Caspase-3 inhibition preserves myocardial geometry and long-term function after infarction

Cardiomyocyte-Specific COMMD1 Deletion Suppresses Ischemia-Induced Myocardial Apoptosis

Copper metabolism MURR domain 1 (COMMD1) increases in ischemic myocardium along with suppressed contractility. Cardiomyocyte-specific deletion of COMMD1 preserved myocardial contractile function in response to the same ischemic insult. This study was undertaken to test the hypothesis that cardiomyocyte protection in COMMD1 myocardium is responsible for the functional preservation of the heart in response to ischemic insult. After ischemic insult, there were significantly more cardiomyocytes in the cardiomyocyte-specific COMMD1 deletion myocardium than that in WT controls. This preservation of cardiomyocytes was paralleled by a significant suppression of apoptosis in the COMMD1 deletion myocardium compared to controls. In searching for the mechanistic understanding of the anti-apoptotic effect of COMMD1 deletion, we found the anti-apoptotic Bcl-2 mRNA and protein expression were upregulated and the pro-apoptotic Bax mRNA and protein expression were downregulated. The critical transcription factor RelA, maintaining a high ratio between Bcl-2 and Bax for anti-apoptotic action, was suppressed by ischemia, but was rescued in the COMMD1 deletion myocardium. Because COMMD1 is critically involved in RelA ubiquitination and degradation, the data obtained here demonstrate that COMMD1 deletion leads to RelA preservation in ischemic myocardium, promoting the Bcl-2 anti-apoptotic pathway and suppressing the Bax pro-apoptotic pathway, and in combination, leading to protection of cardiomyocytes from ischemia-induced apoptosis.

Mitochondria and Inflammation: Cell Death Heats Up

Mitochondrial outer membrane permeabilization (MOMP) is essential to initiate mitochondrial apoptosis. Due to the disruption of mitochondrial outer membrane integrity, intermembrane space proteins, notably cytochrome c, are released into the cytosol whereupon they activate caspase proteases and apoptosis. Beyond its well-established apoptotic role, MOMP has recently been shown to display potent pro-inflammatory effects. These include mitochondrial DNA dependent activation of cGAS-STING signaling leading to a type I interferon response. Secondly, via an IAP-regulated mechanism, MOMP can engage pro-inflammatory NF-κB signaling. During cell death, apoptotic caspase activity inhibits mitochondrial dependent inflammation. Importantly, by engaging an immunogenic form of cell death, inhibiting caspase function can effectively inhibit tumorigenesis. Unexpectedly, these studies reveal mitochondria as inflammatory signaling hubs during cell death and demonstrate its potential for therapeutic exploitation.

The protective effect of activating Nrf2 / HO-1 signaling pathway on cardiomyocyte apoptosis after coronary microembolization in rats

BACKGROUND

Myocardial apoptosis is closely related to myocardial injury caused by coronary microembolization (CME).Nuclear factor erythroid 2-like (Nrf2) has been taken into account as an inhibitor of apoptosis in various tissues. Thus, this research aims to investigate which part Nrf2/HO-1 signaling pathway plays in myocardial apoptosis process following the effect of CME on rats.

METHODS

Separate 40 rats then form them into a group of shame, a group of CME, a group of CME plus AAV-Nrf2(AAV-Nrf2 (CME) group) and a group of CME plus AAV-control (AAV-control (CME) group) stochastically and averagely. Rat CME was established by injecting into the left ventricular chamber, with or without pretreatment of adeno-associated virus Nrf2 (AAV-Nrf2). Echocardiological measurements, using Terminal-deoxynucleoitidyl Transferase Mediated Nick End Labeling (TUNEL) to stain, conducting Quantitative PCR in real time (RT-PCR) as well as Western blotting to evaluate the impacts of them functionally, morphologically and molecularly in CME.

RESULTS

Nrf2 decreased in cardiomyocytes after CME. Upregulation of Nrf2 inside an organism through AAV connect to improving the function of heart as well as attenuating myocardial apoptosis, following the restrain of proapoptotic mRNAs and proteins like caspase-3, caspase-9 and bax expressing as well as the increase of antiapoptotic mRNA and proteins like HO-1 and bcl-2 expressing.

CONCLUSION

Activation of Nrf2/HO-1 pathway can improve CME-induced cardiac dysfunction effectively and also reduce the myocardial apoptosis.

Role of soluble Fas ligand in myocardial remodeling, severity and outcomes of chronic heart failure

Aim. To reveal the specific features of Fas ligand-mediated ischemic myocardial remodeling and those of chronic heart failure (CHF) development during a 12-month prospective follow-up. Subjects and methods. A total of 94 patients with ischemic CHF were examined and divided into 3 groups according to NYHA Functional Class (FC): 1) FC II CHF in 35 patients; 2) FC III CHF in 31; 3) FC IV CHF in 28. According to the results of the 12-month follow-up, the patients were randomized into 2 groups: A) 49 patients with a favorable course of cardiovascular disease and B) 45 patients with its poor course. Serum soluble Fas ligand (sFas-L) levels were measured by enzyme immunoassay. Results. In the patients with CHF, the baseline sFas-L levels substantially exceeded that in the control group by 3—6 times (p

Trimetazidine pretreatment inhibits myocardial apoptosis and improves cardiac function in a Swine model of coronary microembolization

OBJECTIVE

Trimetazidine (TMZ) is a well-known anti-ischemic agent; however, its efficacy and mechanism of cardioprotection on coronary microembolization (CME) are largely unknown. The present study was undertaken to determine whether TMZ pretreatment could attenuate myocardial apoptosis and improve cardiac function in a swine model of CME.

METHODS

Fifteen swine were randomly and equally divided into a sham-operated (control) group, CME group and CME plus TMZ (TMZ) group. CME was induced by injecting inert plastic microspheres (42 μm in diameter) into the left anterior descending artery. For the control group, the same dose of normal saline was substituted for the microspheres, and the TMZ group was pretreated with TMZ 30 min before microsphere injection. Cardiac function was assessed by echocardiography, myocardial apoptosis was detected by TUNEL staining, and the expression levels of cleaved caspase-9/3 were measured by Western blot 12 h after operation.

RESULTS

Compared to the control group, cardiac function in the CME group was significantly decreased (p < 0.05); however, TMZ pretreatment showed significantly improved cardiac function as compared to the CME group (p < 0.05). The myocardial apoptotic rate and the expression levels of cleaved caspase-9/3 increased remarkably in CME group as compared with the control group (p < 0.001). Again, TMZ pretreatment significantly reduced the apoptotic rate and also the expression levels of cleaved caspase-9/3 (p < 0.001).

CONCLUSION

The present study demonstrated that TMZ pretreatment could significantly inhibit CME-induced myocardial apoptosis and improve cardiac function, and that the cardioprotective effect appeared to be mediated by the blockade of the mitochondrial apoptotic pathway. These results emphasize the importance of TMZ pretreatment in the therapy of CME-induced myocardial injury.

Intrinsic-mediated caspase activation is essential for cardiomyocyte hypertrophy

Cardiomyocyte hypertrophy is the cellular response that mediates pathologic enlargement of the heart. This maladaptation is also characterized by cell behaviors that are typically associated with apoptosis, including cytoskeletal reorganization and disassembly, altered nuclear morphology, and enhanced protein synthesis/translation. Here, we investigated the requirement of apoptotic caspase pathways in mediating cardiomyocyte hypertrophy. Cardiomyocytes treated with hypertrophy agonists displayed rapid and transient activation of the intrinsic-mediated cell death pathway, characterized by elevated levels of caspase 9, followed by caspase 3 protease activity. Disruption of the intrinsic cell death pathway at multiple junctures led to a significant inhibition of cardiomyocyte hypertrophy during agonist stimulation, with a corresponding reduction in the expression of known hypertrophic markers (atrial natriuretic peptide) and transcription factor activity [myocyte enhancer factor-2, nuclear factor kappa B (NF-κB)]. Similarly, in vivo attenuation of caspase activity via adenoviral expression of the biologic effector caspase inhibitor p35 blunted cardiomyocyte hypertrophy in response to agonist stimulation. Treatment of cardiomyocytes with procaspase 3 activating compound 1, a small-molecule activator of caspase 3, resulted in a robust induction of the hypertrophy response in the absence of any agonist stimulation. These results suggest that caspase-dependent signaling is necessary and sufficient to promote cardiomyocyte hypertrophy. These results also confirm that cell death signal pathways behave as active remodeling agents in cardiomyocytes, independent of inducing an apoptosis response.

Caspase-3 as a therapeutic target for heart failure

INTRODUCTION

Heart failure is a condition with significant morbidity and high mortality. It is likely to become unmanageable in the rapidly increasing aging population, due mainly to lack of effective treatment. Apoptosis is one of the major mechanisms causing cardiomyocyte loss in the failing hearts of both human patients and animal models. Thus, anti-apoptosis has been proposed as a provocative new concept for preventive and therapeutic strategies for heart failure.

AREAS COVERED

This review summarizes evidence that apoptotic cells in heart are not completely committed to death. They are likely to be targeted for reversing the cardiac dysfunction. Drugs that inhibit the progression of apoptosis help restore systolic function, reverse remodeling or even prevent heart failure. Inhibitors of caspase-3, the major executors of apoptosis, have been shown to hold great promises for apoptosis interruption in heart tissues.

EXPERT OPINION

Although the underlying cause and the pathophysiological role of apoptosis remain elusive, antiapoptotic therapy has emerged as an enigma for heart failure. Caspases promote the progressive loss of contractile function in heart failure by facilitating the degradation of myofibrillar proteins. Selective inhibition of the proteolytic functions of caspase-3 may represent an attractive approach to attenuate or reverse heart failure.

The antiapoptotic effect of granulocyte colony-stimulating factor reduces infarct size and prevents heart failure development in rats

BACKGROUND/AIM

Granulocyte colony-stimulating factor (G-CSF) reduces myocardial injury and improves cardiac function after myocardial infarction (MI). We investigated the early alterations provided by G-CSF and the chronic repercussions in infarcted rats.

METHODS

Male Wistar rats (200-250g) received vehicle (MI) or G-CSF (MI-GCSF) (50 μg/kg, sc) at 7, 3 and 1 days before MI surgery. Afterwards MI was produced and infarct size was measured 1 and 15 days after surgery. Expression of anti- and proapoptotic proteins was evaluated immediately before surgery. 24 hours after surgery, apoptotic nuclei were evaluated. Two weeks after MI, left ventricular (LV) function was evaluated, followed by in situ LV diastolic pressure-volume evaluation.

RESULTS

Infarct size was decreased by 1 day pre-treatment before occlusion (36±2.8 vs. 44±2.1% in MI; P<0.05) and remained reduced at 15 days after infarction (28±2.2 vs. 36±1.4% in MI; P<0.05). G-CSF pretreatment increased Bcl-2 and Bcl-xL protein expression, but did not alter Bax in LV. Apoptotic nuclei were reduced by treatment (Sham: 0.46±0.42, MI: 15.5±2.43, MI-GCSF: 5.34±3.34%; P<0.05). Fifteen days after MI, cardiac function remained preserved in G-CSF pretreated rats. The LV dilation was reduced in MI-G-CSF group as compared to MI rats, being closely associated with infarct size.

CONCLUSION

The early beneficial effects of G-CSF were essentials to preserve cardiac function at a chronic stage of myocardial infarction.

Promotion of CHIP-Mediated p53 Degradation Protects the Heart From Ischemic Injury

Rationale : The number of patients with coronary heart disease, including myocardial infarction, is increasing and novel therapeutic strategy is awaited. Tumor suppressor protein p53 accumulates in the myocardium after myocardial infarction, causes apoptosis of cardiomyocytes, and plays an important role in the progression into heart failure.

Objectives : We investigated the molecular mechanisms of p53 accumulation in the heart after myocardial infarction and tested whether anti-p53 approach would be effective against myocardial infarction.

Methods and Results : Through expression screening, we found that CHIP (carboxyl terminus of Hsp70-interacting protein) is an endogenous p53 antagonist in the heart. CHIP suppressed p53 level by ubiquitinating and inducing proteasomal degradation. CHIP transcription was downregulated after hypoxic stress and restoration of CHIP protein level prevented p53 accumulation after hypoxic stress. CHIP overexpression in vivo prevented p53 accumulation and cardiomyocyte apoptosis after myocardial infarction. Promotion of CHIP function by heat shock protein (Hsp)90 inhibitor, 17-allylamino-17-demethoxy geldanamycin (17-AAG), also prevented p53 accumulation and cardiomyocyte apoptosis both in vitro and in vivo. CHIP-mediated p53 degradation was at least one of the cardioprotective effects of 17-AAG.

Conclusions : We found that downregulation of CHIP level by hypoxia was responsible for p53 accumulation in the heart after myocardial infarction. Decreasing the amount of p53 prevented myocardial apoptosis and ameliorated ventricular remodeling after myocardial infarction. We conclude that anti-p53 approach would be effective to treat myocardial infarction.

Apoptosis as a mechanism for the elimination of cardiomyocytes after acute myocardial infarction

Apoptosis is recognized as a mechanism of cell loss in the setting of acute myocardial infarction (AMI). Whether it contributes to myocyte elimination late after AMI has not yet been confirmed. We attempted to identify the features of apoptosis in myocytes that survived AMI. A search for ongoing apoptosis was performed in samples obtained from 38 human hearts: group I (n = 10), noncardiac death (control); and group II (n = 28), left ventricular aneurysm (in 20 patients, the samples were collected during aneurysmectomy and from 8 at autopsy). The morphometric evaluation included the degree of cellular hypertrophy, density of the capillary network, extent of myocytolysis, and features of apoptosis. Immunohistochemistry for caspase-3 and Bcl-2 was used as a prerequisite for transmission electron microscopy. Slides showing the strongest reaction for caspase-3 and negative for Bcl-2 were selected for transmission electron microscopy. CD-34 immunohistochemistry was used to quantify the capillary density. A significant reduction in capillary density was observed compared to the control group (1,085.6 + or - 205.0/mm(2) vs 2,968.7 + or - 457.3/mm(2); p <0.001). Myocytes that survived the acute phase of AMI were significantly hypertrophied (24.5 + or - 4.7 microm vs 14.5 + or - 1.6 microm; p <0.001) and showed a moderate to severe degree of myocytolysis. The average intensity score of the immunohistochemistry reactions for caspase-3 was 8.2 + or - 3.8. Using transmission electron microscopy, apoptotic bodies were found in caspase-3-positive samples. In conclusion, the expression of caspase-3 and the presence of apoptotic bodies confirmed apoptosis as a common pathway of cardiomyocyte death in the setting of a limited blood supply after AMI.

Caspase-independent cell death: leaving the set without the final cut

Apoptosis is dependent upon caspase activation leading to substrate cleavage and, ultimately, cell death. Although required for the apoptotic phenotype, it has become apparent that cells frequently die even when caspase function is blocked. This process, termed caspase-independent cell death (CICD), occurs in response to most intrinsic apoptotic cues, provided that mitochondrial outer membrane permeabilization has occurred. Death receptor ligation can also trigger a form of CICD termed necroptosis. In this review, we will examine the molecular mechanisms governing CICD, highlight recent findings demonstrating recovery from conditions of CICD and discuss potential pathophysiological functions of these processes.

Caspases in myocardial infarction

The discovery of apoptosis sheds a new light on the role of cell death in myocardial infarction and other cardiovascular diseases. There is mounting evidence that apoptosis plays an important role at multiple points in the evolution of myocardial infarction, and comprises not only cardiomyocytes but also inflammatory cells, as well as cells of granulation tissue and fibrous tissue. It appears that apoptosis contributes to cardiomyocyte loss in the border zone and in remote myocardium in the early phase, as well as months after myocardial infarction, thus playing a role in remodeling and development of heart failure after myocardial infarction. Apoptosis, being a highly regulated process, is a potential target for therapeutic intervention. Caspases are the key effector molecules in apoptosis, and are therefore a particularly attractive target for pharmacological modulation of apoptosis. Although several potential therapeutic agents have been tested in animal models of ischemia/reperfusion heart injury with some success, nearly none of the specific antiapoptotic agents have reached the stage of clinical research.

Bax deficiency reduces infarct size and improves long-term function after myocardial infarction

We have previously found that, following myocardial ischemia/reperfusion injury, isolated hearts from bax gene knockout mice [Bax(-/-)] exhibited higher cardioprotection than the wild-type. We here explore the effect of Bax(-/-), following myocardial infarction (MI) in vivo. Homozygotic Bax(-/-) and matched wild-type were studied. Mice underwent surgical ligation of the left anterior descending coronary artery (LAD). The progressive increase in left-ventricular end diastolic diameter, end systolic diameter, in Bax(-/-) was significantly smaller than in Bax(+/+) at 28 d following MI (p < 0.03) as seen by echocardiography. Concomitantly, fractional shortening was higher (35 +/- 4.1% and 27 +/- 2.5%, p < 0.001) and infarct size was smaller in Bax(-/-) compared to the wild-type at 28 days following MI (24 +/- 3.7 % and 37 +/- 3.3%, p < 0.001). Creatine kinase and lactate dehydrogenase release in serum were lower in Bax(-/-) than in Bax(+/+) 24 h following MI. Caspase 3 activity was elevated at 2 h after MI only in the wild-type, but reduced to baseline values at 1 and 28 d post-MI. Bax knockout mice hearts demonstrated reduced infarct size and improved myocardial function following permanent coronary artery occlusion. The Bax gene appears to play a significant role in the post-MI response that should be further investigated.

The Possible Role of Caspase-3 in Pathological and Physiological Cardiac Hypertrophy in Rats

The present study has been designed to investigate the effect of Ac-DEVD-CHO, a specific caspase-3 inhibitor in partial abdominal aortic constriction for 4 week-induced pathological and chronic swimming training for 8 week-induced physiological cardiac hypertrophy. Ac-DEVD-CHO (2 mg/kg intraperitoneally, day(-1)) treatment was started three days before partial abdominal aortic constriction and chronic swimming test and it was continued for 4 weeks in partial abdominal aortic constriction and 8 weeks in chronic swimming test experimental model. The left ventricular (LV) function and LV hypertrophy were assessed by measuring LV developed pressure, dp/dt(max), dp/dt(min), ratio of LV weight to body weight, LV wall thickness, LV collagen content, protein content and RNA concentration. Further, venous pressure and mean arterial blood pressure were recorded. The partial abdominal aortic constriction but not chronic swimming test produced LV dysfunction by decreasing LV developed pressure, dp/dt(max), dp/dt(min.)and increasing LV collagen content. Further, partial abdominal aortic constriction and chronic swimming test were noted to produce LV hypertrophy by increasing ratio of LV weight to body weight, LV wall thickness, LV protein content and LV RNA concentration. Moreover, in contrast to chronic swimming test, partial abdominal aortic constriction has significantly increased venous pressure and mean arterial blood pressure. The Ac-DEVD-CHO has markedly attenuated partial abdominal aortic constriction-induced LV dysfunction, LV hypertrophy, increase in venous pressure and mean arterial blood pressure. However it did not modulate chronic swimming test-induced LV hypertrophy. These results have implicated caspase-3 in partial abdominal aortic constriction-induced LV dysfunction and pathological cardiac hypertrophy. However, caspase-3 may not be involved in chronic swimming test-induced physiological cardiac hypertrophy.

Redox stress and the contributions of BH3-only proteins to infarction

Ischemia followed by reperfusion is the primary cause of tissue injury and infarction during heart attack and stroke. The initiating stimulus is believed to involve reactive oxygen species that are produced during reperfusion when electron transport resumes in the mitochondria after suppression by ischemia. Programmed death has been shown to be a significant component of infarction, and evidence indicates that multiple pathways are initiated during both ischemia and reperfusion phases. Major infarction is preceded by severe ischemia that includes hypoxia, intracellular acidosis, glucose depletion, loss of ATP, and elevation of cytoplasmic calcium. The superimposition of a reactive oxygen surge on the latter condition provides the impetus for maximal damage. Compelling evidence implicates mitochondria not only as the source of initiating ROS but also as the focal sensors that translate the redox stress signal into a cellular-death response. Pivotal to this response are the BH3-only proteins that are activated by death signals and regulate mitochondrial communication with executioner proteins in the cytoplasm. The BH3-only proteins do this by controlling the activity of pores and channels in the outer mitochondrial membrane. To date at least six BH3-only proteins have been shown to contribute to ischemia-reperfusion death pathways in heart and/or brain; these include Bnip3, PUMA, Bid, Bad, HGTD-P, and Noxa. Here we review the evidence for these cell-death pathways and discuss their relevance to ischemic disease and infarction.

Transcriptome analysis of the ischemia-reperfused remodeling myocardium: temporal changes in inflammation and extracellular matrix

cDNA microarray analysis was performed to screen 15,000 genes and expressed sequence tags (ESTs) to identify changes in the ischemia-reperfused (I-R) rat myocardial transcriptome in the early ( day 2) and late ( day 7) inflammatory phases of acute myocardial infarction. Lists of candidate genes that were affected by I-R transiently (2 or 7 days only) or on a more sustained basis (2 and 7 days) were derived. The candidate genes represented three major functional categories: extracellular matrix, apoptosis, and inflammation. To expand on the findings from microarray studies that dealt with the two above-mentioned time points, tissues collected from days 0, 0.25, 2, 3, 5, and 7 after reperfusion were examined. Acute myocardial infarction resulted in upregulation of IL-6 and IL-18. Genes encoding extracellular matrix proteins such as types I and III collagen were upregulated in day 2, and that response progressively grew stronger until day 7 after I-R. Comparable response kinetics was exhibited by the candidate genes of the apoptosis category. Caspases-2, -3, and -8 were induced in response to acute infarction. Compared with the myocardial tissue from the sham-operated rats, tissue collected from the infarct region stained heavily positive for the presence of active caspase-3. Laser microdissection and pressure catapulting technology was applied to harvest infarct and adjacent noninfarct control tissue from a microscopically defined region in the rat myocardium. Taken together, this work presents the first evidence gained from the use of DNA microarrays to understand the molecular mechanisms implicated in the early and late inflammatory phases of the I-R heart.

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.

Acute myocardial infarction and heart failure: Role of apoptosis

Apoptosis is a key pathologic feature in acute myocardial infarction and heart failure. Experimental animal studies have shown beneficial effects of inhibiting apoptosis. Understanding the mechanisms involved in the apoptotic cascade may be useful in better understanding of heart failure and its management. Not only in vivo detection of apoptosis may prove clinically useful in the diagnosis and risk stratification of patients with ischemic heart disease, but anti-apoptotic treatments (specific and non-specific) may be effective in the prevention and treatment of post-infarction remodelling and heart failure.