Podrez E A, Febbraio M, Sheibani N, Schmitt D, Silverstein R L, Hajjar D P, Cohen P A, Frazier W A, Hoff H F, Hazen S L
Department of Cell Biology, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
J Clin Invest. 2000 Apr;105(8):1095-108. doi: 10.1172/JCI8574.
The oxidative conversion of LDL into an atherogenic form is considered a pivotal event in the development of cardiovascular disease. Recent studies have identified reactive nitrogen species generated by monocytes by way of the myeloperoxidase-hydrogen peroxide-nitrite (MPO-H(2)O(2)-NO(2)(-)) system as a novel mechanism for converting LDL into a high-uptake form (NO(2)-LDL) for macrophages. We now identify the scavenger receptor CD36 as the major receptor responsible for high-affinity and saturable cellular recognition of NO(2)-LDL by murine and human macrophages. Using cells stably transfected with CD36, CD36-specific blocking mAbs, and CD36-null macrophages, we demonstrated CD36-dependent binding, cholesterol loading, and macrophage foam cell formation after exposure to NO(2)-LDL. Modification of LDL by the MPO-H(2)O(2)-NO(2)(-) system in the presence of up to 80% lipoprotein-deficient serum (LPDS) still resulted in the conversion of the lipoprotein into a high-uptake form for macrophages, whereas addition of less than 5% LPDS totally blocked Cu(2+)-catalyzed LDL oxidation and conversion into a ligand for CD36. Competition studies demonstrated that lipid oxidation products derived from 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphocholine can serve as essential moieties on NO(2)-LDL recognized by CD36. Collectively, these results suggest that MPO-dependent conversion of LDL into a ligand for CD36 is a likely pathway for generating foam cells in vivo. MPO secreted from activated phagocytes may also tag phospholipid-containing targets for removal by CD36-positive cells.
低密度脂蛋白(LDL)氧化转化为致动脉粥样硬化形式被认为是心血管疾病发展过程中的关键事件。最近的研究已确定单核细胞通过髓过氧化物酶 - 过氧化氢 - 亚硝酸盐(MPO - H₂O₂ - NO₂⁻)系统产生的活性氮物质是将LDL转化为巨噬细胞高摄取形式(NO₂ - LDL)的新机制。我们现在确定清道夫受体CD36是负责小鼠和人类巨噬细胞对NO₂ - LDL进行高亲和力和饱和性细胞识别的主要受体。使用稳定转染CD36的细胞、CD36特异性阻断单克隆抗体和CD36基因敲除巨噬细胞,我们证明了暴露于NO₂ - LDL后,CD36依赖性结合、胆固醇负载和巨噬细胞泡沫细胞形成。在高达80%的脂蛋白缺乏血清(LPDS)存在下,MPO - H₂O₂ - NO₂⁻系统对LDL的修饰仍导致脂蛋白转化为巨噬细胞的高摄取形式,而添加少于5%的LPDS则完全阻断Cu²⁺催化的LDL氧化并转化为CD36的配体。竞争研究表明,源自1 - 棕榈酰 - 2 - 花生四烯酰 - sn - 甘油 - 3 - 磷酸胆碱的脂质氧化产物可作为CD36识别的NO₂ - LDL上的必需部分。总体而言,这些结果表明MPO依赖性将LDL转化为CD36的配体可能是体内产生泡沫细胞的途径。活化吞噬细胞分泌的MPO也可能标记含磷脂靶标以便被CD36阳性细胞清除。
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