氧化型低密度脂蛋白对3T3-L1脂肪细胞胆固醇流出的影响

Effects of oxidized low-density lipoprotein on cholesterol effluxin 3T3-L1 cells

目的:观察氧化型低密度脂蛋白(oxidized low-density lipoprotein,ox-LDL)干预是否刺激分化成熟的3T3-L1脂肪细胞胆固醇流出,并探讨其机制。方法:3T3-L1细胞促分化成熟后,给予不同浓度的ox-LDL(0～50μg/mL)干预8或24h;在以25μg/mL ox-LDL预处理脂肪细胞24h后,再以10μmol/L22(R)-羟基胆固醇干预24h,收集细胞,采用逆转录聚合酶链反应(reverse transcription polymer-ase chain reaction,RT-PCR)测定脂肪细胞三磷酸腺苷结合盒转运体A1(ATP binding cassette transporterA1,ABCA1),B族I型清道夫受体(scavenger receptor class B type I,SR-BI)和肝X受体α(liver X receptorα,LXRα)mRNA表达,采用液体闪烁计数器检测载脂蛋白A-I(apolipoprotein A-I,apoA-I)介导的细胞内胆固醇流出。结果:低浓度ox-LDL(12.5～25μg/mL)干预24h可增加脂肪细胞ABCA1,LXRα和SR-BImRNA的表达,并促进apoA-I介导的胆固醇流出,而高浓度(50μg/mL)则无此作用。将脂肪细胞用25μg/mL ox-LDL预处理24h,再用10μmol/L22(R)-羟基胆固醇干预细胞,ABCA1和LXRαmRNA表达均有显著增加(P<0.01),同时apoA-I介导的胆固醇流出增加,而SR-BImRNA表达无明显改变。结论:低浓度ox-LDL不仅可促进脂肪细胞LXRα-ABCA1-apoA-I通路,还可上调SR-BI表达,加速细胞内胆固醇流出。Ox-LDL这种新的作用不仅有利于维持脂肪细胞内胆固醇的动态平衡,还可能具有抗动脉粥样硬化作用。

Objective To explore whether oxidized low-density lipoprotein （ox-LDL） can stimulate the cholesterol efflux in fully differentiated 3T3-L1 cells and the possible mechanism.Methods Fully differentiated 3T3-L1 cells were incubated in the medium containing various concentrations of ox-LDL （ 0 to 50 μg/mL） for 8 or 24 hours. 22 （R） -Hydroxycholesterol （ 10 μmol/ L） was exposed to preconditioned adipocytes with 25 μg/mL ox-LDL for 24 hours. Reverse transcription polymerase chain reaction （RT-PCR） was used to evaluate ATP binding cassette transporter A1 （ABCA1） , scavenger receptor class B type I （SR-BI） , and liver X receptor α （LXRα） mRNA expression. Cholesterol efflux mediated by apolipoprotein A-I （ apoA-I ） was determined using liquid scintillator. Results Low levels （12.5 -25 μg/mL ） of ox-LDL could increase cholesterol efflux via the enhancement of ABCA1 pathway and SR-BI expression, whereas the higher concentrationtion （50 μg/mL） could not. In adipocytes preincubated with 25 μg/mL ox-LDL for 24 hours, 22 （R）-hydroxycholesterol could increase ABCA1 and LXRα mRNA and apoA-I-mediated cholesterol efflux, but had no effect on the SR-BI mRNA expression. Conclusion Low levels of ox-LDL may enhance the LXRα- ABCAI-apoA-I pathway in adipocytes, up-regulate SR-BI mRNA expression,and then increase the cholesterol efflux. This in adipocytes, up-regulate SR-BI mRNA expression, new effect of ox-LDL will not only make contribution to cholesterol homeostasis in adipocytes, but also be potentially atheroprotective.