Oxidative stress is associated with XIAP and Smac/DIABLO signaling pathways in mouse brains after transient focal cerebral ischemia.
OBJECTIVE
The interaction of X chromosome-linked inhibitor-of-apoptosis protein (XIAP) with second mitochondria-derived activator of caspase (Smac)/direct inhibitor-of-apoptosis protein-binding protein with low pI (DIABLO) contributes to regulation of apoptosis after a variety of cell death stimuli, and in our reported in vivo transient focal cerebral ischemia (tFCI) model. We have also reported 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 XIAP signaling pathway and oxidative stress in the regulation of apoptosis after tFCI.


METHODS
We used a tFCI model of SOD1 transgenic mice and wild-type littermates to examine the expression of XIAP and Smac/DIABLO by Western blotting and the interaction of XIAP with Smac/DIABLO (XIAP/Smac) or caspase-9 (XIAP/caspase-9) by coimmunoprecipitation. The direct oxidation of 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
Direct oxidative injury to cytosolic and mitochondrial proteins was reduced by SOD1 after tFCI. The individual oxidized carbonyls in XIAP, mitochondrial Smac/DIABLO, and caspase-9 were also reduced by SOD1. Expression of XIAP and XIAP/caspase-9 was promoted, whereas translocation of Smac/DIABLO and XIAP/Smac was reduced, by SOD1 after tFCI.


CONCLUSIONS
These results suggest that overexpression of SOD1 may affect the XIAP pathway after tFCI by reducing the direct oxidative reaction to XIAP regulators after reperfusion injury.
Saito
Atsushi
A
Department of Neurosurgery, Stanford University School of Medicine, Stanford, Calif 94305-5487, USA.
Hayashi
Takeshi
T
Okuno
Shuzo
S
Nishi
Tatsuro
T
Chan
Pak H
PH
D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D001921:Brain / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D002546:Ischemic Attack, Transient / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D024101:Mitochondrial Proteins / Q000378:metabolism*; D018384:Oxidative Stress; D011506:Proteins / Q000378:metabolism*; D015398:Signal Transduction; D013482:Superoxide Dismutase / Q000235:genetics / Q000502:physiology*; D000072105:Superoxide Dismutase-1; D051636:X-Linked Inhibitor of Apoptosis Protein
D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; C499605:Diablo protein, mouse; D024101:Mitochondrial Proteins; D011506:Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1