Interaction of risk factors, comorbidities, and comedications with ischemia/reperfusion injury and cardioprotection by preconditioning, postconditioning, and remote conditioning

Impact of hyperglycemia on myocardial ischemia-reperfusion susceptibility and ischemic preconditioning in hearts from rats with type 2 diabetes

Background

The mechanisms underlying increased mortality in patients with diabetes and admission hyperglycemia after an acute coronary syndrome may involve reduced capacity for cardioprotection. We investigated the impact of hyperglycemia on exogenously activated cardioprotection by ischemic preconditioning (IPC) in hearts from rats with type 2 diabetes mellitus (T2DM) that were endogenously cardioprotected by an inherent mechanism, and the involvement of myocardial glucose uptake (MGU) and myocardial O-linked β-N-acetylglucosamine (O-GlcNAc).

Methods and results

In isolated, perfused rat hearts subjected to ischemia–reperfusion, infarct size (IS) was overall larger during hyper- ([Glucose] = 22 mmol/L]) than normoglycemia ([Glucose] = 11 mmol/L]) (p < 0.001). IS was smaller in 12-week old Zucker diabetic fatty rats with recent onset T2DM (fa/fa) than in rats without T2DM (fa/+) (n = 8 in each group) both during hyperglycemia (p < 0.05) and normoglycemia (p < 0.05). IPC (2 × 5 min cycles) reduced IS during normo- (p < 0.01 for both groups) but not during hyperglycemia independently of the presence of T2DM. During hyperglycemia, an intensified IPC stimulus (4 × 5 min cycles) reduced IS only in hearts from animals with T2DM (p < 0.05). IPC increased MGU and O-GlcNAc levels during reperfusion in animals with and without T2DM at normoglycemia (MGU: p < 0.05, O-GlcNAc: p < 0.01 for both groups) but not during hyperglycemia. Intensified IPC at hyperglycemia increased MGU (p < 0.05) and O-GlcNAc levels (p < 0.05) only in hearts from animals with T2DM.

Conclusion

While the effect of IPC is reduced during hyperglycemia in rats without T2DM, endogenous cardioprotection in animals with T2DM is not influenced by hyperglycemia and the capacity for exogenous cardioprotection by IPC is preserved. MGU and O-GlcNAc levels are increased by exogenously induced cardioprotection by IPC but not by endogenous cardioprotection in animals with T2DM reflecting different underlying mechanisms by exogenous and endogenous cardioprotection.

Impact of Anesthetic Regimen on Remote Ischemic Preconditioning in the Rat Heart In Vivo

Remote ischemic preconditioning (RIPC) seems to be a promising cardioprotective strategy with contradictive clinical data suggesting the anesthetic regimen influencing the favorable impact of RIPC. This study aimed to investigate whether cardio protection by RIPC is abolished by anesthetic regimens. Male Wistar rats were randomized to 6 groups. Anesthesia was either maintained by pentobarbital (Pento) alone or a combination of sevoflurane (Sevo) and remifentanil or propofol (Prop) and remifentanil in combination with and without RIPC. RIPC reduced infarct size in Pento- and Sevo-anesthetized rats (Pento-RIPC: 30% ± 9% versus Pento-control [Con]: 65% ± 6%, P < .001; Sevo-RIPC: 31% ± 6% versus Sevo-Con: 61% ± 8%, P < .001), but RIPC did not initiate cardio protection in Prop-anesthetized animals (Prop-RIPC: 59% ± 6% versus Prop-Con: 59% ± 8%, P = 1.000). Cardio protection by RIPC is abolished by Prop.

Up-regulation of ANXA1 suppresses polymorphonuclear neutrophil infiltration and myeloperoxidase activity by activating STAT3 signaling pathway in rat models of myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MIRI) is recognized as a major cause of morbidity and mortality which is commonly associated with coronary artery disease. In recent studies, annexin A1 gene (ANXA1) has been discovered to be involved in the treatment for MIRI. In this study, the primary focus was on the molecular mechanism of ANXA1 in polymorphonuclear neutrophil (PMN) infiltration and myeloperoxidase (MPO) activity in rats with MIRI. Initially, microarray analysis was carried out in order to identify differentially expressed genes. Moreover, a rat model of MIRI was established for evaluating the expression of ANXA1, signal transducer and activator of transcription 3 (STAT3) and vascular endothelial growth factor (VEGF) in myocardial tissues. Following this, the ANXA1 vector, siRNA-ANXA1, and Stattic (inhibitor of STAT3 signaling pathway) were utilized for analyzing the regulatory role of ANXA1 in physiological indexes, hemodynamic parameters, inflammatory factors, myocardial infarct size, MPO activity, PMN infiltration, and apoptosis of PMNs. Furthermore, the relationship between ANXA1 and STAT3 signaling pathway was analyzed. Initially, a reduction in the expression of ANXA1, STAT3 and VEGF in myocardial tissues of MIRI rats was found. To elaborate, overexpressed ANXA1 inhibited levels of inflammatory factors, the activation of PMN infiltration, reduced the degree of PMN infiltration, and decreased the apoptosis of PMNs. More importantly, down-regulated ANXA1 inhibited the activation of STAT3 signaling pathway, which thereby suppressed VEGF expression. With this all taken into account, the present study presents that up-regulated ANXA1 inhibits PMN infiltration and MPO activity by activation of STAT3 signaling pathway in rats with MIRI.

Extracellular vesicles in diagnostics and therapy of the ischaemic heart: Position Paper from the Working Group on Cellular Biology of the Heart of the European Society of Cardiology

Extracellular vesicles (EVs)—particularly exosomes and microvesicles (MVs)—are attracting considerable interest in the cardiovascular field as the wide range of their functions is recognized. These capabilities include transporting regulatory molecules including different RNA species, lipids, and proteins through the extracellular space including blood and delivering these cargos to recipient cells to modify cellular activity. EVs powerfully stimulate angiogenesis, and can protect the heart against myocardial infarction. They also appear to mediate some of the paracrine effects of cells, and have therefore been proposed as a potential alternative to cell-based regenerative therapies. Moreover, EVs of different sources may be useful biomarkers of cardiovascular disease identities. However, the methods used for the detection and isolation of EVs have several limitations and vary widely between studies, leading to uncertainties regarding the exact population of EVs studied and how to interpret the data. The number of publications in the exosome and MV field has been increasing exponentially in recent years and, therefore, in this ESC Working Group Position Paper, the overall objective is to provide a set of recommendations for the analysis and translational application of EVs focussing on the diagnosis and therapy of the ischaemic heart. This should help to ensure that the data from emerging studies are robust and repeatable, and optimize the pathway towards the diagnostic and therapeutic use of EVs in clinical studies for patient benefit.

Protective effect of celastrol on myocardial ischemia-reperfusion injury

OBJECTIVE

Celastrol, a major active constituent of Tripterygium wilfordii, has antioxidant, anti-inflammatory, and anticancer effects. However, whether celastrol can exert protective effect on myocardial ischemia-reperfusion injury (MIRI) is unknown. The aim of this study was to test the protective effect of celastrol on MIRI and elucidate its underlying mechanism.

METHODS

Cardiomyocytes (H9c2 cells) were subjected to hypoxia for 8 h followed by reoxygenation for 4 h to create hypoxia/reoxygenation (H/R) model, an in vitro MIRI model. Celastrol was added to the medium 60 min before the H/R process . Cell viability was detected using MTT assay. Myocardial injury was evaluated by measuring lactate dehydrogenase (LDH) and creatine kinase MB isoenzyme (CK-MB) activity. Changes in mRNA and protein expression of TNF-α, IL-1ß, and nuclear factor-K B (NF-K B) were measured with RT-qPCR assay and western blot analysis.

RESULTS

Results showed that low-dose celastrol (20 and 50 nM) treatment significantly increased cell viability and decreased LDH and CK-MB activity in the condition of H/R, but high-dose celastrol (200 and 400 nM) resulted in extra injury to cardiomyocytes. Moreover, treatment with 50 nM celastrol significantly downregulated mRNA and protein expression of TNF-α and IL-1ß. Meanwhile, NF-K B mRNA and protein in the nucleus were also correspondingly reduced.

CONCLUSION

Our study demonstrated that low-dose celastrol could prevent MIRI in cardiomyocytes by inhibiting the activation of NF-K B, and celastrol may be a potential therapeutic agent for preventing MIRI.

Effect of Ischemic Preconditioning and Postconditioning on Exosome-Rich Fraction microRNA Levels, in Relation with Electrophysiological Parameters and Ventricular Arrhythmia in Experimental Closed-Chest Reperfused Myocardial Infarction

We investigated the antiarrhythmic effects of ischemic preconditioning (IPC) and postconditioning (PostC) by intracardiac electrocardiogram (ECG) and measured circulating microRNAs (miRs) that are related to cardiac conduction. Domestic pigs underwent 90-min. percutaneous occlusion of the mid left anterior coronary artery, followed by reperfusion. The animals were divided into three groups: acute myocardial infarction (AMI, n = 7), ischemic preconditioning-acute myocardial infarction (IPC-AMI) (n = 9), or AMI-PostC (n = 5). IPC was induced by three 5-min. episodes of repetitive ischemia/reperfusion cycles (rI/R) before AMI. PostC was induced by six 30-s rI/R immediately after induction of reperfusion 90 min after occlusion. Before the angiographic procedure, a NOGA endocardial mapping catheter was placed again the distal anterior ventricular endocardium to record the intracardiac electrogram (R-amplitude, ST-Elevation, ST-area under the curve (AUC), QRS width, and corrected QT time (QTc)) during the entire procedure. An arrhythmia score was calculated. Cardiac MRI was performed after one-month. IPC led to significantly lower ST-elevation, heart rate, and arrhythmia score during ischemia. PostC induced a rapid recovery of R-amplitude, decrease in QTc, and lower arrhythmia score during reperfusion. Slightly higher levels of miR-26 and miR-133 were observed in AMI compared to groups IPC-AMI and AMI-PostC. Significantly lower levels of miR-1, miR-208, and miR-328 were measured in the AMI-PostC group as compared to animals in group AMI and IPC-AMI. The arrhythmia score was not significantly associated with miRNA plasma levels. Cardiac MRI showed significantly smaller infarct size in the IPC-AMI group when compared to the AMI and AMI-PostC groups. Thus, IPC led to better left ventricular ejection fraction at one-month and it exerted antiarrhythmic effects during ischemia, whereas PostC exhibited antiarrhythmic properties after reperfusion, with significant downregulaton of ischemia-related miRNAs.

Effect of ischemic preconditioning on cardiovascular outcomes in patients with symptomatic coronary artery disease: a cohort study

BACKGROUND

Despite the powerful myocardial protection of ischemic preconditioning (IP) observed in experimental studies, it remains a challenge to observe such protection in humans. Thus, the aim of this study was to evaluate the possible effects of IP on clinical outcomes in patients with coronary artery disease (CAD).

PATIENTS AND METHODS

In this cohort study, patients with multivessel CAD, preserved systolic ventricular function, and stable angina were prospectively selected. They underwent two sequential exercise stress tests (EST) to evaluate IP presence. IP was considered present if patients had an improvement in the time to the onset of 1.0-mm STsegment deviation in the second EST. The primary end point was the composite rate of cardiac death, nonfatal myocardial infarction, or revascularization during 1-year follow-up. Patients with (IP+) and without (IP-) the cardioprotective mechanism were compared regarding clinical end points.

RESULTS

A total of 229 patients completed EST and had IP evaluated: 165 (72%) were IP+ and 64 (28%) were IP - patients. Of these, 218 patients had complete follow-up. At 1-year, event-free survival regarding the primary end point was 95.5 versus 83.6% (P = 0.0024) and event-free survival regarding cardiac death or myocardial infarction was 99.4 versus 91.7% (P=0.0020), respectively, in IP + and IP - groups. The unadjusted hazard ratio (IP + /IP-) for the primary end point was 4.63 (1.52-14.08). After multivariate analysis, IP was still significantly associated with better clinical outcomes (P = 0.0025).

CONCLUSION

This data suggest that IP may contribute to better clinical outcomes in patients with ischemic heart disease.

Lycopene restores the effect of ischemic postconditioning on myocardial ischemia‑reperfusion injury in hypercholesterolemic rats

Ischemic postconditioning (IPoC) has been demonstrated to prevent myocardial ischemia-reperfusion injury (MIRI), but its cardioprotective effect is abrogated by hypercholesterolemia. The aim of the present study was to determine whether lycopene (LP), a type of carotenoid, can restore the cardioprotective effect of IPoC in hypercholesterolemic rats. Male Wistar rats were fed a cholesterol-enriched diet for 12 weeks to establish a hypercholesterolemic model. The rat hearts were isolated and subjected to 30 min ischemia and 60 min reperfusion using a Langendorff apparatus. LP was administered to the rats intraperitoneally for 5 consecutive days prior to ischemia and reperfusion. Myocardial pathological changes, infarct size and cell apoptosis were measured by hematoxylin and eosin, triphenyltetrazolium chloride and TUNEL staining, respectively. The changes in endoplasmic reticulum (ER) stress markers, the reperfusion injury salvage kinase (RISK) pathway and mitochondrial apoptosis-related proteins were detected by western blotting. Overall, the results demonstrated that low-dose LP in combination with IPoC ameliorated myocardial histopathological changes, reduced the infarct size and release of cardiac enzymes, and decreased cardiomyocyte apoptosis in hypercholesterolemic rats, but no beneficial effects were achieved by the same dose of LP or IPoC treatment were used alone. Furthermore, the combination of LP and IPoC inhibited the expression of glucose-regulated protein 78 and C/EBP homologous protein, increased the phosphorylation levels of AKT, ERK1/2 and glycogen synthase kinase-3β, repressed mitochondrial permeability transition pore opening, and reduced the expression of cytochrome c, cleaved caspase-9 and cleaved caspase-3. Collectively, these findings demonstrated that LP can restore the cardioprotective effects of IPoC on MIRI in hypercholesterolemic rats, and this restoration by LP was mediated by inhibition of ER stress and reactivation of the RISK pathway in hypercholesterolemic rat myocardium.

Luteolin Attenuates Cardiac Ischemia/Reperfusion Injury in Diabetic Rats by Modulating Nrf2 Antioxidative Function

Luteolin has been reported to attenuate ischemia/reperfusion (I/R) injury in the diabetic heart through endothelial nitric oxide synthase- (eNOS-) related antioxidative response. Though the nuclear factor erythroid 2-related factor 2 (Nrf2) is regarded as a key endogenous factor to reduce diabetic oxidative stress, whether luteolin reduces cardiac I/R injury in the diabetic heart via enhancing Nrf2 function needs to be clarified. We hypothesized that pretreatment with luteolin could alleviate cardiac I/R injury in the diabetic heart by affecting the eNOS/Nrf2 signaling pathway. The diabetic rat was produced by a single injection of streptozotocin (65 mg/kg, i.p.) for 6 weeks, and then, luteolin (100 mg/kg/day, i.g.), eNOS inhibitor L-NAME, or Nrf2 inhibitor brusatol was administered for the succedent 2 weeks. After that, the isolated rat heart was exposed to 30 min of global ischemia and 120 min of reperfusion to establish I/R injury. Luteolin markedly ameliorated cardiac function and myocardial viability; upregulated expressions of heme oxygenase-1, superoxide dismutase, glutathione peroxidase, and catalase; and reduced myocardial lactate dehydrogenase release, malondialdehyde, and 8-hydroxydeoxyguanosine in the diabetic I/R heart. All these ameliorating effects of luteolin were significantly reversed by L-NAME or brusatol. Luteolin also markedly reduced S-nitrosylation of Kelch-like ECH-associated protein 1 (Keap1) and upregulated Nrf2 and its transcriptional activity. This effect of luteolin on Keap1/Nrf2 signaling was attenuated by L-NAME. These data reveal that luteolin protects the diabetic heart against I/R injury by enhancing eNOS-mediated S-nitrosylation of Keap1, with subsequent upregulation of Nrf2 and the Nrf2-related antioxidative signaling pathway.

Use of Multifactorial Treatments to Address the Challenge of Translating Experimental Myocardial Infarct Reduction Strategies

Myocardial tissue damage that occurs during an ischemic event leads to a spiraling deterioration of cardiac muscle structural and functional integrity. Reperfusion is the only known efficacious strategy and is the most commonly used treatment to reduce injury and prevent remodeling. However, timing is critical, and the procedure is not always feasible for a variety of reasons. The complex molecular basis for cardioprotection has been studied for decades but formulation of a viable therapeutic that can significantly attenuate myocardial injury remains elusive. In this review, we address barriers to the development of a fruitful approach that will substantially improve the prognosis of those suffering from this widespread and largely unmitigated disease. Furthermore, we proffer that ephrinA1, a candidate molecule that satisfies many of the important criteria discussed, possesses robust potential to overcome these hurdles and thus offers protection that surpasses the limitations currently observed.

Impact of Anesthetics on Cardioprotection Induced by Pharmacological Preconditioning

Anesthetics, especially propofol, are discussed to influence ischemic preconditioning. We investigated whether cardioprotection by milrinone or levosimendan is influenced by the clinically used anesthetics propofol, sevoflurane or dexmedetomidine. Hearts of male Wistar rats were randomised, placed on a Langendorff system and perfused with Krebs–Henseleit buffer (KHB) at a constant pressure of 80 mmHg. All hearts underwent 33 min of global ischemia and 60 min of reperfusion. Three different anesthetic regimens were conducted throughout the experiments: propofol (11 μM), sevoflurane (2.5 Vol%) and dexmedetomidine (1.5 nM). Under each anesthetic regimen, pharmacological preconditioning was induced by administration of milrinone (1 μM) or levosimendan (0.3 μM) 10 min before ischemia. Infarct size was determined by TTC staining. Infarct sizes in control groups were comparable (KHB-Con: 53 ± 9%, Prop-Con: 56 ± 9%, Sevo-Con: 56 ± 8%, Dex-Con: 53 ± 9%; ns). Propofol completely abolished preconditioning by milrinone and levosimendan (Prop-Mil: 52 ± 8%, Prop-Lev: 52 ± 8%; ns versus Prop-Con), while sevoflurane did not (Sevo-Mil: 31 ± 9%, Sevo-Lev: 33 ± 7%; p < 0.05 versus Sevo-Con). Under dexmedetomidine, results were inconsistent; levosimendan induced infarct size reduction (Dex-Lev: 36 ± 6%; p < 0.05 versus Dex-Con) but not milrinone (Dex-Mil: 51 ± 8%; ns versus Dex-Con). The choice of the anesthetic regimen has an impact on infarct size reduction by pharmacological preconditioning.

12-Week Exercise Training, Independent of the Type of Exercise, Attenuates Endothelial Ischaemia-Reperfusion Injury in Heart Failure Patients

Introduction: Reperfusion is required to salvage ischaemic tissue, but also causes further damage (i.e., ischaemia/reperfusion-injury). Heart failure patients reveal exaggerated ischaemia/reperfusion-injury, whilst traditional ischaemic preconditioning cannot prevent ischaemia/reperfusion-injury. Exercise training may be a more powerful preconditioning stimulus, especially high-intensity interval training given the similarities with ischaemic preconditioning. Therefore, we examined the impact of 12-week continuous training vs. high-intensity interval training on brachial artery endothelial ischaemia/reperfusion-injury in heart failure patients New York Heart Association-class II-III.

Methods: Twenty heart failure patients (male:female 19:1, 64 ± 8 years, ejection fraction 38 ± 6%) were allocated to 12-weeks of high-intensity interval training (10^∗1-min 90% maximal workload – 2.5-min 30% maximal workload) or continuous training (30-min 60–75% maximal workload). Before and after the intervention, we measured brachial artery endothelial function with flow-mediated dilation (FMD) before and after ischaemia/reperfusion (5-min ischemic exercise, 15-min reperfusion).

Results: Ischaemia/reperfusion caused a significant decline in FMD (continuous training (n = 10): 5.2 ± 2.5 to 3.4 ± 1.6%, high-intensity interval training (n = 10): 5.3 ± 2.6 to 3.5 ± 1.6%, P = 0.01), which was not different between groups (P > 0.05). Training improved maximal workload and fitness (P < 0.05), with no differences between groups (P > 0.05). Exercise training did not alter FMD (P > 0.05), whilst ischaemia/reperfusion did not impair FMD after exercise training (continuous training: 4.8 ± 3.0 to 4.2 ± 2.3%, high-intensity interval training: 4.7 ± 2.5 to 3.8 ± 2.3%, P > 0.05). No changes were found in FMD before or after ischaemia/reperfusion after 12-weeks in controls (n = 9).

Conclusion: We found that 12-week exercise training in heart failure patients mitigated endothelial ischaemia-reperfusion injury, an effect independent of the type of exercise. These changes may contribute to the cardioprotective effects of exercise training, whilst our findings highlight the potency of exercise as a preconditioning stimulus.

ESC Working Group on Cellular Biology of the Heart: position paper for Cardiovascular Research: tissue engineering strategies combined with cell therapies for cardiac repair in ischaemic heart disease and heart failure

Morbidity and mortality from ischaemic heart disease (IHD) and heart failure (HF) remain significant in Europe and are increasing worldwide. Patients with IHD or HF might benefit from novel therapeutic strategies, such as cell-based therapies. We recently discussed the therapeutic potential of cell-based therapies and provided recommendations on how to improve the therapeutic translation of these novel strategies for effective cardiac regeneration and repair. Despite major advances in optimizing these strategies with respect to cell source and delivery method, the clinical outcome of cell-based therapy remains unsatisfactory. Major obstacles are the low engraftment and survival rate of transplanted cells in the harmful microenvironment of the host tissue, and the paucity or even lack of endogenous cells with repair capacity. Therefore, new ways of delivering cells and their derivatives are required in order to empower cell-based cardiac repair and regeneration in patients with IHD or HF. Strategies using tissue engineering (TE) combine cells with matrix materials to enhance cell retention or cell delivery in the transplanted area, and have recently received much attention for this purpose. Here, we summarize knowledge on novel approaches emerging from the TE scenario. In particular, we will discuss how combinations of cell/bio-materials (e.g. hydrogels, cell sheets, prefabricated matrices, microspheres, and injectable matrices) combinations might enhance cell retention or cell delivery in the transplantation areas, thereby increase the success rate of cell therapies for IHD and HF. We will not focus on the use of classical engineering approaches, employing fully synthetic materials, because of their unsatisfactory material properties which render them not clinically applicable. The overall aim of this Position Paper from the ESC Working Group Cellular Biology of the Heart is to provide recommendations on how to proceed in research with these novel TE strategies combined with cell-based therapies to boost cardiac repair in the clinical settings of IHD and HF.

Clinical significance of chronic myocardial ischemia in coronary artery disease patients

Myocardial ischemia is considered the cornerstone of the treatment of patients with coronary artery disease (CAD). Although the deleterious effects of myocardial infarction, the maximum expression of ischemia, have been extensively studied and described, the clinical effects of chronic, documented myocardial ischemia are not completely clarified. The first studies that compared therapies for coronary disease focused on the presence of anatomical features and assessed ischemia based on the interpretation of the findings of obstructive atherosclerotic lesions. They suggested that revascularization interventions did not confer any clinical advantage over medical therapy (MT), in terms of cardiac or overall death. Other retrospective studies that were dedicated to assessing the impact of documented stress-induced ischemia on cardiovascular outcomes have suggested a prognostic impact of chronic ischemia. However, this has been questioned in recent studies. Moreover, the previous understanding that chronic ischemia could lead to worsening of ventricular function was not confirmed in a recent study. Thus, the prognostic significance of stress-induced ischemia has been questioned. Regarding treatment options, although some previous analyses have suggested that interventional therapies would reduce cardiovascular events in CAD patients with documented ischemia, recent post-hoc studies and metanalysis have shown distinct results. In this review article, the authors discuss myocardial ischemia, the different responses of the myocardium to ischemic insults, ischemic preconditioning, and the main findings of recent studies about the clinical aspects and treatment of patients with chronic, documented myocardial ischemia.

Sensory Neuropathy Affects Cardiac miRNA Expression Network Targeting IGF-1, SLC2a-12, EIF-4e, and ULK-2 mRNAs

Background: Here we examined myocardial microRNA (miRNA) expression profile in a sensory neuropathy model with cardiac diastolic dysfunction and aimed to identify key mRNA molecular targets of the differentially expressed miRNAs that may contribute to cardiac dysfunction. Methods: Male Wistar rats were treated with vehicle or capsaicin for 3 days to induce systemic sensory neuropathy. Seven days later, diastolic dysfunction was detected by echocardiography, and miRNAs were isolated from the whole ventricles. Results: Out of 711 known miRNAs measured by miRNA microarray, the expression of 257 miRNAs was detected in the heart. As compared to vehicle-treated hearts, miR-344b, miR-466b, miR-98, let-7a, miR-1, miR-206, and miR-34b were downregulated, while miR-181a was upregulated as validated also by quantitative real time polymerase chain reaction (qRT-PCR). By an in silico network analysis, we identified common mRNA targets (insulin-like growth factor 1 (IGF-1), solute carrier family 2 facilitated glucose transporter member 12 (SLC2a-12), eukaryotic translation initiation factor 4e (EIF-4e), and Unc-51 like autophagy activating kinase 2 (ULK-2)) targeted by at least three altered miRNAs. Predicted upregulation of these mRNA targets were validated by qRT-PCR. Conclusion: This is the first demonstration that sensory neuropathy affects cardiac miRNA expression network targeting IGF-1, SLC2a-12, EIF-4e, and ULK-2, which may contribute to cardiac diastolic dysfunction. These results further support the need for unbiased omics approach followed by in silico prediction and validation of molecular targets to reveal novel pathomechanisms.

Post-Genomic Methodologies and Preclinical Animal Models: Chances for the Translation of Cardioprotection to the Clinic

Although many cardioprotective strategies have demonstrated benefits in animal models of myocardial infarction, they have failed to demonstrate cardioprotection in the clinical setting highlighting that new therapeutic target and treatment strategies aimed at reducing infarct size are urgently needed. Completion of the Human Genome Project in 2001 fostered the post-genomic research era with the consequent development of high-throughput “omics” platforms including transcriptomics, proteomics, and metabolomics. Implementation of these holistic approaches within the field of cardioprotection has enlarged our understanding of ischemia/reperfusion injury with each approach capturing a different angle of the global picture of the disease. It has also contributed to identify potential prognostic/diagnostic biomarkers and discover novel molecular therapeutic targets. In this latter regard, “omic” data analysis in the setting of ischemic conditioning has allowed depicting potential therapeutic candidates, including non-coding RNAs and molecular chaperones, amenable to pharmacological development. Such discoveries must be tested and validated in a relevant and reliable myocardial infarction animal model before moving towards the clinical setting. Moreover, efforts should also focus on integrating all “omic” datasets rather than working exclusively on a single “omic” approach. In the following manuscript, we will discuss the power of implementing “omic” approaches in preclinical animal models to identify novel molecular targets for cardioprotection of interest for drug development.

Systemic Blockade of ACVR2B Ligands Protects Myocardium from Acute Ischemia-Reperfusion Injury

Activin A and myostatin, members of the transforming growth factor (TGF)-β superfamily of secreted factors, are potent negative regulators of muscle growth, but their contribution to myocardial ischemia-reperfusion (IR) injury is not known. The aim of this study was to investigate if activin 2B (ACVR2B) receptor ligands contribute to myocardial IR injury. Mice were treated with soluble ACVR2B decoy receptor (ACVR2B-Fc) and subjected to myocardial ischemia followed by reperfusion for 6 or 24 h. Systemic blockade of ACVR2B ligands by ACVR2B-Fc was protective against cardiac IR injury, as evidenced by reduced infarcted area, apoptosis, and autophagy and better preserved LV systolic function following IR. ACVR2B-Fc modified cardiac metabolism, LV mitochondrial respiration, as well as cardiac phenotype toward physiological hypertrophy. Similar to its protective role in IR injury in vivo, ACVR2B-Fc antagonized SMAD2 signaling and cell death in cardiomyocytes that were subjected to hypoxic stress. ACVR2B ligand myostatin was found to exacerbate hypoxic stress. In addition to acute cardioprotection in ischemia, ACVR2B-Fc provided beneficial effects on cardiac function in prolonged cardiac stress in cardiotoxicity model. By blocking myostatin, ACVR2B-Fc potentially reduces cardiomyocyte death and modifies cardiomyocyte metabolism for hypoxic conditions to protect the heart from IR injury.

Ischaemic and hypoxic conditioning: potential for protection of vital organs

NEW FINDINGS

What is the topic of this review? Remote ischaemic preconditioning (RIPC) and hypoxic preconditioning as novel therapeutic approaches for cardiac and neuroprotection. What advances does it highlight? There is improved understanding of mechanisms and signalling pathways associated with ischaemic and hypoxic preconditioning, and potential pitfalls with application of these therapies to clinical trials have been identified. Novel adaptations of preconditioning paradigms have also been developed, including intermittent hypoxia training, RIPC training and RIPC-exercise, extending their utility to chronic settings.

ABSTRACT

Myocardial infarction and stroke remain leading causes of death worldwide, despite extensive resources directed towards developing effective treatments. In this Symposium Report we highlight the potential applications of intermittent ischaemic and hypoxic conditioning protocols to combat the deleterious consequences of heart and brain ischaemia. Insights into mechanisms underlying the protective effects of intermittent hypoxia training are discussed, including the activation of hypoxia-inducible factor-1 and Nrf2 transcription factors, synthesis of antioxidant and ATP-generating enzymes, and a shift in microglia from pro- to anti-inflammatory phenotypes. Although there is little argument regarding the efficacy of remote ischaemic preconditioning (RIPC) in pre-clinical models, this strategy has not consistently translated into the clinical arena. This lack of translation may be related to the patient populations targeted thus far, and the anaesthetic regimen used in two of the major RIPC clinical trials. Additionally, we do not fully understand the mechanism through which RIPC protects the vital organs, and co-morbidities (e.g. hypercholesterolemia, diabetes) may interfere with its efficacy. Finally, novel adaptations have been made to extend RIPC to more chronic settings. One adaptation is RIPC-exercise (RIPC-X), an innovative paradigm that applies cyclical RIPC to blood flow restriction exercise (BFRE). Recent findings suggest that this novel exercise modality attenuates the exaggerated haemodynamic responses that may limit the use of conventional BFRE in some clinical settings. Collectively, intermittent ischaemic and hypoxic conditioning paradigms remain an exciting frontier for the protection against ischaemic injuries.

Activation of AMPK/SIRT1 axis is required for adiponectin-mediated preconditioning on myocardial ischemia-reperfusion (I/R) injury in rats

Background

Adiponectin (AD) cardioprotective activities are mediated by AMPK, a fuel-sensing molecule sharing common targets and cellular activities with SIRT-1. Whether AD preconditioning may involve SIRT-1 activity is not known; however, the protective role of SIRT-1 during ischemia and the potential interplay between AMPK and SIRT-1 suggest this possibility.

Methods

Isolated hearts from male Sprague-Dawley rats (n = 85) underwent ischemia/reperfusion (I/R, 30/180 min). Preconditioning with resveratrol (RSV, SIRT-1 activator) was compared to preconditioning with AD alone, or in combination with compound C (CC, AMPK inhibitor) or sirtinol (STN, SIRT-1 inhibitor). For each heart, left ventricular end-diastolic pressure (LVEDP), left ventricular developed pressure (dLVP), coronary flow (CF) and left ventricular infarct mass (IM) were measured, together with the phosphorylation/activation status of AMPK, LKB1, eNOS and SIRT-1, at the beginning (15 min) and at the end (180 min) of reperfusion.

Results and conclusions

When compared to I/R, both RSV and AD improved cardiac function and reduced IM (p < 0.01, p < 0.05, respectively). Cardioprotective effects of AD were completely reversed in the AD+CC group, and significantly attenuated in the AD+STN group. Both RSV and AD increased eNOS, AMPK and LKB1 phosphorylation (for each parameter: p < 0.05 vs. I/R, in both RSV and AD treatment groups) at 15 min of reperfusion, and SIRT-1 activity at the end of reperfusion (p < 0.01, p < 0.05 vs. I/R, respectively). Interestingly, AD-mediated phosphorylation of AMPK and LKB1, and SIRT-1 deacetylation activity was markedly reduced in both the AD+CC and AD+STN groups (p < 0.05 vs. AD). Thus, AD-mediated cardioprotection requires both AMPK and SIRT-1 signaling pathways, that act as a component of a cycle and regulate each other’s activities.

Naringenin Attenuates Myocardial Ischemia-Reperfusion Injury via cGMP-PKGIα Signaling and In Vivo and In Vitro Studies

Endoplasmic reticulum (ER) stress and oxidative stress contribute greatly to myocardial ischemia-reperfusion (MI/R) injury. Naringenin, a flavonoid derived from the citrus genus, exerts cardioprotective effects. However, the effects of naringenin on ER stress as well as oxidative stress under MI/R condition and the detailed mechanisms remain poorly defined. This study investigated the protective effect of naringenin on MI/R-injured heart with a focus on cyclic guanosine monophosphate- (cGMP-) dependent protein kinase (PKG) signaling. Sprague-Dawley rats were treated with naringenin (50 mg/kg/d) and subjected to MI/R surgery with or without KT5823 (2 mg/kg, a selective inhibitor of PKG) cotreatment. Cellular experiment was conducted on H9c2 cardiomyoblasts subjected to simulated ischemia-reperfusion treatment. Before the treatment, the cells were incubated with naringenin (80 μmol/L). PKGIα siRNA was employed to inhibit PKG signaling. Our in vivo and in vitro data showed that naringenin effectively improved heart function while it attenuated myocardial apoptosis and infarction. Furthermore, pretreatment with naringenin suppressed MI/R-induced oxidative stress as well as ER stress as evidenced by decreased superoxide generation, myocardial MDA level, gp91^phox expression, and phosphorylation of PERK, IRE1α, and EIF2α as well as reduced ATF6 and CHOP. Importantly, naringenin significantly activated myocardial cGMP-PKGIα signaling while inhibition of PKG signaling with KT5823 (in vivo) or siRNA (in vitro) not only abolished these actions but also blunted naringenin's inhibitory effects against oxidative stress and ER stress. In summary, our study demonstrates that naringenin treatment protects against MI/R injury by reducing oxidative stress and ER stress via cGMP-PKGIα signaling. Its cardioprotective effect deserves further clinical study.

Multitarget Strategies to Reduce Myocardial Ischemia/Reperfusion Injury: JACC Review Topic of the Week

Many treatments have been identified that confer robust cardioprotection in experimental animal models of acute ischemia and reperfusion injury. However, translation of these cardioprotective therapies into the clinical setting of acute myocardial infarction (AMI) for patient benefit has been disappointing. One important reason might be that AMI is multifactorial, causing cardiomyocyte death via multiple mechanisms, as well as affecting other cell types, including platelets, fibroblasts, endothelial and smooth muscle cells, and immune cells. Many cardioprotective strategies act through common end-effectors and may be suboptimal in patients with comorbidities. In this regard, emerging data suggest that optimal cardioprotection may require the combination of additive or synergistic multitarget therapies. This review will present an overview of the state of cardioprotection today and provide a roadmap for how we might progress towards successful clinical use of cardioprotective therapies following AMI, focusing on the rational combination of judiciously selected, multitarget therapies. This paper emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Circulating mediators of remote ischemic preconditioning: search for the missing link between non-lethal ischemia and cardioprotection

Acute myocardial infarction (AMI) is one of the leading causes of mortality and morbidity worldwide. There has been an extensive search for cardioprotective therapies to reduce myocardial ischemia-reperfusion (I/R) injury. Remote ischemic preconditioning (RIPC) is a phenomenon that relies on the body's endogenous protective modalities against I/R injury. In RIPC, non-lethal brief I/R of one organ or tissue confers protection against subsequent lethal I/R injury in an organ remote to the briefly ischemic organ or tissue. Initially it was believed to be limited to direct myocardial protection, however it soon became apparent that RIPC applied to other organs such as kidney, liver, intestine, skeletal muscle can reduce myocardial infarct size. Intriguing discoveries have been made in extending the concept of RIPC to other organs than the heart. Over the years, the underlying mechanisms of RIPC have been widely sought and discussed. The involvement of blood-borne factors as mediators of RIPC has been suggested by a number of research groups. The main purpose of this review article is to summarize the possible circulating mediators of RIPC, and recent studies to establish the clinical efficacy of these mediators in cardioprotection from lethal I/R injury.

Down-regulation of myocardial infarction associated transcript 1 improves myocardial ischemia-reperfusion injury in aged diabetic rats by inhibition of activation of NF-κB signaling pathway

OBJECTIVE

This study is performed to investigate the effect of long chain noncoding RNA myocardial infarction associated transcript 1 (MIRT1) on myocardial ischemia reperfusion (I/R) injury in aged diabetic rats.

METHODS

The aged diabetic rat model and myocardial I/R injury model were established. Through injecting MIRT1 siRNA into caudal vein of rats, the cardiac function, myocardial pathological injury, myocardial fibrosis, cardiomyocytes apoptosis, oxidative stress and inflammatory injury of myocardial tissue of rats were measured.

RESULTS

For diabetic I/R rats, the expression of MIRT1 in myocardial tissue was increased, the activation of nuclear factor kappa B (NF-κB) signaling pathway was increased, the degree of damage to cardiac function was aggravated, the area of myocardial pathological injury and myocardial fibrosis was enlarged, the degree of cardiomyocytes apoptosis was increased, the degree of oxidative stress and inflammatory injury was increased. After inhibiting the expression of MIRT1, the activation of NF-κB signaling pathway was inhibited, the damage of cardiac function and cardiomyopathy was alleviated, the area of myocardial fibrosis was decreased, the degree of myocardial apoptosis was decreased, the degree of oxidative stress and inflammatory injury was obviously improved.

CONCLUSION

Our study highlights that down-regulation of MIRT1 improves myocardial I/R injury in aged diabetic rats by inhibition of activation of NF-κB signaling pathway.

Dyslipidemia in Ischemia/Reperfusion Injury

Ischemic heart disease is the main cause of morbidity and mortality in the developed world. Although reperfusion therapies are currently the best treatment for this entity, the restoration of blood flow leads, under certain circumstances, to a form of myocardial damage called reperfusion injury. Several studies have shown that age, sex, smoking, diabetes and dyslipidemia are risk factors for cardiovascular diseases. Among these risk factors, dyslipidemias are present in 40% of patients with ischemic heart disease and represent the clinical factor with the greatest impact on the prognosis of patients with cardiovascular diseases. It is known that during reperfusion the increase of the oxidative stress is perhaps one of the most important mechanisms implicated in cell damage. That is why several researchers have studied protective mechanisms against reperfusion injury, such as the ischemic pre- and post- conditioning, making emphasis mainly on the reduction of oxidative stress. However, few of these efforts have been successfully translated into the clinical setting. The controversial results in regards to the relation between cardioprotective mechanisms and dyslipidemia/hypercholesterolemia are mainly due to the difference among quality, composition and the time of administration of hypercholesterolemic diets, as well as the difference in the species used in each of the studies. Therefore, in order to compare results, it is crucial that all variables that could modify the obtained results are taken into consideration.

Tranexamic Acid Does Not Influence Cardioprotection by Ischemic Preconditioning and Remote Ischemic Preconditioning

Prior studies have suggested that the antifibrinolytic drug aprotinin increases the infarct size after ischemia and reperfusion (I/R) and attenuates the effect of ischemic preconditioning (IPC). Aprotinin was replaced by tranexamic acid (TXA) in clinical practice. Here, we investigated whether TXA influences I/R injury and/or cardioprotection initiated by IPC and/or remote ischemic preconditioning (RIPC). Anesthetized male Wistar rats were randomized to 6 groups. Control animals were not further treated. Administration of TXA was combined with and without IPC and RIPC. Estimated treatment effect was 20%. Compared to control group (56% ± 11%), IPC reduced infarct size by 46% (30% ± 6%; mean difference, 26%; 95% confidence interval, 19-33; P < .0001), and RIPC reduced infarct size by 29% (40% ± 8%; mean difference, 16%; 95% confidence interval, 9-24; P < .011). Additional application of TXA had no effect on I/R injury and cardioprotection by IPC or RIPC. TXA does not abolish infarct size reduction by IPC or RIPC.

Pharmacological preconditioning with the cellular stress inducer thapsigargin protects against experimental sepsis

Previous studies have shown that pretreatment with thapsigargin (TG), a cellular stress inducer, produced potent protective actions against various pathologic injuries. So far there is no information on the effects of TG on the development of bacterial sepsis. Using lipopolysaccharides- and cecal ligation/puncture-induced sepsis models in mice, we demonstrated that preconditioning with a single bolus administration of TG conferred significant improvements in survival. The beneficial effects of TG were not mediated by ER stress induction or changes in Toll-like receptor 4 signaling. In vivo and in cultured macrophages, we identified that TG reduced the protein production of pro-inflammatory cytokines, but exhibited no significant effects on steady state levels of their transcriptions. Direct measurement on the fraction of polysome-bound mRNAs revealed that TG reduced the translational efficiency of pro-inflammatory cytokines in macrophages. Moreover, we provided evidence suggesting that repression of the mTOR (the mammalian target of rapamycin) signaling pathway, but not activation of the PERK (protein kinase R-like endoplasmic reticulum kinase)-eIF2α (eukaryotic initiation factor 2α) pathway, might be involved in mediating the TG effects on cytokine production. In summary, our results support that pharmacological preconditioning with TG may represent a novel strategy to prevent sepsis-induced mortality and organ injuries.

Hypothermic perfusion of donor heart with a preservation solution supplemented by mesenchymal stem cells

BACKGROUND

Heart transplantation is the definitive treatment for end-stage heart failure. A shortage of donor hearts forced transplant programs to accept older donors and longer ischemic times. Previous studies have suggested that administration of mesenchymal stem cells (MSCs) or their conditioned medium (CM) protects the heart against ischemia/reperfusion injury (IRI). We hypothesized that the preservation of donor hearts with a CM would protect the graft from IRI after prolonged storage in 15-month-old rats and investigated mRNA changes attributable to CM.

METHODS

Rat MSCs were isolated and cultured. The CM was used and characterized by a 90-antibody array, revealing the presence of 28 factors involved in apoptosis, inflammation, and oxidative stress. Hearts from 15-month-old donor rats were explanted and continuously perfused for 5 hours with oxygenated, 4°C cardioplegic solution, and supplemented with either regular cell culture medium (control group) or CM. The hearts were then heterotopically transplanted. We evaluated in-vivo left ventricular graft function 1.5 hours after transplantation and the myocardial expression of 120 genes using polymerase chain reaction arrays.

RESULTS

Systolic contractility and relaxation parameters were significantly reduced in 15-month-old rats compared with the young rats. After transplantation, systolic function (dP/dt_max: 1,197 ± 94 vs 1,825 ± 279 mm Hg/s at 140 µl; p < 0.05) and diastolic function (dP/dt_min: 737 ± 168 vs 1,200 ± 166 mm Hg/s at 140 µl, p < 0.05) were significantly improved in the CM group compared with controls. Among the genes surveyed, the expressions of 66 were altered. Genes of pro-inflammatory cytokines and interleukins were down-regulated, whereas expression of the anti-oxidant gene superoxide dismutase-2 was up-regulated in the CM-treated grafts compared with the control group grafts.

CONCLUSIONS

Perfusion of donor hearts with CM protects against myocardial IRI in 15-month-old rats.

Human Tissue-Engineered Model of Myocardial Ischemia-Reperfusion Injury

IMPACT STATEMENT

Reducing ischemia-reperfusion injury would significantly improve patient survival. Current preclinical models are inadequate because they rely on animals, which do not emulate human physiology and the clinical setting. We developed a human tissue platform that allowed us to assess the human cardiac response, and demonstrated the platform's utility by measuring injury during ischemia-reperfusion and the effects of cardioprotective strategies. The model provides a foundation for future studies on how patient-specific backgrounds may affect response to therapeutic strategies. These steps will be necessary to help translate therapies into the clinical setting.

Effects of Ischemic Preconditioning on Abdominal Aortic Aneurysm Repair: A Systematic Review and Meta-analysis

BACKGROUND

Ischemic preconditioning is an innate mechanism of cytoprotection against ischemia, with potential for end-organ protection. The primary goal of this study was to systematically review the literature to determine the effect of ischemic preconditioning on outcomes after open and endovascular abdominal aortic aneurysm (AAA) repair.

METHODS

The methodology followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. We included randomized clinical trials that evaluated the effect of remote ischemic preconditioning (RIPC) in reducing morbidity and mortality in patients undergoing open or endovascular AAA repair surgery. The primary outcomes were death, myocardial infarction, and renal impairment. Outcomes were addressed separately for open AAA repair and endovascular AAA repair (EVAR). Data were collected on patient characteristics, methodology, and preconditioning protocol for each trial.

RESULTS

Nine trials of ischemic preconditioning in aortic aneurysm surgery were included with a total of 599 patients; 336 patients were included in the open AAA repair meta-analysis, and 263 patients were included in the EVAR meta-analysis. For both open and endovascular repairs, ischemic preconditioning did not have a significant effect on death, myocardial infarction, or renal impairment requiring dialysis.

CONCLUSIONS

The randomized clinical trials investigating the effect of ischemic preconditioning on outcomes after open and endovascular AAA repair that have been completed to date have not been adequately powered to evaluate improvements in patient-important outcomes. The evidence is insufficient to support the use of ischemic preconditioning for AAA repair in clinical practice. The variability in treatment effect across studies may be explained by clinical and methodological heterogeneity.

Effects of Cardiovascular Risk Factors on Cardiac STAT3

Nuclear, mitochondrial and cytoplasmic signal transducer and activator of transcription 3 (STAT3) regulates many cellular processes, e.g., the transcription or opening of mitochondrial permeability transition pore, and its activity depends on the phosphorylation of Tyr705 and/or Ser727 sites. In the heterogeneous network of cardiac cells, STAT3 promotes cardiac muscle differentiation, vascular element formation and extracellular matrix homeostasis. Overwhelming evidence suggests that STAT3 is beneficial for the heart, plays a role in the prevention of age-related and postpartum heart failure, protects the heart against cardiotoxic doxorubicin or ischaemia/reperfusion injury, and is involved in many cardioprotective strategies (e.g., ischaemic preconditioning, perconditioning, postconditioning, remote or pharmacological conditioning). Ischaemic heart disease is still the leading cause of death worldwide, and many cardiovascular risk factors contribute to the development of the disease. This review focuses on the effects of various cardiovascular risk factors (diabetes, aging, obesity, smoking, alcohol, depression, gender, comedications) on cardiac STAT3 under non-ischaemic baseline conditions, and in settings of ischaemia/reperfusion injury with or without cardioprotective strategies.

Icariin protects cardiomyocytes against ischaemia/reperfusion injury by attenuating sirtuin 1-dependent mitochondrial oxidative damage

BACKGROUND AND PURPOSE

Icariin, a major active ingredient in traditional Chinese medicines, is attracting increasing attention because of its unique pharmacological effects against ischaemic heart disease. The histone deacetylase, sirtuin-1, plays a protective role in ischaemia/reperfusion (I/R) injury, and this study was designed to investigate the protective role of icariin in models of cardiac I/R injury and to elucidate the potential involvement of sirtuin-1.

EXPERIMENTAL APPROACH

I/R injury was simulated in vivo (mouse hearts), ex vivo (isolated rat hearts) and in vitro (neonatal rat cardiomyocytes and H9c2 cells). Prior to I/R injury, animals or cells were exposed to icariin, with or without inhibitors of sirtuin-1 (sirtinol and SIRT1 siRNA).

KEY RESULTS

In vivo and in vitro, icariin given before I/R significantly improved post-I/R heart contraction and limited the infarct size and leakage of creatine kinase-MB and LDH from the damaged myocardium. Icariin also attenuated I/R-induced mitochondrial oxidative damage, decreasing malondialdehyde content and increasing superoxide dismutase activity and expression of Mn-superoxide dismutase. Icariin significantly improved mitochondrial membrane homeostasis by increasing mitochondrial membrane potential and cytochrome C stabilization, which further inhibited cell apoptosis. Sirtuin-1 was significantly up-regulated in hearts treated with icariin, whereas Ac-FOXO1 was simultaneously down-regulated. Importantly, sirtinol and SIRT1 siRNA either blocked icariin-induced cardioprotection or disrupted icariin-mediated mitochondrial homeostasis.

CONCLUSIONS AND IMPLICATIONS

Pretreatment with icariin protected cardiomyocytes from I/R-induced oxidative stress through activation of sirtuin-1 /FOXO1 signalling.

Volatile anesthetics versus propofol in the cardiac surgical setting of remote ischemic preconditioning: a secondary analysis of a Cochrane Systematic Review

INTRODUCTION

So far, the concept of remote ischemic preconditioning (RIPC) failed its translation from experimental to clinical studies. In addition to our Cochrane Systematic Review, we systematically assessed the use of the intravenous anesthetic propofol, as a potential confounding factor.

EVIDENCE ACQUISITION

We searched CENTRAL, MEDLINE, Embase and Web of Science. We included randomized controlled trials comparing RIPC with no RIPC in adult patients scheduled for coronary artery bypass graft surgery (with or without valve surgery) receiving either exclusively propofol or exclusively volatile anesthetics. Two authors independently assessed methodological quality and extracted data. We report odds ratios (ORs) with 95% confidence intervals as our summary statistics are based on random-effects models.

EVIDENCE SYNTHESIS

We included 14 studies involving 4060 participants. We found no difference in treatment effect between the propofol and volatile anesthetic groups when RIPC or no RIPC is applied on a composite endpoint (all-cause mortality, non-fatal myocardial infarction and/or any new stroke), all-cause mortality, non-fatal myocardial infarction, stroke, or length of stay on ICU. On cardiac markers, RIPC did show a treatment effect on cardiac troponin T measured as AUC 72 hours (SMD -0.80, CI -1.34, -0.25) in the propofol group. However, these findings have to be interpreted with great caution, to date only a very limited number of patients received volatile anesthetics in RIPC trials (minimum N.=15, maximum N.=232).

CONCLUSIONS

Present data do not permit a final assessment regarding the role of volatile or intravenous anesthetics as a possible confounding factor in RIPC trials.

The Mitochondrial Translocator Protein and the Emerging Link Between Oxidative Stress and Arrhythmias in the Diabetic Heart

The mitochondrial translocator protein (TSPO) is a key outer mitochondrial membrane protein that regulates the activity of energy-dissipating mitochondrial channels in response to oxidative stress. In this article, we provide an overview of the role of TSPO in the systematic amplification of reactive oxygen species (ROS) through an autocatalytic process known as ROS-induced ROS-release (RIRR). We describe how this TSPO-driven process destabilizes the mitochondrial membrane potential leading to electrical instability at the cellular and whole heart levels. Finally, we provide our perspective on the role of TSPO in the pathophysiology of diabetes, in general and diabetes-related arrhythmias, in particular.

Intra-coronary morphine versus placebo in the treatment of acute ST-segment elevation myocardial infarction: the MIAMI randomized controlled trial

BACKGROUND

Experimental studies suggest that morphine may protect the myocardium against ischemia-reperfusion injury by activating salvage kinase pathways. The objective of this two-center, randomized, double-blind, controlled trial was to assess potential cardioprotective effects of intra-coronary morphine in patients with ST-segment elevation myocardial infarction (STEMI) referred for primary percutaneous intervention.

METHODS

Ninety-one patients with STEMI were randomly assigned to intracoronary morphine (1 mg) or placebo at reperfusion of the culprit coronary artery. The primary endpoint was infarct size/left ventricular mass ratio assessed by magnetic resonance imaging on day 3-5. Secondary endpoints included the areas under the curve (AUC) for troponin T and creatine kinase over three days, left ventricular ejection fraction assessed by echocardiography on days 1 and 6, and clinical outcomes.

RESULTS

Infarct size/left ventricular mass ratio was not significantly reduced by intracoronary morphine compared to placebo (27.2% ± 15.0% vs. 30.5% ± 10.6%, respectively, p = 0.28). Troponin T and creatine kinase AUCs were similar in the two groups. Morphine did not improve left ventricular ejection fraction on day 1 (49.7 ± 10.3% vs. 49.3 ± 9.3% with placebo, p = 0.84) or day 6 (48.5 ± 10.2% vs. 49.0 ± 8.5% with placebo, p = 0.86). The number of major adverse cardiac events, including stent thrombosis, during the one-year follow-up was similar in the two groups.

CONCLUSIONS

Intracoronary morphine at reperfusion did not significantly reduce infarct size or improve left ventricular systolic function in patients with STEMI. Presence of comorbidities in some patients may contribute to explain these results.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01186445 (date of registration: August 23, 2010).

Milrinone-Induced Postconditioning Requires Activation of Mitochondrial Ca2+-sensitive Potassium (mBKCa) Channels

OBJECTIVES

Cardioprotection by postconditioning requires activation of mitochondrial large-conductance Ca2+-sensitive potassium (mBKCa) channels. The involvement of these channels in milrinone-induced postconditioning is unknown. The authors determined whether cardioprotection by milrinone-induced postconditioning involves activation of mBKCa channels in the rat heart in vitro.

DESIGN

Randomized, prospective, blinded laboratory investigation.

SETTING

Experimental laboratory.

PARTICIPANTS

Male Wistar rats.

INTERVENTIONS

Hearts of male Wistar rats were randomized, placed on a Langendorff system, and perfused with Krebs-Henseleit buffer at a constant pressure of 80 mmHg. All hearts were subjected to 33 minutes of global ischemia and 60 minutes of reperfusion. At the onset of reperfusion, hearts were perfused with different concentrations of milrinone (0.3-100 μM) for determination of a dose-effect curve. In a second set of experiments, 3 μM milrinone was administered in combination with the mBKCa channel inhibitor paxilline (1 μM). Infarct size was determined by triphenyltetrazoliumchloride staining.

MEASUREMENTS AND MAIN RESULTS

In control animals, infarct size was 37 ± 7%. Milrinone at a concentration of 3 μM reduced infarct size to 22 ± 7% (p < 0.05 v control). Higher milrinone concentrations did not confer stronger protection. Paxilline completely blocked milrinone-induced cardioprotection whereas paxilline alone had no effect on infarct size.

CONCLUSIONS

This study shows that activation of mBKCa channels plays a pivotal role in milrinone-induced postconditioning.

Remote ischaemic conditioning for prevention of acute kidney injury after valvular heart surgery: a randomised controlled trial

BACKGROUND

Repeated remote ischaemic conditioning (RIC) during weaning from cardiopulmonary bypass and in the early postoperative period may confer protection against acute kidney injury (AKI). We evaluated the effect of repeated RIC on the incidence of AKI in patients undergoing valvular heart surgery.

METHODS

Patients were randomised into either the RIC (n=120) or control (n=124) group. A pneumatic tourniquet was placed on each patient's thigh. Upon removal of the aortic cross-clamp, three cycles of inflation for 5 min at 250 mm Hg (with 5 min intervals) were applied in the RIC group. Additionally, three cycles of RIC were repeated at postoperative 12 and 24 h. AKI was diagnosed based on the Kidney Disease: Improving Global Outcomes guideline. The incidences of renal replacement therapy, permanent stroke, sternal wound infection, newly developed atrial fibrillation, mechanical ventilation >24 h, and reoperation for bleeding during hospitalisation were recorded.

RESULTS

The incidences of AKI were not significantly different between the control (19.4%) and RIC (15.8%) groups (a difference of 3.5 percentage points; 95% confidence interval: -6.8%-13.9%; P=0.470). Perioperative serum creatinine concentrations were similar in the control and RIC groups (P=0.494). Fluid balance, urine output, blood loss, transfusion, and vasopressor/inotropic requirements were not significantly different between the groups (all P>0.05). The occurrences of a composite of morbidity and mortality endpoints were not significantly different between the control (46.0%) and RIC (39.2%) groups (a difference of 6.8 percentage points; 95% confidence interval: -6.4%-20.0%; P=0.283).

CONCLUSIONS

The results of our study do not support repeated RIC to decrease the incidence of AKI after valvular heart surgery.

CLINICAL TRIAL REGISTRATION

NCT02720549.

Melatonin Protects Against Hypoxia/Reoxygenation-Induced Dysfunction of Human Umbilical Vein Endothelial Cells Through Inhibiting Reactive Oxygen Species Generation

BACKGROUND

Hypoxia/reoxygenation (H/R) in human umbilical vein endothelial cells (HUVECs) induces oxidative stress and eventually leads to vascular injury.

OBJECTIVE

The aim of this study was to examine the effect of melatonin on HUVECs injured by H/R and explore the underlying mechanisms.

MATERIALS AND METHODS

A model of HUVECs under hypoxia/reoxygenation was established. Cell migration and adhesive ability was measured by wound healing and adhesion assays. Cell proliferation was measured by EdU assay. Production of reactive oxygen species (ROS) was evaluated by CM-H2DCFDA staining. Actin cytoskeleton rearrangement was examined by immunofluorescence. Western blotting analysis were used to analyze P38 and HSP27 phosphorylation levels.

RESULTS

H/R inhibited HUVEC proliferation, cell migratory and adhesive capacities, whereas melatonin (1~100 μM) inhibited these effects in a dose-dependent manner. Melatonin alone did not affect HUVEC viability, however, it inhibited the increase in ROS production and cytoskeleton disruption elicited by H/R, and it dose-dependently prevented H/R-induced upregulation of P38 and HSP27 phosphorylation. In addition, the ROS scavenger N-acetyl-L-cysteine markedly inhibited increased phosphorylation levels of P38 and HSP27 under H/R.

CONCLUSIONS

Melatonin may have a potential clinical effect in trials of H/R-induced vascular injury through its antioxidant property.

In vitro Models of Ischemia-Reperfusion Injury

Timely reperfusion after a myocardial infarction is necessary to salvage the ischemic region; however, reperfusion itself is also a major contributor to the final tissue damage. Currently, there is no clinically relevant therapy available to reduce ischemia-reperfusion injury (IRI). While many drugs have shown promise in reducing IRI in preclinical studies, none of these drugs have demonstrated benefit in large clinical trials. Part of this failure to translate therapies can be attributed to the reliance on small animal models for preclinical studies. While animal models encapsulate the complexity of the systemic in vivo environment, they do not fully recapitulate human cardiac physiology. Furthermore, it is difficult to uncouple the various interacting pathways in vivo. In contrast, in vitro models using isolated cardiomyocytes allow studies of the direct effect of therapeutics on cardiomyocytes. External factors can be controlled in simulated ischemia-reperfusion to allow for better understanding of the mechanisms that drive IRI. In addition, the availability of cardiomyocytes derived from human induced pluripotent stem cells (hIPS-CMs) offers the opportunity to recapitulate human physiology in vitro. Unfortunately, hIPS-CMs are relatively fetal in phenotype, and are more resistant to hypoxia than the mature cells. Tissue engineering platforms can promote cardiomyocyte maturation for a more predictive physiologic response. These platforms can further be improved upon to account for the heterogenous patient populations seen in the clinical settings and facilitate the translation of therapies. Thereby, the current preclinical studies can be further developed using currently available tools to achieve better predictive drug testing and understanding of IRI. In this article, we discuss the state of the art of in vitro modeling of IRI, propose the roles for tissue engineering in studying IRI and testing the new therapeutic modalities, and how the human tissue models can facilitate translation into the clinic.

Whole-Body MR Imaging: The Novel, "Intrinsically Hybrid," Approach to Metastases, Myeloma, Lymphoma, in Bones and Beyond

Whole-body MR imaging (WB-MR imaging) has become a modality of choice for detecting bone metastases in multiple cancers, and bone marrow involvement by multiple myeloma or lymphoma. Combination of anatomic and functional sequences imparts an inherently hybrid dimension to this nonirradiating tool and extends the screening of malignancies outside the skeleton. WB-MR imaging outperforms bone scintigraphy and CT and offers an alternative to PET in many tumors by time of lesion detection and assessment of treatment response. Much work has been done to standardize procedures, optimize sequences, validate indications, confirm preliminary research into new applications, rendering clinical application more user-friendly.

Selegiline reduces adiposity induced by high-fat, high-sucrose diet in male rats

BACKGROUND AND PURPOSE

Incidence and severity of obesity are increasing worldwide, however, efficient and safe pharmacological treatments are not yet available. Certain MAO inhibitors reduce body weight, although their effects on metabolic parameters have not been investigated. Here, we have assessed effects of a widely used, selective MAO-B inhibitor, selegiline, on metabolic parameters in a rat model of diet-induced obesity.

EXPERIMENTAL APPROACH

Male Long-Evans rats were given control (CON) or a high-fat (20%), high-sucrose (15%) diet (HFS) for 25 weeks. From week 16, animals were injected s.c. with 0.25 mg·kg^-1 selegiline (CON + S and HFS + S) or vehicle (CON, HFS) once daily. Whole body, subcutaneous and visceral fat was measured by CT, and glucose and insulin tolerance were tested. Expression of glucose transporters and chemokines was assessed by quantitative RT-PCR.

KEY RESULTS

Selegiline decreased whole body fat, subcutaneous- and visceral adiposity, measured by CT and epididymal fat weight in the HFS group, compared with HFS placebo animals, without influencing body weight. Oral glucose tolerance and insulin tolerance tests showed impaired glucose homeostasis in HFS and HFS + S groups, although insulin levels in plasma and pancreas were unchanged. HFS induced expression of Srebp-1c, Glut1 and Ccl3 in adipose tissue, which were alleviated by selegiline.

CONCLUSIONS AND IMPLICATIONS

Selegiline reduced adiposity, changes in adipose tissue energy metabolism and adipose inflammation induced by HFS diet without affecting the increased body weight, impairment of glucose homeostasis, or behaviour. These results suggest that selegiline could mitigate harmful effects of visceral adiposity.

Remote Limb Ischemic Conditioning and Motor Learning: Evaluation of Factors Influencing Response in Older Adults

Remote limb ischemic conditioning (RLIC) is a clinically feasible method of promoting tissue protection against subsequent ischemic insult. Recent findings from our lab demonstrated that RLIC robustly enhances motor learning in young, healthy humans. The next step is to determine which individuals would receive maximum benefit from RLIC before applying these findings to clinical rehabilitation populations such as stroke. Numerous factors, such as age, sex, body mass index (BMI), and cardiovascular comorbidities may influence the response. Sixty-nine participants aged 40-80 were randomized to receive either RLIC (n = 33) or sham (n = 36) conditioning. Participants underwent seven consecutive sessions consisting of RLIC or sham conditioning with a blood pressure cuff on the upper extremity and motor training on a stability platform balance task, with two follow-up sessions. Balance change (post-test-pre-test) was compared across participants, groups, and the factors of age, sex, BMI, and comorbidities. Participants in both groups improved their performance on the balance task from pre- to post-test. Overall balance change was independently associated with age and BMI. There was no difference in balance change between RLIC and Sham groups. However, RLIC significantly enhanced balance performance in participants with no comorbidities. Compared with our previous study in young adults, middle-aged and older adults demonstrated smaller improvements on the balance task. RLIC enhanced learning in middle-aged and older adults only in the absence of pre-defined comorbidities. RLIC may be a promising tool for enhancing motor recovery, but the accumulation of comorbidity with age may decrease its effectiveness.

Type 2 diabetes mellitus worsens neurological injury following cardiac arrest: an animal experimental study

Background

Cardiac arrest carries a poor prognosis. The typical cardiac arrest patient is comorbid, and studies have shown that diabetes mellitus is an independent risk factor for increased mortality after cardiac arrest. Despite this, animal studies lack to investigate cardiac arrest in the setting of diabetes mellitus.

We hypothesize that type 2 diabetes mellitus in a rat model of cardiac arrest is associated with increased organ dysfunction when compared with non-diabetic rats.

Methods

Zucker diabetic fatty (ZDF) rats (n = 13), non-diabetic Zucker lean control (ZLC) rats (n = 15), and non-diabetic Sprague Dawley (SprD) rats (n = 8), underwent asphyxia-induced cardiac arrest. Animals were resuscitated and monitored for 180 min after return of spontaneous circulation (ROSC).

Blood levels of neuron-specific enolase were measured to assess neurological injury. Cardiac function was evaluated by echocardiography.

Results

No differences in cardiac output or neuron-specific enolase existed between the groups at baseline. Median levels of neuron-specific enolase 180 min after ROSC was 10.8 μg/L (Q₂₅;Q₇₅—7.6;11.3) in the ZDF group, which was significantly higher compared to the ZLC group at 2.0 μg/L (Q₂₅;Q₇₅—1.7;2.3, p < 0.05) and the SprD group at 2.8 μg/L (Q₂₅;Q₇₅—2.3;3.4, p < 0.05). At 180 min after ROSC, cardiac output was 129 mL/min/kg (SD 45) in the ZDF group, which was not different from 106 mL/min/kg (SD 31) in the ZLC group or 123 mL/min/kg (SD 26, p = 0.72) in the SprD group.

Conclusions

In a cardiac arrest model, neuronal injury is increased in type 2 diabetes mellitus animals compared with non-diabetic controls. Although this study lacks to uncover the specific mechanisms causing increased neuronal injury, the establishment of a cardiac arrest model of type 2 diabetes mellitus lays the important foundation for further experimental investigations within this field.