Role of chromium(V), glutathione thiyl radical and hydroxyl radical intermediates in Chromium(VI)‐induced DNA Damage

Aiyar, Jayshree; Borges, Kim M.; Floyd, Robert A.; Wetterhahn, Karen E.

doi:10.1080/02772248909357432

Cited by 98 publications

(79 citation statements)

References 29 publications

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“…DNA damage by reactive oxygen species upon chromium (5,26). In this study, DNA repair enzymes, such as CC2272 and CC2200, were up-regulated (Table 7).…”

Section: Resultsmentioning

confidence: 52%

Whole-Genome Transcriptional Analysis of Heavy Metal Stresses in Caulobacter crescentus

et al. 2005

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The bacterium Caulobacter crescentus and related stalk bacterial species are known for their distinctive ability to live in low-nutrient environments, a characteristic of most heavy metal-contaminated sites. Caulobacter crescentus is a model organism for studying cell cycle regulation with well-developed genetics. We have identified the pathways responding to heavy-metal toxicity in C. crescentus to provide insights for the possible application of Caulobacter to environmental restoration. We exposed C. crescentus cells to four heavy metals (chromium, cadmium, selenium, and uranium) and analyzed genome-wide transcriptional activities postexposure using an Affymetrix GeneChip microarray. C. crescentus showed surprisingly high tolerance to uranium, a possible mechanism for which may be the formation of extracellular calcium-uranium-phosphate precipitates. The principal response to these metals was protection against oxidative stress (up-regulation of manganese-dependent superoxide dismutase sodA). Glutathione S-transferase, thioredoxin, glutaredoxins, and DNA repair enzymes responded most strongly to cadmium and chromate. The cadmium and chromium stress response also focused on reducing the intracellular metal concentration, with multiple efflux pumps employed to remove cadmium, while a sulfate transporter was down-regulated to reduce nonspecific uptake of chromium. Membrane proteins were also up-regulated in response to most of the metals tested. A two-component signal transduction system involved in the uranium response was identified. Several differentially regulated transcripts from regions previously not known to encode proteins were identified, demonstrating the advantage of evaluating the transcriptome by using whole-genome microarrays.Potentially hazardous levels of heavy metals have dispersed into subsurface sediment and groundwater in a number of metal-contaminated sites and represent a challenge for environmental restoration. Effective bioremediation of these sites requires knowledge of genetic pathways for resistance and biotransformation by component organisms within a microbial community. However, a comprehensive understanding of bacterial mechanisms of heavy metal toxicity and resistance has yet to be achieved. While many metals are essential to microbial function, heavy metals, i.e., most of those with a density above 5 g/cm 3 , have toxic effects on cellular metabolism (46). The majority of heavy metals are transition elements with incompletely filled d orbitals providing heavy metal cations which can form complex compounds with redox activity (46,70). Therefore, it is important to the health of the organism that the intracellular concentrations of heavy metal ions are tightly controlled. However, due to their structural and valence similarities to nontoxic metals, heavy metals are often transported into the cytoplasm through constitutively expressed nonspecific transport systems (46). As such, heavy metals invariably find their way into the cell. Once inside the cell, toxic effects of heavy metals...

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“…DNA damage by reactive oxygen species upon chromium (5,26). In this study, DNA repair enzymes, such as CC2272 and CC2200, were up-regulated (Table 7).…”

Section: Resultsmentioning

confidence: 52%

Whole-Genome Transcriptional Analysis of Heavy Metal Stresses in Caulobacter crescentus

et al. 2005

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“…ESR analysis revealed that the reduction of Cr(VI) caused by these reagents proceeded up to Cr(V). It was also suggested that Cr(V) is actually a toxic and mutagenic agent (2,15,16). Some reports showed that glutathione reductase (22), DT-diaphorase (7), aldehyde oxidase (3), and cytochrome P-450 (8,19,23) have Cr(VI)-reducing activity.…”

Section: Resultsmentioning

confidence: 99%

NAD(P)H-dependent chromium (VI) reductase of Pseudomonas ambigua G-1: a Cr(V) intermediate is formed during the reduction of Cr(VI) to Cr(III)

et al. 1992

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An NAD(P)H-dependent Cr(VI) reductase (molecular weight = 65,000) was purified from a Cr(VI)-resistant bacterium, Pseudomonas ambigua G-1. Stoichiometric analysis of the enzymatic reaction showed that the enzyme catalyzed the reduction of 1 mol of Cr(VI) to Cr(III) while consuming 3 mol of NADH as an electron donor. Chromium(VI) was reduced to Cr(V) by one equivalent NADH molecule in the absence of the enzyme.Electron spin resonance analysis showed that Cr(V) species (g = 1.979) was formed during the enzymatic reduction. The amount of Cr(V) species formed was about 10 times larger than that of the nonenzymatic reduction. These findings show that the Cr(VI) reductase reduced Cr(VI) to Cr(HI) (14) found NAD(P)H-dependent Cr(VI)-reducing activity in the cell-free supernatant fluids from Pseudomonas putida. Das and Chandra (6) have reported that Cr(VI) was reduced to Cr(III) in the presence of NAD(P)H in the cell extract of Streptomyces species. A membrane-associated chromate reduction system was also reported. Ohtake and coworkers (20) and Wang and coworkers (26)(27)(28) have shown that Cr(VI) was reduced to Cr(III) under anaerobic conditions by Enterobacter cloacae and its reduction was caused by the respiratory chain system of the cell membrane. We considered that these bacterial Cr(VI) reduction systems contribute to its detoxification by Cr(VI)-resistant bacteria. However, the Cr(VI) reductase has not yet been purified, and the details of the reaction mechanism are still unclear.P. ambigua G-1 was able to grow in medium containing up to 20 mM K2CrO4 (13). The Cr(VI)-reducing activity (11) of this strain was more thermostable than that of other pseudomonads (14). The Cr(VI)-sensitive mutants of this strain lost the reducing activity (12). These results indicate that this strain is a good source to investigate the Cr(VI) reduction mechanism which contributes to Cr(VI) detoxication.In the present paper, we report the purification of NAD(P)H-dependent Cr(VI) reductases of P. ambigua G-1 and the analysis of the catalytic mechanism of Cr(VI) reduction by the enzymes. Preparation of Cr(VI) reductase. Cells grown in 4 liters of L broth at 37°C were harvested at the late logarithmic phase, washed twice with 20 mM Tris-HCl, pH 7.2, suspended in 100 ml of the same buffer, and disrupted by sonication. After removal of the unbroken cells by centrifugation (1,500 x g, 30 min), the supernatant fluid was heat treated at 60°C for 2 min and centrifuged (1,500 x g, 30 min). The supernatant fluid was separated on a DE32 column (3.5 by 6 cm; Whatman Ltd., Maidstone, England) previously equilibrated with buffer A (50 mM glucose in 20 mM Tris-HCl, pH 7.2), and proteins were eluted with 0.4 M NaCl in buffer A at a flow rate of 100 ml/h. The fractions carrying the Cr(VI)-reducing activity were concentrated and separated by Cu2" chelate affinity chromatography using an AF-chelate Toyopearl 650M column (2.6 by 4 cm; Toso Ltd., Tokyo, Japan) which was sequentially equilibrated with 200 PM CUSO4 solution and buffer B (0.5 M NaCl in buf...

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“…Although the mechanism(s) involved remains to be fully elucidated (2), intracellular reduction of CrVI by cellular reductants such as reduced glutathione (GSH) and ascorbic acid and the subsequent generation of partially reduced chromium species such as CrV and CrIV are believed to be important (11). In addition, reduction of CrVI may also result in the concomitant generation of reactive oxygen species including hydroxyl radicals (˙OH), singlet oxygen (O), superoxide (O 2˙) and hydrogen peroxide (12)(13)(14)(15). In addition to reductive activation of CrVI, the antioxidant nature of GSH may also play a protective role in detoxification of reactive oxygen species and partially reduced chromium species.…”

Section: Introductionmentioning

confidence: 99%

Interindividual Variability in Response to Sodium Dichromate–Induced Oxidative DNA Damage: Role of the Ser326Cys Polymorphism in the DNA-Repair Protein of 8-Oxo-7,8-Dihydro-2′-Deoxyguanosine DNA Glycosylase 1

Lee

Hodges

Chipman

2005

Cancer Epidemiology, Biomarkers &Amp; Prevention

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Although the genotoxic mechanism(s) of hexavalent chromium (CrVI) carcinogenicity remain to be fully elucidated, intracellular reduction of CrVI and concomitant generation of reactive intermediates including reactive oxygen species and subsequent oxidative damage to DNA is believed to contribute to the process of carcinogenesis. In the current study, substantial interindividual variation (7.19-25.84% and 8.79-34.72% tail DNA as assessed by conventional and FPGmodified comet assay, respectively) in levels of DNA strand breaks after in vitro treatment of WBC with sodium dichromate (100 Amol/L, 1 hour) was shown within a group of healthy adult volunteers (n = 72) as assessed by both comet and formamidopyrimidine glycosylase -modified comet assays. No statistically significant correlation between glutathione S-transferases M1 or T1, NADPH quinone oxidoreductase 1 (codon 187) and X-ray repair cross complementation factor 1 (codon 194) genotypes and individual levels of DNA damage were observed.

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Role of chromium(V), glutathione thiyl radical and hydroxyl radical intermediates in Chromium(VI)‐induced DNA Damage

Cited by 98 publications

References 29 publications

Whole-Genome Transcriptional Analysis of Heavy Metal Stresses in Caulobacter crescentus

Whole-Genome Transcriptional Analysis of Heavy Metal Stresses in Caulobacter crescentus

NAD(P)H-dependent chromium (VI) reductase of Pseudomonas ambigua G-1: a Cr(V) intermediate is formed during the reduction of Cr(VI) to Cr(III)

Interindividual Variability in Response to Sodium Dichromate–Induced Oxidative DNA Damage: Role of the Ser326Cys Polymorphism in the DNA-Repair Protein of 8-Oxo-7,8-Dihydro-2′-Deoxyguanosine DNA Glycosylase 1

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