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

Different Effects of Quercetin Glycosides and Quercetin on Kidney Mitochondrial Function—Uncoupling, Cytochrome C Reducing and Antioxidant Activity

Flavonols are found in plants as aglycones and as glycosides. Antioxidant activity of flavonols may occur via several mechanisms within the cell, and mitochondria as a target may play an important role. There is a lack of information about the influence of the sugar moiety on biological activity of flavonoid glycosides. The aims of study were to investigate the effects of quercetin and its glycosides on mitochondrial respiration rates at various metabolic states, and to evaluate their antioxidant potential using chemical and biological approaches. Mitochondrial function was measured using an oxygraphic method, cytochrome c reduction spectrophotometrically, H2O2 generation in mitochondria fluorimetrically, and antioxidant activity of flavonoids using an HPLC-post column system. Our data revealed that quercetin and its glycosides isoquercitrin, rutin, and hyperoside uncouple kidney mitochondrial respiration (increasing the State 2 respiration rate) and significantly reduce cytochrome c. Moreover, quercetin, and its glycosides decrease the production of mitochondrial H2O2 and possess radical scavenging and ferric reducing capacities. The highest activity was characteristic for quercetin, showing that the sugar moiety significantly diminishes its activity. In conclusion, our results show the efficient radical scavenging, ferric and cytochrome c reducing capacities, and uncoupling properties of quercetin and its glycosides, as well as the importance of the sugar residue and its structure in the regulation of kidney mitochondrial function.

Caffeic Acid Phenethyl Ester Protects Kidney Mitochondria against Ischemia/Reperfusion Induced Injury in an In Vivo Rat Model

To improve ischemia/reperfusion tolerance, a lot of attention has been focused on natural antioxidants. Caffeic acid phenethyl ester (CAPE), an active component of the resinous exudates of the buds and young leaves of Populus nigra L., Baccharis sarothroides A., etc., and of propolis, possesses unique biological activities such as anti-inflammatory, antioxidant, immunomodulating, and cardioprotective effects, among others. There is a lack of studies showing a link between the antioxidant potential of CAPE and the mechanism of protective action of CAPE at the level of mitochondria, which produces the main energy for the basic functions of the cell. In the kidney, ischemia/reperfusion injury contributes to rapid kidney dysfunction and high mortality rates, and the search for biologically active protective compounds remains very actual. Therefore, the aim of this study was to identify the antioxidant potential of CAPE and to investigate whether CAPE can protect rat kidney mitochondria from in vivo kidney ischemia/reperfusion induced injury. We found that CAPE (1) possesses antioxidant activity (the reducing properties of CAPE are more pronounced than its antiradical properties); CAPE effectively reduces cytochrome c; (2) protects glutamate/malate oxidation and Complex I activity; (3) preserves the mitochondrial outer membrane from damage and from the release of cytochrome c; (4) inhibits reactive oxygen species (ROS) generation in the Complex II (SDH) F site; (5) diminishes ischemia/reperfusion-induced LDH release and protects from necrotic cell death; and (6) has no protective effects on succinate oxidation and on Complex II +III activity, but partially protects Complex II (SDH) from ischemia/reperfusion-induced damage. In summary, our study shows that caffeic acid phenethyl ester protects kidney mitochondrial oxidative phosphorylation and decreases ROS generation at Complex II in an in vivo ischemia/reperfusion model, and shows potential as a therapeutic agent for the development of pharmaceutical preparations against oxidative stress-related diseases.

Increased Succinate Accumulation Induces ROS Generation in In Vivo Ischemia/Reperfusion-Affected Rat Kidney Mitochondria

Mitochondria are recognized as main reactive oxygen species (ROS) producers, involving ROS generation by mitochondrial complexes I and III. Lately, the focus has been shifting to the ROS generation by complex II. Contribution of complex II (SDH) to ROS generation still remains debatable, especially in in vivo settings. Moreover, it is not completely defined at what time of ischemia the first alterations in mitochondria and the cell begin, which is especially important with renal arterial clamping in vivo during kidney surgery, as it predicts the postischemic kidney function. The aim of this study on an in vivo rat kidney ischemia/reperfusion model was to determine if there is a connection among (a) duration of kidney ischemia and mitochondrial dysfunction and (b) succinate dehydrogenase activity, succinate accumulation, and ROS generation in mitochondria at low and saturating succinate concentrations. Our results point out that (1) mitochondrial disturbances can occur even after 30 min of kidney ischemia/reperfusion in vivo and increase progressively with the prolonged time of ischemia; (2) accumulation of succinate in cytosol after ischemia/reperfusion correlated with increased H₂O₂ generation mediated by complex II, which was most noticeable with physiological succinate concentrations; and (3) ischemia/reperfusion induced cell necrosis, indicated by the changes in LDH activity. In conclusion, our new findings on the accumulation of succinate in cytosol and changes in SDH activity during kidney ischemia/reperfusion may be important for energy production after reperfusion, when complex I activity is suppressed. On the other hand, an increased activity of succinate dehydrogenase is associated with the increased ROS generation, especially with physiological succinate concentrations. All these observations play an important role in understanding the mechanisms which occur in the early phase of ischemia/reperfusion injury in vivo and may provide new ideas for novel therapeutic approaches or injury prevention; therefore, more detailed studies are necessary in the future.

Ginkgetin aglycone attenuates the apoptosis and inflammation response through nuclear factor-kB signaling pathway in ischemic-reperfusion injury

AIMS

Acute myocardial infarction (AMI) is one of the most threaten disease in the world. Ginkgetin aglycone (GA) was a new kind of Ginkgo biloba, involved in various diseases, including kidney injury and acute pancreatitis. However, the function of GA in AMI remains unknown. The aim of the study was to investigate the characteristics and function of GA in ischemic-reperfusion injury.

METHODS

H₂ O ₂ - and CoCl ₂ -treated H9C2 cells were used to analyze the function of GA in vitro. Caspase 3, interleukin-6 (IL-6), and tumor necrosis factor-α were detected to evaluate the apoptosis and inflammation response. Rat AMI was performed to elucidate the function in vivo.

RESULTS

We found that GA could reduce the apoptosis and improved cell survival of H₂ O ₂ -treated H9C2 cardiomyocytes and CoCl ₂ -treated H9C2 cells. GA attenuated CoCl ₂ -induced inflammatory response and the level of cleaved caspase 33, suggesting that GA could alleviate the cell apoptosis. GA improved the cardiac function and attenuated the inflammatory cell infiltration in vivo. We also found that nuclear factor-kB signaling pathway, which was activated under hypoxia environment, was also suppressed in the GA-treated group.

CONCLUSION

We verified the function and mechanism of GA and provide evidence that GA may play a vital role in ischemic-reperfusion injury, and understanding the precise role of GA will undoubtedly shed new light on the clinical treatment.

Small structural changes on a hydroquinone scaffold determine the complex I inhibition or uncoupling of tumoral oxidative phosphorylation

Mitochondria participate in several distinctiveness of cancer cell, being a promising target for the design of anti-cancer compounds. Previously, we described that ortho-carbonyl hydroquinone scaffold 14 inhibits the complex I-dependent respiration with selective anti-proliferative effect on mouse mammary adenocarcinoma TA3/Ha cancer cells; however, the structural requirements of this hydroquinone scaffold to affect the oxidative phosphorylation (OXPHOS) of cancer cells have not been studied in detail. Here, we characterize the mitochondrial metabolism of TA3/Ha cancer cells, which exhibit a high oxidative metabolism, and evaluate the effect of small structural changes of the hydroquinone scaffold 14 on the respiration of this cell line. Our results indicate that these structural changes modify the effect on OXPHOS, obtaining compounds with three alternative actions: inhibitors of complex I-dependent respiration, uncoupler of OXPHOS and compounds with both actions. To confirm this, the effect of a bicyclic hydroquinone (9) was evaluated in isolated mitochondria. Hydroquinone 9 increased mitochondrial respiration in state 4o without effects on the ADP-stimulated respiration (state 3ADP), decreasing the complexes I and II-dependent respiratory control ratio. The effect on mitochondrial respiration was reversed by 6-ketocholestanol addition, indicating that this hydroquinone is a protonophoric uncoupling agent. In intact TA3/Ha cells, hydroquinone 9 caused mitochondrial depolarization, decreasing intracellular ATP and NAD(P)H levels and GSH/GSSG ratio, and slightly increasing the ROS levels. Moreover, it exhibited selective NAD(P)H availability-dependent anti-proliferative effect on cancer cells. Therefore, our results indicate that the ortho-carbonyl hydroquinone scaffold offers the possibility to design compounds with specific actions on OXPHOS of cancer cells.

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

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 μL/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 μL/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 μL/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 μL/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.

Direct effects of Vaccinium myrtillus L. fruit extracts on rat heart mitochondrial functions

In this study, the direct influence of bilberry (Vaccinium myrtillus) fruit extracts (aqueous and ethanolic) rich in anthocyanins on the oxidative phosphorylation of isolated rat heart mitochondria was investigated in vitro. Higher concentrations of bilberry extracts concentration-dependently inhibited mitochondrial state 3 respiration (by 23%-61%) with pyruvate plus malate, mildly (by 1.2- to 1.3-fold) uncoupled the oxidative phosphorylation, and increased (by 30%-87%) the state 4 respiration rate in the presence of exogenous cytochrome c. Succinate oxidation was less affected. Pure anthocyanins, the main components of used extracts, malvidin-3-glucoside, malvidin-3-galactoside, and cyanidin-3-galactoside, had no effect on oxidation of pyruvate plus malate. A statistically significant decrease in H2 O2 production by mitochondria was found in the presence of bilberry fruit extracts. Our findings show that bilberry fruit anthocyanin-rich extracts possess direct effects on rat heart mitochondrial function in vitro. These findings give the first insights into the mechanism(s) of their action on cellular energy metabolism.

Ginkgo biloba extract reduces high-glucose-induced endothelial adhesion by inhibiting the redox-dependent interleukin-6 pathways

BACKGROUND

Chronic elevation of glucose level activates vascular inflammation and increases endothelial adhesiveness to monocytes, an early sign of atherogenesis. This study aimed to elucidate the detailed mechanisms of high-glucose-induced endothelial inflammation, and to investigate the potential effects of Ginkgo biloba extract (GBE), an antioxidant herbal medicine, on such inflammation.

MATERIALS AND METHODS

Human aortic endothelial cells were cultured in high glucose or mannitol as osmotic control for 4 days. The expression of cytokines and adhesion molecules and the adhesiveness of endothelial cells to monocytes were examined. The effects of pretreatment of GBE or N-acetylcysteine, an antioxidant, were also investigated.

RESULTS

Either high glucose or mannitol significantly increased reactive oxygen species (ROS) production, interleukin-6 secretion, intercellular adhesion molecule-1 (ICAM-1) expression, as well as endothelial adhesiveness to monocytes. The high-glucose-induced endothelial adhesiveness was significantly reduced either by an anti-ICAM-1 antibody or by an interleukin-6 neutralizing antibody. Interleukin-6 (5 ng/ml) significantly increased endothelial ICAM-1 expression. Piceatannol, a signal transducer and activator of transcription (STAT) 1/3 inhibitor, but not fludarabine, a STAT1 inhibitor, suppressed high-glucose-induced ICAM-1 expression. Pretreatment with GBE or N-acetylcysteine inhibited high-glucose-induced ROS, interleukin-6 production, STAT1/3 activation, ICAM-1 expression, and endothelial adhesiveness to monocytes.

CONCLUSIONS

Long-term presence of high glucose induced STAT3 mediated ICAM-1 dependent endothelial adhesiveness to monocytes via the osmotic-related redox-dependent interleukin-6 pathways. GBE reduced high-glucose-induced endothelial inflammation mainly by inhibiting interleukin-6 activation. Future study is indicated to validate the antioxidant/anti-inflammatory strategy targeting on interleukin-6 for endothelial protection in in vivo and clinical hyperglycemia.

The cardioprotective effect of mildronate is diminished after co-treatment with L-carnitine

Mildronate, an inhibitor of L-carnitine biosynthesis and uptake, is a cardioprotective drug whose mechanism of action is thought to rely on the changes in concentration of L-carnitine in heart tissue. In the present study, we compared the cardioprotective effect of mildronate (100 mg/kg) and a combination of mildronate and L-carnitine (100 + 100 mg/kg) administered for 14 days with respect to the observed changes in l-carnitine level and carnitine palmitoyltransferase I (CPT-I)-dependent fatty acid metabolism in the heart tissues. Concentrations of L-carnitine and its precursor γ-butyrobetaine (GBB) were measured by ultraperformance liquid chromatography with tandem mass spectrometry. In addition, mitochondrial respiration, activity of CPT-I, and expression of CPT-IA/B messenger RNA (mRNA) were measured. Isolated rat hearts were subjected to ischemia-reperfusion injury. Administration of mildronate induced a 69% decrease in L-carnitine concentration and a 6-fold increase in GBB concentration in the heart tissue as well as a 27% decrease in CPT-I-dependent mitochondrial respiration on palmitoyl-coenzyme A. In addition, mildronate treatment induced a significant reduction in infarct size and also diminished the ischemia-induced respiration stimulation by exogenous cytochrome c. Treatment with a combination had no significant impact on L-carnitine concentration, CPT-I-dependent mitochondrial respiration, and infarct size. Our results demonstrated that the mildronate-induced decrease in L-carnitine concentration, concomitant decrease in fatty acid transport, and maintenance of the intactness of outer mitochondrial membrane in heart mitochondria are the key mechanisms of action for the anti-infarction activity of mildronate.

Uncoupling and antioxidant effects of ursolic acid in isolated rat heart mitochondria

Ursolic acid (1), a pentacyclic triterpene acid, is one of the major components of certain traditional medicinal plants and possesses a wide range of biological effects, such as anti-inflammatory, antioxidative, and cytotoxic activities. Furthermore, 1, when present at 1.6-5 ng/mL concentrations in commercial herbal preparations used for patients with cardiac disorders, may also exert pro-cardiac activities. There are several indirect suggestions that the cardioprotective mechanism of ursolic acid could involve the mitochondria; however the mechanism of action is still not known. Therefore, the effects of 0.4-200 ng/mL ursolic acid (1) on the functions of isolated rat heart mitochondria oxidizing either pyruvate and malate, succinate, or palmitoyl-l-carnitine plus malate were investigated. It was found that 1 induced a statistically significant uncoupling of oxidative phosphorylation. A statistically significant decrease in H₂O₂ production in the mitochondria was observed after incubation with 5 ng/mL 1. This effect was comparable to the effectiveness of the classical uncoupler carbonyl cyanide 3-chlorophenylhydrazone. Since mild mitochondrial uncoupling has been proposed as one of the mechanisms of cardioprotection, the present results indicate that ursolic acid (1) has potential use as a cardioprotective compound.