Regulation of Fas antibody induced neutrophil apoptosis is both caspase and mitochondrial dependent

Resolution of neutrophil mediated inflammation is achieved, in part, throug h induction of neutrophil apoptosis, This constitutively expressed programm e can be delayed by inflammatory mediators and induced by ligation of the F as receptor. However, functional activation of the neutrophil results in re sistance to Fas signalled death. We evaluated the effects of Fas antibody e ngagement on caspase activation and mitochondrial permeability, and the imp act of co-stimulation by lipopolysaccharide (LPS) or granulocyte macrophage -colony stimulating factor (GM-CSF) on these events. Fas engagement by an a gonistic anti-Fas antibody resulted in enhanced caspase 3 and 8 activity an d increased mitochondrial permeability. Studies with pharmacological inhibi tors of caspase activity showed that activation of caspase 8 occurred befor e, and activation of caspase 3 occurred after mitochondrial disruption. The mitochondrial stabilising agent bongkrekic acid also inhibited caspase act ivation and apoptosis, LPS, GM-CSF and increased glutathione stabilised the mitochondria and inhibited caspase 3, Caspase 8 activity was also inhibite d by co-stimulation through a mechanism independent of mitochondrial stabil isation, Glutathione directly inhibited caspase 3 and 8 activity. We conclu de inhibition of Fas antibody induced apoptosis by inflammatory proteins is associated with augmented mitochondrial stability and reduced caspase 3 ac tivity that may be glutathione mediated. (C) 1999 Federation of European Bi ochemical Societies.