Monoisopropylglutathione ester protects A549 cells from the cytotoxic effects of sulphur mustard

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Abstract
1 The A549 cell line was used to assess the toxicity of sulphur mustard (HD), using gentian violet (GV) and neutral red (NR) dyes as indicators of cell viability. It was found that exposure to concentrations in excess of 40 ?M HD resulted in a rapid onset of toxicity. 2 The ability of monoisopropylglutathione ester (MIPE) to protect A549 cells against the effects of a 100 ?M challenge dose ofHD was determined using the NR and GV assays. It was found that MIPE (8 mM) could protect cells against the effects ofHD though MIPE had to be present at the time of HD challenge. Cultures protected with MIPE were two times more viable than HD exposed cells 48 h after HD challenge when using the GV and NR assays to assess viability. Observations by phase contrast microscopy of NR and GV stained cultures confirmed these findings. Addition of MIPE after previously exposing the A549 cultures to HD (for up to 5 min) maintained cell viability at 72% compared to 37% for unprotected cultures, after which time viability fell significantly so that at 10 min there was no difference in viability between the MIPE treated and untreated cultures. 3 Pretreating A549 cultures with MIPE for 1 h followed by its removal prior to HD challenge did not maintain cell viability. Treatment of cultures with HD for 1 h followed by addition of MIPE did not maintain the viability of the cultures, thus the window within which it was possible for MIPE to rescue cell cultures from the effects of HD was of short duration. 4 High performance liquid chromatography was used to determine the biochemical basis of the actions of MIPE. It was found that whilst intracellular levels of cysteine were increased up to 40-fold following treatment of A549 cell cultures with MIPE, levels of reduced glutathione did not rise. The lack of protection seen in cultures pretreated with MIPE for 1 h prior to HD exposure suggests that raising intracellular cysteine levels was not an effective strategy for protecting cells from the effects of HD. The protection observed is probably due to extra cellular inactivation of HD by MIPE.