BACKGROUND:Hypoxia has a major regulatory impact on the electrical activity transmission in the myocardium, and it is involved in the development of tachyarrhythmia disease. Anchor protein G (ankyrin-G, ANK-G) is associated with voltage-gated Na+ channels (Nav1.5), but its specific role and mechanism have not been fully defined. In this experiment, we investigated the role and mechanism of hypoxia on cardiomyocyte electrophysiology of voltage-gated Na+ channel, as well as the intervention effect of ankyrin-G by simulating the environment of cardiomyocytes during hypoxia through hypoxia-treated murine atrial myocytes (HL-1). METHODS:The HL-1 cells were divided into 6 groups: normoxia group (NO), hypoxia group (HO), ANK-G-overexpressing hypoxia-negative group (ANK-G NC), ANK-G-overexpressing hypoxia group (ANK-G), ANK-G-silenced hypoxia-negative group (shANK-G NC), and ANK-G-silenced hypoxia group (shANK-G). ANK-G overexpression was induced using lentiviral vectors through the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 system. The characteristics of sodium ion channel current (INa) were observed through the whole-cell patch clamp technique. Western blotting was used to detect the expression of ANK-G and Nav1.5 channel proteins, and the distribution of Nav1.5 channel on HL-1 cells was observed by confocal microscope. RESULTS:Under hypoxic conditions, the INa peak current amplitude (p < 0.01) and density (p < 0.01) of HL-1 cells increased. Compared with the normoxia group, the steady-state inactivation curve of the hypoxia group shifted to the right. The protein levels of ANK-G and Nav1.5 channels were increased under hypoxia (p < 0.001). In the ANK-G group, the upregulation of ANK-G protein increased the distribution of Nav1.5 channel in the cell membrane under the hypoxic condition (p < 0.01). CONCLUSIONS:Hypoxia increases the INa amplitude and density of HL-1 cells, and the gating mechanism of INa is related to steady-state inactivation. Hypoxic condition triggers the upregulation of the ANK-G protein expression, which promotes the redistribution of Nav1.5 channel proteins in the cell membrane, thereby augmenting INa peak current amplitude and density.

心房颤动(简称房颤)是最常见的心律失常疾病,是心源性脑卒中的主要原因.房颤严重影响患者生活质量,且其并发症具有高度致残、致死危害,目前已经成为严重的公共卫生问题.超重和肥胖是心血管疾病的一个重要危险因素,其与房颤的相关性是近年来研究的热点.本文旨在探讨肥胖与房颤的相关性.

Aim The aim was to study the effect of Allitridum (Allicin) on the heterologous expression of the late sodium current on the ΔKPQ-SCN5A mutations in HEK293 cells, with a view to screening new drugs for the treatment of long QT syndrome type 3 (LQT3). Methods and Results The ΔKPQ-SCN5A plasmid was transiently transferred into HEK293 cells by liposome technology and administered by extracellular perfusion, and the sodium current was recorded by whole-cell patch-clamp technology. Application of Allicin 30 μM reduced the late sodium current (INa,L) of the Nav1.5 channel current encoded by ΔKPQ-SCN5A from 1.92 ± 0.12 to 0.65 ± 0.03 pA/pF (P < 0.01, n = 15), which resulted in the decrease of INa,L/INa,P (from 0.94% ± 0.04% to 0.32% ± 0.02%). Furthermore, treatment with Allicin could move the steady-state inactivation of the channel to a more negative direction, resulting in an increase in channel inactivation at the same voltage, which reduced the increase in the window current and further increased the inactivation of the channel intermediate state. However, it had no effect on channel steady-state activation (SSA), inactivation mechanics, and recovery dynamics after inactivation. What’s more, the Nav1.5 channel protein levels of membrane in the ΔKPQ-SCN5A mutation were enhanced from 0.49% ± 0.04% to 0.76% ± 0.02% with the effect of 30 mM Allicin, close to 0.89% ± 0.02% of the WT. Conclusion Allicin reduced the late sodium current of ΔKPQ-SCN5A, whose mechanism may be related to the increase of channel steady-state inactivation (SSI) and intermediate-state inactivation (ISI) by the drug, thus reducing the window current.

目的 通过建立大鼠急性低氧运动模型,观察大鼠单个心室肌细胞瞬时外向钾电流(Ito)的改变,在细胞水平探究模拟高原低氧条件下力竭运动对心脏电生理的影响.方法 将40只健康雄性清洁级SD大鼠随机分为低氧运动组、低氧安静组、常氧运动组和常氧安静组,每组10只.利用小动物低压氧舱和常氧状态下进行力竭运动试验.取出各组大鼠心脏,利用灌流酶解法分离大鼠单个心室肌细胞,采用全细胞膜片钳技术记录大鼠单个心室肌细胞的瞬时外向钾电流.采用SPSS 20.0统计软件进行数据处理,多组间比较采用ANOVA方差分析,组间两两比较采用SNK-q检验.结果 与常氧安静组比较,+40 mV时,低氧运动组的Ito电流密度显著降低,且低于低氧安静组及常氧运动组,此效应呈现电压依赖性.门控机制研究显示,低氧运动时大鼠心肌细胞Ito稳态激活曲线失活向超极化方向移动,而稳态失活曲线则向去极化方向移动,二者综合效应使Ito电流显著降低.结论 急性低氧运动可通过改变钾通道稳态激活与稳态失活过程,降低大鼠心室肌细胞Ito,这可能是急性低氧运动导致心律失常的主要原因之一.