Delayed neutrophil apoptosis in sepsis is associated with reduced Caspase-3 activity

Apoptosis or programmed cell death is effected through a family of proteases called caspases. Mature neutrophils undergo spontaneous apoptosis mediated in part by the proapoptotic enzyme caspase-3. Since circulating neutrophils from patients with sepsis show delayed apoptosis, we evaluated caspase-3 activity in experimental and clinical sepsis.

Methods

Neutrophils from septic patients and normal controls were treated with pyrrolidine dithiocarbamate (PDTC), an inhibitor of NFκB with or without preincubation with LPS. Apoptosis was assessed as propidium iodide uptake by flow cytometry at 24 h. Caspase-3 expression was determined by western blots and activity was determined spectrophotometrically using a specific substrate (DEVD-AMC).

Results

Caspase-3 activity was reduced by exposure to LPS and in sepsis patients (results follow, mean ± SEM). Apoptosis was stimulated by PDTC in all groups.

Incubation of neutrophils with PDTC in a separate group of 4 of 6 patients with similar organ dysfunction scores demonstrated no increase in CPP32 expression at 4 h of in vitro culture.

Conclusion

Caspase-3 activity is reduced in clinical and experimental sepsis. Modulation of effector caspase activity may represent a novel approach to hasten the resolution of an inflammatory response.

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