Dual Characteristics of Apoptosis and Survival in Cerebellar Purkinje Cells Four Days After Transient Global Ischemia

Whether apoptotic cell death occurs in cerebellar Purkinje cells following transient global ischemia remains unclear. Histologic, immunofluorescent and ultramicroscopic methods were used to assess ischemic outcomes in rats. A pilot study using fluorescence labeling [TUNEL-caspase 3-activated peptide (C3AP)-DAPI] revealed key apoptotic characteristics including nuclear TUNEL-positive, nuclear membrane blebs (NMBs), and cytoplasmic C3AP-positive structures, in addition to transport of TUNEL-positive round structures into cytoplasm and projections in ischemic Purkinje cells but not in controls 4 days after ischemia. A formal follow-up study confirmed that 8% of Purkinje cells 4 days following ischemia exhibited TUNEL-positivity and/or NMBs, while Purkinje cells in controls did not. TUNEL-positive Purkinje cells displayed reduced intensity of Calbindin D28K-ifl/MitoTracker (living cell markers) labeling as compared to controls (p < 0.01). Ultramicroscopic evidence of apoptosis included mitochondrial fragmentation and loss in addition to NMBs and cytosolic deposit of nuclear autophagosomes. Interestingly, 71% of the Purkinje cells exhibited autophagy activity after ischemia. Ultramicroscopic characteristics of survival in ischemic Purkinje cells included a centrally located nucleus, no significant chromatin condensation, stable nuclear and intact cytoplasmic membranes, and normal peripheral spacing of the Purkinje cells. In conclusion, four days after transient global ischemia, cerebellar Purkinje cells exhibited both apoptotic and survival characteristics. Further research warrants investigation of the underlying mechanisms.