Modulation of proline-rich akt substrate survival signaling pathways by oxidative stress in mouse brains after transient focal cerebral ischemia.

BACKGROUND AND PURPOSE

A proline-rich Akt substrate (PRAS) contributes to the regulation of apoptosis after a variety of cell death stimuli, as well as in an in vivo transient focal cerebral ischemia (tFCI) model. We reported previously that overexpression of copper/zinc-superoxide dismutase (SOD1) reduces apoptotic cell death after tFCI. Our present study was designed to clarify the relationship between the PRAS signaling pathway and oxidative stress in the regulation of apoptosis after tFCI.

METHODS

We used a tFCI model with SOD1 transgenic mice and wild-type littermates to examine the expression of phosphorylated PRAS (pPRAS) by Western blotting and immunohistochemistry and the interaction of pPRAS with phosphorylated Akt (pPRAS/pAkt) or the 14-3-3 protein (pPRAS/14-3-3) by coimmunoprecipitation. Direct oxidation of the carbonyl groups, an indication of oxidative injury to total and individual proteins caused by tFCI, was examined using a 2,4-dinitrophenylhydrazone reaction assay.

RESULTS

Expression of pPRAS, pPRAS/pAkt, and pPRAS/14-3-3 decreased 2 hours after tFCI. Oxidized hydroethidine did not colocalize with expression of pPRAS. Individual oxidized carbonyls in pPRAS remarkably increased 2 hours after tFCI but were significantly reduced by SOD1 2 hours after tFCI. Expression of pPRAS, pPRAS/pAkt, and pPRAS/14-3-3 was promoted by SOD1 during the same time course.

CONCLUSIONS

These results suggest that overexpression of SOD1 may affect the PRAS pathway after tFCI by reducing the direct oxidative reaction to pPRAS after reperfusion injury.