bay-73-6691 and Acute-Disease

Inhibition of leukocyte adhesion to the vascular endothelium represents a novel and important approach for decreasing sickle cell disease (SCD) vaso-occlusion. Using a humanized SCD-mouse-model of tumor necrosis factor-α-induced acute vaso-occlusion, we herein present data demonstrating that short-term administration of either hydroxyurea or the phosphodiesterase 9 (PDE9) inhibitor, BAY73-6691, significantly altered leukocyte recruitment to the microvasculature. Notably, the administration of both agents led to marked improvements in leukocyte rolling and adhesion and decreased heterotypic red blood cell-leukocyte interactions, coupled with prolonged animal survival. Mechanistically, these rheologic benefits were associated with decreased endothelial adhesion molecule expression, as well as diminished leukocyte Mac-1-integrin activation and cyclic guanosine monophosphate (cGMP)-signaling, leading to reduced leukocyte recruitment. Our findings indicate that hydroxyurea has immediate beneficial effects on the microvasculature in acute sickle-cell crises that are independent of the drug's fetal hemoglobin-elevating properties and probably involve the formation of intravascular nitric oxide. In addition, inhibition of PDE9, an enzyme highly expressed in hematopoietic cells, amplified the cGMP-elevating effects of hydroxyurea and may represent a promising and more tissue-specific adjuvant therapy for this disease.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Acute Disease; Anemia, Sickle Cell; Animals; Antisickling Agents; Cell Adhesion; Cell Communication; Cyclic GMP; Disease Models, Animal; Endothelium, Vascular; Erythrocytes; Female; Humans; Hydroxyurea; Leukocyte Rolling; Leukocytes; Male; Mice; Mice, Inbred C57BL; Pyrazoles; Pyrimidines; Tumor Necrosis Factor-alpha; Vascular Diseases