Oxidant damage of the lipids and proteins of the erythrocyte membranes in unstable hemoglobin disease. Evidence for the role of lipid peroxidation

Antiphosphatidylserine Immunoglobulin M and Immunoglobulin G Antibodies Are Higher in Vivax Than Falciparum Malaria, and Associated With Early Anemia in Both Species

BACKGROUND

Anemia is a major complication of vivax malaria. Antiphosphatidylserine (PS) antibodies generated during falciparum malaria mediate phagocytosis of uninfected red blood cells that expose PS and have been linked to late malarial anemia. However, their role in anemia from non-falciparum Plasmodium species is not known, nor their role in early anemia from falciparum malaria.

METHODS

We measured PS immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies in Malaysian patients with vivax, falciparum, knowlesi, and malariae malaria, and in healthy controls, and correlated antibody titres with hemoglobin. PS antibodies were also measured in volunteers experimentally infected with Plasmodium vivax and Plasmodium falciparum.

RESULTS

PS IgM and IgG antibodies were elevated in patients with vivax, falciparum, knowlesi, and malariae malaria (P < .0001 for all comparisons with controls) and were highest in vivax malaria. In vivax and falciparum malaria, PS IgM and IgG on admission correlated inversely with admission and nadir hemoglobin, controlling for parasitemia and fever duration. PS IgM and IgG were also increased in volunteers infected with blood-stage P. vivax and P. falciparum, and were higher in P. vivax infection.

CONCLUSIONS

PS antibodies are higher in vivax than falciparum malaria, correlate inversely with hemoglobin, and may contribute to the early loss of uninfected red blood cells found in malarial anemia from both species.

Targeting Oncogenic Nuclear Factor Kappa B Signaling with Redox-Active Agents for Cancer Treatment

SIGNIFICANCE

Nuclear factor kappa B (NF-κB) signaling is essential under physiologically relevant conditions. However, aberrant activation of this pathway plays a pertinent role in tumorigenesis and contributes to resistance. Recent Advances: The importance of the NF-κB pathway means that its targeting must be specific to avoid side effects. For many currently used therapeutics and those under development, the ability to generate reactive oxygen species (ROS) is a promising strategy.

CRITICAL ISSUES

As cancer cells exhibit greater ROS levels than their normal counterparts, they are more sensitive to additional ROS, which may be a potential therapeutic niche. It is known that ROS are involved in (i) the activation of NF-κB signaling, when in sublethal amounts; and (ii) high levels induce cytotoxicity resulting in apoptosis. Indeed, ROS-induced cytotoxicity is valuable for its capabilities in killing cancer cells, but establishing the potency of ROS for effective inhibition of NF-κB signaling is necessary. Indeed, some cancer treatments, currently used, activate NF-κB and may stimulate oncogenesis and confer resistance.

FUTURE DIRECTIONS

Thus, combinatorial approaches using ROS-generating agents alongside conventional therapeutics may prove an effective tactic to reduce NF-κB activity to kill cancer cells. One strategy is the use of thiosemicarbazones, which form redox-active metal complexes that generate high ROS levels to deliver potent antitumor activity. These agents also upregulate the metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), which functions as an NF-κB signaling inhibitor. It is proposed that targeting NF-κB signaling may proffer a new therapeutic niche to improve the efficacy of anticancer regimens.

5-N-Carboxyimino-6-N-chloroaminopyrimidine-2,4(3H)-dione as a hypochlorite-specific oxidation product of uric acid

Although uric acid is known to react with many reactive oxygen species, its specific oxidation products have not been fully characterized. We now report that 5-N-carboxyimino-6-N-chloroaminopyrimidine-2,4(3H)-dione (CCPD) is a hypochlorite (ClO^-)-specific oxidation product of uric acid. The yield of CCPD was 40-70% regardless of the rate of mixing of ClO^- with uric acid. A previously reported product, allantoin (AL), was a minor product. Its yield (0-20%) decreased with decreasing rate of mixing of ClO^- with uric acid, indicating that allantoin is less important in vivo. Kinetic studies revealed that the formation of CCPD required two molecules of ClO^- per uric acid reacted. The identity of CCPD was determined from its molecular formula (C₅H₃ClN₄O₄) measured by LC/time-of-flight mass spectrometry and a plausible reaction mechanism. This assumption was verified by the fact that all mass fragments (m/z -173, -138, -113, and -110) fit with the chemical structure of CCPD and its tautomers. Isolated CCPD was stable at pH 6.0-8.0 at 37°C for at least 6 h. The above results and the fact that uric acid is widely distributed in the human body at relatively high concentrations indicate that CCPD is a good marker of ClO^- generation in vivo.

Microfluidic analysis of red blood cell deformability as a means to assess hemin-induced oxidative stress resulting from Plasmodium falciparum intraerythrocytic parasitism

Hemolytic anemia is one of the hallmarks of malaria and leads to an increase in oxidized heme (hemin) within the plasma of infected individuals. While scavenger proteins sequester much of the circulating heme, it has been hypothesized that extracellular heme may play a central role in malaria pathogenesis. We have previously developed the multiplex fluidic plunger (MFP) device for the measurement of red blood cell (RBC) deformability. Here, we demonstrate that the measurement of changes in RBC deformability is a sensitive method for inferring heme-induced oxidative stress. We further show that extracellular hemin concentration correlates closely with changes in RBC deformability and we confirm that this biophysical change correlates with other indicators of cell stress. Finally, we show that reduced erythrocyte deformability corresponds with both erythrophagocytosis and RBC osmotic fragility. The MFP microfluidic device presents a simple and potentially inexpensive alternative to existing methods for measuring hemolytic cell stress that could ultimately be used to perform clinical assessment of disease progression in severe malaria.

Parabanic acid is the singlet oxygen specific oxidation product of uric acid

Uric acid quenches singlet oxygen physically or reacts with it, but the oxidation product has not been previously characterized. The present study determined that the product is parabanic acid, which was confirmed by LC/TOFMS analysis. Parabanic acid was stable at acidic pH (<5.0), but hydrolyzed to oxaluric acid at neutral or alkaline pH. The total yields of parabanic acid and oxaluric acid based on consumed uric acid were ~100% in clean singlet oxygen production systems such as UVA irradiation of Rose Bengal and thermal decomposition of 3-(1,4-dihydro-1,4-epidioxy-4-methyl-1-naphthyl)propionic acid. However, the ratio of the amount of uric acid consumed to the total amount of singlet oxygen generated was less than 1/180, indicating that most of the singlet oxygen was physically quenched. The total yields of parabanic acid and oxaluric acid were high in the uric acid oxidation systems with hydrogen peroxide plus hypochlorite or peroxynitrite. They became less than a few percent in peroxyl radical-, hypochlorite- or peroxynitrite-induced oxidation of uric acid. These results suggest that parabanic acid could be an in vivo probe of singlet oxygen formation because of the wide distribution of uric acid in human tissues and extracellular spaces. In fact, sunlight exposure significantly increased human skin levels of parabanic acid.

Low levels of serum ferritin and moderate transferrin saturation lead to adequate hemoglobin levels in hemodialysis patients, retrospective observational study

Background

Optimal iron levels in patients on hemodialysis are currently unknown, and a higher level than that for the healthy population is usually set for such patients considering the use of erythropoiesis-stimulating agents or the occurrence of chronic inflammation. However, excessive iron causes oxidative stress and impairment of its utilization by cells. Therefore we investigated the relationship between hemoglobin (Hb) level and iron status in hemodialysis patients to identify the optimal iron levels for patients undergoing hemodialysis.

Methods

A total of 208 outpatients on maintenance hemodialysis were followed up between July 2006 and June 2007. Men accounted for 64.9% cases [mean age, 59.3 ± 13.1 years and median dialysis history, 7.7 (3.6–13.2) years], and diabetic nephropathy accounted for 25.0% cases. Hemoglobin level was measured twice a month and serum ferritin, serum iron, and total iron-binding capacity were measured once a month. The doses of recombinant human erythropoietin and low-dose iron supplement were adjusted to maintain a hemoglobin level of 10–11 g/dL, according to the guidelines of the Japanese Society for Dialysis Therapy. Hepcidin was measured at baseline. Using the mean values for 1-year period, the relationships among hemoglobin, serum ferritin levels, and transferrin saturation levels were investigated based on a receiver operating characteristic curve and a logistic regression model. In addition, the correlations among serum ferritin, transferrin saturation, and hepcidin levels were analyzed by Pearson product—moment correlation coefficient and linear regression model.

Results

By receiver operating characteristic curve, the cutoff point of serum ferritin and transferrin saturation levels with a hemoglobin ≥10 g/dL showed <90 ng/mL (sensitivity: 69.1%, specificity: 72.1%, p < 0.001) and ≥20% (sensitivity: 77.6%, specificity: 48.8%, p = 0.302).

Upon logistic regression model analysis with a hemoglobin ≥10 g/dL as the endpoint, the analysis of odds ratios relative to a group with serum ferritin ≥90 ng/mL and transferrin saturation <20% revealed that the group with serum ferritin <90 ng/mL and transferrin saturation ≥20% had the highest ratio: 46.75 (95% confidence interval: 10.89–200.70, p < 0.001). In Pearson product—moment correlation coefficient, hepcidin showed a strong positive correlation with serum ferritin [r = 0.78 (95% confidence interval: 0.72–0.83, p < 0.001)] and a weak positive correlation with transferrin saturation [r = 0.18 (95% confidence interval: 0.04–0.31, p = 0.010)]. In the multivariable analyses of the linear regression model, a positive relationship was shown between hepcidin and serum ferritin [β-coefficient of 0.30 (95% confidence interval: 0.27–0.34, p < 0.001)]; however, no relationship was shown with transferrin saturation [β-coefficient of 0.09 (95% confidence interval: −0.31–0.49, p = 0.660)].

Conclusions

In this study, the iron status of serum ferritin <90 ng/mL and transferrin saturation ≥20% was optimal in hemodialysis patients receiving recombinant human erythropoietin for anemia therapy. This result indicates that the threshold values for the optimal iron status may be lower than those currently recommended in iron-level management guideline.

Protective effect of Scutellaria species on AAPH-induced oxidative damage in human erythrocyte

BACKGROUND

Scutellaria baicalensis is a well-known plant in traditional Chinese medicine. Recently, several Scutellaria species with therapeutic potential have been recognized worldwide. Scutellaria colebrookiana and Scutellaria violacea, native to the Western Ghats of India, are reported to possess free radical scavenging efficacy. At present, the protective effect of these Scutellaria spp. against 2,2' azobis (2-amidinopropane) hydrochloride (AAPH)-induced oxidative damage in human erythrocytes has been analyzed.

METHODS

Oxidative stress in erythrocyte was induced by AAPH. The inhibition of hemolysis, membrane lipid peroxidation, and protein damage by chloroform extracts of Scutellaria spp. was assessed biochemically. Phytochemicals of the extracts were analyzed by Fourier transform infrared spectrophotometer (FTIR).

RESULTS

Approximately 95% of erythrocytes were lysed by AAPH over 3 h of incubation. Significant reduction in hemolysis was observed by the extracts, and the IC50 values were 18.3 and 23.5 μg/mL for S. colebrookiana and S. violacea, respectively. Both the extracts were found to inhibit AAPH-induced lipid peroxidation in ghost membrane with IC50 92±2.8 and 70±5.6 μg/mL. In the analysis of the membrane proteins using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the AAPH-induced degradation of actin was found reduced by both the extracts. The FTIR spectrum revealed the presence of polyphenols, carboxylic acids, alkanes, and aromatic compounds in extracts. In quantitative analysis, the total polyphenolic content estimated was 380±0.23 and 203.7±1.4 mg of gallic acid equivalent per gram extract of S. colebrookiana and S. violacea.

CONCLUSIONS

Results indicate that S. colebrookiana and S. violacea are capable of protecting erythrocytes from oxidative damage. This cytoprotective effect of the extract is possibly by its antioxidant property.

Healthy Dietary Patterns and Oxidative Stress as Measured by Fluorescent Oxidation Products in Nurses' Health Study

Healthy diets may lower oxidative stress and risk of chronic diseases. However, no previous studies examined associations between diet and fluorescent oxidation products (FlOP), a global marker of oxidative stress. We evaluated associations between healthy eating patterns (Alternative Healthy Eating Index (AHEI), Dietary Approach to Stop Hypertension (DASH), and Alternate Mediterranean Diet (aMED)) and FlOP, measured at three excitation/emission wavelengths (FlOP_360, FlOP_320, FlOP_400) from 2021 blood samples collected from 1688 women within the Nurses’ Health Study. AHEI, DASH, and aMED scores were significantly positively associated with FlOP_360 and FlOP_320 concentrations (p-trend ≤ 0.04), but not associated with FlOP_400. Among specific food groups that contribute to these diet scores, significantly positive associations were observed with legumes and vegetables for FlOP_360, vegetables and fruits for FlOP_320, and legumes and alcohol for FlOP_400. Inverse associations were observed with nuts, sweets or desserts, and olive oil for FlOP_360, nuts for FlOP_320 and sweets or desserts for FlOP_400 (all p-trend ≤ 0.05). However, FlOP variation due to diet was small compared to overall FlOP variation. In conclusion, AHEI, DASH, and aMED scores were unexpectedly positively, but weakly, associated with FlOP_360 and FlOP_320. However, these findings should be interpreted cautiously as the determinants of FlOP concentrations are not fully understood.

Diabetes-induced oxidative stress in the vitreous humor

Purpose

Diabetes is accompanied by fundamental rearrangements in redox homeostasis. Hyperglycemia triggers the production of reactive oxygen and nitrogen species which contributes to tissue damage in various target organs. Proliferative diabetic retinopathy (PDR) is a common manifestation of diabetic complications but information on the possible role of reactive intermediates in this condition with special regard to the involvement of the vitreous in PDR-associated redox alterations is scarce.

The aim of the study was to determine key parameters of redox homeostasis [advanced glycation endproducts (AGE); protein carbonyl and glutathione (GSH)] content in the vitreous in PDR patients.

Methods

The study population involved 10 diabetic patients undergoing surgery for complications of proliferative diabetic retinopathy and 8 control (non-diabetic) patients who were undergoing surgery for epiretinal membranes. Vitreal fluids were assayed for the above biochemical parameters.

Results

We found elevated levels of AGE in the vitreous of PDR patients (812.10 vs 491.69 ng AGE/mg protein). Extent of protein carbonylation was also higher in the samples of diabetic patients (2.08 vs 0.67 A/100 μg protein). The GSH content also increased in the vitreous of PDR patients as compared to the control group (4.54 vs 2.35 μmol/μg protein), respectively.

Conclusion

The study demonstrates that diabetes-associated redox alterations also reach the vitreous with the most prominent changes being increased protein carbonylation and increased antioxidant levels.

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Vitreal AGE levels are elevated in PDR patients.

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Extent of protein carbonylation is higher in the vitreal samples of PDR patients.

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The glutathione content is increased in the vitreous of PDR patients.

Plasma fluorescent oxidation products and risk of estrogen receptor-negative breast cancer in the Nurses' Health Study and Nurses' Health Study II

Findings from epidemiologic studies of oxidative stress biomarkers and breast cancer have been mixed, although no studies have focused on estrogen receptor-negative (ER-) tumors which may be more strongly associated with oxidative stress. We examined prediagnostic plasma fluorescent oxidation products (FlOP), a global biomarker of oxidative stress, and risk of ER- breast cancer in a nested case-control study in the Nurses' Health Study and Nurses' Health Study II. ER- breast cancer cases (n = 355) were matched to 355 controls on age, month/time of day of blood collection, fasting status, menopausal status, and menopausal hormone use. Conditional logistic regression models were used to examine associations of plasma FlOP at three emission wavelengths (FlOP_360, FlOP_320, and FlOP_400) and risk of ER- breast cancer. We did not observe any significant associations between FlOP measures and risk of ER- breast cancer overall; the RRQ4vsQ1 (95 %CI) 0.70 (0.43-1.13), p trend = 0.09 for FlOP_360; 0.91(0.56-1.46), p trend = 0.93 for FlOP_320; and 0.62 (0.37-1.03), p trend = 0.10 for FlOP_400. Results were similar in models additionally adjusted for total carotenoid levels and in models stratified by age and total carotenoids. Although high (vs. low) levels of FIOP_360 and FIOP_400 were associated with lower risk of ER- breast cancer in lean women (body mass index (BMI) < 25 kg/m(2)) but not in overweight/obese women, these differences were not statistically significant (pint = 0.23 for FlOP_360; pint = 0.37 for FlOP_400). Our findings suggest that positive associations of plasma FlOP concentrations and ER- breast cancer risk are unlikely.

The metabolites of glutamine prevent hydroxyl radical-induced apoptosis through inhibiting mitochondria and calcium ion involved pathways in fish erythrocytes

The present study explored the apoptosis pathways in hydroxyl radicals ((∙)OH)-induced carp erythrocytes. Carp erythrocytes were treated with the caspase inhibitors in physiological carp saline (PCS) or Ca(2+)-free PCS in the presence of 40μM FeSO4/20μM H2O2. The results showed that the generation of reactive oxygen species (ROS), the release of cytochrome c and DNA fragmentation were caspase-dependent, and Ca(2+) was involved in calpain activation and phosphatidylserine (PS) exposure in (∙)OH-induced carp erythrocytes. Moreover, the results suggested that caspases were involved in PS exposure, and Ca(2+) was involved in DNA fragmentation in (∙)OH-induced fish erythrocytes. These results demonstrated that there might be two apoptosis pathways in fish erythrocytes, one is the caspase and cytochrome c-dependent apoptosis that is similar to that in mammal nucleated cells, the other is the Ca(2+)-involved apoptosis that was similar to that in mammal non-nucleated erythrocytes. So, fish erythrocytes may be used as a model for studying oxidative stress and apoptosis in mammal cells. Furthermore, the present study investigated the effects of glutamine (Gln)'s metabolites [alanine (Ala), citrulline (Cit), proline (Pro) and their combination (Ala10Pro4Cit1)] on the pathways of apoptosis in fish erythrocytes. The results displayed that Ala, Cit, Pro and Ala10Pro4Cit1 effectively suppressed ROS generation, cytochrome c release, activation of caspase-3, caspase-8 and caspase-9 at the physiological concentrations, prevented Ca(2+) influx, calpain activation, PS exposure, DNA fragmentation and the degradation of the cytoskeleton and oxidation of membrane and hemoglobin (Hb) and increased activity of anti-hydroxyl radical (AHR) in (∙)OH-induced carp erythrocytes. Ala10Pro4Cit1 produced a synergistic effect of inhibited oxidative stress and apoptosis in fish erythrocytes. These results demonstrated that Ala, Cit, Pro and their combination can protect mammal erythrocytes and nucleated cells against oxidative stress and apoptosis. The studies supported the use of Gln, Ala, Cit and Pro as oxidative stress and apoptosis inhibitors in mammal cells and the hypothesis that the inhibited effects of Gln on oxidative stress and apoptosis are at least partly dependent on that of its metabolites in mammalian.

Protection against oxidative damage in human erythrocytes and preliminary photosafety assessment of Punica granatum seed oil nanoemulsions entrapping polyphenol-rich ethyl acetate fraction

The main purpose of the present study is to evaluate the ability of nanoemulsion entrapping pomegranate peel polyphenol-rich ethyl acetate fraction (EAF) prepared from pomegranate seed oil and medium chain triglyceride to protect human erythrocyte membrane from oxidative damage and to assess preliminary in vitro photosafety. In order to evaluate the phototoxic effect of nanoemulsions, human red blood cells (RBCs) are used as a biological model and the rate of haemolysis and photohaemolysis (5 J cm(-2) UVA) is assessed in vitro. The level of protection against oxidative damage caused by the peroxyl radical generator AAPH in human RBCs as well as its effects on bilayer membrane characteristics such as fluidity, protein profile and RBCs morphology are determined. EAF-loaded nanoemulsions do not promote haemolysis or photohaemolysis. Anisotropy measurements show that nanoemulsions significantly retrain the increase in membrane fluidity caused by AAPH. SDS-PAGE analysis reveals that AAPH induced degradation of membrane proteins, but that nanoemulsions reduce the extension of degradation. Scanning electron microscopy examinations corroborate the interaction between AAPH, nanoemulsions and the RBC membrane bilayer. Our work demonstrates that Punica granatum nanoemulsions are photosafe and protect RBCs against oxidative damage and possible disturbance of the lipid bilayer of biomembranes. Moreover it suggests that these nanoemulsions could be promising new topical products to reduce the effects of sunlight on skin.

Phobic Anxiety and Plasma Levels of Global Oxidative Stress in Women

BACKGROUND AND OBJECTIVES

Psychological distress has been hypothesized to be associated with adverse biologic states such as higher oxidative stress and inflammation. Yet, little is known about associations between a common form of distress - phobic anxiety - and global oxidative stress. Thus, we related phobic anxiety to plasma fluorescent oxidation products (FlOPs), a global oxidative stress marker.

METHODS

We conducted a cross-sectional analysis among 1,325 women (aged 43-70 years) from the Nurses' Health Study. Phobic anxiety was measured using the Crown-Crisp Index (CCI). Adjusted least-squares mean log-transformed FlOPs were calculated across phobic categories. Logistic regression models were used to calculate odds ratios (OR) comparing the highest CCI category (≥6 points) vs. lower scores, across FlOPs quartiles.

RESULTS

No association was found between phobic anxiety categories and mean FlOP levels in multivariable adjusted linear models. Similarly, in multivariable logistic regression models there were no associations between FlOPs quartiles and likelihood of being in the highest phobic category. Comparing women in the highest vs. lowest FlOPs quartiles: FlOP_360: OR=0.68 (95% CI: 0.40-1.15); FlOP_320: OR=0.99 (95% CI: 0.61-1.61); FlOP_400: OR=0.92 (95% CI: 0.52, 1.63).

CONCLUSIONS

No cross-sectional association was found between phobic anxiety and a plasma measure of global oxidative stress in this sample of middle-aged and older women.

Fluorescent oxidation products and risk of coronary heart disease: a prospective study in women

Background

Oxidative stress is implicated in the etiology of coronary heart disease (CHD). New measures to capture oxidative stress are warranted. Fluorescent oxidation products (FlOPs) can be measured in plasma and have been shown to reflect levels of oxidative stress and to predict risk of CHD in men over 6 years of follow‐up. The objective of this study is to determine whether measures of FlOPs are associated with risk of CHD in women over an extended follow‐up period.

Methods and Results

We measured FlOP by spectrofluorometer in a nested case–control study within the Nurses' Health Study, with baseline blood collection in 1990 and follow‐up of 397 incident CHD cases through 2004 matched 1:2 with controls. Level of FlOPs was independently associated with CHD. The relative risk across extreme quintiles was 1.64 (95% confidence interval [CI], 1.06 to 2.53) when adjusted for lifestyle factors, lipids and C‐reactive protein (P trend across quintiles=0.01). A slightly stronger association was observed when analyses were restricted to women fasting >8 hours at blood draw (RR, 1.91; 95% CI, 1.16 to 3.15). In exploratory time to event analyses, high levels of FlOPs measured ≥5 years before the CHD event, but not closer to the CHD event, were associated with the risk of CHD.

Conclusions

Higher levels of FlOPs were associated with the risk of CHD in women. The association appeared strongest for long‐term prediction of CHD events.

Plasma florescent oxidation products and breast cancer risk: repeated measures in the Nurses' Health Study

Reactive oxygen species (ROS), normally generated through biologic processes, may damage DNA, lipids, and proteins. ROS are balanced through enzymatic mechanisms and exogenous antioxidants; imbalance results in oxidative stress. Limited data suggest an association between oxidative stress and breast cancer. We evaluated pre-diagnostic plasma fluorescent oxidation products (FlOP), a global biomarker of oxidative stress, and breast cancer risk in a nested case-control study in the Nurses' Health Study. Participants provided two blood samples (1989-1990 and 2000-2002) (N = 18,743). 377 women developed breast cancer between the second collection and June 1, 2006. Cases were matched to 377 controls. Relative fluorescent intensity at three different excitation/emission wavelengths (FlOP_360, FlOP_320, FlOP_400) were quantified in both samples, providing distant (≥10 years before diagnosis) and proximate (≤6 years before diagnosis) measures of oxidative stress. We observed no association between FlOP and breast cancer risk in proximate or distant samples (e.g., proximate extreme quartiles: FlOP_360, RR 0.8, 95 % CI 0.5-1.3, p trend = 0.49; FlOP_320, RR 1.1, 95 % CI 0.7-1.7, p trend = 0.53; FlOP_400, RR 1.3, 95 % CI 0.8-2.0, p trend = 0.80). In general no association was observed when cross-classifying or averaging proximate and distant exposure (e.g., extreme quartile of averages: FlOP_360, OR 0.9, 95 % CI 0.6-1.4, p trend = 0.82; FlOP_400, OR 0.9, 95 % CI 0.6-1.4, p trend = 0.55), with the exception of a significant trend for average FlOP_320 (extreme quartiles, OR 1.6, 95 % CI 1.0-2.4, p trend = 0.02). We did not observe important associations between FlOP and breast cancer risk in this large prospective study, though our data suggest women with consistently high FlOP_320 may be at increased risk.

α-Hemoglobin stabilizing protein (AHSP) markedly decreases the redox potential and reactivity of α-subunits of human HbA with hydrogen peroxide

α-Hemoglobin stabilizing protein (AHSP) is a molecular chaperone that binds monomeric α-subunits of human hemoglobin A (HbA) and modulates heme iron oxidation and subunit folding states. Although AHSP·αHb complexes autoxidize more rapidly than HbA, the redox mechanisms appear to be similar. Both metHbA and isolated met-β-subunits undergo further oxidation in the presence of hydrogen peroxide (H(2)O(2)) to form ferryl heme species. Surprisingly, much lower levels of H(2)O(2)-induced ferryl heme are produced by free met-α-subunits as compared with met-β-subunits, and no ferryl heme is detected in H(2)O(2)-treated AHSP·met-α-complex at pH values from 5.0 to 9.0 at 23 °C. Ferryl heme species were similarly not detected in AHSP·met-α Pro-30 mutants known to exhibit different rates of autoxidation and hemin loss. EPR data suggest that protein-based radicals associated with the ferryl oxidation state exist within HbA α- and β-subunits. In contrast, treatment of free α-subunits with H(2)O(2) yields much smaller radical signals, and no radicals are detected when H(2)O(2) is added to AHSP·α-complexes. AHSP binding also dramatically reduces the redox potential of α-subunits, from +40 to -78 mV in 1 m glycine buffer, pH 6.0, at 8 °C, demonstrating independently that AHSP has a much higher affinity for Fe(III) versus Fe(II) α-subunits. Hexacoordination in the AHSP·met-α complex markedly decreases the rate of the initial H(2)O(2) reaction with iron and thus provides α-subunits protection against damaging oxidative reactions.

A novel cytofluorometric assay for the detection and quantification of glucose-6-phosphate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked enzymopathy that affects hundreds of millions of people worldwide, conferring increased risk of neonatal jaundice and oxidant-induced hemolytic anemia. Screening and diagnosis of G6PD deficiency is currently performed using genetic or biochemical assays, the former being cost ineffective in populations with significant allelic heterogeneity, and the latter being limited in ability to detect female heterozygotes. Cytochemical assays can obviate these shortcomings, but at the expense of added technical complexity and labor. We describe here a simple, novel cytofluorometric method that extends the classic methemoglobin reduction test, assessing G6PD deficiency at the level of an individual erythrocyte. In preliminary testing in Malian children, there was strong concordance between our method and established genetic and biochemical techniques. The assay is robust and economical, and could serve as a screening method as well as a research tool, especially for high-throughput applications such as flow cytometry.

Caffeic acid and quercetin protect erythrocytes against the oxidative stress and the genotoxic effects of lambda-cyhalothrin in vitro

Lambda-cyhalothrin (LTC) is a synthetic pyrethroid with a broad spectrum of insecticidal and acaricidal activities used to control wide range of insect pests in a variety of applications. The aim of this study was to examine (i) the potency of LTC to induce oxidative stress response in rat erythrocytes in vitro and (ii) the role of caffeic acid (20 μM) and/or quercetin (10 μM) in preventing the cytotoxic effects. Erythrocytes were divided into four portions. The erythrocytes of the first portion were incubated for 4 h at 37°C with different concentrations (0, 50 and 100 μM) of LTC. The others portions were pretreated with caffeic acid and/or quercetin for 30 min prior to LTC incubation. Lipid peroxidation, protein oxidation, antioxidant enzyme activities and DNA damage were examined. LTC at different concentrations causes increased levels of lipid peroxidation, protein oxidation, DNA damage and decreased antioxidant enzyme activities. Combined caffeic acid and quercetin pretreatments significantly reduced the levels of lipid peroxidation markers, that is thiobarbituric acid reactive substance (TBARS), protein carbonyls (PCO) and decreased DNA damage in LTC portion. Further, combined caffeic acid and quercetin pretreatment maintain antioxidant enzyme activities and glutathione content near to normal values. These results suggest that LTC exerts its toxic effect by increasing lipid peroxidation, altering the antioxidant enzyme activities and DNA damage. Caffeic acid and quercetin pretreatments prevent the toxic effects of LTC, suggesting their role as a potential antioxidant.

Protection of human erythrocyte using Crinum asiaticum extract and lycorine from oxidative damage induced by 2-amidinopropane

The intention of this investigation was to evaluate the free radical scavenging activity and erythrocyte protective activity of ethanolic extract of Crinumasiaticum (L) and lycorine. The ethanolic extract of C. asiaticum (L) and lycorine were found to have different levels of antioxidant properties in the test models. Both ethanolic extract of C. asiaticum (L) (0.5–2.5 mg/ml) and lycorine (0.010 mg–0.050 mg/ml) increases the percentage of lipid peroxidation inhibition (26.25 ± 0.23% and 19.25 ± 0.23%) and enhances the free radical scavenging activity (20.92 ± 0.22% and 20.52 ± 0.22%), scavenging of hydrogen peroxide (25.67 ± 0.17% and 23.07 ± 0.3%) superoxide anion scavenging activity (27.69 ± 0.16% and 16.09 ± 0.7%) at concentration of 2.5 and 0.050 mg of C. asiaticum (L) and lycorine, respectively. But compared with tocopherol (P < 0.05) less activity was observed by C. asiaticum (L) and lycorine. The ethanolic extract of C. asiaticum (L) and lycorine were normalized to reduce the level of glutathione and also to sustain the status of protein in erythrocytes during the peroxyl radical [2,2-azobis (2-amidinopropane) dihydrochloride (AAPH)] induced oxidative damage in ex vivo model. The present results of the investigations demonstrated that protective nature of the C. asiaticum (L) and lycorine will be considered as a significant natural antioxidant source.

Altered membrane structure and surface potential in homozygous hemoglobin C erythrocytes

Background

Hemoglobin C differs from normal hemoglobin A by a glutamate-to-lysine substitution at position 6 of beta globin and is oxidatively unstable. Compared to homozygous AA erythrocytes, homozygous CC erythrocytes contain higher levels of membrane-associated hemichromes and more extensively clustered band 3 proteins. These findings suggest that CC erythrocytes have a different membrane matrix than AA erythrocytes.

Methodology and Findings

We found that AA and CC erythrocytes differ in their membrane lipid composition, and that a subset of CC erythrocytes expresses increased levels of externalized phosphatidylserine. Detergent membrane analyses for raft marker proteins indicated that CC erythrocyte membranes are more resistant to detergent solubilization. These data suggest that membrane raft organization is modified in CC erythrocytes. In addition, the average zeta potential (a measure of surface electrochemical potential) of CC erythrocytes was ≈2 mV lower than that of AA erythrocytes, indicating that substantial rearrangements occur in the membrane matrix of CC erythrocytes. We were able to recapitulate this low zeta potential phenotype in AA erythrocytes by treating them with NaNO₂ to oxidize hemoglobin A molecules and increase levels of membrane-associated hemichromes.

Conclusion

Our data support the possibility that increased hemichrome deposition and altered lipid composition induce molecular rearrangements in CC erythrocyte membranes, resulting in a unique membrane structure.

Redox imbalance, macrocytosis, and RBC homeostasis

The erythrocyte represents a major component of the antioxidant capacity of the blood through the enzymes contained in the cell, the glutathione system, and the low-molecular-weight antioxidants of the erythrocyte membrane. A further major red blood cell contribution is in regenerating consumed redox equivalents via the oxidative pentose phosphate pathway and glutathione reductase. Moreover, its extracellular antioxidant capacity, its mobility, and the existence of reducing equivalents far in excess of its normal requirements make erythrocytes function as an effective oxidative sink in the organism. That is why red blood cell metabolism and homeostasis strongly affect the antioxidant properties of the whole body. Conversely, the relation between macrocytosis and oxidative stress has not been fully delineated. Reviewing the mechanisms involved in red blood cell homeostasis in cases of redox imbalance is crucial in identification of factors that could potentially improve erythrocyte survival and defense against oxidant damage.

Protection from oxidative damage using Bidens pilosa extracts in normal human erythrocytes

Bidens pilosa (B. pilosa) is well known in Taiwan as a traditional Chinese medicine. The purpose of this study was to evaluate the ability of both the ethanol (EtOH) and ethylacetate/ethanol (EA/EtOH) extracts from the whole B. pilosa plant, to protect normal human erythrocytes against oxidative damage in vitro. It was determined that the oxidative hemolysis and lipid/protein peroxidation of erythrocytes induced by the aqueous peroxyl radical [2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)] were suppressed by both EtOH (50-150 microg/ml) and EA/EtOH (25-75 microg/ml) extracts of B. pilosa in concentration- and time-dependent manners. B. pilosa extracts also prevented the decline of superoxide dismutase (SOD) activity and the depletion of cytosolic glutathione (GSH) and ATP in erythrocytes. These results imply that B. pilosa may have protective antioxidant properties.

Morphological and biochemical perturbations in rat erythrocytes following in vitro exposure to Fenvalerate and its metabolite

Erythrocytes are a convenient model to understand the membrane oxidative damage induced by various xenobiotic-prooxidants. In this investigation, we have examined the potency of Fenvalerate (FEN) and its metabolite, p-chlorophenyl isovaleric acid (p-CPIA) to induce oxidative stress response in rat erythrocytes in vitro in terms of lipid peroxidation and effects on selected antioxidant enzymes. Susceptibility of erythrocytes to FEN exposure was further investigated in terms of morphological alterations by scanning electron microscopy and protein damage by gel electrophoresis of erythrocyte ghosts. Following in vitro exposure, FEN caused a significant induction of oxidative damage in erythrocytes at concentrations beyond 0.1 mM as evidenced by increased thiobarbituric acid reactive substances (TBARS) levels. The response was both concentration and time dependent. At higher concentrations, significant decreases in the activities of vital antioxidant enzymes viz., catalase, superoxide dismutase, glutathione transferase and glutathione reductase were also discernible clearly suggesting the potency of both, parent compound and its metabolite to induce oxidative stress in erythrocytes. Scanning electron micrographs of erythrocytes following FEN exposure at higher concentrations revealed various degrees of distortion in shape and ruptured membranes. Furthermore, gel electrophoresis studies revealed consistent and significant aggregation of only band 3 protein in erythrocyte membranes exposed to either FEN or p-CPIA at higher concentrations. These in vitro findings show that FEN and its metabolite have the propensity to cause significant oxidative damage in rat erythrocytes, which is associated with marked damage to membrane proteins. These data suggest that both structural and functional perturbations may ensue in erythrocytes following exposure to FEN at higher concentrations under in vivo situations.

Long-term therapy with recombinant human erythropoietin increases CD8+ T-cell apoptosis in haemodialysis patients

BACKGROUND

We intended to assess the intensity of apoptosis in the CD4+ and CD8+ T-lymphocytes of haemodialysis (HD) patients on recombinant human erythropoietin (rHuEpo).

METHODS

The expression of Fas, tumour necrosis factor-alpha receptors (TNFRI and TNFRII) and the CD28 molecule on lymphocytes was evaluated in 15 HD patients before and during treatment with rHuEpo. In cultures of peripheral blood mononuclear cells (PBMCs) stimulated with rHuEpo, phytohaemagglutinin and camptothecin, our measures of apoptosis were the percentages of cells with subdiploid DNA content and of annexin V-stained cells. Results, Therapy with rHuEpo did not affect CD4+ T cells but decreased the percentage of CD8+ T cells in peripheral blood. The intensity of apoptosis in both CD4+ and CD8+ T cells at baseline was lower in HD patients than in healthy volunteers, and increased in those treated with rHuEpo. In vitro, rHuEpo did not induce apoptosis in PBMCs. The percentage of CD8+Fas+ T cells was constant, while that of CD8+TNFRI+ cells declined during follow-up. There was an increase in the percentage of CD28+ T cells, mainly in the CD8+ compartment, as early as 1 month after the introduction of rHuEpo.

CONCLUSIONS

Treatment with rHupo caused a decline of CD8+ T cells in HD patients, which most probably was mediated via the TNFRI-related apoptotic pathway and was independent of Fas expression. Apoptosis in vitro was not directly influenced by rHuEpo, suggesting that the process in vivo was only initiated by rHuEpo supplementation.

Oxidation of hemoglobin to methemoglobin in intact erythrocyte by a hydroperoxide induces formation of glutathionyl hemoglobin and binding of alpha-hemoglobin to membrane

Biochemical consequences of oxidation of hemoglobin (Hb) in intact human erythrocytes were studied. The incubation of washed erythrocyte with 1mM tert-butylhydroperoxide induced an increase in glutathionyl-Hb (G-Hb). The formation of G-Hb occurred linearly until 10 min in parallel with the formation of methemoglobin (metHb) after exhaustion of reduced glutathione. The results show that metHb, but not normal Hb, reacts with oxidized glutathione to form G-Hb. G-Hb was confirmed by immunoblotting with anti-glutathione antibody and the formation of G-Hb was accompanied by parallel decrease in beta-globin detected with a reversed phase HPLC. Electrophoretic studies showed time-dependent increase in membrane-associated alpha-Hb until 10 min, indicating that a part of unpaired alpha-Hb bound to the membrane. Pre-beta-globin increased despite the decrease in beta-globin and a part of the increase was independent of the decrease in beta-globin. Pre-beta-globin reacted with anti-glutathione antibody, but it differs from G-Hb in many features.

Protection of oxidative damage by aqueous extract from Antrodia camphorata mycelia in normal human erythrocytes

Antrodia camphorata (A. camphorata) is well known in Taiwan as a traditional Chinese medicine. The purpose of this study was to evaluate the ability of aqueous extract from A. camphorata mycelia to protect normal human erythrocytes against oxidative damage in vitro. Oxidative hemolysis and lipid/protein peroxidation of erythrocytes induced by the aqueous peroxyl radical [2,2'-Azobis(2-amidinopropane) dihydrochloride, AAPH] were suppressed by A. camphorata mycelia in a time-and concentration-dependent manner. A. camphorata mycelia also prevented the depletion of cytosolic antioxidant glutathione (GSH) and ATP in erythrocytes. Moreover, cultured human endothelial cell damage induced by AAPH was suppressed by A. camphorata mycelia. Interestingly, A. camphorata mycelia exhibited significant cytotoxicity against leukemia HL-60 cells but not against cultured human endothelial cells. These results imply that A. camphorata mycelia may have protective antioxidant and anticancer properties.

Iron release, oxidative stress and erythrocyte ageing

Iron, to be redox cycling active, has to be released from its macromolecular complexes (ferritin, transferrin, hemoproteins, etc.). Iron is released from hemoglobin or its derivatives in a nonprotein-bound, desferrioxamine-chelatable form (DCI) in a number of conditions in which the erythrocytes are subjected to oxidative stress. Such conditions can be related to toxicological events (haemolytic drugs) or to physiological situations (erythrocyte ageing, reproduced in a model of prolonged aerobic incubation), but can also result from more subtle circumstances in which a state of ischemia-reperfusion is imposed on erythrocytes (e.g., childbirth). The released iron could play a central role in oxidation of membrane proteins and senescent cell antigen (SCA) formation, one of the major pathways for erythrocyte removal. Iron chelators able to enter cells (such as ferrozine, quercetin, and fluor-benzoil-pyridoxal hydrazone) prevent both membrane protein oxidation and SCA formation. The increased release of iron observed in beta-thalassemia patients and newborns (particularly premature babies) suggests that fetal hemoglobin is more prone to release iron than adult hemoglobin. In newborns the release of iron in erythrocytes is correlated with plasma nonprotein-bound iron and may contribute to its appearance.

Effects of ascorbate on membrane phospholipids and tocopherols of intact erythrocytes during peroxidation by t-butylhydroperoxide: comparison with effects of dithiothreitol

Peroxidation of intact human erythrocytes by t-butylhydroperoxide (tBHP)) was studied. By incubation of the erythrocytes with 1 mM tBHP, reduced glutathione (GSH) was exhausted within 1 min, and tocopherols (Toc) and phospholipids (PL) decreased to nearly their lowest levels (in this study) within 5 min. The rate of decrease of alpha-Toc was faster than that of gamma-Toc, but alpha-Toc was never exhausted. The rates of decrease of Toc were faster than that of PL. Malondialdehyde increased slowly to reach a maximal value at 30 min. Methemoglobin (metHB) reached a maximum at 15 min. The maximal levels of these substances were maintained until 90 min incubation, which indicated that the peroxidation by tBHP had stopped spontaneously until at least 90 min. By the incubation with tBHP for 30 min, phosphatidylethanolamine (PE) and alpha-Toc decreased to about 70 and 30% of control levels, respectively, and gamma-Toc and GSH were almost exhausted. Ascorbate (0.1 mM) afforded protection of 92% to PE, 50% to alpha-Toc, and 65% to gamma-Toc against peroxidation, but ascorbate had no preventive effect at all on the formation of metHB and the decrease of GSH. These results may indicate that ascorbate-mediated protection of the membrane PL against the peroxidation depends primarily on Toc. On the other hand, dithiothreitol (DTT) (5 mM) almost completely prevented the formation of metHB, and DTT completely protected the PL and Toc against peroxidation, indicating the importance of sulfhydryl groups in erythrocytes.

Iron release in erythrocytes from patients with beta-thalassemia

Our previous studies have shown that iron is released in a free (desferrioxamine-chelatable) form when erythrocytes undergo oxidative stress (incubation with oxidizing agents or aerobic incubation in buffer for 24-60 h (a model of rapid in vitro ageing)). The release is accompanied by oxidative alterations of membrane proteins as well as by the appearance of senescent antigen, a signal for termination of old erythrocytes. In hemolytic anemias by hereditary hemoglobin alterations an accelerated removal of erythrocytes occurs. An increased susceptibility to oxidative damage has been reported in beta-thalassemic erythrocytes. Therefore we have investigated whether an increased iron level and an increased susceptibility to iron release could be observed in the erythrocytes from patients with beta-thalassemia. Erythrocytes from subjects with thalassemia intermedia showed an extremely higher content (0 time value) of free iron and methemoglobin as compared to controls. An increase, although non-statistically-significant, was seen in erythrocytes from subjects with thalassemia major. Upon aerobic incubation for 24 h the release of iron in beta-thalassemic erythrocytes was by far greater than in controls, with the exception of thalassemia minor. When the individual values for free iron content (0 time) seen in thalassemia major and intermedia were plotted against the corresponding values for HbF, a positive correlation (P < 0.001) was observed. Also, a positive correlation (P < 0.01) was seen between the values for free iron release (24 h incubation) and the values for HbF. These results suggest that the presence of HbF is a condition favourable to iron release. Since in beta-thalassemia the persistance of HbF is related to the lack or deficiency of beta chains and therefore to the excess of alpha chains, the observed correlation between free iron and HbF, is consistent with the hypothesis by others that excess of alpha chains represents a prooxidant factor.

Aging and red blood cell membrane: a study of centenarians

Successful aging, characterized by little or no loss in physiological functions, should be the usual aging process in centenarians. It is known that well-preserved physiological functions depend on the proper functioning of cell systems. In this article we focus on cell membrane integrity and study the red blood cell membrane to evaluate the effect of physiological aging in centenarians. Fifteen healthy, self-sufficient centenarians, mean age 103 years, were examined by assessing hemocytometric values and some relevant characteristics of the erythrocyte membrane, i.e., the cholesterol/phospholipid molar ratio, the distribution of phospholipid classes and their fatty acid composition, the integral and skeletal protein profiles. The centenarians showed a significant decrease in the red blood cell count (p < 0.0002), hemoglobin (p < 0.0002), and hematocrit (p < 0.0005). The red blood cell membrane showed a significantly increased cholesterol/phospholipid molar ratio (p < 0.01), with a concomitant increase in polyunsaturated fatty acids in phosphatidylcholine (p < 0.001) and, to a lesser extent, in phosphatidylethanolamine. The electrophoretic pattern of membrane proteins was qualitatively normal compared to controls but the densitometric analysis showed a significant increase in the integral protein band 4.2 (p < 0.05) and in the skeletal protein actin (p < 0.001). Extreme longevity seems to be associated with a substantial integrity of the erythrocyte membrane. Moreover, the evident increase in polyunsaturated fatty acids and in actin are likely to improve the membrane fluidity and to strengthen the membrane structure.

Priapism following splenectomy in an unstable hemoglobin: hemoglobin Olmsted beta 141 (H19) Leu-->Arg

We report a case of severe priapism occurring in a patient with an unstable hemoglobin, Hb Olmsted (beta 141 Leu-->Arg) This is a rare hemoglobin variant, which until now has been reported only once. The clinical course of the 12-year-old boy was characterized by severe hemolytic anemia leading to splenectomy and cholecystectomy at the of 3.5 years. The priapism occurred 8 years after splenectomy, during a hemolytic febrile episode and required aspiration of the corpora cavernosa. This report raises the question of the benefit of splenectomy in patients suffering from a chronic hemolytic anemia such as that due to an unstable hemoglobin. This treatment lowers the frequency and the severity of acute hemolytic attacks, but several cases of vascular complications have been reported after splenectomy.

Oxygen free radicals in rat limbic structures after kainate-induced seizures

Several indices of free radical generation were determined in limbic structures after kainate (KA)-induced seizure activity in adult and postnatal day (PND) 12 and 17 rats. Superoxide dismutase, catalase, and glutathione peroxidase activities were measured in piriform cortex and hippocampal subfields at 8, 16, 48 h, and 5 days after KA injection in adults and pups, and also at 3 weeks postinjection in adults. KA-induced seizure activity had no significant effect on enzyme activities in PND 12 and 17 rats. In adults, superoxide dismutase and catalase activities were significantly increased at 5 days after KA administration, and returned to preinjection levels by 3 weeks. Glutathione peroxidase activity was also increased significantly at 5 days postinjection, but remained elevated at 3 weeks. Lipid peroxidation, as indicated by malondialdehyde (MDA) concentration, exhibited an early significant increase at 8 and 16 h, followed at 48 h and 5 days by a significant decrease. At 3 weeks postinjection, MDA levels were still significantly decreased in CA3 and dentate gyrus. KA administration in PND 12 and 17 rats had no significant effect on MDA content. KA-induced seizure activity in adults also resulted in a large and sustained increase in protein oxidation in piriform cortex and hippocampus. The early increase in MDA and protein oxidation in adult rats strongly suggests the involvement of oxygen free radicals in the initial phases of KA-induced pathology, whereas the changes in scavenging enzyme activities and MDA content at 5 days and 3 weeks post KA injection possibly reflect glial proliferation subsequent to neuronal death.

Junctional sites of erythrocyte skeletal proteins are specific targets of tert-butylhydroperoxide oxidative damage

The oxidative denaturation of the erythrocyte membrane, which is considered a major cause of the haemolytic process, was evaluated upon 'in vitro' oxidative stress with tertbutylhydroperoxide. Biochemical and ultrastructural analyses were performed to point out the effect of this substance on the skeletal network, which is mainly responsible for red cell shape and viability. Moreover, cell morphology was observed by scanning electron microscopy and membrane rigidity assessed by EPR measurements. The most relevant features of the membrane denaturation were, (i) lipid peroxidation, as assessed by malonidialdehyde production, (ii) spectrin and ankyrin degradation with simultaneous globin binding to the membrane, as evidenced by electrophoretic pattern of red cell ghosts. These phenomena were related to the drug concentration in the incubation medium, and accompanied by depletion of intracellular reduced glutathione. The denaturation of protein components hindered the release of spectrin in a hypotonic extraction medium and could be only partially reversed by dithiothreitol. The extensive membrane protein and lipid degradation, at high drug concentration, was coherent with a marked increase of membrane order (membrane 'rigidity'). No clustering of intramembrane proteins was shown by the transmission electron microscopy images. At the same time scanning electron microscopy demonstrated shrinking and disco-stomatocytic deformation of erythrocytes. Ultrastructural analysis of the membrane skeleton by fluorescence-labelling of spectrin and actin, allowed to point out that exposure to t-BHP caused the marginalization of spectrin and the rearrangement of actin molecules with formation of micro aggregates, so that a detachment of actin from the spectrin network was suggested. In addition to the generalized damage of red cell membrane, tertbutylhydroperoxide was found to induce a specific alteration of the skeletal network at the horizontal junction sites involving spectrin, actin, and protein 4.1 and thus to modify the cytoskeletal assembly. This effect on the membrane skeletal components was consistent with the hypothesis that oxidative stress plays a key role in the haemolytic process.

Mechanism of macrophage recognition of SH-oxidized erythrocytes: recognition of glycophorin A on erythrocytes by a macrophage receptor for sialosaccharides

Mouse erythrocytes treated with diamide, an SH-oxidizing agent, attach to mouse resident peritoneal macrophages in the absence of serum. The mechanism by which macrophages recognize the SH-oxidized erythrocytes was investigated. Although phosphatidylserine-liposomes inhibited the macrophage recognition, there was no detectable phosphatidylserine on the outer surface of diamide-treated erythrocytes. It is unlikely that phosphatidylserine, that has been proposed to be a determinant in the recognition of some pathologic erythrocytes by macrophages, is involved in the recognition of diamide-treated erythrocytes. Sialyl lactose and glycophorin A effectively inhibited the macrophage recognition, while lactose and neuraminidase-treated glycophorin A did not. Disialoganglioside GD1a, but not monosialoganglioside GM1, partially inhibited the recognition. Trypsinized erythrocytes, in which majority of glycophorin A glycopeptides were expected to be removed from the cell surface, poorly attached to macrophages after diamide treatment. Therefore, it is likely that an interaction between glycophorin A on diamide-treated erythrocytes and a macrophage receptor for sialosaccharides is involved in the recognition. Similar inhibition specificity was observed in the macrophage recognition of erythrocytes treated with periodate, an oxidant that induces disulfide-dependent erythrocyte changes causing macrophage recognition, and of erythrocytes treated with SH-blocking agents, N-ethylmaleimide and p-chloromercuribenzoic acid, that were also found to be susceptible to macrophage recognition in the absence of serum. These results suggest that the macrophages recognize sialosaccharide chains of glycophorin A molecules on SH-oxidized or SH-blocked erythrocytes through a receptor for sialosaccharides.

Menadione-induced cytotoxicity effects on human erythrocyte membranes studied by electron paramagnetic resonance

Menadione (2-methyl-1,4-naphthoquinone) is cytotoxic to hepatocytes. In order to begin to investigate the changes in the physical state of membranes induced by this cytotoxic substance, electron paramagnetic resonance (EPR) spin-labeling techniques were used in conjunction with spin labels specific for cytoskeletal proteins, bilayer lipids, or cell-surface sialic acid or galactose to investigate erythrocyte membranes. We studied the molecular effects of oxidation of 200 microM menadione on the different membrane domains. The major findings are: (1) menadione increases protein-protein interactions (P < 0.001) of cytoskeletal proteins, (2) there is a slightly significant increase in the rotational motion of spin-labeled sialic acid (P < 0.05), while (3) the physical state of galactose residues was unaffected by menadione. Since glycophorin is coupled to the major cytoskeletal protein, spectrin, by protein 4.1, we suggest that menadione-induced oxidation could alter the conformation of protein 4.1. As a consequence, single or multiple sites of weakness could be induced leading to the alteration of the interactions of the cytoskeletal network and its anchoring domains in the membrane. These results are discussed with reference to possible mechanisms involved in the cytotoxic action of menadione.

The assessment of the HO. scavenging action of therapeutic agents

A new method is reported for the assessment of the HO. scavenging action of therapeutic agents. It is based on the photolysis of zinc oxide and has a detection limit of 3.3%. The scavenging order of the compounds tested was penicillamine > rentiapril > ascorbic acid > cysteine > glutathione > thiomalic acid > N-acetylcysteine > myocrysin > methionine. None were as effective as DMSO. It is argued that these compounds can have an in vivo protective effect where HO. is produced from oxidant producing cells, thus limiting radical induced damage.

Headspace gas chromatography of volatile lipid peroxidation products from human red blood cell membranes

An improved headspace capillary gas chromatographic (GC) method was developed to measure the oxidative susceptibility of human red blood cell (RBC) membranes. This method analyzed volatile peroxidation products of both n-6 (hexanal and pentane) and n-3 (propanal) polyunsaturated fatty acids. Oxidative susceptibility tests were standardized by incubating in a sealed 10-mL headspace bottle 0.25 or 1 mL of human RBC membrane in 40 mM phosphate buffer for 1 hr at 37 degrees C with a mixture of Fe++, ascorbic acid and H2O2. Sodium dodecyl sulfate increased significantly the amount of hexanal measured by headspace GC. By this standard headspace method, in one series of red blood cell membranes (RBCM) samples a four-fold variation in oxidative susceptibility was observed in RBCM from blood freshly drawn from six healthy subjects. In another series of RBCM samples a sixteen-fold variation in oxidative susceptibility was noted in frozen RBCM from blood freshly drawn from five healthy subjects. Correlation between hexanal formation and polyunsaturated fatty acids (PUFA) depletion provided good evidence that under these standard conditions hexanal is exclusively derived from the oxidation of arachidonic acid. Hydroperoxides of arachidonic acid are more readily formed and decomposed than those of linoleic acid in the presence of Fe++, ascorbic acid and H2O2 to produce hexanal as the main product that can be readily analyzed by headspace GC. This method may provide a useful tool to study susceptibility toward lipid peroxidative damage in human RBC membranes.

Oxidative damage by phenylhydrazine diminishes erythrocyte anion transport

Human erythrocytes were exposed to oxidative stress by treatment with the slowly hemolytic drug phenylhydrazine. Phenylhydrazine has been previously shown to trigger the production of toxic oxygen metabolites including O-2 and H2O2 and the formation of Heinz bodies. The concentration-dependent formation of Heinz bodies was confirmed using optical microscopy. Heinz body formation was accompanied by surface protuberances as shown by scanning electron microscopy. The formation of Heinz bodies was accompanied by inhibition of anion translocation. Anion translocation was measured using the anionic fluorescent substrate analog N-(2-aminoethylsulfonate)-7-nitrobenz-2-oxa-1,3-diazole (NBD-taurine). The efflux of NBD-taurine was measured by continuous monitoring of transport by fluorescence (CMTF). The mean value of the kinetic rate constant for transport, k, was found to be -0.090 +/- 0.017 min-1. Phenylhydrazine was found to decrease k to less than one-half of control values in a dose-dependent fashion. The disruption of anion translocation may be related to the oxidative effects of phenylhydrazine and to the generation of Heinz bodies, which bind to the N-terminal domain of band 3.

Influence of splenectomy on the properties of erythrocytes with hemoglobin Volga disease

Hemoglobin Volga is a rare unstable hemoglobin in which there is a replacement of an internal alanine residue, beta 27 (B9), by an aspartate. From a clinical point of view it is characterized by a moderately severe Heinz body hemolytic anemia. A possible clue to the cause of the hemolysis is the increased vulnerability to oxidation of Hb Volga, with increased free radical turnover and consequent damage to the red cell membrane. Splenectomy performed on carriers of Hb Volga may have a positive outcome leading to improvements in both the clinical condition of the patient and hematological variables such as hemoglobin concentration and bilirubin concentration. With the aim of defining a more complete biochemical picture of the beneficial effect of splenectomy in this disease, we have evaluated some enzymic activities of the red cells of a young patient with Hb Volga disease, before and after splenectomy. In particular, we have investigated the activity of superoxide dismutase (superoxide: superoxide oxidoreductase), glutathione peroxidase (GSH peroxidase, glutathione: hydrogen-peroxidase oxidoreductase) and catalase (hydrogen-peroxide: hydrogen-peroxide oxidoreductase) that catalyze reactions relevant to the steady-state concentration of potentially toxic oxygen derivatives such as O2- and H2O2. Besides, we have carried out experiments on the erythrocytic membrane to evaluate eventual changes on the chemical (i.e. peroxidation) and physico-chemical (i.e. fluidity) properties following surgery.

Membrane alterations in G6PD- and PK-deficient erythrocytes exposed to oxidizing agents

After in vitro treatment of normal, glucose-6-phosphate dehydrogenase-deficient or pyruvate kinase-deficient human erythrocytes with three different oxidizing agents, the extent of lipid peroxidative degradation and the alterations of membrane proteins were evaluated. Exposure to tert-butylhydroperoxide induced, most markedly in G6PD- and PK-deficient erythrocytes, a reduction of protein bands 1, 2, 2.1, 3, 4.1, 4.2, and 5, with the appearance of high-molecular-weight aggregates and of "new" polypeptide components in the 29- to 23-kDa region and with a marked increase of membrane-bound globin. Malonyldialdehyde production was highest in G6PD-deficient cells and relatively low in PK-deficient ones. Methylene blue, which had similar but less relevant effects on lipid peroxidation, in G6PD-deficient erythrocytes caused a conspicuous appearance of high-molecular-weight aggregates and a simultaneous relevant decrease of bands 1 and 2 and of membrane-bound globin; it brought about an almost opposite effect in PK-deficient red cells. Acetylphenylhydrazine, which under our conditions appeared the mildest agent, failed, in normal and PK-deficient erythrocytes, to increase malonyldialdehyde production or to alter membrane proteins, whereas it caused, in G6PD-deficient cells, a slight decrease of bands 1 and 2, a more pronounced decrease of band 3, and a marked increase of bands 4.5 and 4.9.

Hemin-promoted peroxidation of red cell cytoskeletal proteins

Hemin-induced crosslinking of the erythrocyte membrane proteins was analyzed at three levels: (i) whole membranes, (ii) integrated or dissociated cytoskeletons, and (iii) isolated forms of the three main cytoskeletal proteins, spectrin, actin, and protein 4.1. Addition of H2O2 and hemoglobin to resealed membranes from without did not affect any of the membrane proteins. Hemin that can transport across the membrane induced, in the presence of H2O2, crosslinking of protein 4.1 and spectrin. Both free hemin and hemoglobin added with H2O2 induced crosslinking of integer cytoskeletons and mixtures of isolated cytoskeletal proteins, but hemin was always more active. Of the three major cytoskeletal proteins, spectrin and protein 4.1 were most active while the participation of actin was only minor. The yield of crosslinked products was increased in all reaction mixtures with pH, with an apparent pK above 9.0. Replacement of H2O2 by phenylhydrazine and tert-butyl hydroperoxide resulted in crosslinking of the same proteins, but with lower activity than H2O2. Bityrosines, which were identified by their specific fluorescence emission characteristics, were formed in reaction mixtures containing hemin and hydrogen peroxide and either spectrin or protein 4.1, but not actin. On the basis of fact that bityrosines were revealed only in reaction mixtures that produced protein adducts, formation of intermolecular bityrosines was analyzed to be involved in crosslinking of the cytoskeletal proteins. Since the levels of membrane-intercalated hemin are correlated with aggregation of membrane proteins, it is suggested that the peroxidative properties of hemin are responsible for its toxicity.

Erythrocyte pathology and mechanisms of Heinz body-mediated hemolysis in cats

Despite the frequency of both oxidant drug-induced and spontaneous Heinz body formation in cats, the cellular and biochemical mechanisms by which Heinz bodies result in red blood cell (RBC) destruction and hemolytic anemia in this species remain unknown. Feline spleens are non-sinusoidal and inefficient at removing Heinz body-containing RBC from the circulation; therefore, alternative mechanisms must be involved in accelerated RBC destruction. Propylene glycol (PG) ingestion causes dose-dependent Heinz body formation and decreased RBC survival in cats. We investigated several aspects of Heinz body-containing RBC from three cats ingesting diets that provided 8.0 g PG/kg body weight for up to 3 weeks, in order to characterize cellular lesions that are associated with the presence of Heinz bodies and that might contribute to chronic, accelerated RBC destruction, as well as to gain insight into the mechanism by which PG induces Heinz body formation. Erythrocytes with PG-induced Heinz bodies had decreased levels of reduced glutathione and adenosine triphosphate and reduced deformability. There was no change in hemoglobin isoelectric focusing or membrane lipid peroxidation. Electrophoretic patterns of Heinz body-containing RBC membranes were significantly altered, and membrane surface charge distribution was disturbed. Progressively protruding Heinz bodies suggested that extrusion of Heinz bodies may be a means of cell healing and/or destruction in the absence of splenic pitting. When compared to results obtained using RBC from cats treated with the oxidant drug phenylhydrazine, significant differences were noted in packed cell volume, turbidity index, membrane heme, and morphologic appearance of Heinz bodies. Our results indicate that multiple cellular abnormalities develop in RBC with PG-induced Heinz bodies that do not cause acute hemolysis but that may shorten RBC survival. Propylene glycol-induced Heinz bodies provide an ideal model for studying the chronic effects of Heinz bodies on RBC structure and function and may be useful in understanding the mechanisms of formation and the consequences of endogenous Heinz bodies in cats.

Unstable hemoglobins

About 70 variants of Hb A with associated hemolytic disorders have been reported during the past 30 years. I have classified them according to four grades of severity of chronic hemolysis. Acute episodes of severe hemolysis may be seen in all classes. In addition, some 80 variants without overt hemolysis have given positive results with in vitro hemoglobin instability tests. The stereochemical bases for instability can be conjectured in most cases, although few unstable hemoglobins have actually been studied by X-ray crystallography. The mechanisms for denaturation of normal Hb A and its acceleration in unstable hemoglobins were proposed some 15 years ago. The alterations of membrane lipids and proteins leading to red cell senescence and the relevance of hemoglobin denaturation to this process are presently being investigated. Several "hyperunstable" variants are clinically silent, or equivalent to a thalassemia, probably because of very efficient degradation of the abnormal chains.

Membrane protein lesions in erythrocytes with Heinz bodies

We studied Heinz body-containing erythrocytes with three different unstable hemoglobins: Nottingham, Brockton, and unclassified. We demonstrated two classes of membrane protein defects in unstable hemoglobin-containing cells (UH-RBCs), a defect of the spectrin-depleted inside-out vesicle (UH-IOV), and a defect of spectrin (UH-spectrin) itself. The composition of UH-IOVs is the same as control with respect to quantity of ankyrin and proportion inside-out. However, UH-IOVs bind even less spectrin than IOVs derived from sickle erythrocytes (SS-IOVs), suggesting a severe functional defect in the ankyrin of UH-RBCs (UH-ankyrin). Further evidence that UH-ankyrin is abnormal is demonstrated by the virtual absence of ankyrin in isotonic membrane shells of UH-RBCs (UH-shells), and abnormal mobility and decreased binding of the 72-kD (spectrin-binding) alpha-chymotryptic fragment of UH-ankyrin (UH-72-kD) to control spectrin. All UH-RBC membranes were spectrin-deficient (60% of control). In addition, spectrin isolated from UH-RBCs (UH-spectrin) was abnormal in two respects: (a) presence of a fast-moving band on nondenaturing polyacrylamide gels of both 0 degree C and 37 degrees C extracts, and (b) decreased binding to actin in the presence of protein 4.1. UH-spectrin did exhibit normal self-association, binding to IOVs and binding to actin in the absence of protein 4.1. This pattern of normal and abnormal spectrin functions has been described for spectrin subjected to mild diamide oxidation, suggesting the role of oxidation is the pathogenesis of membrane defect(s) of erythrocytes with abnormal hemoglobins.