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Introduction
Strokes are characterized by significant rates of mortality and disability (1), and there is increasing interest in elucidating the underlying pathological mechanisms and identifying potential treatment strategies. Previous clinical studies have suggested several effective interventions to improve prognosis (2–4). Following ischemic stroke, the restoration of blood flow is key to tissue repair and functional recovery, however, reperfusion following a period of ischemia may result in cerebral ischemia-reperfusion (CIR) injury. During ischemic injury, several pathological processes are involved, including excitotoxicity, oxidative stress, inflammation and necrotic and apoptotic cell death (5).
The fate of neuronal cells following ischemic stroke is determined by the balance between cell survival and death. Autophagy is regarded as one cell survival mechanism and can be induced by various stress conditions, including oxidative stress and endoplasmic reticulum stress. Following cerebral ischemia and spinal cord injury, enhanced autophagy has been demonstrated (6,7). In different circumstances, autophagy can either prompt cell survival or enhance cell death (8,9). Studies have also indicated that knockdown of Beclin-1 or LC3 significantly suppresses autophagy and enhances cell apoptosis (10,11).
Enhanced autophagy has been identified in cerebral ischemia injury, including global and focal ischemia (12). Following focal CIR, the protein levels of Beclin 1 and LC3 have been found to be significantly upregulated in the post-ischemic brain tissues of rats (13). Transient middle cerebral artery occlusion (MCAO) has been observed to significantly upregulate the numbers of cathepsin D, LAMP1-positive neurons in neonatal rats. In addition, marked punctuate autophagosomal labeling (LC3) and marked lysosomal labeling (cathespin D and LAMP1) are found in the neurons (14). The protein level of cathepsin B is also significantly increased. These results indicate that autophagy is important in neuronal death following focal CIR.
The role of autophagy remains controversial, however increasing studies have indicated consistent autophagy activation following CIR (15,16). The present study aimed to examine the correlation between the expression of Atg1/pULK and LC3 in the cerebral cortex and focal CIR injury, thereby investigating the effect of CIR on autophagy in brain cells.
Materials and methods
Animals
A total of 8 adult male Sprague-Dawley rats (220–230 g), provided by the Animal Facility, Health Science Center of Peking University (Beijing, China), were housed in two laboratory animal cages and maintained at 25±1°C with 65±5% humidity...