Effects of propofol on ischemia-induced ventricular arrhythmias and mitochondrial ATP-sensitive potassium channels

KATP channels are regulators of programmed cell death and targets for the creation of novel drugs against ischemia/reperfusion cardiac injury

BACKGROUND

The use of percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI) is associated with a mortality rate of 5%-7%. It is clear that there is an urgent need to develop new drugs that can effectively prevent cardiac reperfusion injury. ATP-sensitive K+ (KATP ) channel openers (KCOs) can be classified as such drugs.

RESULTS

KCOs prevent irreversible ischemia and reperfusion injury of the heart. KATP channel opening promotes inhibition of apoptosis, necroptosis, pyroptosis, and stimulation of autophagy. KCOs prevent the development of cardiac adverse remodeling and improve cardiac contractility in reperfusion. KCOs exhibit antiarrhythmic properties and prevent the appearance of the no-reflow phenomenon in animals with coronary artery occlusion and reperfusion. Diabetes mellitus and a cholesterol-enriched diet abolish the cardioprotective effect of KCOs. Nicorandil, a KCO, attenuates major adverse cardiovascular event and the no-reflow phenomenon, reduces infarct size, and decreases the incidence of ventricular arrhythmias in patients with acute myocardial infarction.

CONCLUSION

The cardioprotective effect of KCOs is mediated by the opening of mitochondrial KATP (mitoKATP ) and sarcolemmal KATP (sarcKATP ) channels, triggered free radicals' production, and kinase activation.

Nicorandil Ameliorates Doxorubicin-Induced Cardiotoxicity in Rats, as Evaluated by 7 T Cardiovascular Magnetic Resonance Imaging

PURPOSE

Doxorubicin-induced cardiotoxicity (DIC) is a common side effect of doxorubicin chemotherapy, and a major mechanism of DIC is inflammation. However, no effective method exists to prevent DIC. In the present study, we investigated the cardioprotective effects of nicorandil against DIC using multiparametric cardiac magnetic resonance (CMR) imaging and elucidated the anti-inflammatory properties of nicorandil in rat models.

METHODS

Male Sprague-Dawley rats received four weekly intraperitoneal doxorubicin doses (4 mg/kg/injection) to establish the DIC model. After treatment with or without nicorandil (3 mg/kg/day) or diazoxide (10 mg/kg/day) orally, all the groups underwent weekly CMR examinations, including cardiac function and strain assessment and T2 mapping, for 6 weeks. Additionally, blood samples and hearts were collected to examine inflammation and histopathology.

RESULTS

According to our results, the earliest DIC CMR parameter in the doxorubicin group was T2 mapping time prolongation compared with the DIC rats treated with nicorandil (doxorubicin+nicorandil group) at week 2. Subsequently, the left ventricular ejection fraction (LVEF) and global peak systolic myocardial strain in the doxorubicin group were significantly reduced, and nicorandil effectively inhibited these effects at week 6. Our results were confirmed by histopathological evaluations. Furthermore, nicorandil treatment had a protective effect against the doxorubicin-induced inflammatory response. Interestingly, similar protective results were obtained using the KATP channel opener diazoxide.

CONCLUSION

Collectively, our findings indicate that nicorandil application ameliorates DIC in rats with significantly higher cardiac function and myocardial strain and less fibrosis, apoptosis and inflammatory cytokine production. Nicorandil prevents T2 abnormalities in the early stages of DIC, showing a high clinical value for early nicorandil treatment in chemotherapy patients.

Deep sedation as temporary bridge to definitive treatment of ventricular arrhythmia storm

Background:

Electrical storm and incessant ventricular tachycardia (VT) are characterized by the clustering of episodes of VT or ventricular fibrillation (VF) and are associated with a poor prognosis. Autonomic nervous system activity influences VT threshold, and deep sedation may be useful for the treatment of VT emergencies.

Methods:

We reviewed data from conscious patients admitted to our intensive care unit (ICU) due to monomorphic VT, polymorphic VT or VF at our tertiary center between 2010 and 2018.

Results:

A total of 46 conscious patients with recurrent ventricular arrhythmia, refractory to initial treatment, were referred to the ICU. The majority (n = 31) were stabilized on usual care. The remaining treatment-refractory 15 patients (57 years (range 9–74), 80% males, seven with implantable cardioverter-defibrillators) with VT/VF storm (n = 11) or incessant VT (n = 4) due to ischemic heart disease (n = 10), cardiomyopathy (n = 2), primary arrhythmia (n = 2) and one patient post valve surgery, were deeply sedated and intubated. A complete resolution of VT/VF within minutes to hours was achieved in 12 patients (80%), partial resolution in two (13%) and one (7%) patient died due to ventricular free-wall rupture. One patient with recurrent VT episodes needing repeated deep sedation developed necrotic caecum. No other major complications were seen. Thirteen (87%) patients were alive after a mean follow-up of 3.7 years.

Conclusion:

Deep sedation was effective and safe for the temporary management of malignant VT/VF refractory to usual treatment. In emergencies, deep sedation may be widely accessible at both secondary and tertiary centers and a clinically useful bridge to definitive treatment of VT.

Role of Oxidative Stress in the Genesis of Ventricular Arrhythmias

Ventricular arrhythmias, mainly lethal arrhythmias, such as ventricular tachycardia and fibrillation, may lead to sudden cardiac death. These are triggered as a result of cardiac injury due to chronic ischemia, acute myocardial infarction and various stressful conditions associated with increased levels of circulating catecholamines and angiotensin II. Several mechanisms have been proposed to underlie electrical instability of the heart promoting ventricular arrhythmias; however, oxidative stress which adversely affects ion homeostasis due to changes in the ion channel structure and function, seems to play a critical role in eliciting different types of ventricular arrhythmias. Prevention or mitigation of the severity of ventricular arrhythmias due to antioxidants has been indicated as the fundamental contribution in the field of preventive cardiology; however, novel interventions have to be developed for greater effectiveness and specificity in attenuating the adverse effects of oxidative stress. In this review, we have attempted to discuss proarrhythmic effects of oxidative stress differing in time and concentration dependence and highlight a molecular and cellular concept how it alters cardiac cell automaticity and conduction velocity sensitizing the probability of ventricular arrhythmias with resultant sudden cardiac death due to ischemic heart disease and other stressful situations. It is concluded that pharmacological approaches targeting multiple mechanisms besides oxidative stress might be more effective in the treatment of ventricular arrhythmias than current antiarrhythmic therapy.

Propofol Alleviates Apoptosis Induced by Chronic High Glucose Exposure via Regulation of HIF-1α in H9c2 Cells

BACKGROUND

The sedative anesthetic, propofol, is a cardioprotective agent for hyperglycemia-induced myocardial hypertrophy and dysfunction in rats. However, the specific protective mechanism has not been clarified.

METHODS AND RESULTS

In this experiment, we used H9c2 cells subjected to 22 mM glucose lasting for 72 hours as an in vitro model of cardiomyocyte injury by hyperglycemia and investigated the potential mechanism of propofol against hyperglycemic stress in cells. Propofol (5, 10, or 20 μM) was added to the cell cultures before and during the high glucose culture phases. Cell viability and levels of ROS were measured. The levels of proinflammatory cytokines were tested by ELISA. The levels of SIRT3, SOD2, PHD2, HIF-1α, Bcl-2, P53, and cleaved caspase-3 proteins were detected by western blotting. Our data showed that propofol attenuated high glucose-induced cell apoptosis accompanied by a decrease in the level of reactive oxygen species (ROS) and proinflammatory cytokines. Meanwhile, propofol decreased the apoptosis of H9c2 cells via increasing the expression of Bcl-2, SIRT3, SOD2, and PHD2 proteins and decreasing the expression of cleaved caspase-3, P53, and HIF-1α. Real-time PCR analysis showed that propofol did not significantly change the HIF-1α but increase PHD2 at mRNA level. HIF-1α silence significantly decreased apoptosis and inflammation in H9c2 cell during high glucose stress. Pretreatment of IOX2 (the inhibitor of PHD2) inhibited cell viability until the concentration reached 200 μM during high glucose stress. However, 50 μM TYP (the inhibitor of SIRT3) significantly inhibited cell viability during high glucose stress. Delayed IOX2 treatment for 6 hours significantly inhibited cell viability during high glucose stress.

CONCLUSIONS

Propofol might alleviate cell apoptosis via SIRT3-HIF-1α axis during high glucose stress.

Propofol attenuates H2O2-induced oxidative stress and apoptosis via the mitochondria- and ER-medicated pathways in neonatal rat cardiomyocytes

Previous studies have shown that propofol, an intravenous anesthetic commonly used in clinical practice, protects the myocardium from injury. Mitochondria- and endoplasmic reticulum (ER)-mediated oxidative stress and apoptosis are two important signaling pathways involved in myocardial injury and protection. The present study aimed to test the hypothesis that propofol could exert a cardio-protective effect via the above two pathways. Cultured neonatal rat cardiomyocytes were treated with culture medium (control group), H₂O₂ at 500 μM (H₂O₂ group), propofol at 50 μM (propofol group), and H₂O₂ plus propofol (H₂O₂ + propofol group), respectively. The oxidative stress, mitochondrial membrane potential (ΔΨm) and apoptosis of the cardiomyocytes were evaluated by a series of assays including ELISA, flow cytometry, immunofluorescence microscopy and Western blotting. Propofol significantly suppressed the H₂O₂-induced elevations in the activities of caspases 3, 8, 9 and 12, the ratio of Bax/Bcl-2, and cell apoptosis. Propofol also inhibited the H₂O₂-induced reactive oxygen species (ROS) generation, lactic dehydrogenase (LDH) release and mitochondrial transmembrane potential (ΔΨm) depolarization, and restored the H₂O₂-induced reductions of glutathione (GSH) and superoxide dismutase (SOD). In addition, propofol decreased the expressions of glucose-regulated protein 78 kDa (Grp78) and inositol-requiring enzyme 1α (IRE1α), two important signaling molecules in the ER-mediated apoptosis pathway. Propofol protects cardiomyocytes from H₂O₂-induced injury by inhibiting the mitochondria- and ER-mediated apoptosis signaling pathways.

The Effect of Propofol on Mitochondrial Fission during Oxygen-Glucose Deprivation and Reperfusion Injury in Rat Hippocampal Neurons

The neuroprotective role of propofol in transient global and focal cerebral ischemia reperfusion (I/R) animal model has recently been highlighted. However, no studies have conducted to explore the relationship between mitochondrial fission/fusion and I/R injury under the intervention of propofol. Moreover, neuroprotective mechanism of propofol is yet unclear. Culturing primary hippocampal cells were subjected to oxygen-glucose deprivation and re-oxygenation (OGD/R) model, as a model of cerebral I/R in vitro. Methods CCK-8 assay was used to test the effect of propofol on cell viability. We examined the effect of propofol on mitochondrial ultrastructure and mitochondrial fission evoked by OGD/R with transmission electron microscopy and immunofluorescence assay. To investigate possible neuroprotective mechanisms, the authors then examined whether propofol could inhibit calcium-overload, calcineurin (CaN) activation and the phosphorylation of dynamin-related protein 1 (Drp1) during the period of OGD/R, as well as the combination of Drp1-ser 637 and fission 1 (Fis1) protein by immunofluorescence assay, ELISA and double-labeling immunofluorescence analysis. Finally, the expression of Drp1-ser 637 and Fis1, apoptosis inducing factor (AIF) and cytochrome C (Cyt C) were detected by western blot. When added in culture media during OGD period, propofol (0.1μM-50μM) could alleviate neurons injury and protect mitochondrial ultrastructure, meanwhile inhibit mitochondrial fission. Furthermore, the concentration of intracellular free Ca2+, CaN activition and the phosphorylation of Drp1-ser637 were suppressed, as well as the translocation and combination of Drp1-ser 637 and Fis1. The authors also found that the expression of Cyt C, AIF, Drp1-ser637 and Fis1 were down-regulated. Notably, high dose of propofol (100μM-200μM) were confirmed to decrease the survival of neurons based on results of cell viability. Propofol could inhibit mitochondrial fission and mitochondrial apoptotic pathway evoked by OGD/R in rat hippocampal neurons, which may be via depressing calcium-overload.

KATP Channels in the Cardiovascular System

KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease.

Mitochondrial involvement in propofol-induced cardioprotection: An in vitro study in human myocardium

Propofol has been shown to exert cardioprotection, but the underlying mechanisms remain incompletely understood. We examined: (1) whether propofol-induced cardioprotection depended on the time and the dose of administration; (2) the role of mitochondrial adenosine triphosphate-sensitive potassium channels, nitric oxide synthase, and mitochondrial respiratory chain activity in propofol-induced cardioprotection. Human right atrial trabeculae were obtained during cardiopulmonary bypass for coronary artery bypass and aortic valve replacement. Isometric force of contraction of human right atrial trabeculae hanged in an oxygenated Tyrode's solution was recorded during 30-min hypoxia and 60-min reoxygenation (Control). Propofol 0.1, 1, and 10 µM was administered: (1) 5 min before hypoxia until the end of the experiment; (2) 5 min followed by 5-min washout before hypoxia; (3) during the reoxygenation period, propofol 10 µM was administered in presence of 5-hydroxydecanoate (antagonist of mitochondrial adenosine triphosphate-sensitive potassium channels), and NG-nitro-L-arginine methyl ester (inhibitor of nitric oxide synthase). In addition, mitochondria were isolated from human right atrial at 15 min of reoxygenation. The effect of propofol on activity of the mitochondrial respiratory chain complexes was evaluated by spectrophotometry. The force of contraction (% of baseline) and the complex activity between the different groups were compared with an analysis of variance and post hoc test. Propofol 10 µM administered during the reoxygenation period significantly improved the recovery of force of contraction at the end of reoxygenation (82 ± 6% of baseline value vs. 49 ± 6% in Control; P < 0.001). The beneficial effects of propofol 10 µM were abolished by co-administration with 5-hydroxydecanoate (53 ± 8%) or NG-nitro-L-arginine methyl ester (57 ± 6%). Propofol 10 µM significantly increased enzymatic activities of the mitochondrial respiratory chain complexes, in reoxygenation period, compared to their respective untreated controls. In conclusion, in human myocardium, propofol-induced cardioprotection was mediated by mitochondrial adenosine triphosphate-sensitive potassium channels opening, nitric oxide synthase activation and stimulation of mitochondrial respiratory chain complexes, in early reoxygenation period.

Late Post-Conditioning with Sevoflurane after Cardiac Surgery--Are Surrogate Markers Associated with Clinical Outcome?

Introduction

In a recent randomized controlled trial our group has demonstrated in 102 patients that late post-conditioning with sevoflurane performed in the intensive care unit after surgery involving extracorporeal circulation reduced damage to cardiomyocytes exposed to ischemia reperfusion injury. On the first post-operative day the sevoflurane patients presented with lower troponin T values when compared with those undergoing propofol sedation. In order to assess possible clinical relevant long-term implications in patients enrolled in this study, we performed the current retrospective analysis focusing on cardiac and non-cardiac events during the first 6 months after surgery.

Methods

All patients who had successfully completed the late post-conditioning trial were included into this follow-up. Our primary and secondary endpoints were the proportion of patients experiencing cardiac and non-cardiac events, respectively. Additionally, we were interested in assessing therapeutic interventions such as initiation or change of drug therapy, interventional treatment or surgery.

Results

Of 102 patients analyzed in the primary study 94 could be included in this follow-up. In the sevoflurane group (with 41 patients) 16 (39%) experienced one or several cardiac events within 6 months after cardiac surgery, in the propofol group (with 53 patients) 19 (36%, p=0.75). Four patients (9%) with sevoflurane vs. 7 (13%) with propofol sedation had non-cardiac events (p=0.61). While a similar percentage of patients suffered from cardiac and/or non-cardiac events, only 12 patients in the sevoflurane group compared to 20 propofol patients needed a therapeutic intervention (OR: 0.24, 95% CI: 0.04-1.43, p=0.12). A similar result was found for hospital admissions: 2 patients in the sevoflurane group had to be re-admitted to the hospital compared to 8 in the propofol group (OR 0.23, 95% CI: 0.04-1.29, p=0.10).

Conclusions

Sevoflurane does not seem to provide protection with regard to the occurrence of cardiac and non-cardiac events in the 6-month period following cardiac surgery with the use of extracorporeal circulation. However, there was a clear trend towards fewer interventions (less need for treatment, fewer hospital admissions) associated with sevoflurane post-conditioning in patients experiencing any event. Such results might encourage launching large multicenter post-conditioning trials with clinical outcome defined as primary endpoint.

Cardioprotective effect of propofol against oxygen glucose deprivation and reperfusion injury in H9c2 cells

BACKGROUND

The intravenous anesthetic propofol is reported to be a cardioprotective agent against ischemic-reperfusion injury in the heart. However, the regulatory mechanism still remains unclear.

METHODS

In this study, we used H9c2 cell line under condition of oxygen glucose deprivation (OGD) followed by reperfusion (OGD/R) to induce in vitro cardiomyocytes ischemia-reperfusion injury. Propofol (5, 10, and 20 μM) was added to the cell cultures before and during the OGD/R phases to investigate the underlying mechanism.

RESULTS

Our data showed that OGD/R decreased cell viability, and increased lactate dehydrogenase leakage, and reactive oxygen species and malondialdehyde production in H9c2 cells, all of which were significantly reversed by propofol. Moreover, we found that propofol increased both the activities and protein expressions of superoxide dismutase and catalase. In addition, propofol increased FoxO1 expression in a dose-dependent manner and inhibited p-AMPK formation significantly.

CONCLUSIONS

These results indicate that the propofol might exert its antioxidative effect through FoxO1 in H9c2 cells, and it has a potential therapeutic effect on cardiac disorders involved in oxidative stress.

Interaction between interleukin-1 beta and angiotensin II receptor 1 in hypothalamic paraventricular nucleus contributes to progression of heart failure

The central mechanisms by which interleukin-1 beta (IL-1β) and angiotension II receptor 1 (AT1-R) contribute to sympathoexcitation in heart failure (HF) are unclear. In this study, we determined whether an interaction between IL-1β and AT1-R in the paraventricular nucleus (PVN) contributes to progression of HF. Rats were implanted with bilateral PVN cannulae and subjected to coronary artery ligation or sham surgery (Sham). Subsequently, animals were treated for 4 weeks through PVN infusion with either vehicle, losartan (LOS, 200 μg/day), IL-1β (IL, 1 μg/day), or IL-1β along with LOS (LOS+IL). HF rats had higher levels of corticotropin-releasing hormone (CRH), norepinephrine (NE), and glutamate (Glu); lower levels of gamma-aminobutyric acid (GABA); and more positive fra-like activity in PVN when compared with Sham rats. HF rats also had higher levels of NE, epinephrine (EPI), and IL-1β in plasma. PVN infusion of LOS attenuated the decreases in GABA and the increases in CRH, NE, and Glu in the PVN of HF rats. IL-1β could further increase the expression of CRH, NE, Glu, EPI, and IL-1β and decrease GABA expression. Treatment with IL-1β along with LOS could eliminate the effects of IL-1β. These findings suggest that an interaction between AT1-R and IL-1β in the PVN contributes to progression in HF.