Erythrocyte NADPH oxidase activity modulated by Rac GTPases, PKC, and plasma cytokines contributes to oxidative stress in sickle cell disease. Blood. 2013;121:2099-2107. [PMID: 23349388 DOI: 10.1182/blood-2012-07-441188]

In vivo upstream factors of mouse hepatotoxic mechanism with sustained hepatic glutathione depletion: Acetaminophen metabolite-erythrocyte adducts and splenic macrophage-generated reactive oxygen species

Investigation of acetaminophen (APAP)-induced liver damage recently indicated the significance of phagocytic NADPH oxidase (NOX)-derived reactive oxygen species (ROS) and ferroptosis in the liver. Here, we focused on phagocytosis by iron-containing erythrocyte-devouring splenic macrophages and explored upstream factors of known APAP hepatotoxic mechanisms in vivo. Splenectomy did not alter hepatic cytochrome P450 (CYP) 2E1 activity or hepatic glutathione (GSH) content. APAP injection into splenectomized mice almost completely suppressed increases in plasma alanine aminotransferase levels and centrilobular hepatic necrosis showing the spleen to be a critical tissue in APAP-induced liver damage. Hepatic GSH was recovered to approximately 50 % content at 8 h. In non-splenectomized mice, liver damage was dramatically suppressed by a sensitive redox probe (DCFH-DA), macrophage-depleting clodronate (CL), and a NOX2 inhibitor. APAP treatment resulted in markedly stronger fluorescence intensity from DCFH-DA due to excessive ROS around splenic macrophages, which was lost upon co-treatment with a CYP inhibitor and CL. Deformed erythrocytes disappeared in mice co-treated with DCFH-DA, CL, the NOX2 inhibitor, and the CYP inhibitor. Simultaneously, these four compounds significantly improved APAP-depleted GSH levels. The CYP inhibitor also prevented the formation of APAP-cell adducts in the blood and spleen. In the spleen, CL co-treatment markedly reduced the number of adducts. Splenic ferrous iron levels were significantly elevated by APAP. Therefore, we demonstrated that splenic macrophages devoured APAP metabolite-erythrocyte adducts and subsequently splenic macrophage-related ROS caused sustained hepatic GSH depletion and excessive erythrocyte deformation around 7 h. Our data indicate in vivo upstream factors of known APAP hepatotoxic mechanisms.

Ginseng total saponin improves red blood cell oxidative stress injury by regulating tyrosine phosphorylation and glycolysis in red blood cells

BACKGROUND

Oxidative stress is the main cause of many diseases, but because of its complex pathogenic factors, there is no clear method for treating it. Ginseng total saponin (GTS) an important active ingredients in Panax ginseng C.A. Mey (PG) and has potential therapeutic ability for oxidative stress due to various causes. However, the molecular mechanism of GTS in the treating oxidative stress damage in red blood cells (RBCs) is still unclear.

PURPOSE

This study aimed to examine the protective effect of GTS on RBCs under oxidative stress damage and to determine its potential mechanism.

METHODS

The oxidative stress models of rat RBCs induced by hydrogen peroxide (H2O2) and exhaustive swimming in vivo and in vitro was used. We determined the cell morphology, oxygen carrying capacity, apoptosis, antioxidant capacity, and energy metabolism of RBCs. The effect of tyrosine phosphorylation (pTyr) of Band 3 protein on RBCs glycolysis was also examined.

RESULTS

GTS reduced the hemolysis of RBCs induced by H2O2 at the lowest concentration. Moreover, GTS effectively improved the morphology, enhanced the oxygen carrying capacity, and increased antioxidant enzyme activity, adenosine triphosphate (ATP) levels, and adenosine triphosphatase (ATPase) activity in RBCs. GTS also promoted the expression of membrane proteins in RBCs, inhibited pTyr of Band 3 protein, and further improved glycolysis, restoring the morphological structure and physiological function of RBCs.

CONCLUSIONS

This study shows, that GTS can protect RBCs from oxidative stress damage by improving RBCs morphology and physiological function. Changes in pTyr expression and its related pTyr regulatory enzymes before and after GTS treatment suggest that Band 3 protein is the main target of GTS in the treating endogenous and exogenous oxidative stress. Moreover, GTS can enhance the glycolytic ability of RBCs by inhibiting pTyr of Band 3 protein, thereby restoring the function of RBCs.

A pharmacokinetic-pharmacodynamic analysis of l-glutamine for the treatment of sickle cell disease: Implications for understanding the mechanism of action and evaluating response to therapy

The mechanisms of action of l-glutamine for the treatment of sickle cell disease (SCD) are not well understood and there are no validated clinical biomarkers to assess response. We conducted a three-week, dose-ascending trial of glutamine and measured the pharmacokinetic (PK) exposure parameters, peak concentration (Cmax) and area under the curve (AUC). We used a panel of biomarkers to investigate the pharmacodynamics (PD) of glutamine and studied PK-PD relationships. There was no plasma accumulation of glutamine, glutamate, arginine or other amino acids over time, but modestly improved arginine bioavailability was observed. In standard analysis by dose levels over time, there were no measurable effects on blood counts, viscosity, ektacytometry or reactive oxygen species (ROS). In PK-PD analysis, however, higher glutamine exposure (Cmax or AUC) was associated with increased whole blood viscosity and cellular dehydration, yet also with higher haemoglobin concentration, increased haematocrit-to-viscosity ratio, decreased reticulocyte ROS, improved RBC deformability and decreased point of sickling. This novel PK-PD analysis identified biomarkers reflecting the positive and negative effects of glutamine, helping to elucidate its mechanisms of action in SCD. PK-optimized dosing to achieve glutamine exposure (AUC or Cmax) that is associated with salutary biological effects should be studied to support its therapeutic use.

Differential Responses of Young and Old Erythrocytes Stored with Vitamin C and Vitamin E in Additive Solution-7

Oxidative stress (OS) causes biochemical and morphological alterations in erythrocytes. The primary factors contributing to OS are aging and storage. Antioxidants significantly alleviate OS. Therefore, this study aimed to investigate the response of young and old erythrocytes to vitamin C and vitamin E during storage. Erythrocytes were separated into young and old by the Percoll method. Each erythrocyte subpopulation was categorized into the i) Control (additive solution-7 [AS-7]) and ii) vitamin C and vitamin E in AS-7 (VC+VE) groups and stored for 21 days at 4°C. OS, antioxidant, and aging markers were analyzed on days 1, 14, and 21. The activity of antioxidant enzymes was similar throughout storage in young cells. However, superoxide dismutase activity elevated in old cells (Control and VC+VE) on days 1 and 21. Catalase (CAT) activity increased on days 14 and 21, whereas glutathione peroxidase (GPX) increased on days 1 and 14 in old Controls. However, in old VC+VE, CAT increased on day 21 and GPX increased on day 1. Advanced oxidation protein products, superoxides, glutathione, and uric acid increased in old cells throughout storage. Malondialdehyde decreased in old VC+VE compared with old Control on days 14 and 21. Sialic acids and glutamate oxaloacetate transaminase activity were higher in young cells compared to old cells. Young cells exhibited lower oxidative changes throughout storage. Vitamin C and vitamin E were effective in maintaining the redox balance in old cells. These findings emphasize the need for specific approaches for different subpopulations during erythrocyte banking.

Impacts of oxidative stress and anti-oxidants on the development, pathogenesis, and therapy of sickle cell disease: A comprehensive review

Sickle cell disease (SCD) is the most severe monogenic hemoglobinopathy caused by a single genetic mutation that leads to repeated polymerization and depolymerization of hemoglobin resulting in intravascular hemolysis, cell adhesion, vascular occlusion, and ischemia-reperfusion injury. Hemolysis causes oxidative damage indirectly by generating reactive oxygen species through various pathophysiological mechanisms, which include hemoglobin autoxidation, endothelial nitric oxide synthase uncoupling, reduced nitric oxide bioavailability, and elevated levels of asymmetric dimethylarginine. Red blood cells have a built-in anti-oxidant system that includes enzymes like sodium dismutase, catalase, and glutathione peroxidase, along with free radical scavenging molecules, such as vitamin C, vitamin E, and glutathione, which help them to fight oxidative damage. However, these anti-oxidants may not be sufficient to prevent the effects of oxidative stress in SCD patients. Therefore, in line with a recent FDA request that the focus to be placed on the development of innovative therapies for SCD that address the root cause of the disease, there is a need for therapies that target oxidative stress and restore redox balance in SCD patients. This review summarizes the current state of knowledge regarding the role of oxidative stress in SCD and the potential benefits of anti-oxidant therapies. It also discusses the challenges and limitations of these therapies and suggests future directions for research and development.

Glycative stress as a cause of macular degeneration

People are living longer and rates of age-related diseases such as age-related macular degeneration (AMD) are accelerating, placing enormous burdens on patients and health care systems. The quality of carbohydrate foods consumed by an individual impacts health. The glycemic index (GI) is a kinetic measure of the rate at which glucose arrives in the blood stream after consuming various carbohydrates. Consuming diets that favor slowly digested carbohydrates releases sugar into the bloodstream gradually after consuming a meal (low glycemic index). This is associated with reduced risk for major age-related diseases including AMD, cardiovascular disease, and diabetes. In comparison, consuming the same amounts of different carbohydrates in higher GI diets, releases glucose into the blood rapidly, causing glycative stress as well as accumulation of advanced glycation end products (AGEs). Such AGEs are cytotoxic by virtue of their forming abnormal proteins and protein aggregates, as well as inhibiting proteolytic and other protective pathways that might otherwise selectively recognize and remove toxic species. Using in vitro and animal models of glycative stress, we observed that consuming higher GI diets perturbs metabolism and the microbiome, resulting in a shift to more lipid-rich metabolomic profiles. Interactions between aging, diet, eye phenotypes and physiology were observed. A large body of laboratory animal and human clinical epidemiologic data indicates that consuming lower GI diets, or lower glycemia diets, is protective against features of early AMD (AMDf) in mice and AMD prevalence or AMD progression in humans. Drugs may be optimized to diminish the ravages of higher glycemic diets. Human trials are indicated to determine if AMD progression can be retarded using lower GI diets. Here we summarized the current knowledge regarding the pathological role of glycative stress in retinal dysfunction and how dietary strategies might diminish retinal disease.

Red Blood Cells as Therapeutic Target to Treat Sickle Cell Disease

Significance: Sickle cell disease (SCD) is the most common inherited diathesis affecting mostly underserved populations globally. SCD is characterized by chronic pain and fatigue, severe acute painful crises requiring hospitalization and opioids, strokes, multiorgan damage, and a shortened life span. Symptoms may appear shortly after birth, and, in less developed countries, most children with SCD die before attaining age 5. Hematopoietic stem cell transplant and gene therapy offer a curative therapeutic approach, but, due to many challenges, are limited in their availability and effectiveness for a majority of persons with SCD. A critical unmet need is to develop safe and effective novel targeted therapies. A wide array of drugs currently undergoing clinical investigation hold promise for an expanded pharmacological armamentarium against SCD. Recent Advances: Hydroxyurea, the most widely used intervention for SCD management, has improved the survival in the Western world and more recently, voxelotor (R-state-stabilizer), l-glutamine, and crizanlizumab (anti-P-selectin antibody) have been approved by the Food and Drug Administration (FDA) for use in SCD. The recent FDA approval emphasizes the need to revisit the advances in understanding the core pathophysiology of SCD to accelerate novel evidence-based strategies to treat SCD. The biomechanical breakdown of erythrocytesis, the core pathophysiology of SCD, is associated with intrinsic factors, including the composition of hemoglobin, membrane integrity, cellular volume, hydration, andoxidative stress. Critical Issues and Future Directions: In this context, this review focuses on advances in emerging nongenetic interventions directed toward the therapeutic targets intrinsic to sickle red blood cells (RBCs), which can prevent impaired rheology of RBCs to impede disease progression and reduce the sequelae of comorbidities, including pain, vasculopathy, and organ damage. In addition, given the intricate pathophysiology of the disease, it is unlikely that a single pharmacotherapeutic intervention will comprehensively ameliorate the multifaceted complications associated with SCD. However, the availability of multiple drug options affords the opportunity for individualized therapeutic regimens tailored to specific SCD-related complications. Furthermore, it opens avenues for combination drug therapy, capitalizing on distinct mechanisms of action and profiles of adverse effects.

Diabetic Retinopathy: New Treatment Approaches Targeting Redox and Immune Mechanisms

Diabetic retinopathy (DR) represents a severe complication of diabetes mellitus, characterized by irreversible visual impairment resulting from microvascular abnormalities. Since the global prevalence of diabetes continues to escalate, DR has emerged as a prominent area of research interest. The development and progression of DR encompass a complex interplay of pathological and physiological mechanisms, such as high glucose-induced oxidative stress, immune responses, vascular endothelial dysfunction, as well as damage to retinal neurons. Recent years have unveiled the involvement of genomic and epigenetic factors in the formation of DR mechanisms. At present, extensive research explores the potential of biomarkers such as cytokines, molecular and cell therapies, antioxidant interventions, and gene therapy for DR treatment. Notably, certain drugs, such as anti-VEGF agents, antioxidants, inhibitors of inflammatory responses, and protein kinase C (PKC)-β inhibitors, have demonstrated promising outcomes in clinical trials. Within this context, this review article aims to introduce the recent molecular research on DR and highlight the current progress in the field, with a particular focus on the emerging and experimental treatment strategies targeting the immune and redox signaling pathways.

Micropump integrated white blood cell separation platform for detection of chronic granulomatous disease

White blood cells (WBCs) are robust defenders during antigenic challenges and prime immune cell functioning indicators. High-purity WBC separation is vital for various clinical assays and disease diagnosis. Red blood cells (RBCs) are a major hindrance in WBC separation, constituting 1000 times the WBC population. The study showcases a low-cost micropump integrated microfluidic platform to provide highly purified WBCs for point-of-care testing. An integrated user-friendly microfluidic platform was designed to separate WBCs from finger-prick blood (⁓5 μL), employing an inertial focusing technique. We achieved an efficient WBC separation with 86% WBC purity and 99.99% RBC removal rate in less than 1 min. In addition, the microdevice allows lab-on-chip colorimetric evaluation of chronic granulomatous disease (CGD), a rare genetic disorder affecting globally. The assay duration, straight from separation to disease detection, requires only 20 min. Hence, the proposed microfluidic platform can further be implemented to streamline various clinical procedures involving WBCs in healthcare industries.

Impaired hemoglobin clearance by sinusoidal endothelium promotes vaso-occlusion and liver injury in sickle cell disease

Sickle cell disease (SCD) is a monogenic disorder that affects 100,000 African-Americans and millions of people worldwide. Intra-erythrocytic polymerization of sickle hemoglobin (HbS) promotes erythrocyte sickling, impaired rheology, ischemia and hemolysis, leading to the development of progressive liver injury in SCD. Liver-resident macrophages and monocytes are known to enable the clearance of HbS; however, the role of liver sinusoidal endothelial cells (LSEC) in HbS clearance and liver injury in SCD remains unknown. Using real-time intravital (in vivo) imaging in mice liver as well as flow cytometric analysis and confocal imaging of primary human LSEC, we show for the first time that liver injury in SCD is associated with accumulation of HbS and iron in the LSEC, leading to senescence of these cells. Hemoglobin uptake by LSEC was mediated by micropinocytosis. Hepatic monocytes were observed to attenuate LSEC senescence by accelerating HbS clearance in the liver of SCD mice; however, this protection was impaired in P-selectin-deficient SCD mice secondary to reduced monocyte recruitment in the liver. These findings are the first to suggest that LSEC contribute to HbS clearance and HbS-induced LSEC senescence promotes progressive liver injury in SCD mice. Our results provide a novel insight into the pathogenesis of hemolysis-induced chronic liver injury in SCD caused by LSEC senescence. Identifying the regulators of LSEC-mediated HbS clearance may lead to new therapies to prevent the progression of liver injury in SCD.

Mechanism of hypoxia-induced damage to the mechanical property in human erythrocytes-band 3 phosphorylation and sulfhydryl oxidation of membrane proteins

Introduction: The integrity of the erythrocyte membrane cytoskeletal network controls the morphology, specific surface area, material exchange, and state of erythrocytes in the blood circulation. The antioxidant properties of resveratrol have been reported, but studies on the effect of resveratrol on the hypoxia-induced mechanical properties of erythrocytes are rare. Methods: In this study, the effects of different concentrations of resveratrol on the protection of red blood cell mor-phology and changes in intracellular redox levels were examined to select an appropriate concentration for further study. The Young's modulus and surface roughness of the red blood cells and blood viscosity were measured via atomic force microsco-py and a blood rheometer, respectively. Flow cytometry, free hemoglobin levels, and membrane lipid peroxidation levels were used to characterize cell membrane damage in the presence and absence of resveratrol after hypoxia. The effects of oxida-tive stress on the erythrocyte membrane proteins band 3 and spectrin were further investigated by immunofluorescent label-ing and Western blotting. Results and discussion: Resveratrol changed the surface roughness and Young's modulus of the erythrocyte mem-brane, reduced the rate of eryptosis in erythrocytes after hypoxia, and stabilized the intracellular redox level. Further data showed that resveratrol protected the erythrocyte membrane proteins band 3 and spectrin. Moreover, resistance to band 3 pro-tein tyrosine phosphorylation and sulfhydryl oxidation can protect the stability of the erythrocyte membrane skeleton net-work, thereby protecting erythrocyte deformability under hypoxia. The results of the present study may provide new insights into the roles of resveratrol in the prevention of hypoxia and as an antioxidant.

Apoptosis and eryptosis: similarities and differences

Eryptosis is a regulated cell death (RCD) of mature erythrocytes initially described as a counterpart of apoptosis for enucleated cells. However, over the recent years, a growing number of studies have emphasized certain differences between both cell death modalities. In this review paper, we underline the hallmarks of eryptosis and apoptosis and highlight resemblances and dissimilarities between both RCDs. We summarize and critically discuss differences in the impact of caspase-3, Ca2+ signaling, ROS signaling pathways, opposing roles of casein kinase 1α, protein kinase C, Janus kinase 3, cyclin-dependent kinase 4, and AMP-activated protein kinase to highlight a certain degree of divergence between apoptosis and eryptosis. This review emphasizes the crucial importance of further studies that focus on deepening our knowledge of cell death machinery and identifying novel differences between cell death of nucleated and enucleated cells. This might provide evidence that erythrocytes can be defined as viable entities capable of programmed cell destruction. Additionally, the revealed cell type-specific patterns in cell death can facilitate the development of cell death-modulating therapeutic agents.

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 metabolism

Our aim is to present an updated overview of the erythrocyte metabolism highlighting its richness and complexity. We have manually collected and connected the available biochemical pathways and integrated them into a functional metabolic map. The focus of this map is on the main biochemical pathways consisting of glycolysis, the pentose phosphate pathway, redox metabolism, oxygen metabolism, purine/nucleoside metabolism, and membrane transport. Other recently emerging pathways are also curated, like the methionine salvage pathway, the glyoxalase system, carnitine metabolism, and the lands cycle, as well as remnants of the carboxylic acid metabolism. An additional goal of this review is to present the dynamics of erythrocyte metabolism, providing key numbers used to perform basic quantitative analyses. By synthesizing experimental and computational data, we conclude that glycolysis, pentose phosphate pathway, and redox metabolism are the foundations of erythrocyte metabolism. Additionally, the erythrocyte can sense oxygen levels and oxidative stress adjusting its mechanics, metabolism, and function. In conclusion, fine-tuning of erythrocyte metabolism controls one of the most important biological processes, that is, oxygen loading, transport, and delivery.

Eriocitrin Disrupts Erythrocyte Membrane Asymmetry through Oxidative Stress and Calcium Signaling and the Activation of Casein Kinase 1α and Rac1 GTPase

BACKGROUND

Hemolysis and eryptosis result in the premature elimination of circulating erythrocytes and thus contribute to chemotherapy-related anemia, which is extremely prevalent in cancer patients. Eriocitrin (ERN), a flavanone glycoside in citrus fruits, has shown great promise as an anticancer agent, but the potential toxicity of ERN to human erythrocytes remains unstudied.

METHODS

Erythrocytes were exposed to anticancer concentrations of ERN (10-100 μM) for 24 h at 37 °C, and hemolysis and associated markers were quantified using colorimetric assays. Eryptosis was assessed by flow cytometric analysis to detect phosphatidylserine (PS) exposure by annexin-V-FITC, intracellular Ca2+ using Fluo4/AM, and oxidative stress with 2-,7-dichlorodihydrofluorescin diacetate (H2DCFDA). ERN was also tested against specific signaling inhibitors and anti-hemolytic agents.

RESULTS

ERN caused significant, concentration-dependent hemolysis at 20-100 μM. ERN also significantly increased the percentage of eryptotic cells characterized by Ca2+ elevation and oxidative stress. Furthermore, the hemolytic activity of ERN was significantly ameliorated in the presence of D4476, NSC23766, isosmotic urea and sucrose, and polyethylene glycol 8000 (PEG). In whole blood, ERN significantly elevated MCV and ESR, with no appreciable effects on other peripheral blood cells.

CONCLUSIONS

ERN promotes premature erythrocyte death through hemolysis and eryptosis characterized by PS externalization, Ca2+ accumulation, membrane blebbing, loss of cellular volume, and oxidative stress. These toxic effects, mediated through casein kinase 1α and Rac1 GTPase, can be ameliorated by urea, sucrose, and PEG. Altogether, these novel findings are relevant to the further development of ERN as an anticancer therapeutic.

Erythroid Cells as Full Participants in the Tumor Microenvironment

The tumor microenvironment is an important factor that can determine the success or failure of antitumor therapy. Cells of hematopoietic origin are one of the most important mediators of the tumor-host interaction and, depending on the cell type and functional state, exert pro- or antitumor effects in the tumor microenvironment or in adjacent tissues. Erythroid cells can be full members of the tumor microenvironment and exhibit immunoregulatory properties. Tumor growth is accompanied by the need to obtain growth factors and oxygen, which stimulates the appearance of the foci of extramedullary erythropoiesis. Tumor cells create conditions to maintain the long-term proliferation and viability of erythroid cells. In turn, tumor erythroid cells have a number of mechanisms to suppress the antitumor immune response. This review considers current data on the existence of erythroid cells in the tumor microenvironment, formation of angiogenic clusters, and creation of optimal conditions for tumor growth. Despite being the most important life-support function of the body, erythroid cells support tumor growth and do not work against it. The study of various signaling mechanisms linking tumor growth with the mobilization of erythroid cells and the phenotypic and functional differences between erythroid cells of different origin allows us to identify potential targets for immunotherapy.

Stimulation of Hemolysis and Eryptosis by α-Mangostin through Rac1 GTPase and Oxidative Injury in Human Red Blood Cells

BACKGROUND

Chemotherapy-related anemia is prevalent in up to 75% of patients, which may arise due to hemolysis and eryptosis. Alpha-mangostin (α-MG) is a polyphenolic xanthonoid found in the mangosteen tree (Garcinia mangostana) whose antitumor medicinal properties are well-established. Nevertheless, the potential toxic effects of α-MG on red blood cells (RBCs) have, as of yet, not been as well studied.

METHODS

RBCs were exposed to 1-40 μM of α-MG for 24 h at 37 °C. Hemolysis and related markers were measured using colorimetric assays, eryptotic cells were identified through Annexin-V-FITC, Ca2+ was detected with Fluo4/AM, and oxidative stress was assessed through H2DCFDA using flow cytometry. The toxicity of α-MG was also examined in the presence of specific signal transduction inhibitors and in whole blood.

RESULTS

α-MG at 10-40 μM caused dose-dependent hemolysis with concurrent significant elevation in K+, Mg2+, and LDH leakage, but at 2.5 μM it significantly increased the osmotic resistance of cells. A significant increase was also noted in Annexin-V-binding cells, along with intracellular Ca2+, oxidative stress, and cell shrinkage. Moreover, acetylcholinesterase activity was significantly inhibited by α-MG, whose hemolytic potential was significantly ameliorated by the presence of BAPTA-AM, vitamin C, NSC23766, and isosmotic sucrose but not urea. In whole blood, α-MG significantly depleted intracellular hemoglobin stores and was selectively toxic to platelets and monocytes.

CONCLUSIONS

α-MG possesses hemolytic and eryptotic activities mediated through Ca2+ signaling, Rac1 GTPase activity, and oxidative injury. Also, α-MG leads to accelerated cellular aging and specifically targets platelet and monocyte populations in a whole blood milieu.

Oxidative Stress in Healthy and Pathological Red Blood Cells

Red cell diseases encompass a group of inherited or acquired erythrocyte disorders that affect the structure, function, or production of red blood cells (RBCs). These disorders can lead to various clinical manifestations, including anemia, hemolysis, inflammation, and impaired oxygen-carrying capacity. Oxidative stress, characterized by an imbalance between the production of reactive oxygen species (ROS) and the antioxidant defense mechanisms, plays a significant role in the pathophysiology of red cell diseases. In this review, we discuss the most relevant oxidant species involved in RBC damage, the enzymatic and low molecular weight antioxidant systems that protect RBCs against oxidative injury, and finally, the role of oxidative stress in different red cell diseases, including sickle cell disease, glucose 6-phosphate dehydrogenase deficiency, and pyruvate kinase deficiency, highlighting the underlying mechanisms leading to pathological RBC phenotypes.

Keap1-Nrf2 Heterodimer: A Therapeutic Target to Ameliorate Sickle Cell Disease

Sickle cell disease (SCD) is a monogenic inheritable disease characterized by severe anemia, increased hemolysis, and recurrent, painful vaso-occlusive crises due to the polymerization of hemoglobin S (HbS)-generated oxidative stress. Up until now, only four drugs are approved for SCD in the US. However, each of these drugs affects only a limited array of SCD pathologies. Importantly, curative therapies, such as gene therapy, or hematopoietic stem cell transplantation are not available for every patient because of their high costs, availability of donor matching, and their serious adverse effects. Therefore, there is an unmet medical need for novel therapeutic strategies that target broader SCD sequelae. SCD phenotypic severity can be alleviated by increasing fetal hemoglobin (HbF) expression. This results in the inhibition of HbS polymerization and thus sickling, and a reduction in oxidative stress. The efficacy of HbF is due to its ability to dilute HbS levels below the threshold required for polymerization and to influence HbS polymer stability in RBCs. Nuclear factor-E2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein-1 (Keap1)-complex signaling is one of the most important cytoprotective signaling controlling oxidative stress. Nrf2 is present in most organs and, after dissociation from Keap1, it accumulates in the cytoplasm, then translocates to the nucleus where it binds to the antioxidant response element (ARE) sequences and increases the expression of various cytoprotective antioxidant genes. Keeping this in mind, various researchers have proposed a role of multiple agents, more importantly tert-Butylhydroquinone (tBHQ), curcumin, etc., (having electrophilic properties) in inhibiting keap1 activity, so that Nrf2 can translocate to the nucleus to activate the gamma globin gene, thus maintaining alpha-hemoglobin-stabilizing protein (AHSP) and HbF levels. This leads to reduced oxidative stress, consequently minimizing SCD-associated complications. In this review, we will discuss the role of the Keap-1–Nrf2 complex in hemoglobinopathies, especially in SCD, and how this complex might represent a better target for more effective treatment options.

Reticulocyte mitochondrial retention increases reactive oxygen species and oxygen consumption in mouse models of sickle cell disease and phlebotomy-induced anemia

Sickle cell disease (SCD) is caused by a mutation of the β-globin gene that results in the production of hemoglobin S (HbS). People with SCD experience anemia, severe acute pain episodes, persistent chronic pain, multiorgan damage, and a reduced life span. The pathophysiology of SCD caused by the polymerization of HbS on deoxygenation results in red cell deformability and the generation of reactive oxygen species (ROS). These 2 factors lead to red cell fragility and hemolysis. Reticulocytosis is an independent predictor of disease morbidity and mortality in SCD. We previously established that humans and mice with SCD exhibit abnormal mitochondrial retention in erythrocytes increasing ROS-associated hemolysis. Here, we investigated the hypothesis that mitochondrial retention and increased ROS are a consequence of stress erythropoiesis. Our results show clearly that stress erythropoiesis in phlebotomized, anemic AA mice results in mitochondrial retention and increased ROS in reticulocytes. We observed that elevated mitochondrial retention in reticulocytes also alters oxygen consumption and potentially contributes to increased HbS polymerization and red blood cell hemolysis. Therefore, these events occurring due to stress erythropoiesis contribute significantly to the pathology of SCD and suggest new therapeutic targets.

Red blood cells from endothelial nitric oxide synthase-deficient mice induce vascular dysfunction involving oxidative stress and endothelial arginase I

BACKGROUND & AIMS

Nitric oxide bioactivity (NO) from endothelial NO synthase (eNOS) importantly contributes to the maintenance of vascular homeostasis, and reduced eNOS activity has been associated with cardiovascular disease. Emerging evidence suggests interaction(s) between red blood cells (RBCs) and the endothelium in vascular control; however, the specific role of RBC eNOS is less clear. We aimed to investigate the hypothesis that a lack of RBC eNOS induces endothelial dysfunction.

METHODS & RESULTS

RBCs from global eNOS knockout (KO) and wildtype (WT) mice were co-incubated ex vivo overnight with healthy mouse aortic rings, followed by functional and mechanistic analyses of endothelium-dependent and independent relaxations. RBCs from eNOS KO mice induced endothelial dysfunction and vascular oxidative stress, whereas WT RBC did not. No differences were observed for endothelium-independent relaxations. This eNOS KO RBC-induced endothelial dysfunctional phenotype was prevented by concomitant co-incubation with reactive oxygen species scavenger (TEMPOL), arginase inhibitor (nor-NOHA), NO donor (detaNONOate) and NADPH oxidase 4 (NOX4) inhibitor. Moreover, vessels from endothelial cell-specific arginase 1 KO mice were resistant to eNOS KO-RBC-induced endothelial dysfunction. Finally, in mice aortae co-incubated with RBCs from women with preeclampsia, we observed a significant reduction in endothelial function compared to when using RBCs from healthy pregnant women or from women with uncomplicated gestational hypertension.

CONCLUSIONS

RBCs from mice lacking eNOS, and patients with preeclampsia, induce endothelial dysfunction in adjacent blood vessels. Thus, RBC-derived NO bioactivity acts to prevent induction of vascular oxidative stress occurring via RBC NOX4-derived ROS in a vascular arginase-dependent manner. Our data highlight the intrinsic protective role of RBC-derived NO bioactivity in preventing the damaging potential of RBCs. This provides novel insight into the functional relationship between RBCs and the vasculature in health and cardiovascular disease, including preeclampsia.

Redox Status of Erythrocytes as an Important Factor in Eryptosis and Erythronecroptosis

Overall, reactive oxygen species (ROS) signalling significantly contributes to initiation and mo-dulation of multiple regulated cell death (RCD) pathways. Lately, more information has become available about RCD modalities of erythrocytes, including the role of ROS. ROS accumulation has therefore been increasingly recognized as a critical factor involved in eryptosis (apoptosis of erythrocytes) and erythro-necroptosis (necroptosis of erythrocytes). Eryptosis is a Ca2+-dependent apoptosis-like RCD of erythrocytes that occurs in response to oxidative stress, hyperosmolarity, ATP depletion, and a wide range of xenobiotics. Moreover, eryptosis seems to be involved in the pathogenesis of multiple human diseases and pathological processes. Several studies have reported that erythrocytes can also undergo necroptosis, a lytic RIPK1/RIPK3/MLKL-mediated RCD. As an example, erythronecroptosis can occur in response to CD59-specific pore-forming toxins. We have systematically summarized available studies regarding the involvement of ROS and oxidative stress in these two distinct RCDs of erythrocytes. We have focused specifically on cellular signalling pathways involved in ROS-mediated cell death decisions in erythrocytes. Furthermore, we have summarized dysregulation of related erythrocytic antioxidant defence systems. The general concept of the ROS role in eryptotic and necroptotic cell death pathways in erythrocytes seems to be established. However, further studies are required to uncover the complex role of ROS in the crosstalk and interplay between the survival and RCDs of erythrocytes.

Puerarin: A review of its mechanisms of action and clinical studies in ophthalmology

BACKGROUND

Pueraria is the common name of the dried root of either Pueraria montana var. lobata (Willd.) Maesen & S.M.Almeida ex Sanjappa & Predeep (syn. Pueraria lobata (Willd.) Ohwi) or Pueraria montana var. thomsonii (Benth.) M.R.Almeida (syn. Pueraria thomsonii Benth.). Puerarin is a C-glucoside of the isoflavone daidzein extracted from Pueraria. It has been widely investigated to explore its therapeutic role in eye diseases and the molecular mechanisms.

PURPOSE

To collect the available literature from 2000 to 2022 on puerarin in the treatment of ocular diseases and suggest the future required directions to improve its medicinal value.

METHOD

The content of this review was obtained from databases such as Web of Science, PubMed, Google Scholar, China National Knowledge Infrastructure (CNKI), and the Wanfang Database.

RESULTS

The search yielded 428 articles, of which 159 articles were included after excluding duplicate articles and articles related to puerarin but less relevant to the topic of the review. In eleven articles, the bioavailability of puerarin was discussed. Despite puerarin possesses diverse biological activities, its bioavailability on its own is poor. There are 95 articles in which the therapeutic mechanisms of puerarin in ocular diseases was reported. Of these, 54 articles discussed the various signalling pathways related to occular diseases affected by puerarin. The other 41 articles discussed specific biological activities of puerarin. It plays a therapeutic role in ophthalmopathy via regulating nuclear factor kappa-B (NF-ĸB), mitogen-activated protein kinases (MAPKs), PI3K/AKT, JAK/STAT, protein kinase C (PKC) and other related pathways, affecting the expression of tumour necrosis factor α (TNF-α), interleukin-1β (IL-1β), intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), superoxide dismutase (SOD), B-cell lymphoma-2 (Bcl-2) and other cytokines resulting in anti-inflammatory, antioxidant and anti-apoptotic effects. The clinical applications of puerarin in ophthalmology were discussed in 25 articles. Eleven articles discussed the toxicity of puerarin. The literature suggests that puerarin has a good curative effect and can be used safely in clinical practice.

CONCLUSION

This review has illustrated the diverse applications of puerarin acting on ocular diseases and suggested that puerarin can be used for treating diabetic retinopathy, retinal vascular occlusion, glaucoma and other ocular diseases in the clinic. Some ocular diseases are the result of the combined action of multiple factors, and the effect of puerarin on different factors needs to be further studied to improve a more complete mechanism of action of puerarin. In addition, it is necessary to increase the number of subjects in clinical trials and conduct clinical trials for other ocular diseases. The information presented here will guide future research studies.

Advanced glycation end products in diabetic retinopathy and phytochemical therapy

Advanced glycation end products (AGEs) are generated by the nonenzymatic glycation of proteins or lipids. Diabetic retinopathy (DR) is one common complication in patients with diabetes. The accumulation of AGEs in retinal cells is strongly associated with the development of DR. AGEs can induce the breakdown of redox balance and then cause oxidative stress in retinal cells, exerting cytopathic effects in the progression of DR. The interaction between AGEs and the receptor for AGE (RAGE) is involved in multiple cellular pathological alterations in the retina. This review is to elucidate the pathogenetic roles of AGEs in the progression of DR, including metabolic abnormalities, lipid peroxidation, structural and functional alterations, and neurodegeneration. In addition, disorders associated with AGEs can be used as potential therapeutic targets to explore effective and safe treatments for DR. In this review, we have also introduced antioxidant phytochemicals as potential therapeutic strategies for the treatment of DR.

Erythrocyte oxidative stress and thrombosis

Thrombosis is a common disorder with a relevant burden of morbidity and mortality worldwide, particularly among elderly patients. Growing evidence demonstrated a direct role of oxidative stress in thrombosis, with various cell types contributing to this process. Among them, erythrocytes produce high quantities of intracellular reactive oxygen species (ROS) by NADPH oxidase activation and haemoglobin autoxidation. Concomitantly, extracellular ROS released by other cells in the blood flow can be uptaken and accumulate within erythrocytes. This oxidative milieu can alter erythrocyte membrane structure, leading to an impaired erythrocyte function, and promoting erythrocytes lysis, binding to endothelial cells, activation of platelet and of coagulation factors, phosphatidylserine exposure and release of microvesicles. Moreover, these abnormal erythrocytes are able to adhere to the vessel wall, contributing to thrombin generation within the thrombus. This process results in accelerated haemolysis and in a hypercoagulable state, in which structurally impaired erythrocytes contribute to increase thrombus size, to reduce its permeability and susceptibility to lysis. However, the wide plethora of mechanisms by which oxidised erythrocytes contribute to thrombosis is not completely elucidated. This review discusses the main biochemical aspects linking erythrocytes, oxidative stress and thrombosis, addressing their potential implication for clinical and therapeutic management.

The Effect of β-Carotene, Tocopherols and Ascorbic Acid as Anti-Oxidant Molecules on Human and Animal In Vitro/In Vivo Studies: A Review of Research Design and Analytical Techniques Used

Prolonged elevated oxidative stress (OS) possesses negative effect on cell structure and functioning, and is associated with the development of numerous disorders. Naturally occurred anti-oxidant compounds reduce the oxidative stress in living organisms. In this review, antioxidant properties of β-carotene, tocopherols and ascorbic acid are presented based on in vitro, in vivo and populational studies. Firstly, environmental factors contributing to the OS occurrence and intracellular sources of Reactive Oxygen Species (ROS) generation, as well as ROS-mediated cellular structure degradation, are introduced. Secondly, enzymatic and non-enzymatic mechanism of anti-oxidant defence against OS development, is presented. Furthermore, ROS-preventing mechanisms and effectiveness of β-carotene, tocopherols and ascorbic acid as anti-oxidants are summarized, based on studies where different ROS-generating (oxidizing) agents are used. Oxidative stress biomarkers, as indicators on OS level and prevention by anti-oxidant supplementation, are presented with a focus on the methods (spectrophotometric, fluorometric, chromatographic, immuno-enzymatic) of their detection. Finally, the application of Raman spectroscopy and imaging as a tool for monitoring the effect of anti-oxidant (β-carotene, ascorbic acid) on cell structure and metabolism, is proposed. Literature data gathered suggest that β-carotene, tocopherols and ascorbic acid possess potential to mitigate oxidative stress in various biological systems. Moreover, Raman spectroscopy and imaging can be a valuable technique to study the effect of oxidative stress and anti-oxidant molecules in cell studies.

Rapid degradation of protein tyrosine phosphatase 1B in sickle cells: Possible contribution to sickle cell membrane weakening

Although both protein tyrosine phosphatases and kinases are constitutively active in healthy human red blood cells (RBCs), the preponderance of phosphatase activities maintains the membrane proteins in a predominantly unphosphorylated state. We report here that unlike healthy RBCs, proteins in sickle cells are heavily tyrosine phosphorylated, raising the question regarding the mechanism underpinning this tyrosine phosphorylation. Upon investigating possible causes, we observe that protein tyrosine phosphatase 1B (PTP1B), the major erythrocyte tyrosine phosphatase, is largely digested to a lower molecular weight fragment in sickle cells. We further find that the resulting truncated form of PTP1B is significantly less active than its intact counterpart, probably accounting for the intense tyrosine phosphorylation of Band 3 in sickle erythrocytes. Because this tyrosine phosphorylation of Band 3 promotes erythrocyte membrane weakening that causes release of both membrane vesicles and cell free hemoglobin that in turn initiates vaso-occlusive events, we conclude that cleavage of PTP1B could contribute to the symptoms of sickle cell disease. We further posit that methods to inhibit proteolysis of PTP1B could mitigate symptoms of the disease.

Erythroid lineage Jak2V617F expression promotes atherosclerosis through erythrophagocytosis and macrophage ferroptosis

Elevated hematocrit is associated with cardiovascular risk; however, the causality and mechanisms are unclear. The JAK2^V617F (Jak2^VF) mutation increases cardiovascular risk in myeloproliferative disorders and in clonal hematopoiesis. Jak2^VF mice with elevated WBCs, platelets, and RBCs display accelerated atherosclerosis and macrophage erythrophagocytosis. To investigate whether selective erythroid Jak2^VF expression promotes atherosclerosis, we developed hyperlipidemic erythropoietin receptor Cre mice that express Jak2^VF in the erythroid lineage (VFEpoR mice). VFEpoR mice without elevated blood cell counts showed increased atherosclerotic plaque necrosis, erythrophagocytosis, and ferroptosis. Selective induction of erythrocytosis with low-dose erythropoietin further exacerbated atherosclerosis with prominent ferroptosis, lipid peroxidation, and endothelial damage. VFEpoR RBCs had reduced antioxidant defenses and increased lipid hydroperoxides. Phagocytosis of human or murine WT or JAK2^VF RBCs by WT macrophages induced ferroptosis, which was prevented by the ferroptosis inhibitor liproxstatin-1. Liproxstatin-1 reversed increased atherosclerosis, lipid peroxidation, ferroptosis, and endothelial damage in VFEpoR mice and in Jak2^VF chimeric mice simulating clonal hematopoiesis, but had no impact in controls. Erythroid lineage Jak2^VF expression led to qualitative and quantitative defects in RBCs that exacerbated atherosclerosis. Phagocytosis of RBCs by plaque macrophages promoted ferroptosis, suggesting a therapeutic target for reducing RBC-mediated cardiovascular risk.

Redox Balance in β-Thalassemia and Sickle Cell Disease: A Love and Hate Relationship

β-thalassemia and sickle cell disease (SCD) are inherited hemoglobinopathies that result in both quantitative and qualitative variations in the β-globin chain. These in turn lead to instability in the generated hemoglobin (Hb) or to a globin chain imbalance that affects the oxidative environment both intracellularly and extracellularly. While oxidative stress is not among the primary etiologies of β-thalassemia and SCD, it plays a significant role in the pathogenesis of these diseases. Different mechanisms exist behind the development of oxidative stress; the result of which is cytotoxicity, causing the oxidation of cellular components that can eventually lead to cell death and organ damage. In this review, we summarize the mechanisms of oxidative stress development in β-thalassemia and SCD and describe the current and potential antioxidant therapeutic strategies. Finally, we discuss the role of targeted therapy in achieving an optimal redox balance.

Reprogramming of red blood cell metabolism in Zika virus-infected donors

BACKGROUND

Diseases caused by arthropod-borne viruses remain a burden to global health; in particular, Zika virus (ZIKV) has been reported in 87 countries and territories. In healthy blood donors, ZIKV RNA can be detected in red blood cells (RBCs) months after infection, clearance of detectable nucleic acid in plasma, and seroconversion. However, little information is available on the impact of ZIKV infection to metabolism.

STUDY DESIGN AND METHODS

We applied mass spectrometry-based metabolomics and lipidomics approaches to investigate the impact of ZIKV infection on RBCs over the course of infection. ZIKV-infected blood donors (n = 25) were identified through molecular and serologic methods, which included nucleic acid amplification testing and real-time polymerase chain reaction (PCR) for detection of ZIKV RNA and enzyme-linked immunosorbent assay (ELISA) for detection of flavivirus-specific IgM and IgG.

RESULTS

In ZIKV RNA-positive donors, we observed lower glucose and lactate levels, and higher levels of ribose phosphate, suggestive of the activation of the pentose phosphate pathway. The top pathways altered in RBCs from ZIKV-IgM-positive donors include amino acid metabolism and biosynthesis, fatty acid metabolism and biosynthesis, linoleic acid and arachidonate metabolism and glutathione metabolism. RBCs from ZIKV-infected donors had increased levels of early glycolytic metabolites, and higher levels of metabolites of the pentose phosphate pathway. Alterations in acyl-carnitine and fatty acid metabolism are consistent with impaired membrane lipid homeostasis in RBCs from ZIKV IgM positive donors.

CONCLUSION

RBC from healthy blood donors who had been infected by ZIKV are characterized by long-lasting metabolic alterations even months after infection has resolved.

Peroxiredoxin-2 recycling is slower in denser and pediatric sickle cell red cells

Peroxiredoxin-2 (Prx-2) is a critical antioxidant protein in red blood cells (RBC). Prx-2 is oxidized to a disulfide covalently-bound dimer by H₂ O₂ , and then reduced back by the NADPH-dependent thioredoxin-thioredoxin reductase system. The reduction of oxidized Prx-2 is relatively slow in RBCs. Since Prx-2 is highly abundant, Prx-2s' peroxidase catalytic cycle is not considered to be limiting under normal conditions. However, whether Prx-2 recycling becomes limiting when RBCs are exposed to stress is not known. Using three different model systems characterized by increased oxidative damage to RBCs spanning the physiologic (endogenous RBCs of different ages), therapeutic (cold-stored RBCs in blood banks) and pathologic (RBCs from sickle cell disease (SCD) patients and humanized SCD mice) spectrum, basal levels of Prx-2 oxidation and Prx-2 recycling kinetics after addition of H₂ O₂ were determined. The reduction of oxidized Prx-2 was significantly slower in older versuin older versus younger RBCs, in RBCs stored for 4-5 weeks compared to 1 week, and in RBC from pediatric SCD patients compared to RBCs from control non-SCD patients. Similarly, the rate of Prx-2 recycling was slower in humanized SCD mice compared to WT mice. Treatment of RBC with carbon monoxide (CO) to limit heme-peroxidase activity had no effect on Prx-2 recycling kinetics. Treatment with glucose attenuated slowed Prx-2 recycling in older RBCs and SCD RBCs, but not stored RBCs. In conclusion, the reduction of oxidized Prx-2 can be further slowed in RBCs, which may limit the protection afforded by this antioxidant protein in settings associated with erythrocyte stress.

The antibacterial activity of erythrocytes from Clarias fuscus associated with phagocytosis and respiratory burst generation

It is widely known that red blood cells (RBCs) are responsible for respiration and the transport of gas. However, recent reports have also described the immune properties of RBCs, therefore creating new understanding for the functionality of RBCs. However, little is known about the immunological role of RBCs in bony fish. In this study, we used RBCs from Clarias fuscus as a model and demonstrate that these cells exhibited phagocytic ability with both latex beads and bacteria. Scanning electron microscopy and transmission electron microscopy provided visual confirmation of the phagocytotic process in RBCs. In addition, we used flow cytometry and fluorescence microscopy to analyse the rate of phagocytosis in RBCs. We found that RBCs exhibited stable phagocytotic ability with latex beads ranging from 0.5 to 1.0 μm in size. In response to bacterial stimulation, RBCs produced reactive oxygen species (ROS) and nitric oxide synthase (NOS), which are harmful to bacteria. RBCs also have an antioxidant system. Under conditions of oxidative stress, the expression levels of antioxidant enzymes, and particularly those of superoxide dismutase（SOD） increased significantly. Our results show that the erythrocytes of bony fish are phagocytic and also produce ROS which are toxic to bacteria. In addition, RBCs have an antioxidant system that removes excess ROS production to protect cells from oxidative damage.

Xanthohumol Induces ROS through NADPH Oxidase, Causes Cell Cycle Arrest and Apoptosis

Reactive oxygen species (ROS) are either toxic in excess or essential for redox signalling at the physiological level, which is closely related to the site of generation. Xanthohumol (XN) is an important natural product of hops (Humulus lupulus L.) and was reported to induce ROS in mitochondria. While in the present study, our data indicate that NADPH oxidase (NOX) is another site. In human acute myeloid leukemia HL-60 cells, we first identified that cell proliferation was inhibited by XN without affecting viability, and this could be alleviated by the antioxidant N-acetyl-L-cysteine (NAC); cell cycles were blocked at G1 phase, apoptosis was induced in a dose-dependent manner, and malondialdehyde (MDA) content was upregulated. XN-induced ROS generation was detected by flow cytometry, which can be inhibited by diphenyleneiodonium chloride (DPI, a NOX inhibitor), while not by N^G-methyl-L-arginine acetate (L-NMMA, a nitric oxide synthase inhibitor). The involvement of NOX in XN-induced ROS generation was further evaluated: immunofluorescence assay indicated subunits assembled in the membrane, and gp91^phox knockdown with siRNA decreased XN-induced ROS. Human red blood cells (with NOX, without mitochondria) were further selected as a cell model, and the XN-induced ROS and DPI inhibiting effects were found again. In conclusion, our results indicate that XN exhibits antiproliferation effects through ROS-related mechanisms, and NOX is a source of XN-induced ROS. As NOX-sourced ROS are critical for phagocytosis, our findings may contribute to the anti-infection and anti-inflammatory effect of XN.

Interleukin-1 receptor antagonism leads to improved anaemia in a murine model of sickle cell disease and is associated with reduced ex vivo platelet-mediated erythrocyte sickling

Sickle cell disease (SCD) is associated with haemolytic anaemia and secondary activation of leucocytes and platelets, which in turn may further exacerbate haemolysis. As cytokine signalling pathways may participate in this cycle, the present study investigated whether pharmacological blockade of the interleukin-1 receptor (IL-1R) would mitigate anaemia in a murine model of SCD. Within 2 weeks of treatment, reduced markers of haemolysis were observed in anakinra-treated mice compared to vehicle-treated mice. After 4 weeks of anakinra treatment, mice showed increased numbers of erythrocytes, haemoglobin, and haematocrit, along with reduced reticulocytes. Blood from anakinra-treated mice was less susceptible to ex vivo erythrocyte sickling and was resistant to exogenous IL-1β-mediated sickling. Supernatant generated from IL-1β-treated platelets was sufficient to promote erythrocyte sickling, an effect not observed with platelet supernatant generated from IL-1R^-/- mice. The sickling effect of IL-1β-treated platelet supernatant was inhibited by a transforming growth factor-β (TGF-β) neutralising antibody, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibition, and superoxide scavengers, but replicated by recombinant TGF-β. In conclusion, pharmacological IL-1R antagonism leads to improved anaemia in a murine SCD model. IL-1β stimulation of platelets promotes erythrocyte sickling. This effect may be mediated by platelet-derived TGF-β-induced reactive oxygen species generation though erythrocyte NADPH oxidase.

The Role of RBC Oxidative Stress in Sickle Cell Disease: From the Molecular Basis to Pathologic Implications

Sickle cell disease (SCD) is an inherited monogenic disorder and the most common severe hemoglobinopathy in the world. SCD is characterized by a point mutation in the β-globin gene, which results in hemoglobin (Hb) S production, leading to a variety of mechanistic and phenotypic changes within the sickle red blood cell (RBC). In SCD, the sickle RBCs are the root cause of the disease and they are a primary source of oxidative stress since sickle RBC redox state is compromised due to an imbalance between prooxidants and antioxidants. This imbalance in redox state is a result of a continuous production of reactive oxygen species (ROS) within the sickle RBC caused by the constant endogenous Hb autoxidation and NADPH oxidase activation, as well as by a deficiency in the antioxidant defense system. Accumulation of non-neutralized ROS within the sickle RBCs affects RBC membrane structure and function, leading to membrane integrity deficiency, low deformability, phosphatidylserine exposure, and release of micro-vesicles. These oxidative stress-associated RBC phenotypic modifications consequently evoke a myriad of physiological changes involved in multi-system manifestations. Thus, RBC oxidative stress in SCD can ultimately instigate major processes involved in organ damage. The critical role of the sickle RBC ROS production and its regulation in SCD pathophysiology are discussed here.

Caffeic acid: an antioxidant with novel antisickling properties

It is well documented that caffeic acid (3,4‐dihydroxycinnamic acid) (CA) interacts with and inhibits the oxidative reactions of myoglobin (Mb) and hemoglobin (Hb), and this interaction underlies its antioxidative action in meat. Sickle cell hemoglobin (HbS) is known for its tendency to oxidize more readily than normal HbA in the presence of hydrogen peroxide (H₂O₂), which leads to a more persistent and highly oxidizing ferryl Hb (HbFe⁴⁺). We have investigated the effects of CA on HbS oxidation intermediates, specifically on the ferric/ferryl forms. At a low concentration of H₂O₂ (0.5‐fold over heme), we observed a fivefold reduction in the amount of HbFe⁴⁺ accumulated in a mixture of ferric and H₂O₂ solution. Higher levels of H₂O₂ (onefold and twofold over heme) led to a lesser threefold and twofold reduction in the content of HbFe⁴⁺, respectively, possibly due to the saturation of the binding sites on the Hb molecule. The most intriguing finding was that when 5‐molar excess CA over heme was used, and a considerable increase in the delay time of HbS polymerization to approximately 200 s was observed. This delay in polymerization of HbS is theoretically sufficient to avoid microcapillary blockage and prevent vasoconstrictions in vivo. Mass spectrometry analysis indicated that CA was more extensively covalently bonded to βCys⁹³ than to βCys¹¹² and αCys¹⁰⁴. The dual antioxidant and antisickling properties of CA may be explored further to maximize its therapeutic potential in SCD.

Extracellular Vesicles in Sickle Cell Disease: Plasma Concentration, Blood Cell Types Origin Distribution and Biological Properties

Prototype of monogenic disorder, sickle cell disease (SCD) is caused by a unique single mutation in the β-globin gene, leading to the production of the abnormal hemoglobin S (HbS). HbS polymerization in deoxygenated condition induces the sickling of red blood cells (RBCs), which become less deformable and more fragile, and thus prone to lysis. In addition to anemia, SCD patients may exhibit a plethora of clinical manifestations ranging from acute complications such as the frequent and debilitating painful vaso-occlusive crisis to chronic end organ damages. Several interrelated pathophysiological processes have been described, including impaired blood rheology, increased blood cell adhesion, coagulation, inflammation and enhanced oxidative stress among others. During the last two decades, it has been shown that extracellular vesicles (EVs), defined as cell-derived anucleated particles delimited by a lipid bilayer, and comprising small EVs (sEVs) and medium/large EVs (m/lEVs); are not only biomarkers but also subcellular actors in SCD pathophysiology. Plasma concentration of m/lEVs, originated mainly from RBCs and platelets (PLTs) but also from the other blood cell types, is higher in SCD patients than in healthy controls. The concentration and the density of externalized phosphatidylserine of those released from RBCs may vary according to clinical status (crisis vs. steady state) and treatment (hydroxyurea). Besides their procoagulant properties initially described, RBC-m/lEVs may promote inflammation through their effects on monocytes/macrophages and endothelial cells. Although less intensely studied, sEVs plasma concentration is increased in SCD and these EVs may cause endothelial damages. In addition, sEVs released from activated PLTs trigger PLT-neutrophil aggregation involved in lung vaso-occlusion in sickle mice. Altogether, these data clearly indicate that EVs are both biomarkers and bio-effectors in SCD, which deserve further studies.

Modulatory Effect of Chaetomorpha gracilis on Erythrocytes Functions and Metabolic Disorders in Mice Fed a High-cholesterol Diet

The current study was carried out to estimate the protective effect of methanolic extract of Chaetomorpha gracilis (MECG) against High Cholesterol Diet (HCD) induced erythrocyte damage in mice. The results of the in vitro assay showed that MECG have higher antioxidant capacities in the DPPH, TAC, ABTS, NBT, NO^. inhibition assays. The HPLC analysis confirmed that this potential antioxidant seems to be due to the active compounds, in particular polyphenols, flavonoids. HCD promoted oxidative stress with a rise the level of malonaldehyde (MDA), advanced oxidation protein product (AOPP) levels and a significant decrease of the Vitamin C content, as well the antioxidant enzyme activities such as superoxide dismutase and glutathione peroxidase. In addition, HCD treatment caused significant lipid profile disorders via increase the cholesterol, triglycerides and LDL levels and reduction HDL-Ch level. A statistically significant decrease of Mg²⁺ and Ca²⁺ ATPase activities accompanied with a severe damage in the erythrocytes structure and hematological parameters alterations were also noted in hypercholesterolemic mice. Pre-treatment with MECG significantly restored biochemical markers and pathological lesions. It can be suggest that supplementation of MECG displays high potential to quench free radicals and attenuates high cholesterol diet induced erythrocytes oxidative stress and related damages.

Erythrocytes: Central Actors in Multiple Scenes of Atherosclerosis

The development and progression of atherosclerosis (ATH) involves lipid accumulation, oxidative stress and both vascular and blood cell dysfunction. Erythrocytes, the main circulating cells in the body, exert determinant roles in the gas transport between tissues. Erythrocytes have long been considered as simple bystanders in cardiovascular diseases, including ATH. This review highlights recent knowledge concerning the role of erythrocytes being more than just passive gas carriers, as potent contributors to atherosclerotic plaque progression. Erythrocyte physiology and ATH pathology is first described. Then, a specific chapter delineates the numerous links between erythrocytes and atherogenesis. In particular, we discuss the impact of extravasated erythrocytes in plaque iron homeostasis with potential pathological consequences. Hyperglycaemia is recognised as a significant aggravating contributor to the development of ATH. Then, a special focus is made on glycoxidative modifications of erythrocytes and their role in ATH. This chapter includes recent data proposing glycoxidised erythrocytes as putative contributors to enhanced atherothrombosis in diabetic patients.

Novel perspectives on redox signaling in red blood cells and platelets in cardiovascular disease

The fundamental physiology of circulating red blood cells (RBCs) and platelets involving regulation of oxygen transport and hemostasis, respectively, are well-described in the literature. Their abundance in the circulation and their interaction with the vascular wall and each other have attracted the attention of other putative physiological and pathophysiological effects of these cells. RBCs and platelets are both important regulators of redox balance harboring powerful pro-oxidant and anti-oxidant (enzymatic and non-enzymatic) capacities. They are also involved in the regulation of vascular tone mainly via export of nitric oxide bioactivity and adenosine triphosphate. Of further importance are emerging observations that these cells undergo functional alterations when exposed to risk factors for cardiovascular disease and during developed cardiometabolic diseases. Under these conditions, the RBCs and platelets contribute to increased oxidative stress by their formation of reactive species including superoxide anion radical, hydrogen peroxide and peroxynitrite. These alterations trigger key changes in the vascular wall characterized by enhanced oxidative stress, reduced nitric oxide bioavailability and endothelial dysfunction. Additional pathophysiological effects are triggered in the heart resulting in increased susceptibility to ischemia-reperfusion injury with impairment in cardiac function. Pharmacological interventions aiming at restoring circulating cell function has been shown to exert marked beneficial effects on cardiovascular function. In this review, we summarize the current knowledge of RBC and platelet biology with special focus on redox biology, their roles in the development of cardiovascular disease and potential therapeutic strategies targeting RBC and platelet dysfunction. Finally, the complex and scarcely understood interaction between RBCs and platelets is discussed.

Mn porphyrins as a novel treatment targeting sickle cell NOXs to reverse and prevent acute vaso-occlusion in vivo

In sickle cell disease (SCD), adhesion of sickle red blood cells (SSRBCs) and activated leukocytes in inflamed venules affects blood rheology, causing vaso-occlusive manifestations and vital reduction in microvascular blood flow. Recently, we found that NADPH oxidases (NOXs) create a vicious feedback loop within SSRBCs. This positive feedback loop mediates SSRBC adhesion to the endothelium. We show for the first time the therapeutic effectiveness of the redox-active manganese (Mn) porphyrins MnTnBuOE-2-PyP5+ (MnBuOE; BMX-001) and MnTE-2-PyP5+ (MnE; BMX-010, AEOL10113) to treat established vaso-occlusion in a humanized sickle mouse model of an acute vaso-occlusive crisis using intravital microscopy. These Mn porphyrins can suppress SSRBC NOX activity. Subcutaneous administration of only 1 dose of MnBuOE or MnE at 0.1 to 2 mg/kg after the inflammatory trigger of vaso-occlusion, or simultaneously, reversed and reduced leukocyte and SSRBC adhesion, diminished leukocyte rolling, restored blood flow, and increased survival rate. Furthermore, MnBuOE and MnE administered to sickle mice subcutaneously at 0.1 to 1 mg/kg for 28 days (except on weekends) did not exacerbate anemia, which seemed to be due to downregulation of both SSRBC reactive oxygen species production and exposure of the eryptotic marker phosphatidylserine. In addition, Mn porphyrins ameliorated leukocytosis, venous blood gases, endothelial activation, and organ oxidative damage. Our data suggest that Mn porphyrins, likely by repressing NOX-mediated adhesive function of SSRBCs and activated leukocytes, could represent a novel, safe therapeutic intervention to treat or prevent the establishment of acute pain crises. These NOX-targeted antioxidants merit further assessment in SCD clinical trials.

Sickle cell vaso-occlusion: The dialectic between red cells and white cells

The pathophysiology of sickle cell anemia, a hereditary hemoglobinopathy, has fascinated clinicians and scientists alike since its description over 100 years ago. A single gene mutation in the HBB gene results in the production of abnormal hemoglobin (Hb) S, whose polymerization when deoxygenated alters the physiochemical properties of red blood cells, in turn triggering pan-cellular activation and pathological mechanisms that include hemolysis, vaso-occlusion, and ischemia-reperfusion to result in the varied and severe complications of the disease. Now widely regarded as an inflammatory disease, in recent years attention has included the role of leukocytes in vaso-occlusive processes in view of the part that these cells play in innate immune processes, their inherent ability to adhere to the endothelium when activated, and their sheer physical and potentially obstructive size. Here, we consider the role of sickle red blood cell populations in elucidating the importance of adhesion vis-a-vis polymerization in vaso-occlusion, review the direct adhesion of sickle red cells to the endothelium in vaso-occlusive processes, and discuss how red cell- and leukocyte-centered mechanisms are not mutually exclusive. Given the initial clinical success of crizanlizumab, a specific anti-P selectin therapy, we suggest that it is appropriate to take a holistic approach to understanding and exploring the complexity of vaso-occlusive mechanisms and the adhesive roles of the varied cell types, including endothelial cells, platelets, leukocytes, and red blood cells.

Vasculopathy in Sickle Cell Disease: From Red Blood Cell Sickling to Vascular Dysfunction

Sickle cell disease (SCD) is a hereditary disorder that leads to the production of an abnormal hemoglobin, hemoglobin S (HbS). HbS polymerizes in deoxygenated conditions, which can prompt red blood cell (RBC) sickling and leaves the RBCs more rigid, fragile, and prone to hemolysis. SCD patients suffer from a plethora of complications, ranging from acute complications, such as characteristic, frequent, and debilitating vaso-occlusive episodes to chronic organ damage. While RBC sickling is the primary event at the origin of vaso-occlusive processes, other factors that can further increase RBC transit times in the microcirculation may also be required to precipitate vaso-occlusive processes. The adhesion of RBC and leukocytes to activated endothelium and the formation of heterocellular aggregates, as well as increased blood viscosity, are among the mechanisms involved in slowing the progress of RBCs in deoxygenated vascular areas, favoring RBC sickling and promoting vascular occlusion. Chronic inflammatory processes and oxidative stress, which are perpetuated by hemolytic events and ischemia-reperfusion injury, result in this pan cellular activation and some acute events, such as stroke and acute chest syndrome, as well as chronic end-organ damage. Furthermore, impaired vasodilation and vasomotor hyperresponsiveness in SCD also contribute to vaso-occlusive processes. Treating SCD as a vascular disease in addition to its hematological perspective, the present article looks at the interplay between abnormal RBC physiology/integrity, vascular dysfunction and clinical severity in SCD, and discusses existing therapies and novel drugs in development that may ameliorate vascular complications in the disease. © 2021 American Physiological Society. Compr Physiol 11:1785-1803, 2021.

Donor Age and Red Cell Age Contribute to the Variance in Lorrca Indices in Healthy Donors for Next Generation Ektacytometry: A Pilot Study

The ability of red blood cells (RBCs) to transport gases, their lifespan as well as their rheological properties invariably depend on the deformability, hydration, and membrane stability of these cells, which can be measured by Laser optical rotational red cell analyser (Lorrca® Maxsis, RR Mechatronics). The osmoscan mode of Lorrca is currently used in diagnosis of rare anemias in clinical laboratories. However, a broad range of normal values for healthy subjects reduces the sensitivity of this method for diagnosis of mild disease phenotype. In this pilot study, we explored the impact of age and gender of 45 healthy donors, as well as RBC age on the Lorrca indices. Whereas gender did not affect the Lorrca indices in our study, the age donors had a profound effect on the O_hyper parameter. To study the impact of RBC age on the osmoscan parameters, we have isolated low (L)-, medium (M)-, or high (H)- density fractions enriched with young, mature, and senescent RBCs, respectively, and evaluated the influence of RBC age-related properties, such as density, morphology, and redox state, on the osmoscan indices. As before, O_hyper was the most sensitive parameter, dropping markedly with an increase in RBC density and age. Senescence was associated with a decrease in deformability (EI_max) and tolerability to low and high osmolatites (Area). L-fraction was enriched with reticulocytes and cells with high projected area and EMA staining, but also contained a small number of cells small in projected area and most likely, terminally senescent. L-fraction was on average slightly less deformable than mature cells. The cells from the L-fraction produced more oxidants and NO than all other fractions. However, RBCs from the L-fraction contained maximal levels of reduced thiols compared to other fractions. Our study suggests that reference values for O_hyper should be age-stratified, and, most probably, corrected for the average RBC age. Further multi-center study is required to validate these suggestions before implementing them into clinical practice.

Sickle Cell Disease: Role of Oxidative Stress and Antioxidant Therapy

Sickle cell disease (SCD) is the most common hereditary disorder of hemoglobin (Hb), which affects approximately a million people worldwide. It is characterized by a single nucleotide substitution in the β-globin gene, leading to the production of abnormal sickle hemoglobin (HbS) with multi-system consequences. HbS polymerization is the primary event in SCD. Repeated polymerization and depolymerization of Hb causes oxidative stress that plays a key role in the pathophysiology of hemolysis, vessel occlusion and the following organ damage in sickle cell patients. For this reason, reactive oxidizing species and the (end)-products of their oxidative reactions have been proposed as markers of both tissue pro-oxidant status and disease severity. Although more studies are needed to clarify their role, antioxidant agents have been shown to be effective in reducing pathological consequences of the disease by preventing oxidative damage in SCD, i.e., by decreasing the oxidant formation or repairing the induced damage. An improved understanding of oxidative stress will lead to targeted antioxidant therapies that should prevent or delay the development of organ complications in this patient population.

The Worst Things in Life are Free: The Role of Free Heme in Sickle Cell Disease

Hemolysis is a pathological feature of several diseases of diverse etiology such as hereditary anemias, malaria, and sepsis. A major complication of hemolysis involves the release of large quantities of hemoglobin into the blood circulation and the subsequent generation of harmful metabolites like labile heme. Protective mechanisms like haptoglobin-hemoglobin and hemopexin-heme binding, and heme oxygenase-1 enzymatic degradation of heme limit the toxicity of the hemolysis-related molecules. The capacity of these protective systems is exceeded in hemolytic diseases, resulting in high residual levels of hemolysis products in the circulation, which pose a great oxidative and proinflammatory risk. Sickle cell disease (SCD) features a prominent hemolytic anemia which impacts the phenotypic variability and disease severity. Not only is circulating heme a potent oxidative molecule, but it can act as an erythrocytic danger-associated molecular pattern (eDAMP) molecule which contributes to a proinflammatory state, promoting sickle complications such as vaso-occlusion and acute lung injury. Exposure to extracellular heme in SCD can also augment the expression of placental growth factor (PlGF) and interleukin-6 (IL-6), with important consequences to enthothelin-1 (ET-1) secretion and pulmonary hypertension, and potentially the development of renal and cardiac dysfunction. This review focuses on heme-induced mechanisms that are implicated in disease pathways, mainly in SCD. A special emphasis is given to heme-induced PlGF and IL-6 related mechanisms and their role in SCD disease progression.

Sub-Fractions of Red Blood Cells Respond Differently to Shear Exposure Following Superoxide Treatment

Simple Summary

Deformation of red blood cells (RBCs) is essential in order to pass through the smallest blood vessels. This cell function is impaired in the presence of high levels of free radicals and shear stress that highly exceeds the physiological range. In contrast, shear stress within the physiological range positively affects RBC function. RBCs are a heterogeneous cell population in terms of RBC age with different RBC deformability described for young and old RBCs, but whether these different sub-populations tolerate mechanical and oxidative stress to the same extent remains unknown. The results of the present investigation revealed lower RBC deformability of old RBCs compared to young RBCs and comparable reductions in RBC deformability of the sub-populations caused by free radicals. Physiological shear stress did not further affect free radical content within the RBCs and reversed the deleterious effects of free radicals on RBC deformability of old RBCs only by improving RBC deformability. The changes were aimed to be explained by changes in the formation of nitric oxide (NO), but outputs of NO generation appeared dependent on cell age. These novel findings highlight a yet less-described complex relation between shear stress, free radicals, and RBC mechanics.

Abstract

Red blood cell (RBC) deformability is an essential component of microcirculatory function that appears to be enhanced by physiological shear stress, while being negatively affected by supraphysiological shears and/or free radical exposure. Given that blood contains RBCs with non-uniform physical properties, whether all cells equivalently tolerate mechanical and oxidative stresses remains poorly understood. We thus partitioned blood into old and young RBCs which were exposed to phenazine methosulfate (PMS) that generates intracellular superoxide and/or specific mechanical stress. Measured RBC deformability was lower in old compared to young RBCs. PMS increased total free radicals in both sub-populations, and RBC deformability decreased accordingly. Shear exposure did not affect reactive species in the sub-populations but reduced RBC nitric oxide synthase (NOS) activation and intriguingly increased RBC deformability in old RBCs. The co-application of PMS and shear exposure also improved cellular deformability in older cells previously exposed to reactive oxygen species (ROS), but not in younger cells. Outputs of NO generation appeared dependent on cell age; in general, stressors applied to younger RBCs tended to induce S-nitrosylation of RBC cytoskeletal proteins, while older RBCs tended to reflect markers of nitrosative stress. We thus present novel findings pertaining to the interplay of mechanical stress and redox metabolism in circulating RBC sub-populations.

Functional relevance of Gedunin as a bona fide ligand of NADPH oxidase 5 and ROS scavenger: An in silico and in vitro assessment in a hyperglycemic RBC model

Clinical evidence suggests that type 2 diabetes therapy can greatly benefit from the suppression of reactive oxygen species generation and the activation or restoration of cellular antioxidant mechanisms. In human, NADPH oxidase (NOX) is the main producer of reactive oxygen species (ROS) that supress the activity of endogenous antioxidant enzymes. In the present study, the antioxidant potential of Gedunin was studied. In silico findings reveal its strong binding affinity with NOX5 C terminal HSP90 binding site that disrupts NOX5 stability and its ability to generate ROS, leading to restoration antioxidant enzymes activities. It was found that Gedunin suppressed hyperglycaemia induced oxidative stress in an in vitro RBC model and markedly reversed glucose induced changes including haemoglobin glycosylation and lipid peroxidation. A significant restoration of activities of cellular antioxidant enzymes; superoxide dismutase, catalase and glutathione peroxidase in the presence of Gedunin revealed its ability to reduce oxidative stress. These results substantiated Gedunin as a bona fide inhibitor of human NOX5 and a ROS scavenging antioxidant with promising therapeutic attributes including its natural origin and inhibition of multiple diabetic targets.

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In silico study reveals Gedunin as a bonafied ligand of human NOX5.

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Gedunin binds at NADPH oxidase C terminal HSP90 binding site and inhibits ROS formation.

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Gedunin reverses hemoglobin glycosylation, lipid peroxidation and restores activity of cellular antioxidant enzymes.

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Gedunin exhibits antioxidant property with dual mode of action: as an ROS scavenger and NOX5 inhibitor.