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目的 研究人单核细胞系在分化为巨噬细胞及转化为泡沫细胞过程中酰基CoA :胆固醇酰基转移酶 1(ACAT1)活性的改变及其机制。方法 体外培养人THP 1单核细胞系 ,由佛波酯作用使其分化为巨噬细胞 ,后者再由氧化低密度脂蛋白 (Ox LDL)进一步作用转变为泡沫细胞。此过程中以放射性同位素标记底物法检测ACAT1活性的变化 ,并用Westernblot法检测ACAT1蛋白的表达及RT PCR法检测ACAT1mRNA的水平。结果 在单核细胞分化为巨噬细胞的过程中ACAT1活性升高了 2倍 ,差异具有显著性 (P <0 0 5 ) ,酶蛋白及mRNA水平呈现类似变化趋势 ,在进一步转化为泡沫细胞过程中 ,ACAT1活性、酶蛋白及mRNA仍处于较高水平 ,但与巨噬细胞相比差异无显著性。结论 单核细胞分化为巨噬细胞的过程中ACAT1转录水平的上调导致酶蛋白量合成增加 ,从而使ACAT1活性也大为增强 ,而Ox LDL对ACAT1活性影响则不明显。
AIM To investigate the changes of acyl CoA: cholesterol acyltransferase 1 (ACAT1) activity in human monocytic cell lines and their differentiation into macrophages and their transformation into foam cells. Methods Human THP 1 monocyte line was cultured in vitro and was induced to differentiate into macrophages by phorbol ester. The latter was further transformed into foam cells by oxidized low density lipoprotein (Ox LDL). In this process, the changes of ACAT1 activity were detected by radioisotope labeling substrate method. The expression of ACAT1 protein was detected by Western blot and the level of ACAT1 mRNA by RT PCR. Results The activity of ACAT1 increased 2 folds during differentiation of monocytes into macrophages, the difference was significant (P <0 05). The protein and mRNA levels of ACAT1 showed a similar trend. In the process of further transformation into foam cells ACAT1 activity, enzyme protein and mRNA are still at a high level, but no significant difference compared with macrophages. Conclusion The up-regulation of ACAT1 transcription during monocyte differentiation into macrophages results in the increase of protein synthesis and the increase of ACAT1 activity. However, the effect of Ox LDL on ACAT1 activity is not obvious.