Cardioprotective effects of anesthetic preconditioning in rats with ischemia-reperfusion injury: propofol versus isoflurane

Propofol Provides Cardiac Protection by Suppressing the Proteasome Degradation of Caveolin-3 in Ischemic/Reperfused Rat Hearts

The mechanisms underlying propofol's cardioprotective role remain elusive. Caveolin-3 (Cav-3) has been shown to mediate both opioids- and volatile anesthetics-induced cardioprotection against ischemia/reperfusion (I/R) injury. We hypothesize that the cardioprotective role of propofol is mediated through Cav-3 and its regulation of PI3K/Akt/GSK3β signal pathway. Rats or H9c2 cardiomyocytes were exposed to propofol before I/R or simulated ischemia/reperfusion (SI/R). Propofol pretreatment significantly decreased left ventricle infarct size in vivo (P < 0.05) and terminal deoxynucleotidyl transferase nick-end labeling-positive cells both in vivo and in vitro (P < 0.05), along with an increased Cav-3 protein expression and binding of Cav-3 to p85-subunit of PI3K. No significant change in Cav-3 mRNA expression in left ventricle tissues was found in either I/R or propofol-treated groups. Methyl-β-cyclodextrin or Cav-3 siRNA was used to knockdown Cav-3 expression in vitro, which virtually abolished propofol-induced cardiac protection and PI3K/Akt/GSK3β pathway activation. In contrast, MG132, a proteasome inhibitor, could significantly restore SI/R-induced Cav-3 decrease. It is concluded that Cav-3 mediates propofol-induced cardioprotection against I/R injury and the relevant PI3K/Akt/GSK3β activation. The downregulation of Cav-3 under SI/R may be caused by proteasome degradation, and this process can be prevented by propofol.

Activation of Endocannabinoid Receptor 2 as a Mechanism of Propofol Pretreatment-Induced Cardioprotection against Ischemia-Reperfusion Injury in Rats

Propofol pretreatment before reperfusion, or propofol conditioning, has been shown to be cardioprotective, while its mechanism is unclear. The current study investigated the roles of endocannabinoid signaling in propofol cardioprotection in an in vivo model of myocardial ischemia/reperfusion (I/R) injury and in in vitro primary cardiomyocyte hypoxia/reoxygenation (H/R) injury. The results showed that propofol conditioning increased both serum and cell culture media concentrations of endocannabinoids including anandamide (AEA) and 2-arachidonoylglycerol (2-AG) detected by LC-MS/MS. The reductions of myocardial infarct size in vivo and cardiomyocyte apoptosis and death in vitro were accompanied with attenuations of oxidative injuries manifested as decreased reactive oxygen species (ROS), malonaldehyde (MDA), and MPO (myeloperoxidase) and increased superoxide dismutase (SOD) production. These effects were mimicked by either URB597, a selective endocannabinoids degradation inhibitor, or VDM11, a selective endocannabinoids reuptake inhibitor. In vivo study further validated that the cardioprotective and antioxidative effects of propofol were reversed by selective CB2 receptor antagonist AM630 but not CB1 receptor antagonist AM251. We concluded that enhancing endogenous endocannabinoid release and subsequent activation of CB2 receptor signaling represent a major mechanism whereby propofol conditioning confers antioxidative and cardioprotective effects against myocardial I/R injury.

Detection of Myocardial Injury Using miRNAs Expression as Genetic Biomarkers in Acute Cardiac Care

Cardiovascular disease is a leading cause of death globally. At present, there are many ways to diagnose this pathophysiology. The greatest disadvantages related to current biomarkers are their low specificity, low selectivity and low accuracy. A new method, extensively studied recently, is the expression of miRNAs, used as genetic biomarkers for the early diagnosis of cardiovascular diseases. This paper presents an update of miRNAs species expression that can serve as early diagnostic biomarkers and for the continuous monitoring of patients with cardiovascular disease.

Pulmonary Protective Effects of Remote Ischaemic Preconditioning with Postconditioning in Patients Undergoing Cardiac Surgery Involving Cardiopulmonary Bypass: A Substudy of the Remote Ischaemic Preconditioning with Postconditioning Outcome trial

BACKGROUND

The RISPO (Remote Ischemic Preconditioning with Postconditioning Outcome) trial evaluated whether remote ischaemic preconditioning (RIPC) combined with remote ischaemic postconditioning (RIPostC) improves the clinical outcomes of patients undergoing cardiac surgery. This substudy of the RISPO trial aimed to evaluate the effect of RIPC with RIPostC on pulmonary function in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB).

METHODS

Sixty-five patients were enrolled (32: control and 33: RIPC-RIPostC). In the RIPC-RIPostC group, four cycles of 5min ischaemia and 5min reperfusion were administered before and after CPB to the upper limb. Peri-operative PaO2/FIO2 ratio, intra-operative pulmonary shunt, and dynamic and static lung compliance were determined.

RESULTS

The mean PaO2/ FIO2 was significantly higher in the RIPC-RIPostC group at 24h after surgery [290 (96) vs. 387 (137), p=0.001]. The incidence of mechanical ventilation for longer than 48h was significantly higher in the control group (23% vs. 3%, p<0.05). However, there were no significant differences in other pulmonary profiles, post-operative mechanical ventilation time, and duration of intensive care unit stay.

CONCLUSIONS

In our study, RIPC-RIPostC improved the post-operative 24h PaO2/FIO2 ratio. Remote ischaemic preconditioning-Remote ischaemic postconditioning has limited and delayed pulmonary protective effects in cardiac surgery patients with CPB.

Postoperative Hyperoxia (60%) Worsens Hepatic Injury in Mice

Background:

Liver damage by ischemia and reperfusion injury is a risk factor for morbidity and mortality after liver surgery. Postoperative oxygen treatment is routinely applied in the postanesthesia and intensive care unit after liver surgery. The risks of aggravating the injury by increasing inspiratory oxygen from 21 to 60% in the postoperative period were investigated in mice.

Methods:

Parameters of liver injury were compared after induction of hepatic ischemia–reperfusion injury, by clamping the left liver lobe for 45 min, and reperfusion for 24 h either under normoxic (21% oxygen) or hyperoxic (60% oxygen) conditions (n = 22 per group). The extent of tissue injury and oxidative responses was analyzed in the presence or absence of polymorphonuclear leukocytes, functional Kupffer cells, and the p47phox unit of the nicotinamide adenine dinucleotide phosphate oxidase (n = 6 to 11 per group).

Results:

Compared with postoperative normoxic conditions, hyperoxia increased cell damage (glutamate-pyruvate transaminase: 1,870 [±968 SD] vs. 60% 2,981 [±1,038 SD], 21 vs. 60% oxygen, in U/l as mean ± SD; P &lt; 0.01), liver weights (341 ± 52 vs. 383 ± 44, 21 vs. 60% oxygen, in mg as mean ± SD; P = 0.02), damage scores (1.9 ± 0.8 vs. 3.1 ± 1.0, 21 vs. 60% oxygen, score as mean ± SD; P = 0.02), and reactive oxygen species (15.0 ± 12.0 vs. 30.4 ± 19.2, 21 vs. 60% oxygen, in μmol/l as mean ± SD; P &lt; 0.05). The aggravation of the tissue damaging effects as a result of hyperoxia was not seen in mice with depletions of polymorphonuclear leukocytes or Kupffer cells, or with nonfunctioning nicotinamide adenine dinucleotide phosphate oxidase.

Conclusion:

Liver injury after ischemia was significantly aggravated by hyperoxia as a consequence of immune cell-mediated oxidative burst. Further studies are needed to elucidate whether routine delivery of high inspirational oxygen concentrations postoperatively should be limited.

Reducing the oxidative stress mediates the cardioprotection of bicyclol against ischemia-reperfusion injury in rats

OBJECTIVE

To investigate the beneficial effect of bicyclol on rat hearts subjected to ischemia-reperfusion (IR) injuries and its possible mechanism.

METHODS

Male Sprague-Dawley rats were intragastrically administered with bicyclol (25, 50 or 100 mg/(kg∙d)) for 3 d. Myocardial IR was produced by occlusion of the coronary artery for 1 h and reperfusion for 3 h. Left ventricular hemodynamics was continuously monitored. At the end of reperfusion, myocardial infarct was measured by 2,3,5-triphenyltetrazolium chloride (TTC) staining, and serum lactate dehydrogenase (LDH) level and myocardial superoxide dismutase (SOD) activity were determined by spectrophotometry. Isolated ventricular myocytes from adult rats were exposed to 60 min anoxia and 30 min reoxygenation to simulate IR injuries. After reperfusion, cell viability was determined with trypan blue; reactive oxygen species (ROS) and mitochondrial membrane potential of the cardiomyocytes were measured with the fluorescent probe. The mitochondrial permeability transition pore (mPTP) opening induced by Ca(2+) (200 μmol/L) was measured with the absorbance at 520 nm in the isolated myocardial mitochondria.

RESULTS

Low dose of bicyclol (25 mg/(kg∙d)) had no significant improving effect on all cardiac parameters, whereas pretreatment with high bicyclol markedly reduced the myocardial infarct and improved the left ventricular contractility in the myocardium exposed to IR (P<0.05). Medium dose of bicyclol (50 mg/(kg∙d)) markedly improved the myocardial contractility, left ventricular myocyte viability, and SOD activity, as well decreased infarct size, serum LDH level, ROS production, and mitochondrial membrane potential in rat myocardium exposed to IR. The reduction of ventricular myocyte viability in IR group was inhibited by pretreatment with 50 and 100 mg/(kg∙d) bicyclol (P<0.05 vs. IR), but not by 25 mg/(kg∙d) bicyclol. The opening of mPTP evoked by Ca(2+) was significantly inhibited by medium bicyclol.

CONCLUSIONS

Bicyclol exerts cardioprotection against IR injury, at least, via reducing oxidative stress and its subsequent mPTP opening.

Propofol improves recovery of the isolated working hypertrophic heart from ischaemia-reperfusion

The general anaesthetic propofol shows promise in protecting normal hearts against various cardiac insults, but little is known about its cardioprotective potential in hypertrophic hearts. This study tested the hypothesis that propofol at a clinically relevant dose would enhance functional recovery in hypertrophic hearts following ischaemia. Hypertrophic hearts from spontaneously hypertensive rats and hearts from their normotensive controls, Wistar Kyoto Rats, were equilibrated in the working mode prior to global normothermic ischaemia. Reperfusion commenced with 10 min in Langendorff mode, followed by 30-min working reperfusion. Functional performance was measured throughout the working mode, whilst reperfusion damage was assessed from myocardial troponin I release during Langendorff reperfusion. Where used, 4 μg/ml propofol was added 10 min before ischaemia and was washed out 10 min into working reperfusion. An additional protocol investigated recovery of hearts protected by normothermic hyperkalaemic cardioplegic arrest. Following 20-min ischaemia, reperfusion damage was significantly worse in hypertrophic hearts compared to normal hearts, whilst addition of propofol to hypertrophic hearts significantly improved the aortic flow (31 ± 5.8 vs. 11.6 ± 2.0 ml/min, n = 6-7 ± SE, p < 0.05). Propofol also conferred significant protection following 30-min ischaemia where the recovery of cardiac output and stroke volume was similar to that for cardioplegia alone. Incubation with propofol improved the NADH/NAD(+) ratio in freshly isolated cardiomyocytes from hypertrophic hearts, suggesting possible improvements in metabolic flux. These findings suggest that propofol at the clinically relevant dose of 4 μg/ml is as effective as cardioplegic arrest in protecting hypertrophic hearts against ischaemia-reperfusion.

A comparative study of cardioprotective effect of three anesthetic agents by measuring serum level of troponin-T after coronary artery bypass grafting

BACKGROUND

Cardiac surgery is associated with some degree of myocardial injury. Preconditioning first described in 1986 was pharmacologic and non- pharmacologic. Among the long list of anesthetic drugs, isoflurane as an inhaling agent along with midazolam and propofol as injectable substances have been documented to confer some preconditioning effects on myocardium.

OBJECTIVES

In this study cardiac Troponin T (cTnT) ,as a reliable marker, was used for evaluating myocardial injury.

METHODS

This prospective double blind study was comprised of 60 patients scheduled for CABG and were randomly assigned into three groups who received infusion of propofol or midazolam or isoflorane. Surgical procedures and anesthetics were similar for 3 groups. cTnT measured preoperatively and at 12, 24 and 36hr after arrival in ICU.

RESULTS

There were no statistically significant differences in mean cTnT levels between three groups in the preoperative period and 12-24 hours after arrival in ICU. However, mean cTnT in 3 groups at 36 hours after arrival in ICU were different (P< 0.013) and cTnT level was significantly higher in midazolam group (P<0.001) and lowest in isoflurane group (P=0.002).

CONCLUSION

There were significant differences on cTnT levels between anesthetic groups of isofluran, midazolam and propofol at 36 hr after surgery. Preconditioning effect of isoflurane was higher than the other two groups.

Propofol post-conditioning protects against cardiomyocyte apoptosis in hypoxia/reoxygenation injury by suppressing nuclear factor-kappa B translocation via extracellular signal-regulated kinase mitogen-activated protein kinase pathway

BACKGROUND AND OBJECTIVE

Perioperative myocardial ischaemia leads to an exceedingly high mortality. Previous studies have indicated that propofol pre-conditioning could mimic the cardioprotective effects of ischaemic pre-conditioning. The purpose of this study was to determine whether propofol post-conditioning is cardioprotective and to explore the possible molecular mechanism of propofol post-conditioning.

METHODS

Primary cultured neonatal rat cardiomyocytes were exposed to 12 h of hypoxia followed by 4 h of reoxygenation (H/R) and post-conditioned by different concentrations of propofol at the onset of reperfusion with and without a specific inhibitor of extracellular signal-regulated kinases (ERKs). Cell apoptosis and the generation of intracellular reactive oxygen species were measured using FACScalibur flow cytometric analysis. ERK1/2 phosphorylation and nuclear factor-kappa B (NF-κB) translocation were determined by western blot and immunofluorescence, respectively.

RESULTS

Propofol post-conditioning enhanced cell viability (86.6 ± 6.5 versus 64.1 ± 3.4%) and reduced apoptosis (3.6 ± 0.4 versus 12.5 ± 2.1%) to protect cardiomyocytes against H/R injury. Meanwhile, propofol post-conditioning stimulated expression of phosphor-ERKs. H/R markedly induced p65 NF-κB nuclear translocation in cardiomyocytes, whereas propofol post-conditioning significantly suppressed H/R-primed NF-κB translocation. Moreover, addition of the mitogen-activated protein kinase kinase 1 inhibitor U0126 into cardiomyocytes 30 min before H/R eliminated the cardioprotection of propofol post-conditioning.

CONCLUSION

Propofol exerts cardioprotection when administered at the early phase of reperfusion. The effect is mediated through decrease in cardiomyocyte apoptosis and NF-κB nucleus translocation potentially via ERK signalling pathways.