Selective Targeting of Selenocysteine in Thioredoxin Reductase by the Half Mustard 2-Chloroethyl Ethyl Sulfide in Lung Epithelial Cells

Environmental and Occupational Medicine, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
Chemical Research in Toxicology (Impact Factor: 3.53). 03/2010; 23(6):1045-53. DOI: 10.1021/tx100040k
Source: PubMed


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.

Download full-text


Available from: Yi-Hua Jan, Oct 08, 2015
23 Reads
  • Source
    • "This is supported by findings that expression of intact and cleaved poly (ADP-ribose) polymerase (PARP), a DNA repair enzyme important in both of these processes, is upregulated in lung cells following vesicant exposure [27e30]. Recent mechanistic studies in lung cells have suggested that vesicants may also exert cytotoxicity by selectively targeting enzymes involved in regulating cellular homeostasis including thioredoxin reductase [31]. Thioredoxin reductase contains a unique selenocysteine in its active site, and vesicants inhibit enzyme activity by binding to this amino acid. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Sulfur mustard (SM) is highly toxic to the lung inducing both acute and chronic effects including upper and lower obstructive disease, airway inflammation, and acute respiratory distress syndrome, and with time, tracheobronchial stenosis, bronchitis, and bronchiolitis obliterans. Thus it is essential to identify effective strategies to mitigate the toxicity of SM and related vesicants. Studies in animals and in cell culture models have identified key mechanistic pathways mediating their toxicity, which may be relevant targets for the development of countermeasures. For example, following SM poisoning, DNA damage, apoptosis, and autophagy are observed in the lung, along with increased expression of activated caspases and DNA repair enzymes, biochemical markers of these activities. This is associated with inflammatory cell accumulation in the respiratory tract and increased expression of tumor necrosis factor-α and other proinflammatory cytokines, as well as reactive oxygen and nitrogen species. Matrix metalloproteinases are also upregulated in the lung after SM exposure, which are thought to contribute to the detachment of epithelial cells from basement membranes and disruption of the pulmonary epithelial barrier. Findings that production of inflammatory mediators correlates directly with altered lung function suggests that they play a key role in toxicity. In this regard, specific therapeutic interventions currently under investigation include anti-inflammatory agents (e.g., steroids), antioxidants (e.g., tocopherols, melatonin, N-acetylcysteine, nitric oxide synthase inhibitors), protease inhibitors (e.g., doxycycline, aprotinin, ilomastat), surfactant replacement, and bronchodilators. Effective treatments may depend on the extent of lung injury and require a multi-faceted pharmacological approach.
    Pulmonary Pharmacology &amp Therapeutics 02/2011; 24(1):92-9. DOI:10.1016/j.pupt.2010.09.004 · 2.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Deep submicron-gate MOSFETs have been fabricated on ultrathin Si film of 30 nm, 50 nm, and 100 nm in thickness on SIMOX (separation by implanted oxygen) substrates. CMOS ring oscillators of 51 stages were fabricated to evaluate propagation delay. A high performance of 21.5 ps/stage ( V <sub>D</sub>=2.5 V at room temperature) was observed for a 0.25-μm-gate CMOS ring oscillator on the SIMOX substrate with Si film of 100 nm in thickness. By reducing the thickness of Si film on SIMOX substrates down to 30 nm, excellent immunity from short channel effects that is, independence of threshold voltage from gate length and low subthreshold voltage swings, was found
    Electron Devices Meeting, 1989. IEDM '89. Technical Digest., International; 01/1990
  • [Show abstract] [Hide abstract]
    ABSTRACT: Organizational learning oriented classifier system (OCS) is a new architecture proposed by us for an evolutionary computational model. We have shown its effectiveness in large scale problems with printed circuit board (PCB) redesign using computer aided design (CAD). The paper proposes a novel reinforcement learning method for multiagents with OCS for more practical and engineering use. To validate the effectiveness of our method, we have conducted experiments on real scale PCB design problems for electric appliances. The experimental results have suggested that: (1) our method has found feasible solutions with the same quality of those by human experts; (2) the solutions are globally better than those by the conventional reinforcement learning methods with regard to both the total wiring length and the number of iterations
    Evolutionary Computation Proceedings, 1998. IEEE World Congress on Computational Intelligence., The 1998 IEEE International Conference on; 06/1998
Show more

Similar Publications