Ischemic-reperfused Hearts Research Articles

Exercise training may reduce fragmented mitochondria in the ischemic-reperfused heart through DRP1.

Mitochondrial fission is a key trigger of cardiac ischemia-reperfusion injuries (IR). Exercise training is an efficient cardioprotective strategy, but its impact on mitochondrial fragmentation during IR remains unknown. Using isolated rat hearts, we found that exercise training limited the activation of dynamin-like protein 1 and limited mitochondrial fragmentation during IR. These results support the hypothesis that exercise training contributes to cardioprotection through its capacity to modulate the mitochondrial fragmentation during IR.

Cardiac-derived extracellular vesicles improve mitochondrial function to protect the heart against ischemia/reperfusion injury by delivering ATP5a1

BackgroundNumerous studies have confirmed the involvement of extracellular vesicles (EVs) in various physiological processes, including cellular death and tissue damage. Recently, we reported that EVs derived from ischemia-reperfusion heart exacerbate cardiac injury. However, the role of EVs from healthy heart tissue (heart-derived EVs, or cEVs) on myocardial ischemia-reperfusion (MI/R) injury remains unclear.ResultsHere, we demonstrated that intramyocardial administration of cEVs significantly enhanced cardiac function and reduced cardiac damage in murine MI/R injury models. cEVs treatment effectively inhibited ferroptosis and maintained mitochondrial homeostasis in cardiomyocytes subjected to ischemia-reperfusion injury. Further results revealed that cEVs can transfer ATP5a1 into cardiomyocytes, thereby suppressing mitochondrial ROS production, alleviating mitochondrial damage, and inhibiting cardiomyocyte ferroptosis. Knockdown of ATP5a1 abolished the protective effects of cEVs. Furthermore, we found that the majority of cEVs are derived from cardiomyocytes, and ATP5a1 in cEVs primarily originates from cardiomyocytes of the healthy murine heart. Moreover, we demonstrated that adipose-derived stem cells (ADSC)-derived EVs with ATP5a1 overexpression showed much better efficacy on the therapy of MI/R injury compared to control ADSC-derived EVs.ConclusionsThese findings emphasized the protective role of cEVs in cardiac injury and highlighted the therapeutic potential of targeting ATP5a1 as an important approach for managing myocardial damage induced by MI/R injury.

Exosomes from myoblasts induced by hypoxic preconditioning improved ventricular conduction by increasing Cx43 expression in hypothermia ischemia reperfusion hearts.

Exosomes from myoblasts induced by hypoxic preconditioning improved ventricular conduction by increasing Cx43 expression in hypothermia ischemia reperfusion hearts.

Degradation of the α-Carboxyl Terminus 11 Peptide: In Vivo and Ex Vivo Impacts of Time, Temperature, Inhibitors, and Gender in Rat.

In previous research, a synthetic α-carboxyl terminus 1 (αCT1) peptide derived from connexin 43 (Cx43) and its variant (αCT11) showed beneficial effects in an ex vivo ischemia-reperfusion (I/R) heart injury model in mouse. In an in vivo mouse model of cryo-induced ventricular injury, αCT1 released from adhesive cardiac patches reduced Cx43 remodeling and arrhythmias, as well as maintained cardiac conduction. Whether intravenous injection of αCT1 or αCT11 produces similar outcomes has not been investigated. Given the possibility of peptide degradation in plasma, this study utilized in vivo I/R cardiac injury and ex vivo blood plasma models to examine factors that may limit the therapeutic potential of peptide therapeutics in vivo. Following tail vein administration of αCT11 (100 μM) in blood, no effect on I/R infarct size was observed in adult rat hearts on day 1 (D1) and day 28 (D28) after injury (p > 0.05). There was also no difference in the echocardiographic ejection fraction (EF%) between the control and the αCT11 groups (p > 0.05). Surprisingly, αCT11 in blood plasma collected from these rats was undetectable within ∼10 min after tail vein injection. To investigate factors that may modulate αCT11 degradation in blood, αCT11 was directly added to blood plasma isolated from normal rats without I/R and peptide levels were measured under different experimental conditions. Consistent with in vivo observations, significant αCT11 degradation occurred in plasma within 10 min at 22 and 37 °C and was nearly undetectable by 30 min. These responses were reduced by the addition of protease/phosphatase (PTase/PPTase) inhibitors to the isolated plasma. Interestingly, no significant differences in αCT11 degradation in plasma were noted between male and female rats. We conclude that fast degradation of αCT11 is likely the reason that no beneficial effects were observed in the in vivo I/R model and inhibition or shielding from PTase/PPTase activity may be a strategy that will assist with the viability of peptide therapeutics.

Potential protective effects of L-carnitine against myocardial ischemia/reperfusion injury in a rat model.

Myocardial ischemia/reperfusion (I/R) injury is a growing concern for global public health. This study seeks to explore the potential protective effects of L-carnitine (LC) against heart ischemia-reperfusion injury in rats. To induce I/R injury, the rat hearts underwent a 30-min ligation of the left anterior descending coronary artery, followed by 24h of reperfusion. We evaluated cardiac function through electrocardiography and heart rate variability (HRV) and conducted pathological examinations of myocardial structure. Additionally, the study investigated the influence of LC on myocardial apoptosis, inflammation, and oxidative stress in the context of I/R injury. The results show that pretreatment with LC led to improvements in the observed alterations in ECG waveforms and HRV parameters in the nontreated ischemic reperfusion model group, althoughmost of these changes did not reach statistical significance. Similarly, although without a significant difference, LC reduced the levels of proinflammatory cytokines when compared to the values in the nontreated ischemic rat group. Furthermore, LC restored the reduced expressions of SOD1, SOD2, and SOD3. Additionally, LC significantly reduced the elevated Bax expressions and showed a nonsignificant increase in Bcl-2 expression, resulting in a favorable adjustment of the Bcl-2/Bax ratio. We also observed a significant enhancement in the histological appearance of cardiac muscles, a substantial reduction in myocardial fibrosis, and suppressed CD3 + cell proliferation in the ischemic myocardium. This small-scale, experimental, in vivo study indicates that LC was associated with enhancements in the pathological findings in the ischemic myocardium in the context of ischemia/reperfusion injury in this rat model. Although statistical significance was not achieved, LC exhibits potential and beneficial protective effects against I/R injury. It does so by modulating the expression of antioxidative and antiapoptotic genes, inhibiting the inflammatory response, and enhancing autonomic balance, particularly by increasing vagal tone in the heart. Further studies are necessary to confirm and elaborate on these findings.

Data-Independent Acquisition Proteomics and N-Terminomics Methods Reveal Alterations in Mitochondrial Function and Metabolism in Ischemic-Reperfused Hearts.

Myocardial ischemia-reperfusion (IR) (stunning) injury triggers changes in the proteome and degradome of the heart. Here, we utilize quantitative proteomics and comprehensive degradomics to investigate the molecular mechanisms of IR injury in isolated rat hearts. The control group underwent aerobic perfusion, while the IR injury group underwent 20 min of ischemia and 30 min of reperfusion to induce a stunning injury. As MMP-2 activation has been shown to contribute to myocardial injury, hearts also underwent IR injury with ARP-100, an MMP-2-preferring inhibitor, to dissect the contribution of MMP-2 to IR injury. Using data-independent acquisition (DIA) and mass spectroscopy, we quantified 4468 proteins in ventricular extracts, whereby 447 proteins showed significant alterations among the three groups. We then used subtiligase-mediated N-terminomic labeling to identify more than a hundred specific cleavage sites. Among these protease substrates, 15 were identified following IR injury. We identified alterations in numerous proteins involved in mitochondrial function and metabolism following IR injury. Our findings provide valuable insights into the biochemical mechanisms of myocardial IR injury, suggesting alterations in reactive oxygen/nitrogen species handling and generation, fatty acid metabolism, mitochondrial function and metabolism, and cardiomyocyte contraction.

Conditional knock out of cytosolic thioredoxin (Trx) in cardiomyocytes impairs cardiac function and exacerbates ischemia-reperfusion injury

Abstract Introduction Coronary heart disease with myocardial infarction (MI) is a leading cause of mortality in the world despite timely reperfusion of occluded coronary artery. Myocardial damage due to restoration of blood flow, known as reperfusion injury account for about 50% of final MI size. The role of Trx in protection against myocardial ischemia reperfusion has been reported; however, these studies were mostly performed using ex vivo isolated mouse/rat heart with retrograde perfusion or with injected rhTrx. However, the role of loss of Trx specifically in the myocytes using a conditional deletion has never been reported. Here, we determined whether loss of Trx in myocytes would promote ischemia-reperfusion injury, even if the endocardial endothelial cells express normal levels of Trx. Purpose We investigated the effect of specific deletion of Trx in cardiomyocytes on base-line cardiac function and cardiac function in ischemia-reperfusion of heart using conditional knockout of Trx (aMHC-Trx-KO) in the cardiomyocytes with normal levels of Trx in the endothelial cells to determine specifc contribution of Trx in cardiac function in I/R. Methods A Trx floxed mouse line was created with introduction of loxP sites flanking the mouse Trx gene. Further, the conditional deletion of Trx in cardiomyocytes was produced by breeding homozygous Trx-floxed (Trxfl/fl) mice with aMHC-Cre mice strain. The resulting aMHC-Trx-KO mice was identified by genotyping and conditional deletion of Trx in myocytes was achieved by injecting Tomoxifen (75mg/Kg in oil). The aMHC-Trx-KO mice were subjected to 30 minutes of ischemia by ligation of left descending coronary artery(LAD) and reperfusion was performed by release of slipknot and allowing blood flow of 60 minutes before sacrificing animals. The animal protocol was approved by the IACUC of the Texas Tech University Health Sciences Center, Lubbock. Echocardiography on animals was performed using Vevo 3100 (Visual Sonic). Statistical analysis was performed by Prism 8.0 (GraphPad). Results Deletion of Trx caused significant cardiac dysfunction in aMHC-Trx-KO mice compared to Trxfl/fl mice without treatment with tomoxifen. The ejection fraction (EF%, 52.82 vs. 73.83) and fractional shortening (FS%, 41.42 vs.25.89) were significantly reduced. Further, these mice subjected to I/R showed exacerbated cardiac dysfunction with significant decrease in heart rate and did not survive the reperfusion. We also found significant mitochondrial structural abnormalities and mitochondrial dysfunction in aMHC-Trx-KO mice compared to non-transgenic or Trxfl/fl mice without tomoxifen treatment. Conclusion Deletion of Trx in cardiomyocyte causes significant myocardial dysfunction. Further, Trx is required to protect against myocardial dysfunction in ischemia-reperfusion injury. Our data also suggest that cardiac mitochondria is specifically impacted by loss of Trx deletion.Figure-1

Apelin receptor inhibition in ischemia-reperfused mouse hearts protected by endogenous n-3 polyunsaturated fatty acids.

Background: While the protective effects of n-3 polyunsaturated fatty acids (PUFAs) on cardiac ischemia-reperfusion (IR) injury have been previously reported, limited data are available regarding how these fatty acids affect membrane receptors and their downstream signaling following IR injury. We aimed to identify potential receptors activated by n-3 PUFAs in IR hearts to understand the regulatory mechanisms of these receptors. Methods: We used fat-1 mice, which naturally have elevated levels of n-3 PUFAs, and C57BL/6J mice as a control group to create a myocardial IR injury model through Langendorff perfusion. We assessed the impact of endogenous n-3 PUFAs on left ventricular function, myocardial infarct size, myocardial apoptosis, and ATP production. RNA sequencing (RNA-seq) and bioinformatics analysis were conducted to identify molecular targets affected by n-3 PUFAs. Based on these analyses we then treated IR hearts of WT and fat-1 mice with an antagonist (ML221) or an agonist (apelin-13) for the predicted receptor to assess cardiac contractile function and intracellular signaling pathways. An in vitro hypoxia-reoxygenation (HR) model was also used to confirm the effects of n-3 PUFAs on the examined intracellular signaling pathways. Results: Endogenous n-3 PUFAs protected cardiac structure and function in post-IR hearts, and modulated phosphorylation patterns in the PI3K-AKT-mTOR signaling pathways. RNA-seq analysis revealed that n-3 PUFAs affected multiple biological processes as well as levels of the apelin receptor (APLNR). Consistent with a role for the PLNNR, ML221 synchronized the activation of the PI3K-AKT-mTOR signaling axis, suppressed the expression of PKCδ and phosphorylated p38α, upregulated PKCε expression, upregulated or restored the phosphorylation of myofilaments, and prevented myocardial injury and contractile dysfunction in WT IR hearts. By contrast, apelin-13 disrupted the PI3K-AKT-mTOR signaling axis in post-IR fat-1 hearts. The phosphorylation signaling targeted by APLNR inhibition in post-IR fat-1 hearts was also observed after treating HR cells with eicosatetraenoic acid (EPA). Conclusion: Endogenous n-3 PUFAs protect against post-IR injury and preserve cardiac contractile function possibly through APLNR inhibition. This inhibition synchronizes the PI3K-AKT-mTOR axis, suppresses detrimental phosphorylation signaling, and restores or increases myofilament phosphorylation in post-IR hearts. The beneficial effects observed in fat-1 transgenic mouse hearts can be attributed, at least in part, to elevated EPA levels. This study is the first to demonstrate that n-3 PUFAs protect hearts against IR injury through APLNR inhibition.

Erythropoietin-mediated cardioprotection in hearts subjected to ischemia reperfusion.

Several studies provide evidence that erythropoietin (EPO) could play an important role in the recovery of the heart subjected to ischemia-reperfusion. In this regard, it has been suggested that EPO could be involved in protein kinase B (Akt) activation as a cell survival protein. The aim of the present study was to investigate the effects of EPO on the Akt/glycogen synthase kinase 3 beta (GSK-3β) pathway in the presence or absence of wortmannin (W, Akt inhibitor) and its relationship with mitochondrial morphology and function preservation in ischemic-reperfused rat hearts. EPO improved the functional recovery of the heart subjected to ischemia-reperfusion, reduced the release of CK and the infarct size, and promoted preservation of the mitochondrial structure. Moreover, it reduced tissue lactate content and preserved glycogen in order to prevent ischemia. The results showed greater Akt activation, accompanied by preservation of swelling and mitochondrial calcium retention capacity, as well as an increase in ATP synthesis capacity. These results were accompanied by an inhibition of GSK-3β, suggesting regulation of Akt on the opening of the mitochondrial permeability transition pore. All these beneficial effects exerted by acute treatment with EPO were prevented by W. The present study provided novel evidence that EPO not only enhances intrinsic activation of Akt during myocardial ischemia-reperfusion but also promotes GSK-3β inhibition, contributing to mitochondrial structure and function preservation.

Oxidization of optic atrophy 1 cysteines occurs during heart ischemia-reperfusion and amplifies cell death by oxidative stress

During cardiac ischemia-reperfusion, excess reactive oxygen species can damage mitochondrial, cellular and organ function. Here we show that cysteine oxidation of the mitochondrial protein Opa1 contributes to mitochondrial damage and cell death caused by oxidative stress. Oxy-proteomics of ischemic-reperfused hearts reveal oxidation of the C-terminal C786 of Opa1 and treatment of perfused mouse hearts, adult cardiomyocytes, and fibroblasts with H2O2 leads to the formation of a reduction-sensitive ∼180 KDa Opa1 complex, distinct from the ∼270 KDa one antagonizing cristae remodeling. This Opa1 oxidation process is curtailed by mutation of C786 and of the other 3 Cys residues of its C-terminal domain (Opa1TetraCys). When reintroduced in Opa1−/− cells, Opa1TetraCys is not efficiently processed into short Opa1TetraCys and hence fails to fuse mitochondria. Unexpectedly, Opa1TetraCys restores mitochondrial ultrastructure in Opa1−/− cells and protects them from H2O2-induced mitochondrial depolarization, cristae remodeling, cytochrome c release and cell death. Thus, preventing the Opa1 oxidation occurring during cardiac ischemia-reperfusion reduces mitochondrial damage and cell death induced by oxidative stress independent of mitochondrial fusion.

Abstract 103: Regulation Of Cardiac PTEN/Akt Signaling By Moderate Intra-Ischemic Therapeutic Hypothermia

Introduction: Previous studies demonstrate a critical role for Akt in mediating cardioprotection by therapeutic hypothermia. However, the mechanism of hypothermia-induced Akt activation remains poorly understood. Akt activation is determined in part by PTEN activity and degradation. Hypothesis: We hypothesized that moderate intra-ischemic cooling activates Akt in the ischemic-reperfused heart due to enhanced PTEN degradation. Methods: Rat hearts were isolated and perfused media containing 5 mM glucose. LV function was monitored continuously by an intraventricular balloon. Rate-pressure product (RPP=heart rate x LV developed pressure) was monitored as an index of cardiac function. Hearts in the normothermic control group (I/R) were subjected to 20 min. of global, no-flow ischemia followed by reperfusion at 37 °C. In the hypothermia intervention group (I/R+TH), hearts were cooled to 30 °C at the start of ischemia and then rewarmed 10 min. after reperfusion. Coronary perfusate was collected from the pulmonary artery at preischemic baseline and 10 min. after reperfusion. Ventricular tissue was harvested at 0 or 30 min. after reperfusion for western blotting. Results: RPP was significantly higher in the I/R+TH group (n=7) compared to the I/R group (n=8) at 30 min. post-reperfusion (24,725 ± 1,112 mmHg*beats/min. vs. 18,237 ± 2,223 mmHg*beats/min., p<0.05). Coronary perfusate taurine concentration was significantly higher in the I/R group compared to the I/R+TH group at 10 min. post-reperfusion (19 ± 4 μM vs. 5 ± 1 μM, p<0.01). Akt serine473 phosphorylation was significantly higher in the I/R+TH group compared to the I/R group at 0 min. post-reperfusion (p<0.01), but significantly lower at 30 min. post-reperfusion (p<0.01). Additionally, TH enhanced total PTEN expression at 0 min. (p<0.05) and 30 min. (p<0.01) post-reperfusion without affecting the ratio of phospho-PTEN/PTEN. Conclusion: Intra-ischemic cooling was associated with temporal changes in Akt phosphorylation despite enhanced PTEN expression. Additionally, modulation of cardiac taurine release by hypothermia should be carefully considered in future studies assessing taurine as a biomarker for cardiac arrest and ischemic heart pathologies.

Timed use of digoxin prevents heart ischemia-reperfusion injury through a REV-ERBα-UPS signaling pathway.

Myocardial ischemia-reperfusion injury (MIRI) induces life-threatening damages to the cardiac tissue and pharmacological means to achieve cardioprotection are sorely needed. MIRI severity varies along the day-night cycle and is molecularly linked to components of the cellular clock including the nuclear receptor REV-ERBα, a transcriptional repressor. Here we show that digoxin administration in mice is cardioprotective when timed to trigger REV-ERBα protein degradation. In cardiomyocytes, digoxin increases REV-ERBα ubiquitinylation and proteasomal degradation, which depend on REV-ERBα ability to bind its natural ligand, heme. Inhibition of the membrane-bound Src tyrosine-kinase partially alleviated digoxin-induced REV-ERBα degradation. In untreated cardiomyocytes, REV-ERBα proteolysis is controlled by known (HUWE1, FBXW7, SIAH2) or novel (CBL, UBE4B) E3 ubiquitin ligases and the proteasome subunit PSMB5. Only SIAH2 and PSMB5 contributed to digoxin-induced degradation of REV-ERBα. Thus, controlling REV-ERBα proteostasis through the ubiquitin-proteasome system is an appealing cardioprotective strategy. Our data support the timed use of clinically-approved cardiotonic steroids in prophylactic cardioprotection.

Discovery of 5-(3,4-dihydroxybenzylidene)-1,3-dimethylpyrimidine- 2,4,6(1H,3H,5H)-trione as a novel and effective cardioprotective agent via dual anti-inflammatory and anti-oxidative activities

Myocardial ischemia/reperfusion (MI/R) injury is still the huge unmet medical need without effective therapy in clinic. It is critical to develop pharmacological intervention to scavenge ROS and inhibit NLRP3 activation to have a double benefit against MI/R injury. Cinnamamide derivatives have been demonstrated to possess anti-oxidative and anti-inflammatory activities. Previously, we have reported that a cinnamamide derivative 2 exerts excellent cardioprotective effect via mediation of intracellular oxidative stress via Nrf2 up-regulation against MI/R. In the present study, seventeen compounds have been optimized using cinnamamide-barbiturate hybrid 2 as the lead compound and their cardioprotective activities against MI/R were further determined in vitro and in vivo. Among them, compound 7 showed the most potent cardioprotective effect and low cytotoxicity. While cardiomyocytes were invased by hydrogen peroxide, compound 7 exhibited more excellent cardioprotective effect than that of luteolin and metoprolol, the positive control employed in the present study, as demonstrated by dramatically elevated cell survival rate and decreased LDH leakage rate. Moreover, compound 7 markedly inhibited cardiac expressions of inflammasome activation and pro-inflammatory cytokines release (i.e. NLRP3, IL-1β, IL-18), simultaneouly increasing endogenous antioxidative proteins (i.e. Nrf2, HO-1 and SOD) in vitro. In the rat MI/R model, compound 7 pretreatment profoundly reduced cardiac infarct size in MI/R rats and reversed abnormal changes in myocardial enzymes and lipid peroxidation levels in heart tissues. Mechanistically, compound 7 revealed significant cardioprotective effects by inhibiting NLRP3 and its downstream inflammatory chemokine IL-1β, as well as up-regulating Nrf2 in vivo. Furthermore, at the active site of the co-crystal of NLRP3 and Nrf2, compound 7 exhibited higher binding force in the molecular docking study, which was consistent with the in vitro results. Therefore, compound 7 is expected to be a potential cardioprotective agent possessing dual anti-inflammatory and anti-oxidative activities. Our work provides an important therapeutic strategy for the treatment of ischemic-reperfused heart disease.

415.4: Ischemia Minimization Improves Cardiac Function in an Ex Vivo Xeno Working Heart Model

Introduction: Previous studies showed that ischemia minimization (IM), accomplished by perfusing the heart xenograft during storage, prevents ‘initial cardiac xenograft dysfunction’ (ICXD) and enables prolonged survival following orthotopic cardiac xenotransplantation. Here we report initial observations in a model designed to evaluate effects on heart performance associated with IM and genetic modifications targeted to address xeno-injury mechanisms in a working ex vivo model of ICXD. Method: Hearts from genetically modified and wildtype (WT) pigs were procured after flushing with cold preservation solution (UW, 4oC) and stored for 3 hours either in cold saline (0.9%, 4oC: cold storage (CS)) or were perfused with oxygenated STEEN Solution with RBCs (IM). IM perfusion at 40 mmHg was initiated at room temperature for 20 minutes to facilitate homogeneous graft perfusion before cooling to 4oC for the remainder of the storage period. The genetically modified hearts either had combined knockouts of three specific xenogeneic carbohydrate genes (GTKO, CMAHKO, b4GALNT2KO: TKO) with variable expression of human transgenes (hTG) including complement and thrombo-regulatory proteins (n=29); or GTKO with additional expression of hCD55 (GTKO.hCD55; n=3). Heart function and laboratory parameters were assessed at specific timepoints on a working heart rig while perfused with freshly collected heparinized whole human blood. Troponin I was used as a marker for myocardial injury. Results: In total, 41 hearts were perfused ex vivo, 23 after CS (TKO + hTG n=14, GTKO.hCD55 n=2, WT n=7), and 18 after IM (TKO + hTG n=15, GTKO.hCD55 n=1, WT n=2). Cardiac output (mL/min) was significantly improved for the IM group at all loading conditions relative to CS, (see figure 1). There was a strong trend toward reduced troponin I release, particularly within the first 60 minutes of perfusion (see figure 2). Conclusion: IM is protective with respect to cardiac function following pig heart ischemia and subsequent reperfusion with human blood in an ex vivo model of heart xenotransplantation. The hypothesis that variation in physiologic and biochemical outcomes within groups is influenced by variable expression of complement and coagulation pathway regulatory genes is being investigated.

ISCHEMIC REPERFUSION INJURY IN HYPERTENSIVE RAT HEART

Objective: In patients with cardiovascular disease, myocardial ischaemia reperfusion damage is the leading cause of death. Sustained myocardial ischaemia–reperfusion causes cardiomyocyte death and coronary microvascular injury in different ways. Patients with hypertension who undergo cardiac ischemia-reperfusion have more severe clinical outcomes. Design and method: The mechanism, on the other hand, is missing. We use an angiotensin II successfully produced hypertension rat model to investigate the effect of hypertension on cardiac ischemia-reperfusion injury. We successfully established in vitro myocardial ischemia-reperfusion in normal and hypertensive rat hearts using the Langendorff perfusion system. Results: Our results reveal that after 30 minutes of ischemia and an hour of reperfusion, the beating pattern of the hypertensive heart was poorer than that of the sham heart. We also used a Transmission Electron Microscope to examine the morphology of myocardial cells and mitochondria, and discovered that the mitondria structure was dramatically destroyed in the hypertension model compared to the sham model, and that some myocytes in the hypertension model have abnormal morphology after 30 minutes of ischemia and an hour of reperfusion. To assess mitochondrial function, mitochondria were extracted from an ischemia-reperfused heart and Mitochondrial Function Indexes were calculated. When oligomycin was used to block ATP synthase, the formation of reactive oxygen species (ROS) and mitochondrial membrane potential MMP increased considerably in the hypertension group. Furthermore, when FCCP was utilized as a proton collapser and antimycin A was used to block mitochondrial complex III, the generation of reactive oxygen species (ROS) mitochondrial membrane potential MMP in the hypertension group rose significantly at add additional oil substrate. When the hypertension group is given the substrate succinate or oligomycin to block ATP synthase, oxygen consumption increases significantly. Conclusions: Taken together, our research reveals that hypertension can significantly increase the damage caused by myocardial ischemia reperfusion. As a result, hypertension during myocardial ischemia should be given special attention.

Berberine alleviates myocardial ischemia–reperfusion injury by inhibiting inflammatory response and oxidative stress: the key function of miR-26b-5p-mediated PTGS2/MAPK signal transduction

Context Berberine has myocardial protective effects. Objectives The protective effects of berberine on heart ischemia–reperfusion (I/R) injury were explored. Materials and methods Human cardiomyocytes were divided into control group, oxygen-glucose deprivation/re-oxygen (OGD/R) (2 h OGD with 24 h reoxygenation) group, OGD/R + low group (5 μM berberine for 24 h) and OGD/R + high group (10 μM berberine for 24 h). Twenty-four Wistar rats were divided into sham group, I/R group (45 min occlusion with 2 h reperfusion), I/R + berberine group (50 mg/kg berberine 1 h before I/R surgery) and I/R + berberine + antagomir (intraperitoneally injected with miR-26b-5p antagomir). MicroRNA profile, effects of berberine on I/R or OGD/R-induced injuries, and the role of miR-26b-5p in the function of berberine were explored. Results OGD/R treatment suppressed viability (0.41 ± 0.05 vs. 0.87 ± 0.13, p< 0.05), while induced apoptosis (6.6 ± 1.0% vs. 26.3 ± 4.8%, p< 0.05) in cardiomyocytes, which was restored by berberine (viability: 0.64 ± 0.01 for 5 μM and 0.72 ± 0.01 for 10 μM, p< 0.05; apoptosis: 10.9 ± 2.2 for 5 μM and 7.9 ± 1.3 for 10 μM). Berberine induced miR-26b-5p and inhibited PTGS2/MAPK pathway. MiR-26b-5p inhibition counteracted the protective function of berberine. In rats, berberine (50 mg/kg) improved heart histological structure and suppressed inflammatory response, which was impaired by miR-26b-5p inhibition. Discussion and conclusions Berberine exerted anti-I/R function in heart by inducing miR-26b-5p and suppressing the PTGS2/MAPK pathway. These data promote the application of berberine as an anti-I/R agent.

Modified Technique for the Use of Neonatal Murine Hearts in the Langendorff Preparation

The use of the ex-vivo retrograde perfused heart has long been a cornerstone of ischemia-reperfusion investigation since its development by Oskar Langendorff over a century ago. Although this technique has been applied to mice over the last 25 years, its use in this species has been limited to adult animals. Development of a successful method to consistently cannulate the neonatal murine aorta would allow for the systematic study of the isolated retrograde perfused heart during a critical period of cardiac development in a genetically modifiable and low-cost species. Modification of the Langendorff preparation enables cannulation and establishment of reperfusion in the neonatal murine heart while minimizing ischemic time. Optimization requires a two-person technique to permit successful cannulation of the newborn mouse aorta using a dissecting microscope and a modified commercially available needle. The use of this approach will reliably establish retrograde perfusion within 3 min. Because the fragility of the neonatal mouse heart and ventricular cavity size prevents direct measurement of intraventricular pressure generated using a balloon, use of a force transducer connected by a suture to the apex of the left ventricle to quantify longitudinal contractile tension is necessary. This method allows investigators to successfully establish an isolated constant-flow retrograde-perfused newborn murine heart preparation, permitting the study of developmental cardiac biology in an ex-vivo manner. Importantly, this model will be a powerful tool to investigate the physiological and pharmacological responses to ischemia-reperfusion in the neonatal heart.

CREG mitigates neonatal HIE injury through survival promotion and apoptosis inhibition in hippocampal neurons via activating AKT signaling.

Neonatal hypoxic ischemic encephalopathy (Neonatal HIE) is a common but serious disease caused by perinatal asphyxia injury in newborns. Elevated neuronal apoptosis plays an important role in the injury process post hypoxia ischemia of the brain, which accurate mechanism is still worthy to be studied. Cellular repressor of E1A-stimulated genes (CREG) possesses the protective effect in ischemia-reperfusion in multiple organs, including livers and hearts. The main purpose of this work was to investigate whether CREG was involved in alleviating neonatal HIE and explore the possible mechanisms. We found that CREG expression was downregulated in the hippocampus of neonatal HIE rats as well as oxygen-glucose deprivation/reperfusion (OGD/R)-treated hippocampal neurons. Besides, CREG overexpression promoted survival while inhibited apoptosis in OGD/R-induced hippocampal neurons accompanied by AKT signaling activation, which could be reversed by CREG silence. In addition, the protective effects of CREG overexpression could be antagonized by AKT deactivation, indicating the function of CREG was attributed by regulating AKT pathway. Collectedly, we demonstrated that CREG protected hippocampal neurons from hypoxic ischemia-induced injury through regulating survival and apoptosis via activating AKT signaling pathway.

The Effect of Resveratrol on Sphingosine-1 and Oxidative/ Nitrosative Stress in an Experimental Heart Ischemia Reperfusion Model

Abstract Objectives: Resveratrol (RSV) is a natural polyphenolic compound showing significant antioxidant effects. In this study, we aimed to investigate the effects of resveratrol on the sphingosine-1-phosphate (S1P) and oxidative stress biomarkers in hearth ischemia-reperfusion (I/R). Materials and Methods: The biochemical and histopathological effects of RSV on cardiac ischemia-reperfusion injury were investigated through ELISA- and light microscope. Results: We observed statistically significant differences between the treatment group and the control group in terms of malondialdehyde (MDA) level, catalase (CAT) and superoxide dismutase (SOD) activities (p&lt;0.05). Histopathologically, we also observed decreased Polymorphonuclear Leucocyte (PMNL) infiltration, myocardial edema, miyositolysis in the treatment group compared to the I/R and sham groups. Conclusion: Resveratrol may play an important role in cardiac I/R injury through its anti-inflammatory and antioxidant effects which were biochemically and histopathologically confirmed in the present study.

Matrix Metalloproteinase-2 Inhibition in Acute Ischemia-Reperfusion Heart Injury-Cardioprotective Properties of Carvedilol.

Matrix metalloproteinase 2 (MMP-2) is activated in hearts upon ischemia-reperfusion (IR) injury and cleaves sarcomeric proteins. It was shown that carvedilol and nebivolol reduced the activity of different MMPs. Hence, we hypothesized that they could reduce MMPs activation in myocytes, and therefore, protect against cardiac contractile dysfunction related with IR injury. Isolated rat hearts were subjected to either control aerobic perfusion or IR injury: 25 min of aerobic perfusion, followed by 20 min global, no-flow ischemia, and reperfusion for 30 min. The effects of carvedilol, nebivolol, or metoprolol were evaluated in hearts subjected to IR injury. Cardiac mechanical function and MMP-2 activity in the heart homogenates and coronary effluent were assessed along with troponin I content in the former. Only carvedilol improved the recovery of mechanical function at the end of reperfusion compared to IR injury hearts. IR injury induced the activation and release of MMP-2 into the coronary effluent during reperfusion. MMP-2 activity in the coronary effluent increased in the IR injury group and this was prevented by carvedilol. Troponin I levels decreased by 73% in IR hearts and this was abolished by carvedilol. Conclusions: These data suggest that the cardioprotective effect of carvedilol in myocardial IR injury may be mediated by inhibiting MMP-2 activation.