Lipoproteins do not modulate the tissue factor activity, plasminogen activator or tumour necrosis factor production induced by lipopolysaccharide stimulation of human monocytes

Upon stimulation with lipopolysaccharides (LPS), monocytes are able to produce tissue factor (TF), the most powerful physiological procoagulant substance known. In several assay systems LPS bound to lipoprotein has been reported to be less active than unbound LPS in stimulating monocytes. In the present study the LPS-induced TF activity was, however, not prevented by lipoproteins (VLDL, LDL, HDL). In fact, the very low density (VLDL) fraction further increased the TF inducing capacity of LPS. The lipoproteins per se mediated reduced plasminogen activator (PA) production in monocytes. LPS had an even more and significant depressing effect on PA production, which was not further decreased in the presence of lipoproteins. Furthermore, LPS-induced release of tumour necrosis factor (TNF), a marker of monocyte activity, was not inhibited by lipoproteins. Our experiments suggest that lipoproteins do not render LPS less effective in stimulating TNF release, procoagulant and fibrinolytic activities in human monocytes.