Association between Oxidative Stress, Genetic Factors, and Clinical Severity in Children with Sickle Cell Anemia.

OBJECTIVES: To investigate the associations between several sickle cell disease genetic modifiers (beta-globin haplotypes, alpha-thalassemia, and glucose-6-phosphate dehydrogenase deficiency) and the level of oxidative stress and to evaluate the association between oxidative stress and the rates of vaso-occlusive events. STUDY DESIGN: Steady-state oxidative and nitrosative stress markers, biological variables, genetic modulators, and vaso-occlusive crisis events requiring emergency admissions were measured during a 2-year period in 62 children with sickle cell anemia (58 SS and 4 Sß0). Twelve ethnic-matched children without sickle cell anemia also participated as healthy controls (AA) for oxidative and nitrosative stress level measurement. RESULTS: Oxidative and nitrosative stress were greater in patients with sickle cell anemia compared with control patients, but the rate of vaso-occlusive crisis events in sickle cell anemia was not associated with the level of oxidative stress. The presence of alpha-thalassemia, but not glucose-6-phosphate dehydrogenase deficiency or beta-globin haplotype, modulated the level of oxidative stress in children with sickle cell anemia. CONCLUSION: Mild hemolysis in children with alpha-thalassemia may limit oxidative stress and could explain the protective role of alpha-thalassemia in hemolysis-related sickle cell complications.

Differential effects of adenylyl cyclase-protein kinase A cascade on shear-induced changes of sickle cell deformability.

BACKGROUND: Erythrocyte deformability is impaired in sickle cell disease (SCD). The regulation of cytoskeletal protein organization plays a key role in erythrocyte deformability. The activation of adenylyl cyclase (AC)/cAMP/Protein kinase A (PKA) signaling pathway was associated with increased deformability in healthy erythrocytes, however the role of this pathway in SCD is unknown. OBJECTIVE: We evaluated mechanical responses of sickle red blood cells under physiological levels of shear stress and the possible link between their deformability and AC/cAMP/PKA signaling pathway. METHODS: The shearing of sickle red blood cells at physiological level (5 Pa) and the measurement of deformability were performed by a laser assisted optical rotational cell analyzer (LORRCA). RESULTS: Red blood cell deformability increased of 2.5-6.5% by blocking the activity of phosphodiesterase with Pentoxifylline (10µM) (p < 0.05). The inhibition of AC with SQ22536 (100µM) produced more significant rise in deformability (+4.8-12%, p < 0.01). No significant change was observed by the inhibition of PKA with H89 (10µM). CONCLUSION: Pentoxifylline and SQ22536 increased the deformability of sickle red blood cells under fluid shear stress. Modulation of the AC/cAMP/PKA pathway could have the potential to be an effective therapeutic approach for SCD through shear-induced improvements of RBC deformability.