Gao Zhen, Zhang Huina, Liu Jian, Lau Chi Wai, Liu Pingsheng, Chen Zhen Yu, Lee Hung Kay, Tipoe George L, Ho Hing Man, Yao Xiaoqiang, Huang Yu
Institute of Vascular Medicine and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong SAR, China.
Institute of Vascular Medicine and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong SAR, China; National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
Biochem Pharmacol. 2014 Oct 15;91(4):474-82. doi: 10.1016/j.bcp.2014.08.009. Epub 2014 Aug 19.
Palmitic acid, one of the saturated free fatty acids, impairs cardiovascular function as manifested by inducing vascular inflammation, apoptosis and over-production of reactive oxygen species (ROS) although the origin for ROS remains unclear. The present study investigated the cellular mechanisms underlying palmitate-induced impairment of endothelial function. Ex vivo treatment in tissue culture with palmitate concentration-dependently attenuated acetylcholine-induced endothelium-dependent relaxations, up-regulated the expression of cyclooxygenase-2 (COX-2) and elevated superoxide formation in mouse aortic endothelial cells (MAECs) measured by dihydroethidium (DHE) staining and electron paramagnetic resonance (EPR) spectroscopy. Superoxide scavengers, COX-2 inhibitor and thromboxane prostanoid (TP) receptor antagonist, but not COX-1 inhibitor reversed the harmful effects of palmitate. Furthermore, palmitate impaired acetylcholine-induced relaxations and raised superoxide in en face endothelium of aortas only from COX-1(-/-) mice but not from COX-2(-/-) mice. Palmitate increased the production and release of TXB2, a stable thromboxane A2 metabolite in mouse aortas, which was abolished by COX-2 inhibitor. Superoxide scavenger did not affect palmitate-induced up-regulated expression of COX-2 in MAECs. Both real time PCR and luciferase reporter gene assay confirmed COX-2 up-regulation in palmitate-treated MAECs and NF-κB was substantially involved in this up-regulation. The present study provides novel evidence that palmitate up-regulates COX-2 through NF-κB-dependent mechanism and resultant COX-2-associated oxidative stress impairs endothelium-dependent relaxations in mouse aortas.
棕榈酸是一种饱和游离脂肪酸，可损害心血管功能，表现为诱导血管炎症、细胞凋亡和活性氧（ROS）过度产生，尽管ROS的来源尚不清楚。本研究调查了棕榈酸诱导内皮功能损害的细胞机制。在组织培养中用棕榈酸进行离体处理，浓度依赖性地减弱了乙酰胆碱诱导的内皮依赖性舒张，上调了环氧合酶-2（COX-2）的表达，并通过二氢乙锭（DHE）染色和电子顺磁共振（EPR）光谱法测定，增加了小鼠主动脉内皮细胞（MAECs）中的超氧化物形成。超氧化物清除剂、COX-2抑制剂和血栓素前列腺素（TP）受体拮抗剂可逆转棕榈酸的有害作用，但COX-1抑制剂则不能。此外，棕榈酸仅损害来自COX-1（-/-）小鼠主动脉的内皮面乙酰胆碱诱导的舒张并增加超氧化物，但不影响COX-2（-/-）小鼠的。棕榈酸增加了小鼠主动脉中稳定的血栓素A2代谢产物TXB2的产生和释放，这被COX-2抑制剂所消除。超氧化物清除剂不影响棕榈酸诱导的MAECs中COX-2表达上调。实时PCR和荧光素酶报告基因测定均证实棕榈酸处理的MAECs中COX-2上调，且核因子κB（NF-κB）大量参与了这种上调。本研究提供了新的证据，表明棕榈酸通过NF-κB依赖性机制上调COX-2，由此产生的COX-2相关氧化应激损害了小鼠主动脉的内皮依赖性舒张。
