Reduction of experimental myocardial infarct size by corticosteroid administration

Review of the Association Between Long-Term and Current Systemic Steroid Use With Electromechanical Complications and Inpatient Mortality After ST-Elevation Myocardial Infarction

Background The impact of long-term systemic steroid use on electrical and mechanical complications following ST-segment elevation myocardial infarction (STEMI) has not been extensively studied. Methods In a retrospective cohort study of the National Inpatient Sample (NIS) from 2018 to 2020, adults admitted with STEMI were dichotomized based on the presence of long-term (current) systemic steroid (LTCSS) use. The primary outcome was all-cause mortality. Secondary outcomes included a composite of mechanical complications, electrical, hemodynamic, and thrombotic complications, as well as revascularization complexity, length of stay (LOS), and total charge. Multivariate linear and logistic regressions were used to adjust for confounders. Results Out of 608,210 admissions for STEMI, 5,310 (0.9%) had LTCSS use. There was no significant difference in the odds of all-cause mortality (aOR: 0.89, 95%CI: 0.74-1.08, p-value: 0.245) and the composite of mechanical complications (aOR: 0.74, 95%CI: 0.25-2.30, p-value: 0.599). LTCSS use was associated with lower odds of ventricular tachycardia, atrioventricular blocks, new permanent-pacemaker insertion, cardiogenic shock, the need for mechanical circulatory support, mechanical ventilation, cardioversion, a reduced LOS by 1 day, and a reduced total charge by 34,512 USD (all p-values: <0.05). There were no significant differences in the revascularization strategy (coronary artery bypass graft (CABG) vs. percutaneous coronary interventions (PCI)) or in the incidence of composite thrombotic events. Conclusion LTCSS use among patients admitted with STEMI was associated with lower odds of electrical dysfunction and hemodynamic instability but no difference in the odds of mechanical complications, CABG rate, all-cause mortality, cardiac arrest, or thrombotic complications. Further prospective studies are needed to evaluate these findings further.

SerpinA3 Promotes Myocardial Infarction in Rat and Cell-based Models

This study aimed to examine the role and molecular mechanism of the nuclear factor κB (NFκB)/serine protease inhibitor A3 (SerpinA3) interaction in myocardial ischemia-reperfusion (IR) injury. First, a rat model for myocardial ischemia-reperfusion injury was established, using 2,3,5-triphenyltetrazolium chloride to measure the size of the myocardial infarction. Pathological variations in myocardial tissue were detected using hematoxylin-eosin staining. Flow cytometry and terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) staining were used to measure cell death in the rat model. The SerpinA3 mRNA and protein expressions in the myocardium of IR-model rats were remarkably higher than those in the control group. Furthermore, the oxidative, inflammatory, and apoptotic activities of the myocardial tissue of SerpinA3-knockdown (KD) rats were significantly improved compared to those in the WT group. SerpinA3-KD also contributed to the recovery of cardiac function in IR-model rats. Additionally, silencing of SerpinA3 inhibited p65 phosphorylation in myocardial tissues and reduced H2O2-induced inflammation, oxidative stress, and apoptosis in myocardial cells. The expression of SerpinA3 increased in myocardial tissue after IR stimulation. Knockdown of SerpinA3 can deactivate NF-κB and reduce inflammation, oxidative stress, and apoptosis in vivo and in vitro, thereby lessening myocardial injury caused by IR. In conclusion, SerpinA3 promotes myocardial infarction in rat and cell-based models by activating NF-κB. However, the mechanism by which increased Serpina3 expression causes downstream NF-κB activation to mediate the proposed, pathological effects in myocardial IR injury remain untested and worthy of future investigations.

Inflammation in Myocardial Ischemia/Reperfusion Injury: Underlying Mechanisms and Therapeutic Potential

Acute myocardial infarction (MI) occurs when blood flow to the myocardium is restricted, leading to cardiac damage and massive loss of viable cardiomyocytes. Timely restoration of coronary flow is considered the gold standard treatment for MI patients and limits infarct size; however, this intervention, known as reperfusion, initiates a complex pathological process that somewhat paradoxically also contributes to cardiac injury. Despite being a sterile environment, ischemia/reperfusion (I/R) injury triggers inflammation, which contributes to infarct expansion and subsequent cardiac remodeling and wound healing. The immune response is comprised of subsets of both myeloid and lymphoid-derived cells that act in concert to modulate the pathogenesis and resolution of I/R injury. Multiple mechanisms, including altered metabolic status, regulate immune cell activation and function in the setting of acute MI, yet our understanding remains incomplete. While numerous studies demonstrated cardiac benefit following strategies that target inflammation in preclinical models, therapeutic attempts to mitigate I/R injury in patients were less successful. Therefore, further investigation leveraging emerging technologies is needed to better characterize this intricate inflammatory response and elucidate its influence on cardiac injury and the progression to heart failure.

Histone methyltransferase KMT2D contributes to the protection of myocardial ischemic injury

Histone H3 lysine 4 (H3K4) methyltransferase 2D (KMT2D) plays an important role in cell development in early life. However, the function of KMT2D in adult cells such as cardiomyocytes or neurons has not been reported. In this study, cardiomyocyte-specific KMT2D knockout (KMT2D-cKO) and control (KMT2D-Ctl) mice were exposed to sham or myocardial ischemia (MI) surgery. Depletion of KMT2D aggravated the ischemic area, led to the increased mortality (26.5% in KMT2D-cKO vs 12.5% in KMT2D-Ctl) of the mice, and weakened the left ventricular systolic function. RNA-seq analysis in cardiac tissues identified genes whose expression was changed by MI and KMT2D deletion. Combined with the genome-wide association study (GWAS) analysis, cardiac disease-associated genes Rasd1, Thsd7a, Ednra, and Tns1 were identified. The expression of the Rasd1 was significantly decreased by MI or the loss of KMT2D in vivo. Meanwhile, ChIP assays demonstrated that either MI or loss of KMT2D attenuated monomethylated H3K4 (H3K4me1) enrichment on the enhancer of Rasd1. By generating a KMT2D knockout (H9C2-KO) H9C2 monoclone, we verified that the expression of Rasd1 was controlled by KMT2D, and the expression of Rasd1 was decreased by serum starvation but not low-(O₂) treatment in H9C2 cells. KMT2D has a protective effect on ischemic myocardium by regulating cardiac disease-associated genes including Rasd1. KMT2D is required for the H3K4me1 deposition on the enhancer of Rasd1. Our data for the first time suggest that KMT2D-mediated Rasd1 expression may play an important protective effect on adult cells during nutritional deficiency caused by ischemic injury.

Hsa_circ_0007059 promotes apoptosis and inflammation in cardiomyocytes during ischemia by targeting microRNA-378 and microRNA-383

Circular RNAs (circRNAs) are a class of non-coding RNA molecules that are associated with not only normal physiological functions but also various diseases, including cardiac diseases such as myocardial infarction (MI). The present study explored the potential role of circRNA_0007059 (circ_0007059) during MI pathogenesis using in vitro studies. Microarray and quantitative PCR analyses demonstrated elevated circ_0007059 expression and downregulated miR-378 and miR-383 expression in H₂O₂-treated mice cardiomyocytes and infarcted hearts of MI mouse model as compared those in relevant controls. Moreover, circ_0007059 knockdown improved cardiomyocyte viability after H₂O₂ treatment as revealed by the CCK-8 and colony formation assays. Flow cytometry and caspase activity assays demonstrated that circ_0007059 suppressed H₂O₂-induced cardiomyocyte apoptosis. Enzyme-linked immunosorbent assays and Western blotting revealed that inflammatory cytokine (interleukin-1β, interleukin-18 and C-C motif chemokine ligand 5) expression was induced by H₂O₂ treatment and that circ_0007059 repressed H₂O₂-induced inflammation. Bioinformatics analyses and dual-luciferase reporter assays showed that circ_0000759 acts as a miR-378 and miR-383 sponge. Furthermore, the upregulation or suppression of miR-378 and miR-383 expression in H₂O₂-treated cardiomyocytes had similar effects on the apoptosis and inflammation of cardiomyocytes as that of circ_0007059 knockdown or overexpression, respectively. Additionally, lentiviral shRNA-circ_0007059 administration to mice with MI considerably reduced the size of infarcted regions and promoted cardiac activity. Collectively, our findings suggest that circ_0007059 expression is upregulated in mice cardiomyocytes in response to oxidative stress and cardiac tissues of MI mouse model, suggesting its involvement in the pathogenesis of MI by targeting miR-378 and miR-383.

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.

MicroRNA-1278 ameliorates the inflammation of cardiomyocytes during myocardial ischemia by targeting both IL-22 and CXCL14

AIMS

This study aimed to elucidate the role of microRNAs (miRNAs) during myocardial infarction (MI) development in vivo and in vitro.

MAIN METHODS

Differentially expressed miRNAs between heart tissue from the MI mouse model and the control mouse were identified via microarray. Quantitative PCR (qPCR) and western blotting (WB) were performed to examine the expression levels of miRNAs and proteins, respectively. EdU-staining and colony formation assay were performed to assess cell viability and growth. Annexin V- and PI-staining-based flow cytometry was used to assess cell apoptosis. An MI mouse model was also established to study the function of miR-1278 in vivo.

KEY FINDINGS

The levels of miR-1278 were reduced in the infarct regions of heart tissues of the MI mouse model and in H2O2-treated newborn murine ventricular cardiomyocytes (NMVCs) compared to those in the heart tissues of healthy mice and non-treated NMVCs. H2O2 treatment suppressed the proliferation of NMVCs, while miR-1278 upregulation improved it. Moreover, we found that miR-1278 inhibited the upregulation of IL-22 and CXCL14 expression in H2O2-treated NMVCs by directly binding with the 3'-UTRs of both IL-22 and CXCL14. Furthermore, restoration of IL-22 and CXCL14 in H2O2-treated NMVCs promoted miR-1278-induced inflammation and apoptosis. Administration of agomiR-1278 to the MI mouse model significantly improved cardiac activity.

SIGNIFICANCE

Collectively, our findings illustrate that the expression of miR-1278 is low in H2O2-treated NMVCs and post-MI cardiac tissues, and the overexpression of miR-1278 in these protects against cell death by modulating IL-22 and CXCL14 expression.

Cardiac MRI Assessment of Mouse Myocardial Infarction and Regeneration

Small animal models are indispensable for cardiac regeneration research. Studies in mouse and rat models have provided important insights into the etiology and mechanisms of cardiovascular diseases and accelerated the development of therapeutic strategies. It is vitally important to be able to evaluate the therapeutic efficacy and have reliable surrogate markers for therapeutic development for cardiac regeneration research. Magnetic resonance imaging (MRI), a versatile and noninvasive imaging modality with excellent penetration depth, tissue coverage, and soft-tissue contrast, is becoming a more important tool in both clinical settings and research arenas. Cardiac MRI (CMR) is versatile, noninvasive, and capable of measuring many different aspects of cardiac functions, and, thus, is ideally suited to evaluate therapeutic efficacy for cardiac regeneration. CMR applications include assessment of cardiac anatomy, regional wall motion, myocardial perfusion, myocardial viability, cardiac function assessment, assessment of myocardial infarction, and myocardial injury. Myocardial infarction models in mice are commonly used model systems for cardiac regeneration research. In this chapter, we discuss various CMR applications to evaluate cardiac functions and inflammation after myocardial infarction.

MicroRNA-200a represses myocardial infarction-related cell death and inflammation by targeting the Keap1/Nrf2 and β-catenin pathways

BACKGROUND

Acute myocardial infarction (MI) is a main cause of emergency death in the world. MicroRNAs (miRs/miRNAs) are a series of small non-coding RNA molecules, which regulate cardiovascular disorders that involve MI. In this study, we explored the function of miR-200a in MI treatment.

METHODS

We observed down-regulation of miR-200a levels and up-regulation of Keap1 and β-catenin levels in H₂O₂-treated newborn murine ventricular cardiomyocytes (NMVCs) and the infarcted heart tissues of MI mouse models, compared to the non-treated NMVCs and normal heart tissues of healthy mice.

RESULTS

CCK-8 and colony formation assays indicated the reduction in NMVC vitality due to H₂O₂ treatment and the recovery of cell vitality due to miR-200a overexpression, respectively. Flow cytometry with Annexin and PI staining indicated the inhibition of H₂O₂-triggered cell apoptosis through ectopically expressed miR-200a. Western blotting and ELISA analyses that detected pro-inflammatory cell factors [interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α] confirmed that miR-200a prevented H₂O₂-induced NMVC inflammation. Moreover, miR-200a inhibited up-regulation of Keap1 and β-catenin expression in H₂O₂-treated NMVCs by directly binding with the 3'-UTR regions of both Keap1 and β-catenin. Furthermore, overexpression of Keap1 and β-cateninin in H₂O₂-treated NMVCs with recovered miR-200a elevated inflammation and apoptosis, respectively.

CONCLUSION

The results showed that miR-200a expression was inhibited in murine cardiomyocytes due to H₂O₂ stress in MI cardiac tissues and overexpressed miR-200a could protect the cells from death by regulating the Keap1/Nrf2 and β-catenin signal transduction pathways.

Action of iron chelator on intramyocardial hemorrhage and cardiac remodeling following acute myocardial infarction

Intramyocardial hemorrhage is an independent predictor of adverse outcomes in ST-segment elevation myocardial infarction (STEMI). Iron deposition resulting from ischemia-reperfusion injury (I/R) is pro-inflammatory and has been associated with adverse remodeling. The role of iron chelation in hemorrhagic acute myocardial infarction (AMI) has never been explored. The purpose of this study was to investigate the cardioprotection offered by the iron-chelating agent deferiprone (DFP) in a porcine AMI model by evaluating hemorrhage neutralization and subsequent cardiac remodeling. Two groups of animals underwent a reperfused AMI procedure: control and DFP treated (N = 7 each). A comprehensive MRI examination was performed in healthy state and up to week 4 post-AMI, followed by histological assessment. Infarct size was not significantly different between the two groups; however, the DFP group demonstrated earlier resolution of hemorrhage (by T2* imaging) and edema (by T2 imaging). Additionally, ventricular enlargement and myocardial hypertrophy (wall thickness and mass) were significantly smaller with DFP, suggesting reduced adverse remodeling, compared to control. The histologic results were consistent with the MRI findings. To date, there is no effective targeted therapy for reperfusion hemorrhage. Our proof-of-concept study is the first to identify hemorrhage-derived iron as a therapeutic target in I/R and exploit the cardioprotective properties of an iron-chelating drug candidate in the setting of AMI. Iron chelation could potentially serve as an adjunctive therapy in hemorrhagic AMI.

The Role of Extracellular DNA and Histones in Ischaemia-Reperfusion Injury of the Myocardium

Despite an increase in the rates of survival in patients suffering myocardial infarction, as yet there is no therapy specifically targeting ischaemia and reperfusion injury of the myocardium. With a greater understanding of immune activation during infarction, more potential treatment targets are now being identified. The innate immune system is believed to play an important role in the myocardium after ischaemia-driven cardiomyocyte death. The release of intracellular contents including DNA into the extracellular space during necrosis and cell rupture is now believed to create a pro-inflammatory milieu which propagates the inflammatory process. DNA and DNA fragments have been shown to activate the innate immune system by acting as Danger-Associated Molecular Patterns (DAMPs), which act as ligands on toll-like receptors (TLRs). Stimulation of TLRs, in turn, can activate intracellular cell death pathways such as pyroptosis. Here, we review the role of DNA fragments during ischaemia and reperfusion, and assess their potential as a target in the quest to preserve cardiomyocyte viability following myocardial infarction.

ELECTROCARDIOGRAM CHANGES IN ADDISON DISEASE: POTENTIAL CLINICAL MARKER FOR ADRENAL CRISIS

Objective

To present a unique phenomenon of a patient in addisonian crisis with electrocardiogram (ECG) anomalies that resolved following glucocorticoid therapy.

Methods

We present the case report followed by discussion with literature review.

Results

A 25-year-old male with Addison disease (AD) presented with a 1-week history of lightheadedness, shortness of breath, chest pain, abdominal pain, postural hypotension, and tachycardia. The patient was diagnosed with addisonian crisis and started on intravenous, high-dose glucocorticoids. An ECG showed right-heart axis deviation and T-wave inversions. In the context of ongoing chest pain, there was concern for myocardial ischemic attack and the patient underwent an extensive cardiac evaluation. Cardiac workup was negative and an echocardiogram showed an ejection fraction of 50 to 55%. The ECG abnormalities resolved 1 day into his hospital admission and his other symptoms resolved 2 days following treatment with steroids.

Conclusion

AD is a rare, potentially lethal, and commonly misdiagnosed disease often first encountered clinically amidst an incident episode of adrenal crisis. Our AD patient was undergoing an adrenal crisis with ECG changes positive for probable cardiac ischemia. Glucocorticoid deficiency has been previously linked with decreased cardiac function and myocardial ischemia, though the underlying mechanisms are not fully clear. This patient recovered within 2 days after receiving corticosteroid supplementation. There have been similar cases previously reported. In each of these, patients underwent extensive and costly workup to evaluate cardiac function, yet all patients fully recovered with corticosteroids. Understanding the physiology and clinical presentation of adrenal crisis will be useful in establishing an earlier diagnosis, thus preventing mortality and avoiding unnecessary, expensive evaluations.

Glucocorticoid stimulation increases cardiac contractility by SGK1-dependent SOCE-activation in rat cardiac myocytes

Aims

Glucocorticoid (GC) stimulation has been shown to increase cardiac contractility by elevated intracellular [Ca] but the sources for Ca entry are unclear. This study aims to determine the role of store-operated Ca entry (SOCE) for GC-mediated inotropy.

Methods and results

Dexamethasone (Dex) pretreatment significantly increased cardiac contractile force ex vivo in Langendorff-perfused Sprague-Dawley rat hearts (2 mg/kg BW i.p. Dex 24 h prior to experiment). Moreover, Ca transient amplitude as well as fractional shortening were significantly enhanced in Fura-2-loaded isolated rat ventricular myocytes exposed to Dex (1 mg/mL Dex, 24 h). Interestingly, these Dex-dependent effects could be abolished in the presence of SOCE-inhibitors SKF-96356 (SKF, 2 μM) and BTP2 (5 μM). Ca transient kinetics (time to peak, decay time) were not affected by SOCE stimulation. Direct SOCE measurements revealed a negligible magnitude in untreated myocytes but a dramatic increase in SOCE upon Dex-pretreatment. Importantly, the Dex-dependent stimulation of SOCE could be blocked by inhibition of serum and glucocorticoid-regulated kinase 1 (SGK1) using EMD638683 (EMD, 50 μM). Dex preincubation also resulted in increased mRNA expression of proteins involved in SOCE (stromal interaction molecule 2, STIM2, and transient receptor potential cation channels 3/6, TRPC 3/6), which were also prevented in the presence of EMD.

Conclusion

Short-term GC-stimulation with Dex improves cardiac contractility by a SOCE-dependent mechanism, which appears to involve increased SGK1-dependent expression of the SOCE-related proteins. Since Ca transient kinetics were unaffected, SOCE appears to influence Ca cycling more by an integrated response across multiple cardiac cycles but not on a beat-to-beat basis.

Hurdles to Cardioprotection in the Critically Ill

Cardiovascular disease is the largest contributor to worldwide mortality, and the deleterious impact of heart failure (HF) is projected to grow exponentially in the future. As heart transplantation (HTx) is the only effective treatment for end-stage HF, development of mechanical circulatory support (MCS) technology has unveiled additional therapeutic options for refractory cardiac disease. Unfortunately, despite both MCS and HTx being quintessential treatments for significant cardiac impairment, associated morbidity and mortality remain high. MCS technology continues to evolve, but is associated with numerous disturbances to cardiac function (e.g., oxidative damage, arrhythmias). Following MCS intervention, HTx is frequently the destination option for survival of critically ill cardiac patients. While effective, donor hearts are scarce, thus limiting HTx to few qualifying patients, and HTx remains correlated with substantial post-HTx complications. While MCS and HTx are vital to survival of critically ill cardiac patients, cardioprotective strategies to improve outcomes from these treatments are highly desirable. Accordingly, this review summarizes the current status of MCS and HTx in the clinic, and the associated cardiac complications inherent to these treatments. Furthermore, we detail current research being undertaken to improve cardiac outcomes following MCS/HTx, and important considerations for reducing the significant morbidity and mortality associated with these necessary treatment strategies.

Gestational Hypoxia and Developmental Plasticity

Hypoxia is one of the most common and severe challenges to the maintenance of homeostasis. Oxygen sensing is a property of all tissues, and the response to hypoxia is multidimensional involving complicated intracellular networks concerned with the transduction of hypoxia-induced responses. Of all the stresses to which the fetus and newborn infant are subjected, perhaps the most important and clinically relevant is that of hypoxia. Hypoxia during gestation impacts both the mother and fetal development through interactions with an individual's genetic traits acquired over multiple generations by natural selection and changes in gene expression patterns by altering the epigenetic code. Changes in the epigenome determine "genomic plasticity," i.e., the ability of genes to be differentially expressed according to environmental cues. The genomic plasticity defined by epigenomic mechanisms including DNA methylation, histone modifications, and noncoding RNAs during development is the mechanistic substrate for phenotypic programming that determines physiological response and risk for healthy or deleterious outcomes. This review explores the impact of gestational hypoxia on maternal health and fetal development, and epigenetic mechanisms of developmental plasticity with emphasis on the uteroplacental circulation, heart development, cerebral circulation, pulmonary development, and the hypothalamic-pituitary-adrenal axis and adipose tissue. The complex molecular and epigenetic interactions that may impact an individual's physiology and developmental programming of health and disease later in life are discussed.

Anti-inflammatory therapies in myocardial infarction: failures, hopes and challenges

In the infarcted heart, the damage-associated molecular pattern proteins released by necrotic cells trigger both myocardial and systemic inflammatory responses. Induction of chemokines and cytokines and up-regulation of endothelial adhesion molecules mediate leukocyte recruitment in the infarcted myocardium. Inflammatory cells clear the infarct of dead cells and matrix debris and activate repair by myofibroblasts and vascular cells, but may also contribute to adverse fibrotic remodelling of viable segments, accentuate cardiomyocyte apoptosis and exert arrhythmogenic actions. Excessive, prolonged and dysregulated inflammation has been implicated in the pathogenesis of complications and may be involved in the development of heart failure following infarction. Studies in animal models of myocardial infarction (MI) have suggested the effectiveness of pharmacological interventions targeting the inflammatory response. This article provides a brief overview of the cell biology of the post-infarction inflammatory response and discusses the use of pharmacological interventions targeting inflammation following infarction. Therapy with broad anti-inflammatory and immunomodulatory agents may also inhibit important repair pathways, thus exerting detrimental actions in patients with MI. Extensive experimental evidence suggests that targeting specific inflammatory signals, such as the complement cascade, chemokines, cytokines, proteases, selectins and leukocyte integrins, may hold promise. However, clinical translation has proved challenging. Targeting IL-1 may benefit patients with exaggerated post-MI inflammatory responses following infarction, not only by attenuating adverse remodelling but also by stabilizing the atherosclerotic plaque and by inhibiting arrhythmia generation. Identification of the therapeutic window for specific interventions and pathophysiological stratification of MI patients using inflammatory biomarkers and imaging strategies are critical for optimal therapeutic design.

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

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

Hesperetin protects against inflammatory response and cardiac fibrosis in postmyocardial infarction mice by inhibiting nuclear factor κB signaling pathway

Cardiac inflammation and cardiac fibrosis are important parts of cardiac remodeling following myocardial infarction (MI), which may be the basic mechanisms of the development of chronic heart failure. The nuclear factor (NF)-κB signaling pathway promotes cardiac inflammation and fibrosis. It has reported that hesperetin inhibits cardiac remodeling induced by pressure overload in mice. However, it has remained elusive whether and how hesperetin has a role in cardiac fibrosis post-MI. Therefore, a mouse model of MI was established by left anterior descending coronary artery ligation. Mice received hesperetin (30 mg/kg/day) or vehicle after surgery. After 8 weeks, all mice underwent echocardiography to evaluate cardiac function. Gene expression of cardiac fibrosis markers such as connective tissue growth factor (CTGF) as well as collagen I and III, and histological analysis were applied to determine the level of cardiac fibrosis. The expression of inflammatory markers such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 were assessed by reverse-transcription quantitative PCR and ELISA, and activation of the NF-κB signaling pathway was detected by western blot analysis. It was found that hesperetin reduced the expression levels of TNF-α, IL-1β, IL-6 and CTGF as well as collagen I and III. The level of collagen deposition in post-MI myocardium was attenuated with the treatment of hesperetin. In additionally, administration of hesperetin inhibited the activation of the NF-κB signaling pathway. These findings indicated that hesperetin may inhibit cardiac inflammation post-MI through blocking the NF-κB signaling pathway, which may be a key mechanism via which hesperetin attenuates cardiac fibrosis.

Getting to the heart of intracellular glucocorticoid regeneration: 11β-HSD1 in the myocardium

Corticosteroids influence the development and function of the heart and its response to injury and pressure overload via actions on glucocorticoid (GR) and mineralocorticoid (MR) receptors. Systemic corticosteroid concentration depends largely on the activity of the hypothalamic-pituitary-adrenal (HPA) axis, but glucocorticoid can also be regenerated from intrinsically inert metabolites by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), selectively increasing glucocorticoid levels within cells and tissues. Extensive studies have revealed the roles for glucocorticoid regeneration by 11β-HSD1 in liver, adipose, brain and other tissues, but until recently, there has been little focus on the heart. This article reviews the evidence for glucocorticoid metabolism by 11β-HSD1 in the heart and for a role of 11β-HSD1 activity in determining the myocardial growth and physiological function. We also consider the potential of 11β-HSD1 as a therapeutic target to enhance repair after myocardial infarction and to prevent the development of cardiac remodelling and heart failure.

Effect of the Kallikrein Inhibitor Aprotinin on Myocardial Ischemia and Necrosis in Man

The effect of administration of aprotinin, a serine esterase inhibitor capable of inactivating kallikrein, on the extent and severity of acute myocardial is chemic injury and subsequent necrosis, was studied in 25 patients. Another group of 25 patients who did not receive aprotinin served as a control group. We administered 100,000 kallikrein inhibitor units (KIU) of aprotinin as a bolus dose, followed by a continuous infusion (4 ml/min) that contained 10,000 KIU/kg in 240 ml of dextrose/water solution, to all 25 patients admitted to the hospital within 30 to 60 minutes after the onset of acute myocardial ischemia.

To measure the effect of aprotinin, three parameters were studied; the sum of S-T segment elevations (ΣST), the development of Q waves, and the predic tion of infarct size by measuring the disappearance rate of creatine phosphoki nase (MB CPK isoenzyme).

The average ΣST in the treated group decreased from 40.5 ± 7.00 mv to 12.95 ± 4.60 mv (P < 0.01); in contrast the control group's ΣST did not change significantly, from 54.25 ± 8.02 to 51.7 ± 6.8. Deeper Q waves evolved in the control group compared to the treated group: ΔQ (6 hours) = 1.0 ST (15 min) + 1.19 (25 patients, r = 0.78); and in the treated group ΔQ (6 hours) = 0.66 ST (15 min) + 0.91 (25 patients, r = 0.65) (P < 0.025).

In the control group the estimated infarct size was 57.4 ± 4 CPK-gram- equivalents (CPK-g-Eq). There was significantly less damage in the treated group: 19 ± 2 CPK-g-Eq (P < 0.01). Thus we conclude that aprotinin dimin ishes myocardial damage.

Wnt11 Gene Therapy with Adeno-associated Virus 9 Improves Recovery from Myocardial Infarction by Modulating the Inflammatory Response

Acute myocardial infarction induces activation of the acute phase response and infiltration of leukocytes to the infarcted area. Moreover, myocardium that is remote from ischemic area also becomes inflamed. Inflammatory reaction clears dead cells and matrix debris, while prolongation or expansion of the inflammatory response results in dysfunction following myocardial infarction. Wnt glycolipoproteins are best characterized as regulators of embryonic development. Recently several reports suggest that they also contribute to the inflammatory response in adult animals. However, the effects of Wnt proteins on myocardial infarction have not been explored. Here we show that Wnt11 expression leads to significant improvements of survival and cardiac function by suppressing infiltration of multiple kinds of inflammatory cells in infarcted heart. Wnt11 protein suppresses gene expression of inflammatory cytokines through the modulation of NF-κB in vitro. These results reveal a novel function of Wnt11 in the regulation of inflammatory response and provide a rationale for the use of Wnt11 to manipulate human diseases that are mediated by inflammation.

Antenatal hypoxia induces epigenetic repression of glucocorticoid receptor and promotes ischemic-sensitive phenotype in the developing heart

Large studies in humans and animals have demonstrated a clear association of an adverse intrauterine environment with an increased risk of cardiovascular disease later in life. Yet mechanisms remain largely elusive. The present study tested the hypothesis that gestational hypoxia leads to promoter hypermethylation and epigenetic repression of the glucocorticoid receptor (GR) gene in the developing heart, resulting in increased heart susceptibility to ischemia and reperfusion injury in offspring. Hypoxic treatment of pregnant rats from day 15 to 21 of gestation resulted in a significant decrease of GR exon 14, 15, 16, and 17 transcripts, leading to down-regulation of GR mRNA and protein in the fetal heart. Functional cAMP-response elements (CREs) at -4408 and -3896 and Sp1 binding sites at -3425 and -3034 were identified at GR untranslated exon 1 promoters. Hypoxia significantly increased CpG methylation at the CREs and Sp1 binding sites and decreased transcription factor binding to GR exon 1 promoter, accounting for the repression of the GR gene in the developing heart. Of importance, treatment of newborn pups with 5-aza-2'-deoxycytidine reversed hypoxia-induced promoter methylation, restored GR expression and prevented hypoxia-mediated increase in ischemia and reperfusion injury of the heart in offspring. The findings demonstrate a novel mechanism of epigenetic repression of the GR gene in fetal stress-mediated programming of ischemic-sensitive phenotype in the heart.

Cardiomyocyte and Vascular Smooth Muscle-Independent 11β-Hydroxysteroid Dehydrogenase 1 Amplifies Infarct Expansion, Hypertrophy, and the Development of Heart Failure After Myocardial Infarction in Male Mice

Global deficiency of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), an enzyme that regenerates glucocorticoids within cells, promotes angiogenesis, and reduces acute infarct expansion after myocardial infarction (MI), suggesting that 11β-HSD1 activity has an adverse influence on wound healing in the heart after MI. The present study investigated whether 11β-HSD1 deficiency could prevent the development of heart failure after MI and examined whether 11β-HSD1 deficiency in cardiomyocytes and vascular smooth muscle cells confers this protection. Male mice with global deficiency in 11β-HSD1, or with Hsd11b1 disruption in cardiac and vascular smooth muscle (via SM22α-Cre recombinase), underwent coronary artery ligation for induction of MI. Acute injury was equivalent in all groups. However, by 8 weeks after induction of MI, relative to C57Bl/6 wild type, globally 11β-HSD1-deficient mice had reduced infarct size (34.7 ± 2.1% left ventricle [LV] vs 44.0 ± 3.3% LV, P = .02), improved function (ejection fraction, 33.5 ± 2.5% vs 24.7 ± 2.5%, P = .03) and reduced ventricular dilation (LV end-diastolic volume, 0.17 ± 0.01 vs 0.21 ± 0.01 mL, P = .01). This was accompanied by a reduction in hypertrophy, pulmonary edema, and in the expression of genes encoding atrial natriuretic peptide and β-myosin heavy chain. None of these outcomes, nor promotion of periinfarct angiogenesis during infarct repair, were recapitulated when 11β-HSD1 deficiency was restricted to cardiac and vascular smooth muscle. 11β-HSD1 expressed in cells other than cardiomyocytes or vascular smooth muscle limits angiogenesis and promotes infarct expansion with adverse ventricular remodeling after MI. Early pharmacological inhibition of 11β-HSD1 may offer a new therapeutic approach to prevent heart failure associated with ischemic heart disease.

Inflammation as a therapeutic target in myocardial infarction: learning from past failures to meet future challenges

In the infarcted myocardium, necrotic cardiomyocytes release danger signals, activating an intense inflammatory response. Inflammatory pathways play a crucial role in regulation of a wide range of cellular processes involved in injury, repair, and remodeling of the infarcted heart. Proinflammatory cytokines, such as tumor necrosis factor α and interleukin 1, are markedly upregulated in the infarcted myocardium and promote adhesive interactions between endothelial cells and leukocytes by stimulating chemokine and adhesion molecule expression. Distinct pairs of chemokines and chemokine receptors are implicated in recruitment of various leukocyte subpopulations in the infarcted myocardium. For more than the past 30 years, extensive experimental work has explored the role of inflammatory signals and the contributions of leukocyte subpopulations in myocardial infarction. Robust evidence derived from experimental models of myocardial infarction has identified inflammatory targets that may attenuate cardiomyocyte injury or protect from adverse remodeling. Unfortunately, attempts to translate the promising experimental findings to clinical therapy have failed. This review article discusses the biology of the inflammatory response after myocardial infarction, attempts to identify the causes for the translational failures of the past, and proposes promising new therapeutic directions. Because of their potential involvement in injurious, reparative, and regenerative responses, inflammatory cells may hold the key for design of new therapies in myocardial infarction.

Translational failure of anti-inflammatory compounds for myocardial infarction: a meta-analysis of large animal models

AIMS

Numerous anti-inflammatory drugs have been tested in large animal studies of myocardial infarction (MI). Despite positive results, translation of anti-inflammatory strategies into clinical practice has proved to be difficult. Critical disparities between preclinical and clinical study design that influence efficacy may partly be responsible for this translational failure. The aim of the present systematic review was to better understand which factors underlie the failure of transition towards the clinic.

METHODS AND RESULTS

Meta-analysis and regression of large animal studies were performed to identify sources that influenced effect size of anti-inflammatory compounds in large animal models of MI. We included 183 studies, containing 3331 large animals. Infarct size (IS) as a ratio of the area at risk (12.7%; 95% confidence interval, CI 11.1-14.4%, P < 0.001) and IS as a ratio of the left ventricle (3.9%; 95% CI 3.1-4.7%, P < 0.001) were reduced in treatment compared with control groups. Effect size was higher when outcome was assessed early after MI (P = 0.013) and where studies included only male animals (P < 0.001). Mortality in treated animals was higher in studies that blinded the investigator during the experiment (P = 0.041) and depended on the type of drug used (P < 0.001).

CONCLUSIONS

As expected, treatment with anti-inflammatory drugs leads to smaller infarct size in large animal MI models. Timing of outcome assessment, sex, and study quality are significantly associated with outcome and may explain part of the translational failure in clinical settings. Effect size depends on the type of drug used, enabling identification of compounds for future clinical testing.

Metformin attenuates myocardial remodeling and neutrophil recruitment after myocardial infarction in rat

Introduction: Acute treatment with metformin has a cardio-protective effects by suppression of inflammatory responses during myocardial infarction (MI) through activation of AMP-activated protein kinase (AMPK). Neutrophils have a pivotal role during MI-induced inflammatory responses. Some anti-inflammatory treatments have decreased cardiac injury and infarct size in MI. Here we evaluated the effects of chronic pre-treatment with metformin on myocardial remodeling and neutrophil recruitment after isoproterenol-induced MI.

Methods: Male wistar rats were randomly assigned into 6 groups (n=6) of untreated control, sham, isoproterenol (Iso), and pre-treated orally with 25, 50, and 100 mg/kg of metformin, twice daily, for 14 days. Isoproterenol was injected subcutaneously (sc) at 13th and 14th days for induction of acute MI. Histopathological examinations were done on the harvested hearts. Number of neutrophils in peripheral blood and their infiltration to myocardium were evaluated by Gimsa staining and myeloperoxidase (MPO) assay, respectively.

Results: Histopathological analysis showed a significant attenuation of isoproterenol-induced cardiomyocyte necrosis and fibrosis by all three doses of metformin. The heart to body weight ratio was also decreased with all doses of metformin. Pre-treatment with metformin in comparison to Iso (MI) group reduced peripheral neutrophils (p<0.05, p<0.01, and p<0.001 at 25, 50, and 100 mg/kg; respectively) as well as MPO activity (p<0.05 and p<0.01 at 50 and 100 mg/ kg, respectively).

Conclusion: Pre-treatment with metformin decreased post-MI myocardial injuries by reducing cardiac remodeling and myocardial neutrophil activity. The results could be explained as a new mechanism for cardio-protective effect of metformin.

Inhibitory effects of cortisone and hydrocortisone on human Kv1.5 channel currents

Glucocorticoids are the primary hormones that respond to stress and protect organisms from dangerous situations. The glucocorticoids hydrocortisone and its dormant form, cortisone, affect the cardiovascular system with changes such as increased blood pressure and cardioprotection. Kv1.5 channels play a critical role in the maintenance of cellular membrane potential and are widely expressed in pancreatic β-cells, neurons, myocytes, and smooth muscle cells of the pulmonary vasculature. We examined the electrophysiological effects of both cortisone and hydrocortisone on human Kv1.5 channels expressed in Xenopus oocytes using a two-microelectrode voltage clamp technique. Both cortisone and hydrocortisone rapidly and irreversibly suppressed the amplitude of Kv1.5 channel current with IC50 values of 50.2±4.2μM and 33.4±3.2μM, respectively, while sustained the current trace shape of Kv1.5 current. The inhibitory effect of cortisone on Kv1.5 decreased progressively from -10mV to +30mV, while hydrocortisone׳s inhibition of the channel did not change across the same voltage range. Both cortisone and hydrocortisone blocked Kv1.5 channel currents in a non-use-dependent manner and neither altered the channel׳s steady-state activation or inactivation curves. These results show that cortisone and hydrocortisone inhibited Kv1.5 channel currents differently, and that Kv1.5 channels were more sensitive to hydrocortisone than to cortisone.

Anti-inflammatory strategies for ventricular remodeling following ST-segment elevation acute myocardial infarction

Acute myocardial infarction (AMI) leads to molecular, structural, geometric, and functional changes in the heart in a process known as ventricular remodeling. An intense organized inflammatory response is triggered after myocardial ischemia and necrosis and involves all components of the innate immunity, affecting both cardiomyocytes and noncardiomyocyte cells. Inflammation is triggered by tissue injury; it mediates wound healing and scar formation and affects ventricular remodeling. Many therapeutic attempts aimed at reducing inflammation in AMI during the past 3 decades presented issues of impaired healing or increased risk of cardiac rupture or failed to show any additional benefit in addition to standard therapies. More recent strategies aimed at selectively blocking one of the key factors upstream rather than globally suppressing the response downstream have shown some promising results in pilot trials. We herein review the pathophysiological mechanisms of inflammation and ventricular remodeling after AMI and the results of clinical trials with anti-inflammatory strategies.

Depression after myocardial infarction: TNF-α-induced alterations of the blood-brain barrier and its putative therapeutic implications

Patients experiencing an acute myocardial infarction (AMI) have a three times higher chance to develop depression. Vice versa, depressive symptoms increase the risk of cardiovascular events. The co-existence of both conditions is associated with substantially worse prognosis. Although the underlying mechanism of the interaction is largely unknown, inflammation is thought to be of pivotal importance. AMI-induced peripheral cytokines release may cause cerebral endothelial leakage and hence induces a neuroinflammatory reaction. The neuroinflammation may persist even long after the initial peripheral inflammation has subsided. Among those selected brain regions that are prone to blood-brain barrier dysfunction, the paraventricular nucleus of the hypothalamus (PVN), a major center for cardiovascular autonomic regulation, is indicated to play a mediating role. Optimal cardiovascular therapy improves cardiovascular prognosis without major effects on depression. By the same token, antidepressant therapy in cardiovascular disease is associated with modest improvement in depressive symptoms, however without improvement in cardiac outcome. The failure of current antidepressants and the growing number of patients suffering from both conditions legitimize the search for better antidepressive therapies, from patients as well as society perspectives. Though we appreciate the mutual character of the interaction between depression and AMI, the present review focuses on the side of AMI induced depression and discusses the role of inflammation, represented by the proinflammatory cytokine TNF-α, as potential underlying mechanism. It is conceivable that inhibition of the inflammatory response post-AMI, through targeted anti-inflammatory pharmacotherapeutical agents may prevent the development of depressive symptoms and ultimately may improve cardiovascular outcomes.

Usefulness of fetuin-A and C-reactive protein concentrations for prediction of outcome in acute coronary syndromes (from the French Registry of Acute ST-Elevation Non-ST-Elevation Myocardial Infarction [FAST-MI])

Fetuin-A is a ubiquitous anti-inflammatory glycoprotein that counteracts proinflammatory cytokine production. Previous studies have shown that low fetuin-A concentration is associated with cardiovascular death and may play an important role in the prognosis of patients with acute coronary syndromes (ACS). The purpose of this study was to assess in large cohort of patients admitted for ACS the prognostic value of fetuin-A adjusted for C-reactive protein value (CRP) and Global Registry of Acute Coronary Events (GRACE) risk score. Plasma fetuin-A and CRP concentrations were measured on day 3 in 754 consecutive patients with ACS (mean age 66 ± 14 years, 404 with ST-segment elevation and 350 without ST-segment elevation) included in the French Registry of Acute ST-Elevation or Non-ST-Elevation Myocardial Infarction (FAST-MI), and these data were correlated to 1-year mortality. Plasma fetuin-A and CRP concentrations at admission averaged 95 ± 27 and 12 ± 16 mg/L, respectively. Overall, 1-year cardiovascular mortality was 10% (28 in-hospital deaths and 51 deaths after discharge), 17% in patients with low fetuin-A (less than the first tertile), 18% with high CRP (higher than the third tertile), and 23% in patients with low fetuin associated with high CRP (p <0.01). In contrast, patients with neither low fetuin-A nor high CRP had a low mortality rate (5%). Multivariate analysis adjusted for GRACE risk score showed that low fetuin-A and high CRP concentration remained associated with outcomes (odds ratio 2.28, 95% confidence interval 1.20 to 4.33). In conclusion, fetuin-A combined with CRP level is associated with cardiovascular death in patients with ACS.

Non-genomic effect of glucocorticoids on cardiovascular system

Glucocorticoids (GCs) are essential steroid hormones for homeostasis, development, metabolism, and cognition and possess anti-inflammatory and immunosuppressive actions. Since glucocorticoid receptor II (GR) is nearly ubiquitous, chronic activation or depletion of GCs leads to dysfunction of diverse organs, including the heart and blood vessels, resulting predominantly from changes in gene expression. Most studies, therefore, have focused on the genomic effects of GC to understand its related pathophysiological manifestations. The nongenomic effects of GCs clearly differ from well-known genomic effects, with the former responding within several minutes without the need for protein synthesis. There is increasing evidence that the nongenomic actions of GCs influence various physiological functions. To develop a GC-mediated therapeutic target for the treatment of cardiovascular disease, understanding the genomic and nongenomic effects of GC on the cardiovascular system is needed. This article reviews our current understanding of the underlying mechanisms of GCs on cardiovascular diseases and stress, as well as how nongenomic GC signaling contributes to these conditions. We suggest that manipulation of GC action based on both GC and GR metabolism, mitochondrial impact, and the action of serum- and glucocorticoid-dependent kinase 1 may provide new information with which to treat cardiovascular diseases.

Effects of xenon and isoflurane on apoptosis and inflammation in a porcine myocardial infarction model

Volatile anaesthetics can reduce the infarction size in myocardial tissue when administered before and during experimentally induced ischaemia. The aim of this study was to investigate whether xenon is beneficial compared to isoflurane in limiting myocardial tissue apoptosis and inflammation induced by experimental ischaemia-reperfusion injury in a porcine right ventricular infarction model. Twenty-one animals used for this study randomly received isoflurane, xenon or thiopental, (n=6-8 per group). Myocardial infarction was induced for 90min, followed by reperfusion for 120min. Tissues from the left and right ventricles were removed from the sites of infarction, reperfusion and remote areas, and processed for immunohistochemistry. Apoptosis (caspase-3 staining) and neutrophilic infiltration (naphthol AS-D chloroacetate-specific esterase) were assessed and evaluated. Statistical analysis was performed using an ANOVA of repeated measures. Density of apoptotic cells were higher in tissues from animals that were anesthetized with xenon. This effect was significant in comparison to isoflurane (p=0.0177). Neutrophilic infiltration was significantly higher in the right compared to the left ventricle (p<0.001), whereas no significant differences in the number of granulocytes based on the anaesthetic regime or the different tissue areas were found. We conclude that xenon, in the early phase of ischaemia and reperfusion, induces a significant increase in apoptosis compared to isoflurane. Therefore, clinical use of this anaesthetic in cardiocompromised patients should be taken with care until more long-term studies have been carried out. The increased neutrophilic infiltration in the right vs. the left ventricle indicates the right ventricle being more susceptible to ischaemia-reperfusion injury.

Treatment with OPN-305, a humanized anti-Toll-Like receptor-2 antibody, reduces myocardial ischemia/reperfusion injury in pigs

BACKGROUND

Toll-like receptor (TLR)-2 is an important mediator of innate immunity and ischemia/reperfusion-induced cardiac injury. We have previously shown that TLR2 inhibition reduces infarct size and improves cardiac function in mice. However, the therapeutic efficacy of a clinical grade humanized anti-TLR2 antibody, OPN-305, in a large-animal model remained to be addressed.

METHODS AND RESULTS

Pigs (n=38) underwent 75 minutes ischemia followed by 24 hours of reperfusion. Saline or OPN-305 (12.5, 6.25, or 1.56 mg/kg) was infused intravenously 15 minutes before reperfusion. Cardiac function and geometry were assessed by echocardiography. Infarct size was calculated as the percentage of the area at risk and by serum Troponin-I levels. Flow cytometry analysis revealed specific binding of OPN-305 to porcine TLR2. In vivo, OPN-305 exhibited a secondary half-life of 8±2 days. Intravenous administration of OPN-305 before reperfusion significantly reduced infarct size (45% reduction, P=0.041) in a dose-dependent manner. In addition, pigs treated with OPN-305 exhibited a significant preservation of systolic performance in a dose-dependent fashion, whereas saline treatment completely diminished the contractile performance of the ischemic/reperfused myocardium.

CONCLUSIONS

OPN-305 significantly reduces infarct size and preserves cardiac function in pigs after ischemia/reperfusion injury. Hence, OPN-305 is a promising adjunctive therapeutic for patients with acute myocardial infarction.

Dexamethasone induces transcriptional activation of Bcl-xL gene and inhibits cardiac injury by myocardial ischemia

Psychological or physical stress causes an elevation of glucocorticoids in the circulating system. Glucocorticoids regulate a variety of physiological functions, from energy metabolism and biochemical homeostasis to immune response. Synthetic steroids are among the most prescribed drugs for immune suppression and chemotherapy. While glucocorticoids are best known for inducing apoptosis in a number of cell types, we have found that corticosteroids at stress relevant levels protect cardiomyocytes from apoptosis. Current study addresses whether glucocorticoids inhibit cardiac injury in vivo. Adult male C57BL6 mice were administered with dexamethasone (20mg/kg, i.p.) or vehicle control 20 h prior to left anterior descending coronary artery occlusion surgery. Myocardial infarction was measured by triphenyl tetrazoliumchloride staining in tissue slices and by levels of cardiac Troponin (cTn I) in the blood. Treatment of dexamethasone markedly reduced infarct size (19.6 ± 4.3%, vs. 29.2 ± 4.9%, p<0.01) and cTn I level in the blood (3.83 ± 0.66 ng/ml vs. 5.62 ± 0.37 ng/ml, p<0.01). In studying the mechanism of such protection, we found that dexamethasone induces the expression of Bcl-xL gene in the myocardium. With cardiomyocytes in culture, glucocorticoids increased transcription of Bcl-xL gene as evidenced by Bcl-xL mRNA increase and promoter activation. The glucocorticoid receptor antagonist mifepristone prevented dexamethasone from inducing cardiac protection or Bcl-xL expression. Our data suggest that activation of glucocorticoid receptor can prevent cardiac injury through transcriptional activation of Bcl-xL gene.

Glucocorticoids Activate Cardiac Mineralocorticoid Receptors During Experimental Myocardial Infarction

Myocardial ischemia-reperfusion leads to significant changes in redox state, decreased postischemic functional recovery, and cardiomyocyte apoptosis, with development and progression of heart failure. Ischemia-reperfusion in the isolated perfused rat heart has been used as a model of heart failure. Clinically, mineralocorticoid receptor blockade in heart failure decreases morbidity and mortality versus standard care alone. The effects of corticosteroids on infarct area and apoptosis were determined in rat hearts subjected to 30 minutes of ischemia and 2.5 hours of reperfusion. Both aldosterone and cortisol increased infarct area and apoptotic index, an effect half-maximal between 1 and 10 nM and reversed by spironolactone. Dexamethasone and mifepristone aggravated infarct area and apoptotic index, similarly reversed by spironolactone. Spironolactone alone reduced infarct area and apoptotic index below ischemia-reperfusion alone, in hearts from both intact and adrenalectomized rats. The present study shows that cardiac damage is aggravated by activation of mineralocorticoid receptors by aldosterone or cortisol or of glucocorticoid receptors by dexamethasone. Mifepristone unexpectedly acted as a glucocorticoid receptor agonist, for which there are several precedents. Spironolactone protected cardiomyocytes via inverse agonist activity at mineralocorticoid receptors, an effect near maximal at a relatively low dose (10 nM). Spironolactone acts not merely by excluding corticosteroids from mineralocorticoid receptors but as a protective inverse agonist at low concentration. Mineralocorticoid receptor antagonists may, thus, provide an additional therapeutic advantage in unstable angina and acute myocardial infarction.

Enterocyte shedding and epithelial lining repair following ischemia of the human small intestine attenuate inflammation

Background

Recently, we observed that small-intestinal ischemia and reperfusion was found to entail a rapid loss of apoptotic and necrotic cells. This study was conducted to investigate whether the observed shedding of ischemically damaged epithelial cells affects IR induced inflammation in the human small gut.

Methods and Findings

Using a newly developed IR model of the human small intestine, the inflammatory response was studied on cellular, protein and mRNA level. Thirty patients were consecutively included. Part of the jejunum was subjected to 30 minutes of ischemia and variable reperfusion periods (mean reperfusion time 120 (±11) minutes). Ethical approval and informed consent were obtained. Increased plasma intestinal fatty acid binding protein (I-FABP) levels indicated loss in epithelial cell integrity in response to ischemia and reperfusion (p<0.001 vs healthy). HIF-1α gene expression doubled (p = 0.02) and C3 gene expression increased 4-fold (p = 0.01) over the course of IR. Gut barrier failure, assessed as LPS concentration in small bowel venous effluent blood, was not observed (p = 0.18). Additionally, mRNA expression of HO-1, IL-6, IL-8 did not alter. No increased expression of endothelial adhesion molecules, TNFα release, increased numbers of inflammatory cells (p = 0.71) or complement activation, assessed as activated C3 (p = 0.14), were detected in the reperfused tissue.

Conclusions

In the human small intestine, thirty minutes of ischemia followed by up to 4 hours of reperfusion, does not seem to lead to an explicit inflammatory response. This may be explained by a unique mechanism of shedding of damaged enterocytes, reported for the first time by our group.

Impact of heterogeneity of human peripheral blood monocyte subsets on myocardial salvage in patients with primary acute myocardial infarction

OBJECTIVES

We examined whether distinct monocyte subsets contribute in specific ways to myocardial salvage in patients with acute myocardial infarction (AMI).

BACKGROUND

Recent studies have shown that monocytes in human peripheral blood are heterogeneous.

METHODS

We studied 36 patients with primary AMI. Peripheral blood sampling was performed 1, 2, 3, 4, 5, 8, and 12 days after AMI onset. Two monocyte subsets (CD14(+)CD16(-) and CD14(+)CD16(+)) were measured by flow cytometry. The extent of myocardial salvage 7 days after AMI was evaluated by cardiovascular magnetic resonance imaging as the difference between myocardium at risk (T2-weighted hyperintense lesion) and myocardial necrosis (delayed gadolinium enhancement). Cardiovascular magnetic resonance imaging was also performed 6 months after AMI.

RESULTS

Circulating CD14(+)CD16(-) and CD14(+)CD16(+) monocytes increased in AMI patients, peaking on days 3 and 5 after onset, respectively. Importantly, the peak levels of CD14(+)CD16(-) monocytes, but not those of CD14(+)CD16(+) monocytes, were significantly negatively associated with the extent of myocardial salvage. We also found that the peak levels of CD14(+)CD16(-) monocytes, but not those of CD14(+)CD16(+) monocytes, were negatively correlated with recovery of left ventricular ejection fraction 6 months after infarction.

CONCLUSIONS

The peak levels of CD14(+)CD16(-) monocytes affect both the extent of myocardial salvage and the recovery of left ventricular function after AMI, indicating that the manipulation of monocyte heterogeneity could be a novel therapeutic target for salvaging ischemic damage.

Glucocorticoid protects rodent hearts from ischemia/reperfusion injury by activating lipocalin-type prostaglandin D synthase-derived PGD2 biosynthesis

Lipocalin-type prostaglandin D synthase (L-PGDS), which was originally identified as an enzyme responsible for PGD2 biosynthesis in the brain, is highly expressed in the myocardium, including in cardiomyocytes. However, the factors that control expression of the gene encoding L-PGDS and the pathophysiologic role of L-PGDS in cardiomyocytes are poorly understood. In the present study, we demonstrate that glucocorticoids, which act as repressors of prostaglandin biosynthesis in most cell types, upregulated the expression of L-PGDS together with cytosolic calcium-dependent phospholipase A2 and COX2 via the glucocorticoid receptor (GR) in rat cardiomyocytes. Accordingly, PGD2 was the most prominently induced prostaglandin in vivo in mouse hearts and in vitro in cultured rat cardiomyocytes after exposure to GR-selective agonists. In isolated Langendorff-perfused mouse hearts, dexamethasone alleviated ischemia/reperfusion injury. This cardioprotective effect was completely abrogated by either pharmacologic inhibition of COX2 or disruption of the gene encoding L-PGDS. In in vivo ischemia/reperfusion experiments, dexamethasone reduced infarct size in wild-type mice. This cardioprotective effect of dexamethasone was markedly reduced in L-PGDS-deficient mice. In cultured rat cardiomyocytes, PGD2 protected against cell death induced by anoxia/reoxygenation via the D-type prostanoid receptor and the ERK1/2-mediated pathway. Taken together, these results suggest what we believe to be a novel interaction between glucocorticoid-GR signaling and the cardiomyocyte survival pathway mediated by the arachidonic acid cascade.

Factors modifying ischemic injury in the isolated rat heart

The extent of ischemic injury has been studied in the isolated working rat heart utilizing an aortic ball valve that reduces the coronary flow. A number of factors were tested including high heart rate, noradrenaline, acidosis, alkalosis, high afterload, beta-blockade, glucose-insulin-potassium (GIK), palmitate and methylprednisolone. Mechanical performance, myocardial contents of ATP, creatine phosphate, glycogen and lactate and the leakage of creatine phosphokinase (CK) from the myocardium to the perfusion buffer were measured and used for determination of the ischemic injury. Tachycardia, noradrenaline and palmitate are factors that markedly increase the ischemic injury in this preparation. GIK and probably metoprolol decrease the release of CK compared with the controls.

A comparative study of cardioselective beta-blockade and diazepam in patients wtih acute myocardial infarction and tachycardia

Eighty-seven patients with an acute myocardial infarction and a pulse rate of greater than or equal to 80/min on admission were randomly allotted to one group given cardioselective beta-blockade, a second group given diazepam, and a third group given placebo. The three groups were comparable in age, sex distribution, previous history of ischemic heart disease, initial pulse rate, blood pressure, pain index, enzyme values, and degree of ST elevation. The acute mortality (within 10 days) did not differ between the groups. The drug treatment elicited no reduction of infarct size, as judged from enzyme levels, degree of reduction of ST elevation, or physical exercise capacity. The reasons for this negative result are discussed. One possibility is that in routine clinical practice the therapeutic intervention starts too late after onset of symptoms. A beneficial effect on mortality among the patients whose treatment started early after onset of symptoms supports this conclusion.