Research Progress of Non-coding RNAs Related to the Pathogenesis of Diabetic Retinopathy
LUO Wenjuan,YU Maixia,DONG Wenping (DepartmentofOphthalmology,the Second HospitalofLanzhou University/the Second Clinical Medical College, Lanzhou University,Lanzhou 73oo3o,Gansu,China)
Abstract:DiabeiciotisrogesiebingisesusdyoalglucoeeabisIentslf studieshavesowtatoodingRNAs(RAs)uchasiRNA,RNA,andRNAareloselyelatedtotepathogensisofDsuch oxidativestressdlabaiidadadasdaetcestvta of ncRNA expression disorders and DR,and proposes future prospects in this field.
Keywords:Diabetic retinopathy; Oxidative stress;ncRNAs;Biomarkers; Theranostic targets
近年來,糖尿病(diabetesmellitus,DM)發病率逐年增加,預計2045年全球糖尿病患者將增加到大約8億[1。糖尿病可導致許多嚴重的眼部并發癥,包括糖尿病性視網膜病變(diabetic retinopathy,DR)、新生血管性青光眼(neovascularglaucoma,NVG),以及白內障等。其中,DR是最主要的微血管并發癥,也是患者致盲的重要原因2。到2045年,預計全球DM并發DR患者人數將增加至約1.6億[3]。導致DR進展的因素包括高血壓、肥胖、高脂血癥及貧血等[4-6。DR是一種高度特異性的神經血管并發癥,根據病理進展可分為非增殖性視網膜病變(non-proliferative retinopathy,NPDR)和以視力喪失為特征的增殖性視網膜病變(prolifera tiveretinopathy,PDR)[7,8]。既往研究表明[9],DR與睡眠呼吸暫停、染色質內組蛋白的翻譯后修正、DNA甲基化及非編碼RNA(non-codingRNAs,ncRNA)等分子機制顯著相關。ncRNA包括微小RNA(mi-croRNA,miRNAs)、長鏈非編碼RNA(Longnon-codingRNA,lncRNA)和環狀RNA(circRNA),可通過充當miRNA海綿支架、結合RNA結合蛋白(RNA-bindingproteins,RBP)等方式調節靶基因表達[]。ncRNA表達失調可引起視網膜細胞損傷、血管生成、氧化應激、白細胞停滯與神經變性等[]。ncRNA可在DR的早期診斷和監測中作為特異性生物標志物[]。ncRNA在DR的病理進展、臨床預后和診斷中發揮著重要作用,本文將對ncRNA表達失調與DR發生的相關研究進行綜述。
1miRNA
miRNA是20\~25個核苷酸長的ncRNA家族成員。miRNAs通過與靶mRNA的
-UTR不完全結合調控靶基因蛋白表達,參與細胞增殖、分化等許多重要的生物過程2。miRNA在體液中具有一定的穩定性、有效回收,以及定量檢測的能力,可作為DR特異性生物標志物,并有助于早期檢測疾病。例如,5種miRNA (hsa-miR-195-5p、hsa-miR-20a-5p、hsa-miR-20b-5p、hsa-miR-27b-3p和hsa-miR-451a)已被驗證可作為區分DR患者分期的生物標志物[13。除此以外,特定的miRNA,如miR-93是DR的潛在生物標志物,可以診斷與預測DR,并監測其進展[14]。

既往大量研究表明,miRNA是DR發病機制中的重要直接調控因子。miRNAs如 l e t- 7 a- 5 p 和miR-211的上調與視網膜微血管內皮細胞增殖增加和下游靶基因沉默調節蛋白1(Sirtuin1,SIRT1)表達抑制相關[15]。此外,DR介導的視網膜微血管內皮細胞中miR-21水平增加,并可能通過靶向磷酸酶張力蛋白同源物(Phosphataseand Tensin Ho-molog,PTEN)激活AKT/ERK1/2信號通路,從而增強
和VEGF表達誘導血管生成。WangY等研究表明,
可能在DR的新生血管形成中發揮關鍵作用。PPARα是
的下游靶點,其過表達挽救了 m i R - 4 0 9 - 5 p 過表達對視網膜微血管內皮細胞增殖、遷移和管形成的促進作用。血管增殖期DR 患者玻璃體液中 m i R - 4 0 9 - 5 p 的表達高于對照組。因此,靶向新血管形成相關的關鍵miRNA可能有效改善DR的血管異常表現。
此外,DR中miRNA表達還可調控氧化應激信號通路。miRNA在DR病變中可調節多種氧化應激相關基因轉錄本的表達。值得注意的是,miRNA-145過表達可降低活性氧(reactive oxygen species,ROS)和丙二醛(malondialdehyde,MDA)水平,增加超氧化物歧化酶活性,并降低高血糖誘導的氧化應激和視網膜內皮細胞凋亡[18]。miR-27b通過下調PI3K/AKT/mTOR通路抑制視網膜色素上皮細胞中ROS產生[19]。另一方面,miR-183激活視網膜色素上皮細胞中PI3K/Akt/VEGF信號通路并增加CD34、一氧化氮合酶(nitric oxide synthase,NOS)和
。未來,通過進一步挖掘DR標志物、開發靶向介導血管異常與氧化應激的miRNA藥物將大大提升DR的臨床診療水平。
2 IncRNA
lncRNA是長度超過200個核苷酸的ncRNA,不具有顯著的蛋白質編碼能力,是ncRNA的重要組成部分。lncRNA可通過不同的分子機制參與包括DM和DR在內的多疾病中的生物學過程,如轉錄后基因調控和表觀遺傳基因沉默[]。lncRNA可以以順式和反式調節方式與靶基因的mRNA形成調控網絡。細胞核內的lncRNA主要在轉錄調控中發揮作用,而胞質lncRNA的關鍵作用之一是作為miR-NA海綿支架發揮作用。lncRNA還可以作為競爭性內源性RNA(competing endogenous RNAs,ceRNA)螯合miRNA調節mRNA表達[]。
X非活性特異性轉錄物(Xinactive specifictranscript,XIST)是一種被廣泛研究的lncRNA,其在從糖尿病小鼠模型和人Muller視網膜細胞系中顯著下調。XIST可作為miRNA的海綿支架發揮功能,其過表達導致miR-21-5p下調。XIST的過表達對細胞凋亡和遷移具有保護作用,還減少了促炎細胞因子的產生[21]。WangL等[22證明,與非DR患者和對照組相比,DR患者的血漿樣本顯示心肌梗死相關轉錄物(myocardial infarction associated transcript,MIAT)過表達。此外,在高糖誘導的動物糖尿病視網膜和內皮細胞中顯示MIAT上調,并參與病理性血管生成。敲低視網膜非編碼RNA3(retinal non-codingRNA3,RNCR3)可減輕視網膜微血管滲漏并抑制高葡萄糖(highglucose,HG)應激下視網膜內皮RF/6A細胞的遷移和管形成。因此,抑制RNCR3可能也是預防DR相關視網膜異常的潛在靶點[23]。此外,另一項研究表明[24],敲低RNCR3顯著抑制視網膜反應性神經膠質增生。抑制RNCR3還可降低細胞因子IL-9、IL-13、IL-17、MCP-1、VEGF和TNF- σ? α?α?α?α 的釋放。此外,玻璃體內給予RNCR3shRNA可抑制神經膠質細胞增殖活性。敲低RNCR3還可減少視網膜細胞凋亡,防止HG誘導的視網膜神經變性[24。總體而言,RNCR3在DR的保護機制中發揮關鍵作用,并可以作為重要的治療靶點[24]。INK4基因座中的反義非編碼RNA(anti-sense non-coding RNA intheINK4locus,ANRIL)表達失調也已被確定為糖尿病視網膜病變發病機制中的關鍵機制[25]。ChenS等[26]的研究顯示,沉默人視網膜內皮細胞(humanretinalendothelialcells,HREC)的ANRIL可抑制VEGF在mRNA和蛋白質水平的表達,從而抑制細胞增殖和管形成。此外,ToraihEA等2的研究觀察到,與無DR 患者和健康受試者相比,T2DM伴DR患者的血清中ANRIL也顯著上調。
缺氧是糖尿病靶器官受損的一種重要機制,轉移相關肺腺癌轉錄本1(metastasis-associated lungadenocarcinomatranscript1,MALAT1)是另一種在DR中被廣泛研究的lncRNA。研究表明,MALAT1表達失調在DR病變機制中起關鍵作用。缺氧可上調缺氧誘導因子-1
(hypoxia-inducible factor- ? ? l α ,HIF-1 α )的活性進而誘導MALAT1啟動子的反式激活[28]。MALAT1可以通過激活環磷酸腺苷(cyclicadenosinemonophosphate,cAMP)-反應元件結合蛋白(responseelementbindingprotein,CREB)和p38MAPK信號通路引起神經細胞變性2。不僅如此,MALAT1過表達可使微血管生長失調,干擾視網膜內皮細胞增殖、遷移和管形成等功能3RadhakrishnanR等3發現,在人視網膜內皮細胞(humanendothelialcellsof theretina,HREC)中MALAT1下調可激活氧化應激傳感器KEAP1,促進NRF2降解增強抗氧化相關基因轉錄。
SOX2重疊轉錄物(SOX2 overlapping transcriptSOX20T)在人類大腦中高度表達并參與視網膜神經功能的調節,在視網膜神經變性過程也發揮著重要作用[32]。既往研究表明[33],在糖尿病小鼠的視網膜細胞、高糖或氧化應激誘導的視網膜神經節細胞(retinal ganglioncells,RGCs)中,SOX2OT的表達降低并且抑制NRF2/HO-1信號通路活性,抑制視網膜神經變性中的抗氧化和神經保護相關機制。與miRNA一樣,lncRNA也可作為DR特異性生物標志物。血液中高水平ENST00000505731和NR-126161lncRNA對DR也具有一定診斷價值[34]。然而,該研究受到樣本量的限制,需要更大規模的前瞻性研究進行驗證。
3circRNA
circRNA是一種通過反向剪接產生的獨特RNA分子,其通過連接
和
末端的共價鍵構成閉環結構[35。由于其環狀結構帶來的高度穩定性,可抵抗核酸外切酶RNaseR的降解。circRNA具有組織特異性和復雜的調節模式,可通過充當miRNA海綿支架調節靶基因表達,還可與RNA結合蛋白(RNA-bindingproteins,RBP)結合調節翻譯[3。此外,cir-cRNA可以編碼小的蛋白質和肽并執行獨立的生物學功能。circRNA的具體分子機制取決于細胞類型或各種病理條件,并且在外周血、良性及病理組織中都可檢測到其高豐度,這使其成為良好的潛在生物標志物。因此,circRNA已成為DR在RNA領域的新穎研究熱點[10]。
ZhangSJ等發現,來自HAS2基因座的cir-cRNA-circ_0005015在DR患者的視網膜、玻璃體、外周血和視網膜前纖維血管膜(preretinalfibrovas-cularmembranes,FVM)中顯著上調。circ_Oo05015可通過充當miRNA海綿支架來損傷視網膜內皮細胞穩定性,并在DR的進展中發揮重要作用。cir-cRNA同源結構域相互作用蛋白激酶3(home-odomain-interacting protein kinase 3,circHIPK3)和circRNA 鋅指蛋白(zinc fingerprotein,ZNF)也發揮類似作用[38.39]。CircZNF532作為
海綿支架調節,上調NG2、LOXL2和CDK2蛋白的表達。維持血管穩定性并降低了視網膜周細胞變性和血管功能障礙[40]。與之相反,WangT等4揭示了circZNF532可作為miR-1243和精氨酸甲基轉移酶1(argi-ninemethyltransferase1,CARM1)的海綿支架促進了高糖誘導的人視網膜微血管內皮細胞(high-glu-cose-concentration-induced human retinal microvas一cularendothelialcell,hRMEC)功能障礙。缺氧誘導周細胞核中高度表達的circRNA常染色質組蛋白賴氨酸甲基轉移酶1(euchromatic histone lysinemethyltransferase1,circEhmt1)可調節另一個cir-cRNA的PWWP結構域(circPWWP2A),上調血管生成素-1/沉默調節蛋白1(sirtuin1,SIRT1)促進DR進展42]。總之,ncRNA通過調節視網膜細胞損傷、脈絡膜血管穩定性、神經變性和抗氧化防御等機制參與調控DR的疾病進展。
4展望
miRNAs、lncRNAs和circRNAs的作用在DR進展中的機制尚未完全了解。研究人員目前主要使用內皮細胞、神經膠質細胞或視網膜色素上皮細胞作為研究對象。這也是由于視覺細胞、雙極細胞和網狀細胞等研究材料較難獲得[43]。此外,將實驗研究中檢測到的ncRNA應用于臨床實踐并不容易,即便僅作為診斷生物標志物仍然需要許多研究。這需要在大樣本患者中進行獨立的表達分析,同時考慮年齡、種族、生活方式和整體健康狀況等因素。未來還需要進一步研究ncRNA分泌到細胞外及其從胞外攝取的直接和間接分子機制。在方法學方面,應進一步改進和標準化ncRNA的提取、定量、分析方法。在未來,ncRNA可能會被納入DM及其并發癥(包括DR)的早期和精確診斷中,這將有利于臨床醫生及早干預DR[43]。除此以外,基于ncRNA開發靶向藥物也可能比傳統治療藥物更有效。針對ncRNA介導的過度細胞增殖和凋亡、炎癥反應和氧化應激的聯合治療策略也可顯著提升DR的治療水平。
5總結
ncRNA表達異常可促進DR進展,其中包括神經元和周細胞受損、視網膜微血管異常等。一些ncRNA可以作為DR診斷的潛在生物標志物,還可作為DR進展的重要調控因子。了解這些機制對于設計有效的預防或減緩DR進展的治療方式至關重要。因此,未來需要開展更多的ncRNA(miRNA、lncRNA、circRNA)參與DR進展的相關機制研究。進一步探索DR相關非侵入性的診斷和預后ncR-NA,以及探索ncRNA在1型或2型糖尿病中DR發展的不同機制。
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收稿日期:2024-06-29;修回日期:2024-07-16編輯/肖婷婷