Meerarani Purushothaman, Smart Eric J, Toborek Michal, Boissonneault Gilbert A, Hennig Bernhard
Department of Animal Sciences, the Graduate Center for Nutritional Sciences, University of Kentucky, Lexington 40546-0215, USA.
Metabolism. 2003 Apr;52(4):493-500. doi: 10.1053/meta.2003.50087.
Vascular endothelial cell activation and dysfunction are critical early events in atherosclerosis. Even though very low or high levels of cholesterol can compromise cellular functions, cholesterol is a critical membrane component and may protect the vascular endothelium from oxidative stress and polyunsaturated fatty acid-mediated inflammatory responses. We have previously shown that the parent omega-6 fatty acid linoleic acid can markedly activate vascular endothelial cells. We now propose that membrane cholesterol can modify and inhibit linoleic acid-mediated endothelial cell dysfunction. To test this hypothesis, pulmonary artery endothelial cells were incubated with cholesterol (0 to 100 micromol/L) for 24 hours and then treated with 90 micromol/L of linoleic acid (18:2n-6) for 6 to 24 hours. In control cells, treatment with linoleic acid reduced intracellular glutathione levels and induced the DNA binding activity of nuclear factor-kappaB (NF-kappaB) leading to the upregulation of interleukin-6 (IL-6). In addition, the expression of endothelial nitric oxide synthase (eNOS) was altered, with linoleic acid increasing eNOS activity. In contrast, enrichment with cholesterol enhanced glutathione levels and reduced the linoleic acid-induced activation of NF-kappaBand the production of IL-6. Prior exposure to 50 micromol/L cholesterol also prevented the fatty acid-induced increase in eNOS activation. Cholesterol loading activated peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a nuclear receptor that can decrease inflammatory responses. Furthermore, the PPAR-gamma agonist thiazolidinedione markedly downregulated the NF-kappaB activation mediated by linoleic acid. Our data suggest that signaling pathways linked to endothelial cell activation by prooxidant and proinflammatory insults may be influenced by cellular cholesterol levels.
血管内皮细胞的激活和功能障碍是动脉粥样硬化早期的关键事件。尽管极低或极高水平的胆固醇会损害细胞功能，但胆固醇是细胞膜的关键组成部分，可能保护血管内皮免受氧化应激和多不饱和脂肪酸介导的炎症反应。我们之前已经表明，母体ω-6脂肪酸亚油酸可显著激活血管内皮细胞。我们现在提出，膜胆固醇可以改变并抑制亚油酸介导的内皮细胞功能障碍。为了验证这一假设，将肺动脉内皮细胞与胆固醇（0至100微摩尔/升）孵育24小时，然后用90微摩尔/升的亚油酸（18:2n-6）处理6至24小时。在对照细胞中，亚油酸处理降低了细胞内谷胱甘肽水平，并诱导了核因子-κB（NF-κB）的DNA结合活性，导致白细胞介素-6（IL-6）上调。此外，内皮型一氧化氮合酶（eNOS）的表达发生改变，亚油酸增加了eNOS活性。相比之下，胆固醇富集提高了谷胱甘肽水平，降低了亚油酸诱导的NF-κB激活和IL-6的产生。预先暴露于50微摩尔/升胆固醇也可防止脂肪酸诱导的eNOS激活增加。胆固醇负荷激活了过氧化物酶体增殖物激活受体-γ（PPAR-γ），这是一种可减少炎症反应的核受体。此外，PPAR-γ激动剂噻唑烷二酮显著下调了亚油酸介导的NF-κB激活。我们的数据表明，与促氧化剂和促炎损伤引起的内皮细胞激活相关的信号通路可能受细胞胆固醇水平影响。
