Apoptosis and heart failure: A critical review of the literature

Natural IgM antibodies: the orphaned molecules in immune surveillance

Natural IgM antibodies are typical victims of prejudices which originated in the mid 80 s. Over the years, these molecules were considered as the pariahs among the immune competent molecules and their characteristic properties, like low affinity, cross-reactivity and pentameric structure, were assessed as useless, difficult, nebulous, etc. Today, mainly based on a few scientists' persistent work and the key discoveries on innate immune recognition, natural IgM antibodies are "back on stage". Their role in the immune response against bacteria, viruses, fungi and possibly modified self-components as well as in therapy and diagnosis of malignancies is accepted. All the so far negatively judged features are seen in a different light, e.g. low affinity seems to be good for function and does not exclude specificity, and cross-reactivity is no longer judged as unspecific, but instead as a very economic way of immune recognition. And at last, with the use of natural IgM antibodies, a new field of tumor-specific targets has been encountered, the carbo-neo-epitopes. Therefore, by having learned from nature, the renaissance of natural IgM antibodies opens a new area of cancer therapeutics and diagnostics.

Myocyte apoptosis during acute myocardial infarction in rats is related to early sarcolemmal translocation of annexin A5 in border zone

Annexin A5 is a Ca2+-dependent phospholipid binding protein well known for its high phosphatidylserine affinity. In vitro, translocation to sarcolemma and externalization of endogenous annexin A5 in the cardiomyocyte has recently been demonstrated to exert a proapoptotic effect. To determine whether these in vitro findings occurred in vivo, we performed myocardial infarction (MI) and studied the time course of apoptosis and annexin A5 localization (0.5 to 8 h) in the border zone around the infarcted area. This zone that was defined as Evans blue unstained and triphenyltetrazolium chloride (TTC) stained, represented 42.3 ± 5.5% of the area at risk and showed apoptotic characteristics (significant increases in caspase 3 activity 2.3-fold at 0.5 h; P < 0.05), transferase-mediated dUTP nick-end labeling-positive cardiomyocytes (15.8 ± 0.8% at 8 h), and DNA ladder. When compared with sham-operated rats, we found that in this area, annexin A5 was translocated to the sarcolemma as early as 0.5 h after MI and that translocation increased with time. Moreover, the amount of annexin A5 was unchanged in the border zone and decreased in the infarcted area after 1 h (77.1 ± 4.8%; P < 0.01 vs. perfused area), suggesting a release in the latter but not in the former. In conclusion, we demonstrated that annexin A5 translocation is an early and rapid event of the whole border zone, likely due to Ca2+increase. Part of this translocation occurred in areas where apoptosis was later detected and suggests that in vivo as in vitro annexin A5 might be involved in the regulation of early apoptotic events during cardiac pathological situations.

Acute renal failure: much more than a kidney disease

Acute renal failure is a frequent clinical problem with an increasing incidence, an unacceptably high mortality rate that has not improved in more than 40 years, and no specific treatment, yet renal failure is not the usual cause of death. The role of inflammation has been documented in both acute renal injury and cardiac dysfunction. Several investigators have shown that congestive heart failure is associated with increased mortality in patients with acute renal failure. This article reviews some of the cardiac and other distant organ effects of acute renal injury that may be important in the morbidity and mortality observed clinically. Cardiac changes after experimental renal ischemia include cytokine induction, leukocyte infiltration, cell death by apoptosis, and impaired function. I propose that the extrarenal effects of kidney injury must be considered in designing therapies. Acute renal failure has systemic consequences and must be thought of as more than a kidney disease.

Transient receptor potential (TRP) protein 7 acts as a G protein-activated Ca2+ channel mediating angiotensin II-induced myocardial apoptosis

Transient receptor potential (TRP) proteins have been identified as cation channels that are activated by agonist-receptor coupling and mediate various cellular functions. TRPC7, a homologue of TRP channels, has been shown to act as a Ca2+ channel activated by G protein-coupled stimulation and to be abundantly expressed in the heart with an as-yet-unknown function. We studied the role of TRPC7 in G protein-activated signaling in HEK293 cells and cultured cardiomyocytes in vitro transfected with FLAG-tagged TRPC7 cDNA and in Dahl salt-sensitive rats with heart failure in vivo. TRPC7-transfected HEK293 cells showed an augmentation of carbachol-induced intracellular Ca2+ transient, which was attenuated under a Ca2+-free condition or in the presence of SK&F96365 (a Ca2+-permeable channel blocker). Upon stimulation with angiotensin II (Ang II), cultured neonatal rat cardiomyocytes transfected with TRPC7 exhibited a significant increase in apoptosis detected by TUNEL staining, accompanied with a decrease in the expression of atrial natriuretic factor and destruction of actin fibers, as compared with non-transfected cardiomyocytes. Ang II-induced apoptosis was inhibited by CV-11974 (Candesartan; Ang II type 1 [AT1] receptor blocker), SK&F96365, and FK506 (calcineurin inhibitor). In Dahl salt-sensitive rats, apoptosis and TRPC7 expression were increased in the failing myocardium, and a long-term treatment with temocapril, an angiotensin-converting enzyme inhibitor, suppressed both. Our findings suggest that TRPC7 could act as a Ca2+ channel activated by AT1 receptors, leading to myocardial apoptosis possibly via a calcineurin-dependent pathway. TRPC7 might be a key initiator linking AT1-activation to myocardial apoptosis, and thereby contributing to the process of heart failure.

Heart-targeted overexpression of Nip3a in zebrafish embryos causes abnormal heart development and cardiac dysfunction

We transiently expressed a proapoptotic protein, Nip3a, by a heart-specific BMP4 promoter in zebrafish embryos and generated two variants of embryos with abnormal heart phenotypes (A and B). Embryos with phenotype A heart defects showed hypoplastic or elongated ventricles, elongated or enlarged atriums with no normal cardiac looping resulting a significant longer SV-BA distance, and bradycardia at 48 h post-fertilization (hpf). Embryos with phenotype B heart defects showed an enlarged fluid-filled pericardium, severe hypoplasia, non-contracting ventricles, and elongated or enlarged slowly beating atriums with no normal looping. Histological sections further revealed the absence of a proper atrioventricular boundary and no endocardial cells lining this region in both 48- and 72-hpf Nip3a-overexpressing embryos, implicating defective endocardial cushion formation. These phenotypes are reminiscent of atrioventricular canal defects in humans. In addition, induced apoptotic myocardium cells were clustered in the presumptive atrioventricular boundary as well as in the adjacent ventricle and atrium of 48- and 72-hpf Nip3a-overexpressing embryos. Nip3a expression was readily detected in 80% epiboly BMP4-Nip3a-injected embryos, and defects in heart development were observed in both the linear heart tube and subsequent chamber formation stages. These results showed that myocyte apoptosis is a universal pathogenic factor for congenital heart failure using zebrafish as a model organism.

Mesenchymal stem cells transmigrate over the endothelial barrier

Mesenchymal stem cells (MSCs) seem to be a useful tool for cellular therapy in injured tissues, e.g. myocardial infarction or cardiomyopathies resulting in heart failure. For therapeutic approaches it is crucial that MSCs cross the endothelial barrier especially in intravascular or rather intracoronary application. Until today little is known about MSCs transmigrating across the endothelium. We performed co-culture experiments of MSCs on an endothelial monolayer to analyse direct interactions. An increasing flattened morphology of the MSCs was followed by a total integration into the monolayer after 2h. We repeated these experiments in isolated heart perfusions with gold-labelled MSCs. Using electron microscopy we detected MSCs exhibited direct cell-cell contacts. Tight junctions between the endothelial cells became abolished resulting in a distinct split between the cells. MSCs developed tight cell-cell contacts and became integrated into the endothelial wall of the capillary vessel. Finally, using confocal laser scanning microscopy, we assessed the ability of the MSCs to fully pass the endothelial barrier. Within the first 30 min, 30+/-8% of MSCs transmigrated, increasing to about half at 60 min (50+/-8%), whereas after 120 min the rate remained nearly unchanged (53+/-10%). This work demonstrates the capability of MSCs for transendothelial migration. Moreover we showed that the vast majority of MSCs migrated within 30 min, an important finding for the exposure times in clinical settings.

Cardiac regeneration

The role and even the existence of new myocyte formation in the adult heart remain controversial. Documentation of cell cycle regulators, deoxyribonucleic acid synthesis, and mitotic images has only in part modified the view that myocardial growth can be accomplished exclusively from hypertrophy of an irreplaceable population of differentiated myocytes. However, myocyte regeneration and death occur physiologically, and these cellular processes are enhanced in pathologic states. These observations have challenged the view of the heart as a postmitotic organ and have proposed a new paradigm in which parenchymal and non-parenchymal cells are continuously replaced by newly formed younger populations of myocytes as well as by vascular smooth muscle and endothelial cells. Heart homeostasis is regulated by a stem cell compartment characterized by multipotent cardiac stem cells that possess the ability to acquire the distinct cell lineages of the myocardium. Similarly, adult bone marrow cells are able to differentiate into cells beyond their own tissue boundary and create cardiomyocytes and coronary vessels. This process has been termed developmental plasticity or transdifferentiation. Because of these properties, bone marrow cells and cardiac stem cells have been employed experimentally in the reconstitution of dead myocardium after infarction. These cell classes hold promise for the treatment of heart failure in humans.

Myocardial apoptosis associated with the expression of proinflammatory cytokines during the course of myocardial infarction

To clarify the role of myocardial apoptosis associated with the expression of proinflammatory cytokines in human myocardial infarction (MI), we have analyzed the expression of apoptosis positive for single-stranded DNA (ss-DNA) antibody, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-8 in 147 samples of infarcted myocardial tissue from 65 patients. ss-DNA-positive apoptotic nuclei were found mainly in cardiomyocytes in the border zones and granulation tissue cells in the infarct foci. The ss-DNA index (SI) of cardiomyocytes (average 0.13%) peaked at stage II (established myocardial necrosis), the value being significantly higher than at stages III (macrophage infiltration), IV (granulation formation), and V (scar formation) (P<0.05), whereas the SI of granulation tissue (average 0.08%) at stages III, IV, and V showed no significant differences between the three stages. These results suggest that cardiomyocyte apoptosis in the border zone is responsible for cellular loss in the acute stage of MI, whereas granulation tissue apoptosis may not be involved in the process of ventricular remodeling. TNF-alpha was expressed in cardiomyocytes in the border zones of infarct foci, but no significant positive correlation was found between SI and TNF-alpha index in cardiomyocytes (r=0.08, P = 0.37), suggesting that TNF-alpha does not serve as a direct trigger of cardiomyocyte apoptosis in vivo. The number of IL-8-positive cells peaked at stage II, and IL-8-myeloperoxidase-double-positive neutrophils were frequently detected, indicating that infiltrating neutrophils are the predominant source of IL-8 in the infarcted myocardium. These results suggest that, in human MI, TNF-alpha produced by cardiomyocytes does not play a critical role in their apoptosis, and that IL-8 produced by neutrophils is responsible for the subsequent accumulation and activation of neutrophils, thus increasing the degree of myocardial damage.

Monocyte-specific Bcl-2 expression attenuates inflammation and heart failure in monocyte chemoattractant protein-1 (MCP-1)-induced cardiomyopathy

OBJECTIVE

Infiltrating inflammatory cells within the myocardium have been shown to be apoptotic, but the significance of apoptotic inflammatory cells to the development of cardiomyopathy remains undefined. Transgenic mice with cardiac-specific expression of MCP-1 exhibit extensive apoptosis of infiltrating mononuclear cells and develop heart failure. Here, we tested the hypothesis that in vivo selective inhibition of apoptosis of infiltrating mononuclear cells would preserve cardiac structure and function and improve survival in this murine model.

METHODS

Mice with cardiac-specific expression of MCP-1 and monocyte-specific expression of Bcl-2 were generated by cross-breeding MCP-1 transgenic mice with hMRP8-Bcl-2 mice that over-express Bcl-2 in the monocytes. Structural and functional parameters and the inflammatory response of the heart were evaluated and compared between the wild-type and transgenic mice.

RESULTS

Expression of Bcl-2 in monocytes results in superior preservation of myocardial structure, cardiac function and a significant prolongation of survival of MCP-1 transgenic mice. The beneficial effects of monocyte-specific Bcl-2 expression are associated with inhibition of apoptosis of infiltrating mononuclear cells, normalization of circulating C-reactive protein levels, attenuation of cellular infiltrates, macrophage activation and production of proinflammatory cytokines, tumor necrosis factor (TNF-alpha), interleukin (IL)-1 beta and IL-6 in the hearts.

CONCLUSIONS

These results demonstrate that apoptosis of infiltrating mononuclear cells plays a detrimental role in the development of heart failure in this murine model, suggesting that modulation of apoptosis of infiltrating mononuclear cells may be of clinical benefit in heart failure.

β2-Adrenergic Stimulation Attenuates Left Ventricular Remodeling, Decreases Apoptosis, and Improves Calcium Homeostasis in a Rodent Model of Ischemic Cardiomyopathy

The benefit of the beta(2)-adrenergic agonist, clenbuterol, in left ventricular assist device patients with dilated cardiomyopathy has been reported, but its effect on ischemic heart failure (HF) is unknown. We investigated whether clenbuterol improves left ventricular remodeling, myocardial apoptosis and has synergy with a beta(1) antagonist, metoprolol, in a model of ischemic HF. Rats were randomized to: 1) HF only; 2) HF + clenbuterol; 3) HF + metoprolol; 4) HF + clenbuterol + metoprolol; and 5) rats with sham surgery. HF was induced by left anterior descending artery (LAD) artery ligation and confirmed by decreased left ventricular fractional shortening, decreased maximum left ventricular dP/dt (dP/dt(max)), and elevated left ventricular end-diastolic pressure (LVEDP) compared with sham rats (p < 0.01). After 9 weeks of oral therapy, echocardiographic, hemodynamic, and ex vivo end-diastolic pressure-volume relationship (EDPVR) measurements were obtained. Immunohistochemistry was performed for myocardial apoptosis and DNA damage markers. Levels of calcium-handling proteins were assessed by Western blot analysis. Clenbuterol-treated HF rats had increased weight gain and heart weights versus HF rats (p < 0.05). EDPVR curves revealed a leftward shift in clenbuterol rats versus metoprolol and HF rats (p < 0.05). The metoprolol-treated group had a lower LVEDP and higher dP/dt(max) versus the HF group (p < 0.05). Clenbuterol and metoprolol groups had decreased myocardial apoptosis and DNA damage markers and increased DNA repair markers versus HF rats (all p < 0.01). Protein levels of the ryanodine receptor and sarcoplasmic reticulum calcium-ATPase were improved in clenbuterol-, metoprolol-, and clenbuterol+metoprolol-treated groups versus HF rats. However, as a combination therapy, there were no synergistic effects of clenbuterol+metoprolol treatment. We conclude that clenbuterol ameliorates EDPVR, apoptosis, and calcium homeostasis but does not have synergy with metoprolol in our model of ischemic HF.

Biochemical dysfunction in heart mitochondria exposed to ischaemia and reperfusion

Heart tissue is remarkably sensitive to oxygen deprivation. Although heart cells, like those of most tissues, rapidly adapt to anoxic conditions, relatively short periods of ischaemia and subsequent reperfusion lead to extensive tissue death during cardiac infarction. Heart tissue is not readily regenerated, and permanent heart damage is the result. Although mitochondria maintain normal heart function by providing virtually all of the heart's ATP, they are also implicated in the development of ischaemic damage. While mitochondria do provide some mechanisms that protect against ischaemic damage (such as an endogenous inhibitor of the F1Fo-ATPase and antioxidant enzymes), they also possess a range of elements that exacerbate it, including ROS (reactive oxygen species) generators, the mitochondrial permeability transition pore, and their ability to release apoptotic factors. This review considers the process of ischaemic damage from a mitochondrial viewpoint. It considers ischaemic changes in the inner membrane complexes I-V, and how this might affect formation of ROS and high-energy phosphate production/degradation. We discuss the contribution of various mitochondrial cation channels to ionic imbalances which seem to be a major cause of reperfusion injury. The different roles of the H+, Ca2+ and the various K+ channel transporters are considered, particularly the K+(ATP) (ATP-dependent K+) channels. A possible role for the mitochondrial permeability transition pore in ischaemic damage is assessed. Finally, we summarize the metabolic and pharmacological interventions that have been used to alleviate the effects of ischaemic injury, highlighting the value of these or related interventions in possible therapeutics.

Treatment with granulocyte colony-stimulating factor ameliorates chronic heart failure

Chronic heart failure remains a leading cause of mortality. Although granulocyte colony-stimulating factor (G-CSF) is reported to have a beneficial affect on postinfarction cardiac remodeling and dysfunction when administered before the onset of or at the acute stage of myocardial infarction (MI), its effect on established heart failure is unknown. We show here that subcutaneous administration of G-CSF greatly improves the function of murine hearts failing due to a large, healed MI. G-CSF changed the geometry of the infarct scar from elongated and thin to short and thick, induced hypertrophy among surviving cardiomyocytes, and reduced myocardial fibrosis. Expression of G-CSF receptor was confirmed in failing hearts and was upregulated by G-CSF treatment. G-CSF treatment also led to activation of signal transducer and activator of transcription-3 and induction of GATA-4 and various sarcomeric proteins such as myosin heavy chain, troponin I and desmin. Expression of metalloproteinase-2 and -9 was also increased in G-CSF-treated hearts, while that of tumor necrosis factor-alpha, angiotensin II type 1 receptor (AT1) and transforming growth factor-beta1 was reduced. Although activation of Akt was noted in G-CSF-treated hearts, vessel density was unchanged, and apoptosis was too rare to exert a meaningful effect. No bone marrow-derived cardiomyocytes or vascular cells were detected in the failing hearts of green fluorescent protein chimeric mice. Finally, beneficial effects of G-CSF on cardiac function were found persisting long after discontinuing the treatment (2 weeks). Collectively, these findings suggest G-CSF administration could be an effective approach to treating chronic heart failure following a large MI.

Disruption of caveolin-1 leads to enhanced nitrosative stress and severe systolic and diastolic heart failure

Although caveolin-1 is not expressed in cardiomyocytes, this protein is assumed to act as a key regulator in the development of cardiomyopathy. In view of recent discordant findings we aimed to elucidate the cardiac phenotype of independently generated caveolin-1 knockout mice (cav-1(-/-)) and to unveil causative mechanisms. Invasive hemodynamic measurements of cav-1(-/-) show a severely reduced systolic and diastolic heart function. Additionally, genetic ablation of caveolin-1 leads to a striking biventricular hypertrophy and to a sustained eNOS-hyperactivation yielding increased systemic NO levels. Furthermore, a diminished ATP content and reduced levels of cyclic AMP in hearts of knockout animals were measured. Taken together, these results indicate that genetic disruption of caveolin-1 is sufficient to induce a severe biventricular hypertrophy with signs of systolic and diastolic heart failure. Collectively, our findings suggest a causative role of a sustained nitrosative stress in the development of the pronounced cardiac impairment.

Synchronous progression of calcium transient-dependent beating and sarcomere destruction in apoptotic adult cardiomyocytes

During early apoptosis, adult cardiomyocytes show unusual beating, suggesting possible participation of abnormal Ca(2+) transients in initiation of apoptotic processes in this cell type. Simultaneously with the beating, these cells show dynamic structural alteration resulting from cytoskeletal disintegration that is quite rapid. Because of the specialized structure and extensive cytoskeleton of cardiomyocytes, we hypothesized that its degradation in so short a time would require a particularly efficient mechanism. To better understand this mechanism, we used serial video microscopy to observe beta-adrenergic stimulation-induced apoptosis in isolated adult rat cardiomyocytes while simultaneously recording intracellular Ca(2+) concentration and cell length. Trains of Ca(2+) transients and corresponding rhythmic contractions and relaxations (beating) were observed in apoptotic cells. Frequencies of Ca(2+) transients and beating gradually increased with time and were accompanied by cellular shrinkage. As the cells shrank, amplitudes of Ca(2+) transients declined and diastolic intracellular Ca(2+) concentration increased until the transients were lost. Beating and progression of apoptosis were significantly inhibited by antagonists against the L-type Ca(2+) channel (nifedipine), ryanodine receptor (ryanodine), inositol 1,4,5-trisphosphate receptor (heparin), sarco(endo)plasmic Ca(2+)-ATPase (thapsigargin), and Na(+)/Ca(2+) exchanger (KB-R7943). Electron-microscopic examination of beating cardiomyocytes revealed progressive breakdown of Z disks. Immunohistochemical analysis and Western blot confirmed that disappearance of Z disk constituent proteins (alpha-actinin, desmin, and tropomyosin) preceded degradation of other cytoskeletal proteins. It thus appears that, in adult cardiomyocyte apoptosis, Ca(2+) transients mediate apoptotic beating and efficient sarcomere destruction initiated by Z disk breakdown.

Ghrelin, the same peptide for different functions: player or bystander?

Ghrelin is a recently discovered brain-gut peptide with two main physiological actions: growth hormone secretagogue activity and food intake inducer. Although its production is prevalently gastric, ghrelin is widely expressed in several tissues, where it might therefore act as a paracrine or autocrine factor. It is becoming clear that ghrelin is much more than a simple growth hormone secretagogue. In addition to its formerly envisaged role, ghrelin has other activities including stimulation of pituitary hormones secretion, modulation of food intake and control of energy metabolism, regulation of gastric and pancreatic activity, and cardiovascular and hemodynamic activities. In addition, modulation of cartilage and bone homeostasis, sleep and behavioral influences, and modulation of the immune system, as well as effects on cell proliferation, are other relevant actions of ghrelin. Thus, the peptide appears to be an important component of an integrated multifaceted regulatory system. In this review, we summarize several aspects of ghrelin biology and attempt to inform the reader with information regarding unexpected functions of this gastric peptide.

Myocardial aging

This review questions the old paradigm that describes the heart as a post-mitotic organ and introduces the notion of the heart as a self-renewing organ regulated by a compartment of multipotent cardiac stem cells (CSCs) capable of regenerating myocytes and coronary vessels throughout life. Because of this dramatic change in cardiac biology, the objective is to provide an alternative perspective of the aging process of the heart and stimulate research in an area that pertains to all of us without exception. The recent explosion of the field of stem cell biology, with the recognition that the possibility exists for extrinsic and intrinsic regeneration of myocytes and coronary vessels, necessitates reevaluation of cardiac homeostasis and myocardial aging. From birth to senescence, the mammalian heart is composed of non-dividing and dividing cells. Loss of telomeric DNA is minimal in fetal and neonatal myocardium but rather significant in the senescent heart. Aging affects the growth and differentiation potential of CSCs interfering not only with their ability to sustain physiological cell turnover but also with their capacity to adapt to increases in pressure and volume loads. The recognition of factors enhancing the activation of the CSC pool, their mobilization, and translocation, however, suggests that the detrimental effects of aging on the heart might be prevented or reversed by local stimulation of CSCs or the intramyocardial delivery of CSCs following their expansion and rejuvenation in vitro. CSC therapy may become, perhaps, a novel strategy for the devastating problem of heart failure in the old population.

Poly(ADP-ribose) polymerase-1-dependent cardiac myocyte cell death during heart failure is mediated by NAD+ depletion and reduced Sir2alpha deacetylase activity

Robust activation of poly(ADP-ribose) polymerase-1 (PARP) by oxidative stress has been implicated as a major cause of caspase-independent myocyte cell death contributing to heart failure. Here, we show that depletion of myocyte NAD levels and the subsequent reduction of Sir2alpha deacetylase activity are the sequential steps contributing to PARP-mediated myocyte cell death. In both failing hearts and cultured cardiac myocytes, the increased activity of PARP was associated with depletion of cellular NAD levels and reduced Sir2alpha deacetylase activity. Myocyte cell death induced by PARP activation was prevented by repletion of cellular NAD levels either by adding NAD directly to the culture medium or by overexpressing NAD biosynthetic enzymes. The beneficial effect of NAD repletion was seen, however, only when Sir2alpha was intact. Knocking down Sir2alpha levels by small interfering RNA eliminated this benefit, indicating that Sir2alpha is a downstream target of NAD replenishment leading to cell protection. NAD repletion also prevented loss of the transcriptional regulatory activity of the Sir2alpha catalytic core domain resulting from PARP activation. We also show that PARP activation and the concomitant reduction of Sir2alpha activity in failing hearts regulate the post-translational acetylation of p53. These data demonstrate that, in stressed cardiac myocytes, depletion of cellular NAD levels forms a link between PARP activation and reduced Sir2alpha deacetylase activity, contributing to myocyte cell death during heart failure.

A positive feedback loop of phosphodiesterase 3 (PDE3) and inducible cAMP early repressor (ICER) leads to cardiomyocyte apoptosis

cAMP plays crucial roles in cardiac remodeling and the progression of heart failure. Recently, we found that expression of cAMP hydrolyzing phosphodiesterase 3A (PDE3A) was significantly reduced in human failing hearts, accompanied by up-regulation of inducible cAMP early repressor (ICER) expression. Angiotensin II (Ang II) and the beta-adrenergic receptor agonist isoproterenol (ISO) also induced persistent PDE3A down-regulation and concomitant ICER up-regulation in vitro, which is important in Ang II- and ISO-induced cardiomyocyte apoptosis. We hypothesized that interactions between PDE3A and ICER may constitute an autoregulatory positive feedback loop (PDE3A-ICER feedback loop), and this loop would cause persistent PDE3A down-regulation and ICER up-regulation. Here, we demonstrate that ICER induction repressed PDE3A gene transcription. PDE3A down-regulation activated cAMP/PKA signaling, leading to ICER up-regulation via PKA-dependent stabilization of ICER. With respect to Ang II, the initiation of the PDE3A-ICER feedback loop depends on activation of Ang II type 1 receptor (AT1R), classical PKC(s), and CREB (cAMP response element binding protein). We further show that the PDE3A-ICER feedback loop is essential for Ang II-induced cardiomyocyte apoptosis. ISO and PDE3 inhibitors also induced the PDE3A-ICER feedback loop and subsequent cardiomyocyte apoptosis, highlighting the importance of this PDE3A-ICER feedback loop and cAMP signaling in cardiomyocyte apoptosis. Our findings may provide a therapeutic paradigm to prevent cardiomyocyte apoptosis and the progression of heart failure by inhibiting the PDE3A-ICER feedback loop.

Myocardial apoptotic index based on in situ DNA nick end-labeling of endomyocardial biopsies does not predict prognosis of dilated cardiomyopathy

BACKGROUND

DNA breaks detected largely by terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate in situ nick end-labeling (TUNEL) are observed in the hearts of patients with diseases such as dilated cardiomyopathy (DCM).

STUDY OBJECTIVES

To determine the prognostic value of TUNEL assays in cases of DCM.

DESIGN, SETTING, AND PARTICIPANTS

DCM patients were selected from among patients who had undergone left ventricular (LV) biopsy during the period from 1994 to 2001 in our hospital. Of those, 46 (35 men and 11 women; mean [+/- SD] age, 58 +/- 11 years) who were followed up for > 3 years after the undergoing the biopsy (mean follow-up period, 4.9 +/- 2.0 years) or died during the follow-up period were entered into the present study. The myocardial apoptotic index was assessed in deparaffinized biopsy specimens that were stained using a conventional TUNEL assay. In addition, all surviving patients received a follow-up echocardiographic examination.

RESULTS

Ten of the 46 biopsy specimens (22%) contained TUNEL-positive myocytes; their mean apoptotic index was 0.44 +/- 1.05%. The apoptotic index showed no relation to cardiac functional parameters determined at the time of biopsy, however. Seven patients died during the follow-up period, and 19 of the surviving patients were readmitted to the hospital because of a worsening of their heart failure. There was no significant difference in the apoptotic indexes of biopsy specimens from the dead and surviving patients, or between the surviving patients who were readmitted to the hospital and those who were not. There was also no significant correlation between the apoptotic index and changes in the LV ejection fraction, LV end-diastolic diameter, or LV posterior wall thickness during follow-up.

CONCLUSION

The apoptotic index derived from TUNEL assays is not predictive of the prognosis of patients with DCM-induced heart failure.

Effect of Astragalus injection on plasma levels of apoptosis-related factors in aged patients with chronic heart failure

OBJECTIVE

To investigate the effect of Astragalus injection (AI) on plasma levels of apoptosis-related factors in aged patients with chronic heart failure (CHF).

METHODS

Seventy-two CHF patients were randomly divided into the AI group (36 cases) treated with AI and the control group (36 cases) treated with conventional treatment. Plasma levels of soluble Fas (sFas), soluble Fas ligand (sFasL), tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) were measured by enzyme-linked immunosorbent assays (ELISA) with monoclonal anti-human antibodies. Besides, New York Heart Association (NYHA) grading was assessed according to improved symptoms and left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV) and left ventricular ejection fraction (LVEF) were assessed by echocardiogram after 4 weeks of treatment.

RESULTS

After 4 weeks of treatment, NYHA grading was markedly improved in the two groups, but it was significantly better in AI group than that in the control group (P < 0.05). As compared with the control group, sFas, sFasL, TNF-alpha and IL-6 in the AI group were obviously lower, the difference between the two groups and between before and after treatment were significant (P < 0.05 or P < 0.01). Moreover, in AI group, LVESV and LVEDV decreased, LVEF increased, which was significantly different than that before treatment (P < 0.05), respectively.

CONCLUSION

AI could lower plasma levels of apoptosis-related factors, and is one of the effective drugs in improving cardiac function in the aged patients with CHF.

Role of apoptosis in ventricular remodeling

Cell loss is a common feature in the failing heart, and this contributes to the relentless progression seen in patients with heart failure. Apoptosis is one of the most common causes of cell loss in animals and humans with heart failure. There is increasing evidence that apoptosis, even while occurring in a low-grade manner, can mediate heart failure. Moreover, inhibiting apoptosis successfully prevents or attenuates heart failure in several animal models. More importantly, apoptosis is one of the few mechanisms that can be easily modulated using pharmacologic or gene therapy approaches. Animal data, obtained in the past few years, have proven the feasibility and success of this approach toward altering the natural history of heart failure. Human studies are pending, but a number of issues such as the type of inhibitor and its optimum timing/dose will need to be resolved before this becomes a reality. Nevertheless, these data will accrue over time, and anti-apoptotic therapy is likely to emerge as an important form of heart failure therapy.

Cardiac remodeling and failure: from molecules to man (Part I)

The process of heart failure appears to be a common and coordinated response to cardiac injury and dysfunction. The contemporary mechanistic viewpoint that predictable, shared, highly regulated events underlie the complex heart failure process implies that an improved understanding of these mechanisms is fundamental to the advancement of cardiovascular biology and the subsequent development of targeted, effective treatment strategies for patients with congestive heart failure (CHF). Cardiac remodeling (CR) is the restructuring and reshaping of the heart that underlies heart failure progression. CR is a major determinant of the clinical course of CHF, irrespective of its etiology. The traditional concepts of cellular remodeling in the failing heart are based on well-established data indicating characteristic alterations in cell size, shape, and the ability to perform contractile work. The role of programmed cell death and the exciting possibility of cardiomyocyte regeneration are areas of intense investigation. Notably, the accumulating data in both animal and human hearts suggesting cardiomyocyte regeneration and renewal indicate that cellular remodeling is a complex and dynamic process that is not completely understood. For the development of new treatments to regenerate and restore failing myocardium, the possibilities offered by controlling cell death and enhancing cell renewal as a therapeutic target are unprecedented. Based on a critical review of the available literature, the traditional concepts and mechanisms describing the regulation of remodeling are largely inadequate. The neurohormonal (RAAS and adrenergic systems) and innovative cytokine hypothesis (TNF-alpha and others) of remodeling and failure do not account for all the cellular and molecular changes that result in the progression of CHF. Given that these contemporary concepts serve as the basis for the majority of our current heart failure treatments, it is not surprising that CHF is an emerging epidemic in our society. To define new therapeutic targets and to control the process of remodeling, novel biomolecules and mechanisms for the coordinated control of CR must be further defined.

Functional role of phosphodiesterase 3 in cardiomyocyte apoptosis: implication in heart failure

BACKGROUND

Myocyte apoptosis plays an important role in pathological cardiac remodeling and the progression of heart failure. cAMP signaling is crucial in the regulation of myocyte apoptosis and cardiac remodeling. Multiple cAMP-hydrolyzing phosphodiesterases (PDEs), such as PDE3 and PDE4, coexist in cardiomyocytes and elicit differential temporal/spatial regulation of cAMP signaling. However, the role of PDE3 and PDE4 in the regulation of cardiomyocyte apoptosis remains unclear. Although chronic treatment with PDE3 inhibitors increases mortality in patients with heart failure, the contribution of PDE3 expression/activity in heart failure is not well known.

METHODS AND RESULTS

In this study we report that PDE3A expression and activity were significantly reduced in human failing hearts as well as mouse hearts with chronic pressure overload. In primary cultured cardiomyocytes, chronic inhibition of PDE3 but not PDE4 activity by pharmacological agents or adenovirus-delivered antisense PDE3A promoted cardiomyocyte apoptosis. Both angiotensin II (Ang II) and the beta-adrenergic receptor agonist isoproterenol selectively induced a sustained downregulation of PDE3A expression and induced cardiomyocyte apoptosis. Restoring PDE3A via adenovirus-delivered expression of wild-type PDE3A1 completely blocked Ang II- and isoproterenol-induced cardiomyocyte apoptosis, suggesting the critical role of PDE3A reduction in cardiomyocyte apoptosis. Moreover, we defined a crucial role for inducible cAMP early repressor expression in PDE3A reduction-mediated cardiomyocyte apoptosis.

CONCLUSIONS

Our results suggest that PDE3A reduction and consequent inducible cAMP early repressor induction are critical events in Ang II- and isoproterenol-induced cardiomyocyte apoptosis and may contribute to the development of heart failure. Drugs that maintain PDE3A function may represent an attractive therapeutic approach to treat heart failure.

Ventricular Assist Device Therapy Normalizes Inducible Nitric Oxide Synthase Expression and Reduces Cardiomyocyte Apoptosis in the Failing Human Heart

OBJECTIVES

We examined the effect of mechanical unloading with ventricular assist device (VAD) therapy on myocardial inducible nitric oxide synthase (iNOS) expression and cardiomyocyte apoptosis in patients with end-stage heart failure (HF).

BACKGROUND

Despite advances in medical therapy, HF continues to be a progressive and ultimately fatal disorder. High levels of iNOS expression are present in the myocardium of failing hearts, suggesting a potential role for iNOS in HF progression.

METHODS

Inducible NOS protein expression was analyzed by Western blotting and cardiomyocyte apoptosis by terminal deoxynucleotidyltransferase dUTP nick end-labeling (TUNEL) in myocardial samples from failing hearts. Included in these analyses were tissues from 9 patients at the time of transplantation (HF-transplant group), 10 patients at the time of VAD insertion (pre-VAD group), and 11 patients undergoing transplant after VAD support (post-VAD group). Seven control samples were obtained at autopsy.

RESULTS

Low or undetectable levels of iNOS were present in controls (0.005 +/- 0.002). The HF-transplant and pre-VAD myocardial specimens exhibited a marked increase in iNOS expression (1.48 +/- 0.34 and 1.29 +/- 0.26, respectively; p < 0.01 for both vs. controls). The increase in iNOS expression was reversed in the post-VAD group (0.36 +/- 0.16; p < 0.01 vs. HF-transplant and pre-VAD groups). The rate of TUNEL-positive cardiomyocytes was high in the pre-VAD group and significantly lower in the post-VAD group (0.64 +/- 0.15% in pre-VAD group and 0.16 +/- 0.07% in post-VAD group; p < 0.01). The iNOS levels correlated significantly with cardiomyocyte apoptosis (r = 0.66, p < 0.01).

CONCLUSIONS

Therapy with VAD normalizes iNOS expression in association with diminished cardiomyocyte apoptosis in the failing heart. Further work is required to define whether a causal relationship exists between iNOS and cardiomyocyte apoptosis.

Array lessons from the heart: focus on the genome and transcriptome of cardiomyopathies

Our understanding of the cardiovascular system has evolved through the years by extensive studies emphasizing the identification of the molecular and physiological mechanisms involved in its normal function and disease pathogenesis. Major discoveries have been made along the way. However, the majority of this work has focused on specific genes or pathways rather than integrative approaches. In cardiomyopathies alone, over 30 different loci have shown mutations with varying inheritance patterns, yet mostly coding for structural proteins. The emergence of microarrays in the early 1990s paved the way to a new era of cardiovascular research. Microarrays dramatically accelerated the rhythm of discoveries by giving us the ability to simultaneously study thousands of genes in a single experiment. In the field of cardiovascular research, microarrays are having a significant contribution, with the majority of work focusing on end-stage cardiomyopathies that lead to heart failure. Novel molecular mechanisms have been identified, known pathways are seen under new light, disease subgroups begin to emerge, and the effects of various drugs are molecularly dissected. This cross-study data comparison concludes that consistent energy metabolism gene expression changes occur across dilated, hypertrophic, and ischemic cardiomyopathies, while Ca2+ homeostasis changes are prominent in the first two cardiomyopathies, and structural gene expression changes accompany mostly the dilated form. Gene expression changes are further correlated to disease genetics. The future of microarrays in the cardiomyopathy field is discussed with an emphasis on optimum experimental design and on applications in diagnosis, prognosis, and drug discovery.

Acute phase lipocalin Ex-FABP is involved in heart development and cell survival

Ex-FABP is an extracellular fatty acid binding protein, expressed during chicken embryo development in cartilage, muscle fibers, and blood granulocytes. Transfection of chondrocytes and myoblasts with anti-sense Ex-FABP cDNA results in inhibition of cell proliferation and apoptosis induction. Ex-FABP expression is dramatically enhanced by inflammatory stimuli and in pathological conditions. In this paper, by in situ whole mount and immunohistochemistry analysis we show that, at early developmental stage, Ex-FABP is diffuse in all tissues of chick embryos. Particularly high level of transcript and protein are expressed in the heart. During acute phase response (APR) induced by endotoxin LPS injection, a marked increase of Ex-FABP mRNA was observed in embryos, highest Ex-FABP expression being in heart and liver. To investigate in vivo the biological role of Ex-FABP, we have directly microinjected chicken embryos with antibody against Ex-FABP. Almost 70% of chicken embryos died and the target tissue was the heart. We detected in heart of the treated embryos a significant increase of apoptotic cells and high level of fatty acids. We propose that the accumulation of fatty acid, specific ligand of Ex-FABP, in the cell microenvironment is responsible of heart cell death, and we suggest that Ex-FABP may act as a survival protein by playing a role as scavenger for fatty acids.

Mechanisms of Cell Survival in Myocardial Hibernation

Myocardial hibernation represents a condition of regional ventricular dysfunction in patients with chronic coronary artery disease, which reverses gradually after revascularization. The precise mechanism mediating the regional dysfunction is still debated. One hypothesis suggests that chronic hypoperfusion results in a self-protecting downregulation in myocardial function and metabolism to match the decreased oxygen supply. An alternative hypothesis suggests that the myocardium is subject to repetitive episodes of ischemic dysfunction resulting from an imbalance between myocardial metabolic demand and supply that eventually creates a sustained depression of contractility. It is generally agreed that hibernating myocardium is submitted repeatedly to ischemic stress, and therefore one question persists: how do myocytes survive in the setting of chronic ischemia? The hallmark of hibernating myocardium is a maintained viability of the dysfunctional myocardium which relies on an increased uptake of glucose. We propose that, in addition to this metabolic adjustment, there must be molecular switches that confer resistance to ischemia in hibernating myocardium. Such mechanisms include the activation of a genomic program of cell survival as well as autophagy. These protective mechanisms are induced by ischemia and remain activated chronically as long as either sustained or intermittent ischemia persists.

Alterations in transmural strains adjacent to ischemic myocardium during acute midcircumflex occlusion

OBJECTIVE

Helically oriented left ventricular fibers assemble into transmural sheets, which are important for wall-thickening mechanics: 15% fiber shortening results in 40% cross-fiber left ventricular wall thickening and a 60% ejection fraction through sheet extension, thickening, and shear. Normal cardiac microstructure and strains are optimized; deviations could result in apoptosis and deleterious matrix remodeling, which degenerates into global cardiomyopathy. We studied alterations in transmural strains adjacent to ischemic myocardium during acute midcircumflex occlusion.

METHODS

Nine sheep had radiopaque markers implanted to measure left ventricular systolic fractional area shortening; 3 transmural bead columns were inserted into the midlateral wall for strain analysis. Three-dimensional marker coordinates were obtained with biplane videofluoroscopy before and during 70 seconds of ischemia. Systolic strains were quantified along circumferential, longitudinal, and radial axes (n = 9) and were transformed into fiber-sheet coordinates by using quantitative microstructural measurements (n = 5).

RESULTS

A functional border was defined in the midlateral left ventricle; ischemia decreased posterolateral fractional area shortening, and anterolateral fractional area shortening increased. In this demarcation junction, subepicardial end-systolic radial wall thickening decreased (0.16 +/- 0.08 vs 0.11 +/- 0.06) and sheet-normal shear was abolished (0.08 +/- 0.04 vs -0.01 +/- 0.03). Longitudinal shortening decreased in the subepicardium and midwall (-0.05 +/- 0.04 vs +/- -0.01 +/- 0.06), but circumferential-radial shear increased at these depths (0.04 +/- 0.04 vs 0.11 +/- 0.05). Subendocardial fiber stretch occurred during early systole (-0.01 +/- 0.03 vs 0.02 +/- 0.03), and end-systolic fiber-sheet shear increased (0.07 +/- 0.01 vs 0.11 +/- 0.04, all P < .05).

CONCLUSIONS

Increased circumferential-radial shear and altered fiber-sheet strains reflect mechanical interactions between ischemic and nonischemic myocardium, which might be important in triggering remodeling processes that evolve into global ischemic cardiomyopathy.

Genetic expression profiles during physiological and pathological cardiac hypertrophy and heart failure in rats

Cardiac hypertrophy is a complex and nonhomogenous response to various stimuli. In this study, we used high-density oligonucleotide microarray to examine gene expression profiles during physiological hypertrophy, pathological hypertrophy, and heart failure in Dahl salt-sensitive rats. There were changes in 404/3,160 and 874/3,160 genes between physiological and pathological hypertrophy and the transition from hypertrophy to heart failure, respectively. There were increases in stress response genes (e.g., heat shock proteins) and inflammation-related genes (e.g., pancreatitis-associated protein and arachidonate 12-lipoxygenase) in pathological processes but not in physiological hypertrophy. Furthermore, atrial natriuretic factor and brain natriuretic protein showed distinctive changes that are very specific to different conditions. In addition, we used a resampling-based gene score-calculating method to define significantly altered gene clusters, based on Gene Ontology classification. It revealed significant alterations in genes involved in the apoptosis pathway during pathological hypertrophy, suggesting that the apoptosis pathway may play a role during the transition to heart failure. In addition, there were significant changes in glucose/insulin signaling, protein biosynthesis, and epidermal growth factor signaling during physiological hypertrophy but not during pathological hypertrophy.

Transcription factor AP-2alpha triggers apoptosis in cardiac myocytes

Idiopathic-dilated cardiomyopathy (IDC) is a common primary myocardial disease of unknown etiology associated with apoptosis, cardiac dilatation, progressive heart failure and increased mortality. An elevation of the transcription factor activator protein 2alpha (AP-2alpha) is involved in vertebrate embryonic development and oncogenesis. Here, we show that AP-2alpha protein is expressed in the human heart and increased in human failing myocardium with IDC. Adenovirus-mediated overexpression of human AP-2alpha triggered apoptosis and increased mRNA levels of Bcl-2 family members Bax and Bcl-x in rat cardiomyocytes. Immunohistological analysis of human myocardium revealed an increased percentage of AP-2alpha-positive nuclei in IDC and, interestingly, a colocalization of AP-2alpha-positive but not -negative cells with a caspase-cleaved fragment of poly(ADP-ribose)polymerase. We suggest AP-2alpha as a novel cardiac regulator implicated in the activation of apoptosis in IDC.

Corticosteroids inhibit cell death induced by doxorubicin in cardiomyocytes: induction of antiapoptosis, antioxidant, and detoxification genes

Psychological or physical stress induces an elevation of corticosteroids in the circulating system. We report here that corticosterone (CT) protects cardiomyocytes from apoptotic cell death induced by doxorubicin (Dox), an antineoplastic drug known to induce cardiomyopathy possibly through reactive oxygen species production. The cytoprotection induced by CT is within the range of physiologically relevant doses. The lowest dose tested, 0.1 microM (or 3.5 microg/dl), inhibited apoptosis by approximately 25% as determined by caspase activity. With 1 microM CT, cardiomyocytes gain a cytoprotective effect after 8 h of incubation and remain protected for at least 72 h. Hydrocortisone, cortisone, dexamethasone, and aldosterone but not androstenedione or cholesterol also induced cytoprotection. Analyses of 20,000 gene expression sequences using Affymetrix high-density oligonucleotide array found that CT caused up-regulation of 140 genes and down-regulation of 108 genes over 1.5-fold. Among the up-regulated genes are bcl-xL, metallothioneins, glutathione peroxidase-3, and glutathione S-transferases. Western blot analyses revealed that CT induced an elevation of bcl-xL but not bcl-2 or proapoptotic factors bax, bak, and bad. Inhibiting the expression of bcl-xL reduced the cytoprotective effect of CT. Our data suggest that CT induces a cytoprotective effect on cardiomyocytes in association with reprogramming gene expression and induction of bcl-xL gene.

Left atrial function, cytokines and soluble apoptotic markers in mitral stenosis: effects of valvular replacement

BACKGROUND

Patients with mitral stenosis (MS) and heart failure (HF) are characterized by changes in the left atrial (LA) function and activation of the apoptotic process. The purpose of the present study was the evaluation of the effect of mitral valve replacement on the LA function, on inflammatory process and apoptotic markers in patients with MS and HF.

METHODS

We studied 30 patients with MS and HF (15 in NYHA III-IV and 15 in NYHA IV) in sinus rhythm (mean age 56.2 +/- 4.6 years), and 20 age and gender matched healthy volunteers. Blood samples were obtained before and 6 months after surgical mitral valve replacement, and plasma levels of soluble Fas/APO-1 receptor (sFas), tumor necrosis factor-alpha (TNF-a) and interleukin-6 (IL-6) were measured. Echocardiographically, LA volumes were measured at mitral valve opening (Vmax), at the onset of left atrial systole (P wave of the electrocardiogram, Vp) and at the mitral valve closure (Vmin). LA contractile function was assessed by the LA active emptying fraction (ACTEF).

RESULTS

After mitral valve replacement, TNF-a, IL-6 and sFas levels, as well as the Vmax LA volume, were significantly reduced (p < 0.05). ACTEF showed a significant postoperative decrease (0.29 +/- 0.09 vs. 0.23 +/- 0.06, p < 0.01) and it was significantly correlated with sFas (r = -0.88, p = 0.001), TNF-a (r = -0.81, p = 0.001) and IL-6 (r = -0.74, p = 0.001) levels.

CONCLUSION

The present findings indicate that mitral valve replacement in patients with mitral valve stenosis, reduces the size of the left atrium, improves left atrial contractile function and depresses inflammatory and apoptotic process.

Role of apoptosis in remodeling after myocardial infarction

The magnitude of an acute myocardial infarction (MI; i.e., number of dead cardiomyocytes) is the most critical determinant of subsequent left ventricular remodeling and heart failure. Also affecting the post-infarction disease process, however, are events occurring during the subacute and chronic stages of the infarction, including late cardiomyocyte death, cardiomyocyte hypertrophy, fibrosis, and expression of various cytokines. Additionally, it has been suggested that apoptosis may be responsible for a significant amount of cardiomyocyte death during the acute ischemic stage, as well as for a progressive loss of surviving cells during the subacute and chronic stages. However, there is very little direct morphological evidence of apoptosis occurring at any stage of MI, despite the availability of much indirect evidence that includes detection of DNA fragmentation and apoptosis-related factors. For that reason, the potential efficacy of therapeutic intervention to prevent apoptosis remains controversial. This review will survey available data from both animals and humans to critically assess the role of cardiomyocyte apoptosis during MI and its relevance to myocardial remodeling and heart failure. Also considered will be nonmyocyte interstitial cells, which have received less attention than myocytes despite definitive evidence of their apoptosis in the infarcted heart and recent studies suggesting that blockade of apoptosis among these cells mitigates post-infarction cardiac remodeling and heart failure. We conclude from our survey that there are many hurdles to surmount before regulation of apoptosis can be clinically applied in the treatment of MI and other heart diseases.

Prognostic value of cardiac troponin T in patients with both acute and chronic stable congestive heart failure: comparison with atrial natriuretic peptide, brain natriuretic peptide and plasma norepinephrine

BACKGROUND

The prognostic value of cardiac troponin T (cTn-T) in a mixture of patients with both acute and chronic congestive heart failure (CHF), simultaneously assessed and compared with neurohormonal factors, has not yet been thoroughly evaluated. Thus, we focused on the prognostic value of cTn-T in comparison with atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and plasma norepinephrine (PNE) in this population.

METHODS

Prognostic correlates of elevation of cTn-T, ANP, BNP, PNE were analyzed in 63 acute and chronic CHF patients followed up to record worsening CHF and cardiac death.

RESULTS

cTn-T (> or =0.03 microg/L) was found in 17.4% (11 of 63) of patients. cTn-T correlated with ANP, BNP, PNE. Acute CHF patients were more positive for cTn-T and BNP. In our cohort, neither cTn-T (> or =0.03 microg/L) nor PNE were associated with increased mortality and worsening HF in CHF patients. After adjustment, BNP was the only independent predictor of cardiac events (RR, 3.23; p=0.01).

CONCLUSIONS

BNP emerged as the only independent predictor of cardiac events in a mixture of patients with both acute and chronic CHF, suggesting that it is the analyte that best reflects long-term prognosis in a diverse population enrolled to mirror the "real world" situation.

ERK1/2 regulates intracellular ATP levels through alpha-enolase expression in cardiomyocytes exposed to ischemic hypoxia and reoxygenation

Extracellular signal-regulated kinase 1/2 (ERK1/2) is known to function in cell survival in response to various stresses; however, the mechanism of cell survival by ERK1/2 remains poorly elucidated in ischemic heart. Here we applied functional proteomics by two-dimensional electrophoresis to identify a cellular target of ERK1/2 in response to ischemic hypoxia. Approximately 1500 spots were detected by Coomassie Brilliant Blue staining of a sample from unstimulated cells. The staining intensities of at least 50 spots increased at 6-h reoxygenation after 2-h ischemic hypoxia. Of the 50 spots that increased, at least 4 spots were inhibited in the presence of PD98059, a MEK inhibitor. A protein with a molecular mass of 52 kDa that is strongly induced by ERK1/2 activation in response to ischemic hypoxia and reoxygenation was identified as alpha-enolase, a rate-limiting enzyme in the glycolytic pathway, by liquid chromatography-mass spectrometry and amino acid sequencing. The expressions of the alpha-enolase mRNA and protein are inhibited during reoxygenation after ischemic hypoxia in the cells containing a dominant negative mutant of MEK1 and treated with a MEK inhibitor, PD98059, leading to a decrease in ATP levels. alpha-Enolase expression is also observed in rat heart subjected to ischemia-reperfusion. The induction of alpha-enolase by ERK1/2 appears to be mediated by c-Myc. The introduction of the alpha-enolase protein into the cells restores ATP levels and prevents cell death during ischemic hypoxia and reoxygenation in these cells. These results show that alpha-enolase expression by ERK1/2 participates in the production of ATP during reoxygenation after ischemic hypoxia, and a decrease in ATP induces apoptotic cell death. Furthermore, alpha-enolase improves the contractility of cardiomyocytes impaired by ischemic hypoxia. Our results reveal that ERK1/2 plays a role in the contractility of cardiomyocytes and cell survival through alpha-enolase expression during ischemic hypoxia and reoxygenation.

Increased expression of poly(ADP-ribose) polymerase-1 contributes to caspase-independent myocyte cell death during heart failure

Poly(ADP-ribose) polymerase-1 (PARP-1) plays a pivotal role in regulating genome stability, cell cycle progression, and cell survival. However, overactivation of PARP has been shown to contribute to cell death and organ failure in various stress-related disease conditions. In this study, we examined the role of PARP in the development and progression of cardiac hypertrophy. We measured the expression of PARP in mouse hearts with physiological (swimming exercise) and pathological (aortic banding) cardiac hypertrophy as well as in human heart samples taken at the time of transplantation. PARP levels were elevated both in swimming and banded mice hearts and demonstrated a linear positive correlation with the degree of cardiac hypertrophy. A dramatic increase (4-fold) of PARP occurred in 6-wk banded mice, accompanied by apparent signs of ventricular dilation and myocyte cell death. PARP levels were also elevated (2- to 3-fold) in human hearts with end-stage heart failure compared with controls. However, we found no evidence of caspase-mediated PARP cleavage in either mouse or human failing hearts. Overexpression of PARP in primary cultures of cardiac myocytes led to suppression of gene expression and robust myocyte cell death. Furthermore, data obtained from the analysis of PARP knockout mice revealed that these hearts produce an attenuated hypertrophic response to aortic banding compared with controls. Together, these results demonstrate a role for PARP in the onset and progression of cardiac hypertrophy and suggest that some events related to cardiac hypertrophy growth and progression to heart failure are mediated by a PARP-dependent mechanism.

Lipoptosis: tumor-specific cell death by antibody-induced intracellular lipid accumulation

A balanced lipid metabolism is crucial for all cells. Disturbance of this homeostasis by nonphysiological intracellular accumulation of fatty acids can result in apoptosis. This was proven in animal studies and was correlated to some human diseases, like lipotoxic cardiomyopathy. Some metabolic mechanisms of lipo-apoptosis were described, and some causes were discussed, but reagents, which directly induce lipo-apoptosis, have thus far not been identified. The human monoclonal IgM antibody SAM-6 was isolated from a stomach cancer patient by using the conventional human hybridoma technology (trioma technique). The addition of SAM-6 to tumor cells leads to an increase in the intracellular accumulation of neutral lipids, followed by tumor cell apoptosis. The antibody SAM-6 does not react with noncancerous human epithelial and fibroblastic cells, because the M(r) 140000 membrane molecule, recognized by the antibody, is specifically expressed on human malignant cells. The antibody is coded by the germ-line genes IgHV3-30.3*01 and IgLV3-1*01 and is a component of the innate immunity to cancer. In this article, we describe an antibody-induced tumor-specific cell death, named lipoptosis. This is, to our knowledge, the first description of this specific form of lipo-apoptosis as an antibody-mediated mechanism of tumor cell killing.

Diphtheria toxin-induced autophagic cardiomyocyte death plays a pathogenic role in mouse model of heart failure

It is still not clear whether loss of cardiomyocytes through programmed cell death causes heart failure. To clarify the role of cell death in heart failure, we generated transgenic mice (TG) that express human diphtheria toxin receptor in the hearts. A mosaic expression pattern of the transgene was observed, and the transgene-expressing cardiomyocytes (17.3% of the total cardiomyocytes) were diffusely scattered throughout the ventricles. Intramuscular injection of diphtheria toxin induced complete elimination of the transgene-expressing cardiomyocytes within 7 days, and approximately 80% of TG showed pathophysiological features characteristic of heart failure and were dead within 14 days. Degenerated cardiomyocytes of the TG heart showed characteristic features indicative of autophagic cell death such as up-regulated lysosomal markers and abundant autophagosomes containing cytosolic organelles like cardiomyocytes of human dilated cardiomyopathy. The heart failure-inducible TG are a useful model for dilated cardiomyopathy, and provided evidence indicating that myocardial cell loss through autophagic cell death plays of a causal role in the pathogenesis heart failure.

Taurine inhibits apoptosis by preventing formation of the Apaf-1/caspase-9 apoptosome

Cardiomyocyte apoptosis contributes to cell death during myocardial infarction. One of the factors that regulate the degree of apoptosis during ischemia is the amino acid taurine. To study the mechanism underlying the beneficial effect of taurine, we examined the interaction between taurine and mitochondria-mediated apoptosis using a simulated ischemia model with cultured rat neonatal cardiomyocytes sealed in closed flasks. Exposure to medium containing 20 mM taurine reduced the degree of apoptosis following periods of ischemia varying from 24 to 72 h. In the untreated group, simulated ischemia for 24 h led to mitochondrial depolarization accompanied by cytochrome c release. The apoptotic cascade was also activated, as evidenced by the activation of caspase-9 and -3. Taurine treatment had no effect on mitochondrial membrane potential and cytochrome c release; however, it inhibited ischemia-induced cleavage of caspase-9 and -3. Taurine loading also suppressed the formation of the Apaf-1/caspase-9 apoptosome and the interaction of caspase-9 with Apaf-1. These findings demonstrate that taurine effectively prevents myocardial ischemia-induced apoptosis by inhibiting the assembly of the Apaf-1/caspase-9 apoptosome.

Alterations in apoptosis regulatory factors during hypertrophy and heart failure

Cardiac hypertrophy from pathological stimuli often proceeds to heart failure, whereas cardiac hypertrophy from physiological stimuli does not. In this study, physiological hypertrophy was created by a daily exercise regimen and pathological hypertrophy was created from a high-salt diet in Dahl salt-sensitive rats. The rats continued on a high-salt diet progressed to heart failure associated with an increased rate of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cardiomyocytes. We analyzed primary cultures of these hearts and found that only cardiomyocytes made hypertrophic by a pathological stimulus show increased sensitivity to apoptosis. Examination of the molecular changes associated with these distinct types of hypertrophy revealed changes in Bcl-2 family members and caspases favoring survival during physiological hypertrophy. However, in pathological hypertrophy, there were more diffuse proapoptotic changes, including changes in Fas, the Bcl-2 protein family, and caspases. Therefore, we speculate that this increased sensitivity to apoptotic stimulation along with proapoptotic changes in the apoptosis program may contribute to the development of heart failure seen in pathological cardiac hypertrophy.

Urinary biopyrrins levels are elevated in relation to severity of heart failure

OBJECTIVES

We investigated the relationship between the urinary levels of biopyrrins and the severity of heart failure (HF).

BACKGROUND

Oxidative stress is evident in heart disease and contributes to the development of ventricular dysfunction in patients with HF. Biopyrrins, oxidative metabolites of bilirubin, have been discovered as potential markers of oxidative stress.

METHODS

We measured the levels of urinary biopyrrins and plasma B-type natriuretic peptide (BNP) in 94 patients with HF (59 men; mean age 65 years) and 47 control subjects (30 men; mean age 65 years). Urine and blood samples were taken after admission in all subjects. Further urine samples were obtained from 40 patients after treatment of HF.

RESULTS

The urinary biopyrrins/creatinine levels (micromol/g creatinine) were the highest in patients in New York Heart Association (NYHA) class III/IV (n = 26; 17.05 [range 7.85 to 42.91]). The urinary biopyrrins/creatinine levels in patients in NYHA class I (n = 35; 3.46 [range 2.60 to 5.42]) or II (n = 33; 5.39 [range 3.37 to 9.36]) were significantly higher than those in controls (2.38 [range 1.57 to 3.15]). There were significant differences in urinary biopyrrins/creatinine levels among each group. The treatment of HF significantly decreased both urinary biopyrrins/creatinine levels (from 7.43 [range 3.84 to 17.05] to 3.07 [range 2.21 to 5.71]) and NYHA class (from 2.5 +/- 0.1 to 1.7 +/- 0.1). Log biopyrrins/creatinine levels were positively correlated with log BNP levels (r = 0.650, p < 0.001).

CONCLUSIONS

These results indicate that urinary biopyrrins levels are increased in patients with HF and are elevated in proportion to its severity.

Minoxidil Attenuates Ischemia-Induced Apoptosis in Cultured Neonatal Rat Cardiomyocytes

The effects of minoxidil (a mitochondrial K+(ATP) channel opener) on ischemia-induced necrosis and apoptosis were examined using a cardiomyocyte model of simulated ischemia, since mitochondrial K+(ATP) channel openers have been suggested to be involved in the mechanisms of cardioprotective action against ischemia/reperfusion injury. In the absence of minoxidil, simulated ischemia led to cellular release of creatine phosphokinase (CPK), morphologic degeneration, and beating cessation within 24 to 72 hours. Based on the Hoechst 33258 staining pattern, a significant number of cells placed in sealed flasks underwent apoptosis. Myocytes treated with 5 microM of minoxidil failed to alter the degree of ischemia-induced CPK loss for 48 to 72 hours. However, minoxidil treatment prevented the loss of beating function in many of the ischemic cells, and attenuated the decline in intracellular ATP content after a 48-hour ischemic incubation. The number of nuclear fragmentation was significantly reduced in minoxidil-treated cells after a 72-hour ischemic insult compared with untreated ischemic cells. This effect was blocked by the mitochondrial K+(ATP) channel antagonist 5-HD. The data suggest that minoxidil renders the cell resistant to ischemia-induced necrosis and apoptosis. The beneficial effects of minoxidil appear to be related to the opening of mitochondrial K+(ATP) channels.

Apoptosis in primary cardiac tumours

Apoptosis, or programmed cell death, is now recognised as an important cellular event during both normal development and specific disease progression. Apoptosis has been suggested to play a critical role in several cardiovascular diseases, but has not yet been identified as a major influence in primary cardiac tumours. A retrospective review of the achieved material at Chang Gung Memorial Hospital revealed seven patients with cardiac myxoma and one with a tumour originating from the crista terminalis, from January 2002 to December 2002. The medical chart, surgical pathology reports and microscopic slides were available in all cases. All patients, including eight cardiac myxomas and one tumour from crista terminalis, were assessed for apoptosis by terminal deoxynucleotidyl transferase nick-end labelling assay. In this study, apoptosis is well documented in all seven myxoma and has even been reported in tumour from the crista terminalis. Interestingly, apoptosis appears related to the nature of the cell properties rather than the incidence of embolism. In conclusion, apoptosis is important in the progression of the primary cardiac tumours, but the mechanism of cardiac tumour regression still remains uncertain.

Acidosis-induced apoptosis in human and porcine heart

BACKGROUND

Acidosis-mediated injury to cardiac myocytes during surgery may lead to progressive heart failure. The nature of this injury, although not well defined, may be caused by induction of apoptosis in cardiac myocytes. We applied fluorescence imaging and biochemical techniques to assess apoptosis in cardiac myocytes excised from human patients and porcine subjects maintained on cardiopulmonary bypass to demonstrate the relationship between acidosis and apoptosis.

METHODS

Multiphoton microscopy was used to image fluorescence signals generated in myocytes deep within atrial and ventricular biopsies for identification of apoptotic changes. The biopsies, obtained during cardiac surgery, were subjected to ex vivo or in vivo acidosis. Proapoptotic markers such as exposure of phosphatidyl serine, cytochrome c, apoptotic protease-activating factor-1, and caspase-3 were identified using fluorescence-based imaging and biochemical assays.

RESULTS

Within 30 minutes of storage in low pH (<7) buffers, apoptosis was detected in human atrial samples, the severity of which correlated well with low pH. Apoptosis was also detected in atrial and ventricular biopsy samples obtained from three porcine subjects maintained on cardiopulmonary bypass and undergoing 110 minutes of aortic cross-clamp and 10 minutes of reperfusion, in which the cardiac pH was 6.36, 7.14, and 7.48. The apoptosis level detected in postacidotic reperfused cardiac tissue was pH dependent and approximately threefold greater than the precross-clamp levels.

CONCLUSIONS

Using fluorescence multiphoton microscopy and biochemical techniques we have assessed a direct correlation between low pH and induction of apoptosis in cardiac samples obtained both from human patients undergoing cardiac surgery and porcine subjects maintained on cardiopulmonary bypass simulating cardiac surgery.

Taurine prevents the ischemia-induced apoptosis in cultured neonatal rat cardiomyocytes through Akt/caspase-9 pathway

Activated Akt kinase has been proposed as a central role in suppressing apoptosis by modulating the activities of Bcl-2 family proteins and/or caspase-9. To study the mechanism underlying the anti-apoptotic effect of taurine, the interaction between taurine and Akt/caspase-9 pathway was examined using a simulated ischemia model with cultured rat neonatal cardiomyocytes sealed in closed flasks. Taurine (20mM) treatment attenuated simulated ischemia-induced decline in the activity of Akt. Although taurine treatment had no effect on the expression of Bcl-2 in mitochondria and the level of cytosolic cytochrome c, it inhibited ischemia-induced cleavage of caspases 9 and 3. Moreover, adenovirus transfer of the dominant negative form of Akt objected taurine-mediated anti-apoptotic effects, cancelling the suppression of caspase-9 and caspase-3 activities by taurine. These findings provide the first evidence that taurine inhibits ischemia-induced apoptosis in cardiac myocytes with the increase in Akt activities, by inactivating caspase-9.

Apoptosis and heart failure: mechanisms and therapeutic implications

A large volume of experimental data supports the presence of apoptosis in failing hearts. Apoptosis in many types of cells results from exposure to cytotoxic cytokines or damaging agents. Cytotoxic cytokines such as tumor necrosis factor (TNF)-alpha or Fas ligand (FasL) bind to their receptors to activate caspase-8, while damaging agents can cause mitochondrial release of cytochrome c, which can initiate activation of caspase-9. Caspase-8 or -9 can activate a cascade of caspases. The p53 protein is often required for damaging agent-induced apoptosis. An imbalance of proapoptotic factors versus prosurvival factors in the bcl-2 family precedes the activation of caspases. Given these typical changes of apoptosis found in many cell types, the apoptotic pathway in cardiomyocytes is somewhat unconventional since in vivo experimental data reveal that apoptosis does not appear to be controlled by TNF-alpha, FasL, p53 or decrease of bcl-2. In vitro and in vivo studies suggest the importance of mitochondria and activation of caspases in cell death occurring in failing hearts. Oxidants, excessive nitric oxide, angiotensin II and catecholamines have been shown to trigger apoptotic death of cardiomyocytes. Eliminating these inducers reduces apoptosis and reverses the loss of contractile function in many cases, indicating the feasibility of the pharmacological application of antioxidants, nitric oxide synthetase inhibitors, ACE inhibitors, angiotensin II receptor antagonists and adrenergic receptor antagonists. Most inducers of apoptosis initiate a cascade of signaling events, including activation of the p38 mitogen-activated protein kinase. Small molecule inhibitors of p38 have been shown to be capable of preventing apoptosis and loss of contractile function associated with ischemia and reperfusion. Although further experimental work is needed, several studies have already indicated the beneficial effect of caspase inhibitors against cell loss and features of heart failure in vitro and in vivo. These studies indicate the importance of inhibiting apoptosis in therapeutic interventions against heart failure.

Transgenic rescue of neurogenic atrophy in the nmd mouse reveals a role for Ighmbp2 in dilated cardiomyopathy

Immunoglobulin mu binding protein 2 (IGHMBP2) is a DNA/RNA helicase with a putative role in transcriptional regulation and splicing. A recessive mutation of the Ighmbp2 gene in neuromuscular degeneration (nmd) mice causes progressive neurogenic atrophy of limb muscles. Affected mice show significant loss of motor neurons with large caliber axons and a moderate reduction of neurons with small caliber axons in the ventral nerve roots of the spinal cord. To investigate the role of Ighmbp2 in the pathogenesis of neuromuscular degeneration, we generated two independent lines of transgenic mice expressing the full-length Ighmbp2 cDNA specifically in neurons. Histopathological evaluation of L4 ventral nerve roots revealed that transgenic expression of the Ighmbp2 cDNA prevented primary motor neuron degeneration, while restoring the normal axonal morphology and density in nmd mice. A similar neuronal improvement is found in mutant mice carrying the CAST/EiJ-derived modifier of nmd (Mnm(C)). Intriguingly, both the transgenic and modified nmd mice went on to develop a previously unobserved cardiac and skeletal myopathy. Necropsy of nmd mice in end-stage heart failure revealed a primary dilated cardiomyopathy with secondary respiratory failure that was confirmed by in vivo ECG and echocardiographic measures. Our results suggest that reduced levels of IGHMBP2 in nmd mice compromise the integrity and function not only of motor neurons but also of skeletal and cardiac myocytes. These findings highlight the important role of IGHMBP2 in the maintenance and survival of these terminally differentiated cell types.