Increase in vulnerability to oxidative damage in cholesterol-modified erythrocytes exposed to t-BuOOH

Susceptibility of erythrocytes from different sources to xenobiotics-induced lysis

As erythrocytes are continuously exposed to plenty of metabolites and toxicants, the aim of the present work is to show whether erythrocytes from different sources may exhibit different susceptibility to hemolysis induced by two classes of xenobiotics, Cnidaria venoms, acting via pore forming mechanism on cell membrane, and Cd²⁺, inducing cell damage mainly via lipid peroxidation. To this end, the hemolytic power of crude venom from stinging cells of the anthozoan Aiptasia mutabilis and from the scyphozoan Pelagia noctiluca has been tested, along with Cd²⁺ (5 to 20 mM), on erythrocytes (0.05% v/v) obtained from either rabbit, or dog, or chicken, or human source. Our results show a more significant susceptibility of rabbit erythrocytes to hemolysis induced by both crude venom and Cd²⁺ than erythrocytes from other sources. This difference seems to rely neither on the different specimens used to extract crude venom, nor on the different mechanism of toxicants. In this light, the present study may contribute: i) to confirm hemolytic test as a suitable biological assay to verify erythrocytes resistance to toxicants; ii) to show variability in hemolytic response to xenobiotics; iii) to propose rabbit erythrocytes as more sensitive to the lytic action of xenobiotics, adding more knowledge to the field of toxicology.

Free radical stress induces DNA damage response in RAW264.7 macrophages during Mycobacterium smegmatis infection

Genomic instability resulting from oxidative stress responses may be traced to chromosomal aberration. Oxidative stress suggests an imbalance between the systemic manifestation of reactive free radicals and biological system's ability to repair resulting DNA damage and chromosomal aberration. Bacterial infection associated insult is considered as one of the major factors leading to such stress conditions. To study free radical responses by host cells, RAW 264.7 macrophages were infected with non-pathogenic M. smegmatis mc²155 at different time points. The infection process was followed up with an assessment of free radical stress, cytokine, toll-like receptors (TLRs) and the resulting DNA damage profiles. Results of CFU count showed that maximum infection in macrophages was achieved after 9 h of infection. Host responses to the infection across different time periods were validated from nitric oxide quantification and expression of iNOS and were plotted at regular intervals. IL-10 and TNF-α expression profile at protein and mRNA level showed a heightened pro-inflammatory response by host macrophages to combat M. smegmatis infection. The expression of TLR4, a receptor for recognition of mycobacteria, in infected macrophages reached the highest level at 9 h of infection. Furthermore, comet tail length, micronuclei and γ-H2AX foci recorded the highest level at 9 h of infection, pointing to the fact that breakage in DNA double strands in macrophage reaches its peak at 9 h of infection. In contrast, treatment with ROS inhibitor N-acetyl-L-cysteine (NAC) prevented host cell death through reduction in oxidative stress and DNA damage response during M. smegmatis infection. Therefore, it can be concluded that enhanced oxidative stress response in M. smegmatis infected macrophages might be correlated with DNA damage response.

Egg Yolk Extracts as Potential Liposomes Shell Material: Composition Compared with Vesicles Characteristics

Our aim was to propose simple extraction process to obtain phospholipids along with yolk-derived vitamins and fats. Five extracts marked as ethanol/acetone, methanol-chloroform/acetone, hot ethanol, hexane, and cold ethanol were developed and compared. Extracts' compositions were analyzed in terms of phospholipid, polar and nonpolar fraction, cholesterol, carotenoids, and tocopherols content. Further, liposomes prepared from extracts were characterized. The highest extraction efficiency was achieved by a one-step hexane procedure. However, that sample, in contrast to the other four extracts, revealed distinctively lower permeability when used for liposomes membrane formation. Principal component analysis proved that major components contents were decisive for liposomes membranes permeability, whereas minor constituents' content controlled zeta potential and Z-average size.

PRACTICAL APPLICATION

Liposomes are nanocarriers widely used in pharmaceutical industry. Due to intravenous route of administration, they have to be produced from phospholipids of very fine purity. On the other hand, there is increasing interest in nanoencapsulation of labile, bioactive substances for manufacturing of health promoting food. Unfortunately, high-price pure phospholipids are prohibitive for food applications. The use of raw material obtained by simple extraction procedure instead of highly purified phospholipids could be an attractive alternative for food industry.

Erythrocytes as a biological model for screening of xenobiotics toxicity

Erythrocytes are the main cells in circulation. They are devoid of internal membrane structures and easy to be isolated and handled providing a good model for different assays. Red blood cells (RBCs) plasma membrane is a multi-component structure that keeps the cell morphology, elasticity, flexibility and deformability. Alteration of membrane structure upon exposure to xenobiotics could induce various cellular abnormalities and releasing of intracellular components. Therefore the morphological changes and extracellular release of haemoglobin [hemolysis] and increased content of extracellular adenosine triphosphate (ATP) [as signs of membrane stability] could be used to evaluate the cytotoxic effects of various molecules. The nucleated RBCs from birds, fish and amphibians can be used to evaluate genotoxicity of different xenobiotics using comet, DNA fragmentation and micronucleus assays. The RBCs could undergo programmed cell death (eryptosis) in response to injury providing a useful model to analyze some mechanisms of toxicity that could be implicated in apoptosis of nucleated cells. Erythrocytes are vulnerable to peroxidation making it a good biological membrane model for analyzing the oxidative stress and lipid peroxidation of various xenobiotics. The RBCs contain a large number of enzymatic and non-enzymatic antioxidants. The changes of the RBCs antioxidant capacity could reflect the capability of xenobiotics to generate reactive oxygen species (ROS) resulting in oxidative damage of tissue. These criteria make RBCs a valuable in vitro model to evaluate the cytotoxicity of different natural or synthetic and organic or inorganic molecules by cellular damage measures.

Cholesterol-nitrone conjugates as protective agents against lipid oxidation: A model membrane study

Free radical scavengers such as α-phenyl-N-tert-butylnitrone (PBN) have been widely used as protective agents in several biological models. We recently designed two PBN derivatives by adding a cholesterol moiety to the parent nitrone to increase its lipophilicity. In addition to the cholesterol, a sugar group was also grafted to enhance the hydrophilic properties at the same time. In the present work we report on the synthesis of a third derivative bearing only a cholesterol moiety and the physical chemical and antioxidant characterization of these three derivatives. We demonstrated they were able to form stable monolayers at the air/water interface and with the two derivatives bearing a sugar group, repulsive interactions with 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC) were observed. We next investigated the interaction with DLPC on a liposome model. Fluorescence spectroscopy experiments showed the addition of a cholesterol moiety causes an ordering effect whereas the presence of the sugar group led to a disordering effect. The protective effect against lipid oxidation was then investigated using dynamic light scattering and the formation of conjugated dienes was quantified spectrophotometrically. Two oxidizing systems were tested, i.e. the AAPH-thermolysis which generates peroxyl radicals and the Fenton reagent which is responsible of the formation of hydroxyl radicals. Due to their membrane localization, the three cholesteryl-PBN derivatives are able to prevent lipid oxidation with the two types of radical inducers but with a different mode of action.

Treatment with garlic restores membrane thiol content and ameliorates lead induced early death of erythrocytes in mice

Sequelae of chronic lead (Pb(2+) ) toxicity includes anemia that is partially due to early death of erythrocytes characterized by excess accumulation of ROS and downregulation of antioxidant system causing oxidative stress and externalization of phosphatidylserine. In this study, pathophysiological based therapeutic application of garlic was evaluated against erythrocyte death. Results suggest that garlic administration prevents oxidative stress, restored the antioxidant balance in erythrocytes of Pb(2+) exposed mice. Moreover, in vitro studies revealed that activity of both scramblase and aminophospholipid translocase could be changed by modifying the critical sulfhydryl groups in presence of dithiothreitol during Pb(2+) exposure. Data also indicated that garlic treatment in Pb(2+) exposed mice exhibited sharp decline in PS exposure and increase in erythrocyte membrane thiol group followed by increase in aminophospholipid translocase activity and decline in scramblase activity. Findings indicated that garlic has the ability to restore the lifespan of erythrocytes during Pb(2+) exposure.

Identification of potential erythrocyte phospholipid fatty acid biomarkers of advanced lung adenocarcinoma, squamous cell lung carcinoma, and small cell lung cancer

New biomarkers for lung cancer would be valuable. Our aim was to analyze the fatty acid profiles of the main phospholipid species in erythrocytes from patients with advanced squamous cell lung carcinoma (SCC), lung adenocarcinoma (ADC), and small cell lung cancer (SCLC) and benign lung diseases (chronic obstructive pulmonary disease (COPD) and asthma) to determine the fatty acids that could be use as lung cancer markers. Twenty-eight, 18, 14, 16, and 15 patients with, respectively, SCC, ADC, SCLC, asthma, and COPD and 50 healthy subjects were enrolled in the study. Fatty acid profiles were investigated using gas chromatography/mass spectrometry followed by receiver operating characteristic (ROC) curve analysis. The fatty acid profiles changed significantly in the different pathologies analyzed. Based on the diagnostic yields and operating characteristics, the most significant fatty acids that might be used as biomarkers were as follows: ADC--arachidonic acid (20:4n6) in phosphatidylcholine and oleic acid (18:1n9) in phosphatidylethanolamine (PE); SCC--eicosapentaenoic acid (20:5n3) in PE and palmitic acid (16:0) in phosphatidylserine + phosphatidylinositol (PS+PI); SCLC--eicosadienoic acid (20:2n6) in PS+PI and lignoceric acid (24:0) in sphingomyelin. In conclusion, fatty acids from erythrocyte phospholipid species might serve as biomarkers in the diagnosis, and probably in other aspects related to clinical disease management, of ADC, SCC, and SCLC.

Biomarkers for disease progression and AAV therapeutic efficacy in feline Sandhoff disease

The GM2 gangliosidoses, Tay-Sachs disease (TSD) and Sandhoff disease (SD), are progressive neurodegenerative disorders that are caused by a mutation in the enzyme β-N-acetylhexosaminidase (Hex). Due to the recent emergence of novel experimental treatments, biomarker development has become particularly relevant in GM2 gangliosidosis as an objective means to measure therapeutic efficacy. Here we describe blood, cerebrospinal fluid (CSF), magnetic resonance imaging (MRI), and electrodiagnostic methods for evaluating disease progression in the feline SD model and application of these approaches to assess AAV-mediated gene therapy. SD cats were treated by intracranial injections of the thalami combined with either the deep cerebellar nuclei or a single lateral ventricle using AAVrh8 vectors encoding feline Hex. Significantly altered in untreated SD cats, blood and CSF based biomarkers were largely normalized after AAV gene therapy. Also reduced after treatment were expansion of the lysosomal compartment in peripheral blood mononuclear cells and elevated activity of secondary lysosomal enzymes. MRI changes characteristic of the gangliosidoses were documented in SD cats and normalized after AAV gene therapy. The minimally invasive biomarkers reported herein should be useful to assess disease progression of untreated SD patients and those in future clinical trials.

Erythrocyte fatty acids as potential biomarkers in the diagnosis of advanced lung adenocarcinoma, lung squamous cell carcinoma, and small cell lung cancer

OBJECTIVES

To analyze the fatty acid profiles of erythrocyte total lipids from patients with advanced squamous cell lung carcinoma (SCC), lung adenocarcinoma (ADC), and small cell lung cancer (SCLC) and benign lung diseases (chronic obstructive pulmonary disease [COPD] and asthma) to reveal the fatty acids that could be used as lung cancer biomarkers.

METHODS

Thirty, 20, 15, 17, and 19 patients with SCC, ADC, SCLC, COPD, and asthma, respectively, and 55 healthy participants were enrolled in our study. Fatty acid profiles were investigated using gas chromatography/mass spectrometry followed by receiver operating characteristic (ROC) curve analysis. Sialic acid (SA) and cytokeratins were measured by the thiobarbituric acid and immunoradiometric methods, respectively.

RESULTS

At least one of the main fatty acids might be used as a biomarker for every type of lung cancer: arachidonic (20:4n6), linoleic (18:2n6), and stearic (18:0) acids for ADC, SCC, and SCLC, respectively. These fatty acids showed diagnostic yields and operating characteristics similar to or higher than the commonly used SA or cytokeratin markers.

CONCLUSIONS

Fatty acids from erythrocyte total lipids might be used as diagnostic biomarkers of lung ADC, SCC, and SCLC. Their use in different aspects of the disease process needs to be explored.

Ginkgo biloba extract (EGb 761) attenuates oxidative stress induction in erythrocytes of sickle cell disease patients

Sickle cell disease promotes hemolytic anemia and occlusion of small blood vessels due to the presence of high concentrations of hemoglobin S, resulting in increased production of reactive oxygen species and decreased antioxidant defense capacity. The aim of this study was to evaluate the protective action of a standardized extract of Ginkgo biloba (EGb 761), selected due to its high content of flavonoids and terpenoids, in erythrocytes of patients with sickle cell anemia (HbSS, SS erythrocytes) subjected to oxidative stress using tert-butylhydroperoxide or 2,2-azobis-(amidinepropane)-dihydrochloride, in vitro. Hemolysis indexes, reduced glutathione, methemoglobin concentrations, lipid peroxidation, and intracellular reactive oxygen species were determined. SS erythrocytes displayed increased rates of oxidation of hemoglobin and membrane lipid peroxidation compared to normal erythrocytes (HbAA, AA erythrocytes), and the concentration of EGb 761 necessary to achieve the same antioxidant effect in SS erythrocytes was at least two times higher than in normal ones, inhibiting the formation of intracellular reactive oxygen species (IC50 of 13.6 µg/mL), partially preventing lipid peroxidation (IC50 of 242.5 µg/mL) and preventing hemolysis (IC50 of 10.5 µg/mL). Thus, EGb 761 has a beneficial effect on the oxidative status of SS erythrocytes. Moreover, EGb 761 failed to prevent oxidation of hemoglobin and reduced glutathione at the concentrations examined.

Experimental Assessment of Moringa oleifera Leaf and Fruit for Its Antistress, Antioxidant, and Scavenging Potential Using In Vitro and In Vivo Assays

We have investigated effect of Moringa oleifera leaf and fruit extracts on markers of oxidative stress, its toxicity evaluation, and correlation with antioxidant properties using in vitro and in vitro assays. The aqueous extract of leaf was able to increase the GSH and reduce MDA level in a concentration-dependent manner. The ethanolic extract of fruit showed highest phenolic content, strong reducing power and free radical scavenging capacity. The antioxidant capacity of ethanolic extract of both fruit and leaf was higher in the in vitro assay compared to aqueous extract which showed higher potential in vivo. Safety evaluation studies showed no toxicity of the extracts up to a dose of 100 mg/kg body weight. Our results support the potent antioxidant activity of aqueous and ethanolic extract of Moringa oleifera which adds one more positive attribute to its known pharmacological importance.

Comparative antioxidant capacities of quercetin and butylated hydroxyanisole in cholesterol-modified erythrocytes damaged by tert-butylhydroperoxide

Phenolic compounds are potent antioxidants that scavenge reactive oxygen species (ROS), protecting the cells against oxidative damage. Their antioxidant capacities are governed by their structural features and the nature and physical state of the cell membrane. Our study compares the protective effects of butylated hydroxyanisole (BHA) and quercetin against the cellular injury induced by oxidative stress, and the influence of membrane cholesterol contents in their antioxidant capacities, analyzing the structural changes and cellular stability of native and cholesterol-modified erythrocytes exposed to tert-butylhydroperoxide in presence of each antioxidant. The data provide clear evidence that BHA affords better protection than quercetin against ROS generation, lipid peroxidation and lipid and GSH losses in oxidized erythrocytes. However, cellular integrity and stability are better protected by quercetin owing to the hemolytic effect of BHA. Both antioxidants suppress the alterations in membrane fluidity with similar efficiency, reducing methemoglobin formation in all oxidized erythrocytes. Membrane cholesterol depletion decreases the protection against the oxidative damage provided by both antioxidants. This lower preservation may be due to low antioxidant contents, a lower antioxidant capacity, or even to an increased oxidative damage in this membrane type as a consequence of environment modifications after cholesterol depletion.

Antioxidant micronutrient supplementation increases erythrocyte membrane fluidity in adults from a rural Chinese community

The objective of the present study was to investigate age-related differences in erythrocyte membrane fluidity (EMF) and changes in antioxidant capacity following supplementation. A total of seventy-four children were randomly divided into two groups: group A1 was the placebo-controlled group and group A2 was supplemented daily with 600 μg retinol, 1·0 mg β-carotene, 100 mg tocopherol, 300 mg ascorbic acid and 200 μg Se. A total of ninety young people were randomly divided into B1 and B2 groups, and ninety-one elderly subjects were divided into C1 and C2 groups. Groups B1 and C1 were placebo-controlled groups, and groups B2 and C2 were daily supplemented with 900 μg retinol, 1·5 mg β-carotene, 200 mg tocopherol, 500 mg ascorbic acid and 400 μg Se. Results showed that plasma malondialdehyde (MDA) was 5·35 μmol/l in children, which was lower than in young and elderly people. The MDA levels of the young and elderly individuals in the treated groups were significantly lower compared with the control groups, but the supplementation did not alter MDA levels in children. At baseline, there was a lower value of polarisation (ρ) and microviscosity (η) in children, indicating a higher EMF, than in both the young and elderly subjects. After the 2-month trial, the ρ and η values of young and elderly subjects in the treated groups decreased significantly in comparison with the placebo groups, indicating an increase in EMF. In conclusion, there was a background of higher MDA levels and lower EMF in young and elderly people than in children, which could be improved by antioxidant supplementation.

Cholesterol attenuates and prevents bilayer damage and breakdown in lipoperoxidized model membranes. A spin labeling EPR study

The stabilizing effect of cholesterol on oxidized membranes has been studied in planar phospholipid bilayers and multilamellar 1-palmitoyl-2-linoleoyl-phosphatidylcholine vesicles also containing either 1-palmitoyl-2-glutaroyl-phosphatidylcholine or 1-palmitoyl-2-(13-hydroxy-9,11-octadecanedienoyl)-phosphatidylcholine oxidized phosphatidylcholine in variable ratio. Lipid peroxidation-dependent membrane alterations in the absence and in the presence of cholesterol were analyzed using Electron Paramagnetic Resonance spectroscopy of the model membranes spin labelled with either cholestane spin label (3-DC) or phosphatidylcholine spin label (5-DSPC). Cholesterol, added to lipid mixtures up to 40% final molar ratio, decreased the inner bilayer disorder as compared to cholesterol-free membranes and strongly reduced bilayer alterations brought about by the two oxidized phosphatidylcholine species. Furthermore, Sepharose 4B gel-chromatography and cryo electron microscopy of aqueous suspensions of the lipid mixtures clearly showed that cholesterol is able to counteract the micelle forming tendency of pure 1-palmitoyl-2-glutaroyl-phosphatidylcholine and to sustain multilamellar vesicles formation. It is concluded that membrane cholesterol may exert a beneficial and protective role against bilayer damage caused by oxidized phospholipids formation following reactive oxygen species attack to biomembranes.

A potential biochemical mechanism underlying the influence of sterol deprivation stress on Caenorhabditis elegans longevity

To investigate the biochemical mechanism underlying the effect of sterol deprivation on longevity in Caenorhabditis elegans, we treated parent worms (P0) with 25-azacoprostane (Aza), which inhibits sitosterol-to-cholesterol conversion, and measured mean lifespan (MLS) in F2 worms. At 25 μM (∼EC(50)), Aza reduced total body sterol by 82.5%, confirming sterol depletion. Aza (25 μM) treatment of wild-type (N2) C. elegans grown in sitosterol (5 μg/ml) reduced MLS by 35%. Similar results were obtained for the stress-related mutants daf-16(mu86) and gas-1(fc21). Unexpectedly, Aza had essentially no effect on MLS in the stress-resistant daf-2(e1370) or mitochondrial complex II mutant mev-1(kn1) strains, indicating that Aza may target both insulin/IGF-1 signaling (IIS) and mitochondrial complex II. Aza increased reactive oxygen species (ROS) levels 2.7-fold in N2 worms, but did not affect ROS production by mev-1(kn1), suggesting a direct link between Aza treatment and mitochondrial ROS production. Moreover, expression of the stress-response transcription factor SKN-1 was decreased in amphid neurons by Aza and that of DAF-28 was increased when DAF-6 was involved, contributing to lifespan reduction.

Age-related loss of phospholipid asymmetry in APP(NLh)/APP(NLh) x PS-1(P264L)/PS-1(P264L) human double mutant knock-in mice: relevance to Alzheimer disease

Using APP(NLh)/APP(NLh) x PS-1(P246L)/PS-1(P246L) human double knock-in (APP/PS-1) mice, we examined whether phosphatidylserine (PtdSer) asymmetry is significantly altered in brain of this familial Alzheimer disease mouse model in an age-dependent manner as a result of oxidative stress, toxic Abeta(1-42) oligomer production, and/or apoptosis. Annexin V (AV) and NBD-PS fluorescence in synaptosomes of wild-type (WT) and APP/PS-1 mice were used to determine PtdSer exposure with age, while Mg(2+) ATPase activity was determined to correlate PtdSer asymmetry changes with PtdSer translocase, flippase, activity. AV and NBD-PS results demonstrated significant PtdSer exposure beginning at 9 months compared to 1-month-old WT controls for both assays, a trend that was exacerbated in synaptosomes of APP/PS-1 mice. Decreasing Mg(2+) ATPase activity confirms that the age-related loss of PtdSer asymmetry is likely due to loss of flippase activity, more prominent in APP/PS-1 brain. Two-site sandwich ELISA on SDS- and FA-soluble APP/PS-1 brain fractions were conducted to correlate Abeta(1-40) and Abeta(1-42) levels with age-related trends determined from the AV, NBD-PS, and Mg(2+) ATPase assays. ELISA revealed a significant increase in both SDS- and FA-soluble Abeta(1-40) and Abeta(1-42) with age, consistent with PtdSer and flippase assay trends. Lastly, because PtdSer exposure is affected by pro-apoptotic caspase-3, levels of both latent and active forms were measured. Western blotting results demonstrated an increase in both active fragments of caspase-3 with age, while levels of pro-caspase-3 decrease. These results are discussed with relevance to loss of lipid asymmetry and consequent neurotoxicity in brain of subjects with Alzheimer disease.

Special relationship between sterols and oxygen: were sterols an adaptation to aerobic life?

A fascinating link between sterols and molecular oxygen (O(2)) has been a common thread running through the fundamental work of Konrad Bloch, who elucidated the biosynthetic pathway for cholesterol, to recent work supporting a role of sterols in the sensing of O(2). Synthesis of sterols by eukaryotes is an O(2)-intensive process. In this review, we argue that increased levels of O(2) in the atmosphere not only made the evolution of sterols possible, but that these sterols may in turn have provided the eukaryote with an early defence mechanism against O(2). The idea that nature crafted sterols as a feedback loop to adapt to, or help protect against, the hazards of O(2) is novel and enticing. We marshal several lines of evidence to support this thesis: (1) coincidence of atmospheric O(2) and sterol evolution; (2) sterols regulate O(2) entry into eukaryotic cells and organelles; (3) sterols act as O(2) sensors across eukaryotic life; (4) sterols serve as a primitive cellular defence against O(2) (including reactive oxygen species). Therefore, sterols may have evolved in eukaryotes partially as an adaptive response to the rise of terrestrial O(2), rather than merely as a consequence of it.

Platelet linoleic acid is a potential biomarker of advanced non-small cell lung cancer

New parameters that could be used as tumor markers for lung cancer would be valuable. Our aim was to analyze the fatty acid profiles of total lipids from erythrocytes and platelets from patients with advanced non-small cell lung cancer (NSCLC), chronic obstructive pulmonary disease (COPD) and asthma to reveal the fatty acids that could be used as NSCLC biomarkers. In our study, 50, 15 and 15 patients with advanced NSCLC, COPD and asthma and 50 healthy subjects were enrolled. Fatty acid profiles were investigated using gas chromatography/mass spectrometry followed by ROC (receiver operating characteristics) curves analysis to gain information about biomarkers. Sialic acid (SA) and cytokeratins were measured by the thiobarbituric acid and immunoradiometric methods respectively. Useful fatty acid markers were as follows: erythrocytes, 22:0 and linoleic acid (LA, 18:2n6); platelets, 16:0, 18:0, and LA. At the cutoff value to obtain maximum accuracy, the best biomarker was platelet LA, with higher diagnostic yields than the commonly used markers SA or cytokeratins (100%, 76%, 75% and 86% sensitivity, specificity, positive predictive value and accuracy, respectively). These findings suggest that platelet LA might be used as a biomarker of NSCLC in relation to different aspects of the disease process that now needs to be explored.

Oxidative process in erythrocytes of individuals with hemoglobin S

The understanding of the oxidative stress mechanisms helps to explain many of the processes of cellular lesion and death, especially those related to the hemolytic diseases. Sickle cell anemia, thalassemias and G6-PD deficiency are among the more frequent genetic anomalies accompanied by oxidative stress. In the sickle cells, one of the factors that predisposes to the hemolytic process is the oxidative degradation of the hemoglobin S due to its deoxigenation leading to hemichrome formation and precipitation as Heinz bodies. The oxidative stress contributes to the sickle process and shortening of the erythrocyte survival. Here we analyzed the oxidative process in erythrocytes of patients with two different genotypes for HbS (AS and SS). Units of blood from donors of the Center of Hematology and Hemotherapy of Paraná (HEMEPAR), from normal individuals (AA) and from heterozygote individuals (AS), and venous blood collected from patients with sickle cell anemia (SS) were analyzed. In order to evaluate the protective action of the vitamins C and E in oxidative stress, erythrocytes were treated with antioxidant substances, vitamin C and vitamin E, and then treated with the oxidant tert-butilhydroperoxide (TBHP). The oxidative action induced by TBHP was observed in erythrocytes AA<AS<SS, by the increase in the content of Heinz bodies, methemoglobin, hemolysis, GSH depletion and lowering activities of the enzymes G6-PD and GR. The protective actions of the vitamins C and E for the oxidative stress induced by TBHP were observed for the erythrocytes in the lowering Heinz bodies, methemoglobin, hemolysis, and partial recovery of GSH more efficiently in AS and SS erythrocytes. Recovery was not observed in the levels of the activities of the enzymes G6-PD and GR, under the vitamins actions. The results obtained confirmed the higher susceptibility of the sickle erythrocyte to oxidation which necessitates precaution in the transfusion adequacy of AS erythrocytes. On the other hand, the protective effect of the vitamins C and E over the oxidative stress observed in erythrocytes AS and SS open perspectives for their use for treatment of patients with sickle cell anemias, as well as in the preservation of transfusional erythrocyte bag units.

Erythrocyte and platelet phospholipid fatty acids as markers of advanced non-small cell lung cancer: comparison with serum levels of sialic acid, TPS and Cyfra 21-1

The phospholipid fatty acid profiles of erythrocytes and platelets from fifty patients with advanced non-small cell lung cancer were investigated using gas chromatography/mass spectrometry, followed by "ROC" curves analysis to gain novel biomarker information. Sialic acid and cytokeratins were also examined. Potentially useful fatty acid markers: Erythrocytes: phosphatidylcholine, 18:2n6 and 20:4n6; phosphatidylethanolamine, 22:4n6 and 22:6n3 + 24:1n9. Platelets: phosphatidylcholine, 22.0; phosphatidylethanolamine, 22:5n3 + 24:0. At the cut-off value to obtain maximum accuracy, the best biomarkers were found in platelets: phosphatidylserine + phosphatidylinositol (PS + PI), 21:0; sphyngomyelin: 20:1n9 and 22:1n9. All these fatty acids showed similar/higher diagnostic yields than the commonly used markers sialic acid or cytokeratins.

Comparison of changes in erythrocyte and platelet phospholipid and fatty acid composition and protein oxidation in chronic obstructive pulmonary disease and asthma

OBJECTIVE

To analyse and compare the phospholipid and fatty acid composition of total lipids and the occurrence of lipid peroxidation and protein oxidation directly in erythrocytes or platelets from chronic obstructive pulmonary disease (COPD) and asthma patients.

PATIENTS

Fifteen consecutive outpatients with COPD (all smokers) and asthma (non-smokers) recruited during a moderate-to-severe (COPD) or moderate (asthma) exacerbation. Fifteen subjects with smoking habits similar to those of COPD patients were studied as a control group.

METHODS

Phospholipid and total fatty acid compositions were analysed by two-dimensional thin layer chromatography or gas chromatography-mass spectrometry, respectively. The lipid fluorescence of lipid extracts was measured by spectrofluorimetry. Protein carbonyl contents and profiles were measured by immunoblot detection.

RESULTS

No differences were found either in erythrocyte or platelet cholesterol or phospholipid levels. Only a decrease in the content of phosphatidylserine + phosphatidylinositol (P<0.003) was detected in platelets from the asthma patients. In erythrocytes, the fatty acid profile changed in both lung pathologies, especially as regards polyunsaturated fatty acids (decreases in arachidonic and 22:4 fatty acid contents). Other observed changes were: COPD, an increase in palmitic fatty acid; asthma, an increase in oleic and decreases in eicosapentaenoic and 22:6 + 24:1 fatty acids. In platelets, the fatty acid profiles revealed many differences between both lung pathologies: COPD, a decrease in 18:1 and increases in 20:5 and 22:5 + 24:0; asthma, a decrease in 20:4 and increase in 22:6 + 24:1. In COPD vs. asthma patients, fatty acid changes were mainly detected in platelets, especially in 18-carbon species, with decreases in stearic and 18:1 fatty acids in the COPD patients. Protein oxidation levels were increased in both lung pathologies in both erythrocytes and platelets.

CONCLUSIONS

COPD and asthma are associated with common or specific changes in the lipid composition of erythrocytes and/or platelets. The data point to lipid peroxidation and protein oxidation phenomena in both types of blood cell, although platelets would be more susceptible to stress.

Erythrophagocytosis by liver macrophages (Kupffer cells) promotes oxidative stress, inflammation, and fibrosis in a rabbit model of steatohepatitis: implications for the pathogenesis of human nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a progressive fibrotic disease, the pathogenesis of which has not been fully elucidated. Here, we report a molecular aspect of this disease elucidated using rabbits fed a cholesterol-rich high-fat diet and exhibiting insulin resistance. The liver in this model showed steatohepatitis with fibrosis and high mRNA expression for some cytokines, heme oxygenase-1, transforming growth factor-beta1, and collagen alpha1(I). Erythrocytes isolated from the model showed marked fragility and the externalization of phosphatidylserine (PS) on the outer leaflet of the membrane and were frequently engulfed by Kupffer cells/macrophages in the hepatic sinusoids. Expression of milk fat globule-epidermal growth factor (EGF)-factor 8, a PS-binding protein, was augmented in the liver. In culture, RAW 264.7 cells engulfed erythrocytes oxidized by tert-butyl hydroperoxide, a process that was inhibited by anti-milk fat globule-EGF-factor 8 antibody. In addition, PS-positive erythrocytes appeared entrapped in the model liver in ex vivo perfusion experiments. Finally, in specimens from NASH patients, the aggregation of erythrocytes in inflammatory hepatic sinusoids was notable. These results indicate that the engulfment of PS-externalized, apoptotic signal-positive, erythrocytes by hepatic macrophages may lead to the deposition of iron derived from hemoglobin in the liver and be involved in the pathogenesis of steatohepatitis.

Oxidation of liposomal cholesterol and its effect on phospholipid peroxidation

Lipid peroxidation is believed to play an important role in the pathogenesis of many diseases. Much research has therefore been devoted to peroxidation of different lipids in biomembranes and in model systems (liposomes) of different compositions. Yet, in spite of the relative simplicity of the liposomes, the existing literature is insufficient to reach definite conclusions regarding basic questions including the susceptibility of cholesterol to oxidation, its effect on the peroxidation of polyunsaturated phospholipids such as palmitoyllinoleoylphosphatidylcholine (PLPC) and how cholesterol influences the effect of water-soluble antioxidants such as urate on the peroxidation. The aim of the present study was to clarify these issues. Its major findings are that: (i) AAPH-induced peroxidation of cholesterol is slow and independent of the peroxidation of PLPC. In turn, AAPH-induced peroxidation of PLPC is not affected by cholesterol, independent of the presence of urate in the system. (ii) Cholesterol is not susceptible to copper-induced oxidation, but its inclusion in PLPC liposomes affects the peroxidation of PLPC, slowing down the initial stage of oxidation but promoting later stages. (iii) Addition of urate accelerates copper-induced peroxidation of PLPC in the absence of cholesterol, whereas in cholesterol-containing liposomes it inhibits PLPC oxidation. We attribute the complexity of the observed kinetics to the known cholesterol-induced rigidization of liquid crystalline bilayers.

Membrane cholesterol contents influence the protective effects of quercetin and rutin in erythrocytes damaged by oxidative stress

Flavonoids are potent scavengers of reactive oxygen species (ROS) that effectively prevent erythrocyte oxidation. Their antioxidant activities are governed by their structural characteristics and their ability to interact with and penetrate lipid bilayers. In order to gain a better understanding of the relationship between cholesterol contents and the antioxidant effectiveness of flavonoids against oxidative damage induced by ROS in cells, here we analyzed the integrity and structural stability of cholesterol-modified (enriched or depleted) and control erythrocytes exposed to tert-butyl hydroperoxide in the presence of quercetin or rutin. In control and cholesterol-enriched erythrocytes, quercetin provided greater protection against lipid peroxidation, ROS formation, and it preserved better cellular integrity than rutin. Both antioxidants suppressed the alterations in membrane fluidity and lipid losses with similar efficiency, reducing hemoglobin oxidation by 30% and GSH losses by 60% in the above-mentioned erythrocytes. Cholesterol depletion reduced the efficiency of the antioxidant power of both flavonoids against oxidative damage induced in the erythrocyte membrane, while a stronger degree of protection of GSH and hemoglobin contents was observed, mainly in the presence of rutin. These findings suggest a preferential incorporation of the antioxidants into the membranes from erythrocytes with normal and high cholesterol contents, whereas they would mainly be located in the cytoplasm of cholesterol-depleted erythrocytes.