The effect of HMS-01 on stably expressed hERG channel currents in HEK293 cells detected with the manualpatch clamp method / 药学实践杂志

Objective To test the cardiac toxicity of new compound HMS-01 and evaluate the safety profile for clinical trials. Methods Manualpatch clamp method was used to measure human Ether-a-go-go-Related Gene (hERG) potassium channel currents with different concentrations of HMS-01. Cisapride was selected as the positive control drug. HMS-01 was diluted to the concentration of 0.3, 1, 3, 10 and 30 µmol/L and applied to the cells. The changes in electrical currents were recorded and the inhibition rate was calculated. Results At the highest concentration of 30µmol/L, the inhibitory rate of HMS-01 on hERG channel was less than 30%. There was no obvious inhibitory effect compared with cisapride. Conclusion Compared with the cisapride, HMS-01 has no obvious inhibitory effect on hERG channel and has no cardiotoxicity.

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

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.

Research Advances on Non-Clinical Evaluation in Vitro of Drug-Induced Arrhythmias / 中国药学杂志

Drug-induced arrhythmia is one of the main causes of failure in drug development, and it is also a major cause of drug withdrawal, therefore, accurate prediction of drug-induced arrhythmia in the non-clinical research stage is the best way to reduce cost. Literature was retrieved by formally searching PubMed, Metstr, CNKI and Baidu Scholar, 1 479 published articles were found through search method, 63 full-text articles were included. After reviewed the relevant literatures, the advantages and disadvantages of the different experimental cells and the related evaluation methods are assessed, in order to provide reference for toxicity evaluation.

The Advance of Escitalopram's Drug-induced QTc Prolongation / 中国药学杂志

Escitalopram, a selective serotonin re-uptake inhibitor (SSRI) antidepressant which is the (S)-enantiomer of citalopram, is worldwide used for the treatment of depressive and anxious disorders in clinical practice, however, recent data have indicated that high therapeutic escitalopram doses may cause the potential of QTc prolongation effect, which is a predisposing factor for arrhythmia. Nevertheless, in March 2012, the Food and Drug Administration (FDA) issued a safety bulletin advising the daily dosage of escitalopram should be restricted to a maximum of 20 mg daily in healthy adults and 10 mg maximum in high risk patients (eg>60 years of age). In this review, we aimed to investigate what factors can affect and how escitalopram gives rise to QTc prolongation.

Downregulation of Herg1 suppresses osteosarcoma proliferation and invasion by targeting Hippo signaling pathway / 中华肿瘤杂志

Objective@#To detect the effect and regulatory mechanism of human ether à go-go related gene 1 (Herg 1) knockdown on the proliferation and invasion of osteosarcoma (OS).@*Methods@#We constructed a recombinant adenovirus vector (Ad5-Herg1-shRNA) expressing short hair RNA (shRNA) against Herg1 and tested the knockdown efficiency. Then, the effects of Herg 1 knockdown on the proliferation, growth and invasion of osteosarcoma were measured by using cell counting kit-8 (CCK-8), wound healing assay, Transwell assay and xenograft model of nude mice, respectively. Tandem affinity purification, mass spectrometry and dual luciferase reporter assay were used to find out the molecules interacted with Herg1. Western blot was used to detect the expressions of large tumor suppressor gene (LATS1), p-LATS1, Yes-associated protein (YAP) and p-YAP in cells after infection of Ad5-Herg1-shRNA.@*Results@#Compared to Ad5-control-shRNA, Ad5-Herg1-shRNA dramatically inhibited the expression of Herg1 in OS cells. The result of CCK8 array demonstrated that 143B cell vitalities of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (65.47±3.90)% and (79.90±1.52)%, significantly lower than (100.00±6.14)% of Ad5-control-shRNA group. Meanwhile, U2OS cell vitality of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (69.69±1.36)% and (76.72±2.75)%, significantly lower than (100.00±3.01)% of Ad5-control-shRNA group (all P<0.001). The results of wound healing array showed that 143B cell migration rates of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (33.03±2.88)% and (36.47±4.16)%, significantly lower than (97.78±2.28)% of Ad5-control-shRNA group. Meanwhile, U2OS cell migration rates of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (68.07±0.90)% and (73.97±1.25)%, significantly lower than (96.50±1.12)% of Ad5-control-shRNA group (all P<0.001). The results of Transwell showed that 143B cell invasion numbers of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were 36.50±12.15 and 44.83±7.62, significantly lower than 195.33±19.68 of Ad5-control-shRNA group. Meanwhile, U2OS cell migration rates of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were 21.83±7.99 and 22.85±7.08, significantly lower than 83.33±12.36 of Ad5-control-shRNA group (all P<0.001). The results of xenograft model of OS showed that the tumor volume and weight of Ad5-Herg1-shRNA group were significantly smaller than of Ad5-control-shRNA group after 14 days and 5 weeks of inoculation, respectively (P<0.001). Moreover, knockdown of Herg1 inhibited the metastasis of OS cells. In mechanism, Herg1 protein interacted with NF2 protein. Knockdown of Herg1 significantly suppressed the expression levels of LATS1 and YAP protein, and promoted the phosphorylation of LATS1 and YAP in OS cells (all P<0.001).@*Conclusion@#Our findings suggest that Herg1 participates in the proliferation and motility of OS cells and may serve as a potential therapeutic target for osteosarcoma patients.

Advances in research on the mechanism of long-QT syndrome caused by traditional Chinese medicine affecting hERG potassium channel / 药学学报

Drug-induced cardiotoxicity is recently a major concern. Cardiotoxicity is the leading cause of drug withdrawal from the market. Long-QT syndrome is one of the most important manifestations of cardiotoxicity. hERG potassium channel is an important target of drug-induced arrhythmia and antiarrhythmia drugs. Traditional Chinese medicine is a traditional medicine in China with a long history and a wide range of clinical use. However, the multi-organ toxicity caused by traditional Chinese medicine is still a problem to be solved. Some traditional Chinese medicines already in clinical use have been withdrawn from the market because of their potential cardiotoxicity or severe arrhythmias. The cardiac toxicity of more than 50 kinds of traditional Chinese medicines causing arrhythmia was reported, while more than 20 of them are induced by affecting on the hERG potassium channels. Therefore, finding out the mechanism of drug-induced long-QT syndrome and the regulatory target of drug intervention is the key research goal in today's medical field. In this paper, we summarized the mechanisms of long-QT syndrome induced by traditional Chinese medicine with Ikr/hERG potassium channel as the main target. It provides a theoretical basis for the rational use of related traditional Chinese medicine in clinical practice, the avoidance of cardiac toxicity and the development of regulatory targets for drug intervention.

Cardiac safety evaluation of berberine combining with berberine-derived medicine / 药学学报

Drug-induced cardiotoxicity is a serious concern in recent years, and acquired long QT syndrome (LQTS) is an important manifestation of cardiotoxicity. hERG gene encodes the α subunit of the rapidly activated delayed rectifier potassium channel (Ikr), which plays an important role in action potential phase 3 repolarization. Drug inhibition of Ikr/hERG channel leads to prolonged QT interval, accompanied by Tdp malignant arrhythmia, which can cause sudden death. We studied the effect of berberines on the hERG K+ channels after combination with rosuvastatin and glibenclamide, and evaluated the cardiac safety of these drugs in combination. Whole cell patch clamp technique was used to detect the effect of the combinations of these drugs on hERG current on HEK293 cells stably expressing hERG gene. The results showed that the inhibitory effects of berberine or dihydroberberberine combined with rosuvastatin on hERG current were higher than single drug (P<0.05), but the combination had no effect on the kinetics of hERG channel. Berberine or dihydroberberberine combined with glibenclamide had higher inhibitory effects on hERG current than the application of single drug (P<0.05) while the time constant of hERG channel inactivation was shortened after the combination (P<0.05). In addition, the combination of berberine and glibenclamide inhibited hERG channel activation (P<0.05). In conclusion, our results demonstrated that the combination of berberine with rosuvastatin or glibenclamide significantly inhibited hERG current and the inhibition effects were higher than the application alone. Therefore, when the two drugs that have inhibitory effects on the hERG channel are combined, the risk of inducing prolonged QT interval is significantly increased, and therefore reducing cardiac safety.

Five years of the CiPA project (2013–2018): what did we learn?

Cases of drug-induced QT prolongation and sudden cardiac deaths resulted in market withdrawal of many drugs and world-wide regulatory changes through accepting the ICH guidelines E14 and S7B. However, because the guidelines were not comprehensive enough to cover the electrophysiological changes by drug-induced cardiac ion channel blocking, CiPA was initiated by experts in governments and academia in the USA, Europe, and Japan in 2013. Five years have passed since the launch of the CiPA initiative that aimed to improve the current ICH guidelines. This report reviews the current achievements of the CiPA initiative and explores unresolved issues.

Effects of Paroxetine on a Human Ether-a-go-go-related Gene (hERG) K⁺ Channel Expressed in Xenopus Oocytes and on Cardiac Action Potential

K⁺ channels are key components of the primary and secondary basolateral Cl- pump systems, which are important for secretion from the salivary glands. Paroxetine is a selective serotonin reuptake inhibitor (SSRI) for psychiatric disorders that can induce QT prolongation, which may lead to torsades de pointes. We studied the effects of paroxetine on a human K⁺ channel, human ether-a-go-go-related gene (hERG), expressed in Xenopus oocytes and on action potential in guinea pig ventricular myocytes. The hERG encodes the pore-forming subunits of the rapidly-activating delayed rectifier K⁺ channel (I(Kr)) in the heart. Mutations in hERG reduce I(Kr) and cause type 2 long QT syndrome (LQT2), a disorder that predisposes individuals to life-threatening arrhythmias. Paroxetine induced concentration-dependent decreases in the current amplitude at the end of the voltage steps and hERG tail currents. The inhibition was concentration-dependent and time-dependent, but voltage-independent during each voltage pulse. In guinea pig ventricular myocytes held at 36℃, treatment with 0.4 µM paroxetine for 5 min decreased the action potential duration at 90% of repolarization (APD₉₀) by 4.3%. Our results suggest that paroxetine is a blocker of the hERG channels, providing a molecular mechanism for the arrhythmogenic side effects of clinical administration of paroxetine.

Acepromazine inhibits hERG potassium ion channels expressed in human embryonic kidney 293 cells

The effects of acepromazine on human ether-à-go-go-related gene (hERG) potassium channels were investigated using whole-cell voltage-clamp technique in human embryonic kidney (HEK293) cells transfected with hERG. The hERG currents were recorded with or without acepromazine, and the steady-state and peak tail currents were analyzed for the evaluating the drug effects. Acepromazine inhibited the hERG currents in a concentration-dependent manner with an IC₅₀ value of 1.5 µM and Hill coefficient of 1.1. Acepromazine blocked hERG currents in a voltage-dependent manner between –40 and +10 mV. Before and after application of acepromazine, the half activation potentials of hERG currents changed to hyperpolarizing direction. Acepromazine blocked both the steady-state hERG currents by depolarizing pulse and the peak tail currents by repolarizing pulse; however, the extent of blocking by acepromazine in the repolarizing pulse was more profound than that in the depolarizing pulse, indicating that acepromazine has a high affinity for the open state of the channels, with a relatively lower affinity for the closed state of hERG channels. A fast application of acepromazine during the tail currents inhibited the open state of hERG channels in a concentration-dependent. The steady-state inactivation of hERG currents shifted to the hyperpolarized direction by acepromazine. These results suggest that acepromazine inhibits the hERG channels probably by an open- and inactivated-channel blocking mechanism. Regarding to the fact that the hERG channels are the potential target of drug-induced long QT syndrome, our results suggest that acepromazine can possibly induce a cardiac arrhythmia through the inhibition of hERG channels.

Effect of mallotoxin against LQT2 induced by E-4031 in isolated guinea pig hearts and cardiomyocytes / 中国药理学通报

Aim To investigate the effect of mallotoxin (MTX) on LQT2 induced by E-4031 in isolated guinea pig hearts and ventricular myocytes.Methods The isolated guinea pig heart underwent retrograde perfusion using Langendorff technique.In order to determine the effects of different concentrations of MTX on QT/QTc interval,transmural dispersion of repolarization (TDR) and index of cardiac electrophysiological balance (iCEB) in the absence and presence of hERG channel blocker E-4031,the electrocardiogram of isolated guinea pig hearts was recorded using Biopac physiological record.Single ventricular myocytes were isolated from guinea pig heart by enzymatic dissociation.Effects of MTX on action potential duration (APD) in the absence and presence of E-4031 were recorded by current clamp mode using whole patch clamp technique.Results MTX shortened the QT interval,reduced TDR,and decreased iCEB in isolated guinea pig heart.MTX could reverse the prolongation of QT interval and the increased TDR induced by E4031.MTX shortened the action potential duration and decreased APDgo,APD60 and APD30 in isolated guinea pig ventricular myocytes.MTX could reverse the prolongation of action potential repolarization duration induced by E-4031.Conclusion MTX shortens QT interval,decreases TDR,reduces iCEB,as well as shortens APD,thus reversing LQT2 induced by E4031.

The effect of lidocaine on hERG K+ channels / 药学学报

We studied the effects of the lidocaine on the hERG K+ channels with a focus on the electrophysiology of the heart. The hERG current was recorded using the conventional whole-cell patch clamp technique and the channel protein expression level was measured with Western blot in HEK 293 cells stablely expressed hERG K+ channels. The langendorff perfusion system was used to record the ECG from isolated rabbit heart. Lidocaine inhibited hERG current in a concentration-dependent manner at 0.3-1 000 μmol·L-1, the IC50 value was 88.63±7.99 μmol·L-1. The inhibitory action was enhanced by positive votalge without changing the votalge-dependent activation of the channel. However, lidocaine inhibited hERG current in a frequency-dependent manner. In addition, chronic incubation of lidocaine did not change the hERG K+ channel protein expression. ECG recordings in the isolated perfused rabbit heart demonstrated that lidocaine (> 100 μmol·L-1) did not affected QTc interval, but decreased the heart rate and prolonged the PR interval and QRS duration. Our results demonstrate that lidocaine potentially inhibits the hERG K+ current at a high concentration, but does not prolonged the QTc of ECG.

Lead compound optimization strategy (5)-reducing the hERG cardiac toxicity in drug development / 药学学报

The potassium channel encoded by the human ether-a-go-go related gene (hERG) plays a very important role in the physiological and pathological processes in human. hERG potassium channel determines the outward currents which facilitate the repolarization of the myocardial cells. Some drugs were withdrawn from the market for the serious side effect of long QT interval and arrhythmia due to blockade of hERG channel. The strategies for lead compound optimization are to reduce inhibitory activity of hERG potassium channel and decrease cardiac toxicity. These methods include reduction of lipophilicity and basicity of amines, introduction of hydroxyl and acidic groups, and restricting conformation.

Drug innovation and reverse thinking / 药学学报

Drug innovation involves an individual molecular operation, and every new molecular entity features a hard-duplicated track of R&D. The transformation from an active compound to a new medicine carries out almost in a chaotic system devoid of regularity and periodic alteration. Since new millennium the dominant position in drug innovation has been occupied by the first-in-class drugs, yet the number of launched follow-on drugs has been distinctly decreased. The innovation of first-in-class drugs is characterized by a high risk throughout the whole process. To achieve initiative and uniqueness of drug discovery, the strategy and method of the inverse thinking might be a feasible way, because the inertial and conformity thinkings in drug discovery normally lead to ensemble with similar drug category. However, the study from the flipside or opposite of things (e.g. targets or effects) brand new routes might be opened. This article is to describe the strategy of reverse thinking in drug discovery by some examples including opioid receptor antagonist eluxadoline, HSP90 activator, hERG channel agonist, covalent drugs, and ultra-small drugs.

Effects of extracellular potassium on expression of HERG gene nonsense mutant L539 fs/47 / 中国病理生理杂志

AIM:To study the effects of extracellular potassium on the protein expression of wild-type HERG and its mutant L539fs/47.METHODS:Wild-type HERG (WT) or its mutant HERG-L539fs/47 (MT) were transfected into HEK293 cells for 36 h.The cells were incubated in different media containing 0.8, 4.3 or 10 mmol/L potassium.Af-ter 6 h of incubation, the protein expression of HERG was detected by flow cytometry.After 12 h of incubation, the locali-zation and quantity of the proteins were detected by laser confocal imaging and Western blot.RESULTS: Different from the retention of mutant protein in cytoplasm, wild-type HERG protein was mainly distributed in the cell membrane.The 2 proteins both increased with the changes of extracellular potassium.Flow cytometry showed that the fluorescence in the 2 groups both increased with the changes of extracellular potassium ( P<0.01 ) .The fluorescence in WT group was signifi-cantly higher than that in MT group (P<0.01).Western blot showed that mutant HERG protein included only one 60 kD band, different from the 135 kD and 155 kD bands in wild-type HERG, which were affected by the changes of extracellular potassium (P<0.05).CONCLUSION:The retention of HERG mutant L539fs/47 protein in the cytoplasm is more than wild-type HERG.Chronic high extracellular potassium keeps the stability of wild-type and mutant HERG proteins on the cell membrane.Chronic low potassium reduces the expression of HERG channel proteins in a time-dependent manner.

Regulatory effect of protein tyrosine phosphatase non-receptor type on the cardiac Kv11.1 (HERG) potas-sium channel / 医学研究生学报

Objective Cardiac HERG potassium channel currents can cause long QT syndrome .The function of the cardiac HERG potassium channel is regulated by tyrosine kinase and phosphatase , and protein tyrosine phosphatase non-receptor type 11 ( PTPN11) negatively regulates the HERG potassium channel .This study aimed to investigate the effect of PTPN 11 on the electrophysio-logical characteristics of the HERG channel . Methods The plasmids of pcDNA3.1-PTPN11-EGFP were constructed by PCR technique and transfected or cotransfected with the pcDNA 3.1-PTPN11-EGFP plasmid into HEK293 cells using Lipofectamine 2000.The patch clamp technique was employed to record the HERG channel currents in the control group ( HEK293 cells transfected with pcDNA3.0-HERG-EGFP), PTPN11 overexpression group (pcDNA3.0-HERG and pcDNA3.1-PTPN6-EGFP cotransfected HEK293 cells), and PTPN11 overexpression with PAO group . Results The pcDNA3.1-PTPN11-EGFP plasmid was successfully constructed .Green fluorescence was observed in the HEK293 cells transfected with pcDNA3.0-HERG-EG-FP or cotransfected with pcDNA3.0-HERG and pcDNA3.1-PTPN11.The maximum densities of pulse and tail currents were significantly decreased in the PTPN11 overexpression group as compared with the control ([31.85 ±5.54] vs [45.92 ±3.18] pApF, P<0.05;[73.82 ±11.31] vs [108.43 ±7.98] pApF, P<0.05) but markedly in-creased in the PTPN11 overexpression with PAO group ([48.08 ±4.32] pApF;[120.06 ±8.02] pApF) (P<0.05).The time con-stant of deactivation was significantly higher in the PTPN 11 overexpression group than in the control ([622.16 ±46.49] vs [440.70 ± 49.49] ms, P<0.05). Conclusion The overexpression of PTPN11 decreases HERG potassium channel currents , which can be re-versed by PAO.This finding provides a theoretical basis for the application of certain regulatory enzymes in the HERG channel as a treat -ment of long QT syndrome .

Blocking effect of fluoxetine on hERG potassium channel activity and inhibition by phorbol-12-myristate-13-acetate / 中国药理学与毒理学杂志

OBJECTlVE To investigate the action mechanism of antidepressant fluoxetine on hERG ( ether-a-go-go-related gene ) potassium channel, and the effect of protein kinase C ( PKC ) agonist phorbol-12-myristate-13-acetate ( PMA) on fluoxetine inhibition. METHODS The whole cell patch clamp technique was used to record the change in hERG potassium current ( IKr ) on HEK293 cells that stably expressed hERG potassium channel ( hERG-HEK293 steady-state cells) , which was treated with fluoxe-tine 0.01, 0.1, 1 and 10μmol·L-1 , to study the concentration-and voltage-dependence of the effects on IKr, and to observe the changes in activation, inactivation and recovery dynamics of hERG potassium channel treated with fluoxetine 1μmol·L-1 . On this basis, the effect of PMA of 1μmol·L-1 on inhibition of fluoxetine 1 μmol·L-1 was explored. RESULTS Fluoxetine 0.01, 0.1, 1 and 10 μmol·L-1 inhibited IKr on hERG-HEK293 steady-state cells in a concentration- and voltage-dependent manner. The half maximal inhibitory concentration ( lC50 ) was about 0. 8 mmol·L-1 , and the Hill coefficient was about 1. 1. Fluoxetine 1 μmol·L-1 could reduce the activation, deactivation and recovery currents of IKr and affect the activation and recovery of hERG potassium channel. After fluoxetine inhibition of IKr became stable, PMA 1 μmol·L-1 could inhibit the blocking effect of fluoxetine on hERG potassium channels. CONCLUSlON Fluoxetine has obvious inhibitory effect on IKr of hERG-HEK293 steady-state cells, but the effect could be inhibited by PKC agonist PMA.

Experimental Research on Effect of Strictosamide Injection on Cardiovascular System / 世界科学技术-中医药现代化

This study was aimed to investigate the effects of high-dose strictosamide injection on cardiovascular sys-tem of anesthetized beagle dogs and to examine the inhibition of strictosamide on ion channels in vitro. Indexes such as changes of systolic blood pressure (Sys), diastolic blood pressure (Dia), mean blood pressure (MBP), heart rate (HR), PR, QRS, QT, QTcb and QTcv at different time points before and after strictosamide injection in dogs were monitored by the polygraph system. The inhibition of strictosamide at different concentrations on hERG potassium channel in CHO-hERG cells and Nav1.5 sodium channel in HEK-293-Nav1.5 cells were measured by whole-cell patch-clamp method. The results showed that compared with the blank control group, Sys, Dia, MBP and HR were obviously declined 15 min after medication in the strictosamide (60, 18 mg·kg-1) group and the vehicle-control group (containing tween-80) (P 0.05). The inhibition of strictosamide on hERG potassium channel and Nav1.5 sodium channel were weak with IC50 values of 560.8 μM and > 900 μM, respectively, which were far greater than the positive controls. It was concluded that sin-gle, high-dose intravenous injection of strictosamide may lead to a lower blood pressure, a slower heart rate and a prolongation on the QT interval in beagle dogs, which returned to basal levels when medication stopped. It was spec-ulated that the reduction of blood pressure and the slowing of heart rate were related to tween-80 contained in the vehicle control group. No significant inhibitory effects were detected on hERG potassium channel and Nav1.5 sodium channel in vitro, which suggested that other mechanisms may be involved in strictosamide-induced QT interval pro-longation in animals.

Effect of promethazine on eIectrophysioIogicaI action of guinea pig hearts / 中国药理学与毒理学杂志

OBJECTIVE To explore the effect and underlying mechanism of promethazine(PMZ) on proarrhythmia in guinea pigs. METHODS ① InvivoECG recordings were made to analyze effects of jugular intravenous(iv)injection of PMZ on ECG in guinea pigs. PMZ was injected in this order:3.83→7.67→15.33→38.33 mg·kg-1 cumulatively. ② In vitroECG recordings were made to analyze effects of PMZ on ECG in isolated hearts of guinea pigs. PMZ was perfused in such order:0. 1 → 1 → 10 →50 μmol·L-1 . ③ L-type Ca2+ currents from ventricular myocytes in guinea pigs were recorded to investi-gate the PMZ's blocking effect. PMZ was perfused in such order:0.1→1→10→50 μmol·L-1→washout.④ hNav1.5 and hERG currents were recorded to investigate the PMZ's blocking effects. PMZ-perfused in such order:1→3→10→30 μmol·L-1 for hNav1.5 current analysis,and 0.3→1→3→10 μmol·L-1 for hERG current analysis. RESULTS ① PMZ(15.33 mg·kg-1 )significantly prolonged QRS intervals in guinea pigs invivoECG(P﹤0.05). PMZ(38.33 mg·kg-1 )prolonged QRS,QTc,and P-R intervals but reduced the heart rate( P﹤0.05). PMZ(10 μmol·L-1 )reduced the heart rate of isolated guinea pig hearts. PMZ 50 μmol·L-1 prolonged QRS and QTc intervals and further reduced the heart rate(P﹤0.05).③ PMZ inhibited the L-type Ca2+ current from ventricular myocytes in guinea pigs in a concentration-dependent manner with the lC50 of(8.9±1.0)μmol·L-1 . ④ PMZ inhibited the hNav1.5 and hERG currents in a concentration-dependent manner with the lC50 of 6.1±1.5 and(1.6±0.2)μmol·L-1 ,respectively. CONCLUSION PMZ might cause arrhythmia at overdoses and incombination with other drugs which have potential blocking effect on /Na ,Ca2+ and /kr currents. The proarrhythmic effect of PMZ might be mediated by the blocking effect on /Na ,Ca2+ and /kr currents.

Expression of HERG1 and Kv3.4 in oral lichen planus / 实用口腔医学杂志

Objective:To investigate the expression of HERG1 and Kv3.4 in normal oral mucosa(NOM)and oral lichen planus (OLP).Methods:20 OLP and 1 6 NOM specimens were collected and immunohistochemically stained(IHC)by SP method for the detection of HERG1 and Kv3.4 protein expression.Results:HERG1 and Kv3.4 were negative or weak-positive in the sapmles of bas-al layer of NOMand non-erosive OLP,but positive in basal layer,spinous layer and granular layer of erosive OLP.The expression of HERG1 and Kv3.4 was higher in OLP than in NOM tissues (P <0.05);and higher in erosive OLP than in non-erosive OLP(P <0.05).In OLP HERG1 expression was positively related to Kv3.4(P <0.05).Conclusion:HERG1 and Kv3.4 may be related to the development of OLP.