Virgolini I, Li S R, Yang Q, Koller E, Sperr W R, Leimer M, Angelberger P, Nimpf J, Schneider W, Valent P
Department of Nuclear Medicine, University of Vienna, Austria.
Arterioscler Thromb Vasc Biol. 1995 Jan;15(1):17-26. doi: 10.1161/01.atv.15.1.17.
Recent data suggest that basophils and mast cells play a potential role in the processing and accumulation of plasma lipoproteins. This study investigated the interactions of 111In-low-density lipoprotein (LDL), 111In-acetyl-LDL, and 111In-very-low-density lipoprotein (VLDL) with purified primary human blood basophils, immortalized human basophils (KU812 cell line), and a human mast cell line, HMC-1. Binding sites for 111In-LDL resolved into curvilinear Scatchard plots indicating two classes of specific binding sites on primary basophils (Bmax1, 7404 sites/cell; Kd1, 1.9 nmol/L; Bmax2, 39,611 sites/cell; Kd2, 29 nmol/L), on KU812 cells (Bmax1, 8290 +/- 2690 sites/cell; Kd1, 2.4 +/- 0.6 nmol/L; Bmax2, 46,470 sites/cell; Kd2, 33.4 +/- 7.8 nmol/L), and on HMC-1 cells (Bmax1, 7840 +/- 360 sites/cell; Kd1, 1.8 +/- 0.8 nmol/L; Bmax2, 61,450 +/- 9900 sites/cell; Kd2, 28.4 +/- 9.4 nmol/L). On KU812 cells, binding of 111In-LDL was displaced by apolipoprotein (apo)-E-rich high-density lipoprotein (HDL) (IC50, 14 +/- 6 nmol/L), LDL (IC50, 29 +/- 11 nmol/L), VLDL (IC50, 55 +/- 21 nmol/L), HDL2 (IC50, 420 +/- 140 nmol/L), and heparin (IC50, 67 +/- 28 nmol/L), whereas no competition was produced by HDL, HDL3, or acetyl-LDL (IC50, > 1 mumol/L). Western blot analysis using the monoclonal antibody C7 confirmed the presence of the LDL receptor on human basophils and HMC-1 cells. 111In-acetyl-LDL binding sites (scavenger receptor) could be detected neither on human basophils nor on HMC-1 cells. 111In-VLDL bound to a single class of high-affinity binding sites on primary basophils (Bmax, 4320 sites/cell; Kd, 10 nmol/L), KU812 cells (Bmax, 4020 +/- 840 sites/cell; Kd, 8 +/- 3 nmol/L), and HMC-1 cells (Bmax, 6143 +/- 1866 sites/cell; Kd, 4 +/- 2 nmol/L). 111In-VLDL binding was displaced by VLDL > LDL > apoE-rich HDL but not by heparin (IC50 > 1 mmol/L). In the presence of prostaglandin E1, the number of 111In-LDL receptors increased by 150% (P < .05) in the high-affinity range and by 170% (P < .01) in the low-affinity range, whereas the number of 111In-VLDL binding sites remained unchanged. VLDL, LDL, HDL, and the subclasses HDL2 and HDL3 inhibited immunological histamine release by primary normal basophils (n = 3) and mast cells (n = 3). Our results provide evidence for the existence of LDL and VLDL binding sites on human basophils and HMC-1 mast cells. The exact biological and pathophysiological roles of these sites remain to be elucidated.
近期数据表明，嗜碱性粒细胞和肥大细胞在血浆脂蛋白的处理和积累过程中发挥着潜在作用。本研究调查了¹¹¹铟标记的低密度脂蛋白（LDL）、¹¹¹铟标记的乙酰化LDL和¹¹¹铟标记的极低密度脂蛋白（VLDL）与纯化的原代人血嗜碱性粒细胞、永生化人嗜碱性粒细胞（KU812细胞系）以及人肥大细胞系HMC-1之间的相互作用。¹¹¹铟-LDL的结合位点解析为曲线型Scatchard图，表明原代嗜碱性粒细胞上存在两类特异性结合位点（Bmax1，7404个位点/细胞；Kd1，1.9 nmol/L；Bmax2，39,611个位点/细胞；Kd2，29 nmol/L），KU812细胞上（Bmax1，8290±2690个位点/细胞；Kd1，2.4±0.6 nmol/L；Bmax2，46,470个位点/细胞；Kd2，33.4±7.8 nmol/L），以及HMC-1细胞上（Bmax1，7840±360个位点/细胞；Kd1，1.8±0.8 nmol/L；Bmax2，61,450±9900个位点/细胞；Kd2，28.4±9.4 nmol/L）。在KU812细胞上，富含载脂蛋白（apo）-E的高密度脂蛋白（HDL）（IC50，14±6 nmol/L）、LDL（IC50，29±11 nmol/L）、VLDL（IC50，55±21 nmol/L）、HDL2（IC50，420±140 nmol/L）和肝素（IC50，67±28 nmol/L）可取代¹¹¹铟-LDL的结合，而HDL、HDL3或乙酰化LDL（IC50＞1 μmol/L）则无竞争作用。使用单克隆抗体C7进行的蛋白质印迹分析证实人嗜碱性粒细胞和HMC-1细胞上存在LDL受体。在人嗜碱性粒细胞和HMC-1细胞上均未检测到¹¹¹铟-乙酰化LDL结合位点（清道夫受体）。¹¹¹铟-VLDL与原代嗜碱性粒细胞上的一类高亲和力结合位点结合（Bmax，4320个位点/细胞；Kd，10 nmol/L），KU812细胞上（Bmax，4020±840个位点/细胞；Kd，8±3 nmol/L），以及HMC-1细胞上（Bmax，6143±1866个位点/细胞；Kd，4±2 nmol/L）。¹¹¹铟-VLDL的结合可被VLDL＞LDL＞富含apoE的HDL取代，但不能被肝素取代（IC50＞1 mmol/L）。在前列腺素E1存在的情况下,¹¹¹铟-LDL受体的数量在高亲和力范围内增加了150%（P＜0.05），在低亲和力范围内增加了170%（P＜0.01），而¹¹¹铟-VLDL结合位点的数量保持不变。VLDL, LDL, HDL以及HDL2和HDL3亚类可抑制原代正常嗜碱性粒细胞（n = 3）和肥大细胞（n = 3）的免疫性组胺释放。我们的数据为人类嗜碱性粒细胞和HMC-1肥大细胞上存在LDL和VLDL结合位点提供了证据。这些位点的确切生物学和病理生理学作用仍有待阐明。
