邱思奇 徐貞貞 沈 紅 楊曙明 陳愛(ài)亮 趙 燕
(1.中國(guó)農(nóng)業(yè)科學(xué)院農(nóng)業(yè)質(zhì)量標(biāo)準(zhǔn)與檢測(cè)技術(shù)研究所,農(nóng)業(yè)部農(nóng)產(chǎn)品質(zhì)量安全重點(diǎn)實(shí)驗(yàn)室,北京100081;2.北京農(nóng)學(xué)院動(dòng)物科學(xué)技術(shù)學(xué)院,北京102206)
基于體外細(xì)胞模型的霉菌毒素毒性評(píng)價(jià)
邱思奇1,2徐貞貞1*沈 紅2楊曙明1陳愛(ài)亮1趙 燕1
(1.中國(guó)農(nóng)業(yè)科學(xué)院農(nóng)業(yè)質(zhì)量標(biāo)準(zhǔn)與檢測(cè)技術(shù)研究所,農(nóng)業(yè)部農(nóng)產(chǎn)品質(zhì)量安全重點(diǎn)實(shí)驗(yàn)室,北京100081;2.北京農(nóng)學(xué)院動(dòng)物科學(xué)技術(shù)學(xué)院,北京102206)
霉菌毒素是由多種真菌產(chǎn)生的次級(jí)代謝產(chǎn)物,廣泛存在于食品和飼料中。霉菌毒素污染的糧食和飼料會(huì)給畜牧業(yè)生產(chǎn)和畜產(chǎn)品質(zhì)量安全帶來(lái)極大隱患。研究霉菌毒素致毒機(jī)理,為今后研究其對(duì)動(dòng)物及人的影響開(kāi)展更深入更全面的研究提供理論依據(jù)。細(xì)胞模型作為一種常用的體外試驗(yàn)方法廣泛用于毒理學(xué)研究中。本文簡(jiǎn)述了黃曲霉毒素B1(AFB1)、赭曲霉毒素A(OTA)、脫氧雪腐鐮刀菌烯醇(DON)、玉米赤霉烯酮(ZEA)和展青霉素(PAT)的一般特性,并綜述了利用細(xì)胞模型進(jìn)行AFB1、OTA、DON、ZEA和PAT毒性、聯(lián)合毒性及致毒機(jī)理研究的進(jìn)展。
霉菌毒素;毒性;細(xì)胞模型
霉菌毒素(mycotoxins)是由鐮刀菌屬(Fusarium)、曲霉菌屬(Aspergillus)和青霉菌屬(Penicillium)等真菌在生長(zhǎng)過(guò)程中產(chǎn)生的次生有毒代謝產(chǎn)物[1-2]。已報(bào)道的300多種霉菌毒素中,以黃曲霉毒素(alatoxin,AF)、單端孢霉烯毒[tichothecenes,如脫氧雪腐鐮刀菌烯醇(deoxynivalenol,DON)和T-2毒素]、赭曲霉毒素A(ochratoxin A,OTA)、玉米赤霉烯酮(zearalenone,ZEA)、伏馬毒素B1(fumonisins B1,FB1)等對(duì)畜牧業(yè)危害最大[1]。霉菌毒素廣泛存在于食品和飼料中,是全球畜牧業(yè)生產(chǎn)、畜產(chǎn)品質(zhì)量安全及食品安全所面臨的一個(gè)重要問(wèn)題[3]。
我國(guó)現(xiàn)行飼料衛(wèi)生國(guó)家標(biāo)準(zhǔn)GB 13078.1—2001、GB 13078.2—2006、GB 13078.3—2007及GB 21693—2008中對(duì)飼料中的黃曲霉毒B1(aflatoxin B1,AFB1)、OTA、ZEA、DON及T-2毒素5種毒素的限量指標(biāo)進(jìn)行了規(guī)定;食品安全國(guó)家標(biāo)準(zhǔn)GB 2761—2011規(guī)定了食品中AFB1、黃曲霉毒M1(aflatoxin M1,AFM1)、DON、展青霉素(patulin,PAT)、OTA及ZEA 6種的限量指標(biāo)。2016年8—12月,我國(guó)頒布了食品安全國(guó)家標(biāo)準(zhǔn)GB 5009.240—2016等9項(xiàng)、10余種霉菌毒素的檢測(cè)標(biāo)準(zhǔn)(國(guó)家衛(wèi)生計(jì)生委食品藥品監(jiān)管總局“2016年第11號(hào)”和“2016年第17號(hào)”公告),其中雜色曲霉素(sterigmatocystin,ST)、桔青霉素(citrinin,CIT)等尚無(wú)對(duì)應(yīng)限量標(biāo)準(zhǔn)。
制定飼料、食品中真菌毒素限量標(biāo)準(zhǔn)和法規(guī)時(shí),需要進(jìn)行科學(xué)及貿(mào)易等方面綜合的風(fēng)險(xiǎn)評(píng)估。影響風(fēng)險(xiǎn)評(píng)估結(jié)果的科學(xué)因素包括:各商品中出現(xiàn)霉菌毒素的可能性和毒理學(xué)數(shù)據(jù)等[4]。對(duì)各類(lèi)霉菌毒素的致毒機(jī)理研究是進(jìn)行食品安全風(fēng)險(xiǎn)評(píng)估的重要基礎(chǔ)。毒理學(xué)研究方法主要有體內(nèi)試驗(yàn)、體外試驗(yàn)、人體觀察及流行病學(xué)研究等方法。其中細(xì)胞模型作為一種重要的體外試驗(yàn)方法,已被應(yīng)用于霉菌毒素毒理學(xué)研究領(lǐng)域中。本文簡(jiǎn)述了AFB1、OTA、DON、ZEA和PAT的一般特性,并綜述了利用細(xì)胞模型進(jìn)行AFB1、OTA、DON、ZEA和PAT毒性、聯(lián)合毒性及致毒機(jī)理研究的進(jìn)展。
1.1 一般特性
AF是通過(guò)聚酮途徑由黃曲霉(Aspergillusflavus)和寄生曲霉(Aspergillusparasiticus)所產(chǎn)生的一種對(duì)人類(lèi)和畜禽危害最大、最常見(jiàn)的霉菌毒素[2]。從1961年開(kāi)始人們先后在糧食中發(fā)現(xiàn)了AFB1、AFB2、AFG1和AFG2,后來(lái)又從牛奶中分離出AFM1和AFM2。其中,AFB1是目前研究最多且已知致癌毒性最強(qiáng)的霉菌毒素。黃曲霉毒素通常由含有1個(gè)雙氫呋喃環(huán)和1個(gè)氧雜萘鄰?fù)幕窘Y(jié)構(gòu)單位構(gòu)成。AF難溶于水、己烷、石油醚,可溶于甲醇、乙醇、氯仿、丙酮;具有熱穩(wěn)定,在焙燒、擠壓、烘烤、蒸煮等過(guò)程也不會(huì)被破壞。
1.2 毒性及致毒機(jī)制
AF主要引起肝臟損傷,有強(qiáng)烈的肝毒性,也會(huì)對(duì)呼吸系統(tǒng)、腎臟、心臟和皮膚造成嚴(yán)重的損害[5-6],在動(dòng)物上的研究都表明其具有強(qiáng)烈的致癌性。其中AFB1是研究時(shí)間最長(zhǎng)、毒性研究相對(duì)最為明確的一種毒素,是已知對(duì)人類(lèi)和動(dòng)物食品污染最嚴(yán)重且致癌性最強(qiáng)的霉菌毒素,2002年被國(guó)際癌癥研究機(jī)構(gòu)(international agency for research on cancer,IARC)列為1類(lèi)致癌物。近年來(lái),針對(duì)AFB1研究以各類(lèi)快速檢測(cè)方法及降毒機(jī)制為主,基于細(xì)胞模型的研究多針對(duì)其致癌分子機(jī)制。
AFB1的致癌機(jī)制報(bào)道有:Yang等[7]研究表明,10 mg/mL AFB1會(huì)抑制人肝癌細(xì)胞HepG2的細(xì)胞活力,誘導(dǎo)HepG2細(xì)胞凋亡。Parveen等[8]研究表明,0.25 μg/mL AFB1還能通過(guò)誘導(dǎo)氧化應(yīng)激對(duì)犬腎細(xì)胞(MDCK)造成損傷。AFB1能與肝細(xì)胞內(nèi)DNA、RNA或蛋白質(zhì)結(jié)合,抑制大分子的合成,導(dǎo)致細(xì)胞癌變或凋亡[9-10];AFB1通過(guò)激活轉(zhuǎn)錄因子E2F1來(lái)上調(diào)腫瘤基因H19的表達(dá),從而促進(jìn)肝癌細(xì)胞的生長(zhǎng)[11]。AFB1可在肝臟中經(jīng)由細(xì)胞色素P450酶轉(zhuǎn)化成反應(yīng)中間體AFB1-8,9-環(huán)氧化合物,該中間體與DNA形成加合物AFB1-7N-鳥(niǎo)嘌呤(AFB1-7N-GUN),對(duì)DNA造成損傷,進(jìn)而導(dǎo)致突變[12-13]。其中,AFB1及其代謝產(chǎn)物外8,9-環(huán)氧AFB1(exo-AFBO)能增強(qiáng)抑癌基因p53突變的敏感性,引起p53基因突變率升高,突變型p53基因具有癌基因的性質(zhì),它會(huì)抑制細(xì)胞凋亡,引起細(xì)胞惡性轉(zhuǎn)化,導(dǎo)致細(xì)胞異常擴(kuò)增,最后形成腫瘤[2,14]。這些報(bào)道主要集中在AFB1及其代謝物exo-AFBO的表觀遺傳基因調(diào)控,比如調(diào)控DNA甲基化、組蛋白修飾、染色質(zhì)凝聚、微小RNA的表達(dá)等方面,從而改變基因表達(dá)[15]。此外,黃曲霉毒素也能誘導(dǎo)表觀遺傳蛋白的改變,100和1 000 nmol/L的AFB1能顯著增加人肺上皮細(xì)胞L-132、永生化角質(zhì)形成細(xì)胞HaCaT、HepG2以及胚腎細(xì)胞HEK 293中的蛋白精氨酸甲基轉(zhuǎn)移酶5(RPMT5)的表達(dá)[16]。
2.1 一般特性
OTA是由青霉菌屬和曲霉菌屬真菌產(chǎn)生[17],是毒性最大、分布最廣、對(duì)人類(lèi)危害嚴(yán)重的一種赭曲霉毒素。OTA是苯丙氨酸與異香豆素結(jié)合體衍生物,是一種無(wú)色結(jié)晶化合物,溶于極性溶劑和碳酸氫鈉溶液,微溶于水,在紫外線照射下呈綠色熒光。OTA溶點(diǎn)為134 ℃,性質(zhì)穩(wěn)定,其甲醇溶液在冰箱中保存1年而不會(huì)分解[18]。
2.2 毒性及致毒機(jī)制
OTA最典型的毒性是腎毒性[19],同時(shí)具有肝毒性、神經(jīng)毒性、免疫毒性[20-21],并有致畸、致突變和致癌等作用[22-23]。1993年,OTA被IARC列為是2B類(lèi)致癌物?;谌肆馨图?xì)胞、綠猴腎細(xì)胞(Vero-E6)、人宮頸癌細(xì)胞(HeLa)、人腎細(xì)胞(IHKE、IHKE、HEK-T-293、HK2)及人胃黏膜上皮細(xì)胞(GES-1)細(xì)胞模型的OTA的毒性見(jiàn)表1,其致毒機(jī)制主要表現(xiàn)在以下幾個(gè)方面:誘導(dǎo)氧化應(yīng)激、破壞細(xì)胞周期、誘導(dǎo)細(xì)胞凋亡、抑制蛋白質(zhì)合成等[24-25]。
3.1 一般特性
DON又稱(chēng)嘔吐毒素,是一種單端孢霉烯族毒素,主要由鐮刀菌產(chǎn)生,它是谷物中最常見(jiàn)的一種霉菌毒素[31]。DON的結(jié)構(gòu)是四環(huán)的倍半萜,固體是一種無(wú)色針狀結(jié)晶,易溶于水、甲醇、含水乙醇和乙酸乙酯等極性溶劑,不溶于正己烷、乙醚等非極性溶劑。DON熔點(diǎn)為151~153 ℃,具有較強(qiáng)的熱抵抗力和耐酸性,pH為4.0時(shí),DON在100和120 ℃加熱60 min均不被破壞,170 ℃加熱60 min也僅少量被破壞[32]。
大量OTA毒性研究表明,OTA產(chǎn)生腎毒性、肝毒性和免疫毒性,是因?yàn)樗c抑制蛋白質(zhì)的合成,造成脂質(zhì)過(guò)氧化和調(diào)節(jié)絲裂原活化蛋白激酶(mitogen-activated protein kinase,MAPK)信號(hào)通路有關(guān)聯(lián),OTA在細(xì)胞內(nèi)經(jīng)代謝活化,產(chǎn)生代謝物能與DNA結(jié)合形成加合物,改變遺傳物質(zhì)結(jié)構(gòu),產(chǎn)生致癌性(圖1)[19]。Darif等[30]研究表明,OTA可通過(guò)調(diào)節(jié)存活蛋白、白細(xì)胞介素(IL)-2和腫瘤壞死因子-α(TNF-α)mRNA的表達(dá)擾亂線粒體功能,激活MAPK信號(hào)通路,從而表現(xiàn)出免疫毒性。盡管部分研究表明OTA通過(guò)與DNA結(jié)合形成加合物,延緩DNA修復(fù),造成細(xì)胞凋亡,但是仍有少量研究未能確定DNA加合物的形成[21]。另有研究表明,OTA的致毒活性與其分子結(jié)構(gòu)有一定的關(guān)系,Rottkord等[28]對(duì)OTA結(jié)構(gòu)中鹵原子和氨基酸基團(tuán)在其致毒活性作用中的研究表明,OTA的氨基酸部分在其與目標(biāo)分子的相互作用中起不可或缺的作用。
3.2 毒性及致毒機(jī)制
DON主要影響胃腸道和免疫系統(tǒng),在動(dòng)物和人類(lèi)身上引起各種疾病,如嘔吐和胃腸炎。目前DON的致癌作用尚不清楚,IARC將其列為3類(lèi)致癌物。淋巴細(xì)胞對(duì)DON的毒性較為敏感,Strasser等[33]研究發(fā)現(xiàn),DON能通過(guò)增加細(xì)胞中脂質(zhì)過(guò)氧化和蛋白質(zhì)氧化而損傷細(xì)胞,抑制小鼠淋巴瘤細(xì)胞(YAC-1)的增殖。與淋巴細(xì)胞相比,肝細(xì)胞對(duì)DON敏感性較弱,但DON同樣能其對(duì)造成氧化損傷[34]。DON對(duì)動(dòng)物和人腸上皮細(xì)胞(IECs)的活力影響較大,低劑量[半抑制濃度(IC50)=0.3~1.5 mg/mL]時(shí)能抑制細(xì)胞增殖,高劑量(IC50=3~15 mg/mL)時(shí)對(duì)人類(lèi)、豬和大鼠腸上皮細(xì)胞有細(xì)胞毒性作用,甚至?xí)T導(dǎo)細(xì)胞凋亡[35-38]。
從分子水平來(lái)看,DON可以和核糖體結(jié)合,抑制DNA、RNA、蛋白質(zhì)的合成,誘導(dǎo)真核細(xì)胞凋亡[39]。Broekaert等[40]對(duì)DON的2種衍生物3-乙?;撗鮀ON(3-acetyl-DON,3-Ac-DON)、15-乙?;撗鮀ON(15-acetyl-DON,15-Ac-DON)和一種代謝物DON-3-葡萄糖苷(DON-3-glucoside,D3G)與DON的細(xì)胞毒性進(jìn)行了比較,采用流式細(xì)胞術(shù)分析其誘導(dǎo)IECs細(xì)胞凋亡情況,發(fā)現(xiàn)細(xì)胞毒性排序?yàn)椋篋3G<<3-Ac-DON OTA:赭曲霉毒素A ochratoxin A;OTHQ:羥基醌赭曲霉毒素 hydroxyquinone ochratoxin;OTB:脫氯赭曲霉毒素 dechloro ochratoxin;OH OTA:羥基赭曲霉毒素A hydroxy ochratoxin A;LIPOX:脂質(zhì)過(guò)氧化 lipid peroxidation;Nox:氮氧化物 nitrogen oxides;ROS 活性氧 reactive oxygen species;DNA damage:DNA損傷;DNA adducts:DNA加合物;Gene mutations:基因突變;Cancer (urinary tract):癌癥(泌尿道);Nephrotoxicity:腎毒性;Binding to plasm protein (90%):與血漿蛋白結(jié)合(90%);Long persistence:長(zhǎng)時(shí)間持續(xù);Transporter:轉(zhuǎn)運(yùn)體;Biotransformation:生物轉(zhuǎn)化;Inhibition of protein synthesis:抑制蛋白合成;Cellular and mitotic deregulation:細(xì)胞和有絲分裂異常;Reduced antioxidant defence:降低抗氧化防御;Biliary and renal excretion(OTA+several OT metabolites):膽汁和腎臟排泄(OTA+幾個(gè)赭曲霉毒素代謝產(chǎn)物);Enterohepatic recirculation:腸肝循環(huán)。 圖1 OTA的生化效應(yīng)總結(jié) Fig.1 Summary of biochemical effects of OTA[19] 4.1 一般特性 ZEA又稱(chēng)F-2毒素,是由鐮刀菌屬真菌尤其是禾谷鐮刀菌(Fusariumgraminearum)產(chǎn)生的一類(lèi)具有雌激素樣作用的霉菌毒素,它廣泛存在于霉變的玉米、高粱、小麥等谷類(lèi)作物和奶中。ZEA屬于二羥基苯甲酸內(nèi)酯類(lèi)化合物,為白色結(jié)晶,顯微鏡下為簇針狀,其熔點(diǎn)為161~163 ℃。ZEA不溶于水,溶于堿性溶液、乙醚、苯、甲醇以及乙醇等。在245 nm紫外光下呈亮藍(lán)色,經(jīng)三氯化鐵(FeCl3)水溶液噴射后呈現(xiàn)紫紅色斑點(diǎn)[42]。 4.2 毒性及致毒機(jī)制 ZEA具有生殖毒性,它與內(nèi)源性雌激素在結(jié)構(gòu)上相似,能像雌激素一樣,通過(guò)與雌激素受體(ER)競(jìng)爭(zhēng)性的結(jié)合,激活雌激素反應(yīng)元件,使受體發(fā)生二聚化,從而發(fā)生一系列擬雌激素效應(yīng)[43]。Li等[44]研究表明,ZEA濃度超過(guò)5 μmol/L時(shí),小鼠睪丸間質(zhì)瘤細(xì)胞(MLTC-1)的活力顯著降低。高劑量ZEA能抑制豬卵泡顆粒細(xì)胞增殖,誘導(dǎo)細(xì)胞凋亡和壞死[45]。ZEA主要在肝臟中代謝,它對(duì)肝臟也能造成一定的毒性。Gazzah等[46]和Kang等[47]研究表明,ZEA能抑制肝細(xì)胞(HepG2、張氏肝細(xì)胞)活力。然而,ZEA對(duì)腸細(xì)胞的影響有所不同,有研究發(fā)現(xiàn),盡管高劑量ZEA能抑制人結(jié)腸癌細(xì)胞(HCT116)活力,但低劑量時(shí)能顯著促進(jìn)HCT116增殖、克隆形成和遷移。 DON:脫氧雪腐鐮刀菌烯醇 deoxynivalenol;Hck:造血細(xì)胞激酶 hematopoietic cell kinase;PKR:蛋白激酶 protein kinase R;ERK:細(xì)胞外調(diào)節(jié)蛋白激酶 extracellular regulated protein kinases;p38:p38蛋白激酶 p38 protein kinase;JNK:c-Jun氨基末端激酶 c-Jun N-terminal kinase;MAPK:絲裂原活化蛋白激酶 mitogen-activated protein kinase;IL-6:白細(xì)胞介素-6 interleukin-6;JAK/STAT:Janus蛋白酪氨酸激酶/信號(hào)轉(zhuǎn)導(dǎo)和轉(zhuǎn)錄激活因子 Janus protein tyrosine kinase/signal transducer and activator of transcription;TNF-α:腫瘤壞死因子-α tumor necrosis factor-α;COX-2:環(huán)氧合酶-2 cyclooxygenase-2;mRNA stability:信使RNA穩(wěn)定性;Bax:凋亡促進(jìn)因子 apoptosis promoting factor;Mitochondrial:線粒體;caspase-3:胱天蛋白酶-3;Cell death pathway:細(xì)胞死亡通路;AKT:絲氨酸/蘇氨酸激酶 serine/threonine kinase;p90Rsk:p90核糖體S6激酶 p90 ribosomal S6 kinase;Cell survival pathway:細(xì)胞存活通路;Apoptosis:凋亡。 圖2 DON在細(xì)胞凋亡進(jìn)程中介導(dǎo)的信號(hào)通路 Fig.2 DON-mediated signal transduction in the apoptotic process[39] ZEA致毒機(jī)制根據(jù)細(xì)胞類(lèi)型和暴露途徑不同有所不同,大多研究表明,ZEA能損傷DNA、誘導(dǎo)氧化應(yīng)激和促進(jìn)細(xì)胞凋亡等。ZEA對(duì)神經(jīng)細(xì)胞SHSY-5Y、倉(cāng)鼠卵巢細(xì)胞CHO-K1和張氏肝細(xì)胞的毒性為增加細(xì)胞內(nèi)活性氧(ROS)水平和造成DNA損傷[48-49]。Kang等[47]采用彗星試驗(yàn)(SCGE)檢測(cè)ZEA對(duì)張氏肝細(xì)胞的毒性,結(jié)果表明,較低濃度ZEA(25 μmol/L)可使DNA損傷,濃度越高,損傷越嚴(yán)重,同時(shí),ZEA還會(huì)對(duì)張氏肝細(xì)胞造成氧化損傷。ZEA也能誘導(dǎo)肝細(xì)胞凋亡。Gazzah等[46]研究發(fā)現(xiàn),ZEA能促進(jìn)HepG2細(xì)胞凋亡。此外ZEA還能誘導(dǎo)山羊睪丸間質(zhì)細(xì)胞GLC和大鼠睪丸支持細(xì)胞凋亡[50-51]。ZEA誘導(dǎo)細(xì)胞凋亡和造成細(xì)胞氧化損傷過(guò)程中參與了信號(hào)轉(zhuǎn)導(dǎo)通路的激活。Zhu等[45]研究了ZEA對(duì)豬卵泡顆粒細(xì)胞的促凋亡作用,發(fā)現(xiàn)用ZEA處理的細(xì)胞中活化的含半胱氨酸的天冬氨酸蛋白水解酶(cysteinyl aspartate specific proteinase,caspase)-3和caspase-9的表達(dá)顯著高于對(duì)照組,表明ZEA通過(guò)激活caspase-3和caspase-9依賴(lài)的線粒體信號(hào)通路而誘導(dǎo)細(xì)胞凋亡。Yu等[52]研究結(jié)果表明,ZEA通過(guò)參與MAPK-依賴(lài)信號(hào)通路的調(diào)節(jié)實(shí)現(xiàn)對(duì)RAW264.7巨噬細(xì)胞造成氧化損傷,導(dǎo)致細(xì)胞死亡。ZEA誘導(dǎo)心肌細(xì)胞自噬途徑的激活。Ben等[53]研究中將ZEA和其衍生物(α-ZOL、β-ZOL)作用于心肌細(xì)胞H9c2,發(fā)現(xiàn)LC3-Ⅱ水平增加,表明ZEA促進(jìn)了心肌細(xì)胞的自噬作用。ZEA的致癌作用仍不明確,IARC將其列為3類(lèi)致癌物。 5.1 一般特性 PAT又稱(chēng)棒曲霉素,由青霉菌屬和曲霉菌屬真菌產(chǎn)生。PAT主要存在于蘋(píng)果、山楂、梨和番茄等水果及其制品中。PAT為無(wú)色棱形晶體,熔點(diǎn)為110.5~112.0 ℃,易溶于水、氯仿、丙酮、乙醇及乙酸乙酯,微溶于乙醚和苯,不溶于石油醚。在氯仿、苯、二氯甲烷等溶劑和酸性溶液中很穩(wěn)定,在水和甲醇中逐漸分解,且在堿性溶液中不穩(wěn)定,易被破壞[54]。 5.2 毒性及致毒機(jī)制 PAT主要影響胃腸道功能、免疫應(yīng)答以及腎功能等。食物進(jìn)入胃腸道,使胃腸道直接暴露于腐敗食物中高濃度的PAT,影響胃腸功能。有研究表明,PAT能增加腸上皮細(xì)胞Caco-2的通透性[55]。Donmez-Altuntas[56]等研究結(jié)果表明,PAT濃度為0.1~7.5 μmol/L能誘導(dǎo)人淋巴細(xì)胞凋亡,濃度為0.3~7.5 μmol/L能誘導(dǎo)人淋巴細(xì)胞壞死。PAT能抑制幾種巨噬細(xì)胞的功能[57],它能抑制人巨噬細(xì)胞分泌干擾素-γ(IFN-γ)和IL-4[58],以及抑制人外周血單核細(xì)胞和人T淋巴細(xì)胞分泌IL-4、IL-13、IFN-γ和IL-10[59],同樣,Marin等[60]研究表明,PAT能減少小鼠淋巴瘤細(xì)胞EL-4產(chǎn)生的IL-2和IL-5。此外,PAT能對(duì)多種細(xì)胞(中國(guó)倉(cāng)鼠卵巢細(xì)胞CHO-K1、HepG2、HCT116和HEK293等)造成氧化損傷[61-63]。PAT誘導(dǎo)細(xì)胞中大量ROS產(chǎn)生和丙二醛(MDA)累積,造成氧化應(yīng)激反應(yīng),同時(shí)損傷DNA。過(guò)量的ROS誘導(dǎo)葡萄糖調(diào)節(jié)蛋白78(GRP78)、生長(zhǎng)停滯及DNA損傷可誘導(dǎo)蛋白34(GADD34)表達(dá)量增加,GRP78是內(nèi)質(zhì)網(wǎng)應(yīng)激的標(biāo)志物,其表達(dá)量增加而導(dǎo)致內(nèi)質(zhì)網(wǎng)應(yīng)激反應(yīng)的出現(xiàn);GADD34是一種促凋亡信號(hào)分子,促進(jìn)細(xì)胞凋亡[63]。另有一項(xiàng)研究發(fā)現(xiàn),生物合成PAT過(guò)程中有2種中間體:E-ascladio和Z-ascladio,前者是PAT合成的直接前體物質(zhì),后者是它的異構(gòu)體[64],這2種中間體對(duì)人肝、腎、腸、免疫細(xì)胞并無(wú)毒性影響[65]?;蛟S研究者可以通過(guò)將PAT轉(zhuǎn)化成E-ascladio和Z-ascladio來(lái)降低PAT的毒性效應(yīng)。PAT的致癌作用不明確,同DON、ZEA一樣被IARC列為第3類(lèi)致癌物。 霉菌毒素一般不會(huì)單一存在,當(dāng)AFB1、AFM1、OTA、DON、ZEA和FB1等2種或多種霉菌毒素同時(shí)存在時(shí),其毒性效應(yīng)大多表現(xiàn)為加和作用或者協(xié)同作用,少數(shù)會(huì)表現(xiàn)為拮抗作用(表2)。針對(duì)霉菌毒素聯(lián)合毒性機(jī)理研究的報(bào)道不多,Ji等[66]采用氣相色譜-飛行時(shí)間質(zhì)譜(GC-TOF/MS)法對(duì)DON和ZEA聯(lián)合作用的小鼠巨噬細(xì)胞Ana-1中代謝組進(jìn)行分析,發(fā)現(xiàn)僅當(dāng)DON和ZEA聯(lián)合作用時(shí),出現(xiàn)了以下4種代謝物:棕櫚酸、1-單棕桐酸甘油酯、5-磷酸核糖和2-脫氧-D-半乳糖,這表明Ana-1細(xì)胞代謝出現(xiàn)了異常,加劇了對(duì)Ana-1細(xì)胞磷酸戊糖途徑的毒性;另外代謝過(guò)程中,DON可能抑制了ZEA的雌激素樣作用。 細(xì)胞模型在評(píng)定霉菌毒素毒性的研究中具有諸多優(yōu)點(diǎn):如細(xì)胞模型易于搭建;試驗(yàn)條件操作簡(jiǎn)單;與動(dòng)物試驗(yàn)法相比,培養(yǎng)細(xì)胞更為經(jīng)濟(jì)省時(shí)等。但是,采用細(xì)胞模型開(kāi)展霉菌毒素的毒性研究也具有一定的局限性,如同種毒素在不同細(xì)胞系、或同種細(xì)胞系在不同試驗(yàn)設(shè)計(jì)的條件下,結(jié)果可能存在差異性;同時(shí),部分細(xì)胞模型所得到的試驗(yàn)結(jié)果與體內(nèi)模型結(jié)果也存在矛盾。然而,值得注意的是,毒素等污染物無(wú)法進(jìn)行人體試驗(yàn),采用人類(lèi)細(xì)胞模型進(jìn)行探索性研究較為合理;同時(shí),可結(jié)合分子生物學(xué)技術(shù),獲得能表達(dá)特定基因或蛋白質(zhì)的細(xì)胞模型,形成較為穩(wěn)定的評(píng)價(jià)模型。利用細(xì)胞模型,結(jié)合生物信息學(xué)及多種組學(xué)研究,可在闡明霉菌毒素毒性分子機(jī)制及作用機(jī)理研究中發(fā)揮不可替代的作用。 本文以多種細(xì)胞為模型,對(duì)AFB1、OTA、DON、ZEN和PAT的毒性及致毒機(jī)理進(jìn)行了綜述?,F(xiàn)有基于體外細(xì)胞模型的研究表明各類(lèi)霉菌毒素均有不同程度的毒性,其可能的致毒機(jī)理為通過(guò)誘導(dǎo)氧化應(yīng)激、引發(fā)細(xì)胞凋亡、損傷DNA、阻滯細(xì)胞周期和改變線粒體膜電位等方式對(duì)多種細(xì)胞造成損傷,部分霉菌毒素還可以參與信號(hào)轉(zhuǎn)導(dǎo)通路,影響蛋白質(zhì)在通路中的正常調(diào)控作用。通過(guò)對(duì)霉菌毒素在體外細(xì)胞模型中的致毒機(jī)制的研究,可豐富霉菌毒素致毒機(jī)制的基礎(chǔ)數(shù)據(jù),為后續(xù)動(dòng)物水平確證提供理論基礎(chǔ),為下一步繼續(xù)篩選解毒藥物及保護(hù)機(jī)制的探究提供了理論基礎(chǔ),為食品安全風(fēng)險(xiǎn)評(píng)估提供重要理論依據(jù)。 表2 霉菌毒素的聯(lián)合毒性 [1] HUSSEIN H S,BRASEL J M.Toxicity,metabolism,and impact of mycotoxins on humans and animals[J].Toxicology,2001,167(2):101-134. 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[75] BENSASSI F,GALLERNE C,EL DEIN O S,et al.Invitroinvestigation of toxicological interactions between the fusariotoxins deoxynivalenol and zearalenone[J].Toxicon,2014,84:1-6. *Corresponding author, assistant professor, E-mail: xuzhenzhen@caas.cn (責(zé)任編輯 武海龍) Evaluation of Mycotoxin Toxicity Based on Cell ModelinVitro QIU Siqi1,2XU Zhenzhen1*SHEN Hong2YANG Shuming1CHEN Ailiang1ZHAO Yan1 (1.InstituteofQualityStandard&TestingTechnologyforAgro-Products,ChineseAcademyofAgriculturalSciences;KeyLaboratoryofAgro-FoodSafetyandQuality,MinistryofAgriculture,Beijing100081,China; 2.CollegeofAnimalScienceandTechnology,BeijingUniversityofAgriculture,Beijing102206,China) Mycotoxins are secondary metabolites produced by various fungi, which are widely found in food and feed. The contamination of mycotoxins on food and feed will result a large risk in livestock production and quality and safety of animal products. It is necessary to study the toxic mechanism of mycotoxins in order to evaluating the risk of food and feed safety. As a commonly used methodinvitro, cell model is widely used in toxicology research. This paper reviews general property, toxicity and toxic mechanism of aflatoxin B1, ochratoxin A, deoxynivalenol, zearalenone and patulin based on cell modelinvitro.[ChineseJournalofAnimalNutrition, 2017, 29(8):2665-2675] mycotoxin; toxicity; cell model 10.3969/j.issn.1006-267x.2017.08.008 2017-02-01 國(guó)家自然科學(xué)基金青年科學(xué)基金項(xiàng)目(31401666);中央級(jí)公益性科研院所基本科研業(yè)務(wù)費(fèi)專(zhuān)項(xiàng)(1610072016014) 邱思奇(1991—),女,湖北應(yīng)城人,碩士研究生,基礎(chǔ)獸醫(yī)學(xué)專(zhuān)業(yè)。E-mail: 623606844@qq.com *通信作者:徐貞貞,助理研究員,E-mail: xuzhenzhen@caas.cn S852.2 A 1006-267X(2017)08-2665-114 ZEA
5 PAT
6 聯(lián)合毒性
7 小 結(jié)