1. ¹Department of Biochemistry and Molecular Biology, Georgetown University School of Medicine, 3900 Reservoir Road NW, Washington, DC 20057, U.S.A.
2. ²Louisiana State University Health Science Center, Department of Pharmacology and Experimental Therapeutics and the Stanley Cancer Center, New Orleans, LA 70112, U.S.A.

Correspondence: Mark E Smulson, Department of Biochemistry and Molecular Biology, Georgetown University School of Medicine, 3900 Reservoir Road NW, Washington, DC 20057, U.S.A. E-mail: smulson@georgetown.edu

³Contributed equally to this work.

Received 2 September 2003; Revised 1 October 2003; Accepted 22 October 2003; Published online 9 February 2004.

Abstract

1. The mechanism of toxicity of sulphur mustard was investigated by examining the biochemical effects of the analog 2-chloroethylethyl sulphide (CEES) in both human Jurkat cells as well as normal human lymphocytes.
2. Exposure of both types of cells to CEES resulted in a marked decrease in the intracellular concentration of the reduced form of glutathione (GSH), and CEES-induced cell death was potentiated by L-buthionine sulphoximine, an inhibitor of GSH synthesis.
3. CEES increased the endogenous production of reactive oxygen species (ROS) in Jurkat cells, and CEES-induced cell death was potentiated by hydrogen peroxide.
4. CEES induced various hallmarks of apoptosis, including collapse of the mitochondrial membrane potential, proteolytic processing and activation of procaspase-3, and cleavage of poly (ADP-ribose) polymerase.
5. The effects of CEES on the accumulation of ROS, the intracellular concentration of GSH, the mitochondrial membrane potential, and caspase-3 activity were all inhibited by pretreatment of cells with the GSH precursor N-acetyl cysteine or with GSH-ethyl ester. Furthermore, CEES-induced cell death was also prevented by these antioxidants.
6. CEES toxicity appears to be mediated, at least in part, by the generation of ROS and consequent depletion of GSH. Given that sulphur mustard is still a potential biohazard, the protective effects of antioxidants against CEES toxicity demonstrated in Jurkat cells and normal human lymphocytes may provide the basis for the development of a therapeutic strategy to counteract exposure to this chemical weapon.