Sevoflurane postconditioning reduces myocardial reperfusion injury in rat isolated hearts via activation of PI3K/Akt signaling and modulation of Bcl-2 family proteins

Effects of Sevoflurane on Apoptosis of Myocardial Cells in IRI Rats

Background

Cardiomyocyte apoptosis functions essentially in ischemia/reperfusion- (I/R-) induced myocardial injury. It is suggested that autophagy is widely implicated in the regulation of cell survival and death. Sevoflurane, as a largely used inhalational general anesthetic, has been shown to have a protective effect on cardiomyocytes. However, it was yet elusive on the underlying mechanisms.

Aim

The objective of this study is to investigate the association of sevoflurane-mediated cardioprotective effects with autophagy regulation.

Methods

An in vitro hypoxia model was established in primary cardiomyocytes from fresh myocardial tissue of the rats. The apoptosis rate of myocardial cells treated with hypoxia and treated with sevoflurane was measured. Western blot and immunocytochemical assay were used to measure the protein expression. The cell proliferation rate and cell apoptosis were measured using the MTT assay and flow cytometry, respectively.

Results

The expression of apoptotic proteins including B cell lymphoma-2 (Bcl-2), CCAAT/enhancer-binding protein homologous protein (CHOP), glucose-regulated protein 78 (GRP78), and Bcl-2-associated X protein (BAX) in myocardium treated with sevoflurane was significantly lower than that in myocardium treated with hypoxia. The expression of adhesion proteins such as intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin in myocardium treated with sevoflurane was higher than that in myocardium treated with hypoxia, suggesting better connectivity of the myocardium.

Conclusion

Sevoflurane treatment reduced the apoptosis of myocardial cells after hypoxia treatment.

Mitochondrial Quality Control in Cardiac-Conditioning Strategies against Ischemia-Reperfusion Injury

Mitochondria are the central target of ischemic preconditioning and postconditioning cardioprotective strategies, which consist of either the application of brief intermittent ischemia/reperfusion (I/R) cycles or the administration of pharmacological agents. Such strategies reduce cardiac I/R injury by activating protective signaling pathways that prevent the exacerbated production of reactive oxygen/nitrogen species, inhibit opening of mitochondrial permeability transition pore and reduce apoptosis, maintaining normal mitochondrial function. Cardioprotection also involves the activation of mitochondrial quality control (MQC) processes, which replace defective mitochondria or eliminate mitochondrial debris, preserving the structure and function of the network of these organelles, and consequently ensuring homeostasis and survival of cardiomyocytes. Such processes include mitochondrial biogenesis, fission, fusion, mitophagy and mitochondrial-controlled cell death. This review updates recent advances in MQC mechanisms that are activated in the protection conferred by different cardiac conditioning interventions. Furthermore, the role of extracellular vesicles in mitochondrial protection and turnover of these organelles will be discussed. It is concluded that modulation of MQC mechanisms and recognition of mitochondrial targets could provide a potential and selective therapeutic approach for I/R-induced mitochondrial dysfunction.

Cardioprotection by post-conditioning with exogenous triiodothyronine in isolated perfused rat hearts and isolated adult rat cardiomyocytes

Ischemic post-conditioning (iPoCo) by coronary re-occlusion/reperfusion during immediate reperfusion after prolonged myocardial ischemia reduces infarct size. Mechanical manipulation of culprit lesions, however, carries the risk of coronary microembolization which may obscure iPoCo's cardioprotection. Pharmacological post-conditioning with exogenous triiodothyronine (T3) could serve as an alternative conditioning strategy. Similar to iPoCo, T3 may activate cardioprotective prosurvival pathways. We aimed to study T3's impact on infarct size and its underlying signal transduction. Hearts were isolated from male Lewis rats (200-380 g), buffer-perfused and subjected to 30 min/120 min global zero-flow ischemia/reperfusion (I/R). In additional hearts, either iPoCo (2 × 30 s/30 s I/R) was performed or T3 (100-500 µg/L) infused at reperfusion. Infarct size was demarcated with triphenyl tetrazolium chloride staining and calculated as percent of ventricular mass. Infarct size was reduced with iPoCo to 16 ± 7% vs. 36 ± 4% with I/R only. The maximum infarct size reduction was observed with 300 µg/L T3 (14 ± 2%). T3 increased the phosphorylation of protein kinase B and mitogen extracellular-regulated-kinase 1/2, both key enzymes of the reperfusion injury salvage kinase (RISK) pathway. Pharmacological RISK blockade (RISK-BL) during reperfusion abrogated T3's cardioprotection (35 ± 10%). Adult ventricular cardiomyocytes were isolated from buffer-perfused rat hearts and exposed to 30 min/5 min hypoxia/reoxygenation (H/R); reoxygenation was initiated without or with T3, respectively, and without or with RISK-BL, respectively. Maximal preservation of viability was observed with 500 µg/L T3 after H/R (27 ± 4% of all cells vs. 5 ± 3% in time-matched controls). Again, RISK-BL abrogated protection (11 ± 3%). Mitochondria were isolated at early reperfusion from buffer-perfused rat hearts without or with iPoCo or 300 µg/L T3, respectively, at reperfusion. T3 improved mitochondrial function (i.e.: increased respiration, adenosine triphosphate production, calcium retention capacity, and decreased reactive oxygen species formation) to a similar extent as iPoCo. T3 at reperfusion reduces infarct size by activation of the RISK pathway. T3's protection is a cardiomyocyte phenomenon and targets mitochondria.

Molecular Aspects of Volatile Anesthetic-Induced Organ Protection and Its Potential in Kidney Transplantation

Ischemia reperfusion injury (IRI) is inevitable in kidney transplantation and negatively impacts graft and patient outcome. Reperfusion takes place in the recipient and most of the injury following ischemia and reperfusion occurs during this reperfusion phase; therefore, the intra-operative period seems an attractive window of opportunity to modulate IRI and improve short- and potentially long-term graft outcome. Commonly used volatile anesthetics such as sevoflurane and isoflurane have been shown to interfere with many of the pathophysiological processes involved in the injurious cascade of IRI. Therefore, volatile anesthetic (VA) agents might be the preferred anesthetics used during the transplantation procedure. This review highlights the molecular and cellular protective points of engagement of VA shown in in vitro studies and in vivo animal experiments, and the potential translation of these results to the clinical setting of kidney transplantation.

Hydrogen sulfide restores sevoflurane postconditioning mediated cardioprotection in diabetic rats: Role of SIRT1/Nrf2 signaling-modulated mitochondrial dysfunction and oxidative stress

Diabetic hearts are vulnerable to myocardial ischemia/reperfusion injury (IRI), but are insensitive to sevoflurane postconditioning (SPC), activating peroxiredoxins that confer cardioprotection. Previous studies have demonstrated that hydrogen sulfide (H₂ S) can suppress oxidative stress of diabetic rats through increasing the expression of silent information regulator factor 2-related enzyme 1 (SIRT1), but whether cardioprotection by SPC can be restored afterward remains unclear. Diabetic rat was subjected to IRI (30 min of ischemia followed by 120 min reperfusion). Postconditioning treatment with sevoflurane was administered for 15 min upon the onset of reperfusion. The diabetic rats were treated with GYY4137 (H₂ S donor) 5 days before the experiment. Myocardial infarct size, mitochondrial structure and function, ATP content, activities of complex I-IV, marker of oxidative stress, SIRT1, nuclear factor E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and NADPH Oxidase-2 (Nox-2) protein expression were detected after reperfusion, and cardiac function was evaluated by echocardiography at 24 h after reperfusion. After H₂ S activated SIRT1 in the impaired myocardium of diabetic rats, SPC significantly upregulated the expression of Nrf2 and its downstream mediator HO-1, thus reduced the expression of Nox-2. In addition, H₂ S remarkably increased cytoplasmic and nuclear SIRT1 which was further enhanced by SPC. Furthermore, H₂ S combined with SPC reduced the production of reactive oxygen species, increased the content of ATP, and maintained mitochondrial enzyme activity. Finally, myocardial infarct size and myocardium damage were decreased, and cardiac function was improved. Taken together, our study proved that H₂ S could restore SPC-induced cardioprotection in diabetic rats by enhancing and promoting SIRT1/Nrf2 signaling pathway mediated mitochondrial dysfunction and oxidative stress.

Long non‑coding RNA H19 protects H9c2 cells against hypoxia‑induced injury by activating the PI3K/AKT and ERK/p38 pathways

Myocardial ischemia/reperfusion injury often leads to adverse cardiovascular outcomes due to severe hypoxia. The present study aimed to evaluate the effects and mechanism of long non-coding RNA H19 (H19) on rat H9c2 cells with hypoxia-induced injury. H9c2 cells were infected with lentiviruses to express H19 or H19-targeting short hairpin RNA (shRNA), or their respective controls, at a multiplicity of infection of 1:100. H19 expression was determined by reverse transcription-quantitative PCR. Hypoxic injury was induced and assessed by analyzing the level of apoptosis, the cell cycle distribution and the mitochondrial membrane potential using flow cytometry in the different groups. The expression of the PI3K/AKT and the ERK/p38 signaling pathways were analyzed using western blotting. It was found that hypoxia stimulated apoptosis, induced G1 phase cell cycle arrest and increased the mitochondrial depolarization rate in H9c2 cells. When compared with the hypoxic model group, the H19 overexpression group had a significantly reduced rate of apoptosis (P=0.016), a smaller G1 population and a higher S phase population (P=0.018 and P=0.031, respectively), and a reduced mitochondrial depolarization rate (P=0.036). By contrast, the H19 shRNA group exhibited the opposite trends, suggesting that hypoxia-induced injury was alleviated by the overexpression of H19 and was aggravated by the knockdown of H19. The present mechanistic studies revealed that H19 may decrease hypoxia-induced cell injury by activating the PI3K/AKT and ERK/p38 pathways. The results of the present study suggested that H19 may alleviate hypoxia-induced myocardial cell injury through the activation of the PI3K/AKT and ERK/p38 pathways.

The Role of Traditional Chinese Medicine in the Regulation of Oxidative Stress in Treating Coronary Heart Disease

Oxidative stress has been closely related with coronary artery disease. In coronary heart disease (CHD), an excess of reactive oxygen species (ROS) production generates endothelial cell and smooth muscle functional disorders, leading to a disequilibrium between the antioxidant capacity and prooxidants. ROS also leads to inflammatory signal activation and mitochondria-mediated apoptosis, which can promote and increase the occurrence and development of CHD. There are several kinds of antioxidative and small molecular systems of antioxidants, such as β-carotene, ascorbic acid, α-tocopherol, and reduced glutathione (GSH). Studies have shown that antioxidant treatment was effective and decreased the risk of CHD, but the effect of the treatment varies greatly. Traditional Chinese medicine (TCM) has been utilized for thousands of years in China and is becoming increasingly popular all over the world, especially for the treatments of cardiovascular diseases. This review will concentrate on the evidence of the action mechanism of TCM in preventing CHD by modulating oxidative stress-related signaling pathways.

Pioglitazone alleviates oxygen and glucose deprivation-induced injury by up-regulation of miR-454 in H9c2 cells

OBJECTIVES

Pioglitazone, an anti-diabetic agent, has been widely used to treat type II diabetes. However, the effect of pioglitazone on myocardial ischemia reperfusion injury (MIRI) is still unclear. Herein, the objective of this study is to learn about the regulation and mechanism of pioglitazone effects on oxygen glucose deprivation (OGD)-induced myocardial cell injury.

MATERIALS AND METHODS

A cellular injury model of OGD-treated H9c2 cells in vitro was constructed to simulate ischemic/reperfusion (I/R) injury. Then, various concentrations of pioglitazone (0, 2.5, 5, 7.5 and 10 μM) were used for the treatment of H9c2 cells, and CCK-8, flow cytometry and western blot assays were performed to examine cell viability, apoptosis, and the protein levels of factors involved in cell cycle and apoptosis in OGD-treated cells. MiR-454 inhibitor was used to suppress miR-454 expression, and whether miR-454 was involved in regulating OGD-induced cell injury was studied. Two key signal pathways were examined to uncover the underlying mechanism.

RESULTS

OGD reduced cell proliferation and induced apoptosis in H9c2 cells (P<0.05, P<0.01 or P< 0.001). OGD-induced injury was significantly attenuated by pioglitazone at the concentration of 5 μM. Additionally, pioglitazone significantly up-regulated miR-454 expression in OGD-injured cells (P< 0.05 or P< 0.01). MiR-454 suppression declined the protective effect of pioglitazone on OGD-injured H9c2 cells (P<0.05 or P< 0.01). Besides, pioglitazone activated PI3K/AKT and ERK/MAPK pathways via up-regulating miR-454.

CONCLUSION

Pioglitazone protected H9c2 cells against OGD-induced injury through up-regulating miR-454, indicating a novel therapeutic strategy for treatment of MIRI.

Blockade of RBP-J-Mediated Notch Signaling Pathway Exacerbates Cardiac Remodeling after Infarction by Increasing Apoptosis in Mice

Background

Ischemic heart disease (IHD) is the major cause of death in patients with cardiovascular disease. Cardiac remodeling is a common pathological change following myocardial infarction (MI), and cardiomyocyte apoptosis plays a key role in this change. Transcription factor recombination signal-binding protein-J (RBP-J)-mediated Notch signaling pathway has been implicated in several inherited cardiovascular diseases, including aortic valve diseases, but whether the RBP-J-mediated Notch signaling pathway plays a role in cardiomyocyte apoptosis after MI is unclear.

Method

We crossed RBP-J^fl/fl mice and Myh6-Cre/Esr1 transgenic mice to delete RBP-J in vivo and to partly inhibit the canonical Notch signaling pathway. MI was induced in mice by permanent ligation of the left anterior descending coronary artery followed by the knockout of RBP-J. Cardiac function and morphology were assessed by echocardiography and histological analysis 4 weeks after infarction. In addition, the expression and regulation of apoptosis-related molecules were examined by real time PCR and western blot.

Results

RBP-J knockout decreased the survival rate and deteriorated post-MI remodeling and function in mice, and this effect was associated with increased cardiomyocyte apoptosis. The potential mechanisms might be related to the downregulated expression of bcl-2, upregulated expression of bax, and cleaved-caspase 3 to exacerbate cardiomyocyte apoptosis.

Conclusion

These findings show that the RBP-J-mediated Notch signaling pathway in cardiomyocytes limits ventricular remodeling and improves cardiac function after MI. The RBP-J-mediated Notch signaling pathway has a protective role in cardiomyocyte apoptosis following cardiac injury.

Protective mechanisms of hypaconitine and glycyrrhetinic acid compatibility in oxygen and glucose deprivation injury

This study investigated the protective effect of the compatibility of hypaconitine (HA) and glycyrrhetinic acid (GA) on H9c2 cells under oxygen and glucose deprivation (OGD)-induced injury, and the possible mechanisms. We found that HA+GA significantly improved pathology and morphology of the nucleus and ultrastructure of H9c2 cells under OGD as determined by Hoechst 33342 staining and transmission electron microscopy (TEM) tests. It also reduced the releases of lactate dehydrogenase (LDH), creatine kinase-myocardial band isoenzyme (CK-MB), and aspartate transaminase (AST) from the cultured supernatant of H9c2 cells, which were tested by enzyme-linked immune sorbent assay (ELISA) kits. In addition, it lessened the apoptotic rate as determined by a fluorescein isothiocyanate-annexin V/propidium iodide (FITC-AV/PI) double staining assay. It was also found that HA+GA might regulate the protein expression associated with the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Overall, the study demonstrated that HA+GA protected H9c2 cells against OGD-induced injury, and the signaling mechanism might be related to the PI3K/Akt signaling pathway.

Cardioprotective effect of the xanthones from Gentianella acuta against myocardial ischemia/reperfusion injury in isolated rat heart

Gentianella acuta (Michx.) Hulten is widely used for the treatment of arrhythmia and coronary heart disease in Ewenki Folk Medicinal Plants and Mongolian Medicine, popularly known as "Wenxincao" in China. To investigate the potential protective role of the xanthones from G. acuta against myocardial I/R injury in isolated rat heart and its possible related mechanism. The protective role of xanthones on myocardial I/R injury was studied on Langendorff apparatus. The hemodynamic parameters including the left ventricular developed pressure (LVDP), the maximum rate of up/down left intraventricular pressure (±dp/dt_max), coronary flow (CF) and heart rate (HR) were recorded during the perfusion. The results demonstrated that the xanthones from G. acuta treatment significantly improved myocardial function (LVDP, ±dp/dt_max and CF), increased the levels of superoxide dismutase (SOD) and catalase (CAT), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), ATP and the ratio of glutathione and glutathione disulfide (GSH/GSSG), whereas suppressed the levels of Lactate dehydrogenase (LDH), creatine kinase (CK) and malondialdehyde (MDA). Furthermore, the xanthones upregulate the level of Bcl-2 protein and downregulate the level of Bax protein. These results indicated that xanthones from G. acuta exhibited cardioprotective effects on myocardial I/R injury through its activities of anti-oxidative effect and anti-apoptosis effect.

High glucose concentration abrogates sevoflurane post-conditioning cardioprotection by advancing mitochondrial fission but dynamin-related protein 1 inhibitor restores these effects

AIM

Hyperglycaemia-induced cell injury is a primary cause of cardiovascular complications in patients with diabetes. In vivo studies demonstrated that sevoflurane post-conditioning (SpostC) was cardioprotective against ischaemia/reperfusion injury, which was blocked by hyperglycaemia. This study investigated whether high glucose concentration abrogated SpostC cardioprotection in vitro by advancing mitochondrial fission and whether mitochondrial division inhibitor-1 (Mdivi-1) restored SpostC cardioprotection in cultured primary neonatal rat cardiomyocytes (NCMs).

METHODS

Primary cultured NCMs in low and high glucose concentrations were subjected to hypoxia/reoxygenation (H/R) injury. SpostC was carried out by adding 2.4% sevoflurane to the cells at the beginning of reoxygenation for 15 min. Cell viability, lactate dehydrogenase (LDH) level, cell death, mitochondrial morphology, mitochondrial membrane potential and mitochondrial permeability transition pore (mPTP) opening level, as well as fission- and fusion-related proteins, were measured after H/R injury. Mdivi-1 treatment was performed 40 min before hypoxia to inhibit DRP1.

RESULTS

SpostC protected cultured cardiomyocytes by increasing cell viability and reducing the LDH level and cell death following H/R, but high glucose concentration eliminated the cardioprotective effect. High glucose concentration abrogated SpostC cardioprotection via mitochondrial fragmentation (evidenced by decreased mitochondrial interconnectivity and elongation) and facilitation of mPTP opening. Decreased mitochondrial membrane potential was investigated with increased DRP1, FIS1 and MFN2 and decreased MFN1 and OPA1 expressions. Mdivi-1 (100 μmol L^-1 ) inhibited excessive mitochondrial fission and restored the cardioprotective effect of SpostC in high glucose conditions.

CONCLUSION

SpostC-induced cardioprotection against H/R injury was impaired under high glucose concentrations, but the inhibition of excess mitochondrial fission restored these effects.

RISK pathway is involved in oxytocin postconditioning in isolated rat heart

The reperfusion injury salvage kinase (RISK) pathway is a fundamental signal transduction cascade in the cardioprotective mechanism of ischemic postconditioning. In the present study, we examined the cardioprotective role of oxytocin as a postconditioning agent via activation of the RISK pathway (PI3K/Akt and ERK1/2). Animals were randomly divided into 6 groups. The hearts were subjected under 30minutes (min) ischemia and 100min reperfusion. OT was perfused 15min at the early phase of reperfusion. RISK pathway inhibitors (Wortmannin; an Akt inhibitor, PD98059; an ERK1/2 inhibitor) and Atosiban (an OT receptor antagonist) were applied either alone 10min before the onset of the ischemia or in the combination with OT during early reperfusion phase. Myocardial infarct size, hemodynamic factors, ventricular arrhythmia, coronary flow and cardiac biochemical marker were measured at the end of reperfusion. OT postconditioning (OTpost), significantly decreased the infarct size, arrhythmia score, incidence of ventricular fibrillation, Lactate dehydrogenase and it increased coronary flow. The cardioprotective effect of OTpos was abrogated by PI3K/Akt, ERK1/2 inhibitors and Atosiban. Our data have shown that OTpost can activate RISK pathway mostly via the PI3K/Akt and ERK1/2 signaling cascades during the early phase of reperfusion.

Sevoflurane postconditioning attenuates cardiomyocyte hypoxia/reoxygenation injury via restoring mitochondrial morphology

Background

Anesthetic postconditioning is a cellular protective approach whereby exposure to a volatile anesthetic renders a tissue more resistant to subsequent ischemic/reperfusion event. Sevoflurane postconditioning (SPostC) has been shown to exert cardioprotection against ischemia/reperfusion injury, but the underlying mechanism is unclear. We hypothesized that SPostC protects cardiomyocytes against hypoxia/reoxygenation (H/R) injury by maintaining/restoring mitochondrial morphological integrity, a critical determinant of cell fate.

Methods

Primary cultures of neonatal rat cardiomyocytes (NCMs) were subjected to H/R injury (3 h of hypoxia followed by 3 h reoxygenation). Intervention with SPostC (2.4% sevoflurane) was administered for 15 min upon the onset of reoxygenation. Cell viability, Lactate dehydrogenase (LDH) level, cell death, mitochondrial morphology, mitochondrial membrane potential and mitochondrial permeability transition pore (mPTP) opening were assessed after intervention. Mitochondrial fusion and fission regulating proteins (Drp1, Fis1, Mfn1, Mfn2 and Opa1) were assessed by immunofluorescence staining and western blotting was performed to determine the level of protein expression.

Results

Cardiomyocyte H/R injury resulted in significant increases in LDH release and cell death that were concomitant with reduced cell viability and reduced mitochondrial interconnectivity (mean area/perimeter ratio) and mitochondrial elongation, and with reduced mitochondrial membrane potential and increased mPTP opening. All the above changes were significantly attenuated by SPostC. Furthermore, H/R resulted in significant reductions in mitochondrial fusion proteins Mfn1, Mfn2 and Opa1 and significant enhancement of fission proteins Drp1 and Fis1. SPostC significantly enhanced Mfn2 and Opa1 and reduced Drp1, without significant impact on Mfn1 and Fis1.

Conclusions

Sevoflurane postconditioning attenuates cardiomyocytes hypoxia/reoxygenation injury (HRI) by restoring mitochondrial fusion/fission balance and morphology.

Na(+)/Ca(2+) exchanger 1 (NCX-1) mediates the anti-apoptotic effect of Akt1 in neonatal rat cardiomyocytes during ischemia/reperfusion

The purpose of this study was to investigate the anti-apoptotic role of Akt1 gene in neonatal rat cardiomyocytes and the relationship with Na(+)/Ca(2+) exchanger 1 (NCX1) during ischemia/reperfusion (IR). The cultured original rat cardiomyocytes were randomly divided into five groups: normal control group (C group), hypoxia/reoxygenation group (HR group), the control vector pLVX-EGFP-3FLAG group (CV group), the gene pLVX-EGFP-3FLAG-Akt1 transfection group (A group), and Akt1 inhibitor LY294002 group (LY group). Cardiomyocyte vitality was determined using MTT, and the apoptosis was determined by TUNEL to verify the anti-apoptotic role of Akt1. The mRNA levels of Akt1 and NCX1 were determined by RT-PCR, the protein expression of Akt1, p-Akt1, NCX1 and the apoptotic proteins of mitochondrial pathway cytochrome C (Cyto C) and caspase-9 were measured by Western blot. As a result, transfected Akt1 (A group) showed increased myocardial cell viability and reduced apoptosis, with increase in Akt1 expression and decrease in NCX1 expression. The levels of apoptotic proteins Cyto C and caspase-9 also declined. This study demonstrated that lentivirus-mediated transfection of Akt1 played an anti-apoptotic role during IR of rat cardiomyocytes, via inhibition of NCX1 and other mitochondrial proteins.

The mechanisms of cardio-protective effects of desflurane and sevoflurane at the time of reperfusion: anaesthetic post-conditioning potentially translatable to humans?

Myocardial conditioning is actually an essential strategy in the management of ischaemia-reperfusion injury. The concept of anaesthetic post-conditioning is intriguing, its action occurring at a pivotal moment (that of reperfusion when ischaemia reperfusion lesions are initiated) where the activation of these cardio-protective mechanisms could overpower the mechanisms leading to ischaemia reperfusion injuries. Desflurane and sevoflurane are volatile anaesthetics frequently used during cardiac surgery. This review focuses on the efficacy of desflurane and sevoflurane administered during early reperfusion as a potential cardio-protective strategy. In the context of experimental studies in animal models and in human atrial tissues in vitro, the mechanisms underlying the cardio-protective effect of these agents and their capacity to induce post-conditioning have been reviewed in detail, underlining the role of reactive oxygen species generation, the activation of the cellular signalling pathways, and the actions on mitochondria along with the translatable actions in humans; this might well be sufficient to set the basis for launching randomized clinical studies, actually needed to confirm this strategy as one of real impact.

Cardioprotective Effects of Astragalin against Myocardial Ischemia/Reperfusion Injury in Isolated Rat Heart

This study aims to evaluate the cardioprotective effects of astragalin against myocardial ischemia/reperfusion (I/R) injury in isolated rat heart. The cardioprotective effects of astragalin on myocardial I/R injury were investigated on Langendorff apparatus. Adult male Sprague-Dawley rats were randomly divided into five groups. The results showed that astragalin pretreatment improved myocardial function. Compared with I/R group, lactate dehydrogenase (LDH) and creatine kinase (CK) activities in coronary flow decreased in astragalin pretreatment groups, whereas superoxide dismutase (SOD) activity and glutathione/glutathione disulfide (GSH/GSSG) ratio significantly increased. The levels of malondialdehyde (MDA), intracellular reactive oxygen species (ROS), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) decreased in astragalin-treated groups. The infarct size (IS) and apoptosis rate in hearts from astragalin-treated groups were lower than those in hearts from the I/R group. Western blot analysis also revealed that astragalin preconditioning significantly reduced Bax level, whereas Bcl-2 was increased in the myocardium. Therefore, astragalin exhibited cardioprotective effects via its antioxidative, antiapoptotic, and anti-inflammatory activities.

Protective Effect of Sevoflurane Postconditioning against Cardiac Ischemia/Reperfusion Injury via Ameliorating Mitochondrial Impairment, Oxidative Stress and Rescuing Autophagic Clearance

Background and Purpose

Myocardial infarction leads to heart failure. Autophagy is excessively activated in myocardial ischemia/reperfusion (I/R) in rats. The aim of this study is to investigate whether the protection of sevoflurane postconditioning (SPC) in myocardial I/R is through restored impaired autophagic flux.

Methods

Except for the sham control (SHAM) group, each rat underwent 30 min occlusion of the left anterior descending coronary (LAD) followed by 2 h reperfusion. Cardiac infarction was determined by 2,3,5-triphenyltetrazolium chloride triazole (TTC) staining. Cardiac function was examined by hemodynamics and echocardiography. The activation of autophagy was evaluated by autophagosome accumulation, LC3 conversion and p62 degradation. Potential molecular mechanisms were investigated by immunoblotting, real-time PCR and immunofluorescence staining.

Results

SPC improved the hemodynamic parameters, cardiac dysfunction, histopathological and ultrastructural damages, and decreased myocardial infarction size after myocardial I/R injury (P < 0.05 vs. I/R group). Compared with the cases in I/R group, myocardial ATP and NAD⁺ content, mitochondrial function related genes and proteins, and the expressions of SOD2 and HO-1 were increased, while the expressions of ROS and Vimentin were decreased in the SPC group (P < 0.05 vs. I/R group). SPC significantly activated Akt/mTOR signaling, and inhibited the formation of Vps34/Beclin1 complex via increasing expression of Bcl2 protein (P < 0.05 vs. I/R group). SPC suppressed elevated expressions of LC3 II/I ratio, Beclin1, Atg5 and Atg7 in I/R rat, which indicated that SPC inhibited over-activation of autophagy, and promoted autophagosome clearance. Meanwhile, SPC significantly suppressed the decline of Opa1 and increases of Drp1 and Parkin induced by I/R injury (P < 0.05 vs. I/R group). Moreover, SPC maintained the contents of ATP by reducing impaired mitochondria.

Conclusion

SPC protects rat hearts against I/R injury via ameliorating mitochondrial impairment, oxidative stress and rescuing autophagic clearance.

Activation of Akt and cardioprotection against reperfusion injury are maximal with only five minutes of sevoflurane postconditioning in isolated rat hearts

It had been proved that administration of sevoflurane for the first two minutes of reperfusion effectively protects the heart against reperfusion injury in rats in vivo. Our aim was to investigate the duration of effective sevoflurane administration and its underlying mechanism in isolated rat hearts exposed to global ischemia/reperfusion (I/R) injury. Adult male Sprague-Dawley rats were randomly divided into six groups (n=12): a sham-operation group, an I/R group, and four sevoflurane postconditioning groups (S2, S5, S10, and S15). In the S2, S5, S10, and S15 groups, the duration times of sevoflurane administration were 2, 5, 10, and 15 min after the onset of reperfusion, respectively. The isolated rat hearts were mounted on the Langendorff system, and after a period of equilibrium were subjected to 40 min global ischemia and 120 min reperfusion. Left ventricular (LV) hemodynamic parameters were monitored throughout each experiment and the data at 30 min of equilibrium and 30, 60, 90, and 120 min of reperfusion were analyzed. Myocardial infarct size at the end of reperfusion (n=7 in each group) and the expression of myocardial phosphorylated Akt (p-Akt) after 15-min reperfusion were determined in a duplicate set of six groups of rat hearts (n=5 in each group). Compared with the I/R group, the S5, S10, and S15 groups had significantly improved left ventricular end-diastolic pressure (LVEDP), left ventricular developed pressure (LVDP), and the maximal rate of rise or fall of the LV pressure (±dP/dtmax), and decreased myocardial infarct size (P<0.05), but not the S2 group. After 15 min of reperfusion, the expression of p-Akt was markedly up-regulated in the S5, S10, and S15 groups compared with that in the I/R group (P<0.05), but not in the S2 group. Sevoflurane postconditioning for 5 min was sufficient to activate Akt and exert maximal cardioprotection against I/R injury in isolated rat hearts.

Notch 1 signalling inhibits cardiomyocyte apoptosis in ischaemic postconditioning

AIM

Recent studies have demonstrated that Notch signalling pathway is an important mediator of cardiac repair and regeneration after myocardial infarction. However, the mechanism by which Notch signalling pathway is mediating cardioprotection after ischaemic postconditioning (IPost) is still not understood thoroughly. The aim of the present study was to investigate the mechanism by which Notch signalling pathway mediated the cardioprotection effect after IPost.

METHODS

Rat heart-derived H9c2 cells were randomly divided into six groups as follows: Control group, hypoxia/reoxygenation group (H/R), H/R+N1ICD group, H-post group, H-post+Notch-1miRNA group, and Mock group. We used pcDNA3.1-Myc-His plasmid and RNA interference (RNAi) to activate/inhibit the expression of Notch-1 in H9c2 cell lines. The Bcl-2, Bax genes and proteins were assessed by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and Western blot analysis. The effects of Notch 1 signalling on cell survival, proliferation and apoptosis were detected by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) and flow cytometry analysis, respectively. Furthermore, Notch 1 signalling induced the disruption of mitochondrial membrane potential, thus leading to the activation of caspase-9/-3 measured using the colorimetric activity assay.

RESULTS

We found Notch 1 signalling reduced cardiomyocyte apoptosis in IPost through regulating the expression of Bcl-2, Bax and activation of caspase-9 and -3. We found that after transfected with pcDNA3.1-Myc-His plasmid, activation of the Notch 1 gene effectively promoted cell proliferation and inhibited apoptosis. The Notch 1 upregulation was accompanied by an upregulation of Bcl-2 and a downregulation of Bax. In addition, a paralled increase in caspase-9/-3 activities was observed. These effects were blunted by transfected with Notch-1 miRNA in the H9c2 cells.

CONCLUSION

Notch 1 signalling has a cardioprotection effect, which may result from cardiomyocyte apoptosis, by means of regulating the expression of cell apoptosis inhibiting proteins Bcl-2, Bax and the activation of caspase-9 and -3.

Post-conditioning: promising answers and more questions

Volatile anesthetic agents have been used for decades in the peri-operative setting. Data from the past 15 years have shown that pre-injury administration of volatile anesthetic can decrease the impact of ischemia-reperfusion injury on the heart, brain, and kidney. Recent data demonstrated that volatile agents administered shortly after injury can decrease the ischemia-reperfusion injury. Several questions need to be answered to optimize this therapeutic target, but this is a promising era of secondary injury mitigation.

Sufentanil postconditioning protects the myocardium from ischemia-reperfusion via PI3K/Akt-GSK-3β pathway

BACKGROUND

Previous studies have shown that opioid postconditioning reduces apoptosis through antiapoptotic signaling. The present study evaluated whether sufentanil could induce cardioprotection after ischemia-reperfusion (I/R) and whether the PI3K/Akt-GSK-3β pathway modulates antiapoptotic proteins in sufentanil postconditioning.

METHODS

We subjected male Sprague-Dawley rats to 30 min of myocardial ischemia and 2 h of reperfusion. We randomized rats into seven groups: sham, I/R, sufentanil postconditioning (I/R+sufen), sham plus sufentanil (sham+sufen), sham plus 15 μg · kg(-1) intravenous wortmannin (PI3K inhibitor), I/R plus wortmannin, and sufentanil plus wortmannin. We induced sufentanil postconditioning with 3 μg · kg(-1) sufentanil for 3 min in the beginning of reperfusion after 30 min ischemia. We assessed hemodynamics, myocardial infarct size, number of apoptotic cardiomyocytes, total Akt and GSK-3β, phosphorylated Akt and GSK-3β, caspase-3, Bax, and Bcl-2 protein expression.

RESULTS

The I/R+sufen group had significantly reduced infarct size compared with the I/R group (23.3% ± 9.0% versus 50.1% ± 7.4%; P < 0.05). The apoptotic index of cardiomyocytes was significantly reduced with sufentanil treatment (20.0% ± 3.5%) compared with the I/R group (47.0% ± 6.3%; P < 0.05). The I/R+sufen group reduced the expression of protein-cleaved caspase-3 and Bax, and increased Bcl-2, phosphorylated Akt, and GSK3β compared with the I/R group. Wortmannin eliminated the cardioprotection produced with sufentanil treatment.

CONCLUSIONS

Sufentanil postconditioning can induce myocardial protection by activating the PI3K/Akt-GSK-3β pathway and modulating Bax and Bcl-2 expression.

The mitochondrial permeability transition pore and its role in anaesthesia-triggered cellular protection during ischaemia-reperfusion injury

This review summarises the most recent data in support of the role of the mitochondrial permeability transition pore (mPTP) in ischaemia-reperfusion injury, how anaesthetic agents interact with this molecular channel, and the relevance this holds for current anaesthetic practice. Ischaemia results in damage to the electron transport chain of enzymes and sets into play the assembly of a non-specific mega-channel (the mPTP) that transgresses the inner mitochondrial membrane. During reperfusion, uncontrolled opening of the mPTP causes widespread depolarisation of the inner mitochondrial membrane, hydrolysis of ATP, mitochondrial rupture and eventual necrotic cell death. Similarly, transient opening of the mPTP during less substantial ischaemia leads to differential swelling of the intermembrane space compared to the mitochondrial matrix, rupture of the outer mitochondrial membrane and release of pro-apoptotic factors into the cytosol. Recent data suggests that cellular protection from volatile anaesthetic agents follows specific downstream interactions with this molecular channel that are initiated early during anaesthesia. Intravenous anaesthetic agents also prevent the opening of the mPTP during reperfusion. Although by dissimilar mechanisms, both volatiles and propofol promote cell survival by preventing uncontrolled opening of the mPTP after ischaemia. It is now considered that anaesthetic-induced closure of the mPTP is the underlying effector mechanism that is responsible for the cytoprotection previously demonstrated in clinical studies investigating anaesthetic-mediated cardiac and neuroprotection. Manipulation of mPTP function offers a novel means of preventing ischaemic cell injury. Anaesthetic agents occupy a unique niche in the pharmacological armamentarium available for use in preventing cell death following ischaemia-reperfusion injury.

Inhibition of sevoflurane postconditioning against cerebral ischemia reperfusion-induced oxidative injury in rats

The volatile anesthetic sevoflurane is capable of inducing preconditioning and postconditioning effects in the brain. In this study, we investigated the effects of sevoflurane postconditioning on antioxidant and immunity indexes in cerebral ischemia reperfusion (CIR) rats. Rats were randomly assigned to five separate experimental groups I–V. In the sham group (I), rats were subjected to the same surgery procedures except for occlusion of the middle cerebral artery and exposed to 1.0 MAC sevoflurane 90 min after surgery for 30 min. IR control rats (group II) were subjected to middle cerebral artery occlusion (MCAO) for 90 min and exposed to O₂ for 30 min at the beginning of reperfusion. Sevoflurane 0.5, 1.0 and 1.5 groups (III, IV, V) were all subjected to MCAO for 90 min, but at the beginning of reperfusion exposed to 0.5 MAC, 1.0 MAC or 1.5 MAC sevoflurane for 30 min, respectively. Results showed that sevoflurane postconditioning can decrease serum tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), nitric oxide (NO), nitric oxide synthase (NOS) and increase serum interleukin-10 (IL-10) levels in cerebral ischemia reperfusion rats. In addition, sevoflurane postconditioning can still decrease blood lipid, malondialdehyde (MDA) levels, infarct volume and increase antioxidant enzymes activities, normal pyramidal neurons density in cerebral ischemia reperfusion rats. It can be concluded that sevoflurane postconditioning may decrease blood and brain oxidative injury and enhance immunity indexes in cerebral ischemia reperfusion rats.

Myocardial postconditioning: next step to cardioprotection

Myocardial ischemia is a condition in which lack of blood flow to the cardiac muscle occurs resulting in deficient oxygen and nutrient supply to the heart. The restoration of blood flow to an organ or tissue is termed reperfusion. Brief episodes of ischemia and reperfusion given after prolonged ischemia and at the onset of reperfusion denotes postconditioning. Myocardial postconditioning is a phenomenon in which myocardium from lethal ischemia-reperfusion injury is protected. However, numerous experimental studies reveal that the cardioprotective effects of postconditioning are suppressed in various pathological states. This review critically discusses the mechanisms involved in the cardioprotective effects of postconditioning and factors affecting the cardioprotective potential of myocardial postconditioning.

Gender-related difference of sevoflurane postconditioning in isolated rat hearts: focus on phosphatidylinositol-3-kinase/Akt signaling

BACKGROUND

Previous studies have reported that female gender confers cardioprotection against ischemia/reperfusion (I/R) injury, partly because estrogen activates phosphatidylinositol-3-kinase/Akt (PI3K/Akt) pathway. We have previously proven that cardioprotection of sevoflurane postconditioning is mediated by PI3K/Akt pathway in male rats. The purpose of the present study was to determine whether the cardioprotection of sevoflurane postconditioning is influenced by gender, and the role of PI3K/Akt pathway in such gender difference.

MATERIALS AND METHODS

Isolated hearts from 2-mo-old male and female SD rats were subjected to ischemia for 40 min and reperfusion for 2 h in the Langendorff apparatus, and were randomly assigned to the following groups: no ischemia/reperfusion (CON), ischemia/reperfusion (I/R), I/R+sevoflurane postconditioning (I/R+SPC), I/R+100 nM wortmannin (I/R+WOR), and I/R+SPC+WOR. Postconditioning was performed with administration of 3.0% sevoflurane at the first 10 min of reperfusion. Left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), and myocardial lactate dehydrogenase (LDH) release were measured. Infarct size was detected by riphenyltetrazolium chloride staining. The protein expression of total Akt (t-Akt) and phosphorylated Akt (Ser(473)) (p-Akt) were determined by Western blot.

RESULTS

The I/R group showed lower LVDP and higher LVEDP than CON group in the same gender during reperfusion period. The LDH release and infarct size were smaller in the female I/R group (P < 0.05 versus male I/R group). Sevoflurane postconditioning markedly improved left ventricular function and decreased LDH, infarct size in the male I/R+SPC group (P < 0.05 versus male I/R group) but not in the female I/R+SPC group. Wortmannin abolished the cardioprotection of sevoflurane postconditioning in the male I/R+SPC+Wort group (P < 0.05 versus male I/R+SPC group), and markedly increased the infarct size and LVEDP and decreased LVDP in female rats. The t-Akt protein expression was no significant difference in all groups. The ratio of p-Akt/t-Akt expression in the male CON group was a little lower than that in the female CON group, but there was no statistical significance. In male rats, the ratio of p-Akt/t-Akt was no difference between CON and I/R group, but it was higher in I/R+SPC group than that in I/R group (P < 0.05). In female rats, the level of p-Akt was markedly increased by I/R, which was markedly higher than that in male I/R group (P < 0.05). However, p-Akt was not different between I/R and I/R+SPC groups. Wortmannin decreased the p-Akt expression in both male and female rats.

CONCLUSIONS

It is concluded that female rat hearts showed greater resistance to I/R injury, and sevoflurane postconditioning developed cardioprotection in male rats but not in female rats. The PI3K/Akt pathway may be involved in the cardioprotection by both sevoflurane postconditioning and gender.