王一涵 漆光紫 李文學 岑育芳 韋俊宏 唐玉航 龐雅琴
【摘要】 目的 利用生物信息學方法探索酒精性肝病(alcoholic liver disease,ALD)潛在的關(guān)鍵基因并通過實驗驗證,為尋找ALD潛在的生物標志物提供依據(jù)。方法 從美國國立生物技術(shù)信息中心(National Center for Biotechnology Information,NCBI)的公共基因芯片數(shù)據(jù)平臺(Gene Expression Omnibus,GEO)的數(shù)據(jù)庫下載兩個基因表達譜芯片(GSE28619和GSE100901),利用GEO2R篩選出酒精性肝病實驗組與正常對照組的差異表達基因(differentially expressed genes,DEGs),對DEGs進行基因本體論(gene ontology,GO)與京都基因和基因組百科全書(Kyoto encyclopedia of genes and genomes ,KEGG)信號通路的富集分析,進一步應用STRING數(shù)據(jù)庫構(gòu)建蛋白質(zhì)的相互作用網(wǎng)絡,用Cytoscape來篩選出關(guān)鍵基因。構(gòu)建ALD小鼠模型,通過RT-qPCR驗證篩選出關(guān)鍵基因。結(jié)果 總共鑒定出173個DEGs,GO顯示DEGs生物學功能主要涉及5個KEGG通路,包括補體和凝血級聯(lián)、膽固醇代謝、視黃醇代謝、藥物代謝-細胞色素P450、膽汁分泌相關(guān)信號通路,結(jié)合蛋白質(zhì)相互作用網(wǎng)絡(protein-protein interaction,PPI)和CytoHubba的結(jié)果,篩選出SERPINC1、AHSG、FGG、FGA、ITIH3、FGB、APOB、ALB和APOH 9個關(guān)鍵基因,通過RT-qPCR檢測驗證,發(fā)現(xiàn)與WT小鼠相比,ALD小鼠肝臟ALB、APOB和FGB 的mRNA表達上調(diào)(P<0.05),而ITIH3、FGG和SERPINC1的 mRNA表達下調(diào)(P<0.05)。結(jié)論 ALB、APOB、 FGB、ITIH3、FGG、SERPINC1 有望成為ALD潛在的生物標志物。
【關(guān)鍵詞】 生物信息學;酒精性肝??;基因;生物標志物
中圖分類號:R575.5;Q811.4 文獻標志碼:A DOI:10.3969/j.issn.1003-1383.2023.05.002
【Abstract】 Objective To explore the potential key genes of alcoholic liver disease (ALD) by bioinformatics methods and to validate them through experiments, so as to provide basis for searching for potential biomarkers of ALD. Methods Two gene expression profile chips (GSE28619 and GSE100901) were downloaded from the database of the public GeneChip Data Platform(Gene Expression Omnibus, GEO) of the National Center for Biotechnology Information (NCBI) in the United States. GEO2R was used to select differentially expressed genes (DEGs) in ALD group and control group. The enrichment analysis of gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) signaling pathways in DEGs was conducted. Furthermore, STRING database was applied to construct the interaction network of proteins, and key genes were screened by Cytoscape. ALD mice models were constructed and key genes were screened by RT-qPCR validation.Results A total of 173 DEGs were identified. GO showed that the biological functions of DEGs mainly involved in five KEGG pathways, including complement and coagulation cascade, cholesterol metabolism, retinol metabolism, drug metabolism-cytochrome P450, and bile secretion-related signaling pathways. Based on the results of protein-protein interaction network (PPI) and CytoHubba, 9 key genes, namely, SERPINC1, AHSG, FGG, FGA, ITIH3, FGB, APOB, ALB, and APOH, were screened out. RT-qPCR detection found that compared with WT mice, the mRNA expressions of ALB, APOB, and FGB in the liver of ALD mice upregulated (P<0.05), while the mRNA expressions of ITIH3, FGG, and SERPINC1 downregulated (P<0.05).Conclusion ALB, APOB, FGB, ITIH3, FGG and SERPINC1 are expected to be potential biomarkers for ALD.
【Key words】 bioinformatics; alcoholic liver disease(ALD); gene; biomarkers
酒精性肝病(alcoholic liver disease,ALD)俗稱酒精肝,是全球最普遍的肝病之一[1],根據(jù)世界衛(wèi)生組織的調(diào)查,2016年全球酒精導致3000萬人死亡,占全球死亡人數(shù)的5.3%,占全球疾病負擔的5.1%[2]。近年來,ALD導致的病死率有所增加。在美國,酒精已超過丙型肝炎病毒成為肝臟相關(guān)疾病死亡的主要病因,自2007年以來ALD年齡標準化病死率持續(xù)性增長,年增長率為3.1%[3]。酒精通過抑制線粒體β氧化和增加脂肪酸合成,導致甘油三酯、磷脂和膽固醇脂的積累,從而誘導脂肪在肝臟中沉積,形成酒精性脂肪性肝炎并伴有肝細胞損傷和氣球樣改變等病理特征[4],大量飲酒導致肝臟慢性炎癥和細胞外基質(zhì)的沉積和纖維化,而晚期纖維化可導致肝臟結(jié)構(gòu)紊亂和肝實質(zhì)纖維化,進展至肝硬化階段[5]。慢性的肝損傷、氧化應激炎癥、纖維化和酒精代謝物的致癌作用可能導致DNA突變,使疾病向肝細胞癌的方向發(fā)展[6-7]。目前ALD的診斷仍需通過活檢來進行,但由于其是一種侵入性的檢查手段,患者的接受程度普遍不高,迫切需要尋找ALD發(fā)展相關(guān)的生物標志物用于篩查和診斷。
通量技術(shù)在潛在生物標志物中應用廣泛[9],臨床生物信息學作為一種新興的研究方法,是疑難雜癥的診斷、治療和預后等方面很有前景的研究方法之一[10]。這些方法已廣泛應用于肝癌、胃癌等癌癥的檢查[11-13]。在一些非腫瘤疾病中,通過生物信息學分析也發(fā)現(xiàn)了許多有價值的新型生物標志物[14-16]。因此,本研究通過生物信息學初步探索ALD的生物標志物和分子機制,預測與ALD相關(guān)的潛在關(guān)鍵基因,并通過ALD小鼠模型,對其肝組織采用RT-qPCR進行關(guān)鍵基因驗證,為ALD新生標志物的發(fā)現(xiàn)和應用提供借鑒價值。
1 材料與方法
1.1 數(shù)據(jù)來源
從GEO數(shù)據(jù)庫(https://www.ncbi.nlm.nih.gov/geo/)中篩選出兩個mRNAs基因芯片數(shù)據(jù)集(GSE28619和GSE100901),篩選標準是兩個數(shù)據(jù)集共同差異基因較多。GSE28619數(shù)據(jù)庫芯片平臺是GPL570[HG-U133_Plus_2] Affymetrix Human Genome U133 Plus 2.0 Array;GSE100901數(shù)據(jù)庫芯片平臺是GPL13667[HG-U219]Affymetrix Human Genome U219 Array。
1.2 差異表達基因(differentially exprsssed gense,DEGs)篩選
利用GEO2R(http://www.ncbi.nlm.nih.gov/geo/geo2r)對ALD組和對照組的樣本進行DEGs分析統(tǒng)計,以P<0.05和|log2(FC)|>1.0為標準篩選出DEGs。用“ggplot2”R語言包可視化繪制火山圖,用 R包(ComplexHeatmap)可視化制成熱圖,用可視化軟件Funrich(http://funrich.org/)生成韋恩圖。
1.3 DEGs的基因本體論(gene ontology,GO)及京都基因和基因組百科全書(Kyoto encyclopedia of genes and genomes,KEGG)分析
通過在線數(shù)據(jù)庫DAVID(https://david.ncifcrf.gov/),分析GO功能富集數(shù)據(jù),分別通過生物過程(biological process,BP)、細胞成分 (cellular component,CC)、分子功能(molecularfunction,MF)對分析的基因進行注釋和分類。KEGG包含生物學功能、疾病、化學物質(zhì)、藥物和生物學通路等數(shù)據(jù)集。統(tǒng)計方法為EASE Score或Fisher Exact,GO和KEGG各項篩選條件為P<0.05[17]。根據(jù)分析結(jié)果用“ggplot2”R語言包繪制氣泡圖。
1.4 DEGs的PPI網(wǎng)絡構(gòu)建和關(guān)鍵基因篩選
STRING(https://string-db.org/)可用來呈現(xiàn)和評估PPI網(wǎng)絡[18]。將本研究篩選出的所有DEGs導入STRING,利用 STRING分析工具,進一步探尋DEGs之間潛在的聯(lián)系[19]。篩選條件設置為:置信度≥0.15,互作最大值為0。然后把STRING的計算結(jié)果導入 Cytoscape軟件[20],挖掘PPI網(wǎng)絡中連接最為緊密的集合[21],應用的是分子復合物檢測(molecular complex detection,MCODE)插件,參數(shù)設置為默認篩選參數(shù)。此外應用cytoHubba插件篩選出PPI網(wǎng)絡中前幾個關(guān)鍵位置的基因。
1.5 構(gòu)建ALD小鼠模型,通過RT-qPCR驗證篩選出關(guān)鍵基因
本研究采集了廣州疾病預防控制中心毒理科共包括3只ALD小鼠(喂常規(guī)飼料和10%酒精為唯一飲料,連續(xù)喂養(yǎng)30 d)和3只正常的WT小鼠(喂常規(guī)飼料和水)的肝組織,實驗動物使用許可證號為SYXK(粵)2018-0002。采集肝臟樣本后立即在液氮中冷凍,并根據(jù)既定方案提取RNA。根據(jù)說明書使用PrimeScript RT reagent Kit with gDNA Eraser(Takara)試劑盒進行互補DNA(cDNA)合成,擴增條件設置如下:95 ℃啟動10分鐘,進行40個循環(huán),95 ℃持續(xù)15秒,60 ℃持續(xù)30秒,以小鼠的β-actin作為內(nèi)參(參照基因),使用2-ΔΔCt計算。本研究中使用的引物序列見表1。
1.6 統(tǒng)計學方法
WT小鼠和ALD小鼠的肝組織9個關(guān)鍵基因mRNA的表達資料采用SPSS 25.0建立數(shù)據(jù)庫并進行統(tǒng)計分析。mRNA的表達水平用(±s)描述,兩組之間的比較采用獨立樣本t檢驗。同時利用GraphPad Prism 7軟件對WT小鼠和ALD小鼠的肝組織9個關(guān)鍵基因mRNA的表達進行作圖。檢驗水準:α=0.05,雙側(cè)檢驗。
2 結(jié) 果
2.1 DEGs篩選結(jié)果
從GEO數(shù)據(jù)庫中檢索出兩個數(shù)據(jù)集基因表達譜(GSE28619和GSE100901),包括健康對照樣本和ALD實驗樣本。GSE28619包含了3個健康對照樣本和3個ALD實驗樣本,與對照組相比,ALD組有911個上調(diào)基因,684 個下調(diào)基因(|log2(FC)|>1.0,P<0.05);GSE100901包含了8個健康對照樣本和8個ALD實驗樣本,與對照組相比,ALD組有2259個上調(diào)基因,2867個下調(diào)基因(|log2(FC)|>1.0,P<0.05),繪制可視化的火山圖和熱圖(圖1,圖2)。比較所有DEGs的基因表達譜,并繪制韋恩圖(圖3),共有173個基因為兩個數(shù)據(jù)集共有的DEGs。
2.2 DEGs的GO和KEGG分析結(jié)果
采用DAVID數(shù)據(jù)庫對總的DEGs進行GO和KEGG 信號通路富集分析,結(jié)果如圖4所示,GO功能包括BP、MF、CC,GO富集分析后發(fā)現(xiàn),DEGs主要定位在含膠原蛋白的細胞外基質(zhì)、血液微粒、血漿脂蛋白顆粒、脂蛋白顆粒、高密度脂蛋白顆粒成分;分子功能主要涉及糖胺聚糖結(jié)合、肝素結(jié)合、肽酶抑制劑活性、內(nèi)肽酶抑制劑活性、硫化合物結(jié)合;生物過程主要包含細胞外的結(jié)構(gòu)組織、急性炎癥反應、蛋白質(zhì)活化、羧酸生物合成過程、有機酸生物合成過程;KEGG分析顯示,DEGs主要與補體和凝血級聯(lián)、膽固醇代謝、視黃醇代謝、藥物代謝-細胞色素P450、膽汁分泌信號通路有關(guān)。
2.3 DEGs的PPI網(wǎng)絡分析結(jié)果和關(guān)鍵基因篩選
在STRING數(shù)據(jù)庫的基礎上,通過Cytoscape對DEGs進行PPI分析并進行可視化(圖5),根據(jù)Cytoscape產(chǎn)生的節(jié)點度評分,將SERPINC1、AHSG、FGG、FGA、ITIH3、FGB、APOB、ALB和APOH 前9個基因作為潛在的核心基因(圖6)。
2.4 RT-qPCR驗證WT小鼠和ALD小鼠的肝組織9個關(guān)鍵基因mRNA的表達情況
對WT小鼠和ALD小鼠肝臟的肝細胞進行RNA提取,并通過RT-qPCR檢測,結(jié)果顯示,ALD小鼠ALB、APOB和FGB的 mRNA表達均高于WT小鼠,差異均有統(tǒng)計學意義(P<0.05);ALD小鼠ITIH3、FGG和SERPINC1的mRNA表達均低于WT小鼠,差異均有統(tǒng)計學意義(P<0.05)(表2,圖7)。結(jié)果提示,與WT小鼠肝組織相比,ALB、APOB和FGB的mRNA在ALD小鼠肝組織表達上調(diào),與GEO數(shù)據(jù)庫中的測序結(jié)果差異表達趨勢一致,ITIH3、FGG和SERPINC1的mRNA在ALD小鼠肝組織表達下調(diào),與GEO數(shù)據(jù)庫中的測序結(jié)果差異表達趨勢一致。
3 討 論
ALD的發(fā)病機制是多因素的,包含環(huán)境、遺傳和生活習慣等[22]。在我們的研究中,總共鑒定出192個DEGs,GO功能分類結(jié)果表明,DEGs生物學功能主要涉及5個KEGG通路,包括補體和凝血級聯(lián)、膽固醇代謝、視黃醇代謝、藥物代謝-細胞色素P450、膽汁分泌相關(guān)信號通路,結(jié)合PPI和CytoHubba的結(jié)果,篩選出SERPINC1、AHSG、FGG、FGA、ITIH3、FGB、APOB、ALB和APOH 前9個關(guān)鍵基因,并且通過RT-qPCR檢測發(fā)現(xiàn),與正常鼠肝組織相比,ALB、APOB和FGB的mRNA在ALD組表達上調(diào),ITIH3、FGG和SERPINC1的mRNA在ALD組表達下調(diào)。
ALB、APOB、FGB、ITIH3、FGG和SERPINC1多在肝功能和免疫反應方面起作用。ALB的主要功能是調(diào)節(jié)血液的膠體滲透壓[23],作為血漿中鋅、鈣和鎂主要的轉(zhuǎn)運蛋白[24],當肝臟損傷、血液循環(huán)不暢和水腫時,ALB升高[25]。APOB是乳糜微粒(ApoB-48)、低密度脂蛋白(ApoB-100)和VLDL (ApoB-100)的主要蛋白質(zhì)成分[26],其作為一種識別信號,通過載脂蛋白b/E受體與細胞結(jié)合并內(nèi)化為LDL顆粒[27],可能對ALD脂肪變化進程有推進作用。纖維蛋白原β(FGB)被蛋白酶凝血酶切割產(chǎn)生單體,其與纖維蛋白原α(FGA)和纖維蛋白原γ(FGG)一起聚合形成不溶性纖維蛋白基質(zhì)[28],而纖維蛋白沉積也與感染有關(guān),它可以防止IFNG介導出血[29],還可以通過先天性和T細胞介導的途徑促進抗菌免疫反應[30],可能與ALD引起的肝臟炎癥有關(guān)。ITIH3作為血清中透明質(zhì)酸的載體,是透明質(zhì)酸與其他基質(zhì)蛋白(包括組織中細胞表面的細胞表面的蛋白質(zhì))之間的結(jié)合蛋白,可調(diào)節(jié)透明質(zhì)酸的定位、合成和降解,這對于經(jīng)歷生物過程的細胞至關(guān)重要[31],有止血、血小板活化的作用,可能與ALD引起肝功能改變有關(guān)[32]。FGG與FGA和FGB一起聚合形成不溶性纖維蛋白基質(zhì)[33],在止血中具有主要功能[34]。SERPINC1是血漿中最重要的絲氨酸蛋白酶抑制劑,可調(diào)節(jié)凝血級聯(lián)反應,在肝素存在下其抑制活性極大增強[35],可能與ALD引起肝功能改變有關(guān)。我們的研究結(jié)果將為下一步探索ALD潛在的生物標志物、疾病發(fā)生發(fā)展的病理生理機制和新治療的方案提供基礎和依據(jù)。
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(收稿日期:2023-03-15 修回日期:2023-04-06)
(編輯:黃研研)
基金項目:國家自然科學基金(81960595,81360438,81660549);廣西自然科學基金(2019JJD140011);2022年右江民族醫(yī)學院碩士研究生創(chuàng)新計劃項目(YXCXJH2022010)
作者簡介:王一涵,男,住院醫(yī)師,在讀碩士研究生,研究方向:分子毒理學。E-mail:452158749@qq.com
通信作者:龐雅琴。E-mail:pangyaqin@126.com