Background:Inflamed endothelial cells (ECs) trigger atherogenesis, especially at arterial regions experiencing disturbed blood flow. UCP2 (Uncoupling protein 2), a key mitochondrial antioxidant protein, improves endothelium-dependent relaxation in obese mice. However, whether UCP2 can be regulated by shear flow is unknown, and the role of endothelial UCP2 in regulating inflammation and atherosclerosis remains unclear. This study aims to investigate the mechanoregulation of UCP2 expression in ECs and the effect of UCP2 on endothelial inflammation and atherogenesis.Methods:In vitro shear stress simulation system was used to investigate the regulation of UCP2 expression by shear flow. EC-specific Ucp2 knockout mice were used to investigate the role of UCP2 in flow-associated atherosclerosis.Results:Shear stress experiments showed that KLF2 (Krüppel-like factor 2) mediates fluid shear stress-dependent regulation of UCP2 expression in human aortic and human umbilical vein ECs. Unidirectional shear stress, statins, and resveratrol upregulate whereas oscillatory shear stress and proinflammatory stimuli inhibit UCP2 expression through altered KLF2 expression. KLF2 directly binds to UCP2 promoter to upregulate its transcription in human umbilical vein ECs. UCP2 knockdown induced expression of genes involved in proinflammatory and profibrotic signaling, resulting in a proatherogenic endothelial phenotype. EC-specific Ucp2 deletion promotes atherogenesis and collagen production. Additionally, we found endothelial Ucp2 deficiency aggravates whereas adeno-associated virus-mediated EC-Ucp2 overexpression inhibits carotid atherosclerotic plaque formation in disturbed flow-enhanced atherosclerosis mouse model. RNA-sequencing analysis revealed FoxO1 (forkhead box protein O1) as the major proinflammatory transcriptional regulator activated by UCP2 knockdown, and FoxO1 inhibition reduced vascular inflammation and disturbed flow-enhanced atherosclerosis. We showed further that UCP2 level is critical for phosphorylation of AMPK (AMP-activated protein kinase), which is required for UCP2-induced inhibition of FoxO1.Conclusions:Altogether, our studies uncover that UCP2 is novel mechanosensitive gene under the control of fluid shear stress and KLF2 in ECs. UCP2 expression is critical for endothelial proinflammatory response and atherogenesis. Therapeutic strategies enhancing UCP2 level may have therapeutic potential against atherosclerosis.

中文翻译：

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内皮 UCP2 是动脉粥样硬化的机械敏感抑制剂


背景：发炎的内皮细胞 (EC) 会引发动脉粥样硬化形成，尤其是在血流受到干扰的动脉区域。 UCP2（解偶联蛋白 2）是一种关键的线粒体抗氧化蛋白，可改善肥胖小鼠的内皮依赖性松弛。然而，UCP2是否可以通过剪切流调节尚不清楚，内皮UCP2在调节炎症和动脉粥样硬化中的作用仍不清楚。本研究旨在探讨UCP2在ECs中表达的力学调控以及UCP2对内皮炎症和动脉粥样硬化的影响。方法：采用体外剪切应力模拟系统研究剪切流对UCP2表达的调节作用。使用EC特异性Ucp2敲除小鼠来研究UCP2在血流相关动脉粥样硬化中的作用。结果：剪切应力实验表明，KLF2（Krüppel样因子2）介导人主动脉和人动脉中UCP2表达的流体剪切应力依赖性调节。脐静脉 EC。单向剪切应力、他汀类药物和白藜芦醇上调，而振荡剪切应力和促炎刺激通过改变 KLF2 表达来抑制 UCP2 表达。 KLF2 直接与 UCP2 启动子结合，上调其在人脐静脉 EC 中的转录。 UCP2 敲低诱导参与促炎和促纤维化信号传导的基因表达，导致促动脉粥样硬化内皮表型。 EC 特异性Ucp2缺失促进动脉粥样硬化形成和胶原蛋白产生。此外，我们发现在血流紊乱增强的动脉粥样硬化小鼠模型中，内皮Ucp2缺乏会加剧，而腺相关病毒介导的EC- Ucp2过表达会抑制颈动脉粥样硬化斑块形成。 RNA测序分析显示FoxO1（叉头盒蛋白O1）是UCP2敲除激活的主要促炎转录调节因子，抑制FoxO1可减少血管炎症并扰乱血流增强的动脉粥样硬化。我们进一步表明，UCP2 水平对于 AMPK（AMP 激活蛋白激酶）的磷酸化至关重要，而 AMPK 是 UCP2 诱导的 FoxO1 抑制所必需的。结论：总而言之，我们的研究发现 UCP2 是流体剪切控制下的新型机械敏感基因EC 中的应激和 KLF2。 UCP2 表达对于内皮促炎症反应和动脉粥样硬化形成至关重要。提高 UCP2 水平的治疗策略可能具有对抗动脉粥样硬化的治疗潜力。