Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53225, USA.
Am J Physiol Heart Circ Physiol. 2012 Apr 15;302(8):H1574-83. doi: 10.1152/ajpheart.01122.2011. Epub 2012 Feb 3.
Arachidonic acid is metabolized to four regioisomeric epoxyeicosatrienoic acids (EETs) by cytochrome P-450. 5,6-, 8,9-, 11,12-, and 14,15-EET are equipotent in relaxing bovine coronary arteries (BCAs). Vasorelaxant effects of EETs are nonselectively antagonized by 14,15-epoxyeicosa-5(Z)-enoic acid. The 11,12-EET analogs, 20-hydroxy-11,12-epoxyeicosa-8(Z)-enoic acid (20-H-11,12-EE8ZE) and 11,12,20-trihydroxyeicosa-8(Z)-enoic acid (11,12,20-THE8ZE) were synthesized and tested for antagonist activity against EET-induced relaxations in BCAs. In U-46619-preconstricted arterial rings, 5,6-, 8,9-, 11,12-, and 14,15-EET caused concentration-dependent relaxations with maximal relaxations ranging from 80 to 96%. Preincubation of arteries with 20-H-11,12-EE8ZE (10(-5) M) inhibited relaxations to 14,15- and 11,12-EET, but not 5,6- and 8,9-EET; however, greatest inhibitory effect was against 11,12-EET (maximal relaxation = 80.6 ± 4.6 vs. 26.7 ± 7.4% without and with 20-H-11,12-EE8ZE, respectively). Preincubation with the soluble epoxide hydrolase inhibitor (tAUCB, 10(-6) M) significantly enhanced the antagonist effect of 20-H-11,12-EE8ZE against 14,15-EET-induced relaxations (maximal relaxation = 86.6 ± 4.4 vs. 27.8 ± 3.3%, without and with 20-H-11,12-EE8ZE and tAUCB) without any change in its effect against 11,12-EET-induced relaxations. In contrast to the parent compound, the metabolite, 11,12,20-THE8ZE (10(-5) M), significantly inhibited relaxations to 11,12-EET and was without effect on other EET regioisomers. Mass spectrometric analysis revealed conversion of 20-H-11,12-EE8ZE to 11,12,20-THE8ZE by incubation with BCA. The conversion was blocked by tAUCB. 14,15-Dihydroxy-eicosa-5Z-enoic acid (a 14,15-EET antagonist), but not 11,12,20-THE8ZE (an 11,12-EET antagonist), inhibited BCA relaxations to arachidonic acid and flow-induced dilation in rat mesenteric arteries. These results indicate that 11,12,20-THE8ZE is a selective antagonist of 11,12-EET relaxations and a useful pharmacological tool to elucidate the function of 11,12-EET in the cardiovascular system.
花生四烯酸被细胞色素 P-450 代谢为四种区域异构的环氧二十碳三烯酸（EETs）。5,6-、8,9-、11,12-和 14,15-EET 在松弛牛冠状动脉（BCAs）方面具有同等效力。EET 的血管舒张作用被 14,15-环氧二十碳五烯酸非选择性拮抗。11,12-EET 类似物，20-羟基-11,12-环氧二十碳-8（Z）-烯酸（20-H-11,12-EE8ZE）和 11,12,20-三羟基二十碳-8（Z）-烯酸（11,12,20-THE8ZE）被合成并测试其对 BCAs 中 EET 诱导的松弛的拮抗活性。在 U-46619 预收缩的动脉环中，5,6-、8,9-、11,12-和 14,15-EET 引起浓度依赖性松弛，最大松弛幅度从 80%到 96%不等。动脉预孵育 20-H-11,12-EE8ZE（10(-5) M）抑制 14,15-和 11,12-EET 的松弛，但不抑制 5,6-和 8,9-EET；然而，最大的抑制作用是针对 11,12-EET（最大松弛=80.6±4.6%，无 20-H-11,12-EE8ZE 和有 20-H-11,12-EE8ZE 分别为 26.7±7.4%）。可溶性环氧化物水解酶抑制剂（tAUCB，10(-6) M）的预孵育显著增强了 20-H-11,12-EE8ZE 对 14,15-EET 诱导的松弛的拮抗作用（最大松弛=86.6±4.4%，无和有 20-H-11,12-EE8ZE 和 tAUCB 分别为 27.8±3.3%），而对 11,12-EET 诱导的松弛无任何影响。与母体化合物相比，代谢物 11,12,20-THE8ZE（10(-5) M）显著抑制 11,12-EET 的松弛作用，对其他 EET 区域异构体无作用。质谱分析显示，20-H-11,12-EE8ZE 在与 BCA 孵育时转化为 11,12,20-THE8ZE。这种转化被 tAUCB 阻断。14,15-二羟基二十碳五烯酸（14,15-EET 拮抗剂），而不是 11,12,20-THE8ZE（11,12-EET 拮抗剂），抑制 BCA 对花生四烯酸的松弛作用和大鼠肠系膜动脉的血流诱导扩张。这些结果表明，11,12,20-THE8ZE 是 11,12-EET 松弛的选择性拮抗剂，是阐明 11,12-EET 在心血管系统中功能的有用药理学工具。
