Introduction: Subarachnoid hemorrhage (SAH) results in a high mortality rate, despite sophisticated medical management and neurosurgical techniques. Recent studies have emphasized the importance of acute brain injury after SAH. Oxidative stress plays important roles in the pathogenesis of acute brain injury after SAH. We have reported that copper/zincsuperoxide dismutase (SOD1) is a crucial endogenous enzyme responsible for eliminating superoxide, and that overexpression of SOD1 reduces cell injury after SAH. In cerebral ischemia, SOD1 overexpression decreased ischemic neuronal death through activation of the Akt/GSK3b survival pathway. In this study, we investigate the relationship between SOD1 and the Akt/GSK3b pathway in acute brain injury after SAH. We address this issue by examining apoptotic cell death, superoxide production, and phosphorylation of Akt/GSK3b after SAH, using both wild-type (Wt) and SOD1 transgenic (Tg) rats. Materials and methods: To examine the relationship between SOD1 and the Akt/GSK3b pathway following SAH, we used a perforation SAH model in both Wt and SOD1 Tg rats. One, 6 and 24 hours after SAH, samples were taken from the cerebral cortex, and used for Western blot analysis and immunohistochemical analysis. To investigate apoptotic cell death in acute brain injury after SAH, DNA fragmentation was analyzed with a commercial enzyme immunoassay. Early production of superoxide anions (O2?) during SAH was investigated with the use of hydroethidine (HEt). Results: The mortality rate at 24 hours for the SOD1 Tg rats (7.69%) was significantly decreased compared with the Wt rats (31.4%). DNA fragmentation in the SOD1 Tg rats was significantly decreased at 24 hours compared with the Wt rats at the same time point. O2? production shown by oxidized HEt signals was observed in the cerebral cortex at 1 hour in the Wt rats, and was markedly decreased in the SOD1 Tg rats. Western blot analysis showed that immunoreactivity of phospho-Akt and phospho-GSK3b was significantly increased at 6 hours compared with the control brain samples in the Wt rats. In the SOD1 Tg rats, the increase in phospho-Akt and phospho-GSK3b levels was more prominent and persistent. In a comparison between the two groups, phospho-Akt and phospho-GSK3b were significantly increased at 24 hours in the SOD1 Tg rats. An immunohistochemistry study showed slight immunoreactivity of phospho-Akt and phospho-GSK3b in the cerebral cortex of the control brains. This immunoreactivity became stronger at 24 hours in both groups. In the SOD1 Tg rats, phospho-Akt and phospho-GSK3b expression at 24 hours was more prominent than in the Wt rats. A double immunofluorescent study demonstrated that phospho-Akt-positive cells colocalized with phospho-GSK3b-positive cells in the cerebral cortex 6 hours after SAH. Moreover, phospho-GSK3b-positive cells colocalized with neurons at the same time point. Conclusions: This study suggests that oxidative stress plays a significant role in acute brain injury after SAH, and that the neuroprotection of SOD1 is partly mediated by activation of the Akt/GSK3b survival pathway. Reducing oxidative stress, thereby activating the survival pathway, could be a therapeutic target for acute brain injury after SAH in a clinical situation.
|Journal||Journal of Cerebral Blood Flow and Metabolism|
|Issue number||SUPPL. 1|
|Publication status||Published - 2007 Nov 13|
ASJC Scopus subject areas
- Clinical Neurology
- Cardiology and Cardiovascular Medicine