Vitamins and Minerals
Objectives : Sickle Cell Disease (SCD) is caused by a single point mutation in the β-globin gene, resulting in the polymerization of the altered hemoglobin βS in hypoxic conditions, affecting millions of people worldwide. Previous studies have shown that there are lower selenium levels and reduced activity of the antioxidant selenoprotein GPX1 in SCD patients. The objective of this study was to investigate the consequences of selenium deficiency in a SCD mouse model.
Methods : Humanized SCD (HbSS) mice (Townes model) and wild type (HbAA) mice were purchased from Jackson Laboratories (Bar Harbor, ME). Mice were fed either a selenium-deficient (< 0.01 mg/kg) or a selenium adequate (0.1 mg/kg) diet for 4 weeks. Hematological testing was performed using the ADVIATM 120 analyzer (Bayer Corporation, NY). Mitochondrial retention and reactive oxygen species (ROS) were measured by flow cytometry with a BD LSRFortessaTM analyzer using Kaluza analysis software (Beckman Coulter, CA). The oxygen consumption rate (OCR) was measured from isolated red blood cells (RBCs) in real time using the Seahorse Extracellular Analyzer (Agilent, CA).
Results : RBCs normally eject their mitochondria before reaching maturity. However, a previous study demonstrated that there was increased RBC mitochondrial retention in SCD mice and patients when compared to controls. Feeding SCD mice a selenium deficient diet resulted in increased retention of mitochondria in RBCs (26%+6.9%, 5%+3.5%, n=3, p< 0.01), decreased hemoglobin levels (5.7+0.17 g/dl, 7.0+0.83 g/dl, n=3, p< 0.05), and an increased OCR of the RBCs (p< 0.01) in these animals when compared to SCD mice fed a selenium adequate diet.
Conclusions : Providing humanized SCD mice a selenium deficient diet resulted in increased mitochondrial retention in mature RBCs, decrease hemoglobin levels, and increased RBC oxygen consumption. RBC retention of mitochondria is associated with increased ROS and hemolysis, potentially contributing to the pain and vaso-occlusive crises that occur in the disease. These studies indicate that selenium deficiency may contribute to the severity of symptoms experienced by patients with SCD.
Funding Sources :
This work is supported by a grant from the NIH.