巨噬细胞集落刺激因子对小鼠腹腔巨噬细胞清道夫受体途径和细胞内胆固醇酯积聚的影响

为探索巨噬细胞集落刺激因子、清道夫受体、氧化型低密度脂蛋白与动脉粥样硬化的关系，观察了重组人巨噬细胞集落刺激因子对小鼠腹腔巨噬细胞清道夫受体途径的影响以及重组人巨噬细胞集落刺激因子对氧化型低密度脂蛋白所致细胞内胆固醇酯积聚的影响．结果发现重组人巨噬细胞集落刺激因子能增加培养的小鼠腹腔巨噬细胞表面的清道夫受体数目，使之对氧化型低密度脂蛋白的结合和降解呈现剂量和时间依赖性增加，并使细胞内胆固醇酯积聚增多．表明巨噬细胞集落刺激因子可通过增加清道夫受体数目使小鼠腹腔巨噬细胞对氧化型低密度脂蛋白的结合和降解增多，从而增加细胞内胆固醇酯含量，促进动脉壁内泡沫细胞形成．     

蛋白激酶C抑制剂对小鼠腹腔巨噬细胞清道夫受体功能的影响

目的 观察细胞内蛋白磷酸化水平对清道夫受体功能的影响。方法 用蛋白激酶C抑制荆星形孢菌素处理小鼠腹腔巨噬细胞，利用蛋白质印迹试验和放射自显影方法观察药物对细胞表面受体表达的影响，并分别测定对照组和处理组细胞对碘标记的氧化型低密度脂蛋白的结合、降解以及细胞内脂质蓄积的程度。结果 0．4μmol／L蛋白激酶C抑制剂星形孢菌素可以促进细胞结合碘标记的氧化型低密度脂蛋白，增加细胞表面受体的表达，但抑制细胞降解碘标记的氧化型低密度脂蛋白，同时抑制细胞内胆固醇酯的蓄积。结论 以上表明清道夫受体功能与细胞内蛋白质磷酸化水平密切相关。     

巨噬细胞集落刺激因子对小鼠腹腔巨噬细胞抗氧化能力的影响

越来越多的实验结果证实巨噬细胞集落刺激因子在动脉粥样硬化发生过程中的重要作用，为了探讨巨噬细胞集落刺激因子和活性氧与动脉粥样硬化之间的相互关系，观察了巨噬细胞集落刺激因子对培养的小鼠腹腔巨噬细胞抗氧化酶活性的影响。结果发现巨噬细胞集落刺激因子能使小鼠腹腔巨噬细胞谷胱甘肽过氧化物酶活性提高３２％，超氧化物歧化酶的活性提高１２０％，并减轻叔丁基氢过氧化物促巨噬细胞源性泡沫细胞形成，以及提高巨噬细胞的生存数。此结果提示巨噬细胞集落刺激因子提高杭氧化酶活性的作用可能是其虽增加对氧化修饰低密度脂蛋白和胆固醇的摄入却能阻止泡沫细胞形成及动脉粥样硬化发生发展的原因之一。     

两种细胞因子和表皮生长因子、纤维母细胞生长因子对血管平滑肌细胞清道夫受体活性的影响

为探讨有关的细胞因子和生长因子是否影响平滑肌细胞清道夫受体与氧化型低密度脂蛋白结合活性，以Ｃｕ２＋氧化法制备的氧化型低密度脂蛋白免疫豚鼠，制备抗氧化型低密度脂蛋白抗体，在培养的小牛主　动脉平滑肌细胞中，用细胞酶联免疫吸附检测法测定清道夫受体结合氧化型低密度脂蛋白的活性。结果发现，碱性纤维母细胞生长因子、表皮生长因子、肿瘤坏死因子可提高血管平滑肌细胞表面清道夫受体活性，而粒细胞－巨噬细胞集落刺激因子对清道夫受体活性无影响。此结果提示，某些细胞因子、生长因子对平滑肌细胞清道夫受体活性具有调节作用。     

两种细胞因子和表皮生长因子、纤维母细胞生长因子对血管平滑肌细胞清道夫受体活性的影响

为探讨有关的细胞因子和生长因子是否影响平滑肌细胞清道夫受体与氧化型低密度脂蛋白结合活性，以Ｃｕ＾２＋氧化法制备的氧化型低密度脂蛋白免疫豚鼠，制备抗氧化型低密度脂慢白抗体，在培养的小牛主动脉平滑肌细胞中，用细胞酶联免疫吸附检测法测定清道夫受体结合氧化型低密度脂蛋白的活性。结果发现，碱性纤维母细胞生长因子、表皮生长因子、肿瘤坏死因子可提高血管平滑肌细胞表面清道夫受体活性，而粒细胞－巨噬细胞集落刺激因子     

低密度脂蛋白免疫复合物对小鼠腹腔巨噬细胞胆固醇酯蓄积和一氧化氮释放的影响

目的 探讨低密度脂蛋白免疫复合物对小鼠腹腔巨噬细胞胆固醇酯的蓄积和一氧化氮释放的影响。方法 密度梯度超速离心从新鲜人血浆分离天然低密度脂蛋白，与抗低密度脂蛋白抗血清IgG组分制备低密度脂蛋白免疫复合物，低密度脂蛋白免疫复合物与小鼠腹腔巨噬细胞孵育后采用酶荧光法检测细胞胆固醇酯含量，进行细胞形态学观察和组织化学分析．并用硝酸还原酶法测定细胞释放至培养基中的一氧化氮量。结果 低密度脂蛋白免疫复合物剂量依赖性地诱导巨噬细胞内胆固醇酯的大量堆积，其效应显著强于氧化型低密度脂蛋白（P〈0．01）。经低密度脂蛋白免疫复合物处理的巨噬细胞呈典型泡沫细胞状，与猩红强染色，而天然低密度脂蛋白、抗低密度脂蛋白IgG处理的巨噬细胞内未见胆固醇酯的蓄积。此外，低密度脂蛋白免疫复合物剂量依赖性地抑制巨噬细胞一氧化氮的分泌。结论 低密度脂蛋白免疫复合物不仅通过致小鼠腹腔巨噬细胞泡沫化，也通过损伤巨噬细胞分泌一氧化氮的功能参与致动脉粥样硬化作用。     

天然及氧化型脂蛋白(a)与巨噬细胞表面结合

为探讨脂蛋白 (a)及氧化型脂蛋白 (a)在巨噬细胞上的结合和降解途径 ,将生物素标记的脂蛋白与小鼠腹腔巨噬细胞进行结合和竞争性结合试验。结果发现 ,脂蛋白 (a)能以一定的亲和力、可饱和性地与巨噬细胞表面结合 ;低密度脂蛋白对其结合无明显抑制作用 ,而氧化型低密度脂蛋白、氧化型脂蛋白 (a)均能不同程度地抑制这种结合。脂蛋白 (a)经氧化修饰后 ,与巨噬细胞的结合量显著增加。脂蛋白 (a)、低密度脂蛋白不能有效竞争氧化型脂蛋白 (a)的结合 ,而氧化型脂蛋白 (a)和氧化型低密度脂蛋白为有效的竞争性抑制剂。提示脂蛋白 (a)主要经清道夫受体与巨噬细胞表面结合 ;氧化型脂蛋白 (a)除经清道夫受体介导外 ,可能还通过其它特异性受体与巨噬细胞表面结合。     

A型清道夫受体基因敲除小鼠的腹腔巨噬细胞特异性氧化型低密度脂蛋白受体

为研究巨噬细胞表面是否存在特异性氧化型低密度脂蛋白受体 ,选用A型清道夫受体基因敲除小鼠来进行研究。竞争抑制实验发现 ,在乙酰化低密度脂蛋白存在 (终浓度为 2 0 0mg L)的情况下 ,A型清道夫受体基因敲除小鼠的腹腔巨噬细胞对氧化型低密度脂蛋白的摄取降低了 2 4 .8% ,还有大约 80 %的氧化型低密度脂蛋白可能通过特异性受体途径被摄取。蛋白配基印迹技术发现一种膜蛋白 ,分子量为 84～ 97kDa,它不结合乙酰化低密度脂蛋白 ,只结合氧化型低密度脂蛋白 ,并且未标记1 2 5I的氧化型低密度脂蛋白能竞争性抑制1 2 5I标记氧化型低密度脂蛋白与该膜蛋白的结合 ,上述结果提示这种膜蛋白是特异性氧化型低密度脂蛋白受体     

巨噬细胞集落刺激因子对小鼠腹腔巨噬细胞抗氧化能力的影响

越来越多的实验结果证实巨噬细胞集落刺激因子在动脉粥样硬化发生过程中的重要作用，为了探讨巨噬细胞集落刺激因子和活性氧与动脉粥样硬化之间的相互关系，观察了巨噬细胞集落刺激因子对培养的小鼠腹巨噬细胞抗氧化酶活性的影响。结果发现巨噬细胞集落刺激因子能使小鼠腔巨噬细胞谷胱甘肽过氧化物酶活性提高３２％，超氧化歧化酶的活性提高１２０％，并减轻叔丁基氢过氧化物促巨噬细胞源性泡沫细胞形成，以及提高巨噬细胞的生存数。     

硫酸乙酰肝素蛋白聚糖及肝素对巨噬细胞脂质蓄积的抑制作用

用苏丹Ⅳ染色观察巨噬细胞内脂质聚积的变化；通过酶－荧光法检测巨噬细胞内胆固醇含量并检测125Ⅰ标记氧化型低密度脂蛋白降解量来反映巨噬细胞清道夫受体的活性，以探讨硫酸乙酸肝素蛋白聚糖及肝素对巨噬细胞脂质蓄积的影响及机制。结果发现，氧化型低密度脂蛋白（100mg／L）组巨噬细胞的胞浆内可见较多苏丹Ⅳ着色红染颗粒，氧化型低密度脂蛋白（100mg／L）十硫酸乙酰肝素蛋白聚糖（15．5mg／L）组0及氧化型低密度脂蛋白（100mg／L）十肝素（200mg／L）组巨噬细胞内红色颗粒明显少于氧化型低密度脂蛋白组；氧化型低密度脂蛋白十硫酸乙酰肝素蛋白聚糖组及氧化型低密度脂蛋白十肝素组巨噬细胞内总胆固醇和胆固醇酯的含量明显低于氧化型低密度脂蛋白组（P＜0．05，P＜0．01）；硫酸乙酰肝素蛋白聚糖组及肝素组125Ⅰ标记的氧化型低密度脂蛋白降解量均低于对照组。结果提示，硫酸乙酰肝素蛋白聚糖和肝素可能是通过下调清道夫受体活性减少了巨噬细胞对氧化型低密度脂蛋白的摄取而抑制脂质在巨噬细胞内的聚集和泡沫细胞的形成。     

Effect of plasma lipoproteins on cholesterol accumulation in macrophages: comparison of lipoproteins from normal and homozygous familial hypercholesterolemic subjects

Total cholesterol (TC) content of mouse peritoneal macrophages (MPM) increased when incubated with increasing concentrations of normal low density (N-LDL) or very low density (N-VLDL) lipoprotein. Incubation with increasing concentrations of normal high density lipoprotein (N-HDL) caused a decrement in cellular mass of TC in MPM. Incubation of MPM with serum from normal subjects as well as from subjects with homozygous familial hypercholesterolemia (HFH) resulted in a 25% increment in cellular mass of TC, due to an increment in both free cholesterol (FC) and cholesteryl ester (CE) fractions. Accumulation of TC in MPM, due mainly to elevation of CE, was observed when the macrophages were incubated in the presence of LDL or VLDL derived from either group of subjects. N-LDL caused a higher increment in cellular CE compared to HFH-LDL. However, the presence of HFH-VLDL in the medium caused elevation in the cellular TC and CE content to a higher level than did N-VLDL. The presence of N-HDL as well as of HFH-HDL in the medium resulted in a similar decrement in the cholesterol content of MPM. The decrement was expressed in both FC and CE fractions. The present study shows different abilities of normal and HFH plasma lipoproteins to cause cholesterol accumulation in MPM.     

Crystallization of free cholesterol in model macrophage foam cells.

-The present study examined free cholesterol (FC) crystallization in macrophage foam cells. Model foam cells (J774 or mouse peritoneal macrophages [MPMs]) were incubated with acetylated low density lipoprotein and FC/phospholipid dispersions for 48 hours, resulting in the deposition of large stores of cytoplasmic cholesteryl esters (CEs). The model foam cells were then incubated for up to 5 days with an acyl-coenzyme A:cholesterol acyltransferase (ACAT) inhibitor (CP-113,818) in the absence of an extracellular FC acceptor to allow intracellular accumulation of FC. FC crystals of various shapes and sizes formed in the MPMs but not in the J774 macrophages. Examination of the MPM monolayers by microscopy indicated that the crystals were externalized rapidly after formation and thereafter continued to increase in size. Incubating J774 macrophages with 8-(4-chlorophenylthio)adenosine 3':5'-cyclic monophosphate (CPT-cAMP) in addition to CP-113,818 caused FC crystal formation as a consequence of CPT-cAMP stimulation of CE hydrolysis and inhibition of cell growth. In addition, 2 separate cholesterol phases (liquid-crystalline and cholesterol monohydrate) in the plane of the membrane bilayer were detected after 31 hours of ACAT inhibition by the use of small-angle x-ray diffraction of J774 macrophage foam cells treated with CPT-cAMP. Other compounds reported to inhibit ACAT, namely progesterone (20 microgram/mL) and N-acetyl-D-sphingosine (c(2)-ceramide, 10 microgram/mL), induced cellular toxicity in J774 macrophage foam cells and FC crystallization when coincubated with CPT-cAMP. Addition of the extracellular FC acceptors apolipoproteins (apo) E and A-I (50 microgram/mL) reduced FC crystal formation. In MPMs, lower cell density and frequent changes of medium were conducive to crystal formation. This may be due to "dilution" of apoE secreted by the MPMs and is consistent with our observation that the addition of exogenous apoE or apoA-I inhibits FC crystal formation in J774 macrophage foam cells cotreated with CP-113,818 plus CPT-cAMP. These data demonstrate that FC crystals can form from the hydrolysis of cytoplasmic stores of CEs in model foam cells. FC crystal formation can be modulated by the addition of extracellular FC acceptors or by affecting the cellular rate of CE hydrolysis. This process may contribute to the formation of FC crystals in atherosclerotic plaques.     

The LDL receptor is the major pathway for beta-VLDL uptake by mouse peritoneal macrophages

In order to determine the contribution of the low density lipoprotein receptor (LDL-R) to the removal of apoB-containing native lipoproteins by macrophages, we compared the uptake of beta-VLDL in peritoneal macrophages (MPM) from wild type mice and mice lacking the LDL-R. The d<1.006 g/ml lipoproteins obtained from apoE deficient mice fed a high fat diet were poorly degraded by macrophages and caused only a slight formation of CE in macrophages from both types of mice. On the other hand, d<1.006 g/ml lipoproteins obtained from LDL-R deficient mice fed a high fat diet, beta-VLDL with apoE, were avidly taken up by and markedly stimulated CE formation in wild type macrophages, but not in macrophages lacking the LDL-R. The degradation of 125I-labeled-apoE-containing beta-VLDL by wild type MPM was poorly inhibited by unlabeled human LDL, and beta-VLDL without apoE had no effects. In conclusion, we propose that the in vitro uptake of native apoE-enriched lipoproteins by murine macrophages is primarily mediated by the LDL receptor and not by other apoE-recognizing receptor systems such as: the LDL receptor related protein, the VLDL receptor or the triglyceride-rich lipoprotein receptor.     

Angiotensin II administration to atherosclerotic mice increases macrophage uptake of oxidized ldl: a possible role for interleukin-6

The goal of the present study was to elucidate mechanisms for angiotensin II (Ang II) induction of oxidized low density lipoprotein (Ox-LDL) uptake by macrophages, the hallmark of early atherosclerosis. Compared with placebo treatment, Ang II injections (0.1 mL, 10(-7) mol/L per day) for 2 weeks to apolipoprotein E-deficient mice significantly increased Ox-LDL degradation, CD36 mRNA expression, and CD36 protein expression by their peritoneal macrophages (MPMs). These effects were abolished by treatment with losartan (5 to 50 mg/kg per day) before Ang II administration. Because no such effect was obtained in vitro, the ex vivo effect of Ang II on macrophage uptake of Ox-LDL could be mediated by a factor that is not expressed at a significant level in vitro. Because Ang II stimulates cellular production of interleukin-6 (IL-6), we analyzed the possible role of IL-6 as a mediator of Ang II-mediated cellular uptake of Ox-LDL by using several approaches. First, incubations of IL-6 with MPM or IL-6 administration in mice increased macrophage Ox-LDL degradation and CD36 mRNA expression. Second, injection of IL-6 receptor antibodies in mice during Ang II treatment reduced macrophage Ox-LDL uptake and CD36 expression compared treatment with Ang II alone. Finally, Ang II treatment of IL-6-deficient mice did not affect their MPM Ox-LDL uptake and CD36 protein levels. Thus, we conclude that a novel mechanism for Ang II atherogenicity, related to macrophage cholesterol accumulation and foam cell formation, may involve its stimulatory effect on macrophage uptake of Ox-LDL, a process mediated byIL-6.     

Binding site on macrophages that mediates uptake and degradation of acetylated low density lipoprotein, producing massive cholesterol deposition

Resident mouse peritoneal macrophages were shown to take up and degrade acetylated (125)I-labeled low density lipoprotein ((125)I-acetyl-LDL) in vitro at rates that were 20-fold greater than those for the uptake and degradation of (125)I-LDL. The uptake of (125)I-acetyl-LDL and its subsequent degradation in lysosomes were attributable to a high-affinity, trypsin-sensitive, surface binding site that recognized acetyl-LDL but not native LDL. When (125)I-acetyl-LDL was bound to this site at 4 degrees C and the macrophages were subsequently warmed to 37 degrees C, 75% of the cell-bound radioactivity was degraded to mono[(125)I]iodotyrosine within 1 hr. The macrophage binding site also recognized maleylated LDL, maleylated albumin, and two sulfated polysaccharides (fucoidin and dextran sulfate) indicating that negative charges were important in the binding reaction. A similar binding site was present on rat peritoneal macrophages, guinea pig Kupffer cells, and cultured human monocytes but not on human lymphocytes or fibroblasts, mouse L cells or Y-1 adrenal cells, or Chinese hamster ovary cells. Uptake and degradation of acetyl-LDL via this binding site stimulated cholesterol esterification 100-fold and produced a 38-fold increase in the cellular content of cholesterol in mouse peritoneal macrophages. Although the physiologic significance, if any, of this macrophage uptake mechanism is not yet known, we hypothesize that it may mediate the degradation of denatured LDL in the body and thus serve as a "backup" mechanism for the previously described receptor-mediated degradation of native LDL that occurs in parenchymal cells. Such a scavenger pathway might account for the widespread deposition of LDL-derived cholesteryl esters in macrophages of patients with familial hypercholesterolemia in whom the parenchymal cell pathway for LDL degradation is blocked, owing to a genetic deficiency of receptors for native LDL.     

维拉帕米对人外周血单核巨噬细胞代谢低密度脂蛋白的影响

了解低密度脂蛋白的致动脉粥样硬化（ Ａ Ｓ）的机制及维拉帕米的影响。　方法：使用放射配基法观察人单核巨噬细胞对氧化低密度脂蛋白的代谢及维拉帕米的影响。　结果：氧化低密度脂蛋白在人单核巨噬细胞中的结合、摄取和降解较低密度脂蛋白增加。维拉帕米增加人单核巨噬细胞对氧化低密度脂蛋白和低密度脂蛋白的结合和摄取,不伴降解的增加。　结论：低密度脂蛋白经氧化后在人单核巨噬细胞中代谢发生改变,促进 Ａ Ｓ的形成,维拉帕米通过改变其代谢途径,具有抗 Ａ Ｓ的作用。     

Phospholipids in oxidized low density lipoproteins perturb the ability of macrophages to degrade internalized macromolecules and reduce intracellular cathepsin B activity

Previous studies showed that pre-treatment of mouse peritoneal macrophages (MPM) with oxidized low density lipoprotein (oxLDL) repressed subsequent degradation of oxLDL following uptake. Parallel studies on the activity of the lysosomal protease, cathepsin B in MPM and in vitro indicate that oxLDL also induces a reduction in this activity. We now report that pre-treatment of MPM with the lipid portion of oxLDL induced a reduction both in the degradation of internalized small macromolecules such as maleylated (mal) BSA (30%) or larger ones such as aggregated LDL (100%), and in cellular cathepsin B activity (42%). Binding and uptake of malBSA were not affected. Pre-treatment of MPM for 2 h with oxidized phosphatidylcholine (oxPC) isolated from oxLDL or generated from Cu2+-treated 1-palmitoyl-2-linoleoyl phosphatidylcholine (oxPLPC), also inhibited 125I-malBSA degradation and reduced cathepsin B activity in MPM and in vitro. Further separation of oxPLPC and oxPC from oxLDL by thin layer chromatography led to the isolation of a polar lipid fraction possessing most of the biological activity in oxPC. Partial characterization of this fraction from oxPLPC using liquid chromatography/electrospray ionization/mass spectrometry indicated that this polar fraction containing fragmentation products of linoleate, was still comprised of multiple bioactive molecular ions. Collectively, these results suggest that specific oxPC fractions in oxLDL are partially responsible for the alterations in MPM metabolism under study induced by oxLDL.     

Cytotoxic cholesterol is generated by the hydrolysis of cytoplasmic cholesteryl ester and transported to the plasma membrane.

The present study examines the fate and effects of free cholesterol (FC) generated by the hydrolysis of cytoplasmic cholesteryl esters (CE) in model macrophage foam cells. J774 or elicited mouse peritoneal macrophages (MPM) were enriched with CE by incubating with acetylated low density lipoprotein (acLDL) and FC/phospholipid dispersions, thus creating model foam cells. Treatment of the foam cells with the acyl coenzyme-A:cholesterol acyltransferase (ACAT) inhibitor, CP-113,818, in the absence of any extracellular cholesterol acceptors, resulted in cellular toxicity. This was accompanied by an increase in the amount of FC available for oxidation by an exogenous cholesterol oxidase. Furthermore, cellular toxicity was proportional to the size of the oxidase susceptible pool of FC over time. Morphological analysis and in situ DNA fragmentation assay demonstrated the occurrence of apoptosis in the ACAT inhibited cells. Co-treatment with the hydrophobic amine U18666A, an intracellular cholesterol transport inhibitor, led to a dose dependent reduction in cytotoxicity and apoptosis, and blocked the movement of FC into the oxidase susceptible pool. In addition, treating model foam cells with CP-113,818 plus chloroquine, a compound that inhibits the function of acidic vesicles, also diminished cellular toxicity. Staining with the cholesterol binding dye filipin revealed that the macrophages treated with CP-113,818 contained a cholesterol oxidase accessible pool of FC in the plasma membrane. These results suggest that FC generated by the hydrolysis of cytoplasmic CE is transported through acidic vesicles to the plasma membrane, and accumulation of FC in this pool triggers cell death by necrosis and apoptosis.