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
• Cell Line MeSH
• Myocytes, Cardiac physiology   MeSH
• Cardiotonic Agents pharmacology   MeSH
• Myocardial Contraction drug effects   MeSH
• Rats MeSH
• Silybum marianum MeSH
• Rats, Wistar MeSH
• Reserpine pharmacology   MeSH
• Plant Preparations pharmacology   MeSH
• Silybin MeSH
• Silymarin pharmacology   MeSH
• Heart drug effects   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Cardiotonic Agents MeSH
• Reserpine MeSH
• Plant Preparations MeSH
• Silybin MeSH
• Silymarin MeSH

OBJECTIVE: Cell therapies have emerged as a promising approach in medicine. The basis of each therapy is the injection of 1-100×10(6) cells with regenerative potential into some part of the body. Mesenchymal stromal cells (MSCs) are the most used cell type in the cell therapy nowadays, but no gold standard for the labeling of the MSCs for magnetic resonance imaging (MRI) is available yet. This work evaluates our newly synthesized uncoated superparamagnetic maghemite nanoparticles (surface-active maghemite nanoparticles - SAMNs) as an MRI contrast intracellular probe usable in a clinical 1.5 T MRI system. METHODS: MSCs from rat and human donors were isolated, and then incubated at different concentrations (10-200 μg/mL) of SAMN maghemite nanoparticles for 48 hours. Viability, proliferation, and nanoparticle uptake efficiency were tested (using fluorescence microscopy, xCELLigence analysis, atomic absorption spectroscopy, and advanced microscopy techniques). Migration capacity, cluster of differentiation markers, effect of nanoparticles on long-term viability, contrast properties in MRI, and cocultivation of labeled cells with myocytes were also studied. RESULTS: SAMNs do not affect MSC viability if the concentration does not exceed 100 μg ferumoxide/mL, and this concentration does not alter their cell phenotype and long-term proliferation profile. After 48 hours of incubation, MSCs labeled with SAMNs show more than double the amount of iron per cell compared to Resovist-labeled cells, which correlates well with the better contrast properties of the SAMN cell sample in T2-weighted MRI. SAMN-labeled MSCs display strong adherence and excellent elasticity in a beating myocyte culture for a minimum of 7 days. CONCLUSION: Detailed in vitro tests and phantom tests on ex vivo tissue show that the new SAMNs are efficient MRI contrast agent probes with exclusive intracellular uptake and high biological safety.

• Keywords
• magnetic resonance imaging, mesenchymal stromal cells, stem cell labeling, stem cell tracking, superparamagnetic iron oxide nanoparticles,
• MeSH
• Cell Tracking methods   MeSH
• Dextrans chemistry   pharmacokinetics   toxicity   MeSH
• Cell Physiological Phenomena drug effects   MeSH
• Contrast Media chemistry   pharmacokinetics   toxicity   MeSH
• Rats MeSH
• Cells, Cultured MeSH
• Humans MeSH
• Magnetic Resonance Imaging MeSH
• Magnetite Nanoparticles chemistry   toxicity   MeSH
• Mesenchymal Stem Cells chemistry   cytology   drug effects   metabolism   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Comparative Study MeSH
• Names of Substances
• Dextrans MeSH
• ferumoxides MeSH Browser
• Contrast Media MeSH
• Magnetite Nanoparticles 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
• Analysis of Variance MeSH
• Benzimidazoles MeSH
• Fluorescent Dyes MeSH
• Inhibitory Concentration 50 MeSH
• Carbocyanines MeSH
• Myocytes, Cardiac metabolism   MeSH
• Rats MeSH
• Mitochondria metabolism   MeSH
• Molecular Structure MeSH
• Rats, Wistar MeSH
• Reactive Oxygen Species metabolism   MeSH
• Rotenone toxicity   MeSH
• Silymarin chemistry   pharmacology   MeSH
• Oxygen Consumption drug effects   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolocarbocyanine MeSH Browser
• Benzimidazoles MeSH
• dehydrosilybin MeSH Browser
• Fluorescent Dyes MeSH
• Carbocyanines MeSH
• Reactive Oxygen Species MeSH
• Rotenone MeSH
• Silymarin MeSH