To elucidate the mechanism of arrhythmia in healed myocardial infarction (HMI), the changes of action potential duration (APD), transient outward potassium current (Ito), delayed rectifier potassium current (IK) and inward rectifier potassium current (IK1) of left ventricular myocytes in non-infarcted zone of HMI were investigated. Rabbits were randomly assigned into two groups: HMI group, in which animals were subjected to thoracotomy and ligation of the circumflex coronary and sham-operated group, in which rabbits underwent thoracotomy but no conorary ligation. 3 months after the operation, the whole myocyte patch clamp technique was used to record APD, Ito, IK, and IK1 of ventricular myocytes in non-infarcted zone. Our results showed that the membrane capacitance was larger in HMI group than in sham-operated group. Action potential duration was significantly lengthened in HMI group and early afterdepolarization (EAD) appeared in HMI group. The densities of Ito, I(K, tail), and IK1 were reduced significantly in HMI group, from 6.72 +/- 0.42 pA/pF, 1.54 +/- 0.13 pA/pF and 25.6 +/- 2.6 pA/pF in sham-operated group to 4.03 +/- 0.33 pA/pF, 1.14 +/- 0.11 pA/pF and 17.6 +/- 2.3 pA/pF, respectively. It is concluded that the reduced densities of Ito, I(K, tail) and IK1 in ventricular myocytes of non-infarcted zone in HMI were responsible for the prolongation of APD and the presentation of EAD which played important roles in the development of malignant arrhythmia in HMI.
Action Potentials ; Arrhythmia/*etiology ; Heart Ventricles/metabolism ; Myocardial Infarction/complications ; Myocardial Infarction/metabolism ; Myocardial Infarction/*pathology ; Myocytes, Cardiac/*cytology ; Patch-Clamp Techniques ; Potassium Channels/*metabolism

OBJECTIVETo investigate the role of gap junction in ischemic preconditioning (IPC).

METHODSSprague-Dawley rats were subjected to a 30 min coronary artery occlusion followed by 4 h of reperfusion (I/R). Rats were divided into seven groups: I/R, IPC/R, IPC/R + 5-hydroxydecanoic acid (mitochondrial ATP sensitive potassium channel antagonist), I/R + diazoxide (mitochondrial ATP sensitive potassium channel agonist), I/R + 5-hydroxydecanoic acid + diazoxide, I/R + 18beta-glycyrrhetinic acid (gap junction blocker) and I/R + 18beta-glycyrrhetinic acid + 5-hydroxydecanoic acid. Hemodynamics and myocardial infarct size were measured and connexin43 phosphorylation and subcellular distribution were determined by quantitative immunoblotting and confocal immunofluorescence.

RESULTSInfarct size was reduced in IPC/R, I/R + diazoxide and I/R + 18beta-glycyrrhetinic acid group (13.34% +/- 7.87%, 11.02% +/- 2.24%, and 15.03% +/- 11.35%, respectively; P < 0.001 vs. I/R group: 45.81% +/- 7.91%). 5-hydroxydecanoic acid abolished the cardioprotective effects of IPC and diazoxide (46.57% +/- 5.36% and 47.36% +/- 3.17%; P > 0.05 vs. I/R) but not the effects of glycyrrhetinic acid (14.60% +/- 7.36%; P < 0.001 vs. I/R). Phosphorylation of connexin43 was significantly increased, dephosphorylation and connexin43 intracellular redistribution significantly decreased (Cx43 size in the cellular membrane 1.00% +/- 0.35% and 0.83% +/- 0.31%, P < 0.001 vs. I/R: 0.19% +/- 0.06%) by IPC and diazoxide and these effects could be abolished by 5-hydroxydecanoic acid.

CONCLUSIONIschemic preconditioning could reduce myocardial infarction size by activating mitochondrial ATP sensitive potassium channel and modulating connexin43 phosphorylation and internalization.

Animals ; Connexin 43 ; metabolism ; Gap Junctions ; physiology ; Ischemic Preconditioning, Myocardial ; Male ; Myocardial Infarction ; metabolism ; pathology ; Phosphorylation ; Rats ; Rats, Sprague-Dawley

BACKGROUNDIt has been found that cardiac protection afforded by ischemic preconditioning (IPC) is significantly reduced in the senescent myocardium. ADAMTS-1 (a disintesrin and metalloprotease with thrombospondin type 1 motifs) has been shown to inhibit angiogenesis in a variety of in vitro and in vivo assays. The aim of this study was to investigate the age-associated differences in ADAMTS-1 protein expression in rat myocardium after ischemic preconditioning.

METHODSSixty-four young (4 months) and old (24 months) male Sprague-Dawley rats were randomly assigned to an IPC group (40 rats) or a sham group (rats). A model of delayed IPC was induced and rats were sacrificed and myocardial samples were harvested from the ischemic-reperfused region for immunohistochemical detection of ADAMTS-1 at serial time points after IPC. A model of myocardial infarction was produced by ligation of the left anterior descending coronary artery in additional sets of young and old rats after sham or IPC procedures, then age-associated myocardial infarction survival after IPC was calculated.

RESULTSADAMTS-1 expression increased significantly in old rats compared to young rats (P < 0.05). The mean densities of ADAMTS-1 protein at 0, 6, 12, and 24 hours in young-IPC group after IPC were 0.05 ± 0.01, 0.13 ± 0.03, 0.16 ± 0.04, and 0.12 ± 0.03 vs. 0.07 ± 0.03, 0.20 ± 0.03, 0.24 ± 0.05, and 0.21 ± 0.04 in old-IPC group. IPC resulted in diminished survival rates (5/35 vs. 6/14, old-IPC group vs. old-sham group, P < 0.05), reduced left ventricular fractional shortening ((13.9 ± 2.8)% vs. (18.3 ± 2.3)%, P < 0.05) and increased the myocardial infarction size ((37.9 ± 3.2)% vs. (32.8 ± 5.1)%, P < 0.05) in the older rats.

CONCLUSIONSCardioprotection with IPC is attenuated in the older heart. ADAMTS-1 expression induced by IPC is greater in old rats. Over-expression of anti-angiogenic factors might be a potential mechanism behind reduced protection after IPC associated with aging.

ADAM Proteins ; metabolism ; ADAMTS1 Protein ; Aging ; metabolism ; physiology ; Animals ; Immunohistochemistry ; Ischemic Preconditioning, Myocardial ; Male ; Myocardial Infarction ; metabolism ; pathology ; Myocardium ; metabolism ; pathology ; Rats ; Rats, Sprague-Dawley

OBJECTIVESTo analyze the relationship between oxidized low density lipoprotein (oxLDL), angiogenesis and stabilization of atherosclerotic plaques in human coronary arteries; and to investigate the role of oxLDL in creating vulnerable sites in atherosclerotic plaques.

METHODSSamples of coronary arteries were obtained at autopsies of 42 patients with acute coronary syndrome. Eighty randomly selected blocks were studied by immunohistochemistry using antibodies against oxLDL and endothelial cells (factor VIII). Computer-aided planimeter was used for quantitative analysis.

RESULTSIn unstable plaques, percentage of immunoreactive areas for oxLDL was significantly higher than that in stable plaques. Most of the oxLDL were located in shoulder region of these plaques, as compared to the fibrous cap and basal regions. The details of distribution of oxLDL were as follows: shoulder region (20.43 +/- 3.12 for unstable plaques and 17.65 +/- 4.22 for stable plaques), fibrous cap (4.77 +/- 2.03 for unstable plaque and 2.80 +/- 0.22 for stable plaques) and basal region (5.65 +/- 1.65 for unstable plaques and 3.22 +/- 1.02 for unstable plaques). OxLDL was also a main component in the lipid core. In the shoulder region, there was a significant positive correlation between neovascularization and oxLDL (r = 0.8247, P = 0.000).

CONCLUSIONSThe amount of oxLDL is significantly higher in unstable atherosclerotic plaques, especially over the shoulder region. OxLDL in coronary atherosclerotic plaques is thus an important factor in determining stabilization of the plaques. OxLDL may induce influx of inflammatory cells which subsequently leads to decreased plaque stabilization.

Angina, Unstable ; metabolism ; pathology ; Coronary Artery Disease ; metabolism ; pathology ; Humans ; Immunohistochemistry ; Lipoproteins, LDL ; metabolism ; Myocardial Infarction ; metabolism ; pathology ; Neovascularization, Pathologic ; metabolism ; pathology

Recent studies demonstrated that brief period of Ca2+ depletion and repletion (Ca2+ preconditioning, CPC) has strong protective effects against ischemia in a rat heart. CPC and classic preconditioning (IPC) were compared in relation with infarct size and protein kinase C (PKC) isozymes. Isolated Langendorff-perfused rabbit hearts were subjected to 45-min ischemia (Isc) followed by 120-min reperfusion (R) with or without IPC, induced by 5-min Isc and 10-min R. In the CPC hearts, 5-min Ca2+ depletion and 10-min repletion (CPC) were given before 45-min Isc, with or without concurrent PKC inhibition (calphostin C, 200 nmol/L). IPC enhanced recovery of LV function, while CPC did not. Infarct size was significantly reduced by both CPC and IPC (p < 0.05 vs. ischemic control). Membrane PKC was significantly increased from 2.53 +/- 0.07 (baseline, nmol/g tissue) to 3.11+/-0.07, 3.34 +/- 0.11, 3.15 +/- 0.09, and 3.06 +/- 0.08 by IPC, IPC and 45-min Isc, CPC and 45-min Isc, respectively (p < 0.01). Immunoblots of membrane PKC were increased by IPC, IPC and 45-min Isc, and CPC. These effects were abolished by PKC inhibition. Thus, activation of PKC may have trigger role in the mechanism of cardioprotective effect by CPC.
Animals ; Calcium/*pharmacology ; Cardiotonic Agents/*pharmacology ; In Vitro ; *Ischemic Preconditioning, Myocardial ; Isoenzymes/metabolism ; L-Lactate Dehydrogenase/metabolism ; Male ; Myocardial Infarction/*pathology ; Myocardium/enzymology/pathology ; Protein Kinase C/metabolism ; Rabbits

OBJECTIVETo establish a flow cytometric method to detect the alteration of phenotypes and concentration of circulating microvesicles (MVs) from myocardial ischemic preconditioning (IPC) treated rats (IPC-MVs), and to investigate the effects of IPC-MVs on ischemia/reperfusion (I/R) injury in rats.

METHODSMyocardial IPC was elicited by three.cycles of 5-min ischemia and 5-min reperfusion of the left anterior descending (LAD) coronary artery. Platelet-free plasma (PFP) was isolated through two steps of centrifugation at room temperature from the peripheral blood, and IPC-MVs were isolated by ultracentrifugation from PFR PFP was incubated with anti-CD61, anti-CD144, anti-CD45 and anti-Erythroid Cells, and added 1, 2 µm latex beads to calibrate and absolutely count by flow cytometry. For functional research, I/R injury was induced by 30-min ischemia and 120-min reperfusion of LAD. IPC-MVs 7 mg/kg were infused via the femoral vein in myocardial I/R injured rats. Mean arterial blood pressure (MAP), heart rate (HR) and ST-segment of electro-cardiogram (ECG) were monitored throughout the experiment. Changes of myocardial morphology were observed after hematoxylin-eosin (HE) staining. The activity of plasma lactate dehydrogenase (LDH) was tested by Microplate Reader. Myocardial infarct size was measured by TTC staining.

RESULTSTotal IPC-MVs and different phenotypes, including platelet-derived MVs (PMVs), endothelial cell-derived MVs (EMVs), leucocyte-derived MVs (LMVs) and erythrocyte-derived MVs (RMVs) were all isolated which were identified membrane vesicles (<1 Vm) with corresponding antibody positive. The numbers of PMVs, EMVs and RMVs were significantly increased in circulation of IPC treated rats (P<0.05, respectively). In addition, at the end of 120-min reperfusion in I/R injured rats, IPC-MVs markedly increased HR (P<0.01), decreased ST-segment and LDH activity (P < 0.05, P < 0.01). The damage of myocardium was obviously alleviated and myocardial infarct size was significantly lowered after IPC-MVs treatment (P < 0.01).

CONCLUSIONThe method of flow cytometry was successfully established to detect the phenotypes and concentration alteration of IPC-MVs, including PMVs, EMVs, LMVs and RMVs. Furthermore, circulating IPC-MVs protected myocardium against I/R injury in rats.

Animals ; Cell-Derived Microparticles ; metabolism ; Coronary Vessels ; pathology ; Flow Cytometry ; Heart Rate ; Ischemic Preconditioning, Myocardial ; Myocardial Infarction ; physiopathology ; Myocardial Reperfusion Injury ; physiopathology ; Myocardium ; pathology ; Phenotype ; Rats

Sudden cardiac death(SCD) from early myocardial ischemia is often lack of typically morphological findings and clinical manifestation, thus cases of SCD may be suspected as criminal cases. It is necessary to clarify the cause of death, which is significance for medico-legal investigation. This article reviewed the latest advancement in the studies on the application of inorganic ions, CK-MB, cTn, ANP and BNP for certification of death from SCD in order to provide a practical way for diagnosis of SCD in forensic pathology.
Atrial Natriuretic Factor/metabolism* ; Autopsy ; Biomarkers/metabolism* ; Calcium/metabolism* ; Cause of Death ; Creatine Kinase, MB Form/metabolism* ; Death, Sudden, Cardiac/pathology* ; Forensic Pathology ; Humans ; Myocardial Infarction/pathology* ; Myocardial Ischemia/pathology* ; Myocardium/pathology* ; Natriuretic Peptide, Brain/metabolism* ; Troponin/metabolism*

OBJECTIVEMyocardial edema plays an important role in the development of myocardial no-reflow and reperfusion injury after the revascularization of acute myocardial infarction (AMI). The present study investigated whether the effect of ischemic preconditioning (IPC) against myocardial no-reflow and reperfusion injury was related to the reduction of myocardial edema through the protein kinase A (PKA) pathway.

METHODSTwenty-four minipigs were randomized into sham, AMI, IPC, and IPC + H-89 (PKA inhibitor, 1.0 µg · kg(-1) · min(-1)) groups. The area of no-reflow (ANR), area of necrosis (AN), and water content in left ventricle and ischemic-myocardium and non-ischemic area were determined by pathological studies. Microvascular permeability was determined by FITC-labeled dextran staining. Cardiomyocyte cross-sectional area (CSA) and mitochondria cross-sectional area (MSA) were evaluated by histological analysis. Myocardial expression of aquaporins (AQPs) was detected by Western blot.

RESULTSCompared with the MI group, the sizes of no-reflow and infarct were reduced by 31.9% and 46.6% in the IPC group (all P < 0.01), water content was decreased by 5.7% and 4.6% in the reflow and no-reflow myocardium of the IPC group (all P < 0.05), microvascular permeability and cardiomyocytes swelling in the reflow area were inhibited by 29.8% and 21.3% in the IPC group (all P < 0.01), mitochondrial water accumulation in the reflow and no-reflow areas of the IPC group were suppressed by 45.5% and 34.8% respectively (all P < 0.01), and the expression of aquaporin-4, -8, and -9 in the reflow and no-reflow myocardium were blocked in the IPC group. However, these beneficial effects of IPC were partially abolished in the IPC + H-89 group.

CONCLUSIONSThe cardioprotective effects of IPC against no-reflow and reperfusion injury is partly related to the reduction of myocardial edema by inhibition of microvascular permeability and aquaporins up-regulation via PKA pathway.

Animals ; Aquaporins ; metabolism ; Capillary Permeability ; Cyclic AMP-Dependent Protein Kinases ; metabolism ; Edema ; metabolism ; pathology ; Ischemic Preconditioning ; Myocardial Infarction ; metabolism ; pathology ; Myocardial Reperfusion Injury ; metabolism ; pathology ; Myocardium ; metabolism ; pathology ; Swine ; Swine, Miniature

OBJECTIVE: To investigate the signification of CTnI in acute myocardial infarction. METHODS: The model of myocardial infarction was established by ligating the left ventricle branch. Immunohistochemistry and image analysis were used to detect the change of CTnI in the model, and The sensitivity of immunohistochemistry and HE coloration were also compared. RESULTS: The acute myocardial infarction tissue showed obvious depletion of CTnI, there was no characterization of myocardial infarction in HE coloration. CONCLUSION CTnI is sensitive to diagnosis of acute myocardial infarction.
Animals ; Antibodies, Monoclonal ; Disease Models, Animal ; Female ; Immunohistochemistry ; Male ; Myocardial Infarction/metabolism* ; Myocardial Ischemia/pathology* ; Myocardium/pathology* ; Rabbits ; Sensitivity and Specificity ; Time Factors ; Troponin I/metabolism*

OBJECTIVELeft ventricular remodeling (LVR) following myocardial infarction (MI) is a key pathophysiological process in which MI develops into heart failure. The exact mechanism of LVR remains unclear. We performed differential proteomic analysis on the myocardia of rats with LVR after MI, to explore the mechanism of ventricular remodeling after MI.

METHODSIn the LVR group (n = 12), after the anterior descending coronary artery was ligated, the rats were fed for four weeks before the LVR models were established. Rats in the sham-operated group (n = 11) underwent thread-drawing without ligation. The hemodynamic parameters, pathological findings, and proteomics were compared between the two groups.

RESULTSIn the LVR group, the left ventricular end-diastolic pressure increased, the maximal left ventricular pressure increase/decrease ratio decreased significantly, and the left ventricular systolic pressure decreased. H-E staining and Masson staining of cardiac muscle tissues of the LVR group showed myocytolysis, disarray, and collagen proliferation. Twenty-one differentially expressed proteins were detected by proteomic analysis. We validated two proteins using western blot analysis. The differentially expressed proteins could be divided into six categories: energy metabolism-related proteins, cytoskeletal proteins, protein synthesis-related proteins, channel proteins, anti-oxidation- related proteins, and immune-related proteins.

CONCLUSIONThese differentially expressed proteins might play key roles in LVR following MI.

Animals ; Male ; Myocardial Infarction ; complications ; pathology ; Myocardium ; metabolism ; pathology ; Proteome ; analysis ; Proteomics ; Rats ; Rats, Wistar ; Ventricular Remodeling