Mechanisms underlying the enhanced sensitivity of children and at risk individuals to the war gas nitrogen mustard

Nitrogen mustard is a chemical vesicant stockpiled for use as a war gas at numerous locations through out the world including Syria.  Exposure to nitrogen mustard results in morbidity to healthy adults and mortality and morbidity to children and health compromised individuals.  We hypothesized that the developing nervous systems of children mediates enhanced sensitivity to nitrogen mustard.  To investigate this hypothesis we treated undifferentiated (immature) PC12 cells with mechlorethamine hydrochloride (nitrogen mustard, HN2 0-3 mM).  In these studies HN2 treatment resulted in dose- and time-related cell death.  HN2 has been identified as a mediator of oxidative stress; using flow cytometry we determined that exposure to HN2 enhanced intracellular levels of reactive oxidants.  These studies indicate that HN2 treatment results in reduced viability of PC12 cells and is correlated with enhanced oxidant levels in the cells.  In further studies we examined the effects of HN2 on cellular anti-oxidant enzyme expression.  HN2 treatment up-regulated MnSOD and catalase levels and modulated expression of HO-1, NQO1 and NOX2 in the cells, effects not observed in differentiated cells.  These data suggest that HN2 regulates antioxidant gene expression in neuronal cells. Caspase 3 is a mediator of apoptotic cell death, HN2 treatment up regulated active (cleaved) caspase 3, and apoptotic DNA fragmentation.  Taken together, these results indicate that HN2 alters antioxidant enzyme expression, activity of cell death pathways and viability of undifferentiated PC12 cells.  We speculate that apoptosis induced by HN2 mediates, in part, enhanced sensitivity to HN2 in the developing nervous systems of children.