Effects of Tannic Acid, Green Tea and Red Wine on hERG Channels Expressed in HEK293 Cells

Abstract

Tannic acid presents in varying concentrations in plant foods, and in relatively high concentrations in green teas and red wines. Human ether-à-go-go-related gene (hERG) channels expressed in multiple tissues (e.g. heart, neurons, smooth muscle and cancer cells), and play important roles in modulating cardiac action potential repolarization and tumor cell biology. The present study investigated the effects of tannic acid, green teas and red wines on hERG currents. The effects of tannic acid, teas and red wines on hERG currents stably transfected in HEK293 cells were studied with a perforated patch clamp technique. In this study, we demonstrated that tannic acid inhibited hERG currents with an IC50 of 3.4 μM and ~100% inhibition at higher concentrations, and significantly shifted the voltage dependent activation to more positive potentials (Δ23.2 mV). Remarkably, a 100-fold dilution of multiple types of tea (green tea, oolong tea and black tea) or red wine inhibited hERG currents by ~90%, and significantly shifted the voltage dependent activation to more positive potentials (Δ30.8 mV and Δ26.0 mV, respectively). Green tea Lung Ching and red wine inhibited hERG currents, with IC50 of 0.04% and 0.19%, respectively. The effects of tannic acid, teas and red wine on hERG currents were irreversible. These results suggest tannic acid is a novel hERG channel blocker and consequently provide a new mechanistic evidence for understanding the effects of tannic acid. They also revealed the potential pharmacological basis of tea- and red wine-induced biology activities.

Bufalin, a bufanolide steroid from the parotoid glands of the Chinese toad, suppresses hERG K+ currents expressed in HEK293 cells

“…Figure b shows the G‐V curves with controls for bufalin (10 and 100 μ M ) and terfenadine (100 n M ). Terfenadine is a well‐established hERG blocker, and we used the Terfenadine (100 n M ) as a positive control drug to compare the inhibitory efficiency with the bufalin (10, 100 μ M ) . G‐V curves were established from the tail currents at −60 mV, and bufalin 100 μ M significantly shifted the V 1/2 toward more negative potentials.…”

“…In molecular genetic tests, G418 is used to screen the stably transfected cells. In the experiment of preparing the HEK293 cells stably transfected with hERG, neo gene exists in these cells and makes these cells grow in a selective medium containing G418 .…”

The Mechanism Underlying the Protective Effects of Tannic Acid Against Isoproterenol-Induced Myocardial Fibrosis in Mice

“…Previous studies have suggested that TA possessesanti-lipogenic, anticarcinogenic, antiinflammatory, antioxidant, and scavenging activities (Gali et al, 1992;Chu et al, 2016). TA has some potent pharmacological effects, including myocardial protection (Hu et al, 2015;Zhang et al, 2017a;Zhang et al, 2017b), a decrease in L-type Ca 2+ currents in isolated mice ventricular myocytes (Zhu et al, 2016), and a vasodilatory effect via activation of K + channels expressed in HEK293 cells (Chu et al, 2015;Zhang et al, 2016a). However, the relevance of the protective results of TA on chronic MF is not well-defined.…”

Mechanistic Insights into Oxidative Stress and Apoptosis Mediated by Tannic Acid in Human Liver Hepatocellular Carcinoma Cells

“…TA is a glucoside comprising gallic acid polymers that form part of the hydrolysable tannins found to possess anti-oxidative properties that may contribute to their cancer preventive, chemotherapeutic, and anti-inflammatory properties [11][12][13]. In vivo, TA and other green tea polyphenols inhibited the mammary tumour virus promoter, whereas in vitro the proliferation of specific cancer cell lines was inhibited and induced apoptosis [14]. TA has been revealed to exert a significant liver-protective effects in mice with CCl4-induced liver fibrosis [15].…”