How does tissue factor pathway inhibitor inhibit coagulation?

How does tissue factor pathway inhibitor inhibit coagulation?

• A. Inhibition of tissue factor-factor VIIa-factor Xa complex
• B. Conversion of thrombin to prothrombin
• C. Uncoupling factor XIII dependent crosslinking of fibrin
• D. Binding and hiding tissue factor on the endothelial surface

Answer: (A)

Tissue factor pathway inhibitor acts as a brake on the initiation of coagulation by targeting the extrinsic pathway. It binds to the tissue factor–FVIIa complex and, with the help of FXa, forms a inhibited complex that prevents activation of factor X. By blocking the TF–FVIIa complex, TFPI stops the formation of factor Xa and the subsequent burst of thrombin generation that would normally drive clot formation. In other words, TFPI directly inhibits the tissue factor–FVIIa activity (and its collaboration with FXa) to shut down the extrinsic tenase step at the start of coagulation. The other options describe processes TFPI does not mediate: reversing thrombin, interfering with fibrin crosslinking by FXIII, or simply hiding tissue factor on the endothelium.

Tissue factor pathway inhibitor acts as a brake on the initiation of coagulation by targeting the extrinsic pathway. It binds to the tissue factor–FVIIa complex and, with the help of FXa, forms a inhibited complex that prevents activation of factor X. By blocking the TF–FVIIa complex, TFPI stops the formation of factor Xa and the subsequent burst of thrombin generation that would normally drive clot formation. In other words, TFPI directly inhibits the tissue factor–FVIIa activity (and its collaboration with FXa) to shut down the extrinsic tenase step at the start of coagulation. The other options describe processes TFPI does not mediate: reversing thrombin, interfering with fibrin crosslinking by FXIII, or simply hiding tissue factor on the endothelium.