Studies on the regulation of cholesteryl ester synthesis and mechanism of lipid accumulation in macrophage cells

来源于人类单核细胞白血病细胞系THP-1的巨噬细胞在乙酰化低密度脂蛋白（Ac-LDL）存在下通过清除率受体（ScR）培养时积累了酯化胆固醇。在本研究中，我们分离了一种THP-1细胞亚型，当在Ac-LDL存在下培养时，它不能积累酯化胆固醇。与亲本THP-1细胞相比，细胞的Ac-LCL关联和降解量可忽略不计。THP-1亚型细胞不表达ScR mRNA，也不表达脂蛋白脂肪酶。载脂蛋白E mRNA的表达明显高于亲本THP-1细胞。经TPA处理的THP-1亚型细胞培养基可抑制亲本THP-1细胞对Ac-LDL的摄取和ScR的表达。在含TPA的培养基中培养48 h后，分化亚型THP-1细胞的培养基中含有6.9 ng/ml的转化生长因子(TGF)- β 1，而亲本THP-1细胞分泌低于检测水平，小于3 ng/ml。条件培养基对亲本THP-1细胞中ScR表达的抑制作用通过抗tgf - β 1抗体预处理培养基而消除。亲本THP-1细胞在刺激分化后表达的tgf - β 1 mRNA量与sTHP-1细胞一样多。虽然在亲本细胞和亚型THP-1细胞中合成的TGF-beta1的前体形式大小相似，表达水平也相似，但分泌TGF-beta1所必需的潜伏TGF-beta1结合蛋白（LTBP）只能与来自亚型THP-1细胞的抗TGF-beta1抗体共同免疫沉淀。这表明THP-1亚型细胞通过与LTBp形成功能复合物将tgf - β 1分泌到培养基中。我们得出结论，THP-1亚型细胞不能吸收Ac-LDL，因为分泌的tgf - β 1导致ScR被抑制（导致功能丧失）。少

Macrophage cells derived from the human monocytic leukemia cell line, THP-1, accumulate esterified cholesterol when cultivated in the presence of acetylated low-density lipoprotein(Ac-LDL) through scavenger receptors (ScR). In the present study, we isolated a subtype of THP-1 cells that failed to accumulate esterified cholesterol when cultivated in the presence of Ac-LDL.The cells had negligible amounts of cell-association and degradation of Ac-LCL compared to the parent THP-1 cell. The subtype THP-1 cells did not express ScR mRNA as well as that of lipoprotein lipase. In contrast, the expression of apolipoprotein E mRNA was greater than that found in parent THP-1 cells. The culture medium of subtype THP-1 cells treated with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) inhibited the uptake of Ac-LDL and the expression of ScR in parent THP-1 cells. After 48 h incubation in the culture medium containing TPA,the culture medium of differentiated subtype THP-1 cells contained 6.9 ng/ml of tr … More ansforming growth factor (TGF)-beta1, while that of parent THP-1 cells secreted below detection level, which was less than 3 ng/ml. This inhibitory effect of the conditioned medium on the expression of ScR in parent THP-1 cells was abolished by pre-treatment of the culture medium with anti-TGF-beta1 antibodies. Parent THP-1 cells expressed as much amount of TGF-beta1 mRNA as sTHP-1 cells after stimulation of differentiation. Although the precursor forms of TGF-beta1 which were synthesized in both parent and subtype THP-1 cells were of similar size and were expressed at similar levels, latent TGF-beta1-binding protein (LTBP), which is necessary for the secretion of TGF-beta1, could only be co-immunoprecititated with anti- TGF-beta1 antibody from subtype THP-1 cells. This suggests that subtype THP-1 cells secrete TGF-beta1 into the medium by forming a functional complex with LTBp. We conclude that subtype THP-1 cells could not take up Ac-LDL because ScR was inhibited (leading a loss of function) caused by the secreted TGF-beta1. Less