Faculty Collaboration Database

The pro-oxidant chromium(VI) inhibits mitochondrial complex I, complex II, and aconitase in the bronchial epithelium: EPR markers for Fe-S proteins. Free Radic Biol Med 2010 Dec 15;49(12):1903-15

Date

10/05/2010

Pubmed ID

20883776

Pubmed Central ID

PMC3005768

DOI

10.1016/j.freeradbiomed.2010.09.020

Scopus ID

2-s2.0-78650177513 (requires institutional sign-in at Scopus site)   34 Citations

Abstract

Hexavalent chromium (Cr(VI)) compounds (e.g., chromates) are strong oxidants that readily enter cells, where they are reduced to reactive Cr species that also facilitate reactive oxygen species generation. Recent studies demonstrated inhibition and oxidation of the thioredoxin system, with greater effects on mitochondrial thioredoxin (Trx2). This implies that Cr(VI)-induced oxidant stress may be especially directed at the mitochondria. Examination of other redox-sensitive mitochondrial functions showed that Cr(VI) treatments that cause Trx2 oxidation in human bronchial epithelial cells also result in pronounced and irreversible inhibition of aconitase, a TCA cycle enzyme that has an iron-sulfur (Fe-S) center that is labile with respect to certain oxidants. The activities of electron transport complexes I and II were also inhibited, whereas complex III was not. Electron paramagnetic resonance (EPR) studies of samples at liquid helium temperature (10K) showed a strong signal at g=1.94 that is consistent with the inhibition of electron flow through complex I and/or II. A signal at g=2.02 was also observed, which is consistent with oxidation of the Fe-S center of aconitase. The g=1.94 signal was particularly intense and remained after extracellular Cr(VI) was removed, whereas the g=2.02 signal declined in intensity after Cr(VI) was removed. A similar inhibition of these activities and analogous EPR findings were noted in bovine airways treated ex vivo with Cr(VI). Overall, the data support the hypothesis that Cr(VI) exposure has deleterious effects on a number of redox-sensitive core mitochondrial proteins. The g=1.94 signal could prove to be an important biomarker for oxidative damage resulting from Cr(VI) exposure. The EPR spectra simultaneously showed signals for Cr(V) and Cr(III), which verify Cr(VI) exposure and its intracellular reductive activation.

Author List

Myers CR, Antholine WE, Myers JM

MESH terms used to index this publication - Major topics in bold

Aconitate Hydratase
Animals
Biomarkers
Bronchi
Cattle
Cell Line
Chromates
Electron Spin Resonance Spectroscopy
Electron Transport Complex I
Electron Transport Complex II
Enzyme Assays
Epithelial Cells
Humans
In Vitro Techniques
Iron-Sulfur Proteins
Oxidants
Oxidation-Reduction