Mitochondrial protective effects of PARP-inhibition in hypertension-induced myocardial remodeling and in stressed cardiomyocytes.

AIMS: During oxidative stress mitochondria become the main source of endogenous reactive oxygen species (ROS) production. In the present study, we aimed to clarify the effects of pharmacological PARP-1 inhibition on mitochondrial function and quality control processes. MAIN METHODS: L-2286, a quinazoline-derivative PARP inhibitor, protects against cardiovascular remodeling and heart failure by favorable modulation of signaling routes. We examined the effects of PARP-1 inhibition on mitochondrial quality control processes and function in vivo and in vitro. Spontaneously hypertensive rats (SHRs) were treated with L-2286 or placebo. In the in vitro model, 150 µM H2O2 stress was applied on neonatal rat cardiomyocytes (NRCM). KEY FINDINGS: PARP-inhibition prevented the development of left ventricular hypertrophy in SHRs. The interfibrillar mitochondrial network were less fragmented, the average mitochondrial size was bigger and showed higher cristae density compared to untreated SHRs. Dynamin related protein 1 (Drp1) translocation and therefore the fission of mitochondria was inhibited by L-2286 treatment. Moreover, L-2286 treatment increased the amount of fusion proteins (Opa1, Mfn2), thus preserving structural stability. PARP-inhibition also preserved the mitochondrial genome integrity. In addition, the mitochondrial biogenesis was also enhanced due to L-2286 treatment, leading to an overall increase in the ATP production and improvement in survival of stressed cells. SIGNIFICANCE: Our results suggest that the modulation of mitochondrial dynamics and biogenesis can be a promising therapeutical target in hypertension-induced myocardial remodeling and heart failure.

Cardioprotection by resveratrol: A human clinical trial in patients with stable coronary artery disease.

Several beneficial effects of resveratrol (RES), a natural antioxidant present in red wine have already been described. The aim of our study was to investigate if RES had a clinically measurable cardioprotective effect in patients after myocardial infarction. In this double-blind, placebo controlled trial 40 post-infarction Caucasian patients were randomized into two groups. One group received 10 mg RES capsule daily for 3 months. Systolic and diastolic left ventricular function, flow-mediated vasodilation (FMD), several laboratory and hemorheological parameters were measured before and after the treatment. Left ventricular ejection fraction showed an increasing tendency (ns) by RES treatment. However, left ventricular diastolic function was improved significantly (p < 0.01) by RES. A significant improvement in endothelial function measured by FMD was also observed (p < 0.05). Low-density lipoprotein (LDL) level significantly decreased (p < 0.05) in the RES treated group. Red blood cell deformability decreased and platelet aggregation increased significantly in the placebo group (p < 0.05), while resveratrol treatment has prevented these unfavourable changes. Concerning other measured parameters no significant changes were observed neither in placebo nor in RES group. Our results show that resveratrol improved left ventricle diastolic function, endothelial function, lowered LDL-cholesterol level and protected against unfavourable hemorheological changes measured in patients with coronary artery disease (CAD).

QRS Score: a composite index of exercise-induced changes in the Q, R, and S waves during exercise stress testing in patients with ischemic heart disease.

BACKGROUND: To detect ischemic heart disease, the exercise-induced ST-segment displacement is the most frequently used ECG parameter. However, the value of this marker was proven to be limited with varying sensitivity and specificity. A new parameter, called QRS score, emerged to improve the efficacy of exercise testing. METHODS: Our study aimed at evaluating the diagnostic value of QRS score in ischemic heart disease, investigating males and females separately, and examining the effects of heart rate and antiischemic medication. QRS score and cumulative ST depression were calculated in 212 patients and correlated to the findings of the stress myocardial perfusion SPECT (197 subjects) or coronary angiography (54 subjects). RESULTS: An inverse correlation could be found between the QRS score and the results of myocardial SPECT and coronary angiography in the whole population, especially in males; females did not show a significant relationship. In patients with conclusive tests (achieving 85% of the maximal predicted heart rate) QRS score correlated significantly with the results of the stress myocardial perfusion SPECT and coronary angiography. The sensitivity, specificity, and validity of the QRS score surpassed those of the cumulative ST depression in the entire population as well as in patients with conclusive tests. The antiischemic medication did not affect correlation values. CONCLUSION: QRS score was significantly related to the extent of myocardial ischemia and the severity of coronary heart disease, thus along with the analysis of ST-segment displacement may contribute to the more precise evaluation of exercise testing.

Scavenger effect of experimental and clinically used cardiovascular drugs.

Oxygen free radicals play an important role in several physiologic and pathophysiologic processes. In pathophysiologic circumstances they can modify and damage biologic systems. Their functional properties (exposed to high oxygen tension) place red blood cells among the most susceptible cells to the harmful effect of free radicals. Because oxygen free radicals are involved in a wide range of diseases, scavenging these radicals should be an important therapeutic approach. In this study the antioxidant capacities of experimental and clinically used cardiovascular drugs were investigated. Phenazine methosulfate was used to generate free radicals and thus harden red blood cells. Filtration technique and potassium leaking were used to detect the scavenging effect of the examined drugs. The experimental drug H-2545 provided 43% protection against phenazine methosulfate-induced changes in red blood cell filterability (p < 0.001). Although some of the examined, clinically used cardiovascular drugs (carvedilol, metoprolol, verapamil, trimetazidine) also showed significant (p < 0.05) antioxidant effect, they were less efficient than H-2545. The scavenger effect of this novel drug exceeded the antioxidant properties of vitamin E. Modification of mexiletine with a pyrroline ring significantly improved its antioxidant capacity, suggesting that this molecular segment is responsible for the antioxidant effect.

The effect of carvedilol on enhanced ADP-ribosylation and red blood cell membrane damage caused by free radicals.

OBJECTIVE: Previous studies have reported that the beta and alpha adrenoceptor blocker carvedilol has unique protective effects on free radical-induced myocardial injury. The aim of this study was to examine how carvedilol regulates reactive-oxygen-species-mediated signaling and decreases red blood cell membrane damage in heart perfusion and in a rheological model. METHODS: The ischemia-reperfusion-induced oxidative cell damage, and changes in the intracellular signaling mediated by reactive oxygen species and peroxynitrite were studied on rat hearts in a Langendorff perfusion system (n=15). The effect of carvedilol on red blood cell suspension viscosity (hematocrit: 60%) incubated with free radical generator (phenazine methosulphate) was also investigated (n=10). The measurements were performed on a capillary viscosimeter. RESULTS: In both studies a protective effect of carvedilol was found, as the decrease of red blood cell suspension viscosity and K(+) concentration in the supernatant indicated. Carvedilol significantly decreased the ischemia-reperfusion-induced free radical production and the NAD(+) catabolism and reversed the poly- and mono(ADP-ribosyl)ation. Carvedilol also decreased the lipid peroxidation and membrane damages as determined by free malondialdehyde production and the release of intracellular enzymes. The self ADP-ribosylation of isolated poly(ADP-ribose) polymerase was also significantly inhibited by carvedilol. CONCLUSION: Our results show that carvedilol can modulate the reactive-oxygen-species-induced signaling through poly- and mono(ADP-ribosyl)ation reactions, the NAD(+) catabolism in postischemic perfused hearts and has a marked scavenger effect on free radical generator-induced red blood cell membrane damage. All these findings may play an important role in the beneficial effects of carvedilol treatment in different cardiovascular diseases.

Effect of poly(ADP-ribose) polymerase inhibitors on the ischemia-reperfusion-induced oxidative cell damage and mitochondrial metabolism in Langendorff heart perfusion system.

Ischemia-reperfusion induces reactive oxygen species (ROS) formation, and ROS lead to cardiac dysfunction, in part, via the activation of the nuclear poly(ADP-ribose) polymerase (PARP, called also PARS and ADP-RT). ROS and peroxynitrite induce single-strand DNA break formation and PARP activation, resulting in NAD(+) and ATP depletion, which can lead to cell death. Although protection of cardiac muscle by PARP inhibitors can be explained by their attenuating effect on NAD(+) and ATP depletion, there are data indicating that PARP inhibitors also protect mitochondria from oxidant-induced injury. Studying cardiac energy metabolism in Langendorff heart perfusion system by (31)P NMR, we found that PARP inhibitors (3-aminobenzamide, nicotinamide, BGP-15, and 4-hydroxyquinazoline) improved the recovery of high-energy phosphates (ATP, creatine phosphate) and accelerated the reutilization of inorganic phosphate formed during the ischemic period, showing that PARP inhibitors facilitate the faster and more complete recovery of the energy production. Furthermore, PARP inhibitors significantly decrease the ischemia-reperfusion-induced increase of lipid peroxidation, protein oxidation, single-strand DNA breaks, and the inactivation of respiratory complexes, which indicate a decreased mitochondrial ROS production in the reperfusion period. Surprisingly, PARP inhibitors, but not the chemically similar 3-aminobenzoic acid, prevented the H(2)O(2)-induced inactivation of cytochrome oxidase in isolated heart mitochondria, suggesting the presence of an additional mitochondrial target for PARP inhibitors. Therefore, PARP inhibitors, in addition to their important primary effect of decreasing the activity of nuclear PARP and decreasing NAD(+) and ATP consumption, reduce ischemia-reperfusion-induced endogenous ROS production and protect the respiratory complexes from ROS induced inactivation, providing an additional mechanism by which they can protect heart from oxidative damages.

Hemorheological and oxygen free radical associated alterations during and after percutaneous transluminal coronary angioplasty.

Percutaneous transluminal coronary angioplasty (PTCA) is a frequently used method in the treatment of coronary artery disease. Coronary stenosis, endothelial injury, and ischemia-reperfusion caused by the balloon inflation and deflation during this procedure can cause several changes in blood flow. In our study 19 patients (mean age: 58 +/- 9 years) undergoing PTCA were examined. For the laboratory measurements several blood samples were taken from the femoral vein and the coronary sinus before and 30 minutes after PTCA, and from the cubital vein 1, 2, 5 days and 1, 6 months after PTCA. Among hemorheologic parameters hematocrit, plasma fibrinogen level, plasma and whole blood viscosities were measured and corrected blood viscosity value was calculated. To characterize the oxidative stress, samples were analyzed for thiobarbituric acid reactive substances (TBARS) of blood as a marker of lipidperoxidation and changes in the antioxidant system were investigated by measuring the activity of superoxide dismutase, catalase and the concentration of glutathione; superoxide generating capacity of isolated leukocytes and platelet aggregation were examined as markers of cellular activation. Plasma fibrinogen concentration increased markedly during the first and second day after PTCA (p < 0.001), which was accompanied by the elevation of plasma viscosity (p < 0.05). Plasma fibrinogen returned to the baseline at the one-month check-up visit, but there was a significant increase in its concentration by the end of the sixth month follow-up. Apparent whole blood viscosity at 90 s (-1) showed gradually increasing values up to the one- and six-month check-up visits (p < 0.01), which can partially be explained by the elevation of hematocrit. Corrected blood viscosity was significantly elevated on the fifth day already (p < 0.01), and one month later also. Superoxide production of leukocytes showed an increasing tendency (p = 0.05), and blood TBARS was elevated after one day (p < 0.05) and remained higher during the following days. Catalase activity showed significantly increasing values (p < 0.01) during the hospital phase, then at the end of the first month. SOD activity and spontaneous platelet aggregation were higher in the samples from the coronary sinus than in those from the peripheral vein before the procedure; 30 minutes after PTCA increased levels in the peripheral sample were found (p < 0.01). Our findings indicate that PTCA may cause significant changes in the hemorheologic and free radical associated parameters, which can affect the final outcome of this intervention.

[The effect of carvedilol on enhanced adp-ribosylation and red blood cell membrane damage caused by free radicals]. / Carvedilol hatása a szabadgyök indukálta ADP-ribozilációra és vörösvértest membrán károsodásra.

OBJECTIVE: Previous studies have reported that the beta and alpha adrenoceptor blocker carvedilol had unique protective effect on free radical induced myocardial injury. The aim of this study was to examine how carvedilol regulates ROI-mediated signaling and decreases RBC membrane damage in heart perfusion and rheological model. METHODS: The ischemia-reperfusion induced oxidative cell damages, and changes in the intracellular signaling mediated by reactive oxygen species and peroxynitrite were studied on rats, in Langendorff heart perfusion system (n = 15). The effect of carvedilol on red blood cell suspension viscosity (hematocrit: 60%) incubated with free radical generator (phenazine methosulphate) was also investigated (n = 10). The measurements were performed on a capillary viscosimeter. RESULTS: In both studies a protective effect of carvedilol was found, as the decrease of red blood cell suspension viscosity and K+ concentration in the supernatant indicated. Carvedilol significantly decreased the ischemia-reperfusion induced free radical production and the NAD+ catabolism and reversed the poly- and mono-ADP-ribosylation. Carvedilol also decreased the lipid peroxidation and membrane damages as determined by free malondialdehyde production and the release of intracellular enzymes. The self ADP-ribosylation of isolated PARP was also significantly inhibited by carvedilol. CONCLUSION: Our results show that carvedilol can modulate the ROI-induced signaling through poly- and mono-ADP-ribosylation reactions, the NAD+ catabolism in postischemic perfused hearts and has a marked scavenger effect on free radical generator induced red blood cell membrane damage. All these findings may play an important role in the beneficial effects of carvedilol treatment in different cardiovascular diseases.

Hemorheological and hemodynamic parameters in patients with essential hypertension and their modification by alpha-1 inhibitor drug treatment.

Hemorheological factors play an important role in the pathogenesis of different cardiovascular diseases. The hemorheological and hemodynamic parameters in essential hypertension and their possible modification by antihypertensive treatment were examined in the following two studies. In the first study the fundus appearance and hemorheological parameters (plasma and whole blood viscosity (WBV), fibrinogen level) of 33 hypertensive patients (mean age: 55 years) were examined. The fundus appearance showed retinopathy in all the cases between stages I-III. All the measured hemorheological parameters of the examined patients were in the pathological range (WBV at 90 s(-1): 5.18 mPa s) and were significantly (p < 0.01) higher than in healthy controls (WBV at 90 s(-1): 4.18 mPa s). The hemorheological factors showed a parallel deterioration with the fundus appearance, namely their values were significantly (p < 0.01) higher in patients with a fundus appearance stage III (WBV at 90 s(-1): 6.02 mPa s) than stage I (WBV at 90 s(-1): 4.51 mPa s). These results show that there is a correlation between hemorheological parameters and fundus appearance in hypertensives, and this suggests that hemorheological factors may play a role in the development of hypertensive retinopathy. In the second study the hemorheological and hemodynamical effects of Doxazosin, a selective alpha-1-adrenoreceptor blocker agent, was examined in twenty patients (mean age: 54 years) with essential hypertension. Hemorheologic (hematocrit, fibrinogen, plasma and whole blood viscosity) and hemodynamic (cardiac output and index, total peripheral resistance) parameters and plasma lipids were determined. The measurements were carried out before the beginning of the treatment, after 1 week and after 12 weeks treatment periods. Besides significant reduction of blood pressure and total peripheral resistance (p < 0.001), a decrease in cholesterol (p < 0.001) and triglycerides (p < 0.01) levels and a beneficial effect on hemorheological parameters was detected. Fibrinogen and plasma viscosity decreased significantly (p < 0.01). Hematocrit value was also lower after one week (p < 0.001), then an increase could be seen. Whole blood viscosity showed similar changes as hematocrit, but the degree of its final increase was slighter, which was supported by the significantly lower value of corrected blood viscosity (p < 0.05). All these findings indicate that hemorheological factors may play a role in the pathogenesis and in the development of organ damages in hypertension.