A novel role for protein disulfide isomerase ERp18 in venous thrombosis.

Background: Previous studies using genetically modified mouse models and inhibitors have shown that protein disulfide isomerase (PDI) family plays a significant role in arterial thrombosis. However, their role in venous thrombosis remains unknown. In this study, using gene-modified mouse models, we determined whether PDI family members contribute to venous thrombosis.

Methods: Mice deficient of the PDI family members, including PDI, PDIp, ERp57, PDIr, ERp5, ERp27, ERp29, TMX4, ERdj5, and ERp18, were generated. The venous thrombosis phenotype of these deficient strains was evaluated using an inferior vena cava (IVC) stenosis model. Moreover, the recombinant human ERp18 (rhERp18) protein was generated and its reductase activity was assessed using a Di-E-GSSG method. The effect of ERp18 in venous thrombosis was tested in the IVC stenosis model. The levels of von Willebrand factor (vWF) at the site of venous thrombi were measured.

Results: The mice deficient in PDI, PDIp, ERp57, PDIr, ERp5, ERp27, ERp29, TMX4, and ERdj5 had no effects on venous thrombosis in the IVC stenosis model. However, the mice lacking ERp18 developed significantly less venous thrombosis compared with the WT mice. ERp18 contains one CGAC active motif. When WT or ERp18-KO mice received injection of rhERp18-WT or inactive rhERp18-mutant (Mut) protein whose CGAC was mutated to SGAS, rhERp18-Mut protein inhibited venous thrombosis in the IVC stenosis model, suggesting that the role of ERp18 is dependent on its enzymatic activity. As determined by enzyme-linked immunosorbent assay (ELISA) and immunofluorescence staining, the levels of vWF in the plasma at the site of venous thrombus in ERp18-KO mice were significantly lower than those in WT mice.

Conclusion: ERp18 enhances the development of venous thrombosis, and its function and its enzymatic activity and regulation of the vWF release are involved.