Dimitropoulou Christiana, West Lashondra, Field Mary B, White Richard E, Reddy L Manmohan, Falck John R, Imig John D
Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, GA, USA.
Prostaglandins Other Lipid Mediat. 2007 Feb;83(1-2):50-61. doi: 10.1016/j.prostaglandins.2006.09.008. Epub 2006 Nov 7.
Epoxyeicosatrienoic acids (EETs) are considered to be endothelium-derived hyperpolarizing factors, and are potent activators of the large-conductance, Ca(2+)-activated K(+) (BK(Ca)) channel in vascular smooth muscle. Here, we investigate the signal transduction pathway involved in the activation of BK(Ca) channels by 11,12-EET and 11,12-EET stable analogs in rat mesenteric vascular smooth muscle cells. 11,12-EET and the 11,12-EET analogs, 11-nonyloxy-undec-8(Z)-enoic acid (11,12-ether-EET-8-ZE), 11-(9-hydroxy-nonyloxy)-undec-8(Z)-enoic acid (11,12-ether-EET-8-ZE-OH) and 11,12-trans-oxidoeicosa-8(Z)-enoic acid (11,12-tetra-EET-8-ZE), caused vasorelaxation of mesenteric resistance arteries. Mesenteric myocyte whole-cell (perforated-patch) currents were substantially (approximately 150%) increased by 11,12-EET and 11,12-EET analogs. Single-channel recordings were conducted to identify the target for 11,12-EET. 11,12-EET and 11,12-EET analogs also increased mesenteric myocyte BK(Ca) channel activity in cell-attached patches. Similar results were obtained in cell-free patches. Baseline mesenteric myocyte BK(Ca) channel activity (NPo) in cell-free patches averaged less than 0.001 at +50 mV and 11,12-EET (1 micromol/L) increased NPo to 0.03+/-0.02 and 11,12-EET analogs (1 micromol/L) increased NPo to 0.09+/-0.006. Inhibition of protein phosphatase 2A (PP2A) activity with okadaic acid (10 nmol/L) completely reversed 11,12-EET stimulated BK(Ca) channel activity and greatly attenuated 11,12-ether-EET-8-ZE mesenteric resistance artery vasorelaxation. 11,12-EET and 11,12-EET analogs increased mesenteric myocyte PP2A activity by 3.5-fold. Okadaic acid and the EET inhibitor, 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE) inhibited the 11,12-EET mediated increase in PP2A activity. These findings provide initial evidence that PP2A activity contributes to 11,12-EET and 11,12-EET analog activation of mesenteric resistant artery BK(Ca) channels and vasorelaxation.
环氧二十碳三烯酸（EETs）被认为是内皮衍生的超极化因子，并且是血管平滑肌中大电导、Ca(2+) 激活的K(+)（BK(Ca)）通道的强效激活剂。在此，我们研究了大鼠肠系膜血管平滑肌细胞中11,12-EET和11,12-EET稳定类似物激活BK(Ca)通道所涉及的信号转导途径。11,12-EET以及11,12-EET类似物11-壬氧基-十一碳-8(Z)-烯酸（11,12-醚-EET-8-ZE）、11-(9-羟基-壬氧基)-十一碳-8(Z)-烯酸（11,12-醚-EET-8-ZE-OH）和11,12-反式-氧化二十碳-8(Z)-烯酸（11,12-四-EET-8-ZE）可引起肠系膜阻力动脉血管舒张。11,12-EET和11,12-EET类似物使肠系膜肌细胞全细胞（穿孔膜片）电流大幅增加（约150%）。进行单通道记录以确定11,12-EET的作用靶点。11,12-EET和11,12-EET类似物还增加了贴壁膜片中肠系膜肌细胞BK(Ca)通道的活性。在游离膜片中也得到了类似结果。在游离膜片中，肠系膜肌细胞BK(Ca)通道的基线活性（NPo）在+50 mV时平均小于0.001，11,12-EET（1 μmol/L）使NPo增加到0.03±0.02，11,12-EET类似物（1 μmol/L）使NPo增加到0.09±0.006。用冈田酸（10 nmol/L）抑制蛋白磷酸酶2A（PP2A）活性可完全逆转11,12-EET刺激的BK(Ca)通道活性，并大大减弱11,12-醚-EET-8-ZE对肠系膜阻力动脉的血管舒张作用。11,12-EET和11,12-EET类似物使肠系膜肌细胞PP2A活性增加了3.5倍。冈田酸和EET抑制剂14,15-环氧二十碳-5(Z)-烯酸（14,15-EEZE）抑制了11,12-EET介导的PP2A活性增加。这些发现提供了初步证据，表明PP2A活性有助于11,12-EET和11,12-EET类似物激活肠系膜阻力动脉BK(Ca)通道并引起血管舒张。
