Effect of short-term hyperglycemia on protein kinase C alpha activation in human erythrocytes

Signaling mechanisms in red blood cells: A view through the protein phosphorylation and deformability

Intracellular signaling mechanisms in red blood cells (RBCs) involve various protein kinases and phosphatases and enable rapid adaptive responses to hypoxia, metabolic requirements, oxidative stress, or shear stress by regulating the physiological properties of the cell. Protein phosphorylation is a ubiquitous mechanism for intracellular signal transduction, volume regulation, and cytoskeletal organization in RBCs. Spectrin-based cytoskeleton connects integral membrane proteins, band 3 and glycophorin C to junctional proteins, ankyrin and Protein 4.1. Phosphorylation leads to a conformational change in the protein structure, weakening the interactions between proteins in the cytoskeletal network that confers a more flexible nature for the RBC membrane. The structural organization of the membrane and the cytoskeleton determines RBC deformability that allows cells to change their ability to deform under shear stress to pass through narrow capillaries. The shear stress sensing mechanisms and oxygenation-deoxygenation transitions regulate cell volume and mechanical properties of the membrane through the activation of ion transporters and specific phosphorylation events mediated by signal transduction. In this review, we summarize the roles of Protein kinase C, cAMP-Protein kinase A, cGMP-nitric oxide, RhoGTPase, and MAP/ERK pathways in the modulation of RBC deformability in both healthy and disease states. We emphasize that targeting signaling elements may be a therapeutic strategy for the treatment of hemoglobinopathies or channelopathies. We expect the present review will provide additional insights into RBC responses to shear stress and hypoxia via signaling mechanisms and shed light on the current and novel treatment options for pathophysiological conditions.

Erythrocyte Deformability and Na,K-ATPase Activity in Various Pathophysiological Situations and Their Protection by Selected Nutritional Antioxidants in Humans

The physicochemical and functional properties of erythrocytes are worsened in a variety of diseases. Erythrocyte deformability refers to their ability to adjust their shape according to external forces exerted against them in the circulation. It is influenced by the functionality of the Na,K-ATPase enzyme, which is localized in their membranes. The proposed review is focused on knowledge regarding changes in erythrocyte Na,K-ATPase activity, and their impact on erythrocyte deformability in various pathophysiological situations observed exclusively in human studies, as well as on the potential erytroprotective effects of selected natural nutritional antioxidants. A clear link between the erythrocyte properties and the parameters of oxidative stress was observed. The undesirable consequences of oxidative stress on erythrocyte quality and hemorheology could be at least partially prevented by intake of diverse antioxidants occurring naturally in foodstuffs. Despite intensive research concerning the effect of antioxidants, only a small number of investigations on erythrocyte properties in humans is available in databases. It is worth shifting attention from animal and in vitro experiments and focusing more on antioxidant administration in human studies in order to establish what type of antioxidant, in what concentration, and in which individuals it may provide a beneficial effect on the human organism, by protecting erythrocyte properties.

Correlated flickering of erythrocytes membrane observed with dual time resolved membrane fluctuation spectroscopy under different D-glucose concentrations

A correlated human red blood cell membrane fluctuation dependent on D-glucose concentration was found with dual time resolved membrane fluctuation spectroscopy (D-TRMFS). This new technique is a modified version of the dual optical tweezers method that has been adapted to measure the mechanical properties of red blood cells (RBCs) at distant membrane points simultaneously, enabling correlation analysis. Mechanical parameters under different D-glucose concentrations were obtained from direct membrane flickering measurements, complemented with membrane fluidity measurements using Laurdan Generalized Polarization (GP) Microscopy. Our results show an increase in the fluctuation amplitude of the lipid bilayer, and a decline in tension value, bending modulus and fluidity as D-glucose concentration increases. Metabolic mechanisms are proposed as explanations for the results.

The Relationship between Red Blood Cell Distribution Width and Incident Diabetes in Chinese Adults: A Cohort Study

BACKGROUND

Previous studies reported the controvertible association between red blood cell distribution width (RDW) and diabetes. The aim of this study is to explore whether RDW is associated with incident diabetes.

METHODS

We performed this cohort study in 16,971 Chinese adults (9,956 men and 7,015 women, aged 43.3 ± 12.8 years). The level of RDW was measured at baseline (2014). All the participants were further classified into four quartile groups based on baseline RDW. Fasting blood glucose (FBG) and glycated hemoglobin A1c (HbA1c) were measured annually during follow-up (2014-2019). Diabetes was diagnosed if either FBG ≥ 7.0 mmol/L or HbA1c ≥ 6.5%. We used the Cox proportional hazards regression model to evaluate the association between baseline RDW and incident diabetes.

RESULTS

We identified 2,703 new cases of diabetes during five-year follow-up. The incidence was 15.9%. Comparing with participants in the lowest quartile group (reference group), the adjusted hazard ratios (HR) for the risk of diabetes were 1.31 (95% CI: 1.16, 1.48) for the highest quartile group (p trend < 0.001), after adjustment for potential confounders. Further adjusting baseline FBG and HbA1c did not materially change the association between RDW and incident diabetes. Each unit increase of RDW was associated with a 16% higher risk of incident diabetes (HR = 1.16, 95% CI: 1.06, 1.26) in a fully adjusted model. Sensitivity analysis generated similar results with prospective analyses after excluding aged participants, participants who are overweight and with obesity, participants with elevated blood pressure, participants with decreased eGFR, and those with anemia at baseline.

CONCLUSIONS

High RDW was associated with high risk of developing diabetes in Chinese adults. As RDW is an inexpensive, noninvasive, and convenient indicator, RDW might be considered for inclusion in the risk assessment of high-risk groups of diabetes.

Correlation of Hemoglobin A1c with Red Cell Width Distribution and Other Parameters of Red Blood Cells in Type II Diabetes Mellitus

Objective

To determine the correlation of glycated hemoglobin (HbA1c) with red cell width (RDW) and other analytic parameters of red blood cells (RBCs) in type II diabetic patients.

Design

Cross-sectional analytical study.

Place and duration of the study

Al-Tibri Medical College and Hospital Karachi; from July 2017 to January 2018.

Patients and methods

This cross-sectional study was conducted on diagnosed type II diabetic patients visiting the outpatient department of medicine at Al-Tibri Medical College Hospital from July 2017 to January 2018. Diabetes mellitus was diagnosed according to American Diabetes Association (ADA) guidelines. After taking consent and conducting a clinical assessment (include history and physical examination), laboratory tests, such as fasting blood glucose, random blood glucose, complete blood count (CBC), and HbA1c, were collected on proforma.

Results

A total of 119 patients were eligible for the study with a mean age of 48.63±12.462 (range 24-76) years; among those, males were 74 (62.2%) and females were 45 (37.8%). The mean duration of diabetes mellitus (DM) was 6.735±3.759 (range 1-20) years. The mean hemoglobin of patients was 11.59±1.315 gm/dl. The mean corpuscular volume (MCV) was 76.65±11.121 fl and the mean RDW was found to be 18.287±4.352, with the highest value of 30.20. The mean MCH was 30.223±23.873 pg, with the highest value of 38.4 pg. The mean cell hemoglobin concentration (MCHC) was 28.214±4.7498 mg/dl.

The HbA1c of the study population was found to be moderately uncontrolled and the mean HbA1c was 8.278±5.015%, with the highest value of 16.2%. The mean fasting blood sugar was 158±39.50 mg/dl while the mean random blood sugar was 236±57.390 mg/dl.

The correlation of HbA1c with RDW turned out to be significant statistically (p-0.035) while other RBCs and/or hematological parameters, such as MCV, hemoglobin, and platelets, revealed no significant correlation.

Conclusion

The study highlighted that RDW has a significant correlation with HbA1c and is an inexpensive and freely available test so it may be used as a marker of glycemic status.

Red blood cell distribution width and the risk of being in poor glycemic control among patients with established type 2 diabetes

Background

The red cell distribution width (RDW) has been shown to be associated with the incidence and complications of type 2 diabetes (T2D). However, the relevance of RDW with the risk of being in poor glycemic control among patients with established T2D is largely overlooked.

Methods

A total of 702 T2D participants from the REACTION study were enrolled in this study. Blood routine index, fasting plasma glucose, hemoglobin A1c and lipid profile data were available for all of the enrolled population.

Results

The univariate logistic analysis revealed a significant association between RDW and the risk of being in poor glycemic control among T2D subjects with an odds ratio (OR) and a 95% confidence interval (CI) of 0.5 and 0.3–0.8, respectively, for the fourth vs the first quartile of RDW. The association strengthened after multivariable adjustment (OR [95% CI]: 0.3 [0.2–0.7]). Interaction and stratified analyses indicated that this association was seen only among T2D subjects with lower body mass index and/or serum lipid levels.

Conclusion

T2D patients with higher RDW had significantly lower risk of being in poor glycemic control. RDW may contribute to risk assessment for T2D individuals at risk of being in poor glycemic control.

Dielectric Response of Cytoplasmic Water and Its Connection to the Vitality of Human Red Blood Cells. II. The Influence of Storage

Maintaining an appropriate inventory of packaged blood products is a critical part of modern medicine. Consequently, the assessment of red blood cell (RBC) functionality is instrumental for the monitoring of the quality of stored RBC (sRBC) in the blood bank. We present a comprehensive study of sRBC lesion kinetics in SAGM (saline, adenine, glucose, mannitol) solution, using microwave dielectric spectroscopy (0.5-50 GHz) and cell deformability. As part of the research, we have isolated the microwave dielectric response of cytoplasmic water in sRBC. The extracted dielectric parameters are sensitive to the age of the cells and, in particular, to the critical moment of transition from discocyte to echinocyte. From the analysis of the dielectric relaxation as a function of storage-duration, we postulate that the behavior is rooted in the delicate interplay between bound and bulk water in the cellular interior. In particular, the microwave dielectric response reflects the moment when the continuous diffusion of oxygen to the cell and the oxygenation of hemoglobin affects the role played by water in the maintenance of cell integrity. These results open a possible new avenue for the noninvasive inspection of stored red blood cells, permitting a true inventory system for the modern blood bank.

Dielectric Response of Cytoplasmic Water and Its Connection to the Vitality of Human Red Blood Cells: I. Glucose Concentration Influence

The vitality of red blood cells depends on the process control of glucose homeostasis, including the membrane's ability to "switch off" d-glucose uptake at the physiologically specific concentration of 10-12 mM. We present a comprehensive study of human erythrocytes suspended in buffer solutions with varying concentrations of d-glucose at room temperature, using microwave dielectric spectroscopy (0.5 GHz-50 GHz) and cell deformability characterization (the Elongation ratio). By use of mixture formulas the contribution of the cytoplasm to the dielectric spectra was isolated. It reveals a strong dependence on the concentration of buffer d-glucose. Tellingly, the concentration 10-12 mM is revealed as a critical point in the behavior. The dielectric response of cytoplasm depends on dipole-matrix interactions between water structures and moieties, like ATP, produced during glycolysis. Subsequently, it is a marker of cellular health. One would hope that this mechanism could provide a new vista on noninvasive glucose monitoring.

Diabetic foot disease is associated with reduced erythrocyte deformability

The pathogenesis of diabetic foot disease is multifactorial and encompasses microvascular and macrovascular pathologies. Abnormal blood rheology may also play a part in its development. Using a cell flow analyser (CFA), we examined the association between erythrocyte deformability and diabetic foot disease. Erythrocytes from diabetic patients with no known microvascular complications (n = 11) and patients suffering from a diabetic foot ulcer (n = 11) were isolated and their average elongation ratio (ER) as well as the ER distribution curve were measured. Average ER was decreased in the diabetic foot patients compared with the patients with diabetes and no complications (1·64 ± 0·07 versus 1·71 ± 0·1; P = 0·036). A significant rise in the percentage of minimally deformable red blood cells RBCs in diabetic foot patients compared with the patients with no complications was observed (37·89% ± 8·12% versus 30·61% ± 10·17%; P = 0·039) accompanied by a significant decrease in the percentage of highly deformable RBCs (12·47% ± 4·43% versus 17·49% ± 8·17% P = 0·046). Reduced erythrocyte deformability may slow capillary flow in the microvasculature and prolong wound healing in diabetic foot patients. Conversely, it may be the low-grade inflammatory state imposed by diabetic foot disease that reduces erythrocyte deformability. Further study of the rheological changes associated with diabetic foot disease may enhance our understanding of its pathogenesis and aid in the study of novel therapeutic approaches.

Red cell distribution width in type 2 diabetic patients

OBJECTIVE

To study the indices of some elements of the complete blood count, in type 2 diabetic patients, in comparison with nondiabetic healthy controls; and to find out the effects of glycemic control and different medications on these indices. To the best of our knowledge, this study is novel in our environment and will serve as a foundation for other researchers in this field.

METHODS

This retrospective study included 260 type 2 diabetic patients on treatment and 44 healthy control subjects. Sex, age, weight, height, blood pressure, complete blood count, fasting plasma glucose, hemoglobin A1c (HbA1c), and lipid profile data, were available for all of the study population. For diabetic patients, data on duration of diabetes and all medications were also available.

RESULTS

Red cell distribution width (RDW) was significantly higher in diabetic patients than in control subjects (P=0.008). It was also higher in patients with uncontrolled glycemia (HbA1c >7%) than those with good control (HbA1c ≤7%; P=0.035). Mean platelet volume (MPV) was comparable in both diabetic patients and healthy controls (P=0.238). RDW and MPV did not significantly correlate with fasting plasma glucose, HbA1c, or duration of diabetes. Both aspirin and clopidogrel did not show a significant effect on MPV. Both insulin and oral hypoglycemic agents did not show a significant effect on RDW, mean corpuscular volume, MPV, platelet count, or white blood cell count. Diabetic patients treated with indapamide or the combined thiazides and angiotensin receptor blockers showed no significant difference in RDW when compared with the control subjects.

CONCLUSION

RDW, which is recently considered as an inflammatory marker with a significant predictive value of mortality in diseased and healthy populations, is significantly higher in diabetic patients than healthy subjects and is particularly higher in uncontrolled glycemia. None of the studied hypoglycemic agents showed a significant effect on RDW. Diabetic hypertensive patients receiving antihypertensive therapy in the form of indapamide or the combined therapy of thiazides and angiotensin receptor blockers have RDW values comparable to those of the healthy population.

ICln: a new regulator of non-erythroid 4.1R localisation and function

To optimise the efficiency of cell machinery, cells can use the same protein (often called a hub protein) to participate in different cell functions by simply changing its target molecules. There are large data sets describing protein-protein interactions (“interactome”) but they frequently fail to consider the functional significance of the interactions themselves. We studied the interaction between two potential hub proteins, ICln and 4.1R (in the form of its two splicing variants 4.1R⁸⁰ and 4.1R¹³⁵), which are involved in such crucial cell functions as proliferation, RNA processing, cytoskeleton organisation and volume regulation. The sub-cellular localisation and role of native and chimeric 4.1R over-expressed proteins in human embryonic kidney (HEK) 293 cells were examined. ICln interacts with both 4.1R⁸⁰ and 4.1R¹³⁵ and its over-expression displaces 4.1R from the membrane regions, thus affecting 4.1R interaction with ß-actin. It was found that 4.1R⁸⁰ and 4.1R¹³⁵ are differently involved in regulating the swelling activated anion current (I_Cl,swell) upon hypotonic shock, a condition under which both isoforms are dislocated from the membrane region and thus contribute to I_Cl,swell current regulation. Both 4.1R isoforms are also differently involved in regulating cell morphology, and ICln counteracts their effects. The findings of this study confirm that 4.1R plays a role in cell volume regulation and cell morphology and indicate that ICln is a new negative regulator of 4.1R functions.

Storage-induced damage to red blood cell mechanical properties can be only partially reversed by rejuvenation

BACKGROUND

The storage of red blood cells (RBC) is associated with impairment of their properties that can induce a circulatory risk to recipients. In a preceding study (2009), we reported that post-storage rejuvenation (RJ) of stored RBC (St-RBC) efficiently reduced the storage-induced RBC/endothelial cell interaction, while only partially reversing the level of intracellular Ca(2+), reactive oxygen species, and surface phosphatidylserine. In the present study, we examined the RJ effectiveness in repairing St-RBC mechanical properties.

METHODS

RBC, stored in CPDA-1 without pre-storage leukoreduction, were subjected to post-storage RJ, and the deformability, osmotic fragility (OF), and mechanical fragility (MF) of the rejuvenated St-RBC (St-RBCRj) were compared to those of untreated St-RBC and of freshly-collected RBC (F-RBC).

RESULTS

5-week storage considerably increased OF and MF, and reduced the deformability of St-RBC. All alterations were only partially (40-70%) reversed by RJ, depending on the extent of the damage: the greater the damage, the lesser the relative effect of RJ.

CONCLUSION

The findings of the present and preceding studies suggest that different St-RBC properties are differentially reversed by RJ, implying that some of the changes occur during storage and are irreversible.