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Preferential Efflux of Phytosterols over Cholesterol from Macrophages
Author(s) -
Hovenkamp E.,
Lourbakos A.,
Duchateau G. S. M. J. E.,
Tareilus E. W.,
Trautwein E. A.
Publication year - 2007
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-007-3119-4
Subject(s) - lipidology , efflux , clinical chemistry , cholesterol , chemistry , biochemistry , food science , environmental chemistry
Phytosterols are structurally similar to cholesterol. Increased dietary intake of phytosterols effectively lowers LDL‐cholesterol. Since phytosterols are incorporated in a growing number of foods and some of the ingested phytosterols reach the circulation, accumulation of phytosterols in foam‐cell‐prone cells such as macrophages might occur. Therefore we examined the influx and efflux of phytosterols by human THP‐1 macrophages. The influx rates of methyl‐β‐cyclodextrin delivered phytosterols did not significantly differ from that of cholesterol (~3.8 pmol/min per mg cellular protein), neither did the total influx of oxidised LDL delivered phytosterols differ from that of cholesterol. The efflux of β‐sitosterol and sitostanol from preloaded THP‐1 cells to HDL was more efficient than the efflux of campesterol and cholesterol (rate constants of 0.41 ± 0.04/h, 0.62 ± 0.08/h, 0.23 ± 0.05/h and 0.29 ± 0.03/h, respectively). The efflux of β‐sitosterol was not associated with a dominant transfer to ApoA‐I, nor did ABCA1 induction‐promoted cholesterol efflux to the level observed for β‐sitosterol. Our data show that THP‐1 macrophages take up phytosterols, but have efficient mechanisms to remove phytosterols from their cellular compartments. Consequently, it is less likely that macrophages preferentially accumulate phytosterols over cholesterol and hence promote foam‐cell formation in vivo.