Effects of cholesterol and lipoproteins on endocytosis by a monocyte-like cell line

Identification of low density lipoprotein as a regulator of Fc receptor-mediated phagocytosis.

“…Incubation of U-937 cells for 24 hr in medium containing delipidated serum depletes cellular cholesterol without affecting growth rate or viability (11,12,16). The cellular cholesterol content was 12.6 ± 3.7 ,g/mg of protein for cells cultured in RPMI/FCS with IFN-y and dropped to 3.8 ± 2.0 ,ug/mg of protein for cells cultured in medium containing delipidated serum and IFN-y ( Table 1).…”

“…Since our previous study (10) and degradation (12). LDL also restored the cellular cholesterol content to 20.7 ± 2.5 ,g/mg of protein ( (Fig.…”

“…Lipoproteins were mixed with growth medium containing 10% DLFCS to give a final concentration of 0.2 mg of lipoprotein protein per ml (12). This medium was sterilized by filtration through a 0.45-,tm filter and stored at 4°C.…”

“…Cells and Growth Conditions. A strain of human monocyte cell line U-937 that is a cholesterol auxotroph (10)(11)(12)(14)(15)(16) was grown at 37°C in suspension cultures in RPMI 1640 with 10% heat-inactivated FCS (RPMI/FCS), as described (10). To establish the effect of IFN-y on phagocytosis, U-937 cells were incubated at 2 x 105 per ml in 50 ml of RPMI/FCS per 75-cm2 culture flask (Falcon) for 24 hr in the presence (500 units/ml) or absence of IFN-y prior to measurement of phagocytic activity.…”

“…x 105 cells per ml in medium containing IFN-'y (500 units/ml) and 10% FCS, 10% DLFCS, or Where used, cholesterol was added as an ethanol/BSA mixture (10)(11)(12)(14)(15)(16). Ethanol (100 p.l) containing 0.5 mg of cholesterol was added to 1.35 ml of 5% BSA in 0.14 M NaCl.…”