[Effect of quercetin on proteasome activity in the aorta and heart tissues of spontaneously hypertensive rats]

To determine the role of proteasome proteolysis in the pathogenesis of hypertension, we have studied the proteolytic activity of the proteasome in the aorta and heart tissues of rats with spontaneous hypertension (line SHR), and used quercetin, the drug that can inhibit the activity of this multicatalytic complex. In the aorta of SHR, the activities of the proteasome were not significantly different from that observed in Wistar rats. At the same time, in the heart tissues the trypsin-like (at 40%, P > 0.05), and chymotrypsin-like (by 1.7 times, P < 0.03) activities were significantly less in SHR. Significant morphological changes (fibrosis of the left ventricle was 4.7%, aorta intima width was increased and heart weight index was higher by 21.6% (3.7 +/- 0.6 mg/g) compared with Wistar rats (2.9 +/- 0,4 mg/g, P < 0.004) were observed in these animals functional disorders (reduced stroke volume by 3 times (P < 0.0001), ejection fraction by 2.5 times (P < 0.0001), increased end diastolic pressure by 6.5 times (P < 0.005), end systolic pressure by 15% (P < 0.004)) were revealed. Pharmacological drug "Qvercetin" effectively inhibited trypsin-like and chymotrypsin-like proteasome activities in the aorta (2.7-fold (P < 0.005) and 2-fold (P < 0.003), correspondingly) and trypsin-like, and peptidyl-glutamyl peptide-hydrolyzing-like activities (2.4-fold, P > 0.05 and 9.3-fold, P < 0.02, correspondingly) activities in the heart, leading to a significant improvement of morphological and functional parameters of the heart. Whereas the drug "Qvercetin" that is widely used in clinical practice (especially in therapy of acute myocardial infarction) it could be recommended for the use in prevention of cardiac remodeling with high level of blood pressure.

[The changes in the activity of tripeptidyl peptidase II in experimental atherosclerosis and hypertension]

The changes in the activity of intracellular proteolytic systems are important mechanisms in the damage of blood vessels walls and arterial hypertension. Tripeptidyl peptidase II (TPP II) is one of the giant intracellular protease that is still poorly known. It fulfils hydrolysis of peptides, coming from proteasomal proteolysis. Modeling of cholesterol atherosclerosis in rabbits (1% of cholesterol in diet for 2 month) results in the significant decrease of TPP II activity in aorta tissues. This diet in spontaneously hypertensive rats (SHR) leads to a decrease of TPP II activity in aorta tissues (on 50%, P < 0.05) but has no influence on the activity of TPP II in Wistar rats. Application of Quercetin prevents the inhibition of TPP II activity in aorta tissues of rabbits and SHR at experimental hypercholesterolemia. The data received show that changes in the activity of TPP II play an important role in pathogenesis of blood vessels wall in atherosclerosis and arterial hypertension.

[RNA interference of proteasome subunit of PSMbeta7 gene restricts proteasome subunit PSMbeta1 and PSMbeta5 mRNA expression and peptidyl-glutamyl peptide-hydrolyzing proteasome activity in neonatal cardiomyocytes]

Using small interfering RNA (siRNA) transfection of neonatal cardiomyocytes to inhibit expression of nonproteolytic proteasome beta7 subunit, we observed a significant decrease in beta1 proteolytic subunit mRNA expression. Proteasome peptidyl-glutamyl peptide-hydrolyzing activity decreased to 28% (0.48 +/- 0.2 nM AMC/min) compared to control (1.7 +/- 0.5 nM AMC/min) (P < 0.05). Beta5 Subunit mRNA expression decreased 21 times (P < 0.05) with no changes in its chymotrypsin-like activity. Proteasome trypsin-like activity and activity of another proteolytic enzyme tripeptidyl-peptidase II remained unchanged.

[Effect of medical form of flocalin on the course of myocardial reperfusion injury]

In experiments on anaesthetized dogs with modeling of experimental ischemia (90 min) and reperfusion (180 min), the cardioprotective influence of the pharmacological preconditioning caused by intragastric (with a help of catheter) introduction of medicinal form (tablets) of new fluorine-containing opener of ATP-sensitive potassium channels flocalin was shown. Flocalin was introduced in a dose 2.2 mg/kg, which in the conditions of physiological norm has a minimum influence on the parameters of cardiohemodynamic. The conducted research allowed to define the changes of these parameters during development of antiischemic protective effect of pharmacological preconditioning, caused by the medicinal form of flocalin, and describes basic cardioprotective mechanisms, related to the changes of cardiohemodynamic in the dynamics of ischemia-reperfusion of myocardium. In our opinion, to positive influences of flocalin, which are possibly related to cardioprotective action, it is possible to add the prevention of an increase of general peripheral resistance, resistance of coronal vessels of heart, and relative preservation of myocardium contractility in the period of reperfusion. Also these positive effects can be explained by moderate decrease of blood pressure that decreases the loading on the damaged heart and allows to preserve cardiac emission in the first period of ischemia. One of the major indexes of development of protective mechanism of pharmacological preconditioning caused by preischemic introduction of medicinal form of flocalin is the diminishing of infarct size of myocardium in experiments with ischemia-reperfusion of myocardium on 42.53% +/- 2.91% versus control experiments.

[Interrelation between cardiac pump function disturbances and cardiac contractility after beta-adrenergic hyperstimulation of the heart in rats]

The complex of structural and functional changes of myocardium was investigated in experiments with rats with chronic beta-adrenergic activation for 1 month. We observed substantial attenuation of myocardial pump function, particularly reduction of stroke volume by 38.50% (P < 0.01), cardiac output by 42.38% (P < 0.01), and ejection fraction by 35.61% (P < 0.01). Furthermore, 2-fold increase of end-diastolic left ventricular pressure (P < 0.01) and rise of active relaxation constant Tau by 12.91% (P < 0.05) were observed. This indicates on an impaired diastolic function of the heart that is associated with accumulation of connective tissue elements in myocardium and increase of its end-diastolic stiffness that finally leads to cardiac pump function disturbances. Surprisingly, myocardial contractility was considerably augmented not only after the treatment with beta-adrenergic agonist but also on the 26th day after drug cessation. This phenomenon is associated with elevation of dP/dt(max) by 49.9% (P < 0.01), 2.5-fold increase of end-systolic elastance (P < 0.01) as well as maximal myocardial elastance by 42.53% (P < 0.05). It can be explained by compensatory influence of increased contractility that nevertheless failed to maintain adequate cardiac pump function and furthermore it may result in depletion of cardiac energy resource.

[Effects of ubiquitin gene silencing in anoxia-reoxygenation of cultured cardiomyocytes]

Ubiquitin-dependent proteasomal proteolysis is crucialin the turnover of cardiomyocytes functional proteins (actin, myosin, ion channels at. al.), therefore, investigation of cell death after ubiquitin (UBB) gene silencing using RNA interference and anoxia-reoxygenation (AR) modeling appears to be attractive. Cardiomyocytes were transfected by siRNA to ubiquitin gene using electroporation procedure, and then primary culture was treated by 30 min of anoxia and 60 min of reoxygenation. The number of living, necrotic and apoptotic cardiomyocytes was determined by fluorescence microscopy. The level of UBB and proteasome subunits beta5 (PSMB5) and beta9 (PSMB9) mRNA expression was estimated by real-time PCR. It was shown that UBB mRNA expression was increased by 2.1 times after AR modelling (P < 0.05). Small interference RNA injection in cell culture decreased ubiquitin, PSMB5 and PSMB9 expression by 2.4 (P < 0.05), 1.3 (P > 0.05) and 1.6 (P < 0.05) times, respectively, compared with control (scrambled siRNA introduction). At the same time, the number of living cardiomyocytes decreased to 70.26 +/- 1.54%, P<0.05, and the level of necrotic cells, apoptotic cells and cells with signs of autophagy augmented by 25.92 +/- 1.52%, (P = 0.38), 4.32 +/- 0.53% (P = 0.15) and 38.2 +/- 3.81% (P = 0.001), respectively. Ubiquitin silencing after AR (30 min/l h) increased the number of living cells by 3.7% and decreased the number of necrotic cells by 4.7% and did not alter the apoptotic and autophagic cells populations. The data obtained indicate that ubiquitin gene silencing, mRNA expression of which augmented during AR, induces necrotic and autophagic death of intact neonatal cardiomyocytes in culture, but enhances the AR resistance of these cells to some extent.

[Second anoxia-reoxygenation does not cause the apoptotic cell death of cultured neonatal cardiomyocytes]

The cells death and genes expression in neonatal cardiomyocytes culture at two anoxia-reoxygenation modeling were investigated. The primary culture of neonatal cardiomyocytes was undergone 30 min of anoxia followed by 24 h (A-R1) and the second anoxia-reoxygenation--30 min and 60 min respectively (A-R2). The percentages of living, necrotic, apoptotic and autophagic cells were determined by staining with bis-benzimide, propidium iodide and monodansylcadaverine. Anoxia-reoxygenation significantly influenced the ratio of living, necrotic, apoptotic and autophagic cells both at its first A-RI and second A-R2 episodes. It was shown that the main mechanism of cell death after the both periods of anoxia-reoxygenation is necrosis. The changes of mRNA levels of genes of heat shock proteins HSP70 and HSP90, antiapoptotic protein Bcl2 and key regulator of autophagy FRAP in cardiomyocytes culture were established. The data obtained allow to make suggestion that in 24 h after the first episode of anoxia-reoxygenation A-R1 the overexpression of heat shock proteins starts the cascade of reactions that causes the necrotic cell death prevalent and the blocking of apoptotic program at second anoxia-reoxygenation A-R2.

[SiRNA-mediated silencing of 5-lipoxygenase gene (ALOX5) reduces necrosis of neonatal cardiomyocytes in anoxia-reoxygenation]

In experiments on the primary culture of isolated neonatal rat cardiomyocytes it was determined that cardiomyocytes express ALOX5 gene encoding enzyme 5-lipoxygenase. Anoxia-reoxygenation does not affect significantly the expression of 5-lipoxygenase mRNA in cardiomyocytes. Transfection of 5-lipoxygenase-specific small interfering RNA's (siRNA) into cardiomyocytes lead to a significant reduction of 5-lipoxygenase mRNA expression in cardiomyocytes 24 hours after transfection. ALOX5 gene silencing resulted in improved viability of cell population (by 13.3% P < 0.001) due to decreased number of necrotic (by 14.6%, P < 0.001), but not apoptotic, cells during anoxia-reoxygenation. Our results indicate that siRNA against ALOX5 effectively protects cardiomyocytes against anoxia-reoxygenation injury.

[Cardioprotective effects of flokalin in experiments in vivo: influence on hemodynamic and myocardial lesions in ischemia-reperfusion]

In experiments on anaesthetized dogs with modeling of experimental ischemia (90 min) and reperfusion (180 min) the cardioprotective influence of the preischemic activation of ATP-sensitive potassium (K(ATP)) channels by intravenous introduction of flokalin, a new fluorine-containing opener of these channels was shown. Flokalin was introduced in dose 0.1 mg/kg of animal body weight which practically did not change the parameters of hemodynamic in conditions of normoxia. Thus, the experiments performed about flokalin influence on changes of cardiohemodynamic during ischemia-reperfusion of myocardium showed certain features of ischemia-reperfusion syndrome development under conditions of K(ATP) channels activity stimulation. In our opinion, positive influence offlokalin can be explained by moderate decrease of blood pressure that decreases loading of the damaged heart and allows to preserve cardiac emission in the first period of ischemia. Also, these positive effects can be explained by prevention of the increase of coronal vessel resistance and relative preservation of myocardium contractility indexes by flokalin in the period of reperfusion. All protective properties of flokalin showed above result in diminishing of infarct size of myocardium after ischemia-reperfusion on 37% versus control experiments.

[Ultrastructural changes in isolated cardiomyocytes in modeling of endoplasmic reticulum stress]

At modeling of endoplasmatic reticulum (ER) stress by it classic inducer thapsigargin, anoxia-reoxygenation and simultaneous inhibition ofproteasomal proteolysis, autophagy and apoptosis a diversity of ultrastructural peculiarities was shown. Their comparison allows to make a conclusion that changes in these groups of experiments are similar and typical for ER stress. Thapsigargin application was shown to result in accumulation of giant mitochondria in perinuclear zone of cardiomyocytes. Some of these mitochondria had destroyed and high condensed matrix. The structure of ER was normal but in some regions of cells the dilation of ER cisterns occurred that, to our opinion, is an essential sign of ER stress. In another group of cells thapsigargin caused dehydratation and osmiophilia of cytoplasm, significant dilation of ER cisterns, partial or complete degranulation of these organelles that often formed vacuoles with high electron density material. Also, the significant decrease of the number and size of mitochondria that had partially destroyed and condensed matrix was observed in these cells. The accumulation of lipofuscin and myophilament destruction at preservation of sarcoplasmic membrane integrity was detected. However, in conditions of simultaneous inhibition ofproteasomal proteolysis, aytophagy and apoptosis the loss of membrane integrity was shown, and we propose that it unconditionally should cause necrotic cell death. That was confirmed by use of fluorogenic dyes to detect necrosis and apoptosis. Our data indicate the important role of ER stress in processes of cardiomyocytes death at anoxia-reoxygenation and inhibition of proteasomal and autophagic proteolysis.

[Cardioprotective effects of flokalin: relative role of activation of sarcolemmal and mitochondrial adenosine triphosphate-dependent potassium channels]

In experiments on isolated Langendorff perfused hearts of guinea pig with modeling of ischemia (20 min) and reperfusion (40 min) the cardioprotective effects of flokalin were shown. Preliminary preischemic perfusion of isolated heart with flokalin (5 mM) for 5 minutes has significantly improved the recovery of contractive function ofischemic myocardium at repcrfusion. Particularly, recovery of systolic and developed pressure was improved and the increasing of end-diastolic pressure in left ventricle was prevented. The vasoconstriction of coronary vessels was prevented and number of extrasystols at reperfusion of ischemic heart was decreased. Morphological studies have shown that flokalin prevents the significant damage of myocardial structure and the development of hypercontraction of myofibrils at ischemia-reperfusion of myocardium. It also preserves the intact sarcolemma and intracellular organelles. The intact structure of mitochondria also was saved by flokalin that maintains the energy potential of myocardium. Using the selective blocker of mitochondrial K(ATP) channels 5-hydroxydecanoate (200 mM) allows to determine the relative role of sarcolemmal and mitochondrial K(ATP) channels activation in these effects. It was shown that mitochondrial as well as sarcolemmal K(ATP) channels play role in the recovery of ischemic myocardium functions: first are responsible for recovery of contractive function and second are responsible for coronary blood flow recovery.

[Identification of E-4031-sensitive potassium current component in murine P19 embryonic carcinoma cell line differentiated in cardiomyocytes]

Pluripotent mouse P19 embryonic carcinoma cells represent a convenient in vitro model for studying various aspects of cardiac differentiation. Here by using whole-cell patch-clamp recording we have identified the rapid delayed rectifier K+ current, I(Kr) in P19 cell induced to differentiate into cardiac phenotype by DMSO (1%). Cardiac differentiation was confirmed by the appearance of spontaneously beating cells, their morphological features, ultrastructural clusterization of mitochondria around contraction elements, expression of cardiac actin mRNAs and MLC2v, and by the presence of inward sodium and calcium currents. I(Kr) was isolated based on the sensitivity to the specific blocker, E-4031, which at concentration of 1 MM blocked more than 50% of the total outward K+ current. However, in contrast to I(Kr) in native cardiac myocytes and in heterologous systems expressing I(Kr)-carrying ERG1 potassium channel, E-4031-sensitive K+ current in cardiac-like P19 cells lacked characteristic inward rectification, suggesting specific regulation and/or subunit composition of endogenous ERG -based channel in these cells. Establishing the reason(s) for this phenomenon will advance the understanding of the mechanisms of I(Kr)-channel rectification. Cardiac-differentiated P19 cells might also be useful for studying pharmacological modulation of I(Kr), which is recognized target for cardiotoxic side effects of numerous drugs.

[Phospholipid membrane modification as a protection factor of the myocardium during stress injury]

In experiments on the isolated rat hearts we investigated the influence of phospholipid membrane modification by omega-3 polyunsaturated fatty acids (PUFAs) on the heart reactivity to adrenergic influences, myocardial ultrastructure and peroxidation processes under the immobilization stress. It was shown that omega-3 PUFAs reduced ultrastructural changes in the heart, limited lipid peroxidation and attenuated inotropic response of the heart to exogenous norepinephrine.

[Acute myocardial ischemia-reperfusion injury: role of nitric oxide system]

In experiments on the closed-chest dogs it was shown that NOS inhibition resulted in the significant alterations of hemodynamic indices (coronary and peripheral vascular resistance, cardiac output and heart rate) under local myocardial ischemia/reperfusion in comparison with control experiments. At the first time it was shown that NOS inhibition activated the autophagic destruction of cardiomyocytes in the ischemic myocardium and could reduce an area of functionally active myocardium. L-arginine administration attenuated cardio- and hemodynamic disturbances, that substantially improved the course of ischemia/reperfusion, diminished the ultrastructural changes in myocardium and prevented development of autophagic programmed cell death.

[Apoptotic, autophagic, and oncotic death of cardiomyocytes in anoxia-reoxygenation]

In experiments on isolated rat neonatal cardiomyocytes under anoxia-reoxygenation it was established the different types of cell death: non-programmed (oncotic) and programmed (apoptotic and autophagic). Propidium iodide and Hoechst 33342 staining revealed that alive, necrotic and apoptotic cell ratio after anoxia-reoxygenation was 77%, 14%, 9% respectively (86%, 9.6% and 4.4% in control). Electron microscopy of neonatal rat cardiomyocytes allows us to clarify the ultrastructural peculiarities of each type of cell death. Cytoplasm hydratation, swelling, cell membrane components vacuolization and sarcollemmal integrity alteration were typical for necrosis. The features of apoptosis include: cytoplasm osmiophylia, cell organelle destruction, chromatin condensation and nucleus fragmentation as well as blebs and apoptotic body formation. Autophagic cell death was characterized by the presence of large amount of different size vacuoles accompanied by significant cytoplasm osmiophylia, chromatin condensation or nucleus picnosis (nucleus fragmentation was not observed in these cells) and preservation of sarcollemmal integrity. The autophagic cardiomyocytes destruction was proved by specific monodansylcadaverine staining of vacuolar structures. We first showed the anoxia-reoxygenation-related autophagic cell death of neonatal rat cardiomyocytes. These results strongly suggest the necessity of autophagic cell death investigation in pathogenesis of cardiovascular diseases.

[Changes of nitric oxide system during acute myocardial ischemic reperfusion]

The reciprocal changes of NOS and arginase activity during acute myocardial ischaemia (90 min) and reperfusion (180 min) was shown in experiments on chest-closed dogs with spontaneous breathing. NOS activity in the ischemia injured myocardial decreased on 60% while arginase activity increased on 487%. Levels of both alternative pathways of L-arginine metabolism altered reciprocally too. NO2(-)-level was reduced on 57%, and urea level increased on 665%. The same changes were in arterial blood, started from 10 min of ischemia. These changes can play an important role for development of acute ischaemia treatment.

[The protective effect of omega-3 polyunsaturated fatty acids on the activity of the isolated rat heart during myocardial ischemia-reperfusion]

It was produced plant-derived product, an omega-3 acid-enriched substrate (64%). In our study we tested the influence of this preparation, which is supposed a membrane-modifying agent, on the processes of damage to the isolated heart under conditions of ischemia-reperfusion. Animals took this substrate as nutrient addition to usually everyday diet. We assumed disorders in cardiodynamics and contractile functions of the myocardium (we measured a perfusion pressure in coronary vessel, left ventricular pressure and dp/dt) and in structure of cardiomyocytes. All mentioned parameters was much better after ischemia-reperfusion in hearts from animals which took an omega-3 acid-enriched substrate in course of 4 week before experiments than in hearts from control animals. Conclusions. Omega-3 polyunsaturated acids exert protective effect on functioning and structure of the isolated rat heart during ischemia-reperfusion.

[The correction of disorders in arachidonic acid metabolism in coronary spasm of an immune origin]

The effect of phosphocreatine and hydroxamate-linoleate (an inhibitor of lipoxigenase) on development of the pathologic process in coronary vessels with immune (cytotoxic) injury of the heart was studied in the experiments on narcotized dogs. Development of the immune response after administration of cardiac serum resulted in development of large transmural damage of the left ventricle myocardium, increased resistance of coronary vessels and changed coronary vascular reactions, which correlates with changes in arachidonic acid metabolism. Experimental data described in this report demonstrate the efficiency of membrane coronary vessels stabilization and inhibition of a lipoxygenase pathway in arachidonic acid metabolism in protection of immune damage of the heart and coronary vessels.