肥大细胞改变THP-1巨噬细胞源性泡沫细胞胆固醇含量及抑制胆固醇流出

目的：以THP-1巨噬细胞源性泡沫细胞为研究对象，探讨肥大细胞（MC）对THP-1巨噬细胞源性泡沫细胞内胆固醇含量、分配和流出的影响及机制。方法： THP-1巨噬细胞源性泡沫细胞在MC颗粒释放物存在或缺乏下与高密度脂蛋白3（HDL₃）共育。高效液相色谱检测泡沫细胞内总胆固醇(TC)、游离胆固醇(FC)和酯化胆固醇(EC)含量，用液体闪烁计数器检测细胞内胆固醇流出，运用逆转录聚合酶链反应检测三磷酸腺苷结合盒转运体A1(ABCA1)的mRNA水平，采用琼脂糖凝胶电泳和聚丙烯酰胺凝胶电泳检测HDL₃及apoA-Ⅰ的降解。结果： MC组泡沫细胞内TC、FC明显高于对照组（TC对照组为527.3 mg/g，MC组为917.9 mg/g）；EC/TC比值低于对照组（7.6% vs 47.5%）；细胞内胆固醇流出少于对照组(26.92％±2.6％ vs 40.98％±3.4％,P<0.05)；而泡沫细胞ABCA1的mRNA水平与对照组无明显差异。MC颗粒释放物处理HDL₃后，聚丙烯酰胺凝胶电泳结果显示，约有28%的apoA-Ⅰ被降解，在分子量26 kD左右处出现了新的条带，产生了1个26 kD的小多肽。结论：肥大细胞可通过降解HDL₃及apoA-Ⅰ抑制细胞内胆固醇流出而增加细胞内胆固醇蓄积，这个作用与ABCA1表达无直接关系。

Mast cells change cellular cholesterol content and inhibit cholesterol efflux from THP-1 macrophage-derived foam cells

AIM:Mast cells (MC) are present in the arterial intima,the site of atherogenesis. The present studies explore the effect of MC on cholesterol content,distribution and efflux in THP-1 macrophage-derived foam cells (THP-1FCs）. METHODS:THP-1FCs were incubated with high-density lipoproteins 3 (HDL₃) in the absence or presence of mast cell granules (MCGs) harvested from compound 48/80-stimulated rat peritoneal MC. The intracellular cholesterol level,cholesterol effluxing capacity,ATP-binding cassette transporter A1(ABCA1) mRNA and HDL₃ treated with MCGs were detected to characterize the role of MC on intracellular cholesterol. RESULTS:MCGs had high levels of cellular total cholesterol(TC),free cholesterol(FC) but not esterifed cholesterol(EC) compared to control group where the TC concentrations ranged from 527.3 mg/g to 917.9 mg/g cellular protein with EC accounting for 7.6% of the cholesterol. Cholesterol efflux was 14% less in MCGs group compared to control group. ABCA1 mRNA expression in MCG-treated THP-1FCs remained unchanged in 20 hours. In contrast,treatment of HDL₃ with MCGs resulted in rapid degradation of the main HDL₃ apoliproteins,apoA-Ⅰ. SDS-PAGE revealed that a minor polypeptide band with about 26 kD molecular mass appeared below the apoA-Ⅰband. Densitometric analysis of the gel demonstrated that ≈ 28% of apoA-Ⅰhad been degraded by the MCGs. CONCLUSION:These results indicate that MC decreases cholesterol efflux,increases cellular accumulation in TC and FC by depleting HDL₃ and apoA-Ⅰ,but not by inhibiting ABCA1 mRNA expression.