Alternative use of isoflurane and propofol confers superior cardioprotection than using one of them alone in a dog model of cardiopulmonary bypass

Organ damage evaluation in a temperature-controlled circulatory arrest rat model

BACKGROUND

Deep hypothermic circulatory arrest (DHCA) is commonly used in adult aortic surgery and pediatric complex congenital heart disease, and is associated with pathophysiological changes and postoperative complications. Here, a temperature-controlled circulatory arrest model in rats was established to study the suitable temperature of circulatory arrest by investigating the damage to body organs under different temperatures.

METHODS

Thirty Sprague‒Dawley rats were randomly divided into 5 equal groups for DHCA experiments: I (15-20 °C), II (20-25 °C), III (25-30 °C), IV (normothermic cardiopulmonary bypass), and V (sham operation group). Blood gas analysis, homodynamic parameters, and intervals of cardiac recovery were measured at different time points in all groups. Morphological changes in intestinal tissue were observed under light and electron microscopes. Oxidative stress was measured by MPO activity, MDA, and SOD content. Tissue damage was confirmed by serum detection of ALT, AST, BUN, Cr, and LDH. To examine the inflammatory response, cytokines, including IL-1, IL-4, IL-10, IFN-γ, and TNF-α, were detected.

RESULTS

The extracorporeal circulation technique caused damage to the body; the degree of the damage caused by the circulatory arrest technique may be related to circulating temperature, with the least amount of damage occurring at 20-25 °C compared to 15-20 °C and 25-30 °C. Ischemia and hypoxia can cause intestinal tissue damage, which manifests primarily as a loss of the intestinal mucosal barrier. Ischemic intestinal damage caused by DHCA was not associated with inflammation.

CONCLUSION

The study provides new insights into the pathophysiologic mechanisms of DHCA.

Isoflurane Preconditioning May Attenuate Cardiomyocyte Injury Induced by Hypoxia/Reoxygenation Possibly by Regulating miR-363-3p

This study attempted to explore whether miR-363-3p play a role in the isoflurane (ISO)-mediated protective effect of cardiomyocyte injury induced by hypoxia/reoxygenation (H/R). A myocardial cell injury model was established, and the different preconditioning ISO concentrations were screened and determined. The miR-363-3p level was detected by RT-qPCR. The effects of miR-363-3p on proliferation and apoptosis of H9c2 cells were detected by CCK-8 assay and flow cytometry. Myocardial injury indexes were determined by enzyme-linked immunosorbent assay (ELISA). The interaction of miR-363-3p with the 3'-UTR of the KLF2 gene was confirmed by luciferase reporter gene assay. ISO pretreatment can reduce the up-regulation of miR-363-3p after H/R injury. ISO pretreatment reduces the inhibition of cell viability and the promotion of cell apoptosis induced by H/R stimuli, while the overexpression of miR-363-3p counteracts the protective effect of ISO pretreatment. Meanwhile, ISO pretreatment also reduced the level of markers of H/R-induced myocardial injury. Moreover, luciferase reporter analysis showed that KLF2 was the downstream target gene of miR-363-3p. ISO pretreatment may alleviate H/R-induced cardiomyocyte injury by regulating miR-363-3p.

Propofol Upregulates MicroRNA-30b to Inhibit Excessive Autophagy and Apoptosis and Attenuates Ischemia/Reperfusion Injury In Vitro and in Patients

Evidence reveals that propofol protects cells via suppressing excessive autophagy induced by hypoxia/reoxygenation (H/R). Previously, we found in a genome-wide microRNA profile analysis that several autophagy-related microRNAs were significantly altered during the process of H/R in the presence or absence of propofol posthypoxia treatment (P-PostH), but how these microRNAs work in P-PostH is still largely unknown. Here, we found that one of these microRNAs, microRNA-30b (miR-30b), in human umbilical vein endothelial cells (HUVECs) was downregulated by H/R treatment but significantly upregulated by 100 M propofol after H/R treatment. miR-30b showed similar changes in open heart surgery patients. By dual-luciferase assay, we found that Beclin-1 is the direct target of miR-30b. This conclusion was also supported by knockdown or overexpression of miR-30b. Further studies showed that miR-30b inhibited H/R-induced autophagy activation. Overexpression or knockdown of miR-30b regulated autophagy-related protein gene expression in vitro. To clarify the specific role of propofol in the inhibition of autophagy and distinguish the induction of autophagy from the damage of autophagy flux, we used bafilomycin A1. LC3-II levels were decreased in the group treated with propofol combined with bafilomycin A1 compared with the group treated with bafilomycin A1 alone after hypoxia and reoxygenation. Moreover, HUVECs transfected with Ad-mCherry-GFP-LC3b confirmed the inhibitory effect of miR-30b on autophagy flux. Finally, we found that miR-30b is able to increase the cellular viability under the H/R condition, partially mimicking the protective effect of propofol which suppressed autophagy via enhancing miR-30b and targeting Beclin-1. Therefore, we concluded that propofol upregulates miR-30b to repress excessive autophagy via targeting Beclin-1 under H/R condition. Thus, our results revealed a novel mechanism of the protective role of propofol during anesthesia. Clinical Trial Registration Number. This trial is registered with ChiCTR-IPR-14005470. The name of the trial register: Propofol Upregulates MicroRNA-30b to Repress Beclin-1 and Inhibits Excessive Autophagy and Apoptosis.

Electroacupuncture preconditioning attenuates myocardial ischemia-reperfusion injury by inhibiting mitophagy mediated by the mTORC1-ULK1-FUNDC1 pathway

Myocardial ischemia/reperfusion (I/R) is an important complication of reperfusion therapy for myocardial infarction, and trimetazidine is used successfully for treatment of ischemic cardiomyopathy by regulating mitochondrial function. Moreover, electroacupuncture (EA) preconditioning was demonstrated to be cardioprotective in both in vivo rodent models and in patients undergoing heart valve replacement surgery. However, the mechanisms have not been well elucidated. Mitophagy, mediated by the mTORC1-ULK1-FUNDC1 (mTOR complex 1-unc-51-like autophagy-activating kinase 1-FUN14 domain-containing 1) pathway, can regulate mitochondrial mass and cell survival effectively to restrain the development of myocardial ischemia/reperfusion injury (MIRI). In this study, we hypothesized that EA preconditioning ameliorated MIRI via mitophagy. To test this, rapamycin, an mTOR inhibitor, was used. The results showed that EA preconditioning could reduce the infarct size and risk size, and decrease the ventricular arrhythmia score and serum creatine kinase-myocardial band isoenzyme (CK-MB), lactate dehydrogenase (LDH), and cardiac troponin T (cTnT) in MIRI rats. Moreover, it also attenuated MIRI-induced apoptosis and mitophagy accompanied by elevated mTORC1 level and decreased ULK1 and FUNDC1 levels. However, these effects of EA preconditioning were blocked by rapamycin, which aggravated MIRI, reduced adenosine triphosphate (ATP) production, and antagonized infarct size reduction. In conclusion, our results indicated that EA preconditioning protected the myocardium against I/R injury by inhibiting mitophagy mediated by the mTORC1-ULK1-FUNDC1 pathway.

Intravenous Anesthetic Protects Hepatocyte from Reactive Oxygen Species-Induced Cellular Apoptosis during Liver Transplantation In Vivo

Background

Liver transplantation leads to liver ischemia/reperfusion (I/R) injury, resulting in early graft dysfunction and failure. Exacerbations of oxidative stress and inflammatory response are key processes in the development of liver I/R injury. Intravenous anesthetic propofol potent effects on free radical scavenging and protects livers against I/R injury. However, the role and mechanism of propofol-mediated hepatic protection in liver transplantation is poorly understood. The aim of this study was to evaluate the role of propofol postconditioning in the liver I/R injury after liver transplantation.

Methods

Forty-eight rats were randomly divided into six groups: rats receiving either sham operation or orthotopic autologous liver transplantation (OALT) in the absence or presence of propofol (high dose and low dose) postconditioning or intralipid control or VAS2870 (Nox2 special inhibitor). Eight hours after OALT or sham operation, parameters of organ injury, oxidative stress, inflammation, and NADPH-associated proteins were assessed.

Results

After OALT, severe liver pathological injury was observed that was associated with increases of serum AST and ALT, which were attenuated by propofol postconditioning. In addition, especially high dose of propofol postconditioning reduced TNF-α, IL-1β, IL-6, TLR4, and NF-κB inflammatory pathway, accompanied with decrease of neutrophil elastase activity, MPO activity, 8-isoprotane, p47^phox and gp91^phox protein expressions, and increase of SOD activity. Inhibition of Nox2 by VAS2870 conferred similar protective effects in liver transplantation.

Conclusion

Liver transplantation leads to severe inflammation and oxidative stress with NADPH oxidase activation. Propofol postconditioning reduces liver I/R injury after liver transplantation partly via inhibiting NADPH oxidase Nox2 and the subsequent inflammation and oxidative stress.

Direct evidence that hypoxia triggers the cardioprotective response of ischemic preconditioning in a dog double-circuit cardiopulmonary bypass model

AIMS

It has been widely accepted that ischemic preconditioning (IPC) exhibits a promising and reproducible cardioprotective effect against ischemia/reperfusion (I/R) injury. However, the actual trigger that amplifies the molecular signaling and protects I/R heart is still unclear.

MAIN METHODS

To separate the factors involved in IPC, we established a dog double-circuit cardiopulmonary bypass (CPB) model, which consists of a systemic circuit and a coronary circuit. Forty-two male adult beagle dogs were randomly allocated into 7 groups: sham, I/R, IPC, hypoxia preconditioning (HPC), accumulated metabolite preconditioning (MPC), oxygenated or deoxygenated erythrocytes preconditioning (OxyEPC and DeoxyEPC). After pretreatment, dogs were subjected to 2 h-cardiac arrest and 2 h-reperfusion.

KEY FINDINGS

There were no differences in the cardiac function and hemodynamic parameters at baseline among groups. Like IPC, the hypoxia-related pretreatments HPC and DeoxyEPC improved post-arrest left ventricular systolic/diastolic performance and reduced pulmonary vascular resistance. The cardiac oxygen (O₂) utilization was also greatly elevated in these hypoxia-related pretreatment groups, as evidenced by increased cardiac O₂ consumption (VO₂) and O₂ extraction index (O₂EI) and suppressed lactate level. Besides, we did not observe improvement of these parameters in the MPC and OxyEPC groups. Further study indicated that these hypoxia-related pretreatments were associated with the attenuation of pro-inflammatory cytokines release and the elevation of complex I-supported mitochondrial respiration.

SIGNIFICANCE

With a dog double-circuit CPB model, we demonstrated that hypoxia is the actual trigger to initiate the cardioprotective effect of IPC in vivo, which was related to reduced cardiac inflammation and ameliorated complex-I supported mitochondrial function.

High-Dose Polymerized Hemoglobin Fails to Alleviate Cardiac Ischemia/Reperfusion Injury due to Induction of Oxidative Damage in Coronary Artery

Objective. Ischemia/reperfusion (I/R) injury is an unavoidable event for patients in cardiac surgery under cardiopulmonary bypass (CPB). This study was designed to investigate whether glutaraldehyde-polymerized human placenta hemoglobin (PolyPHb), a hemoglobin-based oxygen carrier (HBOC), can protect heart against CPB-induced I/R injury or not and to elucidate the underlying mechanism. Methods and Results. A standard dog CPB model with 2-hour cardiac arrest and 2-hour reperfusion was established. The results demonstrated that a low-dose PolyPHb (0.1%, w/v) provided a significant protection on the I/R heart, whereas the high-dose PolyPHb (3%, w/v) did not exhibit cardioprotective effect, as evidenced by the impaired cardiac function, decreased myocardial oxygen utilization, and elevated enzymes release and pathological changes. Further study indicated that exposure of isolated coronary arteries or human umbilical vein endothelial cells (HUVECs) to a high-dose PolyPHb caused impaired endothelium-dependent relaxation, which was companied with increased reactive oxygen species (ROS) production, reduced superoxide dismutase (SOD) activity, and elevated malonaldehyde (MDA) formation. Consistent with the increased oxidative stress, the NAD(P)H oxidase activity and subunits expression, including gp91^phox, p47^phox, p67^phox, and Nox1, were greatly upregulated. Conclusion. The high-dose PolyPHb fails to protect heart from CPB-induced I/R injury, which was due to overproduction of NAD(P)H oxidase-induced ROS and resultant endothelial dysfunction.

Peri-operative anaesthetic myocardial preconditioning and protection - cellular mechanisms and clinical relevance in cardiac anaesthesia

Preconditioning has been shown to reduce myocardial damage caused by ischaemia–reperfusion injury peri-operatively. Volatile anaesthetic agents have the potential to provide myocardial protection by anaesthetic preconditioning and, in addition, they also mediate renal and cerebral protection. A number of proof-of-concept trials have confirmed that the experimental evidence can be translated into clinical practice with regard to postoperative markers of myocardial injury; however, this effect has not been ubiquitous. The clinical trials published to date have also been too small to investigate clinical outcome and mortality. Data from recent meta-analyses in cardiac anaesthesia are also not conclusive regarding intra-operative volatile anaesthesia. These inconclusive clinical results have led to great variability currently in the type of anaesthetic agent used during cardiac surgery. This review summarises experimentally proposed mechanisms of anaesthetic preconditioning, and assesses randomised controlled clinical trials in cardiac anaesthesia that have been aimed at translating experimental results into the clinical setting.

Angiotensin-converting enzyme inhibitor captopril reverses the adverse cardiovascular effects of polymerized hemoglobin

AIM

Cell-free hemoglobin-based oxygen carriers (HBOCs) may increase the risk of myocardial infarction and death. We studied the effect of an angiotensin-converting enzyme (ACE) inhibitor on HBOC-induced adverse cardiovascular outcomes and elucidated the underlying mechanisms.

RESULTS

With a dog cardiopulmonary bypass model, we demonstrated that a high-dose HBOC (3%, w/v) did not reduce-but aggravated-cardiac ischemia/reperfusion injury. Animals administered a high-dose HBOC experienced coronary artery constriction and depression of cardiac function. Exposure of isolated coronary arteries or human umbilical vein endothelial cells to high-dose HBOC caused impaired endothelium-dependent relaxation, increased endothelial cell necrosis/apoptosis, and elevated NAD(P)H oxidase expression (gp91(phox), p47(phox), p67(phox), and Nox1) and reactive oxygen species (ROS) production. All observed adverse outcomes could be suppressed by the ACE inhibitor captopril (100 μM). Co-incubation with free radical scavenger tempol or NAD(P)H oxidase inhibitor apocynin had no effect on captopril action, suggesting that the positive effects of captopril are ROS- and NAD(P)H oxidase dependent. ACE inhibition by captopril also contributed to these effects. In addition, bioavailable nitrite oxide (NO) reduced by high-dose HBOC was preserved by captopril. Furthermore, HBOC, at concentrations greater than 0.5%, inhibited large conductance Ca(2+)-activated K(+) channel currents in vascular smooth muscle cells in a dose-dependent manner, although captopril failed to improve current activity, providing additional evidence that captopril's effects are mediated by the endothelium, but not by the smooth muscle.

INNOVATION AND CONCLUSION

Captopril alleviates high-dose HBOC-induced endothelial dysfunction and myocardial toxicity, which is mediated by synergistic depression of NAD(P)H oxidase subunit overproduction and increases in vascular NO bioavailability.

Establishment of a novel rat model without blood priming during normothermic cardiopulmonary bypass

OBJECTIVE

An effective animal model was needed for research on the pathophysiology of cardiopulmonary bypass (CPB). Rat models were considered suitable for research into CPB, recently. The aim of the article is to establish a simple and safe CPB model without blood priming in rats, containing the advantages of controlling temperature precisely, being similar to the clinical process and laying the foundation for the further study of a deep hypothermic circulatory arrest (DHCA) model.

MATERIALS AND METHODS

Ten Sprague-Dawley rats, divided into a CPB group (n=7) and a sham group (n=3), received sevoflurane inhalation anesthesia and were maintained in an anesthesia state by intubation. The entire CPB circuit consisted of a reservoir, a membrane oxygenator, a roller pump, a heat exchanger and a heat cooler, all of which were connected via silicon tubes. The volume of the priming solution, composed of 6% HES130/0.4 and 125 IU heparin, was less than 12 ml. In the CPB group, a 22G catheter was placed in the left femoral artery for monitoring arterial blood pressure, a 20G catheter was placed in a tail artery for arterial inflow and a homemade, multiorificed catheter was inserted into a right jugular vein for venous drainage. After 90 minutes, the CPB process was terminated when vital signs were stable. In the sham group, the same surgical process was conducted except for the venous drainage. Post-oxygenator blood gas and hemodynamic parameters were measured at each time point before CPB, during CPB and after CPB.

RESULTS

All CPB processes were successfully achieved. Blood gas analysis and hemodynamic parameters of each time point were in accordance with normal ranges. The vital signs of all rats were stable.

CONCLUSION

The establishment of CPB without blood priming in rats can be achieved successfully. The rat model could be used to study short-term or long-term organ injury mechanisms caused by CPB. Furthermore, on the basis of the precise control of temperature and the depth of anesthesia, the DHCA model in rats could be developed further to study pathophysiological changes of neurological and other organ functions in the future.