Histones Induce the Procoagulant Phenotype of Endothelial Cells through Tissue Factor Up-Regulation and Thrombomodulin Down-Regulation

Abstract

The high circulating levels of histones found in various thrombotic diseases may compromise the anticoagulant barrier of endothelial cells. We determined how histones affect endothelial procoagulant tissue factor (TF) and anticoagulant thrombomodulin (TM). Surface antigens, soluble forms, and mRNA levels of TF and TM were measured by flow cytometry, ELISA, and real-time RT-PCR, respectively. TF and TM activity were measured using procoagulant activity, thrombin generation, or chromogenic assays. Involvement of the toll-like receptor (TLR) was assessed using the neutralizing antibodies. Histones dose-dependently induced surface antigens, activity and mRNA levels of endothelial TF. Histone-treated endothelial cells significantly shortened the lag time and enhanced the endogenous thrombin potential of normal plasma, which was normalized by a TF neutralizing antibody. Histones induced phosphatidylserine and protein-disulfide isomerase expression in endothelial cells. Histones also reduced the surface antigen, activity, and mRNA levels of endothelial TM. Polysialic acid and heparin reversed the histone-induced TF up-regulation and TM down-regulation. Activated protein C did not affect the TF up-regulation, but interrupted TM down-regulation. TLR2, and TLR4 inhibitors partially blocked the TF up-regulation. Histones induced the endothelial procoagulant phenotype through TF up-regulation and TM down-regulation. The effects of histones were partly mediated by TLR2, TLR4. Strategies to inhibit the harmful effects of histones in endothelial cells may be required in order to prevent a thrombotic environment.

Mechanisms of erosion of atherosclerotic plaques

“…4647 In addition, histones, elastase, and MPO-generated hypochlorous acid each induce endothelial TF production. 48495036 Supporting these in vitro studies, clinical data implicate NETs in coronary disease, venous thrombosis, and other thrombotic conditions. 51525354 Thrombi retrieved from the culprit arteries of ACS patients show higher levels of NET markers.…”

Neutrophil‐mediated vascular barrier injury: Role of neutrophil extracellular traps

“…106 Other therapeutic targets that have potential to address histone-dependent NET-mediated cytotoxicity include inter-alpha inhibitor protein, chondroitin sulfate, and high molecular weight hyaluronan for their ability to bind and neutralize histones. 107 Histones may also play a role in thrombosis by upregulating tissue factor and downregulating thrombomodulin, [108][109][110] or by stimulating the release of von Willebrand factor from the endothelium. 111 Together, histones remain a key effector in NET-mediated microvascular hyperpermeability, and more studies to elucidate downstream signaling mechanisms are needed to fully understand their role in disrupting the endothelial barrier.…”

Neutrophil extracellular trap components increase the expression of coagulation factors

“…To date, one of the sole proposed mechanisms implicated in TF expression induced by histones in monocytes is the activation of the TLR2-4/nuclear factor-κB pathway. In that report, it was demonstrated that the selective blockade of TLR2 or TLR4 inhibited the overexpression of TF following activation with H4, among other histones (13). Notably, the expression of TLR4 has been reported in hepatocytes and it may be implicated in the overexpression of hemostatic factors and/or HNF4α as well as TF (39).…”

“…The pathogenic role of histones in thrombosis was first proposed by showing that injection of histones in mice induced thrombotic lesions similar to those observed in severe sepsis (12). Indeed, histones have been reported to induce tissue factor (TF; also known as factor III) upregulation and thrombomodulin downregulation leading to a procoagulant phenotype, hence they are considered as damage-associated molecular patterns (DAMPs) (13). DAMPs are recognized as danger signals by Toll-like receptors (TLRs), but the molecular mechanism remains unclear (14)(15)(16).…”