Hydrogen peroxide causes the fatal injury to human fibroblasts exposed to oxygen radicals

Effect of centrophenoxine and BCE-001 treatment on lateral diffusion of proteins in the hepatocyte plasma membrane as revealed by fluorescence recovery after photobleaching in rat liver smears

The average lateral diffusion coefficient of proteins (D) in the cell membrane of hepatocytes has been measured in liver smears by fluorescence recovery after photobleaching (FRAP), based on the so-called peroxide-induced autofluorescence (PIAF) deriving from the oxidation of riboflavin bound to membrane proteins. It has been previously shown that D displays a significant negative linear age correlation. The in vivo effects of two drugs were tested on this parameter. Young (2.7 months) and old (24-26 months) male rats received centrophenoxine (CPH) or a new drug (BCE-001) by either intraperitoneal (i.p.) injection or per os through a gastric tube for 26 to 42 days. D was measured on a double-blind basis in the hepatocyte plasma membrane of treated and control groups. The CPH and BCE-001 treatments did not affect the value of D in the young rats. However, the latter drug increased their growth rate. An increase of D in old animals was induced by treatment with either drug. When the drug effects in old rats were compared, BCE-001 proved to be more efficient than CPH, and at the same time was able to significantly retard the age-dependent loss of body weight characteristic of these animals at the age of approximately 2 years. Our results are in good accord with the predictions of the membrane hypothesis of aging as regards the role of properly placed OH. free radical scavengers in the improvement of membrane and overall cell function.

Cytotoxicity of the hypoxanthine-xanthine oxidase system on V79 cells: comparison of the effects of SOD and CuDIPS

The hypoxanthine - xanthine oxidase system generates an extracellular flux of superoxide anion radical (O2.-) and hydrogen peroxide (H2O2). Catalase but not superoxide dismutase (SOD) protects V79 cells exposed to the hypoxanthine - xanthine oxidase system, showing that H2O2 is the major reactive oxygen species involved in the cytotoxicity of such a system. In contrast to SOD, the lipophilic SOD like compound CuII (diisopropylsalicylate)2 (CuDIPS) exhibits some protection at non cytotoxic concentration. It is also found that methanol partially protects cells exposed to the hypoxanthine-xanthine oxidase system. It appears that in our experimental conditions (temperature, ionic strength and pH) the protective effect afforded by methanol and CuDIPS is due to the inhibition of the xanthine oxidase activity.

Synergistic cytolysis mediated by hydrogen peroxide combined with peptide defensins

Possible cytolytic interactions between hydrogen peroxide (H2O2) and neutrophil granule proteins were studied. Preliminary experiments demonstrated synergistic cytolysis when erythro-leukemia targets were exposed to H2O2 combined with a low molecular weight (approximately 3900) granule extract that was predominantly composed of peptide defensins. The synergistic interaction was confirmed when sublytic concentrations of H2O2 were combined with defensin preparations that had been purified to homogeneity. Synergy was concentration dependent in regard to both molecules and could not be explained by trace contamination of defensin preparations with myeloperoxidase. Sequential addition experiments suggested that synergistic lysis required a simultaneous exposure to both cytotoxins. In the presence of sublytic concentrations of H2O2, the binding of iodinated defensin to targets was significantly increased, providing a possible explanation for the observed synergy. Since both molecules are concurrently secreted by activated neutrophils, this interaction may be important during leukocyte-mediated anti-tumor effects or inflammatory tissue injury.

Induction of repair functions by hydrogen peroxide in Chinese hamster cells

Hydrogen peroxide has been found to kill Chinese hamster V79 cells as an exponential function of dose. When a small dose (0.9 microgram/ml for 1 h) was used as a pretreatment, before exposure to higher concentrations of the same agent, the cells became more resistant to killing than those which were not so pretreated. The presence of cycloheximide or benzamide, during this pretreatment, inhibited this observed increase in resistance. This pretreatment also resulted in decreased killing efficiency by MNNG and gamma-rays, but had no effect upon UV-light-induced killing. The results suggest that proteins (repair enzymes?) are synthesized after treatment with the small dose of hydrogen peroxide, and that these induced proteins enhance the cellular repair functions for agents causing DNA breaks.

Binding of haptoglobin, inter-alpha-trypsin inhibitor, and alpha 1 proteinase inhibitor to synovial fluid hyaluronate and the influence of these proteins on its degradation by oxygen derived free radicals

Synovial fluid from 201 normal and pathological knee joints was subjected to gel filtration by Sepharose CL-2B chromatography to separate hyaluronic acid (HA) from unbound proteins, which were retarded on this column. HA from all normal fluids was excluded from the gel and contained 1% or less bound protein. Synovial fluids taken from joints of patients with rheumatoid arthritis (RA) contained considerably more protein bound to HA. In 46% of RA samples the level of protein was greater than 4%, whereas only one fluid examined from osteoarthritic joints contained this amount. The proteins bound to HA from RA joints were identified by sodium dodecyl sulphate/polyacrylamide gel electrophoresis (SDS-PAGE) and immunodiffusion techniques as the acute phase proteins alpha 1 proteinase inhibitor, inter-alpha-trypsin inhibitor, and haptoglobin. The average relative percentages of these proteins bound to HA were 17.6%, 32.6%, and 29.2% respectively. These HA-protein complexes could be generated in vitro by mixing normal (low protein) HA with any one of the three acute phase proteins. The HA-protein complexes formed in vitro with inter-alpha-trypsin inhibitor or haptoglobin, and those isolated from RA synovial fluids, were more resistant to degradation by oxygen derived free radicals (ODFR) than HA from normal fluids. From these findings we conclude that certain acute phase proteins diffusing into synovial fluid during inflammatory episodes may play an important part in protecting HA from depolymerisation by activated phagocytes.

Monocyte and polymorphonuclear leukocyte toxic oxygen metabolite production in multiple sclerosis

Lipid-laden macrophages, which are predominantly derived from blood monocytes, are present at sites of active multiple sclerosis demyelination and are assumed to be involved in the demyelinating process. These inflammatory cells produce a variety of toxic oxygen metabolites which can mediate host tissue destruction. We measured production of two oxygen metabolites by monocytes and polymorphonuclear leukocytes in MS patients and controls. Stimulated monocytes produced significantly more hydrogen peroxide, superoxide, and chemiluminescence in the MS group than controls. The polymorphonuclear leukocyte, an inflammatory cell that appears to contribute little to MS demyelination, did not demonstrate increased production of toxic oxygen metabolites in the MS patients as compared to controls. These results suggest that blood monocytes in MS patients are primed to produce increased amounts of cytotoxic oxygen metabolites when exposed to inflammatory stimuli.

Interactions between isolated hepatocytes and Kupffer cells in iron metabolism: a possible role for ferritin as an iron carrier protein

Like the rat peritoneal macrophage, the isolated Kupffer cell is capable of processing and releasing iron acquired by phagocytosis of immunosensitized homologous red blood cells. When erythrophagocytosis is restrained to levels which do not affect cell viability, about one red cell per macrophage, close to 50% of iron acquired from red cells is released within 24 hr in the form of ferritin. Immunoradiometric assay of the extracellular medium indicates that 160 ng ferritin are released by 10(6) Kupffer cells after 24-hr incubation at 37 degrees C. Iron release is temperature-dependent, the rate at 37 degrees C being nearly 5-fold greater than at 4 degrees C. As estimated by sucrose-gradient ultracentrifugation, ferritin released by the erythrophagocytosing Kupffer cell averages 2,400 iron atoms per molecule. When reincubated with isolated hepatocytes, this released ferritin is rapidly taken up by the cells. Via this process, hepatocytes may accumulate more than 160,000 iron atoms per cell per min. Such accumulation is not impeded by the presence of iron-loaded transferrin in the culture medium, but is markedly depressed by rat liver ferritin. In contrast to the conservation of transferrin during its interaction with hepatocytes, the protein shell of the ferritin molecule is rapidly degraded into trichloroacetic acid-soluble fragments. Ferritin-mediated transfer of iron from Kupffer cells to hepatocytes may help explain the resistance of the liver to iron deficiency as well as the liver's susceptibility to iron overload.

Aspects of in vitro placental perfusion: effects of hyperoxia and phenol red

The study of a number of parameters of placental function indicated that the perfused human placental lobe maintained its structural and functional integrity when PO2 levels in buffer perfusate were near physiological values, despite low O2 consumption. High O2 content in the perfusate may reduce placental transfer either through a direct vasoconstrictor effect or in combination with the destruction of vascular cyclo-oxygenase, resulting in the reduced synthesis of the vasodilator prostacyclin. A similar mechanism may be involved in the reduction of placental transfer observed in the presence of phenol red. These studies suggest that aspects of in vitro methodologies which may relate to prostaglandin production deserve careful consideration and further study.

Iron metabolism in the erythrophagocytosing Kupffer cell

Like the peritoneal macrophage, the isolated Kupffer cell is capable of processing and releasing iron acquired by phagocytosis of immunosensitized homologous red blood cells. When erythrophagocytosis is restrained to levels which do not affect cell viability, or less than 1.5 red cells/macrophage (phagocytic index of 150%), over 40% of iron acquired from red cells is released within 24 hr. More active erythrophagocytosis results in greater release of iron but progressive deterioration in cell viability. Iron release is temperature-dependent, the rate at 37 degrees C being nearly 5-fold greater than at 4 degrees C. Inclusion of either desferrioxamine or apotransferrin in the culture medium augments iron release by 25 to 30%, with both agents together having an almost additive effect. Despite its effect on iron release, apotransferrin is not found in sonicates of Kupffer cells, while desferrioxamine appears to chelate iron within the cells. Ascorbate also enhances iron release, but at the expense of cell viability. Neither chloroquine nor colchicine at concentrations which do not affect cell viability influence iron release. The inflammatory state, characterized by hypoferremia due to impaired processing or release of iron by the reticuloendothelial system, may be modeled in vitro when serum from rats bearing turpentine-induced abscesses is included in the culture medium. Attempts to delineate the humoral agent responsible for this effect have not been successful, iron release being insensitive to the presence of interleukin-1, gamma-interferon and tumor necrosis factor.

Gentamicin enhanced production of hydrogen peroxide by renal cortical mitochondria

Agents that affect mitochondrial respiration have been shown to enhance the generation of reactive oxygen metabolites. On the basis of the well-demonstrated ability of gentamicin to alter mitochondrial respiration (stimulation of state 4 and inhibition of state 3), it was postulated that gentamicin may enhance the generation of reactive oxygen metabolites by renal cortical mitochondria. The aim of this study was to examine the effect of gentamicin on the production of hydrogen peroxide (measured as the decrease in scopoletin fluorescence) in rat renal cortical mitochondria. The hydrogen peroxide generation by mitochondria was enhanced from 0.17 +/- 0.02 nmol . mg-1 . min-1 (n = 14) in the absence of gentamicin to 6.21 +/- 0.67 nmol . mg-1 . min-1 (n = 14) in the presence of 4 mM gentamicin. This response was dose dependent with a significant increase observed at even the lowest concentration of gentamicin tested, 0.01 mM. Production of hydrogen peroxide was not increased when gentamicin was added to incubation media in which mitochondria or substrate was omitted or heat-inactivated mitochondria were used. The gentamicin-induced change in fluorescence was completely inhibited by catalase (but not by heat-inactivated catalase), indicating that the decrease in fluorescence was due to hydrogen peroxide. Thus this study demonstrates that gentamicin enhances the production of hydrogen peroxide by mitochondria. Because of their well-documented cytotoxicity, reactive oxygen metabolites may play a critical role in gentamicin nephrotoxicity.

The synthesis of hyaluronic acid by human synovial fibroblasts is influenced by the nature of the hyaluronate in the extracellular environment

Various cell lines of human synovial fibroblasts derived from synovium obtained at the time of biopsy or total joint-replacement surgery have been established. The synthesis of 3H-labelled hyaluronic acid (HA) in these cells has been determined, and the effects of adding HA of varying molecular size to the cultured cells examined. The results obtained clearly show that the in vitro synthesis of HA by these cells is influenced by the concentration and molecular weight (MW) of the HA in their extracellular environment. Synovial fibroblasts derived from an osteoarthritic joint demonstrated the most marked response on exposure to exogenous HA, showing a stimulation of HA synthesis with preparations of weight-average molecular weight (Mw) greater than 5 X 10(5) in a concentration dependent manner. HA preparations with Mw less than 5 X 10(5) showed little or no effect except at high concentrations where a suppression of biosynthesis was observed. A model to explain these findings is proposed.

Generation of superoxide by immunologically stimulated normal human neutrophils and possible modulation by intracellular and extracellular SOD and rheumatoid factors

Rheumatoid synovial fluids generated significantly greater amounts of superoxide, lysosomal enzymes, and superoxide dismutase from neutrophils into extracellular fluid than osteoarthritic synovial fluids. Rheumatoid factors isolated from serum suppressed superoxide-generating activity of performed immune complexes, but did not suppress that of intermediate-sized immune complexes isolated from RA serum. Synovial fluid neutrophils has a greater capacity to generate superoxide and lower intracellular superoxide dismutase activity, compared with peripheral neutrophils of the corresponding patients. These results suggest that neutrophil superoxide release may be modulated, both by rheumatoid factor and by intracellular and extracellular superoxide dismutase.

Cultured skin fibroblasts in schizophrenia: acute growth and susceptibility to damage

The study of cultured fibroblasts derived from skin biopsies of patients with inherited neurodegenerative disorders has aided in the elucidation of their pathological basis. This usefulness might be expected to extend to the study of fibroblast characteristics in schizophrenia in view of recent evidence of neurodegenerative changes in the disorder. In this study, the acute growth characteristics and response to toxic oxygen metabolites of fibroblast cell lines derived from skin biopsies of patients with schizophrenia (n = 9) are compared with those derived from psychiatric patients with various diagnoses not associated with a deteriorating course (controls = 11). No significant differences between the cell lines of the two patient groups are found.

The use of sodium bicarbonate and hydrogen peroxide in periodontal therapy: a review

The comparative benefits from the use of sodium bicarbonate and hydrogen peroxide over the use of a commercial dentifrice in periodontal therapy is controversial. The consensus of the clinical research indicates that application by patients of sodium bicarbonate and hydrogen peroxide offers no advantage over the preestablished, properly performed home oral hygiene procedures. Any improvements in clinical and microbial parameters generally were attributed to scaling and root planing. The studies that have reported beneficial results with sodium bicarbonate and hydrogen peroxide have used additional antimicrobial agents, concomitant professional application of these substances, and scaling and root planing. In one of these reports, inorganic salts and chloramine-T were delivered subgingivally throughout root-planing procedures, in addition to home application of inorganic salts. Most of these patients also received at least one course of systemic tetracycline therapy. Because this study had no control group, it is impossible to determine whether this program is more effective than are other periodontal therapy programs. A more controlled clinical study involving professional application of sodium bicarbonate, sodium chloride, hydrogen peroxide, and povidone-iodine has shown greater gains in clinical attachment and bone mass than has brushing with toothpaste and water. Again, subgingival scaling and root planing were necessary to attain these results. Because multiple topical agents were applied in both of these reports and systemic antimicrobial agents were used by the Keyes group, it is impossible to determine which agent was responsible for the improvements. Further, professional application may be the crucial factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative study of the enzymatic defense systems against oxygen-derived free radicals: the key role of glutathione peroxidase

Human WI-38 diploid fibroblasts have been cultivated under high toxic O2 pressure, and their survival curves are reported. Superoxide dismutase, catalase, or glutathione peroxidase provided some protection when injected in the cells exposed to O2. This protective effect, recorded after 3 or 4 days of incubation, was the most pronounced when cells were injected just before oxygen exposure. Quantitative injection assays have been performed for the three enzymes. Surprisingly, glutathione peroxidase was found to be much more effective than both catalase and superoxide dismutase, the latter being particularly inefficient.

Free radical scavenging systems and the effect of peroxide damage in aged human skin fibroblasts

One prominent theory of aging postulates an accumulation of cell damage resulting from nonenzymatic chemical reactions between important cellular components and free radicals. Fibroblast lines derived from skin biopsies of psychiatric patients ranging in age from 22 to 70 were evaluated soon after adaptation to culture. No significant correlation was found between donor age and the detoxification enzyme activities of superoxide dismutase (SOD) or aryl hydrocarbon hydroxylase (AHH) or susceptibility to damage by oxygen metabolites as measured by cell viability or lactate dehydrogenase (LDH) leakage.

Catalase protection of neuronal survival in vitro is not directed to the accumulation of peroxides in the culture medium

Walicke et al. (1986, J. Neurosci. 6, 1114-1121) have shown that catalase can replace the pyruvate requirement for survival of CNS neurons cultured in vitro. Since presently the only known function of catalase is the enzymatic degradation of hydrogen peroxide to water and oxygen, the simplest interpretation of the ability of catalase to support neuronal survival would be that catalase removes from the culture medium hydrogen peroxide. To test this hypothesis 8-day embryonic chick forebrain cells were cultured for 24 hr in a modified Eagle's Basal Medium with the serum-free supplement N1 (HEBM/N1) in the presence or absence of Phenol Red, 20 micrograms/ml catalase, 1 mM pyruvate, and/or 25 mM N-2-hydroxyethylpiperazine-N'-2-ethane-sulfonic acid (HEPES) on a polyornithine-laminin substratum. The various media were then assayed for peroxide content using the potassium iodide method described by Wang and Nixon (1978, In Vitro 14, 714-722). The present data reveal that (1) HEBM/N1 normally contains approximately 50 microM peroxides, little of which is hydrogen peroxide, (2) the organic peroxide levels accumulating in this medium are not reduced by either catalase or pyruvate, and (3) medium modifications can reduce to no longer detectable levels the peroxides accumulating in the medium, but catalase or pyruvate is still required for neuronal survival. We conclude that catalase must exert its survival-promoting action at levels other than peroxides accumulating in the culture medium.

Intracellular calcium homeostasis during hydrogen peroxide injury to cultured P388D1 cells

The effects of exposure of cultured P388D1 cells to H2O2 on intracellular free calcium ([Ca++]i) was investigated utilizing the intracellular fluorescent calcium chelator "Quin 2." [Ca++]i rose from approximately 150 nM to greater than 2 microM over a time course that was strongly dependent on the concentration of H2O2 used (5 X 10(-5) to 5 X 10(-3) M). After exposure of P388D1 cells to 5 X 10(-3) M H2O2, Quin 2 was fully saturated between 15 and 30 min exposure. During this time, no apparent change in the rate of equilibration of 45Ca++ from the extracellular medium could be detected, whereas in cells preloaded with 45Ca, net 45Ca was lost from the cells at a greater rate than controls. Measurements of total cellular calcium by atomic absorption spectroscopy confirmed that there was a net loss of calcium from the cells during the first 30 min. At time points greater than 45 min after exposure to H2O2 the influx of extracellular 45Ca and net intracellular Ca++, Na+ and K+ rapidly increased. Half times for H2O2 catabolism by the cells varied from about 8 min at 5.0 X 10(-4) M H2O2 to 14.0 min at 5.0 X 10(-3) M. When the total [Ca++]i-buffering capacity of the Quin 2 pool was varied by increasing the loading of intracellular Quin 2 by 68-fold (1.1 X 10(2) - 7.6 X 10(3) amol per cell), the rate of rise of [Ca++]i was depressed by only 1.6-fold following exposure to 5 mM H2O2. During the rise of intracellular [Ca++]i, cell morphology was observed by both light and scanning electron microscopy and revealed that "surface blebs" appeared during this phase of injury. Both the rise in [Ca++]i and "blebbing" were observable before any loss in cell viability was detected by either loss of Trypan blue exclusion or loss of preloaded 51Cr from the cells. From these results we conclude the following, H2O2 exposure induces a dose-dependent disturbance of intracellular calcium homeostatis; the rise in [Ca++]i is mediated by exposure to H2O2 in the early phase of the injury, and is not dependent on the continuing presence of the oxidant; the rate of rise of [Ca++]i is largely independent of the quantity of calcium mobilized to the Quin 2 pool; during the early phase (less than 30 min) of rise of [Ca++]i, only intracellular calcium is involved in the response; these events occur concomitantly with gross morphological changes to the plasma membrane.(ABSTRACT TRUNCATED AT 400 WORDS)

Kidney glomerular explants in serum-free media: role of individual medium components in cell outgrowth

Guinea pig glomeruli were grown for 22 days in a serum-free medium composed of Waymouth's MB 752/1 supplemented with sodium pyruvate, nonessential amino acids, and antibiotics. To this basic medium was added insulin, transferrin, selenium (Se), tri-iodothyronine, or fibronectin (FN) - either singly, or in various combinations - and sequential quantitative studies of the glomerular outgrowths were performed. Total cells in glomerular outgrowths, mitotic index, and glomerular attachment rate were determined and compared with values for glomerular outgrowths in media containing either no additions or all of the above components. FN was required for whole glomerular attachment, while transferrin plus FN was required for mitosis in glomerular cell outgrowths. Insulin and tri-iodothyronine slightly increased glomerular cell outgrowth by slightly increasing whole glomerular attachment, but had little effect on mitosis in glomerular outgrowths. The effect of Se was complex. Se did not affect whole glomerular attachment or mitosis in the presence of transferrin plus FN. However, in a medium containing transferrin, FN, and 3-amino-1,2,4-triazole (AT) (an inhibitor of catalase and glutathione peroxidase), Se increased total cell number but had little effect on the glomerular attachment rate or the mitotic index. Morphologic analysis of glomeruli early in culture suggested that Se may act by decreasing the amount of or delaying the time of cell death. In all of the media tested, total DNA was relatively constant over the course of 22 days, suggesting the possibility that glomerular cells cultured in a serum-free medium are part of a cell renewal system.

Antioxidant defense mechanisms of endothelial cells: glutathione redox cycle versus catalase

The importance of the glutathione (GSH) redox cycle and of catalase as intracellular antioxidant defense systems in cultured endothelial cells against an extracellular flux of H2O2, a critical mediator of polymorphonuclear leukocyte-induced oxidant injury of endothelial cells, was examined. The activities of different parts of the GSH redox cycle were impaired by 1,3-bis(2-chloroethyl)-1-nitrosourea, buthionine sulfoximine, diethyl maleate and 2-cyclohexene-1-one. Catalase activity was inhibited by 3-amino-1,2,4-triazole. After an impairment of the GSH redox cycle, but not of catalase, the susceptibility of pulmonary artery endothelial cells to an attack by H2O2 was dramatically increased independent of the source of extracellularly generated hydrogen peroxide (i.e., glucose oxidase or stimulated polymorphonuclear leukocytes). Exogenous catalase, d-alpha-tocopherol, and particularly Trolox, the chroman compound of tocopherol, but not phytol, the fatty acid side chain of tocopherol, provided almost complete protection of the endothelial cells against a H2O2-mediated attack. Additional fluorometric studies suggested that H2O2 is scavenged by the antioxidants before it hits the target cells.

Peroxidative aggregation of myelin membrane proteins

The exposure of CNS myelin to reactive oxygen species (ROS) generated by a Cu2+-H2O2 system results in the aggregation of membrane proteins. Integral and peripheral membrane proteins are equally vulnerable and the denaturation is not mediated by the SH groups. The aggregated proteins retain their original antigenicity as determined by immunoblot technique. The aggregation of proteins is not limited to myelin and can be elicited in the preparation of other cerebral membranes. The effect of ROS on membrane proteins can also be demonstrated in cerebral slices incubated in the presence of the ROS-generating system. Furthermore, the peroxidation inactivates membrane-bound enzymes as exemplified by myelin cyclic nucleotide phosphatase (CNP). Competitive inhibition studies with various scavengers and quenchers of ROS implicate singlet oxygen as a major mediator in the Cu2+-H2O2 oxidizing system responsible for the peroxidative aggregation of membrane proteins.

Characteristics of the active oxygen in covalent binding of the pesticide methoxychlor to hepatic microsomal proteins

This study examined the characteristics of the active oxygen species involved in generation of the reactive intermediate of methoxychlor which covalently binds to liver microsomal proteins. The possibility that the active oxygen participating in the above reaction is the superoxide anion (O2-) or a species generated from O2- was examined with the help of superoxide dismutase (SOD) and with an SOD-mimetic agent, CuDIPS [Cu2+(3,5-diisopropylsalicylic acid)2]. It was observed that, whereas CuDIPS inhibited covalent binding of methoxychlor metabolite(s), SOD did not. However, ZnDIPS [Zn2+(3,5-diisopropylsalicylic acid)2], which exhibits no SOD-mimetic activity, did not inhibit covalent binding. Furthermore, both CuDIPS and ZnDIPS had little or no effect on the formation of demethylated (polar) metabolites of methoxychlor, demonstrating that the inhibition of covalent binding by CuDIPS was not merely due to a general inhibition of the hepatic monooxygenase system. These findings suggested that O2- was involved in covalent binding, but was not accessible to SOD. Additional support for O2- involvement stems from the observation that alpha-tocopheryl acid succinate markedly inhibited covalent binding of methoxychlor. The possibility that hydrogen peroxide (H2O2) was involved in covalent binding of methoxychlor appears unlikely. Catalase had no effect on covalent binding when NADPH was the cofactor, and the use of H2O2 in place of NADPH did not yield covalent binding. Certain scavengers of hydroxyl radical (ethanol, t-butanol and benzoate) inhibited, and other known scavengers (DMSO and mannitol) did not inhibit, covalent binding. EDTA stimulated binding, desferal (desferrioxamine) exhibited no effect on binding, and diethylenetriaminepentaacetic acid (DETAPAC) inhibited binding. A possible explanation for this observation is that the Fe2+ needed for generation of X OH is much more easily obtained from Fe3+-EDTA than from Fe3+-desferal, which resists reduction. The inhibitory effect by DETAPAC may be due to chelation of another metal which is needed for the reaction. Lastly, certain scavengers of singlet oxygen inhibited covalent binding with little effect on the formation of polar metabolites of methoxychlor. In conclusion, these studies support the involvement of X OH and singlet oxygen, possibly derived from O2-, in the formation of the reactive methoxychlor intermediate.(ABSTRACT TRUNCATED AT 400 WORDS)

Escherichia coli xthA mutant is not hypersensitive to ascorbic acid/copper treatment--an H2O2 generating reaction

Ascorbate (vitamin C) in the presence of copper yields H2O2, which seems to be responsible for its toxic effects in bacteria. However, we found that the Escherichia coli xthA mutant strain, which is hypersensitive to H2O2, has almost the same sensitivity as the wild-type strain to ascorbate and copper treatment. Our results suggest that the DNA damage induced in E. coli by H2O2 generated in oxidized ascorbate solutions is different from that induced by direct H2O2 treatment.

Kidney glomerular explants in serum-free media: demonstration of intracellular antioxidant enzymes and active oxygen metabolites

Guinea pig glomeruli were grown for 22 d in a serum-free medium composed of Waymouth's MB 752/l supplemented with sodium pyruvate, nonessential amino acids, and antibiotics (the basic medium). Intracellular cellular activity of the antioxidant enzymes superoxide dismutase (SOD; both copper-zinc [Cu,Zn] and manganese [Mn] forms) and catalase, and intracellular active oxygen metabolites (hydrogen peroxide [H2O2] and superoxide [O2-.]) were measured with time in culture. The results were compared to results obtained from glomeruli grown in different serum-free media, including the basic medium plus fibronectin (FN), the basic medium plus transferrin and FN, and a complex medium containing insulin, transferrin, selenium (Se), triiodothyronine, and FN (complete medium). In general, although the intracellular activity of antioxidant enzymes and active oxygen metabolites varied over time in culture in all media, there were only a few statistically significant differences among different media. Both CuZn SOD and Mn SOD activity were demonstrated in isolated glomeruli. The CuZn SOD activity per DNA ratio decreased slightly with time in culture in all media tested except the complete medium, in which CuZn SOD activity per DNA ratio remained more constant. The Mn SOD activity per DNA ratio did not vary significantly over time in culture. Catalaselike activity was very low in isolated glomeruli and declined sharply with time in culture in all media except the complete medium. Both H2O2 and O2-. were detected intracellularly in glomerular culture. Our results indicate that intracellular antioxidant enzymes and active oxygen metabolites in glomeruli vary with time in culture and, in some instances, with culture conditions.

An experimental model for hydrogen peroxide-induced tissue damage. Effects of a single inflammatory mediator on (peri)articular tissues

Hydrogen peroxide is receiving increasing attention as a mediator of tissue damage during inflammation. To evaluate its destructive potential in vivo, we devised a model in which hydrogen peroxide is, initially, the sole mediator of tissue damage. Glucose oxidase, which was made cationic to obtain good retention in tissue, was injected intraarticularly in mouse knee joints. This enzyme produces hydrogen peroxide, using endogenous glucose as a substrate. The local production of hydrogen peroxide induced drastic vascular damage, as measured by 99mTc uptake and leakage of 125I-albumin. The chondrocyte proteoglycan synthesis was severely inhibited, as measured by 35SO4 incorporation. Histologic examination showed impressive inflammatory and degenerative changes, including periarticular infiltration, chondrocyte death, subchondral erosions, and muscle necrosis. Intraarticular administration of catalase could inhibit these vascular effects and cartilage damage. Systemic administration of ebselen, a synthetic glutathione peroxidase-like compound, provided partial protection. Indomethacin and piroxicam were not effective in the acute phase. We think this model is useful both for testing drugs that are purported to act as scavengers of hydrogen peroxide and for studying chronic destructive processes.

Hydrogen peroxide toxicity may be enhanced by heat shock gene induction in Drosophila

Recent evidence suggests that low dose exposure of cells to hydrogen peroxide and/or induction of heat shock protein (HSP) synthesis will render cells resistant to the lethal effects of a subsequent high dose hydrogen peroxide stress. We explored this possibility in the Drosophila melanogaster Schneider tissue culture line 2. It was found that chronic low dose exposure (1 mM H2O2 for 3 days) resulted in marked potentiation of the toxic effects of a subsequent high dose exposure (50 mM H2O2 for 1 h), as assessed by impairment of uridine incorporation and cell proliferation. Cells preexposed to low dose H2O2 exhibited enhanced heat shock gene transcription upon exposure to high dose H2O2, as compared to cells that did not receive low dose preexposure. Transcriptional induction of the heat shock genes by a mild non-toxic heat shock resulted in marked enhancement of the anti-proliferative effects of a subsequent H2O2 exposure. Thus, low dose hydrogen peroxide exposure or mild heating results in subsequent enhancement of high dose hydrogen peroxide toxicity; this effect correlates with enhanced heat shock gene expression. Possible mechanisms are discussed.

Protection of mammalian cells by o-phenanthroline from lethal and DNA-damaging effects produced by active oxygen species

Active oxygen species are suspected as being a cause of the cellular damage that occurs at the site of inflammation. Phagocytic cells accumulate at these sites and produce superoxide ion, hydrogen peroxide and hydroxyl radical. The ultimate killing species, the cellular target and the mechanism whereby the lethal injury is produced are unknown. We exposed mouse fibroblasts to xanthine oxidase and acetaldehyde, a system which mimics the membrane of phagocytic cells in terms of production of oxygen species. We observed that the generation of these species produced DNA strand breaks and cellular death. The metal chelator o-phenanthroline completely abolished the former effect, and at the same time it effectively protected the cells from lethal injuries. Because complexing iron o-phenanthroline prevents the formation of hydroxyl radical by the Fendon reaction (Fe(II) + H2O2----Fe(III) + OH- + OH.), it is proposed that most of the cell death and DNA damage are brought about by OH radical, produced from other species by iron-mediated reactions.

Human vascular smooth muscle cells and endothelial cells lack catalase activity and are susceptible to hydrogen peroxide

51Cr release as lytic and cell detachment as nonlytic injury were employed to estimate neutrophil-mediated injury of cultured human vascular smooth muscle cells and endothelial cells. The reagents hydrogen peroxide or hypoxanthine-xanthine oxidase produced dose-dependent killing and nonlytic cell detachment, which were specifically inhibited by catalase but not by superoxide dismutase. The concentration of hydrogen peroxide or xanthine oxidase to induce cell detachment was less than lytic dose, suggesting that cell detachment was a much more sensitive assay of injury. Neutrophil-mediated cell lysis averaged 15% at most and was mostly dependent on hydrogen peroxide, while neutrophil-mediated cell detachment was nearly 100% and its dependency on hydrogen peroxide varied from 46% to 60%. These results suggest that vascular smooth muscle cells and endothelial cells in neutrophil-mediated events are destroyed by a hydrogen peroxide-dependent process, mainly via a nonlytic cell detachment mechanism. There was no striking difference of sensitivity to hydrogen peroxide between vascular smooth muscle cells and endothelial cells. Vascular smooth muscle cells and endothelial cells contained fairly high concentrations of superoxide dismutase, but not catalase, activity. The sensitivity of these cells to hydrogen peroxide but not to superoxide may arise from the fact that these cells lack intracellular catalase activity. The injury of vascular cells, which constitute important components of blood vessels, may lead to vascular injury and subsequent tissue damage.

Current concepts regarding adult respiratory distress syndrome

Adult respiratory distress syndrome (ARDS) is a multietiologic acute and progressive pulmonary dysfunction that may be precipitated by any of a number of pathogenic agents. Clinical and experimental studies suggest that activation of complement and blood neutrophils plays a significant role in the development of pulmonary vascular injury, which is an important pathophysiological feature of ARDS. Although the specific cellular and biochemical mechanisms resulting in the development of ARDS are unknown, it has been suggested that oxygen-derived free radicals generated from complement-activated granulocytes may be involved, directly or indirectly, in the destruction of lung vascular endothelium and alveolar tissue matrix. This hypothesis is supported by recent experimental studies showing that acute lung injury secondary to systemic complement activation can largely be prevented by interventions that scavenge for hydroxyl radicals or restrict availability of ionic iron.

Detoxification of H2O2 by cultured rabbit lens epithelial cells: participation of the glutathione redox cycle

Although it has been shown that cultured rabbit lenses can adequately defend against the 0.03-0.05 mM level of H2O2 normally found in aqueous humor, the contribution of the epithelium in this process has not been well defined. In the present study, the peroxide-detoxifying ability of the epithelium is evaluated in cultured rabbit lens cells established from 4-6-day-old rabbits and compared to that of skin fibroblasts from rabbits of the same age. When cells were cultured in medium containing H2O2, the concentration of peroxide rapidly decreased; however, various concentrations could be maintained for 3-hr periods by using glucose oxidase to enzymically generate H2O2. At an extracellular level of 0.03 mM H2O2, the rate of detoxification of peroxide by epithelial cells was 2 mumol H2O2 (8 x 10(5) cells)-1 3 hr-1, twice as fast as that for fibroblasts. Epithelial cells contained a high level of reduced glutathione (GSH) equal to 36 nmol (8 x 10(5) cells)-1, twice that present in the fibroblasts. The concentration of GSH in 8 x 10(5) epithelial cells, a number of cells normally present in one intact rabbit lens epithelium, remained constant during 3 hr of exposure to H2O2 levels as high as 0.03 mM, even though the amount of H2O2 taken up under these conditions was sufficient to oxidize completely the cellular GSH every 2 min. In contrast, the GSH content of fibroblasts declined at levels of peroxide above 0.01 mM. Participation of the glutathione redox cycle in the H2O2-detoxification process was demonstrated from studies of hexose monophosphate shunt (HMPS) activity as measured by oxidation of [1-14C]-labeled glucose. The oxidation of [1-14C]-glucose in epithelial cells was stimulated 13 times that of controls during exposure to 0.04-0.05 mM H2O2, while the corresponding increase in oxidation of [6-14C]-labeled glucose was only 1.6 times. In contrast, maximum shunt activity in fibroblasts occurred at 0.03-0.04 mM H2O2 and was six times the control value. The growth potential of the cells following a 3-hr exposure to H2O2 was also used as a measure of oxidant toxicity in both cell types. Concentrations of H2O2 up to 0.03 mM had no effect on the growth of 8 x 10(5) epithelial cells but did diminish the growth of the same number of fibroblasts. Cell density was found to be an important parameter in the ability of the cells to tolerate H2O2.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition of proteoglycan synthesis by hydrogen peroxide in cultured bovine articular cartilage

Oxygen-derived reactive species, generated enzymatically by the action of xanthine oxidase upon hypoxanthine, significantly inhibit proteoglycan synthesis by cultured bovine articular cartilage (Bates, E.J., Lowther, D.A. and Handley, C.J. (1984) Ann. Rheum. Dis. 43, 462-469). Here we extend these investigations and show, through the use of catalase and the specific iron chelator diethylenetriaminepentaacetic acid, that the active species involved is H2O2 and not the hydroxyl radical. Incubations of cartilage with H2O2 at concentrations of 1 X 10(-4) M and above are also inhibitory to proteoglycan synthesis. Subsequent recovery of the tissue is dependent upon the initial dose of xanthine oxidase or H2O2. Xanthine oxidase at 84 mU per incubation results in a prolonged inhibition of proteoglycan synthesis which is still apparent after 14 days in culture. Lower concentrations of xanthine oxidase (21-66 mU) are inhibitory to proteoglycan synthesis, but the tissue is able to synthesise proteoglycans at near normal rates after 3 days in culture. The inhibition of proteoglycan synthesis by 1 X 10(-4) M H2O2 is completely reversed after 5 days in culture, whereas 1 X 10(-3) M H2O2 results in a more prolonged inhibition. The synthesis of the proteoglycan core protein is inhibited, but the ability of the newly formed proteoglycans to aggregate with hyaluronic acid is unimpaired.

The hemolytic activity of citral: evidence for free radical participation

In the present investigation the hemolytic properties of citral were examined. Tests with different concentrations of citral showed that hemolysis of rat erythrocytes commenced after a lag period the length of which depended on the concentration of the hemolysin and tended to 100% hemolysis. Comparison of the characteristics of the hemolysis induced by high and low citral concentrations, indicated that two mechanisms are involved--a non specific steroid--terpenoid or glutathione depletion mechanism dominating at high citral concentrations and a free radical mechanism dominating at low citral concentrations. Experiments performed with various free radical scavengers indicate that 1O2 might be involved.

Antioxidant protection: a function of tracheobronchial and gastrointestinal mucus

It is proposed that one of the functions of the mucus layers lining the respiratory tract and gastrointestinal system is the scavenging of highly reactive oxygen-derived species. This would provide antioxidant protection to the underlying mucosal epithelial cells.

Oxygen free-radicals mediate an inhibition of proteoglycan synthesis in cultured articular cartilage

Superoxide radical, generated enzymatically by the action of xanthine oxidase on hypoxanthine, significantly inhibited proteoglycan synthesis by cultured bovine articular cartilage. This inhibition was not due to the generation of uric acid or to the generation of superoxide per se. It was immediate in onset and still evident after six days in culture. The inhibition was similar for both 35S-sulphate and 3H-acetate incorporation into glycosaminoglycans and could not be reversed by addition of beta-D-benzyl xyloside. Protein synthesis was also inhibited.

Correlation between cytotoxic effect of hydrogen peroxide and the yield of DNA strand breaks in cells of different species

The rate of loss of reproductive capacity produced by hydrogen peroxide was shown to be 6-times faster for human fibroblasts than for Chinese hamster fibroblasts. Mouse fibroblasts exhibited an intermediate response. The explanation for that does not lie in the different capacities of these cells to destroy H2O2. The kinetics of repair of single-strand breaks although slightly different for the three cell lines also does not provide a full explanation for the different sensitivity. What was shown to correlate well with the killing effect was the yield of strand breaks produced by H2O2 in the DNA of cells from the three species. A similar H2O2 concentration produced 5-10-times more strand breaks in human DNA than in hamster DNA and 2-4-times more than in mouse DNA. This ratio holds for different cell lines from human and hamster and thus seems to be species-specific. Based on our previous findings we propose that this difference may lie in the amount of chromatin-bound iron and the level of superoxide ion in these cells.

In vivo formation of single-strand breaks in DNA by hydrogen peroxide is mediated by the Haber-Weiss reaction

Phenanthroline and bipyridine, strong chelators of iron, protect DNA from single-strand break formation by H2O2 in human fibroblasts. This fact strongly supports the concept that these DNA single-strand breaks are produced by hydroxyl radicals generated by a Fenton-like reaction between intracellular Fe2+ and H2O2: H2O2 + Fe2+----Fe3+ + OH- + OH: Corroborating this idea is the fact that thiourea, an effective OH radical scavenger, prevents the formation of DNA single-strand breaks by H2O2 in nuclei from human fibroblasts. The copper chelator diethyldithiocarbamate, a strong inhibitor of superoxide dismutase, greatly enhances the in vivo production of DNA single-strand breaks by H2O in fibroblasts. This supports the idea that Fe3+ is reduced to Fe2+ by superoxide ion: O divided by 2 + Fe3+----O2 + Fe2+; and therefore that the sum of this reaction and the Fenton reaction, namely the so-called Haber-Weiss reaction, H2O2 + O divided by 2----O2 + OH- + OH; represents the mode whereby OH radical is produced from H2O2 in the cell. EDTA completely protects DNA from single-strand break formation in nuclei. The chelator therefore removes iron from the chromatin, and although the Fe-EDTA complex formed is capable of reacting with H2O2, the OH radical generated under these conditions is not close enough to hit DNA. Therefore iron complexed to chromatin functions as catalyst for the Haber-Weiss reaction in vivo, similarly to the role played by Fe-chelates in vitro.

Mechanisms of the killing of cultured hepatocytes by hydrogen peroxide

Mechanisms of H2O2-induced cell injury were explored in primary cultures of rat hepatocytes. Cells prepared from male rats and cultured for 1 day prior to treatment were killed by H2O2 either added directly to the medium at 0.25-2 mM or generated in situ by glucose oxidase (0.25-2 U/ml) or xanthine oxidase (20-120 mM/ml) and 2 mM xanthine. Catalase protected the cells in each case. Lipid peroxidation as measured by the accumulation of malondialdehyde (MDA) preceded the cell death due to H2O2 added directly to the cultures or generated in the medium. The antioxidants N,N'-diphenyl-p-phenylenediamine (DPPD) and promethazine prevented the accumulation of MDA in both cases and protected the cells treated with H2O2 directly. DPPD and promethazine did not react directly with H2O2. Other antioxidants including butylated hydroxytoluene, vitamin E, and N-propylgallate had varied protective activity against the addition of H2O2 in proportion to their ability to reduce MDA accumulation. In glucose oxidase-treated cultures, DPPD and promethazine prevented the cell killing during the first hour but failed to protect between 1 and 3 h despite prevention of lipid peroxidation. The cell killing between 1 and 3 h in the presence of DPPD was prevented by catalase indicating its dependence upon continued generation of H2O2. Further addition of H2O2 in the presence of DPPD also increased the number of dead cells without lipid peroxidation. The data are consistent with at least two mechanisms of hepatocyte killing by H2O2. The first pathway is prevented by the antioxidants DPPD and promethazine and is very likely related to the peroxidation of membrane phospholipids. The second is independent of lipid peroxidation yet dependent upon the continued presence of H2O2.

Superoxide and hydrogen peroxide-dependent lipid peroxidation in intact and triton-dispersed erythrocyte membranes

Isolated erythrocyte membranes incubated with xanthine, xanthine oxidase, and Fe(III) underwent lipid peroxidation, as indicated by the thiobarbituric acid reaction and iodometric determination of hydroperoxides. In detergent-free medium (phosphate buffered saline) peroxidation was inhibited by superoxide dismutase, catalase, and EDTA; but was promoted by OH. scavangers, eg. mannitol. Generation of OH. in the system via iron-catalyzed reduction of H2O2 by O-2 was demonstrated by EPR spectrometry using spin trapping. In membranes treated with Triton X-100 lipid peroxidation was stimulated by EDTA and suppressed by OH. traps. This and other evidence suggests that OH. in the medium was an effective initiator of lipid peroxidation in detergent-dispersed membranes, but not in intact membranes.

The adhesins of Mycoplasma gallisepticum and M. pneumoniae

The growth of M. gallisepticum was monitored in regard to their capacity to haemagglutinate. The maximal potential was with cells grown for about 22 h. M. gallisepticum, like M. pneumoniae, possess a Triton shell intracellular filamentous structure which is revealed by exposing the cells to a relatively low concentration of Triton-X100. The adhesin of M. gallisepticum was partially purified on sialoglycopeptide conjugated to Sepharose-4B. The adhesin fraction was primarily composed of one polypeptide of about 75,000 molecular weight.

Hemolysis caused by cetomacrogol 1000: evidence for hydroxyl radical participation

The mechanism of cetomacrogol 1000-induced hemolysis was investigated. Previous conclusions that peroxides are involved in the hemolytic process were confirmed. The possibility that hydrogen peroxide, superoxide, hydroxyl radical, or singlet oxygen, which are known to induce hemolysis, are involved in cetomacrogol 1000-induced hemolysis was tested by using specific inhibitors and inactivators. The hydroxyl radical (OH.) was shown to be the only apparent oxygen species involved in cetomacrogol 1000-induced hemolysis. Its contribution to the hemolytic potency of the surfactant is approximately 30%.

Trichothecene-induced hemolysis. I. The hemolytic activity of T-2 toxin

In the present investigation, the hemolytic properties of T-2 toxin were examined. Tests with different concentrations of T-2 toxin showed that essentially complete hemolysis of rat erythrocytes commenced after a lag period, the length of which depended on the concentration of toxin. Comparison of the characteristics of hemolysis caused by T-2 toxin, saponins, H2O2, and polyoxyethylene surfactants showed great similarity between T-2 toxin and the latter two which proceed by a free radical mechanism. The same mechanism was suggested for hemolysis caused by T-2 toxin on the basis of the additional following observations: (1) darkness inhibited hemolysis; (2) specific free radical scavengers, i.e., vitamin E, mannitol, and histidine, inhibited hemolysis caused by T-2 toxin.

Dietary carcinogens and anticarcinogens. Oxygen radicals and degenerative diseases

The human diet contains a great variety of natural mutagens and carcinogens, as well as many natural antimutagens and anticarcinogens. Many of these mutagens and carcinogens may act through the generation of oxygen radicals. Oxygen radicals may also play a major role as endogenous initiators of degenerative processes, such as DNA damage and mutation (and promotion), that may be related to cancer, heart disease, and aging. Dietary intake of natural antioxidants could be an important aspect of the body's defense mechanism against these agents. Many antioxidants are being identified as anticarcinogens. Characterizing and optimizing such defense systems may be an important part of a strategy of minimizing cancer and other age-related diseases.