High-density lipoprotein protects vascular endothelial cells from indoxyl sulfate insults through its antioxidant ability

Chronic kidney disease (CKD) patients have a high risk of cardiovascular disease. Indoxyl sulfate (IS) is a uremic toxin that has been shown to inhibit nitric oxide production and cause cell senescence by inducing oxidative stress. High-density lipoprotein (HDL) has a protective effect on the cardiovascular system; however, its impacts on IS-damaged endothelial cells are still unknown. This study aimed to explore the effects of exogenous supplement of HDL on vascular endothelial cells in a uremia-mimic environment. Tube formation, migration, adhesion, and senescence assays were used to evaluate the cell function of human aortic endothelial cells (HAECs). Reactive oxygen species generation was measured by using Amplex red assay. L-NAME and MCI186 were used as a nitric oxide synthase inhibitor and a free radical scavenger, respectively. HDL exerted anti-inflammatory and antioxidant effects via HIF-1α/HO-1 activation and IL-1β/TNF-α/IL-6 inhibition in IS-stimulated HAECs. HDL improved angiogenesis ability through upregulating Akt/eNOS/VEGF/SDF-1 in IS-stimulated HAECs. HDL decreased endothelial adhesiveness via downregulating VCAM-1 and ICAM-1 in IS-stimulated HAECs. Furthermore, HDL reduced cellular senescence via upregulating SIRT1 and downregulating p53 in IS-stimulated HAECs. Importantly, the above beneficial effects of HDL were mainly due to its antioxidant ability. In conclusion, HDL exerted a comprehensive protective effect on vascular endothelial cells against damage from IS through its antioxidant ability. The results of this study might provide a theoretical basis for potential HDL supplementation in CKD patients with endothelial damage.

慢性肾脏病（Chronic kidney disease, CKD）患者罹患心血管疾病的风险显著升高。吲哚硫酸酯（Indoxyl sulfate, IS）是一种尿毒症毒素，已有研究证实其可通过诱导氧化应激抑制一氧化氮生成并诱发细胞衰老。高密度脂蛋白（High-density lipoprotein, HDL）对心血管系统具有保护作用，但其对吲哚硫酸酯损伤的内皮细胞的具体作用仍不明晰。本研究旨在探究外源性补充高密度脂蛋白对尿毒症模拟环境中血管内皮细胞的影响。本研究采用管形成实验、迁移实验、黏附实验及衰老实验，对人主动脉内皮细胞（human aortic endothelial cells, HAECs）的细胞功能进行评估。采用Amplex red法检测活性氧的生成水平。分别选用L-NAME与MCI186作为一氧化氮合酶抑制剂与自由基清除剂。在吲哚硫酸酯刺激的人主动脉内皮细胞中，高密度脂蛋白可通过激活缺氧诱导因子1α（HIF-1α）、血红素氧合酶1（HO-1）通路，并抑制白细胞介素1β（IL-1β）、肿瘤坏死因子α（TNF-α）及白细胞介素6（IL-6）的表达，发挥抗炎与抗氧化作用。高密度脂蛋白可通过上调蛋白激酶B（Akt）、内皮型一氧化氮合酶（eNOS）、血管内皮生长因子（VEGF）及基质细胞衍生因子1（SDF-1）通路，提升吲哚硫酸酯刺激后人主动脉内皮细胞的血管生成能力。高密度脂蛋白可通过下调血管细胞黏附分子1（VCAM-1）与细胞间黏附分子1（ICAM-1）的表达，降低吲哚硫酸酯刺激后人主动脉内皮细胞的黏附性。此外，高密度脂蛋白可通过上调沉默信息调节因子1（SIRT1）并下调p53的表达，缓解吲哚硫酸酯刺激后人主动脉内皮细胞的细胞衰老进程。值得注意的是，高密度脂蛋白的上述保护作用主要依赖其抗氧化活性。综上，高密度脂蛋白可通过其抗氧化活性，对吲哚硫酸酯损伤的血管内皮细胞发挥全面的保护作用。本研究结果可为慢性肾脏病合并内皮损伤患者实施高密度脂蛋白补充疗法提供理论依据。