Inhibition of neutrophil apoptosis by antioxidants in culture medium

Neutrophil apoptosis is an important mechanism that has implications for understanding the life span and toxic potentials of neutrophils at inflamed sights. In this study the authors examined the possibility that reactive oxygen species (ROS) released by neutrophils can regulate neutrophil survival. Cu,Zn-superoxide dismutase (Cu,Zn-SOD), Mn-SOD, and catalase in culture media were significantly effective in delaying the spontaneous apoptosis, suggesting that ROS play an important role in the resolution of inflammation by inducing neutrophil apoptosis. In this experiment, boiled Cu,Zn-SOD had no effect on inhibiting the apoptosis, but boiled Mn-SOD from Bacillus stearothermophilus was more effective in inhibiting the apoptosis than untreated Mn-SOD at the same dose. However, the boiled Mn-SOD showed only 80% of O₂ ^- inhibitable activity compared with the untreated Mn-SOD. This effect may be attributed to the partial liberation of manganese because MnCl₂ inhibited the apoptosis effectively. Furthermore, Cu,Zn-SOD was effective in delaying apoptosis only when added to the culture within the first 3 h of incubation, suggesting that the isolation of neutrophils from peripheral blood enhances apoptosis of neutrophils.