The A549 cell line was used as a model of the deep lung to study the toxicity and mechanism of action of sulphur mustard (HD), using the neutral red (NR) dye retention and gentian violet (GV) assays as indices of cell viability. It was found that exposure to concentrations in excess of 40 μM HD resulted in a rapid onset of toxicity. Exposure to 1000 μM HD reduced viability in A549 cell cultures to 61% after 2 h (control cultures=100%), whereas exposure to 40 μM HD did not result in deleterious effects until 26 h at which point viability fell to only 84% (NR assay). Agarose gel electrophoresis of cell cultures exposed to 40 and 1000 μM HD and harvested at 4.5, 19 and 43 h after exposure to HD, indicated that cell death was due to necrosis, despite the observation that at the higher concentration of HD cells displayed many of the features common to cells undergoing apoptotic death. The ability of hexamethylenetetramine (HMT) to protect A549 cells against the effects of an LC50 challenge dose of HD was assessed using the GV and NR assays. It was found that HMT (15 mM) could protect cells against the effects of HD though HMT had to be present at the time of HD challenge. Cultures treated with HD only were 49% viable at 48 h after HD challenge, compared to 101% for protected cultures (NR assay) and 58% and 91% for unprotected and protected cultures respectively using the GV assay. Morphological observations of GV and NR stained cultures confirmed these findings. HMT concen trations of 2.5 to 25 mM were used. Maximal protection against the toxic effects of HD (LC50) was found at 10 to 25 mM HMT. Over this concentration range, HMT did not exert any toxic effects on A549 cells. Pretreatment of A549 cultures with HMT followed by its removal prior to HD challenge had no protective effect. Similarly, treating cultures with HD followed by addition of HMT did not increase the viability of the cultures, even if the HMT was added immediately after HD exposure. HMT was found to protect against the toxic effects ofHD, though it must be present at the time ofHD challenge. A549 cells were found to be a valuable experimental model for studying the toxicology of HD and other lung damaging agents, and for screening other compounds for potential therapeutic efficacy as a prelude to studies with non- transformed cell culture systems and in vivo models.
Comparative Toxic Effects of Manufactured Nanoparticles and Atmospheric Particulate Matter in Human Lung Epithelial Cells
