丙二醛和Cu~（2＋）对低密度脂蛋白修饰的比较研究

实验比较了丙二醛修饰的低密度脂蛋白（ＭＤＡ－ＬＤＬ）和氧化修饰的低密度脂蛋白（ｏ－ＬＤＬ）的某些理化性质;用放射性受体分析法,从标记配体的可饱和性、可逆性、高亲和力和立体选择性等几方面,证实在小鼠腹腔巨噬细胞（ＭＰＭ）表面存在有特异的ＭＤＡ－ＬＤＬ受体,获得了一系列能反应受体特征的参数;同时,还将ＭＤＡ－ＬＤＬ受体的特征和ｏ－ＬＤＬ的受体特征进行了比较。这些结果将有助于进一步研究ＭＰＭ清道夫受体的多态性及其与动脉粥样硬化的发病原理和防治的关系。     

I型胶原对巨噬细胞摄取氧化低密度脂蛋白的作用

为探讨胶原的存在对细胞摄取氧化低密度脂蛋白（ｏｘ－ＬＤＬ）的影响,本研究在体外制成Ｉ型胶原凝胶和巨噬细胞实验体系,ＬＤＬ经Ｃｕ＾２＋催化氧化,丙二醛（ＭＤＡ）及乙酰化修饰后,与胶原的结合能力明显增强,但４－羟基壬烯醛（ＨＮＥ）修饰的ＬＤＬ与胶原的结合能力反应不如天然ＬＤＬ。当小鼠腹腔巨噬细胞培养在胶原凝胶上时,其对ｏｘ－ＬＤＬ的摄取明显减少,这时大部分ｏｘ－ＬＤＬ为胶原凝胶所结合,如用细胞松弛素Ｄ     

I型胶原对低密度脂蛋白氧化反应敏感性的影响

在胶原存在条件下低密度脂蛋白（ＬＤＬ）的氧化反应性的改变一直未见报道,通过在体外分离大鼠Ｉ型胶原并制成胶原凝胶,发现铜离子（Ｃｕ＾２＋）介导的ＬＤＬ氧化反应的潜伏期明显延长,所生成的硫代巴比妥酸反应物（ＴＢＡＲＳ）最大值远低于对照组,胶原组氧化ＬＤＬ（ｏｘ－ＬＤＬ）的相对电泳迁移率（ＲＥＭ）也较对照组为低;在偶氮类化合物２,２＇－盐酸脒基丙烷（ＡＡＰＨ）诱导的ＬＤＬ氧化过程中,胶原组与对照组的ＬＤ     

天然及氧化修饰脂蛋白对人动脉平滑肌细胞原癌基因表达的影响

动脉平滑肌细胞（ＳＭＣ）的增殖在动脉粥样硬化（ＡＳ）的形成过程中极其重要。我们在建立人主动脉ＳＭＣ体外培养方法的基础上,观察了ＬＤＬ,ＶＬＤＬ及ＨＤＬ和相应的氧化修饰型脂蛋白对培养人ＳＭＣｓｉｓ,ｊｕｎ,Ｈ－ｒａｓ原癌基因及Ｒｂ抗癌基因转录表达的影响。结果表明：（１）ＨＤＬ对ＳＭＣｓｉｓ,ｊｕｎ,ｒａｓ基因表达无影响;（２）ＬＤＬ和ＶＬＤＬ有使这些基因表达增加的趋势;（３）ｏｘ－ＬＤＬ,ｏｘ－ＶＬＤＬ和ｏｘ－ＨＤＬ具有使ＳＭＣｓｉｓ,ｊｕｎ,和ｒａｓ基因表达显著增强的作用（Ｐ＜０．０１）,且其作用较相应的天然脂蛋白大（Ｐ＜０．０１）;（４）天然和氧化修饰型脂蛋白对Ｒｂ基因表达均无影响。据上述结果推测：ＬＤＬ,ＶＬＤＬ,ｏｘ－ＬＤＬ,ｏｘ－ＶＬＤＬ和ｏｘ－ＨＤＬ的致ＡＳ作用可能与刺激ＳＭＣｓｉｓ,ｊｕｎ和ｒａｓ原癌基因表达增加有关。     

Ⅰ型胶原对巨噬细胞摄取氧化低密度脂蛋白的作用

为探讨胶原的存在对细胞摄取氧化低密度脂蛋白（ｏｘ－ＬＤＬ）的影响,本研究在体外制成Ⅰ型胶原凝胶和巨噬细胞实验体系。ＬＤＬ经Ｃｕ２＋催化氧化,丙二醛（ＭＤＡ）及乙酰化修饰后,与胶原的结合能力明显增强,但４－羟基壬烯醛（ＨＮＥ）修饰的ＬＤＬ与胶原的结合能力反而不如天然ＬＤＬ。当小鼠腹腔巨噬细胞培养在胶原凝胶上时,其对ｏｘ－ＬＤＬ的摄取明显减少,这时大部分ｏｘ－ＬＤＬ为胶原凝胶所结合。如用细胞松弛素Ｄ（细胞非特异性吞噬抑制剂）处理巨噬细胞,在无胶原存在时,可见细胞对ｏｘ－ＬＤＬ的降解明显减少;而有胶原时,细胞的降解量则无明显变化,其水平与无胶原时的细胞处理组相当。上述结果提示,Ⅰ型胶原的存在可能阻止了巨噬细胞通过非特异性吞噬途径摄取ｏｘ－ＬＤＬ。     

氧化HDL_2在大鼠肝窦状隙细胞内代谢

大鼠肝窦状隙细胞培养结果显示：氧化高密度脂蛋白２（ｏｘ－ＨＤＬ２）对异硫氰酸荧光素（ＦＩＴＣ）荧光标记ｏｘ－ＨＤＬ２的细胞结合有竞争抑制作用,而ＨＤＬ２则无。细胞内吞ＦＩＴＣ－ｏｘ－ＨＤＬ２的荧光强度（ＦＳ）和［３Ｈ］ＣＥ－ｏｘ－ＨＤＬ２（ｒ－ｏｘ－ＨＤＬ２）的放射强度分别是内吞ＦＩＴＣ－ＨＤＬ２的４５．５％和ｒＨＤＬ２的６１．４％。内吞ＦＳ主要存在于三氯醋酸（ＴＣＡ）沉淀部分,而放射强度主要存在于ＴＣＡ上清液部分。细胞释放的ＦＳ和放射活性分别是内吞量的６７．７％和１０．９％,且主要存在于ＴＣＡ可沉淀部分。结果提示：（１）大鼠肝窦状隙细胞可能存在着ｏｘ－ＨＤＬ受体,该受体不同于ＨＤＬ受体。（２）ｏｘ－ＨＤＬ２在细胞内代谢方式与ＨＤＬ２相似,均没有经历溶酶体分解途径。在细胞内载脂蛋白与胆固醇酯（ＣＥ）组分经历一个解离过程。细胞截留大部分ＣＥ后,将载脂蛋白（Ａｐｏ）与剩余ＣＥ重组成脂蛋白并以逆向胞饮方式释放到胞外。（３）氧化修饰减弱ＨＤＬ２逆向转运胆固醇能力     

氧化修饰极低密度脂蛋白增强其致动脉粥样硬化作用

研究了氧化修饰极低密度脂蛋白（ｏｘ－ＶＬＤＬ）对小白鼠腹腔巨噬细胞内脂质堆积作用及其机制。经Ｃｕ~（２＋）修饰后ＶＬＤＬ的电泳迁移率及脂质过氧化物含量均显著增加。ｏｘ－ＶＬＤＬ更易导致小鼠腹腔巨噬细胞内脂质堆积。以相同浓度（３００μｇＴＧ／ｍＬ）或不同浓度（２００─５００μｇＴＧ／ｍＬ）的ｏｘ－ＶＬＤＬ及正常ＶＬＤＬ（ｎ－ＶＬＤＬ）与巨噬细胞温育２４ｈ,前者使巨噬细胞内ＴＧ堆积均比后者显著（Ｐ＜０．０１）。同时,随ｏｘ－ＶＬＤＬ的脂质过氧化物含量（ＴＢＡＲＳ水平）增加,巨噬细胞内ＴＧ含量的百分率相应增加。以５０μｇ蛋白／ｍＬ的ｎ－ＬＤＬ,ｏｘ－ＬＤＬ,ｎ－ＶＬＤＬ及ｏｘ－ＶＬＤＬ与巨噬细胞温育６０ｈ。细胞内ＣＥ堆积中氧化组均比正常组高（Ｐ＜０．０１）。巨噬细胞对~（１２５）Ｉ－ｎ－ＶＬＤＬ与~（１２５）Ｉ－ｏｘ－ＶＬＤＬ的结合、降曲线均有饱和趋势。两结合曲线无明显差异,但细胞对后者降解的量比前者多。结合的竞争实验表明,ｎ－ＶＬＤＬ能抑制大部分~（１２５）Ｉ－ｏｘ－ＶＬＤＬ与细胞结合,而Ａｃ－ＬＤＬ只能抑制小部分。结果表明ｏｘ－ＶＬＤＬ主要通过受体途径：大部分经过ｎ－ＶＬＤＬ受体,小部分经过清道夫受体被巨噬细胞摄     

天然及氧化修饰脂蛋白对人动脉平滑肌细胞原癌基因…

动脉平滑肌细胞（ＳＭＣ）的增殖在动脉粥样硬化（ＡＳ）的形成过程中极其重要。我们在建立人主动脉ＳＭＣ体外培养方法的基础上,观察了ＬＤＬ,ＶＬＤＬ及ＨＤＬ和相应的氧化修饰型脂蛋白对培养人ＳＭＣ ｓｉｓ,ｊｕｎ,Ｈ－ｒａｓ原癌基因及Ｒｂ抗癌基因转录表达的影响。结果表明：（１）ＨＤＬ对ＳＭＣｓｉｓ,ｊｕｎ,ｒａｓ基因表达无影响;（２）ＬＤＬ和ＶＬＤＬ有使这些基因表达增加的趋势;（３）ｏｘ－ＬＤＬ,ｏｘ－Ｖ     

丙二醛和Cu^2＋对低密度脂蛋白修饰的比较研究

实验比较了丙二醛修饰的低密度脂蛋白和氧化修饰的低密度脂蛋白的某些理化性质,用放射性受体分析法,从标记配体的可饱和性,可逆性,高亲和力和立体选择性等几方面,证实在小鼠腹腔巨噬细胞表面存在特异的ＭＤＡ－ＬＤＬ受体,获得了一系列能反应受体特征的参数,同时,还将ＭＤＡ－ＬＤＬ受体的特征和ｏ－ＬＤＬ的受体特征进行了比较。这些结构将有助于进一步研究ＭＰＭ清道夫受体的多态性及其与动脉粥弱硬化的发病原理和防治的关     

短杆菌肽S与脂膜结合前后的H／D交换动力学的研究

短杆菌肽Ｓ（ＧＳ）是一个十肽分子（环－（Ｌ－Ｖａｌ－Ｌ－Ｏｒｎ－Ｌ－Ｌｅｕ－Ｄ－Ｐｈｅ－Ｌ－Ｐｒｏ）２）,是由两个β转角和两个β片层结构所构成［１］。ＧＳ的功能是通过破坏葛兰氏阴性菌的膜结构来完成其抗菌活性。迄今为止,人们对ＧＳ与膜结合特点的研究结果还不一致。Ｄａｔｅｍａｎ等人利用２Ｈ－ＮＭＲ,３１Ｐ－ＮＭＲ和ＤＳＣ等技术研究了ＧＳ与ＤＰＰＣ多层脂膜的相互作用,指出肽仅仅作用于膜表面［２］;而Ｈｉｇａｓｈｉｊｉｍａ等［３］及张凤立等用２Ｄ－ＮＭＲ的研究结果［４］表明,ＧＳ的疏水部分应插入膜内。蛋白质及多肽的Ｈ／Ｄ交换动力学受其分子内氢键,分子空间结构的致密度及其周边环境如膜环境［５］的影响。我们利用衰减全反射红外光谱（ＡＴＲ－ＦＴＩＲ）对与脂膜结合前后的短杆菌肽Ｓ的Ｈ／Ｄ交换动力学进行了研究,实验结果提示ＧＳ插入了脂膜双层。     

Binding and uptake of differently oxidized low density lipoprotein in mouse peritoneal macrophages and THP-1 macrophages: involvement of negative charges as well as oxidation-specific epitopes

Oxidatively modified low-density lipoprotein (LDL) has been found in vivo, and oxidized LDL (oxLDL) could bind to scavenger receptors, leading to foam cell formation. Macrophages bear a number of different scavenger receptors for oxLDL, and macrophages of different origins may have a different scavenger receptor repertoire. In addition, LDL oxidized to different degrees may differ in the ability to bind macrophage scavenger receptors. In this study, we characterized the patterns of the binding and uptake of differently oxidized LDL in mouse peritoneal macrophages (MPM) and human THP-1 macrophages, and the influence of negative charge and oxidation-specific epitopes in oxLDL on these processes. Thresholds of increased binding and uptake in MPM were found when LDL was oxidized to the degrees with a relative electrophoretic mobility (REM) of 2.6 (minor threshold) and 3.0 (major threshold), corresponding to 49 and 57%, respectively, of the loss of free amino groups in these oxLDL. There was no threshold for the binding of oxLDL to THP-1 macrophages, while for uptake, a major threshold with REM of 3.0 (57% free amino groups lost) was found. The presence of the F(ab')(2) fragments of the monoclonal antibody OB/04, which was raised against copper-oxidized LDL, led to the reduction of the binding and uptake, respectively, of Eu(3+)-oxLDL (REM:3.6) in MPM by 31 and 29%, and by 19 and 22% in THP-1 macrophages. It is concluded that LDL oxidized to different degrees binds differently to macrophages, and the patterns of binding and uptake are different for MPM and human THP-1 macrophages. Both, the negative charge and the oxidation-specific epitopes of oxLDL are involved in these processes.     

Cell membrane damage is involved in the impaired survival of bone marrow stem cells by oxidized low‐density lipoprotein

Cell therapy with bone marrow stem cells (BMSCs) remains a viable option for tissue repair and regeneration. A major challenge for cell therapy is the limited cell survival after implantation. This study was to investigate the effect of oxidized low‐density lipoprotein (ox‐LDL, naturally present in human blood) on BMSC injury and the effect of MG53, a tissue repair protein, for the improvement of stem cell survival. Rat bone marrow multipotent adult progenitor cells (MAPCs) were treated with ox‐LDL, which caused significant cell death as reflected by the increased LDH release to the media. Exposure of MAPCs to ox‐LDL led to entry of fluorescent dye FM1‐43 measured under confocal microscope, suggesting damage to the plasma membrane. Ox‐LDL also generated reactive oxygen species (ROS) as measured with electron paramagnetic resonance spectroscopy. While antioxidant N‐acetylcysteine completely blocked ROS production from ox‐LDL, it failed to prevent ox‐LDL‐induced cell death. When MAPCs were treated with the recombinant human MG53 protein (rhMG53) ox‐LDL induced LDH release and FM1‐43 dye entry were significantly reduced. In the presence of rhMG53, the MAPCs showed enhanced cell survival and proliferation. Our data suggest that membrane damage induced by ox‐LDL contributed to the impaired survival of MAPCs. rhMG53 treatment protected MAPCs against membrane damage and enhanced their survival which might represent a novel means for improving efficacy for stem cell‐based therapy for treatment of diseases, especially in setting of hyperlipidemia.     

A low density lipoprotein-sized particle isolated from human atherosclerotic lesions is internalized by macrophages via a non-scavenger-receptor mechanism

A lipoprotein particle designated A-LDL, which contains apolipoprotein B (apoB) and which is the size of plasma low density lipoproteins (LDL), was isolated from homogenates of human aortic athersclerotic plaques by a combination of affinity chromatography and gel-filtration. Compared to plasma LDL, A-LDL was more electronegative, its hydrated density was lower and more heterogeneous, and its protein-to-lipid ratio was lower. In addition, apoB in A-LDL was highly degraded, and A-LDL was recognized by mouse peritoneal macrophages (MPM) as indicated by its ability to stimulate cholesterol esterification. Cholesterol esterification was saturable with an apparent Km of 100 micrograms of A-LDL cholesterol/ml. Stimulation of cholesterol esterification was linear with time, leading to extensive accumulation of cholesteryl ester in MPM over a 48-hr time interval. The uptake or degradation of acetyl-LDL (radiolabeled either in the protein with 125I or hydrophobic core with [3H]cholesteryl ether) was markedly decreased by excess unlabeled acetyl-LDL but not by A-LDL, and excess acetyl-LDL did not inhibit the uptake or degradation of labeled A-LDL. However, a 10-fold excess of A-LDL also failed to inhibit the uptake of labeled A-LDL. This finding was consistent with the observation that, unlike the saturable stimulation of cholesterol esterification in MPM induced by A-LDL, the uptake of cholesteryl ether-labeled A-LDL was almost linear over a 0-400 micrograms cholesterol/ml range. This discrepancy between dose response curves for A-LDL, which did not occur for acetyl-LDL, could be eliminated by a 24-hr postincubation period in the absence of lipoprotein, suggesting that A-LDL is catabolized less efficiently than acetyl-LDL following internalization. In summary, we conclude that A-LDL uptake by MPM occurs via a low affinity-high capacity process. Although the uptake of A-LDL is not readily saturated, it is of sufficient affinity to lead to lipid loading of macrophages even when A-LDL is present at relatively low concentrations. If these mechanisms are operative in vivo, they could explain how foam cells in human fatty streak lesions develop.     

氧化修饰与丙二醛修饰的低密度脂蛋白对巨噬细胞高密度脂蛋白结合量及胆固醇酯聚集的影响

本文用Cu~(2+)(引发氧化修饰)和脂质过氧化降解产物丙二醛(MDA)对低密度脂蛋白(LDL)进行修饰,观察了两种修饰的LDL对巨噬细胞高密度脂蛋白_3(HDL_3)结合量及细胞内胆固醇酯聚集的影响。结果说明:1.Cu~(2+)和MDA修饰的LDL都可使巨噬细胞HDL_3结合量下降,细胞内脂质过氧化物(LPO)含量升高,但当处理细胞在含10％无脂血清(LPDS)培养液中继续培养时,由MDA修饰的LDL(MDA-LDL)导致的HDL_3结合量降低又有一定的恢复,细胞内LPO含量不再升高,而Cu~(2+)修饰的LDL(Cu~(2+)-LDL)处理的细胞继续培养时,HDL_3结合量则继续下降,细胞LPO含量则继续升高。2.由Cu~(2+)-LDL导致的巨噬细胞HDL_3结合量下降与细胞LPO含量升高之间呈负相关(r=-0.81,P<0.01)。3.MDA-LDL和Cu~(2+)-LDL都可造成巨噬细胞胆固醇酯聚集,但MDA-LDL造成的胆固醇酯可被HDL_3大量清除而Cu~(2+)-LDL造成的胆固醇酯聚集则不能。     

Enhanced binding of phospholipase-A2-modified low density lipoprotein by human adipocytes

Recognition of low density lipoprotein (LDL) by human adipocytes is not dependent on the classical LDL (apoprotein B-E) receptor. To assess whether LDL phospholipids have a role in adipocyte-LDL interactions, binding studies were carried out with human LDL modified with cobra venom phospholipase A2 (PLA2) and freshly isolated adipocytes and purified adipocyte plasma membranes prepared from surgical biopsies. LDL incubated with PLA2 showed increased monoacylphospholipid content, decreased diacylphospholipid content, and increased anodic migration on agarose gel electrophoresis. LDL cholesterol, triglyceride, and protein content remained unchanged. Typically, modification of 16 and 47% of LDL phospholipids enhanced specific binding of 125I-labelled LDL to plasma membranes progressively from 3.1 micrograms LDL bound/mg membrane protein (control) to 5.8 and 28.2 micrograms LDL bound/mg membrane protein, respectively. Nonspecific binding was not altered significantly. Excess unlabelled native LDL and high density lipoprotein (HDL3) effectively inhibited binding of PLA2-modified LDL. Freshly isolated adipocytes also showed enhanced binding and uptake of PLA2-modified LDL (0.1 vs. 0.9 micrograms LDL/10(6) cells x 2 h), control vs. modified). The results demonstrate that alterations of LDL phospholipids significantly enhance LDL binding and suggest a regulatory role for phospholipids in lipoprotein-cell interaction. Furthermore, the results support the view that human adipose tissue may be involved in the metabolism of modified lipoproteins, in vivo.     

Macrophage receptors responsible for distinct recognition of low density lipoprotein containing pyrrole or pyridinium adducts: models of oxidized low density lipoprotein

Oxidation of low density lipoproteins (LDL) induced by incubation with Cu(2+) ions results in the formation of a heterogeneous group of aldehydic adducts on lysyl residues (Lys) of apolipoprotein B (apoB) that are thought to be responsible for the uptake of oxidized LDL (oxLDL) by macrophages. To define the structural and chemical criteria governing such cell recognition, we induced two modifications of lysines in LDL that mimic prototypic adducts present in oxLDL; namely, epsilon-amino charge-neutralizing pyrrolation by treatment with 2,5-hexanedione (hdLDL), and epsilon-amino charge-retaining pyridinium formation via treatment with 2,4,6-trimethylpyrylium (tmpLDL). Both modifications led to recognition by receptors on mouse peritoneal macrophages (MPM). To assess whether the murine scavenger receptor class A-I (mSR-A) was responsible for recognition of hdLDL or tmpLDL in MPM, we measured binding at 4 degrees C and degradation at 37 degrees C of these modified forms of (125)I-labeled LDL by mSR-A-transfected CHO cells. Although uptake and degradation of hdLDL by mSR-A-transfected CHO cells was quantitatively similar to that of the positive control, acLDL, tmpLDL was not recognized by these cells. However, both tmpLDL and hdLDL were recognized by 293 cells that had been transfected with CD36. In the human monocytic cell line THP-1 that had been activated with PMA, uptake of tmpLDL was significantly inhibited by blocking monoclonal antibodies to CD36, further suggesting recognition of tmpLDL by this receptor. Macrophage uptake and degradation of LDL oxidized by brief exposure to Cu(2+) was inhibited more effectively by excess tmpLDL and hdLDL than was more extensively oxidized LDL, consistent with the recognition of the former by CD36 and the latter primarily by SR-A.Collectively, these studies suggest that formation of specific pyrrole adducts on LDL leads to recognition by both the mSR-A and mouse homolog of CD36 expressed on MPM, while formation of specific pyridinium adducts on LDL leads to recognition by the mouse homolog of CD 36 but not by mSR-A. As such, these two modifications of LDL may represent useful models for dissecting the relative contributions of specific modifications on LDL produced during oxidation, to the cellular uptake of this heterogeneous ligand.     

N‐acetylcysteine prevents oxidized low‐density lipoprotein‐induced reduction of MG53 and enhances MG53 protective effect on bone marrow stem cells

MG53 is an important membrane repair protein and partially protects bone marrow multipotent adult progenitor cells (MAPCs) against oxidized low‐density lipoprotein (ox‐LDL). The present study was to test the hypothesis that the limited protective effect of MG53 on MAPCs was due to ox‐LDL‐induced reduction of MG53. MAPCs were cultured with and without ox‐LDL (0‐20 μg/mL) for up to 48 hours with or without MG53 and antioxidant N‐acetylcysteine (NAC). Serum MG53 level was measured in ox‐LDL‐treated mice with or without NAC treatment. Ox‐LDL induced significant membrane damage and substantially impaired MAPC survival with selective inhibition of Akt phosphorylation. NAC treatment effectively prevented ox‐LDL‐induced reduction of Akt phosphorylation without protecting MAPCs against ox‐LDL. While having no effect on Akt phosphorylation, MG53 significantly decreased ox‐LDL‐induced membrane damage and partially improved the survival, proliferation and apoptosis of MAPCs in vitro. Ox‐LDL significantly decreased MG53 level in vitro and serum MG53 level in vivo without changing MG53 clearance. NAC treatment prevented ox‐LDL‐induced MG53 reduction both in vitro and in vivo. Combined NAC and MG53 treatment significantly improved MAPC survival against ox‐LDL. These data suggested that NAC enhanced the protective effect of MG53 on MAPCs against ox‐LDL through preventing ox‐LDL‐induced reduction of MG53.     

Lipoproteins of the extravascular space: enhanced macrophage degradation of low density lipoproteins from interstitial inflammatory fluid

Current evidence has demonstrated that cholesteryl ester-loaded macrophages are important components of the atherosclerotic lesion. Additional studies have implicated low density lipoproteins (LDL) and circulating monocytes as central to the origin of lipid-laden foam cells found in the arterial wall. This is a result of the finding of accelerated macrophage uptake of LDL chemically modified by reaction with malondialdehyde (MDA-LDL), acetic anhydride (Ac-LDL), or incubation with arterial cells in vitro. In concert with these chemical modifications, we have previously demonstrated selective in vivo modification of LDL isolated from interstitial inflammatory fluid (IF) of the rabbit. Utilizing the polyvinyl sponge implant model, we reported that IF-LDL had an altered chemical composition, electrophoretic mobility, and particle size distribution when compared to LDL isolated from homologous plasma (WP-LDL). In this study reported herein, we examined the metabolism of IF-LDL by resident mouse peritoneal macrophages (MPM) in culture. IF-LDL was degraded substantially faster by MPM, and resulted in a substantial increase in cellular cholesteryl ester when compared to cells incubated with WP-LDL. IF-LDL binding to MPM was inhibited by Ac-LDL derived from WP-LDL, but only minimally by unmodified WP-LDL. Transmission electron microscopy of MPM revealed extensive lipid deposition in cells incubated with Ac-LDL and IF-LDL. These results implicate LDL from interstitial inflammatory fluid as an in vivo modified lipoprotein that can enhance uptake via the acetyl LDL receptor pathway in resident macrophages.     

Lipid biosynthesis and metabolism of native and acetylated low density lipoproteins in macrophages stimulated by zymosan in vivo and in vitro]

The effects of zymosan on lipid metabolism in mouse peritoneal macrophages (MPM) in vitro and in vivo were studied with special reference to the following parameters: i) 14C-oleate incorporation into cholesteryl esters (CE), triglycerides (TG), and phospholipids (PL) in MPM incubated with low density lipoproteins (LDL) and acetylated LDL; ii) cholesteryl-14C-oleate-acetyl LDL uptake and 125I-acetyl LDL degradation; iii) oxidative modification of LDL. Zymosan administered to mice caused significant stimulation of 14C-oleate incorporation into CE, TG, and PL with no effect on 3H-cholesterol (Ch) incorporation into CE or 3H-glycerol incorporation into TG and PL in MPM. The 14C-oleate incorporation into cellular lipids was unaffected by 18-hour incubation of MPM with zymosan (100-500 micrograms/ml) but increased after incubation of unstimulated MPM with blood serum and peritoneal fluid harvested harvested from zymosan-treated mice. One possible explanation of this phenomenon is oleyl-CoA formation induction in cytokine-stimulated MPM in vivo. Zymosan decreased the Ch-14C-oleate-acetyl LDL uptake, 125I-acetyl LDL degradation, and Ch esterification in the presence of acetyl LDL in MPM both in vitro and in vivo. An increase in Ch esterification after incubation of MPM with zymosan for 6-18 hours in the presence of LDL was accompanied by an increase in lipid peroxidation of LDL and its electrophoretic mobility. The data obtained suggest that the macrophage acetyl LDL receptor pathway may be inhibited by zymosan and that cytokines released from zymosan-stimulated cells may influence the generation of foam cells.     

蛋白激酶C抑制剂对U937细胞清道夫受体功能的影响

为了解细胞内蛋白质磷酸化水平对清道夫受体功能的影响,用蛋白激酶Ｃ抑掉剂形孢菌素（ｓｔａｕｒｏｓｐｏｒｉｎｅ,ＳＴＡ）处理人Ｕ９３７细胞,分别测定对照组和处理组细胞对碘标记的氧化低密度脂蛋白（＾１２５Ｉ）ｏｘ－ＬＤＬ的降解,结合,细胞表面受体复合物的内移以及细胞内脂质蓄积的程度,并利用放射自显影方法观察药物对细胞表面受体表达的影响,结果发现ＳＴＡ可以促进细胞结合（＾１２５Ｉ）ｏｘ－ＬＤＬ增加细胞表面