Lada Aaron T, Willingham Mark C, St Clair Richard W
Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
J Lipid Res. 2002 Apr;43(4):618-28.
To study macrophage lipid droplet composition and the effects of TG on cholesteryl ester (CE) physical state, hydrolysis, and cholesterol efflux, a technique was developed to remove the majority of accumulated TG with minimal effect on CE content. THP-1 macrophages were incubated with acetylated LDL, and the accumulated TG was depleted by incubation with the acyl-CoA synthetase inhibitor triacsin D in the presence of albumin. Before TG removal, all cellular lipid droplets were isotropic as determined by polarizing light microscopy. When the TG concentration was reduced, anisotropic lipid droplets were visible, indicating a change in physical state, and suggesting that TG and CE originally accumulated in mixed lipid droplets. This change in physical state of lipid droplets was associated with slower rates of CE hydrolysis and cholesterol efflux. Although lipid droplets within the same cell had a similar physical state after TG depletion, there was considerable variability among cells in the physical state of their lipid droplets. In conclusion, THP-1 macrophages store accumulated CE and TG in mixed droplets, and the proportion of CE to TG varies among cells. Reducing accumulated TG altered CE physical state, which in turn affected hydrolysis of CE and cholesterol efflux.
为了研究巨噬细胞脂滴组成以及甘油三酯（TG）对胆固醇酯（CE）物理状态、水解和胆固醇流出的影响，开发了一种技术，该技术能去除大部分积累的TG，同时对CE含量的影响最小。将THP-1巨噬细胞与乙酰化低密度脂蛋白一起孵育，然后在白蛋白存在的情况下，用酰基辅酶A合成酶抑制剂三辛素D孵育以耗尽积累的TG。在去除TG之前，通过偏光显微镜观察，所有细胞脂滴都是各向同性的。当TG浓度降低时，可见各向异性脂滴，这表明物理状态发生了变化，并提示TG和CE最初积累在混合脂滴中。脂滴物理状态的这种变化与CE水解和胆固醇流出速率减慢有关。尽管在TG耗尽后，同一细胞内的脂滴具有相似的物理状态，但不同细胞之间脂滴的物理状态存在相当大的差异。总之，THP-1巨噬细胞将积累的CE和TG储存在混合脂滴中，并且CE与TG的比例在不同细胞之间有所不同。减少积累的TG会改变CE的物理状态，进而影响CE的水解和胆固醇流出。
