Fas expression and apoptosis correlate with cardiac dysfunction in patients with dilated cardiomyopathy

Doxorubicin induces cardiotoxicity through upregulation of death receptors mediated apoptosis in cardiomyocytes

Doxorubicin is a highly effective anticancer agent but causes cardiotoxicity in many patients. The mechanisms of doxorubicin-induced cardiotoxicity remain incompletely understood. Here we investigated doxorubicin-induced cytotoxicity in human induced pluripotent stem cells-derived cardiomyocytes (iPS-CMs). We found that doxorubicin and related anthracycline agents (e.g., daunorubicin, idarubicin, and epirubicin) significantly upregulated the expression of death receptors (DRs) (TNFR1, Fas, DR4 and DR5) in iPS-derived cardiomyocytes at both protein and mRNA levels. The resulting iPS-CMs cells underwent spontaneous apoptosis which was further enhanced by physiologically relevant death ligands including TNF-related apoptosis inducing ligand (TRAIL). Furthermore, TRAIL potentiated doxorubicin-induced decrease in beating rate and amplitude of iPS-derived cardiomyocytes. These data demonstrate that the induction of death receptors in cardiomyocytes is likely a critical mechanism by which doxorubicin causes cardiotoxicity.

Cardiomyocyte apoptosis is related to left ventricular dysfunction and remodelling in dilated cardiomyopathy, but is not affected by growth hormone treatment

BACKGROUND AND AIMS

Cardiomyocyte apoptosis (CA) is a common feature of end-stage heart failure. We examined whether CA is associated with cardiac dysfunction and remodelling in heart failure due to dilated cardiomyopathy and studied the effect of human growth hormone (hGH) on CA.

METHODS AND RESULTS

We studied 38 patients, included in a phase III multi-center, randomised, double-blind and placebo-controlled trial of biosynthetic hGH treatment in dilated cardiomyopathy, at baseline and after 14 weeks treatment. Twenty-six patients received hGH and 12 received placebo. CA was quantified in endomyocardial biopsies using the TUNEL assay. CA correlated with left ventricular size (r=0.43, p=0.007). Compared to patients with CA below the median of 0.53%, patients with CA above the median had significantly larger left ventricular volumes and lower ejection fractions (EF) by echocardiography (median (interquartile range)) 200 ml (84) vs. 257 ml (134) and 27% (11) vs. 23% (9). Expression of the Fas receptor was associated with a high rate of CA. hGH treatment significantly increased serum IGF-1 levels, but it had no effect on CA or cardiac structure and function.

CONCLUSION

CA is related to left ventricular enlargement and dysfunction in dilated cardiomyopathy. CA is not affected by short-term treatment with hGH.

Granulocyte Colony-Stimulating Factor Reduces Cardiomyocyte Apoptosis and Improves Cardiac Function in Adriamycin-Induced Cardiomyopathy in Rats

BACKGROUND

Cardiomyocyte apoptosis reportedly participates in the occurrence and progression of dilated cardiomyopathy (DCM). Recent studies have shown that granulocyte colony-stimulating factor (G-CSF) enhances bone marrow cells migration to the damaged heart in the DCM model and improves the ultrastructure of the cardiomyocyte in adriamycin (ADR) induced DCM. However, its influence on cardiac pump function and cardiomyocyte apoptosis has not been studied.

METHODS AND MATERIALS

Wistar Rats were randomly grouped into control, ADR, ADR+PBS, ADR+G-CSF group (n = 10). ADR (2.5 mg/kg, 6 times for 2 weeks) was administered intraperitoneally in all rats except the control group. After 2 weeks, the rats in ADR+G-CSF group were injected with G-CSF (50 microg/kg/day for 8 days) subcutaneously. Cardiac function was evaluated by echocardiogram and cardiac catheterization after 4 weeks. Cardiomyocytes apoptosis and apoptosis-related protein Fas were detected by in situ terminal deoxynucleotidyl transferase assay (TUNEL method) and Western blot, respectively.

RESULTS

The ADR and ADR+PBS groups showed significant deteriorations of left ventricular functions and high cardiomyocyte apoptosis index, as well as high Fas expressions. Meanwhile, the ADR+G-CSF group showed significant improvement in LV function, inhibition of cardiomyocyte apoptosis compared with the ADR and ADR+Phosphate-Buffered Saline PBS group. The Fas protein expression was remarkably attenuated as well.

CONCLUSION

Our results suggest that administration of G-CSF inhibited cardiomyocyte apoptosis and Fas protein expression and contributes to improving cardiac pump function in vivo in ADR induced DCM rat model.

Don't lose heart--therapeutic value of apoptosis prevention in the treatment of cardiovascular disease

Cardiovascular disease is a leading cause of death worldwide. Loss of function or death of cardiomyocytes is a major contributing factor to these diseases. Cell death in conditions such as heart failure and myocardial infarction is associated with apoptosis. Apoptotic pathways have been well studied in non-myocytes and it is thought that similar pathways exist in cardiomyocytes. These pathways include death initiated by ligation of membrane-bound death receptors, release of pro-apoptotic factors from mitochondria or stress at the endoplasmic reticulum. The key regulators of apoptosis include inhibitors of caspases (IAPs), the Bcl-2 family of proteins, growth factors, stress proteins, calcium and oxidants. The highly organized and predictive nature of apoptotic signaling means it is amenable to manipulation. A thorough understanding of the apoptotic process would facilitate intervention at the most suitable points, alleviating myocardium decline and dysfunction. This review summarizes the mechanisms underlying apoptosis and the mediators/regulators involved in these signaling pathways. We also discuss how the potential therapeutic value of these molecules could be harnessed.

TNF-related apoptosis-inducing ligand and its decoy receptor osteoprotegerin in nonischemic dilated cardiomyopathy

Apoptosis has been attributed an essential role in dilated cardiomyopathy (DCM) recently. We assessed expression of TNF-related apoptosis-inducing ligand (TRAIL) and its decoy receptor osteoprotegerin (OPG) in men with nonischemic DCM, who underwent coronary angiography and endomyocardial biopsy (EMB) after exclusion of coronary artery disease compared to control patients. TRAIL plasma concentrations were elevated in DCM (p=0.02 vs. controls), and were positively correlated with left ventricular enddiastolic diameter (r=0.15, p=0.04), whereas OPG plasma levels did not differ between both groups (p=0.96). In EMB of DCM patients, TRAIL and OPG protein were detected by immunohistochemistry but not in controls. Furthermore, gene expression in EMB or peripheral blood leukocytes (PBL) of DCM patients assessed by real-time PCR showed an increase of TRAIL mRNA in PBL (p=0.01 vs. controls), whereas OPG mRNA was upregulated in endomyocardial specimens (p<0.001 vs. controls). In conclusion, myocardial overexpression of antiapoptotic OPG in DCM patients may represent a compensatory mechanism to limit systemic activation of TRAIL in patients with congestive heart disease.

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.

Possible cause of taurine-deficient cardiomyopathy: potentiation of angiotensin II action

Taurine, an amino acid that exhibits anti-angiotensin II and osmoregulatory activity, is found in very high concentration in the heart. When the intracellular content of taurine is dramatically reduced, the heart develops contractile defects and undergoes an eccentric form of hypertrophy. The development of myocyte hypertrophy has been largely attributed to angiotensin II, whose growth properties are antagonized by taurine. Overt heart failure is usually associated with myocyte death, including death due to angiotensin II-induced apoptosis. However, the effect of taurine deficiency on angiotensin II-induced apoptosis has not been examined. To investigate this effect, taurine-deficient cells, produced by incubating rat neonatal cardiomyocytes with medium containing the taurine transport inhibitor, beta-alanine, were exposed to angiotensin II. The peptide increased terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL) staining and caspase 9 activation more in the taurine-deficient than the normal cell. Angiotensin II also promoted the translocation of protein kinase C (PKC)epsilon and PKCdelta, the expression of Bax, and the activation of c-Jun N-terminal kinase (JNK), effects that were greater in the taurine-deficient cell. However, the data ruled out a role for extracellular signal-related kinase (ERK), Bad, and p38 mitogen-activated protein kinase in the beta-alanine-angiotensin II interaction. Because PKC and JNK affect the expression and phosphorylation state of certain Bcl-2 family members, they appear to contribute to the potentiation of angiotensin II-induced apoptosis by taurine deficiency.

Ghrelin and des-acyl ghrelin inhibit cell death in cardiomyocytes and endothelial cells through ERK1/2 and PI 3-kinase/AKT

Ghrelin is an acyl-peptide gastric hormone acting on the pituitary and hypothalamus to stimulate growth hormone (GH) release, adiposity, and appetite. Ghrelin endocrine activities are entirely dependent on its acylation and are mediated by GH secretagogue (GHS) receptor (GHSR)-1a, a G protein-coupled receptor mostly expressed in the pituitary and hypothalamus, previously identified as the receptor for a group of synthetic molecules featuring GH secretagogue (GHS) activity. Des-acyl ghrelin, which is far more abundant than ghrelin, does not bind GHSR-1a, is devoid of any endocrine activity, and its function is currently unknown. Ghrelin, which is expressed in heart, albeit at a much lower level than in the stomach, also exerts a cardio protective effect through an unknown mechanism, independent of GH release. Here we show that both ghrelin and des-acyl ghrelin inhibit apoptosis of primary adult and H9c2 cardiomyocytes and endothelial cells in vitro through activation of extracellular signal-regulated kinase-1/2 and Akt serine kinases. In addition, ghrelin and des-acyl ghrelin recognize common high affinity binding sites on H9c2 cardiomyocytes, which do not express GHSR-1a. Finally, both MK-0677 and hexarelin, a nonpeptidyl and a peptidyl synthetic GHS, respectively, recognize the common ghrelin and des-acyl ghrelin binding sites, inhibit cell death, and activate MAPK and Akt.These findings provide the first evidence that, independent of its acylation, ghrelin gene product may act as a survival factor directly on the cardiovascular system through binding to a novel, yet to be identified receptor, which is distinct from GHSR-1a.

Lack of apoptosis in patients with progressive external ophthalmoplegia and mutated adenine nucleotide translocator-1 gene

Adenine nucleotide translocator-1 (ANT-1), encoded by chromosome 4 (4q34-35 locus), is a component of the mitochondrial permeability transition pores that are involved in apoptotic mechanisms. We studied muscle biopsies from seven individuals with autosomal dominant progressive external ophthalmoplegia caused by ANT-1 mutations. We found no instance of terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) positivity nor significant expression of apoptosis-related proteins. Furthermore, there was no morphological evidence of apoptosis at the ultrastructural level. Thus, degeneration of muscle in this disorder is nonapoptotic.

Autophagic degeneration as a possible mechanism of myocardial cell death in dilated cardiomyopathy

In failing hearts, cardiomyocytes degenerate and interstitial fibrosis, which indicates cardiomyocyte loss, becomes more prominent in the myocardium. However, the precise mechanism of cardiomyocyte degeneration that leads to cell death is still unclear, although it is presumed that lysosomal function and autophagy play an important role because lysosomal activity increases under stress such as hypoxia. Myocardium that had been resected during partial left ventriculectomy performed in patients with dilated cardiomyopathy (DCM) was examined. Under light microscopy, some cardiomyocytes had a marked scarcity of myofibrils and had prominent cytoplasmic vacuolization. Atrophic and degenerated cardiomyocytes were often observed adjacent to replacement fibrotic tissue. Immunohistochemistry showed positivity for lysosome-associated membrane protein and a lysosomal catheptic enzyme in vacuoles of various sizes in the cardiomyocytes and these lysosomal markers were markedly increased in atrophic and degenerated cardiomyocytes. Electron microscopy revealed that degenerated cardiomyocytes had many vacuoles containing intracellular organelles, such as mitochondria, and were considered to be autophagic vacuoles. In DCM hearts, autophagy appeared to be associated not only with degradation of damaged intracellular organelles but also with progressive destruction of cardiomyocytes. It is possible that autophagic degeneration is one of the mechanisms of myocardial cell death.

Damaged myocytes as detected by the colocalization of DNA fragmentation and tissue transglutaminase and their prognostic significance in enterovirus-associated dilated cardiomyopathy

BACKGROUND

Apoptotic cardiac myocytes have been described in chronic heart failure, but no data exist on the relationship between these 'damaged' myocytes and myocardial detection of enterovirus RNA often associated with dilated cardiomyopathy (DCM).

DESIGN

In patients with idiopathic DCM, endomyocardial biopsy samples were studied for enteroviral RNA by one step reverse transcription-polymerase chain reaction (PCR) and a subsequent hybridization of the PCR product using a Southern blot technique. The endomyocardial biopsies were further investigated for markers of cell damage and apoptosis: DNA fragmentation and expression of tissue-transglutaminase (TTG) in the myocytes using the in-situ endlabelling method or an anti-TTG-staining, respectively. To assess the prognostic significance of these two markers the correlation between the percentage of myocytes positive both for DNA fragmentation and TTG (the index of damaged myocytes) and the hemodynamic course of the patients during a mean follow-up period of 15.9 +/- 6.2 months was investigated prospectively by echocardiography.

RESULTS

In 14 (45%) of the 31 patients with idiopathic DCM, enteroviral RNA was found in the endomyocardial biopsy samples, while 17 patients (55%) were enterovirus-negative. In enterovirus-positive patients, the index of 'damaged' myocytes was significantly lower (10.7 +/- 4.9% vs. 19.2 +/- 8.8%, P = 0.002) and the left ventricular ejection fraction (LVEF) improved significantly (P = 0.00017 vs. P = 0.13) during long-term follow-up. In addition, a weak negative correlation was seen between the index of damaged myocytes and the changes in LVEF in all patients during long-term follow-up (r = - 0.48, P = 0.004).

CONCLUSION

Our results favour the view that enterovirus-positive patients with DCM have less damaged myocytes and a better haemodynamic course than enterovirus-negative patients.

Unresolved issues regarding the role of apoptosis in the pathogenesis of ischemic injury and heart failure

Apoptosis is "suicidal" programmed cell death followed by necrosis, i.e. cellular degradation. This review presents a critical evaluation of the methods used for detection of apoptosis and on data regarding the role of apoptosis in ischemia and heart failure.

METHODS

DNA laddering by electrophoresis and the TUNEL method in histology for the final stage of apoptosis, Annexin V labeling, evidence of caspase activation, cleavage of substrates, measurements of mitochondrial pro-apoptotic and anti-apoptotic factors (Bcl-2, Bax and others) and determination of the mitochondrial transitional pore potential. Much work has been carried out regarding the mechanism and the importance of apoptosis in ischemia and heart failure but many issues still remain unsolved: (1)Time needed for completion of apoptosis from stimulus to DNA fragmentation? (2)Importance of mitochondrial pathway considering the fact that cardiomyocytes contain the highest volume density of mitochondria of all mammalian cells (25% in humans, 37% in mice)? (3)Means of removal of dead cells, disconnection at the intercalated disc from neighbouring myocytes, time frame of this process? (4)Reversibility of apoptosis? (5)Differences between physiological (postnatal differentiation of the conduction system) v pathological apoptotic cell death? (6)Why do cells, under ischemic conditions, die by either apoptosis or oncosis? (7)Is apoptosis an epiphenomenon or a true cause of heart failure? (8)Quantification of the rate of apoptosis in different pathophysiological situations? Clarification of these unresolved issues will then allow an estimation of the importance of apoptosis in cardiac pathophysiology and, if necessary because the role of apoptosis has been established, the development of new therapeutic concepts.

Adenine nucleotide translocase-1, a component of the permeability transition pore, can dominantly induce apoptosis

Here, we describe the isolation of adenine nucleotide translocase-1 (ANT-1) in a screen for dominant, apoptosis-inducing genes. ANT-1 is a component of the mitochondrial permeability transition complex, a protein aggregate connecting the inner with the outer mitochondrial membrane that has recently been implicated in apoptosis. ANT-1 expression led to all features of apoptosis, such as phenotypic alterations, collapse of the mitochondrial membrane potential, cytochrome c release, caspase activation, and DNA degradation. Both point mutations that impair ANT-1 in its known activity to transport ADP and ATP as well as the NH(2)-terminal half of the protein could still induce apoptosis. Interestingly, ANT-2, a highly homologous protein could not lead to cell death, demonstrating the specificity of the signal for apoptosis induction. In contrast to Bax, a proapoptotic Bcl-2 gene, ANT-1 was unable to elicit a form of cell death in yeast. This and the observed repression of apoptosis by the ANT-1-interacting protein cyclophilin D suggest that the suicidal effect of ANT-1 is mediated by specific protein-protein interactions within the permeability transition pore.