Study of apoptotic signaling pathway after transient cerebral ischemia

• Main Authors: Chou Hsin Yu, 周心語
• Other Authors: Lu Hsi Chi
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/19755187296645864759

碩士 === 東海大學 === 食品科學系 === 98 === Stroke, also known as cerebral ischemia, is one common disease of humans. In studying the pathophysiological alterations of stroke, an animal model of transient focal cerebral ischemia in rat was established. Through this animal model of stroke, we were interested to investigate potential post-ischemic brain alterations, particular in the regulation of post-ischemic apoptosis. Global examination found that ischemia/reperfusion caused a significant loss in body weight and deficits in neurobehavior and motor coordination. Ischemia/reperfusion insult caused brain infarction. Histological examination revealed a remarkable atrophy of neuronal nuclei, cell apoptosis, neurofilament loss, and microglia and astrocyte activation. To further elicit the inflammatory response, the activation of resident microglia, the infiltration of neutrophils, macrophages, and B lymphcytes, and the expression of pro-inflammatory mediator cyclooxygenase-2 were detected in ischemic brain tissues. Using TUNEL staining to detect apoptosis-related chromosome breakage, a significant TUNEL-positive signal was detected in cerebral cortex, hippocampus, and striatum after cerebral ischemia/reperfusion. An elevation of protein expression in extrinsic apoptosis pathway-associated molecules such as TNF-α receptor 1, Fas, TNF-α, FADD, and Bid was detected by western blot after cerebral ischemia/reperfusion. Intriguingly, cerebral ischemia/reperfusion also increased the expression of FLIP, a natural antagonist against extrinsic apoptosis. Regarding the intrinsic apoptosis pathway, cerebral ischemia/reperfusion decreased anti-apoptotic Bcl-2 and Bcl-xL expression but increased pro-apoptotic Bad, PUMA, and Bax expression. The apparent expression of p53, a transcription factor critical to apoptosis induction, was detected in ischemic tissues. In addition to caspase-dependent apoptotic cascades, the expression of caspase-independent apoptotic molecule AIF was elevated after cerebral ischemia/reperfusion. Enzymatic measurement further showed the activation of caspase-3, caspase-8, and caspase-9 after cerebral ischemia/reperfusion. These findings suggest that cerebral ischemia/reperfusion triggers caspase-independent and caspase-dependent apoptotic cascades leading to post-ischemic apoptosis.