Oxidative stress activates red cell adhesion to laminin in sickle cell disease

Vaso-occlusive crises are the hallmark of sickle cell disease (SCD). They are believed to occur in two steps, starting with adhesion of deformable low-dense red blood cells (RBC), or other blood cells such as neutrophils, to the wall of post-capillary venules, followed by trapping of denser RBC or leukocytes in the areas of adhesion because of reduced effective lumen-diameter. In SCD, RBC are heterogeneous in terms of density, shape, deformability and surface proteins, which accounts for the differences observed in their adhesion and resistance to shear stress. Sickle RBC exhibit abnormal adhesion to laminin mediated by Lu/BCAM protein at their surface. This adhesion is triggered by Lu/BCAM phosphorylation in reticulocytes but such phosphorylation does not occur in mature dense RBC despite firm adhesion to laminin. In this study, we investigated the adhesive properties of sickle RBC sub-populations and addressed the molecular mechanism responsible for the increased adhesion of dense RBC to laminin in the absence of Lu/BCAM phosphorylation. We provide evidence for the implication of oxidative stress in post-translational modifications of Lu/BCAM that impact its distribution and cis-interaction with glycophorin C at the cell surface activating its adhesive function in sickle dense RBC.