Blood antioxidant nutrients in riparian villagers of the Brazilian Amazon: its associations with wet/dry seasons and modulation by sociodemographic determinants / Antioxidantes sanguíneos provenientes da dieta em ribeirinhos da Amazônia Brasileira: suas relações com sazonalidade e determinantes sociodemográficos

Abstract This study associates blood antioxidants like copper (Cu), manganese (Mn), selenium (Se), zinc (Zn), β-carotene, lycopene and vitamins (A and E) to sociodemographic features and seasonality in communities from the Tapajós River region, Brazilian Amazon. We observed increased Mn, Se and Zn levels compared to the average Brazilian population, whereas this is only the case for β-carotene in the rainy season. Lycopene levels fall within the reference range, although lower than those found in other Brazilian regions. Cu, Se, Zn, β-carotene, lycopene and vitamin E levels vary among seasons. β-carotene, Mn and Se vary among communities. Se and Zn vary with smoking habits and sex, respectively. In addition, β-carotene and vitamins (A and E) are altered by alcohol consumption. Villagers who both farmed and fished present higher Cu and lower β-carotene levels than participants with a single occupation. Vitamin E levels depend upon the individual state of origin. These data provide important baseline information for antioxidant status in this Amazonian riparian population.

Resumo O presente estudo reporta as concentrações plasmáticas dos antioxidantes cobre (Cu), manganês (Mn), selênio (Se), zinco (Zn), β-caroteno, licopeno e vitaminas (A e E) em moradores da região do Rio Tapajós, Pará, Amazônia, e as relaciona com características sociodemográficas e sazonalidade (seca e cheia). Os teores de Mn, Se e Zn foram acima dos valores de referência (VR) e daqueles achados em outras regiões do Brasil, enquanto para o β-caroteno tal achado ocorreu apenas na estação da cheia. Os valores de licopeno foram dentro dos VR, porém abaixo dos achados em outras regiões do Brasil. Os níveis de Cu, Se, Zn, β-caroteno, licopeno e vitamina E variaram entre as estações. Variação intercomunitária foi constatada para β-caroteno, Mn e Se. Os teores de Se e Zn foram alterados, respectivamente, por tabagismo e sexo. Os níveis de β-caroteno e vitaminas (A e E) alteraram-se com o consumo de bebida alcoólica. A vitamina E foi dependente do estado de origem. Participantes que desempenhavam ambas as profissões de agricultor e pescador apresentavam teores de Cu superiores e de β-caroteno inferiores comparativamente àqueles que desempenhavam uma única profissão. Esses dados fornecem informações sobre os teores de antioxidantes para essa população amazônica.

Effects of genetic polymorphisms on antioxidant status and concentrations of the metals in the blood of riverside Amazonian communities co-exposed to Hg and Pb.

There have been reports of genetic effects affecting the metabolism of Hg and Pb individually, and thus modulating their toxicities. However, there is still a knowledge gap with respect to how genetics may influence the toxicities of these toxic metals during a co-exposure scenario. This present study is therefore aimed at investigating the effects of polymorphisms in genes (GSTM1, GSTT1, GSTP1, GCLM, GCLC, GPx1, ALAD, VDR and MDR1) that have been implicated in Hg and Pb metabolisms affects the kinetics of these metals, as well as various blood antioxidant status parameters: MDA and GSH, and the activities of CAT, GPx and ALAD among populations that have been co-exposed to both Hg and Pb. Study subjects (207 men; 188 women) were from an Amazonian population in Brazil, exposed to Hg and Pb from diet. The blood levels of Hg and Pb were determined by ICP-MS while genotyping were performed by PCR assays. The median values of Hg and Pb in blood were 39.8µg/L and 11.0µg/dL, respectively. GSTM1, ALAD and VDR polymorphisms influenced Hg in blood (ß=0.17; 0.37 and 0.17; respectively, p<0.050) while variations on GCLM, GSTT1 and MDR1 (TT) modulated the concentrations of Pb among the subjects (ß=-0.14; 0.13 and -0.22; re-spectively, p<0.050). GSTT1 and GCLM polymorphisms also are associated to changes of MDA concentrations. Persons with null GSTM1 genotype had higher activity of the antioxidant enzyme CAT than carries of the allele. Individuals with deletion of both GSTM1 and GSTT1 had a decreased expression of GPx compared to those that expressed at least, one of the enzymes. ALAD 1/2 subjects had lower ALAD activity than individuals with the non-variant genotype. Our findings give further support that polymorphisms related to Hg and Pb metabolism may modulate Hg and Pb body burden and, consequently metals-induced toxicity.

Exogenous and endogenous antioxidants attenuate the lipid peroxidation in workers occupationally exposed to paints.

Occupational exposure to organic solvents present in paints is responsible for an increased production of reactive species, thus enabling the development of several diseases. Besides, both exo- and endogenous antioxidant defense systems are necessary to avoid oxidative tissue damage. This study investigated possible protective effects of the exo- and endogenous antioxidants on oxidative damage in painters occupationally exposed to organic solvents (n = 42) and controls (n = 28). Retinol, lycopene and ß-carotene were significantly lower in the exposed group. Despite the fact that blood toluene was below the biological exposure limits, malondialdehyde levels and antioxidant enzyme activities were increased, whereas reduced glutathione levels were decreased in painters, compared to nonexposed subjects. Moreover, multivariate regression models showed that reduced glutathione and carotenoids (mainly ß-carotene) have the major influence on lipid peroxidation (LPO). The present work suggests that the exogenous antioxidants, such as carotenoids, could protect occupationally exposed subjects to xenobiotics from LPO.

Polymorphisms in glutathione-related genes modify mercury concentrations and antioxidant status in subjects environmentally exposed to methylmercury.

Methylmercury (MeHg) toxicity may vary widely despite similar levels of exposure. This is hypothetically related to genetic differences in enzymes metabolizing MeHg. MeHg causes oxidative stress in experimental models but little is known about its effects on humans. The aims of the present study was to evaluate the effects of polymorphisms in glutathione (GSH)-related genes (GSTM1, GSTT1, GSTP1 and GCLM) on Hg concentrations in blood and hair, as well as MeHg-related effects on catalase (CAT) and glutathione-peroxidase (GPx) activity and GSH concentrations. Study subjects were from an Amazonian population in Brazil chronically exposed to MeHg from fish. Hg in blood and hair were determined by ICP-MS, CAT, GPx and GSH were determined by spectrophotometry, and multiplex PCR (GSTM1 and GSTT1) and TaqMan assays (GSTP1 and GCLM) were used for genotyping. Mean Hg concentrations in blood and hair were 48±36 µg/L and 14±10 µg/g. Persons with the GCLM-588 TT genotype had lower blood and hair Hg than did C-allele carriers (linear regression for Hg in blood ß=-0.32, p=0.017; and hair ß=-0.33; p=0.0090; adjusted for fish intake, age and gender). GSTM1*0 homozygous had higher blood (ß=0.20; p=0.017) and hair Hg (hair ß=0.20; p=0.013). Exposure to MeHg altered antioxidant status (CAT: ß=-0.086; GSH: ß=-0.12; GPx: ß=-0.16; all p<0.010; adjusted for gender, age and smoking). Persons with GSTM1*0 had higher CAT activity in the blood than those with GSTM1. Our data thus indicate that some GSH-related polymorphisms, such as GSTM1 and GCLM may modify MeHg metabolism and Hg-related antioxidant effects.

Evaluation of lipid damage related to pathological and physiological conditions.

Several diseases and xenobiotics are known to generate reactive species that may trigger oxidative stress when not properly scavenged by the antioxidant defenses and result in tissue damage. We investigated lipid peroxidation (LPO) as a possible mechanism for tissue damage in some pathologies, in the normal aging process, and in subjects exposed to organic solvents. Plasmatic malondialdehyde (MDA) was quantified by high-performance liquid chromatography with visible wavelength detection in 239 subjects and divided into the following: acute myocardium infarction (AMI), diabetes without complications (D) and hemodialysis (HD) patients; into healthy children, adults, and elderly, all nonexposed to xenobiotics; and into painters occupationally exposed to organic solvents (P). Troponin, glycated hemoglobin, and transminases [aspartate aminotransferase (AST) and alanine aminotransferase] were analyzed. An increase in LPO was observed in AMI, D, HD, and P groups, when compared to healthy adults. No correlation between MDA and age was found. Further, we found positive correlations between MDA versus troponin (r = 0.47), MDA versus HbA1c (r = 0.56), and MDA versus AST (r = 0.41) in AMI, diabetics, and painters, respectively. This work has demonstrated increased lipid and protein damages in myocardium and blood, along with an alteration of hepatic transaminase activities and induction of LPO, suggesting that MDA levels are important to evaluate the extent of tissue alterations and development of acute and chronic conditions.

Evaluation of glutathione S-transferase GSTM1 and GSTT1 polymorphisms and methylmercury metabolism in an exposed Amazon population.

Over the last decades, the presence of methylmercury (MeHg) in the Amazon region of Brazil and its adverse human health effects have given rise to much concern. The biotransformation of MeHg occurs mainly through glutathione (GSH) in the bile mediated by conjugation with glutathione S-transferases (GST). Epidemiological evidence has shown that genetic polymorphisms may affect the metabolism of MeHg. The aim of this study was to evaluate the association between GST polymorphisms, GSH, and Hg levels in blood (B-Hg) and in hair (H-Hg) of an Amazon population chronically exposed to the metal through fish consumption. Blood and hair samples were collected from 144 volunteers (71 men, 73 women). B-Hg and H-Hg levels were determined by inductively coupled plasma-mass spectrometry, and GSH levels were evaluated by a spectrophotometric method. GSTM1 and T1 genotyping evaluation were carried out by multiplex polymerase chain reaction (PCR). Mean levels of B-Hg and H-Hg were 37.7 ± 24.5 µg/L and 10.4 ± 7.4 µg/g, respectively; GSH concentrations ranged from 0.52 to 2.89 µM/ml of total blood. Distributions for GSTM1/T1, GSTM1/GSTT1*0, GSTM1*0/T1, and GSTM1*0/GSTT1*0 genotypes were 35.4, 22.2, 25.0, and 17.4%, respectively. GSTT1 genotype carriers presented lower levels of B-Hg and H-Hg when compared to other genotypes carriers. In addition, GSTM1*0/GSTT1*0 individuals presented higher Hg levels in blood and hair than subjects presenting any other genotypes. There appeared to be no evidence of an effect of polymorphisms on GSH levels. Therefore, our data suggest that GST polymorphisms may be associated with MeHg detoxification.

Evaluation of genotoxicity and oxidative damage in painters exposed to low levels of toluene.

Toluene is an organic solvent used in numerous processes and products, including industrial paints. Toluene neurotoxicity and reproductive toxicity are well recognized; however, its genotoxicity is still under discussion, and toluene is not classified as a carcinogenic solvent. Using the comet assay and the micronucleus test for detection of possible genotoxic effects of toluene, we monitored industrial painters from Rio Grande do Sul, Brazil. The putative involvement of oxidative stress in genetic damage and the influences of age, smoking, alcohol consumption, and exposure time were also assessed. Although all biomarkers of toluene exposure were below the biological exposure limits, painters presented significantly higher DNA damage (comet assay) than the control group; however, in the micronucleus assay, no significant difference was observed. Painters also showed alterations in hepatic enzymes and albumin levels, as well as oxidative damage, suggesting the involvement of oxidative stress. According to multiple linear regression analysis, blood toluene levels may account for the increased DNA damage in painters. In summary, this study showed that low levels of toluene exposure can cause genetic damage, and this is related to oxidative stress, age, and time of exposure.

The relationships between exogenous and endogenous antioxidants with the lipid profile and oxidative damage in hemodialysis patients.

BACKGROUND: We sought to investigate the relationships among the plasma levels of carotenoids, tocopherols, endogenous antioxidants, oxidative damage and lipid profiles and their possible effects on the cardiovascular risk associated with hemodialysis (HD) patients. METHODS: The study groups were divided into HD and healthy subjects. Plasma carotenoid, tocopherol and malondialdehyde (MDA) levels, as well as erythrocyte reduced glutathione (GSH), were measured by HPLC. Blood antioxidant enzymes, kidney function biomarkers and the lipid profiles were analyzed by spectrophotometric methods. RESULTS: Plasma lycopene levels and blood glutathione peroxidase (GPx) activity were significantly decreased in HD patients compared with healthy subjects. Total cholesterol, low-density lipoprotein cholesterol (LDL-c), creatinine, urea, MDA, GSH, superoxide dismutase (SOD) and catalase (CAT) were significantly increased in HD (p < 0.05). Lycopene levels were correlated with MDA (r = -0.50; p < 0.01), LDL-c (r = -0.38; p = 0.01) levels, the LDL-c/HDL-c index (r = -0.33; p = 0.03) and GPx activity (r = 0.30; p = 0.03). Regression models showed that lycopene levels were correlated with LDL-c (ß estimated = -31.59; p = 0.04), while gender was correlated with the TC/HDL-c index and triglycerides. Age did not present a correlation with the parameters evaluated. GPx activity was negatively correlated with MDA levels and with the LDL-c/HDL-c and CT/HDL-c indexes. CONCLUSIONS: Lycopene may represent an additional factor that contributes to reduced lipid peroxidation and atherogenesis in hemodialysis patients.

Evaluation of toxic effects of a diet containing fish contaminated with methylmercury in rats mimicking the exposure in the Amazon riverside population.

This study was designed to evaluate the effects of a diet rich in fish contaminated with MeHg, mimicking the typical diet of the Amazon riverside population, in rats. Animals were randomly assigned to one of three groups with eight rats in each group: Group I-control, received commercial ration; Group II-received a diet rich in uncontaminated fish; Group III-received a diet rich in fish contaminated with MeHg. Treatment time was 12 weeks. Oxidative stress markers were evaluated, as well as the effects of this diet on DNA stability, systolic blood pressure (SBP), nitric oxide (NO) levels and histological damage in different tissues. There was a significant increase in SBP values in rats fed with MeHg-contaminated fish diet after the 10th week of the treatment. As far as oxidative stress biomarkers are concerned, no differences were observed in reduced glutathione and protein carbonyl levels, glutathione peroxidase, catalase, superoxide dismutase or δ-aminolevulinate dehydratase activities between the groups of animals receiving contaminated and uncontaminated fish diets. On the other hand, malondialdehyde levels increased significantly in rats fed with contaminated fish. NO levels were similar in all groups. DNA migration showed augmented in rats exposed to contaminated fish and histopathological analyses showed weak but significant leukocyte infiltration. Thus, we conclude that the MeHg-contaminated fish diet induced a slight lipid peroxidation and genotoxicity. However, these effects seem to be much less pronounced than when rats are exposed to aqueous solution containing CH3HgCl. Our findings support the contention that the chemical form of MeHg in fish or fish nutrients such as polyunsaturated fatty acids, Se or vitamin E could minimize the toxic effects of MeHg exposure in fish-eating communities.

N-acetylcysteine on oxidative damage in diabetic rats.

N-acetylcysteine (NAC) is a potent mucolitic agent and also an antioxidant. Its antioxidant action is due to its ability to stimulate reduced glutathione (GSH) synthesis, therefore maintaining intracellular levels. The aim of this study was to evaluate the effects of NAC administered intraperitoneally (i.p.) in a decreasing of oxidative tissue damage in the liver and kidney of alloxan-induced diabetic rats, especially on thiolic groups (nonproteic and proteic groups). Adult male Wistar rats (200-350 g) were used; diabetes was induced accordingly by a single i.p. injection of alloxan monohydrate, and the control group received a similar volume of the vehicle. Lipid peroxidation (LPO) biomarker (malondialdehyde; MDA), δ-ALA-D activity, GSH, superoxide dismutase (SOD), and glutathione peroxidase (GPx) were quantified to assess the oxidative stress. All tests were performed in tissue homogenates. Creatinine, urea, aspartate transaminase, and alanine transaminase were determined by commercial kits, using serum samples. A significant decrease in LPO (i.e., hepatic and renal) and an increase in δ-aminolevulinate dehydratase activity, especially in the renal tissue, were observed. Also, NAC at 75 mg/kg showed more effective restoration of oxidative stress biomarkers than NAC at 25 mg/kg. Our findings suggest that NAC can be used as an antioxidant agent in diabetes, exhibiting modulatory action on the oxidative stress biomarkers analyzed in this work. Moreover, these findings can contribute to others' research, regarding the utilization of NAC to ALA-D activity restoration in the kidneys.

Association among microalbuminuria and oxidative stress biomarkers in patients with type 2 diabetes.

AIM: Hyperglycemia in diabetes mellitus (DM) may be one of the most important factors responsible for the development of oxidative stress, which promotes the main complications in DM patients. Therefore, this study evaluated if the hyperglycemia could be related to oxidative stress biomarkers, lipid profile, and renal function in type 2 diabetes patients without clinic complications. METHODS: Plasmatic malondialdehyde (MDA), serum protein carbonyl (PCO), serum creatinine levels, microalbuminuria, glycated hemoglobin, and lipid profile were analyzed in 37 type 2 diabetic patients and 25 subjects with no diabetes. RESULTS: Serum creatinine levels were within the reference values, but microalbuminuria presented increased levels in all the patients compared with controls (P < 0.05) and above of the reference values. The MDA, PCO, low-density lipoprotein, and triglyceride levels showed positive correlation with microalbuminuria levels. Moreover, glycated hemoglobin presented positive correlation with MDA, PCO, and microalbuminuria levels. CONCLUSIONS: The hyperglycemia could be responsible for the increase of the microalbuminuria levels and for the oxidation process in lipids and proteins in DM patients. Therefore, we suggested that the microvascular lesion is a direct consequence from hyperglycemia and an indirect one from the increased oxidative stress. Malondialdehyde and protein carbonyl levels could be suggested as additional biochemical evaluation to verify tissue damage in type 2 DM patients.

Possíveis efeitos do cobre sanguíneo sobre parâmetros hematológicos em idosas / Possible effects of blood copper on hematological parameters in elderly

INTRODUÇÃO: O cobre é um elemento traço essencial e sua homeostase é importante, principalmente em idosos, uma vez que seu metabolismo está associado a doenças neurodegenerativas e distúrbios na eritropoiese, entre outros. OBJETIVO: O presente estudo avaliou a associação entre cupremia, parâmetros hematológicos e estresse oxidativo. MATERIAIS E MÉTODOS: Amostras de sangue de 39 mulheres idosas (grupo de estudo) e de 20 indivíduos adultos saudáveis (grupo-controle) foram coletadas. As concentrações de cobre sérico foram quantificadas por espectrometria de massa por plasma indutivamente acoplado (ICP-MS), a atividade e o índice de reativação da enzima δ-aminolevulinato desidratase (ALA-D) foram determinados por espectrofotometria e parâmetros sanguíneos foram analisados em sistema automatizado. Os resultados foram expressos em média ± desvio padrão (DP). RESULTADOS: As concentrações de cobre, parâmetros hematológicos e índice de reativação da ALA-D para ambos os grupos encontraram-se dentro dos valores de referência. Porém, a atividade da ALA-D (11,47 ± 2,81 U.L-1) foi significativamente inferior no grupo de estudo em comparação com o grupo-controle. Correlações de Spearman (observadas somente nas mulheres idosas) entre as concentrações de cobre versus hemoglobina, hematócrito e atividade da ALA-D foram -0,384; -0,408 e -0,395, respectivamente (p < 0,05). No entanto, o índice de reativação da ALA não apresentou correlação com a cupremia. DISCUSSÃO E CONCLUSÃO: Os resultados mostraram que o cobre, mesmo estando nos limites considerados valores de referência, pode estar envolvido na inibição da ALA-D, o que pode alterar parâmetros hematológicos, como a síntese de hemoglobina. Neste sentido, sugere-se que os níveis de referência para o cobre em idosos sejam reavaliados.

INTRODUCTION: Copper is an essential trace element, and its homeostasis is important, mainly among the elderly, since their metabolism is associated with neurodegenerative diseases and erythropoiesis disorders, among others. OBJECTIVE: This study evaluated the association among cupremia, hematological parameters and oxidative stress. MATERIAL AND METHODS: Blood samples from 39 elderly women (study group) and 20 health individuals (control group) were collected. The concentrations of serum copper were quantified by ICP-MS. The activity and enzyme ALA-D reactivation index were determined by spectrophotometry and blood parameters were analyzed in the automated system. The results were expressed as mean ± standard deviation. RESULTS: Concentrations of copper, hematological parameters and ALA-D reactivation were within the reference values in both groups. However, ALA-D activity (11.47 ± 2.81 UL-1) was significantly lower in the study group compared to the control group. Spearman correlations (observed only in elderly women) between copper concentration versus hemoglobin, hematocrit and ALA-D activity were -0.384, -0.408 and -0.395, respectively (p < 0.05). Nonetheless, ALA reactivation index was not related to cupremia. DISCUSSION AND CONCLUSION: The results showed that copper, although it is within accepted reference values, may be involved in ALA-D inhibition, which may affect hematological parameters such as hemoglobin synthesis. Thus, the reference levels for copper in the elderly should be reviewed.

Mercury exposure and oxidative stress in communities of the Brazilian Amazon.

This study was designed to assess possible associations between biomarkers of mercury (Hg) exposure and oxidative stress in fish-eating Amazonian communities. Clinical samples were obtained from riparians living in the Brazilian Amazon. Biomarkers of oxidative stress (glutathione - GSH, glutathione peroxidase - GSH-Px, catalase - CAT, activity and reactivation index of delta-aminolevulinate dehydratase - ALA-D (R%) were determined in blood. Total Hg was measured in whole blood (B-Hg), plasma (P-Hg) and hair (H-Hg). Association between biomarkers of Hg exposure and oxidative stress were examined using multiple regression models, including age, gender, alcohol consumption, smoking status, fish consumption and then stratified for gender. Significant inverse relations were observed between GSH-Px, GSH, CAT, ALA-D activity and B-Hg or H-Hg (p<0.05). ALA-D reactivation index was positively related to B-Hg (p<0.0001). P-Hg was directly related to ALA-D reactivation index and inversely associated with GSH-Px, GSH, and ALA-D activity (p<0.05). When stratified for gender, women showed significant inverse associations between all biomarkers of Hg exposure and CAT (p<0.05) or GSH (p<0.05), while for men only P-Hg showed a significant inverse relation with GSH (p<0.001). Our results clearly demonstrated an association between Hg exposure and oxidative stress. Moreover, for B-Hg, P-Hg and H-Hg gender differences were present.

Sub-chronic exposure to methylmercury at low levels decreases butyrylcholinesterase activity in rats.

In this study, we examined the effects of low levels and sub-chronic exposure to methylmercury (MeHg) on butyrylcholinesterase (BuChE) activity in rats. Moreover, we examined the relationship between BuChE activity and oxidative stress biomarkers [delta-aminolevulinic acid dehydratase (delta-ALA-D) and malondialdehyde levels (MDA)] in the same animals. Rats were separated into three groups (eight animals per group): (Group I) received water by gavage; (Group II) received MeHg (30 microg/kg/day) by gavage; (Group III) received MeHg (100 microg/kg/day). The time of exposure was 90 days. BuChE and ALA-D activities were measured in serum and blood, respectively; whereas MDA levels were measured in plasma. We found BuChE and ALA-D activities decreased in groups II and III compared to the control group. Moreover, we found an interesting negative correlation between plasmatic BuChE activity and MDA (r = -0.85; p < 0.01) and a positive correlation between plasmatic BuChE activity and ALA-D activities (r = 0.78; p < 0.01), thus suggesting a possible relationship between oxidative damage promoted by MeHg exposure and the decrease of BuChE activity. In conclusion, long-term exposure to low doses of MeHg decreases plasmatic BuChE activity. Moreover, the decrease in the enzyme is strongly correlated with the oxidative stress promoted by the metal exposure. This preliminary finding highlights a possible mechanism for MeHg to reduce BuChE activity in plasma. Additionally, this enzyme could be an auxiliary biomarker on the evaluation of MeHg exposure.

The plasma retinol levels as pro-oxidant/oxidant agents in haemodialysis patients.

BACKGROUND: Oxidative stress is a process involved in haemodialysis-related pathologies such as cerebrovascular diseases. Retinol is the major circulating form of vitamin A and it is elevated in haemodialysis (HD) patients. It is known that these patients present anaemia that is not totally responsive to erythropoietin. The aim of this study was to evaluate the influence of plasma retinol levels on oxidative stress biomarkers, especially on delta-aminolevulinate dehydratase. METHODS: Plasma retinol and malondialdehyde (MDA) levels were quantified by HPLC-UV/VIS; blood activities of catalase (CAT), superoxide dismutase (SOD) and delta-aminolevulinate dehydratase (ALA-D) were analysed by spectrophotometric methods, in HD patients (n = 29) and healthy subjects (n = 20). RESULTS: The MDA and retinol levels, SOD and CAT activities were significantly increased in HD patients. ALA-D activity was significantly decreased. Retinol levels were correlated with MDA levels (r = 0.68), CAT (r = 0.39), SOD (r = 0.40) and ALA-D (r = -0.55). A partial correlation between retinol levels with ALA-D (r = 0.43), SOD (r = 0.30) and CAT (r = 0.36) activity was found, utilizing MDA levels as co-variable. CONCLUSION: Higher retinol levels may be associated with the increase of SOD and CAT activities, but this increase was not sufficient to prevent the lipid peroxidation and ALA-D thiolic group oxidation. In this manner, our results could suggest that high retinol levels contribute as an additional factor to the oxidative tissue damage.

Low levels of methylmercury induce DNA damage in rats: protective effects of selenium.

In this study we examined the possible antigenotoxic effect of selenium (Se) in rats chronically exposed to low levels of methylmercury (MeHg) and the association between glutathione peroxidase (GSH-Px) activity and DNA lesions (via comet assay) in the same exposed animals. Rats were divided into six groups as follows: (Group I) received water; (Group II) received MeHg (100 mug/day); (Group III) received Se (2 mg/L drinking water); (Group IV) received Se (6 mg/L drinking water); (Group V) received MeHg (100 mug/day) and Se (2 mg/L drinking water); (Group VI) received MeHg (100 mug/day) and Se (6 mg/L drinking water). Total treatment time was 100 days. GSH-Px activity was determined spectrophotometrically and DNA damage was determined by comet assay. Mean GSH-Px activity in groups I, II, III, IV, V and VI were, respectively: 40.19 +/- 17.21; 23.63 +/- 6.04; 42.64 +/- 5.70; 38.50 +/- 7.15; 34.54 +/- 6.18 and 41.39 +/- 11.67 nmolNADPH/min/gHb. DNA damage was represented by a mean score from 0 to 300; the results for groups I, II, III, IV, V and VI were, respectively: 6.87 +/- 3.27; 124.12 +/- 13.74; 10.62 +/- 3.81; 13.25 +/- 1.76; 86.87 +/- 11.95 and 76.25 +/- 7.48. There was a significant inhibition of GSH-Px activity in group II compared with group I (P < 0.05). Groups V and VI did not show a difference in enzyme activity compared with groups III and IV, showing the possible protective action of Se. Comet assay presented a significant difference in DNA migration between group II and group I (P < 0.0001). Groups V and VI showed a significant reduction in MeHg-induced genotoxicity (P < 0.001) when compared with group II. A negative correlation (r = -0.559, P < 0.05) was found between GSH-Px activity and DNA lesion, showing that the greater the DNA damage, the lower the GSH-Px activity. Our findings demonstrated the oxidative and genotoxic properties of MeHg, even at low doses. Moreover, Se co-administration reestablished GSH-Px activity and reduced DNA damage.

Butyrylcholinesterase activity is reduced in haemodialysis patients: is there association with hyperhomocysteinemia and/or oxidative stress?

OBJECTIVES: To quantify serum butyrylcholinesterase activity in haemodialysis patients and to evaluate if the homocysteine levels and/or oxidative stress biomarkers have an effect on butyrylcholinesterase. MATERIALS AND METHODS: Blood samples were collected from patients and healthy subjects (control). The plasma homocysteine and TBARS levels; serum butyrylcholinesterase activity; blood delta aminolevulinic acid dehydratase (ALA-D) activity and methahaemoglobin were analyzed. The mortality of the patients was also evaluated after 3 years. RESULTS: The homocysteine was increased and butyrylcholinesterase decreased compared to control (p<0.05). TBARS and methahaemoglobin were increased and ALA-D decreased (p<0.05). The following correlations were found: homocysteine with butyrylcholinesterase (-0.44); methahaemoglobin (0.41); ALA-D (-0.68); and TBARS (0.66). The partial correlation between homocysteine with butyrylcholinesterase, withdrawn the effect of TBARS, was -0.30; all p<0.05. Moreover, it was observed that 22% of the patients died due to cardiovascular problems. CONCLUSION: Thus, our findings support a direct association between the reduction of butyrylcholinesterase by the increase of homocysteine and an indirect effect by increase in oxidative stress.

The influence of the hemodialysis treatment time under oxidative stress biomarkers in chronic renal failure patients.

UNLABELLED: Oxidative stress possibly helps to promote the progression and complication of chronic renal failure (CRF). Hemodialysis (HD) may aggravate oxidative stress. In addition long time of treatment may intensify the oxidative stress. Thus, the aim of this study was to evaluate the effect of prolonged HD treatment under parameters of the oxidative stress. METHODS: Plasmatic thiobarbituric acid reactive substances (TBARS), plasmatic malondialdehyde (MDA), blood delta-aminolevulinate dehydratase (ALA-D) activity, ALA-D reactivation index, and erythrocytic reduced glutathione (GSH) were measured into two different groups of HD patients: recent treatment (n=36; HD duration: 17.7+/-1.71 months), and long time of treatment (n=26; HD duration: 82.2+/-6.32 months), and in a control group (n=40). RESULTS: Plasmatic TBARS and MDA levels were both elevated in HD patients. However, only MDA levels had positive correlation with time of HD treatment. Blood ALA-D activity was decreased in HD patients. The ALA-D reactivation index showed increase in HD patients, and it had correlation with the time of HD treatment. Erythrocytic GSH levels were increased in HD patients. CONCLUSIONS: Our results indicated that MDA levels and ALA-D reactivation index may be the better biomarkers to evaluate chronic oxidative stress in comparison with others markers analyzed in this study.

Quantification of reduced glutathione by HPLC-UV in erythrocytes of hemodialysis patients.

Reduced glutathione (GSH) is a well-known multifunctional antioxidant. Its depletion is linked to a number of pathologies, such as renal insufficiency. Feasible methodologies in clinical chemistry are vital. Therefore a methodology for GSH quantification was optimized and validated by HPLC-UV. Important aspects such as acid deproteinization and GSH stability were established. The erythrocytes were hemolyzed, deproteinized, derivatized with 5,5-dithio-bis (2-nitrobenzoic) acid and analyzed using HPLC, on an RP18 gradient elution, lambda=330 nm. The method was applied to hemodialysis patients (n=75) compared with healthy subjects (n=40). The assay was linear from 0.5 to 3.0 mm (r2>0.99). The intra- and inter-run reproducibilities were obtained with CV%<10%. The accuracy (bias %) ranged from 1.32 to -6.38%, and the recovery was >94%. The derivatized sample was stable for 60 days at -20 degrees C. The GSH levels in hemodialysis patients showed a significant increase compared with healthy subjects (p<0.05) and an inverse correlation with age (r=-0.286; p=0.013) was found. This method used UV detection, reduction of the phosphate concentration in the mobile phase and effective protein removal with trichloroacetic acid. The method proved to be reproducible, precise, accurate and stable. Thus, it can be suggested for routine laboratory tests for the verification of physiopathological conditions.

The influence of the serum vitamin C levels on oxidative stress biomarkers in elderly women.

OBJECTIVES: To verify if there is influence of the vitamin C blood levels on oxidative stress markers in elderly people. In order to verify it, women from a public retirement home were compared to non-institutionalized ones; all of them were in healthy conditions. DESIGN AND METHODS: Vitamin C, albumin, reduced glutathione, malondialdehyde (MDA), protein carbonyls and delta-aminolevulinate dehydratase activity (ALA-D) were analyzed in older women either from a public retirement home (n=45) or non-institutionalized (n=22). RESULTS: The institutionalized ones showed significant decrease for vitamin C levels (p=0.002), ALA-D and MDA (p<0.05). Correlations were found between vitamin C and both albumin and ALA-D, also between ALA-D and both protein carbonyls and age. CONCLUSIONS: The institutionalized women presented decreased vitamin C, albumin, MDA and ALA-D compared to non-institutionalized. Thus, it could be suggested that vitamin C tends to protect blood thiolic proteins. Moreover, its blood delta-aminoevulinate dehydratase activity seemed to be an additional biomarker of oxidation stress in healthy elderly.