Ischemic-reperfused Rat Hearts Research Articles

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.

Sevoflurane Preconditioning Confers Delayed Cardioprotection by Upregulating AMP-Activated Protein Kinase Levels to Restore Autophagic Flux in Ischemia-Reperfusion Rat Hearts

BackgroundVolatile anesthetic preconditioning confers delayed cardioprotection against ischemia/reperfusion injury (I/R). AMP-activated protein kinase (AMPK) takes part in autophagy activation. Furthermore, autophagic flux is thought to be impaired after I/R. We hypothesized that delayed cardioprotection can restore autophagic flux by activating AMPK.Material/MethodsAll male rat hearts underwent 30-min ischemia and 120-min reperfusion with or without sevoflurane exposure. AMPK inhibitor compound C (250 μg/kg, iv) was given at the reperfusion period. Autophagic flux blocker chloroquine (10 mg/kg, ip) was administrated 1 h before the experiment. Myocardial infarction, nicotinamide adenine dinucleotide (NAD+) content, and cytochrome c were measured. To evaluate autophagic flux, the markers of microtubule-associated protein 1 light chain 3 (LC3) I and II, P62 and Beclin 1, and lysosome-associated membrane protein-2 (LAMP 2) were analyzed.ResultsThe delayed cardioprotection enhanced post-ischemic AMPK activation, reduced infarction, CK-MB level, NAD+ content loss and cytochrome c release, and compound C blocked these effects. Sevoflurane restored impaired autophagic flux through a lower ratio of LC3II/LC3I, downregulation of P62 and Beclin 1, and higher expression in LAMP 2. Consistently, compound C inhibited these changes of autophagy flux. Moreover, chloroquine pretreatment abolished sevoflurane-induced infarct size reduction, CK-MB level, NAD+ content loss, and cytochrome c release, with concomitant increase the ratios of LC3II/LC3I and levels of P62 and Beclin 1, but p-AMPK expression was not downregulated by chloroquine.ConclusionsSevoflurane exerts a delayed cardioprotective effects against myocardial injury in rats by activation of AMPK and restoration of I/R-impaired autophagic flux.

Remifentanil-induced preconditioning has cross-talk with A1 and A2B adenosine receptors in ischemic-reperfused rat heart.

The purpose of this study was to determine whether there is a cross-talk between opioid receptors (OPRs) and adenosine receptors (ADRs) in remifentanil preconditioning (R-Pre) and, if so, to investigate the types of ADRs involved in the cross-talk. Isolated rat hearts received 30 min of regional ischemia followed by 2 hr of reperfusion. OPR and ADR antagonists were perfused from 10 min before R-Pre until the end of R-Pre. The heart rate, left ventricular developed pressure (LVDP),velocity of contraction (+dP/dtmax), and coronary flow (CF) were recorded. The area at risk and area of necrosis were measured. After reperfusion, the LVDP, +dP/dtmax,and CF showed a significant increase in the R-Pre group compared with the control group (no intervention before or after regional ischemia). These increases in the R-Pre group were blocked by naloxone, a nonspecific ADR antagonist, an A1 ADR antagonist, and an A2B ADR antagonist. The infarct size was reduced significantly in the R-Pre group compared with the control group. The infarct-reducing effect in the R-Pre group was blocked by naloxone, the nonspecific ADR antagonist, the A1 ADR antagonist, and the A2B ADR antagonist. The results of this study demonstrate that there is cross-talk between ADRs and OPRs in R-Pre and that A1 ADR and A2B ADR appear to be involved in the cross-talk.

Ginkgolide B Reduces the Degradation of Membrane Phospholipids to Prevent Ischemia/Reperfusion Myocardial Injury in Rats

Platelet-activating factor (PAF), a bioactive phospholipid, plays an important role in the integrity of the cellular membrane structure, and is involved in the pathogenesis of myocardial ischemia/reperfusion (IR) injuries. In this study, we tested the hypothesis that blockage of PAF receptor by BN 52021 (Ginkgolide B) can prevent IR-induced degradation of the myocardial membrane phospholipid, and deterioration of the cardiac function. Rat hearts in situ were subjected to 5 min ischemia and followed by 10 min reperfusion. Cardiac performances during periods of ischemia and reperfusion were monitored, and the amount of membrane phospholipids was analyzed. Myocardial total phospholipids, phosphatidylcholine, and phosphatidylethanolamine were decreased significantly in ischemia-reperfusion rat hearts compared with those of sham-operated rat hearts. Degradation of the membrane phospholipid was accompanied by the deterioration of cardiac functions and increase in serum lactate dehydrogenase (LDH) activity. BN 52021 (15 mg/kg), given by intravenous infusion 10 min prior to the left anterior descending coronary artery occlusion, reduced IR-related degradation of the myocardial phospholipids, the activity of serum LDH, and was concomitant with improvement of cardiac function. Furthermore, we demonstrated that the production of PAF was increased and BN 52021 decreased cellular damage in cultured anoxic cardiomyocytes. These results indicated that PAF antagonist BN 52021 has a protective effect against IR-induced myocardial dysfunction and degradation of the membrane phospholipids.

Remifentanil postconditioning has cross talk with adenosine receptors in the ischemic-reperfused rat heart

BackgroundAlthough there is a possibility of cross talk between opioid and adenosine signaling pathways in the ischemic-reperfused myocardium, it is not clear that an ultra-short–acting opioid receptor agonist remifentanil-induced postconditioning (RPostC) has cross talk with adenosine receptor (ADR). The purpose of this study was to determine whether there is cross talk with ADR in RPostC. Materials and methodsIsolated rat hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. RPostC was induced by 100 ng/mL of remifentanil perfusion, 5 min before reperfusion, followed by 5 min of reperfusion. The nonspecific opioid receptor antagonist naloxone (NAL) and the nonspecific ADR antagonist 8-(p-sulfophenyl) theophylline hydrate (8-SPT) were perfused for a 20-min period, 10 min before RPostC to the end of RPostC. Western blot analysis was performed to detect phospho-ERK1/2 in cultured cardiomyocytes. ResultsIn cultured cardiomyocytes, remifentanil incubation significantly increased the phosphorylation of ERK1/2 and this effect was blocked by both NAL and 8-SPT (P < 0.01 and P < 0.05, respectively). RPostC significantly reduced infarct size over ischemic area at risk from 34.1 ± 10.5% to 16.6 ± 7.5% (P < 0.05 versus control). The infarct-limitation effect of RPostC was reversed by both NAL (33.8 ± 13.0%, P < 0.05) and 8-SPT (35.7 ± 14.5%, P < 0.01). ConclusionsThis study strongly implies that the intracellular signaling pathways of cardioprotection by RPostC has cross talk with ADR in the ischemic-reperfused myocardium.

Role of mitochondrial permeability transition pore and mitochondrial ATP-sensitive potassium channels in the protective effects of ischemic preconditioning in isolated hearts from fed and fasted rats.

The aim of the present study was to assess whether the protective effects of ischemic preconditioning (PC) are associated with activation of the mitochondrial ATP-sensitive potassium channels (mitoKATP) and if there is any relationship between the activity of these channels and the mitochondrial permeability transition pore (MPTP) opening in ischemic-reperfused rat hearts under different nutritional conditions. Langendorff-perfused hearts of fed and 24-h fasted rats were exposed to 25 min of no-flow global ischemia plus 30 min of reperfusion. Fasting accelerated functional recovery and attenuated MPTP opening. The mitoKATP blocker, 5-hydroxydecanoic (HD), did not influence functional recovery and MPTP opening induced by ischemia-reperfusion in the fed hearts but partially reversed the beneficial effects of fasting. PC and the mitoKATP opener, diazoxide (DZ), improved functional recovery, preserved cell viability, and inhibited MPTP opening in both fed and fasted hearts. The protection elicited by PC and DZ on contractile recovery and MPTP opening was reversed by HD, which did not affect cell viability. Altogether, these results argue for a role of mitoKATP and its impact on preservation mitochondrial inner membrane permeability as a relevant factor in the improvement of contractile function in the ischemic-reperfused rat heart. They also suggest that the functional protection elicited by PC may be related to this mechanism.

Effect of telmisartan on VEGF-induced and VEGF-independent angiogenic responsiveness of coronary endothelial cells in normal and streptozotocin (STZ)-induced diabetic rats

Telmisartan possesses endothelial protective effects due to angiotensin II type 1 receptor antagonist, peroxisome proliferator-activated receptor γ (PPARγ) agonist and antioxidant action. Therefore, our objective was to study effect of telmisartan on angiogenic responsiveness of coronary endothelial cells (cECs) of normal and diabetic rats. Male Wistar rats were divided into six groups, normal rats, diabetic rats 30 d. (30 days after administration of STZ), diabetic rats 60 ds. (60 days after administration of STZ), telmisartan-treated normal rats (2 mg/kg, p.o., for 15 days before isolation of hearts), telmisartan-treated diabetic rats 30 ds, and telmisartan-treated diabetic rats 60 ds. Each group was further divided into two subgroups, sham rat hearts and ischemia-reperfused rat hearts. After isolation of cEC from each subgroup, angiogenic responsiveness and nitric oxide releasing properties were studied using chorioallantoic membrane (CAM) assay and Griess method, respectively. cEC of normal rats showed significant increase in angiogenic responsiveness in presence of vascular endothelial growth factor (VEGF) but not in absence of it. This activity was attenuated by pretreatment of cEC with l-NAME, wortmannin and chelerythrine. Diabetes and ischemia reperfusion injury suppressed angiogenic responsiveness of cEC. Telmisartan treatment showed significant increase in VEGF-induced angiogenic responsiveness and nitric oxide releasing properties of cECs of all subgroups as compared to their respective non-treated subgroups. These effects of telmisartan were significantly inhibited by pretreatment of cECs with l-NAME and wortmannin but not with chelerythrine. Our data suggest that telmisartan improves VEGF-induced coronary angiogenic activity in normal and diabetic rats via stimulation of PI3K/eNOS/NO pathway.

Piceatannol facilitates conduction block and ventricular fibrillation induction in ischemia-reperfused rabbit hearts with pacing-induced heart failure

BackgroundPiceatannol, a hydroxystilbene natural product, has been reported to exert antiarrhythmic action via INa inhibition and slow INa inactivation in ischemia-reperfused (IR) rat hearts. The present study aimed to clarify the proarrhythmic property of piceatannol during regional IR injury in failing rabbit hearts. MethodsHeart failure (HF) was induced by rapid right ventricular pacing for 4weeks. The IR model was created by coronary artery ligation for 30min, followed by reperfusion for 15min in vivo. Simultaneous voltage and intracellular Ca2+ (Cai) optical mapping was then performed in isolated Langendorff-perfused hearts (n=11 in each HF and control group). Action potential duration (APD) restitution, arrhythmogenic alternans and VF inducibility were evaluated by a dynamic pacing protocol. Conduction velocity was measured along lines across the IR and non-IR zones during pacing. Piceatannol (10μM) was administered after baseline studies. ResultsIn the HF group, piceatannol decreased conduction velocity, induced rate-dependent regional inhomogeneity of conduction delay and wavelength shortening, slowed Cai decay, and facilitated arrhythmogenic alternans instead of APD prolongation to increase VF inducibility. In the control group, the proarrhythmic effects of piceatannol on APD restitution, arrhythmogenic alternans and conduction delay were offset by its antiarrhythmic effects (APD and wavelength prolongation), resulting in a neutral effect on VF inducibility. ConclusionsPiceatannol (10μM) is proarrhythmic in failing rabbit hearts with regional IR injury. The increased VF inducibility by piceatannol in HF suggests that its undesirable effects are more pronounced than its benefits in failing hearts.

SPECT Imaging of Inflammatory Response in Ischemic–Reperfused Rat Hearts Using a 99mTc-Labeled Dual-Domain Cytokine Ligand

Soluble tumor necrosis factor (TNF) receptor-2 (TNFR2) and interleukin-1 receptor antagonist (IL-1ra) were fused to the Fc portion of IgG1 using recombinant DNA technology. The resulting dual-domain cytokine ligand, TNFR2-Fc-IL-1ra, specifically binds to TNF and to the type I IL-1 receptor (IL-1RI). This study was designed to characterize the kinetic profile of (99m)Tc-labeled TNFR2-Fc-IL-1ra (TFI) for imaging inflammatory response in an ischemic-reperfused (IR) rat heart model. The IR model was created by ligating the left coronary artery for 45 min, followed by 2-h reperfusion. Cardiac SPECT images of TFI in the IR model (n = 6) were dynamically acquired for 3 h. Correlative data of myocardial TFI distribution versus microsphere-determined tissue blood flow were acquired in 3 extra IR hearts. Inflammation targeting affinity of TFI was compared with 2 individual cytokine radioligands, (99m)Tc-IL-1ra-Fc (IF) and (99m)Tc-TNFR2-Fc (TF) (n = 6 each group). Myocardial cytokine expression was evaluated by immunochemical assay. Increased TFI uptake was found in the ischemic area and correlated with the severity of ischemia. At 3 h after injection, the ratio of hot-spot accumulation in the ischemic area to a remote viable zone was 5.39 ± 1.11 for TFI, which was greater than that for IF (3.28 ± 0.81) and TF (3.29 ± 0.75) (P < 0.05). The in vivo uptake profiles of TFI, TF, and IF were consistent with ex vivo radioactive measurements and correlated with upregulated IL-1 and TNF expression. The dual-domain TFI is promising for noninvasive detection of inflammatory reactions in IR myocardium because of its more potent affinity to the inflammatory sites compared with TF and IF.

The role of central oxytocin in stress-induced cardioprotection in ischemic-reperfused heart model

Background and purposeThere is growing evidence that stress contributes to cardiovascular disease and triggers the release of oxytocin. Moreover previous studies confirmed oxytocin mimics the protection associated with ischemic preconditioning. The present study was aimed to assess the possible cardioprotective effects of the centrally released oxytocin in response to stress and intracerebroventricular (i.c.v.) administration of exogenous oxytocin in ischemic-reperfused isolated rat heart. Methods and subjectsRats were divided in two main groups and all of them were subjected to i.c.v. infusion of vehicle or drugs: unstressed rats [control: vehicle, oxytocin (OT; 100ng/5μl), atosiban (ATO; 4.3μg/5μl) as oxytocin antagonist, ATO+OT] and stressed rats [St: stress, OT+St, ATO+St]. After anesthesia, hearts were isolated and subjected to 30min regional ischemia and 60min reperfusion (IR). Acute stress protocol included swimming for 10min before anesthesia. Myocardial function, infarct size, coronary flow, ventricular arrhythmia, and biochemical parameters such as creatine kinase and lactate dehydrogenase were measured. Ischemia-induced ventricular arrhythmias were counted during the occlusion period. ResultsThe plasma levels of oxytocin and corticosterone were significantly elevated by stress. Unexpectedly hearts of stressed rats showed a marked depression of IR injury compared to control group. I.c.v. infusion of oxytocin mimicked the cardioprotective effects of stress, yet did not elevate plasma oxytocin level. The protective effects of both stress and i.c.v. oxytocin were blocked by i.c.v. oxytocin antagonist. ConclusionsThese findings suggest that i.c.v. infusion of exogenous oxytocin and centrally released endogenous oxytocin in response to stress could play a role in induction of a preconditioning effect in ischemic-reperfused rat heart via brain receptors.

Poly(ADP-ribose) polymerase inhibition prevents reactive oxygen species induced inhibition of aldehyde dehydrogenase2 activity

Lipid peroxidation plays a critical role in cardiovascular diseases. Aldehydes are the major end products of lipid peroxidation and can be metabolized into less reactive chemical species by aldehyde dehydrogenase 2 (ALDH2). However, ALDH2 dehydrogenase activity can be affected by many factors including reactive oxygen species. To elucidate how reactive oxygen species inhibit ALDH2 dehydrogenase activity, we stimulated human aortic endothelial cells (HAECs) with oxidized low-density lipoproteins (ox-LDL) and performed a myocardial ischemia–reperfusion model. Ox-LDL treatment and ischemia–reperfusion injury inhibited ALDH2 dehydrogenase activity. Poly(ADP-ribose) polymerase (PARP) was activated by ox-LDL stimulation and ischemia–reperfusion injury and PARP inhibition partly restored ALDH2 dehydrogenase activity in ox-LDL treated HAECs and ischemia–reperfusion rat hearts. SIRT3 was upregulated by ox-LDL stimulation and ischemia–reperfusion injury and downregulated by PARP inhibition. Using siRNA to knock down SIRT3, we demonstrated that SIRT3 mediated deacetylation decreased ALDH2 dehydrogenase activity and PARP inhibition partly restored ALDH2 dehydrogenase activity through preventing SIRT3 expression and subsequently preserving ALDH2 acetylation.

Diabetes mellitus attenuates myocardial preconditioning of desflurane in ischemia-reperfused rat heart

Desflurane has been commonly used in anesthesia that possesses a cardioprotective effect against ischemia-reperfusion. We evaluated whether diabetes mellitus affected desflurane preconditioning induced cardioprotection in ischemia-reperfusion rat hearts in view of pro- and anti-apoptotic signaling pathways and Ca2+ homeostasis. Streptozotocin-induced, diabetic rats and age-matched wild-type Sprague-Dawley rats were subjected to a left anterior descending coronary artery occlusion for 30 min followed by 1 hr of reperfusion. Myocardial infarct size, activities of Akt, ERK1/2, Bcl-2, Bax and cytochrome c, and gene expression influencing Ca2+ homeostasis were examined. Desflurane preconditioning significantly reduced myocardial infarct size compared to ischemia-reperfusion in wild-type rats but not in diabetic rats. In addition, decrease in Akt, ERK1/2, and Bcl-2, and the increase in Bax and cytochrome c by ischemia-reperfusion was reduced by desflurane preconditioning. In diabetic rat hearts, however, desflurane preconditioning failed to recover the phosphorylation state of Akt and ERK1/2 and to repress apoptotic signaling in association with impoverished modulation of abnormal changes in sarcoplasmic reticulum proteins in ischemia-reperfusion rat hearts. These results suggest that diabetes mellitus attenuated desflurane preconditioning against ischemia-reperfusion, which might be associated with reduced recovery of the activities of proteins involved in anti-apoptotic signaling pathways and sarcoplasmic reticulum.

Effects of 7-hydroxycoumarin (umbelliferone) on isolated perfused and ischemic-reperfused rat heart

7-Hydroxycoumarin (CAS 93-35-6, 7-HC) is the main coumarin (1,2-benzopyrone) metabolite and the therapeutic active molecule. It exhibits antioxidant properties in vitro and may share with other coumarin derivatives vasodilator effects. The aim of the study was to assess the effects of 7-HC on isolated perfused and ischemic-reperfused rat heart. After a 10-min perfusion, an increase in the coronary flow was observed with 7-HC at 10(-4) mol/l (p = 0.002) as well as an increase in left ventricular developed pressure with 7-HC at 10(-5) mol/l (p = 0.038). The increase in coronary flow is not solely explained by the increase in inotropism. It appears to be also induced through a direct vasodilator effect which, however, does not involve the release of vasodilator prostaglandins since it was not inhibited by indometacin. After the 30-min global ischemia and the 45-min reperfusion period, 7-HC at 10(-5) mol/l induced an increase in left ventricular developed pressure (p = 0.042) and in the ratio of heart rate x left ventricular developed pressure over oxygen consumption (p = 0.036).

Marital status in relation to case fatality after myocardial infarction — A population based study

Objective: Aquaporin-1 (AQP1), which was present in both human and rat hearts, mediated the water transport, however, Xinshuitong capsule (XC), an aquaretic herbal compound, whether affects AQP1 pathway remains unclear.Materials and methods: 20 male Sprague– Dawley rats (280±83 g) underwent 30 min ischemia by ligation of anterior coronary artery followed by 2 h reperfusion. Animals were randomly treated with XC (0.5 g/kg i.p, during ischemia and reperfusion) or vehiclewith 5 sham rats as controls. The animalswere killed at 1, 2, 4, 8 and 16 h after surgery. In vitro, AQP1 gene in cardiomyocytes was knocked down or underwent hypoxia/reoxygenation exposed to XC (10, 20, 40 and 80 μg/mL). The ultrastructure of cardiomyocytes was observedby transmission electronmicroscope. AQP1 inmRNAand protein expressions were determined for all hearts by laser confocal fluorescence microscopy. Results: Vehicle rats showed a prominent cells edema, mitochondrial swelling associated with crest and membrane disruption with abundant lipid-like structures in the cytoplasm at 1–4 h, and a high incidence of plasmamembrane rupture at 8–16 h. With an increase in cell volume, a higher fluorescence of AQP1 was detected in the ischemic center and the border zone than in the noninfarcted area. By contrast, XC can significantly ameliorate cells morphology in vivo and in vitro. Compared to the controls, the XC-treated cells showed more tolerant to hypoxic stress, which related to XC dosage in the hypoxia–reoxygenation experiments. XC can further significantly up-regulate AQP1 mRNA and its protein expressions in the XC-treated rat hearts. Identical results were also detected in the XC-treated hypoxia–reoxygenation cells with a marked increase in AQP1 mRNA and its protein than the control. Knocked down gene AQP1, XC presented little effect on the change in cell size. Conclusions: The data suggest that XC canpreserve the profile of cardiomyocytes via up-regulation of AQP1pathway in the ischemia–reperfusion rat hearts.

Xinshuitong capsule ameliorates hypertrophy of cardiomyocytes via aquaporin pathway in the ischemia–reperfusion rat hearts

Objective: Aquaporin-1 (AQP1), which was present in both human and rat hearts, mediated the water transport, however, Xinshuitong capsule (XC), an aquaretic herbal compound, whether affects AQP1 pathway remains unclear.Materials and methods: 20 male Sprague– Dawley rats (280±83 g) underwent 30 min ischemia by ligation of anterior coronary artery followed by 2 h reperfusion. Animals were randomly treated with XC (0.5 g/kg i.p, during ischemia and reperfusion) or vehiclewith 5 sham rats as controls. The animalswere killed at 1, 2, 4, 8 and 16 h after surgery. In vitro, AQP1 gene in cardiomyocytes was knocked down or underwent hypoxia/reoxygenation exposed to XC (10, 20, 40 and 80 μg/mL). The ultrastructure of cardiomyocytes was observedby transmission electronmicroscope. AQP1 inmRNAand protein expressions were determined for all hearts by laser confocal fluorescence microscopy. Results: Vehicle rats showed a prominent cells edema, mitochondrial swelling associated with crest and membrane disruption with abundant lipid-like structures in the cytoplasm at 1–4 h, and a high incidence of plasmamembrane rupture at 8–16 h. With an increase in cell volume, a higher fluorescence of AQP1 was detected in the ischemic center and the border zone than in the noninfarcted area. By contrast, XC can significantly ameliorate cells morphology in vivo and in vitro. Compared to the controls, the XC-treated cells showed more tolerant to hypoxic stress, which related to XC dosage in the hypoxia–reoxygenation experiments. XC can further significantly up-regulate AQP1 mRNA and its protein expressions in the XC-treated rat hearts. Identical results were also detected in the XC-treated hypoxia–reoxygenation cells with a marked increase in AQP1 mRNA and its protein than the control. Knocked down gene AQP1, XC presented little effect on the change in cell size. Conclusions: The data suggest that XC canpreserve the profile of cardiomyocytes via up-regulation of AQP1pathway in the ischemia–reperfusion rat hearts.

Delayed Preconditioning by Sevoflurane Elicits Changes in the Mitochondrial Proteome in Ischemia-Reperfused Rat Hearts

Delayed myocardial preconditioning by volatile anesthetics involves changes in DNA transcription and translation. Mitochondria play a central role in myocardial ischemia/reperfusion (I/R) injury and in ischemic or pharmacologic preconditioning. In this study, we investigated whether there are alterations in myocardial mitochondrial protein expression after volatile anesthetic preconditioning (APC) to examine the underlying mechanisms of delayed cardioprotection. Thirty-six Sprague-Dawley rats were randomly assigned to 1 of 3 groups (n = 12 for each group). Rats in the delayed APC group were exposed to sevoflurane (2.5% for 60 minutes) 24 hours before myocardial ischemia was induced. Myocardial ischemia in the I/R and APC groups was induced by left coronary artery occlusion for 30 minutes, followed by 120 minutes of reperfusion. The control group received no treatment. The mitochondria fractions were prepared by differential centrifugation with density gradient isolation for proteomic analysis. Two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry was used to identify differences in the protein expression from mitochondria of the rat hearts. Fifteen differentially expressed mitochondrial proteins between the APC group and I/R group were identified and the expression patterns of 2 of the proteins were confirmed by Western blot analysis. These proteins were associated with mitochondrial substrate metabolism, respiration, and adenosine triphosphate (ATP)/adenosine diphosphate transport. The modifications of the mitochondrial proteome suggest an enhanced capacity of mitochondria to maintain myocardial ATP levels after I/R injury. Delayed sevoflurane myocardial preconditioning induces mitochondrial proteome remodeling, which mainly involves proteins that are related to ATP generation and transport. Therefore, proteomic changes related to bioenergetic balance may be the mechanistic basis of delayed anesthetic myocardial preconditioning.

Involvement of calcineurin in ischemic myocardial damage

Calcineurin (CaN) has been reported as a critical mediator for cardiac hypertrophy and cardiac myocyte apoptosis. Ischemia is associated with multiple alterations in the extracellular and intracellular signaling of cardiomyocytes and may act as an inducer of apoptosis. Rat ischemic heart showed significant increase in CaN activity. In ischemic-reperfused hearts, the expression of CaN A was significantly low and immunoreactivity was observed in proteolytic bands of 46 kDa. Immunohistochemical studies showed strong staining of immunoreactivity in rat hearts that had undergone 30 minutes of ischemia followed by 30 minutes of reperfusion, similar to that found in human ischemic heart. To elucidate the mechanism of proteolysis of CaN A in ischemic-reperfused rat heart, in vitro proteolysis of bovine cardiac CaN by m-calpain was carried out. In the presence of Ca2+, the 60−kDa subunit (CaN A) was degraded to a 46-kDa immunoreactive fragment, whereas in the presence of Ca2+/CaM, immunoreactive fragments of 48 and 54 kDa were observed. Calpains are Ca2+-dependent cysteine proteases that regulate various enzymes, transcription factors, and structural proteins through limited proteolysis. The increase in CaN activity and strong immunostaining observed in ischemic-reperfused rat heart may be due to the calpain-mediated proteolysis of this CaM-dependent phosphatase. These studies remain an important area of in-depth investigation.

Effects of des-aspartate-angiotensin I on myocardial ischemia-reperfusion injury in rats

The present study investigated the actions of des-aspartate-angiotensin I (DAA-I) on infarct size and three early inflammatory events in acute myocardial ischemia-reperfusion injury in rats. The rationale was based on earlier findings showing that chronic daily administration of DAA-I attenuated infarct size of ischemic-reperfused rat heart, and cardiac hypertrophy in pressure overload rats. Anesthetized rats were subjected to 45 min of ischemia and 5 h of reperfusion. Infarcted area, serum creatine kinase, and tissue myeloperoxidase activity were determined. The expression of intercellular adhesion molecule-1 (ICAM-1) was also investigated by immunohistochemistry and Western blotting. Intravenous administration of DAA-I at 5 min post reperfusion reduced myocardial infarct size by 45.5%, lowered serum creatine kinase activity, decreased myeloperoxidase activity in cardiac tissue, and inhibited the expression of ICAM-1 in cardiac capillary endothelium. The maximum effective dose was 1013 pmol/kg, and the cardioprotective actions of DAA-I were blocked by indomethacin. The data showed that the cardioprotection accorded by DAA-I was the result of its anti-inflammatory actions on early inflammatory processes in myocardial ischemia-reperfusion injury. The anti-inflammatory processes were indomethacin sensitive and probably mediated by prostaglandins.

The effects of fentanyl combined with sevoflurane postconditioning on myocardial functions of isolated ischemia-reperfused rat heart

Objective To investigate the effects of fentanyl combined with sevoflurane postconditioning on myocardial functions of isolated ischemia-reperfused rat hearts.Methods Depending on the different treatments given at 10 min after reperfusion started,isolated perfused rat hearts were randomly assigned to the following four groups(n=10):ischemia/reperfusion (Con),sevoflurane postconditioning (SPC),fentanyl postconditioning (Fent),and fentanyl plus sevoflurane postconditioning (Fent+SPC). All of the hearts were subjected to 40 min global myocardial ischemia and 120 min reperfusion. Left ventricular systolic pressure(LVSP),Left ventricular developed pressure (LVDP),maximum increasing rate of LVDP(+dp/dt),maximum decreasing rate of LVDP (-dp/dt),heart rate (HR) and coronary flow (CF) were recorded. Lactate dehydrogenase(LDH) was measured. Infarct size was determined by triphenyltetrazolium chloride staining.Results LVSP,LVDP,±dp/dt,and CF were higher in SPC group than in Con group at all points of reperfusion (P＜0.05). Compared with SPC group,the Fent and Fent+SPC group (P＜0.05) had significantly improved LVSP and LVDP at the beginning 15 min of reperfusion,which were gradually reduced and lower than SPC group at all time points after 60 min of reperfusion. There were no significant diffirences in HR among four groups. The values of ±dp/dt and CFin Fent and Fent+SPC group were dramatically improved in the early stage of reperfusion(P＜0.05),while similar to the Con group at the end of reperfusion. The SPC,Fent and Fent+SPC group had a significantly reduced LDH release and decreased infarct size compared with the Con group [(22.7±2.3)%, (20.6±2.8)%, (21.3±3.3)% vs.(45.8±3.2)%,respectively; P＜0.05).Conclusion Sevoflurane postconditioning improves myocardial Key words: Sevoflurane; Fentanyl; Postconditioning; Ischemia/Reperfusion; Myocardial function

BAS/BSCR34 Is an increased AMPK activation during ischaemia essential for the protection of the heart against infarction?

BackgroundDuring ischaemia, AMPK activation occurs in order to provide energy from alternative resources. However, AMPK activity is known to be impaired in diabetes. We hypothesised that enhancing AMPK activation above...