Oxidative status of red blood cells, neutrophils, and platelets in paroxysmal nocturnal hemoglobinuria

A Pleiotropic Nanomedicine Mitigates Splenic Hyperplasia, Ineffective Erythropoiesis, G6PDH Anomaly through Redox Buffering in Preclinical Mice Model

Here, we present a pleiotropic nanomedicine-a smart, functionalized redox buffering nanoparticle-that may be used to treat hematological diseases, associated splenic hyperplasia, and issues related to restricted erythropoiesis. With a diameter of 5-7 nm, the spherical nanomaterial is made of manganese oxide and citrate. Here, we have produced the novel nanomaterial and, using cutting-edge electron microscopic and spectroscopic techniques, extensively assessed its redox buffering potential in vitro with its structural integrity. Using an appropriate animal model (Phenylhydrazine, PHz, intoxicated C57BL/6J mice), we assessed the therapeutic efficacy of the redox buffering nanomedicine in the treatment of anemia and related consequences. We have further investigated the intricate molecular mechanism of the nanomedicine and its therapeutic impact, which includes increased erythropoiesis and G6PDH production, decreased inflammatory responses, mitigation of splenic hyperplasia, and synergistic intracellular redox buffering. To the best of our knowledge, our studies would find relevance in the innovative management of anemia, decreased erythropoiesis, and splenic hyperplasia.

Thrombosis in Paroxysmal Nocturnal Hemoglobinuria (PNH): From Pathogenesis to Treatment

Paroxysmal Nocturnal Hemoglobinuria (PNH) constitutes a rare bone marrow failure syndrome characterized by hemolytic anemia, thrombotic events (TEs), and bone marrow aplasia of variable degrees. Thrombosis is one of the major clinical manifestations of the disease, affecting up to 40% of individuals with PNH. Venous thrombosis is more prevalent, affecting mainly unusual sites, such as intrabdominal and hepatic veins. TEs might be the first clinical manifestation of PNH. Complement activation, endothelial dysfunction, hemolysis, impaired bioavailability of nitric oxide, and activation of platelets and neutrophils are implicated in the pathogenesis of TEs in PNH patients. Moreover, a vicious cycle involving the coagulation cascade, complement system, and inflammation cytokines, such as interleukin-6, is established. Complement inhibitors, such as eculizumab and ravulizumab (C5 inhibitors), have revolutionized the care of patients with PNH. C5 inhibitors should be initiated in patients with PNH and thrombosis, while they constitute a great prophylactic measure for TEs in those individuals. Anticoagulants, such as warfarin and low-molecular-weight heparin, and, in selected cases, direct oral anticoagulants (DOACs) should be used in combination with C5 inhibitors in patients who develop TEs. Novel complement inhibitors are considered an alternative treatment option, especially for those who develop extravascular or breakthrough hemolysis when terminal inhibitors are administered.

Safety Profile of Monoclonal Antibodies and Subsequent Drug Developments in the Treatment of Paroxysmal Nocturnal Hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a clonal stem cell disease characterized by intravascular hemolysis due to the targeting of affected red blood cells by the complement system. Eculizumab and ravulizumab are two monoclonal antibodies that inhibit the complement system's components and have been shown to significantly improve survival and quality of life. This review describes the role of these monoclonal antibodies in the treatment of PNH with an emphasis on their safety profile. The challenges in the use of these drugs and new drugs in various stages of drug development are also described, which may be helpful in addressing some of these challenges.

Protein Susceptibility to Peroxidation by 4-Hydroxynonenal in Hereditary Hemochromatosis

Iron overload caused by hereditary hemochromatosis (HH) increases free reactive oxygen species that, in turn, induce lipid peroxidation. Its 4-hydroxynonenal (HNE) by-product is a well-established marker of lipid peroxidation since it reacts with accessible proteins with deleterious consequences. Indeed, elevated levels of HNE are often detected in a wide variety of human diseases related to oxidative stress. Here, we evaluated HNE-modified proteins in the membrane of erythrocytes from HH patients and in organs of Hfe^-/- male and female mice, a mouse model of HH. For this purpose, we used one- and two-dimensional gel electrophoresis, immunoblotting and MALDI-TOF/TOF analysis. We identified cytoskeletal membrane proteins and membrane receptors of erythrocytes bound to HNE exclusively in HH patients. Furthermore, kidney and brain of Hfe^-/- mice contained more HNE-adducted protein than healthy controls. Our results identified main HNE-modified proteins suggesting that HH favours preferred protein targets for oxidation by HNE.

Development and validation of a flow cytometric assay for detecting reactive oxygen species in the erythrocytes of healthy dogs

OBJECTIVE

To validate the use of a flow cytometric assay that uses 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) to measure reactive oxygen species in the erythrocytes of healthy dogs.

ANIMALS

50 healthy adult dogs.

PROCEDURES

Erythrocytes were incubated with DCFH-DA or a vehicle control (dimethyl sulfoxide), then incubated with (stimulated) or without (unstimulated) hydrogen peroxide. The flow cytometric assay was evaluated for specificity with increasing concentrations of DCFH-DA and hydrogen peroxide, and a polynomial regression line was applied to determine optimal concentrations. For precision, samples were analyzed 5 consecutive times for determination of intra- and interassay variability. Stability of samples stored at 4°C for up to 48 hours after blood collection was determined with flow cytometric analysis. Coefficient of variation (CV) was considered acceptable at 20%. Baseline measurements were used to determine an expected range of median fluorescence intensity for unstimulated erythrocytes incubated with DCFH-DA.

RESULTS

Erythrocytes were successfully isolated, and stimulated samples demonstrated higher median fluorescence intensity, compared with unstimulated samples. The intra-assay CV was 11.9% and 8.9% and interassay CV was 11.9% and 9.1% for unstimulated and stimulated samples, respectively. Unstimulated samples were stable for up to 24 hours, whereas stimulated samples were stable for up to 48 hours.

CONCLUSIONS AND CLINICAL RELEVANCE

Flow cytometry for the measurement of reactive oxygen species in the erythrocytes of healthy dogs by use of DCFH-DA had acceptable specificity, precision, and stability. Flow cytometry is a promising technique for evaluating intraerythrocytic oxidative stress for healthy dogs.

The Redox Balance and Membrane Shedding in RBC Production, Maturation, and Senescence

Membrane shedding in the form of extracellular vesicles plays a key role in normal physiology and pathology. Partial disturbance of the membrane-cytoskeleton linkage and increased in the intracellular Ca content are considered to be mechanisms underlying the process, but it is questionable whether they constitute the primary initiating steps. Homeostasis of the redox system, which depends on the equilibrium between oxidants and antioxidants, is crucial for many cellular processes. Excess oxidative power results in oxidative stress, which affects many cellular components, including the membrane. Accumulating evidence suggests that oxidative stress indirectly affects membrane shedding most probably by affecting the membrane-cytoskeleton and the Ca content. In red blood cells (RBCs), changes in both the redox system and membrane shedding occur throughout their life-from birth-their production in the bone marrow, to death-aging in the peripheral blood and removal by macrophages in sites of the reticuloendothelial system. Both oxidative stress and membrane shedding are disturbed in diseases affecting the RBC, such as the hereditary and acquired hemolytic anemias (i.e., thalassemia, sickle cell anemia, and autoimmune hemolytic anemia). Herein, I review some data-based and hypothetical possibilities that await experimental confirmation regarding some aspects of the interaction between the redox system and membrane shedding and its role in the normal physiology and pathology of RBCs.

Vitamin C-Sources, Physiological Role, Kinetics, Deficiency, Use, Toxicity, and Determination

Vitamin C (L-ascorbic acid) has been known as an antioxidant for most people. However, its physiological role is much larger and encompasses very different processes ranging from facilitation of iron absorption through involvement in hormones and carnitine synthesis for important roles in epigenetic processes. Contrarily, high doses act as a pro-oxidant than an anti-oxidant. This may also be the reason why plasma levels are meticulously regulated on the level of absorption and excretion in the kidney. Interestingly, most cells contain vitamin C in millimolar concentrations, which is much higher than its plasma concentrations, and compared to other vitamins. The role of vitamin C is well demonstrated by miscellaneous symptoms of its absence-scurvy. The only clinically well-documented indication for vitamin C is scurvy. The effects of vitamin C administration on cancer, cardiovascular diseases, and infections are rather minor or even debatable in the general population. Vitamin C is relatively safe, but caution should be given to the administration of high doses, which can cause overt side effects in some susceptible patients (e.g., oxalate renal stones). Lastly, analytical methods for its determination with advantages and pitfalls are also discussed in this review.

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.

Multi-Omics Analysis Provides Novel Insight into Immuno-Physiological Pathways and Development of Thermal Resistance in Rainbow Trout Exposed to Acute Thermal Stress

In recent years, poikilothermic animals such as fish have increasingly been exposed to stressful high-temperature environments due to global warming. However, systemic changes in fish under thermal stress are not fully understood yet at both the transcriptome and proteome level. Therefore, the objective of this study was to investigate the immuno-physiological responses of fish under extreme thermal stress through integrated multi-omics analysis. Trout were exposed to acute thermal stress by raising water temperature from 15 to 25 °C within 30 min. Head-kidney and plasma samples were collected and used for RNA sequencing and two-dimensional gel electrophoresis. Gene enrichment analysis was performed: differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) were identified to interpret the multi-omics results and identify the relevant biological processes through pathway analysis. Thousands of DEGs and 49 DEPs were identified in fish exposed to thermal stress. Most of these genes and proteins were highly linked to DNA replication, protein processing in the endoplasmic reticulum, cell signaling and structure, glycolysis activation, complement-associated hemolysis, processing of released free hemoglobin, and thrombosis and hypertension/vasoconstriction. Notably, we found that immune disorders mediated by the complement system may trigger hemolysis in thermally stressed fish, which could have serious consequences such as ferroptosis and thrombosis. However, antagonistic activities that decrease cell-free hemoglobin, heme, and iron might be involved in alleviating the side effects of thermally induced immuno-physiological disorders. These factors may represent the major thermal resistance traits that allow fish to overcome extreme thermal stress. Our findings, based on integration of multi-omics data from transcriptomics and proteomics analyses, provide novel insight into the pathogenesis of acute thermal stress and temperature-linked epizootics.

Reactive oxygen species, glutathione, and vitamin E concentrations in dogs with hemolytic or nonhemolytic anemia

BACKGROUND

Red blood cells (RBC) are uniquely susceptible to oxidative injury. Oxidative stress is both a cause for, and effect, of anemia in people but this has been minimally documented in dogs.

OBJECTIVE

To describe direct and indirect markers of oxidative stress in anemic dogs.

HYPOTHESIS

Anemic dogs will have oxidative stress when compared to healthy dogs.

ANIMALS

Forty-seven dogs with anemia (10 with hemolytic anemia) and 70 healthy control dogs.

METHODS

Prospective, cross-sectional study. Anemic dogs were identified from the patient population, and medical records were reviewed to classify the anemia as hemolytic or nonhemolytic. Flow cytometry was used to detect reactive oxygen species (ROS) in erythrocyte isolates. Reduced glutathione (GSH) concentrations were measured in both plasma and hemolysate samples, and vitamin E was measured in serum.

RESULTS

Anemic dogs (both hemolytic and nonhemolytic) had significantly lower median RBC hemolysate GSH concentrations (3.1 μM [0.4-30.8]) when compared to healthy dogs (7.0 μM [0.5-29.7]; P = .03). Dogs with hemolytic anemia had significantly higher median plasma GSH (7.6 μM [0.4-17.8]) when compared to dogs with nonhemolytic anemia (1.6 μM [0.01-7.1]; P = .04) and healthy dogs (2.8 μM [0.1-29.9]; P < .0001). Reactive oxygen species were detectable in all samples, but there was no difference in ROS or vitamin E between groups.

CONCLUSIONS AND CLINICAL IMPORTANCE

Oxidative stress is present in anemic dogs. Derangements in biomarkers of oxidative stress are different in dogs with hemolytic anemia and nonhemolytic anemia.

First exploratory study on the metabolome from plasma exosomes in patients with paroxysmal nocturnal hemoglobinuria

INTRODUCTION

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disease in which patients are at increased risk of thrombosis. The mechanisms underlying the associated thrombosis risk are still poorly understood, although it is known that Eculizumab, the drug of choice for symptomatic patients, prevents thrombotic events. Exosomes are extracellular vesicles that can carry and disseminate genetic material, tumor biomarkers and inflammatory mediators. To date, the metabolite cargo of plasma exosomes from PNH patients has not yet been explored. In this pilot trial, we compared the metabolome of plasma exosomes from PNH patients with that of healthy subjects in order to provide further insights into this rare disease.

RESULTS

We used a non-targeted metabolomics approach with UPLC-ESI-QTOF-MS/MS and GC-MS platforms. Multivariate analyses revealed the differential occurrence (p < .001) of 78 metabolites in plasma exosomes from PNH patients vs healthy control subjects. Remarkably, prostaglandin F2-alpha (6.1-fold), stearoyl arginine (5.3-fold) and 26-hydroxycholesterol-3-sulfate (11.2-fold) were higher in PNH patients vs healthy controls (p < .001).

CONCLUSIONS

This is the first description on the differential metabolite cargo occurring in plasma exosomes from PNH patients. Our results could contribute to the search for possible prognostic biomarkers of thrombotic risk in patients with PNH. Further research in a larger cohort to validate these results is warranted.

Paroxysmal Nocturnal Hemoglobinuria with Glucose-6-Phosphate Dehydrogenase Deficiency: A Case Report and Review of the Literature

In this study, we are describing a female patient with paroxysmal nocturnal hemoglobinuria (PNH) and glucose-6-phosphate dehydrogenase (G6PD) deficiency. Both diseases are known to cause hemolytic anemia that mediates the hemolysis of RBCs through several mechanisms. In PNH the hemolysis is mediated through complement activation and oxidative stress. G6PD enzyme is crucial in preventing damage to cellular structures caused by oxygen-free radicles. In G6PD deficiency the hemolysis is mediated through the oxidative stress created by oxygen-free radicles. Since both diseases mediate hemolysis through the oxidative stress, we hypothesize that both conditions have facilitated an effect on each other and this will reflect on the response to treatment, and this response to treatment could vary based on whether the two mutations occurred in the same gene or in two different X chromosomes. Having diagnosed PNH, the management is very expensive and not all the patients can afford it, especially our patient who is a maid by occupation. So, the real challenge in our case is to monitor her in subsequent visits and to plan the treatment keeping in mind her financial status.

Oxidative stress, eryptosis and anemia: a pivotal mechanistic nexus in systemic diseases

The average lifespan of circulating erythrocytes usually exceeds hundred days. Prior to that, however, erythrocytes may be exposed to oxidative stress in the circulation which could cause injury and trigger their suicidal death or eryptosis. Oxidative stress activates Ca²⁺ -permeable nonselective cation channels in the cell membrane, thus, stimulating Ca²⁺ entry and subsequent cell membrane scrambling resulting in phosphatidylserine exposure and activation of Ca²⁺ -sensitive K⁺ channels leading to K⁺ exit, hyperpolarization, Cl^- exit, and ultimately cell shrinkage due to loss of KCl and osmotically driven water. While the mechanistic link between oxidative stress and anemia remains ill-defined, several diseases such as diabetes, hepatic failure, malignancy, chronic kidney disease and inflammation have been identified to display both increased oxidative stress as well as eryptosis. Recent compelling evidence suggests that oxidative stress is an important perpetrator in accelerating erythrocyte loss in different systemic conditions and an underlying mechanism for anemia associated with these pathological states. In the present review, we discuss the role of oxidative stress in reducing erythrocyte survival and provide novel insights into the possible use of antioxidants as putative antieryptotic and antianemic agents in a variety of systemic diseases.

Oxidative stress in paroxysmal nocturnal hemoglobinuria and other conditions of complement-mediated hemolysis

The complement (C') system and redox status play important roles in the physiological functioning of the body, such as the defense system, but they are also involved in various pathological conditions, including hemolytic anemia. Herein, we review the interaction between the C' and the redox systems in C'-mediated hemolytic anemias, paroxysmal nocturnal hemoglobinuria (PNH) and autoimmune hemolytic anemia, including acute hemolytic transfusion reaction. Blood cells in these diseases have been shown to have increased oxidative status, which was further elevated by interaction with activated C'. The results suggest that oxidative stress, in conjunction with activated C', may cause the underlying symptoms of these diseases, such as intra- and extravascular hemolysis and thrombotic complications. Antioxidants ameliorate oxidative stress by preventing generation of free radicals, by scavenging and preventing their accumulation, and by correcting their cellular damage. Antioxidants have been shown to reduce the oxidative stress and inhibit hemolysis as well as platelet activation mediated by activated C'. This raises the possibility that treatment with antioxidants might be considered as a potential therapeutic modality for C'-mediated hemolytic anemias. Currently, eculizumab, a humanized monoclonal antibody that specifically targets the C' protein C5, is the main treatment modality for PNH. However, because antioxidants are well tolerated and relatively inexpensive, they might be considered as potential adjuvants or an alternative therapeutic modality for PNH and other C'-mediated hemolytic anemias.

The Effect of Fermented Papaya Preparation on Radioactive Exposure

Exposure to ionizing radiation causes cellular damage, which can lead to premature cell death or accumulation of somatic mutations, resulting in malignancy. The damage is mediated in part by free radicals, particularly reactive oxygen species. Fermented papaya preparation (FPP), a product of yeast fermentation of Carica papaya Linn, has been shown to act as an antioxidant. In this study, we investigated the potential of FPP to prevent radiation-induced damage. FPP (0-100 μg/ml) was added to cultured human foreskin fibroblasts and myeloid leukemia (HL-60) cells either before or after irradiation (0-18 Gy). After 1-3 days, the cells were assayed for: intracellular labile iron, measured by staining with calcein; reactive oxygen species generation, measured with dichlorofluorescein diacetate; apoptosis, determined by phosphatidylserine exposure; membrane damage, determined by propidium iodide uptake; and cell survival, determined by a cell proliferation assay. DNA damage was estimated by measuring 8-oxoguanine, a parameter of DNA oxidation, using a fluorescent-specific probe and by the comet assay. These parameters were also assayed in bone marrow cells of mice treated with FPP (by adding it to the drinking water) either before or after irradiation. Somatic mutation accumulation was determined in their peripheral red blood cells, and their survival was monitored. FPP significantly reduced the measured radiation-induced cytotoxic parameters. These findings suggest that FPP might serve as a radioprotector, and its effect on DNA damage and mutagenicity might reduce the long-term effects of radiation, such as primary and secondary malignancy.

Gαs proteins activate p72(Syk) and p60-c-Src tyrosine kinases to mediate sickle red blood cell adhesion to endothelium via LW-αvβ3 and CD44-CD44 interactions

G protein-coupled receptors (GPCRs) have been suggested as new drug targets to treat a variety of diseases. In sickle cell disease (SCD), the LW erythrocyte adhesion receptor can be activated by stimulation of β2 adrenergic receptors (β2ARs), to mediate sickle erythrocyte (SSRBC) adhesion to endothelium. However, the involvement of tyrosine protein kinases in β2AR signaling to activate SSRBC adhesion to endothelium has not been thoroughly elucidated. Either direct activation with Cholera toxin of Gαs protein, which acts downstream of β2ARs, or inhibition with Pertussis toxin of Gαi, mediating suppression of adenylyl cyclase, increased SSRBC adhesion to endothelium over baseline adhesion. This effect involved the non-receptor tyrosine kinases, p72(Syk) and p60-c-Src, which were more abundant in SSRBCs than in normal erythrocytes. In contrast, Pertussis toxin and Cholera toxin failed to increase adhesion of normal erythrocytes. SSRBC Gαi inhibition also increased phosphorylation of p72(Syk) and p60-c-Src. Further, we investigated the relevance of activation of p72(Syk) and p60-c-Src, and identified LW (ICAM-4, CD242) and CD44 as the erythroid adhesion molecules both physically interacting with activated p60-c-Src. As a result, SSRBC LW underwent increased tyrosine phosphorylation, leading to SSRBC LW and CD44 binding to endothelial αvβ3 integrin and CD44, respectively. These data provide in vitro mechanistic evidence that p60-c-Src, which could act downstream of Gαs/p72(Syk), associates with LW and CD44 on SSRBCs leading to their interactions with endothelial αvβ3 and CD44, respectively. Thus, increased activation of these signaling mechanisms in SSRBCs could initiate or exacerbate vascular occlusion, the hallmark of SCD.

Activation of the alternative pathway of complement during the acute phase of typical haemolytic uraemic syndrome

Haemolytic uraemic syndrome (HUS) is characterized by haemolytic anaemia, thrombocytopenia and acute renal failure. We studied the activation state of classical and alternative pathways of complement during the acute phase of Shiga toxin-associated HUS by performing a prospective study of 18 patients and 17 age-matched healthy controls to evaluate C3, C3c, C4, C4d, Bb and SC5b-9 levels. SC5b-9 levels were increased significantly in all patients at admission compared to healthy and end-stage renal disease controls, but were significantly higher in patients presenting with oliguria compared to those with preserved diuresis. C3 and C4 levels were elevated significantly at admission in the non-oliguric group when compared to controls. No significant differences were found for C4d values, whereas factor Bb was elevated in all patients and significantly higher in oliguric patients when compared to both controls and non-oliguric individuals. A positive and significant association was detected when Bb formation was plotted as a function of plasma SC5b-9 at admission. Bb levels declined rapidly during the first week, with values not significantly different from controls by days 3 and 5 for non-oligurics and oligurics, respectively. Our data demonstrate the activation of the alternative pathway of complement during the acute phase of Stx-associated HUS. This finding suggests that complement activation may represent an important trigger for the cell damage that occurs during the syndrome.

Potential utility of melatonin as an antioxidant therapy in the management of sickle cell anemia

This study aimed to assess antioxidant effects of melatonin treatment compared to N-acetylcysteine (NAC) and to their combination in a sickle cell suspension. Sickle erythrocytes were suspended in phosphate-buffered saline, pH 7.4, composing external control group. They were also suspended and incubated at 37°C either in the absence (experimental control group) or in the presence of NAC, melatonin and their combination at concentrations of 100 pm, 100 nm and 100 μm for 1 hr (treatment groups). The melatonin influences were evaluated by spectrophotometric [hemolysis degree, catalase (CAT), glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), and superoxide dismutase (SOD) activities] and chromatographic methods [glutathione (GSH) and malondialdehyde (MDA) levels]. Incubation period was able to cause a rise about 64% on hemolysis degree as well as practically doubled the lipid peroxidation levels (P < 0.01). However, almost all antioxidants tested treatments neutralized this incubation effect observed in MDA levels. Among the antioxidant biomarkers evaluated, we observed a modulating effect of combined treatment on GPx and SOD activities (P < 0.01), which showed ~25% decrease in their activities. In addition, we found an antioxidant dose-dependent effect for melatonin on lipid peroxidation (r = -0.29; P = 0.03) and for combined antioxidant treatments also on MDA levels (r = -0.37; P = 0.01) and on SOD activity (r = -0.54; P < 0.01). Hence, these findings contribute with important insight that melatonin individually or in combination with NAC may be useful for sickle cell anemia management.

A mouse model to study thrombotic complications of thalassemia

Patients with β-thalassemia major and mainly intermedia have an increased risk for developing venous and arterial thrombosis which may be related to circulating pathological red blood cells (RBC) and continuous platelet activation. In the present study we used a modified thalassemic mice model in conjunction with a "real-time" carotid thrombus formation procedure to investigate thrombotic complications of thalassemia. Heterozygous Th3/+ mice, which lack one copy of their β-major and β-minor globin genes, exhibit anomalies in RBC size and shape, chronic anemia and splenomegaly which recapitulate the phenotype of human β-thalassemia intermedia. Flow cytometry measurements showed higher reactive oxygen species generation, indicating oxidative stress, in platelets and RBC of the thalassemic mice compared with wild type mice concomitant with an increase in reduced glutathione content which may represent a compensatory response to oxidative stress, and exposed phosphatidylserine which indicates platelet activation. To elucidate the effect of thalassemia on the development of arterial thrombosis, we studied photochemical-induced real-time thrombus formation in the carotid artery of these mice. The results indicated a significantly shorter "time to occlusion" in the thalassemic mice compared to wild type mice, which was prolonged following in vivo aspirin treatment. We suggest that this mouse model may contribute to our understanding of platelet activation and the hypercoagulable state in thalassemia and lay foundations to screening of anti-platelet drugs as well as anti-oxidants as possible therapeutics for prevention of thrombosis in thalassemia patients.

α-Tocopheryl Phosphate as a Bioactive Derivative of Vitamin E: A Review of the Literature

α-Tocopheryl phosphate (α-TP) is a naturally occurring derivative of α-tocopherol (α-T), one of the eight isoforms of vitamin E. α-TP is present at very low intracellular concentrations, traffics across plasma membranes, and affects many important cellular functions. In addition to being a signaling molecule, α-TP has also been shown to possess antioxidant and potentially antiatherosclerotic properties that are more potent than its parent compound (α-T). However, there is little published data on the clinical effects of α-TP supplements, the mechanisms involved in its metabolism and cellular function, and reliable methods for its determination in plasma.

Case Report: Paroxysmal nocturnal hemoglobinuria in a woman heterozygous for G6PD A-

We describe a case of paroxysmal nocturnal hemoglobinuria (PNH) in a woman who is heterozygous for the glucose-6-phosphate dehydrogenase A-   ( G6PDA-) allele. PNH is associated with one or more clones of cells that lack complement inhibition due to loss of function somatic mutations in the PIGA gene.  PIGA encodes the enzyme phosphatidylinositol glycan anchor biosynthesis, class A, which catalyses the first step of glycosylphosphatidylinisotol ( GPI)  anchor synthesis. Two GPI anchored red cell surface antigens regulate complement lysis. G6PD catalyses the first step of the pentose phosphate pathway and enzyme variants, frequent in some populations have been selected because they confer resistance to malaria, are associated with hemolysis in the presence of oxidizing agents including several drugs. The patient had suffered a hemolytic attack after taking co-trimoxazole, a drug that precipitates hemolysis in G6PD deficient individuals. Since both G6PD and PIGA are X-linked we hypothesized that the PIGA mutation was on the X-chromosome carrying the G6PDA- allele. Investigations showed that in fact the PIGA mutation was on the X-chromosome carrying the normal G6PD B allele. We speculate that complement activation on G6PD A- red cells exposed to Bactrim might have triggered complement activation inducing the lysis of G6PD B PNH Type II red blood cells or that the patient may have had a PNH clone expressing G6PDA- at the time of the hemolytic episode.

Altered red cell and platelet adhesion in hemolytic diseases: Hereditary spherocytosis, paroxysmal nocturnal hemoglobinuria and sickle cell disease

OBJECTIVES

Intravascular hemolysis may have important pathophysiological consequences, such as the induction of cellular adhesion and vasculopathy. We compared the adhesive properties of red cells (RBC) and platelets in hereditary spherocytosis (HS), paroxysmal nocturnal hemoglobinuria (PNH) and sickle cell disease (SCD) patients.

DESIGN AND METHODS

The adhesion of RBC and platelets, from patients and healthy subjects, was determined using static adhesion assays. RBC surface markers were characterized by flow cytometry and lactate dehydrogenase (LDH), plasma hemoglobin (pHb) and TNF-α were assayed in serum/plasma samples.

RESULTS

pHb levels were elevated in all three hemolytic diseases, indicating the incidence of intravascular hemolysis. RBC adhesion and TNF-α were augmented in HS and SCD, but not in PNH. Reticulocyte counts were raised in the three diseases, but were higher in HS and SCD than in PNH; high expressions of CD71, CD36 and CD49d were observed on SCD RBC, while CD71 alone was increased on HS and PNH RBC. Splenectomy was associated with reversals of increased pHb, RBC adhesion, reticulocytes, RBC marker expression and inflammation in HS. In contrast, platelet adhesion was elevated in SCD and PNH, but not HS. Platelet adhesion correlated significantly with serum LDH, but not pHb, in the hemolytic disease cohort; interestingly, LDH did not correlate with reticulocytes or pHb levels.

CONCLUSIONS

Results indicate that extravascular, rather than intravascular, hemolysis (and ensuing RBC production) may contribute to elevations in RBC adhesive properties in HS and SCD, while mechanisms peculiar to each disease may augment platelet adhesion in SCD and PNH.

Identification of human erythrocyte cytosolic proteins associated with plasma membrane during thermal stress

The influence of thermal stress on the association between human erythrocyte membranes and cytosolic proteins was studied by exposing erythrocyte suspensions and whole blood to different elevated temperatures. Membranes and cytosolic proteins from unheated and heat-stressed erythrocytes were analyzed by electrophoresis, followed by mass spectrometric identification. Four major (carbonic anhydrase I, carbonic anhydrase II, peroxiredoxin VI, flavin reductase) and some minor (heat shock protein 90α, heat shock protein 70, α-enolase, peptidylprolyl cis-trans isomerase A) cytosolic proteins were found to be associated with the erythrocyte membrane in response to in vitro thermal stress. Unlike the above proteins, catalase and peroxiredoxin II were associated with membranes from unheated erythrocytes, and their content increased in the membrane following heat stress. The heat-induced association of cytosolic proteins was restricted to the Triton shells (membrane skeleton/cytoskeleton). Similar results were observed when Triton shells derived from unheated erythrocyte membranes were incubated with an unheated erythrocyte cytosolic fraction at elevated temperatures. This is a first report on the association of cytosolic catalase, α-enolase, peroxiredoxin VI, peroxiredoxin II and peptidylprolyl cis-trans isomerase A to the membrane or membrane skeleton of erythrocytes under heat stress. From these results, it is concluded that specific cytosolic proteins are translocated to the membrane in human erythrocytes exposed to heat stress and they may play a novel role as erythrocyte membrane protectors under stress by stabilizing the membrane skeleton through their interactions with skeletal proteins.

Thrombosis in paroxysmal nocturnal hemoglobinuria

The most frequent and feared complication of paroxysmal nocturnal hemoglobinuria (PNH) is thrombosis. Recent research has demonstrated that the complement and coagulation systems are closely integrated with each influencing the activity of the other to the extent that thrombin itself has recently been shown to activate the alternative pathway of complement. This may explain some of the complexity of the thrombosis in PNH. In this review, the recent changes in our understanding of the pathophysiology of thrombosis in PNH, as well as the treatment of thrombosis, will be discussed. Mechanisms explored include platelet activation, toxicity of free hemoglobin, nitric oxide depletion, absence of other glycosylphosphatidylinositol-linked proteins such as urokinase-type plasminogen activator receptor and endothelial dysfunction. Complement inhibition with eculizumab has a dramatic effect in PNH and has a major impact in the prevention of thrombosis as well as its management in this disease.

Antioxidant vitamins C and E supplementation increases markers of haemolysis in sickle cell anaemia patients: a randomized, double-blind, placebo-controlled trial

Erythrocytes from sickle cell anaemia (SCA) patients continuously produce larger amounts of pro-oxidants than normal cells. Oxidative stress seems to primarily affect the membrane and results in haemolysis. The use of antioxidants in vitro reduces the generation of pro-oxidants. To evaluate the impact of vitamins C (VitC) and E (VitE) supplementation in SCA patients, patients over 18 years were randomly assigned to receive VitC 1400 mg + VitE 800 mg per day or placebo orally for 180 d. Eighty-three patients were enrolled (44 vitamins, 39 placebo), median age 27 (18-68) years, 64% female. There were no significant differences between the two groups regarding clinical complications or baseline laboratorial tests. Sixty percent of the patients were VitC deficient, 70% were VitE deficient. Supplementation significantly increased serum VitC and E. However, no significant changes in haemoglobin levels were observed, and, unexpectedly, there was a significant increase in haemolytic markers with vitamin supplementation. In conclusion, VitC + VitE supplementation did not improve anaemia and, surprisingly, increased markers of haemolysis in patients with SCA and S-β(0) -thalassaemia. The exact mechanisms to explain this findings and their clinical significance remain to be determined.

α-Tocopheryl phosphate: uptake, hydrolysis, and antioxidant action in cultured cells and mouse

α-Tocopheryl phosphate (α-TP), a water-soluble analogue of α-tocopherol, is found in humans, animals, and plants. α-TP is resistant to both acid and alkaline hydrolysis and may exert its own function in this form in vivo. In this study, the uptake, hydrolysis, and antioxidant action of α-TP were measured using α-TP with a deuterated methyl group, CD(3), at position 5 of the chroman ring (α-TP(CD3)). The hydrolysis of α-TP(CD3) was followed by measuring α-tocopherol containing the CD(3) group, α-T(CD3), in comparison to unlabeled α-tocopherol, α-T(CH3). α-TP(CD3) was incubated with cultured cells, and the intracellular α-T(CD3) formed was measured with HPLC-ECD and GC-MS. α-TP(CD3) was also administered to mice for 4 weeks by mixing in the diet, and α-T(CD3) was measured in plasma, liver, brain, heart, and testis to compare with endogenous unlabeled α-T(CH3). It was found that α-TP(CD3) was taken in and hydrolyzed readily to α-T(CD3) in cultured cells and in mice. The hydrolysis of α-TP(CD3) in cell culture medium was not observed. α-TP protected primary cortical neuronal cells from glutamate-induced cytotoxicity, and α-TP given to mice reduced the levels of lipid peroxidation products in plasma and liver. These results suggest that α-TP is readily hydrolyzed in vivo to α-T, which acts as an antioxidant, and that α-TP may be used as a water-soluble α-T precursor in intravenous fluids, in eye drops, or as a dietary supplement.

Effect of osmotic shock and urea on phosphatidylserine scrambling in thrombocyte cell membranes

Blood passing the renal medulla enters a strongly hypertonic environment challenging functional properties and survival of blood cells. In erythrocytes, exposure to hyperosmotic shock stimulates Ca(2+) entry and ceramide formation with subsequent cell membrane scrambling, an effect partially reversed by high concentrations of Cl(-) or urea. Cell membrane scrambling with phosphatidylserine exposure is part of the procoagulant phenotype of platelets. Coagulation in the hypertonic renal medulla would jeopardize blood flow in the vasa recta. The present study thus explored whether hypertonic environment and urea modify phosphatidylserine exposure of human platelets. FACS analysis was employed to estimate cytosolic Ca(2+) activity with Fluo3 fluorescence, ceramide formation, P-selectin, and glycoprotein IIb/IIIa activation with fluorescent antibodies and phosphatidylserine exposure with annexin V-binding. The spontaneous platelet aggregation was measured by impedance aggregometry. Hyperosmotic shock (addition of 500 mM sucrose or 250 mM NaCl) significantly enhanced cytosolic Ca(2+) activity, ceramide formation, phosphatidylserine exposure, platelet degranulation, and aggregability. Addition of 500 mM urea to isotonic saline did not significantly modify cytosolic Ca(2+) activity, ceramide abundance, or annexin V-binding but significantly blunted the respective effects of hypertonic shock following addition of 500 mM sucrose. In isotonic solutions, both ceramide (20 microM) and Ca(2+) ionophore ionomycin (0.5 microM) increased annexin V-binding, effects again significantly blunted by 500 mM urea. Moreover, oxidative stress by addition of 0.5 mM peroxynitrite increased cytosolic Ca(2+) activity and triggered annexin V-binding, effects again blunted in the presence of 500 mM urea. The observations reveal that hyperosmotic shock and oxidative stress trigger a procoagulant platelet phenotype, an effect blunted by the presence of high urea concentrations.