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Inhibition of tissue-factor-mediated thrombin generation by simvastatin
D Ferro1, S Basili, C Alessandri
1Istituto di I Clinica Medica, Università 'La Sapienza', Policlinico Umberto I, 00185, Rome, Italy.
Insights
Simvastatin directly inhibits thrombin generation by reducing monocyte tissue factor (TF) expression. This study demonstrates a direct mechanism beyond cholesterol reduction for simvastatin's anti-clotting effects.
Area of Science:
- Cardiovascular pharmacology
- Hematology
- Immunology
Background:
- Previous research indicates simvastatin reduces clotting and monocyte tissue factor (TF) expression in vivo.
- The exact mechanisms, particularly the direct impact on clotting activation independent of cholesterol, remain unclear.
Purpose of the Study:
- To investigate if simvastatin directly impacts clotting activation.
- To determine if simvastatin's inhibition of clotting activation is dependent on reduced monocyte TF expression.
Main Methods:
- Developed an in vitro method using LPS-stimulated monocytes to activate the clotting system.
- Measured thrombin generation (prothrombin fragment F1+2) and monocyte TF expression in response to simvastatin treatment.
Main Results:
- Simvastatin dose-dependently inhibited thrombin generation (F1+2 formation) in LPS-stimulated monocytes.
- Simvastatin also dose-dependently inhibited the expression of TF by monocytes.
Conclusions:
- Simvastatin directly inhibits the rate of thrombin generation.
- This inhibition is achieved by interfering with monocyte tissue factor (TF) expression.
Abstract:
A previous study has shown that simvastatin reduces in vivo clotting activation and monocyte tissue factor (TF) expression. This effect, however, was only in part attributable to the reduction of serum cholesterol, suggesting that more than one mechanism may be involved. Furthermore, it was not investigated if the inhibition of clotting activation was dependent upon the reduced expression of monocyte TF. In order to assess if simvastatin directly affects clotting activation, we developed an in vitro method in which clotting system is activated by monocytes stimulated with LPS. Monocytes were prepared from blood taken from healthy volunteers or patients with hypercholesterolemia and incubated with heparinized plasma plus either simvastatin (0.01-10 microM) or medium as control. Samples were then stimulated with LPS (4 microg/ml) and after 6 h the rate of thrombin generation, assessed by prothrombin fragment (F) 1+2, was measured. In separate experiments, we measured the expression of TF by monocytes which were incubated with simvastatin and then stimulated with LPS. The study showed that compared to control, LPS-stimulated monocytes induced abundant formation of F1+2, which was inhibited by simvastatin in a dose-dependent manner. Simvastatin also inhibited dose dependently the monocyte expression of TF. This study suggests that simvastatin inhibits the rate of thrombin generation by directly interfering with the monocyte expression of TF.