Endothelial function in patients with sickle cell anemia during and after sickle cell crises

Prior studies have demonstrated increased adherence of sickle cell erythrocytes to vascular endothelial cells. While decreased production of nitric oxide and increased production of adhesion molecules have been implicated in this pathophysiology, the relative contribution of these mechanisms during acute sickle cell crises as compared to steady state conditions have not been elucidated.

We studied 10 consecutive young adult patients presenting with a sickle cell crisis. Endothelial function was evaluated by a non-invasive brachial artery shear stress method. Serum levels of adhesion molecules were obtained during the crisis. Both brachial artery responsiveness and serum levels of adhesion molecules were then repeated at steady state. Ten age and gender matched volunteers served as a control group. Impaired endothelial function and impaired endothelium-independent vasodilatation were observed in all sickle cell patients during both steady state and during crisis. Flow mediated dilation (FMD)% was 3.25+/- 2.76% during crisis, 4.57+/- 4.11 at steady state, compared with the control group FMD of 11.64+/- 7.69% (p< 0.001). Flow independent dilation was 10.35+/- 11.3% during crisis, 10.03+/- 6.52% at steady state, compared with control group FID of 24.17+/- 11.87% (p< 0.001). Levels of cell adhesion molecules and markers of inflammation were increased in sickle cell crisis patients compared with the control group: sCD40 ligand levels during the acute crisis were over twice the level of normal matched volunteers (p=0.02), and similarly significant increases were seen for E-selectin (p=0.008), ICAM-1 (p=0.037) and VCAM-1 levels (p=0.01). The levels of each of these biomarkers was not significantly increased during acute crises as compared to patients' recovery state.

Sickle cell anemia patients have severe systemic endothelial dysfunction as demonstrated by both brachial artery assessment and increased serum levels of adhesion molecules. These abnormalities characterize not only the sickle cell crisis but also the steady state pathophysiology of sickle cell anemia.