Flow cytometric analysis of the oxidative status of normal and thalassemic red blood cells

The role of antioxidants and iron chelators in the treatment of oxidative stress in thalassemia

On the basis of all the presented data, one can conclude that oxidative stress plays a major role in the pathophysiology of thalassemia and other congenital and acquired hemolytic anemias. Free extracellular (labile plasma iron, LPI) and intracellular (labile iron pool, LIP) iron species that have been identified in thalassemic blood cells are responsible for generation of oxidative stress by catalyzing formation of oxygen radicals over the antioxidant capacity of the cell. Consequently, there is a rationale for iron chelation to eliminate the free-iron species, which in this respect, act like antioxidants. In addition, antioxidants such as vitamin E and polyphenols are also capable of ameliorating increased oxidative stress parameters and, given together with iron chelators, may provide a substantial improvement in the pathophysiology of hemolytic anemias and particularly in thalassemia.

The Clinical Effects of Fermented Papaya Preparation® (FPP®) on Oxidative Stress in Patients with HbE/ β -Thalassaemia

Background:

Red blood cells (RBC) of patients with thalassaemia are under continuous oxidative stress. Fermented papaya preparation® (FPP®) has been shown to have an antioxidative effect and is postulated to reduce the oxidative stress on RBC.

Objective:

To study the clinical effects of FPP® treatment in patients with HbE/β-thalassaemia on RBC indices, oxidative stress and quality of life scores.

Method:

Patients with HbE/β-thalassaemia who do not receive regular blood transfusion were included in the study and were given FPP® daily (3gm 2 times a day) for 12 weeks. Peripheral blood samples were obtained at the initiation of the study and at 4-weekly intervals thereafter for a period of 12 weeks. The following parameters were measured: Haemoglobin (Hb), mean corpuscular volume (MCV), reticulocyte count; Oxidation studies: production of reactive oxygen species (ROS) and intracellular glutathione content (GSH), spontaneously and in response to oxidative stress; Quality of life (QoL) at the start and at the end of 12 weeks using health survey questionnaires.

Results:

Seven patients (5 females and 2 males) were recruited to the study from January 2006 to April 2006. Median age of the study population was 19 years (range 4 to 27yrs). In vitro analyses showed production of significantly less ROS and more GSH following treatment. There was no significant difference in the Hb, MCV, reticulocyte count, clinical parameters or QoL scores. FPP® was well tolerated by all the patients.

Conclusion:

Although oxidative stress parameters were decreased, FPP® did not have any significant effect on the Hb levels or QoL. Longer studies on larger sample size are required to study the long-term clinical effect of FPP® on clinical parameters in patients with Hb E/β-thalassaemia.

Flow cytometric analysis of the oxidative status in human peripheral blood mononuclear cells of workers exposed to welding fumes

Flow cytometry is a simple analytical technique that identifies, counts, and characterizes cells. The oxidative status of cells is influenced by many exogenous sources, such as occupational exposure to welding fumes. This study evaluated flow cytometry as a method to determine the oxidative status of male welders (n = 15) occupationally exposed to welding fumes. Flow cytometric analysis of reactive oxygen species (ROS) was carried out in peripheral blood mononuclear cells (PBMC) by using the probe 2, 7-dichlorodihydrofluorescein diacetate (DCFH-DA). Lipid peroxidation was measured by the decrease of fluor-DHPE fluorescence and intracellular glutathione (GSH) levels by using mercury orange. All of the parameters were also observed under a confocal microscope. The oxidative stress ratio was calculated from the oxidative damage and the antioxidant capacity to give an accurate account of the cellular oxidative status. ROS and lipid peroxidation levels were elevated by approximately 87% and approximately 96%, respectively, and GSH levels lowered approximately 96% in PBMC of workers exposed to welding fumes compared with non-exposed controls. The oxidative stress ratio was significantly higher (p < 0.001) in the exposed group. Flow cytometry can be useful for the measurement of cellular oxidative stress in somatic cells of workers exposed to welding fumes and other occupational settings. Calculating an oxidative stress index may be useful in predicting disease outcomes and whether preventative control measures are efficient.

A naphthoquinone derivative can induce anemia through phosphatidylserine exposure-mediated erythrophagocytosis

A naphthoquinone derivative, beta-lapachone (betaL; 3,4-dihydro-2,2-dimethyl-2H-naphthol[1,2-b]pyran-5,6-dione), is receiving huge attention for its potent therapeutic effects against various diseases. However, during the preclinical safety evaluation, repeated oral treatment of betaL in rats induced anemia, i.e., a significantly decreased erythrocyte count. In this study, in an effort to elucidate the mechanism underlying the betaL-induced anemia, we investigated the effects of betaL on erythrocytes with freshly isolated human erythrocytes in vitro and rat in vivo. betaL did not induce erythrocyte hemolysis, indicating that direct hemotoxicity was not involved in betaL-associated anemia. Meanwhile, phosphatidylserine (PS) exposure along with spherocytic shape change and microvesicle generation, important factors in the facilitation of erythrophagocytosis, were increased significantly by betaL. The PS exposure on erythrocytes was from betaL-induced reactive oxygen species generation and subsequent depletion of reduced glutathione and protein thiol, which culminated in the modified activities of phospholipid translocases, i.e., inhibition of flippase and activation of scramblase. It is important to note that coincubation of macrophage with betaL-treated erythrocyte in vitro showed increased erythrophagocytosis, demonstrating that the removal of erythrocyte by macrophage can be facilitated by betaL-induced PS exposure. In good accordance with these in vitro results, after oral administration of betaL in rats, increased PS exposure and depletion of glutathione were observed along with enhanced splenic sequestration of erythrocytes. In conclusion, these results suggest that betaL-induced anemia might be mediated through the PS exposure and subsequent erythrophagocytosis, providing novel insight into the drug-induced anemia.

Red blood cell transfusion independence following the initiation of iron chelation therapy in myelodysplastic syndrome

Iron chelation therapy is often used to treat iron overload in patients requiring transfusion of red blood cells (RBC). A 76-year-old man with MDS type refractory cytopenia with multilineage dysplasia, intermediate-1 IPSS risk, was referred when he became transfusion dependent. He declined infusional chelation but subsequently accepted oral therapy. Following the initiation of chelation, RBC transfusion requirement ceased and he remained transfusion independent over 40 months later. Over the same time course, ferritin levels decreased but did not normalize. There have been eighteen other MDS patients reported showing improvement in hemoglobin level with iron chelation; nine became transfusion independent, nine had decreased transfusion requirements, and some showed improved trilineage myelopoiesis. The clinical features of these patients are summarized and possible mechanisms for such an effect of iron chelation on cytopenias are discussed.

Differential regulation of redox proteins and chaperones in HbEβ-thalassemia erythrocyte proteome

PURPOSE

In (hemoglobin, Hb) HbEβ-thalassemia, HbE (β-26 Glu→Lys) interacts with β-thalassemia to produce clinical manifestation of varying severity. This is the first proteomic effort to study changes in protein levels of erythrocytes isolated from HbEβ-thalassemic patients compared to normal.

EXPERIMENTAL DESIGN

We have used 2-DE and MALDI-MS/MS-based techniques to investigate the differential proteome profiling of membrane and Hb-depleted fraction of cytosolic proteins of erythrocytes isolated from the peripheral blood samples of HbEβ-thalassemia patients and normal volunteers.

RESULTS

Our study showed that redox regulators such as peroxiredoxin 2, Cu-Zn superoxide dismutase and thioredoxin and chaperones such as α-hemoglobin stabilizing protein and HSP-70 were upregulated in HbEβ-thalassemia. We have also observed larger amounts of membrane associated globin chains and indications of disruption of spectrin-based junctional complex in the membrane skeleton of HbEβ-thalassemic erythrocytes upon detection of low molecular weight fragments of β-spectrin and decrease in β-actin and dematin content.

CONCLUSION AND CLINICAL RELEVANCE

We have observed interesting changes in the proteomic levels of redox regulators and chaperons in the thalassemic hemolysates and have observed strong correlation or association of the extent of such proteomic changes with HbE levels. This could be important in understanding the role of HbE in disease progression and pathophysiology.

Phagocytosis and postphagocytic reaction of cord blood and adult blood monocyte after infection with green fluorescent protein-labeled Escherichia coli and group B Streptococci

BACKGROUND

Neonatal sepsis is characterized by an excessive inflammatory response induced by immune cells (monocytes). We investigated the initial stage of monocyte-pathogen interaction, i.e. bacterial ingestion and degradation at the single-cell level, by comparing a new flow cytometric procedure with culture methods. We also examined the hypothesis that, in terms of phagocytosis-induced cell death (PICD), phenotype, or cytokine production, cord blood monocytes (CBMO) differ from monocytes derived from adults (peripheral blood monocytes, PBMO).

METHODS

Phagocytosis and intracellular degradation were assessed by means of flow cytometry and bacterial cultures of green fluorescent protein-labeled group B Streptococci (GBS) and Escherichia coli. The production of reactive oxygen species (ROS) was measured through luminol-enhanced chemiluminescence. Apoptosis, phenotype, and cytokine production were assessed through flow cytometry.

RESULTS

Flow cytometry and bacterial cultures showed no difference between phagocytosis and degradation of GBS and E. coli by PBMO and CBMO. A high correlation between both methods was observed. No difference in ROS production was evident. In comparison with PBMO, CBMO apoptosis was lower after exposure to GBS and E. coli. Similarities were found between nonapoptotic monocytes and pro-inflammatory monocytes.

CONCLUSIONS

PICD is lower in CBMO during the early stages of monocyte-pathogen interaction. Our results emphasize that monocyte apoptosis has a potential role in tailoring the immune response in neonatal sepsis.

Fluorophotometric determination of hydrogen peroxide with fluorescin in the presence of cobalt (II) and reaction against other reactive oxygen species

A fluorophotometric method for the determination of hydrogen peroxide (H2O2) using fluorescin was developed. This method was based on the oxidative reaction of fluorescin, a colorless, non-fluorescent lactoid fluorescein, by H2O2 to give highly fluorescein fluorescence emission. In the determination of H2O2, the calibration curve exhibited linearity over the H2O2 concentration range of 1.5-310 ng mL(-1) at an emission wavelength of 525 nm with an excitation of 500 nm and with relative standard deviations (n = 6) of 2.51%, 2.48%, and 1.31% for 3.1 ng mL(-1), 30.8 ng mL(-1), and for 308 ng mL(-1) of H2O2, respectively. The detection limit for H2O2 was 1.9 ng mL(-1) six blank determinations was performed (rho = 6). This proposed method was applied to detection of other reactive oxygen species and nitrogen species (ROS/RNS) such as singlet oxygen (1O2), hydroxyl radical (*OH), peroxynitrite (ONOO-) etc., and it was possible to detect them with a high sensitivity. In addition, this proposed method was applied to the recovery tests of H2O2 in calf serum, human saliva, rain water, and wheat noodles; the results were satisfactory.

Fermented papaya preparation as redox regulator in blood cells of beta-thalassemic mice and patients

Many aspects of the pathology in beta-hemoglobinopathies (beta-thalassemia and sickle cell anemia) are mediated by oxidative stress. Fermented papaya preparation (FPP) was tested for its antioxidant effects: the scavenging effect was determined spectrofluorometrically in a cell-free system using 2'-7'-dichlorofluorescin-diacetate (DCF). Both spontaneous and H(2)O(2)-induced DCF oxidations were decreased by FPP in a dose-dependent fashion. Using flow cytometry, it was shown that in vitro treatment of blood cells from beta-thalassemic patients with FPP increased the glutathione content of red blood cells (RBC), platelets and polymorphonuclear (PMN) leukocytes, and reduced their reactive oxygen species, membrane lipid peroxidation and externalization of phosphatidylserine. These effects result in (a) reduced thalassemic RBC sensitivity to hemolysis and phagocytosis by macrophages; (b) improved PMN ability to generate oxidative burst - an intracellular mechanism of bacteriolysis, and (c) reduced platelet tendency to undergo activation, as reflected by fewer platelets carrying external phosphatidylserine. Oral administration of FPP to beta-thalassemic mice (50 mg/mouse/day for 3 months) and to patients (3 g x 3 times/day for 3 months), reduced all the above mentioned parameters of oxidative stress (p < 0.001 in mice and p < 0.005 in patients). These results suggest that FPP, as a potent antioxidant, might alleviate symptoms associated with oxidative stress in severe forms of thalassemia.

Phenylhydrazine as a partial model for beta-thalassaemia red blood cell hemodynamic properties

beta-Thalassaemia is a congenital haemoglobinopathy, associated with red blood cells (RBC) anomalies, leading to impairment of their flow-affecting properties, namely, RBC deformability, self-aggregability, and adherence to endothelial cells (EC). Treatment of normal RBC with phenylhydrazine (PHZ) causes selective association of oxidized alpha-globin chains with the membrane skeleton, leading to reduced RBC deformability, characteristic of beta-thalassaemia. PHZ has thus been used to mimic phenotypes of beta-thalassaemia RBC. The present study was undertaken to further elucidate the suitability of PHZ-treated RBC as a model for beta-thalassemic RBC, by comparing the aggregability and adhesiveness of PHZ-treated RBC to those of RBC from thalassaemia intermedia (TI) patients, using image analysis of RBC under flow. In addition, the externalization of phosphatidylserine (PS), a mediator of RBC/EC interaction, was determined. It was found that PHZ caused enhanced RBC adhesiveness to extracellular matrix, similar to TI-RBC. Furthermore, in both conditions, the enhanced adhesiveness was mediated by PS translocated to the RBC surface. In contrast, PHZ treatment completely abolished RBC aggregability, while TI-RBC aggregability was slightly elevated. It is proposed that PHZ-treated RBC resemble beta-thalassaemia RBC in their deformability and adhesiveness, but not in their aggregability, and thus can be used as a limited model for beta-thalassaemia RBC phenotypes.

Upregulation of neutrophil gelatinase-associated lipocalin, NGAL/Lcn2, in beta-thalassemia patients

BACKGROUND

One of the major consequences in beta- thalassemia is iron overload. Oxidative statuses have been reported in beta-thalassemia patients by several studies. It has been proven that iron plays a critical role in the formation of reactive oxygen species (ROS). More recently, we have found the induction of Lcn2/NGAL expression under oxidative stress condition. In this study, it was assumed that NGAL should be upregulated in beta-thalassemia patients because of oxidative stress condition.

METHODS

Assessment of NGAL expressions in 25 adult beta-thalassemia and 9 pediatric patients was performed by semiquantitative RT-PCR, real-time RT-PCR and ELISA.

RESULTS

Adult beta-thalassemia patients upregulated NGAL expression compared with the normal samples but no upregulation was observed in pediatric patients.

CONCLUSIONS

Upregulation may play an important role in decreasing ROS or iron in beta-thalassemia patients.

N-acetylcysteine amide (AD4) attenuates oxidative stress in beta-thalassemia blood cells

Many aspects of the pathology in beta-hemoglobinopathies (beta-thalassemia and sickle cell anemia) are mediated by oxidative stress. In the present study we tested a novel thiol compound, N-acetylcysteine amide (AD4), the amide form of N-acetyl cysteine (NAC) for its antioxidant effects. Using flow-cytometry, we showed that in vitro treatment of blood cells from beta-thalassemic patients with AD4 elevated the reduced glutathione (GSH) content of red blood cells (RBC), platelets and polymorphonuclear (PMN) leukocytes, and reduced their ROS. These effects resulted in a significant reduced sensitivity of thalassemic RBC to hemolysis and phagocytosis by macrophages. Intra-peritoneal injection of AD4 to beta-thalassemic mice (150 mg/kg) reduced the parameters of oxidative stress (p<0.001). Our results show the superiority of AD4, compared to NAC, in reducing oxidative stress markers in thalassemic cells both in vitro and in vivo.

Oxidative stress in red blood cells, platelets and polymorphonuclear leukocytes from patients with myelodysplastic syndrome

Low-risk myelodysplastic syndrome (MDS) is characterized by cytopenia, mainly anemia, because of ineffective hematopoiesis. Some of the patients with ineffective erythropoiesis, with or without ring sideroblasts in their bone marrow, develop severe anemia requiring frequent blood transfusions and consequently develop iron overload. Excess free iron in cells catalyses the generation of reactive oxygen species (ROS) that cause cell and tissue damage. Using flow cytometry techniques, we compared the oxidative status of red blood cells (RBC), platelets and neutrophils in 14 MDS patients with those of normal donors. The results show that ROS were higher while reduced glutathione (GSH) was lower in their RBC and platelets compared with normal cells. In neutrophils, no difference was found in ROS, while the GSH levels were lower. A correlation (r = 0.6) was found between serum ferritin levels of the patients and the ROS in their RBC and platelets. The oxidative stress was ameliorated by a short incubation with the iron-chelators, the deferrioxamine and deferiprone or with antioxidants such as N-acetylcysteine, suggesting that MDS patients might benefit from treatment with iron-chelators and antioxidants.

Evaluation of the ability of antioxidants to counteract lipid oxidation: Existing methods, new trends and challenges

Oxidative degradation of lipids, especially that induced by reactive oxygen species (ROS), leads to quality deterioration of foods and cosmetics and could have harmful effects on health. Currently, a very promising way to overcome this is to use vegetable antioxidants for nutritional, therapeutic or food quality preservation purposes. A major challenge is to develop tools to assess the antioxidant capacity and real efficacy of these molecules. Many rapid in vitro tests are now available, but they are often performed in dissimilar conditions and different properties are thus frequently measured. The so-called 'direct' methods, which use oxidizable substrates, seem to be the only ones capable of measuring real antioxidant power. Some oxidizable substrates correspond to molecules or natural extracts exhibiting biological activity, such as lipids, proteins or nucleic acids, while others are model substrates that are not encountered in biological systems or foods. Only lipid oxidation and direct methods using lipid-like substrates will be discussed in this review. The main mechanisms of autoxidation and antioxidation are recapitulated, then the four components of a standard test (oxidizable substrate, medium, oxidation conditions and antioxidant) applied to a single antioxidant or complex mixtures are dealt with successively. The study is focused particularly on model lipids, but also on dietary and biological lipids isolated from their natural environment, including lipoproteins and phospholipidic membranes. Then the advantages and drawbacks of existing methods and new approaches are compared according to the context. Finally, recent trends based on the chemometric strategy are introduced as a highly promising prospect for harmonizing in vitro methods.

The oxidative status of blood cells in a murine model of graft-versus-host disease

We studied the oxidative status of red and white blood cells during the development of graft vs host disease (GVHD) as well as the effects of treatment with antioxidants, both in vitro and in vivo. (BALB/c X C57BL/6) F1 mice were conditioned by total body radiation and, 1 day later, transplanted with semi-allogeneic C57BL/6 spleen cells. GVHD was followed by its clinical manifestations. Oxidative stress in red blood cells (RBC), neutrophils, and lymphocytes was assessed by measuring generation of reactive oxygen species and the content of reduced glutathione by flow cytometry after gating of the specific populations. Oxidative stress was noticed 3 weeks after transplantation. It was higher in mice receiving allogeneic spleen cells as compared with mice transplanted with syngeneic cells, suggesting that it was associated with GVHD. The results also demonstrated that treatment with the antioxidants N-acetylcysteine and a derivative of vitamin E (tocopherol succinate, propofol), both in vitro and in vivo, reduced the oxidative stress. The results indicate that various blood cells, including RBC, neutrophils, and lymphocytes, are under oxidative stress and that treatment with antioxidants reduced the stress and, thus, may be useful in ameliorating the severe consequences of GVHD.

Antioxidant therapy in idiopathic tinnitus: preliminary outcomes

BACKGROUND

Reactive oxygen species (ROS) play an important role in several pathogenic processes, damaging various structural and functional cellular components. The endothelium is at major risk of radical-induced lesions and this damage is most manifest in microcirculation. It has been recently observed that ROS are implicated in the pathology of the inner ear and the peripheral and central pathways. In a previous study we detected high serum values of ROS in subjects with idiopathic tinnitus. The purpose of the present study was to evaluate the validity of antioxidant treatment in tinnitus sufferers with high ROS values.

METHODS

The study considered 31 consecutive patients with unilateral idiopathic tinnitus. The mean pure tone audiometric threshold (PTA), tinnitus loudness, subjective disturbance level [visual analogue scale (VAS) determination], and the indirect ROS dosage 48 h before and after medical treatment were evaluated. Patients underwent an 18-week oral treatment with a mix of phospholipids and vitamins (glycerophosphorylcholine, glycerophosphorylethanolamine, beta-carotene, vitamin C, vitamin E).

RESULTS

ROS levels were significantly reduced following antioxidant treatment (malonaldehyde: 2.10 vs. 1.98 mumol/dL, p = 0.003; 4-hydroxynonenal: 2.36 vs. 2.16 mumol/dL, p = 0.002) In addition, great improvement was observed in the reduction of tinnitus (VAS and tinnitus loudness evaluations). No significant changes in audiometric threshold occurred.

CONCLUSIONS

Oral antioxidant therapy in patients with idiopathic tinnitus seems to reduce the subjective discomfort and tinnitus intensity and may be considered as an additional treatment modality.

Molecular therapies in beta-thalassaemia

The beta-thalassaemias have a major global impact on health and mortality. Allogeneic haemopoietic stem cell transplantation is the only approach that may lead to a cure but this approach is not available to most patients. The mainstay treatment for the majority remains life-long blood transfusion in combination with a rigorous regime of iron chelation. Improved understanding of the pathophysiology and molecular basis of the disease has provided clues for more effective strategies that aim to correct the defect in beta-globin chain synthesis at the primary level or redress the alpha/beta-globin chain imbalance at the secondary level. Improved understanding of the molecular basis of the disease complications, such as iron overloading, has also provided clues for potential molecular targets at the tertiary level.

Iron-chelating and free-radical scavenging activities of microwave-processed green tea in iron overload

Secondary iron overload is found in beta-thalassemia (thal) patients because of increased dietary iron absorption and multiple blood transfusions. Excessive iron catalyzes free-radical generation, leading to oxidative damage and vital organ dysfunction. Non-transferrin-bound iron (NTBI) detected in thalassemic plasma is highly toxic and chelatable. Though used to treat iron overload, desferrioxamine (DFO) and deferiprone (L1) also have adverse effects. Green tea (GT) shows many pharmacological effects, particularly antioxidative and iron-chelating capacities. This study was performed to investigate the ability of GT extracts to reduce plasma NTBI concentration and oxidative stress in vitro. The Fe(3+) was found to bind to GT crude extract and form a complex. Green tea crude extract time- and dose-dependently decreased plasma NTBI concentration and counteracted the increase of oxidative stress in both Fe(2+)-EDTA-treated human plasma and erythrocytes. Green tea is a bifunctional natural product that could be relevant for management of iron overload and oxidative stress.

Enhanced oxidative cross-linking of hemoglobin E with spectrin and loss of erythrocyte membrane asymmetry in hemoglobin Ebeta-thalassemia

Oxidative stress to the erythrocytes is associated with formation of large molecular complexes of hemoglobin and the skeletal protein, spectrin. In this work, such complexes are formed with hemoglobin mixtures isolated from patients suffering from HbEbeta-thalassemia with elevated levels of the HbE and purified erythroid spectrin in the presence of hydrogen peroxide. The complexes are separated on 4% SDS-PAGE and analyzed by densitometry. The results indicate enhanced formation of complexes with higher amounts of HbE, the most common hemoglobin variant prevalent in Southeast Asia. The binding affinity of spectrin with hemoglobin, in the absence of hydrogen peroxide, was found to increase with hemoglobin mixtures enriched with HbE. The presence of ATP was also found to decrease the overall yield of such complexes. Flow cytometric measurements of phosphatidylserine on the red cell surface also showed a lower degree of membrane asymmetry in HbEbeta-thalassemic patients than in normal subjects. The present work shows enhanced formation of high molecular weight cross-linked complexes of hemoglobin derivatives with erythroid spectrin in HbEbeta-thalassemia.

Human and mouse hemoglobin association with the transgenic mouse erythrocyte membrane

Transgenic mouse models of hemoglobinopathies unravel pathophysiological mechanisms; yet the validity of the red blood cell (RBC) model of human hemoglobin (hHb) enveloped by a mouse (m) membrane has been questioned. Isoelectric focusing of hHb and mHb from transgenic mRBC shows a greater association of mHb to the mouse membrane compared to normal hHbA, supporting a species-specific Hb-mRBC membrane interaction. Enhanced hmutant Hb (HbE, HbS and HbC)-mRBC membrane affinities correlates with enhanced membrane lipid peroxidation and parallel those reported in hRBC, lending support to transgenic mRBC as models of hemoglobinopathies. Species-specific Hb-membrane interaction may be overridden by Hb charge and conformational alterations.

Red blood cells, platelets and polymorphonuclear neutrophils of patients with sickle cell disease exhibit oxidative stress that can be ameliorated by antioxidants

Sickle cell disease (SCD) is basically a red blood cell (RBC) disorder characterised by sickling and haemolysis, but platelets and polymorphonuclear neutrophils (PMN) are also involved. Oxidative damage may play a role in the pathogenesis of SCD. Using flow cytometry, we measured oxidative-state markers simultaneously in RBC, platelets and PMN obtained from 25 normal donors, nine homozygous (SS) patients and six SS/beta-thalassaemia patients. Reactive oxygen species (ROS) and reduced glutathione (GSH) were measured following staining of blood samples with fluorescence probes and gating on specific subpopulations based on size and granularity. Ten- to 30-fold higher ROS production and 20-50% lower GSH content were found in RBC, platelets and PMN from SCD patients versus those of their normal counterparts. This could in part account for the clinical manifestations, such as haemolysis, a hypercoagulable state, recurrent bacterial infections and vaso-occlusive incidences, in SCD. We further showed that exposure of SCD samples to antioxidants, such as N-acetyl-cysteine, vitamin C and vitamin E, decreased their oxidative stress. These results suggest that antioxidant treatment of patients with SCD could reduce oxidative damage to RBC, PMN and platelets, thereby alleviating symptoms associated with their pathology. The flow cytometry techniques presented herein could assist in monitoring the efficacy of such treatment.

Determination of reactive oxygen species in single human erythrocytes using microfluidic chip electrophoresis

Reactive oxygen species (ROS) are known to not only mediate the damage of cellular constituents but also to regulate cellular signaling. Analysis of ROS is essential if we wish to understand the mechanisms of cellular alterations. In this paper, a microfluidic chip-based approach to the determination of ROS in single erythrocyte was developed by using a simple crossed-channel glass chip with integrated operational functions, including cell sampling, single cell loading, docking, lysing, and capillary electrophoretic (CE) separation with laser-induced fluorescence (LIF) detection. Non-fluorescent dihydrorhodamine 123 (DHR 123), which can be oxidized intracellularly by ROS to the fluorescent rhodamine 123 (Rh 123), was used as the fluorogenic reagent. The effect of pH on the migration time of Rh 123 and detection sensitivity was discussed. The present method minimized dilution of intracellular ROS during reaction with DHR 123 and determination. As a result, an extremely low detection limit of 0.8 amol has been achieved. The time required for complete analysis of one human erythrocyte was less than 3 min. A migration time precision of 4.1% RSD was obtained for six consecutively-injected cells. Upon stimulation with 4 mmol/l H2O2 for 10 min, the intracellular ROS concentration was found to increase on average by about a factor of 8.4.

Chronic oxidative stress reduces the respiratory burst response of neutrophils from beta-thalassaemia patients

Beta-thalassaemia patients are susceptible to infections by mechanisms that are not fully understood. Polymorphonuclear neutrophils (PMN) destroy microbes by producing a burst of reactive oxygen species (ROS) (respiratory burst) in response to bacterial components, as well as to phorbol-myristate-acetate (PMA). In the present study, we compared ROS generation by normal and beta-thalassaemia PMN and assessed their response to PMA. Blood cells were subjected to gelatin separation, staining with dichlorofluorescin-diacetate and flow cytometry. At basal level, the fluorescence (mean fluorescence channel) of normal and thalassaemia PMN were 12.7 +/- 4.5 and 95.6 +/- 19.8 respectively; it changed to 283.4 +/- 72.5 and 39.5 +/- 14.3, respectively, upon PMA stimulation, indicating that thalassaemia PMN have a higher basal ROS but a reduced response to PMA. When normal PMN were treated with the oxidants hydrogen peroxide and butyl-hydroxyperoxide, as well as iron and haemin, which are elevated in thalassaemia, their basal ROS increased 5-22-fold, but the PMA response was abolished. Treating thalassaemic PMN with antioxidants (N-acetyl-L-cysteine or vitamins C and E) reduced their basal ROS but enhanced their PMA response. Our findings indicate that chronically stressed PMN, e.g. in thalassaemia, have reduced capacity to elicit a respiratory burst, which may compromise their antibacterial capacity, and imply prophylactic treatment with antioxidants for recurrent infections.