Rasa Baniene

The effect of crataegus fruit extract and some of its flavonoids on mitochondrial oxidative phosphorylation in the heart.

Crataegus (Hawthorn) fruit extracts (CE) are widely used for the treatment of various cardiovascular diseases (arrhythmias, heart failure, myocardial weakness, etc). Despite the fact that many of these diseases are associated with disturbances of the mitochondria, no data have been found on the effect of CE on their function. The aim of this study was to perform an oxygraphic investigation of the effect of CE (in concentration range from 70 ng/mL to 13.9 µg/mL of Crataegus phenolic compounds (PC)) and its several pure flavonoids on isolated rat heart mitochondria respiring on pyruvate + malate, succinate and palmitoyl‐L‐carnitine + malate. CE at doses under 278 ng/mL of PC had no effect on mitochondrial functions. At concentrations from 278 ng/mL to 13.9 µg/mL of PC, CE stimulated State 2 respiration by 11%–34% with all used substrates, and decreased the mitochondrial membrane potential by 1.2–4.4 mV measured with a tetraphenylphosphonium‐selective electrode and H2O2 production measured fluorimetrically. Similar uncoupling effects on mitochondrial respiration were observed with several pure CE flavonoids. The highest CE concentration also slightly reduced the maximal ADP‐stimulated and uncoupled respiration, which might be due to inhibition of the mitochondrial respiratory chain between flavoprotein and cytochrome c. Whether or not the uncoupling and other effects of CE on mitochondria may be realized in vivo remains to be determined. Copyright

Effects of Ginkgo biloba extract on heart and liver mitochondrial functions: mechanism(s) of action.

Though extracts of Ginkgo biloba leaves (GBE) have a wide pharmacological application, little is known about GBE effects on mitochondria. In this work, effects of ethanolic GBE on the respiration of isolated rat heart and liver mitochondria were investigated. We found that GBE stimulates the pyruvate + malate-dependent State 2 respiration of heart mitochondria and decreases mitochondrial membrane potential. Uncoupling effect of GBE was found to be due to its protonophoric action and is likely to be mediated by the ATP/ADP-translocator and uncoupling proteins. The effect of GBE was less in liver than in heart mitochondria. State 3 respiration of heart mitochondria was slightly stimulated at low and depressed at higher GBE concentrations. Inhibition of State 3 respiration of heart mitochondria was not relieved by uncoupler indicating that GBE may inhibit the respiratory chain complexes or the substrate transport. However, Complex IV of the respiratory chain was not inhibited by GBE. H2O2 generation was attenuated by low concentration of GBE probably due to mild uncoupling. The data suggest that mild but not severe uncoupling activity of GBE may be important in providing pharmacological protection of cellular functions in pathological situations.

Modular kinetic analysis reveals differences in Cd2+ and Cu2+ ion-induced impairment of oxidative phosphorylation in liver.

Impaired mitochondrial function contributes to copper‐ and cadmium‐induced cellular dysfunction. In this study, we used modular kinetic analysis and metabolic control analysis to assess how Cd2+ and Cu2+ ions affect the kinetics and control of oxidative phosphorylation in isolated rat liver mitochondria. For the analysis, the system was modularized in two ways: (a) respiratory chain, phosphorylation and proton leak; and (b) coenzyme Q reduction and oxidation, with the membrane potential (Δψ) and fraction of reduced coenzyme Q as the connecting intermediate, respectively. Modular kinetic analysis results indicate that both Cd2+ and Cu2+ ions inhibited the respiratory chain downstream of coenzyme Q. Moreover, Cu2+, but not Cd2+ ions stimulated proton leak kinetics at high Δψ values. Further analysis showed that this difference can be explained by Cu2+ ion‐induced production of reactive oxygen species and membrane lipid peroxidation. In agreement with modular kinetic analysis data, metabolic control analysis showed that Cd2+ and Cu2+ ions increased control of the respiratory and phosphorylation flux by the respiratory chain module (mainly because of an increase in the control exerted by cytochrome bc1 and cytochrome c oxidase), decreased control by the phosphorylation module and increased negative control of the phosphorylation flux by the proton leak module. In summary, we showed that there is a subtle difference in the mode of action of Cd2+ and Cu2+ ions on the mitochondrial function, which is related to the ability of Cu2+ ions to induce reactive oxygen species production and lipid peroxidation.

Experimental acute pancreatitis induces mitochondrial dysfunction in rat pancreas, kidney and lungs but not in liver

BACKGROUND/AIMSnExcessive systemic inflammatory response syndrome during severe acute pancreatitis (AP) leads to multiple organ dysfunction syndrome, which is the main cause of death and may be associated with primary mitochondrial disturbances. The aim of our study was to evaluate the role of mitochondria during experimental AP in pancreas and vital organs like kidney, lungs and liver within the first 48xa0h.nnnMETHODSnAP was induced in 39 male Wistar rats by intraductal application of sodium taurocholate (5%, 1.75xa0ml/kg). Animals were divided into groups reflecting the time from induction of the AP till collection of tissues (control and 1, 3, 6, 12, 24, 48xa0h). Mitochondria were isolated by differential centrifugation and mitochondrial respiration rates were measured oxygraphically.nnnRESULTSn(1) Mitochondria in pancreas are affected within the first 6xa0hxa0after onset of AP, (2) kidney mitochondria are affected 24xa0hxa0after onset of AP, (3) lungs mitochondria are affected within 48xa0hxa0after onset of AP whereas (4) liver mitochondria remain well preserved within the first 48xa0h. Severe AP-induced decrease in the oxidative phosphorylation of pancreas, kidney and lungs mitochondria was more pronounced with Complex I-linked (glutamate/malate) than with Complex II-linked (succinate) substrates and was associated with inhibition of Complex I.nnnCONCLUSIONnOur data show that the disturbances of mitochondrial energy metabolism in pancreas, kidney and lungs may play an important role in the development and progression of AP as a systemic disease.

The effect of Leonurus cardiaca herb extract and some of its flavonoids on mitochondrial oxidative phosphorylation in the heart.

Motherwort (Leonurus cardiaca) possesses antibacterial, antioxidant, anti-inflammatory, and analgesic activities, and is used as a complementary remedy to improve heart function and blood circulation. Since cardiovascular diseases are often associated with an alteration of mitochondria, the main producers of ATP in cardiac muscle cells, the aim of our work was to determine bioactive constituents present in motherwort aerial parts extract in ethanol and investigate their effects on the functions of cardiac mitochondria. Quantitative determination of polyphenols in L.xa0cardiaca herb extract was performed by HPLC. Mitochondrial respiration rates were evaluated using a Clark-type oxygen electrode. Mitochondrial ROS generation was determined fluorimetrically with Amplex Red and horseradish peroxidase. The results showed that constituents (chlorogenic acid, orientin, quercetin, hyperoside, and rutin) of L.xa0cardiaca herb extract uncouple (by 20-90u200a%) mitochondrial oxidation from phosphorylation, partially inhibit (by ~u200940u200a%) the mitochondrial respiratory chain in cases of pyruvate and malate as well as succinate oxidation, and effectively attenuate the generation of free radicals in mitochondria. Since partial uncoupling of mitochondria, respiratory inhibition, and decreased ROS production are proposed as possible mechanisms of cardioprotection, our results imply that L. cardiaca herb extract could be a useful remedy to protect cardiac muscles from the effects of pathogenic processes.

Analysis of effects of 2,2',5,5'-tetrachlorobiphenyl on the flux control in oxidative phosphorylation system in rat liver mitochondria.

Modular kinetic analysis reveals that the environmental pollutant 2,2,5,5-tetrachlorobiphenyl (2,2,5,5-TCB) affects a large number of steps in oxidative phosphorylation in rat liver mitochondria. 2,2,5,5-TCB increases membrane permeability to ions, and inhibits NADH dehydrogenase, cytochrome bc1, cytochrome oxidase (all in the respiratory chain) and ATP-synthase (in the phosphorylation subsystem). Surprisingly, flux control distribution does not change. A kinetic model for oxidative phosphorylation was used to simulate these findings, and it was found that combined large changes in the processes indicated indeed left the flux control largely unchanged. In addition, computational analysis with the model indicated that the adenine nucleotide translocator might be inhibited by 2,2,5,5-TCB.

Influence of ethanol extract of Ginkgo biloba leaves on the isolated rat heart work and mitochondria functions.

Abstract: In this study, we attempted to elucidate whether the effects of ethanol extract of Ginkgo biloba leaves (GBE) observed previously on isolated rat heart mitochondria may be realized in situ (in case of isolated heart perfused under normal conditions and under ischemia–reperfusion). We found that GBE at low concentrations (0.01, 0.05, and 0.1 &mgr;L/mL) does not affect the heart rate and parameters of electrocardiogram (ECG) but produces a small increase in the coronary flow. Higher concentration of GBE (0.2 and 0.3 &mgr;L/mL) diminished the heart rate, decreased the coronary flow, and tended to enhance the parameters of ECG. The contractility of isolated rat heart and mitochondrial nicotinamide adenine dinucleotide reduced form fluorescence decreased in a GBE concentration-dependent manner. Mitochondria isolated from hearts pre-perfused with GBE (0.05 &mgr;L/mL) for 20 minutes before nonflow global ischemia–reperfusion (45 min/15 min) showed higher respiratory rates with pyruvate + malate in state 2 and state 3, higher respiratory control index, and diminished H2O2 generation compared with untreated group. Higher GBE concentration, 0.4 &mgr;L/mL, had no effect on H2O2 generation and did not prevent the ischemia–reperfusion-induced decrease of pyruvate + malate oxidation in state 3 but even enhanced it. However, in the case of nonischemic perfusions, this GBE concentration had no significant effect on these parameters of respiratory functions of isolated heart mitochondria.

Tetraphenylphosphonium inhibits oxidation of physiological substrates in heart mitochondria

We show that tetraphenylphosphonium inhibits oxidation of palmitoylcarnitine, pyruvate, malate, 2-oxoglutarate and glutamate in heart mitochondria in the range of concentration (1–5 µM) commonly used for the determination of mitochondrial membrane potential. The inhibition of 2-oxoglutarate (but not other substrate) oxidation by tetraphenylphosphonium is dependent on the concentration of 2-oxoglutarate and on extramitochondrial free calcium, and the kinetic plots are consistent with a mixed type of inhibition. Our results indicate that tetraphenylphosphonium interacts with enzymes, specifically involved in the oxidation of 2-oxoglutarate, most possibly, 2-oxoglutarate dehydrogenase. (Mol Cell Biochem 174: 67-70, 1997)

Short ischemia induces rat kidney mitochondria dysfunction.

Renal artery clamping itself induces renal ischemia which subsequently causes renal cell injury and can lead to renal failure. The duration of warm ischemia that would be safe for postoperative kidney function during partial nephrectomy remains under investigations. Mitochondria play an important role in pathophysiology of ischemia-reperfusion induced kidney injury, however relation between ischemia time and mitochondrial dysfunction are not fully elucidated. Thus, the effects of renal ischemia (20xa0min, 40xa0min and 60xa0min) on mitochondrial functions were investigated by using in vitro rat ischemia model. Thus, electronmicroscopy showed that at short (20xa0min) ischemia mitochondria start to swell and the damage increases with the duration of ischemia. In accordance with this, a significant decrease in mitochondrial oxidative phosphorylation capacity was observed already after 20xa0min of ischemia with both, complex I dependent substrate glutamate/malate (52xa0%) and complex II dependent substrate succinate (44xa0%) which further decreased with the prolonged time of ischemia. The diminished state 3 respiration rate was associated with the decrease in mitochondrial Complex I activity and the release of cytochrome c. Mitochondrial Ca2+ uptake was diminished by 37–49xa0% after 20–60xa0min of ischemia and caspase-3 activation increased by 1.15–2.32-fold as compared to control. LDH activity changed closely with increasing time of renal ischemia. In conclusion, even short time (20xa0min) of warm ischemia in vitro leads to renal mitochondrial injury which increases progressively with the duration of ischemia.

Effects of standardized extract of Ginkgo biloba leaves EGb761 on mitochondrial functions: mechanism(s) of action and dependence on the source of mitochondria and respiratory substrate

In this work, the effects of standardized dry extract of Ginkgo biloba leaves, EGb761, on the respiration of rat heart and liver mitochondria were investigated. We revealed uncoupling of oxidative phosphorylation in rat heart mitochondria by EGb761 which was not observed in liver mitochondria respiring on pyruvate + malate; oxidation of succinate in heart mitochondria was inhibited by EGb761, concentration-dependently, almost completely at 1.00xa0mg/mL. Uncoupling effect of EGb761 was found to be due to increase in H+ and K+ permeability of inner membrane of mitochondria which is most likely to be mediated by the ATP/ADP-translocator and uncoupling proteins. EGb761 depressed State 3 respiration with pyruvate + malate (similarly in heart and liver mitochondria) and succinate (stronger than with pyruvate + malate) but not respiratory chain Complex IV; inhibition of respiration was not restored by uncoupler indicating the inhibitory action of EGb761 on the respiratory complexes preceding to Complex IV and/or on the substrate transport. Moreover, EGb761 rapidly reduced pure cytochrome c. This property of EGb761 together with the observed uncoupling of oxidative phosphorylation and reduction of H2O2 accumulation may be beneficial for the cell in the prevention of apoptosis and protection of cellular functions in pathological situations.