Oxidants and antioxidants: state of the art

Topical agents used in association with cosmetic surgery

Effective cosmetic surgery depends on proper preparation of the skin prior to the procedure, excellent wound care, and an appropriate postoperative skin maintenance program. Accomplishing this goal requires a thorough understanding of topical agents. Substances applied to the skin can alter barrier function, permeability, transepidermal water loss, immune response, wound repair, vasostability, collagen deposition, epidermal turnover, and melanin formation, to name a few. Each of these skin characteristics can affect the quality of the end surgical result. This article discusses topical agents used in association with cosmetic surgery.

Effects of physical exercise in pre-and postmenopausal women on lipid peroxidation and antioxidant systems

The effects of moderate physical activity were studied in 19 postmenopausal and 25 premenopausal women on the enzymatic (superoxide dismutase and catalase) and non-enzymatic (vitamins A and E) antioxidant systems and on the processes of lipid peroxidation (malondialdehyde), and to see whether there is any variation in oxidative stress indicators between the postmenopausal and non-menopausal women. The subjects were also studied anthropometrically. At the end of a training period, there was a decrease in body fat percentage and in various skin folds. Neither group presented a rise in lipid peroxidation levels, although there was a significant (p<0.05) rise in superoxide dismutase activity in the postmenopausal women.

Lesão pulmonar de reperfusão

A lesão de isquemia-reperfusão constitui-se em um evento fisiopatológico comum a diversas doenças da prática clínica diária. O pulmão pode ser alvo da lesão de isquemia-reperfusão diretamente, como no edema pulmonar após transplante ou na resolução de tromboembolismo; ou ainda ser atingido à distância, como nos casos de choque ou por lesão de reperfusão em intestino ou em membros inferiores, como ocorre no pinçamento da aorta, utilizado nas cirurgias de aneurisma. Dentre os mediadores envolvidos na lesão de isquemia-reperfusão, foram identificados espécies reativas tóxicas de oxigênio (ERTO), mediadores lipídicos, como a tromboxana, moléculas de adesão em neutrófilos e endotélio, fator de necrose tumoral, dentre outros. As medidas terapêuticas para a lesão de reperfusão ainda são utilizadas no plano experimental e em poucos estudos clínicos. São utilizados: antioxidantes, bloqueadores de mediadores lipídicos, inibidores da interação entre leucócito e endotélio ou substâncias que favoreçam o fluxo sanguíneo pós-isquêmico.

Role of reactive oxygen species in occupational and environmental obstructive pulmonary diseases

Free radicals and their metabolites, also called reactive oxygen species (ROS), have been implicated in the pathogenesis of many diseases. Because of its continuous exposure to toxic pollutants in the ambient air, such as cigarette smoke, air pollution, and mineral dusts, the lung is very vulnerable to ROS-induced injury. In this review, the role of ROS in the pathogenesis of obstructive lung diseases is reviewed. A central theme in this review is the pivotal role of transition metals such as iron, vanadium, and nickel in ROS-induced cell damage, not only in exposure to mineral dusts but also in cigarette smoke and air pollution.

Novel esters and amides of nonsteroidal antiinflammatory carboxylic acids as antioxidants and antiproliferative agents

A series of phenolic antioxidant ester and amide derivatives of the nonsteroidal antiinflammatory drug naproxen was designed to have both antiinflammatory and cytoprotective activity. Compounds were evaluated in vitro both for antioxidant activity, as assessed indirectly by thiobarbituric acid reactive substance (TBARS) formation in a membrane lipid peroxidation assay, and for antiproliferative activity, as indexed by the inhibition of DNA synthesis in cultured human vascular endothelial cells. Compounds of this series exhibited potent antioxidant activity, with IC50 values (1.6-11.63 microM) 2-6-fold lower than that of Trolox (6-hydroxy-2,5, 7,8-tetramethylchroman-2-carboxylic acid) and 400-1300-fold lower than that of vitamin E. Structural modifications of the ester or amide substructure (5a and 6a) did not affect antioxidant activity, but methylation of the 6-hydroxy substituent resulted in compound 6f which was devoid of antioxidant activity. Although indistinguishable in antioxidant activity, the amide derivatives tended to be more potent as antiproliferative agents than the corresponding esters. The IC50's for the amide derivatives (3, 5a-e, 8) ranged from 2 to 7 microM, while the IC50's for the structurally related esters (1, 2a-c, 6a-e) ranged from 9 to 22 microM. Moreover, studies with compound 6a indicate that the observed inhibition of DNA synthesis is reversible, suggesting that the antiproliferative activity is due to a cytostatic rather than cytotoxic activity of the compounds. Thus, the antioxidant-naproxen derivatives represent a novel series of agents that both protect against free-radical damage and possess cytostatic activity in vascular endothelial cells. Studies are in progress to assess the utility of these compounds as potential components of an ocular irrigating solution.

Demyelination: the role of reactive oxygen and nitrogen species

This review summarises the role that reactive oxygen and nitrogen species play in demyelination, such as that occurring in the inflammatory demyelinating disorders multiple sclerosis and Guillain-Barré syndrome. The concentrations of reactive oxygen and nitrogen species (e.g. superoxide, nitric oxide and peroxynitrite) can increase dramatically under conditions such as inflammation, and this can overwhelm the inherent antioxidant defences within lesions. Such oxidative and/or nitrative stress can damage the lipids, proteins and nucleic acids of cells and mitochondria, potentially causing cell death. Oligodendrocytes are more sensitive to oxidative and nitrative stress in vitro than are astrocytes and microglia, seemingly due to a diminished capacity for antioxidant defence, and the presence of raised risk factors, including a high iron content. Oxidative and nitrative stress might therefore result in vivo in selective oligodendrocyte death, and thereby demyelination. The reactive species may also damage the myelin sheath, promoting its attack by macrophages. Damage can occur directly by lipid peroxidation, and indirectly by the activation of proteases and phospholipase A2. Evidence for the existence of oxidative and nitrative stress within inflammatory demyelinating lesions includes the presence of both lipid and protein peroxides, and nitrotyrosine (a marker for peroxynitrite formation). The neurological deficit resulting from experimental autoimmune demyelinating disease has generally been reduced by trial therapies intended to diminish the concentration of reactive oxygen species. However, therapies aimed at diminishing reactive nitrogen species have had a more variable outcome, sometimes exacerbating disease.

Exercise-induced increase in hydrogen peroxide plasma levels is diminished by endurance training after myocardial infarction

We have investigated the influence of physical training on exercise-induced changes in free radical activity in patients after myocardial infarction. Seventeen patients admitted to the cardiac rehabilitation center performed a bicycle ergometry before and after a 3-week endurance training program. The oxygen consumption and carbon dioxide production were measured and the ECG and the systemic blood pressure were monitored during the tests. Blood samples for acid-base equilibrium, lactic acid levels and hydrogen peroxide concentrations were collected directly before and after each exercise test. Exercise-induced increases in systolic blood pressure, heart rate and rate-pressure product as well as lactic acid concentrations were significantly less marked during the bicycle ergometry performed after the rehabilitation program. During the initial exercise test hydrogen peroxide levels increased significantly from 7.15+/-0.74 micromol/l before to 9.09+/-1.04 micromol/l 3 min after the test (P=0.0229). In contrast, no significant changes in hydrogen peroxide concentrations were observed during the exercise test performed after the training (6.31+/-1.05 micromol/l before the test, 5.85+/-1.08 micromol/l after the test, P=0.201). These observations suggest that physical training may have a beneficial influence on free radicals' generation in patients after myocardial infarction.

Oxidative stress and the pathogenesis of heart failure

There is strong evidence for an adverse role of oxidative stress in CHF in both animals and humans. Antioxidant supplement have been very effective in the treatment of animal paradigms; however, the data for the possible benefits of treatment for patients with CHF is either retrospective or inferential. Such information is important and should be the subject of prospective randomized trials.

Effect of hyperoxia on human macrophage cytokine response

In the development of lung damage induced by oxidative stress, it has been proposed that changes in alveolar macrophages (AM) function with modifications in cytokine production may contribute to altered repair processes. To characterize the changes in profiles of cytokine production by macrophages exposed to oxidants, the effects of hyperoxia (95% O2) on interleukin (IL)-1 beta, IL-6, IL-8, and tumour necrosis factor-alpha (TNF-alpha) expression were studied. Experiments were first performed using AM obtained from control subjects and children with interstitial lung disease. Results showed that a 48 h O2 exposure was associated with two distinct patterns of response: a decrease in TNF-alpha, IL-1 beta and IL-6 expression, and an increase in IL-8. To complete these observations we used U937 cells that were exposed for various durations to hyperoxia. We confirmed that a 48 h O2 exposure led to similar changes with a decrease in TNF-alpha, IL-1 beta and IL-6 production and an increase in IL-8. Interestingly, this cytokine response was preceded during the first hours of O2 treatment by induction of TNF-alpha, IL-1 beta and IL-6. These data indicate that hyperoxia induces changes in the expression of macrophages inflammatory cytokines, and that these modifications appear to be influenced by the duration of O2 exposure.

Nutritional modulation of cytokine biology

The pro-inflammatory cytokines and oxidant molecules produced during the inflammatory response, which follows infection and injury, may be beneficial, or detrimental to the patient, depending on the amounts and contexts in which they are produced. Aberrant or excessive production has been implicated in inflammatory disease, and sepsis. The upregulation of cytokine production by NF kappa B and NFIL-6 activation by oxidants increases the likelihood of cytokine-induced mortality and morbidity. Complex systems exist for the control of cytokine production and oxidant actions. The former include the hormones of the hypothalamo-pituitary-adrenal axis, acute phase proteins, and endogenous inhibitors of interleukin (IL)-1 and tumor necrosis factor (TNF). The latter include endogenously synthesized antioxidants, such as glutathione and dietary antioxidants, such as tocopherols, ascorbates and cachectins. Nutrients change cytokine production and potency by influencing tissue concentrations of many of the molecules involved in cytokine biology. Monounsaturated fatty acids and omega-3 polyunsaturated fatty acids (PUFAs) suppress TNF and IL-1 production and actions, while n-6 PUFAs exert the opposite effect. Changes in eicosanoid production are more likely to underlie this effect than alterations in membrane fluidity. Low antioxidant intake results in enhanced cytokine production and effects. The anorexia that follows infection and injury, may be purposeful to permit release of substrate from endogenous sources to support and control the inflammatory process. Therefore, prior as well as concurrent nutrient intake are of importance in determining the outcome of the inflammatory response.

Effect of stobadine on carbon tetrachloride-induced erythrocyte membrane changes in rats

Our previous study showed that stobadine is effective against ischemia/reperfusion-induced gastric mucosal injury. The present study examined the ability of stobadine to protect erythrocyte membrane against free radical injury after long-term carbon tetrachloride (CCl4) application. The erythrocyte membrane changes were established using colloid-osmotic hemolysis. The significant increase of colloid-osmotic hemolysis was found in animals treated with CCl4. CCl4 also increased formation of thiobarbituric acid-reactive substances (TBARs) and decreased thiol group content. Stobadine in both doses (10.0 and 20.0 mg.kg-1) protected erythrocyte membrane against CCl4-induced injury. The membrane lipid bilayer is the most affected part of the erythrocyte membrane. In presence of stobadine, CCl4-induced lipid peroxidation was partially or totally prevented whereas the level of total membrane thiols was increased. Based on these results, it can be concluded that protective effect of stobadine on CCl4-induced erythrocyte membrane changes should be related to its antioxidant properties.

The effect of indolinic and quinolinic nitroxide radicals on trout erythrocytes exposed to oxidative stress

The purpose of this study was to evaluate the ability of indolinic and quinolinic nitroxide radicals to protect trout (Salmo irideus) erythrocytes against oxidative stress. By using laurdan as a fluorescence probe, it was observed that the nitroxides inhibited the shift towards a gel phase of liposomes prepared with phospholipids extracted from trout erythrocyte membranes prior to the hemolytic event. In addition, the presence of 100 microM nitroxides in these liposomes protected the latter against lipid peroxidation determined by monitoring conjugated diene formation. However, the short chain analogue of the indolinic nitroxide and the quinolinic nitroxide had a negative effect on trout hemolysis, contrary to what has already been observed in previous studies on human RBCs (red blood cells). The half-time (t1/2) of the hemolytic process was 174 +/- 4.02 min for the former and 184 +/- 4.30 min for the latter compared to the control, 283 +/- 5.05 min. Furthermore, the nitroxides remarkably increased the autoxidation rate of both trout and human hemoglobin to met-Hb. Even though protection at the membrane level is conferred by the nitroxides during the early stages of lipid peroxidation, their antioxidative ability might be overwhelmed at a later stage by other mechanisms such as the increased autoxidation of hemoglobin in the presence of the nitroxides, thus giving a possible explanation for the early induction of hemolysis induced by the nitroxides. The superoxide scavenging ability of all the nitroxides used was also evaluated through chemiluminescence.

Antioxidant activity of some ascorbic and cinnamic acids derivatives

Some 4-benzoyl 3-hydroxy furan-2 (5H) ones (3a-d) and 2-amino 3-hydroxymethyl 4-aryl 4-oxo 2-butenoic acids (4a-h) have been synthesized. Compound 3c with an isobutyl substituent in the 5-position of the furan ring was the most effective (IC50 = 8.69 x 10(-4) M) in scavenging the superoxide anion. In vivo, 3c was also protective against reperfusion injury.

Oxidative stress in hemodialyzed patients and the long-term effects of dialyzer reuse practice

OBJECTIVES

To investigate the existence of an altered oxidant/ antioxidant balance in patients on regular hemodialysis treatment (RHT) and whether there is any effect of dialyzer reuse on oxidative damage and antioxidative mechanism.

DESIGN AND METHODS

Malondialdehyde (MDA) levels and glutathione peroxidase (GPx) activities in both plasma and erythrocytes, plasma selenium (Se) levels, and erythrocyte superoxide dismutase (SOD) activities of RHT patients were determined at the beginning and end of 4-month reuse period.

RESULTS

When compared to healthy controls, both plasma and erythrocyte MDA levels were found to be significantly higher in RHT patients before the dialyzer reuse practice; whereas both plasma and erythrocyte GPx activities, erythrocyte SOD activity, and also plasma Se levels were lower in the same patient group than those of controls. When statistical comparison was made on RHT patients between before and after the reuse period, the decreases in MDA levels but increases in the enzyme activities and also an increase in plasma Se levels were observed after the reuse period. However, erythrocyte SOD activities and plasma Se levels measured after the reuse period were not found to be statistically different from the control values; MDA levels still remained elevated above the control values, and GPx activities were not attained to those of controls, after the reuse practice. In addition, positive correlations were found between activities of erythrocyte SOD and GPx enzymes, between GPx and Se levels and negative correlations between the activities of both enzymes and MDA levels in erythrocytes of patients on RHT.

CONCLUSION

These findings may indicate that dialyzer reuse may provide, at least partly, an improvement on oxidative stress in patients on RHT.

Factors associated with variations in pulmonary function among elderly Japanese-American men

OBJECTIVE

To identify lifestyle, anthropometric, biochemical, and clinical characteristics associated with pulmonary function in elderly men.

DESIGN

Cross-sectional population-based study.

PARTICIPANTS

Japanese-American men (n=3,111) aged 71 to 93 years, who completed spirometry at the fourth examination of the Honolulu Heart Program (1991 to 1993).

METHODS

Pulmonary function measurements (FEV1 and FVC) were obtained using American Thoracic Society guidelines. Potential factors associated with pulmonary function were examined using Pearson correlation coefficients and general linear models. Age- and height-adjusted mean levels of FEV1 and FVC were compared across quintiles of continuous variables and by status of prevalent disease and medication or vitamin use. Stepwise multiple linear regression was used to identify factors independently associated with pulmonary function overall and among never smokers.

RESULTS

A number of correlates of pulmonary function were initially identified. In multivariate analyses, age, current smoking, pack-years of smoking, emphysema, asthma, wheezing without colds, subscapular skinfold thickness, ECG abnormality, heart rate, WBC count, and eosinophil count were all negatively and independently associated with FEV1, while height, grip strength, physical activity, and mean corpuscular hemoglobin concentration were positively associated. With a few exceptions, similar relations were observed with FVC and among never-smokers.

CONCLUSION

Cigarette smoking, respiratory symptoms and disease, and several cardiovascular risk factors were independently associated with pulmonary function in elderly Japanese-American men. In most cases, inadequate control for smoking does not appear to account for these associations. Results suggest that a number of factors that are correlates of FEV1 and FVC in younger age groups are also associated with pulmonary function beyond the age of 70 years.

Enhanced chemiluminescent assay for measuring the total antioxidant capacity of serum, saliva and crevicular fluid

This paper reports the development of an enhanced chemiluminescent (ECL) assay for measuring the total antioxidant (AO) capacity of serum, saliva and a fluid collectable from the gum margin called gingival crevicular fluid (GCF). The theory behind the assay is explained, and the optimum conditions for the assay, and for storage of reagents and clinical samples is described. Calibration lines were linear (R > or = 0.99; P < 0.0001) and the within batch coefficient of variations for a water soluble vitamin E analogue (Trolox), serum and saliva samples were < 5%. In saliva and GCF, a characteristic AO response not seen in serum of the same patients, was identified. Total peripheral (serum) and local (saliva) AO capacities (mumol/L Trolox) were investigated in patients with (n = 18) and without (n = 16) adult periodontitis. Serum AO status did not differ between groups. Salivary total AO concentrations were lower in the peridontitis (P) group [175 (53) mumol/L] than in the non-periodontitis (NP) group [254 (110) mumol/L1: P < 0.01], as were saliva:serum AO ratio's [0.37 (0.11) versus 0.5 (0.18): P < 0.01]. Periodontitis patients may have a reduced salivary AO concentration, which could result from, or predispose to, the damaging effects of reactive oxygen species (ROS). The potential for ROS production in the oral and periodontal environment may explain the presence of a specific antioxidant in oral fluids that is not detectable in serum. The ECL assay described provides a rapid, simple and reproducible method of measuring total antioxidant defence in small volumes of biological fluids.

Rapid alteration of tau in oligodendrocytes after focal ischemic injury in the rat: involvement of free radicals

Glial inclusions containing the microtubule-associated protein tau are present in a variety of chronic neurodegenerative conditions. We now report a rapid and time-dependent increase of tau immunoreactivity within oligodendrocytes after focal cerebral ischemia in the rat. The number of tau positive oligodendrocytes in the ipsilateral subcortical white matter increased six- to eightfold by 40 minutes after permanent middle cerebral artery occlusion (MCAO). Tau was detected using antibodies that label both the N- and C-terminal of the protein, suggesting accumulation of full-length protein within these cells. Pretreatment with the spin trap agent alpha-phenyl-tert-butyl-nitrone (PBN)(100mg/kg) reduced the number of tau-positive oligodendrocytes by 55% in the subcortical white matter of the ischemic hemisphere compared with untreated animals at 40 minutes after MCAO. In contrast, pretreatment with glutamate receptor antagonists MK-801 (0.5 mg/kg) or 2,3-dihydroxy-6-nitro-7-sulpfamoyl-benzo(f)quinoxaline (NBQX) (2 x 30 mg/kg), failed to reduce the number of tau-positive oligodendrocytes after 40 minutes of ischemia. The results indicate that oligodendrocytes respond rapidly to an ischemic challenge and that free radical-mediated mechanisms are involved in the cascade leading to increased tau immunoreactivity.

Upregulation of Intracellular Glutathione by Fibroblast-Derived Factor(s): Enhanced Survival of Activated T Cells in the Presence of Low Bcl-2

Activated interleukin-2 (IL-2)–dependent T cells express high levels of Bcl-2 protein. On cytokine withdrawal, Bcl-2 expression decreases and the cells die rapidly by apoptosis. We have previously shown that the survival of IL-2–deprived T cells can be promoted by factor(s) secreted by fibroblasts. Here we report that reduced glutathione (GSH), but not its oxidized counterpart GSSG, also enhances the in vitro survival of these cells. Exogenous GSH mediates its effect intracellularly, as (1) endogenous glutathione concentrations are increased up to fivefold in the presence of GSH, and (2) acivicin, an inhibitor of transmembrane GSH transport, abrogates GSH-dependent survival. The GSH-rescued T cells do not proliferate and express only low levels of Bcl-2, resembling WI38 fibroblast-rescued T cells. We, therefore, investigated a role for GSH in fibroblast-promoted T-cell survival. We show that WI38-promoted survival results in elevated GSH levels in surviving T cells and is abrogated by buthionine sulfoximine (BSO), an inhibitor of GSH synthesis. Furthermore, both WI38-promoted T-cell survival and GSH upregulation are associated with large molecular weight molecules (&lt;30 kD). Thus, the upregulation of GSH by WI38 fibroblasts appears to be crucial in their ability to enhance the survival of cytokine-deprived activated T cells in vitro.

Oxidative stress in silicosis: evidence for the enhanced clearance of free radicals from whole lungs

We hypothesized that reactive oxygen species (ROS) may be involved in the pathogenesis of silicosis. To investigate ROS' dependent pathophysiological processes during silicosis we studied the kinetic clearance of instilled stable nitroxide radicals (TEMPO). Antioxidant enzymes' superoxide dismutase (SOD) and glutathione peroxidase (GPx), and lipid peroxidation were also studied in whole lungs of rats exposed to crystalline silica (quartz) and sham exposed controls. Low frequency L-band electron spin resonance spectroscopy was used to measure the clearance of TEMPO in whole-rat lungs directly. The clearance of TEMPO followed first order kinetics showing significant differences in the rate for clearance between the diseased and sham exposed control lungs. Comparison of TEMPO clearance rates in the sham exposed controls and silicotic rats showed an oxidative stress in the rats exposed to quartz. Studies on the antioxidant enzymes SOD and GPx in the lungs of silicotic and sham exposed animals supported the oxidative stress and accelerated clearance of TEMPO by up regulated levels of enzymes in quartz exposed animals. Increased lipid peroxidation potential in the silicotics also supported a role for enhanced generation of ROS in the pathogenesis of silica-induced lung injury. These in vivo experiments directly demonstrate, for the first time, that silicotic lungs are in a state of oxidative stress and that increased generation of ROS is associated with enhanced levels of oxidative enzymes and lipid peroxidation. This technique offers great promise for the elucidation of ROS induced lung injury and development of therapeutic strategies for the prevention of damage.

Models of DNA structure achieve almost perfect discrimination between normal prostate, benign prostatic hyperplasia (BPH), and adenocarcinoma and have a high potential for predicting BPH and prostate cancer

In our previous studies of DNA, wavenumber-absorbance relationships of infrared spectra analyzed by principal components analysis (PCA) were expressed as points in space. Each point represented a highly discriminating measure of structural modifications that altered vibrational and rotational motion, thus changing the spatial orientation of the points. PCA/Fourier transform-infrared technology has now provided a virtually perfect separation of clusters of points representing DNA from normal prostate tissue, BPH, and adenocarcinoma. The findings suggest that the progression of normal prostate tissue to BPH and to prostate cancer involves structural alterations in DNA that are distinctly different. The hydroxyl radical is likely a major contributor to these structural alterations, which is consistent with previous studies of breast cancer. Models based on logistic regression of infrared spectral data were used to calculate the probability of a tissue being BPH or adenocarcinoma. The models had a sensitivity and specificity of 100% for classifying normal vs. cancer and normal vs. BPH, and close to 100% for BPH vs. cancer. Thus, the PCA/Fourier transform-infrared technology was shown to be a powerful means for discriminating between normal prostate tissue, BPH and prostate cancer and has considerable promise for risk prediction and clinical application.

Activity of the antioxidant enzymes superoxide dismutase and glutathione peroxidase in fetal erythrocytes

It is generally accepted that the balance between the formation and inactivation of reactive oxygen species may be abolished within the perinatal period, as a consequence of rapid changes in tissue oxygen concentration and the development of antioxidant defence enzyme activities. We studied the ontogeny of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) in fetal blood samples. The activity of SOD in fetal erythrocytes taken in the 17th gestational week was the same as that in erythrocytes of healthy blood donors. On the other hand, GPx activity was significantly lower between the 17th and 25th gestational week and at the time of delivery, compared with the healthy adult control. Our results suggest that the supposed underdevelopment of the antioxidant system in the lungs or in the other organs of premature infants cannot be monitored by SOD and GPx activities in erythrocytes, because these reach adult levels before the 17th week for SOD and from the 26th to the 35th gestational week for GPx, with lower levels from the 17th to the 25th week and at term.

Tumor progression to the metastatic state involves structural modifications in DNA markedly different from those associated with primary tumor formation

Wavenumber-absorbance relationships of infrared spectra of DNA analyzed by principal components analysis may be expressed as points in space. Each point represents a highly discriminating measure of DNA structure. Structural modifications of DNA, such as those induced by free radicals, alter vibrational and rotational motion and consequently change the spatial location of the points. Using this technology to analyze breast tumor DNA, we revealed a 94 degrees difference in direction between the progression of normal DNA-->primary tumor DNA and the progression of primary tumor DNA-->metastatic tumor DNA (P < 0.001). This sharp directional change was accompanied by a substantial increase in the structural diversity of the metastatic tumor DNA (P = 0.003), which, on the basis of the volume of the core cluster of points, could comprise as many as 11 x 10(9) different phenotypes. This suggests that the heterogeneity and varied physiological properties known to characterize malignant tumor cell populations may at least partially arise from these diverse phenotypes. The evidence suggests that the progression to the metastatic state involves structural modifications in DNA that are markedly different from the modifications associated with the formation of the primary tumor. Overall, the findings of this and earlier studies imply that the observed DNA alter-ations are a pivotal factor in the etiology of breast cancer and a formidable barrier to overcome in intervention to control the disease. In terms of cancer etiology and prediction, the technology described has potentially wide application to studies in which the structural status of DNA is an important consideration.

Hepatocytes from metallothionein-I and II knock-out mice are sensitive to cadmium- and tert-butylhydroperoxide-induced cytotoxicity

Metallothionein (MT) has been proposed to play an important role in heavy metal detoxication and in the scavenging of free radicals. Effects of MT on the cytotoxicity of cadmium (Cd), tert-butylhydroperoxide (t-BHP) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were examined using primary hepatocyte cultures from control (C57BL/6J) and MT-I and II knock-out (MT-null) mice. Compared to control hepatocytes, MT-null hepatocytes had minimal Cd-binding proteins (MT equivalents), but cellular glutathione concentration was similar to the control hepatocytes. MT-null hepatocytes were more sensitive than controls to the cytotoxic effects of Cd (50-300 microM) and t-BHP (125-500 microM), as indicated by the levels of lactate dehydrogenase released into the medium. Cd and t-BHP also produced more lipid peroxidation in MT-null hepatocytes than in control cells, as demonstrated by the abundance of thiobarbituric acid-reactive substances. However, MT-null hepatocytes were equally sensitive as controls to the cytotoxicity of MNNG (0.5-2.0 mM), suggesting that MT does not protect against MNNG-induced cytotoxicity. These results support the hypothesis that constitutive MT levels affect the sensitivity of mammalian cells to Cd and oxidative stress.

The role of free radicals in p-aminophenol-induced nephrotoxicity: does reduced glutathione have a protective effect?

The role of free radicals in p-aminophenol (PAP)-induced nephrotoxicity and effects of reduced glutathione (GSH) were investigated. We injected PAP in one group of rats and PAP plus GSH in a second group. All parameters were measured in the renal tissue. Superoxide dismutase (SOD) activity in the PAP + GSH group (7.1 +/- 0.36 U/mg protein) was found to be significantly higher than in the control group (4.9 +/- 0.13) (P < 0.001). Catalase (CAT) was found to be significantly low in both groups (P < 0.001 in the PAP group (13.48 +/- 0.85 U/mg protein), P < 0.01 in the PAP + GSH group (18.75 +/- 1.17) as compared to the control group (41.03 +/- 0.93)). Glutathione peroxidase (GPx) in the PAP and PAP + GSH groups was found to be significantly high (P < 0.01 in the PAP group (5.32 +/- 0.033 U/mg protein), P < 0.001 in the PAP + GSH group (6.48 +/- 0.1)) as compared to the control group (2.93 +/- 0.093)). Similarly, glutathione reductase (GSSGR) in the PAP (0.023 +/- 0.002 U/mg protein), and PAP + GSH (0.025 +/- 0.001) groups was found to be significantly high as compared to the control group (0.014 +/- 0.001) (P < 0.001). GSH in the PAP (161.93 +/- 8.3 mg/mg protein) and PAP + GSH (170.7 +/- 4.51) groups were found to be significantly higher than the control group (104.91 +/- 3.0) (P < 0.001). Malondialdehyte (MDA) in the PAP (11.2 +/- 0.62 nmol/mg protein) and PAP + GSH (9.72 +/- 0.46) groups was found to be significantly higher than in the control group (5.54 +/- 0.51)(P < 0.001). Free radicals might have a major role in the PAP-induced nephrotoxicity. GSH increased nephrotoxicity.

Exhaled ethane and antioxidant vitamin supplements in active smokers

To determine the effect of nutritional agents on lipid peroxidation, 10 smokers were given 6 mg beta carotene, 200 IU vitamin E, and 250 mg vitamin C 4 times daily for 3 weeks. Lipid peroxidation was assessed by measuring baseline and postsupplementation levels of exhaled ethane. There was a 29% decrease in mean (+/-SD) exhaled ethane (4.06 +/- 1.49 vs 2.90 +/- 1.29 pmol.kg-1.min-1), with individual levels decreasing in 8 of the 10 smokers (p < 0.05, Wilcoxon sign rank test). Three nonsmokers had very low baseline levels of ethane that did not change with supplementation. Ethane production correlated with active (packs per day) and lifelong (pack-years) tobacco consumption. Also, a strong correlation was found between the decline in ethane output after micronutrient supplementation and the presupplement FEV1. Therefore, antioxidant vitamin supplementation resulted in attenuation of smoking-related lipid peroxidation, and the decreases in ethane production appears to be associated with preserved lung function.

Involvement of hydroxyl radicals in neurogenic airway plasma exudation and bronchoconstriction in guinea-pigs in vivo

1. Cigarette smoke induces plasma exudation in the airways of rodents by activation of capsaicin-sensitive 'sensory-efferent' nerves. The response is mediated predominantly by substance P (SP) and the magnitude of exudation is regulated by neutral endopeptidase (NEP). The component(s) of the smoke responsible for the activation of the nerves may be reactive oxygen radicals. We investigated the effect of the hydroxyl radical scavenger dimethylthiourea (DMTU), a regulator of superoxide anion, superoxide dismutase (SOD), and a regulator of hydrogen peroxide, catalase, on plasma exudation (measured using Evans blue dye) induced by cigarette smoke in guinea-pig main bronchi in vivo. The effect of DMTU on plasma exudation and non-cholinergic bronchoconstriction (measured as pulmonary insufflation pressure, PIP) induced by electrical stimulation of the vagus nerves was also assessed. Interaction between hydroxyl radicals and NEP was assessed with the NEP inhibitor phosphoramidon. 2. In each of the experiments, cigarette smoke increased plasma exudation by approximately 200% above air-exposed controls. Acute administration of DMTU (1.5 g kg-1, i.v. for 20 min) significantly reduced cigarette smoke-induced plasma exudation by 69%. In contrast, neither SOD (240,000 u kg-1, i.v.) nor catalase (400,000 u kg-1, i.v.) significantly affected the exudative response. 3. Chronic pretreatment with DMTU (1.25 g kg-1 over 4 days) significantly reduced bronchial plasma exudation induced by cigarette smoke by 72%. Phosphoramidon (1.5 mg kg-1, i.v.) completely reversed the inhibition by DMTU of cigarette smoke-induced plasma exudation. 4. Vagal stimulation increased plasma exudation by approximately 200% and PIP by approximately 250%. Acute treatment with DMTU had no significant inhibitory effect on these responses, whereas chronic pretreatment inhibited them by approximately 80%. Phosphoramidon reversed the inhibition by chronic DMTU. 5. SP (1 nmol kg-1) increased plasma exudation by approximately 250%, a response which was not inhibited by either acute or chronic DMTU. 6. We conclude that hydroxyl radicals, rather than superoxide anion or hydrogen peroxide, are involved in the induction of neurogenic plasma exudation and bronchoconstriction induced by cigarette smoke or by electrical stimulation of the vagus nerves. These radicals also affect the activity of NEP. Acute DMTU may affect directly the neural actions of hydroxyl radicals contained in the cigarette smoke. Chronic pretreatment with DMTU may inhibit the neurogenic airway responses by effects on tachykinin biosynthesis and/or axonal transport.

N-acetylcysteine: pharmacological considerations and experimental and clinical applications

The diversity of application of the thiol drug NAC in both the experimental setting, as a tool for the study of the mechanisms and consequences of oxidative stress, and the clinical setting, as a therapeutic agent, clearly reflects the central role played by the redox chemistries of the group XVI elements, oxygen and sulfur, in biology. As our understanding of such redox processes increases, particularly their roles in specific pathophysiological processes, new avenues will open for the use of NAC in the clinical setting. As a drug, NAC represents perhaps the ideal xenobiotic, capable of directly entering endogenous biochemical processes as a result of its own metabolism. Thus, it is hoped that the experience gained with this unique agent will help in future efforts to design antioxidants and chemoprotective principles which are able to more accurately utilize endogenous biochemical processes for cell- or tissue-specific therapy.

Lipid peroxidation and antioxidant enzymes in CAPD patients

The mechanisms of free-radical injury include reactions with proteins, nucleic acids, and polysaccharides; and covalent binding to membrane components and initiation of lipid peroxidation. Cells have developed antioxidant defense to prevent free-radical injury including superoxide dismutase (SOD) and glutathione peroxidase (GPx). Significantly higher concentrations of total malondialdehyde (MDA) in plasma (1.22 +/- 0.42 vs. 0.64 +/- 0.22 micromol/L, p < 0.0001) as well as erythrocytes (2.56 +/- 1.28 vs. 1.03 +/- 0.44 micromol/L, p < 0.0001) of the CAPD patients were found when compared to the control group. The free MDA in plasma and the erythrocytes do not differ significantly in continuous ambulatory peritoneal dialysis (CAPD) patients and the control group. A significantly lower activity of GPx in erythrocytes of CAPD patients (17.85 +/- 2.63 U/g Hb vs. 23.26 +/- 3.61 U/g Hb, p < 0.0001) was found when compared to the control group, but the SOD activity in erythrocytes is not different (2272.36 +/- 579.92 U/g Hb vs. 2347.13 +/- 502.51 U/g Hg, NS). Our results show an increase of total MDA in erythrocytes and plasma. MDA is the product of lipid peroxidation with decreasing activity of GPx, which is capable of detoxifying peroxides. The activity of SOD did not change in CAPD patients. These results propose a possible role of free radicals with reduced antioxidant activity of GPx in CAPD patients and indicate that they could play some role in other pathological conditions such as atherogenesis and hemolysis.

Xanthine oxidase activity in bronchoalveolar lavage fluid from patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a serious respiratory pathology characterized by irreversible limitation of expiratory flow and includes chronic obstructive bronchitis, chronic airflow limitation, and emphysema. To determine whether xanthine oxidase activity increased in the airspaces of COPD patients, we examined bronchoalveolar lavage fluid (BAL) from COPD patients recruited during a 2-year clinical study. Filtered BAL supernatant from COPD patients and healthy nonsmoking controls was examined by fluorometric analysis of DNA unwinding (FADU) and spectrophotometric assays (cytochrome c reduction kinetics and uric acid kinetics). Compared to controls, filtered BAL supernatant of subjects with COPD exhibited a detectable clastogenic activity probably related to superoxide production. The method of BAL preparation as an acellular system strongly suggests that superoxide production may be due to xanthine oxidase activity.

Spermine prevent iron accumulation and depress lipofuscin accumulation in cultured myocardial cells

The present work demonstrates that spermine prevents aging in cultured myocytes exposed to oxidative stress. It is found that physiological levels of spermine reduce lipofuscin accumulation with 20%, and that the antioxidative effect compares with vitamin E. By autometallography we also demonstrate that spermine prevent accumulation of free iron in the myocytes, probably by acting as a chelating agent. The effect compares to that of deferoxamine. These data provide additional insight into the antioxidative mechanism of spermine, and suggest that spermine may prevent diseases related to the Fenton reaction, as well as retard aging reactions.

Magnesium, calcium and trace elements in spontaneously hypertensive rats

1. Using three strains, which showed severe hypertension, mild hypertension and normotension, respectively, the relationships between electrolytes or trace elements and vascular complications combined with the factor of ageing were investigated. 2. In ash materials of some tissues old female SHRSP and old WKY showed a decrease of selenium in many tissues when compared to adult female SHRSP and WKY, respectively. 3. In cellular supernatant fraction, SHRSP showed a decrease of magnesium in many tissues and an elevation of the calcium to magnesium ratio when compared to age-matched WKY and SHRSR. 4. In diabetic rats induced by streptozotocin, myocardial magnesium decreased, resulting in an elevation of the myocardial calcium to magnesium ratio. 5. Alpha tocopherol concentration was lower in both the myocardium and cerebrum of old female SHRSR when compared to that of adult female SHRSR. 6. From these findings the elevation of calcium to magnesium ratio was found in old rats and SHRSP, indicating the tendency of tissue deterioration in these rats. 7. Tissue selenium also decreased in old rats and SHRSP and this decrement was probably related to the peroxidation in tissue damage.

Oligodendroglial precursor cell susceptibility to hypoxia is related to poor ability to cope with reactive oxygen species

Oligodendrocyte precursors and astrocytes in 2-week-old rat primary glial cultures survived 24 h of anoxia, suggesting both cell types could survive using glycolysis for ATP synthesis; however, when the hypoxia developed gradually, the majority of oligodendrocyte precursor cells died within 24 h of the beginning of the experiment but astrocytes survived. Similarly when cultures were exposed to an atmosphere of 1% oxygen, but not 2% or greater, oligodendrocyte precursors died within 24 h. Much more lipid peroxidation was seen under conditions of hypoxia than under conditions of anoxia suggesting that oligodendrocyte precursors died under the former condition because of free radical-induced damage. Using 5-(and -6)-carboxy-2',7'-dichlorodihydrofluorescein (DCFH) as an intracellular probe of oxidative stress, we have demonstrated directly on living cells that oligodendrocyte precursors have a poorer ability to scavenge free radicals than astrocytes. Furthermore, when free radicals were induced to form in the cells either by cysteine auto-oxidation or menadione redox cycling, oligodendrocyte precursors were more readily damaged than astrocytes. We conclude that oligodendroglial precursor cells are exquisitively sensitive to reactive oxygen species.

The sterilization of honey with cobalt 60 gamma radiation: a study of honey spiked with spores of Clostridium botulinum and Bacillus subtilis

Unprocessed honey is a recognized wound-healing remedy. However, to make clinical use of honey acceptable, it should be sterile. To find the lowest dose of irradiation needed for sterilization, six batches of honey (a-f) were gamma irradiated with 6, 12, 18, 22 and 25 kGy Cobalt-60. After a dose of 25 kGy the antibacterial activity was not altered. Presumably glucose oxidase (EC 1.1.3.4), which produces hydrogen peroxide, is not easily damaged by irradiation. Amylase activity on the other hand was significantly reduced to 19%, 19%, 21%, 22%, 43% in batches a), b), c), d) and f) respectively, whereas no decrease was observed in batch e). All batches spiked with approximately 10(6) spores from Cl. botulinum or B. subtilis per 50 g honey proved to be sterile after irradiation with a dose of 25 kGy. Honey was also spiked with Cl. botulinum at up to 5000 spores per 50 g honey, which is the upper limit of natural contamination. The sterilizing dose in this case was 18 kGy.

Anti-oxidant actions of oxymethazoline and xylomethazoline

Anti-oxidant actions of oxymethazoline and xylomethazoline were investigated by measuring inhibition of microsomal lipid peroxidation and hydroxyl radical scavenging activity. Oxymethazoline was shown to be a potent inhibitor of lipid peroxidation (IC50 = 4.9 microM at t = 15 min, IC50 = 8.1 microM at t = 30 min), in contrast to xylomethazoline. Both compounds were excellent hydroxyl radical scavengers. Their rate constants (ks = 1.1 x 10(12) M-1 s-1 for oxymethazoline and ks = 4.7 x 10(10) M-1 s-1 for xylomethazoline) exceeded the rate constant of a known powerful scavenger cimetidine (ks = 1.8 x 10(10) M-1 s-1). The difference in inhibiting lipid peroxidation might be explained by the fact that only oxymethazoline has a hydroxy group which can donate a hydrogen atom and terminate the chain reaction of lipid peroxidation. The mechanism of hydroxyl radical scavenging activity is still unclear. Moreover oxymethazoline seems to have a different mode of action in scavenging hydroxyl radicals than xylomethazoline and cimetidine which results in an extremely high rate constant. Because oxidants play a role in tissue damage in inflammation, it was hypothesized that especially oxymethazoline and to a lesser extent xylomethazoline may have an additional beneficial effect, due to their anti-oxidant properties, in the topical treatment of nasal inflammation.

Monohydroxyethylrutoside as protector against chronic doxorubicin-induced cardiotoxicity

1. The clinical use of the antitumour agent, doxorubicin, is largely limited by the development of a cumulative dose-related cardiotoxicity. This toxicity is generally believed to be caused by the formation of oxygen free radicals. In earlier studies it was established that flavonoids, naturally occurring antioxidants, can provide some degree of protection. In this study we investigated whether 7-monohydroxyethylrutoside (monoHER), a powerful antioxidative flavonoid with extremely low toxicity, can provide protection to an extent comparable to the clinically successful Cardioxane (ICRF-187). 2. Balb/c mice of 20-25 g were equipped i.p. with a telemeter to measure ECG. They were given 6 i.v. doses of doxorubicin (4 mg kg-1) at weekly intervals. ICRF-187 (50 mg kg-1) or monoHER (500 mg kg-1) were administered i.p. 1 h before doxorubicin administration. In the 2 monoHER groups the treatment continued with either 1 or 4 additional injections per week. A saline and monoHER treated group served as controls. After these 6 weeks, they were observed for another 2 weeks. 3. At the end of this study (week 8) the ST interval had increased by 16.7 +/- 2.7 ms (mean +/- s.e. mean) in doxorubicin-treated mice. At that time, the ST interval had increased by only 1.8 +/- 0.9 ms in ICRF-187 co-mediated mice and in monoHER co-medicated mice by only 1.7 +/- 0.8 and 5.1 +/- 1.7 ms (5- and 2-day schedule, respectively, all P < 0.001 relative to doxorubicin and not significantly different from control). The ECG of the control animals did not change during the entire study. The QRS complex did not change in either group.4. It can be concluded that monoHER protects against doxorubicin-induced cardiotoxicity and merits further evaluation in this respect.

Gas chromatographic differentiation between myeloperoxidase activity and Fenton-type oxidants

Several pathological situations are characterized by the production of reactive oxygen species (ROS), whereby different sources such as activated leukocytes and xanthine oxidase seem to be mainly responsible. The contribution of immigrating activated neutrophils to symptom development during inflammatory processes or after reperfusion of ischemic tissues is a matter of continuing discussion. We present a simple method for the differentiation between oxygen activating reactions in which neutrophil-derived myeloperoxidase is involved. The method is based on the gas chromatographic detection of ethylene, which is formed by the reaction of alpha-keto-gamma-methylthiobutyric acid (KMB) or 1-amino-cyclopropane-1-carboxylic acid (ACC) with ROS. In the presence of OH-radical-type oxidants, only KMB yields ethylene whereas ACC is fragmented by myeloperoxidase-derived species (OCl-, chloramines). The amounts of ethylene may be used as an indicator for the relative contribution of Fenton-type or myeloperoxidase-catalyzed reactions.

Differential sensitivity to hydrogen peroxide of dopaminergic and noradrenergic neurotransmission in rat brain slices

Oxidative stress, induced by hydrogen peroxide, has been implicated in the pathogenesis of Parkinson's disease. Only scarce information is available if and how hydrogen peroxide, a side product of catecholamine (CA) breakdown, interferes with CAergic neurotransmission. Therefore, we investigated the effect of hydrogen peroxide on the release of [3H]dopamine (DA) and [3H]noradrenaline (NA) from rat striatal and cortical tissue slices, respectively. Hydrogen peroxide (0.01-1 mM) stimulated the spontaneous release of [3H]DA from striatal slices. Its effect on [3H]NA release from cortical slices, however, was much smaller than on DA release and occurred only in concentrations above 0.1 mM. Furthermore, only in concentrations of 1 mM or higher did a stimulation of spontaneous release of radioactivity from striatal slices incubated with [3H]choline occur. Omission of calcium significantly enhanced the effect on DA release, and an increase of calcium significantly reduced it. Blockade of vesicular storage with reserpine (0.3 microM) almost completely abolished [3H]DA release induced by hydrogen peroxide. Following incubation of striatal slices with [3H]NA in the presence of the NA (re)uptake blocker desmethylimipramine (0.3 microM), NA release was observed at a concentration (0.1 mM) at which no effect occurred in cortical slices. Moreover, under these conditions [3]NA and [3H]DA release from striatal slices reached comparable levels. Our results show that hydrogen peroxide induces a nonexocytotic release of DA and NA by interfering with the vesicular uptake and/or storage of these CAs. However, the striatal DA storage system, irrespective of the presence of either DA or NA, appeared to be substantially more sensitive to this effect than its cortical equivalent for storage of NA.

Experimental thrombosis model induced by free radicals. Application to aspirin and other different substances

A large number of experimental studies suggests that oxygen free radicals play a major role in the pathogenesis of the myocardial lesions observed during the sequence ischemia-reperfusion. The purpose of this study was to determine whether oxygen free radicals can induce thrombosis. In so doing we have developed a new experimental thrombosis model. Reproducible focal thrombosis has been achieved by irradiating mesenteric arterioles of rat for variable time with green filtered light issuing from a mercury lamp after systemic injection of different rose bengal doses. The number of emboli that remove in the blood (N), the duration of total occlusion (T) and the number of emboli per minute were then measured. As control, no rose bengal administration was done and the vessels were exposed to the filtered light. In comparison with this control, results clearly showed that free radicals always induced thrombosis and the induced thrombus was mainly composed of platelets. In this new thrombosis model induced by free radicals antithrombotic drugs (aspirin, 200 mg/Kg, heparin, 2 mg/Kg) and antioxidants (vitamin C, 10 and 20 mg/Kg, allopurinol, 200 and 300 mg/Kg, vitamin E, 500 and 1000 mg/Kg) have been tested. Results have shown that only heparin and vitamin E had an antithrombotic effect on thrombus formation induced by free radicals. This model should be useful in studying the effects of different drugs and could lead to new treatment modalities for ischemic accident and other cardiovascular diseases.

Effects of indolinic and quinolinic aminoxyls on protein and lipid peroxidation of rat liver microsomes

A study on peroxyl radical induced oxidation of rat liver microsomal membranes in the presence of different indolinic and quinolinic aminoxyls (Scheme 1) was carried out in order to test their efficiency as antioxidants in lipid and protein peroxidation. The extent of lipid peroxidation was quantified by the amount of malondialdehyde (MDA) produced, and the measurement of carbonyl residues was used as an index of microsomal protein oxidation. The results obtained suggest that lipid soluble indolinic and quinolinic aminoxyls are efficient in protecting lipids and proteins of biological membranes against oxidation. The efficacy of these aminoxyls as protectors of lipids and proteins was much higher than the water soluble TEMPOL. Moreover, the hydrophobic aminoxyls were more effective in preventing protein than lipid oxidation at low concentrations (1-20 microM). However, at high concentration (100 microM), lipid as opposed to protein oxidation was almost completely inhibited. The data supports the hypothesis that proteins probably have a different oxidation pattern from lipids.

Oxidative stress and living cells

The review deals with the effects of reactive oxygen species, both radical and nonradical (e.g. hydrogen peroxide), on cells and organisms. The chemical and biochemical aspects include description of individual reactive oxygen species, chemical reactions giving rise to them, their interconversions and interactions with metals (Fe2+, Cu2+, Cu+) and other substances (scavengers, antioxidants). The biological aspects concern the specific features and locations of cellular enzyme systems involved in radical production and/or removal. Major harmful effects of the species on the molecular (protein oxidation, lipid peroxidation, damage to DNA) and cellular level (effect on signal transduction, on cell membrane functions and on gene expression) are surveyed. Methods whereby cells and organisms cope with the onslaught of these reactive species are reviewed as well as implications for plant, animal and human health.

Involvement of thiol groups in the impairment of cardiac sarcoplasmic reticular phospholipase D activity by oxidants

Considerable phospholipase D (PLD) activity is localized in myocardial sarcoplasmic reticular (SR) membranes, where it may take part in the regulation of Ca2+ movements. In this study, we examined thiol group dependence as a possible regulatory mechanism for SR PLD. SR membranes isolated from rat heart were exposed to four types of thiol group modifiers, which all induced a decrease in SR PLD activity that was prevented by dithiothreitol. Furthermore, since abnormalities in thiol status and Ca2+ homeostasis are characteristic for the myocardial cell damage induced by oxidative stress, we also studied the effects of oxidants on the SR PLD activity. The enzyme was not affected by xanthine-xanthine oxidase, but was depressed by hydrogen peroxide and by hypochlorous acid. These inhibitory effects were prevented by catalase as well as by methionine and dithiothreitol, respectively. Furthermore, reduced glutathione protected against the hydrogen peroxide-induced depression, whereas oxidized glutathione inhibited SR PLD. The results indicate that SR PLD activity is inhibited by nonradical oxidants, hydrogen peroxide and hypochlorous acid, through reversible modification of associated thiol groups. Thus, the enzyme may be controlled by the glutathione redox status of the cardiac cell.

Prospects for the use of antioxidant therapies

Free radical oxidative stress has been implicated in the pathogenesis of a variety of human diseases. Natural antioxidant defences have been found to be defective in many of the same diseases. This has led to suggestions that oxidative damage and therefore disease progression may be retarded by supplementing natural antioxidant defences. Potential antioxidant therapy includes natural antioxidant enzymes and vitamins or synthetic agents with antioxidant activity. Diseases where antioxidant therapy may be beneficial include diabetes mellitus, reperfusion injury, inflammatory diseases and the prevention of chronic processes such as atherosclerosis and carcinogenesis. Further well controlled prospective clinical trials of antioxidants are required to establish the efficacy and tolerability of antioxidant therapy in the treatment of human diseases.