In Vitro neurotoxic and DNA-damaging properties of nitrogen mustard

Sulfur mustard and nitrogen mustard (HN2) are reported to produce neurobehavioral and neuropathological changes in animals and humans, but the mechanisms are unknown. We examined the cytotoxic properties of HN2 in cultures of dividing and post-mitotic neurons and astrocytes, which comprise the majority of cells in the central nervous system. Cultures of rat cerebellar astrocytes, post-mitotic granule cell neurons or dividing and terminally differentiated human SY5Y neuroblastoma cell cultures were treated with various concentrations of HN2 for 24 h. After treatment, culture medium was removed, the cell monolayer was incubated for 30 min with calcein-AM (green, live cells) and propidium iodide (red, dead cells) in control medium, the fluorochrome-containing medium was removed and replaced with control medium and cell density and viability were examined by fluorescence and light microscopy. Extensive cell loss (>90%) was observed in rat neuronal and SY5Y neuroblastoma cell cultures treated with 10 μM HN2, whereas cell loss was similar to controls in comparably treated astrocyte cultures. The DNA from HN2-treated cultures of rat neurons and SY5Y neuroblastoma cells was examined by high-performance liquid chromatography with electrochemical detection for the major HN2 DNA adduct N-(2-hydroxyethyl)-N[2-(7-guaninyl)ethyl]methylamine (GMOH). GMOH was detected in rat neuronal (85 fmol μg^-1 DNA) and SY5Y neuroblastoma cell cultures (46 fmol μg^-1 DNA) treated with 10 μM HN2 for 24 h, but was not detected in comparably treated astrocyte cell cultures. These findings are consistent with HN2 preferentially targeting neurons in vivo, possibly through a mechanism involving DNA damage.