Mechanisms of oxidant-induced changes in erythrocytes

Seabra PS, Fonseca ADN, de Azevedo Sousa KM, de Oliveira SBB, Carneiro ADS, Coleman MD, Monteiro MC. Alpha-Lipoic Acid and Its Enantiomers Prevent Methemoglobin Formation and DNA Damage Induced by Dapsone Hydroxylamine: Molecular Mechanism and Antioxidant Action

Dapsone (DDS) therapy can frequently lead to hematological side effects, such as methemoglobinemia and DNA damage. In this study, we aim to evaluate the protective effect of racemic alpha lipoic acid (ALA) and its enantiomers on methemoglobin induction. The pre- and post-treatment of erythrocytes with ALA, ALA isomers, or MB (methylene blue), and treatment with DDS-NOH (apsone hydroxylamine) was performed to assess the protective and inhibiting effect on methemoglobin (MetHb) formation. Methemoglobin percentage and DNA damage caused by dapsone and its metabolites were also determined by the comet assay. We also evaluated oxidative parameters such as SOD, GSH, TEAC (Trolox equivalent antioxidant capacity) and MDA (malondialdehyde). In pretreatment, ALA showed the best protector effect in 2.5 µg/mL of DDS-NOH. ALA (1000 µM) was able to inhibit the induced MetHb formation even at the highest concentrations of DDS-NOH. All ALA tested concentrations (100 and 1000 µM) were able to inhibit ROS and CAT activity, and induced increases in GSH production. ALA also showed an effect on DNA damage induced by DDS-NOH (2.5 µg/mL). Both isomers were able to inhibit MetHb formation and the S-ALA was able to elevate GSH levels by stimulating the production of this antioxidant. In post-treatment with the R-ALA, this enantiomer inhibited MetHb formation and increased GSH levels. The pretreatment with R-ALA or S-ALA prevented the increase in SOD and decrease in TEAC, while R-ALA decreased the levels of MDA; and this pretreatment with R-ALA or S-ALA showed the effect of ALA enantiomers on DNA damage. These data show that ALA can be used in future therapies in patients who use dapsone chronically, including leprosy patients.

Protective effect of Terminalia arjuna against alcohol induced oxidative damage of rat erythrocyte membranes

Background

Alcohol is a widely abused drug with many health implications, mainly caused by the oxidative and nitrosative stress on different body parts. Ayurvedic herbalism authenticates the multiple therapeutic applications of Terminalia arjuna bark due to its rich phytochemical repertoire.

Objective

To observe the extent of oxidative damage caused to erythrocytes by alcohol and assess the protective ability of T. arjuna bark powder aqueous extract (AETA) against the damage.

Materials and methods

Wister albino rats were categorized into four groups of eight rats per group; first group (control) was fed with glucose, second group was given alcohol at a dose of 20% v/v; 5g alcohol/kg b. wt/day, third group was co-administered with AETA (0.5 g/kg b. wt/day) and alcohol and the fourth group was kept on bark extract alone. Blood samples were collected and evaluated for different biochemical parameters after the completion of the treatment period.

Results

Alcohol significantly increased the erythrocyte membrane protein carbonyl and malondialdehyde (MDA) contents, along with a concomitant decrease in the membrane antioxidant status, when compared to the control group. Chromatographic analysis of the alcohol-treated rat erythrocyte membranes revealed altered membrane individual phospholipid contents and fluidity properties. Alcohol-induced morphological changes in the erythrocytes and its effect on decreasing the resistance of hypotonic shock induced by NaCl are evident from the hemolysis curves. However, AETA administration to alcoholic rats beneficially modulated the membrane properties anvd protected erythrocytes from damage.

Conclusion

Results suggest that AETA protects erythrocytes from alcohol-induced oxidative stress, biophysical, and biochemical changes very effectively.

Low dose exposure of patulin and protective effect of epicatechin on blood cells in vitro

In the present study, we aimed to assess antioxidant status in erythrocytes in vitro after patulin (PAT) and epicatechin exposure by measuring antioxidant enzymes (superoxide-dismutase - SOD, glutathione peroxidase - GPx and catalase - CAT) and parameters associated with oxidative stress (malondialdehyde - MDA and ROS). We also investigated the effect of PAT on viability and count of lymphocytes and lymphocyte subpopulations in rabbit blood in vitro. Whole blood of rabbits was used for analysis of antioxidant changes in rabbit erythrocytes after epicatechin and PAT treatment (separately or in combination, at concentrations of 0.2; 2; 20; 200 µg mL^-1 of epicatechin and 0.5; 5; 10 µg mL^-1 of PAT). Whole blood of rabbits was also used for analysis of count and viability of lymphocytes after PAT treatment at concentrations of 10; 25 and 50 µg mL^-1. Results from our experiment confirmed the ability of epicatechin to protect cells against oxidative stress and lipoperoxidation. Our findings indicate that mycotoxin PAT in low concentrations did not affect the activity of antioxidant enzymes in erythrocytes of rabbits significantly. Only slight non-significant changes in lymphocytes count after treatment with low doses of PAT in rabbit blood were observed.

Barrêto-Júnior R. Biochemical responses, blood gas, oxidative stress and lipid peroxidation of goats transfused with fresh or stored whole homologous blood

ABSTRACT: Blood transfusion is a therapeutic procedure of great importance for veterinary medicine, in spite of only few studies in the literature on hemotherapy in goats. We aimed to evaluate the biochemical, blood gas, oxidative stress and lipid peroxidation of goats submitted to homologous transfusion of fresh whole blood or stored for 15 and 35 days. Eighteen adult male goats were submitted to a single phlebotomy to remove 30% of the blood volume, and we transfused 20mL/kg of whole blood stored in CPDA-1 bags according to the experimental group, being: G0 composed goats who received fresh blood, G15 and G35 goats that received blood stored for 15 and 35 days, respectively. For the biochemical evaluation, blood gas, oxidative stress and lipid peroxidation, blood samples were collected at the following moments: before the induction of anemia (TC0); 6 hours after phlebotomy and before transfusion (TC1); 1, 6, 12, 24 and 96 hours after transfusion (T1, T6, T12, T24 and T96 respectively); 8, 16 and 32 days after transfusion (T8d, T16d and T32d respectively). Before transfusion, blood samples were also withdrawn from the bags for the same analyzes. Statistical analyzes were performed in the statistical program GRAPHPAD PRISM 5.0, adopting a significance level of 5%. The bags of blood stored for 15 and 35 days showed more biochemical changes, blood gas, oxidative stress and lipid peroxidation than fresh blood bags. As for the biochemical analysis, after the transfusion was observed an increase of the total protein, albumin, glucose and creatine kinase in the 3 groups, and elevation of total bilirubin, direct bilirubin, and urea in G15 and G35. The changes observed in the blood gas analysis had no clinical significance, as they were within the reference values for the species. The goats that received stored blood showed disorder in their antioxidant system through alteration of the SOD activity. In the analysis of lipid peroxidation no difference between the groups for the concentration of malondialdehyde was found. Thus, it can be concluded that transfusion of whole fresh stored blood in goats did not compromise the blood gases, lipid peroxidation and liver and renal functions of the transfused animals. In addition, the method was proved to be efficient to restore, among other components, the total protein and albumin. The transfusion, as performed in this study, proved to be safe for used in the clinical practice of goats.

Hematological indicators in pygmy wood mouse Apodemus uralensis (Muridae, Rodentia) populations as markers of the environmental radiation exposure: East Urals radioactive trace (Russia)

The hematological effects of chronic radiation exposure in males of the pygmy wood mouse (Apodemus uralensis Pall., 1811) from the East Urals radioactive trace (EURT) area were assessed, taking into account population abundance and reproductive status (immature, ripening, and mature yearlings). For this purpose, we analyzed the morpho-functional characteristics of erythrocytes (red cell indices [MCV, MCH, MCHC], red cell count, activity of antioxidant enzymes [GSH-Px, CAT], lipid peroxidation, glycolysis, osmotic resistance, methaemoglobin content) and blood plasma components (free hemoglobin, total lipids, total cholesterol, and glucose) in the background territory and the EURT area; these areas have a density of soil contamination with ⁹⁰Sr of 12,851 and 198 kBq × m^-2, respectively (four and two order of magnitude higher than the background value). The data indicate the "hyperfunctional" state of the erythrocyte, aimed at activation of the gas transport function of blood in the radioactive environment. This, as a consequence, determines the insufficiency of energy supply of the cell defense system necessary to maintain the structural integrity of the membrane. Intensification of membrane lipid peroxidation, reduction of osmotic resistance and GSH-Px activity in red cells, an increase in the degree of intravascular hemolysis, and tendency towards erythropenia indicate the processes of accelerated aging of erythrocytes and their more pronounced destruction in the circulatory bed. The level of the hematological response increased with increasing radiation burden and was more pronounced with a large population size. The interaction effect of "overpopulation" and "radioactive pollution" was observed to a lesser degree for ripening males, and was very small for sexually mature animals. Immature males from the EURT head part with internal whole-body radiation doses of 0.0045-0.35 mGy/day can be considered as the most sensitive group to the factors synergy, including radiation damage and overabundance population.

Erythrocyte osmotic fragility and general health status of adolescent Sprague Dawley rats supplemented with Hibiscus sabdariffa aqueous calyx extracts as neonates followed by a high-fructose diet post-weaning

High-fructose diets (HFD) can cause oxidative damage to tissues including erythrocyte cell membranes. Hibiscus sabdariffa (HS) has protective antioxidant properties. Rats were used to investigate whether the consumption of HS by neonates would result in long-term effects on their erythrocyte osmotic fragility (EOF) and general health when later fed a high-fructose diet post-weaning through adolescence. Eighty of four-day-old Sprague Dawley rat pups were divided randomly into three treatment groups. The controls (n = 27) received distilled water at 10 ml/kg b. w, while the other groups received either 50 mg/kg (n = 28) or 500 mg/kg (n = 25) of an HS aqueous calyx extract orally till post-natal day 14. The rats in each group were weaned and divided into two subgroups; one continued on normal rat chow, and the other received fructose (20% w/v) in their drinking water for 30 days. Blood was collected in heparinised tubes and added to serially diluted (0.0-0.85%) phosphate-buffered saline to determine the EOF. Clinical markers of health status were determined with an automated chemical analyser. HS extracts did not programme metabolism in the growing rats to alter their general health and EOF in response to the HFD.

Relationship between plasma glycation with membrane modification, oxidative stress and expression of glucose trasporter-1 in type 2 diabetes patients with vascular complications

BACKGROUND OF STUDY

Enhanced protein glycation in diabetes causes irreversible cellular damage through membrane modifications. Erythrocytes are persistently exposed to plasma glycated proteins; however, little are known about its consequences on membrane. Aim of this study was to examine the relationship between plasma protein glycation with erythrocyte membrane modifications in type 2 diabetes patients with and without vascular complications.

METHOD

We recruited 60 healthy controls, 85 type 2 diabetic mellitus (DM) and 75 type 2 diabetic patients with complications (DMC). Levels of plasma glycation adduct with antioxidants (fructosamine, protein carbonyl, β-amyloids, thiol groups, total antioxidant status), erythrocyte membrane modifications (protein carbonyls, β-amyloids, free amino groups, erythrocyte fragility), antioxidant profile (GSH, catalase, lipid peroxidation) and Glut-1 expression were quantified.

RESULT

Compared with controls, DM and DMC patients had significantly higher level of glycation adducts, erythrocyte fragility, lipid peroxidation and Glut-1 expression whereas declined levels of plasma and cellular antioxidants. Correlation studies revealed positive association of membrane modifications with erythrocyte sedimentation rate, fragility, peroxidation whereas negative association with free amino groups, glutathione and catalase.

CONCLUSION

Our data suggest that plasma glycation is associated with oxidative stress, Glut-1 expression and erythrocyte fragility in DM patients. This may further contribute to progression of vascular complications.

Persistence of the otoprotective effect: how long does otoprotection against amikacin lasts?

There is evidence that a “resistance phenomenon” occurs when a none-damaging dose of amikacin protects the hair cells from ototoxicity. Our goal is to prove that this resistance is persistent.

Method

Experimental study - 14 albino guinea pigs (Cavia porcellus) divided into three groups. The auditory function was assessed by distortion product otoacoustic emissions (DPOAE): before exposure to amikacin, on the 15th day after the non-damaging dose was injected, at the end of the damage dose injection and prior to decapitation.

Results

Group A (control) presented normal hearing and histological pattern. Group B (amikacin 20 mg/kg/day (IM) for 30 days and affecting dose (400 mg/kg/day) for 12 days and Group C (same protocol of Group B, but kept for 60 days and slaughtered), the DPOAE confirmed normal auditory function in the pre-exposure and maintenance of the standard-dose; however, significant loss of auditory function after the end of the damaging dose injection.

Conclusion

The protection phenomenon did not extended for a period of 30 to 60 days after the application of damaging doses of amykacin.

Influence of coadministration of artemether and lumefantrine on selected plasma biochemical and erythrocyte oxidative stress indices in female Wistar rats

Among the artemisinin-based combination therapy (ACT) regimens, artemisinin derivative, artemether in combination with lumefantrine (artemether-lumefantrine, AL) has achieved excellent results in the fight against malarial scourge. In this study, we evaluated the toxic potential of these drugs at the therapeutic doses in female Wistar rats. Animals were randomly divided into four groups: those administered 1% Tween 80 (control), those administered artemether (4 mg/kg body weight), those administered lumefantrine (24 mg/kg body weight), and those coadministered artemether (4 mg/kg body weight) and lumefantrine (24 mg/kg body weight). The drugs were orally administered twice daily for 3 days by gastric intubation after which selected plasma biochemical indices, and erythrocytes antioxidant defence and lipid peroxidation markers were evaluated. Coadministration of artemether and lumefantrine raised liver and renal function markers and increased atherogenic index. While reduced glutathione, glucose-6-phosphate dehydrogenase (G6PD) and catalase activities were reduced, glutathione peroxidase and glutathione-s-transferase activities increased in all the treated groups compared to the control group. The drugs caused significant (p < 0.05) elevation of malondialdehyde (MDA) levels compared to the control group. These results imply that coadministration of artemether and lumefantrine may increase the risks of atherosclerosis as well as liver and renal function impairments in the users. In addition, the drugs may also promote oxidative stress in the erythrocytes.

Stabilization of erythrocytes against oxidative and hypotonic stress by tannins isolated from sumac leaves (Rhus typhina L.) and grape seeds (Vitis vinifera L.)

Erythrocytes are constantly exposed to ROS due to their function in the organism. High tension of oxygen, presence of hemoglobin iron and high concentration of polyunsaturated fatty acids in membrane make erythrocytes especially susceptible to oxidative stress. A comparison of the antioxidant activities of polyphenol-rich plant extracts containing hydrolysable tannins from sumac leaves (Rhus typhina L.) and condensed tannins from grape seeds (Vitis vinifera L.) showed that at the 5-50 μg/ml concentration range they reduced to the same extent hemolysis and glutathione, lipid and hemoglobin oxidation induced by erythrocyte treatment with 400 μM ONOO(-) or 1 mM HClO. However, extract (condensed tannins) from grape seeds in comparison with extract (hydrolysable tannins) from sumac leaves stabilized erythrocytes in hypotonic NaCl solutions weakly. Our data indicate that both hydrolysable and condensed tannins significantly decrease the fluidity of the surface of erythrocyte membranes but the effect of hydrolysable ones was more profound. In conclusion, our results indicate that extracts from sumac leaves (hydrolysable tannins) and grape seeds (condensed tannins) are very effective protectors against oxidative damage in erythrocytes.

Erythrocyte oxidative damage in rat treated with CCl4

Owing to the presence of hemoglobin and polyunsaturated fatty acids, erythrocytes are a convenient model to understand membrane oxidative damage induced by various xenobiotic pro-oxidants. This study investigated the antioxidant activity of vanillin, a naturally occurring food-flavoring agent, against carbon tetrachloride (CCl4)-induced erythrocyte damages in Wistar albino rats. A single injection of CCl4 (1 ml/kg, intraperitoneally [i.p.]) caused a significant induction of oxidative damage as evidenced by increased thiobarbituric acid reactive substances, protein carbonyl levels and osmotic fragility accompanied with a significant decrease in Na+/K+-ATPase and Ca2+-ATPase activities. Furthermore, catalase and superoxide dismutase activities were significantly elevated, while glutathione levels, glutathione- S-transferase and glutathione peroxidase activities were markedly reduced in the erythrocytes of CCl4-treated rats. Pretreatment of rats with vanillin (150 mg/kg/day, i.p.) for 3 consecutive days before CCl4 injection protected erythrocytes against the increase of lipid peroxidation and degradation of membrane proteins compared to CCl4-treated rats and exhibited marked prevention against CCl4-induced oxidative stress, alterations of membrane-bound enzymes as well as erythrocyte osmotic fragility. Our results suggest that vanillin plays a protective and curative role against the harmful effects of CCl4 on erythrocytes, thus ensuring membrane cell integrity.

Ameliorative effect of vitamin C on chronic chlorpyrifos-induced erythrocyte osmotic fragility in Wistar rats

Chronic exposure to chlorpyrifos (CPF) has been shown to cause increased lipoperoxidative changes in the erythrocyte membranes. The relationship between chronic CPF-induced lipoperoxidative changes and erythrocyte fragility has not been elucidated. The aim of the present study is to evaluate the role of lipoperoxidation on CPF-induced erythrocyte fragility and the ameliorative effect of vitamin C. Twenty animals divided at random into four groups of five animals each served as subject for this study. Rats in group I served as the control group and were given only soya oil at a dose of 2 mL/kg body weight (b.w.). Rats in group II were dosed with vitamin C (100 mg/kg b.w.) and then supplemented with soya oil (2 mL/kg b.w.), while those in group III were administered with CPF only at a dose of 10.6 mg/kg b.w. (~one-eighth of the previously determined median lethal dose [LD(50)]). Rats in group IV were pretreated with 100 mg/kg b.w. of vitamin C, and then dosed with CPF at a dose of 10.6 mg/kg b.w., 30 min later. The different treatment regimens were orally administered daily for a period of 17 weeks. Blood collected from the animals at the end of the test period were analyzed for erythrocyte osmotic fragility and malonaldehyde (MDA) concentration as an index of lipid peroxidation. The study showed that CPF caused significant increase in erythrocyte fragility and MDA concentration, which were ameliorated by pretreatment with vitamin C. In conclusion, the study showed that CPF-evoked erythrocyte fragility due to increased lipoperoxidative changes was ameliorated by pretreatment with vitamin C.

Carbofuran-induced toxicity in rats: protective role of vitamin C

Erythrocytes are prone to oxidative stress due to the presence of hemoglobin and polyunsaturated fatty acids. Oxidative stress (OS) is associated with increased osmotic fragility (OF) of erythrocytes. Organophosphate and organocarbamate pesticides are known to cause OS in erythrocytes. We have investigated the effect of a single sub-acute dose of carbofuran (CF), an organocarbamate pesticide and ameliorating role of vitamin C on OF and OS in erythrocytes of Wistar rats. OF and OS were assessed by determining membrane stability in terms of erythrocyte OF and the activities of free radicals scavenging enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST). We observed a significant alteration in the mean erythrocyte fragility (MEF) at relatively higher NaCl concentration (0.67%) as compared to MEF at 0.55%, 0.58% and 0.56% of NaCl in control, vitamin C- and vitamin C + CF-treated groups, respectively. The activities of CAT and SOD were observed to be elevated by 74.35% and 85.56%, respectively, with significance level of p < or = 0.001, whereas GST activity got significantly (p < or = 0.001) diminished by 46.30% in the erythrocytes of CF-treated rats. Vitamin C treatment exhibited marked (p < or = 0.05) prevention of carbofuran-induced oxidative stress as well as erythrocyte osmotic fragility in the Wistar rats. These results suggest that CF treatment induces OF and OS in the erythrocytes of rats, and pretreatment with vitamin C can mitigate these toxic effects.

Induction of oxidative stress in erythrocytes of male rats subchronically exposed to a mixture of eight metals found as groundwater contaminants in different parts of India

Exposure of animals and humans to different metal components through contaminated drinking water can result in a wide range of adverse clinical conditions. Toxicological consequences arising from the concurrent repeated exposure to multiple metal contaminants are not known. The purpose of the present study was to evaluate the oxidative stress-inducing potential of a mixture of eight metals (arsenic, cadmium, lead, mercury, chromium, nickel, manganese, iron), representative of groundwater contamination in different areas of India, in erythrocytes of male rats subchronically exposed to environmentally relevant doses via drinking water. The selection of these metals, as determined by literature survey of groundwater contamination in India, was primarily based on the frequency of their occurrence and contamination level above World Health Organization maximum permissible limit (MPL) in drinking water. Male albino Wistar rats were exposed to the metal mixture at 0, 1, 10, and 100 times the mode concentrations (the most frequently occurring concentration) of the individual metals in drinking water for 90 days. In addition, one group of rats was also exposed to the mixture at a concentration equal to the MPL of individual components. The oxidative stress in erythrocytes was evaluated by assessing the magnitude of malondialdehyde production and reduced glutathione (GSH) content and the activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), and glutathione reductase (GR) after 30, 60, and 90 days of exposure. MPL and 1x dose levels did not cause any changes. The mixture at 10x and 100x doses caused dose- and time-dependent effects. After 30 days, the 10x dose did not cause any changes except increase in SOD activity. The 100x dose increased the activities of SOD, catalase and GR and the GSH level, but caused no alterations in lipid peroxidation (LPO) and GPx activity. After 60 days, the 10x dose did not cause any changes. The 100x dose increased LPO and decreased all the antioxidant parameters, except GSH. After 90 days, both 10x and 100x levels elevated LPO. The 10x dose decreased GSH level and activities of SOD and catalase, but not of GPx and GR, whereas the 100x dose decreased all the antioxidative systems. Overall, the present study demonstrates that the subchronic exposure of male rats to the mixture of metals via drinking water results in induction of oxidative stress and concomitant reduction in antioxidative defense system in erythrocytes at 10 and 100 times the mode concentrations of the individual metals in contaminated groundwater.

Cyclosporine A induced changes to plasma and erythrocyte antioxidant defences

Organ transplant recipients develop pronounced cardiovascular disease, and decreased antioxidant capacity in plasma and erythrocytes is associated with the pathogenesis of this disease. These experiments tested the hypothesis that the immunosuppressant cyclosporine A (CsA) alters erythrocyte redox balance and reduces plasma antioxidant capacity. Female Sprague-Dawley rats were randomly assigned to a control or CsA treated group. Treatment animals received 25 mg/kg/day of CsA via intraperitoneal injection for 18 days. Control rats were injected with the same volume of the vehicle. Three hours after the final CsA injection, rats were exsanguinated and plasma analysed for total antioxidant status (TAS), alpha-tocopherol, malondialdehyde (MDA), and creatinine. Erythrocytes were analysed for superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and glucose-6-phosphate dehydrogenase (G6PD) activities, alpha-tocopherol, and MDA. CsA administration resulted in a significant (P < 0.05) decrease in plasma TAS and significant increases (P < 0.05) in plasma creatinine and MDA. Erythrocyte CAT was significantly (P < 0.05) increased in CsA treated rats compared to controls. There were no significant differences (P > 0.05) in erythrocyte SOD, GPX, G6PD, alpha-tocopherol or MDA between groups. In summary, CsA alters erythrocyte antioxidant defence and decreases plasma total antioxidant capacity.

Antioxidant supplementation enhances erythrocyte antioxidant status and attenuates cyclosporine-induced vascular dysfunction

The aim of this study was to determine the effects of dietary antioxidant supplementation with alpha-tocopherol and alpha-lipoic acid on cyclosporine-induced alterations to erythrocyte and plasma redox balance, and cyclosporine-induced endothelial and smooth muscle dysfunction. Rats were randomly assigned to either control, antioxidant, cyclosporine or cyclosporine + antioxidant treatments. Cyclosporine A was administered for 10 days after an 8-week feeding period. Plasma was analyzed for alpha-tocopherol, total antioxidant capacity, malondialdehyde and creatinine. Erythrocytes were analyzed for glutathione, methemoglobin, superoxide dismutase, catalase, glutathione peroxidase, glucose-6-phosphate dehydrogenase, alpha-tocopherol and malondialdehye. Vascular endothelial and smooth muscle function was determined in vitro. Antioxidant supplementation resulted in significant increases in erythrocyte alpha-tocopherol concentration and glutathione peroxidase activity in both of the antioxidant-supplemented groups. Cyclosporine administration caused significant decreases in glutathione concentration, methemoglobin concentration and superoxide dismutase activity. Antioxidant supplementation attenuated the cyclosporine-induced decrease in superoxide dismutase activity. Cyclosporine therapy impaired both endothelium-independent and -dependent relaxation of the thoracic aorta, and this was attenuated by antioxidant supplementation. In summary, dietary supplementation with alpha-tocopherol and alpha-lipoic acid attenuated the cyclosporine-induced decrease in erythrocyte superoxide dismutase activity and attenuated cyclosporine-induced vascular dysfunction.

Effect of vitamins C and E on oxidative processes in human erythrocytes

The oxidative action of 1 mmol l(-1) phenylhydrazine hydrochloride (PH) was studied on human erythrocytes treated with the antioxidants vitamin C (vit. C) and vitamin E (vit. E). The erythrocytes were resuspended in PBS to obtain 35% cell packed volume, and then submitted to the oxidative action of PH for 20 min, with or without previous incubation for 60 min with vit. C or vit. E. Heinz bodies and methemoglobin formation by PH were inhibited in the presence of vit. C. At the concentration of 90 mmol l(-1), vit. C, not only seemed to lose its antioxidant effect, but it also promoted an increase in methemoglobin formation. Vit. C (0.5-80 mmol l(-1)) did not protect against GSH depletion by PH. Vit. C alone produced insignificant hemolysis, but, in the presence of PH, the hemolysis indices were more accentuated. Heinz body formation by PH was inhibited in the presence of vit. E. Formation of methemoglobin induced by PH was decreased by vit. E (0.1-2 mmol l(-1)), although vit. E (3-80 mmol l(-1)) did not lower the concentration of methemoglobin and did not lead to the recovery of the GSH depleted by PH. The results obtained suggest that vit. C and vit. E contribute to the decrease in oxidative stress caused by PH.

Cyclosporine A-Induced Changes to Erythrocyte Redox Balance is Time Course-Dependent

Cyclosporine A-treated transplant recipients develop pronounced cardiovascular disease and have increased oxidative stress and altered antioxidant capacity in erythrocytes and plasma. These experiments investigated the time-course of cyclosporine A-induced changes to redox balance in plasma and erythrocytes. Rats were randomly assigned to either a control or cyclosporine A-treated group. Treatment animals received 25 mg/kg of cyclosporine A via intraperitoneal injection for either 7 days or a single dose. Control rats were injected with the same volume of the vehicle. Three hours after the final injections, plasma was analysed for total antioxidant status, alpha-tocopherol, malondialdehyde, and creatinine. Erythrocytes were analysed for reduced glutathione (GSH), alpha-tocopherol, methaemoglobin, malondialdehyde, and the activities of superoxide dismutase, catalase, GSH peroxidase, and glucose-6-phosphate dehydrogenase (G6PD). Cyclosporine A administration for 7 days resulted in a significant increase (P<0.05) in plasma malondialdehyde, methaemoglobin, and superoxide dismutase and catalase activities. There was a significant decrease (P<0.05) in erythrocyte GSH concentration and G6PD activity in cyclosporine A animals. There were no significant differences (P>0.05) between groups following a single dose of cyclosporine A in any of the measures. In summary, cyclosporine A alters erythrocyte redox balance after 7 days administration, but not after a single dose.

Oxidative stress during the chronic phase after stroke

Stroke is a complex disease originating and developing on the background of genetic predisposition and interaction between different risk factors that chronically damage blood vessels. The search for an effective treatment of stroke patients is the main priority of basic and clinical sciences. The chronic phase of stroke provides possibilities for therapy directed toward stimulation of recovery processes as well as prophylaxis, which reduces the probability of subsequent cerebrovascular events. Oxidative stress is a potential contributor to the pathophysiological consequences of stroke. The aim of the present review is to summarize the current knowledge of the role of oxidative stress during the chronic phase after stroke and its contribution to the initiation of subsequent stroke. The relationship among inflammation, hemostatic abnormalities, and platelet activation in chronic stroke patients is discussed in the context of ongoing free radical processes and oxidative damage. Free radical-mediated effects of increased plasma level of homocysteine and its possible contribution to the processes leading to recurrent stroke are discussed as well. The status of the antioxidant defense system and the degree of oxidative damage in the circulation of stroke survivors are examined. The results are interpreted in view of the effects of the vascular risk factors for stroke that include additional activation of inflammatory and free radical mechanisms. Also, the possibilities for combined therapy including antioxidants in the acute and convalescent stages of stroke are considered. Future investigations are expected to elucidate the role of free radical processes in the chronic phase after stroke and to evaluate the prophylactic and therapeutic potential of anti-radical agents.

Decreased membrane fluidity and altered susceptibility to peroxidation and lipid composition in overweight and obese female erythrocytes

The increased generation of reactive oxygen species that occurs in the condition of obesity may be responsible for oxidative injury to erythrocyte membranes, which could lead to a decrease in tissue oxygenation. Therefore, we have looked into the effects of obesity on both indexes of oxidative damage and physical-chemical properties of erythrocyte membranes in 50 overweight or obese [25 < body mass index (BMI) < 33], normotensive, nondiabetic women and 50 age-matched lean healthy women (BMI < 25). In the obese group compared with the lean group, we found that a) the onset of free radical-induced erythrocyte hemolysis and the ratio between reduced and oxidized glutathione were reduced, whereas the rate of free radical-induced damage increased; b) the n-3 fatty acid and the phospholipid contents decreased; c) the ratio between cholesterol and phospholipids increased; and d) the membrane fluidity decreased. These findings suggest an impairment of erythrocyte membrane physical-chemical properties in overweight and obese people as a consequence of oxidative injury that might be part of a pathogenetic mechanism responsible for obesity-related pathologies such as atherosclerosis and hypertension.

Caffeic Acid Phenethyl Ester Improves Oxidative Erythrocyte Damage in a Rat Model of Thermal Injury

Oxygen-derived free radicals impair cell membrane functions and induce circulatory disturbances, and free radicals, such as superoxide anion, hydrogen peroxide, hydroxyl radicals, and peroxynitrite, have been suggested to play important roles in the pathogenesis of major burn injuries. The present study investigated the effects of thermal injury on erythrocyte lipid peroxidation and antioxidant status and investigated the effects of caffeic acid phenethyl ester (CAPE), a new antioxidant and anti-inflammatory agent, in rats subjected to thermal injury. Burn injury caused a remarkable increase in erythrocyte lipid peroxidation, levels of nitric oxide (NO), and activities of antioxidant enzymes and xanthine oxidase (XO). The treatment with CAPE decreased both activity of burn-induced XO activity and levels of NO in the erythrocytes. In conclusion, CAPE treatment resulted in decreased erythrocyte lipid peroxidation in thermal injury and helped to prevent oxidative damage by decreasing activity of XO and levels of NO.

Inhibitory effects of cocoa flavanols and procyanidin oligomers on free radical-induced erythrocyte hemolysis

Excessive peroxidation of biomembranes is thought to contribute to the initiation and progression of numerous degenerative diseases. The present study examined the inhibitory effects of a cocoa extract, individual cocoa flavanols (-)-epicatechin and (+)-catechin, and procyanidin oligomers (dimer to decamer) isolated from cocoa on rat erythrocyte hemolysis. In vitro, the flavanols and the procyanidin oligomers exhibited dose-dependent protection against 2,2'-azo-bis (2-amidinopropane) dihydrochloride (AAPH)-induced erythrocyte hemolysis between concentrations of 2.5 and 40 microM. Dimer, trimer, and tetramer showed the strongest inhibitory effects at 10 microM, 59.4%, 66.2%, 70.9%; 20 microM, 84.1%, 87.6%, 81.0%; and 40 microM, 90.2%, 88.9%, 78.6%, respectively. In a subsequent experiment, male Sprague-Dawley rats (approximately 200 g; n = 5-6) were given a 100-mg intragastric dose of a cocoa extract. Blood was collected over a 4-hr time period. Epicatechin and catechin, and the dimers (-)-epicatechin-(4beta>8)-epicatechin (Dimer B2) and (-)-epicatechin-(4beta>6)-epicatechin (Dimer B5) were detected in the plasma with concentrations of 6.4 microM, and 217.6, 248.2, and 55.4 nM, respectively. Plasma antioxidant capacity (as measured by the total antioxidant potential [TRAP] assay) was elevated (P < 0.05) between 30 and 240 min following the cocoa extract feeding. Erythrocytes obtained from the cocoa extract-fed animals showed an enhanced resistance to hemolysis (P < 0.05). This enhanced resistance was also observed when erythrocytes from animals fed the cocoa extract were mixed with plasma obtained from animals given water only. Conversely, plasma obtained from rats given the cocoa extract improved the resistance of erythrocytes obtained from rats given water only. These results show cocoa flavanols and procyanidins can provide membrane protective effects.

Oxygenated carotenoid lutein and progression of early atherosclerosis: the Los Angeles atherosclerosis study

BACKGROUND

Carotenoids are hypothesized to explain some of the protective effects of fruit and vegetable intake on risk of cardiovascular disease. The present study assessed the protective effects of the oxygenated carotenoid lutein against early atherosclerosis.

METHODS AND RESULTS

EPIDEMIOLOGY

Progression of intima-media thickness (IMT) of the common carotid arteries over 18 months was determined ultrasonographically and was related to plasma lutein among a randomly sampled cohort of utility employees age 40 to 60 years (n=480). Coculture: The impact of lutein on monocyte response to artery wall cell modification of LDL was assessed in vitro by quantification of monocyte migration in a coculture model of human intima. Mouse models: The impact of lutein supplementation on atherosclerotic lesion formation was assessed in vivo by assigning apoE-null mice to chow or chow plus lutein (0.2% by weight) and LDL receptor-null mice to Western diet or Western diet plus lutein. IMT progression declined with increasing quintile of plasma lutein (P for trend=0.007, age-adjusted; P=0.0007, multivariate). Covariate-adjusted IMT progression (mean+/-SEM) was 0.021+/-0.005 mm in the lowest quintile of plasma lutein, whereas progression was blocked in the highest quintile (0.004+/-0.005 mm; P=0.01). In the coculture, pretreatment of cells with lutein inhibited LDL-induced migration in a dose-dependent manner (P<0.05). Finally, in the mouse models, lutein supplementation reduced lesion size 44% in apoE-null mice (P=0.009) and 43% in LDL receptor-null mice (P=0.02).

CONCLUSIONS

These epidemiological, in vitro, and mouse model findings support the hypothesis that increased dietary intake of lutein is protective against the development of early atherosclerosis.

Metabolism of lipid peroxidation product, 4-hydroxynonenal (HNE) in rat erythrocytes: role of aldose reductase

Lipid peroxidation represents a significant source of erythrocyte dysfunction and aging. Because the toxicity of lipid peroxidation appears to be in part due to aldehydic end products, we examined, in rat erythrocytes, the metabolism of 4-hydroxy-trans-2-nonenal (HNE), one of the most abundant and toxic lipid-derived aldehydes. Packed erythrocytes, 0.1 ml, completely metabolized 20 nmoles of HNE in 20 min. The glutathione conjugate of HNE and 4-hydroxynonanoic acid (HNA) represented 70 and 25% of the total metabolism, respectively. Approximately 70% of the metabolites were extruded to the medium. Upon electrospray ionization mass spectrometry, the glutathione conjugate resolved into two distinct species corresponding to glutathionyl HNE (GS-HNE) and glutathionyl 1,4-dihydroxynonene (GS-DHN). The concentration of GS-DHN formed was twice that of GS-HNE. Inhibition of aldose reductase by sorbinil and tolrestat led to a selective decrease in the formation of GS-DHN, although the extent of HNE glutathiolation was unaffected. Inhibitors of aldehyde or alcohol dehydrogenase, i.e., cyanamide and 4-methyl pyrazole, had no effect on the formation of HNA and GS-DHN, indicating that these enzymes are not significant participants in the erythrocyte HNE metabolism. Thus, oxidation to HNA, conjugation with glutathione, and further reduction of the conjugate by aldose reductase appear to be the major pathways of HNE metabolism in erythrocytes. These pathways may be critical determinants of erythrocyte toxicity due to lipid peroxidation-derived aldehydes.

Lipid peroxidation, antioxidant enzymes and glutathione levels in human erythrocytes exposed to colloidal iron hydroxide in vitro

The free form of the iron ion is one of the strongest oxidizing agents in the cellular environment. The effect of iron at different concentrations (0, 1, 5, 10, 50, and 100 microM Fe3+) on the normal human red blood cell (RBC) antioxidant system was evaluated in vitro by measuring total (GSH) and oxidized (GSSG) glutathione levels, and superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px) and reductase (GSH-Rd) activities. Membrane lipid peroxidation was assessed by measuring thiobarbituric acid reactive substance (TBARS). The RBC were incubated with colloidal iron hydroxide and phosphate-buffered saline, pH 7.45, at 37 degrees C, for 60 min. For each assay, the results for the control group were: a) GSH = 3.52 +/- 0.27 microM/g Hb; b) GSSG = 0.17 +/- 0.03 microM/g Hb; c) GSH-Px = 19.60 +/- 1.96 IU/g Hb; d) GSH-Rd = 3.13 +/- 0.17 IU/g Hb; e) catalase = 394.9 +/- 22.8 IU/g Hb; f) SOD = 5981 +/- 375 IU/g Hb. The addition of 1 to 100 microM Fe3+ had no effect on the parameters analyzed. No change in TBARS levels was detected at any of the iron concentrations studied. Oxidative stress, measured by GSH kinetics over time, occurs when the RBC are incubated with colloidal iron hydroxide at concentrations higher than 10 microM of Fe3+. Overall, these results show that the intact human RBC is prone to oxidative stress when exposed to Fe3+ and that the RBC has a potent antioxidant system that can minimize the potential damage caused by acute exposure to a colloidal iron hydroxide in vitro.

Suppressive effect of FC-43 perfluorocarbon emulsion on enhanced oxidative haemolysis in the early postburn phase

The effect of FC-43 perfluorocarbon emulsion on resistance of red blood cells to oxidative haemolysis and lipid peroxidation was evaluated in rats (full skin thickness burns over 15-20 per cent of total body surface area). The content of erythrocyte malonyl dialdehyde (MDA), alpha-tocopherol, glutathione (reduced and oxidized forms) and oxidative haemolysis were measured at 24 h after burn injury. Four groups were employed: (1) non-burned non-treated, (2) non-burned but treated with FC-43 perfluorocarbon emulsion (5 ml/kg bodymass i.v.), (3) burned non-treated, (4) burned but treated with FC-43 emulsion (5 ml/kg bodymass i.v.). The non-burned groups showed no significant differences in oxidative haemolysis, MDA levels or alpha-tocopherol and glutathione content. In the burned non-treated group the oxidative haemolysis elevated by 190 per cent (P < 0.001), MDA content increased by 43 per cent (P < 0.05), whereas the concentration of alpha-tocopherol and reduced glutathione (GSH) decreased significantly by 36 per cent and 18 per cent, respectively. The results showed reduction in the postburn MDA content by 30 per cent (P < 0.02) and oxidative haemolysis by 44 per cent (P < 0.001) after treatment with FC-43 emulsion. FC-43 emulsion did not change significantly the levels of alpha-tocopherol and GSH in erythrocytes after thermal injury. It is concluded that FC-43 perfluorocarbon emulsion administration suppresses early postburn lipid peroxidation and increases the resistance of red blood cells to oxidative haemolysis.

Inhibitory effects of jasmine green tea epicatechin isomers on free radical-induced lysis of red blood cells

Jasmine green tea is an excellent source of natural polyphenol antioxidants including mainly (-) epicatechin (EC), (-) epicatechin gallate (ECG), (-) epigallocatechin (EGC) and (-) epigallocatechin gallate (EGCG). The present study was to test our hypothesis that ingestion of jasmine tea would protect red blood cell (RBC) membrane from free radical-induced oxidation if jasmine tea epicatechin isomers could be absorbed and circulated in blood. When incubated with RBC suspension, all four epicatechin isomers purified from jasmine tea exhibited a strong protection for RBC membrane to hemolysis induced by 2,2'-azo-bis(2-amidinopropane) dihydrochloride (AAPH), an azo free radical initiator. The inhibitory effect was dose-dependent at the concentrations of 2.5 microM to 40 microM. The fatty acid analysis revealed that all four epicatechin isomers significantly prevented loss of arachidonic acid (20:4n-6) and docosahexaenoic acid (22:6n-3) in RBC incubated under the same conditions. Although the in vitro antioxidative activity of EGCG and ECG was more effective than EGC and EC, the latter two isomers were more important in vivo in scavenging free radicals. This was because only EGC and EC instead of EGCG and ECG were circulating in blood stream after a gavage-dose of 100 mg jasmine tea GTP mixture. In fact, ingestion of jasmine tea GTP extracts was associated with a significant decrease in susceptibility of RBC to hemolysis in rats.

Increased antioxidant capacity, suppression of free radical damage and erythrocyte aggrerability after combined application of alpha-tocopherol and FC-43 perfluorocarbon emulsion in early postburn period in rats

Certain rheological disorders such as enhanced aggregation and reduced deformability of erythrocytes are closely associated with microcirculatory disturbances, decreased tissue oxygen supply and represent a major problem in severely burnt patients [1-4]. Vitamin E (alpha-tocopherol) and vitamin A (retinol) exert an important plasma antioxidant properties against free radical-induced damage [11,12]. They possess chain-breaking properties and act as synergists [13]. Plasma antioxidant capacity may be decreased in severely burnt patients as a result of the enhanced consumption and inadequate restoration of antioxidants in the conditions of activated peroxidative process [14]. Treatment with alpha-tocopherol suppresses lipid peroxidation in blood and therefore improves erythrocyte rheology [15]. Perfluorocarbon emulsions improve microcirculation and rheological blood properties [16-18] and preserve the structure and function of endothelial cells [19]. The very small particle size, low viscosity and high oxygen carrying capacity ensure their penetration into the microvasculature even under conditions of ischemia and acidosis [20, 21]. Perfluorocarbons have been reported to inhibit leukocyte activation and superoxide radical production [22]. The aim of the present study was to examine the antioxidant capacity, free radical mediated damage and erythrocyte aggregation in plasma of rats with thermal skin injury in the early postburn period and to evaluate the effect of treatment with alpha-tocopherol and FC-43 perfluorocarbon emulsion alone and in combination. We might conclude that thermal skin injury in rats reduces the antioxidant capacity, enhances free radical mediated damage and erythrocyte aggregation on the third hour after injury. The combined application of alpha-tocopherol and FC-43 perfluorocarbon emulsion immediately after thermal skin injury in rats increases plasma antioxidant capacity, decreases free radical mediated damage of erythrocytes and suppresses their aggregation on the third hour after the injury.

N-allylsecoboldine as a novel antioxidant against peroxidative damage

N-Allylsecoboldine was evaluated for antioxidant properties by studying its ability to react with relevant reactive oxygen species, and its protective effect on human erythrocytes under oxidative stress. Using brain homogenates, we found that N-allylsecoboldine dose dependently inhibited lipid peroxidation (IC50 = 4.80 +/- 0.16 microM) and markedly scavenged stable nitrogen-centered radicals. N-Allylsecoboldine was a very efficient scavenger for inhibiting peroxyl radical-mediated destruction of B-phycoerythrin, with a stoichiometry factor of 4.40 +/- 0.59. It also trapped the hydroxyl radicals with a second-order rate constant of 6.92 +/- 0.86 x 10(9) M-1 S-1. Additionally, human erythrocyte oxidative hemolysis induced by aqueous peroxyl radical or hydrogen peroxide was suppressed by N-allylsecoboldine. It not only attenuated the extent of lipid peroxidation but also decreased the formation of the high-molecular weight proteins and degradation of the band 6 protein in radical-treated erythrocytes. It also inhibited the shortening of Russell's viper venom-clotting time mediated by prelytic radical-treated erythrocytes. In the presence of exogenous oxidative stress, hemolysis and lipid peroxidation were significantly enhanced in beta-thalassemic erythrocytes, as compared to the normal control. These elevated detrimental effects could be prevented by N-allylsecoboldine. It is concluded that N-allylsecoboldine may act as an effective antioxidant and protect cells against oxidative damage.

Inhibition by activated neutrophils of the Ca2+ pump ATPase of intact red blood cells

Human neutrophils, activated by phorbol myristate acetate in the presence of intact red blood cells (RBCs), caused inhibition of the Ca2+ pump ATPase of the RBCs and fragmentation of the enzyme as well as other membrane proteins. Inhibition of the Ca2+ pump ATPase of intact RBCs was directly related to the neutrophil concentration and the time of incubation. Ca2+ pump ATPase activity was partially protected by the addition of exogenous glutathione-glutathione peroxidase, but not by superoxide dismutase. The addition of sodium azide, a potent inhibitor of endogenous RBC catalase, enhanced inhibition of the Ca2+ pump ATPase of intact RBCs. Examination by SDS-polyacrylamide gel electrophoresis of membrane proteins isolated from RBCs preincubated with activated neutrophils showed gross changes in banding patterns as compared to controls. Thus, a significant amount of methemoglobin appeared to be associated with the membrane proteins, and, in general, protein bands appeared to be more diffuse and less defined than proteins in control lanes. In addition, there was an increase in the low molecular weight protein bands. Using a monoclonal antibody to the Ca2+ pump ATPase, it was shown that the 140 kDa band representing the Ca2+ pump ATPase decreased, with concomitant appearance of two low molecular weight bands running at 8.2 and 6.8 kDa in the membrane proteins from RBCs preincubated with activated neutrophils. The data are interpreted to suggest that inhibition of the Ca2+ pump ATPase in intact RBCs under these conditions occurred as a result of: neutrophil-derived superoxide, dismutation of superoxide, to H2O2, diffusion of H2O2 into RBCs, a Fenton type reaction between oxyhemoglobin, and H2O2 producing hydroxyl radical and/or a ferryl radical capable of promoting protein fragmentation of RBC membrane proteins, including the plasma membrane Ca2+ pump ATPase.

Homogentisic acid and structurally related compounds as intermediates in plasma soluble melanin formation and in tissue toxicities

Homogentisic acid (HGA) spontaneously starts to undergo oxidation and polymerization soon after the beginning of incubation in human blood or plasma at 37 degrees C, and forms plasma soluble melanins (PSM). Haemolysis accompanies this process in blood. The addition of equimolar quantities of antioxidants delays this oxidation significantly (isoascorbic acid by 2:30-4:00 h; glutathione by 3:20-4:05 h; D-penicillamine by 5:00-5:45 h). HGA is a phenylalanine and tyrosine metabolite, related structurally to the catecholamines and other precursors of melanins. HGA is normally metabolized by the enzyme homogentisic acid oxidase. When this enzyme is genetically missing, part of HGA is excreted in the urine, another part polymerizes darkens many tissues (ochronosis), and produces widespread degenerative changes in cartilage and other connective tissues, joints, blood vessels, heart valves, kidneys and in other tissues. Collectively this disorder is known as alcaptonuria, for which no satisfactory treatment is known. The causes of both alcaptonuric arthritis and rheumatoid arthritis are thought to involve increased oxidative stress. Inflammation of joints and connective tissue damage are involved in both diseases. Oxygen radicals are suspected to cause inflammation and cellular damage. Hydroxyl radicals degrade hyaluronic acid (the viscous synovial fluid of joints). High levels of products of free radical reactions, with fluorescence excitation (ex) and emission (em) maxima in the wavelength ranges of those of PSM (ex 320-400 and em 400-470) were reported in the blood sera and synovial fluids of patients with rheumatoid arthritis.(ABSTRACT TRUNCATED AT 250 WORDS)

Melanin quantitation from human erythrocytes; interference by haeme derivatives

Precipitates were obtained by 6 N HCl hydrolysis of human erythrocytes and subsequent extractions with ethanol-ether 1:1 and with tetrahydrofuran. The mean quantity of these precipitates (n = 16) was 16.60 +/- 1.60 (standard deviation) mg/ml, (15.09 +/- 1.45 mg/g) and from saline washed erythrocyte samples (n = 8) 16.65 +/- 0.73 mg/ml, (15.14 +/- 0.67 mg/g). A large part of these precipitates (about 74%) is associated with haemoglobin (in average 12.34 mg/ml). Melanins account for the difference (16.60-12.34) = 4.26 mg/ml, approximately 8.7% of haemoglobin-free erythrocyte solids. Precipitates from red cells, and from haemoglobin produced similar UV-VIS and IR spectra. The precipitates from haemoglobin are mainly derivatives of haeme (about 97%); the remaining approximately 3% are melanins from globin. The total melanins are about 1.3% of haeme-free solids of erythrocytes. Precipitation from the erythrocytes with 6 N HCl was also achieved in practically complete argon atmosphere, and similar quantities were obtained as those in air with the same UV-VIS and IR spectra. Since granules or solid particles are not found in the cytoplasm of normal human erythrocytes, we conclude that soluble melanins are present. Small amounts of melanins can be present in the membranes as well, since the precursors of melanins: norepinephrine, epinephrine are present in these membranes.