Abstract:

Objective To investigate the regulation of signal transducers and activators of transcription 3(STAT3) phosphorylation in the neuroprotection of ischemic postconditioning(PC) in tree shrews and to explore the neuroprotection mechanisms of ischemic PC. Methods Tree shrews were randomly grouped into control，ischemia 4 hours，ischemia 24 hours，ischemic PC 4 hours and ischemic PC 24 hours (n=5). Ten animals were used for HE staining(n=5) and electron microscopy (n=5)．The model of thrombotic cerebral ischemia was induced by photochemical reaction in tree shrews and the ischemic PC was established at hour 4 after ischemia followed by clipped ipsilateral common caroyid artery on the ischemia side (5 minutes×3). The changes of cerebral infarction area were measured with TTC staining. The histological and ultrastructural changes of cortex and hippocampus were observed by HE staining and electron microscope,respectively. The expression of total STAT3 (t-STAT3) and phosphorylated STAT3(p-STAT3) protein in the cortical tissue were detected by Western blotting. Results The ischemic group showed cortical vascular endothelial cell edema, cortical and hippocampal neurons pycnosis, mitochondrial swelling and partial disrupt, the damage was obvious and the cerebral infarction area was (24.78±2.06)% at hour 24 after cerebral ischemia. With the time prolonging of ischemia, the phosphorylation of STAT3 in the cortical neurons was significantly increased (0.24±0.1, P<0.01）at hour 4 and increased continuously (0.32±0.1, P<0.01）at hour 24 after cerebral ischemia. But the damage of vascular endothelial cell and neurons was alleviated and the cerebral infarction area was decreased (17.67±1.90)% (P<0.01）at hour 24 after ischemic PC. Compared with the ischemia group, the phosphorylation of STAT3 was further increased at hour 4 (0.41±0.09, P<0.01）and was significantly increased at hour 24 (0.70±0.11, P<0.01）after ischemic PC. Conclusion Cerebral ischemia may lead to compensatory increase of STAT3 phosphorylation and the neuroprotection of ischemic PC may be related to the promotion of STAT3 phosphorylation in tree shrews.

Key words: Photochemistry, Cerebral ischemia, Postconditioning, Signal transducers and activators of transcriptions 3, Neuroprotection, Western blotting, Tree shrew