Apoptosis: pathophysiology and therapeutic implications for the cardiac surgeon

Melatonin ameliorates myocardial injury by reducing apoptosis and autophagy of cardiomyocytes in a rat cardiopulmonary bypass model

Background

Myocardial injury is a frequent complication after cardiac surgery with cardiopulmonary bypass (CPB). This study aimed to test the hypothesis that melatonin could attenuate myocardial injury in a rat CPB model.

Methods

Eighteen male Sprague-Dawley rats were randomly divided into three groups, n = 6 for each group: the sham operation (SO) group, CPB group and melatonin group. Rats in the SO group underwent cannulation without CPB, rats in CPB group intraperitoneal injected an equal volume of vehicle daily for 7 days before being subjected to CPB and rats in melatonin group intraperitoneal injected 20 mg/kg of melatonin solution daily for 7 days before being subjected to CPB. After 120 min for CPB, the expression levels of plasma interleukin (IL) -6, IL-1β, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), creatine kinase (CK) -MB and cardiac troponin T (cTnT) were measured. Reactive oxygen species (ROS) were detected by dihydroethidium (DHE). Apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining. Mitochondrial damage and autophagosomes were detected by electron microscopy. Apoptosis inducing factor (AIF) was detected by immunofluorescence. The expression of B cell lymphoma/leukemia2 associated X (Bax), B cell lymphoma/leukemia 2 (Bcl-2), cytochrome C (Cyto-C), cleaved caspase-9, AKT, p-AKT, signal transducer and activator of transcription 3 (STAT3), p-STAT3, LC3, P62, mechanistic target of rapamycin kinase (mTOR), p-mTOR and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were determined using western blotting.

Results

Melatonin significantly decreased the levels of IL-1β, IL-6, MDA, CK-MB and cTnT and increased the levels of SOD and GSH-Px, all of which were altered by CPB. Melatonin reduced cardiomyocyte superoxide production, the apoptosis index and autophagy in cardiomyocytes induced by CPB. The AKT, STAT3 and mTOR signaling pathways were activated by melatonin during CPB.

Conclusion

Melatonin may serve as a cardioprotective factor in CPB by inhibiting oxidative damage, apoptosis and autophagy. The AKT, STAT3 and mTOR signaling pathways were involved in this process.

The spectrum of myocardial homeostasis mechanisms in the settings of cardiac surgery procedures (Review)

Classic cardiac surgery, determined through the function of cardiopulmonary bypass machine and myocardial cardioplegic arrest, represents the most controlled scenario for cardiomyocyte homeostatic disturbances due to systemic inflammatory response and myocardial reperfusion injury. An increasing number of studies have demonstrated that myocardial cell homeostasis in cardiac surgery procedures is a sequence of molecularly interrelated and overlapping mechanisms in the form of apoptosis, autophagy and necrosis, which are activated by a plethora of induced inflammatory mediators and gene-related signaling pathways. In this study, we outline the molecular mechanisms of the cardiomyocyte adaptive homeostatic process and the associated clinical implications, in the settings of classic cardiac surgery procedures.

Polymorphisms of extrinsic death receptor apoptotic genes (FAS -670 G>A, FASL -844 T>C) in coronary artery disease

Apoptosis plays an important role in atherogenesis and rupture of vulnerable plaques in coronary artery disease. FAS and FAS ligand (FASL) induce apoptosis when FAS binds to FAS-L. However sFas blocks apoptosis by binding to FAS and FASL or sFasL. The present study is sought to examine the role of extrinsic apoptotic genes (FAS, FASL) polymorphism and serum levels of FAS, FASL in the pathogenesis and susceptibility to CAD in south Indian population. The study included 300 CAD patients and 300 healthy controls. Lipid profiles, sFas, sFasL were estimated by commercially available kits. FAS -670 G>A, FASL -844 T>C genotypes were analyzed by PCR-RFLP. Secondary structures of pre mRNA were analyzed by the Vienna RNA webserver and gene-gene and gene-environment interactions were determined by MDR analysis. Total cholesterol, triglyceride and LDL levels were significantly high in CAD patients compared to the controls. Molecular analysis revealed that the frequency of the AA genotype of FAS (54% vs 27%) and CC genotypes of FASL (10.3% vs 1.3%) were high in CAD patients compared to controls. Secondary structure analysis of FAS and FASL confirmed our molecular analysis. sFas levels were low while serum sFasL were high in CAD patients. MDR analysis revealed synergistic effects of gene polymorphisms and additive effects of epidemiological factors on risk of CAD. Polymorphisms of FAS (-670 G/A), FASL (-844 T/C) and their circulating levels play an important role in the pathology of CAD.

Inflammation, oxidative stress and postoperative atrial fibrillation in cardiac surgery

Postoperative atrial fibrillation (POAF) is a common complication of cardiac surgery that occurs in up to 60% of patients. POAF is associated with increased risk of cardiovascular mortality, stroke and other arrhythmias that can impact on early and long term clinical outcomes and health economics. Many factors such as disease-induced cardiac remodelling, operative trauma, changes in atrial pressure and chemical stimulation and reflex sympathetic/parasympathetic activation have been implicated in the development of POAF. There is mounting evidence to support a major role for inflammation and oxidative stress in the pathogenesis of POAF. Both are consequences of using cardiopulmonary bypass and reperfusion following ischaemic cardioplegic arrest. Subsequently, several anti-inflammatory and antioxidant drugs have been tested in an attempt to reduce the incidence of POAF. However, prevention remains suboptimal and thus far none of the tested drugs has provided sufficient efficacy to be widely introduced in clinical practice. A better understanding of the cellular and molecular mechanisms responsible for the onset and persistence of POAF is needed to develop more effective prediction and interventions.

Genetic maneuvers to ameliorate ventricular function in heart failure: therapeutic potential and future implications

Gene therapy to treat heart failure has evolved into a growing field of investigation yielding remarkable results in preclinical models. Whether these results will persist in clinical trials remains to be seen. However, researchers still face a number of obstacles that need to be overcome before this treatment can be employed effectively. Efforts are required to identify better vectors with minimal side effects and maximal efficiency and durability. There is also a need to develop less invasive and more effective techniques to deliver these vectors. This review will discuss different methods to achieve these goals, the various pathologic mechanisms that have been targeted so far and those with strong potential for use in the future.

Exercise training enhanced SIRT1 longevity signaling replaces the IGF1 survival pathway to attenuate aging-induced rat heart apoptosis

Cardiovascular disease is the second leading cause of death (9.1 %) in Taiwan. Heart function deteriorates with age at a rate of 1 % per year. As society ages, we must study the serious problem of cardiovascular disease. SIRT1 regulates important cellular processes, including anti-apoptosis, neuronal protection, cellular senescence, aging, and longevity. In our previous studies, rats with obesity, high blood pressure, and diabetes exhibiting slowed myocardial performance and induced cell apoptosis were reversed via sports training through IGF1 survival signaling compensation. This study designed a set of experiments with rats, in aging and exercise groups, to identify changes in myocardial cell signaling transduction pathways. Three groups of three different aged rats, 3, 12, and 18 months old, were randomly divided into aging groups (C3, A12, and A18) and exercise groups (E3, AE12, and AE18). The exercise training consisted of swimming five times a week with gradual increases from the first week from 20 to 60 min for 12 weeks. After the sports training process was completed, tissue sections were taken to observe cell organization (hematoxylin and eosin (H&E) stain) and apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays) and to observe any changes in the myocardial tissues and proteins (Western blotting). The experimental results show that cardiomyocyte apoptotic pathway protein expression increased with age in the aging groups (C3, A12, and A18), with improvement in the exercise group (E3, AE12, and AE18). However, the expression of the pro-survival p-Akt protein decreased significantly with age and reduced performance. The IGF1R/PI3K/Akt survival pathway in the heart of young rats can indeed be increased through exercise training. As rats age, this pathway loses its original function, even with increasing upstream IGF1. However, levels of SIRT1 and its downstream target PGC-1α were found to increase with age and compensatory performance. Moreover, exercise training enhanced the SIRT longevity pathway compensation instead of IGF1 survival signaling to improve cardiomyocyte survival.

Diuretics prevent thiazolidinedione-induced cardiac hypertrophy without compromising insulin-sensitizing effects in mice

Much concern has arisen regarding critical adverse effects of thiazolidinediones (TZDs), including rosiglitazone and pioglitazone, on cardiac tissue. Although TZD-induced cardiac hypertrophy (CH) has been attributed to an increase in plasma volume or a change in cardiac nutrient preference, causative roles have not been established. To test the hypothesis that volume expansion directly mediates rosiglitazone-induced CH, mice were fed a high-fat diet with rosiglitazone, and cardiac and metabolic consequences were examined. Rosiglitazone treatment induced volume expansion and CH in wild-type and PPARγ heterozygous knockout (Pparg(+/-)) mice, but not in mice defective for ligand binding (Pparg(P465L/+)). Cotreatment with the diuretic furosemide in wild-type mice attenuated rosiglitazone-induced CH, hypertrophic gene reprogramming, cardiomyocyte apoptosis, hypertrophy-related signal activation, and left ventricular dysfunction. Similar changes were observed in mice treated with pioglitazone. The diuretics spironolactone and trichlormethiazide, but not amiloride, attenuated rosiglitazone effects on volume expansion and CH. Interestingly, expression of glucose and lipid metabolism genes in the heart was altered by rosiglitazone, but these changes were not attenuated by furosemide cotreatment. Importantly, rosiglitazone-mediated whole-body metabolic improvements were not affected by furosemide cotreatment. We conclude that releasing plasma volume reduces adverse effects of TZD-induced volume expansion and cardiac events without compromising TZD actions in metabolic switch in the heart and whole-body insulin sensitivity.

Circulating miRNAs reflect early myocardial injury and recovery after heart transplantation

BACKGROUND

MicroRNAs (miRNAs) are short, single-stranded and non-coding RNAs, freely circulating in human plasma and correlating with vary pathologies. In this study, we monitored early myocardial injury and recovery after heart transplantation by detecting levels of circulating muscle-specific miR-133a, miR-133b and miR-208a.

METHODS

7 consecutive patients underwent heart transplantation in Fuwai hospital and 14 healthy controls were included in our study. Peripheral vein blood was drawn from patients on the day just after transplantation (day 0), the 1st, 2nd, 3rd, 7th and 14th day after transplantation respectively. Serum from peripheral blood was obtained for cardiac troponin I (cTnI) measurement. Plasma was centrifuged from peripheral blood for measuring miR-133a, miR-133b and miR-208a by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The plasma concentration of miRNAs were calculated by absolute quantification method. The sensitivity and specificity of circulating miRNAs were revealed by receiver operating characteristic curve (ROC) analysis. Correlations between miRNAs and cTnI / perioperative parameters were analyzed.

RESULTS

Similar to cTnI, miR-133a, miR-133b and miR-208a all showed dynamic changes from high to low levels early after operation. The Sensitivity and specificity of miRNAs were: miR-133a (85.7%,100%), miR-208a (100%,100%), and miR-133b (90%,100%). Correlations between miRNAs and cTnI were statistically significant (p < 0.05), especially for miR-133b (R2 = 0.813, p < 0.001). MiR-133b from Day 0-Day 2 (r > 0.98, p < 0.01), and cTnI from Day 1- Day 3 (r > 0.86, p < 0.05) had strong correlations with bypass time, particularly parallel bypass time. Obviously, miR-133b had a better correlation than cTnI. Circulating miR-133b correlated well with parameters of heart function such as central venous pressure (CVP), pulmonary capillary wedge pressure (PCWP), cardiac output (CO) and inotrope support, while cTnI only correlated with 3 of the 4 parameters mentioned above. MiR-133b also had strong correlations with ventilation time (r > 0.99, p < 0.001) and length of ICU stay (r > 0.92, p < 0.05), both of which reflected the recovery after operation. The correlation coefficients of miR-133b were also higher than that of cTnI.

CONCLUSIONS

The dynamic change in circulating muscle-specific miRNAs, especially miR-133b can reflect early myocardial injury after heart transplantation. And miR-133b may have advantages over cTnI in forecasting graft dysfunction and recovery of patients after operation.

Mitochondria: the hemi of the cell

There are many organelles within a cell, each with individual responsibilities required for life. Of these organelles, the mitochondria are the hemi of the cell, producing the energy necessary for cell function. Reactive oxygen species can cause mitochondrial dysfunction and contribute to many diseases often seen in emergency departments. When reactive oxygen species are produced, the mitochondria undergo functional and structural changes causing the release of cytochrome c. Cytochrome c is responsible for activating apoptotic pathways leading to cell death. Apoptosis, or programmed cell death, is needed to maintain homeostasis in the body; however, when this occurs prematurely by an increase in reactive oxygen species production, many pathological conditions can occur. Clinicians in emergency departments caring for patients with different diseases should consider that the mitochondria may play an important role in patients' recovery. For instance, myocardial infarctions and burns are two examples of altered physiologic states that play a role in mitochondrial dysfunction. Awareness of the different treatments that target the mitochondria will prepare emergency department clinicians to better care for their patients.

Preconditioning and stem cell survival

The harsh ischemic and cytokine-rich microenvironment in the infarcted myocardium, infiltrated by the inflammatory and immune cells, offers a significant challenge to the transplanted donor stem cells. Massive cell death occurs during transplantation as well as following engraftment which significantly lowers the effectiveness of the heart cell therapy. Various approaches have been adopted to overcome this problem nevertheless with multiple limitations with each of these current approaches. Cellular preconditioning and reprogramming by physical, chemical, genetic, and pharmacological manipulation of the cells has shown promise and "prime" the cells to the "state of readiness" to withstand the rigors of lethal ischemia in vitro as well as posttransplantation. This review summarizes the past and present novel approaches of ischemic preconditioning, pharmacological and genetic manipulation using preconditioning mimetics, recombinant growth factor protein treatment, and reprogramming of stem cells to overexpress survival signaling molecules, microRNAs, and trophic factors for intracrine, autocrine, and paracrine effects on cytoprotection.

Thyroid hormone as a therapeutic option for treating ischaemic heart disease: from early reperfusion to late remodelling

Thyroid hormone (TH), apart from its "classical" actions on cardiac contractility and heart rhythm, appears to regulate various intracellular signalling pathways related to response to stress and cardiac remodelling. There is now accumulating experimental and clinical evidence showing a beneficial effect of TH on limiting myocardial ischaemic injury, preventing/reversing post infarction cardiac remodelling and improving cardiac hemodynamics. Thyroid analogs have already been developed and may allow TH use in clinical practice. However, the efficacy of TH in the treatment of cardiac diseases is now awaiting to be tested in large clinical trials.

Thyroid hormone improves postischaemic recovery of function while limiting apoptosis: a new therapeutic approach to support hemodynamics in the setting of ischaemia-reperfusion?

Although it has long been recognized that thyroid hormone is an effective positive inotrope, its efficacy in supporting hemodynamics in the acute setting of ischaemia and reperfusion (R) without worsening reperfusion injury remains largely unknown. Thus, we investigated the effects of triiodothyronine (T3) on reperfusion injury in a Langendorff-perfused rat heart model of 30 min zero-flow ischaemia and 60 min of (R) with or without T3 (40 microg/l) at R, T3-R60, n = 11 and CNT-R60, n = 10, respectively. Furthermore, phosphorylated levels of intracellular kinases were measured at 5, 15 and 60 min of R. T3 markedly improved postischaemic recovery of left ventricular developed pressure (LVDP%); 56.0% (SEM, 4.4) in T3-R60 versus 38.8% (3.1) in CNT-R60, P < 0.05. Furthermore, LDH release was significantly lower in T3-R60. Apoptosis detection by fluorescent probe optical imaging showed increased fluorescent signal in CNT-R60 hearts, while the signal was hardly detectable in T3-R60 hearts. Similarly, caspase-3 activity was found to be 78.2 (8.2) in CNT-R60 vs 40.5 (7.1) in T3-R60 hearts, P < 0.05. This response was associated with significantly lower levels of phospho-p38 MAPK at any time point of R. No significant changes in phospho- ERK1/2 and JNK levels were observed between groups. Phospho-Akt levels were significantly lower in T3 treated group at 5 min and no change in phospho-Akt levels were observed at 15 and 60 min between groups. In conclusion, T3 administration at reperfusion can improve postischaemic recovery of function while limiting apoptosis. This may constitute a paradigm of a positive inotropic agent with anti-apoptotic action suitable for supporting hemodynamics in the clinical setting of ischaemia-reperfusion.

Strategies to promote donor cell survival: combining preconditioning approach with stem cell transplantation

Stem cell transplantation has emerged as a potential modality in cardiovascular therapeutics due to their inherent characteristics of self-renewal, unlimited capacity for proliferation and ability to cross lineage restrictions and adopt different phenotypes. Constrained by extensive death in the unfriendly milieu of ischemic myocardium, the results of heart cell therapy in experimental animal models as well as clinical studies have been less than optimal. Several factors which play a role in early cell death after engraftment in the ischemic myocardium include: absence of survival factors in the transplanted heart, disruption of cell-cell interaction coupled with loss of survival signals from matrix attachments, insufficient vascular supply and elaboration of inflammatory cytokines resulting from ischemia and/or cell death. This article reviews various signaling pathways involved in triggering highly complex forms of cell death and provides critical appreciation of different novel anti-death strategies developed from the knowledge gained from using an ischemic preconditioning approach. The use of pharmacological preconditioning for up-regulation of pro-survival proteins and cardiogenic markers in the transplanted stem cells will be discussed.

Bone marrow-derived mesenchymal stem cells for treatment of heart failure: is it all paracrine actions and immunomodulation?

Despite significant advances in medical and surgical management of heart failure, mostly of ischaemic origin, the mortality and morbidity associated with it continue to be high. Pluripotent stem cells are being evaluated for treatment of heart failure. Bone marrow-derived mesenchymal stem cells (MSCs) have been extensively studied. Emerging evidence suggests that locally delivered MSCs can lead to an improvement in ventricular function, but the cellular and molecular mechanisms involved remain unclear. Myocardial regeneration, as proposed by many researchers as the underlying mechanism, has failed to convince the scientific community. Recently some authors have ascribed improvement in ventricular function to paracrine actions of MSCs.A lot has been written about the host immune response triggered by embryonic stem cells and the consequent need for immunosuppression. Not enough work has been done on immune interactions involving allogeneic bone marrow cells. Full potential of stem cell therapy can be realised only when we are able to use allogeneic cells. The potential use of MSCs in cellular therapy has recently prompted researchers to look into their interaction with the host immune response. MSCs have immunomodulatory properties. They cause suppression of proliferation of alloreactive T cells in a dose-dependent manner.Tissue injury causes inflammation and release of several chemokines, cytokines and growth factors. They can cause recruitment of bone marrow-derived MSCs to the injured area. We review the literature on paracrine actions and immune interactions of allogeneic MSCs.

Levosimendan in patients with acute myocardial ischaemia undergoing emergency surgical revascularization

BACKGROUND AND OBJECTIVE

Levosimendan is a calcium-sensitizing drug that enhances myocardial contractility without increasing intracellular calcium. By activating adenosine triphosphate-dependent potassium channels it exerts cardioprotective and vasodilatory effects.

METHODS

A retrospective matched pair analysis was performed in 52 patients undergoing emergency coronary artery bypass grafting for acute myocardial ischaemia with or without cardiogenic shock. A total of 27 patients received levosimendan (bolus 6 microg kg(-1); continuous infusion 0.2 microg kg(-1) min(-1)) in addition to catecholamines, while 25 patients were treated with catecholamines only.

RESULTS

Predicted mortality by logistic EuroSCORE was 42% (14-90%) in the levosimendan group and 38% (9-90%) in the control group (median, range). Cardiogenic shock was diagnosed in 52% of the patients in both groups. Compared to the control group, levosimendan-treated patients had fewer intra-aortic balloon pumps inserted (33% vs. 76%, P 0.05) and need for dialysis (11% levosimendan; 32% control, P > 0.05) did not reach statistical significance. Length of hospital stay did not differ (14 +/- 18 days, levosimendan; 13 +/- 19 days, control; P > 0.05) between the two groups.

CONCLUSION

In this retrospective matched pair analysis of 52 patients undergoing emergency coronary artery bypass grafting for acute ischaemia, levosimendan reduced morbidity. The reduced morbidity did not translate into reductions in mortality or length of stay. A larger, prospective randomized trial is warranted to confirm the potentially beneficial effects of levosimendan in patients with acute ischaemia.

Influence of hypothermia on right atrial cardiomyocyte apoptosis in patients undergoing aortic valve replacement

BACKGROUND

There is increasing evidence that programmed cell death can be triggered during cardiopulmonary bypass (CPB) and may be involved in postoperative complications. The purpose of this study was to investigate whether apoptosis occurs during aortic valve surgery and whether modifying temperature during CPB has any influence on cardiomyocyte apoptotic death rate.

METHODS

20 patients undergoing elective aortic valve replacement for aortic stenosis were randomly assigned to either moderate hypothermic (ModHT group, n = 10, 28 degrees C) or mild hypothermic (MiHT group, n = 10, 34 degrees C) CPB. Myocardial samples were obtained from the right atrium before and after weaning from CPB. Specimens were examined for apoptosis by flow cytometry analysis of annexin V-propidium iodide (PI) and Fas death receptor staining.

RESULTS

In the ModHT group, non apoptotic non necrotic cells (annexin negative, PI negative) decreased after CPB, while early apoptotic (annexin positive, PI negative) and late apoptotic or necrotic (PI positive) cells increased. In contrast, no change in the different cell populations was observed over time in the MiHT group. Fas expression rose after reperfusion in the ModHT group but not in MiHT patients, in which there was even a trend for a lower Fas staining after CPB (p = 0.08). In ModHT patients, a prolonged ischemic time tended to induce a higher increase of Fas (p = 0.061).

CONCLUSION

Our data suggest that apoptosis signal cascade is activated at early stages during aortic valve replacement under ModHT CPB. This apoptosis induction can effectively be attenuated by a more normothermic procedure.

Cardiomyocyte Apoptosis After Antegrade and Retrograde Cardioplegia

BACKGROUND

Retrograde cardioplegia alone is often used in aortic valve and aortic root surgery. Due to the differences in venous anatomy between the right and the left side of the heart, retrograde cardioplegia is associated with incomplete protection of the right side. Since some apoptotic cardiomyocyte death is inevitable during an open heart surgery, we compared the extent of cardiomyocyte apoptosis in the left and right ventricles after antegrade and retrograde cardioplegia in a pig ischemia-reperfusion model.

METHODS

Pigs (n = 16, mean weight 30 kg) were openly assigned into the groups of antegrade and retrograde cardioplegia. After aortic cross-clamping, 500 mL of cold crystalloid (modified St Thomas) cardioplegia was administered into the ascending aorta or the coronary sinus. Aortic cross-clamp time was 30 minutes. Cardiomyocyte apoptosis was measured using the terminal transferase mediated ddUTP nick end-labeling (TUNEL) assay and immunohistochemical (IHC) staining for active caspase-3 in myocardial biopsies obtained before ischemia and after 90 minutes of reperfusion.

RESULTS

Apoptotic cardiomyocytes were significantly increased after ischemia-reperfusion as shown by both the TUNEL assay and caspase-3 activation. In the right ventricle, retrograde cardioplegia was associated with a 3.4-fold higher amount (TUNEL assay) of apoptotic cardiomyocytes as compared with antegrade cardioplegia (0.107% vs 0.032%, p < 0.05). A similar difference was also found in the left ventricle, although at a lower level (0.027% vs 0.012%, p < 0.05).

CONCLUSIONS

Increased apoptotic death of cardiomyocytes after retrograde cardioplegia as compared with the antegrade procedure implicates that retrograde cardioplegia alone provides inferior cardioprotection against irreversible ischemia-reperfusion injury both in the right and the left ventricle.