A novel automated direct measurement method for total antioxidant capacity using a new generation, more stable ABTS radical cation

Measurement of the total antioxidant response using a novel automated method in subjects with nonalcoholic steatohepatitis

BACKGROUND

Oxidative stress, an increase in oxidants and/or a decrease in antioxidant capacity, is one of the potential biochemical mechanisms involved in the pathogenesis of nonalcoholic steatohepatitis. We aimed to investigate the total antioxidant response using a novel automated method in nonalcoholic steatohepatitis subjects. As a reciprocal measure, we also aimed to determine total peroxide level in the same plasma samples.

METHODS

Twenty-two subjects with biopsy proven nonalcoholic steatohepatitis and 22 healthy controls were enrolled. Total antioxidant response and total peroxide level measurements were done in all participants. The ratio percentage of total peroxide level to total antioxidant response was regarded as oxidative stress index.

RESULTS

Total antioxidant response of subjects with nonalcoholic steatohepatitis was significantly lower than controls (p < 0.05), while mean total peroxide level and mean oxidative stress index were higher (all p < 0.05). In subjects with nonalcoholic steatohepatitis, fibrosis score was significantly correlated with total peroxide level, total antioxidant response and oxidative stress index (p < 0.05, r = 0.607; p < 0.05, r = -0.506; p < 0.05, r = 0.728, respectively). However, no correlation was observed between necroimflamatory grade and those oxidative status parameters (all p > 0.05).

CONCLUSION

Nonalcoholic steatohepatitis is associated with increased oxidant capacity, especially in the presence of liver fibrosis. The novel automated assay is a reliable and easily applicable method for total plasma antioxidant response measurement in nonalcoholic steatohepatitis.

Plasma total antioxidant capacity, lipid peroxidation, and erythrocyte antioxidant enzyme activities in patients with rheumatoid arthritis and osteoarthritis

OBJECTIVES

The metabolism of cells in inflammatory and noninflammatory arthritic joint diseases is subject to complex environmental controls. The aim of the present study was to investigate the total antioxidant capacity (TAC), levels of lipid peroxidation (LPO), and antioxidant enzyme activities in patients with rheumatoid arthritis (RA) and osteoarthritis (OA).

DESIGN AND METHODS

Plasma levels of TAC, malondialdehyde (MDA), the activities of some erythrocyte antioxidant enzymes, as well as erythrocyte sedimentation rates (ESR) were estimated in patients with RA and OA and compared with controls.

RESULTS

The plasma TAC levels were significantly lower in the RA group than the OA and control group (P < 0.05). Plasma MDA concentrations were significantly higher in patients with RA than those with OA and healthy subjects (P < 0.05). Erythrocyte GSH-Px and CAT activities were found to be significantly lower in patients with RA than those with OA and healthy subjects (P < 0.05, P < 0.05, respectively). However, there were no significant differences in erythrocyte SOD activities between the groups (P > 0.05). ESR were significantly higher in RA patients than in healthy subjects and patients with OA (P < 0.01). Moreover, there were significant negative correlations between TAC vs. MDA, ESR vs. TAC, and a positive correlation between ESR vs. MDA in the RA group (r = -0.398, P < 0.05; r = -0.422, P < 0.05; r = 0.530, P < 0.05, respectively).

CONCLUSIONS

Our results demonstrated that levels of LPO are increased in patients with RA compared to patients with OA. In addition, plasma TAC levels are decreased in RA due to its inflammatory character. We conclude that detecting plasma TAC levels with this novel method may be used as a routine and rapid test to verify the levels of oxidative stress in RA. Furthermore, correlating TAC and LPO levels with acute phase reactants such as ESR may give some clues about disease activity in RA.

Increased oxidative stress associated with the severity of the liver disease in various forms of hepatitis B virus infection

Background

Oxidative stress can be defined as an increase in oxidants and/or a decrease in antioxidant capacity. There is limited information about the oxidative status in subjects with hepatitis B virus infection. We aimed to evaluate the oxidative status in patients with various clinical forms of chronic hepatitis B infection.

Methods

Seventy-six patients with hepatitis B virus infection, in whom 33 with chronic hepatitis, 31 inactive carriers and 12 with cirrhosis, and 16 healthy subjects were enrolled. Total antioxidant response and total peroxide level measurement, and calculation of oxidative stress index were performed in all participants.

Results

Total antioxidant response was significantly lower in cirrhotics than inactive HbsAg carriers and controls (p = 0.008 and p = 0.008, respectively). Total peroxide level and oxidative stress index was significantly higher in cirrhotic (p < 0.001, both) and chronic hepatitis B subjects (p < 0.001, both) than inactive HbsAg carriers and controls. Total antioxidant response was comparable in chronic hepatitis B subjects, inactive HbsAg carriers and controls (both, p > 0.05/6). Total peroxide level and oxidative stress index were also comparable in inactive HBsAg carriers and controls (both, p > 0.05/6). Serum alanine amino transferase level was positively correlated with total peroxide level and oxidative stress index only in chronic hepatitis B subjects (p = 0.002, r = 0.519 and p = 0.008, r = 0.453, respectively).

Conclusion

Oxidative stress occurs secondarily to increased total lipid peroxidation and inadequate total antioxidant response and is related to severity of the disease and replication status of virus in hepatitis B infection.

A new automated colorimetric method for measuring total oxidant status

OBJECTIVES

To develop a new, colorimetric and automated method for measuring total oxidation status (TOS).

DESIGN AND METHODS

The assay is based on the oxidation of ferrous ion to ferric ion in the presence of various oxidant species in acidic medium and the measurement of the ferric ion by xylenol orange. The oxidation reaction of the assay was enhanced and precipitation of proteins was prevented. In addition, autoxidation of ferrous ion present in the reagent was prevented during storage. The method was applied to an automated analyzer, which was calibrated with hydrogen peroxide and the analytical performance characteristics of the assay were determined.

RESULTS

There were important correlations with hydrogen peroxide, tert-butyl hydroperoxide and cumene hydroperoxide solutions (r=0.99, P<0.001 for all). In addition, the new assay presented a typical sigmoidal reaction pattern in copper-induced lipoprotein autoxidation. The novel assay is linear up to 200 micromol H2O2 Equiv./L and its precision value is lower than 3%. The lower detection limit is 1.13 micromol H2O2 Equiv./L. The reagents are stable for at least 6 months on the automated analyzer. Serum TOS level was significantly higher in patients with osteoarthritis (21.23+/-3.11 micromol H2O2 Equiv./L) than in healthy subjects (14.19+/-3.16 micromol H2O2 Equiv./L, P<0.001) and the results showed a significant negative correlation with total antioxidant capacity (TAC) (r=-0.66 P<0.01).

CONCLUSIONS

This easy, stable, reliable, sensitive, inexpensive and fully automated method that is described can be used to measure total oxidant status.

Reactions of Biological Oxidants with Selenourea: Formation of Redox Active Nanoselenium

Reactions of biological oxidizing agents, such as hydroxyl radicals ((*)OH), singlet oxygen ((1)O(2)), hydrogen peroxide (H(2)O(2)), and peroxynitrite (ONOO(-)) with selenourea were studied. The kinetics of the reactions was followed using time-resolved techniques, and the bimolecular rate constants were determined. In all these reactions, under aerated conditions, elemental red selenium was produced as one of the reaction products. The average size of the selenium particles could be controlled and stabilized in the range of 20-100 nm with the addition of bovine serum albumin (BSA) or sodium dodecyl sulfate (SDS). The particles were characterized by dynamic light scattering studies (DLS), which revealed that the size and distribution of the particles depended mainly on the amount of selenourea undergoing oxidation. Other factors such as the nature of the oxidant and the concentration of the stabilizer also are important in stabilizing the particles. Nanoselenium-reduced ABTS(*-) to colorless ABTS(2-) (ABTS = 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) and oxidized dichlorodihydrofluoresecein diacetate (DCFA) to fluorescent dichlorofluorescein (DCF) indicating its ability to participate in redox and free radical reactions. The reactivity of selenium nanoparticles with these systems varied linearly with the surface area of the particles. The studies demonstrate that selenourea undergoes oxidation with both one-electron and two-electron oxidants to produce elemental selenium, which, on stabilization to nanometer size, exhibits size-dependent redox activity.

Increased DNA damage in patients with complete hydatidiform mole

The pathologic mechanisms underlying the gestational trophoblastic diseases are largely unexplored, but are thought to involve oxidative damage to the maternal vasculature and also to the placenta. In this study we have assessed the plasma levels of total antioxidant response (TAR) and the levels of endogenous DNA damage--determined by the comet assay--in peripheral blood lymphocytes from 13 women with complete hydatidiform mole (CHM) and compared these with those of 12 healthy pregnant controls and 10 healthy non-pregnant controls. Significantly lower mean levels of plasma TAR were found in patients with CHM compared with healthy pregnant controls (1.08+/-0.29 versus 1.17+/-0.14 mmol Trolox Eq/L, p<0.05) and with healthy non-pregnant controls (1.08+/-0.29 versus 1.38+/-0.12 mmol Trolox Eq/L, p<0.05). Significantly higher mean levels of endogenous DNA damage were observed in patients with CHM than in healthy pregnant controls (234.5+/-50.74 versus 125.7+/-45.4 AU, p<0.05) or in healthy non-pregnant controls (234.5+/-50.74 versus 104.0+/-49.6 AU, p<0.05). We observed an inverse correlation between the plasma TAR and the levels of endogenous DNA damage (r=-0.64, p<0.01), in that the levels of oxidative damage to the DNA were found to parallel the decrease in the plasma TAR in the CHM group. These results reveal a relationship between the extracellular and intracellular (as reflected by damage to the DNA) levels of oxidation. Our observations suggest that there is a link between the increased levels of oxidative stress and the increase in endogenous DNA damage seen in patients with CHM, as compared with those seen in normal pregnancy. However, the nature of this link, and whether it is direct or indirect, remains to be explored.

Measurement of the total antioxidant response in preeclampsia with a novel automated method

OBJECTIVES

Preeclampsia is one of the most serious complications of pregnancy. Free radical damage has been implicated in the pathophysiology of this condition. In this study, we aimed to measure the antioxidant capacity in plasma samples from normotensive and preeclamptic pregnant women to evaluate their antioxidant status using a more recently developed automated measurement method.

STUDY DESIGN

Our study group contained 42 women, 24 of whom had preeclampsia, while 18 had normotensive pregnancies. We measured the total plasma antioxidant capacity for all patients, as well as the levels of four major individual plasma antioxidant components; albumin, uric acid, ascorbic acid and bilirubin, and as a reciprocal measure, their total plasma peroxide levels.

RESULTS

Statistically significant differences (determined using Student's t-test) were noted between the normotensive and the preeclamptic groups for their total antioxidant responses and their vitamin C levels (1.31 +/- 0.12 mmol versus 1.06 +/- 0.41 mmol Trolox eq./L; 30.2 +/- 17.83 micromol/L versus 18.1 +/- 11.37 micromol/L, respectively), which were both considerably reduced in the preeclamptic patients. In contrast, the total plasma peroxide levels were significantly elevated in this group (49.8 +/- 14.3 micromol/L versus 38.8 +/- 9.6 micromol/L).

CONCLUSIONS

We found a decreased total antioxidant response in preeclamptic patients using a simple, rapid and reliable automated colorimetric assay, which may suitable for use in any routine clinical biochemistry laboratory, and considerably facilitates the assessment of this useful clinical parameter. We suggest that this novel method may be used as a routine test to evaluate and follow up of the levels of oxidative stress in preeclampsia.

Effect of I-deprenyl and gliclazide on oxidant stress/antioxidant status and dna damage in a diabetic rat model

BACKGROUND

This study investigates the possible effect of monoamine oxidase inhibitor (MAOI), selegyline (l-deprenyl), in combination with oral antidiabetic-gliclazide (OAD), in preventing oxidative stress in streptozotocin-induced diabetes model in male Swiss Albino rats by measuring oxidant stress/ DNA damage and antioxidant levels.

METHODS

Diabetic rats were divided into four groups (n = 10) as (1) diabetic untreated (DM), (2) deprenyl treated (DM + D), (3) gliclazide treated (DM + O), and (4) gliclazide and deprenyl treated (DM + O + D). Controls were divided into two groups (n = 8) (1) untreated (C), and (2) deprenyl treated (C + D). Gliclazide 5 mg/kg and/or MAOI 0.25 mg/kg daily were given orally by gavage for 4 weeks. At the end of the 12th week, catalase and superoxide dismutase (SOD) levels in erythrocyte lysates (EL); total antioxidant status (TAS), 8-hydroxy-deoxyguanosine (8-OHdG), malondialdehyde (MDA), and vitamin A and E levels in plasma, MDA, and MAO in liver homogenates were determined.

RESULTS

Diabetic rats showed a decrease in EL-SOD, plasma TAS, and vitamin E, and an increase in plasma 8-OHdG, plasma, and liver MDA levels (p < 0.05). Gliclazide and/or deprenyl decreased 8OHdG levels and increased antioxidant levels and survival when compared with untreated diabetic rats (p < 0.05). The lowest 8-OHdG levels were determined in the DM +O + D group.

CONCLUSIONS

The combined treatment of deprenyl and gliclazide may contribute to the control of the physiopathological mechanisms underlying both the process of aging and type 2 diabetes by reducing oxidant stress and DNA damage, improving antioxidant status, and increasing survival, and may have implications for further clinical studies.

Evaluation of the antioxidant activity by flow injection analysis method with electrochemically generated ABTS radical cation

A Trolox equivalent antioxidant capacity (TEAC) decolourisation assay was adapted to a flow injection analysis (FIA) system and a simple and rapid method for antioxidant activity evaluation was developed. To avoid the time consuming step of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) radical cation preparation by chemical oxidation of ABTS, as in the original TAEC assay, and hence, to shorten the analysis time, the ABTS radical cation was generated on-line by electrochemical oxidation of ABTS in the flow-through electrolysis cell forming a part of the FIA system. The proposed method was optimised with respect to a flow rate, injection volume and ABTS radical cation/carrier ratio. Under the optimised conditions linear calibration graphs for Trolox were obtained over the range 10-100 microM, with a limit of detection 1.6 microM. Good reproducibility (relative standard deviation 1.95%) and sample throughput (32 samples per hour) were achieved. The developed method was applied to the evaluation of the antioxidant activity of pure compounds and samples of some common beverages. In both cases a good correlation between the results obtained by the proposed method and TEAC values evaluated by the classic TAEC decolourisation assay was obtained (r(2)= 0.996 for pure compounds and r(2)= 0.957 for beverage samples).

Comparison of oxidative/antioxidative status of penile corpus cavernosum blood and peripheral venous blood

The aim of the study is to determine and to compare the oxidative and antioxidative status of penile corpus cavernosum and peripheral venous blood. A total of 28 adult healthy males were included in the study. Whole blood was simultaneously withdrawn from penile corpus cavernosum and the cubital vein and their plasma separated. Total antioxidant capacity (TAC), vitamin C, total protein, albumin, uric acid, bilirubin and total peroxide (TP) levels of both plasma samples were measured and compared. While TAC, total protein, albumin, bilirubin and uric acid levels were higher, vitamin C levels were lower in cavernosal blood than that of peripheral blood. On the other hand, TP level was found to be higher in penile blood samples than that of peripheral blood. We thought that the normal erectile process of the penile cavernosal body leads to increased production of oxidants as in the mechanism of ischaemia-reperfusion; however, the increase of TAC can prevent development of oxidative injury.