Peroxynitrite Decreases Rabbit Tissue Factor Activity In Vitro

Tissue factor (TF) is a primary initiator of physiological coagulation in vivo. Peroxynitrite (OONO^-), a molecule formed from nitric oxide (NO) and superoxide (O₂ · ^-), decreases human TF activity in vitro. Coagulopathy has been associated with hepatoenteric ischemia-reperfusion known to involve formation of OONO^-. Further, circulating TF activity decreases in rabbits after hepatoenteric ischemia-reperfusion. We hypothesized that exposure of rabbit TF to OONO ^- would result in a decrease in activity. OONO^- generation was performed with 3-morpholinosydnonimine (SIN-1), a molecule that produces both nitric oxide and superoxide. Rabbit brain TF was incubated at 37°C for 90 min with 1) 0 mM SIN-1, 2) 5 mM SIN-1, 3) 5 mM SIN-1 and 2000 U/mL recombinant human superoxide dismutase (hSOD1), or 4) 2000 U/mL hSOD1 (n = 8 per condition). TF activity was assessed by addition of TF samples to human plasma and measuring clot formation kinetics with a thrombelastograph®. TF exposure to SIN-1 resulted in a 48% decrease in activity that was significantly different from the other three conditions (P < 0.001). There were no significant differences between the other conditions. We conclude that rabbit TF is inhibited by OONO^-, and further investigation to determine the role of OONO^- in coagulopathies associated with hepatoenteric ischemia-reperfusion is warranted.