Polynitroxyl Albumin Prevents Vaso-Occlusion in Transgenic Sickle Mice.

Abstract

Sickle cell disease is characterized by excessive oxidative stress. Sickle patients have enhanced rates of endogenous reactive oxygen species (ROS) production and impaired antioxidant defense mechanisms. We hypothesize that excessive production of ROS promotes activation of vascular endothelium and vaso-occlusion in sickle cell disease. Intravascular ROS production has been shown to trigger the activation of vascular endothelium and increase leukocyte-endothelium interactions. We investigated whether inhibition of intravascular ROS production by treatment with polynitroxyl albumin (PNA), a superoxide dismutase and catalase mimetic agent, could modulate endothelial cell activation and vaso-occlusion in S+S Antilles transgenic sickle mice after hypoxia-reoxygenation. Nuclear factor-kappa B (NF-kB), an oxidant sensitive transcription factor critical for endothelial cell activation, was elevated in lungs and livers of sickle mice and was reduced 2.5 (p=0.043) and 1.5 (p=0.043) fold respectively, by treatment with PNA after hypoxia-reoxygenation. Similarly, vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) were elevated 3 to 4.7 fold in the same organs (p<0.05). After treatment with PNA, VCAM-1 expression was reduced 2.3 fold in lungs (p=0.014) and 1.5 fold in livers (p=0.006), ICAM-1 expression decreased 1.7 fold in lungs (p=0.014) and 2 fold in livers (p=0.007). Control studies using human serum albumin had no effect on NF-kB activation or adhesion molecule expression in sickle mice. These anti-inflammatory effects of PNA on endothelium corresponded with changes in blood flow in dorsal skin venules. Intravital microscopy revealed that PNA significantly inhibited hypoxia-reoxygenation-induced leukocyte rolling (3.8 fold inhibition, p<0.001) and completely inhibited vaso-occlusion (p<0.001) in venules in the dorsal skin of transgenic sickle mice. We speculate that therapies that reduce ROS will result in improved organ perfusion in sickle cell disease.