探討hinokitiol於中風動物模式之神經保護作用

The neuroprotective effect of hinokitiol in a transient focal ischemia/reperfusion rat model

羅鈞允(Jun-Yun Luo)

指導教授 ： 許銘仁

共同指導教授 ： 許準榕

臺北醫學大學/醫學院/醫學科學研究所/碩士(2010年)

https://doi.org/10.6831/TMU.2010.00100

摘要

在已開發中國家，腦中風為血管性疾病致死率及發病率主因之一。可區分為缺血性及出血性二大類，其中缺血性腦中風發生率高於出血性腦中風，而相關缺血性腦中風之病理機轉也受到廣泛的研究，但有關缺血性腦中風之治療藥物卻沒有相當的進展。神經保護製劑為缺血性腦中風治療藥物之一，但不幸的，臨床上對腦缺血再灌流傷害有效的神經保護劑仍付之闕如。由於中大腦動脈為人類缺血性腦中風最容易發生之部位，因此，中大腦動脈缺血/再灌流動物模式為目前最普遍用來研究缺血性腦中風藥物的實驗模式。
Hinokitiol又稱為β-thujaplicin，為tropolone類化合物，存在於天然柏科植物的心材之中，具有多種生物活性，包括抗氧化、抗發炎以及螯合鐵離子等等。然而，hinokitiol對於缺血/再灌流所造成的損傷其保護神經細胞之能力迄今尚未被研究。
本論文之研究目的即在評估hinokitiol對於中大腦動脈缺血再灌流動物模式所引起之傷害是否具有神經保護作用；另外，更進一步的探討藥物是否具有抑制或減少腦部缺血性再灌流傷害所引起之發炎或是細胞凋亡反應的能力。hinokitiol (0.2 mg/kg i.p. and 0.5 mg/kg i.p.)能夠明顯且有意義地分別減少25.15 % 及49.59 % 由缺血再灌流傷害所引起之梗塞面積。接著實驗再進一步從分子層面測試hinokitiol對此傷害之神經保護機轉，經由西方墨點法分析後，發現預防性投與hinokitiol皆能明顯減少iNOS、HIF-1α、TNF-α及caspase-3表現。根據這些結果發現，hinokitiol具有神經保護能力藉以避免腦部缺血再灌流傷害。此效果可能的機轉為透過減少iNOS 表現而減少氧化壓力傷害，抑制發炎前細胞激素TNF-α表現而降低發炎反應的進行，也抑制caspase-3及HIF-1α表現以避免神經細胞凋亡。然而，更精確的神經保護機轉仍待未來利用細胞實驗研究其中更進一步的訊息傳遞反應。

關鍵字

扁柏酚 ； 腦梗塞 ； 中風 ； 中大腦動脈阻塞

並列摘要

Stroke is a leading cause of mortality and morbidity in developed countries. Stroke can be divided into 2 entities: ischemic or hermorrhagic. The incidence of ischemic stroke is higher than hermorrhagic type. The pathophysiological mechanisms of brain injury after focal ischemia have been investigated widely, but the development of novel treatment agents for acute ischemic stroke has not progressed as well. One strategy for treating acute stroke patients is the neuroprotective agents. Unfortunately, clinical trials using various neuroprotective agents for ischemic/ reperfusion injury are still ineffectual. Because the middle cerebral artery is the vessel mostly occluded in ischemic stroke, so the middle cerebral artery ischemia/ reperfusion of rodents provides an excellent animal model that is relevant to ischemic stroke in human.
Hinokitiol, also known as β-thujaplicin, is a tropolone-related compound found in the heart wood of several cupressaceous plants. It has a wide variety of biological functions, including anti-oxidative, anti-inflammatory, and iron chelating activities. However, the ability of hinokitiol to protect neuronal cells from ischemia/reperfusion injury has not been studied so far.
Study goal of the thesis was therefore to evaluate the neuroprotective effects of hinokitiol in a cerebral ischemia-reperfusion injury animal model, and the inhibitory effects on inflammatory response and expression of apoptosis. We tested the effects of hinokitiol in transient focal cerebral ischemia and reperfusion rat model. Hinokitiol (0.2 mg/kg i.p. and 0.5 mg/kg i.p.) markedly attenuated the infarct volume about 25.15 % and 49.59 % respectively at 24 hours after middle cerebral artery occlusion. Subsequently, we examined the neuropreotective mechanisms of hinokitiol in the molecular and cellular　pathophysiology of brain injury　after focal ischemia. In western blotting, we found that pretreatment with hinokitiol may significantly reduce the expression of iNOS, HIF-1α, TNF-α and caspase-3.
According to these findings, hinokitiol has neuroprotective effects against cerebral ischemia and reperfusion injury. Moreover, the beneficial results may be due to the reduction of iNOS, the suppression of pro-inflammatoy cytokine TNF-α and the inhibition of apoptotic of caspase-3 and HIF-1α. However, the exact mechanisms of their neuroprotective effects at cellular signal transduction need to be clarified in the future.

並列關鍵字

hinokitiol ； stroke ； MCAO

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