Department of Pathology, Diabetes and Obesity Center of Excellence, University of Washington School of Medicine, Seattle, WA 98109, USA.
J Lipid Res. 2011 Apr;52(4):782-93. doi: 10.1194/jlr.M013292. Epub 2011 Jan 17.
Long-chain acyl-CoA synthetases (ACSLs) catalyze the thioesterification of long-chain FAs into their acyl-CoA derivatives. Purified ACSL4 is an arachidonic acid (20:4)-preferring ACSL isoform, and ACSL4 is therefore a probable regulator of lipid mediator production in intact cells. Eicosanoids play important roles in vascular homeostasis and disease, yet the role of ACSL4 in vascular cells is largely unknown. In the present study, the ACSL4 splice variant expressed in human arterial smooth muscle cells (SMCs) was identified as variant 1. To investigate the function of ACSL4 in SMCs, ACSL4 variant 1 was overexpressed, knocked-down by small interfering RNA, or its enzymatic activity acutely inhibited in these cells. Overexpression of ACSL4 resulted in a markedly increased synthesis of arachidonoyl-CoA, increased 20:4 incorporation into phosphatidylethanolamine, phosphatidylinositol, and triacylglycerol, and reduced cellular levels of unesterified 20:4. Accordingly, secretion of prostaglandin E₂ (PGE₂) was blunted in ACSL4-overexpressing SMCs compared with controls. Conversely, acute pharmacological inhibition of ACSL4 activity resulted in increased release of PGE₂. However, long-term downregulation of ACSL4 resulted in markedly reduced PGE₂ secretion. Thus, ACSL4 modulates PGE₂ release from human SMCs. ACSL4 may regulate a number of processes dependent on the release of arachidonic acid-derived lipid mediators in the arterial wall.
长链酰基辅酶 A 合成酶（ACSLs）催化长链脂肪酸与辅酶 A 形成硫酯键。纯化的 ACSL4 是一种对花生四烯酸（20:4）具有偏好性的 ACSL 同工酶，因此 ACSL4 可能是完整细胞中脂质介质产生的调节因子。类二十烷酸在血管稳态和疾病中发挥重要作用，但 ACSL4 在血管细胞中的作用在很大程度上尚不清楚。在本研究中，鉴定出人动脉平滑肌细胞（SMCs）中表达的 ACSL4 剪接变体为变体 1。为了研究 ACSL4 在 SMCs 中的功能，过表达 ACSL4 变体 1，用小干扰 RNA 敲低，或急性抑制这些细胞中的 ACSL4 酶活性。ACSL4 的过表达导致花生四烯酰辅酶 A 的合成显著增加，20:4 掺入磷脂酰乙醇胺、磷脂酰肌醇和三酰甘油增加，未酯化 20:4 的细胞水平降低。因此，与对照组相比，ACSL4 过表达的 SMCs 中前列腺素 E₂（PGE₂）的分泌受到抑制。相反，ACSL4 活性的急性药理学抑制导致 PGE₂ 的释放增加。然而，ACSL4 的长期下调导致 PGE₂ 的分泌明显减少。因此，ACSL4 调节人 SMCs 中 PGE₂ 的释放。ACSL4 可能调节动脉壁中依赖于花生四烯酸衍生的脂质介质释放的许多过程。
