Zhu Yi, Liao Hai-Ling, Niu Xiao-Lin, Yuan Yuan, Lin Tong, Verna Lynne, Stemerman Michael B
Division of Biomedical Sciences, University of California, Riverside, CA 92521, USA.
Biochim Biophys Acta. 2003 Dec 30;1635(2-3):117-26. doi: 10.1016/j.bbalip.2003.10.011.
A decrease in the bioavailability of endothelium-derived nitric oxide (NO) is linked to hypercholesterolemia. However, the mechanism by which low density lipoprotein (LDL) mediates endothelial NO synthase (eNOS) dysfunction remains controversial. We investigate the effect of LDL on eNOS regulation in human endothelial cells (ECs). In cultured ECs, a high level of LDL increased the abundance of eNOS and caveolin-1 (Cav-1) in the membrane caveolae and the association of eNOS with Cav-1. Furthermore, it decreased the basal level of NO and blocked NO production stimulated by the calcium ionophore A23187. LDL exposure also increased the formation of stress fibers and the membrane translocation of eNOS. These effects can be blocked by cytochalasin D, an actin cytoskeleton disruptor. In revealing the mechanism underlying the translocation of eNOS, we found that a high level of LDL increased the level of membrane-associated and GTP-formed RhoA and activated the RhoA downstream kinase ROCK-1 activity. Y-27632, a specific inhibitor of ROCK-1, blocked LDL-induced stress fiber formation, eNOS translocation and NO production. In conclusion, a high level of LDL increases the movement of eNOS to membrane caveolae via the increased stress fibers. The RhoA-mediated pathway may play a crucial role in this process in vascular ECs.
内皮源性一氧化氮（NO）生物利用度的降低与高胆固醇血症有关。然而，低密度脂蛋白（LDL）介导内皮型一氧化氮合酶（eNOS）功能障碍的机制仍存在争议。我们研究了LDL对人内皮细胞（ECs）中eNOS调节的影响。在培养的ECs中，高水平的LDL增加了膜小窝中eNOS和小窝蛋白-1（Cav-1）的丰度以及eNOS与Cav-1的结合。此外，它降低了NO的基础水平，并阻断了钙离子载体A23187刺激的NO生成。LDL暴露还增加了应力纤维的形成和eNOS的膜转位。这些作用可被细胞松弛素D（一种肌动蛋白细胞骨架破坏剂）阻断。在揭示eNOS转位的潜在机制时，我们发现高水平的LDL增加了膜相关和GTP形成的RhoA水平，并激活了RhoA下游激酶ROCK-1的活性。ROCK-1的特异性抑制剂Y-27632阻断了LDL诱导的应力纤维形成、eNOS转位和NO生成。总之，高水平的LDL通过增加应力纤维使eNOS向膜小窝移动。RhoA介导的途径可能在血管ECs的这一过程中起关键作用。
