Cox Brian E, Griffin Evelyn E, Ullery Jody C, Jerome W Gray
Department of Pathology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
J Lipid Res. 2007 May;48(5):1012-21. doi: 10.1194/jlr.M600390-JLR200. Epub 2007 Feb 16.
Macrophages incubated with mildly oxidized low density lipoprotein (OxLDL), aggregated low density lipoprotein (AggLDL), or cholesteryl ester-rich lipid dispersions (DISPs) accumulate cholesterol in lysosomes followed by an inhibition of lysosomal cholesteryl ester (CE) hydrolysis. The variety of cholesterol-containing particles producing inhibition of hydrolysis suggests that inhibition may relate to general changes in lysosomes. Lysosome pH is a key mediator of activity and thus is a potential mechanism for lipid-induced inhibition. We investigated the effects of cholesterol accumulation on THP-1 macrophage lysosome pH. Treatment with OxLDL, AggLDL, and DISPs resulted in inhibition of the lysosome's ability to maintain an active pH and concomitant decreases in CE hydrolysis. Consistent with an overall disruption of lysosome function, exposure to OxLDL or AggLDL reduced lysosomal apolipoprotein B degradation. The lysosomal cholesterol sequestration and inactivation are not observed in cholesterol-equivalent cells loaded using acetylated low density lipoprotein (AcLDL). However, AcLDL-derived cholesterol in the presence of progesterone (to block cholesterol egression from lysosomes) inhibited lysosome acidification. Lysosome inhibition was not attributable to a decrease in the overall levels of vacuolar ATPase. However, augmentation of membrane cholesterol in isolated lysosomes inhibited vacuolar ATPase-dependent pumping of H+ ions into lysosomes. These data indicate that lysosomal cholesterol accumulation alters lysosomes in ways that could exacerbate foam cell formation and influence atherosclerotic lesion development.
与轻度氧化的低密度脂蛋白（OxLDL）、聚集的低密度脂蛋白（AggLDL）或富含胆固醇酯的脂质分散体（DISPs）一起孵育的巨噬细胞，会在溶酶体中积累胆固醇，随后抑制溶酶体胆固醇酯（CE）水解。多种产生水解抑制作用的含胆固醇颗粒表明，这种抑制可能与溶酶体的一般变化有关。溶酶体pH是活性的关键调节因子，因此是脂质诱导抑制作用的潜在机制。我们研究了胆固醇积累对THP-1巨噬细胞溶酶体pH的影响。用OxLDL、AggLDL和DISPs处理导致溶酶体维持活性pH的能力受到抑制，同时CE水解减少。与溶酶体功能的整体破坏一致，暴露于OxLDL或AggLDL会降低溶酶体载脂蛋白B的降解。在使用乙酰化低密度脂蛋白（AcLDL）加载的胆固醇等效细胞中未观察到溶酶体胆固醇螯合和失活。然而，在孕酮存在下（以阻止胆固醇从溶酶体中逸出），AcLDL衍生的胆固醇抑制了溶酶体酸化。溶酶体抑制并非归因于液泡ATP酶总体水平的降低。然而，在分离的溶酶体中增加膜胆固醇会抑制液泡ATP酶依赖性的H+离子泵入溶酶体。这些数据表明，溶酶体胆固醇积累以可能加剧泡沫细胞形成并影响动脉粥样硬化病变发展的方式改变溶酶体。
