CD36介导氧化型低密度脂蛋白诱导U937细胞泡沫化和凋亡

Oxidized Low Density Lipoprotein Induced Foam Cell Formation and Apoptosis in U937 Cell Mediated by CD36,One Kind of Scavenger Receptor BI

为探讨清道夫受体CD36在氧化型低密度脂蛋白诱导U937细胞泡沫化和凋亡中的作用 ,用氧化型低密度脂蛋白温育U937细胞 ,观察U937细胞泡沫化过程中CD36的表达时序和泡沫细胞的凋亡 ;用CD36单克隆抗体阻断U937细胞的吞噬作用 ,观察U937细胞吞噬蓄积胆固醇和细胞凋亡的改变。细胞胆固醇以修饰的酶荧光法测定 ;用流式细胞术检测异硫氰酸荧光素 -抗CD36单克隆抗体特异标记的CD36和细胞的凋亡情况 ;用逆转录聚合酶链反应检测CD36mRNA的表达。结果发现 ,80mg/L氧化型低密度脂蛋白与U937细胞温育 2 4h可增加细胞内总胆固醇 ,48h时可形成典型的泡沫细胞 ;CD36表达呈现时序性改变 ,6h即可检出CD36表达增高 ,2 4h达到最高值 ,48h表达略有降低 ,CD36mRNA的转录与CD36的表达一致。用 2 0 0mg/L氧化型低密度脂蛋白与U937细胞温育 2 4h可见U937细胞出现凋亡 ,48h后凋亡峰最明显 ,预先用CD36单克隆抗体阻断可使氧化型低密度脂蛋白致U937细胞凋亡明显减少。实验结果提示 ,CD36介导U937细胞吞噬蓄积氧化型低密度脂蛋白形成泡沫细胞 ,并最终出现凋亡 ;

Aim To explore the role of CD36 in foam cell formation and apoptosis and the time course of expression of CD36 gene and protein in macrophages foamy process induced by oxidized low dlensity lipoprotein (ox-LDL). Methods and Results Human myeloid leukemia U937 cells were incubated with ox-LDL (80 mg/L) for time course(6 h,12 h,24 h or 48 h) treatment. Total cholesterol in U937 cells increased from 143.5 to 419.2 mg/g protein. Flow cytometric analysis results revealed that CD36 protein expression increased from 6 h to 48 h induced by ox-LDL and was highest at 24 h. RT-PCR results showed that CD36 mRNA level increased with time order. The apoptotic cells were determined by flow cytometry and DNA fragmentation assay. Ox-LDL(200 mg/L) could induce U937 cell apoptosis after 24 h and increase after 48 h. Apoptosis were reduced by pre-incubation U937 cell with CD36 mono-antibody. Conclusions U937 cell could bind and internalize ox-LDL and formation in foam cell mediated by CD36. Later, apoptosis of U937 cell after incubated with ox-LDL also mediated by CD36. Accumulation of cholesteryl esters in U937 cells has no negative feedback control on CD36 gene and protein expression.