The Lipid Research Laboratory, Technion Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences, and Rambam Medical Center, 31096 Haifa, Israel.
Atherosclerosis. 2010 Jul;211(1):61-8. doi: 10.1016/j.atherosclerosis.2010.01.025. Epub 2010 Jan 28.
Paraoxonase 1 (PON1) was shown to stimulate HDL binding and HDL-mediated cholesterol efflux from macrophages. This study examined the role of PON1 in the expression of proteins that enhance macrophage HDL binding, i.e. ABCA1 and SR-BI.
ABCA1 expression was similar, whereas SR-BI expression (mRNA and protein determined by FACS, Western blot, or immunocytochemistry) was significantly decreased in peritoneal macrophages from PON1 deficient (MPM-PON1(0)) in comparison to C57Bl/6 (MPM-Control) mice. PON1 deficiency correction with HDL-control, recombinant PON1 (rePON1), or by transfection with a plasmid containing the rePON1 gene, increased SR-BI expression in MPM-PON1(0), whereas rePON1/H115Gln mutant, or the H115Q/H134Q double mutant, which lack catalytic activity, did not stimulate SR-BI expression. Lysophosphatidyl choline (LPC) resulting from PON1 action on macrophage PC, upregulated SR-BI expression in MPM-PON1(0) via activation of ERK1/2 and PI3K. Functionally, HDL bound to MPM-PON1(0) significantly less than to MPM-Control, and failed to inhibit tunicamycin-induced apoptosis, but had no significant effect on HDL-mediated cholesterol efflux from macrophages.
PON1 deficiency in mice is associated with decreased macrophage SR-BI expression, decreased cellular HDL binding, and consequently the loss of HDL-mediated cytoprotection against apoptosis, which may contribute to the accelerated atherosclerosis observed in PON1(0) mice. These findings add new insights into the function of SR-BI in macrophages, and define the potential role of PON1 in regulating SR-BI-mediated HDL protection against macrophages apoptosis.
研究表明，对氧磷酶 1（PON1）可刺激 HDL 与巨噬细胞结合，并促进 HDL 介导的胆固醇外流。本研究旨在探讨 PON1 在增强巨噬细胞 HDL 结合的蛋白表达中的作用，即 ABCA1 和 SR-BI。
ABCA1 的表达相似，而 PON1 缺陷（MPM-PON1(0)）的腹腔巨噬细胞中 SR-BI 的表达（通过 FACS、Western blot 或免疫细胞化学测定的 mRNA 和蛋白）明显低于 C57Bl/6（MPM-Control）小鼠。用 HDL-对照、重组 PON1（rePON1）或含有 rePON1 基因的质粒转染纠正 PON1 缺乏，可增加 MPM-PON1(0)中的 SR-BI 表达，而缺乏催化活性的 rePON1/H115Gln 突变体或 H115Q/H134Q 双突变体则不能刺激 SR-BI 表达。PON1 作用于巨噬细胞 PC 产生的溶血磷脂酰胆碱（LPC）通过激活 ERK1/2 和 PI3K 而上调 MPM-PON1(0)中的 SR-BI 表达。功能上，与 MPM-Control 相比，与 MPM-PON1(0)结合的 HDL 明显减少，并且不能抑制衣霉素诱导的细胞凋亡，但对巨噬细胞中 HDL 介导的胆固醇外流没有显著影响。
小鼠 PON1 缺乏与巨噬细胞 SR-BI 表达减少、细胞 HDL 结合减少以及由此导致 HDL 介导的抗细胞凋亡保护作用丧失有关，这可能导致 PON1(0)小鼠加速动脉粥样硬化的发生。这些发现为 SR-BI 在巨噬细胞中的功能提供了新的见解，并确定了 PON1 在调节 SR-BI 介导的 HDL 保护巨噬细胞凋亡中的潜在作用。
