Journal of Lipid Research, Vol 29, 1379-1385, Copyright © 1988 by Lipid Research, Inc.
Bacterial lipopolysaccharide reduces macrophage lipoprotein lipase levels: an effect that is independent of tumor necrosis factor
JR White, A Chait, SJ Klebanoff, S Deeb and JD Brunzell
Department of Medicine, University of Washington, Seattle 98195.
Human monocyte-derived macrophages secrete lipoprotein lipase (LPL) in
culture. The regulation of human macrophage LPL production is poorly
understood. Since bacterial lipopolysaccharide (LPS) alters production of
several macrophage secretory products, its effect on human monocyte-
derived macrophage LPL was tested. LPS treatment produced a dramatic
dose-dependent decrease in LPL activity in macrophage-conditioned media. At
100 ng/ml LPS, medium LPL activity dropped by 60%. The effect of LPS on
macrophage LPL activity was rapid, was blocked by polymixin B, and was not
due to cytotoxicity. LPS lowers (by about 60%) the steady state level of
LPL mRNA, suggesting that its effect is exerted at the level of mRNA
metabolism. Since LPS stimulates macrophage production of cachectin/tumor
necrosis factor (TNF), a potent inhibitor of LPL production by the 3T3-L1
adipocyte-like cell line, it was determined whether TNF reduces macrophage
LPL levels. Treatment of human macrophages with up to 1000 U/ml of
recombinant human TNF had no effect on macrophage LPL activity. When TNF
was added in combination with LPS, no additional effect on LPL activity was
observed over that seen with LPS alone. Furthermore, the LPS effect was not
blocked by a monoclonal anti-TNF antibody. Thus, bacterial LPS potently
decreases macrophage LPL activity and mass independent of an autocrine
effect of TNF.