Permeability, Cytotoxicity, and Genotoxicity of Chromium(V) and Chromium(VI) Complexes in V79 Chinese Hamster Lung Cells

Dillon, Carolyn T.; Lay, Peter A.; Bonin, Antonio M.; Cholewa, M.; Legge, G.J.F.; Collins, Terrence J.; Kostka, Kimberly L.

doi:10.1021/tx9701541

Cited by 48 publications

(52 citation statements)

References 56 publications

(95 reference statements)

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“…During this reduction, reactive Cr species [Cr(V) and/or Cr(IV)] are formed. These can directly cause oxidative-like damage (Sugden, 1999;Sugden et al, 2001) or they can generate ROS via redox cycling (Tsapakos et al, 1983;Standeven and Wetterhahn, 1991;Shi and Dalal, 1992;Dillon et al, 1998;Shi et al, 1999a;Shi et al, 1999b;Borthiry et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Hexavalent chromium causes the oxidation of thioredoxin in human bronchial epithelial cells

2008

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Hexavalent chromium [Cr(VI)] species such as chromates are cytotoxic. Inhalational exposure is a primary concern in many Cr-related industries and their immediate environments, and bronchial epithelial cells are directly exposed to inhaled Cr(VI). Chromates are readily taken up by cells and are reduced to reactive Cr species which may also result in the generation of reactive oxygen species (ROS). The thioredoxin (Trx) system has a key role in the maintenance of cellular thiol redox balance and is essential for cell survival. Cells normally maintain the cytosolic (Trx1) and mitochondrial (Trx2) thioredoxins largely in the reduced state. Redox western blots were used to assess the redox status of the thioredoxins in normal human bronchial epithelial cells (BEAS-2B) incubated with soluble Na 2 CrO 4 or insoluble ZnCrO 4 for different periods of time. Both chromates caused a doseand time-dependent oxidation of Trx2 and Trx1. Trx2 was more susceptible in that it could all be converted to the oxidized form, whereas a small amount of reduced Trx1 remained even after prolonged treatment with higher Cr concentrations. Only one of the dithiols, presumably the active site, of Trx1 was oxidized by Cr(VI). Cr(VI) did not cause significant GSH depletion or oxidation indicating that Trx oxidation does not result from a general oxidation of cellular thiols. With purified Trx and thioredoxin reductase (TrxR) in vitro, Cr(VI) also resulted in Trx oxidation. It was determined that purified TrxR has pronounced Cr(VI) reducing activity, so competition for electron flow from TrxR might impair its ability to reduce Trx. The in vitro data also suggested some direct redox interaction between Cr(VI) and Trx. The ability of Cr(VI) to cause Trx oxidation in cells could contribute to its cytotoxic effects, and could have important implications for cell survival, redoxsensitive cell signaling, and the cells' tolerance of other oxidant insults.

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Section: Introductionmentioning

confidence: 99%

Hexavalent chromium causes the oxidation of thioredoxin in human bronchial epithelial cells

2008

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“…Electron donors that transfer three electrons in a single step have not been identified in biological systems, so the reduction of Cr(VI) to Cr(III) must proceed stepwise through Cr(V) and/or Cr(IV) which are reactive Cr intermediates. These reactive Cr intermediates, and their potential to generate reactive oxygen species, are likely important components in the toxicity resulting from Cr(VI) exposure [17,[19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Reductive activation of hexavalent chromium by human lung epithelial cells: Generation of Cr(V) and Cr(V)-thiol species

Borthiry

Antholine

Myers

et al. 2008

Journal of Inorganic Biochemistry

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Chromium(VI) compounds (e.g. chromates) are cytotoxic, mutagenic, and potentially carcinogenic. The reduction of Cr(VI) can yield reactive intermediates such as Cr(V) and reactive oxygen species. Bronchial epithelial cells are the primary site of pulmonary exposure to inhaled Cr(VI) and are the primary cells from which Cr(VI)-associated human cancers arise. BEAS-2B cells were used here as a model of normal human bronchial epithelium for studies on the reductive activation of Cr(VI). Cells incubated with Na 2 CrO 4 exhibited two Cr(V) ESR signals, g = 1.979 and 1.985, which persisted for at least one hour. The g = 1.979 signal is similar to that generated in vitro by human microsomes and by proteoliposomes containing P450 reductase and cytochrome b 5 . Unlike many cells in culture, these cells continued to express P450 reductase and cytochrome b 5 . Studies with the non-selective thiol oxidant diamide indicated that the g = 1.985 signal was thiol-dependent whereas the g = 1.979 signal was not. Pretreatment with phenazine methosulfate eliminated both Cr(V) signals suggesting that Cr(V) generation is largely NAD(P)H-dependent. ESR spectra indicated that a portion of the Cr (VI) was rapidly reduced to Cr(III). Cells incubated with an insoluble chromate, ZnCrO 4 , also generated both Cr(V) signals, whereas Cr(V) was not detected with insoluble PbCrO 4 . In clonogenic assays, the cells were very sensitive to Na 2 CrO 4 and ZnCrO 4 , but considerably less sensitive to PbCrO 4 .

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“…The reduction of Cr(VI) to Cr(III), and the resulting formation of reactive intermediates (e.g. Cr(V), Cr(IV), reactive oxygen species), is likely a key component in the toxicity and carcinogenicity of Cr(VI) [18,[20][21][22][23][24]. Reactive Cr intermediates, Cr(V) and Cr(IV), generated by some reductants can participate in Fenton-like reactions with hydrogen peroxide to generate hydroxyl radical [25][26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Reduction of hexavalent chromium by human cytochrome b5: Generation of hydroxyl radical and superoxide

Borthiry

Antholine

Kalyanaraman

et al. 2007

Free Radical Biology and Medicine

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The reduction of hexavalent chromium, Cr(VI), can generate reactive Cr intermediates and various types of oxidative stress. The potential role of human microsomal enzymes in free radical generation was examined using reconstituted proteoliposomes (PLs) containing purified cytochrome b 5 and NADPH:P450 reductase. Under aerobic conditions, the PLs reduced Cr(VI) to Cr(V) which was confirmed by ESR using isotopically pure 53 Cr(VI). When 5-Diethoxyphos-phoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) was included as a spin trap, a very prominent signal for the hydroxyl radical (HO • ) adduct was observed as well as a smaller signal for the superoxide (O 2 •− ) adduct. These adducts were observed even at very low Cr(VI) concentrations (10 μM). NADPH, Cr(VI), O 2 and the PLs were all required for significant HO • generation. Superoxide dismutase eliminated the O 2 • − adduct and resulted in a 30% increase in the HO • adduct. Catalase largely diminished the HO • adduct signal indicating its dependence on H 2 O 2 . Some sources of catalase were found to have Cr(VI)-reducing contaminants which could confound results, but a source of catalase free of these contaminants was used for these studies. Exogenous H 2 O 2 was not needed, indicating that it was generated by the PLs. Adding exogenous H 2 O 2 , however, did increase the amount of DEPMPO/ HO • adduct. The inclusion of formate yielded the carbon dioxide radical adduct of DEPMPO, and experiments with dimethylsulfoxide (DMSO) plus the spin trap α-phenyl-N-tert-butylnitrone (PBN) yielded the methoxy and methyl radical adducts of PBN, confirming the generation of HO • . Quantification of the various species over time was consistent with a stoichiometric excess of HO • relative to the net amount of Cr(VI) reduced. This also represents the first demonstration of a role for cytochrome b 5 in the generation of HO • . Overall, the simultaneous generation of Cr(V) and H 2 O 2 by the PLs and the resulting generation of HO • at low Cr(VI) concentrations could have important implications for Cr(VI) toxicity.

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Permeability, Cytotoxicity, and Genotoxicity of Chromium(V) and Chromium(VI) Complexes in V79 Chinese Hamster Lung Cells

Cited by 48 publications

References 56 publications

Hexavalent chromium causes the oxidation of thioredoxin in human bronchial epithelial cells

Hexavalent chromium causes the oxidation of thioredoxin in human bronchial epithelial cells

Reductive activation of hexavalent chromium by human lung epithelial cells: Generation of Cr(V) and Cr(V)-thiol species

Reduction of hexavalent chromium by human cytochrome b5: Generation of hydroxyl radical and superoxide

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