Quercetin and dehydrosilybin are polyphenols which are known to behave like uncouplers of respiration in isolated mitochondria. Here we investigated whether the effect is conserved in whole cells. Following short term incubation, neither compound uncouples mitochondrial respiration in whole H9c2 cells below 50μM. However, following hypoxia, or long term incubation, leak (state IV with oligomycin) oxygen consumption is increased by quercetin. Both compounds partially protected complex I respiration, but not complex II in H9c2 cells following hypoxia. In a permeabilised H9c2 cell model, the increase in leak respiration caused by quercetin is lowered by increased [ADP] and is increased by adenine nucleotide transporter inhibitor, atractyloside, but not bongkrekic acid. Both quercetin and dehydrosilybin dissipate mitochondrial membrane potential in whole cells. In the case of quercetin, the effect is potentiated post hypoxia. Genetically encoded Ca++ sensors, targeted to the mitochondria, enabled the use of fluorescence microscopy to show that quercetin decreased mitochondrial [Ca++] while dehydrosilybin did not. Likewise, quercetin decreases accumulation of [Ca++] in mitochondria following hypoxia. Fluorescent probes were used to show that both compounds decrease plasma membrane potential and increase cytosolic [Ca++]. We conclude that the uncoupler-like effects of these polyphenols are attenuated in whole cells compared to isolated mitochondria, but downstream effects are nevertheless apparent. Results suggest that the effect of quercetin observed in whole and permeabilised cells may originate in the mitochondria, while the mechanism of action of cardioprotection by dehydrosilybin may be less dependent on mitochondrial uncoupling than originally thought. Rather, protective effects may originate due to interactions at the plasma membrane.

• MeSH
• buněčné linie MeSH
• digitonin farmakologie   MeSH
• fluorescenční mikroskopie MeSH
• konfokální mikroskopie MeSH
• membránový potenciál mitochondrií účinky léků   MeSH
• mitochondriální ADP/ATP-translokasy metabolismus   MeSH
• quercetin farmakologie   MeSH
• silymarin farmakologie   MeSH
• vápník metabolismus   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• dehydrosilybin MeSH Prohlížeč
• digitonin MeSH
• mitochondriální ADP/ATP-translokasy MeSH
• quercetin MeSH
• silymarin MeSH
• vápník MeSH

2,3-dehydrosilybin (DHS) is a minor flavonolignan component of Silybum marianum seed extract known for its hepatoprotective activity. Recently we identified DHS as a potentially cardioprotective substance during hypoxia/reoxygenation in isolated neonatal rat cardiomyocytes. This is the first report of positive inotropic effect of DHS on perfused adult rat heart. When applied to perfused adult rat heart, DHS caused a dose-dependent inotropic effect resembling that of catecholamines. The effect was apparent with DHS concentration as low as 10 nM. Suspecting direct interaction with β-adrenergic receptors, we tested whether DHS can trigger β agonist-dependent gene transcription in a model cell line. While DHS alone was unable to trigger β agonist-dependent gene transcription, it enhanced the effect of isoproterenol, a known unspecific β agonist. Further tests confirmed that DHS could not induce cAMP accumulation in isolated neonatal rat cardiomyocytes even though high concentrations (≥ 10 μM) of DHS were capable of decreasing phosphodiesterase activity. Pre-treatment of rats with reserpine, an indole alkaloid which depletes catecholamines from peripheral sympathetic nerve endings, abolished the DHS inotropic effect in perfused hearts. Our data suggest that DHS causes the inotropic effect without acting as a β agonist. Hence we identify DHS as a novel inotropic agent.

• MeSH
• buněčné linie MeSH
• kardiomyocyty fyziologie   MeSH
• kardiotonika farmakologie   MeSH
• kontrakce myokardu účinky léků   MeSH
• krysa rodu Rattus MeSH
• ostropestřec mariánský MeSH
• potkani Wistar MeSH
• reserpin farmakologie   MeSH
• rostlinné přípravky farmakologie   MeSH
• silibinin MeSH
• silymarin farmakologie   MeSH
• srdce účinky léků   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kardiotonika MeSH
• reserpin MeSH
• rostlinné přípravky MeSH
• silibinin MeSH
• silymarin MeSH

Reactive oxygen species (ROS) originating from mitochondria are perceived as a factor contributing to cell aging and means have been sought to attenuate ROS formation with the aim of extending the cell lifespan. Silybin and dehydrosilybin, two polyphenolic compounds, display a plethora of biological effects generally ascribed to their known antioxidant capacity. When investigating the cytoprotective effects of these two compounds in the primary cell cultures of neonatal rat cardiomyocytes, we noted the ability of dehydrosilybin to de-energize the cells by monitoring JC-1 fluorescence. Experiments evaluating oxygen consumption and membrane potential revealed that dehydrosilybin uncouples the respiration of isolated rat heart mitochondria albeit with a much lower potency than synthetic uncouplers. Furthermore, dehydrosilybin revealed a very high potency in suppressing ROS formation in isolated rat heart mitochondria with IC(50) = 0.15 μM. It is far more effective than its effect in a purely chemical system generating superoxide or in cells capable of oxidative burst, where the IC(50) for dehydrosilybin exceeds 50 μM. Dehydrosilybin also attenuated ROS formation caused by rotenone in the primary cultures of neonatal rat cardiomyocytes. We infer that the apparent uncoupler-like activity of dehydrosilybin is the basis of its ROS modulation effect in neonatal rat cardiomyocytes and leads us to propose a hypothesis on natural ischemia preconditioning by dietary polyphenols.

• MeSH
• analýza rozptylu MeSH
• benzimidazoly MeSH
• fluorescenční barviva MeSH
• inhibiční koncentrace 50 MeSH
• karbocyaniny MeSH
• kardiomyocyty metabolismus   MeSH
• krysa rodu Rattus MeSH
• mitochondrie metabolismus   MeSH
• molekulární struktura MeSH
• potkani Wistar MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• rotenon toxicita   MeSH
• silymarin chemie   farmakologie   MeSH
• spotřeba kyslíku účinky léků   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolocarbocyanine MeSH Prohlížeč
• benzimidazoly MeSH
• dehydrosilybin MeSH Prohlížeč
• fluorescenční barviva MeSH
• karbocyaniny MeSH
• reaktivní formy kyslíku MeSH
• rotenon MeSH
• silymarin MeSH

Myocardial ischemia/reperfusion (IR) injury leads to structural changes in the heart muscle later followed by functional decline due to progressive fibrous replacement. Hence approaches to minimize IR injury are devised, including ischemic pre-and postconditioning. Mild uncoupling of oxidative phosphorylation is one of the mechanisms suggested to be cardioprotective as chemical uncoupling mimics ischemic preconditioning. Uncoupling protein 2 is proposed to be the physiological counterpart of chemical uncouplers and is thought to be a part of the protective machinery of cardiomyocytes. Morphological changes in the mitochondrial network likely accompany the uncoupling with mitochondrial fission dampening the signals leading to cardiomyocyte death. Here we review recent data on the role of uncoupling in cardioprotection and propose that low concentrations of dietary polyphenols may elicit the same cardioprotective effect as dinitrophenol and FCCP, perhaps accounting for the famed "French paradox".

• MeSH
• buněčná smrt účinky léků   MeSH
• dinitrofenoly terapeutické užití   MeSH
• fenoly terapeutické užití   MeSH
• flavonoidy terapeutické užití   MeSH
• iontové kanály metabolismus   MeSH
• ischemické přivykání MeSH
• karbonylkyanid-p-trifluormethoxyfenylhydrazon terapeutické užití   MeSH
• kardiomyocyty metabolismus   patologie   MeSH
• kardiotonika terapeutické užití   MeSH
• lidé MeSH
• mitochondriální proteiny metabolismus   MeSH
• myokard metabolismus   patologie   MeSH
• oxidativní fosforylace * MeSH
• polyfenoly MeSH
• reperfuzní poškození myokardu farmakoterapie   metabolismus   patologie   MeSH
• rozpřahující látky terapeutické užití   MeSH
• signální transdukce účinky léků   MeSH
• uncoupling protein 2 MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• dinitrofenoly MeSH
• fenoly MeSH
• flavonoidy MeSH
• iontové kanály MeSH
• karbonylkyanid-p-trifluormethoxyfenylhydrazon MeSH
• kardiotonika MeSH
• mitochondriální proteiny MeSH
• polyfenoly MeSH
• rozpřahující látky MeSH
• UCP2 protein, human MeSH Prohlížeč
• uncoupling protein 2 MeSH