Abstract
The present study investigated the effects of equol on cardiovascular K+ channel currents. The cardiovascular K+ channel currents were determined in HEK 293 cells stably expressing cloned differential cardiovascular K+ channels with conventional whole-cell patch voltage-clamp technique. We found that equol inhibited hKv1.5 (IC50: 15.3 μM), hKv4.3 (IC50: 29.2 μM and 11.9 μM for hKv4.3 peak current and charge area, respectively), IKs (IC50: 24.7 μM) and IhERG (IC50: 31.6 and 56.5 μM for IhERG.tail and IhERG.step, respectively), but not hKir2.1 current, in a concentration-dependent manner. Interestingly, equol increased BKCa current with an EC50 of 0.1 μM. It had no significant effect on guinea pig ventricular action potentials at concentrations of ≤3 μM. These results demonstrate that equol inhibits several cardiac K+ currents at relatively high concentrations, whereas it increases BKCa current at very low concentrations, suggesting that equol is a safe drug candidate for treating patients with cerebral vascular disorders.
Highlights
Equol [7-hydroxy-3-(4’-hydroxyphenyl)-chroman] is an active metabolite of the soy isoflavone daidzein generated in the intestinal microbial flora in some, but not all, individuals after consuming daidzein[1,2,3]
Our results demonstrated that equol inhibited these cardiac K+ currents at relatively high concentrations, whereas it increased BKCa current at a low concentration range without prolonging action potential duration in guinea pig ventricular myocytes
Equol gradually inhibited the Kv1.5 current, and the inhibitory effect was partially reversed on washout
Summary
Equol [7-hydroxy-3-(4’-hydroxyphenyl)-chroman] is an active metabolite of the soy isoflavone daidzein generated in the intestinal microbial flora in some, but not all, individuals after consuming daidzein[1,2,3]. Biological activities of equol are greater than daidzein in non-vascular systems[4, 5] with superior antioxidant activity[6,7,8,9,10]. An earlier study from Sobey and colleagues demonstrated that equol dilates carotid artery in vitro and basilar artery of normotensive rats in vivo with similar potency to its parent compound daidzein. Equol retains its vasorelaxant activity in carotid arteries from hypertensive rats, whereas effects of daidzein were insignificant, suggesting that equol may be a useful therapeutic agent to treat cerebral vascular disorders[11]. It is believed that equol rather than daidzein itself may contribute to the beneficial effects of soy foods in preventing cardiovascular disorders
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