ABSTRACT
Title
Quercetin interaction with vascular smooth muscle Cav1.2 channels
Authors
P. Mugnai
Dept. of Neuroscience, section of Pharmacology, University of Siena
Dept. of Neuroscience, section of Pharmacology, University of Siena
Abstract
Flavonoids are polyphenolic compounds found in edible plants (i.e. fruits, vegetables, herbs, grains) and beverages (i.e. tea, red wine). Recent findings from this laboratory have highlighted vascular ion channels as important pharmacological targets for flavonoids. These evidences support the hypothesis that these polyphenols dietary flavonoids can affect vascular tone by directly targeting ion channels (Scholz et al. 2010).
Since drug interaction with and drug binding to Cav1.2 channel depend on the experimental conditions that determine its state (Zahradnikova et al. 2007). Cav1.2 channel current recording from operational channels (as is the case with the patch-clamp technique) may represent physiological approach allowing an in-depth analysis of flavonoids target site. Based on this experimental approach, the aim of my second year doctoral work was to characterize the electrophysiological effects of quercetin on vascular ICa1.2. ICa1.2 was recorded using the conventional whole-cell patch-clamp method in single smooth muscle cells isolated from the rat tail main artery. Under control conditions, ICa1.2 elicited with 250 ms clamp pulses (0.067 Hz) to 10 mV from a Vh of -50 mV achieved a stable intensity about 10 min after the whole-cell configuration had been obtained. Neither ICa1.2 intensity nor the current-voltage relationship changed over the next 40 min of recording. In cells treated with 10 µM quercetin, a gradual increase of the current intensity was observed; this gained a maximum value in about 4 min, remained stable for about 10-12 min, and then slowly decreased back to control value. A similar pattern was observed with Ba2+ as the charge carrier. Among the pathways affecting channel function, protein tyrosine kinase and PKCα were investigated as potential targets for quercetin activity. However, neither the protein tyrosine phosphatase inhibitor dephostatine (50 µM) nor the PKCαinhibitor Gö6976 (100 nM) modified quercetin-induced stimulation of ICa1.2. In conclusion, these data suggest that quercetin may exert its effect via direct modulation of Cav1.2 channel.
1) Scholz EP et al. (2010) Cardiovasc Ther 28:46
2) Zahradnikova A et al. (2007) J Pharmacol Exp Ther 322:638
Since drug interaction with and drug binding to Cav1.2 channel depend on the experimental conditions that determine its state (Zahradnikova et al. 2007). Cav1.2 channel current recording from operational channels (as is the case with the patch-clamp technique) may represent physiological approach allowing an in-depth analysis of flavonoids target site. Based on this experimental approach, the aim of my second year doctoral work was to characterize the electrophysiological effects of quercetin on vascular ICa1.2. ICa1.2 was recorded using the conventional whole-cell patch-clamp method in single smooth muscle cells isolated from the rat tail main artery. Under control conditions, ICa1.2 elicited with 250 ms clamp pulses (0.067 Hz) to 10 mV from a Vh of -50 mV achieved a stable intensity about 10 min after the whole-cell configuration had been obtained. Neither ICa1.2 intensity nor the current-voltage relationship changed over the next 40 min of recording. In cells treated with 10 µM quercetin, a gradual increase of the current intensity was observed; this gained a maximum value in about 4 min, remained stable for about 10-12 min, and then slowly decreased back to control value. A similar pattern was observed with Ba2+ as the charge carrier. Among the pathways affecting channel function, protein tyrosine kinase and PKCα were investigated as potential targets for quercetin activity. However, neither the protein tyrosine phosphatase inhibitor dephostatine (50 µM) nor the PKCαinhibitor Gö6976 (100 nM) modified quercetin-induced stimulation of ICa1.2. In conclusion, these data suggest that quercetin may exert its effect via direct modulation of Cav1.2 channel.
1) Scholz EP et al. (2010) Cardiovasc Ther 28:46
2) Zahradnikova A et al. (2007) J Pharmacol Exp Ther 322:638