Ginkgo biloba Extract and Ginkgolide Antiarrhythmic Potential by Targeting hERG and ICa-L Channel

Abstract

We investigated the effects of Ginkgo biloba extract (GBE) and ginkgolide (GLD) on human ether-a-go-go-related gene (hERG)-encoded K+ channels and its underlying mechanisms in the hERG-HEK293 cell line by determining GBE- and GLD-induced changes in action potential duration (APD), L-type calcium currents (ICa-L), and the intracellular calcium concentration ([Ca2+]i) in guinea-pig ventricular myocytes. hERG currents, APD and ICa-L were recorded using the whole-cell patch clamp technique, the [Ca2+]i was examined by an immunofluorescence experiment. In the present study, we found that a low concentration of GBE (0.005 mg/ml) increased hERG currents, but the high concentration of GBE (from 0.05 to 0.25 mg/ml) reduced hERG currents. GLD reduced hERG currents in a concentration-dependent manner (from 0.005 to 0.25 mg/ml). Both GBE and GLD altered kinetics of the hERG channel. GBE accelerated the activation of hERG channels without changing the inactivation curve, but reduced the time constant of inactivation; GLD did not shift the activation or the inactivation curve, but only reduced the time constant of inactivation. Both GBE and GLD shortened the APD, inhibited the ICa-L currents, and decreased the [Ca2+]i in isolated guinea-pig ventricular myocytes. The results indicate that GBE and GLD can prevent ischemic arrhythmias and have an antiarrhythmic effect potential via inhibition of IKr and ICa-L currents. Keywords:: Ginkgo biloba extract (GBE), ginkgolide (GLD), human ether-a-go-go-related gene (hERG) potassium channel, action potential duration (APD), L-type calcium currents (ICa-L)