SEARCH · PubMed Health

Results for “Oxidative Stress”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1992

Role of [Ca2+]i in induction of c-fos, c-jun, and c-myc mRNA in rat PTE after oxidative stress.

Oxidative stress plays an important role in various types of cell injury and tumor promotion. Cells respond to oxidative stress in many ways including changes in membrane organization, ion movements, and altered gene expression, all of which contribute to the subsequent fate of affected cells. In this study, we investigated the expression of the proto-oncogenes c-fos, c-myc, and c-jun, which play a key role in proliferation and differentiation, using primary cultures of rat proximal tubular epithelium exposed to oxidative stress generated by the xanthine/xanthine oxidase system. This system generates superoxide and H2O2 in the extracellular space stimulating the release of active oxygen species from inflammatory cells. c-fos mRNA was expressed within 15 min, peaked at 30 min, and returned to constitutive levels by 3 h. c-jun mRNA began to rise after 30 min, peaked at 120 min, and remained above the constitutive levels up to 180 min. c-myc mRNA expression was less affected by the treatment, with levels increasing gradually over the 180 min period. The expression of c-fos was inhibited by superoxide dismutase but not by catalase and was super-induced by cycloheximide. H2O2 alone did not induce any c-fos mRNA in this system. Chelation of extracellular ionized calcium by EGTA or of intracellular ionized calcium by Quin 2/AM resulted in a marked decrease of c-fos expression. Two protein kinase C inhibitors, H-7 and staurosporine, partly diminished the expression of c-fos, whereas a third, 2-aminopurine, which has a broader spectrum of inhibiting protein kinases, almost completely abolished it. A poly ADP-ribosylation inhibitor, 3-aminobenzamide, had no effect on c-fos expression in this system. Our results show that oxidative stress provokes sequential expression of c-fos, c-jun, and c-myc, mRNA in this order. This c-fos expression appears to be largely controlled by calcium ion movement, which could include protein kinase C activation. Another protein kinase or kinases also appear to play an important role.

Alkaloids↗

PubMed1989

Contribution of 4-hydroxy-2,3-trans-nonenal to the reduction of beta-adrenoceptor function in the heart by oxidative stress.

Oxidative stress reduces adenylate cyclase activity and also the maximal response to beta-adrenoceptor stimulation in the rat heart, while beta-adrenoceptor density is not affected or increased. Since free sulfhydryl groups are essential to beta-adrenoceptor function and the sulfhydryl reactive substance 4-hydroxy-2,3-trans-nonenal (HNE) is responsible for part of the effects of oxidative stress, the effect of HNE on beta-adrenoceptor function in field stimulated left atria of the rat was determined. To this end field stimulated atria were incubated with 10 microM, 100 microM and 1 mM HNE for 25 min. After removing the excess of HNE, beta-adrenoceptor function was determined by measuring the positive inotropic response to (-)-isoproterenol. It was found that 10 microM HNE had no effect on beta-adrenoceptor function, whereas 100 microM HNE reduced the maximal effect to (-)-isoproterenol without affecting the pD2 (-log EC50). At these concentrations, HNE had no effect on either beta-adrenoceptor density or on c-AMP production. After 1 mM HNE, the atria stopped contracting. Since the effects of the synthetic thiol inactivator N-ethyl maleimide were similar to those of HNE, it was concluded that the reduction of beta-adrenoceptor function by HNE is probably the result of alkylation of free sulfhydryl groups. Our results indicate that the reduction of adenylate cyclase activity by oxidative stress is not mediated by the production of HNE, however oxidative stress and HNE both reduce the maximal response to beta-adrenoceptor stimulation.

Adenylyl Cyclases↗

PubMed1992

Effects of ischemia and reperfusion on cardiac tolerance to oxidative stress.

Oxidative stress may affect cardiac function and metabolism. Oxidants are normally inactivated by reacting with reduced glutathione (GSH), with resulting formation and release of oxidized glutathione (GSSG). However, ischemia might affect glutathione metabolism. This might render ischemic hearts less resistant against subsequent oxidant injury during reperfusion, and it might also affect the reliability of GSSG measurements as a means to investigate oxidative stress in reperfused hearts. We compared the metabolic and functional consequences of an oxidant load in control rabbit hearts and in hearts reperfused after 30 min of normothermic total ischemia. In controls, H2O2 infusion (H2O2; 5-30 microM) induced a dose-dependent stimulation of GSSG release and a progressive impairment of cardiac function. At these doses, H2O2 challenge of postischemic hearts resulted in biochemical and functional changes identical to those observed in controls. Release of lactate dehydrogenase (LDH) and of GSH was negligible, similar in both groups. In additional experiments, infusion of H2O2 at a much higher dose (200 microM) elicited a further increase in GSSG release from both groups, although GSSG concentrations were lower in postischemic hearts. The functional effects of the 200 microM H2O2 infusion were similar in both groups, all hearts showing rapid and irreversible deterioration of function. Occurrence of irreversible cell injury was also manifested by a large release of LDH and GSH to a similar extent in both groups. These data demonstrate that cardiac tolerance toward oxidants is largely unaffected by a relatively brief episode of severe ischemia and indicate that GSSG release can be reliably used to investigate oxidative stress in reperfused hearts.

Animals↗

PubMed1988

Biochemical aspects of cellular oxidative stress.

Oxidative stress, as proposed by H. Sies, indicates a change in the prooxidant/antioxidant balance of a biologic system in favour of the former. It is related to oxidative reactions that occur in aerobic metabolism which can damage biomolecules through generation of reactive oxygen species. The oxidative deterioration of polyunsaturated fatty acids of membrane phospholipids (lipid peroxidation) is one of the consequences of oxidative stress, and has been observed in the liver cell under the influence of ethanol or lindane intoxication, associated with the calorigenic action of thyroid hormones, induced by the rupture of t-butyl hydroperoxide by cellular hemoproteins, or in the autoxidation of a disrupted tissue. Apart from noxious challenges, oxidative free-radical processes are important in numerous physiological reactions, such as NADPH oxidase in the function of macrophages, ribonucleotide reduction in DNA metabolism, or in eicosanoids production.

Animals↗

PubMed1991

Vitamin E and oxidative stress.

Oxidative stress can result from or be enhanced by a large variety of conditions, including nutritional imbalance, exposure to chemical and physical agents in the environment, strenuous physical activities, injury, and hereditary disorders. While many enzymes and compounds are involved in protecting cells from the adverse effects of oxidative stress, vitamin E occupies an important and unique position in the overall antioxidant defense. The antioxidant function of vitamin E is closely related to the status of many dietary components. Vitamin E-depleted animals are generally more susceptible to the adverse effects of environmental agents than supplemented animals. Also, vitamin E supplementation is beneficial to certain groups of the population. However, supplementing vitamin E in experimental subjects maintained on a nutritionally adequate diet does not always provide additional protection. Differential metabolic responses in various organs and differences in experimental conditions often contribute in the discrepancies in the literature. The lack of clear evidence for the occurrence of lipid peroxidation or antioxidant function of vitamin E in vivo can be attributed partly to the presence of active pathways for metabolizing hydroperoxides, aldehydes, and other oxidation products. Specific and sensitive techniques for measuring lipid peroxidation products in biological systems are essential for understanding the role of free radical-induced lipid peroxidation in tissue damage and antioxidant function of vitamin E in vivo.

Animals↗

PubMed1991

The balance between Cu,Zn-superoxide dismutase and catalase affects the sensitivity of mouse epidermal cells to oxidative stress.

Oxidants are toxic, but at low doses they can stimulate rather than inhibit the growth of mammalian cells and play a role in the etiology of cancer and fibrosis. The effect of oxidants on cells is modulated by multiple interacting antioxidant defense systems. We have studied the individual roles and the interaction of Cu,Zn-superoxide dismutase (SOD) and catalase (CAT) in transfectants with human cDNAs of mouse epidermal cells JB6 clone 41. Since only moderate increases in these enzymes are physiologically meaningful, we chose the following five clones for in-depth characterization: CAT 4 and CAT 12 with 2.6-fold and 4.2-fold increased catalase activities, respectively, SOD 15 and SOD 3 with 2.3-fold and 3.6-fold increased Cu,Zn-SOD activities, respectively, and SOCAT 3 with a 3-fold higher catalase activity and 1.7-fold higher Cu,Zn-SOD activity than the parent JB6 clone 41. While the increases in enzyme activities were moderate, the human cDNAs were highly expressed in the transfectants. As demonstrated for the clone SOD 15, this discordance between message concentrations and enzyme activities may be due to the low stability of the human Cu,Zn-SOD mRNA in the mouse recipient cells. According to immunoblots the content of Mn-SOD was unaltered in the transfectants. While the activities of glutathione peroxidase were comparable in all strains, the concentrations of reduced glutathione (GSH) were significantly lower in SOD 3 and SOD 15. This decrease in GSH may reflect a chronic prooxidant state in these Cu,Zn-SOD overproducers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

[Alcohol, iron and oxidative stress].

An oxidative stress has been reported to occur at the hepatic level after ethanol administration. We recently reported that such a stress is also apparent at the cerebellar level during acute ethanol intoxication in rats. Since low molecular weight iron chelates (LMW-Fe) are involved in the biosynthesis of aggressive prooxidant species we presently studied the influence of acute and chronic ethanol administration on hepatic and cerebellar total non-heme iron and LMW-Fe. The results show that an acute ethanol load (50 mmoles/kg b. wt.) administered (i.p.) to male Sprague-Dawley rats elicits altogether a decrease in the non-heme iron content of the serum and a highly significant increase in the hepatic and cerebellar non-heme iron concentration. The LMW-Fe content as well as the percentage of total non-heme iron represented by LMW-Fe are increased at the same time in the cytosolic fraction isolated from hepatic and cerebellar homogenates of the acutely ethanol-treated rats. The ethanol-induced disturbances in the non-heme iron content of liver and cerebellum can be prevented by the administration of allopurinol, which is known to reduce the severity of the oxidative stress observed in these tissues after an acute ethanol load. To study the effects of chronic ethanol administration, rats were given during 4 weeks a 10% (v/v) solution of ethanol in water as sole drinking fluid. The average daily ethanol consumption was 7-9 g. In such alcohol-fed rats the non-heme iron content was decreased by 31% in the serum whereas it was increased by 18% in the liver and by 30% in the cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcoholism↗

PubMed1991

AppppA binds to several proteins in Escherichia coli, including the heat shock and oxidative stress proteins DnaK, GroEL, E89, C45 and C40.

The dinucleotide AppppA (5',5'''-P1, P4-diadenosine tetraphosphate) is rapidly synthesized in cells exposed to heat stress or oxidative stress. Stress-induced AppppA accumulation has been observed in all cell types studied to date. In order to study the function(s) of AppppA, we created a mutation in the Escherichia coli gene that encodes the sole AppppN hydrolase (apaH). High levels of AppppA have subsequently been shown to affect many cellular processes, including expression of catabolite repressible genes and the ability to survive starvation, oxidative stress and near-UV irradiation. Nevertheless, the precise role of AppppA remains undefined. In order to better understand the mechanism by which AppppA exerts its effects, we attempted to determine which proteins bind to AppppA by synthesizing (alpha'-32P) 8-N3AppppA for use in photocrosslinking experiments with extract derived from cells with different genetic backgrounds and exposed to various stress conditions. We report here that several E. coli proteins bind AppppA, including the heat shock and oxidative stress proteins DnaK, GroEL, E89, C45 and C40. In addition, we show that apaH mutants, which have high basal levels of AppppA, are hypersensitive to killing by heat.

Affinity Labels↗

PubMed1989

Cytoskeletal alterations in human platelets exposed to oxidative stress are mediated by oxidative and Ca2+-dependent mechanisms.

The metabolism of the redox-active quinone, menadione (2-methyl-1,4-naphthoquinone), in human platelets was associated with superoxide anion production, oxidation and depletion of intracellular glutathione, and modification of protein thiols. The cytoskeletal fraction extracted from menadione-treated platelets exhibited a dose-dependent increase in the amount of cytoskeleton-associated protein and a concomitant loss of protein thiols. These alterations were associated with oxidative modifications of actin, including beta-mercaptoethanol-sensitive crosslinking of actin to form dimers, trimers, and high-molecular-weight aggregates which also contained other cytoskeletal proteins, i.e., alpha-actinin and actin-binding protein. In addition, analysis of the cytoskeletal fraction from platelets treated with high concentrations (greater than or equal to 100 microM) of menadione by polyacrylamide gel electrophoresis under reducing conditions revealed a net decrease in the relative abundance of the individual cytoskeletal polypeptides. Under the same incubation conditions the platelets exhibited a sustained increase in cytosolic Ca2+ concentration. The presence of glucose, or the omission of Ca2+ from the incubation medium, prevented both the increase in cytosolic Ca2+ and the decrease in the relative amounts of cytoskeletal proteins. The latter effect was also largely prevented in platelets loaded with Quin-2 tetraacetoxymethyl ester to buffer the menadione-induced elevation of cytosolic Ca2+. Finally, the presence of a protease inhibitor, leupeptin, in the incubation medium prevented the menadione-induced decrease in the amount of actin-binding protein but not the decrease in the other cytoskeletal proteins. Our findings demonstrate that the multiple effects of oxidative stress on the platelet cytoskeleton are mediated by oxidative as well as by Ca2+-dependent mechanisms.

Actins↗

PubMed1991

Inhibition of glutathione synthesis in the newborn rat: a model for endogenously produced oxidative stress.

A model for oxidative stress is described in which glutathione (GSH) synthesis is selectively blocked in newborn rats by administration of L-buthionine-(S,R)-sulfoximine (BSO). In this model, the normal endogenous physiological formation of reactive oxygen species is largely unopposed, and therefore oxidative tissue damage occurs; because GSH is used for reduction of dehydroascorbate, tissue ascorbate levels decrease. In lung there are decreased numbers of lamellar bodies and decrease of intraalveolar surfactant. Proximal renal tubular, hepatic, and brain damage also occur. A diastereoisomer of BSO that does not inhibit GSH synthesis, L-buthionine-R-sulfoximine, does not produce toxicity; this control experiment renders it unlikely that the observed effects of BSO are produced by the sulfoximine moiety itself. There is correlation between the decrease of mitochondrial GSH levels and mitochondrial and cell damage. Oxidative stress as evaluated by mitochondrial damage and mortality can be prevented by treatment with GSH esters or ascorbate. There is apparent linkage between the antioxidant actions of GSH and ascorbate. This model, which may readily be applied to evaluation of the efficacy of other compounds in preventing oxidative stress, offers an approach to study of other effects of GSH deficiency (e.g., on lipid metabolism, hematopoiesis), and closely resembles oxidative stress that occurs in certain human newborns and in other clinical states.

Aging↗

PubMed2025

Chemoproteomic Profiling of Reactive Cysteines in Response to Oxidative Stress Induced by 6-Hydroxydopamine.

Although oxidative stress is a well-established driver of neurodegeneration, it remains poorly understood as to how the global cysteine (Cys) proteome is remodeled under oxidative stress conditions. Proteins with aberrantly modified cysteines in response to oxidative stress can induce and exacerbate neurodegeneration, contributing to disorders like Alzheimer's, Parkinson's, frontotemporal dementia, and amyotrophic lateral sclerosis. In this study, we induced oxidative stress in SH-SY5Y neuronal cells by subjecting them to the neurotoxin 6-hydroxydopamine (6-OHDA). To identify proteins with altered cysteine oxidation or PTM status, we used a desthiobiotin iodoacetamide (DBIA) probe, which selectively labels cysteines with unmodified and preserved thiols. Using these unbiased chemoproteomic strategies, we identified proteins with reduced Cys reactivity to DBIA in response to 6-OHDA-induced oxidative stress. Many of these proteins are critically involved in biological processes linked to cell stress responses (e.g., mitochondrial oxidative stress and apoptosis). Furthermore, we found that two key Cys on UCHL1 (a deubiquitinase critically involved in neurodegeneration) exhibited enhanced reactivity under oxidative stress conditions. Our study defines the remodeling of the Cys proteome under 6-OHDA-induced oxidative stress conditions. Furthermore, these findings suggest potential cysteine-mediated regulatory mechanisms in response to oxidative stress, providing a valuable resource for further exploration of cysteine modifications in the context of neurodegenerative signaling.

Oxidopamine↗

PubMed1991

Correlations and apparent contradictions in assessment of oxidant stress status in vivo.

Oxidative modifications of biological molecules are essential, but uncontrolled or excessive oxidative activities appear to contribute to many disease states. The mechanisms through which excess oxidant activities cause injury have been studied most extensively for acute responses, particularly for drug-induced tissue damage and cell death, but substantial evidence suggests that chronically elevated oxidative activity may contribute to the development of diseases such as cancer. It is important that the correlation between oxidant stress status and cancer risk be examined directly in humans. A number of methods have been developed for assessing oxidant activities by measuring oxidized products in biological systems, but cross-comparison studies of these different methods are needed. In studies of mechanisms of acute hepatotoxicity, assessments of oxidant stress responses by different analytical methods often have provided data that appear at first glance to be contradictory. Marked oxidant stress responses may be indicated by one or more methods of analysis despite the lack of detectable change in other parameters, whereas in a second experimental model the responses may be reversed. These observations emphasize the need to integrate different analytical approaches into the assessment of oxidant activity in vivo and illustrate the importance for developing a better understanding of the chemical and physiological mechanisms through which the analytical methodologies are related.

Cell Survival↗

PubMed1989

Oxidative stress and muscular dystrophy.

Oxidative stress may be the fundamental basis of many of the structural, functional and biochemical changes characteristic of the inherited muscular dystrophies in animals and humans. The presence of by-products of oxidative damage, and the compensatory increases in cellular antioxidants, both indicate oxidative stress may be occurring in dystrophic muscle. Changes in the proportions and metabolism of cellular lipids, abnormal functions of cellular membranes, altered activity of membrane-bound enzymes such as the SR Ca2+-ATPase, disturbances in cellular protein turnover and energy production and a variety of other changes all indicate that these inherited muscular dystrophies appear more like the results of oxidative stress to muscle than any other type of underlying muscle disturbance. Particular details of these altered characteristics of dystrophic muscle, in combination with current knowledge on the processes of oxidative damage to cells, may provide some insight into the underlying biochemical defect responsible for the disease, as well as direct research towards the ultimate goal of an effective treatment.

Animals↗

PubMed1990

2,3,7,8-Tetrachlorodibenzo-p-dioxin-induced oxidative stress in female rats.

Oxidative stress may play a role in the toxic manifestations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Therefore, the time-dependent effects of 100 micrograms TCDD/kg on various indices of oxidative stress including lipid peroxidation. DNA damage, membrane fluidity, calcium homeostasis, nonprotein sulfhydryl content, and NADPH content of hepatic subcellular fractions of female rats were followed for 12 days. Increases in lipid peroxidation of 400-500% occurred in mitochondrial and microsomal membranes and nuclei, with maximum increases occurring 5-6 days post-treatment. Decreases in the nonprotein sulfhydryl content of mitochondrial and microsomal fractions of approximately 80% were observed by Day 12 posttreatment. Membrane fluidity gradually decreased following administration of TCDD, with decreases of 30-40% being observed in mitochondria, microsomes, and plasma membranes. A sharp increase in the incidence of hepatic nuclear DNA single strand breaks was observed 3 days after treatment with an increase of approximately 600% by Day 9. Following the administration of TCDD, increases of 70-80% occurred in the calcium content of mitochondria and microsomes. An 18% increase in cytosolic calcium was present 12 days after the administration of TCDD. Cytosol and mitochondria both exhibited an initial increase in NADPH content following administration of TCDD, but by Day 12 both had decreased to approximately two-thirds of control values. The results clearly demonstrate that TCDD administration induces an oxidative stress in rat liver. The most pronounced effects were observed in membrane lipid peroxidation and DNA damage with gradual changes being observed in calcium and nonprotein sulfhydryl contents and membrane fluidity.

Animals↗

PubMed1990

Reduction of beta-adrenoceptor function by oxidative stress in the heart.

The effect of oxidative stress on beta-adrenoceptor function in the heart was determined. To this end ventricle membranes, field-stimulated rat left atria and field-stimulated rat right ventricle strips were exposed to 0.1 mM cumene hydroperoxide for 20 min. It was found that oxidative stress increased beta-adrenoceptor number and reduced c-AMP formation in the ventricle membranes. In the rat left atria and rat right ventricle strips the efficacy of beta-adrenoceptor agonists was reduced to approximately 30% of the control value, whereas maximal beta-adrenoceptor-mediated response was reduced to 50%. Using membranes from control atria and from atria exposed to oxidative stress, it was found that oxidative stress had no effect on beta-adrenoceptor density, nor on the affinity of (-)isoproterenol for the receptor. c-AMP production in membranes prepared from atria exposed to oxidative stress was reduced to approximately 30% of the c-AMP production in membranes prepared of control atria. In addition, it was found that the shape of the function that transduces the stimulus which is generated by receptor activation into an effect, is not altered by oxidative stress. It was concluded that the reduction of the efficacy of beta-adrenoceptor agonists by oxidative stress is probably caused by the reduction of c-AMP formation. Because the efficacy of forskolin and of dibutyryl c-AMP was not affected by oxidative stress, the reduced c-AMP formation is probably caused by an impaired coupling between the receptor and adenylate cyclase. The reduction of maximal beta-adrenoceptor-mediated response might be the result of cytotoxic aldehydes that are produced during oxidative stress. In ischemia, catecholamine release and subsequent beta-adrenoceptor hyperstimulation lead to cardiotoxicity. As shown in the present study, oxidative stress reduces beta-adrenoceptor function. This might represent a protective physiological feedback mechanism that protects the heart against excessive beta-adrenoceptor stimulation.

Adrenergic beta-Agonists↗

PubMed1991

Noninvasive measures of oxidative stress status in humans.

Although oxidative stress is thought to be involved in the pathophysiology of several diseases and aging, it is not routinely measured in clinical diagnosis. This is at least partly because accepted and standardized methods for measuring oxidative stress in humans are not yet established. One of the greatest needs in the field of free radical biology is the development of reliable methods for measuring oxidative stress status (OSS) in humans. A listing of some analytical approaches to measuring oxidative stress is provided as well as a listing of some noninvasive techniques that have been used in humans.

Aldehydes↗

PubMed1990

Arterial levels of oxidized glutathione (GSSG) reflect oxidant stress in vivo.

Neutrophil-related, oxidant-mediated injury to the pulmonary microvasculature appears to follow endotoxemia, cutaneous thermal injury, and ischemia-reperfusion injury to the liver or intestine. Glutathione is an important endogenous intracellular oxygen radical scavenger. Plasma concentrations of oxidized glutathione (GSSG) reflect oxidant injury resulting from an overdose of certain oxidatively metabolized drugs. The purpose of this investigation was to evaluate plasma GSSG as an indicator of oxidant stress resulting from activation of the endogenous inflammatory response. An established model of neutrophil- and oxidant-related acute lung injury following intestinal ischemia and reperfusion in rats was used. Intestinal ischemia was induced by clip occlusion of the superior mesenteric artery (SMA) for 120 min. Reperfusion resulted from SMA clip removal. Following reperfusion for 0, 15, or 120 min, plasma GSSG levels in portal vein, inferior vena cava (IVC), and aorta were obtained. Plasma GSSG was undetectable in sham animals and those with intestinal ischemia alone. Following reperfusion, all plasma samples had significant elevations in GSSG. Aortic plasma GSSG after 15 min of reperfusion was significantly elevated compared to both portal vein and IVC plasma GSSG. These data suggest that oxidant stress after intestinal reperfusion is reflected by elevations in plasma GSSG. The step up in plasma GSSG across the pulmonary vascular bed, a site of known oxidant injury, suggests that plasma GSSG may be a useful marker of oxidant stress in vivo, particularly with regard to the pulmonary microvasculature. This simple in vivo approach to assessing oxidant stress related to inflammatory tissue injury may have the potential to be of significant use in the clinical setting.

Animals↗

PubMed1991

Hydrogen peroxide-induced oxidative stress to the mammalian heart-muscle cell (cardiomyocyte): lethal peroxidative membrane injury.

Oxidative stress induced by hydrogen peroxide (H2O2) may contribute to the pathogenesis of ischemic-reperfusion injury in the heart. For the purpose of investigating directly the injury potential of H2O2 on heart muscle, a cellular model of H2O2-induced myocardial oxidative stress was developed. This model employed primary monolayer cultures of intact, beating neonatal-rat cardiomyocytes and discrete concentrations of reagent H2O2 in defined, supplement-free culture medium. Cardiomyocytes challenged with H2O2 readily metabolized it such that the culture content of H2O2 diminished over time, but was not depleted. The consequent H2O2-induced oxidative stress caused lethal sarcolemmal disruption (as measured by lactate dehydrogenase release), and cardiomyocyte integrity could be preserved by catalase. During oxidative stress, a spectrum of cellular derangements developed, including membrane phospholipid peroxidation, thiol oxidation, consumption of the major chain-breaking membrane antiperoxidant (alpha-tocopherol), and ATP loss. No net change in the protein or phospholipid contents of cardiomyocyte membranes accompanied H2O2-induced oxidative stress, but an increased turnover of these membrane constituents occurred in response to H2O2. Development of lethal cardiomyocyte injury during H2O2-induced oxidative stress did not require the presence of H2O2 itself; a brief "pulse" exposure of the cardiomyocytes to H2O2 was sufficient to incite the pathogenic mechanism leading to cell disruption. Cardiomyocyte disruption was dependent upon an intracellular source of redox-active iron and the iron-dependent transformation of internalized H2O2 into products (e.g., the hydroxyl radical) capable of initiating lipid peroxidation, since iron chelators and hydroxyl-radical scavengers were cytoprotective. The accelerated turnover of cardiomyocyte-membrane protein and phospholipid was inhibited by antiperoxidants, suggesting that the turnover reflected molecular repair of oxidized membrane constitutents. Likewise, the consumption of alpha-tocopherol and the oxidation of cellular thiols appeared to be epiphenomena of peroxidation. Antiperoxidant interventions coordinately abolished both H2O2-induced lipid peroxidation and sarcolemmal disruption, demonstrating that an intimate pathogenic relationship exists between sarcolemmal peroxidation and lethal compromise of cardiomyocyte integrity in response to H2O2-induced oxidative stress. Although sarcolemmal peroxidation was causally related to cardiomyocyte disruption during H2O2-induced oxidative stress, a nonperoxidative route of H2O2 cytotoxicity was also identified, which was expressed in the complete absence of cardiomyocyte-membrane peroxidation. The latter mode of H2O2-induced cardiomyocyte injury involved ATP loss such that membrane peroxidation and cardiomyocyte disruption on the one hand and cellular de-energization on the other could be completely dissociated.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗