Pengfei Ge1, Tianfei Luo2, Jizhou Zhang2, Haifeng Wang1, Wenchen Li1, Yongxin Luan1, Feng Ling3, Yi’nan Luo1

1Department of Neurosurgery, First Hospital, Jilin University, Changchun  130021, Jilin Province, China
2Department of Biochemistry and Molecular Biology, Norman Bethune Medical School, Jilin University, Changchun  130021, Jilin Province, China
3Department of Neurosurgery, Xuanwu Hospital, Capital University of Medical Science, Beijing  100053, China

the Postdoctoral Foundation of China, No. 20080440422*; International Cooperation Grant, No. 20070721*; Outstanding Youth Grant of the Science and Technology Department of Jilin Province, No. 20080139*; a grant from the Science and Technology Department of Changchun City, No. 2007128*

Abstract
BACKGROUND: Proteasome dysfunction has been reported to induce abnormal protein aggrega-tion and cell death.
OBJECTIVE: To investigate the effect of proteasome changes on delayed neuronal death in CA1 and dentate gyrus (DG) regions of the rat hippocampus following transient cerebral ischemia.
DESIGN, TIME AND SETTING: A randomized, controlled animal experiment. The study was per-formed at the Department of Biochemistry and Molecular Biology, Norman Bethune Medical College of Jilin University, from September 2006 to May 2008.
MATERIALS: Rabbit anti-19S S10B polyclonal antibody was purchased from Bioreagents, USA; propidium iodide and fluorescently-labeled goat anti-rabbit IgG were purchased from Jackson Im-munoresearch, USA; hematoxylin and eosin staining solution was purchased from Sigma, USA; LSM 510 confocal microscope was purchased from Zeiss, Germany.
METHODS: A total of 40 healthy Wistar rats, male, 4 months old, were randomly divided into sham surgery group (n = 8) and model group (n = 32). Ischemic models were established in the model group by transient clamping of the bilateral carotid arteries and decreased blood pressure. After 20 minutes of global ischemia, the clamp was removed to allow blood flow for 30 minutes, 4, 24, and 72 hours, respectively, with 8 rats at each time point. The bilateral carotid arteries were not ligated in the sham surgery group.
MAIN OUTCOME MEASURES: Neuronal death in the CA1 and DG regions was observed by he-matoxylin-eosin staining. Proteasome expression in CA1 and DG region neurons was detected by immunohistochemistry.
RESULTS: Hematoxylin-eosin staining showed neuronal death in the CA1 region alone at 72 hours of reperfusion following ischemia. In comparison to the sham surgery group, a significant decrease in proteasome expression was observed, by immunohistochemistry, in the CA1 and DG regions in the model group, following 30 minutes, 4, 24, and 72 hours of reperfusion (P < 0.01). After 72 hours of reperfusion following ischemia, proteasome expression had almost completely disappeared in the CA1 region. In contrast, neurons of the DG region showed minimized proteasome expression at 24 hours, with a slight increase at 72 hours (P < 0.01).
CONCLUSION: The alteration of proteasome following ischemia/reperfusion in the neurons of hip-pocampal CA1 and DG regions reduces the ability of cells to degrade abnormal protein, which may be an important factor resulting in delayed neuronal death following transient cerebral ischemia.
Key Words: transient cerebral ischemia; neuronal death; proteasome

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