The involvement of upregulation and translocation of phospho-Rb in early neuronal apoptosis following focal cerebral ischemia in rats.

The aim of this study was to investigate the temporal and spatial relationship between phospho-Rb (ser 795) and neuronal apoptotic death in rats subjected to transient focal cerebral ischemia. We found increased phosphorylation of Rb and translocation from neuronal nucleus to cytoplasm in the penumbra zone at 12 h, 1 day, 3 days and 7 days after middle cerebral artery occlusion (MCAO)/reperfusion, compared with sham-operated controls. At 12 h and 1 day, phospho-Rb appeared to be colocalizated with TUNEL staining in neurons, but staining was not colocalizated at 3 days and 7 days. These results demonstrated that cytoplasmic translocation of phospho-Rb from nucleus of neurons occurs in potential apoptotic neurons in the early stages of ischemia/reperfusion, suggesting that the Rb pathway may only be involved in early neuronal apoptosis and may be not an apoptotic signal in the late stages of transient cerebral ischemia.