In vivo transfer of soluble TNF-alpha receptor 1 gene improves cardiac function and reduces infarct size after myocardial infarction in rats

Targeting Key Inflammatory Mechanisms Underlying Heart Failure: A Comprehensive Review

Inflammation is a major component of heart failure (HF), causing peripheral vasculopathy and cardiac remodeling. High levels of circulating inflammatory cytokines in HF patients have been well recognized. The hallmark of the inflammatory imbalance is the insufficient production of anti-inflammatory mediators, a condition that leads to dysregulated cytokine activity. The condition progresses because of the pathogenic consequences of the cytokine imbalance, including the impact of endothelial dysfunction and adrenergic responsiveness deterioration, and unfavorable inotropic effects on the myocardium. Hence, to develop possible anti-inflammatory treatment options that will enhance the outcomes of HF patients, it is essential to identify the potential pathophysiological mechanisms of inflammation in HF. Inflammatory mediators, such as cytokines, adhesion molecules, and acute-phase proteins, are elevated during this process, highlighting the complex association between inflammation and HF. Therefore, these inflammatory markers can be used in predicting prognosis of the syndrome. Various immune cells impact on myocardial remodeling and recovery. They lead to stimulation, release of alarmins and risk-related molecule patterns. Targeting key inflammatory mechanisms seems a quite promising therapy strategy in HF. Cytokine modulation is only one of several possible targets in the fight against inflammation, as the potential molecular targets for therapy in HF include immune activation, inflammation, oxidative stress, alterations in mitochondrial bioenergetics, and autophagy.

Using models to advance medicine: mathematical modeling of post-myocardial infarction left ventricular remodeling

The heart is an organ with limited capacity for regeneration and repair. The irreversible cell death and corresponding diminished ability of the heart to repair after myocardial infarction (MI), is a leading cause of morbidity and mortality worldwide. In this paper, a new mathematical model is presented to study the left ventricular (LV) remodeling and associated events after MI. The model accurately describes and predicts the interactions among heart cells and the immune system post-MI in the absence of medical interventions. The resulting system of nonlinear ordinary differential equations is studied both analytically and numerically in order to demonstrate the functionality and performance of the new model. To the best of our knowledge, this model is the only one of its kind to consider and correctly apply all of the known factors in diseased heart LV modeling. This model has the potential to provide researchers with a predictive computational tool to better understand the MI pathology and develop various cell-based treatment options, with benefits of lowering the cost and reducing the development time.

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.

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.

EphrinA1-Fc attenuates myocardial ischemia/reperfusion injury in mice

EphrinA1, a membrane-bound receptor tyrosine kinase ligand expressed in healthy cardiomyocytes, is lost in injured cells following myocardial infarction. Previously, we have reported that a single intramyocardial injection of chimeric ephrinA1-Fc at the time of ischemia reduced injury in the nonreperfused myocardium by 50% at 4 days post-MI by reducing apoptosis and inflammatory cell infiltration. In a clinically relevant model of acute ischemia (30min)/reperfusion (24hr or 4 days) injury, we now demonstrate that ephrinA1-Fc reduces infarct size by 46% and completely preserves cardiac function (ejection fraction, fractional shortening, and chamber dimensions) in the short-term (24hrs post-MI) as well as long-term (4 days). At 24 hours post-MI, diminished serum inflammatory cell chemoattractants in ephrinA1-Fc-treated mice reduces recruitment of neutrophils and leukocytes into the myocardium. Differences in relative expression levels of EphA-Rs are described in the context of their putative role in mediating cardioprotection. Validation by Western blotting of selected targets from mass spectrometry analyses of pooled samples of left ventricular tissue homogenates from mice that underwent 30min ischemia and 24hr of reperfusion (I/R) indicates that ephrinA1-Fc administration alters several regulators of signaling pathways that attenuate apoptosis, promote autophagy, and shift from FA metabolism in favor of increased glycolysis to optimize anaerobic ATP production. Taken together, reduced injury is due a combination of adaptive metabolic reprogramming, improved cell survival, and decreased inflammatory cell recruitment, suggesting that ephrinA1-Fc enhances the capacity of the heart to withstand an ischemic insult.

Therapeutic Hypothermia Reduces the Inflammatory Response Following Ischemia/Reperfusion Injury in Rat Hearts

Therapeutic hypothermia (TH) is known to protect against ischemia/reperfusion (I/R) injury. One mechanism of I/R injury includes secondary injury due to the inflammatory cascade. We hypothesized that TH reduces the inflammatory response following I/R injury. Rats were randomized to sham, normothermic, or hypothermic groups and subjected to 1 hour of coronary artery occlusion and 48 hours of reperfusion. Hypothermia was initiated, using the ThermoSuit^® device, 2 minutes after the onset of coronary artery occlusion to a core temperature of 32°C, and then the rats were allowed to rewarm. After 48 hours, rats in the hypothermia group demonstrated a preserved left ventricular fractional shortening by echocardiography. TH decreased the inflammatory cytokines in the risk zone of the heart, which included monocyte chemoattractant protein-1, interleukin-6, tumor necrosis factor-α, and inducible nitric oxide synthase gene expression, and altered expression of the remodeling genes of matrix metalloproteinase and tissue inhibitor of metalloproteinase. Furthermore, rat inflammatory cytokines & receptors PCR array was performed and the data showed that 71 out of 84 genes were upregulated in the risk zone of normothermia hearts versus shams. The upregulation was largely reversed in the risk zone of hypothermia hearts compared to normothermia. TH preserves cardiac function, decreases excessive inflammatory gene expression, and regulates myocardial matrix remodeling related genes.

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.

Pro- and anti-inflammatory cytokines in post-infarction left ventricular remodeling

OBJECTIVES

Acute myocardial infarction (MI) leads to molecular, structural, geometric and functional changes in the heart during a process known as ventricular remodeling. Myocardial infarction is followed by an inflammatory response in which pro- and anti-inflammatory cytokines play a crucial role, particularly in left ventricular remodeling. This study aimed at evaluating serum concentrations of interleukin-8 (IL8), tumor-necrosis-factor-alpha (TNFα) and interleukin-10 (IL10), pro- and anti-inflammatory cytokines, and at correlating them with left ventricular remodeling as assessed by echocardiographic parameters.

METHODS

In a case-control study 30 MI patients were compared with 30 healthy controls. Serum concentrations of IL8, TNFα and IL10 were measured on day 2 and day 30 post-MI by chemiluminescence immunoassay and correlated with echocardiographic parameters.

RESULTS

There was an increase of IL8, and TNFα together with a decrease of IL10 at both time points. IL8 was negatively correlated with the left ventricular end-diastolic diameter (LVEDD) and positively with left ventricular systolic volume. IL10 was negatively correlated with LVEDD and left atrial volume 30days post-MI.

CONCLUSION

The increase of pro-inflammatory cytokines TNFα and IL8 was accompanied by decreased anti-inflammatory IL10. This imbalance between pro- and anti-inflammatory cytokines might contribute to the progression of left ventricular remodeling and may lead to heart failure.

Anti-apoptotic potency of TNFR:Fc gene in ischemia/ reperfusion-induced myocardial cell injury

The aim of the study was to investigate the anti-apoptotic potency of TNFR:Fc gene in ischemia/reperfusion-induced myocardial cell injury and hypoxia/reoxygenation-induced H9c2 rat cardiomyocytes injury. Rats were randomly divided into the following groups (n=8): (1) sham operation group; (2) ischemia-reperfusion (I/R) rats treated with rAAV-EGFP; (3) I/R rats treated with rAAV-TNFR:Fc group. rAAV-EGFP or rAAV-TNFR:Fc was injected intra-myocardial at four sites on the anterior and posterior walls of left ventricle immediately after the construction of I/R-induced AMI model in rats. The effects of TNFR:Fc on apoptosis and cardiacfunction were observed after 72 h of coronary reperfusion. In the in vitro study, apoptosis was analyzed in H9c2 rat cardiomyocytes treated either with nomoxia alone, or hypoxia/reoxygenation in the presence of rAAV-GFP or rAAV-TNFR:Fc. We found that (1) TNFR:Fc gene improved cardiac function (EF, LVESP, LVEDP and dp/dt max) post I/R-induced AMI; (2) TNFR:Fc gene inhibited I/R-induced apoptosis and attenuated the level of TNF-α in serum and cardiac tissue; (3) TNFR:Fc gene prevented apoptosis in hypoxia/reoxygenation-induced H9c2 rat cardiomyocytes associated with inhibition of caspase-3 activation and normalization of ratio of the Bcl-2/Bax. We concluded that TNFR:Fc gene transfection has anti-apoptotic potency in ischemia/reperfusion-induced myocardial cell injury.

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.

Ephrin-Eph signaling as a potential therapeutic target for the treatment of myocardial infarction

Although numerous strategies have been developed to reduce the initial ischemic insult and cellular injury that occurs during myocardial infarction (MI), few have progressed into the clinical arena. The epidemiologic and economic impact of MI necessitates the development of innovative therapies to rapidly and effectively reduce the initial injury and subsequent cardiac dysfunction. The Eph receptors and their cognate ligands, the ephrins, are the largest family of receptor tyrosine kinases, and their signaling has been shown to play a diverse role in various cellular processes. The recent advances in the study of ephrin-Eph signaling have shown promising progress in many fields of medicine. They have been implicated in the pathophysiology of various cancers and in the regulation of inflammation and apoptosis. Recent studies have shown that manipulation of ephrin-Eph cell signaling can favorably influence cardiomyocyte viability and ultimately preserve cardiac function post-MI. In this article, we explore the hypothesis that manipulation of ephrin-Eph signaling may potentially be a novel therapeutic target in the treatment of MI through alteration of the cellular processes that govern injury and wound healing.

Tissue inhibitor of matrix metalloproteinase-3 or vascular endothelial growth factor transfection of aged human mesenchymal stem cells enhances cell therapy after myocardial infarction

Mesenchymal stem cell (MSC) transplantation has been proposed as a potential therapeutic approach for ischemic heart disease, but the regenerative capacity of these cells decreases with age. In this study, we genetically engineered old human MSCs (O-hMSCs) with tissue inhibitor of matrix metalloproteinase-3 (TIMP3) and vascular endothelial growth factor (VEGF) and evaluated the effects on the efficacy of cell-based gene therapy in a rat myocardial infarction (MI) model. Cultured O-hMSCs were transfected with TIMP3 (O-TIMP3) or VEGF (O-VEGF) and compared with young hMSCs (Y-hMSCs) and non-transfected O-hMSCs for growth, clonogenic capacity, and differentiation potential. In vivo, rats were subjected to left coronary artery ligation with subsequent injection of Y-hMSCs, O-hMSCs, O-TIMP3, O-VEGF, or medium. Echocardiography was performed prior to and at 1, 2, and 4 weeks after MI. Myocardial levels of matrix metalloproteinase-2 (MMP2), MMP9, TIMP3, and VEGF were assessed at 1 week. Hemodynamics, morphology, and histology were measured at 4 weeks. In vitro, genetically modified O-hMSCs showed no changes in growth, colony formation, or multi-differentiation capacity. In vivo, transplantation with O-TIMP3, O-VEGF, or Y-hMSCs increased capillary density, preserved cardiac function, and reduced infarct size compared to O-hMSCs and medium control. O-TIMP3 and O-VEGF transplantation enhanced TIMP3 and VEGF expression, respectively, in the treated animals. O-hMSCs genetically modified with TIMP3 or VEGF can increase angiogenesis, prevent adverse matrix remodeling, and restore cardiac function to a degree similar to Y-hMSCs. This gene-modified cell therapy strategy may be a promising clinical treatment to rejuvenate stem cells in elderly patients.

Nonviral delivery of genetic medicine for therapeutic angiogenesis

Genetic medicines that induce angiogenesis represent a promising strategy for the treatment of ischemic diseases. Many types of nonviral delivery systems have been tested as therapeutic angiogenesis agents. However, their delivery efficiency, and consequently therapeutic efficacy, remains to be further improved, as few of these technologies are being used in clinical applications. This article reviews the diverse nonviral gene delivery approaches that have been applied to the field of therapeutic angiogenesis, including plasmids, cationic polymers/lipids, scaffolds, and stem cells. This article also reviews clinical trials employing nonviral gene therapy and discusses the limitations of current technologies. Finally, this article proposes a future strategy to efficiently develop delivery vehicles that might be feasible for clinically relevant nonviral gene therapy, such as high-throughput screening of combinatorial libraries of biomaterials.

Gene therapy for ischemic heart disease

Current pharmacologic therapy for ischemic heart disease suffers multiple limitations such as compliance issues and side effects of medications. Revascularization procedures often end with need for repeat procedures. Patients remain symptomatic despite maximal medical therapy. Gene therapy offers an attractive alternative to current pharmacologic therapies and may be beneficial in refractory disease. Gene therapy with isoforms of growth factors such as VEGF, FGF and HGF induces angiogenesis, decreases apoptosis and leads to protection in the ischemic heart. Stem cell therapy augmented with gene therapy used for myogenesis has proven to be beneficial in numerous animal models of myocardial ischemia. Gene therapy coding for antioxidants, eNOS, HSP, mitogen-activated protein kinase and numerous other anti apoptotic proteins have demonstrated significant cardioprotection in animal models. Clinical trials have demonstrated safety in humans apart from symptomatic and objective improvements in cardiac function. Current research efforts are aimed at refining various gene transfection techniques and regulation of gene expression in vivo in the heart and circulation to improve clinical outcomes in patients that suffer from ischemic heart disease. In this review article we will attempt to summarize the current state of both preclinical and clinical studies of gene therapy to combat myocardial ischemic disease. This article is part of a Special Section entitled "Special Section: Cardiovascular Gene Therapy".

Effect of tumor necrosis factor-α on neutralization of ventricular fibrillation in rats with acute myocardial infarction

The purpose of this study was to explore the effects of tumor necrosis factor-α (TNF-α) on ventricular fibrillation (VF) in rats with acute myocardial infarction (AMI). Rats were randomly classified into AMI group, sham operation group and recombinant human tumor necrosis factor receptor:Fc fusion protein (rhTNFR:Fc) group. Spontaneous and induced VFs were recorded. Monophasic action potentials (MAPs) among different zones of myocardium were recorded at eight time points before and after ligation and MAP duration dispersions (MAPDds) were calculated. Then expression of TNF-α among different myocardial zones was detected. After ligation of the left anterior descending coronary artery, total TNF-α expression in AMI group began to markedly increase at 10 min, reached a climax at 20-30 min, and then gradually decreased. The time-windows of VFs and MAPDds in the border zone performed in a similar way. At the same time-point, the expression of TNF-α in the ischemia zone was greater than that in the border zone, and little in the non-ischemia zone. Although the time windows of TNF-α expression, the MAPDds in the border zone and the occurrence of VFs in the rhTNFR:Fc group were similar to those in the AMI group, they all decreased in the rhTNFR:Fc group. Our findings demonstrate that TNF-α could enlarge the MAPDds in the border zone, and promote the onset of VFs.

TNFα in myocardial ischemia/reperfusion, remodeling and heart failure

TNFα is crucially involved in the pathogenesis and progression of myocardial ischemia/reperfusion injury and heart failure. The formation and release of TNFα and its downstream signal transduction cascade following activation of its two receptor subtypes are characterized. Myocardial TNFα and TNF receptor activation have an ambivalent role in myocardial ischemia/reperfusion injury and protection from it. Excessive TNFα expression and subsequent cardiomyocyte TNF receptor type 1 stimulation induce contractile dysfunction, hypertrophy, fibrosis and cell death, while a lower TNFα concentration and subsequent cardiomyocyte TNF receptor type 2 stimulation are protective. Apart from its concentration and receptor subtype, the myocardial action of TNFα depends on the duration of its exposure and its localization. While detrimental during sustained ischemia, TNFα contributes to ischemic preconditioning protection, no matter whether it is the first, second or third window of protection, and both TNF receptors are involved in the protective signal transduction cascade. Finally, the available clinical attempts to antagonize TNFα in cardiovascular disease, notably heart failure, are critically discussed.

Enhancement of the survival of engrafted mesenchymal stem cells in the ischemic heart by TNFR gene transfection

Autologous or allogeneic mesenchymal stem cells (MSCs) have been used as one of the potential cell sources for cellular cardiomyoplasty. The adverse microenvironment in acute myocardial infarction, however, is considered a deleterious factor for MSC transplantation and cell survival. Tumor necrosis factor (TNF)-alpha is an inflammatory mediator produced during ischemia that may affect the survival of MSCs. In this study, we investigated the enhancement of MSC survival by transfecting cells with the TNF receptor (TNFR) gene, leading to the overproduction of TNFR and the binding of TNF-alpha. Rats with acute myocardial infarction, induced by the occlusion of the left coronary artery, were transplanted with MSC or MSC-TNFR. After 2 weeks of acute myocardial infarction, cardiac function was assessed. Engrafted MSC survival and localization of TNF-alpha protein in infarction myocardium were evaluated. The levels of TNF-alpha and TNFR in the infarction zone were assessed. The results indicate that MSC-TNFR transplantation (1) improved left ventricular function; (2) enhanced engrafted MSC survival in the infarcted myocardium; (3) attenuated the level of TNF-alpha in serum and cardiac tissue; and (4) increased TNFR protein production in the infarcted myocardium. Our results showed that MSC modified by the TNFR gene improved cell viability and thereby has the potential to improve the efficiency of MSC transplantation therapy in the ischemic heart.

Non-viral gene therapy for myocardial engineering

Despite significant advances in surgical and pharmacological techniques, myocardial infarction (MI) remains the main cause of morbidity in the developed world because no remedy has been found for the regeneration of infarcted myocardium. Once the blood supply to the area in question is interrupted, the inflammatory cascade, among other mechanisms, results in the damaged tissue becoming a scar. The goals of cardiac gene therapy are essentially to minimize damage, to promote regeneration, or some combination thereof. While the vector is, in theory, less important than the gene being delivered, the choice of vector can have a significant impact. Viral therapies can have very high transfection efficiencies, but disadvantages include immunogenicity, retroviral-mediated insertional mutagenesis, and the expense and difficulty of manufacture. For these reasons, researchers have focused on non-viral gene therapy as an alternative. In this review, naked plasmid delivery, or the delivery of complexed plasmids, and cell-mediated gene delivery to the myocardium will be reviewed. Pre-clinical and clinical trials in the cardiac tissue will form the core of the discussion. While unmodified stem cells are sometimes considered therapeutic vectors on the basis of paracrine mechanisms of action basic understanding is limited. Thus, only genetically modified cells will be discussed as cell-mediated gene therapy.

Effects of intra-arterial heparin on cytokine levels in the ischemic tissue

The purpose of this study was to evaluate the effects of systemic and intra-arterial application of heparin by measuring tissue levels of inflammatory cytokines. Twenty-one adult male Wistar albino rats were divided into three groups (Group A, B and C). All the rats had undergone ligation of the right femoral artery with 4-0 silk suture to induce limb ischemia. Group A was the control group. In Group B, unfractionated heparin of 1500 U/kg/day was given through the tail vein for 10 days, the same dose was given to distal part of ligated right femoral artery for 10 days in Group C. On the 3rd, 5th, and 10th days, biopsies were taken from rectus femoris muscle on the ischemic extremities. Tumor necrosis factor-α, interleukin-1β, and vascular cell adhesion molecule levels in muscle tissue were measured by a standard enzyme-linked immunoabsorbent assay method. An increase in tumor necrosis factor-α level was found in all three groups throughout the duration of the experiment. The increase in Group C was statistically significant as compared with the other groups. The significant increases that occurred in tumor necrosis factor-α level as a result of intra-arterial application of heparin can be postulated to be one of the results of angiogenesis induced by the heparin in ischemic extremities. This might delay the formation of a necrosis in ischemic extremities, depending on the increased angiogenesis response by means of intra-arterial heparin application and may result in extended vitality of an extremity.

The immune system and cardiac repair

Myocardial infarction is the most common cause of cardiac injury and results in acute loss of a large number of myocardial cells. Because the heart has negligible regenerative capacity, cardiomyocyte death triggers a reparative response that ultimately results in formation of a scar and is associated with dilative remodeling of the ventricle. Cardiac injury activates innate immune mechanisms initiating an inflammatory reaction. Toll-like receptor-mediated pathways, the complement cascade and reactive oxygen generation induce nuclear factor (NF)-kappaB activation and upregulate chemokine and cytokine synthesis in the infarcted heart. Chemokines stimulate the chemotactic recruitment of inflammatory leukocytes into the infarct, while cytokines promote adhesive interactions between leukocytes and endothelial cells, resulting in transmigration of inflammatory cells into the site of injury. Monocyte subsets play distinct roles in phagocytosis of dead cardiomyocytes and in granulation tissue formation through the release of growth factors. Clearance of dead cells and matrix debris may be essential for resolution of inflammation and transition into the reparative phase. Transforming growth factor (TGF)-beta plays a crucial role in cardiac repair by suppressing inflammation while promoting myofibroblast phenotypic modulation and extracellular matrix deposition. Myofibroblast proliferation and angiogenesis result in formation of highly vascularized granulation tissue. As the healing infarct matures, fibroblasts become apoptotic and a collagen-based matrix is formed, while many infarct neovessels acquire a muscular coat and uncoated vessels regress. Timely resolution of the inflammatory infiltrate and spatial containment of the inflammatory and reparative response into the infarcted area are essential for optimal infarct healing. Targeting inflammatory pathways following infarction may reduce cardiomyocyte injury and attenuate adverse remodeling. In addition, understanding the role of the immune system in cardiac repair is necessary in order to design optimal strategies for cardiac regeneration.

TNFR gene-modified mesenchymal stem cells attenuate inflammation and cardiac dysfunction following MI

OBJECTIVES

To investigate the protective effect of tumor necrosis factor receptor (TNFR) gene modified mesenchymal stem cells (MSCs) transplantation against inflammation and cardiac dysfunction following acute myocardial infarction (AMI).

DESIGN

MSCs were extracted from the tibias and femurs of rats and transfected with recombinant adeno-associated viral (rAAV) expressing EGFP (enhanced green fluorescent protein) or p75 (human 75 kilodalton) TNFR at multiplicity of infection of 10(5) particles/cell. Rats with AMI induced by occlusion of the left coronary artery were randomized to MSCs-TNFR transplantation group, MSCs-EGFP transplantation group and MI control group.

RESULTS

The effects of MSCs-TNFR transplantation on cardiac inflammation and left ventricular dysfunction were observed after 2 weeks of MI. We found that: 1) MSCs-TNFR transplantation attenuated protein production and gene expression of inflammatory cytokines TNF-, IL-1beta and IL-6; 2) MSCs-TNFR transplantation inhibited cardiomyocytes apoptosis and 3) MSCs-TNFR transplantation improved left ventricular function.

CONCLUSIONS

The experimental data show that transplantation with rAAV-TNFR transfected MSCs improves left ventricular function following MI through anti-apoptotic and anti-inflammatory mechanisms.

Immuno-inflammatory regulation effect of mesenchymal stem cell transplantation in a rat model of myocardial infarction

BACKGROUND

Mesenchymal stem cells (MSC) have recently been shown to possess immunomodulatory properties in vitro and in vivo. The present study aimed to investigate the regulatory effect of MSC transplantation on the immuno-inflammatory response in myocardial infarction (MI).

METHODS

MI was induced in Sprague-Dawley rats by left anterior descending coronary artery ligation, and the animals were randomly assigned into the following three groups: sham ( n=8); phosphate-buffered saline (PBS) injected (MI+PBS, n=8); and MSC transplantation (MI+MSC, n=8). BrdU-labeled MSC or PBS was transplanted into peri-infarct myocardium by direct myocardial injection. At 1 and 28 days post-transplantation, cardiac function was evaluated by echocardiography. Transplanted cells were investigated through immunohistochemistry. Lymphocyte cytotoxic activity was evaluated with the crystal violet method. The activity of NF-kappaB and protein expression of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6 and IL-10 in myocardium were assessed by immunohistochemistry and Western blot.

RESULTS

Echocardiographic examination revealed that the MSC transplantation prevented left ventricular dilation and dysfunction at 28 days after the operation. BrdU-stained cells were found living in host heart 4 weeks after transplantation. MSC transplantation attenuated the cytotoxic activity of spleen lymphocytes. Transplantation of MSC inhibited the activity of NF-kappaB, attenuated the protein production of TNF-alpha and IL-6, and increased the expression of IL-10 in peri-infarct myocardium.

DISCUSSION

MSC transplantation modulated the immuno-inflammatory response in MI. The immuno-inflammatory regulatory effect of MSC transplantation might partly account for the cardiac protection in myocardial infarction.

Small skin burn injury reduces cardiac tolerance to ischemia via a tumor necrosis factor alpha-dependent pathway

BACKGROUND

Large burns cause systemic inflammation and myocardial depression. We hypothesized that small burns affect cardiac tolerance to ischemia, and that tumor necrosis factor alpha (TNFalpha) signaling through endothelin-1 (ET) and nuclear factor kappa B (NF kappaB) are associated.

METHODS

Mice were randomly assigned to four groups: burn (caused by boiling water on <2% of the body surface area), sham, burn+etanercept (TNFalpha blocker) treatment and sham+etanercept treatment. Twenty-four hours later, hearts were isolated and subjected to global ischemia followed by reperfusion. Additional hearts and burned skin lesions were sampled to evaluate expression of TNFalpha (immunoblotting) and endothelin-1 (radioimmunoassay). A NF kappaB-luciferase reporter mouse was used to evaluate NF kappaB activation.

RESULTS

Baseline cardiac function before ischemia (BI) was only negligibly influenced by burn or etanercept, but was reduced by burn+etanercept. Burn markedly impaired post-ischemic left ventricular function and increased infarct size in comparison with sham-treated mice. Cardiac, but nut cutaneous, expression of TNFalpha was increased in burned mice, while cardiac NF kappaB and endothelin-1 were not influenced. TNFalpha blockade reduced the detrimental effects of burn on cardiac tolerance to ischemia.

CONCLUSIONS

Small cutaneous burns, that did not influence baseline heart function, impaired the tolerance to ischemia. This effect may be mediated through TNFalpha, but does not involve signaling through NF kappaB or endothelin-1.

Anti-inflammation role for mesenchymal stem cells transplantation in myocardial infarction

The aim of the present study was to investigate the role of anti-inflammation for MSCs transplantation in rat models of myocardial infarction. Rats with AMI induced by occlusion of the left coronary artery were randomized to MSCs transplantation group, MI group and sham operated group. The effects of MSCs transplantation on cardiac inflammation and left ventricular remodeling in non-infarcted zone were observed after 4 weeks of MI. We found that MSC transplantation (1) decreased protein production and gene expression of inflammation cytokines TNF-alpha, IL-1beta and IL-6, (2) inhibited deposition of type I and III collagen, as well as gene and protein expression of MMP-1 and TIMP-1, (3) attenuated LV cavitary dilation and transmural infarct thinning, thus prevent myocardial remodeling after myocardial infarction, and (4) increased EF, FS, LVESP and dp/dtmax (P < 0.01), decreased LVDd, LVEDV, LVEDP (P < 0.05). Anti-inflammation role for MSCs transplantation might partly account for the cardiac protective effect in ischemic heart disease.

Tumor necrosis factor-alpha is toxic via receptor 1 and protective via receptor 2 in a murine model of myocardial infarction

Tumor necrosis factor (TNF)-alpha induced in damaged myocardium has been considered to be cardiotoxic. TNF-alpha initiates its biological effects by binding two distinct receptors: R1 (p55) and R2 (p75). Although TNF-alpha has been shown to be cardiotoxic via R1-mediated pathways, little is known about the roles of R2-mediated pathways in myocardial infarction (MI). We created MI in R1 knockout (R1KO), R2KO, and wild-type (WT) mice by ligating the left coronary artery. Functional, histological, and biochemical analyses were performed 4 wk after ligation. Although infarct size was not different among WT, R1KO, and R2KO mice, post-MI survival was significantly improved in R1KO but not R2KO mice. R1KO significantly ameliorated contractile dysfunction after MI, whereas R2KO significantly exaggerated ventricular dilatation and dysfunction. Myocyte hypertrophy and interstitial fibrosis in noninfarct myocardium was exacerbated in R2KO but not in R1KO mice. Expression of R1, which was not affected by MI and was nullified in R1KO mice, was significantly upregulated in R2KO mice. In contrast, expression of R2, which was significantly upregulated by MI and was nullified in R2KO mice, was unaffected in R1KO mice. Meanwhile, TNF-alpha expression, which was significantly upregulated in noninfarct myocardium after MI, was not affected by R1KO or R2KO. However, transcript levels of IL-6, IL-1beta, transforming growth factor-beta, and monocyte chemotactic protein-1, which were significantly upregulated after MI, were significantly downregulated in R1KO mice. In contrast, transcript levels of IL-6 and IL-1beta were significantly further upregulated in R2KO mice. TNF-alpha is toxic via R1 and protective via R2 in a murine model of MI. Selective blockade of R1 may be a candidate therapeutic intervention for MI.

Soluble TNF receptors prevent apoptosis in infiltrating cells and promote ventricular rupture and remodeling after myocardial infarction

OBJECTIVE

Tumor necrosis factor (TNF)-alpha induced in damaged myocardium has been considered to be cardiotoxic. However, the negative results of RENEWAL and ATTACH prompt us to reconsider the role of TNF-alpha in cardiovascular diseases. The present study aimed to evaluate the effects of soluble TNF receptor treatment on myocardial infarction (MI).

METHODS

An adenovirus encoding a 55-kDa TNF receptor-IgG fusion protein (AdTNFR1) was used to neutralize TNF-alpha, and an adenovirus encoding LacZ (AdLacZ) served as control. In the pre-MI treatment protocol, mice were given an intravenous injection of AdTNFR1 or AdLacZ 1 week before left coronary artery ligation to induce MI. In the post-MI treatment protocol, mice were treated with AdTNFR1 or AdLacZ 1 week after left coronary ligation.

RESULTS

Treatment with AdTNFR1 neutralized bioactivity of TNF-alpha that was activated after MI and prevented apoptosis of infiltrating cells in infarct myocardium. However, pre-MI treatment with AdTNFR1 promoted ventricular rupture by reducing fibrosis with further activation of matrix metalloproteinase (MMP)-9. Post-MI treatment with AdTNFR1 exacerbated ventricular dysfunction and remodeling, with enhanced fibrosis of non-infarct myocardium with further MMP-2 activation.

CONCLUSIONS

Both pre- and post-MI treatments with AdTNFR1 were deleterious in a mouse MI model. Thus, TNF-alpha may play not only toxic but also protective roles in MI.

Differential functions of tumor necrosis factor receptor 1 and 2 signaling in ischemia-mediated arteriogenesis and angiogenesis

We have previously shown that tumor necrosis factor (TNF) acts via its two receptors TNFR1 and TNFR2 to elicit distinct signaling pathways in vascular endothelial cells (ECs). Here we used a femoral artery ligation model to demonstrate that TNFR1-knockout (KO) mice had enhanced, whereas TNFR2-KO had reduced, capacity in clinical recovery, limb perfusion, and ischemic reserve capacity compared with the wild-type mice. Consistently, ischemia-initiated collateral growth (arteriogenesis) in the upper limb and capillary formation and vessel maturation (angiogenesis) in the lower limb were enhanced in TNFR1-KO but were reduced in TNFR2-KO mice. Furthermore, our results suggest that vascular proliferation, but not infiltration of macrophages and lymphocytes, accounted for the phenotypic differences between the TNFR1-KO and TNFR2-KO mice. In wild-type animals TNFR2 protein in vascular endothelium was highly up-regulated in response to ischemia, leading to increased TNFR2-specific signaling as determined by the formation TNFR2-TRAF2 complex and activation of TNFR2-specific kinase Bmx/Etk. In isolated murine ECs, activation of TNFR2 induced nuclear factor-kappaB-dependent reporter gene expression, EC survival, and migration. In contrast, activation of TNFR1 caused inhibition of EC migration and EC apoptosis. These data demonstrate that TNFR1 and TNFR2 play differential roles in ischemia-mediated arteriogenesis and angiogenesis, partly because of their opposite effects on EC survival and migration.

Inhibition of TNF-α Reduces Myocardial Injury and Proinflammatory Pathways Following Ischemia-Reperfusion in the Dog

We examined whether tumor necrosis factor-alpha (TNF-alpha) promotes postischemic inflammation and myocardial injury via activation of nuclear factor kappa B (NFkappaB) in an in vivo canine model. Isoflurane-anesthetized dogs underwent closed-chest balloon occlusion of the anterior descending coronary artery for 90 minutes, followed by reperfusion for 3 hours. Dogs randomly received a soluble TNF inhibitor (etanercept, 0.5 mg/kg intravenously) or saline before occlusion. Collateral blood flow and risk region size (RISK) were measured with radioactive microspheres, infarct size (INF) was measured by triphenyltetrazolium chloride staining, inflammation was measured by tissue myeloperoxidase (MPO) activity, intercellular adhesion molecular-1 (ICAM-1) messenger ribonucleic acid (mRNA) was measured by Northern blotting, and ICAM-1 protein expression was measured by Western blotting. NFkappaB activation was measured in nuclear extracts by electrophoretic mobility shift assays. INF/RISK was significantly smaller in the etanercept group than in the saline control group after adjusting for collateral flow (P < 0.009 by analysis of covariance, mean reduction in INF/RISK = 40%, 0.32 +/- 0.09 versus 0.53 +/- 0.09). MPO activity, ICAM-1 mRNA and protein expression, and NFkappaB binding activity were all significantly reduced in the etanercept group. Administration of a soluble TNF-alpha inhibitor reduced NFkappaB activation, ICAM-1 upregulation, and myocardial injury following ischemia-reperfusion. TNF-alpha appears to play a significant role in vivo in the genesis of postischemic inflammation.

Oxidative stress in myocardial ischaemia reperfusion injury: a renewed focus on a long-standing area of heart research

Advances in the treatment of coronary artery disease have seen a significant drop in mortality and morbidity particularly amongst patients with acute myocardial infarction (MI). In particular, percutaneous trans-luminal balloon angioplasty (PTCA) with stenting to re-open atherosclerotic coronary arteries has yielded marked improvement in clinical outcome for patients with acute MI. Furthermore, with the advent of drug-eluting stents occurrence rates for coronary artery restenosis, one common clinical problem associated with angioplasty and stent deployment, have declined markedly. However, coronary restenosis in diabetic patients remains an on-going problem. The success of drug-eluting stents has seen a renewed focus on myocardial ischaemia reperfusion (IR) injury as this represents one area of research where many questions remain unanswered. In particular, the relationship between myocardial IR injury and decreased myocardial micro-vasculature re-flow post PTCA (that ultimately leads to poor clinical outcome and myocardial damage/dysfunction) is one area of research with the potential to decrease current complication rates further in patients suffering myocardial IR injury sustained during MI. This review discusses the role for oxidative stress, oxidant source(s) and both gene regulation and stem-cell therapy as potential strategic targets in the ischaemic myocardium, with the ultimate aim of providing significant cardioprotection in the setting of acute MI.

Regulators of angiogenesis and strategies for their therapeutic manipulation

Angiogenesis provides a mechanism by which delivery of oxygen and nutrients is adapted to compliment changes in tissue mass or metabolic activity. However, maladaptive angiogenesis is integral to the process of several diseases common in Western countries, including tumor growth, vascular insufficiency, diabetic retinopathy and rheumatoid arthritis. Understanding the process of capillary growth, including the identification and functional analyses of key pro- and anti-angiogenic factors, provides knowledge that can be applied to improve/reverse these pathological states. Initially, angiogenesis research focused predominantly on vascular endothelial growth factor (VEGF) as a main player in the angiogenesis cascade. It is apparent now that participation of multiple angiogenic factors and signal pathways is critical to enable effective growth and maturation of nascent capillaries. The purpose of this review is to focus on recent progress in identifying angiogenesis signaling pathways that show promise as targets for successful induction or inhibition of capillary growth. The strategies applied to achieve these contradictory tasks are discussed within the framework of our existing fundamental knowledge of angiogenesis signaling cascades, with an emphasis on comparing the employment of distinctive tactics in modulation of these pathways. Innovative developments that are presented include: (1) inducing a pleiotropic response via activation or inhibition of angiogenic transcription factors; (2) modulation of nitric oxide tissue concentration; (3) manipulating the kallikrein-kinin system; (4) use of endothelial progenitor cells as a means to either directly contribute to capillary growth or to be used as a vehicle to deliver "suicide genes" to tumor tissue.

The systemic inflammatory response is involved in the regulation of K+channel expression in brain via TNF-α-dependent and -independent pathways

TNF-alpha, generated during the systemic inflammatory response, triggers a wide range of biological activities that mediate the neurologic manifestations associated with cancer and infection. Since this cytokine regulates ion channels in vitro (especially Kv1.3 and Kir2.1), we aimed to study Kv1.3 and Kir2.1 expression in brain in response to in vivo systemic inflammation. Cancer-induced cachexia and LPS administration increased plasma TNF-alpha. Kv1.3 and Kir2.1 expression was impaired in brain during cancer cachexia. However, LPS treatment induced Kv1.3 and downregulated Kir2.1 expression, and TNF-alpha administration mimicked these results. Experiments using TNF-alpha double receptor knockout mice demonstrated that the systemic inflammatory response mediates K(+) channel regulation in brain via TNF-alpha-dependent and -independent redundant pathways. In summary, distinct neurological alterations associated with systemic inflammation may result from the interaction of various cytokine pathways tuning ion channel expression in response to neurophysiological and neuroimmunological processes.