Lysophosphatidic acids (LPAs) 為一具有訊息傳導特性的簡單的磷脂質。當其接受器 (LPA receptor；LPAR) 被經內生性或外生性受體 (ligands) 活化後，可以引發多種細胞內訊息傳遞路徑以調控細胞的生理功能。於中樞神經系統 (CNS) 中，LPAR的活化可引發細胞凋亡或促進細胞存活等二相互牴觸之生理反應。我們於之前的研究已經指出，活化因永久性中大腦動脈梗塞 (permanent middle cerebral artery occlusion；pMACO) 所導致缺血性中風的大鼠腦內LPA接受器，可降低腦損傷體積，並提高動物於中風24小時後的存活率。然而，介導此LPA接受器活化而形成的保護作用的細胞內訊息傳遞機制，目前尚未被釐清。
於本研究中，我們以之前建立的大鼠腦缺血性中風模式為基礎，並以LPA接受器之同效劑VPC31143 (VPC) 作為治療藥劑，於雄性Sprague-Dawley大鼠接受pMACO手術30分鐘後，以腹腔注射方式投以0.8 mg/kg之VPC作為治療藥劑。在pMCAO手術後4、8、與24小時，以Garcia score評量表評估pMCAO組與pMCAO後接受VPC治療之大鼠 (pMCAO+VPC組) 的運動與感覺功能，並計算大鼠之中風腦體積 (infarct volume) 與中風腦體積比 (infarct brain volume ratio)，並萃取半球腦片之蛋白質，以西方墨點法來研究經LPA接受器活化的細胞訊息傳遞相關蛋白的表現，並探討LPA接受器可能的保護機制。
實驗結果顯示，LPA接受器經VPC活化後，可減輕由pMCAO造成大鼠的運動與感覺功能的損失，並降低腦中風梗塞的腦體積比。從西方墨點法的分析中，我們發現經由VPC的治療，可降低caspase 3、caspase 8、caspase 9、磷酸化的 p-38 MAPK等促進細胞凋亡的訊息蛋白質於在中風腦組織內的表現。VPC的治療亦同時增加了PI3K、Akt、p-42/44 MAPK等拮抗細胞凋亡的訊息蛋白的磷酸化，並同時增加了粒線體蛋白Bad的磷酸化。此結果顯示，中風鼠腦內的LPA接受器的活化，可活化PI3K及其下游的Akt、MAPK及其他訊息通路傳遞，並增加粒線體內抗凋亡蛋白質的表現，以減低中風後腦組織的細胞凋亡的反應，而達到保護腦組織的目的。

Lysophosphatidic acids (LPAs) belong to a class of simple phospholipids that bears signal transduction property. Upon activation by endogenous or exogenous ligands, LPA receptor (LPAR) could evoke various signal transduction cascades that regulate a wide variety of cellular physiology. In the central nervous system (CNS), activation of LPAR could either trigger the signals for apoptosis or evoke the signal transductions that promote the cell survival. In our previous studies, we have morphometrically and functionally demonstrated the protective effects of VPC31143, an LPAR agonist, against the effects of permanent middle cerebral artery occlusion (pMACO) in a rat model of ischemic stroke. Nevertheless, the intracellular signal transduction mechanisms responsible for such protective effects have yet to be revealed.
In this study we utilized the previously established rat model of ischemic stroke as the study foundation. Male Sprague-Dawley rats were intraperitoneally injected with 0.8 mg/kg of VPC as the therapeutic agent 30 minutes after pMCAO surgery. The motor and sensory functions of rats receiving VPC treatment (pMCAO+VPC group) and those without drug treatment (pMCAO group) were evaluated using Garcia score system at 4, 8, and 24 hrs after the pMCAO surgery. The infarct brain volume and infarct brain volume ratio of these rats were measured and calculated. The regulation of signal transduction proteins VPC-mediated LPAR activation in the ischemic rat brain hemisphere were studied with Western blot and compared to those in the ischemic hemisphere in the absence of VPC.
The study results showed that LPAR activation by VPC attenuated the loss in sensory and motor functions, while concurrently reduced the infarcted brain volume ratio. The Western blot results showed that VPC treatment reduced the expression of pro-apoptotic signal proteins such as caspase 3, caspase 8, caspase 9, and phosphorylated p-38 MAPK in the ischemic hemisphere. VPC treatment also up-regulated the expression of the anti-apoptotic proteins such as PI3K, Akt, and p-42/44 MAPK in the ischemic brain, and also increased the expression of phosphorylated Bad, a mitochondrial protein critical to the integrity of this organelle. Together, the results indicated that actication of LPAR with VPC would trigger the signal pathway of PI3K as well as its downstream signal protein Akt and MAPKs, as well as other signal transduction cascades, and concurrently increase the anti-apoptotic protein expression in mitochondria. Together, these cellular mechanisms could reduce the extent of apoptosis in the ischemic brain tissues and accomplished the goal of brain protection.

論文審定書… i
致謝………… ii
中文摘要…… iii
英文摘要…… iv
目錄………… vi
圖目錄……… vii
前言………… 1
材料與方法… 7
結果與討論… 13
結論………… 23
參考文獻…… 24
圖…………… 29
附錄………… 57

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