Block of hERG Channels by Berberine

Abstract

Berberine prolongs the duration of cardiac action potentials without affecting resting membrane potential or action potential amplitude. Controversy exists regarding whether berberine exerts this action by preferential block of different components of the delayed rectifying potassium current, I(Kr) and I(Ks). Here we have studied the effects of berberine on hERG (I(Kr)) and KCNQ1/KCNE1 (I(Ks)) channels expressed in HEK-293 cells and Xenopus oocytes. In HEK-293 cells, the IC50 for berberine was 3.1 +/- 0.5 microM on hERG compared with 11 +/- 4% decreases on KCNQ1/KCNE1 channels by 100 microM berberine. Likewise in oocytes, hERG channels were more sensitive to block by berberine (IC50 = 80 +/- 5 microM) compared with KCNQ1/KCNE1 channels (approximately 20% block at 300 microM). hERG block was markedly increased by membrane depolarization. Mutation to Ala of Y652 or F656 located on the S6 domain, or V625 located at the base of the pore helix of hERG decreased sensitivity to block by berberine. An inactivation-deficient mutant hERG channel (G628C/S631C) was also blocked by berberine. Together these findings indicate that berberine preferentially blocks the open state of hERG channels by interacting with specific residues that were previously reported to be important for binding of more potent antagonists.

Mitochondria and NMDA Receptor-Dependent Toxicity of Berberine Sensitizes Neurons to Glutamate and Rotenone Injury

“…At concentrations similar to the IC 50 of ≈3 µM for CGN viability, BBR inhibits delayed rectifier currents and HERG channels [15], [25], [68]. At higher concentrations, BBR also inhibits a variety of potassium currents, including inward and outward rectifier, voltage sensitive, and K + channel currents [25], [67]–[69].…”

Phytochemical Compounds and Protection from Cardiovascular Diseases: A State of the Art

“…BBR, at the dosage of 100 mg/kg/day, plays positive inotropic, antiarrhythmic, and vasodilator properties related to the cardiovascular system [ 188 , 189 ]. The antiarrhythmic effects are due, at least in part, to preferential blockade of the components of the delayed rectifying potassium current, I(Kr), and I(Ks) and to increased effective refractory period of Purkinje fibers [ 190 , 191 ].…”

Mechanism and pharmacological rescue of berberine-induced hERG channel deficiency

“…To clarify whether hERG channel deficiency caused by BBR incubation was also on account of Phe656 and Tyr652 binding similar to acute application of BBR. 8 We studied the effects of BBR on mutant channels by transfecting HEK293 cells with WT-hERG, Y652A-hERG, or F656V-hERG. Figure 2A shows Western blot analysis and statistics.…”

“…Previous researches showed that BBR acutely blocks hERG channel in Xenopus oocytes by interacting with the two aromatic amino acid residues (tyrosine [Tyr652] and phenylalanine [Phe656], which are thought as the universal binding sites for various hERG channel blockers) located in S6 transmembrane helix. 8 Drug binding to special residues may induce conformational changes of the hERG channel. 9 In addition, we recently reported that BBR reduces hERG plasma membrane expression, through disrupting trafficking after long-term exposure.…”

“…Previous report illustrated that BBR acutely block hERG channel by interacting with specific residues (Tyr652 and Phe656). 8 However, there was no report to elucidate that the binding sites mediate hERG reduction triggered by BBR incubation. This study uses site-directed mutagenesis to identify the binding sites that mediate long-term effect.…”