Background — Excessive production of nitric oxide (NO) by the inducible isoform of NO synthase (iNOS) is critically involved in endotoxin (ET)-induced hypotension. Tumor necrosis factor-α (TNF-α) plays an important role in induction of iNOS. Because activated protein C (APC), a physiological anticoagulant, inhibits TNF-α production, it might prevent hypotension by inhibiting excessive production of NO. In this study, we examined this possibility using a rat model of septic shock. Methods and Results — Intravenous administration of APC prevented both ET-induced hypotension and the increases in plasma levels of NO 2 − /NO 3 − . The hypotension was also inhibited when APC was administered 30 minutes after ET administration. APC inhibited the increases in lung levels of iNOS activity by inhibiting expression of iNOS mRNA in animals given ET. APC significantly inhibited the increases in lung tissue levels of TNF-α and expression of TNF-α mRNA in animals given ET. Neither DEGR-F.Xa, a selective inhibitor of thrombin generation, nor DIP-APC, an active site-blocked APC, showed any effect on these ET-induced changes. Both inhibition of TNF-α production by leukocytopenia and treatment with anti-rat TNF-α antibody produced effects similar to those induced by APC. Aminoguanidine, a selective inhibitor of iNOS, inhibited both the hypotension and the increases in plasma levels of NO 2 − /NO 3 − in this animal model. Conclusions — These observations strongly suggest that APC inhibits iNOS induction by decreasing TNF-α production, leading to the prevention of ET-induced hypotension. Furthermore, such effects of APC were not dependent on its anticoagulant effects but rather on its serine protease activity.

Child-Pugh class C and a large splenic infarction volume are risk factors for complications after PSE for liver cirrhosis.

Tissue factor pathway inhibitor (TFPI) is an important physiologic inhibitor of the extrinsic pathway of the coagulation system. We investigated whether recombinant TFPI (rTFPI) could reduce pulmonary vascular injury by inhibiting leukocyte activation in rats given lipopolysaccharide (LPS). Pre- or posttreatment of animals with rTFPI significantly inhibited LPS-induced pulmonary vascular injury, as well as coagulation abnormalities. rTFPI significantly inhibited increases in lung tissue levels of tumor necrosis factor (TNF)-alpha, cytokine-induced neutrophil chemoattractant, and myeloperoxidase. Expression of TNF-alpha messenger RNA in the lung after LPS administration was significantly reduced by rTFPI administration. However, neither DX-9065a, a selective inhibitor of Factor Xa, nor recombinant Factor VIIa treated with dansyl-glutamylglycylarginyl-chloromethyl ketone, a selective inhibitor of Factor VIIa, had any effects on LPS-induced pulmonary vascular injury despite their potent anticoagulant effects. rTFPI significantly inhibited TNF-alpha production by LPS-stimulated monocytes in vitro. rTFPI also significantly inhibited several formyl-Met-Leu-Phe-induced neutrophil functions, as well as increases in the expression of CD11b and CD18 on the neutrophil cell surface in vitro. Additionally, rTFPI inhibited increases in levels of intracellular calcium, a second messenger of neutrophil activation, in formyl-Met-Leu-Phe-stimulated neutrophils in vitro. These results strongly suggested that rTFPI reduces pulmonary vascular injury by inhibiting leukocyte activation, as well as coagulation abnormalities in rats given LPS.

MCP-1 production by macrophages is stimulated by neutrophil elastase and oxygen radicals generated by hypoxia, probably due to microthrombus formation after ischemia/reperfusion of the rat liver.