Department of Medicine, New York University School of Medicine, New York, New York, USA.
J Leukoc Biol. 2010 Apr;87(4):683-90. doi: 10.1189/jlb.0709513. Epub 2010 Jan 20.
Immune and inflammatory cells play a critical role in the pathogenesis of atherosclerotic plaques. We have demonstrated that A2ARs inhibit foam cell formation and stimulate production of ABCA1, the primary transporter of lipoproteins. We asked whether the effects of A2ARs on foam cell formation in vitro are mediated by transporters involved in reverse cholesterol transport, ABCA1 and ABCG1. Foam cells were generated from THP-1 cells by incubation with 100 nM PMA for 2 days and incubated with acLDL (50 microg/mL) plus IFN-gamma (500 U/mL) +/- A2AR agonist CGS-21680 (1 microM). Radiolabeled cholesterol (0.2 microCi/ml) was added to cells, and efflux was measured using a liquid scintillation counter. Lentiviral siRNA infection markedly reduces ABCA1 or ABCG1 mRNA in THP-1 cells. Despite diminished ABCG1 expression (KD), CGS-21680 inhibits foam cell formation (81+5% inhibition; P<0.0001 vs. IFN-gamma alone; n=3) but has no effect on foam cell formation in ABCA1 KD cells (5+3% inhibition; P<0.85 vs. IFN-gamma alone; n=3). The A2A agonist increases apoA-I-mediated cholesterol efflux nearly twofold in THP-1-derived macrophages (from 9.5% to 17.5+2.5% [3H]-cholesterol efflux; P<0.0090 vs. control; n=3) but not in ABCA1 KD cells. Activation of Epac, a signaling molecule downstream of the A2AR, increased ABCA1 (23+5%; P<0.0007 vs. control; n=3) and phospho-ABCA1 (13+5%; P<0.0003 vs. control; n=3) protein. These results demonstrate that A2AR occupancy diminishes foam cell formation by stimulating increased reverse cholesterol transport via ABCA1.
免疫和炎症细胞在动脉粥样硬化斑块的发病机制中起着关键作用。我们已经证明，A2AR 抑制泡沫细胞形成并刺激载脂蛋白脂蛋白的主要转运体 ABCA1 的产生。我们想知道 A2AR 对体外泡沫细胞形成的影响是否通过涉及胆固醇逆转运的转运体，即 ABCA1 和 ABCG1 来介导。用 100 nM PMA 孵育 2 天从 THP-1 细胞生成泡沫细胞，并与 acLDL（50μg/ml）+IFN-γ（500U/ml）+/-A2AR 激动剂 CGS-21680（1μM）孵育。向细胞中加入放射性标记的胆固醇（0.2 微Ci/ml），并使用液体闪烁计数器测量流出物。慢病毒 siRNA 感染显著降低 THP-1 细胞中的 ABCA1 或 ABCG1 mRNA。尽管 ABCG1 表达减少（KD），但 CGS-21680 抑制泡沫细胞形成（81+5%抑制；P<0.0001 与 IFN-γ 单独相比；n=3），但对 ABCA1 KD 细胞中的泡沫细胞形成无影响（5+3%抑制；P<0.85 与 IFN-γ 单独相比；n=3）。A2A 激动剂使 THP-1 衍生的巨噬细胞中载脂蛋白 A-I 介导的胆固醇流出增加近两倍（从 9.5%到 17.5+2.5%[3H]-胆固醇流出；P<0.0090 与对照相比；n=3），但在 ABCA1 KD 细胞中则没有。A2AR 的下游信号分子 Epac 的激活增加了 ABCA1（23+5%；P<0.0007 与对照相比；n=3）和磷酸化 ABCA1（13+5%；P<0.0003 与对照相比；n=3）蛋白。这些结果表明，A2AR 占据通过刺激 ABCA1 增加胆固醇逆转运来减少泡沫细胞形成。
