Manintveld, O.C.

Acute coronary syndrome in 3 dimensions: The culprit exposed (Article)

2011-10-11T00:00:00Z

Interaction between pre- and postconditioning in the in vivo rat heart (Article)

2009-11-01T00:00:00Z

Patients with an impending myocardial infarction may be preconditioned by pre-infarct angina. Hence, it is important to establish whether ischemic postconditioning is still effective in preconditioned hearts. We therefore studied in anesthetized rats the effect of postconditioning after coronary artery occlusions (CAO) of 60 min in control hearts, hearts preconditioned by a single 15-min CAO (1IPC15) or a triple 3-min CAO (3IPC3). Furthermore, we studied the effect of postconditioning in hearts that had been pharmacologically preconditioned with intravenous adenosine and in hearts that had become tolerant to 1IPC15. Postconditioning limited infarct size in control hearts, but did not afford additional protection in preconditioned hearts, irrespective of the IPC stimulus. NO synthase inhibition abolished the cardioprotection by postconditioning, both IPC stimuli, and the combination of postconditioning and either IPC stimulus. Postconditioning also failed to afford cardioprotection in hearts protected by adenosine, and in hearts that had become tolerant to cardioprotection by 1IPC15. In accordance with previous observations, postconditioning paradoxically increased infarct size following a 30-min CAO. This detrimental effect was prevented by either IPC stimulus, in a NO synthase-dependent manner. In conclusion, postconditioning does not afford additional protection in preconditioned hearts, irrespective of the preconditioning stimulus and the presence of tolerance to preconditioning. Lack of additional protection may be related to the observation that postconditioning and preconditioning are both mediated via NO synthase. In contrast, the increase in infarct size by postconditioning following a 30-min CAO is abolished by either IPC stimulus. These findings indicate that the interaction between preconditioning and postconditioning is highly dependent on the duration of index ischemia, but independent of the preconditioning stimulus. Copyright

Protection Against Myocardial Ischemia and Reperfusion: Preconditioning, postconditioning and hibernation (Doctoral Thesis)

2008-10-08T00:00:00Z

Ischemic heart disease is currently the leading cause of morbidity and mortality in the industrialized world and is expected to become the leading cause of death world wide by the year 2020 when it will surpass infectious diseases.1, 2 In 2006 42,522 people died of cardiovascular disease (CVD) in the Netherlands. This translates into an average of 116 people per day that die due to CVD. When looking at all cause mortality one in every three persons dies due to CVD. Ischemic heart disease is the main component of this group with 12,491 deaths, while 9,976 deaths are due to cerebrovascular disease. Together they are responsible for 52% of the deaths in CVD. Around 70% of the people with ischemic heart disease die due to an acute myocardial infarction (AMI).3 The impact of CVD on health care is refl ected by the number of invasive interventions: the number of percutaneous coronary interventions (PCI) is still increasing (33,678 in 2006), while the number of open heart surgeries (coronary artery bypass grafting or CABG) is stable over the past 5 years (around 15,000).3 After myocardial infarction, the surviving myocardium undergoes a complex sequence of cardiac remodeling, which may have a benefi cial eff ect on cardiovascular performance in the short-term, but which become detrimental in the long-term and ultimately causes heart failure. In experimental studies, the degree of deleterious remodeling is highly aff ected by the size of the infarct.4 Accordingly, clinical reports indicate that infarct size estimated by peak plasma creatine kinase activity is an independent predictor of left ventricular remodeling and the subsequent development and severity of heart failure.5 In view of the important role myocardial infarct size plays in the etiology of heart failure, limiting infarct size is an important strategy to reduce the incidence and severity of heart failure. Furthermore, infarct limitation is an important therapeutic goal since it is also related to other factors such as severity of ventricular arrhythmias, mortality and loss of productivity. Hence, it is of utmost importance to salvage as much myocardium as possible by initiating reperfusion as rapidly as possible, either by PCI or CABG, in addition to other therapeutic strategies that target the remodeling process (e.g. angiotensin converting enzyme inhibitors).6 This thesis will mainly focus on some of the mechanisms involved in adaptation to ischemia and reperfusion in the myocardium in order to minimize cell death and hence limit infarct size.

Ischemic preconditioning modulates mitochondrial respiration, irrespective of the employed signal transduction pathway (Article)

2008-01-01T00:00:00Z

We tested in the in vivo rat heart the hypothesis that although ischemic preconditioning can employ different signal transduction pathways, these pathways converge ultimately at the level of the mitochondrial respiratory chain. Infarct size produced by a 60-min coronary artery occlusion (69% ± 2% of the area at risk) was limited by a preceding 15-min coronary occlusion (48% ± 4%). Cardioprotection by this stimulus was triggered by adenosine receptor stimulation, which was followed by protein kinase C and tyrosine kinase activation and then mitochondrial K+ATP-channel opening. In contrast, cardioprotection by 3 cycles of 3-min coronary occlusions (infarct size 27% ± 5% of the area at risk) involved the release of reactive oxygen species, which was followed by protein kinase C and tyrosine kinase activation, but was independent of adenosine receptor stimulation and K+ATP-channel activation. However, both pathways decreased respiratory control index (RCI; state-3/state-2, using succinate as complex-II substrate) from 3.1 ± 0.2 in mitochondria from sham-treated hearts to 2.4 ± 0.2 and 2.5 ± 0.1 in hearts subjected to a single 15-min and triple 3-min coronary occlusions, respectively (both P < 0.05). The decreases in RCI were due to an increase in state-2 respiration, whereas state-3 respiration was unchanged. Abolition of cardioprotection by blockade of either signal transduction pathway was paralleled by a concomitant abolition of mitochondrial uncoupling. These observations are consistent with the concept that mild mitochondrial uncoupling contributes to infarct size limitation by various ischemic preconditioning stimuli, despite using different signal transduction pathways. In conclusion, in the in vivo rat heart, different ischemic preconditioning (IPC) stimuli can activate highly different signal transduction pathways, which seem to converge at the level of the mitochondria where they increase state-2 respiration.

The RISK of ROCK (Article)

2007-06-01T00:00:00Z

Cardiac effects of postconditioning depend critically on the duration of index ischemia (Article)

2007-03-01T00:00:00Z

Postconditioning (POC) is known as the phenomenon whereby brief intermittent ischemia applied at the onset of reperfusion following index ischemia limits myocardial infarct size. Whereas there is evidence that the algorithm of the POC stimulus is an important determinant of the protective efficacy, the importance of the duration of index ischemia on the outcome of the effects of POC has received little attention. Pentobarbital sodium-anesthetized Wistar rats were therefore subjected to index ischemia produced by coronary artery occlusions (CAO) of varying duration (15-120 min) followed by reperfusion, without or with postconditioning produced by three cycles of 30-s reperfusion and reocclusion (3POC30). 3POC30 limited infarct size produced by 45-min CAO (CAO45) from 45 ± 3% to 31 ± 5%, and CAO60 from 60 ± 3% to 47 ± 6% (both P ≤ 0.05). In contrast, 3POC30 increased infarct size produced by CAO15 from 3 ± 1% to 19 ± 6% and CAO30 from 36 ± 6 to 48 ± 4% (both P ≤ 0.05). This deleterious effect of 3POC30 was not stimulus sensitive because postconditioning with 3POC5 and 3POC15 after CAO30 also increased infarct size. The cardioprotection by 3POC30 after CAO60 was accompanied by an increased stimulation of Akt phosphorylation at 7 min of reperfusion and a 36% lower superoxide production, measured by dihydroethidium fluorescence, after 2 h of reperfusion. Consistent with these results, cardioprotection by 3POC30 was abolished by phosphatidylinositol-3-OH- kinase inhibition, as well as nitric oxide (NO) synthase inhibition. The deleterious effect of 3POC30 after CAO15 was accompanied by an increased superoxide production with no change in Akt phosphorylation and was not affected by NO synthase inhibition. In conclusion, the effect of cardiac POC depends critically on the duration of the index ischemia and can be either beneficial or detrimental. These paradoxical effects of POC may be related to the divergent effects on Akt phosphorylation and superoxide production. Copyright

Myocardium tolerant to an adenosine-dependent ischemic preconditioning stimulus can still be protected by stimuli that employ alternative signaling pathways. (Article)

2005-03-01T00:00:00Z

Clinical studies on cardioprotection by preinfarct angina are ambiguous, which may involve development of tolerance to repeated episodes of ischemia. Not all preconditioning stimuli use identical signaling pathways, and because patients likely experience varying numbers of episodes of preinfarct angina of different degrees and durations, it is important to know whether myocardium tolerant to a particular preconditioning stimulus can still be protected by stimuli employing alternative signaling pathways. We tested the hypothesis that development of tolerance to a particular stimulus does not affect cardioprotection by stimuli that employ different signaling pathways. Anesthetized rats underwent classical, remote or pharmacological preconditioning. Infarct size (IS), produced by a 60-min coronary artery occlusion (CAO), was determined after 120 min of reperfusion. Preconditioning by two 15-min periods of CAO (2CAO15, an adenosine-dependent stimulus) limited IS from 69 +/- 2% to 37 +/- 6%, but when 2CAO15 was preceded by 4CAO15, protection by 2CAO15 was absent (IS = 68 +/- 1%). This development of tolerance coincided with a loss of cardiac interstitial adenosine release, whereas two 15-min infusions of adenosine (200 microg/min i.v.) still elicited cardioprotection (IS = 40 +/- 4%). Furthermore, cardioprotection was produced when 4CAO15 was followed by the adenosine-independent stimulus 3CAO3 (IS = 50 +/- 8%) or the remote preconditioning stimulus of two 15-min periods of mesenteric artery occlusion (IS = 49 +/- 6%). In conclusion, development of tolerance to cardioprotection by an adenosine-dependent preconditioning stimulus still allows protection by pharmacological or ischemic stimuli intervention employing different signaling pathways.

The tyrosine phosphatase inhibitor bis(maltolato)oxovanadium attenuates myocardial reperfusion injury by opening ATP-sensitive potassium channels. (Article)

2004-06-01T00:00:00Z

Vanadate has been shown to inhibit tyrosine phosphatase, leading to an increased tyrosine phosphorylation state. The latter has been demonstrated to be involved in the signal transduction pathway of ischemic preconditioning, the most potent endogenous mechanism to limit myocardial infarct size. Furthermore, there is evidence that phosphatase inhibition may be cardioprotective when given late after the onset of ischemia, but the mechanism of protection is unknown. We tested the hypothesis that the organic vanadate compound bis(maltolato)oxovanadium (BMOV) limits myocardial infarct size by attenuating reperfusion injury and investigated the underlying mechanism. Myocardial infarction was produced in 112 anesthetized rats by a 60-min coronary artery occlusion, and infarct size was determined histochemically after 180 min of reperfusion. Intravenous infusion of BMOV in doses of 3.3, 7.5, and 15 mg/kg i.v. decreased infarct size dose-dependently from 70 +/- 2% of the area at risk in vehicle-treated rats down to 41 +/- 5% (P < 0.05 versus control), when administered before occlusion. Administration of the low dose just before reperfusion was ineffective, but administration of the higher doses was equally cardioprotective as compared with administration before occlusion. The cardioprotection by BMOV was abolished by the tyrosine kinase inhibitor genistein and by the ATP-sensitive potassium (K(+)(ATP)) channel blocker glibenclamide but was not affected by the ganglion blocker hexamethonium. We conclude that BMOV afforded significant cardioprotection principally by limiting reperfusion injury. The mode of action appears to be by opening of cardiac K(+)(ATP) channels via increased tyrosine phosphorylation.