Inhibition And Molecular Mechanism Determination Of Tripterine On Herg Channels

Triptergium wilfordii is a Chinese traditional drug. Its clinical effect is significant. But due to its side effects, many clinical applications are limited.Tripterine is the first component isolated from it. It has a wide range of pharmacological activities. However, with further researches, it was found to damage the cardiovascular system. In the evaluation of drugs, heart toxicity, the blockade of hERG channel potassium currents is considered as an important indicator.In this study, we used whole cell patch clamp technique to detect the effect of tripterine on hERG. We used different pulse stimulation to determine the effects of IKr, on hERG potassium channel current voltage(I-V)curve, activation and inactivation. And we also combine the PCR site directed mutagenesis to determine the binding sites. In our study, We found tripterine cause a centration dependent inhibition of cardiac hERG potassium channels, the IC50 value is 3.30 μM. The hERG channel current and voltage(I-V) curve was not affected, before and after perfusion 1 μM tripterine, the V1/2 is-15.7 ± 1.07 mV and-15.2 ± 0.40 mV, with S of 8.66 ± 0.55 VS 8.67 ± 0.22. It did not affect the activation of hERG. And the blockade is independent of magnitude of voltage and the length of depolarization time. The high frequency of depolarization pulse voltage stimulation significantly increased the blockade of the hERG current. On this basis, we used PCR site directed mutagenesis technique to constructed 5 channel mutants. The mutation of T623 A, S624 A and F656 A significantly changed the inhibitory effects of the hERG potassium channel currents, which indicates that these sites play an important role in the blockade of tripterine on hERG channel.