A hypothesis on the role of the electrical charge of haemoglobin in regulating the erythrocyte shape

The Impact of Ca2+ on Intracellular Distribution of Hemoglobin in Human Erythrocytes

The membrane-bound hemoglobin (Hb) fraction impacts red blood cell (RBC) rheology and metabolism. Therefore, Hb-RBC membrane interactions are precisely controlled. For instance, the signaling function of membrane-bound deoxy-Hb and the structure of the docking sites in the cytosolic domain of the anion exchanger 1 (AE-1) protein are well documented; however, much less is known about the interaction of Hb variants with the erythrocyte's membrane. Here, we identified factors other than O2 availability that control Hb abundance in the membrane-bound fraction and the possible variant-specific binding selectivity of Hb to the membrane. We show that depletion of extracellular Ca2+ by chelators, or its omission from the extracellular medium, leads to membrane-bound Hb release into the cytosol. The removal of extracellular Ca2+ further triggers the redistribution of HbA0 and HbA2 variants between the membrane and the cytosol in favor of membrane-bound HbA2. Both effects are reversible and are no longer observed upon reintroduction of Ca2+ into the extracellular medium. Fluctuations of cytosolic Ca2+ also impact the pre-membrane Hb pool, resulting in the massive transfer of Hb to the cellular cytosol. We hypothesize that AE-1 is the specific membrane target and discuss the physiological outcomes and possible clinical implications of the Ca2+ regulation of the intracellular Hb distribution.

IMPACT OF LOW SALINITY ON HEMOCYTES MORPHOLOGY AND FUNCTIONAL ASPECTS IN INVASIVE CLAM ANADARA KAGOSHIMENSIS (TOKUNAGA, 1906)

Impact of low salinity on morphology and function of hemocytes in ark clam species Anadara kagoshimensis was investigated using light microscopy and flow cytometry. In control group the water salinity was adjusted to 19.6‰, and experimental group was maintained at 14.8‰ and 8.8‰. Two cell types, amebocytes and erythrocytes, were identified in control group of ark clams. Erythrocytes constituted the main type of the cells, and amounted to 92.3±3.9 %. Hyposalinity changed that proportion: the number of amebocytes decreased 2.7 times and number of erythrocytes increased 7.6 times. Morphometric characteristics of hemocytes didn’t show statistically significant changes. As far as salinity decreased, the number of erythrocyte shades in hemolymph increased (3.5 times at salinity 8.8‰) and, in hemocytes, the reactive oxygen species (ROS) production grew (3.5. times at salinity 8.8‰).

Hemoglobins emerging roles in mental disorders. Metabolical, genetical and immunological aspects

Hemoglobin (Hb) expression in the central nervous system is recently shown. Cooccurences of mental disorders (mainly bipolar disorder (BD) and tic disorders) with β- or α-thalassemia trait or erythrocytosis were witnessed, which may be due to peripheral or central hypoxia/hyperoxia or haplotypal gene interactions. β-Globin genes reside at 11p15.5 close to tyrosine hydroxylase, dopamine receptor DRD4 and Brain Derived Neurotrophic Factor, which involve in psychiatric diseases. α-Globin genes reside at 16p13.3 which associates with BD, tic disorders, ATR-16 Syndrome and Rubinstein Taybi Syndrome (RTS). CREB-Binding Protein (CEBBP)-gene is mutated in RTS, which commonly associates with mood disorders. 16p13.3 region also contains GRIN2A gene encoding N-methyl-d-aspartate receptor-2A and SSTR5 (Somatostatin Receptor-5), again involving in mental disorders. We demonstrated a protective role of minor HbA2 against post-partum episodes in BD and association of higher minor HbF (fetal hemoglobin) levels with family history of psychosis in a BD-patient cohort. HbA2 increases in cardiac ischemia and in mountain dwellers indicating its likely protection against ischemia/hypoxia. HMGIY, a repressive transcription factor of δ-globin chain of HbA2 is increased in lymphocytes of schizophrenics. In autism, deletional mutations were found in BCL11A gene, which cause persistence of HbF at high levels in adulthood. Also, certain polymorphisms in BCL11A strongly associate with schizophrenia. Further, many drugs from anabolic steroids to antimalarial agents elevate HbF and may cause mania. We ascribe a protective role to HbA2 and a maladaptive detrimental role to HbF in psychopathology. We believe that future studies on hemoglobins may pave to discover novel pathogenesis mechanisms in mental disorders.

Higher minor hemoglobin A2 levels in multiple sclerosis patients correlate with lesser disease severity

OBJECTIVE

To define whether minor adult hemoglobin A2 (HbA2, α2δ2) exerts any protective activity in multiple sclerosis (MS).

METHODS

HbA2 levels were measured in 146 MS patients with high performance liquid chromatography and association with MS Severity Scores (MSSS) were determined. HbA2 associations with blood count parameters were also studied using blood counts evaluated on the same day of high performance liquid chromatography sampling. Routine biochemical parameters were also determined to rule out elusively influential factors, such as anemia and thyroid disorders.

RESULTS

HbA2 levels negatively correlated with MSSS (Spearman correlation, R: -0.186, P=0.025). Exclusion of confounding factors with a generalized linear model revealed an even stronger negative correlation between HbA2 and MSSS (P<0.001). HbA2 positively correlated with red blood cells (RBCs) (R=0.350, P<0.001) and in turn, RBCs negatively correlated with MSSS (R=-0.180, P=0.031). Average HbA2 levels were highest among patients treated with interferon β1a.

CONCLUSION

RBC fragility is increased in MS, and recent data suggest that circulating free Hb contributes to neural injury in MS. HbA2 and its oxidative denaturation product hemichrome A2 enhance RBC membrane stability to a greater extent than do major HbA or hemichrome A. Reductions in ischemic cerebrovascular vascular events are reported in β-thalassemia carriers and HbA2 levels are considerably higher in this population. Episodic declines of cerebral blood flow were shown in bipolar disorder, and we have recently shown a protective role of HbA2 against postpartum episodes in females with bipolar disorder. HbA2's erythroprotective functions may reduce free Hb and long-term neural injury in MS.

An in vitro model of a system of electrical potential compensation in extracorporeal circulation

OBJECTIVES

Extracorporeal circulation (ECC) in patients undergoing cardiac surgery induces systemic immune-inflammatory reaction that results in increased postoperative morbidity. Many factors are responsible for the adverse response after ECC. The present in vitro study aimed to investigate electric charges (ECs) generated during ECC, to set a device compensating the ECs, and checking its effect on red blood cells (RBC).

MATERIALS AND METHODS

The electrical signals of blood in ECC were collected by a custom developed low-noise electronic circuit, processed by a digital oscilloscope (DSO) and a dynamic signal analyzer (DSA). The compensation of ECs was performed using a compensation device, injecting a nulling charge into the blood circuit. The compensation effect of the ECs on RBCs was evaluated by scanning electron microscope (SEM).

RESULTS

The electrical analysis performed using both the DSO and the DSA confirmed the EC formation during ECC. The notable electric signals recorded in standard ECC circuits substantially nulled once the compensation device was used, thus confirming efficient EC compensation. After two hours of ECC, the SEM non-blended test on human RBC samples highlighted morphological changes in acanthocytes of the normal biconcave-shaped RBC.

CONCLUSIONS

The outcomes confirm the development of parasitic ECs during ECC and that a suppressor system may decrease the potential damage of ECs. Nevertheless, further studies are ongoing in order to investigate the complex mechanisms related to lymphocytes and platelet morphological and physiological chances during triboelectric charges in ECC.

Minor hemoglobins HbA2 and HbF associate with disease severity in bipolar disorder with a likely protective role of HbA2 against post-partum episodes

BACKGROUND

There exist studies indicating that bipolar disorder (BD) associates with changes in brain blood flow. Human brain with its high demand to oxygen constitutes 2% of the total body weight, while it receives 20% of cardiac output. α and β globin chains of hemoglobin were recently found in neural tissues, yet no study has questioned blood hemoglobins in BD.

METHODS

A total of 120 euthymic BD patients (40 males and 80 females) were analyzed via high performance liquid chromatography (HPLC) to measure minor hemoglobin levels, which were statistically compared with disease characteristics.

RESULTS

Minor hemoglobins HbA2 and HbF associated positively with episode density as a measure of disease severity in BD. An increased level of HbA2 meant significantly less postpartum episodes in child bearing women. HbF levels were higher in patients with a positive family history of any psychotic disorder. Sum of HbA2 and HbF correlated with episode density with a stronger significance (p<0.001) supporting intermittent hypoxia hypothesis in BD.

LIMITATIONS

The study was conducted only on euthymic patients to avoid likely bigger exogenous effects such as electro-convulsive therapy and diverse drug regimes, yet larger comparative studies are needed to support our current findings.

CONCLUSIONS

Higher HbA2 and HbF in more severe bipolar disorder may be compensations against intermittent hypoxias in BD. HbA2 increases following myocardial angina and in mountain dwellers, which may indicate protective roles in extreme conditions. HbF increase may act more as a maladaptation or emerge via haplotypal associations of BD genes and gamma-globin locus at 11p15.5.

The behavior of the human erythrocyte as an imperfect osmometer: A hypothesis

The human erythrocyte does not behave as a perfect osmometer that is its volume does not change as predicted with the change of the tonicity of the medium, as if there was a fraction of the cell water not participating in the osmotic exchange. A mechanism of control of the erythrocyte shape has been previously proposed in which Band 3 (AE1), the protein anion exchanger of Cl(-) and HCO(3)(-), plays a central role. Specifically, decrease and increase of the ratio of its outward-facing conformation and inward-facing conformation (Band 3(o)/Band 3(i)) contract and relax the membrane skeleton, thus favoring echinocytosis and stomatocytosis, respectively. The equilibrium Band 3(o)/Band 3(i) ratio is determined by the Donnan equilibrium ratio of anions and protons, increasing with it (r=Cl(i)(-)/Cl(o)(-)=HCO 3(i)(-)/HCO 3(o)(-)=H(o)(+)/H(i)(+)). The Donnan ratio is influenced by the erythrocyte transport and metabolic activities. The volume change of the human erythrocyte alters the skeleton conformation as it is accompanied by a change of the membrane curvature. Thus, the mechanism could be a hypothesis for explaining the behavior of the human erythrocyte as an imperfect osmometer since the Donnan ratio controls the Band 3(o)/Band 3(i) ratio which controls the volume by a control of the degree of contraction or relaxation of the skeleton. Predictions made by the hypothesis on the Ponder's coefficient R' values in the presence of sucrose or Band 3 substrates slowly transported as well as on the participation of Band 3 in the osmotic hemolysis appear to be corroborated by previous observations. If the hypothesis was valid, it would follow that there is a pressure gradient across the erythrocyte membrane. The equilibrium volume is antagonistically determined by the Donnan ratio per se and Band 3. Band 3, rather than the ratio of surface-to-volume, primarily controls the osmotic hemolysis.

A basis of the acanthocytosis in inherited and acquired disorders

Acanthocytosis refers to the transformation of the normal biconcave disc erythrocyte into one with a few irregularly shaped external projections distributed unevenly at its membrane surface. It is associated with a variety of inherited and acquired disorders. A relationship between the acanthocytosis in chorea-acanthocytosis and an alteration of Band 3, the anion exchange protein, has been previously suggested. We have previously proposed a mechanism of erythrocyte shape control in which decrease and increase of the ratio of the outward-facing (Band 3(o)) and inward-facing (Band 3(i)) conformations of Band 3 contracts and relaxes the membrane skeleton, thus promoting echinocytosis and stomatocytosis, respectively. The equilibrium Band 3(o)/Band 3(i) ratio is determined by the Donnan equilibrium ratio of anions and protons, increasing with the increase of the Donnan ratio. Based on the evidence suggesting that the acanthocyte and echinocyte are interrelated, the mechanism could explain by a decrease of the Donnan ratio the occurrence of acanthocytes in pyruvate kinase and pyrimidine 5'-nucleotidase deficiencies, dehydrated hereditary stomatocytocytosis, In(Lu) phenotype, chorea-acanthocytosis, and McLeod phenotype. Consistent with the proposed mechanism indicating that the membrane skeleton is an important determinant of the erythrocyte shape, is the alteration of its conformation in chorea-acanthocytosis, McLeod phenotype and Fanconi's anemia. In agreement with the proposed mechanism indicating that Band 3 conformation controls the erythrocyte shape are the occurrence of an acanthocytosis in individuals expressing the rare Band 3 HT variant and of alterations of Band 3 properties in chorea-acanthocytosis and In(Lu) phenotype. The observations that the lipid composition or organization are normal in chorea-acanthocytosis and McLeod phenotype are supportive of the proposed mechanism since it postulates that the lipid bilayer has a secondary role in determining the erythrocyte shape. The acanthocytoses in alcoholic cirrhosis and abetalipoproteinemia are accompanied by significant increases of the cholesterol level and of the ratio of sphingomyelin and glycerophospholipids, respectively. However, they could occur by a change of the Band 3 conformation since cholesterol binds specifically to Band 3 and inhibits its anion transport activity, and that sphingomyelin potentiates this inhibition. Thus, the acanthocytosis could involve an alteration of the Band 3 conformation.