Background: Cleavage of poly (ADP-ribose) polymerase (PARP) to an 85K fragment is an early biochemical event in cells dying by apoptosis. This study examined (a) if PARP cleavage also occured in cells undergoing necrosis, and (b) if PARP cleavage occured in the cerebellum after hypoxia-ischaemia(HI).
Subjects and interventions: (a) Neuronal cells or fibroblasts in culture were treated with staurosporine (100 nM) which induces apoptosis or sodium azide (10% w/v) which results in necrosis. (b) Twenty six 14-day-old Wistar rats were subjected to cerebral HI. At 0, 2, 4, 6, 12, or 24 hours after HI animals were sacrificed and the cerebellum investigated for PARP cleavage by western blotting and for apoptosis by in situ end labelling(ISEL).
Results: (a) In vitro, PARP cleavage was detected in both neuronal cells and fibroblasts treated with staurosporine but not with sodium azide. (b) In vivo, PARP cleavage increased immediately following HI, was significantly greater on the side of arterial ligation and reached a maximum(5 fold increase) at 6 hours. ISEL showed widespread apoptosis but was not evident until 12 hours post insult.
Conclusion: PARP cleavage to an 85K fragment occurs in cells undergoing apoptosis but not necrosis and is increased in the cerebellum immediately after HI.