Generation and Export of Red Blood Cell ATP in Health and Disease

Biopreservation and Reversal of Oxidative Injury During Blood Storage by a Novel Curcumin-based Gel Formulation

Blood storage lesion induces cytosolic and membrane changes driven in part by hemoglobin (Hb) oxidation reactions within red blood cells (RBCs). A novel gel formulation containing the antioxidant curcuminoids in a biocompatible solvent system was used to deliver curcumin into RBCs. Incubation of peroxide treated RBCs stored in PBS with curcumin gel led to a reduction in prooxidant ferrylHb and recovery in ATP. Curcumin treatment prevented band 3 tyrosine (Y359 and Y21) phosphorylation. RBCs stored in AS-3 solutions for 28, 35, 42 and 49 days, following a single-dose of 100μM curcuminoids at each time points, caused reduction in protein carbonylation and considerable recovery in ATP levels. Proteomic analysis revealed minimal changes in the proteomic landscape in 35 days. However, a downregulation in fibrinogen was observed in the treated samples which may reduce RBC aggregation. Additionally, we used a guinea pig model where the circulation of infused aged RBCs can be extended (approximately 10%) when treated with curcumin gel at the start of storage. Our data therefore provide mechanistic insights and supportive animal data into benefits of treating stored RBCs with a novel curcuminoid formulation based on the biopreservation of RBC membrane integrity, redox balance, and increased longevity in circulation.

Recent developments in the use of pyruvate kinase activators as a new approach for treating sickle cell disease

ABSTRACT

Pyruvate kinase (PK) is a key enzyme in glycolysis, the sole source of adenosine triphosphate, which is essential for all energy-dependent activities of red blood cells. Activating PK shows great potential for treating a broad range of hemolytic anemias beyond PK deficiency, because they also enhance activity of wild-type PK. Motivated by observations of sickle-cell complications in sickle-trait individuals with concomitant PK deficiency, activating endogenous PK offers a novel and promising approach for treating patients with sickle-cell disease.

Erythronecroptosis: an overview of necroptosis or programmed necrosis in red blood cells

Necroptosis is considered a programmed necrosis that requires receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3), and pore-forming mixed lineage kinase domain-like protein (MLKL) to trigger a regulated cell membrane lysis. Membrane rupture in necroptosis has been shown to fuel innate immune response due to release of damage-associated molecular patterns (DAMPs). Recently published studies indicate that mature erythrocytes can undergo necroptosis as well. In this review, we provide an outline of multiple cell death modes occurring in erythrocytes, discuss possible immunological aspects of diverse erythrocyte cell deaths, summarize available evidence related to the ability of erythrocytes to undergo necroptosis, outline key involved molecular mechanisms, and discuss the potential implication of erythrocyte necroptosis in the physiology and pathophysiology. Furthermore, we aim to highlight the interplay between necroptosis and eryptosis signaling in erythrocytes, emphasizing specific characteristics of these pathways distinct from their counterparts in nucleated cells. Thus, our review provides a comprehensive summary of the current knowledge of necroptosis in erythrocytes. To reflect critical differences between necroptosis of nucleated cells and necroptosis of erythrocytes, we suggest a term erythronecroptosis for necroptosis of enucleated cells.

One-year safety and efficacy of mitapivat in sickle cell disease: follow-up results of a phase 2, open-label study

Targeting the primary pathogenic event of sickle cell disease (SCD), the polymerization of sickle hemoglobin (HbS), may prevent downstream clinical events. Mitapivat, an oral pyruvate kinase (PK) activator, has therapeutic potential by increasing adenosine triphosphate (ATP) and decreasing 2,3-diphosphoglycerate (2,3-DPG), a glycolytic red blood cell (RBC) intermediate. In the previously reported 8-week dose-finding period of this phase 2, investigator-initiated, open-label study, mitapivat was well tolerated and showed efficacy in SCD. Here, the 1-year fixed-dose extension period is reported in which 9 of 10 included patients (90%) aged ≥16 years with SCD (HbSS, HbS/β0, or HbS/β+) continued with mitapivat. Mostly mild treatment-emergent adverse events (AEs) (most commonly, transaminase increase and headache) were still reported. Apart from the reported nontreatment-related serious AE (SAE) of a urinary tract infection in the dose-finding period, 1 nontreatment-related SAE occurred in the fixed-dose extension period in a patient who died of massive pulmonary embolism due to COVID-19. Importantly, sustained improvement in Hb level (mean increase, 1.1 ± 0.7 g/dL; P = .0014) was seen, which was accompanied by decreases in markers of hemolysis. In addition, the annualized rate of vaso-occlusive events reduced significantly from a historic baseline of 1.33 ± 1.32 to 0.64 ± 0.87 (P = .0489) when combining the dose-finding period and fixed-dose extension period. Cellularly, the ATP:2,3-DPG ratio and Hb-oxygen affinity significantly increased and RBC sickling (point of sickling) nonsignificantly reduced. Overall, this study demonstrated 1-year safety and efficacy of treatment with mitapivat in SCD, supporting further evaluation in ongoing phase 2/3 study (RISE UP, NCT05031780). This trial was registered at https://www.clinicaltrialsregister.eu/ as NL8517 and EudraCT 2019-003438-18.

Labile Metabolite Profiling in Human Blood Using Phosphorus NMR Spectroscopy

Phosphorus metabolites occupy a unique place in cellular function as critical intermediates and products of cellular metabolism. Human blood is the most widely used biospecimen in the clinic and in the metabolomics field, and hence an ability to profile phosphorus metabolites in blood, quantitatively, would benefit a wide variety of investigations of cellular functions in health and diseases. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy are the two premier analytical platforms used in the metabolomics field. However, detection and quantitation of phosphorus metabolites by MS can be challenging due to their lability, high polarity, structural isomerism, and interaction with chromatographic columns. The conventionally used 1H NMR, on the other hand, suffers from poor resolution of these compounds. As a remedy, 31P NMR promises an important alternative to both MS and 1H NMR. However, numerous challenges including the instability of phosphorus metabolites, their chemical shift sensitivity to solvent composition, pH, salt, and temperature, and the lack of identified metabolites have so far restricted the scope of 31P NMR. In the current study, we describe a method to analyze nearly 25 phosphorus metabolites in blood using a simple one-dimensional (1D) NMR spectrum. Establishment of the identity of unknown metabolites involved a combination of (a) comprehensively analyzing an array of 1D and two-dimensional (2D) 1H/31P homonuclear and heteronuclear NMR spectra of blood; (b) mapping the central carbon metabolic pathway; (c) developing and using 1H and 31P spectral and chemical shift databases; and finally (d) confirming the putative metabolite peaks with spiking using authentic compounds. The resulting simple 1D 31P NMR-based method offers an ability to visualize and quantify the levels of intermediates and products of multiple metabolic pathways, including central carbon metabolism, in one step. Overall, the findings represent a new dimension for blood metabolite analysis and are anticipated to greatly impact the blood metabolomics field.

Molecular insights into hereditary elliptocytosis and pyropoikilocytosis: NGS uncovers multiple potential candidate genes

Hereditary elliptocytosis (HE) and pyropoikilocytosis (HPP) are considered a group of hemolytic anemias (HE/HPP) due to inherited abnormalities of erythrocyte membrane proteins with a worldwide distribution. Most cases are associated with molecular abnormalities linked to spectrin, band 4.1, and ankyrin. The present study aimed to identify significant molecular signatures on a target panel of 8 genes using whole exome sequencing (WES) in 9 Bahraini patients with elliptocytosis. Case selection was based on presence of anemia not associated with iron deficiency or hemoglobinopathy and demonstrating > 50% elliptocytes in blood smears. The c.779 T > C mutation of SPTA1 (Spectrin alpha), which is a known deleterious missense mutation that inhibits normal association of spectrin molecules to form tetramers, was seen in 4 patients in homozygous (n = 1) and heterozygous (n = 3) states. The αLELY abnormality in association with compound heterozygous mutations in SPTA1 was present in 5 patients (2 associated with the SPTA1 c.779 T > C variant; 3 with c.3487 T > G and various other SPTA1 mutations of uncertain/unknown significance). Seven patients had SPTB (Spectrin beta) mutations, predicted as likely benign by in silico analysis. A novel EPB41 (Erythrocyte Membrane Protein Band 4.1) mutation with potential deleterious impact was also seen. Finally, 2 cases showed an InDel (insertion-deletion mutations) abnormality in the gene that codes for the mechanosensitive ion-channel PIEZO (Piezo Type Mechanosensitive Ion Channel Component 1). PIEZO mutations are reported to cause red cell dehydration but have not been previously described in HE/HPP. Results of this study confirm the involvement of previously reported abnormalities in SPTA1 and suggest possible involvement of other candidate genes in a disorder involving polygenic interactions.

Erythrocyte pyruvate kinase activation in red cell disorders

PURPOSE OF REVIEW

In red cells, pyruvate kinase is a key enzyme in the final step of glycolytic degradative process, which generates a constant energy supply via ATP production. This commentary discusses recent findings on pyruvate kinase activators as new therapeutic option in hereditary red cell disorders such as thalassemic syndromes or sickle cell disease (SCD).

RECENT FINDINGS

Mitapivat and etavopivat are two oral pyruvate kinase activators. Studies in a mouse model for β thalassemia have shown beneficial effects of mitapivat on both red cell survival and ineffective erythropoiesis, with an amelioration of iron homeostasis. This was confirmed in a proof-of-concept study in patients with nontransfusion-dependent thalassemias. Both mitapivat and etavopivat have been evaluated in mouse models for SCD, showing an increased 2-3DPG/ATP ratio and a reduction in haemolysis as well as in sickling. These data were confirmed in proof-of-concept clinical studies with both molecules carried in patients with SCD.

SUMMARY

Preclinical and clinical evidence indicate that pyruvate kinase activators represent new therapeutic option in hemoglobinopathies or SCD. Other red cell disorders such as hereditary spherocytosis or hereditary anaemias characterized by defective erythropoiesis might represent additional areas to investigate the therapeutic impact of pyruvate kinase activators.

Flipping Off and On the Redox Switch in the Microcirculation

Resistance arteries and arterioles evolved as specialized blood vessels serving two important functions: (a) regulating peripheral vascular resistance and blood pressure and (b) matching oxygen and nutrient delivery to metabolic demands of organs. These functions require control of vessel lumen cross-sectional area (vascular tone) via coordinated vascular cell responses governed by precise spatial-temporal communication between intracellular signaling pathways. Herein, we provide a contemporary overview of the significant roles that redox switches play in calcium signaling for orchestrated endothelial, smooth muscle, and red blood cell control of arterial vascular tone. Three interrelated themes are the focus: (a) smooth muscle to endothelial communication for vasoconstriction, (b) endothelial to smooth muscle cell cross talk for vasodilation, and (c) oxygen and red blood cell interregulation of vascular tone and blood flow. We intend for this thematic framework to highlight gaps in our current knowledge and potentially spark interest for cross-disciplinary studies moving forward.

The role of SH groups in the regulation of Gardos channels in glucose deficiency

   Background. Disruption of the energy balance of erythrocytes under conditions of a decrease in the glycolysis level can cause a change in the ion permeability of their membrane.   The aim. To study Ca2+-dependent potassium permeability of the erythrocytes membrane in the presence of SH group modifiers under conditions of glucose deficiency.   Materials and methods. The study used precipitated erythrocytes obtained from the blood of 20 male Wistar rats. The change in the Ca2+-dependent potassium conductivity of the erythrocyte membrane was determined using the potentiometric method. The A23187-and redox-induced hyperpolarization responses of erythrocytes were evaluated.   Results. Glucose deficiency in the medium, as well as the use of the glycolysis inhibitor 2-deoxyglucose, led to an increase in the amplitude of A23187-stimulated membrane hyperpolarization by the opening of the Gardos channels. At the same time, the redox-dependent hyperpolarization of the erythrocyte membrane turned out to be insensitive to a decrease in the glucose content in the medium and to the glycolysis inhibition. The effects of SH group modifiers in the normal incubation medium and under glucose deficiency turned out to be multidirectional and depended on the method of stimulation of Gardos channels.   Conclusion. The results obtained indicate that metabolic disorders in erythrocytes under conditions of glucose deficiency lead to a change in the mechanisms of control of Gardos channels with the participation of SH groups of the proteins of these channels or their regulatory proteins.

Homeostasis of extracellular ATP in uninfected RBCs from a Plasmodium falciparum culture and derived microparticles

Plasmodium falciparum, a dangerous parasitic agent causing malaria, invades human red blood cells (RBCs), causing hemolysis and microvascular obstruction. These and other pathological processes of malaria patients are due to metabolic and structural changes occurring in uninfected RBCs. In addition, infection activates the production of microparticles (MPs). ATP and byproducts are important extracellular ligands modulating purinergic signaling within the intravascular space. Here, we analyzed the contribution of uninfected RBCs and MPs to the regulation of extracellular ATP (eATP) of RBCs, which depends on the balance between ATP release by specific transporters and eATP hydrolysis by ectonucleotidases. RBCs were cultured with P. falciparum for 24-48 h prior to experiments, from which uninfected RBCs and MPs were purified. On-line luminometry was used to quantify the kinetics of ATP release. Luminometry, colorimetry and radioactive methods were used to assess the rate of eATP hydrolysis by ectonucleotidases. Rates of ATP release and eATP hydrolysis were also evaluated in MPs. Uninfected RBCs challenged by different stimuli displayed a strong and transient activation of ATP release, together with an elevated rate of eATP hydrolysis. MPs contained ATP in their lumen, which was released upon vesicle rupture, and were able to hydrolyze eATP. Results suggest that uninfected RBCs and MPs can act as important determinants of eATP regulation of RBCs during malaria. The comparison of eATP homeostasis in infected RBCs, ui-RBCs, and MPs allowed us to speculate on the impact of P. falciparum infection on intravascular purinergic signaling and the control of the vascular caliber by RBCs.

Evolution of red blood cell membrane complement regulatory proteins and rheology in septic patients: An exploratory study

Background

During sepsis, red blood cell (RBC) deformability is altered. Persistence of these alterations is associated with poor outcome. Activation of the complement system is enhanced during sepsis and RBCs are protected by membrane surface proteins like CD35, CD55 and CD59. In malaria characterized by severe anemia, a study reported links between the modifications of the expression of these RBCs membrane proteins and erythrophagocytosis. We studied the evolution of RBCs deformability and the expression of RBC membrane surface IgG and regulatory proteins in septic patients.

Methods

By flow cytometry technics, we measured at ICU admission and at day 3–5, the RBC membrane expression of IgG and complement proteins (CD35, 55, 59) in septic patients compared to RBCs from healthy volunteers. Results were expressed in percentage of RBCs positive for the protein. RBC shape was assessed using Pearson's second coefficient of dissymmetry (PCD) on the histogram obtained with a flow cytometer technique. A null value represents a perfect spherical shape. RBC deformability was determined using ektacytometry by the elongation index in relation to the shear stress (0.3–50 Pa) applied to the RBC membrane. A higher elongation index indicates greater RBC deformability.

Results

RBCs from 11 septic patients were compared to RBCs from 21 volunteers. At ICU admission, RBCs from septic patients were significantly more spherical and RBC deformability was significantly lower in septic patients for all shear stress ≥1.93 Pa. These alterations of shape and deformability persists at day 3–5. We observed a significant decrease at ICU admission only in CD35 expression on RBCs from septic patients. This low expression remained at day 3–5.

Conclusions

We observed in RBCs from septic patients a rapid decrease expression of CD35 membrane protein protecting against complement activation. These modifications associated with altered RBC deformability and shape could facilitate erythrophagocytosis, contributing to anemia observed in sepsis. Other studies with a large number of patients and assessment of erythrophagocytosis were needed to confirm these preliminary data.

Phosphorus metabolism disorders in erythrocytes and lymphocytes among patients with inflammatory breast cancer, infiltrative stomach and colorectal cancer

Energy and plastic potential dysfunction of erythrocytes and lymphocytes among people with inflammatory breast cancer, infiltrative stomach cancer, and infiltrative colon cancer is characterized by a more aggressive clinical course and poor prognosis. We explored the features of energy metabolism and phosphorus metabolism disorders in the erythrocytes and lymphocytes of patients with inflammatory breast cancer, infiltrative stomach cancer, and infiltrative colon cancer as a predicting factor in the course of the disease. 49 people were examined; the 1^st group had infiltrative stomach cancer (n=17); the 2^nd group had infiltrative colon cancer (n=11); the 3^rd group had inflammatory breast cancer (n=21). Glycerol-3-phosphate dehydrogenase activity was 1.8 times reduced (p≤0.005), and the activity of glyceraldehyde-3-phosphate dehydrogenase in erythrocytes of patients with cancer at the main localization increased 2.5 times, compared with normal. Inflammatory breast cancer patients had a statistically significant decrease (p<0.005) in erythrocytes adenosine triphosphate content by an average of 56.5% compared with the normal ratio, and in cases of patients with gastric and colorectal cancer, a decrease of 67%. Excessive use of phosphorus for energy metabolism and adenosine triphosphate production destroys the balance of energetic and plastic potentials of erythrocytes and lymphocytes in inflammatory breast cancer, infiltrative stomach, and infiltrative colorectal cancers patients.