Inhibition of plasmin activity by tranexamic acid does not influence inflammatory pathways during human endotoxemia

Objective - Plasmin activates several proinflammatory pathways at the cellular level in vitro. Lipopolysaccharide (LPS) administration to healthy humans results in a rapid generation of plasmin activity, accompanied by activation of a number of inflammatory systems. Methods and Results - To determine the role of early plasmin activity in LPS-induced inflammation in vivo, 16 healthy males received an intravenous bolus injection with LPS (from Escherichia coli, 4 ng/kg) directly preceded by a 30-minute intravenous infusion of tranexamic acid (2 g, n = 8), a plasmin activation inhibitor, or placebo (n = 8). LPS injection induced marked increases in the plasma levels of D-dimer and plasmin-alpha2-antiplasmin complexes, indicative of plasmin activation and generation, respectively, which were strongly attenuated by tranexamic acid (both P <0.01 versus placebo). However, tranexamic acid did not influence LPS-induced coagulation activation, granulocytosis, neutrophil activation (expression of CD11b, CD66b, and L-selectin) or degranulation (plasma concentrations of elastase-α1-antitrypsin and bactericidal permeability-increasing protein), endothelial cell activation (plasma levels of von Willebrand factor and soluble E-selectin), or cytokine release. Conclusion - These data argue against a role of early plasmin generation in the subsequent activation of other inflammatory pathways during human endotoxemia