Characterization of S-glutathionyl hemoglobin in homozygous sickle cell disease

S-glutathionyl hemoglobin is a proposed biomarker of oxidative stress but has not been measured in sickle cell disease patients. Unlike the S-glutathionyl adduct of normal adult hemoglobin, S-glutathionyl sickle hemoglobin (HbSSG) cannot be directly measured by capillary isoelectric focusing, because it coelutes with fetal hemoglobin (HbF). This suggests that HbF, measured in sickle cell patients with or without hydroxyurea therapy, might contain endogenous HbSSG. As S-glutathionyl hemoglobin can form during sample storage, HbSSG could falsely elevate HbF levels in stored samples. We measured HbSSG based on the quantitative difference in the heterogeneous HbF/HbSSG peak before and after hemolysates were treated with dithiothreitol. Paired t tests showed that dithiothreitol reduced HbF/HbSSG in blood from pediatric sickle cell patients (n=25, mean decrease+/-SD=1.0%+/-0.6, P