Cardiac Ischemic Preconditioning Research Articles

Inhibition of the protective effects of preconditioning in ischemia–reperfusion injury by chronic methadone: the role of pAkt and pSTAT3

Cardiac ischemic preconditioning (Pre) reduces cardiac ischemia–reperfusion injury (IRI) by stimulating opioid receptors. Chronic use of opioids can alter the signaling pathways. We investigated the effects of chronic methadone use on IRI and Pre. The experiments were performed on isolated hearts of male Wistar rats in four groups: IRI, Methadone + IRI (M-IRI), Pre + IRI (Pre-IRI), Methadone + Pre + IRI (M-Pre-IRI). The infarct size (IS) in the Pre-IRI group was smaller than the IRI group (26.8% vs. 47.8%, P < 0.05). In the M-IRI and M-Pre-IRI groups, the infarct size was similar to the IRI group. Akt (Ak strain transforming) phosphorylation in the Pre-IRI, M-IRI, and M-Pre-IRI groups was significantly higher than in the IRI group (0.56 ± 0.15, 0.63 ± 0.20, and 0.93 ± 0.18 vs 0.28 ± 0.17 respectively). STAT3 (signal transducer and activator of transcription 3) phosphorylation in the Pre-IRI and M-Pre-IRI groups (1.38 ± 0.14 and 1.46 ± 0.33) was significantly higher than the IRI and M-IRI groups (0.99 ± 0.1 and 0.98 ± 0.2). Thus, chronic use of methadone not only has no protective effect against IRI but also destroys the protective effects of ischemic preconditioning. This may be due to the hyperactivation of Akt and changes in signaling pathways.

Cardiac ischemic preconditioning promotes cMyBP-C phosphorylation by inhibiting the calpain-mediated proteolysis

Ischemic preconditioning (IPC) has been considered as the most important mean to protect against ischemia/reperfusion (I/R) induced heart injury. It has been reported that cardiac myosin binding protein-C (cMyBP-C) phosphorylation plays an essential role in cardiac protection against I/R-induced heart injury. However, it is still obscured whether IPC-mediated cardiac protection is causally related to cMyBP-C phosphorylation and proteolysis and, if so, what the underlying mechanism is. In this study, IPC was found to increase the phosphorylation level of cMyBP-C, companying with the decreased calpain activity in the collected perfusate samples. Mechanistically, we confirmed that IPC promoted cMyBP-C phosphorylation and inhibited calpain-mediated cMyBP-C proteolysis. Moreover, inhibition of calpain activity significantly increased the phosphorylated cMyBP-C level by using calpain inhibitor (MG-101), and subsequently promoted stabilization and secretion of cMyBP-C. Functionally, adeno-associated virus (AAV)-mediated overexpression of mutated phosphorylation motif site of cMyBP-C exhibited impaired IPC-mediated cardiac protection via proteolysis of the full-length cMyBP-C protein. We concluded that IPC promoted cMyBP-C phosphorylation via inhibition of calpain-mediated proteolysis and participated in IPC-mediated protection against I/R induced heart injury.

P55γ degrades RIP3 via MG53 to suppress ischaemia-induced myocardial necroptosis and mediates cardioprotection of preconditioning.

Regulated necrosis (necroptosis) and apoptosis are important biological features of myocardial infarction, ischaemia-reperfusion (I/R) injury, and heart failure. However, the molecular mechanisms underlying myocardial necroptosis remain elusive. Ischaemic preconditioning (IPC) is the most powerful intrinsic cardioprotection against myocardial I/R injury. In this study, we aimed to determine whether IPC suppresses I/R-induced necroptosis and the underlying molecular mechanisms. We generated p55γ transgenic and knockout mice and used ligation of left anterior descending coronary artery to produce an in vivo I/R model. The effects of p55γ and its downstream molecules were subsequently identified using mass spectroscopy and co-immunoprecipitation and pulldown assays. We found that p55γ expression was down-regulated in failing human myocardium caused by coronary heart disease as well as in I/R mouse hearts. Cardiac-specific p55γ overexpression ameliorated the I/R-induced necroptosis. In striking contrast, p55γ deficiency (p55γ-/-) and cardiac-specific deletion of p55γ (p55γc-KO) worsened I/R-induced injury. IPC up-regulated p55γ expression in vitro and in vivo. Using reporter and chromatin immunoprecipitation assays, we found that Hif1α transcriptionally regulated p55γ expression and mediated the cardioprotection of IPC. IPC-mediated suppression of necroptosis was attenuated in p55γ-/- and p55γc-KO hearts. Mechanistically, p55γ overexpression decreased the protein levels of RIP3 rather than the mRNA levels, while p55γ deficiency increased the protein abundance of RIP3. IPC attenuated the I/R-induced up-regulation of RIP3, which was abolished in p55γ-deficient mice. Up-regulation of RIP3 attenuated the p55γ- or IPC-induced inhibition of necroptosis in vivo. Importantly, p55γ directly bound and degraded RIP3 in a ubiquitin-dependent manner. We identified MG53 as the E3 ligase that mediated the p55γ-induced degradation of RIP3. In addition, we also found that p55γ activated the RISK pathway during IPC. Our findings reveal that activation of the MG53-RIP3 signal pathway by p55γ protects the heart against I/R-induced necroptosis and underlies IPC-induced cardioprotection.

Chronic treatment with rofecoxib but not ischemic preconditioning of the myocardium ameliorates early intestinal damage following cardiac ischemia/reperfusion injury in rats

There is some recent evidence that cardiac ischemia/reperfusion (I/R) injury induces intestinal damage within days, which contributes to adverse cardiovascular outcomes after myocardial infarction. However, it is not clear whether remote gut injury has any detectable early signs, and whether different interventions aiming to reduce cardiac damage are also effective at protecting the intestine. Previously, we found that chronic treatment with rofecoxib, a selective inhibitor of cyclooxygenase-2 (COX-2), limited myocardial infarct size to a comparable extent as cardiac ischemic preconditioning (IPC) in rats subjected to 30-min coronary artery occlusion and 120-min reperfusion. In the present study, we aimed to analyse the early intestinal alterations caused by cardiac I/R injury, with or without the above-mentioned infart size-limiting interventions. We found that cardiac I/R injury induced histological changes in the small intestine within 2 h, which were accompanied by elevated tissue level of COX-2 and showed positive correlation with the activity of matrix metalloproteinase-2 (MMP-2), but not of MMP-9 in the plasma. All these changes were prevented by rofecoxib treatment. By contrast, cardiac IPC failed to reduce intestinal injury and plasma MMP-2 activity, although it prevented the transient reduction in jejunal blood flow in response to cardiac I/R. Our results demonstrate for the first time that rapid development of intestinal damage follows cardiac I/R, and that two similarly effective infarct size-limiting interventions, rofecoxib treatment and cardiac IPC, have different impacts on cardiac I/R-induced gut injury. Furthermore, intestinal damage correlates with plasma MMP-2 activity, which may be a biomarker for its early diagnosis.

Is Cardiac Remote Ischemic Preconditioning (RIPC) More Beneficial in Patients with Diabetes to Reduce Cardiac Troponin I After Elective Percutaneous Coronary Intervention (PCI)?

Background: Intervention of choice for reperfusion is percutaneous coronary intervention (PCI) in patients with coronary artery disease (CAD), but it may have side effects; one of which is myocardial injury. Cardiac remote ischemic preconditioning (RIPC) can potentially reduce these adverse effects, especially in patients with cardiovascular risk factors. Methods: This study received ethics approval on November 29, 2017 (ethics code: HUMS.REC.1396.93; IRCT code: IRCT20180306038978N1). It was performed on 240 patients (120 cases in the RIPC group and 120 cases in the control group). The patients undergoing PCI were randomly assigned to the RIPC group (blood pressure cuff was inflated up to 200 mmHg for 30 minutes on the non-dominant arm, and then deflated for 5 minutes (reperfusion); it was repeated 2 more times (3 times in general) or the control group (an uninflated cuff around the non-dominant arm). Cardiac troponin I (cTnI) was compared between the healthy controls and diabetic patients before and after PCI. Results: No significant difference was observed with regard to positive cTnI (P = 0.136). Positive cTnI was insignificantly higher in the control group compared to the intervention group. However, the frequency of positive cTnI was significantly lower in diabetic patients in the RIPC group compared to the controls (P &lt; 0.001). Conclusions: This study demonstrated that RIPC is beneficial in diabetic patients and reduces the release of cTnI after elective PCI in these patients.

Mitochondrial LonP1 protects cardiomyocytes from ischemia/reperfusion injury in vivo

RationaleLonP1 is an essential mitochondrial protease, which is crucial for maintaining mitochondrial proteostasis and mitigating cell stress. However, the importance of LonP1 during cardiac stress is largely unknown. ObjectiveTo determine the functions of LonP1 during ischemia/reperfusion (I/R) injury in vivo, and hypoxia-reoxygenation (H/R) stress in vitro. Methods and resultsLonP1 was induced 2-fold in wild-type mice during cardiac ischemic preconditioning (IPC), which protected the heart against ischemia-reperfusion (I/R) injury. In contrast, haploinsufficiency of LonP1 (LONP1+/−) abrogated IPC-mediated cardioprotection. Furthermore, LONP1+/− mice showed significantly increased infarct size after I/R injury, whereas mice with 3–4 fold cardiac-specific overexpression of LonP1 (LonTg) had substantially smaller infarct size and reduced apoptosis compared to wild-type controls. To investigate the mechanisms underlying cardioprotection, LonTg mice were subjected to ischemia (45 min) followed by short intervals of reperfusion (10, 30, 120 min). During early reperfusion, the left ventricles of LonTg mice showed substantially reduced oxidative protein damage, maintained mitochondrial redox homeostasis, and showed a marked downregulation of both Complex I protein level and activity in contrast to NTg mice. Conversely, when LonP1 was knocked down in isolated neonatal rat ventricular myocytes (NRVMs), an up-regulation of Complex I subunits and electron transport chain (ETC) activities was observed, which was associated with increased superoxide production and reduced respiratory efficiency. The knockdown of LonP1 in NRVMs caused a striking dysmorphology of the mitochondrial inner membrane, mitochondrial hyperpolarization and increased hypoxia-reoxygenation (H/R)-activated apoptosis. Whereas, LonP1 overexpression blocked H/R-induced cell death. ConclusionsLonP1 is an endogenous mediator of cardioprotection. Our findings show that upregulation of LonP1 mitigates cardiac injury by preventing oxidative damage of proteins and lipids, preserving mitochondrial redox balance and reprogramming bioenergetics by reducing Complex I content and activity. Mechanisms that promote the upregulation of LonP1 could be beneficial in protecting the myocardium from cardiac stress and limiting I/R injury.

Ventilation strategy has a major influence on remote ischaemic preconditioning in mice.

Whether oxygen should be administered acutely during ST‐segment elevation myocardial infarction is debated. Despite this controversy, the possible influence of supplementary oxygen on animal models of ischaemia–reperfusion injury or cardioprotection is rarely considered. We used an in vivo mouse model of ischaemia and reperfusion to investigate the effect of ventilation with room air versus 100% oxygen. The coronary artery of anaesthetized mice was occluded for 40 min. followed by 2‐hrs reperfusion. Infarct size was measured by tetrazolium staining and expressed as a percentage of area at risk, determined using Evan's blue. Unexpectedly, infarct size in mice ventilated with 100% oxygen was significantly smaller than in those ventilated with room air (33 ± 5% versus 46 ± 3%; n = 6; P < 0.01). We tested a standard protocol of 3 × 5 min. cycles of remote ischaemic preconditioning (RIPC) and found this was unable to protect mice ventilated with 100% oxygen. RIPC protocols using 2.5‐ or 10‐min. occlusion were similarly ineffective in mice ventilated with oxygen. Similar disparate results were obtained with direct cardiac ischaemic preconditioning. In contrast, pharmacological protection using bradykinin administered at reperfusion was effective even in mice ventilated with 100% oxygen, reducing infarct size from 33 ± 5% to 21 ± 3% (n = 4–6; P < 0.01). Laser speckle contrast imaging of blood flow and direct pO2 measurements were made in the hindlimb, but these measurements did not correlate with protection. In conclusion, ventilation protocol can have a major influence on infarct size and ischaemic preconditioning protocols in mice.

A Nontargeted UHPLC-HRMS Metabolomics Pipeline for Metabolite Identification: Application to Cardiac Remote Ischemic Preconditioning.

In recent years, the number of investigations based on nontargeted metabolomics has increased, although often without a thorough assessment of analytical strategies applied to acquire data. Following published guidelines for metabolomics experiments, we report a validated nontargeted metabolomics strategy with pipeline for unequivocal identification of metabolites using the MSMLS molecule library. We achieved an in-house database containing accurate m/z values, retention times, isotopic patterns, full MS, and MS/MS spectra. A UHPLC-HRMS Q-Exactive method was developed, and experimental variations were determined within and between 3 experimental days. The extraction efficiency as well as the accuracy, precision, repeatability, and linearity of the method were assessed, the method demonstrating good performances. The methodology was further blindly applied to plasma from remote ischemic pre-conditioning (RIPC) rats. Samples, previously analyzed by targeted metabolomics using completely different protocol, analytical strategy, and platform, were submitted to our analytical pipeline. A combination of multivariate and univariate statistical analyses was employed. Selection of putative biomarkers from OPLS-DA model and S-plot was combined to jack-knife confidence intervals, metabolites' VIP values, and univariate statistics. Only variables with strong model contribution and highly statistical reliability were selected as discriminated metabolites. Three biomarkers identified by the previous targeted metabolomics study were found in the current work, in addition to three novel metabolites, emphasizing the efficiency of the current methodology and its ability to identify new biomarkers of clinical interest, in a single sequence. The biomarkers were identified to level 1 according to the metabolomics standard initiative and confirmed by both RPLC and HILIC-HRMS.

Ketogenic diet in endocrine disorders: Current perspectives.

Ketogenic diet (KD) is a high-fat, adequate-protein, and low-carbohydrate diet that leads to nutritional ketosis, long known for antiepileptic effects and has been used therapeutically to treat refractory epilepsy. This review attempts to summarize the evidence and clinical application of KD in diabetes, obesity, and other endocrine disorders. KD is usually animal protein based. An empiric vegetarian Indian variant of KD has been provided keeping in mind the Indian food habits. KD has beneficial effects on cardiac ischemic preconditioning, improves oxygenation in patients with respiratory failure, improves glycemic control in diabetics, is associated with significant weight loss, and has a beneficial impact on polycystic ovarian syndrome. Multivitamin supplementations are recommended with KD. Recently, ketones are being proposed as super-metabolic fuel; and KD is currently regarded as apt dietary therapy for “diabesity.”

Ischemic Preconditioning Confers Epigenetic Repression of Mtor and Induction of Autophagy Through G9a-Dependent H3K9 Dimethylation.

BackgroundIschemic preconditioning (IPC) protects the heart from prolonged ischemic insult and reperfusion injury through a poorly understood mechanism. Post‐translational modifications of histone residues can confer rapid and drastic switches in gene expression in response to various stimuli, including ischemia. The aim of this study was to investigate the effect of histone methylation in the response to cardiac ischemic preconditioning.Methods and ResultsWe used cardiac biopsies from mice subjected to IPC to quantify global levels of 3 of the most well‐studied histone methylation marks (H3K9me2, H3K27me3, and H3K4me3) with Western blot and found that H3K9me2 levels were significantly increased in the area at risk compared to remote myocardium. In order to assess which genes were affected by the increase in H3K9me2 levels, we performed ChIP‐Seq and transcriptome profiling using microarray. Two hundred thirty‐seven genes were both transcriptionally repressed and enriched in H3K9me2 in the area at risk of IPC mice. Of these, Mtor (Mechanistic target of rapamycin) was chosen for mechanistic studies. Knockdown of the major H3K9 methyltransferase G9a resulted in a significant decrease in H3K9me2 levels across Mtor, increased Mtor expression, as well as decreased autophagic activity in response to rapamycin and serum starvation.Conclusions IPC confers an increase of H3K9me2 levels throughout the Mtor gene—a master regulator of cellular metabolism and a key player in the cardioprotective effect of IPC—leading to transcriptional repression via the methyltransferase G9a. The results of this study indicate that G9a has an important role in regulating cardiac autophagy and the cardioprotective effect of IPC.

Cardiac Remote Ischaemic Preconditioning: Mechanistic and Clinical Considerations.

Brief, non-harmful ischaemic insults to an organ remote from the heart, remote ischaemic preconditioning (RIPC), has been proposed to confer protection to the heart against ischaemia-reperfusion injury. While most clinical trials of RIPC during coronary interventions (PCI) suggest benefit, recent large, multicentre trials in coronary artery bypass surgery suggest a lack of efficacy. Mechanistically, RIPC most likely promotes the release of circulating factors which modulate multiple cellular pathways in the heart, promoting cell survival. This review explores potential mechanisms underlying RIPC and includes a contemporary evaluation of clinical studies in PCI and cardiac surgery, highlighting methodological differences which may explain discrepant findings between these two clinical groups.

WDR26 promotes mitophagy of cardiomyocytes induced by hypoxia through Parkin translocation.

Myocardial ischemia is a heart condition caused by reduction of blood flow to the heart, preventing heart from receiving enough oxygen. Myocardial ischemia is the most common cause of death globally. Heart ischemic preconditioning (IPC) has a protective effect against myocardial cell death induced by ischemia and ischemia-reperfusion injury. WDR26 has recently been identified as a protein that is increased following rat cardiac IPC. WDR26 can promote the proliferation of H9c2 cells and protect cardiomyocytes against oxidative stress through inhibiting apoptosis.However, its role in myocardial ischemia is unclear. The aim of this study was to explore the role of WDR26 in myocardial ischemia and H9c2 cell hypoxia. Our results showed that WDR26 is induced by myocardial ischemia and H9c2 cell hypoxia. WDR26 protects H9c2 cells against hypoxia injury through inhibitingLDH release and increasing cell viability. WDR26 promotes hypoxia-induced autophagy in hypoxia of H9c2 cells. We further demonstrated that in H9c2 cell hypoxia, WDR26 increases mitochondrial membrane potential, thereby increases Parkin translocation of mitochondria. After Parkin is translocated at mitochondria, WDR26 can increase mitochondrial protein ubiquitination in hypoxia of H9c2 cells. WDR26 is a mediator of response to hypoxia, and WDR26 plays an important role in hypoxia-mediated autophagy and mitophagy. This study provides novel insights into the protective role of WDR26 in cardiomyocyte injury during hypoxia. WDR26 may serve as a potential target for the treatment of myocardial ischemia.

Effect of Remote Ischemic Preconditioning on Kidney Injury Among High-Risk Patients Undergoing Cardiac Surgery: A Randomized Clinical Trial

In patients undergoing cardiac surgery remote ischemic preconditioning reduces the rate of acute kidney injury and use of renal replacement therapy.

Determinants of the Efficacy of Cardiac Ischemic Preconditioning: A Systematic Review and Meta-Analysis of Animal Studies.

BackgroundIschemic preconditioning (IPC) of the heart is a protective strategy in which a brief ischemic stimulus immediately before a lethal ischemic episode potently limits infarct size. Although very promising in animal models of myocardial infarction, IPC has not yet been successfully translated to benefit for patients.ObjectiveTo appraise all preclinical evidence on IPC for myocardial infarction and identify factors hampering translation.Methods and resultsUsing systematic review and meta-analysis, we identified 503 animal studies reporting infarct size data from 785 comparisons between IPC-treated and control animals. Overall, IPC reduced myocardial infarction by 24.6% [95%CI 23.5, 25.6]. Subgroup analysis showed that IPC efficacy was reduced in comorbid animals and non-rodents. Efficacy was highest in studies using 2–3 IPC cycles applied <45 minutes before myocardial infarction. Local and remote IPC were equally effective. Reporting of study quality indicators was low: randomization, blinding and a sample size calculation were reported in 49%, 11% and 2% of publications, respectively.ConclusionsTranslation of IPC to the clinical setting may be hampered by the observed differences between the animals used in preclinical IPC studies and the patient population, regarding comorbidity, sex and age. Furthermore, the IPC protocols currently used in clinical trials could be optimized in terms of timing and the number of ischemic cycles applied. In order to inform future clinical trials successfully, future preclinical studies on IPC should aim to maximize both internal and external validity, since poor methodological quality may limit the value of the preclinical evidence.

The 4th Window: A Novel, Clinically Relevant Model of Delayed Ischemic Preconditioning in Conscious, Chronically Instrumented Pigs

Most studies on cardiac ischemic preconditioning (IPC) focused on the 1st or 2nd window, where the preconditioning ischemic stimulus was induced briefly and the cardiac protection all occurred within a few hours or days. More recently 3rd window models have been described with IPC induced over several days. The goal of this investigation was to determine if IPC could be extended for a longer time, making it more clinically relevant. In this new IPC model, which we named the 4th window, pigs, chronically instrumented with coronary blood flow transducers, hydraulic occluders, and ultrasonic wall thickness crystals implanted in potentially ischemic and non‐ischemic zones, underwent IPC induced by 6 episodes of 90 min coronary stenosis (40% reduction in blood flow but no necrosis) every 12 hours over 3 days. 60 min coronary artery occlusion (CAO) followed by 3 days of coronary reperfusion, induced one week after IPC, resulted in infarct size, as a fraction of the area at risk, of 11±2.5%, less (p&lt;0.05) than in the absence of IPC (42±3.9%). Most genes expressed in this model were novel, compared to prior IPC models, included genes mediating angiogenesis. To confirm angiogenesis, we found increased capillary density adjacent to the infarct in the 4th window by 154% (p&lt;0.05), and 38% increased, p&lt;0.05, blood flow (measured with microspheres) during the 60min CAO, compared in the same samples with brief CAO before IPC. In summary, this novel model of 4th window IPC induces angiogenesis and markedly different gene regulation than previous IPC models.

Nlrp3 plays no role in acute cardiac infarction due to low cardiac expression

The Nlrp3 inflammasome is a protein complex consisting of NLRP3, ASC and caspase-1, that upon activation produces a potent pro-inflammatory cytokine, IL-1β. Evidence has accumulated that the Nlrp3 inflammasome contributes to delayed (>3 d) cardiac remodeling processes occurring following cardiac ischemia–reperfusion (I/R). However, from in vitro experiments it is controversial whether Nlrp3 also contributes to the more acute phase of infarct development [ 1 Zuurbier C.J. Jong W.M.C. Eerbeek O. Koeman A. Pulskens W.P. Butter L.M. et al. Deletion of the innate immune NLRP3 receptor abolishes cardiac ischemic preconditioning and is associated with decreased Il-6/STAT3 signaling. PLoS One. 2012; 7: e40643 Crossref PubMed Scopus (67) Google Scholar , 2 Sandanger O. Ranheim T. Vinge L.E. Bliksoen M. Alfsnes K. Finsen A.V. et al. The NLRP3 inflammasome is up-regulated in cardiac fibroblasts and mediates myocardial ischaemia–reperfusion injury. Cardiovasc Res. 2013; 99: 164-174 Crossref PubMed Scopus (319) Google Scholar , 3 Jong W.M.C. Zuurbier C.J. A role for NLRP3 inflammasome in acute myocardial ischemia–reperfusion injury?. Cardiovasc Res. 2013; 99: 226 Crossref PubMed Scopus (5) Google Scholar , 4 Takahashi M. Nlrp3 inflammasome as a novel player in myocardial infarction. Int Heart J. 2014; 55: 101-105 Crossref PubMed Scopus (159) Google Scholar ]. Information on the in vivo effects of Nlrp3 deletion is currently lacking [ [4] Takahashi M. Nlrp3 inflammasome as a novel player in myocardial infarction. Int Heart J. 2014; 55: 101-105 Crossref PubMed Scopus (159) Google Scholar ]. This information is necessary in the decision whether Nlrp3 therapeutic agents should be developed for the early reperfusion phase of cardiac I/R.

Potential role of cardiac chloride channels and transporters as novel therapeutic targets.

The heart and blood vessels express a range of anion currents (e.g. ICl.PKA) and symporter/antiporters (e.g. Cl(-)/HCO3(-) exchanger) that translocate chloride (Cl(-)). They have been proposed to contribute to a variety of physiological processes including cellular excitability, cell volume homeostasis and apoptosis. Additionally there is evidence that Cl(-) currents or transporters may play a role in cardiac pathophysiology. Arrhythmogenesis, the process of cardiac ischaemic preconditioning, and the adaptive remodelling process in myocardial hypertrophy and heart failure have all been linked to such channels or transporters. We have explored the possibility that selective targeting of one or more of these may provide benefit in cardiovascular disease. Existing evidence points to an emerging role of cardiac cell anion channels as potential therapeutic targets, the 'disease-specificity' of which may represent a substantial improvement on current targets. However, the limitations of current techniques hitherto applied (such as developmental compensation in gene-modified animals) and pharmacological agents (which do not at present possess sufficient selectivity for the adequate probing of function) have thus far hindered translation to the introduction of new therapy.

Cardiac remote ischaemic preconditioning reduces periprocedural myocardial infarction for patients undergoing percutaneous coronary interventions: a meta-analysis of randomised clinical trials.

To establish the cardioprotective effect of remote ischaemic preconditioning (RIPC) in patients undergoing percutaneous coronary intervention (PCI). Pubmed (MEDLINE), Cochrane and Embase were systematically searched for randomised controlled trials of RIPC in patients undergoing PCI. Periprocedural myocardial infarction (PMI) was the primary endpoint (defined as troponin elevation >3 times upper reference limit) and C-reactive protein (CRP) was a secondary endpoint. Five studies with 731 patients were included. The median age of the patients was 62 (59-68) years old, 25% were female (23-33), 29% (25-33) had diabetes mellitus, and 26.5% (19-31) presented with multivessel disease. RIPC significantly reduced the incidence of PMI (odds ratio: 0.58 [0.36, 0.93]; I2 43%), with a greater benefit when performed using the lower limb (0.21 [0.07-0.66]) compared to the upper limb (0.67 [0.46-0.99]). This reduction was enhanced for patients with multivessel disease (beta -0.05 [-0.09;-0.01], p=0.01) and with type C lesion (beta -0.014 [-0.04;-0.010], p=0.01) and did not vary according to age, female gender, diabetes mellitus, use of beta-blockers and of angiotensin converting enzyme inhibitors. Absolute risk difference was -0.10 [-0.19, -0.02], with a number needed to treat of 10 [6-50] patients to avoid one event. CRP -0.69 [-1.69, 0.31] was not significantly reduced by RIPC. RIPC reduced the incidence of PMI following PCI, especially when performed in the lower limb and for patients with multivessel disease and complex lesions.

Improved cardioprotection using a novel stepwise ischemic preconditioning protocol in rabbit heart

BackgroundThe current commonly used cardiac ischemic preconditioning (IPC) protocol, involving three 5-min cycles of ischemia–reperfusion (I/R), may not be clinically beneficial because of its acutely deleterious effects on hemodynamics. This study attempted to assess the effects of a novel stepwise IPC scheme on cardiac function, infarct size, and arrhythmogenesis in a rabbit model of prolonged I/R. MethodsAnesthetized open-chest rabbits were subjected to 60-min occlusion of a proximal branch of the left coronary artery followed by 180-min reperfusion. Animals were divided into five groups (n = 6 each): (1) control group (no IPC); (2) 2-min IPC group (three cycles of 2-min IPC); (3) 5-min IPC group (three cycles of 5-min IPC); (4) 10-min IPC group (three cycles of 10-min IPC); and (5) stepwise IPC group (2-, 5-, and 10-min I/R). ResultsCompared with control group, 2-, 5-, and 10-min IPC decreased arrhythmia score by 16%, 67%, and 33%, respectively. Remarkably, stepwise IPC resulted in a 78% reduction of arrhythmias. Stepwise IPC also produced the least ventricular infarct size when compared with 2-, 5-, and 10-min IPC groups (16.4% versus 39.3%, 28.1%, and 38.5%, P < 0.05). ConclusionsThese results suggest that stepwise IPC has better cardioprotective effects against prolonged I/R injury and may serve as an acceptable approach to clinical revascularization procedures on the heart, including catheter-based and surgical approaches.

NLRP3 inflammasome deletion reduces STAT3 signalling in the heart, without affecting acute ischemia-reperfusion necrosis or preconditioning in a closed thorax model of cardiac ischemia-reperfusion

Background: Acute myocardial infarction is associated with an intense inflammatory response that contributes to ischemic-reperfusion (IR) injury of the heart. Here we examine to what extent the NLRP3 inflammasome, an important component of the innate immune system and therefore inflammation, contributes to the acute (< 3 h reperfusion) inflammatory and IR response of the heart in vivo. In addition, as triggers for the activation of NLRP3 inflammasome and ischemic preconditioning (IPC) overlap and we previously reported decreased IL-6/STAT3 signalling in the isolated hearts of NLRP3-/- mice, we examined whether the NLRP3 inflammasome also affected STAT3 signalling, cytokine production and IPC in the in vivo condition. Methods: A closed thorax model was used to induce I (60 min or 30 min) and IPC (3 x 5 min I) through LAD occlusion, followed by 3 hour reperfusion. Electrocardiograms were used to detect ST-segment elevations. Phosphorylated STAT3, STAT3 expression and cytokines were determined in hearts of non-treated (blanco), IR and IPC+IR animals (n=6-8 per group). Results: We first examined whether NLRP3 affected acute infarct size (IS) development following 60 min LAD occlusion and 3 h reperfusion. No differences in IS were observed between WT (45±2%) and NLRP3-/- (42±6%). Next we examined in a milder model of ischemia (30 min), whether NLRP3 affected STAT3 signalling, cytokine generation and ischemic preconditioning. Both STAT3 expression and its activation through phosphorylation were decreased in NLRP3-/- hearts, for all three groups (blanco, IR, and IPC+IR). Although cardiac IL-1β and IL-6 were increased in IR and IPC+IR hearts as compared to non-IR hearts, NLRP3 deletion was without significant effect on cardiac cytokines. However, NLRP3 deletion decreased (p=0.06) plasma IL-6 in IPC+IR animals (45.8±7.8 vs 29.1±2.6 pg/ml for WT and NLRP3-/- animals, respectively). Despite the attenuated STAT3 signalling, NLRP3 deletion was without effect on ischemic preconditioning in the in vivo condition: IPC reduced IS in WT from 38±3% to 26±3%, and in NLRP3-/- from 39±3% to 27±4%. Conclusion: The NOD-like receptor NLRP3 does not acutely affect cardiac ischemia-reperfusion necrosis or ischemic preconditioning in a closed thorax model of ischemia-reperfusion, despite its effect on the signalling of the survival protein STAT3. These data are commensurate with reports in the literature that the inflammasome protein complex is mainly present in fibroblasts, which are only activated in later reperfusion.