ROLE OF NITROGEN IN RED BLOOD CELL ADHESION AND AGGREGATION IN SICKLE CELL DISEASE

Sickle cell disease (SCD) is a genetic hemoglobinopathy characterized by the polymerization of hemoglobin S, leading to the formation of rigid, sickled red blood cells (RBCs). These abnormally shaped cells have an increased tendency to adhere to the vascular endothelium and aggregate, which contributes to microvascular occlusions and the onset of vaso-occlusive crises. Nitric oxide (NO), a crucial molecule for maintaining vascular homeostasis, plays a significant role in regulating RBC adhesion and aggregation. In SCD, the reduced bioavailability of NO due to hemolysis and oxidative stress exacerbates endothelial dysfunction, promoting increased RBC adhesion to the endothelium and enhancing aggregation. In healthy individuals, NO inhibits RBC-endothelial adhesion by modulating the expression of adhesion molecules and promoting vasodilation. However, in SCD, decreased NO levels lead to a pro-adhesive and pro-aggregatory state within the microvasculature. This review explores the role of NO and other nitrogen species in modulating RBC adhesion and aggregation in SCD, highlighting the biochemical mechanisms involved, including the effects of oxidative stress and the formation of peroxynitrite. These disruptions contribute significantly to the pathophysiology of SCD, leading to clinical manifestations such as pain crises, stroke, and organ damage.