Ellsworth J L, Cooper A D, Kraemer F B
J Lipid Res. 1986 Oct;27(10):1062-72.
To characterize lipoprotein uptake by macrophages, we studied J774 murine macrophage-derived cells. Uptake of 125I-labeled beta-VLDL and 125I-labeled chylomicron remnants was saturable, specific, and of high affinity. Maximal specific uptake and the concentration at which half-maximal uptake occurred were similar for both beta-VLDL and chylomicron remnants. Specific uptake of 125I-labeled chylomicrons was only 1/5 that of the other two lipoproteins. Cholesterol loading decreased 125I-labeled chylomicron remnant and 125I-labeled beta-VLDL uptake by 25%. Chylomicron remnants and beta-VLDL were equipotent in cross-competition studies; acetyl-LDL did not compete, and human LDL was a poor competitor. Although the amounts of cell-associated lipoproteins were similar, beta-VLDL and chylomicron remnants had different effects on cellular lipid metabolism. beta-VLDL produced a threefold stimulation while chylomicron remnants caused a decrease in [3H]oleate incorporation into cholesteryl ester. beta-VLDL had no effect while chylomicron remnants caused a threefold increase in [3H]oleate incorporation into triacylglycerol. beta-VLDL produced a 44% suppression and chylomicron remnants produced a 78% increase in HMG-CoA reductase activity. In summary, J774 macrophages express a receptor site that recognizes both beta-VLDL and chylomicron remnants; however, these lipoproteins exhibit strikingly different effects on intracellular lipid metabolism.
为了表征巨噬细胞对脂蛋白的摄取，我们研究了J774小鼠巨噬细胞衍生细胞。125I标记的β-VLDL和125I标记的乳糜微粒残粒的摄取是可饱和的、特异性的且具有高亲和力。β-VLDL和乳糜微粒残粒的最大特异性摄取以及发生半数最大摄取时的浓度相似。125I标记的乳糜微粒的特异性摄取仅为其他两种脂蛋白的1/5。胆固醇负载使125I标记的乳糜微粒残粒和125I标记的β-VLDL摄取减少25%。在交叉竞争研究中，乳糜微粒残粒和β-VLDL具有同等效力；乙酰-LDL不参与竞争，而人LDL是较弱的竞争者。尽管细胞相关脂蛋白的量相似，但β-VLDL和乳糜微粒残粒对细胞脂质代谢有不同影响。β-VLDL产生了三倍的刺激作用，而乳糜微粒残粒导致[3H]油酸掺入胆固醇酯的量减少。β-VLDL没有影响，而乳糜微粒残粒使[3H]油酸掺入三酰甘油的量增加了三倍。β-VLDL使HMG-CoA还原酶活性抑制44%，而乳糜微粒残粒使其增加78%。总之，J774巨噬细胞表达一种识别β-VLDL和乳糜微粒残粒的受体位点；然而，这些脂蛋白对细胞内脂质代谢表现出截然不同的影响。
