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National Institute of Environmental Health Sciences

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Your Environment. Your Health.

Publication Detail

Title: Selective targeting of selenocysteine in thioredoxin reductase by the half mustard 2-chloroethyl ethyl sulfide in lung epithelial cells.

Authors: Jan, Yi-Hua; Heck, Diane E; Gray, Joshua P; Zheng, Haiyan; Casillas, Robert P; Laskin, Debra L; Laskin, Jeffrey D

Published In Chem Res Toxicol, (2010 Jun 21)

Abstract: Thioredoxin reductase (TrxR) is a selenocysteine-containing flavoprotein that catalyzes the NADPH-dependent reduction of oxidized thioredoxin and plays a key role in regulating cellular redox homeostasis. In the present studies, we examined the effects of 2-chloroethyl ethyl sulfide (CEES), a model sulfur mustard vesicant, on TrxR in lung epithelial cells. We speculated that vesicant-induced alterations in TrxR contribute to oxidative stress and toxicity. The treatment of human lung A549 epithelial cells with CEES resulted in a time- and concentration-dependent inhibition of TrxR. Using purified rat liver TrxR, we demonstrated that only the reduced enzyme was inhibited and that this inhibition was irreversible. The reaction of TrxR with iodoacetamide, which selectively modifies free thiol or selenol on proteins, was also markedly reduced by CEES, suggesting that CEES induces covalent modification of the reduced selenocysteine-containing active site in the enzyme. This was supported by our findings that recombinant mutant TrxR, in which selenocysteine was replaced by cysteine, was markedly less sensitive to inhibition by CEES and that the vesicant preferentially alkylated selenocysteine in the C-terminal redox motif of TrxR. TrxR also catalyzes quinone redox cycling, a process that generates reactive oxygen species. In contrast to its inhibitory effects on TrxR activity, CEES was found to stimulate redox cycling. Taken together, these data suggest that sulfur mustard vesicants target TrxR and that this may be an important mechanism mediating oxidative stress and tissue injury.

PubMed ID: 20345183 Exiting the NIEHS site

MeSH Terms: Amino Acid Motifs/drug effects; Animals; Cell Line, Tumor; Epithelial Cells/drug effects*; Epithelial Cells/enzymology; Humans; Lung/cytology*; Mustard Gas/adverse effects; Mustard Gas/analogs & derivatives*; Mustard Gas/pharmacology; Mutant Proteins/antagonists & inhibitors; Mutant Proteins/genetics; Mutant Proteins/metabolism; Oxidation-Reduction/drug effects; Rats; Recombinant Proteins/antagonists & inhibitors; Recombinant Proteins/genetics; Recombinant Proteins/metabolism; Selenocysteine/metabolism*; Thioredoxin-Disulfide Reductase/antagonists & inhibitors; Thioredoxin-Disulfide Reductase/genetics; Thioredoxin-Disulfide Reductase/metabolism*

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