Endothelial-dependent S-Sulfhydration of tissue factor pathway inhibitor regulates blood coagulation

Tissue factor pathway inhibitor (TFPI) is an important regulator of coagulation and a link between inflammation and thrombosis. Here we investigated whether endothelial cell-driven oxidative post-translational modifications could have an impact on TFPI activity. We focused on S-sulfhydration, which is a hydrogen sulfide-dependent post-translational modification that, in endothelial cells, is regulated by the enzyme cystathionine γ-lyase (CSE). The study made use of human primary endothelial cells and blood from healthy individuals or subjects with atherosclerosis as well as from mice lacking endothelial CSE. TFPI was S-sulfhydrated in endothelial cells from healthy individuals and mice, while the loss of endothelial CSE expression/activity reduced its modification. Non-S-sulfhydrated TFPI was no longer able to interact with factor Xa, which facilitated the activation of tissue factor. Similarly, non-S-sulfhydratable TFPI mutants bound less protein S, while supplementation with hydrogen sulfide donors, preserved TFPI activity. Phenotypically, loss of TFPI S-sulfhydration increased clot retraction, suggesting that this post-translational modification is a new endothelial cell-dependent mechanism that contributes to the regulation of blood coagulation.