Tissue factor haploinsufficiency during endotoxin induced coagulation and inflammation in mice

Intervention studies blocking tissue factor (TF) driven coagulation show beneficial effects on survival in endotoxemia models by reducing cytokine production. It is unknown, however, if moderately reduced TF levels influence endotoxemia. The objective was to investigate whether TF haploinsufficiency reduces endotoxin-induced cytokine production in murine cells or in mice. We analyzed the intrinsic capacity of heterozygous TF deficient (TF+/-) leukocytes to produce cytokines. In addition, we determined the consequences of TF haploinsufficiency on endotoxin-induced inflammation during murine endotoxemia. Endotoxin induced the production of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6 and keratinocyte-derived chemokine (KC) in both whole blood and macrophages. Heterozygous TF deficiency reduced endotoxin induced IL-6 and KC levels about two-fold, while TNF-alpha levels were indistinguishable between TF+/- and wild-type cells. In vivo, endotoxin induced a biphasic coagulant response and significant increases in cytokine levels. Surprisingly, both the inflammatory and the coagulant responses were indistinguishable between wild-type and TF+/- mice. At baseline tissues of TF+/- mice showed a 50% reduction in TF activity compared to wild type. Upon endotoxin administration, TF activity increased and the difference between TF+/- and wild-type mice disappeared after 4 h. After 12 h the baseline difference in TF activity was re-established. TF deficiency reduces cytokine production in vitro, but an enhanced induction of TF during murine endotoxemia eliminates this effect in vivo.