Emergency Department, Beijing Anzhen Hospital, Capital Medical University, ChaoYang District, Beijing, China.
Emergency Department, Beijing Anzhen Hospital, Capital Medical University, ChaoYang District, Beijing, China.
J Clin Lipidol. 2017 Sep-Oct;11(5):1168-1176. doi: 10.1016/j.jacl.2017.07.007. Epub 2017 Jul 27.
β-adrenergic receptor (β-AR) was shown to upregulate hepatic apolipoprotein A-I (apoA-I) expression and reverse atherosclerotic plaques in vivo experiments. However, the effect of β-AR on apoA-I expression in vitro is unknown. The specific mechanism underlying β-AR prevention of atherosclerosis is unclear.
The present study was designed to investigate the molecular mechanism of β-AR-mediated regulation of hepatic apoA-I gene expression.
HepG2 cells were preincubated with/without a selective protein kinase A inhibitor (H-89) and then treated with a selective β-AR agonist (BRL37344) or antagonist (SR59230A). The hepatic apoA-I expression was detected by reverse transcription real-time quantitative polymerase chain reaction and Western blot analysis. Enzyme-linked immunosorbent assay was used to evaluate the secretion of apoA-I. A recombinant plasmid containing the apoA-I promoter was constructed and transiently transfected into HepG2 cells, and dual-luciferase reporter assays were used to examine the activity of the apoA-I promoter. A chromatin immunoprecipitation polymerase chain reaction assay was used to evaluate binding activities of hepatocyte nuclear factor-4 (HNF-4), HNF-3, and early growth response protein-1.
β-AR activation significantly upregulated apoA-I expression, promoted apoA-I secretion, and enhanced the activities of the apoA-I promoter, HNF-4, and HNF-3 in hepatocytes, whereas early growth response protein-1 was not affected. Moreover, protein kinase A inhibition partially suppressed the activation of the apoA-I promoter, HNF-4, and HNF-3 and almost completely blocked the upregulation of apoA-I expression induced by β-AR.
β-AR activation increased the activities of the apoA-I promoter, HNF-4, and HNF-3, which might account for the mechanism of β-AR-mediated upregulation of hepatic apoA-I expression. β-AR might exert an anti-atherosclerotic effect by upregulating hepatic apoA-I expression and promoting the cholesterol reverse transport process.
β-肾上腺素能受体（β-AR）被证明可上调肝载脂蛋白 A-I（apoA-I）的表达并在体内实验中逆转动脉粥样硬化斑块。然而，β-AR 在体外对 apoA-I 表达的影响尚不清楚。β-AR 预防动脉粥样硬化的确切机制尚不清楚。
本研究旨在探讨β-AR 介导的肝 apoA-I 基因表达调控的分子机制。
用/不用选择性蛋白激酶 A 抑制剂（H-89）预孵育 HepG2 细胞，然后用选择性β-AR 激动剂（BRL37344）或拮抗剂（SR59230A）处理。通过逆转录实时定量聚合酶链反应和 Western blot 分析检测肝 apoA-I 表达。酶联免疫吸附试验用于评估 apoA-I 的分泌。构建含有 apoA-I 启动子的重组质粒并瞬时转染 HepG2 细胞，双荧光素酶报告基因检测分析 apoA-I 启动子的活性。染色质免疫沉淀聚合酶链反应检测分析肝细胞核因子-4（HNF-4）、HNF-3 和早期生长反应蛋白-1 的结合活性。
β-AR 激活显著上调 apoA-I 表达，促进 apoA-I 分泌，并增强肝细胞 apoA-I 启动子、HNF-4 和 HNF-3 的活性，而早期生长反应蛋白-1 不受影响。此外，蛋白激酶 A 抑制部分抑制 apoA-I 启动子、HNF-4 和 HNF-3 的激活，并几乎完全阻断β-AR 诱导的 apoA-I 表达上调。
β-AR 激活增加了 apoA-I 启动子、HNF-4 和 HNF-3 的活性，这可能是β-AR 介导的肝 apoA-I 表达上调的机制。β-AR 可能通过上调肝 apoA-I 表达和促进胆固醇逆向转运过程发挥抗动脉粥样硬化作用。
