Glutathione depletion-induced neutrophil apoptosis is caspase 3 dependent

Resolving inflammation is a vital step in preventing the persistence of inflammatory disorders. Neutrophils play a major role in tissue damage associated with an inflammatory response. Their death by apoptosis is central to the final resolution of this response. Thiol depletion with diethylmaleate (DEM) or diamide represent important triggers for neutrophil apoptosis. The mechanism by which this process occurs remains unknown. The apoptotic cascade is associated with a number of cellular changes, including caspase activation and mitochondrial permeability. The aims of this study were to determine the role of mitochondrial permeability and the caspase cascade in thiol depletion-induced neutrophil apoptosis. Total cellular glutathione was reduced by DEM and diamide. This reduction was associated with neutrophil apoptosis and an increase in caspase 3 activity. The effects of DEM were blocked by the caspase 3 inhibitor, Z-DEVD-FMK. Mitochondrial permeability that occurred was also increased during this induction of apoptosis. Bongkrekic acid, a mitochondrial membrane stabilizer, inhibited DEM-induced apoptosis. The inhibitors' effects of LPS or GM-CSF on spontaneous neutrophil apoptosis was reversed by DEM, which was mediated by an increase in caspase 3 activity and independent of mitochondrial disruption. Caspase activation is an important step in glutathione depletion-induced apoptosis in resting and inflammatory neutrophils. Regulation of caspase activity may represent a possible target to trigger apoptosis and resolve inflammatory disorders.