Propofol decreases myofilament Ca2+ sensitivity via a protein kinase C-, nitric oxide synthase-dependent pathway in diabetic cardiomyocytes

Uric Acid Deteriorates Load-Free Cell Shortening of Cultured Adult Rat Ventricular Cardiomyocytes via Stimulation of Arginine Turnover

Hyperuricemia is a risk factor for heart disease. Cardiomyocytes produce uric acid via xanthine oxidase. The enzymatic reaction leads to oxidative stress in uric-acid-producing cells. However, extracellular uric acid is the largest scavenger of reactive oxygen species, specifically to nitrosative stress, which can directly affect cells. Here, the effect of plasma-relevant concentrations of uric acid on adult rat ventricular cardiomyocytes is analyzed. A concentration- and time-dependent reduction of load-free cell shortening is found. This is accompanied by an increased protein expression of ornithine decarboxylase, the rate-limiting enzyme of the polyamine metabolism, suggesting a higher arginine turnover. Subsequently, the effect of uric acid was attenuated if other arginine consumers, such as nitric oxide synthase, are blocked or arginine is added. In the presence of uric acid, calcium transients are increased in cardiomyocytes irrespective of the reduced cell shortening, indicating calcium desensitization. Supplementation of extracellular calcium or stimulation of intracellular calcium release by β-adrenergic receptor stimulation attenuates the uric-acid-dependent effect. The effects of uric acid are attenuated in the presence of a protein kinase C inhibitor, suggesting that the PKC-dependent phosphorylation of troponin triggers the desensitizing effect. In conclusion, high levels of uric acid stress cardiomyocytes by accelerating the arginine metabolism via the upregulation of ornithine decarboxylase.

Diabetes with heart failure increases methylglyoxal modifications in the sarcomere, which inhibit function

Patients with diabetes are at significantly higher risk of developing heart failure. Increases in advanced glycation end products are a proposed pathophysiological link, but their impact and mechanism remain incompletely understood. Methylglyoxal (MG) is a glycolysis byproduct, elevated in diabetes, and modifies arginine and lysine residues. We show that left ventricular myofilament from patients with diabetes and heart failure (dbHF) exhibited increased MG modifications compared with nonfailing controls (NF) or heart failure patients without diabetes. In skinned NF human and mouse cardiomyocytes, acute MG treatment depressed both calcium sensitivity and maximal calcium-activated force in a dose-dependent manner. Importantly, dbHF myocytes were resistant to myofilament functional changes from MG treatment, indicating that myofilaments from dbHF patients already had depressed function arising from MG modifications. In human dbHF and MG-treated mice, mass spectrometry identified increased MG modifications on actin and myosin. Cosedimentation and in vitro motility assays indicate that MG modifications on actin and myosin independently depress calcium sensitivity, and mechanistically, the functional consequence requires actin/myosin interaction with thin-filament regulatory proteins. MG modification of the myofilament may represent a critical mechanism by which diabetes induces heart failure, as well as a therapeutic target to avoid the development of or ameliorate heart failure in these patients.

Propofol-induced mitochondrial and contractile dysfunction of the rat ventricular myocardium

Propofol is a short-acting hypnotic agent used in human medicine for sedation and general anesthesia. Its administration can be associated with serious cardiovascular side-effects that include decrease in arterial blood pressure and cardiac output. The aim of the present study was to evaluate propofol effects on mitochondrial respiration, myocardial contractility and electrophysiology in the same samples isolated from the heart ventricles of adult rats. Mitochondrial oxygen consumption was measured in permeabilized samples dissected from free walls of both ventricles using high-resolution respirometry. State LEAK was determined with malate and glutamate. Active respiration was induced by ADP (state PI) and further by succinate, a Complex II substrate (PI+II). Rotenone was injected to measure state PII. Antimycin A, a Complex III inhibitor was used to determine residual oxygen consumption (ROX). N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride and ascorbate were injected simultaneously for respirometric assay of cytochrome c oxidase activity (CIV). Isometric contractions and membrane potentials were determined on multicellular preparations isolated from right and left ventricles. Propofol concentrations used ranged from 0.005 to 0.5 mmol/l. All respiratory parameters were significantly higher in the left control ventricles compared to the right ones. Propofol significantly decreased Complex I activity at concentration 0.025 mmol/l and papillary muscle contraction force at 0.1 mmol/l. Propofol did not affect action potential duration at any concentration studied. Our study suggests that mechanisms contributing to the impaired myocardial contraction during propofol anesthesia might include also mitochondrial dysfunction manifested by compromised activity of the respiratory Complex I.

Propofol protects human keratinocytes from oxidative stress via autophagy expression

Background

The skin consists of tightly connected keratinocytes, and prevents extensive water loss while simultaneously protecting against the entry of microbial pathogens. Excessive cellular levels of reactive oxygen species can induce cell apoptosis and also damage skin integrity. Propofol (2,6-diisopropylphenol) has antioxidant properties. In this study, we investigated how propofol influences intracellular autophagy and apoptotic cell death induced by oxidative stress in human keratinocytes.

Method

The following groups were used for experimentation: control, cells were incubated under normoxia (5% CO₂, 21% O₂, and 74% N₂) without propofol; hydrogen peroxide (H₂O₂), cells were exposed to H₂O₂ (300 µM) for 2 h; propofol preconditioning (PPC)/H₂O₂, cells pretreated with propofol (100 µM) for 2 h were exposed to H₂O₂; and 3-methyladenine (3-MA)/PPC/H₂O₂, cells pretreated with 3-MA (1 mM) for 1 h and propofol were exposed to H₂O₂. Cell viability, apoptosis, and migration capability were evaluated. Relation to autophagy was detected by western blot analysis.

Results

Cell viability decreased significantly in the H₂O₂ group compared to that in the control group and was improved by propofol preconditioning. Propofol preconditioning effectively decreased H₂O₂-induced cell apoptosis and increased cell migration. However, pretreatment with 3-MA inhibited the protective effect of propofol on cell apoptosis. Autophagy was activated in the PPC/H₂O₂ group compared to that in the H₂O₂ group as demonstrated by western blot analysis and autophagosome staining.

Conclusion

The results suggest that propofol preconditioning induces an endogenous cellular protective effect in human keratinocytes against oxidative stress through the activation of signaling pathways related to autophagy.

Hemodynamic and biochemical changes in liver transplantation: A retrospective comparison of desflurane and total intravenous anesthesia by target-controlled infusion under auditory evoked potential guide

OBJECTIVES

Propofol-based total intravenous anesthesia (TIVA) has been used successfully for liver transplantation (LT) in recent years. However, there are few discourses in the literature which focus on the merits and weakness in perioperative management, biochemical changes, and postoperative recovery between TIVA and desflurane anesthesia (DES).

METHODS

We retrospectively compared the circumstances of liver transplantation recipients who had the surgery carried out under propofol-based TIVA or DES in the period from September 2007 to August 2010. Preoperative characteristics, date of intraoperative management, hemodynamic profiles, concentration of anesthetics, biochemical changes, and circumstances of postoperative recovery were retrieved from the hospital database for analysis.

RESULTS

We included 111 patients who received the surgery under either TIVA (n = 66) or DES (n = 45). Patient demographics, baseline laboratory data, operation time, and fluid management did not differ between the two groups. In comparison with the DES group, fewer patients had to be administered norepinephrine (21.2% vs. 42.2%; p = 0.020) in the TIVA group; moreover, the total dosage of norepinephrine was lower (0.003 ± 0.005 mg vs. 0.006 ± 0.008 mg; p = 0.012) in the TIVA group during liver reperfusion phase. Blood lactate level was higher in the DES group than in the TIVA group after the anhepatic phase. TIVA patients woke up faster than those in the DES group (54.0 ± 33.4 minutes vs. 95.0 ± 78.3 minutes; p = 0.034).

CONCLUSION

Our results suggest that propofol-based TIVA may provide better hemodynamics and microcirculation during the anhepatic phase in liver transplantation.

Nitroglycerine-induced nitrate tolerance compromises propofol protection of the endothelial cells against TNF-α: the role of PKC-β2 and NADPH oxidase

Continuous treatment with organic nitrates causes nitrate tolerance and endothelial dysfunction, which is involved with protein kinase C (PKC) signal pathway and NADPH oxidase activation. We determined whether chronic administration with nitroglycerine compromises the protective effects of propofol against tumor necrosis factor (TNF-) induced toxicity in endothelial cells by PKC-β₂ dependent NADPH oxidase activation. Primary cultured human umbilical vein endothelial cells were either treated or untreated with TNF-α (40 ng/mL) alone or in the presence of the specific PKC-β₂ inhibitor CGP53353 (1 μM)), nitroglycerine (10 μM), propofol (100 μM), propofol plus nitroglycerin, or CGP53353 plus nitroglycerine, respectively, for 24 hours. TNF-α increased the levels of superoxide, Nox (nitrate and nitrite), malondialdehyde, and nitrotyrosine production, accompanied by increased protein expression of p-PKC-β₂, gP91phox, and endothelial cell apoptosis, whereas all these changes were further enhanced by nitroglycerine. CGP53353 and propofol, respectively, reduced TNF-α induced oxidative stress and cell toxicity. CGP53353 completely prevented TNF-α induced oxidative stress and cell toxicity in the presence or absence of nitroglycerine, while the protective effects of propofol were neutralized by nitroglycerine. It is concluded that nitroglycerine comprises the protective effects of propofol against TNF-α stimulation in endothelial cells, primarily through PKC-β₂ dependent NADPH oxidase activation.

Morphology and Contractility of Cardiac Myocytes in Early Stages of Streptozotocin-Induced Diabetes Mellitus in Rats

Diabetic cardiomyopathy is the leading cause of mortality in type 1 diabetes. Thus study of cardiomyocyte morphology and function during early stages of diabetes using modern analytical methods is of critical importance. Therefore, using confocal microscopy, we determined metric parameters, volumes and contractility, with calcium transients in isolated left-ventricular myocytes at one week after induction of diabetes in rats. Myocyte volume analysis from 3D confocal scans was performed using an automated contour detection algorithm that took the actual shape of the myocytes into account. We showed a significant reduction in myocyte volume in diabetic animals. We also showed a significant reduction in length and width but not in thickness of the myocytes, which suggests disproportional reorganization of the structure of the heart tissue during short-term diabetes. From a functional point of view, we observed a significant decrease in cell shortening at a stimulation frequency of 0.5 Hz. This was accompanied by a decrease in calcium transient amplitude. Together, these data suggest that impaired calcium handling is one of the factors that contributes to the observed decrease in myocyte shortening during early stages of streptozotocin-induced diabetes in rats.

Protection of the heart by treatment with a divalent-copper-selective chelator reveals a novel mechanism underlying cardiomyopathy in diabetic rats

Background

Intracellular calcium (Ca²⁺) coordinates the cardiac contraction cycle and is dysregulated in diabetic cardiomyopathy. Treatment with triethylenetetramine (TETA), a divalent-copper-selective chelator, improves cardiac structure and function in patients and rats with diabetic cardiomyopathy, but the molecular basis of this action is uncertain. Here, we used TETA to probe potential linkages between left-ventricular (LV) copper and Ca²⁺ homeostasis, and cardiac function and structure in diabetic cardiomyopathy.

Methods

We treated streptozotocin-diabetic rats with a TETA-dosage known to ameliorate LV hypertrophy in patients with diabetic cardiomyopathy. Drug treatment was begun either one (preventative protocol) or eight (restorative protocol) weeks after diabetes induction and continued thereafter for seven or eight weeks, respectively. Total copper content of the LV wall was determined, and simultaneous measurements of intracellular calcium concentrations and isometric contraction were made in LV trabeculae isolated from control, diabetic and TETA-treated diabetic rats.

Results

Total myocardial copper levels became deficient in untreated diabetes but were normalized by TETA-treatment. Cardiac contractility was markedly depressed by diabetes but TETA prevented this effect. Neither diabetes nor TETA exerted significant effects on peak or resting [Ca²⁺]_i. However, diabetic rats showed extensive cardiac remodelling and decreased myofibrillar calcium sensitivity, consistent with observed increases in phosphorylation of troponin I, whereas these changes were all prevented by TETA.

Conclusions

Diabetes causes cardiomyopathy through a copper-mediated mechanism that incorporates myocardial copper deficiency, whereas TETA treatment prevents this response and maintains the integrity of cardiac structure and myofibrillar calcium sensitivity. Altered calcium homeostasis may not be the primary defect in diabetic cardiomyopathy. Rather, a newly-described copper-mediated mechanism may cause this disease.

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.

The use of intra-cellular signaling pathways in anesthesiology and pain medicine field

At the level of individual cells, signaling is crucial in cell division, differentiation, metabolic control and death. Reception of the signals depends on receptor proteins that are usually at the cell surface, and these receptor proteins bind the signal molecule. The binding activates the receptor, which in turn activates one or more of the intra-cellular signaling pathways. These relay chains of molecules, mainly intra-cellular signaling proteins, process the signal inside the receiving cell and distribute it to the appropriate intra-cellular targets. Cell signaling pathways are involved in the pathophysiology of many diseases and also in the mechanisms of action of many drugs, including local and general anesthetics. Knowledge of the basic cell signaling mechanisms is essential for understanding many of the pathophysiologic and pharmacologic mechanisms. Therefore, if we focus on applying the new cellular and molecular biologic research, these efforts could identify the mechanism of diseases and help develop new drugs in the field of anesthesiology and pain medicine.

Propofol protects against hydrogen peroxide-induced injury in cardiac H9c2 cells via Akt activation and Bcl-2 up-regulation

Propofol is a widely used intravenous anesthetic agent with antioxidant properties secondary to its phenol based chemical structure. Treatment with propofol has been found to attenuate oxidative stress and prevent ischemia/reperfusion injury in rat heart. Here, we report that propofol protects cardiac H9c2 cells from hydrogen peroxide (H(2)O(2))-induced injury by triggering the activation of Akt and a parallel up-regulation of Bcl-2. We show that pretreatment with propofol significantly protects against H(2)O(2)-induced injury. We further demonstrate that propofol activates the PI3K-Akt signaling pathway. The protective effect of propofol on H(2)O(2)-induced injury is reversed by PI3K inhibitor wortmannin, which effectively suppresses propofol-induced activation of Akt, up-regulation of Bcl-2, and protection from apoptosis. Collectively, our results reveal a new mechanism by which propofol inhibits H(2)O(2)-induced injury in cardiac H9c2 cells, supporting a potential application of propofol as a preemptive cardioprotectant in clinical settings such as coronary bypass surgery.

Propofol activates and allosterically modulates recombinant protein kinase C epsilon

BACKGROUND

Myocardial protection by anesthetics is known to involve activation of protein kinase C epsilon (PKC epsilon). A key step in the activation process is autophosphorylation of the enzyme at serine 729. This study's objectives were to identify the extent to which propofol interacts with PKC epsilon and to identify the molecular mechanism(s) of interaction.

METHODS

Immunoblot analysis of recombinant PKC epsilon was used to assess autophosphorylation of PKC epsilon at serine 729 before and after exposure to propofol. An enzyme-linked immunosorbant assay kit was used for measuring PKC epsilon activity. Spectral shifts in fluorescence emission maxima of the C1B subdomain of PKC epsilon in combination with the fluorescent phorbol ester, sapintoxin D, was used to identify molecular interactions between propofol and the phorbol ester/diacylglycerol binding site on the enzyme.

RESULTS

Propofol (1 microM) caused a sixfold increase in immunodetectable serine 729 phosphorylated PKC epsilon and increased catalytic activity of the enzyme in a dose-dependent manner. Dioctanoylglycerol-induced or phorbol myristic acetate-induced activation of recombinant PKC epsilon activity was enhanced by preincubation with propofol. Both propofol and phorbol myristic acetate quenched the intrinsic fluorescence spectra of the PKC epsilon C1B subdomain in a dose-dependent manner, and propofol caused a further leftward-shift in the fluorescence emission maxima of sapintoxin D after addition of the C1B subdomain.

CONCLUSIONS

These results demonstrate that propofol interacts with recombinant PKC epsilon causing autophosphorylation and activation of the enzyme. Moreover, propofol enhances phorbol ester-induced catalytic activity, suggesting that propofol binds to a region near the phorbol ester binding site allowing for allosteric modulation of PKC epsilon catalytic activity.

Propofol attenuation of hydrogen peroxide-mediated oxidative stress and apoptosis in cultured cardiomyocytes involves haeme oxygenase-1

BACKGROUND AND OBJECTIVE

Our aim was to investigate the cytoprotective effect of propofol against hydrogen peroxide (H2O2)-mediated injury and the effects on the haeme oxygenase-1 system, which is a possible new cytoprotective pathway of propofol.

METHODS

Primary cultured newborn rat cardiomyocytes were divided into five groups: (1) untreated (Group control); (2) treated with 200 micromol L(-1) H2O2 (Group H) and treated with 200 micromol L(-1) H2O2 in the presence of propofol (25, 50 and 100 micromol L(-1), (3) Group 25P + H, (4) Group 50P + H and (5) Group 100P + H, respectively); added with zinc protoporphyrin IX (ZnPPIX) (10 micromol L(-1)), a potent inhibitor of haeme oxygenase activity, or SC-3060 (0.2 micromol L(-1)), a specific synthetic inhibitor of nuclear factor kappaB. All were incubated for 6 h. The protective effects of propofol were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide cytotoxicity assay, the concentration of malondialdehyde, superoxide dismutase activity and cell apoptosis by enzyme-linked immunosorbent assay (ELISA). Reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis were used to detect haeme oxygenase-1 expression.

RESULTS

Compared with H2O2, propofol concentrations (ranging from 50 to 100 micromol L(-1)) significantly increased haeme oxygenase-1 expression and decreased cardiomyocytes apoptosis, accompanied with a decrease in malondialdehyde, but with an increase in superoxide dismutase activity and cell activity (P < 0.05 and P < 0.01, respectively). The protective effects of propofol were mitigated by the addition of ZnPPIX. The addition of SC-3060 reversed propofol-induced haeme oxygenase-1 expression.

CONCLUSION

Propofol can protect cardiomyocytes against H2O2-mediated cytotoxicity in a dose-dependent manner and increase haeme oxygenase-1 expression, which may partly mediate the cytoprotective effects of propofol.

Propofol Reduces Apoptosis and Up-Regulates Endothelial Nitric Oxide Synthase Protein Expression in Hydrogen Peroxide-Stimulated Human Umbilical Vein Endothelial Cells

BACKGROUND

Vascular endothelial cells play an important role in maintaining cardiovascular homeostasis. Oxidative stress is a critical pathogenic factor in endothelial cell damage and the development of cardiovascular diseases. In this study we evaluated the effects of propofol on oxidative stress-induced endothelial cell insults and the role of serine-threonine kinase Akt modulation of endothelial nitric oxide synthase (eNOS) as a mechanism of protection.

METHODS

Human umbilical vein endothelial cells were used as the experimental model. Hydrogen peroxide (H2O2, 100 microM) was used as the stimulus of oxidative stress. Study groups included 1) control; 2) cells incubated with H2O2 alone; 3) cells incubated with propofol (50 microM) alone; or 4) cells pretreated with propofol 50 microM for 30 min then co-incubated with H2O2. Cell viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and Trypan blue dye exclusion test. Cell apoptosis was evaluated by Hoechst 33258 staining. Caspase-3 activity was determined by the colorimetric CaspACE Assay System. Expressions of Akt, phospho-Akt, and eNOS were detected by Western blotting.

RESULTS

H2O2 decreased cell viability, induced apoptosis, and increased caspase-3 activity in human umbilical vein endothelial cells. Propofol significantly protected cells from H2O2-induced cell damage, apoptosis and decreased H2O2-induced increase in caspase-3 activity. Propofol treatment significantly increased eNOS expression compared to control and H2O2-stimulated cells. There was no significant difference in phospho-Akt (Ser 473 or Thr 308) expression among the groups.

CONCLUSIONS

Propofol 50 microM can reduce H2O2-induced damage and apoptosis in endothelial cells, by suppressing caspase-3 activity and by increasing eNOS expression via an Akt-independent mechanism.