Cholesteryl ester handling by RAW264 macrophages: response to native and acetylated low density lipoprotein.
The effects of LDL and Ac-LDL on the growth properties, morphology, and cholesteryl ester (CE) metabolism of the RAW264 macrophage cell line have been characterized. Cells were grown in media supplemented by a defined media (DM) mixture or fetal bovine serum (FBS). The addition of LDL or Ac-LDL to the culture media did not significantly alter cell growth properties. Cytoplasmic deposition of CE was observed by fluorescence microscopy in macrophages treated with LDL or Ac-LDL but not in untreated controls. Dose-response studies have shown that cholesteryl ester (CE) can accumulate in RAW264 treated with LDL. Cellular cholesterol content saturated at 4 hours with 50 micrograms/ml LDL; this effect may be associated with receptor saturation. Dose-response studies conducted with Ac-LDL in DM have shown dramatic increases in total cell cholesterol content. However, deposition of CE was not observed below Ac-LDL concentrations of 100 micrograms/ml. This indicates that a critical concentration of Ac-LDL must be reached to trigger deposition in DM. In contrast, no critical concentration of Ac-LDL was observed in macrophages grown in medium supplemented with 10% FBS. Cholesterol esterification in response to LDL and Ac-LDL was examined by 14C-oleic acid incorporation into CE. These results confirmed the mass cellular cholesterol and CE measurements. Kinetic studies conducted with RAW264 cells treated with 50 or 100 micrograms/ml Ac-LDL resulted in a cholesterol efflux from the cells at 6-12 hours of incubation. Therefore, these studies show that (1) the nature of CE deposition is highly dependent upon the incubation media and (2) CE deposition is very sensitive to Ac-LDL concentration under certain conditions.
Berg
K A
KA
Dept. of Biological Sciences, Wayne State University, Detroit, MI 48202.
Petty
H R
HR
D000818:Animals; D002460:Cell Line; D002474:Cell-Free System; D002788:Cholesterol Esters / Q000378:metabolism*; D004951:Esterification; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D009829:Oleic Acids / Q000378:metabolism; D002785:Sterol O-Acyltransferase / Q000378:metabolism
D002788:Cholesterol Esters; D008077:Lipoproteins, LDL; D009829:Oleic Acids; C032629:acetyl-LDL; D002785:Sterol O-Acyltransferase