Wen Yichuan, Leake David S
Cardiovascular Research Group, Biomolecular Sciences Section, School of Biological Sciences, University of Reading, Reading, Berkshire, United Kingdom.
Circ Res. 2007 May 11;100(9):1337-43. doi: 10.1161/CIRCRESAHA.107.151704. Epub 2007 Apr 19.
The oxidized low density lipoprotein (LDL) hypothesis of atherosclerosis proposes that LDL undergoes oxidation in the interstitial fluid of the arterial wall. We have shown that aggregated (vortexed) nonoxidized LDL was taken up by J774 mouse macrophages and human monocyte-derived macrophages and oxidized intracellularly, as assessed by the microscopic detection of ceroid, an advanced lipid oxidation product. Confocal microscopy showed that the ceroid was located in the lysosomes. To confirm these findings, J774 macrophages were incubated with acetylated LDL, which is internalized rapidly to lysosomes, and then incubated (chase incubation) in the absence of any LDL. The intracellular levels of oxysterols, measured by HPLC, increased during the chase incubation period, showing that LDL must have been oxidized inside the cells. Furthermore, we found that this oxidative modification was inhibited by lipid-soluble antioxidants, an iron chelator taken up by fluid-phase pinocytosis and the lysosomotropic drug chloroquine, which increases the pH of lysosomes. The results indicate that LDL oxidation can occur intracellularly, most probably within lysosomes.
动脉粥样硬化的氧化型低密度脂蛋白（LDL）假说提出，LDL在动脉壁的组织液中发生氧化。我们已经表明，聚集的（涡旋的）未氧化LDL被J774小鼠巨噬细胞和人单核细胞衍生的巨噬细胞摄取，并在细胞内被氧化，这通过显微镜检测类脂褐素（一种晚期脂质氧化产物）来评估。共聚焦显微镜显示类脂褐素位于溶酶体中。为了证实这些发现，将J774巨噬细胞与乙酰化LDL一起孵育，乙酰化LDL会迅速内化到溶酶体中，然后在没有任何LDL的情况下进行孵育（追踪孵育）。通过高效液相色谱法测量，在追踪孵育期间，氧固醇的细胞内水平升高，表明LDL一定是在细胞内被氧化的。此外，我们发现这种氧化修饰受到脂溶性抗氧化剂、通过液相胞饮作用摄取的铁螯合剂以及增加溶酶体pH值的溶酶体促渗药物氯喹的抑制。结果表明，LDL氧化可能发生在细胞内，很可能发生在溶酶体内。
