- 學位論文
Xanthohumol於暫時性局部腦缺血/再灌流動物模式之保護效果研究
The protective efficacy of xanthohumol in a transient focal ischemia/reperfusion rat model
摘要
腦中風(stroke)又稱為腦血管意外病變(cerebrovascular accident)，乃是供應腦組織氧氣和養分的血管受到阻塞或破裂，因而導致腦細胞無法維持正常生理功能，甚至死亡的情況。腦中風是血管性疾病致死及發病的主要原因之ㄧ，為國內十大疾病死因之第三位，也是國人失能的主要原因。引發腦中風的病理機轉分為缺血性(ischemic)與出血性(hemorrhagic)。其中因腦血管阻塞所引起的中風為缺血性中風，其發生率約佔所有腦中風病人的七至八成。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被應用於研究缺血性腦中風藥物的實驗模式。 黃腐醇(xanthohumol)是啤酒花(Humulus lupulus)的類黃酮類成分之一，從先前的研究指出xanthohumol具有神經鎮定、抗癌、抗氧化、抗菌以及腸胃道反應等藥理作用；而目前xanthohumol的研究大都集中在抗癌和抗氧化方面的活性。由於中大腦動脈缺血/再灌流所造成的傷害主要是來自於氧化壓力及發炎反應，而xanthohumol對於缺血/再灌流所造成的損傷是否具有保護能力，目前尚未被研究。 本論文之研究目的即在評估xanthohumol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。實驗結果顯示，xanthohumol (0.2及0.4 mg/kg i.p.)能夠有意義地減少因缺血再灌流傷害所引起之梗塞面積，並且改善行為能力。從分子層面測試xanthohumol對此傷害之保護機轉，經由西方墨點法分析後，發現預防性給予xanthohumol能夠明顯減少iNOS和HIF-1α蛋白質表現及減少caspase-3的活化以及TNF-α發炎因子的表現。 實驗結果證實，xanthohumol具有保護能力以減少腦部缺血再灌流傷害。此效果可能的機轉為透過減少iNOS表現而降低氧化壓力傷害，抑制發炎前細胞激素TNF-α表現而降低發炎反應的進行，以及抑制caspase-3的活化和HIF-1α表現以減少細胞凋亡。然而，更詳盡的保護機轉仍待進一步的研究。
並列摘要
Stroke is known as a cerebrovascular accident. It is the state of ischemia that localized tissue is unable to maintain physiological condition or even lead to death due to obstruction or rupture of blood vessels in the brain. Stroke is the 3rd leading causes of mortality and morbidity in Taiwan, and it is also a major factor to make the Taiwanese disable. According to the pathological mechanisms, stroke is classified into two main types, ischemic and hemorrhagic stroke. Ischemic stroke is caused by the obstruction of blood vessels. The middle cerebral artery is the vessel mostly affected by cerebral occlusion in ischemic stroke, and thus the middle cerebral artery occlusion model of rodents provides an excellent method that is relevant to ischemic stroke in human. Xanthohumol is one of the major constituents of Humulus lupulus. Xanthohumol has been reported to have sedative properties, estrogenic activities, cancer chemopreventive effects, antioxidant activities, stomachic effects, antibacterial and antifungal effects in recent studies. Oxidative stress and inflammation are major sources of injury from cerebral ischemia and reperfusion. However, the ability of xanthohumol to protect brain tissue from ischemia/reperfusion injury has not been studied so far. In this study, we examined the detailed mechanisms underlying the inhibitory effects of xanthohumol on inflammatory and apoptotic responses induced by middle cerebral artery occlusion in rats. Our experimental results indicated that xanthohumol (0.2 and 0.4 mg/kg i.p.) dose-dependently attenuated focal cerebral ischemia in rats. Pretreatment with xanthohumol, the results showed marked reduction in infarct size and improved neurological scores compared with that of control rats. On the other hand, we examined the possible protection mechanisms of xanthohumol in the molecular and cellular pathophysiology of brain injury after focal ischemia. In western blotting, we found that pretreatment with xanthohumol may significantly reduce the expression of iNOS, HIF-1α, TNF-α and caspase-3. According to these findings, xanthohumol has protective effects against cerebral ischemia and reperfusion injury. Moreover, the beneficial results may be due to the reduction of iNOS, the suppression of proinflammatoy cytokine, TNF-α and the inhibition of caspase-3 and HIF-1α. However, the exact mechanisms of protective effects on brain tissue at cellular signal transduction need to be clarified in the future.