Estradiol up-regulates L-type Ca2+ channels via membrane-bound estrogen receptor/phosphoinositide-3-kinase/Akt/cAMP response element-binding protein signaling pathway

BACKGROUND In long QT syndrome type 2, women are more prone than men to the lethal arrhythmia torsades de pointes. We previously reported that 17 beta-estradiol (E2) up-regulates L-type Ca2+ channels and current (I-Ca,I-L) (similar to 30%) in rabbit ventricular myocytes by a classic genomic mechanism mediated by estrogen receptor-alpha (ER alpha). In long QT syndrome type 2 (I-Kr, blockade or bradycardia), the higher Ca2+ influx via I-Ca,I-L causes Ca2+ overload, spontaneous sarcoplasmic reticulum Ca2+ release, and reactivation of I-Ca,I-L that triggers early afterdepolarizations and torsades de pointes.OBJECTIVE The purpose of this study was to investigate the molecular mechanisms whereby E2 up-regulates I-Ca,I-L which are poorly understood.METHODS H9C2 and rat myocytes were incubated with E2 +/- ER antagonist, or inhibitors of downstream transcription factors, for 24 hours, followed by western blots of Cav1.2 alpha 1C and voltage-clamp measurements of I-Ca,I-L.RESULTS Incubation of H9C2 cells with E2 (10-100 nM) increased I-Ca,I-L density and Cav1.2 alpha 1C expression, which were suppressed by the ER antagonist ICI182,780 (1 mu M). Enhanced I-Ca,I-L and Cav1.2 alpha 1C expression by E2 was suppressed by inhibitors of phosphoinositide-3-kinase (Pi3K) (30 mu M LY294002; P

背景 在2型长QT综合征中，女性比男性更易发生致命性心律失常尖端扭转型室速。我们先前报道，17β - 雌二醇（E2）通过雌激素受体α（ERα）介导的经典基因组机制，使兔心室肌细胞的L型Ca2 +通道和电流（I - Ca，I - L）上调约30%。在2型长QT综合征（I - Kr阻断或心动过缓）中，通过I - Ca，I - L的较高Ca2 +内流导致Ca2 +超载、肌浆网Ca2 +自发释放以及I - Ca，I - L的重新激活，从而触发早后除极和尖端扭转型室速。 目的 本研究的目的是探究E2上调I - Ca，I - L的分子机制，目前对此了解甚少。 方法 将H9C2细胞和大鼠心肌细胞与E2±ER拮抗剂或下游转录因子抑制剂一起孵育24小时，然后进行Cav1.2α1C的蛋白质印迹分析和I - Ca，I - L的电压钳测量。 结果 用E2（10 - 100 nM）孵育H9C2细胞增加了I - Ca，I - L密度和Cav1.2α1C表达，这些作用被ER拮抗剂ICI182,780（1 μM）抑制。E2增强的I - Ca，I - L和Cav1.2α1C表达被磷酸肌醇 - 3 - 激酶（Pi3K）抑制剂（30 μM LY294002；P<0.05）抑制。