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G R Buettner

Publications and source records attributed to G R Buettner.

At least 19 recordsLinked to original sources
PubMed2001

v-Ha-RaS oncogene upregulates the 92-kDa type IV collagenase (MMP-9) gene by increasing cellular superoxide production and activating NF-kappaB.

Matrix metalloproteinase 9 (MMP-9) degrades basement membrane type IV collagen and is expressed during cellular migration and invasion. Here we show that v-Ha-Ras overexpression in rat kidney epithelial cells (REC) caused upregulation of MMP-9 gene expression in part by increasing cellular oxidant levels. v-Ha-Ras mediated the production of superoxide in Ras-transfected cells, which was associated with upregulated MMP-9 gene expression. Conversely, v-Ha-Ras expression decreased steady-state levels of mRNAs from tissue inhibitor of metalloproteinase 1 (TIMP-1), an inhibitor of MMP-9; plasminogen activator inhibitor 1 (PAI-1), which indirectly activates MMP-9 by increasing plasmin levels; and collagen IV, a substrate of MMP-9 and a major component of basement membrane. Gel mobility shift assays demonstrated that Ras overexpression enhanced NF-kappaB, but not AP-1 DNA binding to motifs in the MMP-9 gene promoter. The Ras-induced increase in NF-kappaB DNA binding could be inhibited by treatment with the antioxidants N-acetyl-L-cysteine and glutathione monoester, suggesting that intracellular oxidant levels can mediate MMP-9 transcription. Our findings identify an important role for Ras in the regulation of MMP-9 expression, and suggest that increased superoxide production can upregulate MMP-9 expression and thus contribute to malignant conversion.

Animals↗
PubMed2001

Redox environment of the cell as viewed through the redox state of the glutathione disulfide/glutathione couple.

Redox state is a term used widely in the research field of free radicals and oxidative stress. Unfortunately, it is used as a general term referring to relative changes that are not well defined or quantitated. In this review we provide a definition for the redox environment of biological fluids, cell organelles, cells, or tissue. We illustrate how the reduction potential of various redox couples can be estimated with the Nernst equation and show how pH and the concentrations of the species comprising different redox couples influence the reduction potential. We discuss how the redox state of the glutathione disulfide-glutathione couple (GSSG/2GSH) can serve as an important indicator of redox environment. There are many redox couples in a cell that work together to maintain the redox environment; the GSSG/2GSH couple is the most abundant redox couple in a cell. Changes of the half-cell reduction potential (E(hc)) of the GSSG/2GSH couple appear to correlate with the biological status of the cell: proliferation E(hc) approximately -240 mV; differentiation E(hc) approximately -200 mV; or apoptosis E(hc) approximately -170 mV. These estimates can be used to more fully understand the redox biochemistry that results from oxidative stress. These are the first steps toward a new quantitative biology, which hopefully will provide a rationale and understanding of the cellular mechanisms associated with cell growth and development, signaling, and reductive or oxidative stress.

Cell Cycle↗
PubMed2001

Phospholipid hydroperoxide glutathione peroxidase protects against singlet oxygen-induced cell damage of photodynamic therapy.

Phospholipid hydroperoxide glutathione peroxidase (PhGPx) is an important enzyme in the removal of lipid hydroperoxides (LOOHs) from cell membranes. Cancer treatments such as photodynamic therapy (PDT) induce lipid peroxidation in cells as a detrimental action. The photosensitizers used produce reactive oxygen species such as singlet oxygen ((1)O(2)). Because singlet oxygen introduces lipid hydroperoxides into cell membranes, we hypothesized that PhGPx would provide protection against the oxidative stress of singlet oxygen and therefore could interfere with cancer treatment. To test this hypothesis, human breast cancer cells (MCF-7) were stably transfected with PhGPx cDNA. Four clones with varying levels of PhGPx activity were isolated. The activities of other cellular antioxidant enzymes were not influenced by the overexpression of PhGPx. Cellular PhGPx activity had a remarkable inverse linear correlation to the removal of lipid hydroperoxides in living cells (r = -0.85), and correlated positively with cell survival after singlet oxygen exposure (r = 0.94). These data demonstrate that PhGPx provides significant protection against singlet oxygen-generated lipid peroxidation via removal of LOOH and suggest that LOOHs are major mediators in this cell injury process. Thus, PhGPx activity could contribute to the resistance of tumor cells to PDT.

Blotting, Northern↗
PubMed2001

Nitric oxide synthase inhibitors decrease coronary sinus-free radical concentration and ameliorate myocardial stunning in an ischemia-reperfusion model.

OBJECTIVES: Our objective was to determine the effect of a nitric oxide synthase inhibitor, NG-nitro-L-arginine (L-NNA) on free radical generation and myocardial contractility after ischemia-reperfusion. BACKGROUND: Cardiotoxic free radicals are generated by ischemia-reperfusion sequences. Nitric oxide reacts with superoxide radical to form peroxynitrite, which generates additional free radicals. Our hypothesis was that by inhibiting NO production, free radical formation will be diminished, which should be cardioprotective. METHODS: We studied 32 dogs. Coronary occlusion-reperfusion (20 min each) sequences were created by intracoronary balloon angioplasty inflation-deflation. Using electron paramagnetic resonance, we monitored the coronary sinus concentration of ascorbate free radical (Asc*-), a measure of total oxidative flux. The L-NNA (4.8 mg/kg total) was infused intravenously during occlusion-reperfusion; control dogs received saline. Immunohistochemical staining demonstrated the peroxynitration product nitrotyrosine. RESULTS: In the control dogs Asc*- rose from 3.2 +/- SD 0.5 nmol/l to 4.8 +/- 1.1 nmol/l with reperfusion, a 50% rise. With L-NNA the Asc*- rose from 3.2 +/- 0.9 nmol/l to 4.0 +/- 1.2 nmol/l, a 25% rise (p < 0.01, L-NNA vs. control). Echocardiographic left ventricular fractional area shortening (FAS) in the control dogs declined from 38 +/- 19% (baseline) to 26 +/- 14% (ischemia), and to 22 +/- 11% with reperfusion (p < 0.01 vs. baseline). With L-NNA, FAS declined from 36 +/- 13% (baseline) to 27 +/- 12% (ischemia) but then rose to 33 +/- 14 with reperfusion (p = NS vs. baseline). Nitrotyrosine was present in the myocardium subjected to ischemia-reperfusion, but almost absent in dogs receiving L-NNA. Myocardial perfusion was not altered by L-NNA. CONCLUSIONS: The NO synthase inhibitors decrease coronary sinus free radical concentration and ameliorate myocardial stunning after ischemia-reperfusion.

Animals↗
PubMed2001

V-Ha-Ras overexpression induces superoxide production and alters levels of primary antioxidant enzymes.

Reactive oxygen species have been shown to play important roles in v-Ha-Ras mitogenic signaling. We hypothesized that v-Ha-Ras overexpression would induce superoxide production, and therefore modify expression of the primary antioxidant enzyme system. We have demonstrated that immortal rat kidney epithelial cells stably transduced with constitutively active v-Ha-ras produced significantly larger amounts of superoxide radical than wild-type or vector-transfected control cells. The levels of the primary antioxidant enzymes copper- and zinc-containing superoxide dismutase, manganese-containing superoxide dismutase, catalase, and glutathione peroxidase were increased in the superoxide-overproducing cells. DNA-binding activities of the transcription factors activator protein-1, activator protein-2, and nuclear factor-kappaB were all enhanced in the superoxide-overproducing cells. These v-Ha-ras transduced cells also had a shortened cell doubling time and higher plating efficiency, and displayed greater constitutive levels of phosphorylated mitogen-activated protein kinases. These data demonstrate that v-Ha-Ras overexpression increases superoxide production and this apparently affects a wide variety of cell signaling and redox systems.

Animals↗
PubMed2001

Mechanisms of circulatory and intestinal barrier dysfunction during whole body hyperthermia.

This work tested the hypotheses that splanchnic oxidant generation is important in determining heat tolerance and that inappropriate.NO production may be involved in circulatory dysfunction with heat stroke. We monitored colonic temperature (T(c)), heart rate, mean arterial pressure, and splanchnic blood flow (SBF) in anesthetized rats exposed to 40 degrees C ambient temperature. Heating rate, heating time, and thermal load determined heat tolerance. Portal blood was regularly collected for determination of radical and endotoxin content. Elevating T(c) from 37 to 41.5 degrees C reduced SBF by 40% and stimulated production of the radicals ceruloplasmin, semiquinone, and penta-coordinate iron(II) nitrosyl-heme (heme-.NO). Portal endotoxin concentration rose from 28 to 59 pg/ml (P < 0.05). Compared with heat stress alone, heat plus treatment with the nitric oxide synthase (NOS) antagonist N(omega)-nitro-L-arginine methyl ester (L-NAME) dose dependently depressed heme-.NO production and increased ceruloplasmin and semiquinone levels. L-NAME also significantly reduced lowered SBF, increased portal endotoxin concentration, and reduced heat tolerance (P < 0.05). The NOS II and diamine oxidase antagonist aminoguanidine, the superoxide anion scavenger superoxide dismutase, and the xanthine oxidase antagonist allopurinol slowed the rates of heme-.NO production, decreased ceruloplasmin and semiquinone levels, and preserved SBF. However, only aminoguanidine and allopurinol improved heat tolerance, and only allpourinol eliminated the rise in portal endotoxin content. We conclude that hyperthermia stimulates xanthine oxidase production of reactive oxygen species that activate metals and limit heat tolerance by promoting circulatory and intestinal barrier dysfunction. In addition, intact NOS activity is required for normal stress tolerance, whereas overproduction of.NO may contribute to the nonprogrammed splanchnic dilation that precedes vascular collapse with heat stroke.

Allopurinol↗
PubMed2000

Detailed methods for the quantification of nitric oxide in aqueous solutions using either an oxygen monitor or EPR.

The interest in nitric oxide has grown with the discovery that it has many biological functions. This has heightened the need for methods to quantify nitric oxide. Here we report two separate methods for the quantification of aqueous stock solutions of nitric oxide. The first is a new method based on the reaction of nitric oxide with oxygen in liquid phase (*NO + O2 + 2H2O --> 4HNO2); an oxygen monitor is used to measure the consumption of oxygen by nitric oxide. This method offers the advantages of being both simple and direct. The presence of nitrite or nitrate, frequent contaminants in nitric oxide stock solutions, does not interfere with the quantification of nitric oxide. Measuring the disappearance of dissolved oxygen, a reactant, in the presence of known amounts of nitric oxide has provided verification of the 4:1 stoichiometry of the reaction. The second method uses electron paramagnetic resonance spectroscopy (EPR) and the nitric oxide trap [Fe2+-(MGD)2], (MGD = N-methyl-D-glucamine dithiocarbamate). The nitrosyl complex is stable and easily quantitated as a room temperature aqueous solution. These two methods are validated with Sievers 280 Nitric Oxide Analyzer and cross-checked with standards using UV-Vis spectroscopy. The practical lower limits for measuring the concentration of nitric oxide using the oxygen monitor approach and EPR are approximately 3 microM and 500 nM, respectively. Both methods provide straightforward approaches for the standardization of nitric oxide in solution.

Electron Spin Resonance Spectroscopy↗
PubMed2000

EPR detection of lipid-derived free radicals from PUFA, LDL, and cell oxidations.

We have used the spin trap 5,5-dimethyl-pyrroline-1-oxide (DMPO) and EPR to detect lipid-derived radicals (Ld*) during peroxidation of polyunsaturated fatty acids (PUFA), low-density lipoprotein (LDL), and cells (K-562 and MCF-7). All oxygen-centered radical adducts of DMPO from our oxidizable targets have short lifetimes (<20 min). We hypothesized that the short lifetimes of these spin adducts are due in part to their reaction with radicals formed during lipid peroxidation. We proposed that stopping the lipid peroxidation processes by separating oxidation-mediator from oxidation-substrate with an appropriate extraction would stabilize the spin adducts. To test this hypothesis we used ethyl acetate to extract the lipid-derived radical adducts of DMPO (DMPO/Ld*) from an oxidizing docosahexaenioc acid (DHA) solution; Folch extraction was used for LDL and cell experiments. The lifetimes of DMPO spin adducts post-extraction are much longer (>10 h) than the spin adducts detected without extraction. In iron-mediated DHA oxidation we observed three DMPO adducts in the aqueous phase and two in the organic phase. The aqueous phase contains DMPO/HO* aN approximately aH approximately 14.8 G) and two carbon-centered radical adducts (aN1 approximately 15.8 G, aH1 approximately 22.6 G; aN2 approximately 15.2 G, aH2 approximately 18.9 G). The organic phase contains two long-chain lipid radical adducts (aN approximately 13.5 G, aH approximately 10.2 G; and aN approximately 12.8 G; aH approximately 6.85 G, 1.9 G). We conclude that extraction significantly increases the lifetimes of the spin adducts, allowing detection of a variety of lipid-derived radicals by EPR.

Acetates↗
PubMed2000

Biological effects of menadione photochemistry: effects of menadione on biological systems may not involve classical oxidant production.

Because cell-mediated reduction of menadione leads to the generation of reactive oxygen species (ROS), this quinone is widely used to investigate the effects of ROS on cellular functions. We report that A549 human lung epithelial cells exposed to menadione demonstrate a dose-dependent increase in both intracellular calcium ([Ca(2+)](i)) and ROS formation. The concentrations of menadione required to initiate these two events are markedly different, with ROS detection requiring higher levels of menadione. Modulators of antioxidant defences (e.g. buthionine sulphoximine, 3-amino-1,2,4-triazole) have little effect on the [Ca(2+)](i) response to menadione, suggesting that ROS formation does not account for menadione-dependent alterations in [Ca(2+)](i). Additional evidence suggests that menadione photochemistry may be responsible for the observed [Ca(2+)](i) effects. Specifically: (a) EPR studies with the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) show that light exposure (maximum effect at 340 nm) stimulates menadione-dependent formation of the DMPO/(.)OH spin adduct that was not sensitive to antioxidant interventions; (b) DMPO inhibits menadione and light-dependent increases in [Ca(2+)](i); and (c) light (maximum effect at 340 nm) augments the deleterious effects of menadione on cell viability as determined by (51)Cr release. These photo effects do not appear to involve formation of singlet oxygen by menadione, but rather are the result of the oxidizing chemistry initiated by menadione in the triplet state. This work demonstrates that menadione species generated by photo-irradiation can exert biological effects on cellular functions and points to the potential importance of photochemistry in studies of menadione-mediated cell damage.

Calcium↗
PubMed2000

Myeloperoxidase is involved in H2O2-induced apoptosis of HL-60 human leukemia cells.

We examined the mechanism of H(2)O(2)-induced cytotoxicity and its relationship to oxidation in human leukemia cells. The HL-60 promyelocytic leukemia cell line was sensitive to H(2)O(2), and at concentrations up to about 20-25 micrometer, the killing was mediated by apoptosis. There was limited evidence of lipid peroxidation, suggesting that the effects of H(2)O(2) do not involve hydroxyl radical. When HL-60 cells were exposed to H(2)O(2) in the presence of the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN), we detected a 12-line electron paramagnetic resonance spectrum assigned to the POBN/POBN(.) N-centered spin adduct previously described in peroxidase-containing cell-free systems. Generation of this radical by HL-60 cells had the same H(2)O(2) concentration dependence as initiation of apoptosis. In contrast, studies with the K562 human erythroleukemia cell line, which is often used for comparison with the HL-60, and with high passaged HL-60 cells (spent HL-60) studied under the same conditions failed to generate POBN(.). Cellular levels of antioxidant enzymes superoxide dismutase, glutathione peroxidase, and catalase did not explain the differences between these cell lines. Interestingly, the K562 and spent HL-60 cells, which did not generate the radical, also failed to undergo H(2)O(2)-induced apoptosis. Based on this we reasoned that the difference in H(2)O(2)-induced apoptosis might be due to the enzyme myeloperoxidase. Only the apoptosis-manifesting HL-60 cells contained appreciable immunoreactive protein or enzymatic activity of this cellular enzyme. When HL-60 cells were incubated with methimazole or 4-aminobenzoic acid hydrazide, which are inhibitors of myeloperoxidase, they no longer underwent H(2)O(2)-induced apoptosis. Hypochlorous acid stimulated apoptosis in both HL-60 and spent HL-60 cells, indicating that another oxidant generated by myeloperoxidase induces apoptosis and that it may be the direct mediator of H(2)O(2)-induced apoptosis. Taken together these observations indicate that H(2)O(2)-induced apoptosis in the HL-60 human leukemia cell is mediated by myeloperoxidase and is linked to a non-Fenton oxidative event marked by POBN(.).

Apoptosis↗
PubMed2000

A spectrophotometric method for the direct detection and quantitation of nitric oxide, nitrite, and nitrate in cell culture media.

A method for the spectrophotometric determination of nitric oxide, nitrite, and nitrate in tissue culture media is presented. The method is based on the nitric oxide-mediated nitrosative modification of sulfanilic acid that reacts with N-(1-naphthyl)ethylenediamine dihydrochloride forming an orange-colored product absorbing at 496 nm. Nitric oxide levels were determined in culture media from this absorbance measurement using chemiluminescence standardization. Extinction coefficients of 5400 and 6600 M(-1) cm(-1) were determined for the nitric oxide product in assay solutions containing 0.1 or 100 mM KPO4 buffer (pH 7.4), respectively, with a limit of detection of 1 microM. Acidification of these reactions (pH 2.4) generated a pink-colored product absorbing at 540 nm allowing for quantitation of total nitric oxide/nitrite levels using extinction coefficients of 38,000 and 36,900 M(-1) cm(-1), for the assay solutions described. The limit of detection of this assay was approximately 300 nM. Using the 100 mM KPO4 buffer system, nitrate levels were determined following reduction to nitrite using a copper-coated cadmium reagent with an extinction coefficient of 29,500 M(-1) cm(-1) and a detection limit of 0.5 microM. The utility of these assays was demonstrated in the standardization of nitric oxide-saturated cell culture media, and the release of nitric oxide by the NONOate compound DEA/NO.

Culture Media↗
PubMed2000

Oxygen free radicals mediate the induction of manganese superoxide dismutase gene expression by TNF-alpha.

In this study, the hypothesis that oxygen free radicals act as intracellular messengers is examined. Treatment of human oral carcinoma SCC-25 cells with 200 ng/ml human TNF-alpha for 6 h greatly increased manganese superoxide dismutase (MnSOD) gene expression as detected by western blotting, RT-PCR, and nuclear run-on experiments. In the presence of the oxygen free radical spin trapping reagent, 5,5-dimethyl pyrroline-N-oxide (DMPO), the induction of MnSOD gene expression by TNF-alpha was significantly reduced. Electron paramagnetic resonance experiments showed that the production of oxygen free radicals was enhanced in TNF-alpha treated cells. Taken together, these observations suggest that the induction of MnSOD expression by TNF-alpha is at least partially mediated by intracellular formation of oxygen free radicals, and that superoxide is most likely the initiating species involved in the mediation of MnSOD gene expression by TNF-alpha.

Blotting, Western↗
PubMed2000

Acidic pH amplifies iron-mediated lipid peroxidation in cells.

The goal of our study was to investigate the mechanism by which changes in extracellular pH influence lipid peroxidation processes. Ferrous iron can react with hydroperoxides, via a Fenton-type reaction, to initiate free radical chain processes. Iron is more soluble at lower pH values, therefore we hypothesized that decreasing the environmental pH would lead to increased iron-mediated lipid peroxidation. We used Photofrin, a photosensitizer that produces singlet oxygen, to introduce lipid hydroperoxides into leukemia cells (HL-60, K-562, and L1210). Singlet oxygen reacts with the PUFA of cells producing lipid hydroperoxides. Using EPR spin trapping with POBN, free radical formation from HL-60 cells was only detected when Photofrin, light, and ferrous iron were present. Free radical formation increased with increasing iron concentration; in the absence of extracellular iron, radical formation was below the limit of detection and lipid hydroperoxides accumulated in the membrane. In the presence of iron, lipid-derived radical formation in cells is pH dependent; the lower the extracellular pH (7.5-5.5), the higher the free radical flux; the lower the pH, the greater the membrane permeability induced in K-562 cells, as determined by trypan blue dye exclusion. These data demonstrate that lipid peroxidation processes, mediated by iron, are enhanced with decreasing extracellular pH. Thus, acidic pH not only releases iron from "safe" sites, but this iron will also be more damaging.

Animals↗
PubMed2000

Caloric restriction improves thermotolerance and reduces hyperthermia-induced cellular damage in old rats.

Adult-onset, long-term caloric restriction (CR) prolongs maximum life span in laboratory rodents. However, the effect of this intervention on an organism's ability to cope with a physical challenge has not been explored. We investigated the influence of CR and aging on stress tolerance in old rats exposed to an environmental heating protocol on two consecutive days. We hypothesized that CR would increase heat tolerance by reducing cellular stress and subsequent accrual of oxidative injury. All calorically restricted rats survived both heat exposures compared with only 50% of their control-fed counterparts. CR also decreased heat-induced radical generation, stress protein accumulation, and cellular injury in the liver. In addition, heat stress stimulated marked induction of the antioxidant enzymes manganese-containing superoxide dismutase and catalase, along with strong nuclear catalase expression in liver samples from rats subjected to CR. In contrast, stress-related induction of antioxidant enzymes was blunted, and nuclear catalase expression was unchanged from euthermic conditions in the control-fed group. These data suggest that CR reduces cellular injury and improves heat tolerance of old animals by lowering radical production and preserving cellular ability to adapt to stress through antioxidant enzyme induction and translocation of these proteins to the nucleus.

Adaptation, Physiological↗
PubMed2000

Iron and free radical oxidations in cell membranes.

Brain tissue being rich in polyunsaturated fatty acids, is very susceptible to lipid peroxidation. Iron is well known to be an important initiator of free radical oxidations. We propose that the principal route to iron-mediated lipid peroxidations is via iron-oxygen complexes rather than the reaction of iron with hydrogen peroxide, the Fenton reaction. To test this hypothesis, we enriched leukemia cells (K-562 and L1210 cells) with docosahexaenoic acid (DHA) as a model for brain tissue, increasing the amount of DHA from approximately 3 mole % to 32 mole %. These cells were then subjected to ferrous iron and dioxygen to initiate lipid peroxidation in the presence or absence of hydrogen peroxide. Lipid-derived radicals were detected using EPR spin trapping with alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone (POBN). As expected, lipid-derived radical formation increases with increasing cellular lipid unsaturation. Experiments with desferal demonstrate that iron is required for the formation of lipid radicals from these cells. Addition of iron to DHA-enriched L1210 cells resulted in significant amounts of radical formation; radical formation increased with increasing amount of iron. However, the exposure of cells to hydrogen peroxide before the addition of ferrous iron did not increase cellular radical formation, but actually decreased spin adduct formation. These data suggest that iron-oxygen complexes are the primary route to the initiation of biological free radical oxidations. This model proposes a mechanism to explain how catalytic iron in brain tissue can be so destructive.

Animals↗
PubMed1999

Nitric oxide inhibits iron-induced lipid peroxidation in HL-60 cells.

Nitric oxide ((*)NO) can protect cells against the detrimental effects of reactive oxygen species. Using low-density lipoprotein as well as model systems, it has been demonstrated that (*)NO can serve as a chain-breaking antioxidant to blunt lipid peroxidation. To test the hypothesis that (*)NO can serve as a chain-breaking antioxidant in cell membranes, we examined the effect of (*)NO on iron-induced lipid peroxidation in human leukemia cells. We exposed HL-60 cells to an oxidative stress (20 microM Fe(2+)) and monitored the consumption of oxygen as a measure of lipid peroxidation. Oxygen consumption was arrested by the addition of (*)NO as a saturated aqueous solution. The duration of inhibition of oxygen consumption by (*)NO was concentration-dependent in the 0.4-1.8 microM range. The inhibition ended upon depletion of (*)NO. The addition of (*)NO prior to initiation of peroxidation delayed the onset of peroxidation; the nearer in time it was before Fe(2+) addition, the longer the inhibition. Depletion of cellular glutathione levels by d, l-buthionine-S,R-sulfoximine prior to Fe(2+) addition resulted in a more rapid initial rate of oxygen depletion and a shorter time for the (*)NO-induced inhibition of oxygen consumption. Complementary studies of this iron-induced lipid peroxidation, using thiobarbituric acid reactive substances as a marker, also demonstrated the protective effects of (*)NO. This protection of cells against lipid peroxidation also manifested itself as a reduction in trypan blue uptake, an observation demonstrating the protective effects of (*)NO on membrane integrity. We conclude that (*)NO protects HL-60 human leukemia cells from lipid peroxidation and that this protection ameliorates the toxicity of the oxidation processes initiated by Fe(2+) and dioxygen.

Cell Membrane↗