TNF provokes cardiomyocyte apoptosis and cardiac remodeling through activation of multiple cell death pathways

Nicorandil enhances the efficacy of mesenchymal stem cell therapy in isoproterenol-induced heart failure in rats

Stem cell transplantation has emerged as a promising technique for regenerative medicine in cardiovascular therapeutics. However, the results have been less than optimal. The aim of the present study was to investigate whether nicorandil could offer an additional benefit over bone marrow-derived mesenchymal stem cell therapy in isoproterenol-induced myocardial damage and its progression to heart failure in rats. Isoproterenol was injected subcutaneously for 2 consecutive days at doses of 85 and 170 mg/kg/day, respectively. Nicorandil (3 mg/kg/day) was then given orally with or without a single intravenous bone marrow-derived mesenchymal stem cell administration. Electrocardiography and echocardiography were recorded 2 weeks after the beginning of treatment. Rats were then sacrificed and the ventricle was isolated for estimation of tumor necrosis factor-alpha, vascular endothelial growth factor and transforming growth factor-beta. Moreover, protein expressions of caspase-3, connexin-43 as well as endothelial and inducible nitric oxide synthases were evaluated. Finally, histological studies of myocardial fibrosis and blood vessel density were performed and cryosections were done for estimation cell homing. Combined nicorandil/bone marrow-derived mesenchymal stem cell therapy provided an additional improvement compared to cell therapy alone toward reducing isoproterenol-induced cardiac hypertrophy, fibrosis and inflammation. Notably, combined therapy induced significant increase in angiogenesis and cell homing and prevented isoproterenol-induced changes in contractility and apoptotic markers. In conclusion, combined nicorandil/bone marrow-derived mesenchymal stem cell therapy was superior to cell therapy alone toward preventing isoproterenol-induced heart failure in rats through creation of a supportive environment for mesenchymal stem cells.

Tumor necrosis factor-α confers cardioprotection through ectopic expression of keratins K8 and K18

Tumor necrosis factor-α (TNF-α), one of the major stress-induced proinflammatory cytokines, is upregulated in the heart after tissue injury, and its sustained expression can contribute to the development of heart failure. Whether TNF-α also exerts cytoprotective effects in heart failure is not known. Here we provide evidence for a cardioprotective function of TNF-α in a genetic heart failure model, desmin-deficient mice. The cardioprotective effects of TNF-α are a consequence of nuclear factor-κB (NF-κB)-mediated ectopic expression in cardiomyocytes of keratin 8 (K8) and keratin 18 (K18), two epithelial-specific intermediate filament proteins. In cardiomyocytes, K8 and K18 (K8/K18) formed an alternative cytoskeletal network that localized mainly at intercalated discs (IDs) and conferred cardioprotection by maintaining normal ID structure and mitochondrial integrity and function. Ectopic induction of K8/K18 expression in cardiomyocytes also occurred in other genetic and experimental models of heart failure. Loss of the K8/K18 network resulted in a maladaptive cardiac phenotype following transverse aortic constriction. In human failing myocardium, where TNF-α expression is upregulated, K8/K18 were also ectopically expressed and localized primarily at IDs, which did not contain detectable amounts of desmin. Thus, TNF-α- and NF-κB-mediated formation of an alternative, stress-induced intermediate filament cytoskeleton has cardioprotective function in mice and potentially in humans.

Markers of inflammation in recipients of continuous-flow left ventricular assist devices

Although the newer continuous-flow left ventricular assist devices (CF-LVADs) provide clinical advantages over the pulsatile pumps, the effects of low pulsatility on inflammation are incompletely understood. The objective of our study was to examine the levels of inflammatory mediators in CF-LVAD recipients compared with both healthy control subjects and heart failure patients who were candidates for CF-LVAD support. Plasma levels of chemokines, cytokines, and inflammatory markers were measured in 18 CF-LVAD recipients and compared with those of 14 healthy control subjects and 14 heart failure patients who were candidates for CF-LVADs. The levels of granulocyte macrophage-colony stimulating factor, macrophage inflammatory proteins-1β, and macrophage-derived chemokine were significantly higher in the CF-LVAD group compared with both the heart failure and the healthy control groups, whereas no significant differences were observed between the healthy control subjects and the heart failure groups. Compared with the healthy controls, C-reactive protein, interferon gamma-induced protein-10, monocyte chemotactic protein-1, and interleukin-8 levels were significantly higher in both the CF-LVAD and heart failure groups, but no significant differences were observed between the CF-LVAD recipients and the heart failure patients. Inflammatory markers were elevated in CF-LVAD recipients compared with healthy control subjects and the heart failure patients. Further studies should investigate the clinical implications of elevated levels of inflammation in CF-LVAD recipients.

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

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

MicroRNA-150 protects the mouse heart from ischaemic injury by regulating cell death

AIMS

Cardiac injury is accompanied by dynamic changes in the expression of microRNAs (miRs). For example, miR-150 is down-regulated in patients with acute myocardial infarction, atrial fibrillation, dilated and ischaemic cardiomyopathy as well as in various mouse heart failure (HF) models. Circulating miR-150 has been recently proposed as a better biomarker of HF than traditional clinical markers such as brain natriuretic peptide. We recently showed using the β-arrestin-biased β-blocker, carvedilol that β-arrestin1-biased β1-adrenergic receptor cardioprotective signalling stimulates the processing of miR-150 in the heart. However, the potential role of miR-150 in ischaemic injury and HF is unknown.

METHODS AND RESULTS

Here, we show that genetic deletion of miR-150 in mice causes abnormalities in cardiac structural and functional remodelling after MI. The cardioprotective roles of miR-150 during ischaemic injury were in part attributed to direct repression of the pro-apoptotic genes egr2 (zinc-binding transcription factor induced by ischaemia) and p2x7r (pro-inflammatory ATP receptor) in cardiomyocytes.

CONCLUSION

These findings reveal a pivotal role for miR-150 as a regulator of cardiomyocyte survival during cardiac injury.

Longitudinal assessment of inflammation in recipients of continuous-flow left ventricular assist devices

BACKGROUND

The long-term effects of continuous-flow left ventricular assist device (CF-LVAD) support on trends of inflammatory markers over time are unknown. We examined the hypothesis that the levels of inflammatory markers in CF-LVAD recipients are higher than in healthy controls and that these levels increase over time with long-term CF-LVAD support.

METHODS

We examined the levels of inflammatory markers longitudinally at baseline before CF-LVAD implantation and at 3, 6, and 9 months after implantation. We then compared the levels of inflammatory markers to those in a healthy control group.

RESULTS

Compared with baseline values before CF-LVAD implantation, left ventricular end-diastolic diameter (LVEDd) and left ventricular end-systolic diameter (LVESd) decreased significantly at 3, 6, and 9 months after CF-LVAD implantation. Brain natriuretic peptide (BNP) levels dropped significantly after CF-LVAD implantation but did not normalize. Improvements in ejection fraction at 3, 6, and 9 months after CF-LVAD implantation did not reach significance. Monocyte chemoattractant protein-1, interferon γ-induced protein, and C-reactive protein levels were higher in the CF-LVAD recipients at each of the time points (baseline before CF-LVAD implantation and 3, 6, and 9 months after implantation) compared with levels in healthy controls. In CF-LVAD recipients, serum interleukin-8, tumour necrosis factor-α, and macrophage inflammatory protein-β increased significantly at 9 months, and macrophage-derived chemokine increased at 6 months after CF-LVAD implantation compared with baseline.

CONCLUSIONS

Despite improvements in LV dimensions and BNP levels, markers of inflammation remained higher in CF-LVAD recipients. High levels of inflammation in CF-LVAD recipients may result from heart failure preconditioning or the long-term device support, or both. Because inflammation may be detrimental to CF-LVAD recipients, future studies should determine whether inflammatory pathways are reversible.

Temporal and gefitinib-sensitive regulation of cardiac cytokine expression via chronic β-adrenergic receptor stimulation

Chronic stimulation of β-adrenergic receptors (βAR) can promote survival signaling via transactivation of epidermal growth factor receptor (EGFR) but ultimately alters cardiac structure and contractility over time, in part via enhanced cytokine signaling. We hypothesized that chronic catecholamine signaling will have a temporal impact on cardiac transcript expression in vivo, in particular cytokines, and that EGFR transactivation plays a role in this process. C57BL/6 mice underwent infusion with vehicle or isoproterenol (Iso)±gefitinib (Gef) for 1 or 2 wk. Cardiac contractility decreased following 2 wk of Iso treatment, while cardiac hypertrophy, fibrosis, and apoptosis were enhanced at both timepoints. Inclusion of Gef preserved contractility, blocked Iso-induced apoptosis, and prevented hypertrophy at the 2-wk timepoint, but caused fibrosis on its own. RNAseq analysis revealed hundreds of cardiac transcripts altered by Iso at each timepoint with subsequent RT-quantitative PCR validation confirming distinct temporal patterns of transcript regulation, including those involved in cardiac remodeling and survival signaling, as well as numerous cytokines. Although Gef infusion alone did not significantly alter cytokine expression, it abrogated the Iso-mediated changes in a majority of the βAR-sensitive cytokines, including CCL2 and TNF-α. Additionally, the impact of βAR-dependent EGFR transactivation on the acute regulation of cytokine transcript expression was assessed in isolated cardiomyocytes and in cardiac fibroblasts, where the majority of Iso-dependent, and EGFR-sensitive, changes in cytokines occurred. Overall, coincident with changes in cardiac structure and contractility, βAR stimulation dynamically alters cardiac transcript expression over time, including numerous cytokines that are regulated via EGFR-dependent signaling.

Plasma cytokine profile in tropical endomyocardial fibrosis: predominance of TNF-a, IL-4 and IL-10

Background

The participation of immune/inflammatory mechanisms in the pathogenesis of tropical endomyocardial fibrosis (EMF) has been suggested by the finding of early blood and myocardial eosinophilia. However, the inflammatory activation status of late-stage EMF patients is still unknown.

Methodology/Principal findings

We evaluated pro- and anti-inflammatory cytokine levels in plasma samples from late stage EMF patients. Cytokine levels of Tumor Necrosis Factor (TNF)-α, Interferon (IFN)-γ, Interleukin (IL)-2, IL-4, IL-6, and IL-10 were assayed in plasma samples from 27 EMF patients and compared with those of healthy control subjects. All EMF patients displayed detectable plasma levels of at least one of the cytokines tested. We found that TNF-α, IL-6, IL-4, and IL-10 were each detected in at least 74% of tested sera, and plasma levels of IL-10, IL-4, and TNF-α were significantly higher than those of controls. Plasma levels of such cytokines positively correlated with each other.

Conclusions/Significance

The mixed pro- and anti-inflammatory/Th2circulating cytokine profile in EMF is consistent with the presence of a persistent inflammatory stimulus. On the other hand, the detection of increased levels of TNF-α may be secondary to the cardiovascular involvement observed in these patients, whereas IL-4 and IL-10 may have been upregulated as a homeostatic mechanism to buffer both production and deleterious cardiovascular effects of pro-inflammatory cytokines. Further studies might establish whether these findings play a role in disease pathogenesis.

Inhibition of JNK phosphorylation by a novel curcumin analog prevents high glucose-induced inflammation and apoptosis in cardiomyocytes and the development of diabetic cardiomyopathy

Hyperglycemia-induced inflammation and apoptosis have important roles in the pathogenesis of diabetic cardiomyopathy. We recently found that a novel curcumin derivative, C66, is able to reduce the high glucose (HG)-induced inflammatory response. This study was designed to investigate the protective effects on diabetic cardiomyopathy and its underlying mechanisms. Pretreatment with C66 significantly reduced HG-induced overexpression of inflammatory cytokines via inactivation of nuclear factor-κB in both H9c2 cells and neonatal cardiomyocytes. Furthermore, we showed that the inhibition of Jun NH2-terminal kinase (JNK) phosphorylation contributed to the protection of C66 from inflammation and cell apoptosis, which was validated by the use of SP600125 and dominant-negative JNK. The molecular docking and kinase activity assay confirmed direct binding of C66 to and inhibition of JNK. In mice with type 1 diabetes, the administration of C66 or SP600125 at 5 mg/kg significantly decreased the levels of plasma and cardiac tumor necrosis factor-α, accompanied by decreasing cardiac apoptosis, and, finally, improved histological abnormalities, fibrosis, and cardiac dysfunction without affecting hyperglycemia. Thus, this work demonstrated the therapeutic potential of the JNK-targeting compound C66 for the treatment of diabetic cardiomyopathy. Importantly, we indicated a critical role of JNK in diabetic heart injury, and suggested that JNK inhibition may be a feasible strategy for treating diabetic cardiomyopathy.

Glucose fluctuations increase the incidence of atrial fibrillation in diabetic rats

AIMS

We investigated whether glucose fluctuations aggravate cardiac fibrosis and increase the occurrence of atrial fibrillation (AF) in rats with diabetes mellitus (DM).

METHODS AND RESULTS

Streptozotocin-induced diabetic rats were randomly divided into three groups: uncontrolled DM (U-STZ) group, controlled DM (C-STZ) group, and DM with glucose fluctuations (STZ-GF) group. Glucose fluctuations were induced by fasting for 24 h and additional regular insulin injections (0.5 IU/kg) administered three times per week for three consecutive weeks. C-STZ rats were administered long acting insulin (20 IU/kg) twice a day to control blood glucose levels. Cardiac fibrosis evaluated by Masson trichrome staining and the expressions of collagen type 1, collagen type 3, and α-smooth muscle actin were increased in U-STZ rats compared with C-STZ rats, which were more pronounced in STZ-GF rats. The inducibility of AF was significantly larger in U-STZ rats than C-STZ rats and was greatest in STZ-GF rats. To explore the mechanism of cardiac fibrosis, we investigated the levels of reactive oxygen species (ROS) and apoptosis. The expression of malondialdehyde, an indicator of ROS levels, was significantly upregulated in STZ-GF rats compared with U-STZ rats, along with increased thioredoxin-interacting protein (Txnip) expression in STZ-GF rats. Furthermore, caspase-3 expression and the number of TUNEL-positive cells were significantly increased in STZ-GF rats compared with U-STZ and C-STZ rats.

CONCLUSION

Glucose fluctuations increase the incidence of AF by promoting cardiac fibrosis. Increased ROS levels caused by upregulation of Txnip expression may be a mechanism whereby in glucose fluctuations induce fibrosis.

Moxonidine modulates cytokine signalling and effects on cardiac cell viability

Regression of left ventricular hypertrophy and improved cardiac function in SHR by the centrally acting imidazoline I1-receptor agonist, moxonidine, are associated with differential actions on circulating and cardiac cytokines. Herein, we investigated cell-type specific I1-receptor (also known as nischarin) signalling and the mechanisms through which moxonidine may interfere with cytokines to affect cardiac cell viability. Studies were performed on neonatal rat cardiomyocytes and fibroblasts incubated with interleukin (IL)-1β (5 ng/ml), tumor necrosis factor (TNF)-α (10 ng/ml), and moxonidine (10(-7) and 10(-5) M), separately and in combination, for 15 min, and 24 and 48 h for the measurement of MAPKs (ERK1/2, JNK, and p38) and Akt activation and inducible NOS (iNOS) expression, by Western blotting, and cardiac cell viability/proliferation and apoptosis by flow cytometry, MTT assay, and Live/Dead assay. Participation of imidazoline I1-receptors and the signalling proteins in the detected effects was identified using imidazoline I1-receptor antagonist and signalling protein inhibitors. The results show that IL-1β, and to a lower extent, TNF-α, causes cell death and that moxonidine protects against starvation- as well as IL-1β -induced mortality, mainly by maintaining membrane integrity, and in part, by improving mitochondrial activity. The protection involves activation of Akt, ERK1/2, p38, JNK, and iNOS. In contrast, moxonidine stimulates basal and IL-1β-induced fibroblast mortality by mechanisms that include inhibition of JNK and iNOS. Thus, apart from their actions on the central nervous system, imidazoline I1-receptors are directly involved in cardiac cell growth and death, and may play an important role in cardiovascular diseases associated with inflammation.

Autophagy in desmin-related cardiomyopathy: thoughts at the halfway point

Accumulation of protein aggregates is a hallmark of several neurodegenerative disorders as well as for a number of protein conformation-based diseases, including those affecting muscle, liver and heart. Desminopathy or desmin-related myopathy (DRM) is a skeletal myopathy characterized by bilateral muscle weakness, but is often accompanied by cardiomyopathy as well. DRM can be caused by mutations in desmin, alphaB crystallin, myotilin, Z-band alternatively spliced PDZ-containing protein (ZASP), filamin C (FLNC) or Bcl-2-associated athanogene-3 (BAG3). The common pathological pattern in DRM is accumulation of misfolded proteins, however, clinical manifestations can differ significantly.

Foxp3+ CD4+ T cells improve healing after myocardial infarction by modulating monocyte/macrophage differentiation

RATIONALE

An exaggerated or persistent inflammatory activation after myocardial infarction (MI) leads to maladaptive healing and subsequent remodeling of the left ventricle. Foxp3(+) CD4(+) regulatory T cells (Treg cells) contribute to inflammation resolution. Therefore, Treg cells might influence cardiac healing post-MI.

OBJECTIVE

Our aim was to study the functional role of Treg cells in wound healing post-MI in a mouse model of permanent left coronary artery ligation.

METHODS AND RESULTS

Using a model of genetic Treg-cell ablation (Foxp3(DTR) mice), we depleted the Treg-cell compartment before MI induction, resulting in aggravated cardiac inflammation and deteriorated clinical outcome. Mechanistically, Treg-cell depletion was associated with M1-like macrophage polarization, characterized by decreased expression of inflammation-resolving and healing-promoting factors. The phenotype of exacerbated cardiac inflammation and outcome in Treg-cell-ablated mice could be confirmed in a mouse model of anti-CD25 monoclonal antibody-mediated depletion. In contrast, therapeutic Treg-cell activation by superagonistic anti-CD28 monoclonal antibody administration 2 days after MI led to improved healing and survival. Compared with control animals, CD28-SA-treated mice showed increased collagen de novo expression within the scar, correlating with decreased rates of left ventricular ruptures. Therapeutic Treg-cell activation induced an M2-like macrophage differentiation within the healing myocardium, associated with myofibroblast activation and increased expression of monocyte/macrophage-derived proteins fostering wound healing.

CONCLUSIONS

Our data indicate that Treg cells beneficially influence wound healing after MI by modulating monocyte/macrophage differentiation. Moreover, therapeutic activation of Treg cells constitutes a novel approach to improve healing post-MI.

15-deoxy-Δ¹²,¹⁴-PGJ₂ promotes inflammation and apoptosis in cardiomyocytes via the DP2/MAPK/TNFα axis

Background

Prostaglandins (PGs), lipid autacoids derived from arachidonic acid, play a pivotal role during inflammation. PGD₂ synthase is abundantly expressed in heart tissue and PGD₂ has recently been found to induce cardiomyocyte apoptosis. PGD₂ is an unstable prostanoid metabolite; therefore the objective of the present study was to elucidate whether its final dehydration product, 15-deoxy-Δ^12,14-PGJ₂ (15d-PGJ₂, present at high levels in ischemic myocardium) might cause cardiomyocyte damage.

Methods and results

Using specific (ant)agonists we show that 15d-PGJ₂ induced formation of intracellular reactive oxygen species (ROS) and phosphorylation of p38 and p42/44 MAPKs via the PGD₂ receptor DP2 (but not DP1 or PPARγ) in the murine atrial cardiomyocyte HL-1 cell line. Activation of the DP2-ROS-MAPK axis by 15d-PGJ₂ enhanced transcription and translation of TNFα and induced apoptosis in HL-1 cardiomyocytes. Silencing of TNFα significantly attenuated the extrinsic (caspase-8) and intrinsic apoptotic pathways (bax and caspase-9), caspase-3 activation and downstream PARP cleavage and γH2AX activation. The apoptotic machinery was unaffected by intracellular calcium, transcription factor NF-κB and its downstream target p53. Of note, 9,10-dihydro-15d-PGJ₂ (lacking the electrophilic carbon atom in the cyclopentenone ring) did not activate cellular responses. Selected experiments performed in primary murine cardiomyocytes confirmed data obtained in HL-1 cells namely that the intrinsic and extrinsic apoptotic cascades are activated via DP2/MAPK/TNFα signaling.

Conclusions

We conclude that the reactive α,β-unsaturated carbonyl group of 15d-PGJ₂ is responsible for the pronounced upregulation of TNFα promoting cardiomyocyte apoptosis. We propose that inhibition of DP2 receptors could provide a possibility to modulate 15d-PGJ₂-induced myocardial injury.

Silencing of hepcidin enforces the apoptosis in iron-induced human cardiomyocytes

BACKGROUND

Iron is essential not only for erythropoisis but also for several bioenergetics' processes in myocardium. Hepcidin is a well-known regulator of iron homeostasis. Recently, researchers identified low hepcidin was independently associated with increased 3-year mortality among systolic heart failure patients. In addition, our previous in vivo study revealed that the left ventricular mass index increased in chronic kidney disease patients with lower serum hepcidin. We hypothesize that hepcidin interacts with the apoptotic pathway of cardiomyocytes during oxidative stress conditions.

METHODS

To test this hypothesis, human cardiomyocytes were cultured and treated with ferrous iron. The possible underlying signaling pathways of cardiotoxicity were examined following knockdown studies using siRNAs of hepcidin (siRNA1 was used as a negative control and siRNA2 was used to silence hepcidin).

RESULTS

We found that ferrous iron induces apoptosis in human cardiomyocytes in a dose-dependent manner. This iron-induced apoptosis was linked to enhanced caspase 8, reduced Bcl-2, Bcl-xL, phosphorylated Akt and GATA-4. Hepcidin levels increased in human cardiomyocytes pretreated with ferrous iron and returned to non-iron treated levels following siRNA2 transfection. In iron pretreated cardiomyocytes, the siRNA2 transfection further increased caspase 8 expression and decreased the expression of GATA-4, Bcl-2, Bcl-xL and phosphorylated Akt than iron pretreatment alone, but caspase 9 levels remained unchanged.

CONCLUSIONS

Our findings suggest that hepcidin can rescue human cardiomyocytes from iron-induced apoptosis through the regulation of GATA-4/Bcl-2 and the extrinsic apoptotic pathway.

DTU I isolates of Trypanosoma cruzi induce upregulation of Galectin-3 in murine myocarditis and fibrosis

Chagas heart disease is a major public concern since 30% of infected patients develop cardiac alterations. The relationship between Trypanosoma cruzi discrete typing units (DTUs) and the biological properties exhibited by the parasite population has yet to be elucidated. In this study, we analysed the expression of α-smooth muscle actin (α-SMA) and galectin-3 (Gal-3) associated with cardiac extracellular matrix (ECM) remodelling a murine chronic cardiomyopathy induced by Tc I genotypes. We found the induction of myocarditis was associated with the upregulation of Col I, α-SMA, Gal-3, IFN-γ and IL-13, as analysed by q-PCR. In myocardial areas of fibrosis, the intensity of myocarditis and significant ECM remodelling correlated with the presence of Col I-, Gal-3- and α-SMA-positive cells. These results are promising for the further efforts to evaluate the relevance of Gal-3 in Chagas heart disease, since this galectin was proposed as a prognosis marker in heart failure patients.

Cardiac macrophages and their role in ischaemic heart disease

Cardiac macrophages are abundant in the healthy heart and after myocardial infarction (MI). Different macrophage phenotypes likely promote myocardial health vs. disease. Infarct macrophages are inflammatory and derive from circulating monocytes produced by the haematopoietic system. These cells are centrally involved in inflammatory tissue remodelling, resolution of inflammation during post-MI healing, and left ventricular remodelling. Presumably, macrophages interact with myocytes, endothelial cells, and fibroblasts. Although macrophages are primarily recruited to the ischaemic myocardium, the remote non-ischaemic myocardium macrophage population changes dynamically after MI. Macrophages' known roles in defending the steady state and their pathological actions in other disease contexts provide a road map for exploring cardiac macrophages and their phenotypes, functions, and therapeutic potential. In our review, we summarize recent insights into the role of cardiac macrophages, focus on their actions after ischaemia, and highlight emerging research topics.

Double-stranded RNA-dependent protein kinase deficiency protects the heart from systolic overload-induced congestive heart failure

BACKGROUND

Double-stranded RNA-dependent protein kinase (PKR) is a eukaryotic initiation factor 2α kinase that inhibits mRNA translation under stress conditions. PKR also mediates inflammatory and apoptotic signaling independently of translational regulation. Congestive heart failure is associated with cardiomyocyte hypertrophy, inflammation, and apoptosis, but the role of PKR in left ventricular hypertrophy and the development of congestive heart failure has not been examined.

METHODS AND RESULTS

We observed increased myocardial PKR expression and translocation of PKR into the nucleus in humans and mice with congestive heart failure. To determine the impact of PKR on the development of congestive heart failure, PKR knockout and wild-type mice were exposed to pressure overload produced by transverse aortic constriction. Although heart size increased similarly in wild-type and PKR knockout mice after transverse aortic constriction, PKR knockout mice exhibited very little pulmonary congestion, well-preserved left ventricular ejection fraction and contractility, and significantly less myocardial fibrosis compared with wild-type mice. Bone marrow-derived cells from wild-type mice did not abolish the cardiac protective effect observed in PKR knockout mice, whereas bone marrow-derived cells from PKR knockout mice had no cardiac protective effect in wild-type mice. Mechanistically, PKR knockout attenuated transverse aortic constriction-induced tumor necrosis factor-α expression and leukocyte infiltration and lowered cardiac expression of proapoptotic factors (Bax and caspase-3), so that PKR knockout hearts were more resistant to transverse aortic constriction-induced cardiomyocyte apoptosis. PKR depletion in isolated cardiomyocytes also conferred protection against tumor necrosis factor-α- or lipopolysaccharide-induced apoptosis.

CONCLUSION

PKR is a maladaptive factor upregulated in hemodynamic overload that contributes to myocardial inflammation, cardiomyocyte apoptosis, and the development of congestive heart failure.

Pre-conditioning with CDP-choline attenuates oxidative stress-induced cardiac myocyte death in a hypoxia/reperfusion model

Background. CDP-choline is a key intermediate in the biosynthesis of phosphatidylcholine, which is an essential component of cellular membranes, and a cell signalling mediator. CDP-choline has been used for the treatment of cerebral ischaemia, showing beneficial effects. However, its potential benefit for the treatment of myocardial ischaemia has not been explored yet. Aim. In the present work, we aimed to evaluate the potential use of CDP-choline as a cardioprotector in an in vitro model of ischaemia/reperfusion injury. Methods. Neonatal rat cardiac myocytes were isolated and subjected to hypoxia/reperfusion using the coverslip hypoxia model. To evaluate the effect of CDP-choline on oxidative stress-induced reperfusion injury, the cells were incubated with H₂O₂ during reperfusion. The effect of CDP-choline pre- and postconditioning was evaluated using the cell viability MTT assay, and the proportion of apoptotic and necrotic cells was analyzed using the Annexin V determination by flow cytometry. Results. Pre- and postconditioning with 50 mg/mL of CDP-choline induced a significant reduction of cells undergoing apoptosis after hypoxia/reperfusion. Preconditioning with CDP-choline attenuated postreperfusion cell death induced by oxidative stress. Conclusion. CDP-choline administration reduces cell apoptosis induced by oxidative stress after hypoxia/reperfusion of cardiac myocytes. Thus, it has a potential as cardioprotector in ischaemia/reperfusion-injured cardiomyocytes.

Mouse models of heart failure: cell signaling and cell survival

Heart failure is one of the paramount global causes of morbidity and mortality. Despite this pandemic need, the available clinical counter-measures have not altered substantially in recent decades, most notably in the context of pharmacological interventions. Cell death plays a causal role in heart failure, and its inhibition poses a promising approach that has not been thoroughly explored. In previous approaches to target discovery, clinical failures have reflected a deficiency in mechanistic understanding, and in some instances, failure to systematically translate laboratory findings toward the clinic. Here, we review diverse mouse models of heart failure, with an emphasis on those that identify potential targets for pharmacological inhibition of cell death, and on how their translation into effective therapies might be improved in the future.

In vivo silencing of the transcription factor IRF5 reprograms the macrophage phenotype and improves infarct healing

OBJECTIVES

The aim of this study was to test whether silencing of the transcription factor interferon regulatory factor 5 (IRF5) in cardiac macrophages improves infarct healing and attenuates post-myocardial infarction (MI) remodeling.

BACKGROUND

In healing wounds, the M1 toward M2 macrophage phenotype transition supports resolution of inflammation and tissue repair. Persistence of inflammatory M1 macrophages may derail healing and compromise organ functions. The transcription factor IRF5 up-regulates genes associated with M1 macrophages.

METHODS

Here we used nanoparticle-delivered small interfering ribonucleic acid (siRNA) to silence IRF5 in macrophages residing in MIs and in surgically-induced skin wounds in mice.

RESULTS

Infarct macrophages expressed high levels of IRF5 during the early inflammatory wound-healing stages (day 4 after coronary ligation), whereas expression of the transcription factor decreased during the resolution of inflammation (day 8). Following in vitro screening, we identified an siRNA sequence that, when delivered by nanoparticles to wound macrophages, efficiently suppressed expression of IRF5 in vivo. Reduction of IRF5 expression, a factor that regulates macrophage polarization, reduced expression of inflammatory M1 macrophage markers, supported resolution of inflammation, accelerated cutaneous and infarct healing, and attenuated development of post-MI heart failure after coronary ligation as measured by protease targeted fluorescence molecular tomography-computed tomography imaging and cardiac magnetic resonance imaging (p < 0.05).

CONCLUSIONS

This work identified a new therapeutic avenue to augment resolution of inflammation in healing infarcts by macrophage phenotype manipulation. This therapeutic concept may be used to attenuate post-MI remodeling and heart failure.

Vitamin C prevents stress-induced damage on the heart caused by the death of cardiomyocytes, through down-regulation of the excessive production of catecholamine, TNF-α, and ROS production in Gulo(-/-)Vit C-Insufficient mice

It is thought that vitamin C has protective roles on stress-induced heart damage and the development of cardiovascular diseases, but its precise role and mechanisms are unclear. In the present study, we investigated the specific mechanisms by which vitamin C leads to protecting the heart from stress-induced damage in the Gulo(-/-) mice which cannot synthesize vitamin C like humans. By exposure to stress (1h/day), the heartbeat and cardiac output in vitamin C-insufficient Gulo(-/-) mice were definitely decreased, despite a significant increase of adrenaline (ADR) and noradrenaline (NA) production. A change of cardiac structure caused by the death of cardiomyocytes and an increased expression of matrix metalloprotease (MMP)-2 and -9 were also found. Moreover, lipid peroxidation and the production of tumor necrosis factor-alpha (TNF-α) in the heart were increased. Finally, all vitamin C-insufficient Gulo(-/-) mice were expired within 2 weeks. Interestingly, all of the findings in vitamin C-insufficient Gulo(-/-) mice were completely prevented by the supplementation of a sufficient amount of vitamin C. Taken together, vitamin C insufficiency increases the risk of stress-induced cardiac damage with structural and functional changes arising from the apoptosis of cardiomyocytes.

IL-1 induces proinflammatory leukocyte infiltration and regulates fibroblast phenotype in the infarcted myocardium

In the infarcted myocardium, activation of the inflammatory cascade clears the wound from dead cells, whereas stimulating matrix degradation and chamber dilation, thus contributing to the development of heart failure. IL-1 is critically involved in the postinfarction inflammatory reaction and mediates adverse dilative remodeling. We hypothesized that IL-1 may regulate postinfarction repair and remodeling through cell-specific actions on leukocytes and fibroblasts. Flow cytometry demonstrated that in mouse infarcts, early recruitment of proinflammatory Ly6C(hi) cells expressing IL-1R1, the signaling receptor for IL-1, was followed by infiltration with cells expressing the decoy receptor, IL-1R2. Increased expression of IL-1R2 may serve to terminate IL-1-driven inflammation after infarction. Loss of IL-1 signaling in IL-1R1 null mice globally attenuated leukocyte recruitment, reducing the number of infiltrating Ly6C(hi) and Ly6C(lo) cells. Nonmyeloid CD11b(-) cells harvested during the inflammatory phase of cardiac repair exhibited marked upregulation of chemokines and cytokines; their inflammatory activation was IL-1R1 dependent. Moreover, IL-1β attenuated TGF-β-induced contractile activity of fibroblasts populating collagen pads, attenuated α-smooth muscle actin expression, and stimulated matrix metalloproteinase synthesis in an IL-1R1-dependent manner. The effects of IL-1 on TGF-β responses in cardiac fibroblasts were not due to direct effects on Smad activation, but were associated with endoglin suppression and accentuated expression of bone morphogenetic protein and activin membrane-bound inhibitor, a negative regulator of TGF-β signaling. IL-1 may orchestrate fibroblast responses in the infarct; early stimulation of fibroblast IL-1R1 signaling during the inflammatory phase may prevent premature activation of a matrix-synthetic contractile phenotype until the wound is cleared, and the infarct microenvironment can support mesenchymal cell growth.

A diet supplemented with ALA-rich flaxseed prevents cardiomyocyte apoptosis by regulating caveolin-3 expression

AIMS

n-3 polyunsaturated fatty acids (PUFAs) induce beneficial effects on the heart, but the mechanisms through which these effects are operated are not completely clarified yet. Among others, cardiac diseases are often associated with increased levels of cytokines, such as tumour necrosis factor-α (TNF), that cause degeneration and death of cardiomyocytes. The present study has been carried out to investigate (i) the potential anti-apoptotic effects induced by the n-3 polyunsaturated α-linolenic acid (ALA) in experimental models of cardiac diseases characterized by high levels of TNF, and (ii) the potential role of caveolin-3 (Cav-3) in the mechanisms involved in this process.

METHODS AND RESULTS

An ALA-rich flaxseed diet, administered from weaning to hereditary cardiomyopathic hamsters, prevented the onset of myocardial apoptosis associated with high plasma and tissue levels of TNF preserving caveolin-3 expression. To confirm these findings, isolated neonatal mouse cardiomyocytes were exposed to TNF to induce apoptosis. ALA pre-treatment greatly enhanced Cav-3 expression hampering the internalization of the caveolar TNF receptor and, thus, determining the abortion of the apoptotic vs. survival cascade.

CONCLUSION

This study unveiled the Cav-3 pivotal role in defending cardiomyocytes against the TNF pro-apoptotic action and the ALA capacity to regulate this mechanism preventing cardiac degenerative diseases.

Persistence of apoptosis and inflammatory responses in the heart and bone marrow of mice following whole-body exposure to ²⁸Silicon (²⁸Si) ions

It has been well established that the bone marrow (BM) is a radiosensitive tissue, but the radiosensitivity of the heart is poorly understood. In this study, we investigated the comparative effects of ²⁸Silicon (²⁸Si) ions (one type of heavy ion found in space) on tissue from the heart and the BM of exposed mice. We gave adult male CBA/CaJ mice a whole-body exposure to a total dose of 0, 0.1, 0.25, or 0.5 Gy of 300 MeV/nucleon (n) ²⁸Si ions, using a fractionated schedule (two exposures, 15 days apart that totaled each selected dose). The heart and BM were collected from 5 mice per treatment group at various times up to 6 months post-irradiation. In each mouse, we obtained tissue lysates from the heart and from the total population of BM cells for measuring the levels of cleaved poly (ADP-ribose) polymerase (cleaved PARP, a marker of apoptotic cell death) and the levels of activated nuclear factor-kappa B (NF-κB) and selected NF-κB-regulated cytokines known to be involved in inflammatory responses. Our data showed that, up to 6 months post-irradiation, the levels of apoptotic cell death and inflammatory responses in tissues from the heart and BM collected from exposed mice were statistically higher than those in sham controls. Hence, these findings are suggestive of chronic apoptotic cell death and inflammation in both tissues after exposure to ²⁸Si ions. In summary, our data are indicative of a possible association between exposure to ²⁸Si ions during space flight and long-term health risk.

Cholesteryl esters accumulate in the heart in a porcine model of ischemia and reperfusion

Myocardial ischemia is associated with intracellular accumulation of lipids and increased depots of myocardial lipids are linked to decreased heart function. Despite investigations in cell culture and animal models, there is little data available on where in the heart the lipids accumulate after myocardial ischemia and which lipid species that accumulate. The aim of this study was to investigate derangements of lipid metabolism that are associated with myocardial ischemia in a porcine model of ischemia and reperfusion. The large pig heart enables the separation of the infarct area with irreversible injury from the area at risk with reversible injury and the unaffected control area. The surviving myocardium bordering the infarct is exposed to mild ischemia and is stressed, but remains viable. We found that cholesteryl esters accumulated in the infarct area as well as in the bordering myocardium. In addition, we found that expression of the low density lipoprotein receptor (LDLr) and the low density lipoprotein receptor-related protein 1 (LRP1) was up-regulated, suggesting that choleteryl ester uptake is mediated via these receptors. Furthermore, we found increased ceramide accumulation, inflammation and endoplasmatic reticulum (ER) stress in the infarcted area of the pig heart. In addition, we found increased levels of inflammation and ER stress in the myocardium bordering the infarct area. Our results indicate that lipid accumulation in the heart is one of the metabolic derangements remaining after ischemia, even in the myocardium bordering the infarct area. Normalizing lipid levels in the myocardium after ischemia would likely improve myocardial function and should therefore be considered as a target for treatment.

Inflammatory activation: cardiac, renal, and cardio-renal interactions in patients with the cardiorenal syndrome

Although inflammation is a physiologic response designed to protect us from infection, when unchecked and ongoing it may cause substantial harm. Both chronic heart failure (CHF) and chronic kidney disease (CKD) are known to cause elaboration of several pro-inflammatory mediators that can be detected at high concentrations in the tissues and blood stream. The biologic sources driving this chronic inflammatory state in CHF and CKD are not fully established. Traditional sources of inflammation include the heart and the kidneys which produce a wide range of pro-inflammatory cytokines in response to neurohormones and sympathetic activation. However, growing evidence suggests that non-traditional biomechanical mechanisms such as venous and tissue congestion due to volume overload are also important as they stimulate endotoxin absorption from the bowel and peripheral synthesis and release of pro-inflammatory mediators. Both during the chronic phase and, more rapidly, during acute exacerbations of CHF and CKD, inflammation and congestion appear to amplify each other resulting in a downward spiral of worsening cardiac, vascular, and renal functions that may negatively impact patients' outcome. Anti-inflammatory treatment strategies aimed at attenuating end organ damage and improving clinical prognosis in the cardiorenal syndrome have been disappointing to date. A new therapeutic paradigm may be needed, which involves different anti-inflammatory strategies for individual etiologies and stages of CHF and CKD. It may also include specific (short-term) anti-inflammatory treatments that counteract inflammation during the unsettled phases of clinical decompensation. Finally, it will require greater focus on volume overload as an increasingly significant source of systemic inflammation in the cardiorenal syndrome.

Tumor necrosis factor receptor-associated factor 2 signaling provokes adverse cardiac remodeling in the adult mammalian heart

BACKGROUND

Tumor necrosis factor superfamily ligands provoke a dilated cardiac phenotype signal through a common scaffolding protein termed tumor necrosis factor receptor-associated factor 2 (TRAF2); however, virtually nothing is known about TRAF2 signaling in the adult mammalian heart.

METHODS AND RESULTS

We generated multiple founder lines of mice with cardiac-restricted overexpression of TRAF2 and characterized the phenotype of mice with higher expression levels of TRAF2 (myosin heavy chain [MHC]-TRAF2(HC)). MHC-TRAF2(HC) transgenic mice developed a time-dependent increase in cardiac hypertrophy, left ventricular dilation, and adverse left ventricular remodeling, and a significant decrease in LV+dP/dt and LV-dP/dt when compared with littermate controls (P<0.05 compared with littermate). During the early phases of left ventricular remodeling, there was a significant increase in total matrix metalloproteinase activity that corresponded with a decrease in total myocardial fibrillar collagen content. As the MHC-TRAF2(HC) mice aged, there was a significant decrease in total matrix metalloproteinase activity accompanied by an increase in total fibrillar collagen content and an increase in myocardial tissue inhibitor of metalloproteinase-1 levels. There was a significant increase in nuclear factor-κB activation at 4 to 12 weeks and jun N-terminal kinases activation at 4 weeks in the MHC-TRAF2(HC) mice. Transciptional profiling revealed that >95% of the hypertrophic/dilated cardiomyopathy-related genes that were significantly upregulated genes in the MHC-TRAF2(HC) hearts contained κB elements in their promoters.

CONCLUSIONS

These results show for the first time that targeted overexpression of TRAF2 is sufficient to mediate adverse cardiac remodeling in the heart.

Soluble TNF receptors are associated with infarct size and ventricular dysfunction in ST-elevation myocardial infarction

Objectives

The aim of the study was to investigate circulating markers of apoptosis in relation to infarct size, left ventricular dysfunction and remodeling in an ST-elevation myocardial infarction (STEMI) population undergoing primary percutaneous coronary intervention (PCI).

Background

Immediate re-opening of the acutely occluded infarct-related artery via primary PCI is the treatment of choice in STEMI to limit ischemia injury. However, the sudden re-initiation of blood flow can lead to a local acute inflammatory response with further endothelial and myocardial damage, so-called reperfusion injury. Apoptosis is suggested to be a key event in ischemia-reperfusion injury, resulting in LV-dysfunction, remodeling and heart failure.

Methods

The present study is a prespecified substudy of the F.I.R.E. trial. We included 48 patients with STEMI undergoing primary PCI. Blood samples were collected prior to PCI and after 24 hours. Plasma was separated for later analysis of soluble tumor necrosis factor receptor (sTNFR) 1, sTNFR2, sFas and sFas ligand (sFasL) by ELISA. Infarct size, left ventricular (LV) dysfunction and remodeling were assessed by cardiac magnetic resonance imaging at five days and four months after STEMI.

Results

The levels of sTNFR1 at 24 h as well as the relative increases in sTNFR1 and sTNFR2 over 24 h showed consistent and significant correlations with infarct size and LV-dysfunction at four months. Moreover, both sTNFRs correlated strongly with Troponin I and matrix metalloproteinase (MMP)-2 measurements. Soluble Fas and sFasL did not overall correlate with measures of infarct size or LV-dysfunction. None of the apoptosis markers correlated significantly with measures of remodeling.

Conclusions

In STEMI patients, circulating levels of sTNFR1 and sTNFR2 are associated with infarct size and LV dysfunction. This provides further evidence for the role of apoptosis in ischemia-reperfusion injury.

The non-anticoagulant heparin-like K5 polysaccharide derivative K5-N,OSepi attenuates myocardial ischaemia/reperfusion injury

Heparin and low molecular weight heparins have been demonstrated to reduce myocardial ischaemia/reperfusion (I/R) injury, although their use is hampered by the risk of haemorrhagic and thrombotic complications. Chemical and enzymatic modifications of K5 polysaccharide have shown the possibility of producing heparin-like compounds with low anticoagulant activity and strong anti-inflammatory effects. Using a rat model of regional myocardial I/R, we investigated the effects of an epimerized N-,O-sulphated K5 polysaccharide derivative, K5-N,OSepi, on infarct size and histological signs of myocardial injury caused by 30 min. ligature of the left anterior descending coronary artery followed by 1 or 24 h reperfusion. K5-N,OSepi (0.1-1 mg/kg given i.v. 15 min. before reperfusion) significantly reduced the extent of myocardial damage in a dose-dependent manner. Furthermore, we investigated the potential mechanism(s) of the cardioprotective effect(s) afforded by K5-N,OSepi. In left ventricular samples, I/R induced mast cell degranulation and a robust increase in lipid peroxidation, free radical-induced DNA damage and calcium overload. Markers of neutrophil infiltration and activation were also induced by I/R in rat hearts, specifically myeloperoxidase activity, intercellular-adhesion-molecule-1 expression, prostaglandin-E(2) and tumour-necrosis-factor-α production. The robust increase in oxidative stress and inflammatory markers was blunted by K5-N,OSepi, in a dose-dependent manner, with maximum at 1 mg/kg. Furthermore, K5-N,OSepi administration attenuated the increase in caspase 3 activity, Bid and Bax activation and ameliorated the decrease in expression of Bcl-2 within the ischaemic myocardium. In conclusion, we demonstrate that the cardioprotective effect of the non-anticoagulant K5 derivative K5-N,OSepi is secondary to a combination of anti-apoptotic and anti-inflammatory effects.

Circulating annexin A5 levels after atrial switch for transposition of the great arteries: relationship with ventricular deformation and geometry

Background

Inflammatory cytokines, cardiomyocyte apoptosis, and altered collagen turnover may contribute to unfavourable ventricular remodeling. This unfavourable ventricular remodelling is well documented in patients after atrial switch operation for complete transposition of the great arteries. We therefore tested if levels of circulating markers of inflammation, apoptosis, collagen synthesis, and extracellular matrix degradation are altered in patients after atrial switch operation for transposition of the great arteries.

Methods and Results

Circulating tumour necrosis factor (TNF)-α, annexin A5 (AnxA5), carboxy-terminal propeptide of type I procollagen (PICP), amino-terminal propeptide of type III procollagen (PIIINP), matrix metalloproteinase-1 (MMP-1), and tissue inhibitor of metalloproteinase-1 (TIMP-1) levels were determined in 27 patients aged 25.2±3.1 years and 20 controls. Ventricular myocardial deformation and left ventricular eccentricity index (EI) were determined by speckle tracking and two-dimensional echocardiography, respectively. Compared with controls, patients had significantly higher circulating AnxA5 (p<0.001) and TNF-α (p = 0.018) levels, but similar PICP, PIIINP, MMP-1 and TIMP-1 levels. For the whole cohort, plasma AnxA5 correlated with serum TNF-α (p = 0.002), systemic ventricular global longitudinal strain (GLS) and systolic and early diastolic strain rate (all p<0.001), and subpulmonary ventricular GLS and early diastolic strain rate (both p<0.001). In patients, plasma AnxA5 level correlated positively with subpulmonary ventricular EI (p = 0.027). Multiple linear regression analysis identified systemic ventricular GLS (β = −0.50, p<0.001) and serum TNF-α (β = 0.29, p = 0.022) as significant correlates of plasma AnxA5.

Conclusions

Elevated plasma AnxA5 level in patients after atrial switch operation is associated with impaired systemic myocardial deformation, increased subpulmonary ventricular eccentricity, and increased serum TNF-α level.

Interleukin-10 activates Toll-like receptor 4 and requires MyD88 for cardiomyocyte survival

Toll-like receptors (TLRs) are important in a variety of inflammatory diseases including acute cardiac disorders. TLR4 innate signaling regulates the synthesis of anti-inflammatory cytokine, interleukin-10 (IL-10) upon TLR4 agonists' re-stimulation. Anti-apoptotic action of IL-10 in cardiac dysfunction is generally accepted but its protective mechanism through TLR4 is not yet understood. We studied the effect of IL-10 in the activation of TLR4 downstream signals leading to cardiomyocytes survival. IL-10 caused a significant increase in the expression of CD14, MyD88 and TLR4. TLR4 activation led to the translocation of the interferon regulatory factor 3 (IRF3) into the nucleus. Phosphorylation of IRF3 enhanced mRNA synthesis for IL-1β but not TNF-α and was elevated even after removal of IL-10 stimulation. Furthermore, degradation of inhibitory kappa B (IκB) kinase (Ikk) suggested that IκBβ was the main activating kinase for IRF3-regulated NF-κB activation and phosphorylation of p65. Phosphorylated NF-κB p65 was translocated into the nucleus. Concomitantly, an increase in Bcl-xL activity inhibited Bax and the proteolytic activity of caspase 3 as well as a decrease in PARP cleavage. An inhibition of MyD88, modulated the above listed responses to IL-10 as there was a decrease in TLR4 and IRF3 and an increase in TNF-α mRNA. This was associated with a decrease in NF-κB p65, Bcl-xL mRNA and protein levels as well as there was an activation of Bax and PARP cleavage independent of caspase 3 activation. These data in cardiomyocytes suggest that IL-10 induced anti-apoptotic signaling involves upregulation of TLR4 through MyD88 activation.

Mechanism of TNF-α autocrine effects in hypoxic cardiomyocytes: initiated by hypoxia inducible factor 1α, presented by exosomes

Excessive tumor necrosis factor-α (TNF-α) expression is increasingly thought to be detrimental to cardiomyocytes in acute myocardial infarction. During myocardial ischemia, TNF-α is mainly released from macrophages, but with persistent ischemia, it can originate from cardiomyocytes and contribute to cardiac remodeling. The initiating factor and exact molecular mechanism of TNF-α release from cardiomyocytes is presently unclear. In this study, we investigated direct effects of hypoxia on TNF-α expression of cardiomyocytes, the role of hypoxia inducible factor-1α (HIF-1α) in TNF-α regulation and potential secretory pathway of TNF-α. Elevated TNF-α expression and HIF-1α activation in primary cultured cardiomyocytes under hypoxia were detected by real-time PCR, Western blotting and immunofluorescence. TNF-α mRNA elevation and protein secretion were obviously inhibited by nucleofection of HIF-1α small interfering RNA (siRNA) and treatment with 2-methoxyestradiol (inhibitor of HIF-1α protein). Similar results were observed in HEK293 and HepG2 cells. Putative hypoxia response elements were identified in the human TNF-α gene promoter. Deletion analysis and site-directed mutagenesis demonstrated that HIF consensus binding sites spanning bp-1295 to bp-1292 relative to the transcription start site were functional for activation of the TNF-α promoter which was confirmed by electrophoretic mobility-shift assay (EMSA) and chromatin immunoprecipitation (ChIP) analysis. Exosomes (vesicles mediating a non-classical route of protein secretion) in supernatants from hypoxic cardiomyocytes were identified by an anti-CD63 antibody in Western blot and observed by electron microscopy. The presence of TNF-α within exosomes precipitated from supernatants of hypoxic cardiomyocytes was verified by immunoelectron microscopy and immunoblotting. Results of this study indicate that under hypoxia, HIF-1α initiates expression of TNF-α, mediated by exosomes in cardiomyocytes.

Exercise rescued chronic kidney disease by attenuating cardiac hypertrophy through the cardiotrophin-1 -> LIFR/gp 130 -> JAK/STAT3 pathway

BACKGROUND

Chronic kidney disease (CKD) is usually associated with cardiac apoptosis and/or cardiac hypertrophy. We hypothesized that exercise can reduce the CKD-induced cardiac damage.

METHODS AND RESULTS

The doxorubicin-induced CKD (DRCKD) model was used in rats to compare two exercise models: 60-min running and 60-min swimming. Results indicated that in healthy normal groups, the signals cardiotrophin-1 (CT-1), interleukin 6 (IL-6), leukaemia inhibitory factor receptor (LIFR), and gp130 were upregulated and janus kinase (JAK) and signal transducer and activation of transcription (STAT) were downregulated by both exercises. In contrast, all signals were highly upregulated in CKD. After exercise training, all signals (CT-1, IL-6, LIFR, gp130, and STAT) were downregulated, with JAK being only slightly upregulated in the running group but not in the swimming group. The myocyte death pathway (CT-1/IL-6 → LIFR/gp130 → PI3K → Akt → Bad) was excluded due to no change found for Bad. Nitric oxide (NO; normal, 15.63 ± 0.86 µmol/l) was significantly suppressed in CKD rats (2.95 ± 0.32 µmol/l), and both running and swimming training highly upregulated the NO level to 30.33 ± 1.03 µmol/l and 27.82 ± 2.47 µmol/l in normal subjects and 24.0 ± 3.2 µmol/l and 22.69 ± 3.79 µmol/l in the DRCKD rats, respectively. The endothelial progenic cells CD34 were significantly suppressed in DRCKD rats, which were not rescued significantly by exercise. In contrast, the CD 34 cells were only slightly suppressed in the healthy subjects by exercise.

CONCLUSION

Both exercise regimens were beneficial by rescuing cardiac function in CKD victims. Its action mechanism was by way of inhibiting myocyte death and rescuing cardiac hypertrophy.

Effects of HMG-CoA reductase inhibitor on experimental autoimmune myocarditis

PURPOSE

Myocarditis is an acute inflammatory disease of the heart and is often a precursor of dilated cardiomyopathy. Experimental autoimmune myocarditis (EAM) has been used as a model for human myocarditis. The purpose of this study was to investigate the therapeutic role of 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitor, rosuvastatin, on the development of EAM.

METHODS

Experimental autoimmune myocarditis was induced in BALB/c mice by immunization with murine cardiac α-myosin heavy chain (MyHc-α(614-629) [Ac-SLKLMATLFSTYASAD-OH]). High-dose (10 mg/kg/day) or low-dose (1 mg/kg/day) rosuvastatin or vehicle was administered orally by gastric gavage to mice with EAM from day 0 to day 21 after immunization. On day 21 after immunization, echocardiography was carried out and the severity of myocarditis was detected by histopathological evaluation. Levels of serum tumor necrosis factor (TNF)-α and interleukin (IL)-6 were measured by ELISA. Histopathology was performed using haematoxylin and eosin. With apoptosis examined by Tunel, the expression of active caspase-3 in myocardium was investigated by immunohistochemistry.

RESULTS

Rosuvastatin attenuated the histopathological severity of myocarditis. Cardiac function was improved in the two rosuvastatin-treated groups compared to the non-treated EAM group (LVFS: high-dose rosuvastatin group [group H], 0.38 ± 0.10%; low-dose rosuvastatin group [group L], 0.34 ± 0.06%; non-treated EAM group [group N], 0.29 ± 0.07%. LVEF: group H, 0.80 ± 0.09%; group L, 0.71 ± 0.07%; group N, 0.68 ± 0.07%). Furthermore, treatment with rosuvastatin decreased the expression levels of TNF-α (group H, 65.19 ± 7.06 pg/ml; group L, 108.20 ± 5.28 pg/ml; group N, 239.34 ± 11.65 pg/ml) and IL-6 (group H, 14.33 ± 2.15 pg/ml; group L, 19.67 ± 3.04 pg/ml; group N, 40.39 ± 7.17 pg/ml). The rates of expression of active Caspase-3 and myocardial apoptosis were positively correlated with the scores for myocardial pathology.

CONCLUSIONS

These results demonstrate that administration of rosuvastatin can ameliorate EAM progression, inhibit apoptosis of cardiomyocytes, and preserve cardiac output, and they also suggest rosuvastatin may be a promising novel therapeutic strategy for the clinical treatment of myocarditis.

Stimulation of glucose oxidation protects against acute myocardial infarction and reperfusion injury

AIMS

During reperfusion of the ischaemic myocardium, fatty acid oxidation rates quickly recover, while glucose oxidation rates remain depressed. Direct stimulation of glucose oxidation via activation of pyruvate dehydrogenase (PDH), or secondary to an inhibition of malonyl CoA decarboxylase (MCD), improves cardiac functional recovery during reperfusion following ischaemia. However, the effects of such interventions on the evolution of myocardial infarction are unknown. The purpose of this study was to determine whether infarct size is decreased in response to increased glucose oxidation.

METHODS AND RESULTS

In vivo, direct stimulation of PDH in mice with the PDH kinase (PDHK) inhibitor, dichloroacetate, significantly decreased infarct size following temporary ligation of the left anterior descending coronary artery. These results were recapitulated in PDHK 4-deficient (PDHK4-/-) mice, which have enhanced myocardial PDH activity. These interventions also protected against ischaemia/reperfusion injury in the working heart, and dichloroacetate failed to protect in PDHK4-/- mice. In addition, there was a dramatic reduction in the infarct size in malonyl CoA decarboxylase-deficient (MCD-/-) mice, in which glucose oxidation rates are enhanced (secondary to an inhibition of fatty acid oxidation) relative to their wild-type littermates (10.8 ± 3.8 vs. 39.5 ± 4.7%). This cardioprotective effect in MCD-/- mice was associated with increased PDH activity in the ischaemic area at risk (1.89 ± 0.18 vs. 1.52 ± 0.05 μmol/g wet weight/min).

CONCLUSION

These findings demonstrate that stimulating glucose oxidation via targeting either PDH or MCD decreases the infarct size, validating the concept that optimizing myocardial metabolism is a novel therapy for ischaemic heart disease.

How and when do myocytes die during ischemia and reperfusion: the late phase

While the majority of the cardiac myocyte death that makes up the final infarct occurs during ischemia and the first few minutes of reperfusion, cell death does not stop there. In fact necrosis and apoptosis, and potentially autophagy, can continue in the previously ischemic area for up to 3 days post-reperfusion. Several mechanisms can potentially contribute to this death continuum: (1) myocytes that have already passed the point of no return despite reperfusion; (2) continued dysfunction of the coronary microvasculature; and (3) infiltration of inflammatory cells. The latter in particular leads to elevated myocardial concentrations of reactive oxygen species (ROS), inflammatory cytokines, activation of toll-like receptors, secretion of toxic enzymes, and activation of the complement cascade--all of which can lead to myocyte death. However, there is a considerable lack of studies that comprehensively examine the time course, nature, and mechanisms of post-reperfusion myocyte death. Moreover, cell death types (apoptosis, necrosis, and autophagy) are inextricably linked to one another. Therefore, we do not know whether specific blockade of necrosis during the acute phase of myocyte death will instead enhance apoptosis during the late phase, that is, will we be simply delaying the inevitable? Consequently, the purpose of this article is to briefly review what we do, and more importantly what we do not, know about cardiac cell death in the reperfused heart and what is needed to advance our understanding of this phenomenon.

Regulatory T lymphocytes attenuate myocardial infarction-induced ventricular remodeling in mice

Downregulation of CD4+CD25+ regulatory T lymphocytes (Treg) has been found in local atherosclerotic lesions and in patients with myocardial infarction (MI). However, the roles of Treg in MI and the following inflammatory response have not yet been well elucidated. Therefore, we hypothesized that adoptive transfer of Treg could attenuate the postinfarction inflammatory response protecting from adverse remodeling, and we attempted to elucidate the mechanism of delayed heart failure after MI. To clarify the role of Treg in MI, we used a murine MI model and administered a single intravenous injection of Treg (1 × 10(5)) (treatment, n = 6) or saline (control, n = 7) and sacrificed the mice on day 14. Echocardiograms revealed that Treg improved LV contraction after MI. Histopathology also showed that Treg negated MI-induced LV remodeling. RT-PCR demonstrated that the mRNA levels of IFN-gamma in hearts were lower and Foxp3 in spleens were higher in the treatment group than in the control group. We observed that adoptive Treg transfer could attenuate MI-induced cardiac remodeling through the IFN-gamma and Foxp3 alteration.

Cellular FLICE-inhibitory protein protects against cardiac remodelling after myocardial infarction

Cellular FLICE-inhibitory protein (cFLIP) is a member of the tumour necrosis factor signalling pathway and a regulator of apoptosis, and it has a role in cardiac remodelling following myocardial infarction (MI) that remains largely uncharacterised. This study aimed to determine the function of cFLIP as a potential mediator of post-infarction cardiac remodelling. Our results show diminished cFLIP expression in failing human and murine post-infarction hearts. Genetically engineered cFLIP heterozygous (cFLIP+/-, HET) mice, cardiac-specific cFLIP-overexpressing transgenic (TG) mice and their respective wild-type (WT) and non-transgenic controls were subjected to MI by permanent ligation of their left anterior descending artery. Cardiac structure and function were assessed by echocardiography and pressure-volume loop analysis. Apoptosis, inflammation, angiogenesis, and fibrosis were evaluated in the myocardium. The HET mice showed exacerbated left ventricular (LV) contractile dysfunction, dilatation, and remodelling compared with WT mice 28 days after MI. Impaired LV function in the HET mice was associated with increases in infarct size, hypertrophy, apoptosis, inflammation, and interstitial fibrosis, and reduced capillary density. The TG mice displayed the opposite phenotype after MI. Moreover, adenovirus-mediated overexpression of cFLIP decreased LV dilatation and improved LV function and remodelling in both HET and WT mice. Further analysis of signalling events suggests that cFLIP promotes cardioprotection by interrupting JNK1/2 signalling and augmenting Akt signalling. In conclusion, our results indicate that cFLIP protects against the development of post-infarction cardiac remodelling. Thus, cFLIP gene delivery shows promise as a clinically powerful and novel therapeutic strategy for the treatment of heart failure after MI.

BRCA1 is an essential regulator of heart function and survival following myocardial infarction

The tumour suppressor BRCA1 is mutated in familial breast and ovarian cancer but its role in protecting other tissues from DNA damage has not been explored. Here we show a new role for BRCA1 as a gatekeeper of cardiac function and survival. In mice, loss of BRCA1 in cardiomyocytes results in adverse cardiac remodelling, poor ventricular function and higher mortality in response to ischaemic or genotoxic stress. Mechanistically, loss of cardiomyocyte BRCA1 results in impaired DNA double-strand break repair and activated p53-mediated pro-apoptotic signalling culminating in increased cardiomyocyte apoptosis, whereas deletion of the p53 gene rescues BRCA1-deficient mice from cardiac failure. In human adult and fetal cardiac tissues, ischaemia induces double-strand breaks and upregulates BRCA1 expression. These data reveal BRCA1 as a novel and essential adaptive response molecule shielding cardiomyocytes from DNA damage, apoptosis and heart dysfunction. BRCA1 mutation carriers, in addition to risk of breast and ovarian cancer, may be at a previously unrecognized risk of cardiac failure.

The tumour suppressor BRCA1 is mutated in familial breast and ovarian cancer. Now, Shukla et al. demonstrate that mice lacking BRCA1 in cardiomyocytes are more sensitive to ischaemia than control mice, and that BRCA1 is elevated in human tissues exposed to ischaemia, suggesting a cardioprotective role for BRCA1.

Molecular mechanisms of cardiomyocyte aging

Western societies are rapidly aging, and cardiovascular diseases are the leading cause of death. In fact, age and cardiovascular diseases are positively correlated, and disease syndromes affecting the heart reach epidemic proportions in the very old. Genetic variations and molecular adaptations are the primary contributors to the onset of cardiovascular disease; however, molecular links between age and heart syndromes are complex and involve much more than the passage of time. Changes in CM (cardiomyocyte) structure and function occur with age and precede anatomical and functional changes in the heart. Concomitant with or preceding some of these cellular changes are alterations in gene expression often linked to signalling cascades that may lead to a loss of CMs or reduced function. An understanding of the intrinsic molecular mechanisms underlying these cascading events has been instrumental in forming our current understanding of how CMs adapt with age. In the present review, we describe the molecular mechanisms underlying CM aging and how these changes may contribute to the development of cardiovascular diseases.

Apoptosis in Anthracycline Cardiomyopathy

Apoptosis is a tightly regulated physiologic process of programmed cell death that occurs in both normal and pathologic tissues. Numerous in vitro or in vivo studies have indicated that cardiomyocyte death through apoptosis and necrosis is a primary contributor to the progression of anthracycline-induced cardiomyopathy. There are now several pieces of evidence to suggest that activation of intrinsic and extrinsic apoptotic pathways contribute to anthracycline-induced apoptosis in the heart. Novel strategies were developed to address a wide variety of cardiotoxic mechanisms and apoptotic pathways by which anthracycline influences cardiac structure and function. Anthracycline-induced apoptosis provides a very valid representation of cardiotoxicity in the heart, an argument which has implications for the most appropriate animal models of damaged heart plus diverse pharmacological effects. In this review we describe various aspects of the current understanding of apoptotic cell death triggered by anthracycline. Differences in the sensitivity to anthracycline-induced apoptosis between young and adult hearts are also discussed.