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Published on: July 25, 2011
Copper-zinc superoxide dismutase affects Akt activation after transient focal cerebral ischemia in mice
Nobuo Noshita1, Taku Sugawara, Anders Lewén
1Department of Neurosurgery, Stanford University School of Medicine, Stanford, Calif 94305-5487, USA.
Background And Purpose:
The serine-threonine kinase Akt is activated by phosphorylation at serine-473. After phosphorylation, activated Akt inactivates BAD or caspase-9 or other apoptogenic components, thereby inhibiting cell death. In this study we examined the relationship between Akt phosphorylation and oxidative stress after transient focal cerebral ischemia (FCI) using copper-zinc superoxide dismutase (SOD1) transgenic (Tg) mice.
Methods:
The mice were subjected to 60 minutes of middle cerebral artery occlusion by intraluminal suture blockade followed by 1, 4, and 24 hours of reperfusion. Phospho-Akt expression was examined by immunohistochemistry and Western blot analysis. Production of superoxide anion was assessed by the hydroethidine method in both wild-type mice and SOD1 Tg mice. DNA fragmentation was evaluated by terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling (TUNEL).
Results:
Immunohistochemistry demonstrated that phospho-Akt was constitutively expressed and was decreased in the ischemic core as early as 1 hour after reperfusion, whereas it was temporally increased in the cortex at 4 hours. Phospho-Akt expression was enhanced in the SOD1 Tg mice. Western blot analysis showed that phospho-Akt was maximized 4 hours after reperfusion in the wild-type mice, whereas phospho-Akt was increased as early as 1 hour after ischemia in the SOD1 Tg mice. There was a significant decrease in TUNEL-positive cells in the SOD1 Tg mice compared with the wild-type mice.
Conclusions:
The present study suggests that SOD1 may contribute to the early activation of the Akt cell survival signaling pathway and may attenuate subsequent DNA damage after transient FCI.
Insights
Copper-zinc superoxide dismutase (SOD1) enhances early Akt activation, reducing DNA damage after focal cerebral ischemia. This suggests SOD1 plays a key role in protecting brain cells from ischemic injury.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- The Akt signaling pathway, activated by phosphorylation at serine-473, inhibits apoptosis by inactivating pro-apoptotic factors.
- Oxidative stress is implicated in cell death following ischemic events.
- Copper-zinc superoxide dismutase (SOD1) is a critical enzyme in managing reactive oxygen species.
Purpose of the Study:
- To investigate the interplay between Akt phosphorylation and oxidative stress in the context of transient focal cerebral ischemia (FCI).
- To evaluate the role of SOD1 in modulating Akt activation and neuronal survival following ischemic injury.
Main Methods:
- Transient focal cerebral ischemia (FCI) was induced in wild-type and SOD1 transgenic mice.
- Phospho-Akt expression was quantified using immunohistochemistry and Western blot analysis.
- Superoxide anion production, DNA fragmentation (TUNEL assay), and phospho-Akt levels were assessed at various reperfusion time points.
Main Results:
- Phospho-Akt levels decreased in the ischemic core but increased in the cortex post-FCI.
- SOD1 transgenic mice exhibited enhanced phospho-Akt expression earlier than wild-type mice.
- A significant reduction in DNA fragmentation was observed in SOD1 transgenic mice compared to wild-type controls.
Conclusions:
- SOD1 appears to promote the early activation of the Akt cell survival pathway.
- SOD1 may attenuate DNA damage in the brain following transient focal cerebral ischemia.
- These findings highlight SOD1's protective role in ischemic stroke through modulation of the Akt pathway.
