Batchu S N, Law E, Brocks D R, Falck J R, Seubert J M
Faculty of Pharmacy and Pharmaceutical Sciences, 3126 Dentistry/Pharmacy Centre, University of Alberta, Edmonton, AB, Canada.
J Mol Cell Cardiol. 2009 Jan;46(1):67-74. doi: 10.1016/j.yjmcc.2008.09.711. Epub 2008 Oct 10.
Cytochrome P450 epoxygenases metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) which are in turn converted to dihydroxyeicosatrienoic acids (DHETs) by soluble epoxide hydrolase (sEH). The main objective of this study was to investigate the protective effects of EETs following ischemic injury using an ex vivo electrocardiogram (EKG) model. Hearts from C57Bl/6, transgenic mice with cardiomyocyte-specific overexpression of CYP2J2 (Tr) and wildtype (WT) littermates were excised and perfused with constant pressure in a Langendorff apparatus. Electrodes were placed superficially at the right atrium and left ventricle to assess EKG waveforms. In ischemic reperfusion experiments hearts were subjected to 20 min of global no-flow ischemia followed by 20 min of reperfusion (R20). The EKG from C57Bl/6 hearts perfused with 1 microM 14,15-EET showed less QT prolongation (QTc) and ST elevation (STE) (QTc=41+/-3, STE=2.3+/-0.3; R20: QTc=42+/-2 ms, STE=1.2+/-0.2mv) than control hearts (QTc=36+/-2, STE=2.3+/-0.2; R20: QTc=53+/-3 ms; STE=3.6+/-0.4mv). Similar results of reduced QT prolongation and ST elevation were observed in EKG recording from CYP2J2 Tr mice (QTc=35+/-1, STE=1.9+/-0.1; R20: QTc=38+/-4 ms, STE=1.3+/-0.2mv) compared to WT hearts. The putative epoxygenase inhibitor MS-PPOH (50 microM) and EET antagonist 14,15-EEZE (10 microM) both abolished the cardioprotective response, implicating EETs in this process. In addition, separate exposure to the K(ATP) channel blockers glibenclamide (1 microM) and HMR1098 (10 microM), or the PKA protein inhibitor H89 (50 nM) during reperfusion abolished the improved repolarization in both the models. Consistent with a role of PKA, CYP2J2 Tr mice had an enhanced activation of the PKAalpha regulatory II subunit in plasma membrane following IR injury. The present data demonstrate that EETs can enhance the recovery of ventricular repolarization following ischemia, potentially by facilitating activation of K(+) channels and PKA-dependent signaling.
细胞色素P450环氧合酶将花生四烯酸（AA）代谢为环氧二十碳三烯酸（EETs），而EETs又可被可溶性环氧化物水解酶（sEH）转化为二羟基二十碳三烯酸（DHETs）。本研究的主要目的是使用离体心电图（EKG）模型研究EETs在缺血性损伤后的保护作用。切除C57Bl/6小鼠、心肌细胞特异性过表达CYP2J2的转基因小鼠（Tr）及其野生型（WT）同窝小鼠的心脏，并在Langendorff装置中进行恒压灌注。将电极置于右心房和左心室表面以评估EKG波形。在缺血再灌注实验中，心脏经历20分钟的全心无血流缺血，随后进行20分钟的再灌注（R20）。与对照心脏（QTc = 36±2，STE = 2.3±0.2；R20：QTc = 53±3 ms；STE = 3.6±0.4mv）相比，用1μM 14,15 - EET灌注的C57Bl/6心脏的EKG显示QT间期延长（QTc）和ST段抬高（STE）较少（QTc = 41±3，STE = 2.3±0.3；R20：QTc = 42±2 ms，STE = 1.2±0.2mv）。在CYP2J2 Tr小鼠的EKG记录中观察到与WT心脏相比QT间期延长和ST段抬高减少的类似结果（QTc = 35±1，STE = 1.9±0.1；R20：QTc = 38±4 ms，STE = 1.3±0.2mv）。假定的环氧合酶抑制剂MS - PPOH（50μM）和EET拮抗剂14,15 - EEZE（10μM）均消除了心脏保护反应，表明EETs参与了这一过程。此外，在再灌注期间分别暴露于K（ATP）通道阻滞剂格列本脲（1μM）和HMR1098（10μM）或PKA蛋白抑制剂H89（50 nM）消除了两种模型中改善的复极化。与PKA的作用一致，CYP2J2 Tr小鼠在缺血再灌注损伤后质膜中PKAα调节II亚基激活增强。目前的数据表明，EETs可能通过促进K（+）通道激活和PKA依赖性信号传导来增强缺血后心室复极化的恢复。
