The Interaction between (Ca2++ Mg2+)‐ATPase and the Soluble Activator (Calmodulin) in Erythrocytes Containing Haemoglobin S (original) (raw)
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Erythrocyte membrane ATPase activity in Sickle cell crisis
Asian Journal of Medical Sciences
Background: Sickle cell disease is a genetic disease caused by a point mutation in the beta globin gene on chromosome 11 leading to the substitution of valine in place of glutamic acid in beta subunit of globin molecule. The vaso-occlusive crisis, or sickle cell crisis, is a common painful complication of sickle cell disease in adolescents and adults. Many studies have suggested the alteration in intracellular concentration of various ions associated with sickle cell disease. Aims and Objectives: This study aims to evaluate the activity of red blood cell membrane ATPase activity of sickle cell crisis patients in comparison to sickle cell patients in steady state. Material and Methods: Twenty patients of sickle cell crisis were included in the study. Twenty sickle cell patients in steady state were also registered who served as controls. The RBC Membrane ATPase activity were estimated and expressed as µmol of Pi/µg of protein/hour. Results: The activity of membrane ATPase were found to be significantly high in patients of sickle cell crisis in comparison to steady state ones. Conclusion: Membrane ATPases play a crucial role in the pathophysiology of sickle cell crisis. This study can be a based upon for future studies to understand the pathophysiology of sickle cell crisis and development of diagnostic and treatment modalities for the same.
Turk J …, 2000
The various membrane abnormalities of sickle erythrocytes may result from excessive accumulation of oxidant damage. We measured the sera levels of malondialdehyde, products of lipid peroxidation, Na + -K + /Mg ++ Adenosine 5' triphosphatase (ATPase) and Ca ++ /Mg ++ Adenosine 5' triphosphatase, erythrocyte membrane enzymes, in patients with sickle cell anemia and compared their levels with that of normal controls. MDA, Na + -K + /Mg ++ and Ca ++ /Mg ++ ATPase levels of control groups were 0.90 ± 0.04 nmol/mL, 168 ± 12.9 and 140.6 ± 8.2 nmol Pi/mg prot/hour, respectively. MDA, Na + -K + /Mg ++ and Ca ++ /Mg ++ ATPase levels of patients were 2.02 ± 0.01 nmol/mL, 127.0 ± 8.4 and 110.0 ± 9.6 nmol Pi/mg prot/hour, respectively. Our experimental results showed that there was a significant increase in MDA levels of patients with sickle cell anemia as compared with that of the controls. However, erythrocyte membrane Na + -K + /Mg ++ and Ca ++ /Mg ++ ATPase levels of patients with sickle cell anemia were significantly lower than the, Na + -K + /Mg ++ and Ca ++ /Mg ++ ATPase levels of normal controls.
Effect of papaverine on erythrocyte membrane ATPases in sickle cell anaemia
In-vitro studies were carried out using blood samples of different genotypes AA, AS, and SS obtained from volun-teers to ascertain the effect of Papaverine as a plausible drug in the management of sickle cell anaemia. Some haematological parameters as well as Ca 2+ -ATPase and Na + ,K + -ATPase specific activities were investigated before and after incubation with Papaverine. Results of haemoglobin tests showed that haemoglobin levels in the SS red cells (11.8g/dl) were lower when compared to AA (14.0g/dl) and AS red cells (15.8g/dl). The result of erythrocyte sedimentation rate showed that SS red cells (8mm/hr) had higher value when compared to AS (4mm/hr) and AA red cells (3mm/hr). Plasma Ca 2+ levels were found to be higher in SS (12.9mg) when compared to AA (11.1mg) and AS (8.1mg). There was significant reduction in protein concentration after incubation with Papaverine in the three groups. Papaverine significantly reduced the specific activities of the two ATPases. The highest ...
Calcium Handling in Red Blood Cells of Sickle Cell Disease Patients
Precise control over the intracellular free Ca 2+ level is of key importance for any cell, red blood cells (RBCs) included. Cell fate of erythroid precursor cells, as well as volume, redox state, deformability, aggregability, adherence to the endothelial layer, and membrane stability of circulating RBCs, and as a result RBC longevity, are regulated by Ca 2+ . Several hereditary forms of hemolytic anemia, including sickle cell disease (SCD), are associated with abnormally high Ca 2+ uptake, and as a result, Ca 2+ overload. Multiple organ failure, stroke, and myocardial infarction caused by thrombosis as well as repeated hemolytic and pain crises are induced by irreversible polymerization of deoxygenated hemoglobin S in RBCs of these patients. Dehydration of RBCs speed up sickle cell transformation, extensive oxidation and facilitated proteolysis, as well as increased adherence of circulating RBCs to the endothelial layer, substantially contribute to the sickle cell disease manifestation. As all of these processes are driven by the high intraerythrocytic Ca 2+ levels, inhibition of pathologically high Ca 2+ uptake would be a powerful therapeutic strategy. Molecular identity of ion channels involved in pathologically high permeability of RBC membranes of patients for Ca 2+ is a subject of intensive investigation. Among the identified channels are Piezo channels and N-methyl D-aspartate (NMDA) receptors. The contribution of transient voltage receptor channels (TRPCs), voltage-gated calcium channels Cav2.1, and even voltage-dependent anion channels (VDACs) into the Ca 2+ uptake is currently being debated. This chapter is an overview of the current progress in research in this area followed by an outlook into the potential use of blockers of the cation channels for therapy of SCD patients.
The effect of Papaverine-a calcium channel blocker on erythrocytes membrane enzymes of sickle cells
The study was carried out to determine the effects of papaverine on plasma calcium ion level and the activities of erythrocytes membrane enzymes (Ca 2+ -ATPase and Na + K + -ATPase). The haematological study in sickle cell anaemic individuals showed decreased levels of haemoglobin (Hb), packed cell volume (PCV), red blood cell count (RBC), erythrocyte sedimentation rate (ESR) while there was an increase in platelet count when compared with individuals with genotypes AA and AS. The plasma Ca 2+ levels and Ca 2+ -ATPase and Na + K + -ATPase levels in the sickle cell participant were found to be higher than those of the AA and AS individuals. Addition of 2mg papaverine decreased both the Ca 2+ -ATPase and Na + K + -ATPase activities in all the genotypes studied.
Recently we showed that N-methyl D-aspartate receptors (NMDARs) are expressed in erythroid precursors (EPCs) and present in the circulating red blood cells (RBCs) of healthy humans, regulating intracellular Ca 2+ in these cells. This study focuses on investigating the possible role of NMDARs in abnormally high Ca 2+ permeability in the RBCs of patients with sickle cell disease (SCD). Protein levels of the NMDAR subunits in the EPCs of SCD patients did not differ from those in EPCs of healthy humans. However, the number and activity of the NMDARs in circulating SCD-RBCs was substantially up-regulated, being particularly high during haemolytic crises. The number of active NMDARs correlated negatively with haematocrit and haemoglobin levels in the blood of SCD patients. Calcium uptake via these non-selective cation channels was induced by RBC treatment with glycine, glutamate and homocysteine and was facilitated by de-oxygenation of SCD-RBCs. Oxidative stress and RBC dehydration followed receptor stimulation and Ca 2+ uptake. Inhibition of the NMDARs with an antagonist memantine caused re-hydration and largely prevented hypoxia-induced sickling. The EPCs of SCD patients showed higher tolerance to memantine than those of healthy subjects. Consequently, NMDARs in the RBCs of SCD patients appear to be an attractive target for pharmacological intervention.
British Journal of Haematology, 2009
Ca 2+-calmodulin (Ca 2+-CaM) activates erythrocyte adenosine monophosphate deaminase (AMPD) in conditions of disturbed calcium homeostasis, prompting us to investigate adenine nucleotide metabolic dysregulation in sickle cell disease (SCD). However, higher ATP concentrations in reticulocytes, compared to erythrocytes, confound a comparative evaluation of SCD and normal RBCs. Therefore, a combination of centrifugation and antiCD71-labelled magnetic bead selection was used to prepare reticulocyte-poor fractions (reticulocytes <4% of total RBCs) of SCD RBCs. ATP and total adenine nucleotide concentrations were 12% lower in sickle erythrocytes compared to normal erythrocytes and inosine monophosphate (IMP) concentrations were threefold elevated (all P < 0•05). Furthermore, preincubation with a diffusible CaM antagonist slowed IMP accumulation in sickle erythrocytes during an experimental period of energy imbalance, thus showing that Ca 2+-CaM activates AMPD in SCD. Finally, adenine treatment (100 µmol/1) of ex vivo SCD RBCs significantly expanded ATP levels (16% higher) and reduced phosphatidylserine (PS)exposure, specifically those cells with the highest levels of PS externalization (46% fewer events) (both P-values <0•05 compared to untreated samples). We conclude that Ca 2+-CaM activation of AMPD contributes to increased turnover of the adenine nucleotide pool in sickle erythrocytes and that this metabolic dysregulation promotes PS exposure that may contribute to the pathogenesis of SCD. Keywords red cells; sickle cell anaemia; calmodulin; AMP deaminase; adenosine triphosphate; phosphatidylserine Erythrocytes are unique among human tissues and cells because they do not contain enough adenylosuccinate synthetase activity to sustain measurable anabolic flow through the inosine monophosphate (IMP) to adenosine monophosphate (AMP) branch point of purine nucleotide biosynthesis (Bishop, 1960; Lowy & Dorfman, 1970). The immediate metabolic consequence of this non-functional IMP to AMP branch point pathway is an inability to synthesize adenine