脑缺血大鼠海马信号转导与转录激活子-3的激活及其调控(英文)

Activation of STAT3 induced by cerebral ischemia in rat hippocampus and its possible mechanisms

以往的研究表明 ,在脑缺血 /再灌注的皮层和纹状体组织中信号转导与转录激活子 3 (STAT3 )被激活。本实验旨在研究SD大鼠四动脉结扎诱导的全脑缺血是否引起海马组织STAT3的快速激活及其调控机制。结果表明 ,脑缺血导致STAT3快速磷酸化激活及DNA结合活性增加。胞浆STAT3的磷酸化水平从缺血 5min起就显著增高 ,10min达高峰 (增加约 1 7倍 ) ,然后开始下降。核内STAT3的磷酸化水平则逐渐增加 ,缺血 3 0min时达高峰 (增加约2 3倍 )。电泳迁移率改变分析法显示 ,STAT3的DNA结合活性从缺血 5min起就显著增加 ,3 0min达高峰 (增加约3 2倍 )。进一步的研究表明 ,缺血前 2 0min腹腔注射给药 ,然后缺血 3 0min ,发现蛋白酪氨酸激酶抑制剂染料木黄酮和抗氧化剂N 乙酰半胱氨酸能显著地抑制核内STAT3的磷酸化水平及DNA结合活性的增加 (磷酸化水平从 2 3和2 5倍分别降为 1 2和 1 4倍 ,DNA结合活性则从 2 8和 3 7倍分别降为 1 1和 1 5倍 ) ,而蛋白酪氨酸磷酸酶抑制剂矾酸钠则能明显地促进他们的增高 (磷酸化水平从 2 0倍增到 3 4倍 ,DNA结合活性从 3 1倍增为 5 1倍 )。这些结果提示 ,蛋白酪氨酸激酶和蛋白酪氨酸磷酸酶可能共同参与了缺血诱导STAT3的激活调控 。

It has been demonstrated that signal transducer and activator of transcription-3 (STAT3) is activated after cerebral ischemia/reperfusion (I/R) in cortex and striatum. In this study, we investigated whether STAT3 was rapidly activated in hippocampus by cerebral ischemia without reperfusion in four-vessel occlusion (4-VO) model of Sprague-Dawley (SD) rats. The results showed that tyrosine phosphorylation and DNA binding activity of STAT3 was rapidly increased by ischemia. The p-STAT3 level in cytoplasm increased 5 min after occlusion and reached a peak at 10 min following ischemia (1.7 folds vs sham) by means of immunoblotting (IB). P-STAT3 in nucleus was gradually enhanced with its peak activity occurring at 30 min of ischemia (2.3 folds vs sham). Electrophoretic mobility shift assay (EMSA) with STAT3 probe demonstrated that DNA binding activity of STAT3 in nuclear extracts increased from 5 min and peaked at 30 min of ischemia (3.2 folds vs sham). These changes were prevented by genistein (a protein tyrosine kinase inhibitor) and antioxidant N-acetyl-L-cysteine (NAC), but promoted by sodium orthovanadate (a protein phosphatase inhibitor), which were administered to the SD rats 20 min before ischemia. These results indicate that the activation of STAT3 following cerebral ischemia may be modulated by PTK/PTP, and that this pathway may be of benefit to the adaptation of the hippocampal neurons to oxidative stress.