Abstract
Sickle cell disease (SCD) is an inherited blood disorder caused by a mutation in the β-globin gene, leading to hemoglobin polymerization under low oxygen conditions. This results in sickle-shaped red blood cells (erythrocytes), hemolysis, severe acute and chronic pain, and shortened erythrocyte lifespan. The severity of disease in SCD is linked to the type of hemoglobin mutation, with hemoglobin-SS genotype (HbSS) causing more frequent and severe than hemoglobin-SC genotype (HbSC). We previously identified mitochondrial retention and excessive reactive oxygen species (ROS) production in SCD erythrocytes. Here, we report that patients with SCD with the HbSS exhibit significantly higher erythrocyte mitochondrial retention and ROS levels than those with the HbSC. Mitochondrial retention positively correlates with serum bilirubin and lactate dehydrogenase (LDH), particularly in hydroxyurea-naïve patients. Gene expression analysis using a human autophagy array revealed upregulation of SNCA, GABARAP, GABRAPL2, MAP1LC3B, and CTSB in erythrocyte precursor cells from patients with SCD experiencing severe pain. Immunoblot analyses further confirmed accumulation of gamma-aminobutyric acid type-A receptor-associated protein (GABARAP), GABARAPL1, GABARAPL2, cathepsin-B, and alpha-synuclein in circulating erythrocytes and plasma from patients with SCD compared with controls. Our findings suggest a potential link between dysregulated autophagy proteins and erythrocyte mitochondrial retention in patients with SCD, opening new avenues for therapeutic interventions targeting these proteins to mitigate SCD pathogenesis.