Third Annual Sickle Cell Disease Research and Educational Symposium and Grant Writing Institute and Annual National Sickle Cell Disease Scientific Meeting
Authors: Anna Solovey, Rahn Kollander, Liming Milbauer, Robert Kelm, Robert Hebbel, Mr Oke, B Abolek, Yinka Olayonu, Cecelia Valrie, Karen Gil, Rupa Redding-Lallinger, Charles Daeschner, Theodosia Kalfa, Suvarnamala Pushkaran, Xiuli An, Natalie Collias, Clinton Joiner, Narla Mohandas, Yi Zheng, Jeffrey Lebensburger, Tamara Pestina, Kelli Boyd Dvm, Russell Ware, Derek Persons
Journal: American Journal of Hematology (2009)

Clinical sickle cell anemia is accompanied by abnormal activation of the coagulation system.Studying the sickle transgenic mouse, we previously observed abnormal expression of tissue factor (TF) by the vascular endothelium of the pulmonary veins, an indication of an extreme level of endothelial cell activation in vivo.This was evident in the severe-phenotype sickle mouse (BERK and even hBERK) at ambient air, and in the mild-phenotype sickle mouse (NY1DD) only after exposure to hypoxia/reoxygenation (H/R); in contrast, H/R had no effect on the normal mouse.We now have used various agents and approaches to identify the critical role of inflammation in causing this abnormal tissue factor expression.We found that multiple inhibitors (some specific) of NFkB, the preeminent transcriptional regulator of inflammation, significantly diminished TF expression in the NY1DD H/R model: andrographolide (P<.001), curcumin (P<.001), isohelenin (P<.001), sulfasalazine (P<.05), didox and trimidox (P<.001), and lovastatin (P<.001); hydroxyurea had no effect.In addition, we have bred the NF Bp50-/-knockout state into the NY1DD sickle mouse to identify the basis for tissue factor expression.Combined with marrow transplantation, so that marrow versus vessel wall genotypes can be "mixed and matched," we found that endothelial tissue factor expression in the sickle mouse is primarily dependent upon inflammation.For example, the NF Bp50-/-NY1DD mouse showed complete inhibition of TF expression after H/R (P<.01).When the NF Bp50-/-state was limited to the vessel wall in the sickle mouse, it totally failed to inhibit TF expression; however, when the knockout state was limited to the blood cells, TF inhibition was marked (P<.001).This indicates that it is blood cell NF Bp50 that is critical in endothelial TF expression.Consistent with this, when we infused naïve, unstressed NY1DD sickle mice with peripheral blood monocytes derived from post-H/R NY1DD mice, endothelial TF expression is significantly stimulated (P<.001); control infusion of monocytes from a naïve NY1DD mouse at air did not stimulate TF expression.Additionally, knocking in overexpression of the eNOS transgene in NY1DD sickle mouse, or giving NY1DD mice ad libitum arginine in their drinking water, both significantly diminished endothelial TF expression that had been stimulated by H/R (P<.01, and P<.001, respectively).This arginine treatment was also tested in the more severe hBERK mouse (which exhibitis abnormal TF expression even without any H/R stress): again, arginine significantly decreased TF expression (P<.01).These results support the idea that inflammation induced changes in monocytes, in turn, stimulate vessel wall endothelial cells to abnormally express TF.Insofar as TF expression contributes to sickle disease pathobiology (e.g., to stroke risk), our results identify NO and several anti-inflammatory agents as drugs of potential therapeutic benefit in clinical sickle disease.