Abstract 5484: Activation of Endothelial NF- κ B Signaling Promotes Coagulation by Inhibiting Protein C Anticoagulant Mechanism in Endotoxemic Mice

Abstract

Although the role of systemic activation of NF- κ B pathway in septic coagulation has been well documented, little is known about the mechanistic contribution of endothelial intrinsic NF- κ B signaling in this pathological process. This study defined the causative role of endothelial NF- κ B signaling in septic coagulation. Wild type (WT) and transgenic mice (TG) that conditionally overexpress a mutant I- κ B β , an inhibitor of NF- κ B, selectively on endothelium, were injected with saline (1 ml/kg, i.p.) or E Coli LPS (5 mg/kg, i.p.). Tissue fibrin deposition, plasma markers of coagulation, plasma levels of protein C and plasminogen activator inhibitor-1 (PAI-1) were measured at 6 hours after LPS injection. Immunohistochemical staining of frozen tissue sections of heart, liver and kidney from WT-LPS mice showed a widespread tissue fibrin deposition. Fibrin deposition was not evident in tissue sections of the three organs from TG-LPS mice. Compared with WT-Con and TG-Con mice, WT-LPS mice showed a 79% reduction in plasma fibrinogen level, which was restored to control level in TG-LPS mice. WT-LPS displayed 13.7- and 3.2-fold increase in plasma levels of thrombin-antithrombin and D-dimer, which were reduced by approximately 69% and 37% in TG-LPS mice. Plasma levels of total and activated protein C (mO.D. units) for WT-Con, TG-Con, WT-LPS and TG-LPS groups were: 73.4±2.4, 72.0±3.2, 26.0±6.2 and 58.5±4.7 (p < 0.01, WT-LPS vs other 3 groups), and 45.6±1.6, 43.0±1.2, 2.8±1.8 and 29.9±4.1 (p < 0.01, WT-LPS vs other 3 groups). Plasma level of PAI-1 (ng/ml) for WT-Con, TG-Con, WT-LPS and TG-LPS groups was 0.06±0.05, 0.0±0.0, 31.3±4.8 and 18.1±3.3 (p < 0.05, WT-LPS vs other 3 groups). These results indicate that endothelial intrinsic NF- κ B signaling plays a pivotal role in the activation of coagulation in endotoxemic mice, and suggest that activation of endothelial NF- κ B pathway promotes coagulation by impairing the protein C anticoagulant mechanism and by inhibiting the fibrinolytic system. (Supported by NIH R01GM063907).