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Aims: Old age and diabetes are risk factors that often coexist increasing the vulnerability of the heart to the lethal effects of ischaemia-reperfusion injury (IRI). However, to our knowledge, no investigations have examined IRI and cardioprotective signalling in animal models bearing these co-morbidities concomitantly. The ability of the heart to recover following IRI is greatly dependent on its innate cardioprotective potential, in which a central role is played by Akt. We aimed to investigate in an aging diabetic rat model, the susceptibility of the heart to IRI, the achievability of ischaemic preconditioning (IPC) against this lethal event, and the changes in Akt signalling, as the main prosurvival intracellular pathway., Methods and Results: Our data showed that the isolated hearts of aged, diabetic Goto-Kakizaki rats were more susceptible to sub-lethal injury and not amenable to cardioprotection via IPC, compared with younger diabetic rat hearts. Western blot analysis of the heart tissue suggested a chronic up-regulation of Akt phosphorylation, and reduced expression of the mitochondrial regulator PGC-1α and of the anti-oxidant enzyme catalase, potentially due to the Akt up-regulation. Moreover, no further activation of Akt could be achieved following IPC., Conclusion: An increased susceptibility to IRI in the aged, diabetic heart could be a consequence of impaired Akt signalling due to chronic Akt phosphorylation. Additional Akt phosphorylation required for IPC protection may therefore not be possible in the aged, diabetic rat heart and may explain why this cardioprotective manoeuvre cannot be achieved in these hearts.

Objectives: The aim of this study was to determine the accuracy of the contrast "bolus only" T1 mapping cardiac magnetic resonance (CMR) technique for measuring myocardial extracellular volume fraction (ECV)., Background: Myocardial ECV can be measured with T1 mapping before and after contrast agent if the contrast agent distribution between blood/myocardium is at equilibrium. Equilibrium distribution can be achieved with a primed contrast infusion (equilibrium contrast-CMR [EQ-CMR]) or might be approximated by the dynamic equilibration achieved by delayed post-bolus measurement. This bolus only approach is highly attractive, but currently limited data support its use. We compared the bolus only technique with 2 independent standards: collagen volume fraction (CVF) from myocardial biopsy in aortic stenosis (AS); and the infusion technique in 5 representative conditions., Methods: One hundred forty-seven subjects were studied: healthy volunteers (n = 50); hypertrophic cardiomyopathy (n = 25); severe AS (n = 22); amyloid (n = 20); and chronic myocardial infarction (n = 30). Bolus only (at 15 min) and infusion ECV measurements were performed and compared. In 18 subjects with severe AS the results were compared with histological CVF., Results: The ECV by both techniques correlated with histological CVF (n = 18, r² = 0.69, p < 0.01 vs. r² = 0.71, p < 0.01, p = 0.42 for comparison). Across health and disease, there was strong correlation between the techniques (r² = 0.97). However, in diseases of high ECV (amyloid, hypertrophic cardiomyopathy late gadolinium enhancement, and infarction), Bland-Altman analysis indicates the bolus only technique has a consistent and increasing offset, giving a higher value for ECVs above 0.4 (mean difference ± limit of agreement for ECV <0.4 = -0.004 ± 0.037 vs. ECV >0.4 = 0.040 ± 0.075, p < 0.001)., Conclusions: Bolus only, T1 mapping-derived ECV measurement is sufficient for ECV measurement across a range of cardiac diseases, and this approach is histologically validated in AS. However, when ECV is >0.4, the bolus only technique consistently measures ECV higher compared with infusion., (Copyright © 2013 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Significance: Mitochondria are dynamic organelles capable of changing their shape and distribution by undergoing either fission or fusion. Changes in mitochondrial dynamics, which is under the control of specific mitochondrial fission and fusion proteins, have been implicated in cell division, embryonic development, apoptosis, autophagy, and metabolism. Although the machinery for modulating mitochondrial dynamics is present in the cardiovascular system, its function there has only recently been investigated. In this article, we review the emerging role of mitochondrial dynamics in cardiovascular health and disease., Recent Advances: Changes in mitochondrial dynamics have been implicated in vascular smooth cell proliferation, cardiac development and differentiation, cardiomyocyte hypertrophy, myocardial ischemia-reperfusion injury, cardioprotection, and heart failure., Critical Issues: Many of the experimental studies investigating mitochondrial dynamics in the cardiovascular system have been confined to cardiac cell lines, vascular cells, or neonatal cardiomyocytes, in which mitochondria are distributed throughout the cytoplasm and are free to move. However, in the adult heart where mitochondrial movements are restricted by their tightly-packed distribution along myofibrils or beneath the subsarcolemma, the relevance of mitochondrial dynamics is less obvious. The investigation of transgenic mice deficient in cardiac mitochondrial fission or fusion proteins should help elucidate the role of mitochondrial dynamics in the adult heart., Future Directions: Investigating the role of mitochondrial dynamics in cardiovascular health and disease should result in the identification of novel therapeutic targets for treating patients with cardiovascular disease, the leading cause of death and disability globally.

Coronary heart disease (CHD) is the leading cause of death and disability in Europe. For patients presenting with an acute ST-segment elevation myocardial infarction (STEMI), timely myocardial reperfusion using either thrombolytic therapy or primary percutaneous coronary intervention (PPCI) is the most effective therapy for limiting myocardial infarct (MI) size, preserving left-ventricular systolic function and reducing the onset of heart failure. Despite this, the morbidity and mortality of STEMI patients remain significant, and novel therapeutic interventions are required to improve clinical outcomes in this patient group. Paradoxically, the process of myocardial reperfusion can itself induce cardiomyocyte death-a phenomenon which has been termed 'myocardial reperfusion injury' (RI), the irreversible consequences of which include microvascular obstruction and myocardial infarction. Unfortunately, there is currently no effective therapy for preventing myocardial RI in STEMI patients making it an important residual target for cardioprotection. Previous attempts to translate cardioprotective therapies (antioxidants, calcium-channel blockers, and anti-inflammatory agents) for reducing RI into the clinic, have been unsuccessful. An improved understanding of the pathophysiological mechanisms underlying RI has resulted in the identification of several promising mechanical (ischaemic post-conditioning, remote ischaemic pre-conditioning, therapeutic hypothermia, and hyperoxaemia), and pharmacological (atrial natriuretic peptide, cyclosporin-A, and exenatide) therapeutic strategies, for preventing myocardial RI, many of which have shown promise in initial proof-of-principle clinical studies. In this article, we review the pathophysiology underlying myocardial RI, and highlight the potential therapeutic interventions which may be used in the future to prevent RI and improve clinical outcomes in patients with CHD.

Aims: The diabetic heart is resistant to the myocardial infarct-limiting effects of ischemic preconditioning (IPC). This may be in part due to the downregulation of the phosphatidylinositol 3'-kinase-Akt pathway, an essential component of IPC protection. We hypothesized that treating the diabetic heart with the sulfonylurea, glimepiride, which has been reported to activate Akt, may lower the threshold required to protect the diabetic heart by IPC., Methods: Goto-Kakizaki rats (a type II lean model of diabetes) received glimepiride (20 mg/kg per d, by oral gavage) or vehicle for (a) 3 months (chronic treatment) or (b) 24 hours (subacute treatment). In the third group, glimepiride (10 μmol/L) was administered only to the isolated hearts on the Langendorff apparatus (acute treatment). All hearts were subjected to 35 minutes ischemia and 120 minutes reperfusion ex vivo, at the end of which infarct size was determined by tetrazolium staining. Preconditioning treatment comprised 1 (IPC-1) or 3 (IPC-3) cycles of 5 minutes global ischemia and 10 minutes reperfusion., Results: The diabetic heart was found to be resistant to IPC such that 3-IPC cycles, instead of the usual 1-IPC cycle, were required for cardioprotection. However, pretreatment with glimepiride lowered the threshold for IPC such that both 1 and 3 cycles of IPC elicited cardioprotection: chronic glimepiride treatment (IPC-1 31.9% ± 3.8% and IPC-3 33.5% ± 2.4% vs 43.9% ± 1.4% control, P < .05; N > 6 per group); subacute glimepiride treatment (IPC-1 31.1% ± 3.0% and IPC-3 29.3% ± 3.3% vs 42.2% ± 2.3% control, P < .05 N > 6 per group); and acute glimepiride treatment (IPC-1 28.2% ± 3.7% and IPC-3 24.6% ± 5.4% vs 41.9% ± 5.4% control, P < .05; N > 6 per group). This effect of glimepiride was independent of changes in blood glucose., Conclusions: We report for the first time that glimepiride treatment facilitates the cardioprotective effect elicited by IPC in the diabetic heart.

Background: Coronary revascularization using percutaneous coronary intervention (PCI) is one of the major treatments for patients with stable coronary artery disease, with approximately 1.5 million patients undergoing PCI in the United States and Europe every year. An important neglected complication of PCI is contrast-induced acute kidney injury (CI-AKI)., Design: In this article, we review the definition, pathogenesis and management of CI-AKI and highlight potential therapeutic options for preventing CI-AKI in post-PCI patients., Results: CI-AKI is an important but underdiagnosed complication of PCI that is associated with increased in-hospital morbidity and mortality. Patients with pre-existing renal impairment and diabetes are particularly susceptible to this complication post-PCI. Optimization of the patients' circulating volume remains the mainstay for preventing CI-AKI, although the best strategy for achieving this is still controversial., Conclusion: Following PCI, CI-AKI is an overlooked complication which is associated with significant morbidity and mortality. In this article, we review the pathophysiology of CI-AKI in patients undergoing PCI and discuss the potential therapeutic options for preventing it., (© 2013 The Authors. European Journal of Clinical Investigation © 2013 Stichting European Society for Clinical Investigation Journal Foundation.)

Objectives: Mutations in PTEN inducible kinase-1 (PINK1) induce mitochondrial dysfunction in dopaminergic neurons resulting in an inherited form of Parkinson's disease. Although PINK1 is present in the heart its exact role there is unclear. We hypothesized that PINK1 protects the heart against acute ischemia reperfusion injury (IRI) by preventing mitochondrial dysfunction., Methods and Results: Over-expressing PINK1 in HL-1 cardiac cells reduced cell death following simulated IRI (29.2±5.2% PINK1 versus 49.0±2.4% control; N = 320 cells/group P<0.05), and delayed the onset of mitochondrial permeability transition pore (MPTP) opening (by 1.3 fold; P<0.05). Hearts excised from PINK1+/+, PINK1+/- and PINK1-/- mice were subjected to 35 minutes regional ischemia followed by 30 minutes reperfusion. Interestingly, myocardial infarct size was increased in PINK1-/- hearts compared to PINK1+/+ hearts with an intermediate infarct size in PINK1+/- hearts (25.1±2.0% PINK1+/+, 38.9±3.4% PINK1+/- versus 51.5±4.3% PINK1-/- hearts; N>5 animals/group; P<0.05). Cardiomyocytes isolated from PINK1-/- hearts had a lower resting mitochondrial membrane potential, had inhibited mitochondrial respiration, generated more oxidative stress during simulated IRI, and underwent rigor contracture more rapidly in response to an uncoupler when compared to PINK1+/+ cells suggesting mitochondrial dysfunction in hearts deficient in PINK1., Conclusions: We show that the loss of PINK1 increases the heart's vulnerability to ischemia-reperfusion injury. This may be due, in part, to increased mitochondrial dysfunction. These findings implicate PINK1 as a novel target for cardioprotection.

Coronary heart disease (CHD) is the leading cause of death and disability worldwide. Despite current therapy, the morbidity and mortality for patients with CHD remains significant. The most important manifestations of CHD arise from acute myocardial ischaemia-reperfusion injury (IRI) in terms of cardiomyocyte death and its long-term consequences. As such, new therapeutic interventions are required to protect the heart against the detrimental effects of acute IRI and improve clinical outcomes. Although a large number of cardioprotective therapies discovered in pre-clinical studies have been investigated in CHD patients, few have been translated into the clinical setting, and a significant number of these have failed to show any benefit in terms of reduced myocardial infarction and improved clinical outcomes. Because of this, there is currently no effective therapy for protecting the heart against the detrimental effects of acute IRI in patients with CHD. One major factor for this lack of success in translating cardioprotective therapies into the clinical setting can be attributed to problems with the clinical study design. Many of these clinical studies have not taken into consideration the important data provided from previously published pre-clinical and clinical studies. The overall aim of this ESC Working Group Cellular Biology of the Heart Position Paper is to provide recommendations for optimizing the design of clinical cardioprotection studies, which should hopefully result in new and effective therapeutic interventions for the future benefit of CHD patients.

Organ or tissue dysfunction due to acute ischemia-reperfusion injury (IRI) is the leading cause of death and disability worldwide. Acute IRI induces cell injury and death in a wide variety of organs and tissues in a large number of different clinical settings. One novel therapeutic noninvasive intervention, capable of conferring multiorgan protection against acute IRI, is 'remote ischemic conditioning' (RIC). This describes an endogenous protective response to acute IRI, which is triggered by the application of one or more brief cycles of nonlethal ischemia and reperfusion to one particular organ or tissue. Originally discovered as a therapeutic strategy for protecting the myocardium against acute IRI, it has been subsequently demonstrated that RIC may confer protection against acute IRI in a number of different noncardiac organs and tissues including the kidneys, lungs, liver, skin flaps, ovaries, intestine, stomach and pancreas. The discovery that RIC can be induced noninvasively by applying the RIC stimulus to the skeletal tissue of the upper or lower limb has facilitated its application to a number of clinical settings in which organs and tissues are at high risk of acute IRI. In this article, we review the experimental studies that have investigated RIC in organs and tissues other than the heart, and we explore the therapeutic potential of RIC in preventing organ and tissue dysfunction induced by acute IRI.

Purpose: Clinical and experimental investigations demonstrated that metformin, a widely used anti-diabetic drug, exhibits cardioprotective properties against myocardial infarction. Interestingly, metformin was previously shown to increase the expression of PGC-1α a key controller of energy metabolism in skeletal muscle, which is down-regulated in diabetic conditions. We hypothesized that chronic treatment with metformin could protect the aged, diabetic heart against ischemia-reperfusion injury (IRI) by up-regulating PGC-1α and improving the impaired functionality of diabetic mitochondria., Methods: Following 4 weeks of metformin (300 mg/kg) administered in the drinking water, 12 month-old diabetic Goto Kakizaki and non-diabetic Wistar rat hearts were assigned for infarct measurement following 35 min ischemia and 60 min reperfusion or for electron microscopy (EM) and Western blotting (WB) investigations., Results: Metformin elicited a cardioprotective effect in both non-diabetic and diabetic hearts. In contrast with the diabetic non-treated hearts, the diabetic hearts treated with metformin showed more organized and elongated mitochondria and demonstrated a significant increase in phosphorylated AMPK and in PGC-1α expression., Conclusions: In summary these results show for the first time that chronic metformin treatment augments myocardial resistance to ischemia-reperfusion injury, by an alternative mechanism in addition to the lowering of blood glucose. This consisted of a positive effect on mitochondrial structure possibly via a pathway involving AMPK activation and PGC-1α. Thus, metformin prescribed chronically to patients may lead to a basal state of cardioprotection thereby potentially limiting the occurrence of myocardial damage by cardiovascular events.

Acute myocardial infarction (MI) is a major cause of death and disability worldwide. In patients with MI, the treatment of choice for reducing acute myocardial ischemic injury and limiting MI size is timely and effective myocardial reperfusion using either thombolytic therapy or primary percutaneous coronary intervention (PPCI). However, the process of reperfusion can itself induce cardiomyocyte death, known as myocardial reperfusion injury, for which there is still no effective therapy. A number of new therapeutic strategies currently under investigation for preventing myocardial reperfusion injury have the potential to improve clinical outcomes in patients with acute MI treated with PPCI.

Ischemic heart disease (IHD) is the leading cause of death and disability worldwide. The major pathological consequences of IHD arise from the detrimental effects of acute ischemia-reperfusion injury (IRI) on the myocardium. Therefore, in order to improve clinical outcomes in patients with IHD, novel therapeutic strategies are required to protect the myocardium from acute IRI and preserve cardiac function (cardioprotection). In this regard, endogenous cardioprotective strategies such as ischemic preconditioning (IPC), ischemic postconditioning (IPost) and remote ischemic conditioning (RIC) may provide novel approaches for protecting the heart in clinical settings in which the patient experiences acute myocardial IRI. In this review article, we provide an overview of these endogenous cardioprotective strategies with respect to the pre-clinical experimental literature, exploring their major characteristics and underlying signaling mechanisms. The application of these therapeutic strategies in the clinical setting for potential patient benefit is reviewed in another article in this special issue.

The myocardial microcirculation provides the vital pressure control and metabolic homeostasis for normal muscle function. Microvascular dysfunction is implicated in chronic cardiac disease and can signify higher risk, but its effect in acute myocardial infarction (AMI) can be profound. Modern management of AMI is focussed entirely on timely epicardial coronary patency, but as a result can leave microcirculatory devastation in its wake. The 'no-reflow' phenomenon occurs in up to 40 % of those successfully reperfused following an ST-elevation AMI (STEMI), and reflects significant microvessel injury that at its most severe involves both microvascular obstruction (MVO) and intramyocardial haemorrhage. Myocardial contrast echocardiography and cardiac magnetic resonance imaging have both led the field in establishing MVO as the prime determinant of adverse left ventricular (LV) remodeling, LV dysfunction, heart failure and increased mortality. These imaging techniques will be essential to support future research endeavours and shift focus to the maintenance of microvascular flow in AMI.

Objective: To measure and assess the significance of myocardial extracellular volume (ECV), determined non-invasively by equilibrium contrast cardiovascular magnetic resonance, as a clinical biomarker in health and a number of cardiac diseases of varying pathophysiology., Design: Prospective study., Setting: Tertiary referral cardiology centre in London, UK., Patients: 192 patients were mainly recruited from specialist clinics. We studied patients with Anderson-Fabry disease (AFD, n=17), dilated cardiomyopathy (DCM, n=31), hypertrophic cardiomyopathy (HCM, n=31), severe aortic stenosis (AS, n=66), cardiac AL amyloidosis (n=27) and myocardial infarction (MI, n=20). The results were compared with those for 81 normal subjects., Results: In normal subjects, ECV (mean (95% CI), measured in the septum) was slightly higher in women than men (0.273 (0.264 to 0.282 vs 0.233 (0.225 to 0.244), p<0.001), with no change with age. In disease, the ECV of AFD was the same as in normal subjects but higher in all other diseases (p<0.001). Mean ECV was the same in DCM, HCM and AS (0.280, 0.291, 0.276 respectively), but higher in cardiac AL amyloidosis and higher again in MI (0.466 and 0.585 respectively, each p<0.001). Where ECV was elevated, correlations were found with indexed left ventricular mass, end systolic volume, ejection fraction and left atrial area in apparent disease-specific patterns., Conclusions: Myocardial ECV, assessed non-invasively in the septum with equilibrium contrast cardiovascular magnetic resonance, shows gender differences in normal individuals and disease-specific variability. Therefore, ECV shows early potential to be a useful biomarker in health and disease.

Aims: Haemodynamics alone do not fully explain symptoms and prognosis in clinically severe aortic stenosis (AS). Myocardial disease, specifically diffuse myocardial fibrosis (DMF), may contribute. We used equilibrium contrast cardiovascular magnetic resonance (EQ-CMR) and sought to non-invasively measure DMF in severe AS and determine its clinical significance before and after valve replacement., Methods and Results: Patients with severe AS underwent echocardiography, brain natriuretic peptide (BNP), 6 min walk test (6MWT), and EQ-CMR pre- (n = 63) at baseline and at 6 months post- (n = 42) aortic valve replacement (AVR). EQ-CMR was also performed in 30 normal controls. Baseline: patients with AS had more DMF than controls (18 vs. 13%, P = 0.007) with a wide range (5-38%) that overlapped controls. The extent of diffuse fibrosis correlated inversely with the 6MWT performance (r(2) = 0.22, P = 0.001). Those with severe diastolic dysfunction had more DMF (P = 0.01). On multivariable analysis, the predictors of performance at 6MWT were diffuse fibrosis and BNP (P = 0.003 and 0.02, respectively). Post-op: following valve replacement, morphological and functional parameters improved [6 MWT, LA area, BNP, left ventricular (LV) hypertrophy, and volumes]. LV hypertrophy regression was shown to be cell volume reduction (P < 0.001) and not fibrosis regression (P = 0.54). Of the five deaths over six-month follow-up, four occurred in patients in the highest tertile of DMF., Conclusion: DMF as measured by EQ-CMR is elevated in severe AS vs. normal controls but with a considerable overlap. It correlates with functional capacity at baseline. LV hypertrophy regression 6 months after AVR is cellular rather than fibrosis resolution.

Hypoxia inducible factor (HIF) is an oxygen-sensitive transcription factor that enables aerobic organisms to adapt to hypoxia. This is achieved through the transcriptional activation of up to 200 genes, many of which are critical to cell survival. Under conditions of normoxia, the hydroxylation of HIF by prolyl hydroxylase domain-containing (PHD) enzymes targets it for polyubiquitination and proteosomal degradation by the von Hippel-Lindau protein (VHL). However, under hypoxic conditions, PHD activity is inhibited, thereby allowing HIF to accumulate and translocate to the nucleus, where it binds to the hypoxia-responsive element sequences of target gene promoters. Experimental studies suggest that HIF may act as a mediator of ischemic preconditioning, and that the genetic or pharmacological stabilization of HIF under normoxic conditions, may protect the heart against the detrimental effects of acute ischemia-reperfusion injury. The mechanisms underlying the cardioprotective effect of HIF are unclear, but it may be attributed to the transcriptional activation of genes associated with cardioprotection such as erythropoietin, heme oxygenase-1, and inducible nitric oxide synthase or it may be due to reprogramming of cell metabolism. In this review article, we highlight the role of HIF in mediating both adaptive and pathological processes in the heart, as well as focusing on the therapeutic potential of the HIF-signaling pathway as a target for cardioprotection., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Phosphatidyl-inositol-3-kinase (PI3K)-Akt pathway is essential for conferring cardioprotection in response to ischaemic preconditioning (IPC) stimulus. However, the role of the individual Akt isoforms expressed in the heart in mediating the protective response to IPC is unknown. In this study, we investigated the specific contribution of Akt1 and Akt2 in cardioprotection against ischaemia-reperfusion (I-R) injury. Mice deficient in Akt1 or Akt2 were subjected to in vivo regional myocardial ischaemia for 30 min. followed by reperfusion for 2 hrs with or without a prior IPC stimulus. Our results show that mice deficient in Akt1 were resistant to protection with either one or three cycles of IPC stimulus (42.7 ± 6.5% control versus 38.5 ± 1.9% 1 χ IPC, N = 6, NS; 41.4 ± 6.3% control versus 32.4 ± 3.2% 3 χ IPC, N = 10, NS). Western blot analysis, performed on heart samples taken from Akt1(-/-) mice subjected to IPC, revealed an impaired phosphorylation of GSK-3β, a downstream effector of Akt, as well as Erk1/2, the parallel component of the reperfusion injury salvage kinase pathway. Akt2(-/-) mice, which exhibit a diabetic phenotype, however, were amenable to protection with three but not one cycle of IPC (46.4 ± 5.6% control versus 35.9 ± 5.0% in 1 χ IPC, N = 6, NS; 47.0 ± 6.0% control versus 30.8 ± 3.3% in 3 χ IPC, N = 6; *P = 0.039). Akt1 but not Akt2 is essential for mediating a protective response to an IPC stimulus. Impaired activation of GSK-3β and Erk1/2 might be responsible for the lack of protective response to IPC in Akt1(-/-) mice. The rise in threshold for protection in Akt2(-/-) mice might be due to their diabetic phenotype., (© 2011 The Authors Journal of Cellular and Molecular Medicine © 2011 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.)

Coronary heart disease (CHD) is the leading cause of morbidity and mortality worldwide. For a large number of patients with CHD, coronary artery bypass graft (CABG) surgery remains the preferred strategy for coronary revascularization. Over the last 10 years, the number of high-risk patients undergoing CABG surgery has increased significantly, resulting in worse clinical outcomes in this patient group. This appears to be related to the ageing population, increased co-morbidities (such as diabetes, obesity, hypertension, stroke), concomitant valve disease, and advances in percutaneous coronary intervention which have resulted in patients with more complex coronary artery disease undergoing surgery. These high-risk patients are more susceptible to peri-operative myocardial injury and infarction (PMI), a major cause of which is acute global ischaemia/reperfusion injury arising from inadequate myocardial protection during CABG surgery. Therefore, novel therapeutic strategies are required to protect the heart in this high-risk patient group. In this article, we review the aetiology of PMI during CABG surgery, its diagnosis and clinical significance, and the endogenous and pharmacological therapeutic strategies available for preventing it. By improving cardioprotection during CABG surgery, we may be able to reduce PMI, preserve left ventricular systolic function, and reduce morbidity and mortality in these high-risk patients with CHD.

Background: Novel cardioprotective strategies are required to improve clinical outcomes in high risk patients undergoing coronary artery bypass graft (CABG) ± valve surgery. Remote ischemic preconditioning (RIC), in which brief episodes of non-lethal ischemia and reperfusion are applied to the arm or leg, has been demonstrated to reduce perioperative myocardial injury following CABG ± valve surgery. Whether RIC can improve clinical outcomes in this setting is unknown and is investigated in the effect of remote ischemic preconditioning on clinical outcomes (ERICCA) trial in patients undergoing CABG surgery. (ClinicalTrials.gov Identifier: NCT01247545)., Methods: The ERICCA trial is a multicentre randomized double-blinded controlled clinical trial which will recruit 1,610 high-risk patients (Additive Euroscore ≥ 5) undergoing CABG ± valve surgery using blood cardioplegia via 27 tertiary centres over 2 years. The primary combined endpoint will be cardiovascular death, non-fatal myocardial infarction, coronary revascularization and stroke at 1 year. Secondary endpoints will include peri-operative myocardial and acute kidney injury, intensive care unit and hospital stay, inotrope score, left ventricular ejection fraction, changes of quality of life and exercise tolerance. Patients will be randomized to receive after induction of anesthesia either RIC (4 cycles of 5 min inflation to 200 mmHg and 5 min deflation of a blood pressure cuff placed on the upper arm) or sham RIC (4 cycles of simulated inflations and deflations of the blood pressure cuff)., Implications: The findings from the ERICCA trial have the potential to demonstrate that RIC, a simple, non-invasive and virtually cost-free intervention, can improve clinical outcomes in higher-risk patients undergoing CABG ± valve surgery.

Background: The mechanism underlying remote ischemic conditioning (RIC) remains unclear. We investigated whether RIC protects the heart through the activation of the adenosine receptor and the PI3K-Akt pathway at the onset of myocardial reperfusion., Methods and Results: Domestic pigs (27-35 kg) were subjected to in situ left anterior descending coronary artery ischemia (60 min) followed by reperfusion (180 min) and randomised to the following: (1) Control- No additional intervention; (2) Remote ischemic preconditioning (RIPC)- Four-5 min cycles of lower limb ischemia/reperfusion were administered prior to myocardial ischemia; (3) RIPC  +  Wort or 8-SPT: Wortmannin (Wort 20 μg/kg, a PI3K inhibitor) or 8-sulfophenyltheophylline (8-SPT 10 mg/kg, an adenosine receptor inhibitor) were administered intravenously 30 s before myocardial reperfusion to RIPC-treated animals; (4) Remote ischemic perconditioning (RIPerC)--Four-5 min cycles of lower limb ischemia/reperfusion were applied 1 min before myocardial reperfusion; (5) RIPerC  +  Wort or 8-SPT: Wort or 8-SPT were given 30 s before myocardial reperfusion to RIPerC-treated animals. Both RIPC and RIPerC reduced myocardial infarct size (13.3 ± 2.2% with RIPC, 18.2 ± 2.0% with RIPerC versus 48.8 ± 4.2% in control:P  < 0.05:N ≥ 5/group). Wortmannin abolished the infarct-limiting effects of RIPC (33.2 ± 6% with RIPC + Wort versus 13.3 ± 2.2% with RIPC:P < 0.05:N ≥ 5/group) but not RIPerC (18.0 ± 3.4% with RIPerC + Wort versus 18.2 ± 2.0% with RIPerC:P > 0.05:N ≥ 5/group). 8-SPT did not influence the infarct-limiting effects of either RIPC or RIPerC. Western blot analysis confirmed Wortmannin-sensitive PI3K and Akt activation at myocardial reperfusion in RIPC-treated hearts., Conclusions: In the porcine heart, both RIPC and RIPerC both reduce myocardial infarct size and with RIPC but not RIPerC this cardioprotective effect is associated with the activation of the PI3K-Akt pathway at reperfusion.

For patients presenting with a ST-segment elevation myocardial infarction (STEMI), early myocardial reperfusion by primary percutaneous coronary intervention (PPCI) remains the most effective treatment strategy for limiting myocardial infarct size, preserving left ventricular systolic function, and preventing the onset of heart failure. Recent advances in PCI technology to improve myocardial reperfusion and the introduction of novel anti-platelet and anti-thrombotic agents to maintain the patency of the infarct-related coronary artery continue to optimize PPCI procedure. However, despite these improvements, STEMI patients still experience significant major adverse cardiovascular events. One major contributing factor has been the inability to protect the heart against the lethal myocardial reperfusion injury, which accompanies PPCI. Past attempts to translate cardioprotective strategies, discovered in experimental studies to prevent lethal myocardial reperfusion injury, into the clinical setting of PPCI have been disappointing. However, a number of recent proof-of-concept clinical studies suggest that the heart can be 'conditioned' to protect itself against lethal myocardial reperfusion injury, as evidenced by a reduction in myocardial infarct size. This can be achieved using either mechanical (such as ischaemic postconditioning, remote ischaemic preconditioning, therapeutic hypothermia, or hyperoxaemia) or pharmacological (such as cyclosporin-A, natriuretic peptide, exenatide) 'conditioning' strategies as adjuncts to PPCI. Furthermore, recent developments in cardiac magnetic resonance (CMR) imaging can provide a non-invasive imaging strategy for assessing the efficacy of these novel adjunctive therapies to PPCI in terms of key surrogate clinical endpoints such as myocardial infarct size, myocardial salvage, left ventricular ejection fraction, and the presence of microvascular obstruction or intramyocardial haemorrhage. In this article, we review the therapeutic potential of 'conditioning' to protect the heart against lethal myocardial reperfusion injury in STEMI patients undergoing PPCI.

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., (© 2011 The Authors. British Journal of Pharmacology © 2011 The British Pharmacological Society.)

Remote ischemic conditioning (RIC) is a therapeutic strategy for protecting organs or tissue against the detrimental effects of acute ischemia-reperfusion injury (IRI). It describes an endogenous phenomenon in which the application of one or more brief cycles of non-lethal ischemia and reperfusion to an organ or tissue protects a remote organ or tissue from a sustained episode of lethal IRI. Although RIC protection was first demonstrated to protect the heart against acute myocardial infarction, its beneficial effects are also seen in other organs (lung, liver, kidney, intestine, brain) and tissues (skeletal muscle) subjected to acute IRI. The recent discovery that RIC can be induced non-invasively by simply inflating and deflating a standard blood pressure cuff placed on the upper arm or leg, has facilitated its translation into the clinical setting, where it has been reported to be beneficial in a variety of cardiac scenarios. In this review article we provide an overview of RIC, the potential underlying mechanisms, and its potential as a novel therapeutic strategy for protecting the heart and other organs from acute IRI.

Diabetes mellitus is a major risk factor for ischemic heart disease (IHD). Patients with diabetes and IHD experience worse clinical outcomes, suggesting that the diabetic heart may be more susceptible to ischemia-reperfusion injury (IRI). In contrast, the animal data suggests that the diabetic heart may be either more, equally, or even less susceptible to IRI. The conflicting animal data may be due to the choice of diabetic and/or IRI animal model. Ischemic conditioning, a phenomenon in which the heart is protected against IRI by one or more brief nonlethal periods of ischemia and reperfusion, may provide a novel cardioprotective strategy for the diabetic heart. Whether the diabetic heart is amenable to ischemic conditioning remains to be determined using relevant animal models of IRI and/or diabetes. In this paper, we review the limitations of the current experimental models used to investigate IRI and cardioprotection in the diabetic heart.

The pharmacological inhibition or genetic ablation of cyclophilin-D (CypD), a critical regulator of the mitochondrial permeability transition pore (mPTP), confers myocardial resistance to acute ischemia-reperfusion injury, but its role in post-myocardial infarction (MI) heart failure is unknown. The aim of this study was to determine whether mitochondrial CypD is also a therapeutic target for the treatment of post-MI heart failure. Wild-type (WT) and CypD(-/-) mice were subjected to either sham surgery or permanent ligation of the left main coronary artery to induce MI, and were assessed at either 2 or 28 days to determine the long-term effects of CypD ablation. After 2 days, myocardial infarct size was smaller and left ventricular (LV) function was better preserved in CypD(-/-) mice compared to WT mice. After 28 days, when compared to WT mice, in the CypD(-/-) mice, mortality was halved, myocardial infarct size was reduced, LV systolic function was better preserved, LV dilatation was attenuated and in the remote non-infarcted myocardium, there was less cardiomyocyte hypertrophy and interstitial fibrosis. Finally, ex vivo fibroblast proliferation was found to be reduced in CypD(-/-) cardiac fibroblasts, and in WT cardiac fibroblasts treated with the known CypD inhibitors, cyclosporin-A and sanglifehrin-A. Following an MI, mice lacking CypD have less mortality, smaller infarct size, better preserved LV systolic function and undergo less adverse LV remodelling. These findings suggest that the inhibition of mitochondrial CypD may be a novel therapeutic treatment strategy for post-MI heart failure., (© 2011 The Authors Journal of Cellular and Molecular Medicine © 2011 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.)

The acute administration of atorvastatin has been reported to reduce myocardial infarct size in animal studies. However, this cardioprotective effect is lost with the chronic administration of atorvastatin, although it can be recaptured by administering an acute high-dose of atorvastatin. We hypothesised that pre-treatment with high-dose atorvastatin, on a background of chronic standard 'statin' therapy, would reduce myocardial injury in patients undergoing elective coronary artery bypass graft (CABG) surgery. One hundred and one consenting patients undergoing elective CABG surgery at a single tertiary cardiac centre were recruited into two randomised controlled, single-blinded clinical studies. Study 1: 45 patients were randomised to receive either 160 mg of atorvastatin 2 h preoperatively and 24 h following surgery or their standard statin therapy. Study 2: 56 patients were randomised to receive either 160 mg of atorvastatin 12 h preoperatively and 24 h following surgery or their standard statin therapy. Blood samples for troponin T and creatine kinase were taken prior to surgery and then at 6, 12, 24, 48 and 72 h post-surgery. Cardiac enzyme levels at each time point and the total area-under curve (AUC) were calculated. The group characteristics and surgical methods were well matched. High-dose atorvastatin was not associated with any significant side effects. There was no significant difference in serum troponin T or creatine kinase in either study at each time point or over 72 h. Study 1: AUC, troponin T: atorvastatin 29.6 ± 34.8 μg/L versus control 25.0 ± 22.0 μg/L:P > 0.05. Creatine kinase: atorvastatin 33,544 ± 20,063 IU/L versus control 30,620 ± 10,776 IU/L:P > 0.05. Study 2: AUC, troponin T: atorvastatin 21.8 ± 14.3 μg/L versus control 20.9 ± 8.7 μg/L:P > 0.05. Creatine kinase: atorvastatin 36,262 ± 28,821 IU/L versus control 33,448 ± 14,984:P > 0.05. There were no differences in postoperative outcomes. We report that the administration of high-dose atorvastatin to low risk patients undergoing elective CABG surgery, who are already on standard dose 'statin' therapy is safe, but does not further reduce perioperative myocardial injury.

Objective: The acute administration of high-dose erythropoietin (EPO) on reperfusing ischaemic myocardium has been reported to halve myocardial infarct (MI) size in preclinical studies, but its effect in ST elevation myocardial infarction patients undergoing primary percutaneous coronary intervention (PPCI) remains unknown. We investigated whether high-dose EPO administered as an adjunct to PPCI reduces MI size., Design: Double-blinded, randomised, placebo-controlled., Setting: Single tertiary cardiac centre., Patients: Fifty-one ST elevation myocardial infarction patients undergoing PPCI., Interventions: Patients were randomly assigned to receive either a single intravenous bolus of EPO (50,000 IU) prior to PPCI with a further bolus given 24 h later (n=26) or placebo (n=25)., Main Outcome Measures: MI size measured by 24 h area under the curve troponin T and cardiac magnetic resonance imaging performed on day 2 and at 4 months., Results: EPO treatment failed to reduce MI size (troponin T area under the curve: 114.6±78 μg/ml EPO vs 100.8±68 μg/ml placebo; infarct mass by cardiac magnetic resonance: 33±16 g EPO vs 25±16 g placebo; both p>0.05). Unexpectedly, EPO treatment doubled the incidence of microvascular obstruction (82% EPO vs 47% placebo; p=0.02) and significantly increased indexed left ventricular (LV) end-diastolic volumes (84±10 ml/m(2) EPO vs 73±13 ml/m(2) placebo; p=0.003), indexed LV end-systolic volumes (41±9 ml/m(2) EPO vs 35±11 ml/m(2) placebo; p=0.035) and indexed myocardial mass (89±16 g/m(2) EPO vs 79±11 g/m(2) placebo; p=0.03). At 4 months, there were no significant differences between groups., Conclusions: High-dose EPO administered as an adjunct to PPCI failed to reduce MI size. In fact, EPO treatment was associated with an increased incidence of microvascular obstruction, LV dilatation and increased LV mass. Clinical Trial Registration Information http://public.ukcrn.org.uk/search/StudyDetail.aspx?StudyID=4058 Unique Identifier=Study ID 4058.

Background: Myocardial infarction (MI) can be readily assessed using late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR). Inversion recovery (IR) sequences provide the highest contrast between enhanced infarct areas and healthy myocardium. Applying such methods to small animals is challenging due to rapid respiratory and cardiac rates relative to T1 relaxation., Methods: Here we present a fast and robust protocol for assessing LGE in small animals using a multi-slice IR gradient echo sequence for efficient assessment of LGE. An additional Look-Locker sequence was used to assess the optimum inversion point on an individual basis and to determine most appropriate gating points for both rat and mouse. The technique was applied to two preclinical scenarios: i) an acute (2 hour) reperfused model of MI in rats and ii) mice 2 days following non-reperfused MI., Results: LGE images from all animals revealed clear areas of enhancement allowing for easy volume segmentation. Typical inversion times required to null healthy myocardium in rats were between 300-450 ms equivalent to 2-3 R-waves and ~330 ms in mice, typically 3 R-waves following inversion. Data from rats was also validated against triphenyltetrazolium chloride staining and revealed close agreement for infarct size., Conclusion: The LGE protocol presented provides a reliable method for acquiring images of high contrast and quality without excessive scan times, enabling higher throughput in experimental studies requiring reliable assessment of MI.

Coronary artery disease (CAD) is the leading cause of death and disability worldwide, and early and successful restoration of myocardial reperfusion following an ischemic event is the most effective strategy to reduce final infarct size and improve clinical outcome. This process can, however, induce further myocardial damage, namely acute myocardial ischemia-reperfusion injury (IRI) and worsen clinical outcome. Therefore, novel therapeutic strategies are required to protect the myocardium against IRI in patients with CAD. In this regard, the endogenous cardioprotective phenomenon of "ischemic conditioning," in which the heart is put into a protected state by subjecting it to one or more brief nonlethal episodes of ischemia and reperfusion, has the potential to attenuate myocardial injury during acute IRI. Intriguingly, the heart can be protected in this manner by applying the "ischemic conditioning" stimulus to an organ or tissue remote from the heart (termed remote ischemic conditioning or RIC). Furthermore, the discovery that RIC can be noninvasively applied using a blood pressure cuff on the upper arm to induce brief episodes of nonlethal ischemia and reperfusion in the forearm has greatly facilitated the translation of RIC into the clinical arena. Several recently published proof-of-concept clinical studies have reported encouraging results with RIC, and large multicenter randomized clinical trials are now underway to investigate whether this simple noninvasive and virtually cost-free intervention has the potential to improve clinical outcomes in patients with CAD. In this review article, we provide an update of recently published and ongoing clinical trials in the field of RIC.

Novel approaches are required to improve clinical outcomes in patients with coronary heart disease (CHD). Ischemic conditioning--the practice of applying brief episodes of nonlethal ischemia and reperfusion to confer protection against a sustained episode of lethal ischemia and reperfusion injury--is one potential therapeutic strategy. Importantly, the protective stimulus can be applied before (ischemic preconditioning) or after (ischemic perconditioning) onset of the sustained episode of lethal ischemia, or even at the onset of myocardial reperfusion (ischemic postconditioning). Furthermore, the protective stimulus can be applied noninvasively by placing a blood-pressure cuff on an upper or lower limb to induce brief episodes of nonlethal ischemia and reperfusion (remote ischemic conditioning), a finding that has greatly facilitated the translation of ischemic conditioning to various clinical settings. In addition to mechanical approaches, elucidation of the signal-transduction pathways underlying ischemic conditioning has identified several novel targets for pharmacological conditioning. This Review highlights findings from proof-of-concept clinical studies conducted in the past 5-6 years, in which the therapeutic potential of ischemic and pharmacological conditioning has been realized. Large, randomized, controlled trials are now required to determine whether pharmacological and ischemic conditioning improve clinical end points and outcomes in patients with CHD.

The discovery of ischemic postconditioning (IPost) has rejuvenated the field of cardioprotection. As an interventional strategy to be applied at the onset of myocardial reperfusion, the transition of IPost from a bench-side curiosity to potential clinical therapy has been impressively rapid. Its existence also confirms the existence of lethal myocardial reperfusion injury in man, suggesting that 40%-50% of the final reperfused myocardial infarct may actually be due to myocardial reperfusion injury. Intensive analysis of the signal transduction pathways underlying IPost has identified similarities with the signaling pathways underlying its preischemic counterpart, ischemic preconditioning. In this article, the reperfusion injury salvage kinase pathway and the more recently described survivor activating factor enhancement pathway, two apparently distinct signaling pathways that actually interact to convey the IPost stimulus from the cell surface to the mitochondria, where many of the prosurvival and death signals appear to converge. The elucidation of the reperfusion signaling pathways underlying IPost may result in the identification of novel pharmacological targets for cardioprotection.

Experimental studies have linked the adipocytokines with acute cardioprotection. Whether the adipocytokine, resistin, confers protection is, however, debatable. In the current study, the actions of resistin, administered at reperfusion, were investigated in in vivo and in vitro rodent and in vitro human models of myocardial ischemia-reperfusion (I/R) injury. Resistin did not reduce infarct size in Langendorff-perfused rat hearts or murine hearts perfused in vivo. Resistin also did not protect human atrial muscle subjected to hypoxia-reoxygenation. Although cyclosporin A delayed mitochondrial permeability transition pore (MPTP) opening in murine cardiomyocytes, resistin was ineffective. Western blot analysis revealed that resistin treatment was associated with enhanced phosphorylation of Akt, at both the serine-473 (+ 51.9%, P = .01) and threonine-308 (+107%, P < .01) phosphorylation sites, although not to the extent seen with ischemic preconditioning (+132.5%, P = .002 and +389.1%, P < .01, respectively). We conclude that resistin administered at reperfusion at concentrations/doses equivalent to normal (upper end) and pathological serum levels does not protect against I/R injury or inhibit MPTP opening.

Percutaneous coronary intervention (PCI) has become the predominant procedure for coronary revascularization in patients with both stable and unstable coronary artery disease (CAD). Over the past two decades, technical advances in PCI have resulted in a better and safer therapeutic procedure with minimal procedural complications. However, about 30% of patients undergoing elective PCI sustain myocardial injury arising from the procedure itself, the extent of which is significant enough to carry prognostic importance. The peri-procedural injury which accompanies PCI might therefore reduce some of the beneficial effects of coronary revascularization. The availability of more sensitive serum biomarkers of myocardial injury such as creatine phosphokinase MB isoenzyme (CK-MB), Troponin T, and Troponin I has enabled the quantification of previously undetectable myocardial injury. Peri-procedural myocardial injury (PMI) can also be visualized by cardiac magnetic resonance imaging, a technique which allows the detection and quantification of myocardial necrosis following PCI. The identification of CAD patients at greatest risk of sustaining PMI during PCI would allow targeted treatment with novel therapies capable of limiting the extent of PMI or reducing the number of patients experiencing PMI.

Leptin-induced protection against myocardial ischemia-reperfusion (I/R) injury involves the activation of the reperfusion injury salvage kinase pathway, incorporating phosphatidylinositol 3-kinase-Akt/protein kinase B and p44/42 MAPK, and the inhibition of the mitochondrial permeability transition pore (MPTP). Recently published data indicate that the JAK/STAT signaling pathway, which mediates the metabolic actions of leptin, also plays a pivotal role in cardioprotection. Consequently, in the present study we considered the possibility that JAK/STAT signaling linked to the MPTP may be involved in modulating the cardioprotective actions of leptin. Employing rat in vitro models (Langendorff-perfused hearts and cardiomyocytes) of I/R injury, we investigated the actions of leptin (10 nM), administered at reperfusion, in the presence or absence of the JAK2 inhibitor, AG-490 (5 μM). Leptin reduced infarct size significantly (control, 60.05 ± 7.41% vs. leptin treated, 29.9 ± 3.24%, P < 0.05), protection being abolished by AG-490. Time course studies revealed that leptin caused a 171% (P < 0.001) increase in STAT3/tyrosine-705 phosphorylation at 2.5 min reperfusion; however, increases were not seen at 5, 10, 15, or 30 min reperfusion. Contrasting with STAT3, Akt/serine-473 phosphorylation was not significantly increased until 15 min into the reperfusion phase (140%, P < 0.05). AG-490 blocked the leptin-induced rise in STAT3 phosphorylation seen at 2.5 min reperfusion but did not influence Akt/serine-473 phosphorylation at 15 min. Leptin reduced the MPTP opening (P < 0.001), which was blocked by AG-490. This is the first study to yield evidence that JAK/STAT signaling linked to the MPTP plays a role in leptin-induced cardioprotection. Under the experimental conditions employed, STAT3 phosphorylation appears to have occurred earlier during reperfusion than that of Akt. Further research into the interactions between these two signaling pathways in the setting of I/R injury is, however, required.

Aims: It has been suggested that mitochondrial reactive oxygen species (ROS), Akt and Erk1/2 and more recently the mitochondrial permeability transition pore (mPTP) may act as mediators of ischaemic preconditioning (IPC), although the actual interplay between these mediators is unclear. The aim of the present study is to determine whether the cyclophilin-D (CYPD) component of the mPTP is required by IPC to generate mitochondrial ROS and subsequently activate Akt and Erk1/2., Methods and Results: Mice lacking CYPD (CYPD-/-) and B6Sv129 wild-type (WT) mice were used throughout. We have demonstrated that under basal conditions, non-pathological mPTP opening occurs (indicated by the percent reduction in mitochondrial calcein fluorescence). This effect was greater in WT cardiomyocytes compared with CYPD-/- ones (53 ± 2% WT vs. 17 ± 3% CYPD-/-; P < 0.01) and was augmented by hypoxic preconditioning (HPC) (70 ± 9% WT vs. 56 ± 1% CYPD-/-; P < 0.01). HPC reduced cell death following simulated ischaemia-reperfusion injury in WT (23.2 ± 3.5% HPC vs. 43.7 ± 3.2% WT; P < 0.05) but not CYPD-/- cardiomyocytes (19.6 ± 1.4% HPC vs. 24.4 ± 2.6% control; P > 0.05). HPC generated mitochondrial ROS in WT (four-fold increase; P < 0.05) but not CYPD-/- cardiomyocytes. HPC induced significant Akt phosphorylation in WT cardiomyocytes (two-fold increase; P < 0.05), an effect which was abrogated by ciclosporin-A (a CYPD inhibitor) and N-2-mercaptopropionyl glycine (a ROS scavenger). Finally, in vivo IPC of adult murine hearts resulted in significant phosphorylation of Akt and Erk1/2 in WT but not CYPD-/- hearts., Conclusion: The CYPD component of the mPTP is required by IPC to generate mitochondrial ROS and phosphorylate Akt and Erk1/2, major steps in the IPC signalling pathway.

Mitochondria are dynamic and are able to interchange their morphology between elongated interconnected mitochondrial networks and a fragmented disconnected arrangement by the processes of mitochondrial fusion and fission, respectively. Changes in mitochondrial morphology are regulated by the mitochondrial fusion proteins (mitofusins 1 and 2, and optic atrophy 1) and the mitochondrial fission proteins (dynamin-related peptide 1 and mitochondrial fission protein 1) and have been implicated in a variety of biological processes including embryonic development, metabolism, apoptosis, and autophagy, although the majority of studies have been largely confined to non-cardiac cells. Despite the unique arrangement of mitochondria in the adult heart, emerging data suggest that changes in mitochondrial morphology may be relevant to various aspects of cardiovascular biology-these include cardiac development, the response to ischaemia-reperfusion injury, heart failure, diabetes mellitus, and apoptosis. Interestingly, the machinery required for altering mitochondrial shape in terms of the mitochondrial fusion and fission proteins are all present in the adult heart, but their physiological function remains unclear. In this article, we review the current developments in this exciting new field of mitochondrial biology, the implications for cardiovascular physiology, and the potential for discovering novel therapeutic strategies for treating cardiovascular disease.

Remote ischaemic preconditioning (RIPC) is a therapeutic intervention that has been demonstrated to reduce myocardial injury in the clinical setting. However, the underlying cardioprotective mechanisms remain unclear. We hypothesised that RIPC utilises both humoral and neural pathways to convey the cardioprotective signal from the preconditioned remote organ to the heart. C57BL/6 mice were anaesthetised and subjected to in vivo 30 min coronary artery ischaemia followed by 120 min of myocardial reperfusion, at the end of which myocardial infarct size was measured and expressed as a percentage of the risk zone. RIPC was induced by 3 cycles of 5 min left femoral artery occlusion interspersed with 5 min reperfusion before prolonged myocardial ischaemia with or without femoral vein occlusion (humoral pathway), femoral nerve resection and/or sciatic nerve resection (neural pathway). RIPC resulted in a smaller myocardial infarct size when compared to control. However, occluding the femoral vein completely abolished the infarct-limiting effect of RIPC. Similarly, combined femoral and sciatic nerve resection also abolished the cardioprotective effect of RIPC. Interestingly, femoral nerve or sciatic nerve resection alone only partially abolished the infarct-limiting effect of RIPC. In conclusion, remote limb ischaemic preconditioning reduced myocardial infarct size in the mice in a manner which implicates both a neural and humoral pathway.

Ischaemic postconditioning (brief periods of ischaemia alternating with brief periods of reflow applied at the onset of reperfusion following sustained ischaemia) effectively reduces myocardial infarct size in all species tested so far, including humans. Ischaemic postconditioning is a simple and safe manoeuvre, but because reperfusion injury is initiated within minutes of reflow, postconditioning must be applied at the onset of reperfusion. The mechanisms of protection by postconditioning include: formation and release of several autacoids and cytokines; maintained acidosis during early reperfusion; activation of protein kinases; preservation of mitochondrial function, most strikingly the attenuation of opening of the mitochondrial permeability transition pore (MPTP). Exogenous recruitment of some of the identified signalling steps can induce cardioprotection when applied at the time of reperfusion in animal experiments, but more recently cardioprotection was also observed in a proof-of-concept clinical trial. Indeed, studies in patients with an acute myocardial infarction showed a reduction of infarct size and improved left ventricular function when they underwent ischaemic postconditioning or pharmacological inhibition of MPTP opening during interventional reperfusion. Further animal studies and large-scale human studies are needed to determine whether patients with different co-morbidities and co-medications respond equally to protection by postconditioning. Also, our understanding of the underlying mechanisms must be improved to develop new therapeutic strategies to be applied at reperfusion with the ultimate aim of limiting the burden of ischaemic heart disease and potentially providing protection for other organs at risk of reperfusion injury, such as brain and kidney.