Akt phosphorylation and neuronal survival after traumatic brain injury in mice

The serine-threonine kinase, Akt, is involved in the survival signaling pathways in many cell systems. The present study examined phosphorylation of Akt at serine-473 and DNA fragmentation after traumatic brain injury (TBI) in mice. Immunohistochemistry showed phospho-Akt was decreased in the injured cortex 1 h after TBI, whereas it was temporally increased at 4 h in the perifocal damaged cortex. In the CA1 region of the hippocampus, phospho-Akt was increased after TBI. Western blot analysis showed that Akt was significantly decreased as early as 1 h after trauma; however, the phosphorylation was accelerated at 4 h. Double staining with phospho-Akt and phospho-BAD or phospho-GSK-3beta revealed the colocalization of phospho-Akt and downstream elements. Double staining with phospho-Akt and terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling showed different cellular distributions after TBI. The present study implicates Akt phosphorylation in the signaling pathways that are involved in cell survival after TBI.