Stress proteins as biomarkers of oxidative stress: effects of antioxidant supplements

The potential benefits to health of the supply of antioxidants, either through dietary intake or as supplements, is equivocal. There is a need to develop biomarkers that may act as monitors of cellular defense as influenced by antioxidant status. Thirty-two individuals participated in the project and 19 received supplements for 5 weeks in the form of a capsule containing a defined mixture of antioxidants. No change was noted in levels of superoxide dismutase and glutathione peroxidase following antioxidant supplementation. On the other hand, increase in total antioxidant status and decrease in malondialdehyde, protein carbonyl formation, and erythrocyte hemolysis were noted. In lymphocytes isolated from individuals receiving antioxidant supplements and subjected to a heat shock in the presence of the free radical generator 2, 2'-azobis-(2-amidinopropane)-dihydrochloride, enhanced synthesis of heat shock proteins hsp 105, hsp 90, hsp 70, and hsp 40 by contrast with decreased synthesis of heme oxygenase HO-1 (hsp 32) were noted. We conclude that antioxidant status modulates the synthesis of stress proteins.     

Oxidative stress and antioxidant deficiencies in asthma: potential modification by diet

The lungs of asthmatic patients are exposed to oxidative stress due to the generation of reactive oxygen and nitrogen species as a consequence of chronic airway inflammation. Increased concentrations of NO*, H2O2 and 8-isoprostane have been measured in exhaled breath and induced sputum of asthmatic patients. O2*-, NO*, and halides interact to form highly reactive species such as peroxynitrite and HOBr, which in turn cause nitration and bromination of protein tyrosine residues. Oxidative stress may also reduce glutathione levels and cause inactivation of antioxidant enzymes such as superoxide dismutase, with a consequent increase in apoptosis, shedding of airway epithelial cells and airway remodelling. The oxidant/antioxidant equilibrium in asthmatic patients may be further perturbed by low dietary intakes of the antioxidant vitamins C and E, selenium and flavonoids, with a consequent lowering of the concentrations of these and other non-dietary antioxidants such as bilirubin and albumin in plasma and airway epithelial lining fluid. Although supplementation with vitamins C and E appears to offer protection against the adverse effects of ozone, recent randomised, placebo-controlled trials of vitamin C or E supplements for patients with mild asthma have not shown significant benefits over standard therapy. However, genetic variation in glutathione S-transferase may influence the susceptibility of asthmatic individuals to oxidative stress and the extent to which they are likely to benefit from antioxidant supplementation. Long-term prospective trials are required to determine whether modification of dietary intake will benefit asthma patients and reduce the socio-economic burden of asthma in the community.     

Oxidative stress and antioxidant deficiencies in asthma: potential modification by diet

Abstract

The lungs of asthmatic patients are exposed to oxidative stress due to the generation of reactive oxygen and nitrogen species as a consequence of chronic airway inflammation. Increased concentrations of NO^?, H₂O₂ and 8-isoprostane have been measured in exhaled breath and induced sputum of asthmatic patients. O₂^??, NO^?, and halides interact to form highly reactive species such as peroxynitrite and HOBr, which in turn cause nitration and bromination of protein tyrosine residues. Oxidative stress may also reduce glutathione levels and cause inactivation of antioxidant enzymes such as superoxide dismutase, with a consequent increase in apoptosis, shedding of airway epithelial cells and airway remodelling. The oxidant/antioxidant equilibrium in asthmatic patients may be further perturbed by low dietary intakes of the antioxidant vitamins C and E, selenium and flavonoids, with a consequent lowering of the concentrations of these and other non-dietary antioxidants such as bilirubin and albumin in plasma and airway epithelial lining fluid. Although supplementation with vitamins C and E appears to offer protection against the adverse effects of ozone, recent randomised, placebo-controlled trials of vitamin C or E supplements for patients with mild asthma have not shown significant benefits over standard therapy. However, genetic variation in glutathione S-transferase may influence the susceptibility of asthmatic individuals to oxidative stress and the extent to which they are likely to benefit from antioxidant supplementation. Long-term prospective trials are required to determine whether modification of dietary intake will benefit asthma patients and reduce the socio-economic burden of asthma in the community.     

Total antioxidant levels are low during active TB and rise with anti-tuberculosis therapy

In tuberculosis, oxidative stress is a result of tissue inflammation, poor dietary intake of micronutrients due to illness, free radical burst from activated macrophages, and anti-tuberculosis drugs. These free radicals may in turn contribute towards pulmonary inflammation if not neutralized by antioxidants. The total antioxidant status (TAS) of individuals is a function of dietary, enzymatic, and other systemic antioxidants and is therefore an indicator of the free radical load. Our aim was to evaluate the TAS of healthy and M. tuberculosis-infected persons from a high TB incidence community, as well as tuberculosis patients at various stages of antituberculosis drug treatment and to correlate results with plasma micronutrient levels. Blood plasma samples from TB infected patients and following antituberculosis drug treatment were assayed for TAS, vitamins A, E and Zinc. Statistical analysis of results was by one-way ANOVA and the Tukey multiple comparison post test. Active TB patients showed a significantly lower TAS (P < 0.001) compared to the community controls. We also show that TAS values increase during therapy. Results correlated with micronutrients vitamin A and zinc but vitamin E remained unaffected. We suggest that total antioxidant status of TB patients should be considered for more effective disease control and that diets low in antioxidants may render individuals susceptible to tuberculosis.     

热胁迫对双孢蘑菇抗氧化酶及热激蛋白基因的差异表达的影响

抗氧化酶和热激蛋白是双孢蘑菇Agaricus bisporus抵御逆境胁迫的重要蛋白,高温胁迫下菌丝会通过二者基因的差异表达来减少对自身的损伤.通过对双孢蘑菇菌丝进行40℃热胁迫处理0-120min后发现,随着热胁迫时间延长,菌丝生长速度降低、气生菌丝增多和菌丝分叉明显.转录组分析抗氧化酶和热激蛋白基因差异表达发现,在...     

Effect of dietary sesame oil as antioxidant on brain hippocampus of rat in focal cerebral ischemia

Oxidative stress may be regarded as an imbalance between free radical production and opposing antioxidant defenses. Free radical oxidative stress is implicated in rat cerebral ischemia and naturaceutical antioxidants are dietary supplements that have been reported to have neuroprotective activity. Many studies have reported dietary sesame oil (SO) as an effective antioxidant. In the present study the neuroprotective effect of dietary SO was evaluated against middle cerebral artery occlusion (MCAO)-induced cerebral ischemia injury in rats. Rats were fed on diet (20% SO) for 15 days. The middle cerebral artery of adult male Wistar rat was occluded for 2 h and reperfused for 22 h. The antioxidant properties of brain were measured as levels of reduced glutathione (GSH), glutathione-S-transferase (GST), glutathione peroxide (GPx), glutathione reductase (GR), catalase (CAT), superoxide dismutase (SOD) and thiobarbituric acid reactive substance (TBARS). A decrease in the activity of all the enzymatic and non-enzymatic antioxidants was observed along with an increase in lipid peroxidation (LPO) in MCAO group. The neurobehavioral activity of rats was also observed by using videopath analyzer. Dietary SO improved the antioxidant status in MCAO+SO group when compared with MCAO group. The results of neurobehavioral activity also support our biochemical data. The results obtained suggest protective effect of SO against cerebral ischemia in rat brain through their antioxidant properties.     

Erythrocyte, plasma, and serum antioxidant activities in untreated toxic multinodular goiter patients

Erythrocyte, plasma, and serum antioxidant activities were studied in patients with newly diagnosed and untreated toxic multinodular hyperthyroid goiter and compared to healthy control subjects. Erythrocyte antioxidant enzyme activities, glutathione, malondialdehyde, and ceruloplasmin levels were significantly increased, whereas serum vitamin E, plasma vitamin C, and selenium levels were decreased in hyperthyroid patients compared to control subjects. The findings show that untreated toxic multinodular goiter causes profound alterations in components of the antioxidant system in erythrocytes indicative of increased oxidative stress. Taken together, these data suggest that hyperthyroid patients may benefit from dietary supplements of antioxidants.     

Effects of dietary zinc on gene expression of antioxidant enzymes and heat shock proteins in hepatopancreas of abalone Haliotis discus hannai

The expression patterns of different genes encoding antioxidant enzymes and heat shock proteins were investigated, in present study, by real-time quantitative PCR in the hepatopancreas of abalone Haliotis discus hannai fed with different levels of dietary zinc (6.69, 33.8, 710.6 and 3462.5 mg/kg) for 20 weeks. The antioxidant enzymes include Cu/Zn-superoxide dismutase (Cu/Zn-SOD), Mn-superoxide dismutase (Mn-SOD), catalase (CAT), mu-glutathione-s-transferase (mu-GST) and thioredoxin peroxidase (TPx). The results showed that the mRNA expression of these antioxidant enzymes increased and reached the maximum at the dietary zinc level of 33.8 mg/kg, and then dropped progressively. Expression levels of the heat shock proteins (HSP26, HSP70 and HSP90) firstly increased at 33.8 mg/kg dietary Zn level, and reached to the maximum at 710.6 mg/kg, then dropped at 3462.5 mg/kg (p<0.05). Excessive dietary Zn (710.6 and 3462.5 mg/kg) significantly increases the Zn content and significantly decreases the total antioxidant capacity (T-AOC) in hepatopancreas (p<0.05). These findings showed that dietary Zn (33.8 mg/kg) could highly trigger the expression levels of antioxidant enzymes and heat shock proteins, but excessive dietary Zn (710.6 and 3462.5 mg/kg) induces a high oxidative stress in abalone.     

Effects of dried fish on antioxidant levels in rat liver

Short-term feeding studies were carried out to investigate the effect of ingestion of salted dried fish on alterations in tissue lipid peroxidation and modulation of the activities of detoxification enzymes in liver in order to study the induction of oxidative stress. Rats were fed diets with either 5, 10 and 20% dried mackerel for 4 weeks and levels of antioxidants in liver were estimated. The results showed that the fish intake at 10 and 20% dietary level reduced glutathione with a reciprocal increase in thiobarbituric acid reactive substances and a concomitant decrease in antioxidant vitamins A and C contents in liver. A significant decline in the activities of hepatic glutathione peroxidase and glutathione reductase were also observed at these levels of fish consumption. Kidney gamma-glutamyl transpeptidase activity on the other hand was increased abnormally at 20% fish intake. The results suggested that the dried fish consumption at higher concentrations (at 10 and 20%) for a short period caused lowering of the activities of antioxidative enzymes thereby inducing oxidative stress in rat liver.     

Effect of antioxidant supplementation on the adaptive response of human skin fibroblasts to UV-induced oxidative stress

The effect of supplementation with substances having antioxidant properties on the adaptive responses of human skin fibroblasts to UV-induced oxidative stress was studied in vitro. UVR was found to induce a substantial oxidative stress in fibroblasts, resulting in an increased release of superoxide anions and an increase in lipid peroxidation (shown by an elevated malonaldehyde content). Sub-lethal doses of UVR were also found to induce adaptive responses in the fibroblast antioxidant defences, with a transient rise in catalase and superoxide dismutase activities followed by a slower, large increase in cellular glutathione content. Supplementation of the fibroblasts with the antioxidants, Trolox (a water soluble analogue of alpha-tocopherol), ascorbic acid or beta-carotene, had differential effects on these responses. Trolox supplementation reduced the UVR-induced cellular oxidative stress and adaptive response in a predictable concentration-dependent manner. This was in contrast to ascorbic acid which increased superoxide release from fibroblasts. At low doses, ascorbate supplements also reduced the magnitude of the adaptive increases in catalase and superoxide dismutase activities and increase in glutathione content. Beta-carotene had a similar effect to ascorbic acid, reducing the extent of the adaptations to UVR at lower doses while simultaneously increasing superoxide release and malonaldehyde content. These in vitro data indicate that only the vitamin E analogue suppressed UVR-induced oxidative stress in a predictable manner and suggest that common dietary antioxidants may not be equally effective in reducing the potential deleterious effects of UVR-induced oxidative stress in skin.     

Heat shock of rabbit synovial fibroblasts increases expression of mRNAs for two metalloproteinases, collagenase and stromelysin

Two metalloproteinases, collagenase and stromelysin, are produced in large quantities by synovial fibroblasts in individuals with rheumatoid arthritis. These enzymes play a major role in the extensive destruction of connective tissue seen in this disease. In this study, we show that heat shock of monolayer cultures of rabbit synovial fibroblasts increases expression of mRNA for heat shock protein 70 (HSP-70), and for collagenase and stromelysin. We found that after heat shock for 1 h at 45 degrees C, the mRNA expression for HSP-70 peaks at 1 h and returns to control levels by 3 h. Collagenase and stromelysin mRNA expression is coordinate, reaching peak levels at 3 h and returning to control levels by 10 h. The increase in mRNA is paralleled by an increase in the corresponding protein in the culture medium. 3 h of heat shock at a lower temperature (42 degrees C) is also effective in inducing collagenase and stromelysin mRNAs. Concomitant treatment with phorbol myristate acetate (PMA; 10(-8) or 10(-9) M) and heat shock is not additive or synergistic. In addition, all-trans-retinoic acid, added just before heat shock, prevents the increase in mRNAs for collagenase and stromelysin. Our data suggest that heat shock may be an additional mechanism whereby collagenase and stromelysin are increased during rheumatoid arthritis and perhaps in other chronic inflammatory stress conditions.     

Effect of dietary antioxidant supplementation on fresh semen quality in stallion

In this study, the effect of dietary supplementation of organic selenium, vitamin E, and zinc on raw semen characteristics was evaluated. Ten stallions with normal fertility were divided into two groups: a control group (CG), in which standard diet was provided, and a treated group (TG), in which the standard diet was supplemented with 1500 mg of α-tocopherol acetate, 360 mg of zinc, and 2.5 mg of organic selenium on a daily basis. Semen parameters on fresh semen were evaluated three times in all stallions before antioxidant supplementation (T0) and 30 (T1), 60 (T2), and 90 (T3) d after supplementation. Dietary supplementation with experimental antioxidants resulted in a significant increase in average path velocity (121.9 ± 3.1 μm/sec in TG vs 118.9 ± 4.3 μm/sec in CG), straightness (86.2 ± 2.4 % vs 82.6 ± 3.9 % in TG and CG respectively), viability (75.6 ± 10.2 % in TG vs 72.3 ± 6.9 % in CG) and total seminal plasma antioxidants levels (2.7 ± 0.5 mmol/l vs 1.9 ± 0.4 mmol/l in TG and CG respectively) while progressive motility 69.7 ± 11 % vs 62.2 ± 9.3 % in TG and CG stallions respectively) and abnormal sperm morphology (8.2±1.5 % in TG vs 14.4±4 % in CG) significantly improved in treated stallions after 60 d of supplementation. In contrast with previously reported in other species, a negative effect of antioxidant supplementation on semen concentration was recorded in the TG. A positive correlation between progressive motility and total antioxidants in seminal plasma in both treated and control stallions suggested that motility is affected by oxidative-antioxidative status, and that dietary antioxidant supplementation could increase the ability of spermatozoa to contrast reactive oxygen species or the ability of seminal plasma to reduce the oxidative stress. The improvement of semen parameters after antioxidant supplementation was not linear, and after 30 d (or 60 d for some parameters), a further increase was not noted. This evidence suggested that in our standard conditions, dietary intake of these antioxidants could be slightly under the dietary requirement and further evaluation of the actual nutrition requirements of organic selenium, zinc, and vitamin E in the stallion are needed.     

T lymphocyte stress response. II. Protection of translation and DNA replication against some forms of stress by prior hyperthermic stress

We have compared the effects of a mild heat shock and febrile temperatures on heat-shock protein (hsp) synthesis and development of stress tolerance in T lymphocytes. Our previous studies demonstrated that febrile temperatures (less than or equal to 41 degrees C) induced the synthesis of hsp110, hsp90, and the constitutive or cognate form of hsp70 (hscp70; a weak induction of the strongly stress-induced hsp70 was also observed. In the studies reported herein, we demonstrate that a mild heat shock (42.5 degrees C) reverses this ratio; that is, hsp70 and not hscp70 is the predominate member of this family synthesized at this temperature. Modest heat shock also enhanced the synthesis of hsp110 and hsp90. In order to assess the relationship between hsp synthesis and the acquisition of thermotolerance, purified T cells were first incubated at 42.5 degrees C (induction temperature) and then subsequently subjected to a severe heat-shock challenge (45 degrees C, 30 min). T cells first incubated at a mild heat-shock temperature were capable of total protein synthesis at a more rapid rate following a severe heat shock than control cells (induction temperature 37 degrees C). This phenomenon, which has been previously termed translational tolerance, did not develop in cells incubated at the febrile temperature (induction temperature 41 degrees C). Protection of translation also extended to immunologically relevant proteins such as interleukin-2 and the interleukin-2 receptor. Because clonal expansion is a critical event during an immune response, the effects of hyperthermic stress on DNA replication (mitogen-induced T cell proliferation) was also evaluated in thermotolerant T cells. DNA synthesis in control cells (induction temperature 37 degrees C) was severely inhibited following heat-shock challenge at 44 degrees C or 45 degrees C; in contrast, T cells preincubated at 42.5 degrees C rapidly recovered their DNA synthetic capacity. T cells preincubated at a febrile temperature were moderately protected against hyperthermic stress. The acquisition of thermotolerance was also associated with enhanced resistance to chemical (ethanol)-induced stress but not to heavy metal toxicity (cadmium) or dexamethasone-induced immunosuppression. These studies suggest that prior hsp synthesis may protect immune function against some forms of stress (e.g., febrile episode) but would be ineffective against others such as elevated glucocorticoid levels which normally occur during an immune response.     

Differential response of lymphocytes and neutrophils to high intensity physical activity and to vitamin C diet supplementation

We have determined the effects of chronic vitamin C intake on neutrophil and lymphocyte antioxidant defences during the acute phase immune response induced by intense exercise. Blood samples were taken from 16 voluntary athletes in basal conditions, both immediately after and 1 h after a duathlon competition. Sportsmen's nutrient intakes were determined before the competition. After determining the basal plasmatic ascorbate levels, the results were analysed taking into account the vitamin C intake and their plasmatic levels. Two groups were constituted, the vitamin C supplemented group and the control group, with the dietary vitamin C intake as the only statistical difference between groups. The duathlon competition induced a significant neutrophilia, which was higher in the supplemented group. Lymphocyte antioxidant enzyme activities increased after the competition, with a higher increase in SOD activity in the control group than in the supplemented one. The competition decreased neutrophil antioxidant enzyme activities and neutrophil ascorbate concentration. The decrease in the SOD activity in the supplemented group was higher than in the control group. Finally, the duathlon competition increased the expression of MAC-1 neutrophil adhesion molecule in the supplemented group. High vitamin C intake influenced the response of neutrophils and lymphocytes to oxidative stress induced by exercise, increasing the neutrophil activation.     

Differential Response of Lymphocytes and Neutrophils to High Intensity Physical Activity and to Vitamin C Diet Supplementation

We have determined the effects of chronic vitamin C intake on neutrophil and lymphocyte antioxidant defences during the acute phase immune response induced by intense exercise. Blood samples were taken from 16 voluntary athletes in basal conditions, both immediately after and 1 h after a duathlon competition. Sportsmen's nutrient intakes were determined before the competition. After determining the basal plasmatic ascorbate levels, the results were analysed taking into account the vitamin C intake and their plasmatic levels. Two groups were constituted, the vitamin C supplemented group and the control group, with the dietary vitamin C intake as the only statistical difference between groups. The duathlon competition induced a significant neutrophilia, which was higher in the supplemented group. Lymphocyte antioxidant enzyme activities increased after the competition, with a higher increase in SOD activity in the control group than in the supplemented one. The competition decreased neutrophil antioxidant enzyme activities and neutrophil ascorbate concentration. The decrease in the SOD activity in the supplemented group was higher than in the control group. Finally, the duathlon competition increased the expression of MAC-1 neutrophil adhesion molecule in the supplemented group. High vitamin C intake influenced the response of neutrophils and lymphocytes to oxidative stress induced by exercise, increasing the neutrophil activation.     

A comprehensive analysis of heat shock protein synthesis in human peripheral lymphocytes: the effect of penicillin/streptomycin.

A reliable experimental procedure is described for the simultaneous characterisation of a comprehensive range of heat shock proteins (hsps) in human peripheral lymphocytes. In this system, a mild heat shock from 37 to 42 degrees C for 1 h induced the synthesis of hsps 105, 90, 70, 60, 57, 47, 40, 27 and 16. Densitometric analyses of 35[S]-methionine labelled protein gels indicated that levels of these hsps peaked at 3 to 4 h, following post-heat shock recovery at 37 degrees C. The presence of penicillin and streptomycin in the cell culture medium, appeared to have little effect on the kinetics of hsp synthesis. The present method can be used for relatively small blood samples and its relative ease of application and reproducibility make it appropriate for screening the expression of hsps in human lymphocytes from a range of individuals.     

Ascorbic acid decreases heat shock protein 70 and plasma corticosterone response in broilers (Gallus gallus domesticus) subjected to cyclic heat stress

It is known that ascorbic acid (AA) supplementation can ameliorate the chicken's responses to heat stress. The influence of AA on heart heat shock protein 70 (hsp70) and plasma corticosterone (CS) was evaluated in young male broiler chickens fed either no AA (N-AA) or 500 mg AA /kg (AA) and exposed to cyclic high temperatures (21 to 30 to 21 degrees C) over a 3.5 h period on three consecutive days. Dietary AA supplementation elevated plasma AA and maintained it at high levels after heating, but in N-AA birds, only heat elevated plasma AA. In N-AA fed chickens, plasma CS was elevated and was further increased by heat stress as compared with AA-fed birds. Heart hsp70 expression was greater in N-AA-fed chickens compared to AA-fed chickens, and heat stress further elevated hsp70 in both N-AA- and AA-fed birds. The hsp70 increase after heat was two-fold greater in N-AA- vs. AA-fed birds. Plasma CS and heart hsp70 were positively correlated, plasma AA and heart hsp70 were negatively correlated, and plasma CS and AA were negatively correlated. It was concluded that chickens experience a less severe stress response after exposure to high temperatures when they are provided dietary AA.     

Cloning of the ferrireductase that may be involved in iron transport in the small intestine: revisiting Crane's controversial oxidoreductase

Abstract

Objectives

Oxidative stress and inflammation have been reported to be higher in subjects with depression, but it is unclear whether this is due to inadequate dietary antioxidant intake or the pathophysiology of depression. The aim of this study was to assess the association between dietary and serum antioxidant status with depression scales in young male university students.

Methods

This research was a case–control study carried out on 60 male university students (30 students diagnosed with depression and 30 matched healthy controls). Beck Depression Inventory-II was used to assess the major depressive disorder (MDD) scales. A semi-quantitative food frequency questionnaire and 2-day 24-h recalls were used for dietary assessment. Dietary and serum total antioxidant capacity (TAC) and high-sensitive C-reactive protein (hs-CRP) concentrations were also measured.

Results

MDD subjects consumed less fruits (P < 0.05), legumes (P < 0.001), nuts and seeds (P = 0.003), vitamin C (P = 0.005), beta carotene (P < 0.001), lutein, and zeaxanthin (P = 0.006) than the controls. Moreover, the depressed group had lower serum TAC levels than their controls (P < 0.05). There were no significant differences in serum hs-CRP concentrations and dietary TAC levels between the study groups.

Discussion

Students with depression had significantly lower intake of dietary antioxidants. However, dietary TAC and serum hs-CRP levels were not significantly different between depressed and normal university male students. Intake of foods rich in antioxidants is encouraged in male students.     

Antioxidant status in humans after exposure to hyperbaric oxygen.

Hyperbaric oxygen (HBO) treatment (i.e., exposure to 100% oxygen at a pressure of 2.5 atmosphere absolute (ATA) for a total of 3 x 20 min periods) of human subjects induced DNA damage in the alkaline comet assay with leukocytes and protected against the DNA damaging effects of subsequent in vivo HBO exposures. Furthermore, blood taken 24 h after the first HBO was well protected against the in vitro induction of genotoxic effects by hydrogen peroxide. To investigate the mechanisms which led to this apparent adaptive response, we determined the antioxidant status of blood from subjects before and after HBO. We did not find differences in the plasma concentrations of the antioxidant vitamins A, C and E after HBO treatment. HBO had also no effect on the 'antioxidant power' of the plasma as measured with the FRAP-assay or on the concentration of reduced glutathione determined in the plasma or in lymphocytes. Red cell concentrate activities of superoxide dismutase, catalase, glutathione peroxidase were not influenced by HBO. In contrast, synthesis of the heat shock protein HSP70 which has been implicated to play an important role in cellular protection against oxidative stress, was significantly induced in lymphocytes after a single HBO treatment. To investigate whether intake of antioxidants may protect against HBO-induced DNA damage, we supplemented subjects with vitamin E (800 mg for 7 days) or with N-acetylcysteine (400 mg, 1 h before the HBO treatment). However, these supplementations did not influence the induction of DNA damage by HBO.