Cellular Hydration and Oxidation As Phenotype Modifiers in Sickle Cell Anemia

• Published in: Blood 2016-12, Vol.128 (22), p.2446-2446
• Main Authors: Risinger, Mary A, Dagaonkar, Neha, Christakopoulos, Georgios E, Liu, Jie, Giger Seu, Katie, Konstantinidis, Diamantis G, Quinn, Charles T, Chonat, Satheesh, Joiner, Clinton H, Zhang, Kejian, Kalfa, Theodosia A
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V128.22.2446.2446

Although Sickle Cell Anemia (SCA) is caused by a single nucleotide mutation in the beta globin gene, there is broad phenotypic variability in affected individuals. It would be highly advantageous to be able to predict which SCA patients are most likely to suffer severe complications and which are likely to benefit from specific treatments. Since two of the major pathologic mechanisms in SCA are erythrocyte dehydration and chronic inflammation, alterations in the expression and/or function of proteins affecting these processes may be responsible for heterogeneity in SCA phenotype. We have developed a 23-gene Next-Generation sequencing panel to identify variants in genes involved in erythrocyte hydration and in reactive oxygen species (ROS) generation and reduction in patients with SCA. We have collected blood samples from an initial cohort of 18 SCA patients with severe phenotype, defined by history of stroke or abnormal transcranial Doppler velocities, and 13 SCA patients with mild phenotype for DNA preparation and for specialized testing to evaluate erythrocyte hydration status and ROS generation. Advia Automated Cell Counter results provided the clearest indications of erythrocyte dehydration in patient blood samples. The ability to examine reticulocyte parameters made it possible to evaluate hydration regardless of the frequency of transfusion. Reticulocyte CHCM, MCV, and percent hyperdense cells were significantly different between the two groups and indicative of a greater degree of dehydration in the severe phenotype group. Osmoscans (using a LoRRca ektacytometer) demonstrated a highly significant left shift indicative of erythrocyte dehydration in both mild and severe groups relative to controls (O min and O hyper values significantly decreased). Both phenotypic groups also demonstrated a significantly lower EI max in relation to controls, indicating decreased deformability of sickle erythrocytes. Deformability scans revealed significant increases in SS ½ and decreases in EI max in both groups in relation to the controls. There were significant differences between mild and severe phenotype groups in osmoscan O min and O hyper values and in deformability assay SS ½ and EI max values. The severe group had values closer to the normal values, most likely due to the contribution of transfused blood in the severe phenotype group. There were no significant differences between the mild and severe SCA phenotype groups in intracellular cation levels (K+ and N