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氧化應(yīng)激與自噬

2016-10-14 07:47:21吳艷萍李雅麗曹雪芳李衛(wèi)芬
關(guān)鍵詞:復(fù)合體泛素線粒體

吳艷萍 王 陽(yáng) 李雅麗 曹雪芳 李衛(wèi)芬

(浙江大學(xué)動(dòng)物科學(xué)學(xué)院飼料科學(xué)研究所,教育部動(dòng)物分子營(yíng)養(yǎng)學(xué)重點(diǎn)實(shí)驗(yàn)室,杭州310058)

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氧化應(yīng)激與自噬

吳艷萍王陽(yáng)李雅麗曹雪芳李衛(wèi)芬*

(浙江大學(xué)動(dòng)物科學(xué)學(xué)院飼料科學(xué)研究所,教育部動(dòng)物分子營(yíng)養(yǎng)學(xué)重點(diǎn)實(shí)驗(yàn)室,杭州310058)

自噬是細(xì)胞依賴溶酶體對(duì)蛋白質(zhì)和細(xì)胞器進(jìn)行降解的過(guò)程,能幫助細(xì)胞適應(yīng)各種不良刺激,在維持細(xì)胞內(nèi)環(huán)境穩(wěn)態(tài)和實(shí)現(xiàn)自我更新中起著重要作用。氧化應(yīng)激是機(jī)體氧化和抗氧化系統(tǒng)之間的穩(wěn)態(tài)被破壞而造成的應(yīng)激狀態(tài)。大量研究表明,氧化應(yīng)激中產(chǎn)生的活性氧能誘導(dǎo)自噬產(chǎn)生,而自噬能緩解氧化應(yīng)激造成的損傷,從而保護(hù)細(xì)胞存活。本文主要對(duì)自噬的形成過(guò)程、氧化應(yīng)激誘導(dǎo)自噬產(chǎn)生機(jī)制以及自噬緩解氧化應(yīng)激的途徑等進(jìn)行綜述,以期為畜牧生產(chǎn)中通過(guò)調(diào)控自噬緩解氧化應(yīng)激提供理論依據(jù)。

氧化應(yīng)激;自噬;Atg;活性氧;氧化損傷

1 自噬

1.1自噬的分類

根據(jù)底物種類、轉(zhuǎn)運(yùn)方式和調(diào)控機(jī)制的不同,可將自噬分為大自噬、小自噬和分子伴侶介導(dǎo)的自噬[3]。大自噬指來(lái)源于內(nèi)質(zhì)網(wǎng)的雙層膜將待降解物包裹形成自噬體后與溶酶體融合并降解其內(nèi)容物的過(guò)程,通常所說(shuō)的自噬即為大自噬。小自噬是指溶酶體的膜直接將包裹的物質(zhì)降解。分子伴侶介導(dǎo)的自噬則是指胞質(zhì)內(nèi)的可溶蛋白質(zhì)分子與分子伴侶結(jié)合后被轉(zhuǎn)運(yùn)到溶酶體腔中被降解的過(guò)程。長(zhǎng)期以來(lái),人們認(rèn)為自噬對(duì)降解底物無(wú)選擇性,但隨著研究的深入,發(fā)現(xiàn)在特定情況下自噬會(huì)選擇性降解某類大分子和細(xì)胞器,這類自噬叫選擇性自噬,包括Cvt途徑(cytoplasm-to-vacuole transport,即細(xì)胞質(zhì)到液泡)、過(guò)氧化氫酶體自噬(pexophagy)、線粒體自噬(mitophagy)和內(nèi)質(zhì)網(wǎng)自噬(reticulophagy)等[7]。

1.2自噬的形成與信號(hào)傳導(dǎo)

自噬過(guò)程分為誘導(dǎo)、囊泡核化和延伸、底物識(shí)別、自噬體形成、自噬體和溶酶體融合、底物降解6個(gè)階段[3]。諸多因素誘導(dǎo)細(xì)胞發(fā)生自噬,如營(yíng)養(yǎng)缺失、微生物感染、細(xì)胞損傷、蛋白質(zhì)折疊錯(cuò)誤或聚集和氧化應(yīng)激等[8-9]。細(xì)胞在受到自噬信號(hào)誘導(dǎo)后,胞漿中形成“脂質(zhì)樣”的膜結(jié)構(gòu),稱為自噬泡(phagophore),自噬泡延伸,將待降解物包裹,形成密閉雙層膜自噬體(autophogosome),并與溶酶體融合形成自噬溶酶體(autophagolysosome),從而將包裹的物質(zhì)降解,生成的脂肪酸、氨基酸等物質(zhì)可被運(yùn)輸?shù)桨麧{中被循環(huán)利用。在這個(gè)過(guò)程中,超過(guò)30個(gè)自噬相關(guān)基因(autophagy-related gene,Atg)發(fā)揮作用,并主要通過(guò)以下4個(gè)蛋白質(zhì)復(fù)合體介導(dǎo)自噬形成[10]。

1.2.1ULK1復(fù)合體(ULK1-Atg101-FIP200-Atg13)

ULK1(Atg1的同源物)復(fù)合體參與自噬誘導(dǎo)階段,其主要受哺乳動(dòng)物雷帕霉素靶蛋白(mTOR)和AMP依賴的蛋白激酶(AMPK)信號(hào)調(diào)控。mTOR是細(xì)胞內(nèi)氨基酸、ATP和激素的感受器,當(dāng)細(xì)胞內(nèi)營(yíng)養(yǎng)充足時(shí),mTOR磷酸化Atg13,高度磷酸化的Atg13與ULK1的親和力下降,使ULK1激酶活力下降;而當(dāng)細(xì)胞處于饑餓狀態(tài)或遭受應(yīng)激時(shí),mTOR活性受到抑制,Atg13去磷酸化,ULK1復(fù)合體被激活,并從細(xì)胞質(zhì)中轉(zhuǎn)移到內(nèi)質(zhì)網(wǎng)上誘導(dǎo)自噬泡膜形成[11]。AMPK是一個(gè)重要的自噬正向調(diào)節(jié)因子,一方面可直接抑制mTOR活性誘導(dǎo)自噬產(chǎn)生,另一方面磷酸化的AMPK可激活TSC1-TSC2復(fù)合體,間接抑制mTOR活性,從而誘導(dǎo)自噬[12]。此外,AMPK還可直接與ULK1復(fù)合物結(jié)合,磷酸化ULK1,從而促進(jìn)自噬膜的形成[13]。

1.2.2Ⅲ型磷脂酰肌醇3-激酶(PI3K)復(fù)合體(Beclin1-VPS34-Atg14)

Ⅲ型PI3K復(fù)合體參與自噬泡成核階段。Ⅲ型PI3K的催化亞單位VPS34與Beclin1(Atg6的同源物)、Atg14組成復(fù)合體,被ULK1復(fù)合體激活后,定位至內(nèi)質(zhì)網(wǎng)并生成PI3P,PI3P通過(guò)募集含有PI3P結(jié)合域的效應(yīng)分子如DFCP1(double FYVE-containing protein 1)和WIPI家族蛋白(WD-repeat domain protein interacting with phosphoinositides)而介導(dǎo)形成自噬泡[14]。其中,Beclin1被認(rèn)為是自噬形成的關(guān)鍵因子,除了能調(diào)節(jié)VPS34(vacuolar protein-sorting 34)的脂肪激酶活性外,還是一種多功能蛋白,具有的BH3結(jié)構(gòu)域,能與抗凋亡相關(guān)蛋白如B細(xì)胞淋巴瘤/白血病(B-cell lymphoma/leukemia,Bcl)-2、Bcl-xL結(jié)合,而發(fā)揮調(diào)節(jié)自噬和凋亡的雙重作用。Funderburk等[15]發(fā)現(xiàn)抗凋亡相關(guān)蛋白Bcl-2與Beclin1結(jié)合,將抑制Beclin1和VPS34互作,導(dǎo)致自噬的抑制。

1.2.3Atg12-Atg5-Atg16泛素化復(fù)合體

Atg12-Atg5-Atg16泛素化復(fù)合體參與自噬泡延伸階段。Atg12和Atg5在E1樣酶Atg7和E2樣酶Atg10的作用下能通過(guò)共價(jià)鍵結(jié)合,兩者通過(guò)與Atg16非共價(jià)鍵結(jié)合而成為Atg12-Atg5-Atg16復(fù)合體,轉(zhuǎn)移到自噬泡上參與膜延伸。

1.2.4LC3-Ⅱ-PE泛素化復(fù)合體

LC3-Ⅱ-PE泛素化復(fù)合體參與自噬泡延伸與自噬體形成。哺乳動(dòng)物的微管相關(guān)蛋白1輕鏈3(LC3,Atg8的同源物)能被Atg4切割成可溶性的LC3-Ⅰ,在Atg7和E2樣酶Atg3的作用下與磷脂酰乙醇胺(PE)結(jié)合后形成LC3-Ⅱ-PE參與自噬泡膜延伸,并且對(duì)稱分布于自噬泡的內(nèi)外膜上。當(dāng)自噬體與溶酶體融合時(shí),自噬體內(nèi)的LC3-Ⅱ便被溶酶體中的水解酶降解,因此LC3-Ⅱ含量或LC3-Ⅱ與LC3-Ⅰ比值的大小反映了自噬活性的強(qiáng)弱,是自噬的經(jīng)典標(biāo)記[16]。此外,在選擇性自噬中,LC3-Ⅱ-PE能通過(guò)P62(又稱SQSTM1,一種多功能泛素結(jié)合蛋白)將待降解物轉(zhuǎn)移至自噬體腔中。P62是連接LC3和泛素化待降解物的接頭蛋白,能通過(guò)LIR結(jié)構(gòu)域與LC3結(jié)合,并且其UBA結(jié)構(gòu)域能與待降解物相互作用,三者結(jié)合后能靶向進(jìn)入自噬體,最終被溶酶體降解[17]。P62降解是自噬流發(fā)生的重要標(biāo)志[16]。

2 ROS誘導(dǎo)自噬形成的機(jī)制

ROS是造成氧化應(yīng)激的直接引物,約90%的ROS來(lái)源于線粒體內(nèi)膜呼吸鏈。線粒體呼吸鏈電子泄漏可產(chǎn)生超氧自由基,進(jìn)而生成ROS。眾多研究表明,氧化應(yīng)激下,來(lái)源于線粒體的ROS是自噬的主要誘導(dǎo)者[2,4,18]。ROS能通過(guò)介導(dǎo)自噬形成過(guò)程中的各個(gè)信號(hào)通路誘導(dǎo)自噬產(chǎn)生。

在自噬誘導(dǎo)階段中,ROS能通過(guò)調(diào)控mTOR而誘導(dǎo)自噬發(fā)生。mTOR是一個(gè)關(guān)鍵的自噬負(fù)調(diào)節(jié)因子,其活性受多個(gè)信號(hào)通路如PI3K-絲氨酸/蘇氨酸蛋白激酶(Akt)和AMPK等調(diào)控。研究發(fā)現(xiàn),過(guò)量的ROS可通過(guò)抑制PI3K-Akt-mTOR激活自噬[19];在雄性荷蘭豬離體心臟中灌流七氟烷,產(chǎn)生的ROS能通過(guò)激活A(yù)MPK抑制mTOR信號(hào)通路誘導(dǎo)自噬產(chǎn)生[20]。而在自噬體形成過(guò)程中,ROS主要通過(guò)抑制Atg4的活性調(diào)控自噬,ROS使Atg4失活引起LC3-Ⅱ堆積,使得自噬體增多。研究發(fā)現(xiàn),在饑餓條件下,細(xì)胞產(chǎn)生大量的ROS,尤其是H2O2,將Atg4氧化后能抑制LC3-Ⅱ去脂化,從而保證自噬體延伸[21]。并且,ROS能促進(jìn)待降解物質(zhì)的泛素化,使待降解物與P62和LC3-Ⅱ泛素化結(jié)合后定位于自噬體而被降解[22]。

此外,ROS還能通過(guò)絲裂原活化蛋白激酶(MAPK)信號(hào)通路調(diào)控自噬。MAPK由一組以級(jí)聯(lián)方式依次活化的Akt組成,對(duì)于細(xì)胞的增值、分化、應(yīng)激適應(yīng)及凋亡具有重要的作用,其主要包括c-Jun氨基末端激酶(JNK)、p38激酶和細(xì)胞外信號(hào)調(diào)節(jié)激酶(ERK)。研究發(fā)現(xiàn),MAPK能通過(guò)調(diào)節(jié)激活蛋白1(activator protein-1,AP-1)、叉頭框轉(zhuǎn)錄因子O(forkhead box transcription factor O,F(xiàn)oxO)、核因子-κB(nuclear factor-kappa B,NF-κB)等轉(zhuǎn)錄因子活性調(diào)控自噬相關(guān)基因表達(dá)而影響自噬,許多外源物質(zhì)包括ROS能通過(guò)MAPK激活自噬產(chǎn)生[23]。試驗(yàn)證明,ROS通過(guò)JNK信號(hào)通路誘導(dǎo)體外培養(yǎng)的小鼠間充質(zhì)干細(xì)胞(MSCs)自噬產(chǎn)生[24];p38信號(hào)通路參與ROS激活的自噬體與溶酶體融合階段Atg7以及蛋白質(zhì)泛素化過(guò)程中E3酶的基因表達(dá),并且這個(gè)過(guò)程依賴FoxO轉(zhuǎn)錄的激活[25]。而亞砷酸鹽則能通過(guò)ROS激活細(xì)胞外調(diào)節(jié)蛋白激酶(extracellular regulated protein kinases,ERK)1/2途徑誘導(dǎo)自噬產(chǎn)生[26]。

3 自噬緩解氧化應(yīng)激的途徑

3.1清除受損蛋白質(zhì)和細(xì)胞器,調(diào)控線粒體功能

氧化應(yīng)激下,線粒體ROS穩(wěn)態(tài)被打破,其過(guò)量堆積會(huì)造成膜脂質(zhì)過(guò)氧化反應(yīng),引起細(xì)胞膜、線粒體膜和內(nèi)質(zhì)網(wǎng)膜等結(jié)構(gòu)破壞,從而導(dǎo)致氧化損傷。研究表明,氧化應(yīng)激導(dǎo)致的蛋白質(zhì)和細(xì)胞器損傷,能誘導(dǎo)Beclin1從抗凋亡蛋白Bcl-2上分離形成Beclin1-VPS34-Atg14復(fù)合體,使得膜分離及自噬體成核,從而啟動(dòng)自噬清除受損部位[27]。

持久嚴(yán)重的氧化應(yīng)激將造成線粒體損傷,線粒體自噬是清除受損線粒體的主要途徑,損傷的線粒體去極化并分解成碎片,通過(guò)線粒體自噬而清除。這個(gè)過(guò)程主要受PTEN蛋白激酶1(PINK1)和帕金森基因(Parkin)的調(diào)控。PINK1是一種定位于線粒體外膜的Akt,當(dāng)線粒體跨膜電位低時(shí)處于穩(wěn)定狀態(tài);而當(dāng)線粒體去極化后,PINK1迅速感知并募集泛素化E3酶Parkin將受損線粒體膜泛素化[28],泛素化的線粒體膜被P62識(shí)別后通過(guò)LC3定位至自噬體而降解。同時(shí)研究發(fā)現(xiàn),線粒體自噬還能調(diào)控線粒體功能和ROS水平。用脂多糖(LPS)刺激心肌細(xì)胞造成的過(guò)度氧化應(yīng)激,會(huì)產(chǎn)生大量受損線粒體,使得ROS急劇生成,通過(guò)線粒體自噬途徑能及時(shí)清除受損線粒體,維持ROS在一個(gè)較低水平[29]。自噬功能失調(diào)將導(dǎo)致線粒體功能不正常,在饑餓情況下敲除酵母細(xì)胞自噬相關(guān)基因會(huì)加重ROS的累積[30]。

3.2參與DNA損傷修復(fù)

DNA是ROS攻擊的重要靶分子之一,大量ROS產(chǎn)生將引起DNA分子的堿基修飾和單/雙鏈的斷裂和位點(diǎn)突變等,從而導(dǎo)致DNA損傷[31]。DNA損傷后將激活一系列的細(xì)胞反應(yīng),如DNA損傷修復(fù)。多種不同類型的蛋白介導(dǎo)DNA損傷修復(fù),感知蛋白能迅速識(shí)別受損蛋白,而傳遞蛋白和效應(yīng)蛋白則把信號(hào)從細(xì)胞核傳至胞質(zhì)中,從而啟動(dòng)應(yīng)答,例如激活細(xì)胞周期系統(tǒng),但當(dāng)DNA嚴(yán)重?fù)p傷或無(wú)法修復(fù)時(shí),細(xì)胞將面臨死亡[32]。

自噬是一種細(xì)胞存活機(jī)制,同時(shí)也是一種細(xì)胞死亡類型,因此當(dāng)DNA損傷時(shí),其對(duì)細(xì)胞的存活與死亡至關(guān)重要。試驗(yàn)證明,自噬能參與DNA損傷修復(fù)。當(dāng)敲除自噬相關(guān)基因如Beclin1、抗紫外線相關(guān)基因(ultraviolet irradiation resistance-associated gene,UVRAG)、Atg5和Atg7將導(dǎo)致DNA損傷累積[33-35]。同時(shí)研究發(fā)現(xiàn),輻射引起的氧化應(yīng)激下,抑制ULK1復(fù)合體FIP200(FAK-family interacting protein of 200 ku)將削弱DNA損傷修復(fù),加速細(xì)胞死亡[36]。自噬可通過(guò)直接或間接的途徑參與ROS介導(dǎo)的DNA損傷修復(fù),但其啟動(dòng)機(jī)制目前尚待研究。在酵母細(xì)胞研究中發(fā)現(xiàn),選擇性自噬Cvt途徑在參與DNA損傷修復(fù)中發(fā)揮直接作用,包括激活細(xì)胞周期G2/M階段、促進(jìn)脫氧核糖核苷三磷酸(dNTP)和DNA合成等[37-38]。而在更高等的真核生物中,沒(méi)有直接證據(jù)證明存在Cvt途徑,自噬參與損傷修復(fù)主要是通過(guò)清除線粒體及毒害聚合物,從而從源頭降低ROS水平和DNA損傷累積[39]。其中,介導(dǎo)自噬參與DNA損傷修復(fù)的分子有聚腺苷酸二磷酸核糖轉(zhuǎn)移酶-1(PARP1)和共濟(jì)失調(diào)毛細(xì)血管擴(kuò)張癥突變基因(ataxia-telangiectasia mutated gene,ATM),兩者通過(guò)激活A(yù)MPK和抑制mTOR通路誘導(dǎo)自噬產(chǎn)生[40-41]。此外,作為DNA損傷修復(fù)的主要調(diào)控蛋白P53,在DNA損傷時(shí)能被迅速激活,而研究表明P53能調(diào)控誘導(dǎo)自噬產(chǎn)生的[PTEN(一個(gè)具有雙特異性磷酸酶活性的抑癌基因)、TSC2、AMPK亞單位]以及自噬體形成的基因(ULK1、UVRAG、Atg2、Atg4、Atg7、Atg10等)的表達(dá)[42],從而介導(dǎo)自噬產(chǎn)生。

3.3通過(guò)P62-Kelch樣環(huán)氧氯丙烷相關(guān)蛋白1(Keap1)-核轉(zhuǎn)錄因子紅細(xì)胞系2-p45相關(guān)因子2(Nrf2)途徑發(fā)揮抗氧化作用

Keap1-Nrf2信號(hào)通路是細(xì)胞內(nèi)重要的抗氧化信號(hào)通路之一。在正常生理?xiàng)l件下,Keap1與Nrf2結(jié)合,促進(jìn)Nrf2持續(xù)的泛素化后被蛋白酶體降解。當(dāng)細(xì)胞受到刺激時(shí),ROS增加,氧化Keap1上的半胱氨酸(Cys)殘基,促進(jìn)Nrf2從Keap1上解離,使Nrf2進(jìn)入細(xì)胞核。Nrf2入核后會(huì)與抗氧化反應(yīng)元件(ARE)結(jié)合,促進(jìn)抗氧化蛋白類和Ⅱ相解毒酶等基因的轉(zhuǎn)錄,從而提高細(xì)胞抵抗氧化應(yīng)激的能力[43]。研究表明,泛素化的P62能直接與Keap1相互作用,介導(dǎo)Keap1通過(guò)自噬途徑降解,使Nrf2從Keap1上分離并穩(wěn)定地在細(xì)胞核內(nèi)積累[44];并且,由于P62的增強(qiáng)子上含ARE,使得P62的蛋白質(zhì)表達(dá)也能受Nrf2調(diào)控[45]。因此,這2條途徑形成一個(gè)抗氧化反應(yīng)的正反饋循環(huán)。試驗(yàn)發(fā)現(xiàn),向仔豬體內(nèi)灌喂或腹腔注射10%H2O2,7 d后采樣,仔豬空腸自噬水平顯著升高,并且其極可能與Nrf2-Keap1信號(hào)通路的激活相關(guān)[46]。

此外,由于抗氧化反應(yīng)和自噬均是由氧化應(yīng)激激活的降低ROS水平及清除氧化損傷的2種保護(hù)機(jī)制,而自噬與DNA損傷修復(fù)密切相關(guān),這種現(xiàn)象尤其表現(xiàn)在ROS造成的DNA損傷上[2],一旦弄清其中的分子調(diào)控機(jī)制則能更加明確自噬介導(dǎo)的抗氧化反應(yīng)。

4 抗氧化物通過(guò)自噬緩解氧化應(yīng)激研究展望

氧化應(yīng)激在高度集約化現(xiàn)代養(yǎng)殖業(yè)中的危害已大量顯現(xiàn),氧化應(yīng)激是動(dòng)物眾多疾病的重要誘因。研究發(fā)現(xiàn),懷孕母豬在妊娠期和哺乳期易遭受氧化應(yīng)激,導(dǎo)致產(chǎn)奶性能和繁殖性能下降[47]。而氧化應(yīng)激也是引起“仔豬斷奶應(yīng)激綜合征”的重要原因之一,氧化損傷導(dǎo)致仔豬生產(chǎn)性能降低,影響飼養(yǎng)效益[48]。此外,Hodgkinson等[49]報(bào)道分泌初乳時(shí)期的奶牛處于氧化應(yīng)激狀態(tài)時(shí)牛乳腺組織中血管細(xì)胞間黏附分子-1(VCAM-1)的表達(dá)顯著升高,氧化應(yīng)激引起的急變期細(xì)胞因子的表達(dá)將增加炎癥性組織損傷。在養(yǎng)殖過(guò)程中,由氧化應(yīng)激導(dǎo)致的疾病主要有腸炎、膿血癥、肺炎、心臟病、腹水癥、圍產(chǎn)期疾病、胎衣不下、乳房炎等[50-51],這些疾病已嚴(yán)重影響了畜牧業(yè)生產(chǎn)和經(jīng)濟(jì)效益。

如何通過(guò)營(yíng)養(yǎng)學(xué)調(diào)控緩解氧化應(yīng)激已成為近年來(lái)的研究熱點(diǎn)。大量研究表明,外源添加如微量元素、維生素和植物提取物等抗氧化物質(zhì)能有效地緩解氧化應(yīng)激。而近年來(lái)的研究發(fā)現(xiàn),自噬在外源抗氧化物質(zhì)緩解氧化應(yīng)激中起重要作用。試驗(yàn)表明,血紅素氧合酶-1(HO-1)的激動(dòng)劑原卟啉鈷能增強(qiáng)自噬,降低由LPS誘導(dǎo)的大鼠肝臟氧化損傷[52];在以拘束應(yīng)激建立的氧化應(yīng)激小鼠模型中,天然抗氧化劑白藜蘆醇能上調(diào)線粒體自噬,從而緩解小鼠腹腔巨噬細(xì)胞氧化損傷[53];而在小鼠的肝臟缺血再灌注引起的氧化應(yīng)激模型中,添加維生素D,則能通過(guò)調(diào)控自噬提高抗氧化能力,減緩氧化應(yīng)激[54]。這些抗氧化物質(zhì)大多通過(guò)調(diào)節(jié)自噬信號(hào)通路(P62-Keap1-Nrf2、PI3K-Akt-mTOR、AMPK等)和自噬基因的表達(dá)而誘導(dǎo)自噬產(chǎn)生,從而緩解氧化應(yīng)激、降低細(xì)胞凋亡。例如,二十二碳六烯酸(DHA)除了能激活抗氧化酶外,還能提高Nrf2、P62和Atg5的蛋白質(zhì)表達(dá)激活自噬[55];用5~20 μmol/L的姜黃素預(yù)處理hy926細(xì)胞4 h后,再添加200 μmol/L的H2O2共培養(yǎng)發(fā)現(xiàn),姜黃素能通過(guò)抑制PI3K-Akt-mTOR信號(hào)通路而激活自噬,保護(hù)細(xì)胞免受H2O2誘導(dǎo)的氧化損傷和減緩細(xì)胞凋亡[56]。此外,芹黃素和葒草素可通過(guò)調(diào)控AMPK和Akt-mTOR信號(hào)通路及Bcl-2的表達(dá)激活自噬而保護(hù)細(xì)胞[57-58]。

上述研究顯示,外源添加抗氧化物質(zhì)能調(diào)控細(xì)胞自噬,增強(qiáng)細(xì)胞的抗氧化功能,保護(hù)細(xì)胞免受氧化損傷和延緩細(xì)胞死亡,并且不同的抗氧化物質(zhì)通過(guò)激活不同的自噬信號(hào)通路和自噬相關(guān)基因而緩解氧化應(yīng)激。同時(shí),研究發(fā)現(xiàn)自噬在維持畜禽健康中發(fā)揮著作用。早期斷奶仔豬模型中,仔豬肝臟、脾臟和骨骼肌自噬水平顯著升高,這對(duì)仔豬的營(yíng)養(yǎng)平衡和細(xì)胞功能起著一定作用[59];向荷斯坦斷奶奶牛體內(nèi)靜脈注射不同濃度的谷氨酰胺,自噬水平隨著谷氨酰胺濃度的升高而升高[60];禽白血病J亞群病毒(ALV-J)感染雞成纖維細(xì)胞系DF-1后,自噬功能受損,病毒大量復(fù)制,而用自噬激活劑雷帕霉素處理后,病毒復(fù)制降低,揭示了自噬功能在一定程度上有利于病毒清除[61]。因此,針對(duì)不同的外源抗氧化物質(zhì)物質(zhì),系統(tǒng)地研究其對(duì)自噬及相關(guān)信號(hào)通路的影響,將為抗氧化物質(zhì)緩解動(dòng)物氧化應(yīng)激的分子機(jī)理提供新的研究方向。

5 小 結(jié)

氧化應(yīng)激是造成動(dòng)物生產(chǎn)中經(jīng)濟(jì)損失的重要原因之一,近年來(lái),人們不斷探索如何從營(yíng)養(yǎng)學(xué)角度緩解氧化應(yīng)激的途徑及調(diào)節(jié)機(jī)制。自噬理論的發(fā)展為氧化應(yīng)激的研究提供了新的方向,氧化應(yīng)激可激活自噬產(chǎn)生,而自噬可以清除氧化應(yīng)激造成的損傷,延緩細(xì)胞死亡,維持細(xì)胞內(nèi)穩(wěn)態(tài)。如何通過(guò)調(diào)控自噬來(lái)緩解氧化應(yīng)激將為抗氧化物質(zhì)發(fā)揮其功能的機(jī)理研究提供新的思路。

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*Corresponding author, professor, E-mail: wfli@zju.edu.cn

(責(zé)任編輯菅景穎)

Oxidative Stress and Autophagy

WU YanpingWANG YangLI YaliCAO XuefangLI Weifen*

(Key Laboratory of Molecular Animal Nutrition of Ministry of Education, Institute of Feed Science, College of Animal Science, Zhejiang University, Hangzhou 310058, China)

Autophagy is a lysosome-dependent process aimed at degrading proteins and damaged organelles, in order to preserve cellular homeostasis and self-recycling in diverse conditions of stress. Oxidative stress, is a stress status when the balance of oxidation and anti-oxidation system breaks down, which subsequently cause cellular damage. A growing amount of evidence demonstrate that reactive oxygen species (ROS) generated in oxidative stress is a main inducer of autophagy, and autophagy, in turn, serves to reduce oxidative damage and enhances cell survival. This article mainly described the process of autophagy, the mechanism of autophagy induction by oxidative stress and the pathway of antioxidant function mediated by autophagy. We attempt to provide a theoretical basis of attenuating oxidative stress in livestock production through regulating autophagy.[ChineseJournalofAnimalNutrition, 2016, 28(9):2673-2680]

oxidative stress; autophagy; Atg; ROS; oxidative damage

10.3969/j.issn.1006-267x.2016.09.002

2016-03-21

國(guó)家863計(jì)劃項(xiàng)目(2013AA102800);國(guó)家自然科學(xué)基金項(xiàng)目(31472128)

吳艷萍(1991—),女,江西吉安人,博士研究生,從事益生菌與動(dòng)物腸道健康研究。E-mail: ypwu0902@163.com

李衛(wèi)芬,教授,博士生導(dǎo)師,E-mail: wfli@zju.edu.cn

Q26

A

1006-267X(2016)09-2673-08

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