Nuclear factor-kappa B (NFκB) component p50 in blood mononuclear cells regulates endothelial tissue factor expression in sickle transgenic mice: implications for the coagulopathy of sickle cell disease

Sickle cell anemia is accompanied by the activation of coagulation and thrombosis. We have studied the abnormal expression of tissue factor (IF) by the pulmonary vein endothelium of the mild-phenotype NY1DD sickle transgenic. As detected by immunofluorescence microscopy, this occurs only after the NY1DD mouse is exposed to hypoxia/reoxygenation (H/R), which actually causes ischemia/reperfusion in the sickle cell disease but not the normal mouse model. We tested the hypothesis that the nuclear factor-kappa B (NF kappa B)-activating inflammation that develops in post-H/R NY1DD mice is responsible for this phenotype switch. Various NF kappa B inhibitors (including p50-specific andrographolide) demonstrated that endothelial IF positivity is NF kappa B dependent. Several systemic inflammatory stimulators (tumor necrosis factor (TNF alpha), lipopolysaccharide, thioglycollate, and carageenan) given to control mice showed that the inflammatory promotion of TF expression by only pulmonary vein endothelium is not specific to the sickle cell disease model. We bred the NF kappa B(p50)-/- state into the NY1DD mouse. Combined with marrow transplantation, this allowed the creation of NY1DD mice that were NF kappa B(p50)-/-only in peripheral blood cells (and marrow) versus only in vessel walls (and tissues). This process revealed that endothelial TF expression in the NY1DD mouse is highly dependent on NF kappa B(p50) in peripheral blood mononuclear cells but not in the vessel wall. In confirmation, the infusion of post-H/R sickle mouse blood mononuclear cells into naive NY1DD mice stimulated endothelial IF expression; the infusion of such cells from unstimulated sickle cell disease mice at ambient air did not stimulate IF expression. We conclude that peripheral blood mononuclear cells indirectly promote endothelial IF expression via a NF kappa B(p50)-dependent mechanism. This approach may be relevant to the role of coagulopathy in clinical sickle cell disease. (Translational Research 2010;155:170-177)