Preconditioning and postconditioning: from bench to bedside

Coronary heart disease (CHD) is the leading cause of death world-wide. Since 1990, more people in the world have diedfrom CHD than from any other disease (World Health Organisation, WHO). “Conditioning” the heart to render it more resistant to the detrimental effects of acute ischaemia-reperfusion injury harnesses the endogenous ability of the heart to protect itself. This can be achieved using various mechanical strategies including the application of brief episodes of ischaemia and reperfusion to either the heart itself (ischaemic preconditioning) or an organ/tissue remote from the heart (remote ischaemic preconditioning) prior to the sustained ischaemic insult. Importantly, this form of protection can be mimicked by pharmacological agents capable of recapitulating the protective effect of IPC(pharmacological preconditioning). Preconditioning-induced cardioprotection is clearly restricted to patients undergoing an anticipated ischaemic insult such as in patients undergoing cardiac surgery. In contrast, the other major form of “conditioning” termed postconditioning can be implemented in patients presenting with an acute myocardial infarction after the onset of the sustained ischaemic insult. In this setting, myocardial reperfusion is interrupted with intermittent short-lived episodes of myocardial ischaemia applied to the heart itself (ischaemic postconditioning) or an organ or tissue remote from the heart (remote ischaemic postconditioning) – an effect which can again be mimicked by pharmacological agents (pharmacological postconditioning).This article will briefly review these various forms of“conditioning” examining the underlying mechanistic pathways and their clinical application

Failure to protect the myocardium against ischemia/reperfusion injury after chronic atorvastatin treatment is recaptured by acute atorvastatin treatment A potential role for phosphatase and tensin homolog deleted on chromosome ten?

ObjectivesWe sought to ascertain whether chronic oral therapy with atorvastatin protects against ischemia/reperfusion (I/R) injury.BackgroundWe have recently shown that acute atorvastatin treatment protects against reperfusion-induced injury by activating the PI3K/Akt/eNOS pathway. However, many patients are on chronic statin therapy, and it is necessary to investigate whether this, in itself, provides a therapeutic advantage.MethodsSprague-Dawley rats were orally treated for one day, three days, one week, or two weeks with 20 mg/kg of atorvastatin or vehicle, after which the hearts underwent 35 min of ischemia and 120 min reperfusion (IR). Two additional groups were treated for one or two weeks with atorvastatin and then received a supplementary dose of 40 mg/kg before IR. The risk zone was determined using Evans blue and infarct size (IR%) using triphenyltetrazolium chloride staining.ResultsTreatment with atorvastatin for one and three days significantly reduced infarct size versus controls (38.9 ± 3.1% vs. 56.4 ± 2.3%; 39.3 ± 2.4% vs. 61.3 ± 3.8%, respectively). However, after one or two weeks of treatment, no protection was observed (52.6 ± 3.8% vs. 58.6 ± 4.3%; 58.3 ± 2.7% vs. 52.4 ± 5.7%, respectively). Surprisingly, a supplementary dose of atorvastatin recaptured the protection in the groups treated chronically (36.2 ± 2.8% vs. 58.6 ± 4.3%; 26.8 ± 1.5% vs. 51.2 ± 6.7%, at one and two weeks, respectively). Interestingly, we observed an increased level of phosphatase and tensin homolog deleted on chromosome ten (PTEN), the phosphatidylinositol-3 kinase inhibitor, in the chronic treated hearts.ConclusionsIn conclusion, atorvastatin appears to have an acute protective effect that wanes with time associated with an increase in PTEN levels. This waning protection can be recaptured by an acute high dose given immediately before IR. These results may have protential clinical relevance

The RISK pathway leading to mitochondria and cardioprotection: how everything started

Ischaemic heart disease, which often manifests clinically as myocardial infarction (MI), remains a major cause of mortality worldwide. Despite the development of effective pre-clinical cardioprotective therapies, clinical translation has been disappointing. Nevertheless, the 'reperfusion injury salvage kinase' (RISK) pathway appears to be a promising target for cardioprotection. This pathway is crucial for the induction of cardioprotection by numerous pharmacological and non-pharmacological interventions, such as ischaemic conditioning. An important component of the cardioprotective effects of the RISK pathway involves the prevention of mitochondrial permeability transition pore (MPTP) opening and subsequent cardiac cell death. Here, we will review the historical perspective of the RISK pathway and focus on its interaction with mitochondria in the setting of cardioprotection

Mitochondrial cyclophilin-D as a critical mediator of ischaemic preconditioning

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.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.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

The Diabetic Heart: Too Sweet for Its Own Good?

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

Effect of remote ischaemic conditioning on platelet reactivity and endogenous fibrinolysis in ST-elevation myocardial infarction- a substudy of the CONDI-2/ERIC4 PPCI randomised controlled trial

© The Author(s) 2020. Published by Oxford University Press on behalf of the European Society of Cardiology. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly citedBackground: Remote ischaemic conditioning (RIC) has been shown to reduce myocardial infarct size in animal models of myocardial infarction. Platelet thrombus formation is a critical determinant of outcome in ST-segment elevation myocardial infarction (STEMI). Whether the beneficial effects of RIC are related to thrombotic parameters is unclear. Methods and Results: In a pre-specified substudy of the Effect of Remote Ischaemic Conditioning on clinical outcomes in STEMI patients undergoing Primary Percutaneous Coronary Intervention (ERIC-PPCI) trial, we assessed the effect of RIC on thrombotic status. Patients presenting with STEMI were randomised to immediate RIC consisting of an automated autoRICTM cuff on the upper arm inflated to 200mmHg for 5 minutes and deflated for 5 minutes for 4 cycles (n=53) or sham (n=47). Venous blood was tested at presentation, discharge (48 h) and 6-8 weeks, to assess platelet reactivity, coagulation and endogenous fibrinolysis using the Global Thrombosis Test and thromboelastography (TEG). Baseline thrombotic status was similar in the 2 groups. At discharge, there was some evidence that the time to in vitro thrombotic occlusion under high shear stress was longer with RIC compared to sham (454±105s vs. 403±105s; mean difference 50.1s; 95% confidence interval [CI] 93.7- 6.4, P=0.025), but this was no longer apparent at 6-8 weeks. There was no difference in clot formation or endogenous fibrinolysis between the study arms at any time-point. Conclusion: RIC may reduce platelet reactivity in the first 48h post-STEMI. Further research is needed to delineate mechanisms through which RIC may reduce platelet reactivity, and whether it may improve outcomes in patients with persistent high on-treatment platelet reactivity.Peer reviewedFinal Accepted Versio

Delta opioid receptor stimulation mimics ischemic preconditioning in human heart muscle

AbstractOBJECTIVESThe objective of this study was to examine whether the delta (δ) opioid receptor isoform is expressed in the human heart and whether this receptor improves contractile function after hypoxic/reoxygenation injury.BACKGROUNDDelta opioid receptor agonists mimic preconditioning (PC) in rat myocardium, corresponding to known cardiac δ opioid receptor expression in this species.METHODSThe messenger RNA transcript encoding the δ opioid receptor was identified in human atria and ventricles. To evaluate the cardioprotective role of the opioid receptor, human atrial trabeculae from patients undergoing coronary bypass grafting were isolated and superfused with Tyrode’s solution. A control group underwent 90 min of simulated ischemia and 120 min of reoxygenation. A second group was preconditioned with 3 min simulated ischemia and 7 min reoxygenation. Additional groups included: superfusion with the δ receptor agonist (DADLE) (10 nM), with the δ receptor antagonist naltrindole (10 nM) and with the mitochondrial KATP channel blocker 5-hydroxydecanoate (5HD) (100 μM) either with or without PC, respectively. A final group was superfused with 5HD before DADLE. The end point used was percentage of developed force after 120 min of reoxygenation.RESULTSResults, expressed as means ± SEM, were: control = 32.6 ± 3.8%; PC = 50.5% ± 1.8∗; DADLE = 46.0 ± 3.9%∗; PC + naltrindole = 25.5 ± 3.9%; naltrindole alone = 25.5 ± 4.3%; 5HD + PC = 28.9 ± 7.4%; 5HD alone = 24.1 ± 3.0%; 5HD + DADLE = 26.9 ± 4.4% (∗p < 0.001 vs. controls).CONCLUSIONSHuman myocardium expresses the δ opioid receptor transcript. Stimulation of this receptor appears to protects human muscle from simulated ischemia, similar to PC, and via opening of the mitochondrial KATP channel

Microvesicles and exosomes: new players in metabolic and cardiovascular disease

The past decade has witnessed an exponential increase in the number of publications referring to extracellular vesicles (EVs). For many years considered to be extracellular debris, EVs are now seen as novel mediators of endocrine signalling via cell-to-cell communication. With the capability of transferring proteins and nucleic acids from one cell to another, they have become an attractive focus of research for different pathological settings and are now regarded as both mediators and biomarkers of disease including cardio-metabolic disease. They also offer therapeutic potential as signalling agents capable of targeting tissues or cells with specific peptides or miRNAs. In this review, we focus on the role that microvesicles (MVs) and exosomes, the two most studied classes of EV, have in diabetes, cardiovascular disease, endothelial dysfunction, coagulopathies, and polycystic ovary syndrome. We also provide an overview of current developments in MV/exosome isolation techniques from plasma and other fluids, comparing different available commercial and non-commercial methods. We describe different techniques for their optical/biochemical characterization and quantitation. We also review the signalling pathways that exosomes and MVs activate in target cells and provide some insight into their use as biomarkers or potential therapeutic agents. In summary, we give an updated focus on the role that these exciting novel nanoparticles offer for the endocrine community

Inhibition of NAADP signalling on reperfusion protects the heart by preventing lethal calcium oscillations via two-pore channel 1 and opening of the mitochondrial permeability transition pore

Aims In the heart, a period of ischaemia followed by reperfusion evokes powerful cytosolic Ca2+ oscillations that can cause lethal cell injury. These signals represent attractive cardioprotective targets, but the underlying mechanisms of genesis are ill-defined. Here, we investigated the role of the second messenger nicotinic acid adenine dinucleotide phosphate (NAADP), which is known in several cell types to induce Ca2+ oscillations that initiate from acidic stores such as lysosomes, likely via two-pore channels (TPCs, TPC1 and 2). Methods and results An NAADP antagonist called Ned-K was developed by rational design based on a previously existing scaffold. Ned-K suppressed Ca2+ oscillations and dramatically protected cardiomyocytes from cell death in vitro after ischaemia and reoxygenation, preventing opening of the mitochondrial permeability transition pore. Ned-K profoundly decreased infarct size in mice in vivo. Transgenic mice lacking the endo-lysosomal TPC1 were also protected from injury. Conclusion NAADP signalling plays a major role in reperfusion-induced cell death and represents a potent pathway for protection against reperfusion injury