyme activity, infarct resorption, and adverse structural remodeling (r>0.5).

CONCLUSIONS

Crystallized iron deposition from PMO is directly related to proinflammatory burden, infarct resorption, and adverse left ventricular remodeling in the chronic phase of MI in canines. Therapeutic strategies to combat adverse remodeling could potentially benefit from taking into account the chronic iron-driven inflammatory process.

Cardiac Fibroblast Activation Post-Myocardial Infarction: Current Knowledge Gaps

In response to myocardial infarction (MI), the wound healing response of the left ventricle (LV) comprises overlapping inflammatory, proliferative, and maturation phases, and the cardiac fibroblast is a key cell type involved in each phase. It has recently been appreciated that, early post-MI, fibroblasts transform to a proinflammatory phenotype and secrete cytokines and chemokines as well as matrix metalloproteinases (MMPs). Later post-MI, fibroblasts are activated to anti-inflammatory and proreparative phenotypes and generate anti-inflammatory and proangiogenic factors and extracellular matrix (ECM) components that form the infarct scar. Additional studies are needed to systematically examine how fibroblast activation shifts over the timeframe of the MI response and how modulation at different activation stages could alter wound healing and LV remodeling in distinct ways. This review summarizes current fibroblast knowledge as the foundation for a discussion of existing knowledge gaps.

Inflammatory processes in cardiovascular disease: a route to targeted therapies

Inflammatory processes are firmly established as central to the development and complications of cardiovascular diseases. Elevated levels of inflammatory markers have been shown to be predictive of future cardiovascular events. The specific targeting of these processes in experimental models has been shown to attenuate myocardial and arterial injury, reduce disease progression, and promote healing. However, the translation of these observations and the demonstration of clear efficacy in clinical practice have been disappointing. A major limitation might be that tools currently used to measure 'inflammation' are insufficiently precise and do not provide information about disease site and activity, or discriminate between functionally important activation pathways. The challenge, therefore, is to make measures of inflammation that are more meaningful, and which can guide specific targeted therapies. In this Review, we consider the roles of inflammatory processes in the related pathologies of atherosclerosis and acute myocardial infarction, by providing an evaluation of the known and emerging inflammatory pathways. We highlight contemporary techniques to characterize and quantify inflammation, and consider how they might be used to guide specific treatments. Finally, we discuss emerging opportunities in the field, including their current limitations and challenges that are the focus of ongoing study.

Complement-induced activation of the cardiac NLRP3 inflammasome in sepsis

Cardiac dysfunction develops during sepsis in humans and rodents. In the model of polymicrobial sepsis induced by cecal ligation and puncture (CLP), we investigated the role of the NLRP3 inflammasome in the heart. Mouse heart homogenates from sham-procedure mice contained high mRNA levels of NLRP3 and IL-1β. Using the inflammasome protocol, exposure of cardiomyocytes (CMs) to LPS followed by ATP or nigericin caused release of mature IL-1β. Immunostaining of left ventricular frozen sections before and 8 h after CLP revealed the presence of NLRP3 and IL-1β proteins in CMs. CLP caused substantial increases in mRNAs for IL-1β and NLRP3 in CMs which are reduced in the absence of either C5aR1 or C5aR2. After CLP, NLRP3^-/- mice showed reduced plasma levels of IL-1β and IL-6. In vitro exposure of wild-type CMs to recombinant C5a (rC5a) caused elevations in both cytosolic and nuclear/mitochondrial reactive oxygen species (ROS), which were C5a-receptor dependent. Use of a selective NOX2 inhibitor prevented increased cytosolic and nuclear/mitochondrial ROS levels and release of IL-1β. Finally, NLRP3^-/- mice had reduced defects in echo/Doppler parameters in heart after CLP. These studies establish that the NLRP3 inflammasome contributes to the cardiomyopathy of polymicrobial sepsis.-Kalbitz, M., Fattahi, F., Grailer, J. J., Jajou, L., Malan, E. A., Zetoune, F. S., Huber-Lang, M., Russell, M. W., Ward, P. A. Complement-induced activation of the cardiac NLRP3 inflammasome in sepsis.

Lidocaine Enhances Contractile Function of Ischemic Myocardial Regions in Mouse Model of Sustained Myocardial Ischemia

RATIONALE

Perioperative myocardial ischemia is common in high-risk patients. The use of interventional revascularisation or even thrombolysis is limited in this patient subset due to exceedingly high bleeding risks. Blockade of voltage-gated sodium channels (VGSC) with lidocaine had been suggested to reduce infarct size and cardiomyocyte cell death in ischemia/reperfusion models. However, the impact of lidocaine on cardiac function during sustained ischemia still remains unclear.

METHODS

Sustained myocardial ischemia was induced by ligation of the left anterior descending artery in 12-16 weeks old male BALB/c mice. Subcutaneous lidocaine (30 mg/kg) was used to block VGSC. Cardiac function was quantified at baseline and at 72h by conventional and speckle-tracking based echocardiography to allow high-sensitivity in vivo phenotyping. Infarct size and cardiomyocyte cell death were assessed post mortem histologically and indirectly using troponin measurements.

RESULTS

Ischemia strongly impaired both, global systolic and diastolic function, which were partially rescued in lidocaine treated in mice. No differences regarding infarct size and cardiomyocyte cell death were observed. Mechanistically, and as shown with speckle-tracking analysis, lidocaine specifically improves residual contractility in the ischemic but not in the remote, non-ischemic myocardium.

CONCLUSION

VGSC blockade with lidocaine rescues function of ischemic myocardium as a potential bridging to revascularisation in the setting of perioperative myocardial ischemia.

Targeting Imbalance between IL-1β and IL-1 Receptor Antagonist Ameliorates Delayed Epithelium Wound Healing in Diabetic Mouse Corneas

Patients with diabetes mellitus often develop corneal complications and delayed wound healing. How diabetes might alter acute inflammatory responses to tissue injury, leading to delayed wound healing, remains mostly elusive. Using a streptozotocin-induced type I diabetes mellitus mice and corneal epithelium-debridement wound model, we discovered that although wounding induced marked expression of IL-1β and the secreted form of IL-1 receptor antagonist (sIL-1Ra), diabetes suppressed the expressions of sIL-1Ra but not IL-1β in healing epithelia and both in whole cornea. In normoglycemic mice, IL-1β or sIL-1Ra blockade delayed wound healing and influenced each other's expression. In diabetic mice, in addition to delayed reepithelization, diabetes weakened phosphatidylinositol 3-kinase-Akt signaling, caused cell apoptosis, diminished cell proliferation, suppressed neutrophil and natural killer cell infiltrations, and impaired sensory nerve reinnervation in healing mouse corneas. Local administration of recombinant IL-1Ra partially, but significantly, reversed these pathological changes in the diabetic corneas. CXCL10 was a downstream chemokine of IL-1β-IL-1Ra, and exogenous CXCL10 alleviated delayed wound healing in the diabetic, but attenuated it in the normal corneas. In conclusion, the suppressed early innate/inflammatory responses instigated by the imbalance between IL-1β and IL-1Ra is an underlying cause for delayed wound healing in the diabetic corneas. Local application of IL-1Ra accelerates reepithelialization and may be used to treat chronic corneal and potential skin wounds of diabetic patients.

Crosstalk between the heart and peripheral organs in heart failure

Mediators from peripheral tissues can influence the development and progression of heart failure (HF). For example, in obesity, an altered profile of adipokines secreted from adipose tissue increases the incidence of myocardial infarction (MI). Less appreciated is that heart remodeling releases cardiokines, which can strongly impact various peripheral tissues. Inflammation, and, in particular, activation of the nucleotide-binding oligomerization domain-like receptors with pyrin domain (NLRP3) inflammasome are likely to have a central role in cardiac remodeling and mediating crosstalk with other organs. Activation of the NLRP3 inflammasome in response to cardiac injury induces the production and secretion of the inflammatory cytokines interleukin (IL)-1β and IL-18. In addition to having local effects in the myocardium, these pro-inflammatory cytokines are released into circulation and cause remodeling in the spleen, kidney, skeletal muscle and adipose tissue. The collective effects of various cardiokines on peripheral organs depend on the degree and duration of myocardial injury, with systematic inflammation and peripheral tissue damage observed as HF progresses. In this article, we review mechanisms regulating myocardial inflammation in HF and the role of factors secreted by the heart in communication with peripheral tissues.

Protease-activated receptor 4 deficiency offers cardioprotection after acute ischemia reperfusion injury

Protease-activated receptor (PAR)4 is a low affinity thrombin receptor with less understood function relative to PAR1. PAR4 is involved in platelet activation and hemostasis, but its specific actions on myocyte growth and cardiac function remain unknown. This study examined the role of PAR4 deficiency on cardioprotection after myocardial ischemia-reperfusion (IR) injury in mice. When challenged by in vivo or ex vivo IR, PAR4 knockout (KO) mice exhibited increased tolerance to injury, which was manifest as reduced infarct size and a more robust functional recovery compared to wild-type mice. PAR4 KO mice also showed reduced cardiomyocyte apoptosis and putative signaling shifts in survival pathways in response to IR. Inhibition of PAR4 expression in isolated cardiomyocytes by shRNA offered protection against thrombin and PAR4-agonist peptide-induced apoptosis, while overexpression of wild-type PAR4 significantly enhanced the susceptibility of cardiomyocytes to apoptosis, even under low thrombin concentrations. Further studies implicate Src- and epidermal growth factor receptor-dependent activation of JNK on the proapoptotic effect of PAR4 in cardiomyocytes. These findings reveal a pivotal role for PAR4 as a regulator of cardiomyocyte survival and point to PAR4 inhibition as a therapeutic target offering cardioprotection after acute IR injury.

The circular relationship between matrix metalloproteinase-9 and inflammation following myocardial infarction

Matrix metalloproteinase-9 (MMP-9) regulates remodeling of the left ventricle after myocardial infarction (MI) and is tightly linked to the inflammatory response. The inflammatory response serves to recruit leukocytes as part of the wound healing reaction to the MI injury, and infiltrated leukocytes produce cytokines and chemokines that stimulate MMP-9 production and release. In turn, MMP-9 proteolyzes cytokines and chemokines. Although in most cases, MMP-9 cleavage of the cytokine or chemokine substrate serves to increase activity, there are cases where cleavage results in reduced activity. Global MMP-9 deletion in mouse MI models has proven beneficial, suggesting inhibition of some aspects of MMP-9 activity may be valuable for clinical use. At the same time, overexpression of MMP-9 in macrophages has also proven beneficial, indicating that we still do not fully understand the complexity of MMP-9 mechanisms of action. In this review, we summarize the cycle of MMP-9 effects on cytokine production and cleavage to regulate leukocyte functions. Although we use MI as the example process, similar events occur in other inflammatory and wound healing conditions.

Interleukin-1 in cardiac injury, repair, and remodeling: pathophysiologic and translational concepts

In the infarcted myocardium, necrotic cardiomyocytes release danger signals activating an intense inflammatory reaction that serves to clear the wound from dead cells and matrix debris, but may also extend injury. A growing body of evidence suggests an important role for members of the Interleukin (IL)-1 family in injury, repair and remodeling of the infarcted heart. This review manuscript discusses the pathophysiologic functions of IL-1 in the infarcted and remodeling myocardium and its potential role as a therapeutic target in patients with myocardial infarction. Dead cardiomyocytes release IL-1a that may function as a crucial alarmin triggering the post-infarction inflammatory reaction. IL-1b is markedly upregulated in the infarcted myocardium; activation of the inflammasome in both cardiomyocytes and interstitial cells results in release of bioactive IL-1b in the infarcted area. Binding of IL-1 to the type 1 receptor triggers an inflammatory cascade, inducing recruitment of pro-inflammatory leukocytes and stimulating a matrix-degrading program in fibroblasts, while delaying myofibroblast conversion. IL-1 mediates dilative remodeling following infarction and may play a role in the pathogenesis of post-infarction heart failure. As the wound is cleared from dead cells and matrix debris, endogenous inhibitory signals suppress the IL-1 response resulting in repression of inflammation and resolution of the inflammatory infiltrate. Other members of the IL-1 family (such as IL-18 and IL-33) are also implicated in regulation of the inflammatory and reparative response following myocardial infarction. IL-18 may participate in pro-inflammatory signaling, whereas IL-33 may exert cytoprotective effects. Early clinical trials suggest that IL-1 blockade may be a promising therapeutic strategy for patients with myocardial infarction.

Local immunosuppressive microenvironment enhances migration of melanoma cells to lungs in DJ-1 knockout mice

DJ-1 is an oncoprotein that promotes survival of cancer cells through anti-apoptosis. However, DJ-1 also plays a role in regulating IL-1β expression, and whether inflammatory microenvironment built by dysregulated DJ-1 affects cancer progression is still unclear. This study thus aimed to compare the metastatic abilities of melanoma cells in wild-type (WT) and DJ-1 knockout (KO) mice, and to check whether inflammatory microenvironment built in DJ-1 KO mice plays a role in migration of cancer cells to lungs. First, B16F10 melanoma cells (at 6×10⁴) were injected into the femoral vein of mice, and formation of lung nodules, levels of lung IL-1β and serum cytokines, and accumulation of myeloid-derived suppressor cells (MDSCs) were compared between WT and DJ-1 KO mice. Second, the cancer-bearing mice were treated with an interleukin-1 beta (IL-1β) neutralizing antibody to see whether IL-1β is involved in the cancer migration. Finally, cultured RAW 264.7 macrophage and B16F10 melanoma cells were respectively treated with DJ-1 shRNA and recombinant IL-1β to explore underlying molecular mechanisms. Our results showed that IL-1β enhanced survival and colony formation of cultured melanoma cells, and that IL-1β levels were elevated both in DJ-1 KO mice and in cultured macrophage cells with DJ-1 knockdown. The elevated IL-1β correlated with higher accumulation of immunosuppressive MDSCs and formation of melanoma module in the lung of DJ-1 KO mice, and both can be decreased by treating mice with IL-1β neutralizing antibodies. Taken together, these results indicate that immunosuppressive tissue microenvironment built in DJ-1 KO mice can enhance lung migration of cancer, and IL-1β plays an important role in promoting the cancer migration.

This old heart: Cardiac aging and autophagy

Autophagy, a cellular housekeeping process, is essential to maintain tissue homeostasis, particularly in long-lived cells such as cardiomyocytes. Autophagic activity declines with age and may explain many features of age-related cardiac dysfunction. In this review we summarize the current state of knowledge regarding age-related changes in autophagy in the heart. Recent findings from studies in human hearts are presented, including evidence that the autophagic response is intact in the aged human heart. Impaired autophagic clearance of protein aggregates or deteriorating mitochondria will have multiple consequences including increased arrhythmia risk, decreased contractile function, reduced tolerance to ischemic stress, and increased inflammation; thus autophagy represents a potentially important therapeutic target to mitigate the cardiac consequences of aging. This article is part of a Special Issue entitled CV Aging.

Differential regeneration of myocardial infarction depending on the progression of disease and the composition of biomimetic hydrogel

Hydrogel has been used for regenerating myocardial infraction (MI) as a delivery vehicle for cells and growth factors. This study showed that injectable hyaluronic acid (HA)-based hydrogels alone would effectively regenerate the damaged infarcted heart tissue. We found that there are two major factors of regeneration in MI. One is molecular weight of HA and another is the progression of MI; sub-acute and chronic. Rat MI model was prepared by ligating the left anterior descending coronary artery (LAD). Four weeks after injection of hydrogel, functional analysis of the heart and histological analysis was assessed. When different molecular weight HA-based hydrogels with 50 kDa, 130 kDa, and 170 kDa were applied to the infarcted area in the sub-acute model, 50 kDa HA-based hydrogel showed the most significant regeneration of myocardium as well as functional recovery among samples. For the disease progression, 50 kDa HA-based hydrogels were injected to sub-acute and chronic MI models. The regeneration activity was significantly decreased in the chronic models reflecting that injection timing of the therapeutic agents is also major determinants in the regeneration process. These results suggest that injection time and composition of hydrogel are two major points treating MI.

Translating Koch's postulates to identify matrix metalloproteinase roles in postmyocardial infarction remodeling: cardiac metalloproteinase actions (CarMA) postulates

The first matrix metalloproteinase (MMP) was described in 1962; and since the 1990s, cardiovascular research has focused on understanding how MMPs regulate many aspects of cardiovascular pathology from atherosclerosis formation to myocardial infarction and stroke. Although much information has been gleaned by these past reports, to a large degree MMP cardiovascular biology remains observational, with few studies homing in on cause and effect relationships. Koch's postulates were first developed in the 19th century as a way to establish microorganism function and were modified in the 20th century to include methods to establish molecular causality. In this review, we outline the concept for establishing a similar approach to determine causality in terms of MMP functions. We use left ventricular remodeling postmyocardial infarction as an example, but this approach will have broad applicability across both the cardiovascular and the MMP fields.