| 摘要: | 中風是已開發國家重要的十大死亡原因之一，而興奮神經毒性(excitotoxicity) 藉由引發大量發炎反應、氧化壓力以毀損血腦屏障(BBB)是造成中風腦神經死亡之主要病理機轉；又因成年人腦受傷後之再生能力非常微弱，因此臨床上目前對於中風除少數病人能於中風數小時內到醫院診治即時投予血栓溶解劑外，並無其他有效治療藥物。根據最近的研究，我們注意到若能經由活化下述三大類神經保護分子機轉，可能可以有效增強內生性神經再生，對於中風病人腦部神經再造將有極大的助益，三大類分子機轉包括：1) 抑制glycogen synthase kinase 3 (GSK-3)其相關訊息傳遞網(e.g., p53/CREB/Akt/MMP-9/VEGF/HSF-1)，以有效對抗興奮神經毒性；2) 藉由活化Wnt/β-catenin訊息傳遞激發血腦屏障再造(BBB remodeling)，可同時刺激血管新生(angiogenesis)及神經再生(neurogenesis)；3) 藉由活化Notch -1訊息傳遞及刺激腦部神經滋養因子製造(e.g., Ang 1，Sdf1)可同時強化神經再生(neurogenesis)、神經幹細胞遷徙、修補傷害並促進神經細胞分化。若能藉由找到合適方法或藥物，可同時阻斷興奮神經毒性，強化血腦屏障再造，並促進神經再生、神經遷徙及神經分化，將非常有助於提供中風病人有效之治療方法或藥物。最近許多研究顯示：跑步運動會改變中樞神經生理結構，特別是與學習記憶密切相關的海馬迴，該區可因從事正常跑步運動而增加神經滋養因子表現，並促進血管增生和神經突觸可塑性，這些改變與從事運動能急遽提升神經再生基因之分子機制密切相關，但跑步運動是否真能有效改善中風動物之神經病變並無深入研究，因此我們提出本研究假說：正常跑步運動可以藉由去活化以GSK-3為中心的中風動物腦部相關之神經毒性傷害訊息傳遞機制網，因而降低興奮神經毒性，或可活化Wnt/β-catenin以促進血管新生使血腦屏障再造，或藉由活化Notch-1或Ang 1/Sdf1以促進內生性神經幹細胞(NSCs)增生、遷徙修補及成熟分化。計畫設計理由：此假說乃依據許多文獻報導及我們初步研究發現預先從事正常跑步運動可以顯著促進內生性神經幹細胞增生，若能經由本動物研究計畫，找出預先從事正常跑步運動所能激活之神經保護機轉及可能作用分子標靶，將可提供該機轉及分子標靶做為治療缺血型中風有效之生物標記(biomarker)及藥物標靶(molecular target)。研究目標：藉由探討預先從事正常跑步運動能否改善缺血型中風小鼠之神經功能、神經生化學相關研究，找出正跑步運動所能活化之神經再生機轉及作用分子標的。為達成上述研究目的，我們特訂定以下三項專一研究目標：專一目標#1(第1年)：探討預先從事正跑步運動是否能顯著正常跑步運動保護小鼠腦中風、促進神經再生及改善運動學習記憶能力之分子機轉探討-劉國同副教授 2011/12/27, 9:49 AM 抑制中風鼠腦之GSK-3活性而活化其下游相關神經保護訊息傳遞網(e.g., p53/apoptosis; CREB/Bcl2; CREB/BDNF/PI3K/Akt; MMP-9/angiogenesis & migration; VEGF/angiogenesis; HSF-1/HSP70/NFκB; CREB/BDNF/ neurogenesis)，以有效對抗興奮神經毒性並因而促進血管新生及神經再生；專一目標#2(第2年)：探討跑步運動是否能活化中風鼠腦之Wnt/β-catenin及Ang1/Tie2等相關訊息傳遞，以有效促進血管新生，並激發血腦屏障再造；專一目標#3(第3年)：探討跑步運動是否能經由活化Nothch-1，並刺激滋養因子Ang1/Sdf1製造，以促進內生性神經幹細胞增生、遷徙修補及成熟分化。一般研究方法：使用中腦動脈阻塞缺血型中風小鼠，探討動物中風前3-12週，每天從事正常跑步運動1小時或投予臨床中風治療藥物rt-PA (血栓溶解劑)做為參考比照，比較有無預先從事正常跑步運動之小鼠於中風後7-28天內之活體動物腦神經功能恢復情形、血管新生暨BBB修補情形及內生性神經幹細胞增生及分化情形、評估活體腦部發炎自由基影像及觀察神經行為損傷復原指數，並測量腦梗死區域，對照免疫組織染色及RT-PCR檢驗發炎、氧化壓力、神經凋亡、神經自噬及神經再生能力以了解預先從事正常跑步運動所能活化之神經再造可能分子機轉。預期成果：本研究成果將可了解正常跑步運動保護動物免於中風傷害的機轉，是否與作用在三大類分子機制及關鍵分子標靶，包括是否能：(1)廣泛抑制興奮神經毒性(藉由抑制GSK-3)，(2)促進血管新生/BBB再生(藉由活化Wnt/β-catenin)；(3)促進神經再生(藉由活化Nothch-1))等訊息；將可提供該有效分子標靶做為臨床發展成為治療中風藥物或策略之專一分子標靶考量。
Stroke is one of the leading causes of death in developed countries. It has been well documented that excitotoxicity is the major pathophysiological mechanism associated with stroke by inducing inflammation and oxidative stress-associated disruption of the blood-brain barrier (BBB). These changes cause a great increase in neuronal cell death during ischemic stroke and the regeneration efficiency of neurons in the injured mammalian brain is extremely low. No effective treatment that is able to improve functional recovery exists in the post-ischemic phase aside from thrombolytic during the first few hours after an ischemic stroke, which is available to only a few patients. Recently, we notice that there are three potential strategies that can become therapeutically valuable for treatment of ischemic stroke induced poor functional recovery by enhancing endogenous neurogenesis most possibly by 1) inhibiting glycogen synthase kinase-3 (GSK-3) to activate its associated signaling pathways for neuroprotection against excitotoxicity; 2) remodeling BBB by activating the Wnt/β-catenin signaling pathway to stimulate brain angiogenesis and neurogenesis; 3) activating Notch 1 signaling and enhancing neurotrophic factors (e.g., Ang1 and Sdf1) for the enhancement and recruitment of endogenous neurogenesis. To achieve these benefits, performing strategy concomitantly reducing excitotoxicity, enhancing BBB remodeling/angiogenesis, while also upregulating the generation, migration and maturation of the newly born neuroblasts or neural stem/progenitor cells into injured sites will be very promising for dealing with ischemic stroke. Many reports indicate that regular exercise improves brain function and elevates synaptic plasticity and hippocampal neurogenesis. Performing exercise improves learning activities in adult runners, and is tightly correlated with increased neurogenesis. Exercise has profound benefits for cognitive function both in human and animals; For example, in children and young adults, there is a positive correlation between physical activity and learning; in animal studies, both voluntary and forced running models enhance learning and memory. Central physiological and structural changes resulting from exercise, in particular, in the hippocampus, a brain region important for learning and memory. Running increases neurotrophin gene expression, vascularization, dendritic spine density, and synaptic plasticity. Therefore, the positive relationship between regular running and neurogenesis has raised the hypothesis that newly born neurons associated with regular exercise may mediate, in part, to improve cognition, moving, and learning through which to improve functional recovery that is hampered by ischemic stroke. However, whether regular running can protect mice against ischemic stroke-mediated excitotoxicity by enhancing angiogenesis for BBB remodeling, stimulating endogenous Elucidating the molecular mechanisms involved in regular running-mediated endogenous neurogenesis/differentiation and enhancements in functional recovery, learning and cognition in ischemic stroke mice; Dr KT Liou; 12/27/2011; p 2/3 neurogenesis, migration and differentiation/maturation of neural progenitor/neuroblast via targeting detrimental molecules (e.g., GSK-3) and activating neuroprotective signaling (e.g., Wnt/β-catenin and Notch 1) through which to achieve the protective effects by regular running need more elucidation. In this project, we intend to decipher the specific and fundamental molecular targets involved in regular running (1h/day for 3-12 weeks)-mediated protective effect by using an in vivo ischemic stroke murine model integrated with neurofunctional, neurological, and neurochemical approaches. The central hypothesis is: regular running can target GSK-3 to ameliorate “excitotoxicity”-mediated brain injury, enhance “angiogenesis” to remodel BBB, and promote “neurogenesis” to repair damaged neurons in ischemic stroke mice. This hypothesis is based on our preliminary results that showed regular running 1h daily for 3 weeks can stimulate endogenous neurogenesis in mice. The rationale is: regular running is known to be neuroprotective and we our preliminary data found regular running can protect against ischemic brain damage. To decipher whether and how regular running working on CI/R (ischemic stroke)-mediated excitotoxicity in a murine model will lead to an effective therapeutic application (stroke biomarkers and drug targets) for hypoxia/ischemia-related neuronal disorders. General Goal is: To identify the specific and fundamental molecular targets involved in regular running-mediated neuronal protective effects by using an in vivo ischemic stroke murine model integrated with neurofunctional, neurological, and neurochemical approaches for elucidation of neuronal cell differentiation and maturation. To achieve the research objective, three specific aims will be pursued: Specific Aim #1, to study whether regular running can protect BBB through targeting GSK-3 to activate its associated protective signals to ameliorate excitotoxicity in ischemic murine model; Specific Aim #2, to study whether regular running can promote BBB remodeling by enhancing angiogenesis through activating Wnt/β-catenin and Ang1/Tie2 signaling in ischemic murine model; Specific Aim #3, to study whether regular running can enhance endogenous neurogenesis through Notch1 signaling in ischemic murine model. Expected Results of Specific Aims, We will reveal regular running can enhance endogenous neurogenesis, migration and differentiation of NPCs, through activating Notch1 and neural growth factors in ischemic murine model. This can help to explain how regular running could protect mice against CI/R-induced brain injury and extend the life span of mice with an ischemic stroke. These results could help support regular running to be a beneficial strategy for the handling of ischemic stroke in the clinic. Elucidating the molecular mechanisms involved in regular running-mediated endogenous neurogenesis/differentiation and enhancements in functional recovery, learning and cognition in ischemic stroke mice; Dr KT Liou; 12/27/2011; p 3/3 |
