Aim:
Activated factor X (FXa) plays important roles in the thrombin generation and in inflammation, which is evoked during the endothelial damage. Although rivaroxaban is a selective FXa antagonist, it is one of the key therapies in ischemic heart disease, and yet its function in the state of inactivated coagulation cascade is uncertain. Rivaroxaban blocks FXa in the blood but not the tissue, while factor X is converted to FXa only when glutamic acid is changed to γ-carboxyglutamic acid by vitamin K following the intrinsic clotting factors and/or cellular injury activation. To uncover this aspect, we performed the following experiments.
Methods and results:
Human umbilical vein endothelial cells (HUVECs) were obtained from Lonza Co., Ltd. The cells were grown to 80% confluence and were treated with rivaroxaban (100nM, 500nM, 1000nM, 2000nM respectively) without FXa stimulation for 4 h, 10 h or 24 h. Cells and medium were collected and then their RNA was extracted from the cells. The qPCR of MCP-1, PAR1-4 and the DNA micro arrays (The GeneChip Human Gene 2.0 ST Array, Affymetrix) were performed. There was neither increased nor decreased gene expression significantly in either experimental time course of the qPCRs or the the DNA micro arrays. The ELISA assay of MCP-1 with medium showed non-activated MCP-1. As a next step, cells were treated with 100nM FXa and with/without rivaroxaban in same time course, and cells and medium were collected for further experiments. FXa evoked induction of mRNA levels for several pro-inflammatory cytokines including MCP-1 maximally at 4h, whereas MCP-1 was maximally evoked at 24 h in ELISA assay. Interestingly rivaroxaban inhibited both in all time course, at 4 hour inflammatory phase and at 24 hour inflammatory phase.
Conclusion:
Collectively, these results suggest that rivaroxaban may be safe in the inactivated coagulation state, and has the efficacy to attenuate the endothelial damage evoked by FXa and by pro-inflammatory cytokine genes.