Weis Margaret T, Brady Monica, Moore Mike, Crumley Jason, Stallone John N
Department of Pharmaceutical Sciences, Texas Tech University Health Science Center, Amarillo, 79106, USA.
J Vasc Res. 2005 Jul-Aug;42(4):275-83. doi: 10.1159/000085847. Epub 2005 May 19.
Triacsin C, a fatty acid analog, inhibits endothelial nitric oxide synthetase (eNOS) palmitoylation, increases nitric oxide synthesis and enhances methacholine-induced relaxation of vascular rings. The experiments presented here tested the hypothesis that triacsin C increases the synthesis of PGI(2) and/or endothelial-derived hyperpolarizing factor.
Long-chain fatty acyl CoA synthetase activity (LCFACoAS), agonist-induced prostacyclin synthesis and agonist-induced release of radioactivity in endothelial cells labeled with [(3)H]arachidonic acid were measured in the presence and absence of triacsin C.
Inhibition by triacsin C of palmitoyl CoA formation was significantly greater than inhibition of arachidonoyl CoA formation in solubilized endothelial cell preparations. While 24-hour triacsin C treatment significantly reduced basal 6-keto synthesis, it had no effect on agonist-stimulated synthesis. The release of arachidonic acid metabolites was examined in [(3)H]arachidonate-labeled cells. Triacsin C treatment had no effect on basal or vasopressin-, angiotensin-II-, bradykinin- or ionomycin-induced release of radioactivity, but significantly reduced release in response to isoproterenol or phenylephrine. Expression of neither immunoreactive eNOS nor immunoreactive inducible nitric oxide synthetase (iNOS) was changed by triacsin C treatment, but the fraction of immunoreactive eNOS in the cytoplasm of treated cells was significantly greater as compared to vehicle control cells. Phorbol myristoyl acetate or fenofibrate significantly increased in vitro LCFACoAS activity, and significantly decreased the nitrite/eNOS ratio.
These data indicate that, while triacsin C can inhibit arachidonoyl CoA synthetase in endothelial cells, it does not increase the availability of endogenous substrate for basal or agonist-induced PGI(2) synthesis, nor does it enhance release of arachidonic acid or its metabolites.
三辛素C是一种脂肪酸类似物，可抑制内皮型一氧化氮合酶（eNOS）的棕榈酰化，增加一氧化氮的合成，并增强乙酰甲胆碱诱导的血管环舒张。本文的实验检验了三辛素C增加前列环素（PGI₂）和/或内皮源性超极化因子合成的假说。
在有或无三辛素C存在的情况下，测量长链脂肪酰辅酶A合成酶活性（LCFACoAS）、激动剂诱导的前列环素合成以及用[³H]花生四烯酸标记的内皮细胞中激动剂诱导的放射性释放。
在溶解的内皮细胞制剂中，三辛素C对棕榈酰辅酶A形成的抑制作用明显大于对花生四烯酰辅酶A形成的抑制作用。虽然三辛素C处理24小时显著降低了基础6-酮合成，但对激动剂刺激的合成没有影响。在[³H]花生四烯酸标记的细胞中检测了花生四烯酸代谢产物的释放。三辛素C处理对基础或血管加压素、血管紧张素II、缓激肽或离子霉素诱导的放射性释放没有影响，但显著降低了对异丙肾上腺素或去氧肾上腺素的反应性释放。三辛素C处理并未改变免疫反应性eNOS或免疫反应性诱导型一氧化氮合酶（iNOS）的表达，但与载体对照细胞相比，处理细胞胞质中免疫反应性eNOS的比例显著更高。佛波醇肉豆蔻酸酯或非诺贝特显著增加体外LCFACoAS活性，并显著降低亚硝酸盐/eNOS比值。
这些数据表明，虽然三辛素C可抑制内皮细胞中的花生四烯酰辅酶A合成酶，但它不会增加内源性底物用于基础或激动剂诱导的PGI₂合成的可用性，也不会增强花生四烯酸或其代谢产物的释放。
