Mechanisms of Mitochondrial Dysfunction Induced by Sulfur Mustard in Human Epidermal Keratinocytes (HEK)

Abstract

Exposure of HEK to the chemical warfare agent sulfur mustard (SM) significantly disrupts cell energy metabolism. Our data suggest that one or more enzymes of respiratory complex I may be directly inhibited by SM and that complexes II, III and IV are relatively insensitive. To further localize sites of inhibition, we examined the partial reactions NADH‐ferricyanide reductase and cytochrome c oxidase. 100 μM SM did not inhibit either reaction at 24 hrs post‐exposure. 500 μM inhibited cyt. c oxidase by 25%, possibly secondary to cell death. We conclude that SM inhibits anterior to cytochrome c for succinate and between NADH dehydrogenasecyt. c for NAD‐linked substrates. Our previous data also suggest that SM causes irreversible mitochondrial damage parallel to late stage (18–24 hrs) losses in ATP and cell viability. We examined mitochondrial membrane permeability with JC‐1 and calcein‐AM+CoCl2. At ≤ 8 hrs we saw no changes with ≤ 500 μM SM. At 18–24 hours, 100 μM SM had no effect, but 300 and 500 μM caused losses in membrane potential that, in some cells, coincided with abnormal morphology. The data suggest that collapse of the mitochondrial membrane potential is a key event in SM‐induced cell death, perhaps at the level of the transition pore. Supported by DTRA‐JSTO, Med. S&T Div. The opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the US Army or the DoD.