A comparative evaluation of thiobarbituric acid methods for the determination of malondialdehyde in biological materials

A novel antioxidant N-acetylcysteine amide prevents gp120- and Tat-induced oxidative stress in brain endothelial cells

Free radical production and, consequently, oxidative stress play an important role in the pathogenesis of AIDS and cause damage to lipids, proteins, and DNA. In our previous study, the HIV-1 envelope glycoprotein (gp120) and transregulatory protein (Tat) of HIV-1 have been found to induce oxidative stress in an immortalized endothelial cell line from rat brain capillaries, RBE4 (in vitro model of the blood-brain barrier). Here, we have determined the effects of a novel antioxidant, N-acetylcysteine amide (NACA), on gp120- and Tat-induced oxidative stress. Various oxidative stress parameters, including reduced glutathione (GSH), oxidized glutathione (GSSG), catalase (CAT) activity, and glutathione reductase (GR) activity, as well as malondialdehyde (MDA) levels, were used as measures of oxidative stress. NACA significantly increased the levels of intracellular GSH, CAT, and GR and decreased the levels of MDA in RBE4 cells, showing that oxidatively challenged cells were protected. Gp120- and Tat-induced increases in intracellular reactive oxygen species (ROS) were observed by using the 2',7'-DCF assay; the ROS scavenger, NACA, blocked ROS generation. A well-known apoptosis indicator, caspase-3 activity, was measured and was also found to have been returned to its control levels by NACA. Treatment of RBE4 cells with gp120 and Tat caused an increase in toxicity, as measured by lactate dehydrogenase (LDH) and tetrazolium reduction (MTS) assays. HIV-1 protein-induced toxicity in these cells was blocked by treatment with NACA. These studies show that NACA reverses gp120- and Tat-induced oxidative stress in immortalized endothelial cells.

Molecular biomarkers of oxidative stress in aquatic organisms in relation to toxic environmental pollutants

The potential of oxygen free radicals and other reactive oxygen species (ROS) to damage tissues and cellular components, called oxidative stress, in biological systems has become a topic of significant interest for environmental toxicology studies. The balance between prooxidant endogenous and exogenous factors (i.e., environmental pollutants) and antioxidant defenses (enzymatic and nonenzymatic) in biological systems can be used to assess toxic effects under stressful environmental conditions, especially oxidative damage induced by different classes of chemical pollutants. The role of these antioxidant systems and their sensitivity can be of great importance in environmental toxicology studies. In the past decade, numerous studies on the effects of oxidative stress caused by some environmental pollutants in terrestrial and aquatic species were published. Increased numbers of agricultural and industrial chemicals are entering the aquatic environment and being taken up into tissues of aquatic organisms. Transition metals, polycyclic aromatic hydrocarbons, organochlorine and organophosphate pesticides, polychlorinated biphenyls, dioxins, and other xenobiotics play important roles in the mechanistic aspects of oxidative damage. Such a diverse array of pollutants stimulate a variety of toxicity mechanisms, such as oxidative damage to membrane lipids, DNA, and proteins and changes to antioxidant enzymes. Although there are considerable gaps in our knowledge of cellular damage, response mechanisms, repair processes, and disease etiology in biological systems, free radical reactions and the production of toxic ROS are known to be responsible for a variety of oxidative damages leading to adverse health effects and diseases. In the past decade, mammalian species were used as models for the study of molecular biomarkers of oxidative stress caused by environmental pollutants to elucidate the mechanisms underlying cellular oxidative damage and to study the adverse effects of some environmental pollutants with oxidative potential in chronic exposure and/or sublethal concentrations. This review summarizes current knowledge and advances in the understanding of such oxidative processes in biological systems. This knowledge is extended to specific applications in aquatic organisms because of their sensitivity to oxidative pollutants, their filtration capacity, and their potential for environmental toxicology studies.

Antioxidant vitamins E and C as adjunct therapy of severe acute lower-respiratory infection in infants and young children: a randomized controlled trial

OBJECTIVE

To evaluate the effect of antioxidant Vitamins E and C as adjunct therapy of severe acute lower respiratory infection (ALRI) in children.

DESIGN

Randomized double-blind placebo-controlled clinical trial.

SETTING

A large childrens' hospital serving the urban poor in Kolkata, India.

SUBJECTS

Children aged 2-35 months admitted with severe ALRI.

INTERVENTION

In total, 174 children were randomly assigned to receive alpha-tocopherol 200 mg and ascorbic acid 100 mg twice daily or placebo for 5 days. All children received standard treatment for severe ALRI. Outcome measures were: time taken to recover from a very ill status, fever, tachypnoea, and feeding difficulty; and improvement in oxidative stress and immune response indicated by thiobarbituric acid reacting substances (TBARS) and response to skin antigens, respectively.

RESULTS

Recovery rate ratios (95% CI) using proportional hazards model were 0.89 (0.64-1.25), 1.01 (0.72-1.41), 0.86 (0.57-1.29), and 1.12 (0.77-1.64) for very ill status, feeding difficulty, fever, and tachypnoea, respectively. TBARS values were high and similar in the two groups at admission, discharge, and at 2 weeks follow-up. Serum alpha-tocopherol significantly increased in treated group at discharge. Immune response to skin antigens were very poor at admission and after 2 weeks, in both groups.

CONCLUSION

Infants with severe ALRI failed to benefit from two antioxidant nutrients as adjunct therapy. Severe ALRI in infants may cause cell-mediated immune dysfunction. We need a better understanding of oxidative processes in growing infants to help us better design interventions with antioxidant therapy.

Acute exercise stimulates macrophage function: possible role of NF-κB pathways

Moderate physical activity when performed on a regular basis presents a number of benefits to the whole organism, especially regarding immune system function, such as augmenting resistance to infections and to cancer growth. Although glutamine production by active muscle cells as well as neuroendocrine alterations mediated by the chronic adaptation to exercise may play a role, the entire mechanism by which exercise makes the immune system aware of challenges remains mostly uncovered. This is particularly true for the effects of an acute exercise session on immune function. In this work, circulating monocytes/macrophages from sedentary rats submitted to an acute (1 h) swimming session were tested for the ability of phagocytosing zymosan particles, phorbol myristate acetate (PMA)-induced hydrogen peroxide production, nitric oxide (NO) release (assessed by nitrate and nitrite production) and the expression of NO synthases (NOS-1, NOS-2 and NOS-3). The results showed that an exercise bout induced a 2.4-fold rise in macrophage phagocytic capacity (p = 0.0041), a 9.6-fold elevation in PMA-induced hydrogen peroxide release into the incubation media (1-h, p = 0.0022) and a 95.5%-augmentation in nitrite basal production (1-h incubation; p = 0.0220), which was associated with a marked expression of NOS-2 (the inducible NOS isoform; p = 0.0319), but not in other NOS gene products. Although NOS-2 expression is nuclear factor-kappaB (NF-kappaB)-dependent, no systemic oxidative stress was found, as inferred from the data of plasma TBARS and glutathione disulphide (GSSG) to glutathione (GSH) ratio in circulating blood erythrocytes which remained constant after the acute exercise. Also, no stressful situation seemed to be faced by monocytes/macrophages, since the expression of the 70-kDa heat shock protein (HSP70) remained unchanged. We conclude that NF-kappaB-dependent induction of NOS-2 and macrophage activation must be related to local factor(s) produced in the surroundings of monocytes/macrophages.

Effects of N-acetylcysteine amide (NACA), a novel thiol antioxidant against glutamate-induced cytotoxicity in neuronal cell line PC12

Oxidative stress plays an important role in neuronal cell death associated with many different neurodegenerative conditions such as cerebral ischemia and Parkinson's disease. Elevated levels of glutamate are thought to be responsible for CNS disorders through various mechanisms causing oxidative stress induced by a nonreceptor-mediated oxidative pathway which blocks cystine uptake and results in depletion of intracellular glutathione (GSH). The newly designed amide form of N-acetylcysteine (NAC), N-acetylcysteine amide (NACA), was assessed for its ability to protect PC12 cells against oxidative toxicity induced by glutamate. NACA was shown to protect PC12 cells from glutamate (Glu) toxicity, as evaluated by LDH and MTS assays. NACA prevented glutamate-induced intracellular GSH loss. In addition, NACA restored GSH synthesis in a Glu (10 mM) plus buthionine-sulfoximine (BSO) (0.2 mM)-treated group, indicating that the intracellular GSH increase is independent of gamma-GSC (gamma-glutamylcysteinyl synthetase). The increase in levels of reactive oxygen species (ROS) induced by glutamate was significantly decreased by NACA. Measurement of malondialdehyde (MDA) showed that NACA reduced glutamate-induced elevations in levels of lipid peroxidation by-products. These results demonstrate that NACA can protect PC12 cells against glutamate cytotoxicity by inhibiting lipid peroxidation, and scavenging ROS, thus preserving intracellular GSH.

Protective and detrimental effects of kaempferol in rat H4IIE cells: Implication of oxidative stress and apoptosis

Flavonoids are ubiquitous substances in fruits and vegetables. Among them, the flavonol kaempferol contributes up to 30% of total dietary flavonoid intake. Flavonoids are assumed to exert beneficial effects on human health, e.g., anticancer properties. For this reason, they are used in food supplements at high doses. The aim of this project was to determine the effects of kaempferol on oxidative stress and apoptosis in H4IIE rat hepatoma cells over a broad concentration range. Kaempferol is rapidly taken up and glucuronidated by H4IIE cells. The results demonstrate that kaempferol protects against H2O2-induced cellular damage at concentrations which lead to cell death and DNA strand breaks in the absence of H2O2-mediated oxidative stress. Preincubation with 50 microM kaempferol exerts protection against the loss of cell viability induced by 500 microM H2O2 (2 h) while the same concentration of kaempferol reduces cell viability by 50% in the absence of H2O2 (24 h). Preincubation with 50 microM kaempferol ameliorates the strong DNA damage induced by 500 microM H2O2 while 50 microM kaempferol leads to a significant increase of DNA breakage in the absence of H2O2. Preincubation with 50 microM kaempferol reduces H2O2-mediated caspase-3 activity by 40% (4 h) while the same concentration of kaempferol leads to the formation of a DNA ladder in the absence of H2O2 (24 h). It is concluded that the intake of high dose kaempferol in food supplements may not be advisable because in our cellular model protective kaempferol concentrations can also induce DNA damage and apoptosis by themselves.

Method development and validation for monitoring in vivo oxidative stress: evaluation of lipid peroxidation and fat-soluble vitamin status by HPLC in rat plasma

Monitoring in vivo oxidative stress implicates the evaluation of damage and defence parameters by well-established, validated methods. We report two optimized and validated HPLC methods for measurement of malondialdehyde (MDA) and fat-soluble vitamins in rat plasma. For the MDA method, optimization experiments of the thiobarbituric acid test resulted in the addition of 1% butylhydroxytoluene to the reaction mixture and in a heating time reduction to 40 min, ensuring inhibition of further lipid peroxidation during the test. Validation experiments showed good linearity, precision and recovery. The use of HPLC with coulometric array detection technology permits simultaneous and sensitive analysis of different fat-soluble vitamins and related compounds (tocopherols, retinoids, carotenoids and coenzyme Q10), which are identified by both retention time and electrochemical characteristics. Furthermore, this method is extended to the analysis of coenzyme Q9, the predominant homologue in rats. Validation experiments with rat plasma gave good results.

Effects of airborne fine particulate matter on antioxidant capacity and lipid peroxidation in multiple organs of rats

The purpose of this research was to determine whether airborne fine particulate matter (PM(2.5)) could increase levels of lipid peroxidation and alter intracellular redox status in multiple organs of rats. Thirty-two male Wistar rats were randomly divided into the treated groups using PM(2.5) at different dosages (1.5, 7.5, 37.5 mg/kg) and with a control group using saline. Rats were sacrificed 24 h after one-time intratracheal instillation. Then we investigated the activities of Cu, Zn-superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and the levels of glutathione (GSH) and thiobarbituric acid-reactive substances (TBARS) in hearts, livers, spleens, lungs, kidneys, brains, and testicles. It was found that PM(2.5) at dosages of 7.5 and 37.5 mg/kg significantly increased lipid peroxidation levels in the hearts, livers, lungs, and testicles, decreased SOD, CAT, and GPx activities in the lungs, livers, kidneys, and brains, and depleted GSH levels in all the measured organs compared to the control. There were also differences in the changes of antioxidative enzymes activities and lipid peroxidation levels in seven organs. These results led to a conclusion that airborne PM(2.5) was a systemic toxic agent, not only to respiratory and cardiovascular systems. Its toxic effects might be attributed to oxidative damage mediated by prooxidant/antioxidant imbalance or excess free radicals. Further work is required to explain the toxicity role of PM(2.5) on multiple organs of mammals.

Lipid peroxidation measurement by thiobarbituric acid assay in rat cerebellar slices

Lipid peroxidation by reactive oxygen species (ROS) is known to be involved in the damaging mechanism of several acute and chronic brain disorders. The most prominent and currently used assay as an index for lipid peroxidation products is the thiobarbituric acid assay (TBA test). It is based on the reactivity of an end product of lipid peroxidation, malondialdehyde (MDA) with TBA to produce a red adduct. However, it is known that the MDA levels are frequently overestimated, that the reaction lacks specificity and mainly reflects the susceptibility of brain tissue to the generation and degradation of newly formed lipid hydroperoxides under the TBA test conditions. The present paper shows that artifactual lipid peroxidation by TBA test conditions can be prevented and that the MDA level overestimation can be minimized in cerebellar slices. This can be done by incubating the slices in a continuous tissue perfusion system, by adding butylated hydroxytoluene (BHT) to the homogenization solutions and by carrying out the assay anaerobically on deproteinizated supernatants of cerebellar slice homogenates. The present research also showed that lipid peroxidation products generated during incubation of the slices by hydrogen peroxide (H2O2) could be measured without artifactual interference by the TBA test conditions.

Effects of N-acetylcysteine on lead-exposed PC-12 cells

The neurotoxicity of lead has been well established through numerous studies. However, the cellular processes of lead neurotoxicity, as well as techniques to prevent or reverse cellular damage after lead exposure, remain unknown. If oxidative stress plays a primary role in lead-induced neurotoxicity, antioxidants should assist in reviving lead-exposed cells. The present study explores N-acetylcysteine (NAC) as an antioxidant agent in PC-12 cells after lead exposure. Selective oxidative stress parameters, including glutathione (GSH), glutathione disulfide (GSSG), and malondialdehyde (MDA), were measured in PC-12 cells exposed to various concentrations of lead acetate. Administering NAC after lead exposure improved cell survival as measured by Trypan Blue exclusion. NAC treatment also increased the GSH/GSSG ratio compared to the lead-only group, and reduced MDA to near control levels. These results imply that NAC protects cells from lead-induced oxidative damage by boosting the PC-12 cells' antioxidant defense mechanisms.

HIV-1 viral proteins gp120 and Tat induce oxidative stress in brain endothelial cells

The blood-brain barrier (BBB) has an important role in the development of AIDS dementia. The HIV-1 envelope glycoprotein (gp120) and transregulatory protein (Tat) of HIV-1 are neurotoxic and cytotoxic and have been implicated in the development of HIV dementia. They are known to cause oxidative stress and are associated with disruption of the BBB. Here, we used an immortalized endothelial cell line from rat brain capillaries, RBE4, to determine whether gp120 and Tat can induce oxidative stress in an in vitro model of the BBB. RBE4 cells were exposed to gp120 or Tat and the levels of reduced glutathione (GSH), oxidized glutathione (GSSG), catalase (CAT) activity, glutathione peroxidase (GPx) activity, and glutathione reductase (GR) activity, and malondialdehyde (MDA) used as measures of oxidative stress. Both gp120 and Tat significantly decreased the levels of intracellular GSH, GPx, and GR and increased the levels of MDA in RBE4 cells, showing that the cells were oxidatively challenged. The ratio of GSH/GSSG, a widely accepted indicator of oxidative stress, was also significantly decreased. These studies show that both of these viral proteins can induce oxidative stress in immortalized BBB endothelial cells.

Biomarkers of oxidative stress study II: are oxidation products of lipids, proteins, and DNA markers of CCl4 poisoning?

Oxidation products of lipids, proteins, and DNA in the blood, plasma, and urine of rats were measured as part of a comprehensive, multilaboratory validation study searching for noninvasive biomarkers of oxidative stress. This article is the second report of the nationwide Biomarkers of Oxidative Stress Study using acute CCl4 poisoning as a rodent model for oxidative stress. The time-dependent (2, 7, and 16 h) and dose-dependent (120 and 1200 mg/kg i.p.) effects of CCl4 on concentrations of lipid hydroperoxides, TBARS, malondialdehyde (MDA), isoprostanes, protein carbonyls, methionine sulfoxidation, tyrosine products, 8-hydroxy-2'-deoxyguanosine (8-OHdG), leukocyte DNA-MDA adducts, and DNA-strand breaks were investigated to determine whether the oxidative effects of CCl4 would result in increased generation of these oxidation products. Plasma concentrations of MDA and isoprostanes (both measured by GC-MS) and urinary concentrations of isoprostanes (measured with an immunoassay or LC/MS/MS) were increased in both low-dose and high-dose CCl4-treated rats at more than one time point. The other urinary markers (MDA and 8-OHdG) showed significant elevations with treatment under three of the four conditions tested. It is concluded that measurements of MDA and isoprostanes in plasma and urine as well as 8-OHdG in urine are potential candidates for general biomarkers of oxidative stress. All other products were not changed by CCl4 or showed fewer significant effects.

Role of seminal plasma in damage to turkey spermatozoa during in vitro storage

In vitro storage of turkey spermatozoa is performed without consideration of the potential role of seminal plasma on sperm functions. We report the effects of seminal plasma on membrane permeability, lipid metabolism, energy status, motility and fertility of turkey spermatozoa stored at 4 or 20 degrees C. Phospholipid content (1077 nmol/10(9) spz versus 1219 nmol/10(9) spz at 48 h) and membrane permeability of spermatozoa were significantly damaged by the presence of seminal plasma after 48 h of storage at 4 degrees C, whereas damage to ATP content and fertility occurred earlier damaged by this presence (fertility after 24h storage 51% with seminal plasma versus 71% without). At 20 degrees C, seminal plasma decreased the phospholipid content of spermatozoa in the first hour of storage (1326 nmol/10(9) spz versus 1636 nmol/10(9) spz). Twenty-four hours later, this effect was masked by intense lipid peroxidation. These results show that seminal plasma is deleterious to storage of turkey spermatozoa at 4 degrees C and is involved in phospholipid metabolism of spermatozoa. Lipid peroxidation could be responsible for the acceleration of the degradation of sperm phospholipids during storage at 20 degrees C. However, lipid peroxidation seems not to be active at 4 degrees C. In this case, we suggest that phospholipase activation may contribute to sperm degradation, especially in the presence of seminal plasma.

Low concentrations of flavonoids are protective in rat H4IIE cells whereas high concentrations cause DNA damage and apoptosis

Dietary flavonoids possess a wide spectrum of biochemical and pharmacological actions and are assumed to protect human health. These actions, however, can be antagonistic, and some health claims are mutually exclusive. The antiapoptotic actions of flavonoids may protect against neurodegenerative diseases, whereas their proapoptotic actions could be used for cancer chemotherapy. This study was undertaken to determine whether a cytoprotective dose range of flavonoids could be differentiated from a cytotoxic dose range. Seven structurally related flavonoids were tested for their ability to protect H4IIE rat hepatoma cells against H(2)O(2)-induced damage on the one hand and to induce cellular damage on their own on the other hand. All flavonoids proved to be good antioxidants in a cell-free assay. However, their pharmacologic activity did not correlate with in vitro antioxidant potential but rather with cellular uptake. For quercetin and fisetin, which were readily taken up into the cells, protective effects against H(2)O(2)-induced cytotoxicity, DNA strand breaks, and apoptosis were detected at concentrations as low as 10-25 micromol/L. On the other hand, these flavonoids induced cytotoxicity, DNA strand breaks, oligonucleosomal DNA fragmentation, and caspase activation at concentrations between 50 and 250 micromol/L. Published data on quercetin pharmacokinetics in humans suggest that a dietary supplement of 1-2 g of quercetin may result in plasma concentrations between 10 and 50 micromol/L. Our data suggest that cytoprotective concentrations of some flavonoids are lower by a factor of 5-10 than their DNA-damaging and proapoptotic concentrations.

Incremento de las concentraciones séricas de malondialdehído y glutatión reducido en pacientes con cardiopatía isquémica crónica estable

BACKGROUND AND OBJECTIVE

Cardiovascular diseases are associated with the ischemia/reperfusion phenomena and therefore to the oxidation/antioxidation balance. The aim of this study was to determine malondialdehyde, nitric oxide, glutathione, ascorbic and dehydroascorbic acid in patients with chronic ischemic heart disease.

PATIENTS AND METHOD

32 male patients, with chronic ischemic heart disease, between 40 and 60 years of age were studied. These individuals were divided in two groups: 16 with hypertension and 16 without hypertension. Both groups were compared with 31 healthy male subjects (control group).

RESULTS

Significant differences (p < 0.001) was observed in malondialdehyde between no-hypertension ischemic group: 5.3 (1.5) microM and the hypertension ischemic group: 4.8 (1.3) microM in contrast with the healthy group: 2.2 (0.5) microM. Hypertension ischemic group showed significant greater reduced glutation levels: 286.1 (31.4) microg/ml than control group 262.0 (38.8) microg/ml; p < 0.03 and no-hypertension ischemic group: 256.4 (41.5) microg/ml; p < 0.02. No significant difference in the rest of the parameters for all study groups.

CONCLUSIONS

Oxidation/antioxidation balance during chronic ischemic heart disease can be considered as a good metabolic ischemia indicator, that used in the monitoring and therapeutic evaluation could detect molecular changes that anticipate installation of tissue damage.

Processed tomato products as a source of dietary lycopene: bioavailability and antioxidant properties

Oxidative stress is one of the major contributors to increased risk of chronic diseases. A diet rich in tomatoes and tomato products containing lycopene, a carotenoid antioxidant, has been found to protect against these chronic diseases by mitigating oxidative damage. The study aim was to evaluate the effects of a long-term tomato-rich diet, consisting of various processed tomato products, on bioavailability and antioxidant properties of lycopene. Seventeen healthy human subjects (ten men, seven non-pregnant women) participated in the study. Following a two-week washout period during which subjects avoided foods containing lycopene, all subjects consumed test tomato products including tomato juice, tomato sauce, tomato paste, ketchup, spaghetti sauce, and ready-to-serve tomato soup providing 30 mg of lycopene a day for four weeks. At the end of treatment, serum lycopene level increased significantly (p <0.05), from 181.79 +/- 31.25 to 684.7 +/- 113.91 nmol/L. Similarly, total antioxidant potential increased significantly (p <0.05), from 2.26 +/- 0.015 to 2.38 +/- 0.17 mmol/L Trolox equivalent. Lipid and protein oxidation was reduced significantly (p <0.05). The results suggest that a tomato-rich diet containing different sources of lycopene can increase serum lycopene levels and reduce oxidative stress effectively.

Phototoxicity, distribution and kinetics of association of UVA-activated chlorpromazine, 8-methoxypsoralen, and 4,6,4′-trimethylangelicin in Jurkat cells

Extracorporeal phototherapy (ECP) is a therapeutic approach based on photobiological effects of 8-methoxypsoralen (8-MOP) on white blood cells isolated from the blood, exposed to UVA and then reinfused into the patient. 8-MOP is presently the only drug approved for clinical application of ECP; therefore, identification of other photosensitizers with better photochemical and pharmacokinetic properties might enhance the efficacy of this treatment modality. Among such alternative drugs are 4,6,4'-trimethylangelicin (TMA) and chlorpromazine (CPZ), which have previously been studied in an animal model for ECP. In this current study, cellular bioavailability of 8-MOP, TMA and CPZ was investigated in vitro, using low doses of UVA relevant for the clinical setting of ECP. Our fluorescence microscopy study revealed that 8-MOP and CPZ penetrated readily into the cells, where they accumulated with similar kinetics. No distinct fluorescence was observed in cells incubated with TMA. We found that the phototoxic efficiency of 8-MOP was an order of magnitude greater than that of CPZ, i.e., to obtain a similar reduction in survival of cells subjected to photosensitization by the drugs, the concentration of CPZ needed to be 10 times higher than that of 8-MOP. The photoactivated TMA exhibited the highest pro-apoptotic efficiency. A clear indication of photoinduced formation of reactive oxygen species and peroxidation of lipids was observed only in CPZ-sensitized cells, suggesting different mechanisms for phototoxicity mediated by CPZ and by the two furocoumarins.

The inhibitory effect of flaxseed on the growth and metastasisof estrogen receptor negative human breast cancer xenograftsis attributed to both its lignan and oil components

Our previous studies have shown that dietary flaxseed (FS) can reduce the growth and metastasis of human estrogen receptor negative (ER-) breast cancer in nude mice. The aims of our study were to determine (i) whether the tumor inhibitory effect of FS was due to its oil (FO), lignan secoisolariciresinol diglycoside (SDG), or both components, and (ii) whether the effect on tumor growth was related to increased lipid peroxidation. Athymic nude mice were orthotopically injected with ER- breast cancer cells (MDA-MB-435) and 8 weeks later were fed either the basal diet (BD) or BD supplemented with 10% FS, SDG, FO, or combined SDG and FO (SDG + FO) for 6 weeks. The SDG and FO levels were equivalent to the amounts in the 10% FS. Compared to the BD group, the tumor growth rate was significantly lower (p < 0.05) in the FS, FO, and SDG + FO groups, in concordance with decreased cell proliferation and increased apoptosis; however, these did not significantly relate to the lipid peroxidation, indexed as malonaldehyde (MDA), in the primary tumors. Lung metastasis incidence was reduced (16-70%) by all treatments, significantly in the FS and SDG + FO groups. The distant lymph node metastasis was significantly decreased (52%) only in the FO group. Although the total metastasis incidence was lowered (42%) significantly only in the SDG + FO group, all treatment groups did not differ significantly. In conclusion, FS reduced the growth and metastasis of established ER- human breast cancer in part due to its lignan and FO components, and not to lipid peroxidation.

Supplementation with antioxidant micronutrients and chemotherapy-induced toxicity in cancer patients treated with cisplatin-based chemotherapy: a randomised, double-blind, placebo-controlled study

Cisplatin-induced toxicities are mainly caused by the formation of free radicals, leading to oxidative organ damage. Plasma concentrations of antioxidants decrease significantly during cisplatin chemotherapy for cancer. Forty-eight cancer patients treated with cisplatin-based chemotherapy were randomised in a double-blind manner to receive either supplementation with vitamin C, vitamin E and selenium dissolved in a beverage or to receive a placebo beverage. Primary outcome measures were the amount of nephrotoxicity and ototoxicity induced by cisplatin. No significant differences were found between the two study groups with respect to these primary outcome measures. However, patients who achieved the highest plasma concentrations of the three antioxidant micronutrients had significantly less loss of high-tone hearing. In addition, significant correlations were found between the reduced/oxidised vitamin C ratio and malondialdehyde (MDA), markers of oxidative stress, and cisplatin-induced ototoxicity and nephrotoxicity. The lack of protection against cisplatin-induced toxicities in patients in the intervention arm may be related to poor compliance and/or inadequate supplementation. Supplementation with a higher dose (intensity) and in combination with other antioxidants should be investigated further.

Impairment of cell and plasma redox state in subjects professionally exposed to chromium

BACKGROUND

Chromium (Cr) is widely used in chemical, tannery, building, and metal industries. More recently, it has been demonstrated that Cr induces oxidative stress in mouse brain. Nevertheless very few data exist on in vivo oxidative damage in humans exposed to Cr.

METHODS

Changes in antioxidant parameters both in plasma (acid ascorbic redox state and total antioxidant capacity) and in red blood cells (glutathione (GSH) redox state) of 40 subjects (age 37.65 +/- 7.46; M/F 20/20) professionally exposed to Cr who were recruited from metal, chemistry, and building industries were evaluated. We also evaluated the levels of lipoperoxidation (thiobarbituric acid-reactive material, TBA-RM) and thiol levels in plasma to assess the extent of oxidative stress state. To evaluate Cr exposure rate, we measured urinary-chromium (U-Cr) by an electrothermic atomization-atomic absorption spectrometry (ETA-AAS) method.

RESULTS

In this study, we found that Cr exposure induced a decrease both in GSH (P < 0.0005) and GSH/oxidized glutathione (GSSG) ratio (P < 0.0001) in red blood cells from workers with respect to control subjects. Furthermore, we also demonstrated a significant decrease of plasma acid ascorbic levels (45.7 +/- 14.9 vs. 53.5 +/- 16.5 micromol/L; P < 0.05) and in total plasma antioxidant capacity (1,126.3 +/- 212.2 vs. 1,266.9 +/- 207.8 micromol/L; P < 0.05) in subjects exposed to Cr. No difference was found with regard to TBA-RM and thiol levels.

CONCLUSIONS

This study demonstrated that in humans, an oxidative stress occurs for Cr exposures as low as those considered safe. This oxidative stress appears to be able to affect intracellular and plasmatic antioxidant defense.

Response of rat alveolar type II cells and human lung tumor cells towards oxidative stress induced by hydrogen peroxide and paraquat

The expression of MDR1b coding mRNA is increased in alveolar type II cells from juvenile rat lung in culture. Hydrogen peroxide and paraquat-induced further upregulation supporting that oxidative stress mediated mechanisms are involved in the regulation of MDR1b in rat lung. The expression rates of mRNA for catalase, Cu/Zn-superoxide dismutase (Cu/Zn-SOD) and Mn-superoxide dismutase (Mn-SOD) remains constant during culture and were not modulated by hydrogen peroxide or paraquat. Thus, antioxidative enzymes in primary A II cells from rat lung are not regulated by reactive oxygen species dependent mechanisms. Primary A II cells were substantially more sensitive towards paraquat-induced cytotoxicity and lipid peroxidation than the permanent human lung tumor cell lines H322 and H358. A 100 microM hydrogen peroxide for 2h induces substantial DNA damage which is not paralleled by an increased rate of lipid peroxidation. The expression rate of mRNA coding for catalase and Mn-SOD was not changed and almost the same is true for the activity of catalase and Cu/Zn-SOD. Only 50 microM paraquat induced a significant decrease in catalase activity and an increase in Cu/Zn-SOD activity.

Association of Lipid Peroxidation with Antenatal Betamethasone and Oxygen Radical Disorders in Preterm Infants

INTRODUCTION

Premature infants are highly susceptible to 'oxygen radical diseases' (ORD), including bronchopulmonary dysplasia, intraventricular hemorrhage/white matter injury, retinopathy of prematurity, and necrotizing enterocolitis. The incidence of ORD is reduced following antenatal treatment with betamethasone. Oxidant-mediated injury is characterized at the cellular level by peroxidation of lipid membranes. This results in the generation of malondialdehyde (MDA), which can be quantified indirectly by measurement of thiobarbituric acid-reacting substances (TBARS). There is currently no effective way to quantify the risk for ORD. In this study, we analyzed the correlation of early urinary MDA and TBARS with prenatal betamethasone administration and with the development of ORD.

METHODS

Preterm infants (<30 weeks gestation, n = 25) born at St. Peter's University Hospital were enrolled. Urine samples were collected during the first 10 days of life and stored at -70 degrees C for 0-21 days. TBARS were quantified by spectrophotometric assay, and malondialdehyde levels measured by HPLC. Subjects were screened for the subsequent development of ORD. Betamethasone administration was defined as one or more doses > or =24 h prior to delivery.

RESULTS

Urinary MDA levels increased on days 2-3 and 5-10 relative to day 1 from birth. Maximal urinary MDA concentrations were significantly higher in the ORD group compared to controls, and there was a trend toward increased urinary TBARS in the presence of ORD. Infants receiving prenatal betamethasone demonstrated higher maximal urinary TBARS values during the first 10 days of life than control infants. The length of sample storage from 0 to 3 weeks at -70 degrees C did not significantly affect TBARS measurements.

CONCLUSIONS

Elevated urinary MDA measurements in the first 10 days are correlated with the risk for ORD. Urinary TBARS concentrations, which are correlated with MDA measurements, can be quantified rapidly and are stable for short-term storage. Our findings suggest that urinary TBARS may be adaptable as a practical tool for assessing the risk for ORD in neonatal intensive care unit patients, allowing clinicians to optimize the use of preventive strategies. Antenatal betamethasone is associated with increased urinary TBARS in the first 10 days of life, indicating that the protective effects of corticosteroids are not mediated through reductions in oxidant-mediated lipid peroxidation.

Impact of changes in composition of storage medium on lipid content and quality of turkey spermatozoa

Turkey semen quality is damaged by long term in vitro storage. The objective of the present study was to determine whether changes in energy substrates and antioxidants of semen extender could limit loss of quality and lipid content of turkey spermatozoa during storage. Spermatozoa were incubated in extenders based on Beltsville Poultry Semen Extender (BPSE) to which different energy substrates (acetate, pyruvate and hydroxybutyric acid) or antioxidant (Vitamin E) had been added. Semen was stored at 4 degrees C for 48 h and changes in quality, phospholipid and malondialdehyde (MDA) content of semen were evaluated. Among the different substrates studied, only acetate was able to limit the loss of motility and ATP content after 48 h in vitro storage. Losses of spermatozoal phospholipids were similar when gametes were incubated in an extender without any substrate or in normal BPSE (784-675nmol/10(9) spz versus 837-703 nmol/10(9) spz). However, motility and ATP content were significantly more affected after 48 h of storage in samples incubated without substrates than in BPSE (motility, 2.2 versus 0; ATP, 10 nmol/10(9) spz versus 3 nmol/10(9) spz). The addition of Vitamin E to the extender did not modify either the MDA or phospholipid content of fresh or stored spermatozoa, but increased the motility of stored semen. In conclusion, acetate is an essential substrate for in vitro storage. Spermatozoal phospholipids decreased during storage, but this did not seem to originate from metabolism of endogenous fatty acids. The positive effects of Vitamin E on semen storage did not originate from preservation of lipid oxidation.

Oxidative stress in childhood—in health and disease states

The accumulated information concerning the involvement of reactive oxygen species in many clinical disorders and disease states has led to the potential for intervention with antioxidants in these cases. There are currently numerous clinical trials involving administration of antioxidants in a variety of conditions such as coronary heart disease, cataract, cancer and neurodegenerative diseases. At the same time therapeutic trials aimed at preventing and delaying the aging process are also under investigation. Numerous disorders, in childhood, have also been linked to oxidative damage. The aim of this review is to provide an overview of oxidative stress, its mechanisms, targets and damage incurred, as pertaining specifically to clinical disorders during childhood. The defense mechanisms against oxidation; the enzymatic antioxidants and low molecular weight antioxidants are defined and a number of methods commonly used for evaluation of oxidative stress (methods for measurement of lipid and protein oxidation end products and methods for measurement of antioxidant defense capacity) described. Specific diseases related to oxidative stress in infancy and childhood are reviewed and the possible effect of nutritional intake on oxidative stress in the healthy child discussed. Other issues addressed include the ability of oxidative stress, as measured in plasma to reflect intratissue oxidation, the need for a simple laboratory method for characterization of an oxidative stress 'profile', the proposed role of oxidative stress in biological processes pertaining to growth and maturation and possible implications of unrestricted antioxidant supplementation.

Increased Serum Malondialdehyde and Decreased Nitric Oxide Within 24 Hours of Thrombotic Stroke Onset

BACKGROUND AND PURPOSE

Ischemia/reperfusion generates free oxygen radicals, which react with the unsaturated lipids of biomembranes resulting in the generation products such as malondialdehyde. Malondialdehyde could be a sensor for tissue damage and reperfusion. Nitric oxide, released due to the early arrival of leukocytes in the brain parenchyma, could be a sensor for nonflow phenomenon. Thereby, the purpose of this research was to evaluate the behavior of malondialdehyde and nitric oxide within the 24 hours after the stroke onset.

METHODS

Fifteen patients up to an age of 49 years, admitted to the emergency of University Hospital and Chiquinquirá Hospital in Maracaibo, Venezuela, were examined by a neurologist and underwent 12-lead electrocardiograms and computed tomography for the diagnosis of thrombotic stroke. Serum malondialdehyde and nitric oxide were measured as thiobarbituric acid adducts and total nitrites. Data were collected within the 24 hours after the stroke onset.

RESULTS

Malondialdehyde for patients with stroke had a significant increase (P<0.001) when compared with healthy controls (47.9 +/- 7.1 vs. 1.7 +/- 0.2 micromol/L). Conversely, serum nitric oxide for patients with stroke had a significant decrease (P<0.001) when compared with the control group (14.5 +/- 1.4 vs. 41.3 +/- 3.7 micromol/L). The lowest values of malondialdehyde and the highest values of nitric oxide were observed in two patients, who died.

CONCLUSIONS

Serum levels of malondialdehyde increase, and serum levels of nitric oxide diminish within 24 hours after the onset of thrombotic stroke onset. This suggests that serum malondialdehyde level could be used as potentially reliable and sensitive marker for reperfusion, whereas nitric oxide levels could acts as potential biochemical sensor for nonreflow phenomenon.

Antioxidants protect primary rat hepatocyte cultures against acetaminophen-induced DNA strand breaks but not against acetaminophen-induced cytotoxicity

Acetaminophen, a safe analgesic when dosed properly but hepatotoxic at overdoses, has been reported to induce DNA strand breaks but it is unclear whether this event preceeds hepatocyte toxicity or is only obvious in case of overt cytotoxicity. Moreover, it is not known whether the formation of reactive oxygen species (ROS) is involved in the formation of the DNA strand breaks. In the present study, the dose-response curves for cytotoxicity and DNA strand breaks and the response to antioxidant protection have been compared. In primary hepatocytes from untreated male rats, cytotoxicity as measured by the MTT test and by Neutral Red accumulation was obvious at 10 mM acetaminophen but DNA strand breaks as measured by the comet assay were only found at 25-30 mM acetaminophen. Non-cytotoxic concentrations of three compounds with antioxidant activity, the glutathione precursor N-acetylcysteine (100 micro M), the plant polyphenol silibin (25 micro M) and the antioxidant vitamin alpha-tocopherol (50 micro M), were not able to inhibit acetaminophen toxicity at any acetaminophen concentration, while they completely prevented the formation of DNA strand breaks at 25-30 mM acetaminophen. The occurrence of oxidative stress in our experiments was indicated by a slight increase of malondialdehyde formation at 40 mM acetaminophen and by an adaptive increase in catalase mRNA concentration. We conclude that in acetaminophen-treated hepatocytes ROS-independent cell death and ROS-dependent DNA strand breaks occur which appear not to be causally related as judged from their dose dependency and their response to antioxidants.

Bound malondialdehyde in foods: bioavailability of N,N'-di-(4-methyl-1,4-dihydropyridine-3,5-dicarbaldehyde)lysine

Reactions between lipid peroxidation products and proteins in foods have detrimental nutritional effects, most importantly, losses of essential amino acids. One of the major products of the reaction of malondialdehyde and alkanals with amino groups are 4-substituted 1,4-dihydropyridine-3,5-dicarbaldehyde derivatives. The product of the reaction of lysine with malondialdehyde and acetaldehyde, N,N'-di-(4-methyl-1,4-dihydropyridine-3,5-dicarbaldehyde)lysine (MDDL), has been synthesized and used for in vitro and in vivo bioavailability studies. Release of free lysine did not occur in incubations of MDDL with tissue homogenates. After oral administration of radioactively labeled MDDL, radioactivity was only recovered in feces. Radioactivity was not incorporated into hepatic microsomes after intraperitoneal administration, which would have indicated release of available lysine. These results show that MDDL is a form of unavailable lysine, because it is not metabolized to free lysine and cannot be absorbed from the gut. Thus, formation of this derivative in foods would result in loss of available lysine.

Utility of the TBARS assay in detecting oxidative stress in white sucker (Catostomus commersoni) populations exposed to pulp mill effluent

Recent evidence indicates that contaminant-stimulated free radical production and resulting oxidative damage may be an important mechanism of toxicity in organisms exposed to water-borne contaminants. This study tested the hypothesis that increases in oxidative stress and associated biochemical alterations would be present in white sucker (Catostomus commersoni) living in an environment receiving pulp mill effluent. Consistent increases in liver TBARS and frequent increases in gonadal TBARS were observed immediately downstream of the pulp mill effluent discharge; observable effects were attenuated with distance until they were not significantly different from reference values. Increases detected with the TBARS assay were commensurate with increases detected using the lipid hydroperoxides assay, a mechanistically independent technique. Fish exposed to pulp mill effluent also exhibited significant increases in hepatic free iron and ascorbic acid and a reduced free radical scavenging capacity in the livers of fish downstream of the effluent discharge relative to reference fish. Increases in oxidative stress are not necessarily dependent on increases in lipid substrate or related to reductions in ascorbic acid. TBARS values similar to those observed in fish resident below pulp mill effluent discharges were observed in white sucker 2 h after intraperitoneal injection using 15 mg/kg body weight ferric nitrilotriacetate (Fe(3+) NTA) as a positive control. This study indicates oxidative stress could be a mechanism of toxicity in fish exposed to pulp mill effluent and demonstrates the utility of TBARS in delineating zones of exposure to pulp mill effluent.

Effect of ingestion of thermally oxidized sunflower oil on the fatty acid composition and antioxidant enzymes of rat liver and brain in development

BACKGROUND

The current study was undertaken to assess the effects of oxidized sunflower oil ingestion (obtained by heating at 98 degrees C with air insufflation during 48 h and incorporated at 5% in a fat-free diet) on liver and brain fatty acid composition, and some serum parameters and protective enzymes against peroxidation (glutathione peroxidase, glutathione reductase, catalase and glucose-6-phosphate dehydrogenase).

RESULTS

The main results show that the oxidized oil contains 262 mmol/kg of hydroperoxides, 5.7% of the esters are oxidized and 50.4% are polymerized. In the liver, we noticed that oxidized oil exercises a toxic effect as confirmed by the increase in the thiobarbituric acid reactive substance (TBARS) concentration. In the same way, we noticed that vitamin E exercises a favorable effect in the preservation against free radicals and lipid peroxidation; however, it cannot ensure this protection alone. In the liver, only glutathione peroxidase and glutathione reductase activities were positively correlated with the TBARS concentration. In the treated groups, we also noted changes in the fatty acid profiles of liver and brain homogenates, essentially by the appearance of trans fatty acid (18:1 trans) and an increase in arachidonic acid content.

Reproductive period affects lipid composition and quality of fresh and stored spermatozoa in Turkeys

Semen of Turkeys between 31 and 52 weeks of age was analyzed to investigate the cause of reduction in Turkey fertility at the end of the reproductive period. Sperm motility and viability, lipid concentration, fatty acid composition and lipid peroxides were evaluated on fresh spermatozoa or spermatozoa stored for 48h at 4 degrees C. Fertility of fresh semen was also evaluated. Fertility obtained with fresh semen decreased at 44-47 weeks of age. Ageing was also accompanied by a decrease in sperm viability (at 47 weeks) and later by a decrease in motility of spermatozoa (at 52 weeks). Polyunsaturated fatty acids (PUFAs) were the first lipids of fresh spermatozoa affected by age, especially n-3 and n-9 PUFAs. Changes in these PUFAs were followed by a 30% increase in lipid peroxidation at 47 and 52 weeks of age and a reduction in phospholipid content at 52 weeks. In vitro storage did not cause lipid peroxidation in sperm obtained during the first half of the reproductive period but malondialdehyde (MDA) levels significantly increased in sperm obtained during the second half of this period. In vitro storage also decreased phospholipid content of spermatozoa from 41 weeks of age, and viability and motility regardless of age. In conclusion, lipid alteration mainly originating from PUFAs peroxidation could partly explain the decrease in semen quality and fertility observed with ageing. In addition, lipid peroxidation was increased during in vitro storage of spermatozoa from older Turkeys.

Determination of free malondialdehyde in human serum by high-performance liquid chromatography

Lipid peroxidation involves the oxidative deterioration of polyunsaturated fatty acids in biomembranes and generates a variety of aldehydic products including malondialdehyde (MDA). To demonstrate the occurrence of lipid peroxidation in biological systems, the production of MDA has been shown to be a relevant indicator. Therefore, we describe a new method for measurement of free malondialdehyde in human serum. A simple, rapid but sensitive method for determination of MDA in human serum was applied to goiter patients and control groups. Patients with goiter had high levels of MDA compared to control groups. Our method is fast and practical for clinical measurements. The detection limit was found to be 1.2 x 10(-8) mol L(-1).

Bound malondialdehyde in foods: bioavailability of the N-2-propenals of lysine

The lipid peroxidation product malondialdehyde is mostly bound to proteins in foods as an N-2-propenal derivative that is released as N-epsilon-(2-propenal)lysine by digestive enzymes. N-2-Propenals have been identified as the major forms of malondialdehyde in urine. To determine whether available lysine can be released from the N-2-propenals of lysine in vivo, two preparations containing N-epsilon-(2-propenal)lysine and N-alpha-(2-propenal)lysine or N,N'-di-(2-propenal)lysine were synthesized using radioactively labeled lysine and were administered to rats by gastric intubation and intraperitoneal injection. Both preparations were absorbed from the digestive tract, although not as efficiently as free lysine, but most of the radioactivity was excreted in urine. The radioactive label was also readily excreted after intraperitoneal injection. It is concluded that the N-2-propenals of lysine are fairly stable in vivo, so that, although they are absorbed from the gut, most of the absorbed material is not metabolized and is readily excreted as nonavailable lysine.

Protein and thiol oxidation in cells exposed to peroxyl radicals is inhibited by the macrophage synthesised pterin 7,8-dihydroneopterin

Monocyte cells are exposed to a range of reactive oxygen species (ROS) when they are recruited to a site of inflammation. In this study, we have examined the damage caused to the monocyte-like cell line U937 by peroxyl radicals and characterised the protective effect of the macrophage synthesised compound 7,8-dihydroneopterin. Exposure of U937 cells to peroxyl radicals, generated by the thermolytic breakdown of 2,2'-azobis(amidinopropane) dihydrochloride (AAPH), resulted in the loss of cell viability as measured by thiazolyl blue (MTT) reduction, and lactate dehydrogenase (LDH) leakage. The major form of cellular damage observed was cellular thiol loss and the formation of reactive protein hydroperoxides. Peroxyl radical oxidation of the cells only caused a small increase in cellular lipid oxidation measured. Supplementation of the media with increasing concentrations of 7,8-dihydroneopterin significantly reduced the cellular thiol loss and inhibited the formation of the protein hydroperoxides. High performance liquid chromatography (HPLC) analysis showed 7,8-dihydroneopterin was oxidised by both peroxyl radicals and preformed protein hydroperoxides to predominately 7,8-dihydroxanthopterin. The possibility that 7,8-dihydroneopterin is a cellular antioxidant protecting macrophage proteins during inflammation is discussed.

beta2-Integrin and lipid modifications indicate a non-antioxidant mechanism for the anti-atherogenic effect of dietary coenzyme Q10

Dietary supplementation with coenzyme Q (CoQ) has been proposed to have anti-atherogenic effects by virtue of its antioxidant capacity. To investigate this question, the leukocyte status of 5 males and 5 females (52-68 years) was evaluated before and after supplementation with 200mg CoQ/day for 5 and 10 weeks. CoQ was selectively taken up by mononuclear cells and alpha-tocopherol increased in polynuclear and mononuclear cells. The expression of beta2-integrin CD11b and complement receptor CD35 on the plasma membrane of resting and stimulated monocytes was significantly decreased upon dietary CoQ. Fatty acid and aldehyde analysis revealed that there was a selective increase of arachidonic acid and plasmalogens in only mononuclear cells. These selective lipid changes are not consistent with a general improvement in antioxidant status and indicate that CoQ most likely inhibits a phospholipase A2. Thus, these results strongly suggest that the anti-atherogenic effects of CoQ be mediated by other mechanisms beside its antioxidant protection.

Oxidative stress in a phenylketonuria animal model

Oxidative stress is seen in various metabolic disorders for unknown reasons. Oxidative stress is defined as an imbalance between pro-oxidant and antioxidant status in favor of the former. This study investigated whether oxidative stress exists in phenylketonuria (PKU) using the BTBR-Pah(enu2) animal model for PKU. Animals (14-24 weeks old) were sacrificed and brain and red blood cells (RBCs) were obtained aseptically. The lipid peroxidation by-product, evaluated as malondialdehyde (MDA), was significantly higher in the brains and RBCs of PKU animals (n = 6) than in controls (n = 6). Glutathione/glutathione disulfide, a good indicator for tissue thiol status, was significantly decreased both in the brains and RBCs. Some antioxidant enzymes were also analyzed in RBCs, including glucose-6-phosphate dehydrogenase (G6PD), which provides the RBC's main reducing power, reduced nicotinamide adenine dinucleotide phosphate (NADPH), and catalase detoxifies H2O2 by catalyzing its reduction to O2 and H2O. Both catalase and G6PD were significantly increased in the RBCs of PKU animals.

Dietary vitamin C and vitamin E interact to influence growth and tissue composition of juvenile hybrid striped bass (Morone chrysops (female) x M. saxatilis (male)) but have limited effects on immune responses

Juvenile hybrid striped bass (initially 12.0 g) were fed diets containing deficient, adequate or excessive amounts of vitamin C and/or vitamin E in a factorial arrangement to investigate potential nutritional interaction and effects on immune responses. Nine semipurified diets were supplemented with 0, 25 or 2500 mg vitamin C/kg and 0, 30 or 300 mg vitamin E/kg and fed to fish in triplicate aquaria for 10 wk. Weight gain, feed efficiency, mortality and tissue vitamin levels were significantly (P < or = 0.05) affected by dietary vitamin levels. In addition, a significant interaction between vitamin C and vitamin E was observed. At inclusion levels of 25 and 2500 mg/kg, dietary vitamin C improved feed efficiency and protected fish fed vitamin E-deficient diets from growth depression and mortality. At inclusion levels of 30 and 300 mg/kg, vitamin E prevented mortality in fish fed vitamin C-deficient diets; however, 300 mg vitamin E/kg was necessary to prevent growth depression in vitamin C-deficient fish but was unable to improve feed efficiency. Lysozyme, bacterial killing ability, as well as plasma protein and total immunoglobulin levels of fish were not affected by dietary vitamin levels, whereas respiratory burst activity increased with vitamin E supplementation. Thus, interactions between vitamin C and vitamin E were observed in hybrid striped bass. These interactions may be due to the ability of vitamin C to regenerate vitamin E to its functional form but also suggest an ability of vitamin E to spare vitamin C.

Oxidative stress in rat cortical neurons and astrocytes induced by paraquat in vitro

Oxidative stress has been discussed as crucial mechanism of neuronal cell death in the adult brain. However, it was not clear until now whether neurons are more sensitive to oxidative stress than the other cells in the brain, e.g. astrocytes. Therefore both cell types were exposed to oxidative stress provoked by the redox-cycling compound paraquat. Cortical neurons were found to be more sensitive towards paraquat toxicity than astrocytes as shown by MTT and Neutral Red assay, two different cytotoxicity assays. Mitochondrial functions were determined by the mitochondrial membrane potential and intracellular ATP concentrations. Again cortical neurons were more severely impaired (by paraquat than astrocytes). The production of reactive oxygen species after paraquat exposure was much higher in cortical neurons than in astrocytes and correlated with a higher depletion of GSH (intracellular glutathion). Lipid peroxidation could be shown in astrocytes via the breakdown product malondialdehyde (MDA) whereas in cortical neurons 4-hydroxynonenal (4-HNE) was detected as this endpoint. If and how oxidative stress influences the antioxidant defense was determined via changes in the expression of antioxidant enzymes. Paraquat exposure lead to a 2-3 fold increase of catalase, MnSOD and CuZnSOD mRNA expression in astrocytes. In contrast to astrocytes, in cortical neurons catalase and MnSOD mRNA levels were only marginally elevated above 1.5-fold by treatment with paraquat. Expression levels of glutathione peroxidase (GPx) mRNA were the only one that were not changed in both cell types after paraquat exposure. It is concluded that the more marked increase in expression levels of antioxidant enzymes may render astrocytes more resistant to oxidative stress than neuronal cells.

Chemotherapy-induced chromosomal damage in peripheral blood lymphocytes of cancer patients supplemented with antioxidants or placebo

A total of 27 patients with various types of cancer were treated with cisplatin-based combination chemotherapy. Out of these, 13 patients were randomized to receive supplementation treatment with a beverage containing the antioxidants vitamins C and E, plus selenium, during chemotherapy. The antioxidant mixture was administered to investigate whether it could reduce the potential genotoxic and nephrotoxic effect of the applied chemotherapy. A placebo group of 14 cancer patients received a beverage without selenium or antioxidants. Micronuclei (MN) in cytochalasin B-blocked binucleate (BN) peripheral blood lymphocytes (PBLs) and hypoxanthine phosphoribosyl transferase (HPRT) mutants in PBLs were studied before, during and after chemotherapy as a measure for chemotherapy-induced genotoxic effects. Before chemotherapy, patients mean frequencies of MN and HPRT mutants did not differ from those in a group of 10 healthy subjects. The mean frequency of MN in patients increased significantly after one cycle of chemotherapy (P=0.002). This frequency was still elevated at 2 months after the completion of chemotherapy (not significantly). There was no significant difference in micronuclei frequency (MNF) between the antioxidant and placebo group of patients. Chemotherapy-induced frequencies of MN after three cycles of chemotherapy correlated significantly with the cumulative dose of cisplatin (r=0.58, P=0.012) and the cisplatin-mediated loss of renal function (r=0.53, P=0.03). No consistent change in HPRT mutant frequency following chemotherapy was observed in the placebo and antioxidant group of patients. In conclusion, cisplatin-combination chemotherapy resulted in a cisplatin dose-related increase of the frequency of chromosomal damage. Supplementation with antioxidants did not prevent or reduce this effect.

Protection of U937 cells from free radical damage by the macrophage synthesized antioxidant 7,8-dihydroneopterin

Interferon-gamma stimulation of human macrophages causes the synthesis and release of neopterin and its reduced form 7,8-dihydroneopterin (7,8-NP). The purpose of this cellular response is undetermined but in vitro experiments suggests 7,8-NP is an antioxidant. We have found 7,8-NP can protect monocyte-like U937 cells from oxidative damage. 7,8-NP inhibited ferrous ion and hypochlorite mediated loss of cell viability. Fe++ mediated lipid peroxidation was effectively inhibited by 7,8-NP, however, no correlation was found between peroxide concentration and cell viability. Hypochlorite was scavenged by 7,8-NP, preventing the loss of cell viability. 7,8-NP was less effective in inhibiting H2O2-mediated loss of cell viability with significant inhibition only occurring at high 7,8-NP concentrations. Analysis of cellular protein hydrolysates showed none of the oxidants caused the formation of any protein bound DOPA or dityrosine but did show 7,8-NP prevented the loss of cellular tyrosine by HOCl. Our data suggests macrophages may synthesize 7,8-NP for antioxidant protection during inflammatory events in vivo.

The effects of acute melatonin and ethanol treatment on antioxidant enzyme activities in rat testes

The pineal hormone melatonin (N -acetyl, 5-methoxytryptamine) was recently accepted to act as an antioxidant under both in vivo and in vitro conditions. In this study, we examined the possible preventive effect of melatonin on ethanol-induced lipid peroxidation in rat testes. Thirty-seven male Wistar albino rats, 5.5--6 months old, were randomly divided into four groups (9--10 animals in each). The first group (control animals) received 4% ethanol at similar intervals to the experimental groups to equalize the stress effect. The second group received only melatonin i.p. 7 mg kg(-1)bw three times over 1.5 h intervals. The third group received only 30% alcohol 3 g kg(-1)bw twice daily. The fourth group were treated with melatonin and ethanol according to the above protocol, melatonin injections preceding ethanol treatments. The product of lipid peroxidation, malondialdehyde (MDA) and antioxidant enzymes, superoxide dismutase (Cu--Zn SOD), glutathione peroxidase (GPx) and catalase (CAT) were measured in the post-mitochondrial fraction of the testes. MDA levels were significantly increased due to acute ethanol intoxication. GPx activity was higher in the three experimental groups than the control levels. The activity of CAT was increased significantly in the melatonin plus ethanol-treated group but the other groups appeared not to be influenced by acute ethanol treatment. Cu--Zn SOD activity remained unaltered. These results suggest that antioxidants may be a protective agent for the testicular injury caused by ethanol consumption.

Reaction conditions affecting the relationship between thiobarbituric acid reactivity and lipid peroxides in human plasma

The thiobarbituric acid (TBA) reactivity of human plasma was studied to evaluate its adequacy in quantifying lipid peroxidation as an index of systemic oxidative stress. Two spectrophotometric TBA tests based on the use of either phosphoric acid (pH 2.0, method A) or trichloroacetic plus hydrochloric acid (pH 0.9, method B) were employed with and without sodium sulfate (SS) to inhibit sialic acid (SA) reactivity with TBA. To correct for background absorption, the absorbance values at 572 nm were subtracted from those at 532 nm, which represent the absorption maximum of the TBA:MDA adduct. Method B gave values of TBA-reactive substances (TBARS) 2-fold higher than those detected with method A. SS lowered TBARS by about 50% with both methods, indicating a significant involvement of SA in plasma TBA reactivity. Standard SA, at a physiologically relevant concentration of 1.5 mM, reacted with TBA, creating interference problems, which were substantially eliminated by SS plus correction for background absorbance. When method B was carried out in the lipid and protein fraction of plasma, SS inhibited by 65% TBARS formation only in the latter. Protein TBARS may be largely ascribed to SA-containing glycoproteins and, to a minor extent, protein-bound MDA. Indeed, EDTA did not affect protein TBARS assessed in the presence of SS. TBA reactivity of whole plasma and of its lipid fraction was instead inhibited by EDTA, suggesting that lipoperoxides (and possibly monofunctional lipoperoxidation aldehydes) are involved as MDA precursors in the TBA test. Pretreatment of plasma with KI, a specific reductant of hydroperoxides, decreased TBARS by about 27%. Moreover, aspirin administration to humans to inhibit prostaglandin endoperoxide generation reduced plasma TBARS by 40%. In conclusion, reaction conditions affect the relationship between TBA reactivity and lipid peroxidation in human plasma. After correction for the interfering effects of SA in the TBA test, 40% of plasma TBARS appears related to in vivo generated prostaglandin endoperoxides and only about 60% to lipoperoxidation products. Thus, the TBA test is not totally specific to oxidant-driven lipid peroxidation in human plasma.

Oxidative damage following cerebral ischemia depends on reperfusion - a biochemical study in rat

The extent of brain injury during reperfusion appears to depend on the experimental pattern of ischemia/reperfusion. The goals of this study were: first, to identify the rate of free radicals generation and the antioxidant activity during ischemia and reperfusion by means of biochemical measurement of lipid peroxidation (LPO) and both enzymatic (superoxide dismutase - SOD, catalase - CAT, glutathione peroxidase - GPx) and non-enzymatic antioxidants activity (glutathione - GSH); and second, to try to find out how the pattern of reperfusion may influence the balance between free radical production and clearance. Wistar male rats were subject of four-vessel occlusion model (Pulsinelly & Brierley) cerebral blood flow being controlled by means of two atraumatic arterial microclamps placed on carotid arteries. The level of free radicals and the antioxidant activity were measured in ischemic rat brain tissue homogenate using spectrophotometrical techniques. All groups subjected to ischemia shown an increase of LPO and a reduction of the activity of enzymatic antioxidative systems (CAT, GPx, SOD) and non-enzymatic systems (GSH). For both groups subjected to ischemia and reperfusion, results shown an important increase of LPO but less significant than the levels found in the group with ischemia only. Statistically relevant differences (p<0.01) between continuous reperfusion and fragmented reperfusion were observed concerning the LPO, CAT, SOD and GSH levels, oxidative aggression during fragmented reperfusion being more important.

On-line, continuous and automatic monitoring of extracellular malondialdehyde concentration in anesthetized rat brain cortex

An assay for in vivo, continuous and automatic monitoring of extracellular malondialdehyde concentrations in anesthetized rat brain cortex was developed. This method involved the use of microdialysis perfusion, on-line derivatization and on-line high-performance liquid chromatographic analysis. Microdialysate from an implanted microdialysis probe was on-line reacted with thiobarbituric acid at 80 degrees C for 10 min prior to on-line collection and automatic injection into a HPLC system equipped with a fluorescence detector. This method gave a linear response between the concentrations of the malondialdehyde in the microdialysates and the TEP solution where the microdialysis probe was placed. This method was used to observe the increased extracellular malondialdehyde production following elevated extracellular glutamate levels, which were achieved by perfusion of L-trans-pyrrolidine-2,4-dicarboxylate, a competitive inhibitor of glutamate uptake transporter.

Effect of lithium on cyclosporin induced nephrotoxicity in rats

Psychoactive drugs provide essential intervention in the care of transplant recipients, yet little is known of their interaction with immunosuppressants such as cyclosporin (CSA). Lithium (Li) is an invaluable drug for the treatment of manic disorders in organ transplant patients. As both these drugs are known to produce renal toxicity, the concomitant use of CSA and Li may be potentially harmful. The present study was undertaken to investigate the effect of CSA and Li chloride individually and in combination on renal structure and function of rats. Male Sprague-Dawley rats were divided into the following eight groups of seven animals each: group I, control (vehicle only); group 2, Li (2 mEq/ kg i.p.) alone; group 3, CSA 12.5 mg/kg (subcutaneous); group 4, CSA 25 mg/kg; group 5, CSA 50 mg/kg; group 6, CSA 12.5 mg/kg + Li; group 7, CSA 25 mg/kg + Li; and group 8, CSA 50 mg/kg + Li. The drugs were given once a day for seven days; Li being administered 30 min before CSA. Twenty four hours after the last dose of drugs the animals were sacrificed and blood samples were analyzed for blood urea nitrogen (BUN), serum creatinine (SCr), CSA and Li levels. The left kidney was analyzed for malondialdehyde (MDA) and conjugated dienes (CD) levels and right kidney was used for histopathological studies. Our results showed that Li alone did not produce any significant renal toxicity, whereas CSA dose dependently caused structural and functional changes in kidneys. However, significantly higher structural and functional impairment was observed in the animals treated with Li plus CSA as compared to CSA alone treated animals. Several fold increase in blood Li level was also noticed in the rats concomitantly treated with CSA and Li. A significant increase in MDA and CD in the rats treated with CSA plus Li suggests the role of oxidative stress in drug induced nephrotoxicity. These findings clearly demonstrate that even non toxic doses of Li may significantly exacerbate CSA induced nephrotoxicity in rats. The enhanced nephrotoxicity following concomitant use of these drugs may be attributed to significant increase in the bioavailability of Li and enhanced oxidative stress. Further clinical studies are warranted to investigate the interaction of these nephrotoxic drugs in human subjects.