Vastatins inhibit tissue factor in cultured human macrophages - A novel mechanism of protection against atherothrombosis

We examined the effect of fluvastatin, the first entirely synthetic 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor that is structurally different from other vastatins, on tissue factor (TF) expression in human macrophages spontaneously differentiated in culture from blood monocytes. Fluvastatin decreased TF activity in a dose-dependent manner (1 to 5 mu mol/L) in both unstimulated and lipopolysaccharide-stimulated macrophages, and this reduction paralleled the decrease in immunologically recognized TF protein. The same results were obtained with another lipophilic vastatin, simvastatin, but not with hydrophilic pravastatin. The reduction in TF expression was also observed in macrophages enriched in cholesterol after exposure to 50 mu g/mL acetylated low density lipoprotein. The inhibitory effect of fluvastatin on TF activity and antigen was fully reversible by coincubation with 100 mu mol/L mevalonate or 10 mu mol/L all-trans-geranylgeraniol but not with dolichol, farnesol, or geraniol. Suppression of TF antigen and activity was accompanied by a diminution in TF mRNA levels, which was completely prevented by mevalonate. Furthermore, fluvastatin impaired bacterial lipopolysaccharide-induced binding of c-Rel/p65 heterodimers to a kappa B site in the TF promoter, indicating that this drug influences induction of the TF gene. We conclude that lipophilic vastatins inhibit TF expression in macrophages, and because this effect is prevented by mevalonate and geranylgeraniol, a geranylgeranylated protein plays a crucial role in the regulation of TF biosynthesis. The suppression of TF in macrophages by vastatins indicates a potential mechanism by which these drugs interfere with the formation and progression of atherosclerotic plaque as well as thrombotic events in hyperlipidemic patients.