Evaluation of cardiac safety of hydroxyrutaecarpine, hERG channel inhibitor / 药学学报

ABSTRACT

Drug-induced long QT syndrome (LQTS) has become an important clinical research topic, and the occurrence of acquired long QT syndrome (acLQTS) is mainly caused by drug inhibition of the human ether-α-go-go related gene (hERG) channel. The hERG gene encodes the α subunit of the fast-activating delayed rectifying potassium ion channel (Ikr), which plays an important role in the process of action potential phase 3 repolarization and is also the target of most antiarrhythmic drugs. The purpose of this study was to investigate the effect of hydroxyrutaecarpine (HRU) on the hERG channel and to evaluate its cardiotoxicity. The whole cell patch clamp technique was used to detect the effects of HRU on the current and kinetics of the hERG channel, and to confirm the binding site on the hERG channel. PCR was used to determine the effect of HRU on hERG mRNA expression. Western blotting was used to detect the effects of HRU on the expression of hERG protein and transcription factor Sp1. Immunofluorescence was used to confirm the effects of HRU on localization and expression of hERG protein and transcription factor Sp1. Studies have shown that transient HRU can inhibit hERG current and shorten the inactivation time constant. Its binding sites to the hERG channel are F656 and Y652. After incubation for 24 h, HRU can reduce the expression of hERG protein, inhibit the hERG current, reduce the level of hERG mRNA, and reduce the expression of transcription factor Sp1 in the nucleus and hERG protein in the cytoplasm. Immunofluorescence experiments also showed the same results suggesting that the inhibition of Sp1 expression by HRU is the cause of the decreased expression of hERG mRNA. In conclusion, the acute inhibition of HRU accelerates the channel inactivation process and reduces the inactivation time constant by binding to the F656 and Y652 sites in the hERG channel, thus reducing the hERG current. In addition, HRU also inhibits the expression of hERG protein, mainly by inhibiting the expression of transcription factor Sp1, the transcription function of hERG channel protein is down-regulated, so that the hERG protein is reduced.