Hypoxia/reoxygenation stress increases markers of vaso-occlusive crisis in sickle SAD mice.

In sickle cell disease, the factors involved in vasoocclusive crisis (VOC) include the sickling of red blood cells (RBC), abnormal blood rheology, inflammation, vascular adhesion, oxidative stress, coagulation, and vascular tone modulation. The aim of this study was to further characterize the molecular response of some factors involved in VOC by inducing a hypoxia/reoxygenation stress in sickle SAD mice. Results show that a hypoxia/reoxygenation stress in SAD mice can induce: (i) a decrease in reticulocytes count, and mean corpuscular volume along with an increase in lactate dehydrogenase (p = 0.07) and sickled cell proportion; (ii) a significant increase in lung VCAM-1, ICAM-1, IL-1ß, ET-1, eNOS, and TF mRNA associated with an increase in VCAM-1 expression on lung endothelium; (iii) a rise in cardiac oxidative stress with increased lipid oxidation and decreased anti-oxidant enzyme activities, and (iv) an increase in plasma TNF-α and IL-6 and a decrease in plasma ET-1. In SAD mice, hypoxia/reoxygenation stress induces hemolysis that, together with oxidative stress, inflammation, vascular adhesion, and coagulation, may induce vascular occlusion and consequently RBC sickling. The present results give the kinetics of VOC molecular markers in SAD mice which may aid in testing the efficiency of new therapeutic processes against VOC.

Efficacy of homologous inositol hexaphosphate-loaded red blood cells in sickle transgenic mice.

Patients with sickle cell disease (SCD) can present several severe symptoms during their lifetime, including painful events due to vascular occlusion (VOC). Even though multiple factors are involved in VOC, hypoxia is the most important triggering factor. Inositol hexaphosphate (IHP) reduces the oxygen-haemoglobin affinity thus improving the oxygen release in the blood stream and in the tissues. Thus, IHP-loaded homologous red blood cells (IHP-RBCs) could be able to reduce disorders in SCD. The effectiveness of treatment was assessed in two types of SCD transgenic mice (BERK and SAD). The administration of four repeated injections of IHP-RBCs in BERK mice resulted in an improved survival rate and brain development, prevention of severe anaemia and a greatly lowered risk of VOC. After one injection of IHP-RBCs, SAD mice were subjected to acute hypoxic stress. Analysis of the lungs revealed significantly decreased mRNA levels of molecules involved in intravascular disorders. Our results showed that transfusion of homologous IHP-RBCs, by increasing the oxygen delivery, reduces SCD disorders in sickle transgenic mice.

Inositol hexaphosphate-loaded red blood cells prevent in vitro sickling.

BACKGROUND: Hypoxia is a major cause of painful vaso-occlusive crisis in sickle cell disease (SCD). Simple transfusion and red blood cell (RBC) exchange are commonly used as preventive therapies whose aim is to dilute hemoglobin (Hb)S-containing RBCs (SS-RBCs) with normal RBCs (AA-RBCs) to prevent sickling. We hypothesized that the effectiveness of transfusion could be improved by the encapsulation of inositol hexaphosphate (IHP), an allosteric Hb effector, in transfused AA-RBCs. Indeed, apart from their diluting effect on SS-RBCs, IHP-loaded RBCs (IHP-RBCs) with increased oxygen release capacity could palliate in vivo oxygen deprivation and reduce sickling. STUDY DESIGN AND METHODS: The study was designed to investigate the therapeutic effect of IHP-RBCs transfusion on in vitro sickling of SS-RBCs collected from 20 SCD patients. Patients' RBCs were diluted with various proportions of IHP-RBCs or AA-RBCs (processed or stored RBCs as controls). Resulting suspensions were subjected to deoxygenation followed by partial reoxygenation at 5% oxygen. Sickling was evaluated by microscopy. RESULTS: Stored RBCs (50% dose) used to mimic simple transfusion exhibited a poor antisickling effect (5.6%) and a low response rate (65%). In contrast, IHP-RBCs treatment was seven times more effective resulting in 35% of sickling reduction and a 94% response rate. Sickling was inhibited in a dose-dependent manner: 9.9, 25.1, and 35.0% for IHP-RBCs in percentages of 10, 30, and 50%, respectively. CONCLUSION: Our results indicate that IHP-RBCs prevent in vitro sickling and suggest that it could improve conventional transfusion therapy in terms of transfused volume, frequency, and efficacy.