王 艷, 林繼宗, 陳慶狀, 賈思遠(yuǎn), 馬艷姣, 王 勇△
(1南方醫(yī)科大學(xué)珠江醫(yī)院藥劑科,廣東 廣州 510282;2廣東省中西醫(yī)結(jié)合醫(yī)院藥事管理科,廣東 佛山 528200;3中山大學(xué)附屬第三醫(yī)院肝膽外科,廣東 廣州 510630;4廣州市中西醫(yī)結(jié)合醫(yī)院藥劑科,廣東 廣州 510800;5南方醫(yī)科大學(xué)珠江醫(yī)院燒傷科,廣東 廣州 510282)
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神經(jīng)干細(xì)胞過表達(dá)Hsp75降低Aβ介導(dǎo)的神經(jīng)毒性*
王艷1, 2,林繼宗3,陳慶狀4,賈思遠(yuǎn)5,馬艷姣1,王勇1△
(1南方醫(yī)科大學(xué)珠江醫(yī)院藥劑科,廣東 廣州 510282;2廣東省中西醫(yī)結(jié)合醫(yī)院藥事管理科,廣東 佛山 528200;3中山大學(xué)附屬第三醫(yī)院肝膽外科,廣東 廣州 510630;4廣州市中西醫(yī)結(jié)合醫(yī)院藥劑科,廣東 廣州 510800;5南方醫(yī)科大學(xué)珠江醫(yī)院燒傷科,廣東 廣州 510282)
[摘要]目的: 應(yīng)用腺病毒為載體在體外過表達(dá)熱休克蛋白75(Hsp75),研究Hsp75蛋白過表達(dá)對(duì)神經(jīng)干細(xì)胞在Aβ誘導(dǎo)神經(jīng)毒性中的作用,并初步探討其作用機(jī)制。方法: 體外培養(yǎng)小鼠神經(jīng)干細(xì)胞C17.2,實(shí)驗(yàn)分為對(duì)照組、Aβ處理組、腺病毒陰性感染組和腺病毒Hsp75過表達(dá)感染組。使用熒光顯微鏡觀察腺病毒的感染情況并進(jìn)行細(xì)胞免疫鑒定;倒置相差顯微鏡觀察各組神經(jīng)干細(xì)胞的形態(tài);MTT法檢測細(xì)胞活力;流式細(xì)胞術(shù)檢測細(xì)胞凋亡率;Western blot檢測Hsp75和活化型caspase-3蛋白水平。結(jié)果: 熒光顯微鏡觀察和Western blot檢測表明腺病毒成功感染神經(jīng)干細(xì)胞并高效表達(dá)Hsp75蛋白。此外,腺病毒感染不會(huì)導(dǎo)致細(xì)胞形態(tài)改變及細(xì)胞分化,同時(shí)也不會(huì)影響細(xì)胞活力。與對(duì)照組比較,Aβ處理組及腺病毒陰性感染組細(xì)胞存活率顯著降低(P<0.05),細(xì)胞凋亡率及活化型caspase-3蛋白水平顯著增高(P<0.05);然而,Hsp75過表達(dá)能顯著提高神經(jīng)干細(xì)胞的存活率,減少細(xì)胞凋亡和降低活化型caspase-3蛋白水平(P<0.05)。結(jié)論: Hsp75過表達(dá)對(duì)Aβ誘導(dǎo)損傷的C17.2細(xì)胞具有明顯保護(hù)作用,其機(jī)制可能是與抑制caspase-3途徑依賴的細(xì)胞凋亡有關(guān)。
[關(guān)鍵詞]熱休克蛋白75; C17.2神經(jīng)干細(xì)胞; 細(xì)胞凋亡
阿爾茨海默病(Alzheimer’s disease,AD)又稱老年癡呆癥,是一種以認(rèn)知功能進(jìn)行性下降和情感障礙為特點(diǎn)的中樞神經(jīng)退行性疾病,其病理特征主要表現(xiàn)為細(xì)胞外β-淀粉樣蛋白(amyloid β-protein,Aβ)沉積形成老年斑及胞內(nèi)tau蛋白過度磷酸化引起纖維纏結(jié)[1-2]。大量研究證實(shí),Aβ對(duì)腦細(xì)胞產(chǎn)生的神經(jīng)毒性在AD病理形成過程中發(fā)揮了重要的作用[3- 4]。因此,保護(hù)神經(jīng)細(xì)胞拮抗Aβ誘導(dǎo)的神經(jīng)毒性成為治療AD的重要途徑。
熱休克蛋白75(heat shock protein 75,Hsp75)是一個(gè)主要定位于線粒體,分子量約為75 kD的分子伴侶,對(duì)細(xì)胞存活、增殖及線粒體功能的維護(hù)具有重要的作用。近年來研究表明,Hsp75是一個(gè)抗凋亡蛋白,特別是在心肌細(xì)胞及腫瘤細(xì)胞中都已證實(shí)具有抗凋亡的作用[5-6],但Hsp75過表達(dá)對(duì)保護(hù)神經(jīng)干細(xì)胞拮抗Aβ誘導(dǎo)的細(xì)胞損傷尚未明確。本研究應(yīng)用腺病毒載體在C17.2神經(jīng)干細(xì)胞過表達(dá)人Hsp75基因,以探討Hsp75對(duì)Aβ誘導(dǎo)神經(jīng)干細(xì)胞損傷的保護(hù)作用,為下一步的基因工程化神經(jīng)干細(xì)胞移植治療AD奠定了基礎(chǔ)。
材料和方法
1實(shí)驗(yàn)材料
重組腺病毒為本課題前期實(shí)驗(yàn)包裝,滴度為1×1013PFU/L;C17.2神經(jīng)干細(xì)胞由上海交通大學(xué)金衛(wèi)林教授饋贈(zèng);DMEM、胎牛血清、馬血清購于Gibco;Hsp75、MAP2、GFAP和MBP多克隆抗體、nestin小鼠單克隆抗體均購自Abcam;活化型caspase-3(cleaved caspase-3)抗體購自CST;β-actin和α-tubulin小鼠單克隆抗體購于碧云天生物技術(shù)研究所;Aβ1-42購于USBiological。
2主要方法
2.1神經(jīng)干細(xì)胞培養(yǎng)、實(shí)驗(yàn)分組和處理C17.2細(xì)胞培養(yǎng)于含10%胎牛血清、5%馬血清的DMEM高糖培養(yǎng)基中,孵育于37 ℃、5% CO2培養(yǎng)箱中,取對(duì)數(shù)生長期的細(xì)胞用于實(shí)驗(yàn)。實(shí)驗(yàn)共分為4組:對(duì)照組(control組):細(xì)胞于正常培養(yǎng)基生長;Aβ處理組(C17.2+Aβ組):用含10 μmol/L Aβ1-42的培養(yǎng)基培養(yǎng)神經(jīng)干細(xì)胞;腺病毒陰性感染組(Ad-GFP+Aβ組): 感染了對(duì)照腺病毒的神經(jīng)干細(xì)胞置于含10 μmol/L Aβ1-42的培養(yǎng)基中生長;腺病毒Hsp75過表達(dá)感染組(Ad-Hsp75+Aβ組): 感染了攜帶Hsp75基因腺病毒的神經(jīng)干細(xì)胞,用含10 μmol/L Aβ1-42的培養(yǎng)基處理。以上所有分組的處理時(shí)間均為36 h。
2.2腺病毒感染神經(jīng)干細(xì)胞接種密度為每孔2×105個(gè)C17.2神經(jīng)干細(xì)胞于6孔板,12 h后去除培養(yǎng)基,PBS洗3次,添加感染復(fù)數(shù)為100的病毒液和1 mL無血清的高糖培養(yǎng)基培養(yǎng),2 h后,換正常培養(yǎng)基繼續(xù)培養(yǎng)36 h于熒光顯微鏡下觀察GFP表達(dá)情況,拍片。
2.3Hsp75和cleaved caspase-3蛋白水平的檢測用細(xì)胞裂解液裂解細(xì)胞,離心后取蛋白上清,BCA法測蛋白的含量,進(jìn)行10% SDS聚丙烯酰胺凝膠電泳,10 V恒壓半干轉(zhuǎn)膜1 h,5%脫脂奶粉室溫封閉2 h,過夜孵育Hsp75多克隆抗體和β-actin小鼠單克隆抗體,之后用辣根過氧化物酶結(jié)合的 II 抗結(jié)合,ECL法顯色后掃描。
2.4細(xì)胞形態(tài)學(xué)觀察、免疫鑒定和活力的檢測按上述感染方法,腺病毒感染細(xì)胞36 h后,于倒置相差顯微鏡下觀察細(xì)胞的形態(tài),拍片。接著用4%多聚甲醛固定,10%山羊血清封閉,滴加nestin的I 抗過夜孵育。次日,依次滴加羅丹明山羊抗小鼠IgG的II抗和DAPI室溫孵育,熒光顯微鏡下觀察拍照。干細(xì)胞分化為神經(jīng)元、星形膠質(zhì)細(xì)胞和少突膠質(zhì)細(xì)胞的檢測方法參照上述干細(xì)胞nestin免疫鑒定,只需把 I 抗分別換為MAP2、GFAP、MBP。細(xì)胞活力檢測方法參照下面細(xì)胞存活率的檢測。
2.5細(xì)胞存活率和凋亡的檢測接種于96孔板的C17.2細(xì)胞實(shí)驗(yàn)處理36 h后,吸棄培養(yǎng)基,PBS洗3次,于每孔加入5 g/L的MTT溶液20 μL,37 ℃培養(yǎng)箱中避光孵育4 h,棄去上清液,加入150 μL的二甲基亞砜(DMSO),振蕩混勻使結(jié)晶充分溶解,以酶標(biāo)儀于490 nm波長處檢測A值。將接種于6孔板的細(xì)胞分別實(shí)驗(yàn)處理后用無EDTA的胰酶消化收集細(xì)胞。制成單細(xì)胞懸液收集后1 000 r/min離心5 min,棄掉上清液,加入500 μL的結(jié)合緩沖液、5 μL的Annexin V-APC染色液混勻,室溫避光孵育15 min;再加入10 μL的7-AAD染色液,用流式細(xì)胞儀檢測C17.2細(xì)胞的凋亡率。
3統(tǒng)計(jì)學(xué)處理
數(shù)據(jù)使用SPSS 13.0 統(tǒng)計(jì)軟件分析,結(jié)果使用均數(shù)±標(biāo)準(zhǔn)差(mean±SD)表示,多組間比較采用單因素方差分析。方差齊時(shí)采用SNK法;方差不齊時(shí)則采用Dunnett’s T3法。以P<0.05為差異有統(tǒng)計(jì)學(xué)意義。
結(jié)果
1腺病毒感染后GFP熒光蛋白的觀察和Hsp75過表達(dá)的鑒定
腺病毒感染神經(jīng)干細(xì)胞36 h 后,在熒光顯微鏡下觀察到GFP大量表達(dá),證實(shí)C17.2細(xì)胞已被病毒感染(圖1)。提取總蛋白進(jìn)行Western blot實(shí)驗(yàn),結(jié)果顯示Ad-Hsp75過表達(dá)感染組與正常組和腺病毒陰性感染組Ad-GFP相比,Hsp75蛋白表達(dá)量明顯增加,說明了腺病毒Ad-Hsp75感染的神經(jīng)干細(xì)胞Hsp75基因可以有效表達(dá),見圖2。
2腺病毒感染后細(xì)胞形態(tài)學(xué)觀察、免疫鑒定和活力的檢測
腺病毒感染36 h后,在倒置相差顯微鏡下觀察,腺病毒感染組(Ad-GFP和Ad-Hsp75)的細(xì)胞形態(tài)與對(duì)照組的細(xì)胞形態(tài)一樣。均呈現(xiàn)為細(xì)胞形態(tài)不規(guī)則、呈扁平的形態(tài),細(xì)胞邊界不清,并與鄰近的細(xì)胞相互接觸,證實(shí)了腺病毒的感染不會(huì)改變細(xì)胞的正常形態(tài);此外,MTT結(jié)果顯示3組的細(xì)胞活力無顯著差異,證實(shí)了腺病毒感染C17.2細(xì)胞不會(huì)影響細(xì)胞活力,見圖3。在熒光顯微鏡下觀察到所有細(xì)胞均表達(dá)nestin,然而3組細(xì)胞均不表達(dá)MAP2、GFAP和MBP,說明了腺病毒的感染不會(huì)導(dǎo)致C17.2神經(jīng)干細(xì)胞的分化,見圖4。
Figure 1.GFP expression in C17.2 neural stem cells after adenovirus transfection (×100).
圖1腺病毒感染C17.2神經(jīng)干細(xì)胞的GFP表達(dá)
Figure 2.The expression of Hsp75 protein in the cells. Mean ±SD.n=3.*P<0.05vsAd-Hsp75 group.
圖2Hsp75蛋白在細(xì)胞中的表達(dá)
Figure 3.The morphology and viability of C17.2 neural stem cells. A: the morphology of the cells was observed under inverted phase-contrast microscope (×200); B: the cell viability was detected by MTT assay after transfection. Mean±SD.n=3.
圖3C17.2神經(jīng)干細(xì)胞的形態(tài)學(xué)觀察和細(xì)胞活力檢測
3Hsp75過表達(dá)對(duì)Aβ誘導(dǎo)C17.2細(xì)胞存活率和凋亡率的影響
如圖5所示,與對(duì)照組比較,未感染的神經(jīng)干細(xì)胞和感染了對(duì)照腺病毒的神經(jīng)干細(xì)胞經(jīng)Aβ處理后,細(xì)胞存活率下降,凋亡率明顯增加(P<0.05);用過表達(dá)Hsp75腺病毒感染神經(jīng)干細(xì)胞后,能夠明顯逆轉(zhuǎn)Aβ引起的細(xì)胞活性降低及凋亡增加(P<0.05)。
4Hsp75過表達(dá)對(duì)cleaved caspase-3蛋白水平的影響
從Western blot實(shí)驗(yàn)結(jié)果可見,對(duì)照組神經(jīng)干細(xì)胞cleaved caspase-3蛋白的水平非常低,而用Aβ處理的2個(gè)神經(jīng)干細(xì)胞組(C17.2+Aβ和Ad-GFP+Aβ),其cleaved caspase-3表達(dá)水平明顯增加,與對(duì)照組相比均差異顯著(P<0.05)。用過表達(dá)Hsp75腺病毒感染后,cleaved caspase-3水平明顯下降(P<0.05),見圖6。
討論
大量研究已經(jīng)證實(shí),AD患者顱內(nèi)微環(huán)境改變與Aβ有關(guān),Aβ在腦內(nèi)產(chǎn)生神經(jīng)毒性抑制了神經(jīng)細(xì)胞的生成[7-8]。我們的前期實(shí)驗(yàn)結(jié)果也證實(shí)Aβ1-42不僅能直接影響神經(jīng)干細(xì)胞的增殖,更通過小膠質(zhì)細(xì)胞加強(qiáng)抑制了神經(jīng)干細(xì)胞的增殖與分化[9]。由于C17.2神經(jīng)干細(xì)胞與原代神經(jīng)干細(xì)胞生理功能具有許多相似之處,且同樣具有多潛能分化的功能,在一定的條件下能誘導(dǎo)分化為神經(jīng)元、星形膠質(zhì)細(xì)胞和少突膠質(zhì)細(xì)胞這3種細(xì)胞,被認(rèn)為是研究神經(jīng)干細(xì)胞的一種工具細(xì)胞[10],因此我們采用此細(xì)胞建立模型,研究其過表達(dá)Hsp75以對(duì)抗Aβ介導(dǎo)的神經(jīng)毒性。
Figure 4.The immunofluorescence identification of C17.2 neural stem cells (×400).
圖4C17.2神經(jīng)干細(xì)胞的免疫熒光鑒定
Figure 5.The neural stem cell viability and apoptotic rate in different groups. A: the cell viability was detected by MTT assay; B: the cells were double stained with Annexin V-APC and 7-AAD and analyzed by flow cytometry. Mean±SD.n=3.*P<0.05vscontrol group;#P<0.05vsAd-Hsp75+Aβ group.
圖5各組細(xì)胞存活率和凋亡率的檢測
Figure 6.The protein levels of cleaved caspase-3 in different groups. Mean±SD.n=3.*P<0.05vscontrol group;#P<0.05vsAd-Hsp75+Aβ group.
圖6各組cleaved caspase-3的蛋白水平
Hsp75是一種線粒體分子伴侶,研究已經(jīng)證實(shí)其在腦和心臟中過表達(dá)能維護(hù)線粒體的正常功能,對(duì)維持細(xì)胞內(nèi)環(huán)境的穩(wěn)定起著重要的作用。Hsp75過表達(dá)能夠逆轉(zhuǎn)缺氧引起心肌細(xì)胞的凋亡[5],也能夠降低腦缺血所引起的損傷[11]。然而,Hsp75過表達(dá)在保護(hù)神經(jīng)干細(xì)胞免受Aβ誘導(dǎo)神經(jīng)毒性的作用及其機(jī)制還尚未清楚。實(shí)驗(yàn)中我們選取C17.2神經(jīng)干細(xì)胞作為Hsp75基因感染的靶細(xì)胞,進(jìn)一步去探討Hsp75過表達(dá)在保護(hù)神經(jīng)干細(xì)胞免受Aβ誘導(dǎo)神經(jīng)毒性中的作用。因?yàn)樯窠?jīng)干細(xì)胞是一群相對(duì)靜止的細(xì)胞,利用脂質(zhì)體轉(zhuǎn)染的效率低、毒性較大,因此我們選用了高感染效率、低毒性的腺病毒去感染神經(jīng)干細(xì)胞;考慮到C17.2細(xì)胞是一種具有多潛能分化的干細(xì)胞,在實(shí)驗(yàn)中我們對(duì)感染前后的細(xì)胞進(jìn)行了相關(guān)免疫鑒定。實(shí)驗(yàn)結(jié)果表明,腺病毒感染C17.2神經(jīng)干細(xì)胞,感染率較高;通過Western blot 檢測發(fā)現(xiàn)感染了Hsp75基因的神經(jīng)干細(xì)胞能夠高效表達(dá)Hsp75蛋白;同時(shí)腺病毒感染后不會(huì)改變細(xì)胞的正常形態(tài)和誘導(dǎo)神經(jīng)干細(xì)胞的分化,而且細(xì)胞的活性也不受影響,證實(shí)了腺病毒感染C17.2神經(jīng)干細(xì)胞是一種可行且安全的方法。AD患者腦內(nèi)神經(jīng)細(xì)胞增殖受到抑制,很大程度上是由于腦內(nèi)Aβ誘導(dǎo)神經(jīng)毒性加速了神經(jīng)細(xì)胞的壞死和凋亡;細(xì)胞的凋亡涉及到凋亡調(diào)控因子半胱氨酸蛋白酶,其中激活型caspase-3是凋亡過程中的最終執(zhí)行者,caspase-3的活化程度直接反映了細(xì)胞的凋亡程度。我們的實(shí)驗(yàn)結(jié)果顯示,Hsp75過表達(dá)能夠提高C17.2神經(jīng)干細(xì)胞的存活率,減少細(xì)胞凋亡率;同時(shí)也下調(diào)了cleaved caspase-3蛋白的表達(dá),說明Hsp75過表達(dá)能夠逆轉(zhuǎn)Aβ誘導(dǎo)神經(jīng)干細(xì)胞的凋亡。
綜上所述,Hsp75 過表達(dá)能夠保護(hù)神經(jīng)干細(xì)胞免受Aβ介導(dǎo)的神經(jīng)毒性,其機(jī)制可能與抑制細(xì)胞的凋亡有關(guān)。此外,Hsp75過表達(dá)對(duì)于保護(hù)神經(jīng)干細(xì)胞的具體機(jī)制有待于下一步的研究。
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(責(zé)任編輯: 林白霜, 羅森)
Over-expression of Hsp75 in neural stem cells reduced Aβ-mediated neurotoxicityWANG Yan1, 2, LIN Ji-zong3, CHEN Qin-zhuang4, JIA Si-yuan5, MA Yan-jiao1, WANG Yong1
(1DepartmentofPharmacy,ZhujiangHospital,SouthernMedicalUniversity,Guangzhou510282,China;2DepartmentofPharmacy,GuangdongHospitalofIntegratedChineseandWesternMedicine,Foshan528200,China;3DepartmentofHepatobiliarySurgery,TheThirdAffiliatedHospitalofSunYat-senUniversity,Guangzhou510630,China;4DepartmentofPharmacy,GuangzhouHospitalofIntegratedChineseandWesternMedicine,Guangzhou510800,China;5DepartmentofBurn,ZhujiangHospital,SouthernMedicalUniversity,Guangzhou510282,China.E-mail:yongwh2005@163.com)
[ABSTRACT]AIM: To investigate the effect of heat shock protein 75 (Hsp75) over-expression on Aβ-induced neurotoxicity in the neural stem cells and to explore its mechanism. METHODS: An adenovirus-mediated Hsp75 over-expression vector was usedinvitro. The mouse neural stem cell C17.2 was culturedinvitroand divided into control group, Aβ group, negative adenovirus vector transfection group and Hsp75 over-expression adenovirus vector transfection group. The transfection and cellular immune identification were detected by fluorescence microscopy. The cell morphology was observed under inverted phase-contrast microscope. The cell viability and apoptosis were detected by MTT assay and flow cytometry, respectively. Hsp75 over-expression and cleaved caspase-3 protein level were measured by Western blot. RESULTS: Observation by fluorescence microscopy indicated that C17.2 cells were successfully transfected andHsp75 gene was effectively expressed in the neural stem cells after transfection. In addition, the morphology and viability of the cells did not change and these cells did not differentiate after transfection. As compared with control group, the cell viability in Aβ group and negative adenovirus vector transfection group was significantly decreased (P<0.05), and the cell apoptotic rate and cleaved caspase-3 level (P<0.05) were increased. As compared with Aβ group and negative adenovirus vector transfection group, Hsp75 over-expression significantly increased the cell viability, and decreased the cell apoptosis and cleaved caspase-3 level (P<0.05). CONCLUSION: Hsp75 over-expression protects the neural stem cells against Aβ-induced injury. The mechanism may be related to inhibiting caspase-3 pathway-dependent apoptosis.
[KEY WORDS]Heat shock protein 75; C17.2 neural stem cells; Apoptosis
doi:10.3969/j.issn.1000- 4718.2016.02.019
[中圖分類號(hào)]R363
[文獻(xiàn)標(biāo)志碼]A
通訊作者△Tel: 020-61643555; E-mail: youngwp005@163.com
*[基金項(xiàng)目]廣東省自然科學(xué)基金資助項(xiàng)目(No. S2012010008199; No. S2013010015546)
[收稿日期]2015- 01- 05[修回日期] 2015- 11- 25
[文章編號(hào)]1000- 4718(2016)02- 0302- 05