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過量酒精加重腦卒中損傷的機(jī)制研究

發(fā)布時(shí)間:2018-09-03 13:36
【摘要】:腦卒中又稱腦中風(fēng),腦血管意外,是一種突然起病的腦血液循環(huán)障礙性疾病,包括蛛網(wǎng)膜下腔出血、腦栓塞和腦出血等。腦卒中給人類健康和生命造成極大威脅,具有高發(fā)病率、高致殘率(高達(dá)75%)、高死亡率及高復(fù)發(fā)率等特點(diǎn)。腦卒中發(fā)病后的幸存者中約30%帶有永久性殘疾,,20%生活無法自理,不僅讓罹患者本人極度痛苦,更累及家人和社會。中國每年因腦卒中死亡的患者約有160多萬,在全球范圍內(nèi),每年有460萬人死于此病。并且近年來其發(fā)病率仍然不斷上升,且好發(fā)于中老年人,尤其是60歲以上人群。流行病學(xué)研究表明長期大劑量飲酒是導(dǎo)致各種類型腦卒中的主要風(fēng)險(xiǎn)因素,并且會加重腦缺血對大腦的損傷作用。 酒精的攝入量與腦卒中之間有密切關(guān)聯(lián),適度的酒精攝入可以起到保護(hù)作用,而大量酒精攝入則會產(chǎn)生危害作用。長期過量飲酒人群腦神經(jīng)細(xì)胞活性降低,大腦功能也會隨之衰退,最常見死因就是與心腦血管疾病相關(guān)的并發(fā)癥。然而,攝入大量酒精是否影響中風(fēng)患者的預(yù)后及未來的存活率還不清楚,其分子機(jī)制還有待闡明。一些研究表明長期過量攝入酒精導(dǎo)致的缺血性中風(fēng)的發(fā)病機(jī)理包括:抑制興奮性氨基酸轉(zhuǎn)運(yùn)蛋白和增加NMDA(N-methyl-D-aspartic acid receptor)興奮性等。另一些研究認(rèn)為,長期攝入酒精的危害可通過增加氧化應(yīng)激或者降低肝臟中腦苷磺基轉(zhuǎn)移酶的表達(dá)以降低血清中硫苷含量來實(shí)現(xiàn)。雖然這些理論都可以解釋過量酒精的危害,但具體的致病分子靶點(diǎn)仍不清楚。酒的主要成分乙醇在人體內(nèi)的代謝主要是通過乙醇脫氫酶(Alcohol dehydrogenase,ADH)和乙醛脫氫酶(Aldehyde dehydrogenase,ALDH)。乙醇脫氫酶將乙醇分解為乙醛,乙醛脫氫酶可以進(jìn)一步催化乙醛生成無毒的乙酸,并最終生成二氧化碳和水排出體外。如果這兩種酶在人體內(nèi)含量高,就可以快速分解酒精,酒精的中樞神經(jīng)系統(tǒng)毒性作用就較輕;而乙醛脫氫酶缺少的人,乙醛大量積累,導(dǎo)致產(chǎn)生醉酒的不適癥狀。 乙醛脫氫酶2(Aldehyde dehydrogenase2,ALDH2),是酒精代謝過程中的一種酶,對腦卒中的作用報(bào)道相對較少。我們實(shí)驗(yàn)室先前研究結(jié)果證明激動ALDH2能夠減輕缺血性腦損傷。4-羥基-2-壬烯醛(4-HNE)被證實(shí)是評估腦卒中的危險(xiǎn)因子,在易卒中高血壓大鼠(Stroke-Prone Spontaneously Hypertensive Rats,SHR-SP)血清中有顯著的高表達(dá)。ALDH2這種保護(hù)作用正是通過清除腦內(nèi)過量的4-HNE來實(shí)現(xiàn)的。但是,過量飲酒可導(dǎo)致體循環(huán)中的乙醛水平突然上升。乙醛比乙醇的毒性大,這可能會相對地影響酗酒后ALDH2的功能。 為了更好地理解ALDH2在酗酒導(dǎo)致的中風(fēng)發(fā)病機(jī)理中的作用,我們利用ALDH2抑制劑/激活劑或基因敲除/過表達(dá)等方法,探討其可能的機(jī)制,提出假說:長期大劑量飲酒能夠加重腦卒中損傷,且這種損傷作用是通過積累有毒的醛類物質(zhì),抑制醛脫氫酶活力,進(jìn)而調(diào)節(jié)其下游信號通路實(shí)現(xiàn)的。我們設(shè)計(jì)了相關(guān)實(shí)驗(yàn)并取得了以下實(shí)驗(yàn)結(jié)果。 (1)大劑量酒精加重腦缺血的損害作用 SD大鼠長期飼喂大劑量酒精,能夠增加線栓法MCAO的梗死面積(34.4%±4.8%vs27.0%±4.6%in vehicle, P 0.01);大劑量酒精能夠明顯縮短易卒中型高血壓大鼠SHR-SP的存活時(shí)間,使其更早發(fā)生腦卒中而死亡。 (2)大劑量酒精改變腦內(nèi)ALDH2等電點(diǎn)分布,降低腦內(nèi)酶活性 使用二維電泳技術(shù)檢測長期飼喂大劑量酒精SD大鼠腦內(nèi)蛋白,與正常對照組相比,實(shí)驗(yàn)組動物腦內(nèi)ALDH2等電點(diǎn)分布發(fā)生改變,活性受到抑制(62%±21%vs100%±17%in vehicle, P 0.01),但是肝臟內(nèi)的活性并沒有被抑制。并且在腦內(nèi)和肝臟內(nèi)兩組酶的表達(dá)量并無差異。 (3)大劑量酒精使腦缺血?jiǎng)游锬X內(nèi)醛類物質(zhì)積累加重腦損傷 利用頂空氣相色譜耦合火焰離子化檢測器檢測各組動物血清及腦組織中乙醇和乙醛含量。用ELISA、Western Blotting、免疫組織熒光等方法檢測醛類物質(zhì)如4-HNE、MDA的含量。正常大鼠長期飼喂酒精飼料后,大鼠血清中乙醛、4-HNE和MDA含量并未發(fā)生改變。但在腦缺血后,這些物質(zhì)含量均大幅上升,并且酒精加重了這些有毒物質(zhì)的積累。乙醛能夠直接損傷神經(jīng)元,增大腦梗死面積(46.0%±3.6%vs29.7%±3.2%, P 0.01)。 (4)激活A(yù)LDH2可取消大劑量酒精對腦缺血的損傷作用 原代培養(yǎng)神經(jīng)元OGD12h可誘導(dǎo)神經(jīng)元凋亡,經(jīng)用TUNEL檢測凋亡率。乙醇(300μM)使凋亡損傷加重。ALDH2的激動劑Alda1(10μM)減輕損傷作用達(dá)30%,并且取消了乙醇的對細(xì)胞凋亡的進(jìn)一步加重。拮抗劑Cya(1mM)作用與Alda相反(64.4%±4.82%vs45.4%±4.32%withethanol, P 0.05)。流式細(xì)胞儀檢測結(jié)果趨勢同上。對SD大鼠進(jìn)行線栓法腦梗,在梗死面積和神經(jīng)功能評分上也驗(yàn)證了上述結(jié)果。 (5)過表達(dá)ALDH2取消酒精對腦缺血的損傷作用 SD大鼠腦立體定位注射慢病毒過表達(dá)ALDH2,3周后取腦冰凍切片掃描腦片確認(rèn)轉(zhuǎn)染效率。病毒過表達(dá)后能夠使ALDH2蛋白上調(diào)約63%,基因沉默后蛋白下調(diào)73%。成功感染病毒的大鼠常規(guī)給予6周的大劑量酒精液體飼料,在注射病毒同側(cè)實(shí)施MCAO手術(shù)。乙醇可以增加腦梗死面積,過表達(dá)ALDH2能縮小梗死面積并取消過量酒精對腦梗損傷的加重作用。RNA干擾實(shí)驗(yàn)結(jié)果也與過表達(dá)相符合。 (6)大劑量乙醇可以減少ALDH2與PKC epsilon的結(jié)合 PKC epsilon是ALDH2上游重要蛋白之一,乙醇能夠激活PKC eps ilon使之磷酸化并且在一定范圍內(nèi)與劑量和時(shí)間都成正比。但是大劑量乙醇可以減少ALDH2與PKC epsilon的結(jié)合。結(jié)論:我們的研究結(jié)果顯示,大劑量乙醇通過增加醛的積累,抑制ALDH2活性同時(shí)減少ALDH2與PKC epsilon結(jié)合加重腦損傷。
[Abstract]:Stroke, also known as stroke, cerebrovascular accident, is a sudden onset of cerebral blood circulation disorders, including subarachnoid hemorrhage, cerebral embolism and cerebral hemorrhage. Stroke poses a great threat to human health and life, with high incidence, high disability rate (as high as 75%), high mortality and high recurrence rate. About 30% of the survivors are permanently disabled and 20% of them are unable to take care of themselves, which not only makes them extremely painful, but also affects their families and society. Epidemiological studies have shown that long-term high-dose drinking is a major risk factor for various types of stroke and may exacerbate the brain damage caused by cerebral ischemia.
Alcohol intake is closely associated with stroke. Moderate alcohol intake can protect against the effects of high alcohol intake, which can be harmful. Long-term excessive drinking reduces the activity of brain neurons and leads to deterioration of brain function. The most common cause of death is complications associated with cardiovascular and cerebrovascular diseases. Whether high alcohol intake affects the prognosis and future survival of stroke patients remains unclear, and its molecular mechanisms remain to be elucidated. Other studies suggest that long-term exposure to alcohol can be achieved by increasing oxidative stress or decreasing the expression of brain glycoside sulfotransferase in the liver to reduce glucosinolate levels in the serum. Although these theories can explain the harm of excessive alcohol, the specific molecular targets for the pathogenesis of alcohol are still unclear. Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are the main metabolites in the body. Alcohol dehydrogenase decomposes ethanol into acetaldehyde. Aldehyde dehydrogenase can catalyze acetaldehyde to produce nontoxic acetic acid and eventually produce carbon dioxide and water to be excreted from the body. Alcohol can be quickly decomposed at high levels, and the central nervous system of alcohol has less toxic effects; while aldehyde dehydrogenase deficient people, acetaldehyde accumulated in large quantities, resulting in drunken symptoms.
Aldehyde dehydrogenase 2 (ALDH2), an enzyme in the process of alcohol metabolism, has relatively few reports on the role of stroke. Previous studies in our laboratory have shown that activating ALDH2 can alleviate ischemic brain damage. 4-hydroxy-2-nonenoaldehyde (4-HNE) has been shown to be a risk factor for assessing stroke in stroke-prone hypertension. The protective effect of ALDH2 is achieved by eliminating excessive 4-HNE in the brain. However, excessive alcohol consumption can lead to a sudden increase in acetaldehyde levels in the systemic circulation. Acetaldehyde is more toxic than ethanol, which may have a relative effect on ALD after alcoholism. The function of H2.
In order to better understand the role of ALDH2 in the pathogenesis of alcoholism, we used ALDH2 inhibitor/activator or gene knockout/overexpression methods to explore its possible mechanisms and hypothesized that long-term high-dose drinking could aggravate stroke injury, which was inhibited by accumulation of toxic aldehydes. The activity of aldehyde dehydrogenase is regulated and its downstream signal pathway is realized.
(1) high dose of alcohol aggravates the damage of cerebral ischemia.
Long-term high-dose alcohol could increase the infarct size of MCAO (34.4%+4.8% vs 27.0%+4.6% in vehicle, P 0.01), and high-dose alcohol could significantly shorten the survival time of SHR-SP in stroke-prone hypertensive rats and make them die earlier.
(2) high dose alcohol changed the distribution of ALDH2 isoelectric point in brain and reduced the activity of brain enzymes.
Compared with the control group, the distribution of ALDH2 isoelectric point in the brain of SD rats fed with high dose alcohol for a long time was changed and the activity of ALDH2 isoelectric point was inhibited (62%+21% vs 100%+17% in vehicle, P 0.01), but the activity in the liver was not inhibited. There was no difference in the amount of expression.
(3) large doses of alcohol aggravate brain damage by increasing the aldehyde accumulation in the brain of animals with cerebral ischemia.
The contents of ethanol and acetaldehyde in serum and brain tissues of rats were detected by headspace gas chromatography coupled with flame ionization detector. The contents of aldehydes such as 4-HNE and MDA were detected by ELISA, Western Blotting and immunohistofluorescence. However, after cerebral ischemia, the contents of these substances increased significantly, and the accumulation of these toxic substances was aggravated by alcohol. Acetaldehyde could directly damage neurons and increase the area of cerebral infarction (46.0% + 3.6% vs 29.7% + 3.2%, P 0.01).
(4) activation of ALDH2 can abolish the effect of high-dose alcohol on cerebral ischemia.
The primary cultured neurons were induced to apoptosis by OGD for 12 hours, and the apoptosis rate was detected by TUNEL. Ethanol (300 mu M) aggravated the damage of apoptosis. Alda1 (10 mu M), an agonist of ALDH2, attenuated the injury by 30% and eliminated the further aggravation of apoptosis by ethanol. The antagonist Cya (1mM) had the opposite effect as Alda (64.4% + 4.82% vs 45.4% + 4.32% withethan). The results of flow cytometry showed the same trend. The infarct size and neurological function score of SD rats were also validated.
(5) overexpression of ALDH2 abolished the effect of alcohol on cerebral ischemia.
The transfection efficiency was confirmed by stereotactic injection of lentivirus overexpressing ALDH2 into the brain of SD rats. After overexpression of the virus, the ALDH2 protein was up-regulated by 63% and the protein was down-regulated by 73% after gene silencing. Ethanol can increase the area of cerebral infarction. Overexpression of ALDH2 can reduce the area of infarction and cancel the aggravating effect of excessive alcohol on cerebral infarction.
(6) high dose ethanol can reduce the combination of ALDH2 and PKC epsilon.
PKC EPS ilon is one of the important proteins in the upstream of ALDH2. Ethanol can activate PKC EPS ilon and phosphorylate it in a certain range in direct proportion to the dose and time. However, high dose ethanol can reduce the binding of ALDH2 to PKC EPS ilon. Conclusion: Our results show that high dose ethanol can inhibit ALDH2 activity by increasing aldehyde accumulation. Sex at the same time reduced the combination of ALDH2 and PKC epsilon to aggravate brain damage.
【學(xué)位授予單位】:第二軍醫(yī)大學(xué)
【學(xué)位級別】:博士
【學(xué)位授予年份】:2014
【分類號】:R743.3

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