MONOISOPROPYLGLUTATHIONE ESTER PROTECTS A549 CELLS FROM THE CYTOTOXICEFFECTS OF SULFUR MUSTARD

1 The A549 cell line was used to assess the toxicity of sulphur mustar d (HD), using gentian violet (GV) and neutral red (NR) dyes as indicat ors of cell viability. It was found that exposure to concentrations in excess of 40 mu M HD resulted in a rapid onset of toxicity. 2 The abi lity of monoisopropylglutathione ester (MIPE) to protect A549 cells ag ainst the effects of a 100 mu M challenge dose of HD was determined us ing the NR and GV assays. It was found that MIPE (8 mM) could protect cells against the effects of HD though MIPE had to be present at the t ime 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 mic roscopy of NR and GV stained cultures confirmed these findings. Additi on of MIPE after previously exposing the A549 cultures to HD (for up t o 5 min) maintained cell viability at 72% compared to 37% for unprotec ted 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 IID challenge did not maintain cell v iability. Treatment of cultures with HD for 1 h followed by addition o f MIPE did not maintain the viability of the cultures, thus the window within which it was possible for MIPE to rescue cell cultures from th e effects of HD was of short duration. 4 High performance liquid chrom atography was used to determine the biochemical basis of the actions o f MIPE. It was found that whilst intracellular levels of cysteine were increased up to 40-fold following treatment of A549 cell cultures wit h MIPE, levels of reduced glutathione did not rise. The lack of protec tion seen in cultures pretreated with MIPE for Ih prior to HD exposure suggests that raising intracellular cysteine levels was not an effect ive strategy for protecting cells from the effects of HD. The protecti on observed is probably due to extracellular inactivation of HD by MIP E.