梁燕冰,覃月秋,廖品琥△
與疾病相關(guān)的EPCR基因多態(tài)性研究進(jìn)展
梁燕冰1,覃月秋2,廖品琥1△
內(nèi)皮細(xì)胞蛋白C受體(EPCR)是新發(fā)現(xiàn)的蛋白C抗凝系統(tǒng)中的重要一員,在抗凝、抗炎過程中發(fā)揮作用。由于EPCR單核苷酸多態(tài)性(SNP)的存在,引起可溶性內(nèi)皮細(xì)胞蛋白C受體(sEPCR)表達(dá)水平的改變,影響多種疾病的易感性。本文就EPCR基因多態(tài)性與血栓性疾病、瘧疾、膿毒癥及其他疾病的關(guān)系進(jìn)行綜述。
瘧疾;膿毒癥;腫瘤;內(nèi)皮細(xì)胞蛋白C受體;多態(tài)性,單核苷酸;血栓性疾??;綜述
內(nèi)皮細(xì)胞蛋白C受體(endothelial protein C receptor,EPCR)是蛋白C系統(tǒng)中蛋白C(protein C,PC)及活化蛋白C(actived protein C,APC)的受體,通過PC途徑發(fā)揮細(xì)胞保護(hù)、抗炎、抗凝等作用。PC在凝血酶-血栓調(diào)節(jié)蛋白復(fù)合物存在的條件下,在血管內(nèi)皮細(xì)胞表面被激活形成APC,APC則抑制活化的凝血因子Ⅴ和Ⅷ(FⅤa和FⅧa),從而下調(diào)凝血酶的生成。正常情況下,APC的生成與EPCR、凝血酶、血栓調(diào)節(jié)蛋白、PC等密切相關(guān)。任一環(huán)節(jié)的改變均會引起APC的生成增加或減少,從而引發(fā)各種疾病。隨著人類全基因組計劃的完成,學(xué)者們逐漸認(rèn)識到單核苷酸多態(tài)性(SNP)對疾病的表型、易感性以及藥物敏感性等的重要影響。近年研究發(fā)現(xiàn),EPCR基因多態(tài)性與血栓性疾病、瘧疾、膿毒癥、腫瘤、不良妊娠等有關(guān)。深入研究EPCR基因多態(tài)性將有助于篩查疾病易感的患者,從而實施真正意義上的“個體化”治療。本文簡述了EPCR基因多態(tài)性與多種疾病的關(guān)系,為從遺傳學(xué)方面探討疾病的發(fā)生、發(fā)展提供理論基礎(chǔ)。
1.1 EPCR基因(PROCR)EPCR位于20號染色體q11.2,全長約8 kb,包含4個外顯子和3個內(nèi)含子[1]。外顯子1編碼5′-非編碼區(qū)(UTR)和信號肽,外顯子2和3編碼大部分的細(xì)胞外結(jié)構(gòu)域,外顯子4則編碼蛋白質(zhì)其余部分和3′-UTR[2]。目前已有多項關(guān)于EPCR基因變異從而影響EPCR分子表達(dá)及功能的研究,這些基因改變主要包括外顯子3(6367位點)23 bp嵌入[3],內(nèi)含子2 6333C/T的多態(tài)性,5′-UTR 1651C/G的多態(tài)性[4],外顯子4 6936A/G的多態(tài)性(內(nèi)皮細(xì)胞受體跨膜區(qū)域Ser219Gly的轉(zhuǎn)變)[5]等?;谶@些發(fā)現(xiàn),人類EPCR基因型可分為4種,即H1、H2、H3和極其罕見的H4,其中H1、H3、H4包含1個或多個特殊單體型單核苷酸多態(tài)性(htSNPs),H2則包含所有SNPs常見的等位基因[6-7]。
1.2 EPCR蛋白由PROCR編碼的EPCR蛋白與CD1/主要組織相容性復(fù)合物(MHC)Ⅰ蛋白家族受體具有同源性[2],EPCR對PC/APC具有高親和力,參與PC的活化,并通過谷氨酸(Glutamic acid,GLA)結(jié)構(gòu)域與APC結(jié)合,促發(fā)細(xì)胞內(nèi)抗炎和細(xì)胞信號的傳導(dǎo)[8-10]。在金屬蛋白酶的作用下,EPCR從內(nèi)皮細(xì)胞表面脫落,形成可溶性EPCR(sEPCR),脫落后形成的sEPCR仍保持與PC/APC相結(jié)合的能力,但與膜型EPCR(mEPCR)作用相反,sEPCR則抑制APC的作用[11]。
研究表明,EPCR基因多態(tài)性與血栓形成有關(guān),EPCR基因變異使PC與EPCR之間的相互作用發(fā)生改變,從而增加或降低靜脈血栓形成的風(fēng)險[12]。一項對下肢靜脈血栓患者的研究發(fā)現(xiàn),EPCR rs86718的基因多態(tài)性與下肢靜脈血栓風(fēng)險相關(guān)[13]。EPCR rs867186 A/G(H3基因型)位點AG、GG基因型和G等位基因攜帶者可通過升高血漿sEPCR水平,進(jìn)而增加靜脈血栓栓塞癥(VTE)發(fā)病風(fēng)險;而rs9574 C/G(H1基因型)位點CC基因型及C等位基因卻是VTE的保護(hù)因素,并不影響血漿sEPCR水平[14-15]。在人臍靜脈內(nèi)皮細(xì)胞,H1基因型能提高mEPCR水平,促進(jìn)PC的活化,但對EPCR mRNA的表達(dá)水平?jīng)]有影響;H3基因型能降低mEPCR水平,降低PC活化率,并增加培養(yǎng)基中sEPCR的水平[16]。在兒童卒中風(fēng)險的研究中也發(fā)現(xiàn),無論患兒攜帶的是純合子或是雜合子型的EPCR H3單倍體(rs2069940C/G),他們的sEPCR水平均大于100 ng/mL,說明了H3單倍體與sEPCR水平具有強(qiáng)相關(guān)性,并可以增加兒童卒中的風(fēng)險[17],與Pintao等[18]研究結(jié)果一致,其他的研究也表明了EPCR基因多態(tài)性與血栓形成的易感性有關(guān)[14,19-20]。但也有學(xué)者認(rèn)為sEPCR的水平和(或)EPCR基因多態(tài)性與VTE易感性無關(guān)[21-22]。
EPCR的表達(dá)及其功能的改變,可能影響瘧疾的表型及發(fā)病易感性[23]。微脈管系統(tǒng)的EPCR可以隔離被惡性瘧原蟲感染了的紅細(xì)胞,腦內(nèi)皮細(xì)胞EPCR表達(dá)減少可以導(dǎo)致腦型瘧疾微血管血栓形成[24-25]。相對于其他表型的重癥瘧疾,非洲貝寧地區(qū)的腦型瘧疾患兒sEPCR水平較高[26];而馬拉維地區(qū)的腦型瘧疾患兒sEPCR水平較低[24];但坦桑尼亞及加納的重癥瘧疾患兒sEPCR水平與重癥瘧疾無關(guān)[27-28]。不同地區(qū)EPCR基因變異對瘧疾發(fā)生、發(fā)展的影響不同。來自泰國的一項研究結(jié)果認(rèn)為EPCR rs867186-GG基因型是重癥瘧疾的保護(hù)因素[29],然而坦桑尼亞地區(qū)研究發(fā)現(xiàn)EPCR rs867186 A/G和rs2069948 C/T位點雖然可以引起血漿sEPCR水平升高,但不影響瘧疾發(fā)病的易感性[27],與加納地區(qū)的研究結(jié)果一致[28]。
研究發(fā)現(xiàn),多種炎癥因子如白細(xì)胞介素(IL)-6[30]、IL-8[31]、IL-10[32]等的基因多態(tài)性在不同地區(qū)、種族間的分布頻率存在差異。膿毒癥的臨床治療效果個體差異性較大,可能與遺傳因素有關(guān)。研究表明基因多態(tài)性影響著膿毒癥的發(fā)生發(fā)展過程,如TLR4基因rs11536889位點和CD14基因rs2563298位點均可增加膿毒癥發(fā)病的易感性[33];膿毒癥患者常合并凝血功能紊亂,PC血清水平顯著降低,使用重組人APC(rhAPC)治療后,患者的預(yù)后得到明顯改善[9]。一項膿毒癥動物模型的研究發(fā)現(xiàn),降低EPCR表達(dá)或阻斷APC與EPCR的結(jié)合可以導(dǎo)致宿主對脂多糖(LPS)的炎癥反應(yīng)過度,導(dǎo)致動物的死亡率增加[34],提示EPCR通過調(diào)節(jié)APC及其下游細(xì)胞產(chǎn)生細(xì)胞保護(hù)和抗凝血作用,參與了嚴(yán)重膿毒癥和膿毒癥休克(SS/SS)的發(fā)展[35]。已有研究表明SS/SS患者EPCR基因rs867186 A/G、rs2069940 C/G、rs2069952 C/T位點的多態(tài)性與膿毒癥相關(guān),同時攜帶H1和H3的等位基因可能降低危重患者發(fā)生SS/SS的風(fēng)險[36]。EPCR基因多態(tài)性可影響兒童膿毒癥的發(fā)展過程[37-38]。然而國內(nèi)關(guān)于EPCR基因多態(tài)性與膿毒癥關(guān)系的研究鮮有報道。從分子水平深入探討膿毒癥的發(fā)病機(jī)制,將有助于對疾病的早發(fā)現(xiàn)和早治療。
惡性血液病患者血漿sEPCR水平與血栓形成有關(guān)[39]。EPCR rs867186 A/G基因型可作為急性髓性白血病患者發(fā)生血栓形成的風(fēng)險基因型[5]。EPCR rs2069948位點基因多態(tài)性增加了乳腺癌發(fā)病的易感性[40]。而特定的EPCR基因變異可增加孕期深部靜脈血栓的風(fēng)險或通過改變sEPCR的水平導(dǎo)致不良妊娠結(jié)局[3-4,41]。攜帶EPCR rs867186 A/G變異的腦梗死患者,其血栓形成的風(fēng)險增高[42]。肺癌患者血漿sEPCR水平升高和(或)rs867186 A/G基因型變異與腫瘤并發(fā)血栓事件之間可能相關(guān)[43]。但也有研究發(fā)現(xiàn)冠心病患者循環(huán)sEPCR水平、rs867186 A/G變異均與心血管事件發(fā)生易感性無關(guān)[44]。
EPCR基因多態(tài)性與部分疾病的易感性有關(guān),參與了血栓性疾病、瘧疾、膿毒癥、腫瘤、不良妊娠結(jié)局等疾病的發(fā)生發(fā)展。
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(2016-08-25收稿2016-09-20修回)
(本文編輯李鵬)
Research progress in the disease-related EPCR gene polymorphisms
LIANG Yanbing1,QIN Yueqiu2,LIAO Pinhu1△
1 Department of Critical Medicine,2 Department of Gastroenterology,Affiliated Hospital of Youjiang Medical College for Nationalities,Baise 533000,China△RevisorE-mail:liaopinhu@163.com
As an important part of the protein C anticoagulant system,endothelial protein C receptor(EPCR)plays a critical role in the process of anti-coagulation and anti-inflammation.The presence of EPCR single nucleotide polymorphism(SNP)affects the levels of soluble endothelial protein C receptor(sEPCR),and susceptibility to varieties of diseases.This article reviews the relationship between EPCR gene polymorphisms and thrombotic diseases,malaria,sepsis and other diseases.
malaria;sepsis;neoplasms;endothelial protein C receptor;polymorphism,single nucleotide;thrombotic disease;review
R446
A
10.11958/20160849
國家自然科學(xué)基金資助項目(81560321);2014年廣西醫(yī)學(xué)高層次骨干人才培養(yǎng)“139”計劃培養(yǎng)人選項目;廣西高校急重癥分子免疫研究重點實驗室項目(yy2015ky002);廣西研究生教育創(chuàng)新計劃項目(YCSZ2015222)
1右江民族醫(yī)學(xué)院附屬醫(yī)院重癥醫(yī)學(xué)科(郵編533000),2消化內(nèi)科
梁燕冰(1993),女,研究生在讀,主要從事膿毒癥基因?qū)W機(jī)制的研究
△審校者E-mail:liaopinhu@163.com