脂蛋白诱导平滑肌细胞表达载脂蛋白E及其在动脉粥样硬化斑块中的表达

Oxidized Low Density and Very Low Density Lipoprotein and β Very Low Density Lipoprotein Induce Smooth Muscle Cells to Express Apolipoprotein E and Its Expression in Atherosclerotic Plaques

目的 探讨氧化脂蛋白及β型极低密度脂蛋白 (β VLDL)能否诱导动脉壁细胞表达载脂蛋白E (apoE)及其在动脉粥样硬化中的作用。方法 用超速离心法从正常人血分离得到两种脂蛋白 (n LDL ,n VLDL)并使之氧化 ,同法从兔高脂血分离得 β VLDL ,将所得 5种脂蛋白作用于培养的兔主动脉平滑肌细胞 (SMC) ,用地高辛原位杂交方法检测其apoE的表达。并用同法检测食饵性动脉粥样硬化兔的主动脉粥样斑块中apoE的表达。结果 原位杂交显示 ,体外培养的正常兔主动脉SMC能表达apoE ,5种脂蛋白均能诱导培养的兔主动脉SMC表达高水平的apoEmRNA。在兔主动脉粥样斑块中巨噬细胞源性及肌源性泡沫细胞表达apoE非常明显 ,而正常兔主动脉壁细胞几乎不见apoE表达信号。结论 受各种脂蛋白刺激的培养的SMC及动脉粥样硬化斑块内的泡沫细胞均表达较高水平的apoE ;动脉粥样硬化斑块内的泡沫细胞和培养的SMC内apoE的增加可能参与细胞内胆固醇的流出 。

Objective To understand whether oxidized lipoproteins and β very low density lipoprotein induce arterial wall cells to express apoE, and what a role apoE plays in atherosclerosis. Methods Three lipoproteins (n LDL, n VLDL and β VLDL) were isolated from blood plasma of normal human body and rabbits with hyperlipidemia by ultracentrifugation, and meanwhile, both the former lipoproteins were oxidatively modified by adding CuCl 2. After exposure to the above lipoproteins, apoE mRNA expression in the cultured rabbit aortic SMCs was detected by in situ nuclei acid hybridization using a Digoxigenin labeled apoE cDNA probe. apoE mRNA expression in the dietary atherosclerotic plaques in the aortae of rabbits was detected by the same method as well. Results In situ hybridization showed that cultured rabbit aortic SMCs could express apoE mRNA. All 5 lipoproteins could induce cultured rabbit aortic SMCs to express higher levels of apoE mRNA. Densitometry scans showed that the absorbance of the apoE mRNA expression in the SMCs of n LDL, ox LDL, n VLDL, ox VLDL and β VLDL group was 0 0698, 0 0651, 0 0464, 0 0461 and 0 0557, and was about 2 89 fold, 2 70 fold, 1 92 fold, 1 91 fold and 2 3 fold, as much as that of the control group respectively. Analysis of variance showed that there was a statistically significant difference between groups ( P <0 01). The foam cells in the plaques in aortae of the dietary atherosclerotic rabbits expressed apoE mRNA obviously, whereas little signal of apoE mRNA could be found in the control group. Conclusion Cultured SMCs induced by various types of lipoproteins and the foam cells in atherosclerotic plaques could express higher levels of apoE, and the recruitment of apoE in the foam cells in atherosclerotic plaques and cultured SMCs may be involved in the cholesterol efflux of the cells, and apoE, thereby, may have anti atherogenic effects.