Cyclosporine does not reduce myocardial infarct size in a porcine ischemia-reperfusion model

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

Perspectives on mitochondrial relevance in cardiac ischemia/reperfusion injury

Cardiovascular disease is the most common cause of death worldwide and in particular, ischemic heart disease holds the most considerable position. Even if it has been deeply studied, myocardial ischemia-reperfusion injury (IRI) is still a side-effect of the clinical treatment for several heart diseases: ischemia process itself leads to temporary damage to heart tissue and obviously the recovery of blood flow is promptly required even if it worsens the ischemic injury. There is no doubt that mitochondria play a key role in pathogenesis of IRI: dysfunctions of these important organelles alter cell homeostasis and survival. It has been demonstrated that during IRI the system of mitochondrial quality control undergoes alterations with the disruption of the complex balance between the processes of mitochondrial fusion, fission, biogenesis and mitophagy. The fundamental role of mitochondria is carried out thanks to the finely regulated connection to other organelles such as plasma membrane, endoplasmic reticulum and nucleus, therefore impairments of these inter-organelle communications exacerbate IRI. This review pointed to enhance the importance of the mitochondrial network in the pathogenesis of IRI with the aim to focus on potential mitochondria-targeting therapies as new approach to control heart tissue damage after ischemia and reperfusion process.

What is responsible for acute myocardial infarction in combination with aplastic anemia? A case report and literature review

BACKGROUND

Aplastic anemia (AA) complicated with myocardial infarction (MI) is rare and associated with poor prognosis. Here, we present a case of AA with recurrent acute MI (AMI) in a patient treated with cyclosporine A (CsA) and stanozolol. In this patient, we suspect the long-term use of medication linked to platelets hyperfunction.

CASE SUMMARY

In 2017, a 45-year-old man was rushed to the emergency department of China-Japan Union Hospital due to precordial pain for 5 h. Based on his symptoms, medical history, blood tests, and findings from coronary angiography (CAG), the patient was diagnosed with acute anterior wall, ST-segment elevated MI, Killip II grade, AA, and dyslipidemia. In 2021, the patient was readmitted to the hospital for 2 h due to chest pain. Because the patient’s platelet count was 30 × 10⁹/L and he had severe thrombocytopenia, we performed CAG following platelet transfusion. Optical coherence tomography revealed lipid plaque and thrombus mass in his right coronary artery. The antithrombotic approach was adjusted to employ only anticoagulants (factor Xa inhibitors) and adenosine diphosphate inhibitors (clopidogrel) after assessing the risk of bleeding/thrombotic events. Long-term follow-up revealed that the patient had made a good recovery.

CONCLUSION

Patients with AA should be closely monitored for the risk of thrombosis and cardiovascular events, particularly when taking stanozolol or CsA for an extended period of time.

Widespread intracoronary allogeneic cardiosphere-derived cell therapy with and without cyclosporine in reperfused myocardial infarction

Allogeneic cardiosphere-derived cell (CDC) therapy has been demonstrated to improve myocardial function when administered to reperfused myocardial infarcts. We previously pretreated animals with low-dose cyclosporine immunosuppression to limit allogeneic CDC rejection, but whether it is necessary and, if so, can be initiated at the time of reperfusion remains uncertain. Closed-chest swine (n = 29 animals) were subjected to a 90-min left anterior descending (LAD) coronary artery occlusion. Using a three-way blinded design, we randomized two groups to receive global intracoronary infusions of 20 × 106 CDCs 30 min after reperfusion. A third control group was treated with saline. One CDC group received cyclosporine 10 min before reperfusion (2.5 mg/kg iv and 100 mg/day po), whereas the other groups received placebos. After 1 mo, neither chronic infarct size relative to area at risk (saline control, 46.2 ± 4.0%; CDCs, 46.4 ± 2.1%; and CDCs + cyclosporine, 49.2 ± 3.1%; P = 0.79) nor ejection fraction (saline control, 51 ± 2%; CDCs, 51 ± 2%; and CDC + cyclosporine, 48 ± 2%; P = 0.42) were different among treatment groups. Multiple histological measures of cellular remodeling, myocyte proliferation, and apoptosis were also not different among treatment groups. In contrast to previous studies, we were unable to reproduce the cardioprotective effects demonstrated by allogeneic CDCs without cyclosporine. Furthermore, initiation of intravenous cyclosporine at the time of reperfusion followed by oral therapy was not sufficient to elicit the functional improvement observed in studies where cyclosporine was started 72 h before CDC therapy. This suggests that oral cyclosporine pretreatment may be necessary to effect cardiac repair with allogeneic CDCs.NEW & NOTEWORTHY In a three-way blinded, randomized design, we determined whether allogeneic CDCs administered at reperfusion improved myocardial function and whether intravenous cyclosporine enhanced their efficacy. In contrast to prior studies using oral cyclosporine, CDCs with or without intravenous cyclosporine had no effect on function or infarct size. This indicates that CDCs may be most efficacious for treating chronic LV dysfunction where cyclosporine can be initiated at least 72 h before cell therapy.

Therapeutic Targets for Regulating Oxidative Damage Induced by Ischemia-Reperfusion Injury: A Study from a Pharmacological Perspective

Ischemia-reperfusion (I-R) injury is damage caused by restoring blood flow into ischemic tissues or organs. This complex and characteristic lesion accelerates cell death induced by signaling pathways such as apoptosis, necrosis, and even ferroptosis. In addition to the direct association between I-R and the release of reactive oxygen species and reactive nitrogen species, it is involved in developing mitochondrial oxidative damage. Thus, its mechanism plays a critical role via reactive species scavenging, calcium overload modulation, electron transport chain blocking, mitochondrial permeability transition pore activation, or noncoding RNA transcription. Other receptors and molecules reduce tissue and organ damage caused by this pathology and other related diseases. These molecular targets have been gradually discovered and have essential roles in I-R resolution. Therefore, the current study is aimed at highlighting the importance of these discoveries. In this review, we inquire about the oxidative damage receptors that are relevant to reducing the damage induced by oxidative stress associated with I-R. Several complications on surgical techniques and pathology interventions do not mitigate the damage caused by I-R. Nevertheless, these therapies developed using alternative targets could work as coadjuvants in tissue transplants or I-R-related pathologies

Therapeutic Peptides to Treat Myocardial Ischemia-Reperfusion Injury

Cardiovascular diseases (CVD) including acute myocardial infarction (AMI) rank first in worldwide mortality and according to the World Health Organization (WHO), they will stay at this rank until 2030. Prompt revascularization of the occluded artery to reperfuse the myocardium is the only recommended treatment (by angioplasty or thrombolysis) to decrease infarct size (IS). However, despite beneficial effects on ischemic lesions, reperfusion leads to ischemia-reperfusion (IR) injury related mainly to apoptosis. Improvement of revascularization techniques and patient care has decreased myocardial infarction (MI) mortality however heart failure (HF) morbidity is increasing, contributing to the cost-intense worldwide HF epidemic. Currently, there is no treatment for reperfusion injury despite promising results in animal models. There is now an obvious need to develop new cardioprotective strategies to decrease morbidity/mortality of CVD, which is increasing due to the aging of the population and the rising prevalence rates of diabetes and obesity. In this review, we will summarize the different therapeutic peptides developed or used focused on the treatment of myocardial IR injury (MIRI). Therapeutic peptides will be presented depending on their interacting mechanisms (apoptosis, necroptosis, and inflammation) reported as playing an important role in reperfusion injury following myocardial ischemia. The search and development of therapeutic peptides have become very active, with increasing numbers of candidates entering clinical trials. Their optimization and their potential application in the treatment of patients with AMI will be discussed.

Preclinical trial of a MAP4K4 inhibitor to reduce infarct size in the pig: does cardioprotection in human stem cell-derived myocytes predict success in large mammals?

Reducing infarct size (IS) by interfering with mechanisms for cardiomyocyte death remains an elusive goal. DMX-5804, a selective inhibitor of the stress-activated kinase MAP4K4, suppresses cell death in mouse myocardial infarction (MI), human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs), and 3D human engineered heart tissue, whose fidelity to human biology is hoped to strengthen the route to clinical success. Here, DMX-10001, a soluble, rapidly cleaved pro-drug of DMX-5804, was developed for i.v. testing in large-mammal MI. Following pharmacodynamic studies, a randomized, blinded efficacy study was performed in swine subjected to LAD balloon occlusion (60 min) and reperfusion (24 h). Thirty-six animals were enrolled; 12 were excluded by pre-defined criteria, death before infusion, or technical issues. DMX-10001 was begun 20 min before reperfusion (30 min, 60 mg/kg/h; 23.5 h, 17 mg/kg/h). At all times tested, beginning 30 min after the start of infusion, DMX-5804 concentrations exceeded > fivefold the levels that rescued hPSC-CMs and reduced IS in mice after oral dosing with DMX-5804 itself. No significant reduction occurred in IS or no-reflow corrected for the area at ischemic risk, even though DMX-10001 reduced IS, expressed in grams or % of LV mass, by 27%. In summary, a rapidly cleaved pro-drug of DMX-5804 failed to reduce IS in large-mammal MI, despite exceeding the concentrations for proven success in both mice and hPSC-CMs.

Mitochondrial ion channels as targets for cardioprotection

Acute myocardial infarction (AMI) and the heart failure (HF) that often result remain the leading causes of death and disability worldwide. As such, new therapeutic targets need to be discovered to protect the myocardium against acute ischaemia/reperfusion (I/R) injury in order to reduce myocardial infarct (MI) size, preserve left ventricular function and prevent the onset of HF. Mitochondrial dysfunction during acute I/R injury is a critical determinant of cell death following AMI, and therefore, ion channels in the inner mitochondrial membrane, which are known to influence cell death and survival, provide potential therapeutic targets for cardioprotection. In this article, we review the role of mitochondrial ion channels, which are known to modulate susceptibility to acute myocardial I/R injury, and we explore their potential roles as therapeutic targets for reducing MI size and preventing HF following AMI.

Neutrophil-Related Oxidants Drive Heart and Brain Remodeling After Ischemia/Reperfusion Injury

The inflammatory response associated with myocardial and brain ischemia/reperfusion injury (IRI) is a critical determinant of tissue necrosis, functional organ recovery, and long-term clinical outcomes. In the post-ischemic period, reactive oxygen species (ROS) are involved in tissue repair through the clearance of dead cells and cellular debris. Neutrophils play a critical role in redox signaling due to their early recruitment and the large variety of released ROS. Noteworthy, ROS generated during IRI have a relevant role in both myocardial healing and activation of neuroprotective pathways. Anatomical and functional differences contribute to the responses in the myocardial and brain tissue despite a significant gene overlap. The exaggerated activation of this signaling system can result in adverse consequences, such as cell apoptosis and extracellular matrix degradation. In light of that, blocking the ROS cascade might have a therapeutic implication for cardiomyocyte and neuronal loss after acute ischemic events. The translation of these findings from preclinical models to clinical trials has so far failed because of differences between humans and animals, difficulty of agents to penetrate into specific cellular organs, and specifically unravel oxidant and antioxidant pathways. Here, we update knowledge on ROS cascade in IRI, focusing on the role of neutrophils. We discuss evidence of ROS blockade as a therapeutic approach for myocardial infarction and ischemic stroke.

Translational issues for mitoprotective agents as adjunct to reperfusion therapy in patients with ST-segment elevation myocardial infarction

Pre‐clinical studies have indicated that mitoprotective drugs may add cardioprotection beyond rapid revascularization, antiplatelet therapy and risk modification. We review the clinical efficacy of mitoprotective drugs that have progressed to clinical testing comprising cyclosporine A, KAI‐9803, MTP131 and TRO 40303. Whereas cyclosporine may reduce infarct size in patients undergoing primary angioplasty as evaluated by release of myocardial ischaemic biomarkers and infarct size imaging, the other drugs were not capable of demonstrating this effect in the clinical setting. The absent effect leaves the role of the mitochondrial permeability transition pore for reperfusion injury in humans unanswered and indicates that targeting one single mechanism to provide mitoprotection may not be efficient. Moreover, the lack of effect may relate to favourable outcome with current optimal therapy, but conditions such as age, sex, diabetes, dyslipidaemia and concurrent medications may also alter mitochondrial function. However, as long as the molecular structure of the pore remains unknown and specific inhibitors of its opening are lacking, the mitochondrial permeability transition pore remains a target for alleviation of reperfusion injury. Nevertheless, taking conditions such as ageing, sex, comorbidities and co‐medication into account may be of paramount importance during the design of pre‐clinical and clinical studies testing mitoprotective drugs.

Oxidative Stress in Cell Death and Cardiovascular Diseases

ROS functions as a second messenger and modulates multiple signaling pathways under the physiological conditions. However, excessive intracellular ROS causes damage to the molecular components of the cell, which promotes the pathogenesis of various human diseases. Cardiovascular diseases are serious threats to human health with extremely high rates of morbidity and mortality. Dysregulation of cell death promotes the pathogenesis of cardiovascular diseases and is the clinical target during the disease treatment. Numerous studies show that ROS production is closely linked to the cell death process and promotes the occurrence and development of the cardiovascular diseases. In this review, we summarize the regulation of intracellular ROS, the roles of ROS played in the development of cardiovascular diseases, and the programmed cell death induced by intracellular ROS. We also focus on anti-ROS system and the potential application of anti-ROS strategy in the treatment of cardiovascular diseases.

Programmed necrosis in cardiomyocytes: mitochondria, death receptors and beyond

Excessive death of cardiac myocytes leads to many cardiac diseases, including myocardial infarction, arrhythmia, heart failure and sudden cardiac death. For the last several decades, most work on cell death has focused on apoptosis, which is generally considered as the only form of regulated cell death, whereas necrosis has been regarded to be an unregulated process. Recent findings reveal that necrosis also occurs in a regulated manner and that it is closely related to the physiology and pathophysiology of many organs, including the heart. The recognition of necrosis as a regulated process mandates a re-examination of cell death in the heart together with the mechanisms and therapy of cardiac diseases. In this study, we summarize the regulatory mechanisms of the programmed necrosis of cardiomyocytes, that is, the intrinsic (mitochondrial) and extrinsic (death receptor) pathways. Furthermore, the role of this programmed necrosis in various heart diseases is also delineated. Finally, we describe the currently known pharmacological inhibitors of several of the key regulatory molecules of regulated cell necrosis and the opportunities for their therapeutic use in cardiac disease. We intend to systemically summarize the recent progresses in the regulation and pathological significance of programmed cardiomyocyte necrosis along with its potential therapeutic applications to cardiac diseases. LINKED ARTICLES: This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

Evaluating Novel Targets of Ischemia Reperfusion Injury in Pig Models

Coronary heart diseases are of high relevance for health care systems in developed countries regarding patient numbers and costs. Disappointingly, the enormous effort put into the development of innovative therapies and the high numbers of clinical studies conducted are counteracted by the low numbers of therapies that become clinically effective. Evidently, pre-clinical research in its present form does not appear informative of the performance of treatments in the clinic and, even more relevant, it appears that there is hardly any consent about how to improve the predictive capacity of pre-clinical experiments. According to the steadily increasing relevance that pig models have gained in biomedical research in the recent past, we anticipate that research in pigs can be highly predictive for ischemia-reperfusion injury (IRI) therapies as well. Thus, we here describe the significance of pig models in IRI, give an overview about recent developments in evaluating such models by clinically relevant methods and present the latest insight into therapies applied to pigs under IRI.

Cyclosporine-insensitive mode of cell death after prolonged myocardial ischemia: Evidence for sarcolemmal permeabilization as the pivotal step

A prominent theory of cell death in myocardial ischemia/reperfusion (I/R) posits that the primary and pivotal step of irreversible cell injury is the opening of the mitochondrial permeability transition (MPT) pore. However, the predominantly positive evidence of protection against infarct afforded by the MPT inhibitor, Cyclosporine A (CsA), in experimental studies is in stark contrast with the overall lack of benefit found in clinical trials of CsA. One reason for the discrepancy might be the fact that relatively short experimental ischemic episodes (<1 hour) do not represent clinically-realistic durations, usually exceeding one hour. Here we tested the hypothesis that MPT is not the primary event of cell death after prolonged (60–80 min) episodes of global ischemia. We used confocal microcopy in Langendorff-perfused rabbit hearts treated with the electromechanical uncoupler, 2,3-Butanedione monoxime (BDM, 20 mM) to allow tracking of MPT and sarcolemmal permeabilization (SP) in individual ventricular myocytes. The time of the steepest drop in fluorescence of mitochondrial membrane potential (ΔΨ_m)-sensitive dye, TMRM, was used as the time of MPT (T_MPT). The time of 20% uptake of the normally cell-impermeable dye, YO-PRO1, was used as the time of SP (T_SP). We found that during reperfusion MPT and SP were tightly coupled, with MPT trending slightly ahead of SP (T_SP-T_MPT = 0.76±1.31 min; p = 0.07). These coupled MPT/SP events occurred in discrete myocytes without crossing cell boundaries. CsA (0.2 μM) did not reduce the infarct size, but separated SP and MPT events, such that detectable SP was significantly ahead of MPT (T_SP -T_MPT = -1.75±1.28 min, p = 0.006). Mild permeabilization of cells with digitonin (2.5–20 μM) caused coupled MPT/SP events which occurred in discrete myocytes similar to those observed in Control and CsA groups. In contrast, deliberate induction of MPT by titration with H₂O₂ (200–800 μM), caused propagating waves of MPT which crossed cell boundaries and were uncoupled from SP. Taken together, these findings suggest that after prolonged episodes of ischemia, SP is the primary step in myocyte death, of which MPT is an immediate and unavoidable consequence.

Novel targets and future strategies for acute cardioprotection: Position Paper of the European Society of Cardiology Working Group on Cellular Biology of the Heart

Ischaemic heart disease and the heart failure that often results, remain the leading causes of death and disability in Europe and worldwide. As such, in order to prevent heart failure and improve clinical outcomes in patients presenting with an acute ST-segment elevation myocardial infarction and patients undergoing coronary artery bypass graft surgery, novel therapies are required to protect the heart against the detrimental effects of acute ischaemia/reperfusion injury (IRI). During the last three decades, a wide variety of ischaemic conditioning strategies and pharmacological treatments have been tested in the clinic-however, their translation from experimental to clinical studies for improving patient outcomes has been both challenging and disappointing. Therefore, in this Position Paper of the European Society of Cardiology Working Group on Cellular Biology of the Heart, we critically analyse the current state of ischaemic conditioning in both the experimental and clinical settings, provide recommendations for improving its translation into the clinical setting, and highlight novel therapeutic targets and new treatment strategies for reducing acute myocardial IRI.

Critical Issues for the Translation of Cardioprotection

The translation from numerous successful animal experiments on cardioprotection beyond that by reperfusion to clinical practice has to date been disappointing. Animal experiments often use reductionist approaches and are mostly performed in young and healthy animals which lack the risk factors, comorbidities, and comedications which are characteristics of patients suffering an acute myocardial infarction or undergoing cardiovascular surgery. Conceptually, it is still unclear by how much the time window for successful reperfusion is extended by preconditioning, and how long the duration of ischemia can be so that adjunct cardioprotection by postconditioning at reperfusion still protects. Experimental studies addressing long-term effects of adjunct cardioprotection beyond infarct size reduction, that is, on repair, remodeling, and mortality, are lacking. Technically, reproducibility and robustness of experimental studies are often limited. Grave faults in design and conduct of clinical trials have also substantially contributed to the failure of translation of cardioprotection to clinical practice. Cardiovascular surgery with ischemic cardioplegic arrest is only a surrogate of acute myocardial infarction and confounded by the choice of anesthesia, hypothermia, cardioplegia, and traumatic myocardial injury. Trials in patients with acute myocardial infarction have been performed on agents/interventions with no or inconsistent previous animal data and in patients who had either some reperfusion already at admission or were reperfused too late to expect any myocardial salvage. Of greatest concern is the lack of adequate phase II dosing and timing studies when rushing from promising proof-of-concept trials with surrogate end points such as infarct size to larger clinical outcome trials. Future trials must focus on interventions/agents with robust preclinical evidence, have solid phase II dosing and timing data, and recruit patients who have truly a chance to benefit from adjunct cardioprotection.

Mitochondrial permeability transition in cardiac ischemia-reperfusion: whether cyclophilin D is a viable target for cardioprotection?

Growing number of studies provide strong evidence that the mitochondrial permeability transition pore (PTP), a non-selective channel in the inner mitochondrial membrane, is involved in the pathogenesis of cardiac ischemia-reperfusion and can be targeted to attenuate reperfusion-induced damage to the myocardium. The molecular identity of the PTP remains unknown and cyclophilin D is the only protein commonly accepted as a major regulator of the PTP opening. Therefore, cyclophilin D is an attractive target for pharmacological or genetic therapies to reduce ischemia-reperfusion injury in various animal models and humans. Most animal studies demonstrated cardioprotective effects of PTP inhibition; however, a recent large clinical trial conducted by international groups demonstrated that cyclosporine A, a cyclophilin D inhibitor, failed to protect the heart in patients with myocardial infarction. These studies, among others, raise the question of whether cyclophilin D, which plays an important physiological role in the regulation of cell metabolism and mitochondrial bioenergetics, is a viable target for cardioprotection. This review discusses previous studies to provide comprehensive information on the physiological role of cyclophilin D as well as PTP opening in the cell that can be taken into consideration for the development of new PTP inhibitors.

Mitochondrial Membrane Permeability Inhibitors in Acute Myocardial Infarction: Still Awaiting Translation

Despite therapeutic advances, acute myocardial infarction (AMI) remains a leading cause of morbidity and mortality worldwide. One potential limitation of the current treatment paradigm is the lack of effective therapies to optimize reperfusion after ischemia and prevent reperfusion-mediated injury. Experimental studies indicate that this process accounts for up to 50% of the final infarct size, lending it importance as a potential target for cardioprotection. However, multiple therapeutic approaches have shown potential in pre-clinical and early phase trials but a paucity of clear clinical benefit when expanded to larger studies. Here we explore this history of trials and errors of the studies of cyclosporine A and other mitochondrial membrane permeability inhibitors, agents that appeared to have a promising pre-clinical record yet provided disappointing results in phase III clinical trials.

Ischaemic conditioning and targeting reperfusion injury: a 30 year voyage of discovery

To commemorate the auspicious occasion of the 30th anniversary of IPC, leading pioneers in the field of cardioprotection gathered in Barcelona in May 2016 to review and discuss the history of IPC, its evolution to IPost and RIC, myocardial reperfusion injury as a therapeutic target, and future targets and strategies for cardioprotection. This article provides an overview of the major topics discussed at this special meeting and underscores the huge importance and impact, the discovery of IPC has made in the field of cardiovascular research.

Cyclosporine A in Reperfused Myocardial Infarction: The Multicenter, Controlled, Open-Label CYCLE Trial

BACKGROUND

Whether cyclosporine A (CsA) has beneficial effects in reperfused myocardial infarction (MI) is debated.

OBJECTIVES

This study investigated whether CsA improved ST-segment resolution in a randomized, multicenter phase II study.

METHODS

The authors randomly assigned 410 patients from 31 cardiac care units, age 63 ± 12 years, with large ST-segment elevation MI within 6 h of symptom onset, Thrombolysis In Myocardial Infarction (TIMI) flow grade 0 to 1 in the infarct-related artery, and committed to primary percutaneous coronary intervention, to 2.5 mg/kg intravenous CsA (n = 207) or control (n = 203) groups. The primary endpoint was incidence of ≥70% ST-segment resolution 60 min after TIMI flow grade 3. Secondary endpoints included high-sensitivity cardiac troponin T (hs-cTnT) on day 4, left ventricular (LV) remodeling, and clinical events at 6-month follow-up.

RESULTS

Time from symptom onset to first antegrade flow was 180 ± 67 min; a median of 5 electrocardiography leads showed ST-segment deviation (quartile [Q]1 to Q3: 4 to 6); 49.8% of MIs were anterior. ST-segment resolution ≥70% was found in 52.0% of CsA patients and 49.0% of controls (p = 0.55). Median hs-cTnT on day 4 was 2,160 (Q1 to Q3: 1,087 to 3,274) ng/l in CsA and 2,068 (1,117 to 3,690) ng/l in controls (p = 0.85). The 2 groups did not differ in LV ejection fraction on day 4 and at 6 months. Infarct site did not influence CsA efficacy. There were no acute allergic reactions or nonsignificant excesses of 6-month mortality (5.7% CsA vs. 3.2% controls, p = 0.17) or cardiogenic shock (2.4% CsA vs. 1.5% controls, p = 0.33).

CONCLUSIONS

In the CYCLE (CYCLosporinE A in Reperfused Acute Myocardial Infarction) trial, a single intravenous CsA bolus just before primary percutaneous coronary intervention had no effect on ST-segment resolution or hs-cTnT, and did not improve clinical outcomes or LV remodeling up to 6 months. (CYCLosporinE A in Reperfused Acute Myocardial Infarction [CYCLE]; NCT01650662; EudraCT number 2011-002876-18).

Meeting report from the 2nd International Symposium on New Frontiers in Cardiovascular Research. Protecting the cardiovascular system from ischemia: between bench and bedside

Recent advances in basic cardiovascular research as well as their translation into the clinical situation were the focus at the last "New Frontiers in Cardiovascular Research meeting". Major topics included the characterization of new targets and procedures in cardioprotection, deciphering new players and inflammatory mechanisms in ischemic heart disease as well as uncovering microRNAs and other biomarkers as versatile and possibly causal factors in cardiovascular pathogenesis. Although a number of pathological situations such as ischemia-reperfusion injury or atherosclerosis can be simulated and manipulated in diverse animal models, also to challenge new drugs for intervention, patient studies are the ultimate litmus test to obtain unequivocal information about the validity of biomedical concepts and their application in the clinics. Thus, the open and bidirectional exchange between bench and bedside is crucial to advance the field of ischemic heart disease with a particular emphasis of understanding long-lasting approaches in cardioprotection.

Cyclosporine A reduces microvascular obstruction and preserves left ventricular function deterioration following myocardial ischemia and reperfusion

Postconditioning and cyclosporine A prevent mitochondrial permeability transition pore opening providing cardioprotection during ischemia/reperfusion. Whether microvascular obstruction is affected by these interventions is largely unknown. Pigs subjected to coronary occlusion for 1 h followed by 3 h of reperfusion were assigned to control (n = 8), postconditioning (n = 9) or cyclosporine A intravenous infusion 10–15 min before the end of ischemia (n = 8). Postconditioning was induced by 8 cycles of repeated 30-s balloon inflation and deflation. After 3 h of reperfusion magnetic resonance imaging, triphenyltetrazolium chloride/Evans blue staining and histopathology were performed. Microvascular obstruction (MVO, percentage of gadolinium-hyperenhanced area) was measured early (3 min) and late (12 min) after contrast injection. Infarct size with double staining was smaller in cyclosporine (46.2 ± 3.1 %, P = 0.016) and postconditioning pigs (47.6 ± 3.9 %, P = 0.008) versus controls (53.8 ± 4.1 %). Late MVO was significantly reduced by cyclosporine (13.9 ± 9.6 %, P = 0.047) but not postconditioning (23.6 ± 11.7 %, P = 0.66) when compared with controls (32.0 ± 16.9 %). Myocardial blood flow in the late MVO was improved with cyclosporine versus controls (0.30 ± 0.06 vs 0.21 ± 0.03 ml/g/min, P = 0.002) and was inversely correlated with late-MVO extent (R² = 0.93, P < 0.0001). Deterioration of left ventricular ejection fraction (LVEF) between baseline and 3 h of reperfusion was smaller with cyclosporine (−7.9 ± 2.4 %, P = 0.008) but not postconditioning (−12.0 ± 5.5 %, P = 0.22) when compared with controls (−16.4 ± 5.5 %). In the three groups, infarct size (β = −0.69, P < 0.001) and late MVO (β = −0.33, P = 0.02) were independent predictors of LVEF deterioration following ischemia/reperfusion (R² = 0.73, P < 0.001). Despite both cyclosporine A and postconditioning reduce infarct size, only cyclosporine A infusion had a beneficial effect on microvascular damage and was associated with better preserved LV function when compared with controls.

Role of the MPTP in conditioning the heart - translatability and mechanism

Mitochondria have long been known to be the gatekeepers of cell fate. This is particularly so in the response to acute ischaemia‐reperfusion injury (IRI). Following an acute episode of sustained myocardial ischaemia, the opening of the mitochondrial permeability transition pore (MPTP) in the first few minutes of reperfusion, mediates cell death. Preventing MPTP opening at the onset of reperfusion using either pharmacological inhibitors [such as cyclosporin A (CsA) ] or genetic ablation has been reported to reduce myocardial infarct (MI) size in animal models of acute IRI. Interestingly, the endogenous cardioprotective intervention of ischaemic conditioning, in which the heart is protected against MI by applying cycles of brief ischaemia and reperfusion to either the heart itself or a remote organ or tissue, appears to be mediated through the inhibition of MPTP opening at reperfusion. Small proof‐of‐concept clinical studies have demonstrated the translatability of this therapeutic approach to target MPTP opening using CsA in clinical settings of acute myocardial IRI. However, given that CsA is a not a specific MPTP inhibitor, more novel and specific inhibitors of the MPTP need to be discovered – the molecular identification of the MPTP should facilitate this. In this paper, we review the role of the MPTP as a target for cardioprotection, the potential mechanisms underlying MPTP inhibition in the setting of ischaemic conditioning, and the translatability of MPTP inhibition as a therapeutic approach in the clinical setting.

Linked Articles

This article is part of a themed section on Conditioning the Heart – Pathways to Translation. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue‐8

The mitochondrial permeability transition pore: molecular nature and role as a target in cardioprotection

The mitochondrial permeability transition (PT) - an abrupt increase permeability of the inner membrane to solutes - is a causative event in ischemia-reperfusion injury of the heart, and the focus of intense research in cardioprotection. The PT is due to opening of the PT pore (PTP), a high conductance channel that is critically regulated by a variety of pathophysiological effectors. Very recent work indicates that the PTP forms from the F-ATP synthase, which would switch from an energy-conserving to an energy-dissipating device. This review provides an update on the current debate on how this transition is achieved, and on the PTP as a target for therapeutic intervention. This article is part of a Special Issue entitled "Mitochondria: from basic mitochondrial biology to cardiovascular disease".

The effect of prethrombolytic cyclosporine-A injection on clinical outcome of acute anterior ST-elevation myocardial infarction

INTRODUCTION

Reperfusion injury reduces the benefits of early reperfusion therapies after acute ST-elevation myocardial infarction (STEMI). Cyclosporine-A (CsA) is a potent inhibitor of opening of the mitochondrial permeability transition pore, which has been shown to play a key role in myocardial reperfusion injury. The impact of this treatment on clinical outcomes of acute STEMI remains unknown. Our aim was to investigate the clinical outcomes of using this drug in patients with acute anterior STEMI receiving thrombolytic treatment (TLT).

METHODS

In this double-blinded randomized clinical trial, 101 patients with acute anterior STEMI who were candidate for TLT, were enrolled and randomly assigned into treatment or control groups. Patients in the treatment group received an intravenous bolus injection of 2.5 mg/kg of CsA immediately before TLT. The patients in the control group received an equivalent volume of normal saline. Infarct size, occurrence of major arrhythmias, heart failure, left ventricular ejection fraction (LVEF), TLT-related complications, in-hospital and 6-month mortality rates were investigated.

RESULTS

There were no significant differences among the demographics, myocardial enzyme release, occurrence of major arrhythmias [9 (18%) vs. 12 (23.5%), P = 0.80], heart failure [18 (36%) vs. 19 (38.3%), P = 0.83], LVEF at first day [34.7 ± 9.9% vs. 33.5 ± 8.1%, P = 0.50] or at discharge [37.7 ± 10% vs. 36.1 ± 8.2%, P = 0.43], and in-hospital [4 (8%) vs. 6 (11.8%), P = 0.74] or 6-month mortality rates [9 (18%) vs. 10 (19.6%), P = 0.99] between the CsA vs. the control group.

CONCLUSION

In this study, the prethrombolytic administration of CsA was not associated with a reduction in the infarct size or any improvement in clinical outcomes.

Targeting mitochondria for cardioprotection: examining the benefit for patients

ABSTRACT: 

Mitochondria are critical for sustaining life, not only as the essential powerhouses of cells but as critical mediators of cell survival and death. Mitochondrial dysfunction has been identified as a key perturbation underlying numerous pathologies including myocardial ischemia–reperfusion injury and the subsequent development of impaired left ventricular systolic function and compensatory cardiac hypertrophy. This article outlines the role of mitochondrial dysfunction in these important cardiac pathologies and highlights current cardioprotective strategies and their clinical efficacy in acute myocardial infarction and heart failure patients. Finally, we explore novel mitochondrial targets and evaluate their potential future translation for clinical cardioprotection.

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

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

Pharmacokinetic characterization of intravenous cyclosporine treatment for cardioprotection during resuscitation of asphyxiated newborn piglets

OBJECTIVES

Cyclosporine treatment, as a single intravenous bolus, during resuscitation has been shown to attenuate myocardial injury in asphyxiated newborn piglets. However, the pharmacokinetics of cyclosporine treatment for cardioprotection in newborns has not been studied. We aimed to assess the pharmacokinetics of a single intravenous cyclosporine treatment during resuscitation of asphyxiated newborn piglets and compare these parameters with healthy newborn piglets.

DESIGN

Newborn piglets were acutely instrumented and normocapnic alveolar hypoxia was induced for 2 hours followed by 4 hours of reoxygenation. Piglets were block-randomized to receive a single intravenous bolus of cyclosporine (2.5-25 mg/kg) (n = 8 per group). Eight piglets underwent no hypoxia-reoxygenation and received 10 mg/kg cyclosporine at the corresponding time point. Plasma cyclosporine and troponin concentrations during reoxygenation period were determined by high-pressure liquid chromatography and enzyme-linked immunosorbent assay, respectively. Noncompartmental methods were used to calculate the pharmacokinetic parameters. Cyclosporine concentrations and pharmacokinetic parameters were analyzed by one-way analysis of variance.

SETTING

University animal laboratory.

SUBJECTS

Piglets (1-4 days old, weighing 1.4-2.5 kg).

INTERVENTIONS

Intravenous cyclosporine (2.5, 10, or 25 mg/kg) given during resuscitation.

MEASUREMENTS AND MAIN RESULTS

In the hypoxic-reoxygenated piglets, the plasma AUC(0-4 hrs) and C(max) of cyclosporine at reoxygenation were in the following rank order: 25 > 10 > 2.5 mg/kg treatment (p < 0.001 between groups, analysis of variance). Plasma AUC(0-4 hrs) and C(max) in piglets treated with cyclosporine at 25 mg/kg was associated with increased plasma troponin levels, a marker of myocardial injury, relative to piglets treated with 2.5 and 10 mg/kg. Asphyxiated newborn piglets had higher clearance and lower AUC(0-∞), but similar AUC(0-4 hrs), steady-state volume of distribution, and mean residence time compared with those of healthy newborn piglets.

CONCLUSIONS

This is the first study to demonstrate the pharmacokinetics of intravenous cyclosporine treatment during resuscitation of asphyxiated newborn piglets, which did not appear to different from that of healthy piglets.

Enhanced effect of combining human cardiac stem cells and bone marrow mesenchymal stem cells to reduce infarct size and to restore cardiac function after myocardial infarction

BACKGROUND

Because mesenchymal stem cells (MSCs) induce proliferation and differentiation of c-kit(+) cardiac stem cells (CSCs) in vivo and in vitro, we hypothesized that combining human (h) MSCs with c-kit(+) hCSCs produces greater infarct size reduction compared with either cell administered alone after myocardial infarction (MI).

METHODS AND RESULTS

Yorkshire swine underwent balloon occlusion of the left anterior descending coronary artery followed by reperfusion and were immunosuppressed after MI with cyclosporine and methylprednisolone. Intramyocardial combination hCSCs/hMSCs (1 million cells/200 million cells, n=5), hCSCs alone (1 million cells, n=5), hMSCs alone (200 million cells, n=5), or placebo (phosphate-buffered saline; n=5) was injected into the infarct border zones at 14 days after MI. Phenotypic response to cell therapy was assessed by cardiac magnetic resonance imaging and micromanometer conductance catheterization hemodynamics. Although each cell therapy group had reduced MI size relative to placebo (P<0.05), the MI size reduction was 2-fold greater in combination versus either cell therapy alone (P<0.05). Accompanying enhanced MI size reduction were substantial improvement in left ventricular chamber compliance (end-diastolic pressure-volume relationship; P<0.01) and contractility (preload recruitable stroke work and dP/dtmax; P<0.05) in combination-treated swine. Ejection fraction was restored to baseline in cell-treated pigs, whereas placebo pigs had persistently depressed left ventricular function (P<0.05). Immunohistochemistry showed 7-fold enhanced engraftment of stem cells in the combination therapy group versus either cell type alone (P<0.001).

CONCLUSIONS

Combining hMSCs and hCSCs as a cell therapeutic enhances scar size reduction and restores diastolic and systolic function toward normal after MI. Taken together, these findings illustrate important biological interactions between c-kit(+) CSCs and MSCs that enhance cell-based therapeutic responses.

Cyclosporin A and cardioprotection: from investigative tool to therapeutic agent

Ischaemic heart disease (IHD) is the leading cause of death and disability worldwide. The pathophysiological effects of IHD on the heart most often result from the detrimental effects of acute ischaemia-reperfusion injury (IRI) on the myocardium. Therefore, novel therapeutic targets for protecting the myocardium against acute IRI are required to reduce injury to the heart, preserve cardiac function and improve clinical outcomes in patients with IHD. In this regard, the mitochondrial permeability transition pore (mPTP) has emerged as a critical target for cardioprotection which is readily amenable to intervention at the time of myocardial reperfusion. The formation and opening of the mPTP at the onset of myocardial reperfusion is a major determinant of mitochondrial dysfunction and cardiomyocyte death in the setting of acute IRI. The seminal discovery in the late 1980s that mPTP opening could be pharmacologically inhibited by the immunosuppressive agent, cyclosporin A (CsA), has been fundamental in the elucidation of the critical role of the mPTP as a mediator of acute IRI and, therefore, a viable target for cardioprotection. Its initial role as an investigative tool was used to identify mitochondrial cyclophilin D to be a regulatory component of the mPTP. The mPTP as a viable target for cardioprotection has recently been translated into the clinical setting with CsA reducing myocardial infarct size in patients. In this article, we review the intriguing role of CsA as a tool for investigating the mPTP as a target for cardioprotection and its potential role as a therapeutic agent for patients with IHD.

The role of cyclosporine in the treatment of myocardial reperfusion injury

Myocardial injury in adult, pediatric, and newborn patients is a leading cause of mortality and morbidity. Although the underlying etiologies are different among patient populations, the sequence of initial ischemic-hypoxic injury followed by secondary myocardial reperfusion injury is relatively consistent. Overall infarct size is important because it is believed to be a key determinant of mortality. The detrimental effects of myocardial reperfusion have been proposed to be at least partially related to the formation of mitochondrial permeability transition pore (MPTP). The MPTP is a nonspecific pore, which forms during myocardial reperfusion and allows the release of apoptotic signaling molecules and may also lead to cellular necrosis. Cyclosporine A has been shown to be a potent inhibitor of the MPTP, leading to its study as a potential treatment to limit myocardial reperfusion injury. Multiple adult animal models have demonstrated the protective effects of cyclosporine in ischemia-reperfusion. A recent human pilot clinical trial also reported reduced myocardial injury and infarct size in patients treated with cyclosporine intravenously before percutaneous coronary intervention for ST-elevation myocardial infarction. Despite the paucity of evidence of cyclosporine A demonstrating myocardial protection in pediatric and newborn patients, the existing animal experimental results are promising.

Early versus delayed cyclosporine treatment in cardiac recovery and intestinal injury during resuscitation of asphyxiated newborn piglets

PURPOSE

We previously demonstrated that treating asphyxiated newborn piglets with cyclosporine immediately following resuscitation can improve cardiac and intestinal recovery. However, immediate treatment may not be feasible for a large portion of neonates delivered in peripheral or rural hospitals. Therefore, our objective was to determine if delayed cyclosporine treatment remained effective in treating neonatal asphyxia. We hypothesized that early and delayed cyclosporine treatment would improve cardiac and intestinal recovery during resuscitation of asphyxiated newborn piglets.

METHODS

Thirty piglets (1-4 days old) were instrumented for continuous monitoring of cardiac output and mesenteric hemodynamics. After stabilization, normocapnic alveolar hypoxia (10-15 % oxygen) was instituted for 2 h followed by reoxygenation with 100 % oxygen for 0.5 h, then 21 % for 5.5 h. Piglets were block-randomized to receive either intravenous bolus of cyclosporine A (10 mg/kg) or normal saline (control) at 5 or 120 min of reoxygenation (early or delayed, respectively; n = 8/group). Myocardial and intestinal lactate concentrations as well as histological examinations were determined.

RESULTS

Hypoxic piglets had cardiogenic shock (cardiac output 52 ± 1 % of baseline, mean arterial pressure 32 ± 1 mmHg) and acidosis (pH 6.98 ± 0.1). Although both cyclosporine treatments improved cardiac output (p < 0.05 vs. controls), only early cyclosporine treatment improved stroke volume and systemic oxygen delivery (p < 0.05 vs. controls). Left ventricle and intestinal lactate were lowered in both cyclosporine-treated groups (p < 0.05 vs. controls). Early, but not delayed, cyclosporine treatment also attenuated intestinal injury (p < 0.05 vs. controls).

CONCLUSION

This study demonstrates that treating asphyxiated newborn piglets with cyclosporine within 2 h of resuscitation is effective with superior cardioprotection and intestinal injury attenuation with early treatment.

Cyclosporine treatment improves cardiac function and systemic hemodynamics during resuscitation in a newborn piglet model of asphyxia: a dose-response study

OBJECTIVES

Asphyxiated neonates often have myocardial depression, which is a significant cause of morbidity and mortality. Cardioprotective effects of cyclosporine have been observed in adult patients and animals with myocardial infarction. However, the cardioprotective effect of cyclosporine in neonates has not yet been studied. We hypothesize that cyclosporine will improve cardiac function and reduce myocardial injury in asphyxiated newborn piglets.

DESIGN

Thirty-six piglets (1-4 days old, weighing 1.4-2.5 kg) were acutely instrumented for continuous monitoring of cardiac output and systemic arterial pressure. After stabilization, normocapnic alveolar hypoxia (10% to 15% oxygen) was instituted for 2 hrs followed by reoxygenation with 100% oxygen for 0.5 hrs and then 21% for 3.5 hrs. A nonasphyxiated, sham-operated group was included (n = 4) to control for effects of the surgical model. Plasma troponin and myocardial lactate concentrations were determined as well as morphologic examinations.

SETTING

Neonatal asphyxia and reoxygenation.

SUBJECTS

Newborn (1-4 days old) piglets.

INTERVENTIONS

Piglets were block-randomized to receive intravenous boluses of cyclosporine A (2.5, 10, or 25 mg/kg) or normal saline (control) at 5 mins of reoxygenation (n = 8/group).

MEASUREMENTS AND MAIN RESULTS

Cardiac index, heart rate, systemic oxygenation, plasma troponin, and left ventricular lactate were measured. Hypoxic piglets had cardiogenic shock (cardiac output 40% to 48% of baseline), hypotension (mean arterial pressure 27-31 mm Hg), and acidosis (pH 7.04). Cyclosporine treatment caused bell-shaped improvements in cardiac output, stroke volume, and systemic oxygen delivery (p < .05 vs. controls). Plasma troponin and left ventricle lactate were higher in controls than that of 2.5 and 10 mg/kg cyclosporine-treated groups (p < .05). Although histologic features of myocardial injury were not different among groups, severe damage was observed in mitochondria of control piglets but attenuated in that of cyclosporine (10 mg/kg) treatment.

CONCLUSIONS

Postresuscitation administration of cyclosporine causes preservation of cardiac function and attenuates myocardial injury in newborn piglets after asphyxia-reoxygenation.

Cyclosporin variably and inconsistently reduces infarct size in experimental models of reperfused myocardial infarction: a systematic review and meta-analysis

Cyclosporin is an immunosuppressant that has recently been proposed as a treatment to prevent reperfusion injury in acute myocardial infarction (MI). We aimed to determine the overall efficacy of cyclosporin in experimental studies of acute reperfused MI. We conducted a systematic review and stratified meta-analysis of published studies describing the efficacy of cyclosporin in experimental models of acute reperfused MI. We included all in vivo publications of cyclosporin where infarct size was measured. A literature search identified 29 potential studies of which 20 fulfilled the eligibility criteria. In these studies (involving four species of animals), cyclosporin reduced myocardial infarct size by a standardized mean (95% confidence interval) difference of -1.60 (-2.17, -1.03) compared with controls. Cyclosporin failed to demonstrate a convincing benefit in studies involving pigs. Despite this observation, the overall efficacy of cyclosporin did not differ across species (P= 0.358). The dose of cyclosporin given did not affect final infarct size (P= 0.203). Funnel plots of these data suggested heterogeneity among the studies. Cyclosporin had variable effects on infarct size compared with placebo. Cyclosporin had no effect on myocardial infarct size in swine, raising a question over the potential cardioprotective effects of cyclosporin in man.

Cell death pathways in acute ischemia/reperfusion injury

The consequence of myocardial ischemia is energetic stress, while reperfusion is accompanied by abrupt ionic shifts and considerable oxidative stress. Cells die by apoptotic and necrotic pathways. After the acute injury, the healing myocardium is subject to biomechanical stress and inflammation, which can trigger a smaller but more sustained wave of cell death, as well as changes in the metabolic and functional characteristics of surviving cells. The goal of cardioprotection is to prevent cell death during the acute injury as well as to modulate the detrimental processes that ensue during remodeling. This review will focus on acute injury, and the central premise is that mitochondria are the key determinant of cardiomyocyte fate.

The role of mitochondrial permeability transition in reperfusion-induced cardiomyocyte death depends on the duration of ischemia

Mitochondrial permeability transition (MPT) is critical in cardiomyocyte death during reperfusion but it is not the only mechanism responsible for cell injury. The objectives of the study is to investigate the role of the duration of myocardial ischemia on mitochondrial integrity and cardiomyocyte death. Mitochondrial membrane potential (ΔΨm, JC-1) and MPT (calcein) were studied in cardiomyocytes from wild-type and cyclophilin D (CyD) KO mice refractory to MPT, submitted to simulated ischemia and 10 min reperfusion. Reperfusion after 15 min simulated ischemia induced a rapid recovery of ΔΨm, extreme cell shortening (contracture) and mitochondrial calcein release, and CyD ablation did not affect these changes or cell death. However, when reperfusion was performed after 25 min simulated ischemia, CyD ablation improved ΔΨm recovery and reduced calcein release and cell death (57.8 ± 4.9% vs. 77.3 ± 4.8%, P < 0.01). In a Langendorff system, CyD ablation increased infarct size after 30 min of ischemia (61.3 ± 6.4% vs. 45.3 ± 4.0%, P = 0.02) but reduced it when ischemia was prolonged to 60 min (52.8 ± 8.1% vs. 87.6 ± 3.7%, P < 0.01). NMR spectroscopy in rat hearts showed a rapid recovery of phosphocreatine after 30 min ischemia followed by a marked decay associated with contracture and LDH release, that were preventable with contractile blockade but not with cyclosporine A. In contrast, after 50 min ischemia, phosphocreatine recovery was impaired even with contractile blockade (65.2 ± 4% at 2 min), and cyclosporine A reduced contracture, LDH release and infarct size (52.1 ± 4.2% vs. 82.8 ± 3.6%, P < 0.01). In conclusion, the duration of ischemia critically determines the importance of MPT on reperfusion injury. Mechanisms other than MPT may play an important role in cell death after less severe ischemia.

Cyclosporine A, 2.5 mg/kg, does not reduce myocardial infarct size in a porcine model of ischemia and reperfusion

BACKGROUND

In recent years, cyclosporine A (CsA) has emerged as a promising therapy to limit myocardial ischemic-reperfusion injury, presumably by inhibiting the opening of the mitochondrial permeability transition pore. Results from different large animal models are conflicting, however, with failure to prove beneficial effects of 10 mg/kg CsA administered at reperfusion. Recently, a small clinical study using a bolus of 2.5 mg/kg CsA showed promising but not unequivocal results. The aim of the present study was to estimate the magnitude of a possible infarct reduction with the use of the latter regimen in a closed-chest porcine model for ischemia and reperfusion. Materials and

METHODS

Pigs underwent catheterization with balloon occlusion of the left descending coronary artery for 40 minutes, followed by reperfusion for 4 hours. They were randomized to receive an intravenous bolus 7 minutes before reperfusion of either 2.5 mg/kg CsA (n = 12) or saline (control, n = 11). Hearts were stained to quantify area at risk and infarct size.

RESULTS

Throughout the experiment, there were no differences between the groups in baseline characteristics or hemodynamic variables. CsA treatment did not reduce infarct size as a proportion of area at risk compared with control (51% ± 6% and 54% ± 6%, respectively, P = .75).

CONCLUSION

In a closed-chest porcine model for myocardial ischemia and reperfusion injury, 2.5 mg/kg CsA administered before reperfusion did not reduce infarct size.

Translating novel strategies for cardioprotection: the Hatter Workshop Recommendations

Ischemic heart disease (IHD) is the leading cause of death worldwide. Novel cardioprotective strategies are therefore required to improve clinical outcomes in patients with IHD. Although a large number of novel cardioprotective strategies have been discovered in the research laboratory, their translation to the clinical setting has been largely disappointing. The reason for this failure can be attributed to a number of factors including the inadequacy of the animal ischemia–reperfusion injury models used in the preclinical cardioprotection studies and the inappropriate design and execution of the clinical cardioprotection studies. This important issue was the main topic of discussion of the UCL-Hatter Cardiovascular Institute 6th International Cardioprotection Workshop, the outcome of which has been published in this article as the “Hatter Workshop Recommendations”. These have been proposed to provide guidance on the design and execution of both preclinical and clinical cardioprotection studies in order to facilitate the translation of future novel cardioprotective strategies for patient benefit.