Liandi Kan1, Wei Zhao2, Lanying Pan2, Jianwei Xu2, Qingmao Chen3, Kai Xu3, Liping Xiao2, Yuan Chen4. 1. Department of Pharmacy, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou 310016, PR China. 2. Chinese Herb Medicine Division, Zhejiang Agriculture and Forestry University, 88 North Circle Road, Lin'an 311300, PR China; The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang Agriculture and Forestry University, 88 North Circle Road, Lin'an 311300, PR China. 3. Safety Pharmacology Division, Olivepharmasolutions Ltd, 333 Changhong Road, Wukang 313200, PR China. 4. Chinese Herb Medicine Division, Zhejiang Agriculture and Forestry University, 88 North Circle Road, Lin'an 311300, PR China; The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang Agriculture and Forestry University, 88 North Circle Road, Lin'an 311300, PR China. Electronic address: ychen@zafu.edu.cn.
Abstract
BACKGROUND AND OBJECTIVE: Fritillaria is a Chinese traditional herb. It has a long history and many medicinal usages including antitussive, anti-inflammatory and pain relieving actions. It is also used as food. However, its cardiac safety has not been tested. Peimine is one of the main active compounds of Fritillaria. To be listed as an herb in the Chinese Pharmacopoeia, a special minimal percentage of Peimine in the dry sample of Fritillaria is required. The main concern for cardiac safety determination is the possible inhibition of hERG ion channels. Thus, Peimine was chosen to investigate its inhibitory effects on hERG channels. METHODS: Whole cell patch clamp technique was used. RESULTS AND CONCLUSION: We found that Peimine inhibited the hERG peak tail currents in a concentration dependent manner with an IC50 value of 43.7μM (n=4) by whole cell patch clamp techniques. Multiple results suggest that the inhibition was related to the channel inactivation. First, Peimine inhibition was significantly increased when the prepulse voltage was increased from -30mV to +10mV. Second, increasing prepulse length also significantly increased blockade by Peimine. Third, our finding that the inhibition by Peimine was use-dependent is related to changes in the inactivated state of the channel. Finally, the result that Peimine significantly decreased inactivation constant also suggested that Peimine affect the channel inactivation state. Mutation of Y652 to Alanine reduced sensitivity to Peimine, suggesting that Y652 is an important hERG binding sites for Peimine.
BACKGROUND AND OBJECTIVE: Fritillaria is a Chinese traditional herb. It has a long history and many medicinal usages including antitussive, anti-inflammatory and pain relieving actions. It is also used as food. However, its cardiac safety has not been tested. Peimine is one of the main active compounds of Fritillaria. To be listed as an herb in the Chinese Pharmacopoeia, a special minimal percentage of Peimine in the dry sample of Fritillaria is required. The main concern for cardiac safety determination is the possible inhibition of hERG ion channels. Thus, Peimine was chosen to investigate its inhibitory effects on hERG channels. METHODS: Whole cell patch clamp technique was used. RESULTS AND CONCLUSION: We found that Peimine inhibited the hERG peak tail currents in a concentration dependent manner with an IC50 value of 43.7μM (n=4) by whole cell patch clamp techniques. Multiple results suggest that the inhibition was related to the channel inactivation. First, Peimine inhibition was significantly increased when the prepulse voltage was increased from -30mV to +10mV. Second, increasing prepulse length also significantly increased blockade by Peimine. Third, our finding that the inhibition by Peimine was use-dependent is related to changes in the inactivated state of the channel. Finally, the result that Peimine significantly decreased inactivation constant also suggested that Peimine affect the channel inactivation state. Mutation of Y652 to Alanine reduced sensitivity to Peimine, suggesting that Y652 is an important hERG binding sites for Peimine.