人HCN2基因编码的心脏起搏通道的电生理

目的将人超极化激活的阳离子通道基因2(human hyperpolarization-activated cation channel2,hHCN2)表达于HEK293细胞系上,观察其表达的通道的电生理特点。方法利用全细胞膜片钳技术,记录转染了hHCN2的HEK293细胞上的超极化激活的阳离子流(If)。结果转染hHCN2的HEK293细胞上表达If样内向电流,在超极化时激活,随刺激电压的延长而增大,半数最大激活电压为(-109.1±0.7)mV,曲线斜率为(-12.7±0.7)mV。刺激电压变负时,激活变快。-100mV和-160mV时,激活时间常数分别为(2.5±1.1)s和(217±29)ms。此电流是细胞外钾离子浓度依赖性的,对钠离子和钾离子的相对通透性为0.67。2mmol/L的Cs+可明显抑制此电流。结论目的基因hHCN2在HEK293细胞上成功表达,表达的蛋白能形成有功能的通道,产生If样电流。     

参松养心胶囊对hHCN4起搏电流通道的影响

目的观察通络药物参松养心胶囊提取干粉溶液对人超极化激活的阳离子通道(hHCN4)的影响。方法用细胞外液将参松养心胶囊干粉稀释到0.5%浓度,瞬时转染人类超极化激活的阳离子通道(If)基因hHCN4cDNA到HEK293细胞,利用全细胞膜片钳技术,记录转染了hHCN4的HEK293细胞上的超极化激活的阳离子流。结果If峰值电流密度受到抑制(61.97±16.44vs41.65±13.32,P0.05);但此抑制可逆(53.83±14.26);药物不改变通道激活动力学参数。结论参松养心胶囊提取干粉溶液可逆性抑制hHCN4起搏电流。     

大鼠骨髓基质干细胞起搏电流基因的表达及转染人HCN2的表达及鉴定

目的研究骨髓基质干细胞(mesenchymal stem cells,MSCs)起搏电流基因的表达及转染人超极化激活的环化核苷酸门控通道(hyperpolarization-activated cyclic-nucleotide gated,HCN)亚型2后起搏电流的特点。方法通过实时定量聚合酶链反应(real-time quantitative polymerase chainreaction,real-time PCR)的方法,检测 MSCs 本身起搏电流基因的表达。用脂质体转染的方法,将重组有编码起搏电流基因的质粒 pcDNA3-hHCN2导入 MSCs 中,用全细胞膜片钳技术记录起搏电流(Ⅰ_(hHCN2));用 real-time PCR 和 Western blot 印迹检测目的基因 hHCN2的 mRNA 和蛋白表达。结果MSCs 起搏电流基因 mHCN1、mHCN2、mHCN3、mHCN4在总 HCN 的表达中所占比例分别为(0.08±0.01)%、(77.16±0.03)%、(0.24±0.01)%、(22.53±0.02)%。全细胞膜片钳技术记录到Ⅰ_(hHCN2)得到电流密度一电压曲线,其激活电压约为-80 mV,此电流可以被4 mmol/L的 Cs~+阻断。real-timePCR 检测有 hHCN2 mRNA 的高表达,Western blot 印迹检测有其蛋白的表达。结论 (1)MSCs 起搏电流基因表达以 mHCN2和 mHCN4为主;(2)通过脂质体转染法使 MSCs 成功表达Ⅰ_(hNCN2)起搏电流,为抗心律失常基因治疗的研究奠定了基础。     

mHCN2基因修饰的大鼠骨髓间充质干细胞内向电流的记录及检测

目的构建超极化激活环的环核苷酸门控通道亚型2(mHCN2)基因修饰大鼠骨髓间充质干细胞(mMSCs),采用膜片钳技术记录细胞的内向电流并检测其电生理特征。方法采用密度梯度离心法和贴壁分离法分离获得mMSCs。EcoRⅠ和BamHⅠ双酶切质粒pGH-mHCN2和pIRES2-EGFP,T4连接酶连接,构建质粒pIRES2-EGFP-mHCN2。脂质体将质粒转染至mMSCs,荧光显微镜下鉴定。全细胞膜片钳记录IHCN2并加入起搏电流特异性阻断剂Cs+检测其电流变化。结果酶切鉴定及测序检测证明质粒pIRES2-EGFP-mHCN2构建成功。荧光显微镜下可见转染成功的mMSCs发出绿色荧光。膜片钳记录到转染mHCN2基因的mMSCs的电压依赖性内向电流,其半最大激活电位为-95.1±0.9 mV,阈电位为-60 mV,最大激活电位为-140 mV。电极外液中加Cs+,内向电流几乎被完全抑制。未转染mHCN2的mMSCs未记录到内向电流。结论mHCN2基因在mMSCs中表达具有生理性起搏电流特征的电流,基因修饰的mMSCs有可能替代窦房结起搏细胞在自动除极过程中发挥重要作用。     

稳心颗粒对人超极化激活环核苷酸门控阳离子通道2电生理特性的影响

目的探讨稳心颗粒对人超极化激活环核苷酸门控阳离子通道2(HCN2)电生理特性的影响。方法将人HCN2的mRNA注射到非洲爪蟾卵母细胞,孵育1~2天后,采用双电极电压钳技术观察0.5,1,2,4 g/L稳心颗粒对HCN2通道电流的作用。结果①测试电位-90 mV时,0.5,1,2,4 g/L稳心颗粒分别使HCN2瞬时电流增加17.74%±6.04%,49.26%±8.74%,86.05%±16.15%和124.38%±11.62%,瞬时电流增加50%的药物浓度(EC50)为1.54±0.24 g/L(n=8)。②在测试电位-140 mV到-100 mV水平上,2 g/L稳心颗粒延长HCN2通道激活时间常数:(226.74±31.37 ms vs 143.68±21.45 ms;-140 mV,n=10,P<0.05)③2 g/L稳心颗粒延长HCN2通道去激活时间常数(1 293.54±95.03 ms vs 647.13±61.36 ms;-140 mV,n=10,P<0.05)。结论稳心颗粒呈浓度依赖性增强HCN2瞬时电流,减缓通道激活和去激活过程。     

起搏通道基因亚型HCN4重组腺病毒载体的构建及通道电流检测

目的旨在构建超极化激活环核苷酸门控阳离子通道基因亚型4(HCN4)重组腺病毒载体并鉴定其离子通道功能。方法全长人HCN4基因酶切后亚克隆到腺病毒穿梭载体pAdTrack-CMV,形成含目的基因和绿色荧光蛋白基因的穿梭载体。穿梭载体和病毒骨架载体pAdEasy-1经电穿孔法在BJ5183大肠杆菌中同源重组,重组后的腺病毒载体经PacⅠ酶切线性化后,利用脂质体介导转染到HEK293细胞进行病毒的包装和扩增。用多聚酶链反应(PCR)方法对病毒上清中的HCN4进行检测,并将重组腺病毒感染COS-7细胞,用免疫荧光染色检测HCN4蛋白质的表达,利用全细胞膜片钳方法测定转HCN4基因细胞的电生理功能。结果通过酶切、测序、PCR等证实HCN4通道基因重组腺病毒载体构建正确,免疫荧光检测证实转染AdHCN4的COS-7细胞中HCN4通道基因的表达,膜片钳实验也在转基因细胞中检测到超极化激活的非选择性内向阳离子电流(If)。结论HCN4通道基因重组腺病毒载体的构建成功为进一步研究该离子通道的电生理功能及在心律失常疾病基因治疗方面的潜在应用价值奠定了基础。     

mHCN4基因修饰小鼠骨髓间充质干细胞重建起搏离子流通道

目的观察超极化激活的环核苷酸门控通道亚型4(mHCN4)外源基因对小鼠骨髓间充质干细胞(mMSCs)的转染及其功能表达。方法2个月大昆明小鼠拉颈处死,无菌条件下分离股、胫骨,收集骨髓细胞种植于塑料培养瓶,24h后更换培养液,保留贴壁细胞,待细胞达90%融合时胰酶消化传代培养。收集第3代贴壁细胞,用免疫磁珠法分选CD11b-细胞继续扩增培养。以pUC18、pcDNA3-mHCN4、pIRES2-EGFP、pMSCV-puro等质粒载体为架构,用不同酶类将目的片段连接构建pMSCV-mHCN4-EGFP及pMSCV-EGFP逆转录病毒载体。载体转染PT67包装细胞,收集逆转录病毒上清转染第3代扩增的mMSCs细胞,观察mMSCs的转染效果及阳性转染细胞的mHCN4通道动力学特性。结果mMSCs的转染效率约10%～20%。mHCN4基因转染组可记录到明显的时间依赖性的超极化激活内向电流(If),If的半数最大激活电压为-99.0±5.8mV,在-140mV电压时的激活时间常数为451±61ms。该电流对CsCl高度敏感;对照组细胞在超激化状态下无明显的电流出现。结论mHCN4外源基因可在mMSCs中成功表达起搏离子流通道,基因修饰后的mMSCs有可能成为一种有效的生物起搏种子细胞。     

HERG基因转染HEK293细胞及其编码通道电流的记录

目的建立HERG基因在HEK293细胞稳定表达的方法。方法利用Lipofectamine2000将pCDNA3.0-HERG转染进入HEK293细胞,通过G418筛选阳性克隆细胞系,采用免疫荧光细胞化学方法检测该蛋白的表达,用全细胞膜片钳技术测定HERG基因介导的快速激活延迟整流钾电流(Ikr)。结果免疫荧光细胞化学检测证实转染HEK293细胞中HERG通道蛋白的表达,膜片钳全细胞实验记录到Ikr。结论该方法有效地将HERG基因转染进入HEK293细胞,并稳定表达HERG通道蛋白及介导Ikr。     

人类超极化激活环核苷酸门控阳离子通道基因体内转染大鼠心脏进行生物起搏的初步研究

严重的缓慢性心律失常往往需要置入电子起搏器。然而，电子起搏器自身存在一些局限性。近年来，人们开始探索采用基因治疗和细胞治疗技术构建生物起搏器。目前，构建生物起搏器的策略有多种，其中以通过增强起搏电流（pacemaker current，If）来构建生物起搏器的策略最受关注。If的分子基础是超极化激活环核苷酸门控阳离子通道（hyperpolarization—activated cyclic nucleotide-gated cation channel，HCN）。本研究的目的是探讨利用人类HCN2（hHCN2）转染到大鼠心脏中进行生物起搏的可行性、安全性和时效性。     

人心肌细胞缓慢激活延迟整流钾电流细胞模型的建立

目的建立稳定表达人心肌细胞缓慢激活延迟整流钾电流（IKs）的细胞模型。方法编码IKs通道α亚单位的KCNQ1基因及β亚单位的KCNE1基因共转染HEK 293细胞,潮霉素B筛选,电生理学及药理学方法鉴定。结果KCNQ1/KCNE1基因被成功转入HEK 293细胞,KCNQ1/KCNE1电流与人心肌IKs电流具有相似的电流特性;hKCNQ1/hKCNE1通道反转电位与细胞外钾离子浓度呈线性关系;选择性IKs通道阻断剂Chromanol 293B对KCNQ1/KCNE1电流具有明显而可逆的抑制作用,其IC50（+40 mV）为9.1μmol/L;无钾细胞外液可以增加KCNQ1/KCNE1电流幅度,+40 mV时电流幅度增加（28.6±2.0）%（P<0.01,n=8）,但对其动力学特性无明显影响。结论已经成功构建稳定表达人心肌KCNQ1/KCNE1通道蛋白的HEK 293细胞系,其电生理学特性和药理学特性与人心肌IKs相似,可以作为研究人心肌IKs的细胞模型。     

Calcium influx through hyperpolarization-activated cation channels (I(h) channels) contributes to activity-evoked neuronal secretion

The hyperpolarization-activated cation channels (I(h)) play a distinct role in rhythmic activities in a variety of tissues, including neurons and cardiac cells. In the present study, we investigated whether Ca(2+) can permeate through the hyperpolarization-activated pacemaker channels (HCN) expressed in HEK293 cells and I(h) channels in dorsal root ganglion (DRG) neurons. Using combined measurements of whole-cell currents and fura-2 Ca(2+) imaging, we found that there is a Ca(2+) influx in proportion to I(h) induced by hyperpolarization in HEK293 cells. The I(h) channel blockers Cs(+) and ZD7288 inhibit both HCN current and Ca(2+) influx. Measurements of the fractional Ca(2+) current showed that it constitutes 0.60 +/- 0.02% of the net inward current through HCN4 at -120 mV. This fractional current is similar to that of the low Ca(2+)-permeable AMPA-R (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor) channels in Purkinje neurons. In DRG neurons, activation of I(h) for 30 s also resulted in a Ca(2+) influx and an elevated action potential-induced secretion, as assayed by the increase in membrane capacitance. These results suggest a functional significance for I(h) channels in modulating neuronal secretion by permitting Ca(2+) influx at negative membrane potentials.     

Characterization of hyperpolarization-activated cation currents in mouse anterior pituitary, AtT20 D16:16 corticotropes

The properties of the hyperpolarization-activated inward cation current (Ih) in mouse anterior pituitary, AtT20 D16:16 corticotropes was characterized by whole cell patch clamp recording. In response to hyperpolarizing steps a large, slowly activating, voltage-dependent inward current was activated with a half maximal activation voltage (V0.5) of -96.2+/-3.1 mV with a time constant of 168+/-13 msec determined at -140 mV at room temperature. Ih had a reversal potential of -35.5+/-1.0 mV and -23.3+/-1.4 mV using 5 mM and 25 mM extracellular K+, respectively, with a relative permeability ratio for Na+ and K+ of 0.24. The current was completely blocked by 2 mM extracellular CsCl and partially blocked by ZD7288 (100 microM) but was unaffected by TEA (10 mM) or Ba2+ (1 mM). RT-PCR analysis revealed robust expression of HCN1, but not HCN2 or HCN3, subunits of hyperpolarization-activated cation channels. The endogenous Ih current was weakly activated by cAMP but robustly inhibited by the cAMP antagonist, Rp-8-CPT-cAMPS. Activation or suppression of protein kinase C activity had no significant effect on the Ih current. The data suggest that in AtT20 D16:16 corticotropes Ih is tonically regulated by the cAMP-signaling cascade and may serve to limit excessive hyperpolarization.     

心力衰竭家兔左室短暂外向钾电流下调的分子基础

目的为探讨心力衰竭(简称心衰)兔左室短暂外向钾电流(Ito)下调的分子基础。方法采用结扎家兔冠状动脉左前降支的方法制备缺血性心衰模型。应用膜片钳全细胞记录方法记录左室心肌细胞Ito,描记电流-电压(I-V)曲线;应用半定量-聚合酶链式反应(RT-PCR)法检测电压依赖性Kv1.4和Kv4.3钾通道α亚单位mRNA表达,并以图象分析系统对其进行半定量分析。结果心衰组家兔左室心肌细胞Ito密度较对照组显著降低,I-V曲线明显下移;指令电压为+70mV时,心衰组Ito密度(9.73±0.94pA/pF,n=5)显著低于对照组(14.35±1.16pA/pF,n=4)(P<0.01)。Kv1.4和Kv4.3钾通道α亚单位mRNA表达心衰组(分别为0.66±0.05,0.21±0.02,n=5)也较对照组(分别为0.95±0.07,0.531±0.04,n=5)显著降低(P均<0.01)。结论心衰家兔左室Ito电流密度下调可能受转录水平调节。     

芍药苷对心脏钾通道电生理功能的影响

目的研究芍药苷对内向整流钾电流(IK1)、瞬时外向钾电流(Ito)以及延迟整流钾电流(IKs和IKr)的作用。方法用全细胞膜片钳技术记录大鼠心室肌细胞的Ito和IK1电流。而IKs和IKr电流在转染相应质粒的HEK293细胞上记录。对比芍药苷使用前后的电流图,观察芍药苷对各种离子通道电流的影响。结果在-100mV测试电压下,100μmol/L的芍药苷能使IK1峰值密度从(-25.26±8.21)pA/pF降至(-17.65±6.52)pA/pF,平均抑制率为30.13%(n=6,P<0.05),但对其反转电位以及内向整流特性无影响。此外,100μmol/L芍药苷对Ito、IKs和IKr电流无明显作用。结论芍药苷对IK1电流具有明显的抑制作用,而对Ito、IKs及IKr无明显作用。     

Differential reduction of HCN channel activity by various types of lipopolysaccharide

Recently it was shown that lipopolysaccharide (LPS) impairs the pacemaker current in human atrial myocytes. It was speculated that reduced heart rate variability (HRV), typical of patients with severe sepsis, may partially be explained by this impairment. We evaluated the effect of various types of LPS on the activity of human hyperpolarization-activated cyclic nucleotide-gated channel 2 (hHCN2) expressed in HEK293 cells, and on pacemaker channels in native murine sino-atrial node (SAN) cells, in order to determine the structure of LPS necessary to modulate pacemaker channel function. Application of LPS caused a robust inhibition of hHCN2-mediated current (I_hHCN2) owing to a negative shift of the voltage dependence of current activation and to a reduced maximal conductance. In addition, kinetics of channel gating were modulated by LPS. Pro-inflammatory LPS-types lacking the O-chain did not reduce I_hHCN2, whereas pro-inflammatory LPS-types containing the O-chain reduced I_hHCN2. On the other hand, a detoxified LPS without inflammatory activity, but containing the O-chain reduced I_hHCN2. Similar observations were made in HEK293 cells expressing hHCN4 and in murine SAN cells. This mechanistic analysis showed the novel finding that the O-chain of LPS is required for reduction of HCN channel activity. In the clinical situation the observed modulation of HCN channels may slow down diastolic depolarization of pacemaker cells and, hence, influence heart rate variability and heart rate.     

与HERG钾通道相互作用的FHL2蛋白对该通道功能的调控

目的 筛选与心脏人类果蝇相关基因（HERG）的编码蛋白钾通道存在相互作用的蛋白质,并进一步研究该相互作用蛋白对HERG钾通道的调控作用。方法 ①以带有编码人类心脏HERG钾通道的cDNA为模板,通过PCR方法得到编码人类心脏HERG钾通道氨基末端（404个氨基酸）的DNA片段。将该片段克隆入pGBKT7载体, 构建“诱饵”质粒pGBKT7-HERG-NT。②应用酵母双杂交技术筛选人类心脏cDNA文库。③以PCR法扩增4个半LIM结构域（FHL2）基因的开放读框片段(ORF),并克隆入pcDNA3.0载体。④以pcDNA3.0-herg转染HEK293细胞,应用G418筛选得到HEK293/HERG细胞株。以pcDNA3.0-FHL2转染HEK293细胞,筛选得到HEK293/FHL2细胞株后,再将pcDNA3.0-herg转染入该细胞株。⑤应用膜片钳技术,研究FHL2对HERG通道功能的影响。结果 ①用酵母双杂交技术筛选得到37个阳性克隆,其中含有表达FHL2蛋白的克隆。②膜片钳检测发现,FHL2蛋白在增加HERG电流幅度的同时并调节其激活过程。 结论 FHL2蛋白能与HERG氨基末端相互作用而影响HERG钾通道的功能。     

Kv1.4通道电流与大鼠心室肌细胞瞬间外向钾电流特性的比较

克隆的大鼠外向钾通道Ｋｖ１．４亚型表达于２９３细胞（ＲＣＫ４）。用膜片钳全细胞钳制法系统比较该克隆的大鼠瞬间外向钾电流（Ｉｔｏ）和天然大鼠心室肌细胞Ｉｔｏ的特点和动力学特性。两种通道电流形态相似,呈“Ａ”型电流,在＋４０ｍＶ时电流失活时间常数τ依次为３６．６±２ｍｓ和４１．０±２ｍｓ（Ｐ＞０．０５）。Ｋｖ１．４通道电流激活曲线用二相Ｂｏｌｔｚｍａｎｎ方程拟合,一相半数最大激活电位（Ｖ１／２,１）为－２１．０±３．９ｍＶ、二相半数最大激活电位（Ｖ１／２,２）为２７．０±３．９ｍＶ;天然大鼠心室肌细胞Ｉｔｏ激活曲线用单相Ｂｏｌｔｚｍａｎｎ方程拟合,半数最大激活电位为１０．８±１．１ｍＶ（Ｐ＜０．０５,ｖｓＫｖ１．４通道电流的Ｖ１／２,１）。ＲＣＫ４细胞通道电流半数最大灭活电位（Ｖ１／２）为－４９．８±１．８ｍＶ,斜率因子（ｋ）为３．８±０．２７;天然大鼠心室肌细胞Ｉｔｏ的Ｖ１／２为－３１．６±１．７ｍＶ,ｋ为５．４±０．２１。灭活后再激活的恢复时间比较,Ｋｖ１．４通道电流明显长于天然大鼠心室肌细胞Ｉｔｏ,分别为１．８９±０．２ｓ和３９．２±１．６ｍｓ（Ｐ＜０．０５）。研究表明克隆的大鼠Ｋｖ１．４通道电流与天然大?     

Characterisation of Kv4.3 in HEK293 cells: comparison with the rat ventricular transient outward potassium current.

OBJECTIVE: The Shal (or Kv4) gene family has been proposed to be responsible for primary subunits of the transient outward potassium current (Ito). More precisely, Kv4.2 and Kv4.3 have been suggested to be the most likely molecular correlates for Ito in rat cells. The purpose of the present study was to compare the properties of the rat Kv4.3 gene product when expressed in a human cell line (HEK293 cells) with that of Ito recorded from rat ventricular cells. METHODS: The cDNA encoding the rat Kv4.3 potassium channel was cloned into the pHook2 mammalian expression vector and expressed into HEK293. Patch clamp experiments using the whole cell configuration were used to characterise the electrophysiological parameters of the current induced by Kv4.3 in comparison with the rat ventricular myocyte Ito current. RESULTS: The transfection of HEK293 cells with rat Kv4.3 resulted in the expression of a time- and voltage-dependent outward potassium current. The current activated for potentials positive to -40 mV and the steady-state inactivation curve had a midpoint of -47.4 +/- 0.3 mV and a slope of 5.9 +/- 0.2 mV. Rat ventricular Ito current was activated at potentials positive to -20 mV and inactivated with a half-inactivation potential and a Boltzmann factor of -29.1 +/- 0.7 mV and 4.5 +/- 0.5 mV, respectively. The time course of recovery from inactivation of rat Kv4.3 expressed in HEK293 cells and of Ito recorded from native rat ventricular cells were exponentials with time constants of 213.2 +/- 4.1 msec and 23. +/- 1.5 msec, respectively. Pharmacologically, Ito of rat myocytes showed a greater sensitivity to 4-aminopyridine than Kv4.3 since half-maximal effects were obtained with 1.54 +/- 0.13 mM and 0.14 +/- 0.02 mM on Kv4.3 and Ito, respectively. In both Kv4.3 and Ito, 4-aminopyridine appears to bind to the closed state of the channel. Finally, although a higher level of expression was observed in the atria compared to the ventricle, the distribution of the Kv4.3 gene across the ventricles appeared to be homogeneous. CONCLUSION: The results of the present study show that Kv4.3 channel may play a major role in the molecular structure of the rat cardiac Ito current. Furthermore, because the distribution of Kv4.3 across the ventricle is homogeneous, the blockade of this channel by specific drugs may not alter the normal heterogeneity of Ito current.