The effect of hemolysis on plazma oxidation and nitration in patients with sickle cell disease

Reduced nitric oxide (NO) bioavailability, NO resistance and endothelial dysfunction in cickle cell disease (SCD) results from consumption of NO by plasma cell-free hemoglobin and reactive oxygen species. The aim of this study was to determine the influence of increased hemolysis on plazma oxidation and nitration in SCD patients. Blood was collected from healthy hemoglobin (Hb A) volunteers and steady state homozygous HbSS patients who had not received blood transfusions in the last 3 months. All patients and healthy volunteers enrolled in the study were free from nonsteroidal anti-inflammatory drugs for over 14 days. Diagnosis of SCD patients was based on clinical, familial, and laboratory data, including Hb electrophoresis and estimation of HbF and A2 levels. Hemolysis was characterized by low levels of hemoglobin and haptoglobin and high levels of reticulocyte, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), plasma cell-free hemoglobin, bilirubin, total LDH and dominance of LDH-1 isoenzyme. Plasma 8-isoprostane, protein carbonyl and nitrotyrosine levels were measured to evaluate oxidized lipids, oxidized and nitrated proteins, respectively. Plasma nitrite and nitrate levels were also determined to assess NO production in both SCD patients and controls. Markers of hemolysis were significantly evident in SCD patients compared to controls. Plasma 8-isoprostane, protein carbonyl and nitrotyrosine levels were markedly elevated in SCD patients as compared to the control group. Linear regression analysis revealed a significant inverse correlation between hemoglobin and reticulocyte counts and a significant positive correlation of plasma cell-free hemoglobin with protein carbonyl and nitrotyrosine levels. The obtained data reveals that increased hemolysis observed in SCD influences both plasma protein oxidation and nitration reactions.