Intravenous atenolol and esmolol maintain the protective effect of ischemic preconditioning in vivo

The role of adrenergic and muscarinic receptors in stress-induced cardiac injury

Takotsubo syndrome (TS) is a rare but dangerous disease that can be fatal. The pathogenesis of TS is not well understood because there is no animal model of TS that fully mimics TS. It has now been documented that stress exposure (24 h) of rats induced the state which is similar TS in human: contracture damage of myofibrils, elevation of the serum creatine kinase MB level, increased ^99mTc-pyrophosphate (^99mTc-PYP) accumulation in the heart, QTc interval prolongation, and contractility dysfunction of the heart. Immobilization stress resulted in an increase in coronary blood flow. Emotional stress increased the serum catecholamine level. Blockade of β₁-adrenergic receptor (AR) prevented stress-induced cardiac injury (SICI). Blockade of β₂-AR aggravated stress-induced cardiac injury. Stimulation of β₂-AR increased cardiac tolerance to stress. Inhibition of β₃-AR, α₁-AR had no effect on SICI. Blockade of peripheral muscarinic receptors or α₂-AR aggravated SICI. Pretreatment with the selective β₁-AR antagonist atenolol attenuates stress-induced cardiac contractility dysfunction, but recovery of cardiac contractility is not complete. There is indirect evidence that circulating catecholamines play an important role in SICI. Consequently, the activation of β₁-AR plays a significant role in SICI. However, there are other receptors which are also involved in SICI and require further investigation.

Chronic β1-adrenoceptor blockade impairs ischaemic tolerance and preconditioning in murine myocardium

β-adrenoceptor antagonists are commonly used in ischaemic heart disease (IHD) patients, yet may impair signalling and efficacy of 'cardioprotective' interventions. We assessed effects of chronic β1-adrenoceptor antagonism on myocardial resistance to ischaemia-reperfusion (IR) injury and the ability of cardioprotective interventions [classic ischaemic preconditioning (IPC); novel sustained ligand-activated preconditioning (SLP)] to reduce IR injury in murine hearts. Young male C57Bl/6 mice were untreated or received atenolol (0.5g/l in drinking water) for 4 weeks. Subsequently, two cardioprotective stimuli were evaluated: morphine pellets implanted (to induce SLP, controls received placebo) 5 days prior to Langendorff heart perfusion, and IPC in perfused hearts (3×1.5min ischaemia/2min reperfusion). Atenolol significantly reduced in vivo heart rate. Untreated control hearts exhibited substantial left ventricular dysfunction (~50% pressure development recovery, ~20mmHg diastolic pressure rise) with significant release of lactate dehydrogenase (LDH, tissue injury indicator) after 25min ischaemia/45min reperfusion. Contractile dysfunction and elevated LDH were reduced >50% with IPC and SLP. While atenolol treatment did not modify baseline contractile function, post-ischaemic function was significantly depressed compared to untreated hearts. Atenolol pre-treatment abolished beneficial effects of IPC, whereas SLP protection was preserved. These data indicate that chronic β1-adrenoceptor blockade can exert negative effects on functional IR tolerance and negate conventional IPC (implicating β1-adrenoceptors in IR injury and IPC signalling). However, novel morphine-induced SLP is resistant to inhibition by β1-adrenoceptor antagonism.

Interaction of risk factors, comorbidities, and comedications with ischemia/reperfusion injury and cardioprotection by preconditioning, postconditioning, and remote conditioning

Pre-, post-, and remote conditioning of the myocardium are well described adaptive responses that markedly enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and provide therapeutic paradigms for cardioprotection. Nevertheless, more than 25 years after the discovery of ischemic preconditioning, we still do not have established cardioprotective drugs on the market. Most experimental studies on cardioprotection are still undertaken in animal models, in which ischemia/reperfusion is imposed in the absence of cardiovascular risk factors. However, ischemic heart disease in humans is a complex disorder caused by, or associated with, cardiovascular risk factors and comorbidities, including hypertension, hyperlipidemia, diabetes, insulin resistance, heart failure, altered coronary circulation, and aging. These risk factors induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury per se and responses to cardioprotective interventions. Moreover, some of the medications used to treat these risk factors, including statins, nitrates, and antidiabetic drugs, may impact cardioprotection by modifying cellular signaling. The aim of this article is to review the recent evidence that cardiovascular risk factors and their medication may modify the response to cardioprotective interventions. We emphasize the critical need to take into account the presence of cardiovascular risk factors and concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple risk factors.

Effect of short-acting beta blocker on the cardiac recovery after cardiopulmonary bypass

The objective of this study was to investigate the effect of beta blocker on cardiac recovery and rhythm during cardiac surgeries. Sixty surgical rheumatic heart disease patients were received esmolol 1 mg/kg or the same volume of saline prior to removal of the aortic clamp. The incidence of cardiac automatic re-beat, ventricular fibrillation after reperfusion, the heart rate after steady re-beat, vasoactive drug use during weaning from bypass, the posterior parallel time and total bypass time were decreased by esmolol treatment.

IN CONCLUSION

Esmolol has a positive effect on the cardiac recovery in cardiopulmonary bypass surgeries.

Levosimendan cardioprotection in acutely beta-1 adrenergic receptor blocked open chest pigs

BACKGROUND

Levosimendan and volatile anesthetics have myocardial pre-conditioning effects. beta-1 adrenergic receptor antagonists may inhibit the protective effect of volatile anesthetics. No information exists as to whether this also applies to the pre-conditioning effect of levosimendan. We therefore investigated whether levosimendan added to metoprolol would demonstrate a cardioprotective effect.

METHODS

Three groups of anesthetized open chest pigs underwent 30 min of myocardial ischemia and 90 min of reperfusion by temporary occlusion of the largest side branch from the circumflex artery or the left anterior descending artery. One group (CTRL) served as a control, in another group (BETA), a metoprolol-loading dose was intravenously injected 30 min before ischemia, and in a third group (BETA+L), a levosimendan infusion was added to metoprolol. Myocardial tissue concentrations of glucose, glycerol, and lactate/pyruvate ratio as the primary end-points were investigated with microdialysis in ischemic and non-ischemic tissues.

RESULTS

At the end of the ischemic period, statistically significant differences were only found between CTRL and BETA+L in the ischemic myocardium, with a lower lactate/pyruvate ratio, lower glycerol, and higher glucose concentrations in BETA+L as compared with CTRL. There were no differences in non-ischemic myocardium. From 10 to 90 min of reperfusion, no more differences were found between groups.

CONCLUSION

The cardioprotective effect of levosimendan on ischemic metabolism with a reduction in the myocardial lactate/pyruvate ratio, less glycerol accumulation, and better preserved glucose concentration does not seem to be prevented by beta-1 adrenergic receptor antagonism with metoprolol.

Activation of beta-adrenoceptors mimics preconditioning of rat-isolated atria and ventricles against ischaemic contractile dysfunction

The effects of ischaemia and reoxygenation on cardiac contractile function can be abrogated by ischaemic preconditioning (IPC). We tested whether beta-adrenoceptor agonists could mimic IPC and whether IPC was dependent on beta-adrenoceptor activation in rat-isolated cardiac tissues. Paced left atria and right ventricular strips were set-up in Krebs solution and isometric developed tension recorded. Ischaemia was simulated by replacing with hypoxic glucose-free Krebs solution for 30 min. IPC and isoprenaline (10(-7) M) preconditioning for 10 min were examined. Developed tension post-reoxygenation was expressed as a percentage of the pre-ischaemic baseline. Recovery at 15 min was significantly increased by IPC in atria (47 +/- 4.0% vs. 29.3 +/- 1.7%, p < 0.05) and ventricles (39.0 +/- 5.2% vs. 22.4 +/- 2.8%, p < 0.05). At 60 min, isoprenaline-treated atria recovery (75.8 +/- 16.6%) was significantly (p < 0.05) greater than controls (47.9 +/- 2.3%). Propranolol (10(-6) M) abolished both effects. Therefore, both IPC and beta-adrenoceptor agonist-induced improvement of contractile recovery was propranolol-sensitive and beta-adrenoceptor-mediated.

Landiolol has cardioprotective effects against reperfusion injury in the rat heart via the PKCepsilon signaling pathway

Landiolol, a highly cardioselective beta1-blocker, has cardioprotective effects against ischemia-reperfusion injury, although the precise mechanism is still unclear. The aim of this study was to clarify the cardioprotective mechanism of landiolol. Experiments were performed on Langendorff-perfused rat hearts undergoing 20 min stabilization, and 45 min of ischemia followed by 60 min of reperfusion. Various drugs with or without landiolol (100 microM) were administered before ischemia for 20 min. Preischemic administration of landiolol reduced cardiac cellular damage and improved the recovery of cardiac function by about 40%. The alpha1 blocker prazosin, the protein kinase C (PKC) inhibitor chelerythrine or the K(ATP) channel blocker glibenclamide, but not the selective mitochondrial K(ATP) channel blocker 5-hydroxydecanoate abrogated the cardioprotective effect induced by landiolol. Following landiolol pretreatment the activation of PKCepsilon and heat shock protein 27 were significantly higher than that in control. These data indicate that preischemic application of landiolol induces cardioprotective effects through PKCepsilon-mediated pathway, similar to that afforded by ischemic preconditioning.

Beta-adrenoreceptor antagonists attenuate brain injury after transient focal ischemia in rats

Beta-adrenoreceptor antagonists experimentally reduce cardiac and renal injury after ischemia and are also clinically useful for myocardial infarction and severe burns. In addition, beta-adrenoreceptor antagonists provide neuroprotective effects after focal cerebral ischemia in experimental settings. We conducted the present study to compare the neuroprotective effects of several beta-adrenoreceptor antagonists in rat transient focal cerebral ischemia. Halothane-anesthetized normothermic adult male Sprague-Dawley rats were subjected to 2 h of middle cerebral artery occlusion using the intraluminal suture technique confirmed by laser Doppler flowmetry. Rats received an IV infusion of saline 0.5 mL/h, propranolol 100 microg x kg(-1) x min(-1), carvedilol 4 microg x kg(-1) x min(-1), esmolol 200 microg x kg(-1) x min(-1), or landiolol 50 microg x kg(-1) x min(-1) (n = 6 in each group). Infusion was initiated 30 min before middle cerebral artery occlusion and continued for 24 h. Additional rats received esmolol 50 microg x kg(-1) x min(-1) or landiolol 10 microg x kg(-1) x min(-1) intrathecally (IT) via the cisterna magna (n = 5 in each group), according to the same experimental protocol. The neurological deficit score was evaluated at 22 h after reperfusion, and the brains were removed and stained with triphenyltetrazolium chloride for evaluation of infarct volume. Additional rats that received saline, esmolol, and landiolol IV (n = 6 in each group) were allowed to survive for 7 days followed by measurement of infarct size. Neurological deficit scores were smaller in rats treated with propranolol-IV, carvedilol-IV, esmolol-IV, landiolol-IV, esmolol-IT, and landiolol-IT compared with saline-treated rats (P < 0.05). Cortical and striatum infarct volumes were less in the rats receiving beta-adrenoreceptor antagonists via either IV or IT than in saline-treated rats (P < 0.05). We conclude that beta-adrenoreceptor antagonists improve neurological and histological outcomes after transient focal cerebral ischemia in rats independent of administration route.

The roles of alpha- and beta-adrenoceptor stimulation in myocardial ischaemia

beta-Adrenoceptor (AR) ligands have been the mainstay of cardiovascular therapy for decades, with beta-AR antagonist being used for hypertension, angina and myocardial infarction and adrenaline in use for cardiopulmonary resuscitation for nearly 100 years. Ischaemia of the heart through coronary artery occlusion causes cell injury and death through necrosis and apoptosis. Reperfusion of the ischaemic myocardium results in cardiac dysfunction and infarction. Stimulation of alpha- and beta-ARs in the ischaemic heart have variable and inconsistent effects depending on when the agonist is applied. This review describes the different effects of stimulation of the three established beta-AR subtypes (beta(1)-, beta(2)- and beta(3)-ARs) either before ischaemia (preconditioning) or during ischaemia and reperfusion of the heart (postconditioning). Brief periods of ischaemia preceding a major ischaemic episode can have a protective effect against post-ischaemia-reperfusion damage, known as ischaemic preconditioning. This review considers the role of endogenous catecholamines released during preconditioning and the nature of the adrenoceptor subtypes that mediate these effects. The clinical significance of this to the use of beta-AR antagonists is considered. The transduction pathways and effects on apoptosis of the cardioprotective and deleterious effects of AR activation are considered. This commentary reviews the literature and attempts to bring together a unified synopsis of the effects of adrenoceptor stimulation in myocardial ischaemia and the potential clinical relevance.