ucn-1028-c and Myocardial-Infarction

We have previously reported that brief pressure overload of the left ventricle reduced myocardial infarct (MI) size. However, the role of protein kinase C (PKC) remains uncertain. In this study, we investigated whether pressure overload reduces MI size by activating PKC.. MI was induced by a 40-minute occlusion of the left anterior descending coronary artery and a 3-hour reperfusion in anesthetized Sprague-Dawley rats. MI size was determined using triphenyl tetrazolium chloride staining. Brief pressure overload was achieved by two 10-minute partial snarings of the ascending aorta, raising the systolic left ventricular pressure 50% above the baseline value. Ischemic preconditioning was elicited by two 10-minute coronary artery occlusions and 10-minute reperfusions. Dimethyl sulfoxide (vehicle) or calphostin C (0.1 mg/kg, a specific inhibitor of PKC) was administered intravenously as pretreatment.. The MI size, expressed as the percentage of the area at risk, was significantly reduced in the pressure overload group and the ischemic preconditioning group (19.0 ± 2.9% and 18.7 ± 3.0% vs. 26.1 ± 2.6% in the control group, where p < 0.001). Pretreatment with calphostin C significantly limited the protection by pressure overload and ischemic preconditioning (25.2 ± 2.4% and 25.0 ± 2.3%, where p < 0.001). Calphostin C itself did not significantly affect MI size (25.5 ± 2.4%). Additionally, the hemodynamics, area at risk, and mortality were not significantly different.. Brief pressure overload of the left ventricle reduced MI size. Since calphostin C significantly limited the decrease of MI size, our results suggested that brief pressure overload reduces MI size via activation of PKC.

Topics: Animals; Enzyme Activation; Heart Ventricles; Hemodynamics; Ischemic Preconditioning, Myocardial; Male; Myocardial Infarction; Naphthalenes; Pressure; Protein Kinase C; Rats; Rats, Sprague-Dawley

Although hypoxic late preconditioning (LPC) limits ischemia-reperfusion injury in vitro, its cardioprotective effect is not established in vivo.. In part 1, rats were exposed to 4 h of hypoxia (16%, 12%, 8% oxygen) before 24 h of reoxygenation. In part 2, normoxic rats received early preconditioning with sevoflurane (1 minimum alveolar concentration [MAC] for 3 × 5 min), continuous administration of 1 MAC sevoflurane, or 11 mg · kg · h propofol. Thereafter, all rats underwent 25 min of regional myocardial ischemia and 120 min of reperfusion. After reperfusion, hearts were excised for infarct staining. The expression of protein kinase C (PKC)α and PKCε was assessed by Western blot analysis and the expression of heme oxygenase-1 and vascular endothelial growth factor by reverse transcriptase polymerase chain reaction.. In normoxic control rats, infarct size was 62 ± 6% of the area at risk. Hypoxic LPC reduced infarct size (LPC16: 36 ± 11%, LPC12: 38 ± 10%, LPC8: 39 ± 11%; each P < 0.001) to approximately the same magnitude as sevoflurane-preconditioning (40 ± 8%; P < 0.001). Combined LPC16 and sevoflurane preconditioning was not superior to either substance alone. Continuous sevoflurane or propofol was not protective. The PKC inhibitor calphostin C abolished the cardioprotective effects of LPC16. PKCε, but not PKCα, expression was increased 6 and 28 h after hypoxic LPC. Heme oxygenase-1 and vascular endothelial growth factor were transiently up-regulated after 6 h.. Hypoxic LPC at 8%, 12%, and 16% oxygen reduces infarct size in the rat heart in vivo. This effect is as powerful as sevoflurane-preconditioning. PKCε is a key player in mediating hypoxic LPC.

Topics: Anesthetics, Inhalation; Animals; Blotting, Western; Enzyme Inhibitors; Heart; Heme Oxygenase (Decyclizing); Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Ischemic Preconditioning, Myocardial; Methyl Ethers; Myocardial Infarction; Myocardial Reperfusion Injury; Naphthalenes; Oxygen; Protein Kinase C-alpha; Protein Kinase C-epsilon; Rats; Reverse Transcriptase Polymerase Chain Reaction; Sevoflurane; Vascular Endothelial Growth Factor A

The aim of this study was to determine the role of an a disintegrin and metalloprotease (ADAM) in tyrosine kinase-mediated mechanisms of ischemic preconditioning (PC).. In isolated rabbit hearts, PC was performed with two cycles of 5 min ischemia/5 min reperfusion and infarction was induced by 30 min global ischemia/2 h reperfusion. Translocation of protein kinase C- (PKC-) and tyrosine phosphorylation in the tissue and TNF-alpha in coronary effluent were determined by immunoblotting. PC reduced infarct size from 55.1+/-6.8% of the left ventricle to 24.4+/-5.2%, and this protection was mimicked by pretreatment with 100 nM angiotensin II. Both the PC effect and angiotensin II-induced protection were abolished by genistein and by 10 microM KB-R7785 (KBR), an inhibitor of ADAM12/17, but not by a lower ADAM12-selective dose (1 microM) of KBR. AG1478, an inhibitor of EGF receptor tyrosine kinase, did not inhibit protection afforded by PC. PC provoked release of TNF-alpha into the coronary effluent, which was abolished by 10 microM KBR but not by 1 microM of KBR or calphostin C, a PKC inhibitor. PKC- translocation by PC was not affected by KBR. PC induced tyrosine phosphorylation of 60 and 90 kDa proteins, and this phosphorylation was abolished by 10 microM KBR but not by calphostin C. Pretreatment with TNF-alpha limited infarct size to 16.7+/-3.7% and induced tyrosine phosphorylation of a 60 kDa protein.. The results support the hypothesis that an ADAM contributes to the triggering of a tyrosine kinase-mediated and PKC-independent pathway of PC. The ADAM responsible for this tyrosine kinase-mediated pathway is likely to be ADAM17, which sheds TNF-alpha.

Topics: ADAM Proteins; ADAM17 Protein; Angiotensin II; Animals; Cyclic AMP-Dependent Protein Kinases; Dose-Response Relationship, Drug; Genistein; Glycine; Hydroxamic Acids; Immunoblotting; Ischemic Preconditioning, Myocardial; Metalloendopeptidases; Myocardial Infarction; Naphthalenes; Perfusion; Phosphorylation; Protein-Tyrosine Kinases; Rabbits; Signal Transduction; Tumor Necrosis Factor-alpha

Protein kinase C (PKC) has been known to play an important role in ischemic preconditioning (IP). This study was designed to examine whether the translocation of PKC is associated with the cardioprotective effects of IP in vivo on infarct size and ventricular arrhythmias in a rat model. Using anesthetized rats, heart rate, systolic blood pressure, infarct size and ventricular arrhythmias during 45 min of coronary occlusion were measured. PKC activity was assayed in both the cytosolic and cell membrane fraction. Brief 3-min periods ofischemia followed by 10 min ofreperfusion were used to precondition the myocardium. Calphostin C was used to inhibit PKC. Infarct size was significantly reduced by IP (68.1 (2.5)%, mean (S.E.) vs. 45.2 (3.4)%, p < 0.01). The reduction in infarct size by IP was abolished by pretreatment with calphostin C. The total number of ventricular premature complex (VPC) during 45 min of coronary occlusion was reduced by IP (1474 (169) beats/45 min vs. 256 (82) beats/45 min, p < 0.05). The reduction the total number of VPC induced by IP was abolished by the administration of calphostin C before the episode of brief ischemia. The same tendency was observed in the duration of ventricular tachycardia and the incidence of ventricular fibrillation. PKC activity in the cell membrane fraction transiently increased immediately after IP (100 vs. 142%, p < 0.01) and returned to baseline 15 min after IP. Pretreatment with calphostin C prevented the translocation of PKC. The translocation of PKC plays an important role in the cardioprotective effect of IP on infarct size and ventricular arrhythmias in anesthetized rats.

Topics: Animals; Arrhythmias, Cardiac; Biological Transport, Active; Cell Membrane; Cytosol; Enzyme Inhibitors; Hemodynamics; Ischemic Preconditioning, Myocardial; Male; Myocardial Infarction; Naphthalenes; Protein Kinase C; Rats; Rats, Sprague-Dawley

The aim was to further characterise an experimental model of preconditioning of isolated rabbit cardiomyocytes and to determine the role of adenosine receptor subtypes in initiation of the protective response.. Isolated myocytes were subjected to 5 min preincubation in the presence or absence of glucose and various agonists and antagonists of adenosine receptors. Ischaemic pelleting was preceded by a 30 min postincubation period. Rate and extent of injury during ischaemia was determined by sequential sampling of the pelleted cells and assessment of trypan blue permeability following 85 mOsm swelling.. Myocytes were preconditioned with a 30-50% reduction of injury by a 5 min glucose-free preincubation. Substitution of 5 mM pyruvate for glucose during preincubation did not prevent the protective response. Protection was maintained over a 60-180 min postincubation period. Protection was blocked by 100 microM of the non-specific adenosine A1/A2 antagonist SPT, both when added only during preincubation or only into the ischaemic pellet. Calphostin C, a specific protein kinase C inhibitor at 200 nM, added to the ischaemic pellet blocked protection. Preincubation with R-PIA, the adenosine A1 agonist, did not precondition at an A1 selective dose of 1 microM, but did at 100 microM. The selective A2 agonist CGS 12680 (1 microM) did not precondition. The selective A1/A3 adenosine agonist, APNEA, preconditioned at 1 microM and 200 nM dose levels. Preconditioning induced either by 200 nM APNEA or by glucose-free preincubation was not blocked by 200 nM or 10 microM of the A1 antagonist DPCPX, which has extremely low affinity for A3 receptors, but was blocked by 1 microM of the A1/A3 adenosine antagonist BW 1433U83.. Preconditioning can be induced in isolated myocytes by a 5 min preincubation/30 min postincubation protocol, and a similar protection induced by adenosine agonists with A3, but not A1 selectivity. Preconditioning is blocked by non-selective or selective A1/A3 adenosine antagonists and a specific protein kinase C inhibitor, but not by A1 antagonists with little affinity for A3 receptors. The results suggest that preconditioning in isolated rabbit myocytes requires participation of adenosine receptors with agonist/antagonist binding characteristics of the A3 subtype, and is likely to be mediated by activation of protein kinase C.

Topics: Adenosine; Animals; Antihypertensive Agents; Cells, Cultured; Glucose; Myocardial Infarction; Myocardial Ischemia; Myocardium; Naphthalenes; Phenethylamines; Phenylisopropyladenosine; Polycyclic Compounds; Protein Kinase C; Purinergic Antagonists; Pyruvates; Pyruvic Acid; Rabbits; Receptors, Purinergic P1; Theophylline; Time Factors; Trypan Blue; Xanthines