Hemoglobin Binding to the Red Blood Cell (RBC) Membrane Is Associated with Decreased Cell Deformability

The deformability of red blood cells (RBCs), expressing their ability to change their shape as a function of flow-induced shear stress, allows them to optimize oxygen delivery to the tissues and minimize their resistance to flow, especially in microcirculation. During physiological aging and blood storage, or under external stimulations, RBCs undergo metabolic and structural alterations, one of which is hemoglobin (Hb) redistribution between the cytosol and the membrane. Consequently, part of the Hb may attach to the cell membrane, and although this process is reversible, the increase in membrane-bound Hb (MBHb) can affect the cell's mechanical properties and deformability in particular. In the present study, we examined the correlation between the MBHb levels, determined by mass spectroscopy, and the cell deformability, determined by image analysis. Six hemoglobin subunits were found attached to the RBC membranes. The cell deformability was negatively correlated with the level of four subunits, with a highly significant inter-correlation between them. These data suggest that the decrease in RBC deformability results from Hb redistribution between the cytosol and the cell membrane and the respective Hb interaction with the cell membrane.

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.

Dynamic laboratory control of iron deficiency correction in neurosurgical patients

Introduction. The concept of blood management in relation to the surgical treatment of surgical diseases recommends the correction of iron defi ciency anemia (IDA) at the prehospital stage. However, surgery is often performed for emergency indications, making it necessary to carry out treatment as soon as possible.

Aim – to evaluate the possibilities of using delta hemoglobin (Delta-He) to monitor the effectiveness of IDA therapy in neurosurgical patients at the prehospital stage to reduce the time required to prepare patients for hospitalization.

Materials and methods. A total of 42 patients were treated with high-dose iron preparations (iron [III] carboxymaltosate and iron [III] hydroxide oligoisomaltosate). During the treatment, the dynamics of the number of reticulocytes and the values of the hemoglobin delta were evaluated. Data are presented as median (IQR).

Results. Treatment with high-dose iron preparations led to an increase in Delta-He values starting from days 1–2. Significant changes were recorded by days 3–4 from the start of therapy: from 2.2 (0.3–4.9) pg to 15.5 (13.8–10) pg on day 7. These changes were 2–3 days ahead of the increase in the number of reticulocytes in the corresponding blood samples: the number of reticulocytes significantly increased by days 5–6 from the start of treatment.

Conclusion. The use of high-dose preparations of iron [III] carboxymaltosate and iron [III] hydroxide oligoisomaltosate in the form of infusion made it possible to prepare neurosurgical patients for hospitalization within a week. None of the patients required transfusion of erythrocyte-containing components of donated blood at any stage of surgical treatment. The ability to focus on Delta-He values instead of the number of reticulocytes during iron therapy made it possible to shorten the waiting period for the effect of drug exposure by 2–3 days.

Bile acids profile and redox status in healthy infants

BACKGROUND

At birth, human neonates are more likely to develop cholestasis and oxidative stress due to immaturity or other causes. We aimed to search for a potential association between bile acids profile, redox status, and type of diet in healthy infants.

METHODS

A cross-sectional, exploratory study enrolled 2-month-old full-term infants (n = 32). We measured plasma bile acids (total and conjugated), and red blood cell (RBC) oxidative stress biomarkers. The type of diet (breastfeeding, mixed, formula) was used as an independent variable.

RESULTS

Plasma total bile acids medium value was 14.80 µmol/L (IQR: 9.25-18.00). The plasma-conjugated chenodeoxycholic acid percentage (CDCA%) correlated significantly and negatively with RBCs membrane-bound hemoglobin percentage (MBH%) (r = -0.635, p < 0.01) and with RBC-oxidized glutathione (r = -0.403, p < 0.05) levels. RBC oxidative stress biomarkers (especially MBH%) were predictors of conjugated CDCA%, and this predictive ability was enhanced when adjusted for the type of diet (MBH, r = 0.452, p < 0.001).

CONCLUSIONS

Our data suggest that the bile acid profile might play a role in the regulation of redox status (or vice versa) in early postnatal life. Eventually, the type of diet may have some impact on this process.

IMPACT

The conjugated CDCA% in plasma is negatively correlated with biomarkers of RBC oxidative stress in healthy infants. Specific biomarkers of RBC oxidative stress (e.g. MBH, GSH, GSSG) may be promising predictors of conjugated CDCA% in plasma. The type of diet may influence the predictive ability of hit RBC oxidative stress biomarkers (e.g. MBH, GSH, GSSG). Our findings suggest a link between plasma bile acids profile and the RBC redox status in healthy infants, eventually modulated by the type of diet. The recognition of this link may contribute to the development of preventive and therapeutic strategies for neonatal cholestasis.

The whole-cell kinetic metabolic model of the pH regulation mechanisms in human erythrocytes

Mathematical modeling in recent years helped to obtain answers to questions that were difficult or even impossible to answer experimentally, to predict several unexpected connections in cell metabolism and to understand and importance of certain biochemical reactions. Due to the complexity and variety of processes underlying the mechanisms of intracellular pH (pHi) regulation, mathematical modeling and metabolome analysis are powerful tools for their analysis. In this regard, a mathematical metabolic model for human erythrocytes was created, which combines cellular metabolism with acid-base processes and gas exchange. The model consists of the main metabolic pathways, such as glycolysis, the pentose phosphate pathway, some membrane transport systems, and interactions between hemoglobin and metabolites. The Jacobs-Stewart cycle, which is fundamental in gas exchange and pH regulation, was included to these pathways. The model was created in the COPASI environment, consisted of 85 reactions, the rate of which is based on accurate kinetic equations. The time dependences of reaction flows and metabolite concentrations, as an outcome of calculations, allowed us to reproduce the behaviour of the metabolic system after its disturbance in vitro and to establish the recovery mechanisms or approximation to stationary states. The COPASI simulation environment provides model flexibility by reproducing any experimental design by optimizing direct quantitative comparisons between measured and predicted results. Thus, the procedure of parameters optimization (Parameter Estimation) followed by the solution of the model’s differential equations (Time Course procedure) was used to predict the behaviour of all measured and unmeasured variables over time. The initial intracellular concentrations of CO2, HCO3– in human erythrocytes used for incubation in a phosphate buffer medium were calculated. Changes in CO2, HCO3– content over time were shown. It was established that the regulation of pH in erythrocytes placed in a buffer medium takes place with the participation of two types of processes – fast (takes place in 1.3 s) and slow. It is shown that fast processes are aimed at restoring the intracellular balance between CO2 and HCO3–, slow processes are aimed at establishing the balance of H+ between the cell and the extracellular environment. The role of carbonic anhydrase (CA) and hemoglobin in the processes of pH stabilization is shown and analyzed. The physiological role of the metabolon between band 3 protein (AE1), CA, aquaporin and hemoglobin in maintaining pH homeostasis in the conditions of in vitro experiments are discussed.

Raman Spectroscopic Study of TiO2 Nanoparticles' Effects on the Hemoglobin State in Individual Red Blood Cells

Titanium dioxide (TiO₂) is considered to be a nontoxic material and is widely used in a number of everyday products, such as sunscreen. TiO₂ nanoparticles (NP) are also considered as prospective agents for photodynamic therapy and drug delivery. These applications require an understanding of the potential effects of TiO₂ on the blood system and its components upon administration. In the presented work, we analyze the interaction of TiO₂ nanoparticles of different crystal phases (anatase and rutile) with individual rat Red Blood Cells (RBC) and the TiO₂ influence on the oxygenation state and functionality of RBC, estimated via analysis of Raman spectra of Hemoglobin (Hb) and their distribution along individual RBC. Raman spectral signals also allow localization of the TiO₂ NP on the RBC. No penetration of the NP inside RBC was observed; however, both kinds of TiO₂ NP adsorbed on the RBC membrane can affect the Hb state. Mechanisms involving the NP–membrane–Hb interaction, resulting in partial deoxygenation of Hb and TiO₂ photothermal effect on Hb under Raman laser excitation, are suggested. The possible influence on the safety of TiO₂ use in advanced medical application, especially on the safety and efficiency of photothermal therapy, is discussed.

Vibration influence on the O2-dependent processes activity in human erythrocytes

The early signs of vibration effects on the human body are microcirculation and transcapillary metabolism disorders, accompanied by disruption of the supply to and utilization of oxygen in the tissues and organs. However, there are few experimental studies aimed at finding targets of vibration in cells and determining the action mechanism of vibration. In in vitro experiments, human erythrocytes in buffer solution were exposed to low-frequency vibration (frequency range 8–32 Hz, amplitudes 0.5–0.9 mm) for 3 hours. The dynamics of the accumulation of membrane-bound catalase and hemoglobin and the distribution of ligand hemoglobin in the membrane-bound fraction were studied as the indicators of functional activity of cells. The choice of these indicators is justified by the participation of catalase and hemoglobin in O2-dependent cellular reactions as a part of protein complexes. Since pО2 is a trigger of conformational transitions in the hemoglobin molecule, simultaneously with oxygen transport, hemoglobin signals to different metabolic systems about oxygen conditions in the environment. The studies revealed that in the conditions of vibration, the activity of membrane-associated catalase increased by 40–50% in the frequency range of 12–24 Hz (amplitude 0.5 ± 0.04 mm), by 20–30% in the amplitude of 0.9 mm, but after about 100–120 min exposure the enzyme activity decreased even below the control level. There was a dose-dependent accumulation of membrane-bound hemoglobin during exposure to vibration. In the membrane-bound fraction of hemoglobin, oxyhemoglobin had the highest content (60–80%), while the content of methemoglobin varied 5–20%. During vibrations in the frequency range 12–28 Hz, 0.5 mm, we recorded 10–30% increase in oxyhemoglobin. With increase in the vibration amplitude (0.9 mm) in the frequency range of 16–32 Hz, constant content of oxyhemoglobin was noted at the beginning of the experiment, which tended to decrease during the last exposure time. Frequency of 32 Hz caused increase in the deoxyhemoglobin content in the membrane-bound fraction. The content of methemoglobin (metHb) in erythrocytes significantly increased during exposure to the frequency range of 12–24 Hz, with the amplitude of 0.5 mm (1.3–2.4 times). During the exposure to frequencies of 28 and 32 Hz, we observed the transition of methemoglobin to hemichrome. The content of methemoglobin in the cells was lower and decreased at the end of the experiment when the vibration amplitude was 0.9 mm. In these experimental conditions, no increase in hemichrome content in the membrane-bound fraction was recorded. Therefore, the degree of binding of catalase and hemoglobin with the membrane of erythrocytes that were exposed to vibration and the changes in the content of ligand forms in the composition of membrane-bound hemoglobin are dose-dependent. Low-frequency vibration initiates O2-dependent processes in erythrocytes. Targets of such an influence are nanobubbles of dissolved air (babstons), retained on the surface of erythrocytes due to Coulomb interactions, capable of coagulation and increase in size under the action of vibration. At first, the consequences of these processes are increase in oxygen content in the surface of erythrocytes, and then decrease as a result of degassing. Thus, increase in oxygen content on the surface initiates redox reactions, whereas decrease in oxygen content leads to reconstruction of metabolic processes oriented at overcoming hypoxia.

Optical Trapping and Micro-Raman Spectroscopy of Functional Red Blood Cells Using Vortex Beam for Cell Membrane Studies

There has been a long-standing interest in Raman spectroscopic investigation of optically trapped single functional cells. Optical trapping using a Gaussian beam has helped researchers for decades to investigate single cells suspended in a physiological medium. However, complete and sensitive probing of single cells demands further advancements in experimental methods. Herein, we propose optical trapping and simultaneous micro-Raman spectroscopy of red blood cells (RBCs) in an unconventional face-on orientation using an optical vortex beam. Using this novel method, we are successful in comparing the conformational state of hemoglobin (Hb) molecules near the RBC membrane and inside the bulk of the cell. This method enabled us to successfully probe the oxy/deoxy ratio of Hb molecules near the RBC membrane and inside the bulk of the cell. Because of the face-on orientation, the Raman spectra of RBCs acquired using a vortex beam have a significant contribution from membrane components compared to that recorded using the Gaussian beam.

Carbonyl Stress in Red Blood Cells and Hemoglobin

The paper overviews the peculiarities of carbonyl stress in nucleus-free mammal red blood cells (RBCs). Some functional features of RBCs make them exceptionally susceptible to reactive carbonyl compounds (RCC) from both blood plasma and the intracellular environment. In the first case, these compounds arise from the increased concentrations of glucose or ketone bodies in blood plasma, and in the second-from a misbalance in the glycolysis regulation. RBCs are normally exposed to RCC-methylglyoxal (MG), triglycerides-in blood plasma of diabetes patients. MG modifies lipoproteins and membrane proteins of RBCs and endothelial cells both on its own and with reactive oxygen species (ROS). Together, these phenomena may lead to arterial hypertension, atherosclerosis, hemolytic anemia, vascular occlusion, local ischemia, and hypercoagulation phenotype formation. ROS, reactive nitrogen species (RNS), and RCC might also damage hemoglobin (Hb), the most common protein in the RBC cytoplasm. It was Hb with which non-enzymatic glycation was first shown in living systems under physiological conditions. Glycated HbA1c is used as a very reliable and useful diagnostic marker. Studying the impacts of MG, ROS, and RNS on the physiological state of RBCs and Hb is of undisputed importance for basic and applied science.

Potential role of cytoplasmic protein binding to erythrocyte membrane in counteracting oxidative and metabolic stress

The ability of protein to reversibly bind with membrane components is considered to be one of the oldest mechanisms of cell response to external stimuli. Erythrocytes have a well-developed mechanism of an adaptive response involving sorption-desorption processes, e.g. interactions of key glycolytic enzymes and hemoglobin with band 3 protein. A few publications have shown that under oxidative stress, cytoplasmic enzymes such as catalase, glutathione peroxidase and рeroxiredoxin bind to the erythrocyte membrane. The present work is a continuation of research in this direction to determine the causes and consequences of the interaction of cytoplasmic proteins with the membrane under conditions of oxidative stress and different glucose content. Human erythrocytes were incubated for five hours at 20 °C in an oxidizing medium of AscH – 1 · 10–4 M, Cu2+– 5 · 10–6 M with different glucose content (0–8 mM). Dynamic changes in the accumulation of membrane-bound hemoglobin, the distribution of ligand forms of hemoglobin in the cytoplasmic and membrane-bound fractions, the activity of membrane-associated and cytoplasmic forms of Cu/Zn superoxide dismutase (SOD1) and catalase, H2O2 content in extracellular and intracellular media were recorded. It was shown that binding of catalase and SOD1 to the erythrocyte membrane is initiated by oxidative stress and is a physiological function aimed at complete inactivation of extracellular and H2O2 and protection against their entry into the cell. It was shown that under conditions of glucose depletion and oxidative loading, catalase and SOD1 bind to the erythrocyte membrane, leading to inactivation of these enzymes. Membrane-bound hemoglobin was higher in cells incubated under these conditions than in glucose experiments. Glucose introduced into the incubation medium in an amount 4–8 mM causes complete binding of SOD1 to the membrane of erythrocytes, by involving it in the processes of casein kinase stabilization and glycolytic fluxes regulation. With mild oxidation, the amount of hemoglobin bound to the membrane does not change, indicating the presence of certain binding sites for hemoglobin with membrane proteins. We show that the activity of membrane-bound SOD1 along with the content of ligand forms in the composition of membrane-bound hemoglobin are informative indicators of the metabolic and redox state of erythrocytes.