Attenuation of Myocardial Ischaemic Injury 24 h After Diacylglycerol TreatmentIn Vivo

doi:10.1006/jmcc.1997.0436

Journal of Molecular and Cellular Cardiology

Volume 29, Issue 7, July 1997, Pages 1967-1975

https://doi.org/10.1006/jmcc.1997.0436 Get rights and content

Abstract

Previous work suggests that delayed protection against infarction following ischaemic preconditioning of rabbit myocardium may involve the activation of protein kinase C (PKC). Preconditioning in the presence of chelerythrine, an inhibitor of PKC, abolished the late anti-infarct effect of preconditioning. In the studies described here, we tested the hypothesis that direct PKC activation with an analogue of diacylglycerol, the physiological activator of PKC, would invoke an adaptive mechanism leading to enhanced myocardial tolerance to ischaemia 24 h later. Rabbits were treated with i.v. injections of 1,2-dioctanoyl-sn-glycerol (DiC8) 5 mg/kg or 15 mg/kg or an equivalent volume of vehicle solution. Twenty-four h after pretreatment, the animals were anaesthetised and underwent 30 min coronary artery occlusion with 120 min reperfusion. Infarct size was determined by triphenyltetrazolium staining. In vehicle pretreated rabbits, infarct–risk zone ratio was 32.8±2.6%. Pretreatment with DiC8 5 mg/kg did not significantly affect infarct size (26.3±4.0%), but pretreatment with DiC8 15 mg/kg resulted in a marked reduction in infarct size (18.0±3.4%,P<0.05, 1-way ANOVA). Reduction in infarct size with the higher dose of DiC8 was independent of myocardial risk zone size and systemic haemodynamic parameters during coronary occlusion. The haemodynamic effects of acute administration of DiC8 15 mg/kg were examined in a separate cohort of pentobarbitone-anaesthetised rabbits. The compound was found not to affect systolic blood pressure or heart rate under these conditions. We examined the possibility that increased ischaemic tolerance might be due to induction of the 27 and 72 kDa heat shock proteins (hsp27 and hsp70i) which are known to be cytoprotective and are upregulated by ischaemia and other stressful stimuli. Western blot analysis of left ventricular tissue revealed that neither protein was induced 24 h after treatment with DiC8 15 mg/kg. Thus, infarct limitation 24 h after DiC8 treatment did not appear to be due to increased tissue content of these proteins. The mechanisms of DiC8-induced delayed myocardial protection remain unclear. However, these data are compatible with the hypothesis that activation of PKC isoenzymes is an important intermediate signal of sub-acute cellular adaptation, and results in enhanced tolerance to ischaemia-reperfusion injury in myocardium many hours later.

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Cited by (24)

Lipid partitioning during cardiac stress
2016, Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids
Citation Excerpt :
DAGs are a notorious activator of PKC signaling and PKC activation, primarily the PKCϵ isoform, has been implicated in cardioprotection from ischemia [104–106]. DAG analogs have been given in experimental I–R with some success [107,108]. From these limited studies, it remains to be seen whether the potential increase in DAG content during ischemia is beneficial or detrimental.
It is well documented that fatty acids serve as the primary fuel substrate for the contracting myocardium. However, extensive research has identified significant changes in the myocardial oxidation of fatty acids during acute or chronic cardiac stress. As a result, the redistribution or partitioning of fatty acids due to metabolic derangements could have biological implications. Fatty acids can be stored as triacylglycerols, serve as critical components for biosynthesis of phospholipid membranes, and form the potent signaling molecules, diacylglycerol and ceramides. Therefore, the contribution of lipid metabolism to health and disease is more intricate than a balance of uptake and oxidation. In this review, the available data regarding alterations that occur in endogenous cardiac lipid pathways during the pathological stressors of ischemia–reperfusion and pathological hypertrophy/heart failure are highlighted. In addition, changes in endogenous lipids observed in exercise training models are presented for comparison. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk.
Intracellular diglycerides in relation to glycaemic control in the myocardium: A pilot study in humans
2015, Diabetes and Metabolism
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Specifically to the myocardium, intracellular diglyceride pool may possess significant cardio-protective functions. For example, animal studies have found that diglycerides may be involved in ameliorating the myocardial dysfunction in streptozotocin-induced diabetes [8], or reduce infarcts size during ischemia-reperfusion injury [9,10]. To our best knowledge, no direct measurements of myocardial diglycerides in humans have ever been presented.
Intramyocellular diglycerides have been implicated in the development of insulin resistance in skeletal muscle. In the myocardium, excess lipid storage may also contribute to the appearance of diabetic cardiomyopathy, while diglycerides may have certain cardio-protective functions. However, little is known on intracellular diglyceride accumulation in the human heart. We aimed to determine diglyceride accumulation in the human myocardium in relation to diabetes status.
Six diabetic and six non-diabetic aged human subjects undergoing by-pass surgery participated in the study. Subjects were matched for age and body mass index. Intracellular diglyceride levels were measured in heart biopsy samples. Additional samples were taken from pectoralis major muscle that served as control. Whole body glycaemic control was assessed as the percent glycated haemoglobin.
Intracellular diglycerides were significantly higher in the myocardium compared to pectoralis major (P < 0.05). Although not statistically significant, diabetic subjects tended to accumulate smaller amounts of diglycerides compared to non-diabetic subjects in the myocardium. A linear negative correlation was observed between myocardial diglycerides and glycaemic control (r = 0.632, P < 0.05).
Our data suggest that poor glycaemic control and diabetes may be associated with a defective accumulation of myocardial diglycerides, possibly blunting intracellular processes and contributing to the development of cardiomyopathy.
Intermittent hypoxia-induced delayed cardioprotection is mediated by PKC and triggered by p38 MAP kinase and Erk1/2
2007, Journal of Molecular and Cellular Cardiology
Citation Excerpt :
We showed that IH-induced cardioprotection was abolished when chelerythrine was infused before ischemia. This is in accordance with other studies which have shown, using chelerythrine, a role for PKC in mediating delayed ischemic [13] and pharmacological [26] PC. However, the implication of other kinases cannot be excluded since chelerythrine has been reported to affect some of them [27].
We previously reported that acute intermittent hypoxia (IH) confers delayed cardioprotection against a prolonged ischemic insult in the rat, via the involvement of nitric oxide synthase and K_ATP channels. In the present study, we investigated the role of protein kinase C (PKC), phosphatidylinositol-3-kinase (PI3K), stress activated p38 MAP kinase (MAPK) and extracellular signal-regulated kinase (ERK1/2) using selective inhibitors of these pathways. Adult male rats were exposed to 1-min cycles of IH (10% O₂, 40 s)/normoxia (21% O₂, 20 s) during 4 h or to normoxic cycles. 24 h later, isolated hearts were perfused in Langendorff mode and subjected to a 30-min global ischemia followed by 120 min of reperfusion. Compared to normoxic conditions, IH significantly reduced infarct size (22.2 ± 2.4% vs. 33.8 ± 2.6%, p < 0.05), improved coronary flow and decreased the contracture at reperfusion. When administered before sustained ischemia, chelerythrine (a PKC inhibitor) abolished both the IH-induced reduction in infarct size (36.1 ± 4.9%) and improvement in hemodynamic parameters. In contrast, chelerythrine administration 10 min before IH, did not modify the delayed cardioprotective response. Similarly, wortmannin (a PI3K inhibitor) administration 10 min before IH was unable to block the cardioprotective effects. However, administration of SB203580 (a p38 MAPK inhibitor) and PD98059 (an Erk1/2 inhibitor), 30 min before IH abolished its delayed infarct-sparing effect (32.2 ± 3.4% and 33.9 ± 2.9%, respectively). In addition, 24 h after IH, a significant increase in p38 MAPK and Erk1/2 phosphorylation was observed by Western blot. These results suggest that the delayed preconditioning induced by intermittent hypoxia does not involve the PI3K signalling pathway and that is mediated by PKC and triggered by p38 MAPK and Erk1/2.
Pharmacological modulation, preclinical studies, and new clinical features of myocardial ischemic preconditioning
2000, Pharmacology and Therapeutics
The term “ischemic preconditioning (PC)” was first applied to canine myocardium subjected to brief episodes of ischemia and reperfusion that tolerated a more prolonged episode of ischemia better than myocardium not previously exposed to ischemia. Protective effect of myocardial ischemic PC was demonstrated in several animal species, resulting in the strongest endogenous form of protection against myocardial injury, jeopardized myocardium, infarct size, and arrhythmias other than early reperfusion. New onset angina before acute myocardial infarction, episodes of myocardial ischemia during coronary angioplasty or bypass surgery, and the “warm-up” phenomenon may represent clinical counterparts of the PC phenomenon in humans. Here, we have attempted to summarize pharmacological modulation, preclinical studies, and new clinical features of ischemic PC. To date, the pathophysiological basis of the “chemical PC” is still not well established, and “putting PC in a bottle” for clinical applications still remains a new pharmacological venture.
Modulation of neutrophil migration and superoxide anion release by metoprolol
2000, Journal of Molecular and Cellular Cardiology
S. Dunzendorfer and C. J. Wiedermann. Modulation of Neutrophil Migration and Superoxide Anion Release by Metoprolol. Journal of Molecular and Cellular Cardiology (2000) 32, 915–924. In addition to having anti-sympathotonic effects, beta-blockers are thought to have some adrenoceptor-independent properties. Such ancilliary effects are described for carvedilol acting as oxygen radical scavenger and for propranolol which blocks protein kinase C and phosphatidate phosphohydrolase. The goal of our in vitro experiments was to identify ancilliary effects of the widely used beta-blockers metoprolol and atenolol in neutrophils. Neutrophil chemotaxis was tested using the leading front assay in a modified Boyden microchemotaxis chamber. Respiratory burst activity was detected fluorometrically. Inhibition of protein kinase C activity was tested with purified alpha-, beta- and gamma-isoenzyme preparation. Metoprolol dose-dependently inhibited formyl peptide-stimulated neutrophil chemotaxis and formylpeptide- and phorbol myristate acetate-triggered oxygen free radical production. These actions were not affected by the competitive presence of the beta-receptor agonist, orciprenaline. Effects of metoprolol, as well as of propranolol, and the signaling enzyme blockers were strongly time dependent. Propranolol mimicked effects of staurosporine on respiratory burst, whereas the effects of metoprolol were similar to bisindolylmaleimide, a specific protein kinase C blocker. Atenolol, a hydrophilic beta-blocker, neither affected neutrophil chemotaxis nor respiratory burst. In a cell-free system, metoprolol did not interfere with the activity of the purified protein kinase C alpha-, beta- and gamma-isoenzymes. Adrenoceptor-independent inhibition of neutrophil chemotaxis and free radical production is a novel mode of action of metoprolol that may be relevant for beneficial effects ot the beta-blocker in heart failure and endothelial preconditioning.
Evidence from cultured rat cortical neurons of differences in the mechanism of ischemic preconditioning of brain and heart
1999, Brain Research
Ca²⁺ influx and activation of protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) during nonlethal ischemic preconditioning have been implicated in the protection of the heart against subsequent lethal ischemic injury. Thus, we determined if Ca²⁺ influx, PKC and MAPK also mediate ischemic preconditioning-induced protection in neurons. Preconditioning by exposure of E18 rat cortical cultures to 90 min of nonlethal oxygen–glucose deprivation (OGD) 24 h prior to 180–240 min of lethal OGD was neuroprotective. Exposure to nominally free Ca²⁺, or blockade of the α-amino-hydroxy-5-methyl-isoxazolepropionate (AMPA) receptor with CNQX did not eliminate protection. MAPK activity did not change and PKC activity decreased by 50% relative to normal baseline levels at 0 and 24 h following preconditioning. The sustained decrease in PKC activity was not due to a loss of enzyme as determined from immunoblots using pan and ε-, β- and ζ-specific PKC antibodies. Neuroprotection was maintained with pharmacological inhibition of PKC activity by staurosporine, chelerythrine and calphostin C and MAPK activity by PD 98059 during preconditioning, indicating that activation of these enzymes during preconditioning was not necessary for protection. Therefore, in contrast to cardiac tissue, ischemic preconditioning of neurons does not require activation of PKC and MAP kinase, and protection is maintained with substantial removal of extracellular Ca²⁺ or blockade of the AMPA receptor.

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^☆: Please address all correspondence to: D. M. Yellon, The Hatter Institute for Cardiovascular Studies, Division of Cardiology, University College London Hospital & Medical School, Grafton Way, London WC1E 6DB, UK.

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Regular ArticleAttenuation of Myocardial Ischaemic Injury 24 h After Diacylglycerol TreatmentIn Vivo☆

Abstract

Regular Article
Attenuation of Myocardial Ischaemic Injury 24 h After Diacylglycerol TreatmentIn Vivo☆