The aim of the present study was to test the effects of hydroxyurea (HU) therapy on clinical, hematological and hemorheological parameters in adult patients with sickle cell anemia (SCA). Hematological and hemorheological parameters were measured in 28 SCA patients before HU therapy (i.e., baseline) and at 6, 12 and 24 months of treatment. RBC deformability was determined by ektacytometry at 30 Pa. RBC aggregation properties were investigated by light-backscatter method. Blood viscosity was measured at 225 s-1 by a cone-plate viscometer. The rates of vaso-occlusive crises and acute chest syndrome were lower at 1 and 2 years of HU therapy compared to baseline. The proportion of patients with leg ulcers tended to decrease after 2 years of treatment. Hemoglobin oxygen saturation improved with HU therapy. HU therapy induced a decrease of platelet and white blood cell counts and a rise in fetal hemoglobin level and mean cell volume. While hemoglobin concentrations increased under HU, blood viscosity remained unchanged all along the study. RBC deformability increased over baseline values at 6 months of HU therapy and continued to rise until the end of the follow-up period. In conclusion, the improvement in RBC deformability probably compensates the increase of hemoglobin on blood viscosity and participates to the improvement of the clinical status of patients.

Oxidative stress and haemolysis-associated nitric oxide (NO) depletion plays a crucial role in the development of vasculopathy in sickle cell anaemia (SS). However it remains unknown whether oxidative stress and haemolysis levels influence vascular function in patients with sickle haemoglobin C disease (SC). Microvascular response to heat (using Laser Doppler flowmetry on finger), oxidative stress biomarkers, NO metabolites, endothelin-1 and haematological parameters were compared between patients with SS and SC. Vascular function, oxidative and nitrosative markers were also measured in healthy (AA) children. SS and SC had increased plasma advanced oxidation protein products (AOPP), malondialdehyde, plasma antioxidant activities and NO end products, compared to AA. SC had lower catalase activity compared to AA and SS. Haemolytic rate, glutathione peroxidase and nitrotyrosine concentrations were significantly increased in children with SS compared to SC and AA. SS and SC had impaired microvascular reactivity compared to AA. In SS, the plateau phase of the response to local thermal heating was negatively associated with nitrotyrosine and AOPP. No association between vascular function parameters and oxidative stress markers was observed in SC. Mild haemolysis in SC, compared to SS, may limit oxidative and nitrosative stress and could explain the better preserved microvascular function in this group.

No abstract