Department of Cardiology, The Second Xiang Ya Hospital of Central South University, Changsha, Hunan, PR.
Tohoku J Exp Med. 2010 Mar;220(3):223-8. doi: 10.1620/tjem.220.223.
Cholesterol efflux is the key step of reverse cholesterol transport and has become a therapeutic target against atherosclerosis. Human apolipoprotein A-I (apoA-I) is the main protein in high-density lipoprotein (HDL) and has 243 amino acids. ApoA-I mimetic peptides have no sequence homology to apoA-I but possess the class-A amphipathic helical motif that presents in apoA-I lipid binding domains. D-4F is one of the apoA-I mimetic peptides and exerts diverse atheroprotective functions similar to apoA-I. However, the exact role of D-4F on lipid metabolism in macrophages is not clear yet. Therefore, we studied the effect of D-4F on cholesterol efflux, cAMP levels and expression of ATP-binding cassette transporter A1 (ABCA1) in RAW264.7 mouse macrophages. Cells were incubated with 1, 10, 50 or 100 microg/ml D-4F for 24 hours, and the cholesterol efflux was assessed. Here, D-4F significantly increased the cholesterol efflux in concentration- and time-dependent manners. Concomitantly, D-4F increased intracellular cAMP levels and the expression levels of ABCA1 mRNA and protein in a dose-dependent manner, consistent with the increase in the cholesterol efflux from macrophages. 8-Br-cAMP (cAMP activator) increased the D-4F-mediated cholesterol efflux by 39%. Moreover, the increases in cholesterol efflux and ABCA1 expression induced by 8-Br-cAMP could be inhibited by the treatment with H89, a protein kinase A (PKA) inhibitor. In conclusion, these results suggest that the synthetic peptide D-4F promotes cholesterol efflux in macrophages through the cAMP-PKA-ABCA1 pathway, which may open new avenues for the treatment of atherosclerosis.
胆固醇外排是胆固醇逆转运的关键步骤，已成为抗动脉粥样硬化的治疗靶点。人载脂蛋白 A-I（apoA-I）是高密度脂蛋白（HDL）中的主要蛋白，含有 243 个氨基酸。apoA-I 模拟肽与 apoA-I 没有序列同源性，但具有存在于 apoA-I 脂质结合域中的 A 类两亲性螺旋基序。D-4F 是 apoA-I 模拟肽之一，具有与 apoA-I 相似的多种抗动脉粥样硬化功能。然而，D-4F 对巨噬细胞中脂质代谢的确切作用尚不清楚。因此，我们研究了 D-4F 对 RAW264.7 小鼠巨噬细胞胆固醇外排、cAMP 水平和 ATP 结合盒转运体 A1（ABCA1）表达的影响。细胞用 1、10、50 或 100μg/ml D-4F 孵育 24 小时，评估胆固醇外排。结果表明，D-4F 以浓度和时间依赖的方式显著增加胆固醇外排。同时，D-4F 以剂量依赖的方式增加细胞内 cAMP 水平和 ABCA1 mRNA 和蛋白的表达水平，与巨噬细胞中胆固醇外排的增加一致。8-Br-cAMP（cAMP 激活剂）增加了 39%的 D-4F 介导的胆固醇外排。此外，8-Br-cAMP 诱导的胆固醇外排和 ABCA1 表达的增加可被蛋白激酶 A（PKA）抑制剂 H89 抑制。总之，这些结果表明，合成肽 D-4F 通过 cAMP-PKA-ABCA1 途径促进巨噬细胞中的胆固醇外排，这可能为动脉粥样硬化的治疗开辟新途径。
