杜改梅 胡志華 羅碧平 吳結(jié)革 張淼 晏文梅 劉茂軍
摘要:【目的】研究生長(zhǎng)素(Ghrelin)基因沉默對(duì)仔豬胃酸分泌的調(diào)節(jié)作用,為防治仔豬斷奶后某些消化系統(tǒng)功能障礙或分泌異常研究提供新靶點(diǎn),進(jìn)而闡明Ghrelin對(duì)胃酸分泌的調(diào)節(jié)作用機(jī)制。【方法】采用脂質(zhì)體將RNA干擾沉默的shGhrelin轉(zhuǎn)染體外培養(yǎng)的豬胃黏膜上皮細(xì)胞,優(yōu)化確立最佳轉(zhuǎn)染條件,并通過(guò)熒光定量RT-PCR檢測(cè)shGrelin轉(zhuǎn)染對(duì)胃黏膜上皮細(xì)胞中Ghrelin基因mRNA表達(dá)及H+-K+-ATPase(質(zhì)子泵)活性的影響。【結(jié)果】質(zhì)粒(shGhrelin)與脂質(zhì)體(Lipofectamine 2000)的最佳轉(zhuǎn)染比例為1∶3,最佳轉(zhuǎn)染時(shí)間24 h。與正常對(duì)照組相比,以shGhrelin轉(zhuǎn)染胃黏膜上皮細(xì)胞后,其Ghrelin基因mRNA的表達(dá)顯著降低(P<0.05,下同),H+-K+-ATPase活性也顯著下降?!窘Y(jié)論】采用RNA干擾技術(shù)能沉默胃黏膜上皮細(xì)胞Ghrelin基因表達(dá)和抑制H+-K+-ATPase活性,表明Ghrelin對(duì)胃酸分泌具有重要的調(diào)節(jié)作用。
關(guān)鍵詞: 生長(zhǎng)素(Ghrelin);胃黏膜上皮細(xì)胞;胃酸分泌;RNA干擾
中圖分類(lèi)號(hào): S828 文獻(xiàn)標(biāo)志碼:A 文章編號(hào):2095-1191(2016)08-1396-05
Abstract:【Objective】The regulating effect of Ghrelin gene silencing on gastric acid secretion were investigated, in order to provide new target for digestive system dysfunctions or diacrisis of weaning piglet, and then clarify regulation mechanism of ghrelin in the gastric acid secretion. 【Method】shGhrelin was transfected into in vitro porcine gastric mucosal cells using liposome, and the transfection conditions were further optimized. The effects of shGhrelin transfection on Ghrelin gene mRNA expression and H+-K+-ATPase(proton pump) activity were detected by fluorescent quantitative RT-PCR. 【Result】The results showed that, the optimal transfection ratio of plasmid(shGhrelin) to lipofectamine 2000 was 1∶3, and the optimal transfection time was 24 h. Furthermore, after shGhrelin was transfected into in vitro porcine gastric mucosal cells, Ghrelin gene mRNA expression and H+-K+-ATPase activity were reduced significantly(P<0.05), compared with control group. 【Conclusion】Ghrelin gene expression is silenced successfully by using RNA interference(RNAi) technology, and H+-K+-ATPase activity is inhibited. It indicated that ghrelin plays an important role in regulating gastric acid secretion.
Key words: Ghrelin; gastric mucosal cell; gastric acid secretion; RNA interference
0 引言
【研究意義】在消化系統(tǒng)中,胃是蛋白質(zhì)消化的重要場(chǎng)所,也是抵御有害微生物入侵的重要屏障。胃黏膜組織中壁細(xì)胞分泌的胃酸對(duì)胃蛋白酶原激活起關(guān)鍵作用,同時(shí)具有抑制有害菌增殖的作用。隨著養(yǎng)豬業(yè)規(guī)?;牟粩喟l(fā)展,仔豬斷奶日齡越來(lái)越小,但其胃腸道功能發(fā)育尚未完善,常導(dǎo)致仔豬食欲不良、消化功能紊亂,嚴(yán)重的甚至出現(xiàn)腹瀉或死亡現(xiàn)象等,嚴(yán)重影響我國(guó)養(yǎng)豬業(yè)的健康快速發(fā)展(張宏福和顧憲紅,2001)。因此,有效激發(fā)仔豬內(nèi)源性的胃酸分泌能力,提高斷奶前后仔豬的消化功能是防止其斷奶后腹瀉的關(guān)鍵?!厩叭搜芯窟M(jìn)展】生長(zhǎng)素(Ghrelin)是一種主要由胃粘膜分泌的短肽,與受體結(jié)合可發(fā)揮許多生物學(xué)功能(Kojima et al.,1999,2008;Date et al.,2000;Muller et al.,2015)。Ghrelin免疫活性細(xì)胞主要分布在胃底部泌酸腺黏膜上(Date et al.,2000),將胃部的泌酸區(qū)切除后,機(jī)體的血清Ghrelin含量顯著下降(Ariyasu et al.,2001)。Ghrelin基因在胃底和幽門(mén)部均有表達(dá),但在胃底部的表達(dá)量顯著高于幽門(mén)部(杜改梅等,2005)。近年來(lái),有關(guān)Ghrelin及其受體的研究主要集中在人類(lèi)和鼠類(lèi)上,并證實(shí)胃腸道功能與Ghrelin間存在密切關(guān)系,但有關(guān)Ghrelin對(duì)胃功能發(fā)育的影響作用尚有不同觀點(diǎn)。部分研究揭示,Ghrelin可降低應(yīng)激對(duì)小鼠胃腸道黏膜的損害作用,并促進(jìn)胃腸蠕動(dòng)及食物消化(陳晨,2002;黃希貴等,2004;Levin et al.,2005),或促進(jìn)大鼠胃腸運(yùn)動(dòng)和胃酸分泌(Masuda et al.,2000);但也有研究表明,Ghrelin對(duì)大鼠胃酸分泌具有顯著的抑制作用(Sibilia et al.,2002);而Dornonville等(2004)研究發(fā)現(xiàn),Ghrelin對(duì)胃腸道運(yùn)動(dòng)具有促進(jìn)作用,但對(duì)胃酸分泌無(wú)任何促進(jìn)或抑制作用。即關(guān)于Ghrelin對(duì)胃酸分泌的調(diào)節(jié)作用尚無(wú)定論,有待進(jìn)一步研究闡明?!颈狙芯壳腥朦c(diǎn)】RNA干擾(RNA interference,RNAi)是一種負(fù)責(zé)轉(zhuǎn)錄和轉(zhuǎn)錄后基因沉默機(jī)制(Calero- Nieto et al.,2009),目前已成為研究基因功能的一個(gè)重要工具,在許多疾病的預(yù)防和治療中得到推廣應(yīng)用(Rao et al.,2009)。因此,研究RNA干擾沉默Ghrelin基因?qū)ψ胸i胃酸分泌的影響,對(duì)闡明其調(diào)節(jié)作用機(jī)制具有重要意義?!緮M解決的關(guān)鍵問(wèn)題】通過(guò)RNA干擾沉默Ghrelin基因表達(dá),研究Ghrelin調(diào)節(jié)胃酸分泌的作用,以期為防治仔豬斷奶后某些消化系統(tǒng)功能障礙或分泌異常研究提供新靶點(diǎn),進(jìn)而闡明Ghrelin對(duì)胃酸分泌的調(diào)節(jié)作用機(jī)制。
1 材料與方法
1. 1 試驗(yàn)材料
H+-K+-ATPase Kit和胰蛋白酶(Trypsin)購(gòu)自南京建成生物科技有限公司,DMEM/F-12和Triton X-100購(gòu)自美國(guó)Gibco公司,胎牛血清、Rabbit Monclonal to CK18和FITC標(biāo)志親和純化羊抗兔IgG(H+L)購(gòu)自美國(guó)Sigma公司,Trizol試劑盒和SYBR-Green I購(gòu)自TaKaRa公司,質(zhì)粒pGPU6/GFP/Neo購(gòu)自GenePharma公司;無(wú)內(nèi)毒素質(zhì)粒抽提試劑盒購(gòu)自天根生化科技(北京)有限公司。
1. 2 胃黏膜上皮細(xì)胞培養(yǎng)
迅速剖取斷奶小梅山豬的胃,用含青霉素(500 U/mL)和鏈霉素(500 U/mL)的預(yù)冷(4 ℃)D-Hanks液快速清洗胃內(nèi)容物,充分洗凈后迅速剝離胃黏膜,參照Terano等(1982)的方法進(jìn)行胃黏膜上皮細(xì)胞培養(yǎng)。0.15%胰蛋白酶37 ℃消化30 min,過(guò)銅網(wǎng)后1000 r/min離心5 min;D-Hanks液洗離心沉淀1次,同樣方法離心收集沉淀,用含10%胎牛血清、青霉素(500 U/mL)和鏈霉素(500 U/mL)的DEME/F-12懸浮沉淀,制成細(xì)胞懸液,確保細(xì)胞存活率在95%以上。調(diào)整細(xì)胞密度為2×106個(gè)/mL,置于37 ℃、5% CO2培養(yǎng)箱中培養(yǎng)至細(xì)胞融合達(dá)80%。
1. 3 胃黏膜上皮細(xì)胞免疫熒光鑒定
消化分離生長(zhǎng)良好的黏膜上皮細(xì)胞于96孔板中貼壁生長(zhǎng)24 h,棄培養(yǎng)液,PBS洗3次,每次5 min;于200 μL乙醇中4 ℃固定30 min,PBS洗3次;用1% BSA在37 ℃下封閉30 min,PBS洗3次;加入Rabbit Monclonal to CK18(一抗),37 ℃下孵育1.5 h,PBS洗3次;加入FITC標(biāo)志親和純化羊抗兔IgG(二抗),37 ℃下避光孵育1 h,PBS洗3次。熒光顯微鏡下觀察并拍照,陽(yáng)性信號(hào)為綠色熒光。
1. 4 shGhrelin轉(zhuǎn)染
轉(zhuǎn)染前1 d,將細(xì)胞接種至6孔板中(培養(yǎng)液為不含抗生素的DMEM/F-12),37 ℃、5% CO2培養(yǎng)箱中培養(yǎng),待細(xì)胞生長(zhǎng)至80%融合時(shí)進(jìn)行轉(zhuǎn)染試驗(yàn)。按照Lipofectamine 2000使用說(shuō)明進(jìn)行操作(Elbashir et al.,2001),優(yōu)化shGhrelin和Lipofectamine 2000的混合比例,分別按1∶2、1∶3和1∶4的比例將shGhrelin轉(zhuǎn)染胃黏膜上皮細(xì)胞,同時(shí)設(shè)正常對(duì)照組和陰性對(duì)照組。在DMEM/F-12無(wú)血清培養(yǎng)基加入質(zhì)粒DNA,輕輕混勻;用無(wú)血清的DMEM/F-12稀釋Lipofectamine 2000,輕輕混勻,室溫放置5 min;將稀釋好的Lipofectamine 2000與質(zhì)粒DNA混勻,室溫放置20 min,形成DNA/Lipofectamine復(fù)合物。將復(fù)合物加入到含有細(xì)胞和培養(yǎng)基的6孔板中,來(lái)回輕輕搖晃細(xì)胞培養(yǎng)板。在37 ℃、5% CO2培養(yǎng)箱中溫育,分別于轉(zhuǎn)染后24、48 h熒光檢測(cè)轉(zhuǎn)染情況,選擇轉(zhuǎn)染效率高且細(xì)胞狀態(tài)良好的轉(zhuǎn)染組提取細(xì)胞RNA和總蛋白。
1. 5 實(shí)時(shí)定量RT-PCR檢測(cè)Ghrelin基因mRNA表達(dá)量
轉(zhuǎn)染結(jié)束后,采用Trizol試劑盒提取細(xì)胞中總RNA。測(cè)定總RNA的濃度和純度,并以1.4%瓊脂糖—甲醛變性凝膠電泳檢測(cè)總RNA質(zhì)量。用隨機(jī)引物對(duì)所有樣品RNA進(jìn)行反轉(zhuǎn)錄(RT)以獲得cDNA,RT反應(yīng)體系25.0 μL,其中總RNA 2.0 μg,0.4 mmol/L dNTP 1.0 μL,0.4 μmol/L隨機(jī)引物2.0 μL,加ddH2O至10.0 μL;70 ℃變性5 min后即刻冰上冷卻,加入8 U RNA酶抑制劑、5.0 μL 5×RT Buffer和100 U M-MLV反轉(zhuǎn)錄酶,DEPC水補(bǔ)足至25.0 μL;然后37 ℃反應(yīng)60 min,95 ℃反應(yīng)5 min。以不加反轉(zhuǎn)錄酶的體系作陰性對(duì)照(C1),用于檢測(cè)RNA樣品是否存在基因組DNA污染。Ghrelin基因引物序列根據(jù)GenBank中豬的相關(guān)cDNA序列進(jìn)行設(shè)計(jì),所有引物(表1)由寶生物工程(大連)有限公司合成。
以GAPDH為內(nèi)標(biāo)基因,采用熒光定量RT-PCR檢測(cè)目的基因的表達(dá)量,重復(fù)3次,2-△△Ct統(tǒng)計(jì)分析有效性數(shù)據(jù)。同時(shí)以ddH2O和RNA為模板,檢驗(yàn)是否存在外源和基因組DNA污染。
1. 6 H+-K+-ATPase(質(zhì)子泵)活性測(cè)定
轉(zhuǎn)染結(jié)束后棄培養(yǎng)液,每孔中加入1.0 mL的0.2% Triton X-100,吹打破碎細(xì)胞,收集細(xì)胞破碎液,按試劑盒說(shuō)明進(jìn)行測(cè)定,結(jié)果以反應(yīng)1 h內(nèi)H+-K+-ATPase磷酸化釋放磷量和細(xì)胞總蛋白含量比值來(lái)表示,單位為μmol/mg·h。
1. 7 統(tǒng)計(jì)分析
采用SPSS 11.0進(jìn)行統(tǒng)計(jì)分析,以單因子方差分析(One-way ANOVA)進(jìn)行差異顯著性檢驗(yàn)。
2 結(jié)果與分析
2. 1 胃黏膜上皮細(xì)胞的培養(yǎng)及鑒定結(jié)果
如圖1和圖2所示,胰酶消化法可有效分離獲得胃黏膜上皮細(xì)胞,培養(yǎng)48 h后細(xì)胞大量增殖。通過(guò)免疫熒光鑒定,發(fā)現(xiàn)有大量綠色熒光陽(yáng)性信號(hào),即確定培養(yǎng)的細(xì)胞為仔豬胃黏膜上皮細(xì)胞。
2. 2 shGrelin轉(zhuǎn)染條件優(yōu)化確定
通過(guò)優(yōu)化脂質(zhì)體與質(zhì)粒的比例,最終確定質(zhì)粒(shGhrelin)和脂質(zhì)體(Lipofectamine 2000)比例為1∶3,以轉(zhuǎn)染后24 h的綠色熒光細(xì)胞數(shù)量最多(圖2)。轉(zhuǎn)染48 h后的熒光細(xì)胞數(shù)量與轉(zhuǎn)染24 h的相近,無(wú)明顯變化。
2. 3 shGrelin轉(zhuǎn)染對(duì)胃黏膜上皮細(xì)胞中Ghrelin基因mRNA表達(dá)的影響
與正常對(duì)照組相比,陰性對(duì)照組胃黏膜上皮細(xì)胞中Ghrelin基因mRNA的表達(dá)量未發(fā)生顯著變化(P>0.05,下同),但shGhrelin轉(zhuǎn)染組胃黏膜上皮細(xì)胞中Ghrelin基因mRNA的表達(dá)顯著降低(P<0.05,下同)(圖3)。
2. 4 shGrelin轉(zhuǎn)染對(duì)胃黏膜上皮細(xì)胞中H+-K+-ATPase活性的影響
如圖4所示,shGhrelin轉(zhuǎn)染胃黏膜上皮細(xì)胞后,細(xì)胞中H+-K+-ATPase活性與正常對(duì)照組和陰性對(duì)照組相比顯著下降,而正常對(duì)照組與陰性對(duì)照組間無(wú)顯著差異。
3 討論
目前,隨著RNA干擾技術(shù)的不斷發(fā)展,采用基因沉默闡明相關(guān)基因的功能作用已成為研究熱點(diǎn),但通過(guò)RNA干擾沉默Ghrelin基因表達(dá)來(lái)研究其對(duì)胃酸分泌的調(diào)控作用尚無(wú)文獻(xiàn)報(bào)道。本研究結(jié)果表明,構(gòu)建的shGhrelin表達(dá)載體能高效阻斷胃黏膜上皮細(xì)胞中Ghrelin基因的表達(dá),并顯著降低胃黏膜上皮細(xì)胞中H+-K+-ATPase活性,揭示Ghrelin對(duì)胃酸分泌具有重要的促進(jìn)作用。
已有諸多研究表明,Ghrelin與胃酸分泌具有密切關(guān)系。如Masuda等(2000)、Date等(2001)研究發(fā)現(xiàn),Ghrelin通過(guò)中樞神經(jīng)和迷走神經(jīng)通路可提高胃酸分泌;Sibilia等(2002)研究表明,Ghrelin可抑制胃酸分泌;Dornonville等(2004)研究表明,Ghrelin對(duì)胃酸分泌既無(wú)促進(jìn)作用也無(wú)抑制作用??梢?jiàn),Ghrelin是否參與對(duì)胃酸分泌的調(diào)節(jié),可能與劑量、評(píng)價(jià)胃酸分泌能力的指標(biāo)及處理方法等有關(guān)。本課題組的前期研究結(jié)果表明,仔豬斷奶前后Ghrelin基因表達(dá)的發(fā)育性變化與胃H+-K+-ATPase mRNA表達(dá)呈顯著正相關(guān),同時(shí)揭示外源Ghrelin作用于胃黏膜上皮細(xì)胞,可促進(jìn)黏膜上皮細(xì)胞中H+-K+-ATPase活性(Du et al.,2007);通過(guò)肌肉注射重組Ghrelin也可促進(jìn)仔豬胃酸分泌(Du et al.,2013)。本研究通過(guò)構(gòu)建shGhrelin表達(dá)載體抑制Ghrelin基因mRNA表達(dá)來(lái)觀測(cè)其對(duì)胃H+-K+-ATPase活性的影響,其結(jié)果與本課題組的前期研究結(jié)果一致。因此,本研究建立的Ghrelin基因阻斷胃黏膜上皮細(xì)胞模型為進(jìn)一步研究Ghrelin調(diào)節(jié)胃酸分泌的機(jī)制及其他生物學(xué)功能提供了重要的方法和途徑。
4 結(jié)論
本研究結(jié)果表明,采用RNA干擾技術(shù)能沉默胃黏膜上皮細(xì)胞Ghrelin基因表達(dá)和抑制H+-K+-ATPase活性,表明Ghrelin對(duì)胃酸分泌具有重要的調(diào)節(jié)作用。
參考文獻(xiàn):
陳晨. 2002. 生長(zhǎng)素釋放肽的發(fā)現(xiàn)、發(fā)展及展望[J]. 基礎(chǔ)醫(yī)學(xué)與臨床,22(1):1-5.
Chen C. 2002. The discovery,development and prospects of growth hormone releasing peptides[J]. Basic Medical Sciences and Clinics,22(1):1-5.
杜改梅,石志敏,韋習(xí)會(huì),張磊,趙茹茜. 2005. 斷奶前后仔豬胃組織中g(shù)hrelin基因表達(dá)及內(nèi)源性生長(zhǎng)抑素的作用[J]. 世界華人消化雜志,13(5):604-607.
Du G M,Shi Z M,Wei X H,Zhang L,Zhao R Q. 2005. Expression of ghrelin mRNA in gastric tissue of weaning piglets and the role of endogenous somatosatain[J]. World Chinese Journal of Digestology,13(5):604-607.
黃希貴,焦保衛(wèi),王德壽. 2004. 生長(zhǎng)激素促分泌素受體(GHS-R)的發(fā)現(xiàn)及影響[J]. 動(dòng)物學(xué)雜志,39(2):84-88.
Huang X G,Jiao B W,Wang D S. 2004. GHS-R:a novelly identified GH-secreting protein[J]. Chinese Journal of Zoology,39(2):84-88.
張宏福,顧憲紅. 2001. 仔豬營(yíng)養(yǎng)生理與飼料配制技術(shù)研究[M]. 北京:中國(guó)農(nóng)業(yè)科技出版社.
Zhang H F,Gu X H. 2001. Nutrition Physiology and Diet Formulation Technology of Piglet[M]. Beijing:China Agriculture Science and Technique Press.
Ariyasu H,Takaya K,Tagami T,Ogawa Y,Hosoda K,Akamizu T,Suda M,Koh T,Natsui K,Toyooka S,Shirakami G,Usui T,Shimatsu A,Doi K,Hosoda H,Kojima M,Kangawa K,Nakao K. 2001. Stomach is a major source of circulating ghrelin,and feeding state determines plasma ghrelin-like immunoreactivity levels in humans[J]. The Journal of Clini-
cal Endocrinology and Metablism,86(10):4753-4758.
Calero-Nieto F J,Bert A G,Cockerill P N. 2009. Transcription-dependent silencing of inducible convergent transgenes in transgenic mice[J]. Epigenetics & Chromatin,3(1):463-468.
Date Y,Kojima M,Hosoda H,Sawaguchi A,Mondal M S,Suga-
numa T, Matsukura S, Kangawa K, Nakazato M. 2000. Ghrelin,a novel growth hormone-releasing acylated peptide,is synthesized in a distinct endocrine cell type in the gastrointestinal tracts of rats and humans[J]. Endocrinology,141(11):4255-4261.
Date Y,Nakazato M,Murakami N,Kojima M,Kangawa K,Matsukura S. 2001. Ghrelin acts in the central nervous system to stimulate gastric acid secretion[J]. Biochemical and Biophysical Research Communications,280(3):904-907.
Dornonville C C,Lindstr■m E,Norlén P,H■kanson R. 2004. Ghrelin stimulates gastric emptying but is without effect on acid secretion and gastric endocrine cells[J]. Regulatory Peptides,120(1-3):23-32.
Du G M,Liu M J,Parvizi N,Zhao R Q. 2013. Ectopic expression of ghrelin affects gastric H(+)-K(+)-ATPase activity and expression of GHR/IGF-1 system in weaned mice[J]. Regulatory Peptides,186:12-17.
Du G M,Shi Z M,Wei X H,Liu M J,Zhang L,Zhao R Q. 2007. Expression of gastric ghrelin and H(+)-K(+)-ATPase mRNA in weanling piglets and effect of ghrelin on H(+)-K(+)-
ATPase expression and activity in gastric mucosal cells in vitro[J]. Research in Veterinary Science,82(1):99-104.
Elbashir S M,Harborth J,Lendeckel W,Yalcin A,Weber K,Tuschl T. 2001. Duplexes of 21-nucleotide RNAs mediate RNA interference in cultured mammalian cells[J]. Nature,411:494-498.
Kojima M,Hosoda H,Date Y,Nakazato M,Matsuo H,Kangawa K. 1999. Ghrelin is a growth-hormone-releasing acylated peptide from stomach[J]. Nature,402:656-660.
Kojima M,Ida T,Sato T. 2008. Structure of mammalian and nonmammalian ghrelins[J]. Vitamins and Hormones,77:31-46.
Levin F,Edholm T,Ehrstr■m M,Wallin B,Schmidt P T,Kirchgessner A M,Hilsted L M,Hellstr■m P M,N■slund E. 2005. Effect of peripherally administered ghrelin on gastric emptying and acid secretion in the rat[J]. Regulatory Peptides,131(1-3):59-65.
Masuda Y,Tanaka T,Inomata N,Ohnuma N,Tanaka S,Itoh Z,Hosoda H,Kojima M,Kangawa K. 2000. Ghrelin stimulates gastric acid secretion and motility in rats[J]. Biochemical and Biophysical Research Communications,276(3):905-908.
Muller T D,Nogueiras R,Andermann M L. 2015. Ghrelin[J]. Mo-
lecular Metabolism,4(6):437-460.
Rao D D,Vorhies J S,Senzer N,Nemunaitis J. 2009. siRNA vs. shRNA:similarities and differences[J]. Advanced Drug Delivery Reviews,61(9):746-759.
Sibilia V,Pagani F,Guidobono F,Locatelli V,Torsello A,Deghenghi R,Netti C. 2002. Evidence for a central inhibitory role of growth hormone secretagogues and ghrelin on gastric acid secretion in conscious rats[J]. Neuroendocrinology,75(2):92-97.
Terano A,Ivey K J,Stachura J,Sekhon S,Hosojima H,McKenzie W N Jr,Krause W J,Wyche J H. 1982. Cell culture of rat gastric fundic mucosa[J]. Gastroenterology,83(6):1280-1291.
(責(zé)任編輯 蘭宗寶)