VCAM1, HMOX1 and NOS3 differential endothelial expression may impact sickle cell anemia vasculopathy

Endothelial dysfunction plays a major role in sickle cell anemia (SCA) systemic vasculopathy, with upregulation of adhesion molecules (e.g., VCAM-1), decreased nitric oxide bioavailability, and oxidative stress. We aimed to assess the modulation role of pro-inflammatory and pro-oxidative stimuli on endothelial VCAM1, NOS3, and HMOX1 expression. We also evaluated the effect of the main SCA therapeutic agent, hydroxyurea, on that modulation. Our results showed that two VCAM1 promoter haplotypes, we previously associated with pediatric cerebral vasculopathy and severe hemolysis in SCA, increased promoter activity in TNF-α-stimulated transfected EAhy926 and HBEC cell lines, consistent with a higher VCAM1 expression in macro and microvascular settings. In non-transfected cells, we also observed TNF-α-induced VCAM1 overexpression as well as heme-induced overexpression of HMOX1 in both cell models. Heme did not affect VCAM1 nor NOS3 expression and the latter was also not affected by TNF-α stimulus. Hydroxyurea treatment lowered TNF-induced VCAM1 and NOS3 expression but did not affect heme-induced HMOX1 expression. These data further indicate that VCAM1 haplotypes we studied lead to higher VCAM1 expression affecting not only cerebral but also systemic vasculopathy risk. The differential endothelial expression of VCAM1, NOS3, and HMOX1 also confirms their genetic modulation role in SCA systemic vasculopathy.