Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Superoxides”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 55 records · Page 3Linked to original sources
PubMed1986

Plasma extracellular superoxide dismutase and erythrocyte Cu,Zn-containing superoxide dismutase in alcoholics treated with disulfiram.

Disulfiram has long been used in the treatment of chronic alcoholism. It is in vivo partially reduced to diethyldithiocarbamate, which is an efficient inhibitor of Cu,Zn-containing superoxide dismutase both in vitro and in vivo. The recently described extracellular superoxide dismutase is even more sensitive to diethyldithiocarbamate than Cu,Zn-superoxide dismutase. To test for the possibility that long term treatment with disulfiram leads to inhibiton of the superoxide dismutases, plasma extracellular superoxide dismutase and erythrocyte Cu,Zn-superoxide dismutase were determined in 12 disulfiram-treated alcoholics, and compared with 11 non-treated alcoholics and 19 healthy controls. Plasma extracellular superoxide dismutase was moderately reduced (about 20%) in the disulfiram-treated alcoholics as compared with the non-treated alcoholics and the healthy controls. No effect of disulfiram treatment on erythrocyte Cu,Zn-superoxide dismutase activity was demonstrated.

Adult↗
PubMed1999

Superoxide Anion Generation, Superoxide Dismutase Activity, and Nitric Oxide Release in Human Internal Mammary Artery and Saphenous Vein Segments.

BACKGROUND: Internal mammary artery (IMA) as conduit for a coronary artery bypass graft (CABG) stays patent longer and more often than saphenous vein (SV). However, the precise differences in the biology of IMA and SV are unclear. METHODS AND RESULTS: To examine inherent difference in superoxide anion, superoxide dismutase (SOD) and nitric oxide (NO) formation in IMA and SV as a basis for differences in patency rates, we measured these parameters in vascular segments of patients undergoing CABG. Superoxide anion generation was measured by lucigenin chemiluminescence and reduction of cytochrome c, SOD by inhibition of pyrogallol auto-oxidation, and No as nitrite/nitrate fluorometrically using 2-3-diaminonaphthalene as a probe. Generation of superoxide anion, SOD activity, and No formation were all greater in the IMA than in the SV segments (IMA:SV = 2.6:1, 2.9:1, 1, and 3.0:1, respectively, all P <.010. There was a positive correlation between superoxide anion generation and SOD activity (r = 0.65, P <.05; r = 0.70, P <.05 in IMA and SV, respectively) and NO release (r = 0.68, P <.05; r = 0.75, P <.03 in IMA and SV, respectively). Western blot analysis showed no differences in SOD and NO synthase protein expression in IMA and SV segment homogenates. To examine whether greater superoxide anion generation, SOD activity, and NO formation are unique to IMA, we studied pulmonary artery (PA) and pulmonary vein (PV) segments taken from patients undergoing lung resection. Superoxide anion generation, SOD activity, and NO formation were also found to be greater in PA than in PV segments. CONCLUSIONS: Inherently greater superoxide anion generation and subsequently increased formation of SOD and NO release in IMA (vs SV) may be a factor in the greater patency of the former as CABG conduit. Because both IMA and PA are exposed to pulsatile stretch and cary blood at higher pressure than the SV and PV, it is likely that these 2 factorsd account for the observed differences.

Journal Article↗
PubMed2004

Chemiluminescence detection of superoxide anion release and superoxide dismutase activity: modulation effect of Pulsatilla chinensis.

A novel flow-injection chemiluminescence-based method has been developed for determination of superoxide dismutase (SOD) activity. An in-vitro superoxide anion generation xanthine/xanthine oxidase stable source was established on line with FIA/CL-detection apparatus, for measuring SOD activity. This method can detect SOD in the linear range of 0.002-2.00 U mL(-1) with a detection limit of 0.001 U mL(-1). Another method for detection of superoxide anion is based on the luminol-FeCl(3) chemiluminescence (CL) reaction. This method was used to evaluate superoxide release and SOD activity in rats treated with the traditional Chinese herb Pulsatilla chinensis, which resulted in high clearance of hepatitis B virus (HBV) after treatment of a hepatitis B patient. Interestingly, we found that treatment with Pulsatilla chinensis can specifically increase superoxide release by liver tissues and, at the same time, slightly increase extracellular SOD (ECSOD) activity in plasma; in particular it can markedly increase MnSOD activity in mitochondria in liver tissue. This work revealed a possible mechanism whereby Pulsatilla chinensis prevents possible infection (for example HBV) by specifically increasing superoxide release in the liver and increasing MnSOD activity to minimize superoxide-mediated toxicity.

Animals↗
PubMed2000

Superoxides from mitochondrial complex III: the role of manganese superoxide dismutase.

In this report we show that ubiquinone cytochrome c reductase (complex III) from isolated rat heart mitochondria when inhibited with antimycin A, produces a large amount of superoxide as measured by the chemiluminescent probe coelenterazine. When mitochondria are inhibited with myxothiazol or stigmatellin, there is no detectable formation of superoxide. The antimycin A-sensitive free radical production can be dramatically reduced using either myxothiazol or stigmatellin. This suggests that the antimycin A-sensitive generation of superoxides originates primarily from the Q(o) semiubiquinone. When manganese superoxide dismutase depleted submitochondrial particles (SMP) were inhibited with myxothiazol or stigmatellin, a large superoxide signal was observed. These two inhibitors likely increase the concentration of the Q(i) semiquinone at the N center. The antimycin A-sensitive signal can, in the case of both the mitochondria and the SMP, be dissipated by the addition of copper zinc superoxide dismutase, suggesting that the measured coelenterazine signal was a result of superoxide production. Taken together, this data suggests that free radicals generated from the Q(i) species are more effectively eliminated by MnSOD in intact mitochondria.

Animals↗
PubMed2003

Superoxide reacts with hydroethidine but forms a fluorescent product that is distinctly different from ethidium: potential implications in intracellular fluorescence detection of superoxide.

Hydroethidine (HE) or dihydroethidium (DHE), a redox-sensitive probe, has been widely used to detect intracellular superoxide anion. It is a common assumption that the reaction between superoxide and HE results in the formation of a two-electron oxidized product, ethidium (E+), which binds to DNA and leads to the enhancement of fluorescence (excitation, 500-530 nm; emission, 590-620 nm). However, the mechanism of oxidation of HE by the superoxide anion still remains unclear. In the present study, we show that superoxide generated in several enzymatic or chemical systems (e.g., xanthine/xanthine oxidase, endothelial nitric oxide synthase, or potassium superoxide) oxidizes HE to a fluorescent product (excitation, 480 nm; emission, 567 nm) that is totally different from E+. HPLC measurements revealed that the HE/superoxide reaction product elutes differently from E+. This new product exhibited an increase in fluorescence in the presence of DNA. Mass spectral data indicated that the molecular weight of the HE/superoxide reaction product is 330, while ethidium has a molecular weight of 314. We conclude that the reaction between superoxide and HE forms a fluorescent marker product that is different from ethidium. Potential implications of this finding in intracellular detection and imaging of superoxide are discussed.

Chromatography, High Pressure Liquid↗
PubMed2005

Induction of phenotypes resembling CuZn-superoxide dismutase deletion in wild-type yeast cells: an in vivo assay for the role of superoxide in the toxicity of redox-cycling compounds.

Yeast (Saccharomyces cerevisiae) lacking the enzyme CuZn-superoxide dismutase (sod1delta) display a large number of dioxygen sensitive phenotypes, such as amino acid auxotrophies, sensitivity to elevated temperatures, and sensitivity to 100% dioxygen, which are attributed to superoxide stress. Such cells are exquisitely sensitive to small amounts of the herbicide paraquat (methyl viologen), which is known to produce high fluxes of superoxide in vivo via a redox-cycling mechanism. We report that dioxygen sensitive phenotypes similar to those seen in sod1delta cells can be induced in wild-type cells by treatment with moderate concentrations of paraquat or diquat, another bipyridyl herbicide, providing strong evidence that the mechanism of toxicity for both of these compounds is attributable to superoxide stress. Certain redox-cycling quinone compounds (e.g., menadione and plumbagin) are also far more toxic toward sod1delta than to wild type. However, treatment of wild-type yeast with menadione or plumbagin did not induce sod1delta-like phenotypes, although toxicity was evident. Thus, their toxicity in wild type cells is predominantly, but not exclusively, due to mechanisms unrelated to superoxide production. Further evidence for a different basis of toxicity toward wild-type yeast in these two classes of redox-cycling compounds includes the observations that (i) growth in low oxygen alleviated the effects of paraquat and diquat but not those of menadione or plumbagin and (ii) activity of the superoxide sensitive enzyme aconitase is affected by very low concentrations of paraquat but only by higher, growth inhibitory concentrations of menadione. These results provide the basis for an easy qualitative assay of the contribution of redox-cycling to the toxicity of a test compound. Using this method, we analyzed the Parkinsonism-inducing compound 1-methyl-4-phenylpyridinium and found that redox cycling and superoxide toxicity are not the predominant factor in its toxic mechanism.

1-Methyl-4-phenylpyridinium↗
PubMed1999

In vitro inhibition of superoxide anion production and superoxide dismutase activity by zinc in human spermatozoa.

The in vitro effect of zinc on superoxide anion (O2-) generation and on SOD-like activity in spermatozoa of infertile men was investigated. The formation of superoxide anion was stimulated by NADPH and the level of superoxide anion was measured by the reduction of ferricytochrome c. Both Percoll-isolated (n = 14) and washed spermatozoa (n = 14) exposed to 1 mmol/L zinc (60 min, 37 degrees C), released less (p < 0.002 and p < 0.04, respectively) superoxide anions than did zinc-untreated spermatozoa. These results implicate a possible role for zinc as a scavenger of excessive superoxide anions produced by defective spermatozoa in semen after ejaculation. Additionally, zinc was found to dose-dependently inhibit superoxide dismutase (SOD)-like activity of spermatozoa in vitro. The inhibition of SOD-like activity by an equal concentration of zinc (1 mmol/L) was less pronounced in oligospermic (p < 0.002; n = 16) and asthenozoospermic (p < 0.0005; n = 20) than in normozoospermic samples (p < 0.0001; n = 20). This differential ability of zinc to inhibit SOD-like activity may be relevant to the physiological function of spermatozoa in fertilization. The evidence that zinc may elicit an inhibition of both superoxide anion production and SOD-like activity in human spermatozoa, indicate the existence of novel, zinc-related mechanism(s) involved in the oxidative events occurring after ejaculation, with a possible modulatory effect on germ cell function.

Humans↗
PubMed1997

Generation of superoxide anion and localization of CuZn-superoxide dismutase in the vascular tissue of spinach hypocotyls: their association with lignification.

The sites of generations of superoxide anions and hydrogen peroxide in cross sections of hypocotyls from spinach seedlings were located by staining with nitroblue tetrazolium (NBT) and with starch-iodide, respectively. Formazan, produced upon the reduction of NBT by superoxide, was observed mainly in the vascular tissue only in the presence of inhibitors of CuZn-superoxide dismutase (CuZn-SOD), and its formation was suppressed under anaerobic conditions. Thus, NBT was reduced to formazan specifically by the superoxide anions generated in vascular tissue. The reduction of NBT was suppressed by inhibitors of NAD(P)H oxidase, but neither by cyanide nor azide, indicating the involvement of NAD(P)H oxidase in the generation of superoxide anions in the vascular tissue. Starch-I2 complex also was formed in the vascular tissue, but not in the presence of either the CuZn-SOD inhibitor or the NAD(P)H oxidase inhibitor, indicating that the hydrogen peroxide is produced via the catalytic disproportionation with CuZn-SOD of the superoxide generated by NAD(P)H oxidase. Generations of superoxide anions and hydrogen peroxide in the vascular tissue were particularly apparent in the xylem and associated with the sites of distribution of CuZn-SOD as determined by an immunohistochemical method, and also with the location of lignin as determined by the phloroglucin-HCl reaction.

Enzyme Inhibitors↗
PubMed1980

Superoxide anion-generating activities of macrophages as studied by using cytochalasin E and lectins as synergistic stimulants for superoxide release.

Treatment of macrophages with cytochalasin E in combination with a lectin was found to stimulate the generation of superoxide anions (O2-) very efficiently. The macrophages stimulated with concanavalin A, phytohemagglutinin or wheat germ agglutinin released superoxide, but cells pretreated with cytochalasin E released much greater amounts of superoxide, without notable lag time, upon stimulation with the lectin. Wheat germ agglutinin was found to be the most efficient stimulant among the lectins tested. Superoxide generation in guinea pig macrophages was shown to be dependent largely on cytoplasmic glucose metabolism and to some extent on mitochondrial respiration, since the superoxide release was largely but not totally inhibited by 2-deoxyglucose and to a lesser extent by antimycin A or KCN. The method presented is sensitive and allows rapid assay of the superoxide-generating activity with only 1--5 X 10(5) macrophages for a single determination. In application of this technique, elevation of the superoxide-generating activity was shown with macrophages elicited by chemical inflammation or those obtained from mice after treatment with tubercle bacilli.

Animals↗
PubMed1990

Alteration of endogenous glutathione peroxidase, manganese superoxide dismutase, and glutathione transferase activity in cells transfected with a copper-zinc superoxide dismutase expression vector. Explanation for variations in paraquat resistance.

Transfection of a human pSV2 (copper-zinc) superoxide dismutase expression vector into murine fibroblasts resulted in stable clones producing increased amounts of copper-zinc superoxide dismutase. A marked increase in endogenous glutathione peroxidase activity (up to 285%) and a smaller increase in glutathione transferase activity (up to 16%) also occurred. Manganese superoxide dismutase activity was decreased in all clones, whereas catalase and NADPH reductase activities were not affected. Alterations in glutathione peroxidase and manganese superoxide dismutase activities correlated with increases in copper-zinc superoxide dismutase activity. Whereas all clones were resistant to paraquat, a direct correlation between copper-zinc superoxide dismutase activity and resistance to paraquat did not exist. In agreement with previous reports clones expressing the highest copper-zinc superoxide dismutase activity did not display the highest resistance to paraquat. However, there was a direct correlation between the increase in glutathione peroxidase activity and paraquat resistance (p less than 0.002).

Animals↗
PubMed1987

Human copper-zinc superoxide dismutase complements superoxide dismutase-deficient Escherichia coli mutants.

An Escherichia coli double mutant, sodAsodB, that is deficient in both bacterial superoxide dismutases (Mn superoxide dismutase and iron superoxide dismutase) is unable to grow on minimal medium in the presence of oxygen and exhibits increased sensitivity to paraquat and hydrogen peroxide. Expression of the evolutionarily unrelated eukaryotic CuZn superoxide dismutase in the sodAsodB E. coli mutant results in a wild-type phenotype with respect to aerobic growth on minimal medium and in resistance to paraquat and hydrogen peroxide. This supports the hypothesis that superoxide dismutation is the in vivo function of these proteins. Analysis of the growth of sodAsodB cells containing plasmids encoding partially active CuZn superoxide dismutases, produced by in vitro mutagenesis, shows a correlation between cell growth and enzyme activity. Thus, the sodAsodB strain provides a controlled selection for varying levels of superoxide dismutase activity.

Copper↗
PubMed1982

[Superoxide-dismutase and superoxide-radical-release in rheumatoid arthritis (author's transl)].

Polymorphonuclear leukocytes (PMNs) release superoxide anion (O-2) when they are exposed to a phagocytic stimulus. Intracellularly the copper-containing enzyme superoxide dismutase (SOD) protects against the toxic effects of O-2. To investigate the role of O-2 and SOD in the inflammatory process we determined the O-2 release and SOD content in PMNs. In PMNs of children with rheumatoid arthritis the SOD activity was diminished compared to healthy controls. Upon stimulation with opsonized zymosan PMNs obtained from children with rheumatoid arthritis generated greater amounts of superoxide anion than control cells. The "SOD deficiency" in PMNs of children with rheumatoid arthritis may promote this extreme release of the toxic superoxide radical inducing the damage of the connective tissue. The involvement of superoxide dismutase and superoxide anion in inflammatory process may induce further studies, leading hopefully to an appropriate understanding or even to new principles in the treatment of the rheumatoid arthritis.

Adolescent↗
PubMed2004

Overexpression and purification of Treponema pallidum rubredoxin; kinetic evidence for a superoxide-mediated electron transfer with the superoxide reductase neelaredoxin.

Superoxide reductases are a class of non-haem iron enzymes which catalyse the monovalent reduction of the superoxide anion O2- into hydrogen peroxide and water. Treponema pallidum (Tp), the syphilis spirochete, expresses the gene for a superoxide reductase called neelaredoxin, having the iron protein rubredoxin as the putative electron donor necessary to complete the catalytic cycle. In this work, we present the first cloning, overexpression in Escherichia coli and purification of the Tp rubredoxin. Spectroscopic characterization of this 6 kDa protein allowed us to calculate the molar absorption coefficient of the 490 nm feature of ferric iron, epsilon=6.9+/-0.4 mM(-1) cm(-1). Moreover, the midpoint potential of Tp rubredoxin, determined using a glassy carbon electrode, was -76+/-5 mV. Reduced rubredoxin can be efficiently reoxidized upon addition of Na(2)IrCl(6)-oxidized neelaredoxin, in agreement with a direct electron transfer between the two proteins, with a stoichiometry of the electron transfer reaction of one molecule of oxidized rubredoxin per one molecule of neelaredoxin. In addition, in presence of a steady-state concentration of superoxide anion, the physiological substrate of neelaredoxin, reoxidation of rubredoxin was also observed in presence of catalytic amounts of superoxide reductase, and the rate of rubredoxin reoxidation was shown to be proportional to the concentration of neelaredoxin, in agreement with a bimolecular reaction, with a calculated k(app)=180 min(-1). Interestingly, similar experiments performed with a rubredoxin from the sulfate-reducing bacteria Desulfovibrio vulgaris resulted in a much lower value of k(app)=4.5 min(-1). Altogether, these results demonstrated the existence for a superoxide-mediated electron transfer between rubredoxin and neelaredoxin and confirmed the physiological character of this electron transfer reaction.

Bacterial Proteins↗
PubMed1987

Superoxide-dependent redox cycling of citrate-Fe3+: evidence for a superoxide dismutaselike activity.

Citrate-Fe3+, reportedly a physiological chelate, exhibits superoxide dismutaselike activity, as evidenced by the inhibition of xanthine oxidase-dependent cytochrome c reduction; the dismutation of xanthine oxidase-generated superoxide to hydrogen peroxide and oxygen, and the enhanced disproportionation of potassium superoxide. The catalytic activity of citrate-Fe3+ corresponds, on a molar basis, to 0.03% of that of copper- and zinc-containing superoxide dismutase. Although weak, this activity enables citrate-Fe3+ to inhibit superoxide and ADP-Fe3+ -dependent peroxidation of extracted microsomal lipids. Also, the dismutase activity of citrate-Fe3+ interferes with its ability to promote lipid peroxidation. It is proposed that chelation of Fe3+ by citrate may represent a protective mechanism against the deleterious consequences of superoxide generation.

Chelating Agents↗
PubMed2003

Modeling the influence of superoxide dismutase on superoxide and nitric oxide interactions, including reversible inhibition of oxygen consumption.

A mathematical mass transport model was constructed in cylindrical geometry to follow coupled biochemical reactions and diffusion of oxygen, nitric oxide, superoxide, peroxynitrite, hydrogen peroxide, nitrite, and nitrate around a blood vessel. Computer simulations were performed for a 50 microm internal diameter arteriole to characterize mass transport in five concentric regions (blood, plasma layer, endothelium, vascular wall, perivascular tissue). Steady state gradients in nitric oxide, oxygen partial pressure, superoxide, and peroxynitrite, and associated production of hydrogen peroxide, nitrite, and nitrate were predicted for varying superoxide production rates, superoxide dismutase concentrations, and other physiological conditions. The model quantifies how competition between superoxide scavenging by nitric oxide and superoxide dismutase catalyzed removal varies spatially. Reversible inhibition of oxygen consumption by nitric oxide, which causes increased tissue oxygenation at deeper locations, was also included in the model. The mass transport model provides insight into complex interactions between reactive oxygen and nitrogen species in blood and tissue, and provides an objective way to evaluate the relative influence of different biochemical pathways on these interactions.

Arteries↗
PubMed1980

Properties of spermatozoal superoxide dismutase and lack of involvement of superoxides in metal-ion-catalysed lipid-peroxidation and reactions in semen.

1. The distribution and properties of superoxide dismutase were examined in mammalian semen, and the enzyme was used to investigate the role of superoxides in metal-ion-catalysed lipid-peroxidation reactions in spermatozoa. 2. Superoxide dismutase activity was detected in seminal plasma and spermatozoa from all species studied, exceptionally high activity being found in donkey semen. The enzyme is easily solubilized from spermatozoa, as 85-90% of the total activity is released by cold shock, a relatively mild form of cellular damage. 3. Purification and characterization of the enzyme from supernatant fractions prepared from cold-shocked boar spermatozoa showed it to be cyanide-sensitive, to have a mol.wt. of 31 000, a pI of 5.9 and to contain 1.85 g-atoms of copper and 1.91 g-atoms of zinc per mol of protein. However, extensive sonication of spermatozoa released a small amount of a cyanide-insensitive enzyme, presumably a mangano superoxide dismutase, from the mitochondrial matrix. 4. The presence of superoxide dismutase in spermatozoa, either intracellularly or extracellularly, did not inhibit ascorbate/Fe2+-catalysed lipid-peroxidation reactions, suggesting that superoxides are not essential intermediates in this system.

Animals↗
PubMed1986

Copper + zinc and manganese superoxide dismutases inhibit deoxyribose degradation by the superoxide-driven Fenton reaction at two different stages. Implications for the redox states of copper and manganese.

When OH. radicals are formed in a superoxide-driven Fenton reaction, in which O2.- is generated enzymically, deoxyribose degradation is effectively inhibited by CuZn- and Mn-superoxide dismutases. The products of this reaction are H2O2 and a Fe3+-EDTA chelate. The mixing of H2O2 and a Fe3+-EDTA chelate also generates OH. radicals able to degrade deoxyribose with the release of thiobarbituric acid-reactive material. This reaction too is inhibited by CuZn- and Mn-superoxide dismutases, suggesting that most of the OH. is formed by a non-enzymic O2.--dependent reduction of the Fe3+-EDTA chelate. Since the reaction between the Fe3+-EDTA chelate and H2O2 leads to a superoxide dismutase-inhibitable formation of OH. radicals, it could suggest a much wider protective role for the superoxide dismutase enzymes in biological systems. Urate produced during the reaction of xanthine oxidase and hypoxanthine limits deoxyribose degradation as well as the effectiveness of the superoxide dismutase enzymes to inhibit damage to deoxyribose by H2O2 and the Fe3+-EDTA chelate. Some of this damage may result from an O2.--independent pathway to OH. formation in which urate reduces the ferric complex.

Cations, Divalent↗
PubMed2001

Accumulation of manganese in Neisseria gonorrhoeae correlates with resistance to oxidative killing by superoxide anion and is independent of superoxide dismutase activity.

As a facultative aerobe with a high iron requirement and a highly active aerobic respiratory chain, Neisseria gonorrhoeae requires defence systems to respond to toxic oxygen species such as superoxide. It has been shown that supplementation of media with 100 microM Mn(II) considerably enhanced the resistance of this bacterium to oxidative killing by superoxide. This protection was not associated with the superoxide dismutase enzymes of N. gonorrhoeae. In contrast to previous studies, which suggested that some strains of N. gonorrhoeae might not contain a superoxide dismutase, we identified a sodB gene by genome analysis and confirmed its presence in all strains examined by Southern blotting, but found no evidence for sodA or sodC. A sodB mutant showed very similar susceptibility to superoxide killing to that of wild-type cells, indicating that the Fe-dependent SOD B did not have a major role in resistance to oxidative killing under the conditions tested. The absence of a sodA gene indicated that the Mn-dependent protection against oxidative killing was independent of Mn-dependent SOD A. As a sodB mutant also showed Mn-dependent resistance to oxidative killing, then it is concluded that this resistance is independent of superoxide dismutase enzymes. Resistance to oxidative killing was correlated with accumulation of Mn(II) by the bacterium. We hypothesize that this bacterium uses Mn(II) as a chemical quenching agent in a similar way to the already established process in Lactobacillus plantarum. A search for putative Mn(II) uptake systems identified an ABC cassette-type system (MntABC) with a periplasmic-binding protein (MntC). An mntC mutant was shown to have lowered accumulation of Mn(II) and was also highly susceptible to oxidative killing, even in the presence of added Mn(II). Taken together, these data show that N. gonorrhoeae possesses a Mn(II) uptake system that is critical for resistance to oxidative stress.

Antioxidants↗