calcimycin and beta-Thalassemia

This study aimed to investigate any correlation between the extent of phosphatidylserine (PS) asymmetry and sialylated glycoconjugate levels with the faster clearance of circulating erythrocytes in haemoglobin E (HbE) beta-thalassaemia. Erythrocytes from peripheral blood samples of different HbEbeta-thalassaemia patients showed loss of PS asymmetry measured by annexin V binding using flow cytometry. Maximum PS exposure was found when HbE was 50-60% and HbF was <20% indicating a possible correlation with severity of the disease. Separation of erythrocytes into aged and younger cells showed higher loss of PS asymmetry in the younger erythrocytes of HbEbeta-thalassaemia patients when compared with normal blood, where PS asymmetry was lost only in the older cells. Sialylated glycoconjugate measurement using the lectins wheatgerm agglutinin and pokeweed mitogen showed loss of sialic acid and N-acetyl-D-glucosamine-bearing glycoproteins in the order normal

Topics: Acetylglucosamine; Adolescent; Adult; Apoptosis; beta-Thalassemia; Calcimycin; Calcium; Cellular Senescence; Child; Child, Preschool; Erythrocyte Membrane; Erythrocytes; Female; Glycoconjugates; Hemoglobin E; Humans; Infant; Lectins; Male; N-Acetylneuraminic Acid; Phosphatidylserines

beta thalassemia (beta thal) in DBA/2J mice is a consequence of the spontaneous and complete deletion of the beta major globin gene. Homozygous beta thal mice have clinical and biological features similar to those observed in human beta thal intermedia. Erythrocytes in human beta thal are characterized by a relative cell dehydration and reduced K+ content. The role of this erythrocyte dehydration in the reduced erythrocyte survival, which typifies the disease, has not previously been evaluated. We examined for 1 month the effects on the anemia and the erythrocyte characteristics of beta thal mice of daily treatment with either clotrimazole (CLT), an inhibitor of red blood cell (RBC) dehydration via the Gardos channel, or human recombinant erythropoietin (r-HuEPO), or hydroxyurea (HU). The use of either r-HuEPO or HU induced a significant increase in hemoglobin (Hb), hematocrit (Hct), erythrocyte K+ and a decrease in percent reticulocytes, suggesting improved erythrocyte survival. CLT alone decreased only mean corpuscular hemoglobin concentration (MCHC) and cell density and increased cell K+. Thus, though the Gardos channel plays a major role in cell dehydration of murine beta thal erythrocyte survival. Combination therapy with r-HuEPO plus HU produced no incremental benefit beyond those of single drug therapy. However, addition of CLT to r-HuEPO, to HU, or to combined r-HuEPO plus HU led to statistically significant increase in Hb, Hct, and erythrocyte K+ compared with any of the regimens without CLT. These results suggest that CLT not only inhibits erythrocyte dehydration, but also potentiates the erythropoietic and cellular survival responses to r-HuEPO and HU.

Topics: Animals; beta-Thalassemia; Body Water; Calcimycin; Calcium; Calcium Channel Blockers; Chlorides; Clotrimazole; Disease Models, Animal; Drug Synergism; Drug Therapy, Combination; Erythrocyte Aging; Erythrocyte Count; Erythrocyte Deformability; Erythrocytes, Abnormal; Erythropoietin; Female; Gene Deletion; Globins; Hematocrit; Humans; Hydroxyurea; Intracellular Fluid; Male; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Mice, Mutant Strains; Potassium; Potassium Channels; Recombinant Proteins; Reticulocytes; Rubidium