The procoagulant phospholipid dependent clotting time and the initiation phase of thrombin generation test are mandatory for the evaluation of the risk for severe early onset preeclampsia

Thrombin cleaves membrane-bound endoglin potentially contributing to the heterogeneity of circulating endoglin in preeclampsia

Increased levels of soluble endoglin (sEng) are found in serum, plasma, and urine of preeclampsia patients. sEng is released from membrane-bound endoglin through the proteolytic activity of metalloproteases, but its structural heterogeneity suggests the involvement of additional proteases. Considering the roles of thrombin and sEng in preeclampsia pathogenesis, we investigated whether thrombin cleaves endoglin. Sequence analysis revealed a conserved peptide in endoglin similar to the α-thrombin cleavage site of protease-activated receptor-1. Western blot analysis of plasma from preeclamptic women showed endoglin fragments consistent with thrombin-mediated cleavage. Incubation of purified endoglin with thrombin generated specific fragments, whose N- and C-terminal sequencing confirmed the predicted cleavage sites. Furthermore, thrombin treatment of endoglin-expressing cells released sEng and reduced cell surface endoglin. These findings suggest that multiple protease-targeted cleavage sites lead to the generation of sEng fragments, which may reflect endothelial dysfunction and preeclampsia progression.

Increased contact activated endogenous thrombin potential in pregnant women with preeclampsia

Preeclampsia is a worldwide contributor to maternal and fetal morbidity and mortality. Women with preeclampsia are in a hyper-coagulable state with increased risk of thromboembolic disease later in life compared with normal pregnant women. The contact system (CAS) in plasma can mediate thrombin generation and is an important contributor to thrombus growth, but the activation of CAS during pregnancy complicated by preeclampsia is not yet elucidated, and CAS may play a role in the pathophysiology of preeclampsia. Therefore, the aim of the study is to address thrombin generation, and in particular, the capacity of the CAS-mediated pathway in patients with preeclampsia compared with pregnant controls. One hundred and seventeen women with preeclampsia and matched controls were included. The project was registered at www.clinicaltrials.gov as NCT04825145. CAS and tissue factor induced thrombin generation, proteins C and S, antithrombin, and histidine-rich glycoprotein (HRG) were assessed. Women with preeclampsia had significantly increased CAS and tissue factor-induced endogenous thrombin potential (ETP), and HRG compared with controls, P  = 0.022, P  = 0.024, and P  = 0.02, respectively. The concentrations of protein C and antithrombin were significantly reduced in the preeclampsia group, P  = 0.024 and P  < 0.0001, respectively. No significant difference in the concentration of protein S was detected, P  = 0.06. This study demonstrates a significant increased CAS-induced ETP and an overall decrease of important regulators of coagulation in women with preeclampsia compared with controls. These aspects can contribute to the hyper-coagulable state characterizing preeclampsia.