Advance Publication Journal of Atherosclerosis and Thrombosis Vol. 23, No. ● Journal of Atherosclerosis and Thrombosis 1 Review Accepted for publication: November 4, 2015 Published online: December 22, 2015 Long Noncoding RNAs in Atherosclerosis Liguo Jian 1, Dongdong Jian 2, Qishan Chen 2 and Li Zhang 2 Liguo Jian and Dongdong Jian contributed equally to this work. 1 2
Department of Cardiology, The Second Affiliated Hospital of Zhengzhou University, Henan, PR China. Department of Cardiology, the First Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang, PR China
Long noncoding RNAs (lncRNAs) were a group of non-protein-coding RNAs ＞ 200 nucleotides and participated in biological processes and pathophysiological conditions in vivo or in vitro. Recently, more and more lncRNAs interfering with the progress of atherosclerosis were identified and characterized in the atherogenic cells such as vascular smooth muscle cells (VSMCs), endothelial cells (ECs), and monocytes/macrophages showing that lncRNAs play an important role in the occurrence of atherosclerosis. In this review, we summarized and highlighted the lncRNAs that play a role in the process of atherosclerosis. This study may provide helpful insights regarding further study of lncRNAs associated with atherosclerosis. J Atheroscler Thromb, 2016; 23: 000-000. Key words: Long noncoding RNA, VSMCs, ECs, Monocyte/macrophages, Atherosclerosis
Introduction Cardiovascular disease (CVD) is the most important cause of mortality worldwide, and its underlying reason was atherosclerosis 1). In contrast to the small number of coding transcripts ( ＜ 3%) of the total genome, the majority of noncoding transcripts (＞ 80%) has been previously described as “junk” transcripts or transcriptional noise 2, 3). Because the first lncRNA X inactive specific transcript (XIST) was initially discovered in the 1990s 4, 5), several lncRNAs that play vital roles in cancer progression and metastasis, cell proliferation, and apoptosis were identified by a growing number of studies 6-8). Therefore, identifying the correlation between lncRNAs and atherosclerosis may help us better understand the pathogenesis of atherosclerosis and find new treatment for patients with CVD. This study will introduce lncRNAs and summarize the current understanding of lncRNAs in the process of atherosclerosis. Address for correspondence: Li Zhang, Department of Cardiology, the First Affiliated Hospital, School of Medicine, Zhejiang University, 79 Qingchun Road, Hangzhou, Zhejiang, 310003, PR China E-mail: [email protected] Received: September 18, 2015 Accepted for publication: November 4, 2015
Definition, Classification, and Functional Mechanisms of lncRNAs LncRNAs are broadly classified as transcripts nt with limited coding potential 9). RNA polymerase II processing, 5´ cap, and 3´ polyadenylation are common features of lncRNAs like protein-coding RNAs. However, they lack distinct open reading frames and are generally expressed at much lower levels in contrast to mRNAs 10-12). Recently, because of the high-throughput sequencing technologies, lncRNAs have been identified and found to be important regulators of gene transcription in cancers and other diseases including vascular disease 2, 13). There are 145331 and 74963 lncRNA genes for humans and mice, respectively, as shown in NONCODE database (version4.0; http:// www.noncode.org). However, whether all these lncRNAs have biological functions was unclear because only few of them have been characterized to date. Corresponding to their association with nearby mRNAs, the generally accepted categorization of lncRNAs was divided into five groups (Fig. 1): (a) Sense: the transcription product of protein-coding genes after splicing (from the same mRNA chain); (b) Antisense: produced by the complementary strand of protein-coding genes (from the opposite mRNA
＞ 200
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Advance Publication Jian et al . Journal of Atherosclerosis and Thrombosis Accepted for publication: November 4, 2015 Published online: December 22, 2015
Fig. 1. The classification of lncRNAs. Yellow indicates mRNA coding genes and gray indicates the noncoding genes.
chain); (c) Intronic: stemming from the introns of the protein-coding genes; (d) Intergenic: located between two protein-coding genes [termed long intergenic noncoding RNAs (lincRNAs)]; and (e) Bidirectional: produced by the upstream sequence and the opposite direction of protein-coding genes 3, 14). Although the study of functional mechanisms of lncRNAs is yet in the infancy stage, in terms of our current understanding, the mechanism of lncRNAs can be briefly divided into the following categories. Epigenetic Regulation Epigenetics, which mostly consists of changes in histone post-translational modifications and chromatin structure, refers to the heritable changes in gene phenotypes without the DNA sequence changes 15-17). LncRNAs can regulate the gene expression at the epigenetic level. Researches demonstrate that lncRNA can combine with chromatin remodeling complexes resulting in a specific mode of histone modification, activating or inhibiting transcription; therefore, lncRNA play a key role in genomic imprinting and dosage compensation effect 18-21). For example, XIST is a well-known lncRNA which plays an important role in the X chromosome inactivation in female mammals 22). The 5´ end of XIST has a repeated motif known as “repeat A” which can directly bond to EZH2, the catalytic subunit of Polycomb repressive
complex 2 (PRC2). Then, PRC2 catalyzed repressive epigenetic modifications such as trimethylation of histone H3 lysine 27 (H3K27me3), which cause transcriptional silencing of the X chromosome 23-25). Mohammad et al 26) found that Kcnq1ot1 ncRNA was required for the maintenance of the ubiquitously imprinted gene (UIG) silencing and was involved in directing and maintaining the CpG methylation at somatic differentially methylated regions. Transcriptional Regulation LncRNAs can regulate gene transcription by regulating the activity of transcriptional factors, interfering with the adjacent gene expression, blocking the promoter regions, and regulating the combination with proteins. Berghoff and his colleagues 27) found that lncRNA-Evf2 could repress Dlx5/6 gene expression by regulating Dlx5/6 enhancer site-specific methylation. Martens et al 28) found that lncRNA-SRG1 transcript across the SER3 promoter interferes with the binding of activators, thus regulating SER3 repression. Martianov et al 29) demonstrated that noncoding RNA could directly interact with the general transcription factor IIB and format a stable complex, which could dissociate the preinitiation complex and major promoter, thus decreasing dihydrofolate reductase gene expression. Wang et al 30) found that ncRNA CCND1 could recruit an RNA-binding protein
Advance Publication LncRNAs in Atherosclerosis Journal of Atherosclerosis and Thrombosis 3 Accepted for publication: November 4, 2015 Published online: December 22, 2015
Fig. 2. The brief expression and functions of lncRNAs in pro-atherogenic cells.
TLS to the CCND1 promoter causing gene-specific repression of CCND1. Post-Transcriptional Regulation LncRNAs can regulate the alternative splicing, degradation, and stability of mRNA. Lin et al 31) found that perturbation of lncRNA ΣRNA (human MALAT1) altered splicing activity of genes that encode the RNA-binding proteins serine/arginine rich (SR) proteins and heterogeneous nuclear ribonucleoproteins (hnRNPs), which themselves participate in RNA processing. Souquere et al 32, 33) found that lncRNA-NEAT1 transcripts could constrain the geometry of paraspeckle bodies (PSPs), which prompt nuclear retention of mRNAs with A-I edition at the 3´ end noncoding regions, preventing mRNA translation into protein. Kretz 34) demonstrates that the lncRNA-terminal differentiation-induced ncRNA (TINCR could directly bind to mRNAs through a 25 nucleotide “TINCR box” motif, thus regulating the stability of target mRNAs. Molecular Sponges LncRNAs can act as endogenous decoys for miRNAs. For example, miR-135 and miR-133 could tar-
get MEF2C and MAML1, respectively, to regulate myoblast differentiation. A long intergenic noncoding RNA linc-MD1 has two miRNA bonding sites, which can sponge miR-135 and miR-133 y, thus regulating the expression levels of MEF2C and MAML1 2, 35). Long Noncoding RNAs in Atherogenic Cells Vascular smooth muscle cells (VSMCs), endothelial cells (ECs), and macrophages are the primary cells that contribute to atherosclerotic lesion formation 36-38). Therefore, we will elaborate lncRNAs associated with these three cell lines that may play a role in the process of atherosclerosis (Fig. 2). Moreover, we summarized the verified species and conditions of the known pro-atherogenic lncRNAs (Table 1). Long Noncoding RNAs in Vascular Physiological or Pathological Processes Recently, several studies demonstrated that the chromosome 9p21 (Chr9p21) locus is the strongest genetic risk factor for coronary artery disease 39, 40). This region is adjacent to INK4 locus that encodes a lncRNA termed ANRIL (also termed CDKN2B-AS). ANRIL expression was observed in several atherogenic
Advance Publication Jian et al . Journal of Atherosclerosis and Thrombosis Accepted for publication: November 4, 2015 Published online: December 22, 2015
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Table 1. The verified species of pro-atherogenic lncRNAs LncRNA
Species
Verified
MIAT MALAT1 ANRIL lincRNA-p21 lnc-Ang362 SENCR lnc-MC lincRNA-Cox2 lincRNA-DYNLRB2-2 APOA1-AS H19 HIF1A-AS1
Human/Mouse/Rat Human/Mouse Human Human/Mouse Rat Human Human Mouse Mouse Human/Monkey Human/Mouse Human
in vitro/in vivo in vitro/in vivo in vitro/in vivo in vitro/in vivo in vitro in vitro in vitro in vitro in vitro/in vivo in vitro/in vivo in vitro in vitro
cells and tissues such as SMCs, ECs, monocytederived macrophages, and RNA samples extracted from carotid and arterectomy 41). Moreover, the severity of atherosclerosis with ANRIL expression has been described 39, 42). Yap et al found that knockdown of ANRIL was associated with increased cyclin-dependent kinase inhibitors 2A (CDKN2A) expression and decreased H3K27me3 43). However, Kotake et al showed that ANRIL knockdown by shRNA resulted in increased CDKN2B expression by disturbing SUZ12 binding to the Chr9p21 locus 44). There are conflicts regarding CDKN2A or CDKN2B expression mediated by ANRIL knockdown, the significant decrease of cell proliferation, which play a key role in atherogenesis were observed 43-45). Moreover, Holdt et al found that Alu motifs are essential for the pro-atherogenic functions of ANRIL. ANRIL regulates target genes through the Alu motifs located in ANRIL and the promoters of target-genes resulting in increased cell proliferation, cell adhesion, and decreased apoptosis, which all play critical roles in the process of atherosclerosis 41). Differential transcript variants have different regulations and biological properties suggest a complex mechanism of ANRIL, which makes its function poorly understood 3). Jarinova et al 46) found that the levels of the short variants DQ485454 and EU741058 were increased and the long variant DQ485453 was decreased in the whole blood RNA from the carriers of the risk alleles. Another study confirmed the transcript EU741058 was increased, but the transcript variant DQ485454 showed no change in peripheral blood mononuclear cells and atherosclerotic plaques from risk haplotype carriers. Furthermore, the correlation of transcripts EU741058 and NR_003529 with the severity of atherosclerosis were further con-
firmed 47). Long Noncoding RNAs Regulate the Function of ECs Pathological angiogenesis, which was usually caused by cell proliferation, cell motility, immune or inflammation response, plays a critical role in atherosclerosis 48). Yan at al 48) found that lncRNA-MIAT (also termed retinal noncoding RNA 2 or Gomafu) can be induced by high glucose and MIAT knockdown inhibited endothelial cell proliferation, migration, and tube formation, thus ameliorating retinal microvascular dysfunction in diabetes mellitus – induced rats. Further study confirmed that VEGF, TNF-α, and intercellular adhesion molecule-1 (ICAM1) expressions were increased when MIAT was knockdown. Furthermore, VEGF has 3 miR-150-5p sites and luciferase assay showed that miR-150-5p could directly target and repress VEGF expression 48, 49). LncRNA-MIAT functions as miR-150-5p sponge and affecting the de-repression of VEGF in retinal endothelial cells. During the process of angiogenesis, lncRNA-MIAT is significantly upregulated and the sponge effect decreased the miR-150-5p level, thereby upregulating the level of VEGF, thus regulating endothelial cell function by a lncRNA-MIAT-miR-150-5pVEGF feedback loop. LncRNA MALAT1, which was first described as Metastasis Associated in Lung Adenocarcinoma Transcript, was recently found to regulate genes in endothelial cells and induce proliferation by bioinformatics analysis 50). Katharina et al 51) found that MALAT1 silencing by siRNA or LNA GapmeRs induced a phenotype switch of the endothelial cells from a proliferation state to a promigratory state. This type of phenotype switch results in a block in vessel outgrowth
Advance Publication LncRNAs in Atherosclerosis Journal of Atherosclerosis and Thrombosis 5 Accepted for publication: November 4, 2015 Published online: December 22, 2015 through increasing migratory and basal sprouting capacity, while inhibiting the cell cycle progression in vitro and in vivo. The mechanism was further demonstrated by quantitative reverse transcriptase-PCR that the cell cycle regulatory genes, particularly CCNA2, CCNB1, and CCNB2, were decreased, but the cell cycle inhibitory genes p21 and p27Kip1 were increased during MALAT1silencing. A recent study showed that MALAT1 is expressed in both endothelial and muscle cells and promotes skeletal muscle differentiation 52). Further study of MALAT1 in other pro-atherogenic cells such as myocytes or SMCs may be possible and meaningful.
expression and several SMC contractile proteins and increased two promigatory genes MDK and PTN, thus significantly increased SMC migration. The regulating targets of SENCR is unclear, but the induced promigratory effect by SENCR silencing can be inhibited by 2 upregulated genes, suggesting these 2 genes may participate in the phenotype of SENCR. Because SENCR was located in the cytoplasm and transcribed in antisense orientation to the Fli1 gene, but does not affect its expression, we may speculate that SENCR function as a miRNA sponge or exhibit RNA-protein interactions in the cytoplasm based on our current knowledge.
Long Noncoding RNAs in SMCs Vascular smooth muscle cells (VSMCs) proliferation and neointima formation play a dominant role in the process of atherosclerotic lesion development. As an essential and most important molecule in cell cycle and apoptosis control, p53 also plays a critical role in atherosclerosis 53-55). Several studies demonstrated that the development of atherosclerosis was accompanied with the inactivation of p53 56-58). Huarte et al found that lincRNA-p21, which was a p53-induced lncRNA and function as a component of the p53 pathway, could downregulate various p53 target genes by interacting with p53 repressive complex 59). Wu et al 60) confirmed that lincRNA-p21 suppresses cell proliferation and induces apoptosis and more importantly, lincRNA-p21 knockdown results in obvious neointimal hyperplasia. They found that lincRNA-p21 enhances p53 activity by directly binding to mouse double minute 2 (MDM2), thus decreasing MDM2-mediated inhibition of p53 and facilitating p53 binding to p300 for acetylation. A previous study has confirmed that angiotensin II could induce hyperproliferation and hypertrophy of VSMCs 61). Leung et al 62) identified a lncRNA in the angiotensin-induced SMCs and termed it lnc-Ang362. They found that lnc-Ang362 knockdown decreased the proliferation of SMCs and further confirmed that lnc-Ang362 was proximal to miR-221 and miR-222 and obviously attenuated the expression of the two miRNAs. Because miR-222 and miR-221 are wellknown participants in proliferation of VSMCs 63, 64), the proliferation-induced effects of lnc-Ang362 may represent the host transcript for the two miRNAs. Using of RNA-sequencing studies, Bell et al 65) revealed 31 unannotated lncRNAs from human coronary artery smooth muscle cells and investigated a lncRNA SENCR (smooth muscle and endothelial cell enriched migration/differentiation-associated lncRNA). SENCR knockdown decreased myocardin
Long Noncoding RNAs and Monocyte/ Macrophages Accumulation of cholesterol by macrophages is one of the pathological hallmarks of atherosclerosis 66). The differentiation of monocyte/macrophage is controlled by a complicated process including the coordinated expression of stage-specific transcription factors, various cytokines and ncRNAs 67, 68). Chen et al 69) found that PU.1-regulated two ncRNAs, lncRNA monocyte (lnc-MC) and miR-199a-5p, which have opposing roles during the differentiation of monocyte/ macrophage. Lnc-MC could promote monocyte/macrophage differentiation through function as a miR199a-5p sponge and decrease repression on ACVR1B (activin A receptor type 1B) expression, which was an important regulator of monocyte/macrophage differentiation. Carpenter et al 70) found that the lincRNACox2, which could be upregulated by TLR2-ligands in a MyD88 and NFκB dependent manner in murine macrophages, can both decrease (e.g., Ccl5) and induce (e.g., IL-6) expression of cytokines relevant in atherosclerosis. However, whether these lncRNAs have direct effects in the process of atherosclerosis and its detailed mechanisms requires further investigation. Other Long Noncoding RNAs Associated with Atherosclerosis Atherosclerosis is a complicated pathological process promoted by several factors. Except these lncRNAs directly acting on pro-atherogenic cells, there are various other lncRNAs play different kinds of roles in this process. For example, Hu et al 71) identified a lincRNA-DYNLRB2-2, which can be significantly induced by Ox-LDL, promoted cholesterol efflux mediated by ABCA1 and inhibited inflammation through GPR119 (G protein-coupled receptor 119) in THP-1 macrophage-derived foam cells, thus decreasing atherosclerosis in apoE−/− mice. Wang et
Advance Publication Jian et al . Journal of Atherosclerosis and Thrombosis Accepted for publication: November 4, 2015 Published online: December 22, 2015
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al 72) identified a dendritic cell-specific lncRNA termed lnc-DC playing a critical role in the differentiation of dendritic cells from human monocytes and mouse bone marrow, a cell type playing important roles in atherosclerosis 73). Another study has shown that lncRNA APOA1-AS function as a negative transcriptional regulator and distinct histone methylation patterns modulator of APOA1 74), a major component of HDL particles associated with reduced atherosclerosis 75). Former studies in human atherosclerotic plaques and carotid artery injury model of rat identified that lncRNA H19 is re-expressed 76, 77). Furthermore, Gao et al showed that H19 polymorphisms were associated with the risk of coronary artery disease (CAD). Furthermore, the T variant of rs217727 and the A variant of rs2067051 was associated with increased and decreased risk of CAD, respectively 78). Moreover, several studies confirm that lncRNA HIF1A-AS1 knockdown decreases apoptosis and promote proliferation VSMC 79-81), but whether it plays a role in atherosclerosis is yet unknown. Conclusion These studies suggest that lncRNAs are emerging important players in the process of atherosclerosis. However, only a small part of pro-atherogenic lncRNAs were identified and expounds up to present. Functional mechanism study of lncRNAs is yet in its infancy stages and requires further investigation. Actually, the poor conservative, various transcript variants, and low expression level of most lncRNAs challenged our further research. However, gain or loss of function approaches and pharmacological inhibition studies suggest that lncRNAs participate in atherosclerosis and may be potential therapeutic targets. As such, lncRNA research may provide a new breakthrough for the possibility of conquering atherosclerosis. Conflicts of Interest There are no funding sources or conflicts of interest to declare. References 1) Peters SA, den Ruijter HM, Bots ML, Moons KG. Improvements in risk stratification for the occurrence of cardiovascular disease by imaging subclinical atherosclerosis: a systematic review. Heart. 2012; 98: 177-184 2) Leung A, Natarajan R. Noncoding RNAs in vascular disease. Current opinion in cardiology. 2014; 29: 199-206 3) Uchida S, Dimmeler S. Long noncoding RNAs in cardiovascular diseases. Circulation research. 2015; 116: 737750
4) Kornfeld JW, Bruning JC. Regulation of metabolism by long, non-coding RNAs. Frontiers in genetics. 2014; 5: 57 5) Penny GD, Kay GF, Sheardown SA, Rastan S, Brockdorff N. Requirement for Xist in X chromosome inactivation. Nature. 1996; 379: 131-137 6) Arase M, Horiguchi K, Ehata S, Morikawa M, Tsutsumi S, Aburatani H, Miyazono K and Koinuma D: Transforming growth factor-beta-induced lncRNA-Smad7 inhibits apoptosis of mouse breast cancer JygMC(A) cells. Cancer science, 2014; 105: 974-982 7) Wang K, Long B, Zhou LY, Liu F, Zhou QY, Liu CY, Fan YY and Li PF: CARL lncRNA inhibits anoxia-induced mitochondrial fission and apoptosis in cardiomyocytes by impairing miR-539-dependent PHB2 downregulation. Nature communications, 2014; 5: 3596 8) Yang Y, Li H, Hou S, Hu B, Liu J, Wang J. The noncoding RNA expression profile and the effect of lncRNA AK126698 on cisplatin resistance in non-small-cell lung cancer cell. PloS one. 2013; 8: e65309 9) Klattenhoff CA, Scheuermann JC, Surface LE, Bradley RK, Fields PA, Steinhauser ML, Ding H, Butty VL, Torrey L, Haas S, Abo R, Tabebordbar M, Lee RT, Burge CB and Boyer LA: Braveheart, a long noncoding RNA required for cardiovascular lineage commitment. Cell, 2013; 152: 570-583 10) Cabili MN, Trapnell C, Goff L, Koziol M, Tazon-Vega B, Regev A and Rinn JL: Integrative annotation of human large intergenic noncoding RNAs reveals global properties and specific subclasses. Genes & development, 2011; 25: 1915-1927 11) Khalil AM, Guttman M, Huarte M, Garber M, Raj A, Rivea Morales D, Thomas K, Presser A, Bernstein BE, van Oudenaarden A, Regev A, Lander ES and Rinn JL: Many human large intergenic noncoding RNAs associate with chromatin-modifying complexes and affect gene expression. Proceedings of the National Academy of Sciences of the United States of America, 2009; 106: 1166711672 12) Guttman M, Garber M, Levin JZ, Donaghey J, Robinson J, Adiconis X, Fan L, Koziol MJ, Gnirke A, Nusbaum C, Rinn JL, Lander ES and Regev A: Ab initio reconstruction of cell type-specific transcriptomes in mouse reveals the conserved multi-exonic structure of lincRNAs. Nature biotechnology, 2010; 28: 503-510 13) Leung A, Stapleton K, Natarajan R. Functional Long Non-coding RNAs in Vascular Smooth Muscle Cells. Current topics in microbiology and immunology. 2015 14) Pan YF, Feng L, Zhang XQ, Song LJ, Liang HX, Li ZQ and Tao FB: Role of long non-coding RNAs in gene regulation and oncogenesis. Chinese medical journal, 2011; 124: 2378-2383 15) Ringrose L, Paro R. Epigenetic regulation of cellular memory by the Polycomb and Trithorax group proteins. Annual review of genetics. 2004; 38: 413-443 16) Moazed D. Mechanisms for the inheritance of chromatin states. Cell. 2011; 146: 510-518 17) Ragunathan K, Jih G, Moazed D. Epigenetics. Epigenetic inheritance uncoupled from sequence-specific recruitment. Science. 2015; 348: 1258699
Advance Publication LncRNAs in Atherosclerosis Journal of Atherosclerosis and Thrombosis 7 Accepted for publication: November 4, 2015 Published online: December 22, 2015 18) Rinn JL, Kertesz M, Wang JK, Squazzo SL, Xu X, Brugmann SA, Goodnough LH, Helms JA, Farnham PJ, Segal E and Chang HY: Functional demarcation of active and silent chromatin domains in human HOX loci by noncoding RNAs. Cell, 2007; 129: 1311-1323 19) Saxena A, Carninci P. Long non-coding RNA modifies chromatin: epigenetic silencing by long non-coding RNAs. BioEssays: news and reviews in molecular, cellular and developmental biology. 2011; 33: 830-839 20) Rizki G, Boyer LA. Lncing Epigenetic Control of Transcription to Cardiovascular Development and Disease. Circulation research. 2015; 117: 192-206 21) Mercer TR, Mattick JS. Structure and function of long noncoding RNAs in epigenetic regulation. Nature structural & molecular biology. 2013; 20: 300-307 22) Zhao J, Sun BK, Erwin JA, Song JJ, Lee JT. Polycomb proteins targeted by a short repeat RNA to the mouse X chromosome. Science. 2008; 322: 750-756 23) Plath K, Fang J, Mlynarczyk-Evans SK, Cao R, Worringer KA, Wang H, de la Cruz CC, Otte AP, Panning B and Zhang Y: Role of histone H3 lysine 27 methylation in X inactivation. Science, 2003; 300: 131-135 24) Wang J, Mager J, Chen Y, Schneider E, Cross JC, Nagy A and Magnuson T: Imprinted X inactivation maintained by a mouse Polycomb group gene. Nature genetics, 2001; 28: 371-375 25) Froberg JE, Yang L, Lee JT. Guided by RNAs: X-inactivation as a model for lncRNA function. Journal of molecular biology. 2013; 425: 3698-3706 26) Mohammad F, Pandey GK, Mondal T, Enroth S, Redrup L, Gyllensten U and Kanduri C: Long noncoding RNAmediated maintenance of DNA methylation and transcriptional gene silencing. Development, 2012; 139: 2792-2803 27) Berghoff EG, Clark MF, Chen S, Cajigas I, Leib DE, Kohtz JD. Evf2 (Dlx6as) lncRNA regulates ultraconserved enhancer methylation and the differential transcriptional control of adjacent genes. Development. 2013; 140: 4407-4416 28) Martens JA, Laprade L, Winston F. Intergenic transcription is required to repress the Saccharomyces cerevisiae SER3 gene. Nature. 2004; 429: 571-574 29) Martianov I, Ramadass A, Serra Barros A, Chow N, Akoulitchev A. Repression of the human dihydrofolate reductase gene by a non-coding interfering transcript. Nature. 2007; 445: 666-670 30) Wang X, Arai S, Song X, Reichart D, Du K, Pascual G, Tempst P, Rosenfeld MG, Glass CK and Kurokawa R: Induced ncRNAs allosterically modify RNA-binding proteins in cis to inhibit transcription. Nature, 2008; 454: 126-130 31) Lin R, Roychowdhury-Saha M, Black C, Watt AT, Marcusson EG, Freier SM and Edgington TS: Control of RNA processing by a large non-coding RNA overexpressed in carcinomas. FEBS letters, 2011; 585: 671676 32) Souquere S, Beauclair G, Harper F, Fox A, Pierron G. Highly ordered spatial organization of the structural long noncoding NEAT1 RNAs within paraspeckle nuclear bodies. Molecular biology of the cell. 2010; 21: 4020-
4027 33) Clemson CM, Hutchinson JN, Sara SA, Ensminger AW, Fox AH, Chess A and Lawrence JB: An architectural role for a nuclear noncoding RNA: NEAT1 RNA is essential for the structure of paraspeckles. Molecular cell, 2009; 33: 717-726 34) Kretz M, Siprashvili Z, Chu C, Webster DE, Zehnder A, Qu K, Lee CS, Flockhart RJ, Groff AF, Chow J, Johnston D, Kim GE, Spitale RC, Flynn RA, Zheng GX, Aiyer S, Raj A, Rinn JL, Chang HY and Khavari PA: Control of somatic tissue differentiation by the long non-coding RNA TINCR. Nature, 2013; 493: 231-235 35) Cesana M, Cacchiarelli D, Legnini I, Santini T, Sthandier O, Chinappi M, Tramontano A and Bozzoni I: A long noncoding RNA controls muscle differentiation by functioning as a competing endogenous RNA. Cell, 2011; 147: 358-369 36) Onat D, Brillon D, Colombo PC, Schmidt AM. Human vascular endothelial cells: a model system for studying vascular inflammation in diabetes and atherosclerosis. Current diabetes reports. 2011; 11: 193-202 37) Martinet W, Schrijvers DM, De Meyer GR. Molecular and cellular mechanisms of macrophage survival in atherosclerosis. Basic research in cardiology. 2012; 107: 297 38) Ho-Tin-Noe B, Michel JB. Initiation of angiogenesis in atherosclerosis: smooth muscle cells as mediators of the angiogenic response to atheroma formation. Trends in cardiovascular medicine. 2011; 21: 183-187 39) McPherson R, Pertsemlidis A, Kavaslar N, Stewart A, Roberts R, Cox DR, Hinds DA, Pennacchio LA, Tybjaerg-Hansen A, Folsom AR, Boerwinkle E, Hobbs HH and Cohen JC: A common allele on chromosome 9 associated with coronary heart disease. Science, 2007; 316: 1488-1491 40) Helgadottir A, Thorleifsson G, Manolescu A, Gretarsdottir S, Blondal T, Jonasdottir A, Jonasdottir A, Sigurdsson A, Baker A, Palsson A, Masson G, Gudbjartsson DF, Magnusson KP, Andersen K, Levey AI, Backman VM, Matthiasdottir S, Jonsdottir T, Palsson S, Einarsdottir H, Gunnarsdottir S, Gylfason A, Vaccarino V, Hooper WC, Reilly MP, Granger CB, Austin H, Rader DJ, Shah SH, Quyyumi AA, Gulcher JR, Thorgeirsson G, Thorsteinsdottir U, Kong A and Stefansson K: A common variant on chromosome 9p21 affects the risk of myocardial infarction. Science, 2007; 316: 1491-1493 41) Holdt LM, Hoffmann S, Sass K, Langenberger D, Scholz M, Krohn K, Finstermeier K, Stahringer A, Wilfert W, Beutner F, Gielen S, Schuler G, Gabel G, Bergert H, Bechmann I, Stadler PF, Thiery J and Teupser D: Alu elements in ANRIL non-coding RNA at chromosome 9p21 modulate atherogenic cell functions through trans-regulation of gene networks. PLoS genetics, 2013; 9: e1003588 42) Holdt LM and Teupser D: Recent studies of the human chromosome 9p21 locus, which is associated with atherosclerosis in human populations. Arteriosclerosis, thrombosis, and vascular biology, 2012; 32: 196-206 43) Yap KL, Li S, Munoz-Cabello AM, Raguz S, Zeng L, Mujtaba S, Gil J, Walsh MJ and Zhou MM: Molecular interplay of the noncoding RNA ANRIL and methylated histone H3 lysine 27 by polycomb CBX7 in transcrip-
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tional silencing of INK4a. Molecular cell, 2010; 38: 662674 44) Kotake Y, Nakagawa T, Kitagawa K, Suzuki S, Liu N, Jian et al. Kitagawa M and Xiong Y: Long non-coding RNA ANRIL is required for the PRC2 recruitment to and silencing of p15(INK4B) tumor suppressor gene. Oncogene, 2011; 30: 1956-1962 45) Lusis AJ: Atherosclerosis. Nature, 2000; 407: 233-241 46) Jarinova O, Stewart AF, Roberts R, Wells G, Lau P, Naing T, Buerki C, McLean BW, Cook RC, Parker JS and McPherson R: Functional analysis of the chromosome 9p21.3 coronary artery disease risk locus. Arteriosclerosis, thrombosis, and vascular biology, 2009; 29: 1671-1677 47) Holdt LM, Beutner F, Scholz M, Gielen S, Gabel G, Bergert H, Schuler G, Thiery J and Teupser D: ANRIL expression is associated with atherosclerosis risk at chromosome 9p21. Arteriosclerosis, thrombosis, and vascular biology, 2010; 30: 620-627 48) Yan B, Yao J, Liu JY, Li XM, Wang XQ, Li YJ, Tao ZF, Song YC, Chen Q and Jiang Q: lncRNA-MIAT regulates microvascular dysfunction by functioning as a competing endogenous RNA. Circulation research, 2015; 116: 11431156 49) Zachary I: VEGF signalling: integration and multi-tasking in endothelial cell biology. Biochemical Society transactions, 2003; 31: 1171-1177 50) Ji P, Diederichs S, Wang W, Boing S, Metzger R, Schneider PM, Tidow N, Brandt B, Buerger H, Bulk E, Thomas M, Berdel WE, Serve H and Muller-Tidow C: MALAT-1, a novel noncoding RNA, and thymosin beta4 predict metastasis and survival in early-stage non-small cell lung cancer. Oncogene, 2003; 22: 8031-8041 51) Michalik KM, You X, Manavski Y, Doddaballapur A, Zornig M, Braun T, John D, Ponomareva Y, Chen W, Uchida S, Boon RA and Dimmeler S: Long noncoding RNA MALAT1 regulates endothelial cell function and vessel growth. Circulation research, 2014; 114: 13891397 52) Watts R, Johnsen VL, Shearer J and Hittel DS: Myostatin-induced inhibition of the long noncoding RNA Malat1 is associated with decreased myogenesis. American journal of physiology Cell physiology, 2013; 304: C9951001 53) Guevara NV, Kim HS, Antonova EI and Chan L: The absence of p53 accelerates atherosclerosis by increasing cell proliferation in vivo. Nature medicine, 1999; 5: 335339 54) Merched AJ, Williams E and Chan L: Macrophage-specific p53 expression plays a crucial role in atherosclerosis development and plaque remodeling. Arteriosclerosis, thrombosis, and vascular biology, 2003; 23: 1608-1614 55) van Vlijmen BJ, Gerritsen G, Franken AL, Boesten LS, Kockx MM, Gijbels MJ, Vierboom MP, van Eck M, van De Water B, van Berkel TJ and Havekes LM: Macrophage p53 deficiency leads to enhanced atherosclerosis in APOE*3-Leiden transgenic mice. Circulation research, 2001; 88: 780-786 56) Mercer J and Bennett M: The role of p53 in atherosclerosis. Cell cycle, 2006; 5: 1907-1909 57) Jackson SP and Bartek J: The DNA-damage response in
human biology and disease. Nature, 2009; 461: 10711078 58) Mercer J, Figg N, Stoneman V, Braganza D and Bennett MR: Endogenous p53 protects vascular smooth muscle cells from apoptosis and reduces atherosclerosis in ApoE knockout mice. Circulation research, 2005; 96: 667-674 59) Huarte M, Guttman M, Feldser D, Garber M, Koziol MJ, Kenzelmann-Broz D, Khalil AM, Zuk O, Amit I, Rabani M, Attardi LD, Regev A, Lander ES, Jacks T and Rinn JL: A large intergenic noncoding RNA induced by p53 mediates global gene repression in the p53 response. Cell, 2010; 142: 409-419 60) Wu G, Cai J, Han Y, Chen J, Huang ZP, Chen C, Cai Y, Huang H, Yang Y, Liu Y, Xu Z, He D, Zhang X, Hu X, Pinello L, Zhong D, He F, Yuan GC, Wang DZ and Zeng C: LincRNA-p21 regulates neointima formation, vascular smooth muscle cell proliferation, apoptosis, and atherosclerosis by enhancing p53 activity. Circulation, 2014; 130: 1452-1465 61) Brasier AR, Recinos A, 3rd and Eledrisi MS: Vascular inflammation and the renin-angiotensin system. Arteriosclerosis, thrombosis, and vascular biology, 2002; 22: 1257-1266 62) Leung A, Trac C, Jin W, Lanting L, Akbany A, Saetrom P, Schones DE and Natarajan R: Novel long noncoding RNAs are regulated by angiotensin II in vascular smooth muscle cells. Circulation research, 2013; 113: 266-278 63) Zhu N, Zhang D, Chen S, Liu X, Lin L, Huang X, Guo Z, Liu J, Wang Y, Yuan W and Qin Y: Endothelial enriched microRNAs regulate angiotensin II-induced endothelial inflammation and migration. Atherosclerosis, 2011; 215: 286-293 64) Liu X, Cheng Y, Zhang S, Lin Y, Yang J and Zhang C: A necessary role of miR-221 and miR-222 in vascular smooth muscle cell proliferation and neointimal hyperplasia. Circulation research, 2009; 104: 476-487 65) Bell RD, Long X, Lin M, Bergmann JH, Nanda V, Cowan SL, Zhou Q, Han Y, Spector DL, Zheng D and Miano JM: Identification and initial functional characterization of a human vascular cell-enriched long noncoding RNA. Arteriosclerosis, thrombosis, and vascular biology, 2014; 34: 1249-1259 66) Glass CK and Witztum JL: Atherosclerosis. the road ahead. Cell, 2001; 104: 503-516 67) Friedman AD: Transcriptional control of granulocyte and monocyte development. Oncogene, 2007; 26: 6816-6828 68) El Gazzar M and McCall CE: MicroRNAs regulatory networks in myeloid lineage development and differentiation: regulators of the regulators. Immunology and cell biology, 2012; 90: 587-593 69) Chen MT, Lin HS, Shen C, Ma YN, Wang F, Zhao HL, Yu J and Zhang JW: PU.1-Regulated Long Noncoding RNA lnc-MC Controls Human Monocyte/Macrophage Differentiation through Interaction with MicroRNA 199a-5p. Molecular and cellular biology, 2015; 35: 32123224 70) Carpenter S, Aiello D, Atianand MK, Ricci EP, Gandhi P, Hall LL, Byron M, Monks B, Henry-Bezy M, Lawrence JB, O,Neill LA, Moore MJ, Caffrey DR and Fitzgerald KA: A long noncoding RNA mediates both activation
Advance Publication LncRNAs in Atherosclerosis Journal of Atherosclerosis and Thrombosis 9 Accepted for publication: November 4, 2015 Published online: December 22, 2015 and repression of immune response genes. Science, 2013; 341: 789-792 71) Hu YW, Yang JY, Ma X, Chen ZP, Hu YR, Zhao JY, Li SF, Qiu YR, Lu JB, Wang YC, Gao JJ, Sha YH, Zheng L and Wang Q: A lincRNA-DYNLRB2-2/GPR119/GLP1R/ABCA1dependent signal transduction pathway is essential for the regulation of cholesterol homeostasis. Journal of lipid research, 2014; 55: 681-697 72) Wang P, Xue Y, Han Y, Lin L, Wu C, Xu S, Jiang Z, Xu J, Liu Q and Cao X: The STAT3-binding long noncoding RNA lnc-DC controls human dendritic cell differentiation. Science, 2014; 344: 310-313 73) Manthey HD and Zernecke A: Dendritic cells in atherosclerosis: functions in immune regulation and beyond. Thrombosis and haemostasis, 2011; 106: 772-778 74) Halley P, Kadakkuzha BM, Faghihi MA, Magistri M, Zeier Z, Khorkova O, Coito C, Hsiao J, Lawrence M and Wahlestedt C: Regulation of the apolipoprotein gene cluster by a long noncoding RNA. Cell reports, 2014; 6: 222230 75) Lund-Katz S and Phillips MC: High density lipoprotein structure-function and role in reverse cholesterol transport. Sub-cellular biochemistry, 2010; 51: 183-227 76) Han DK, Khaing ZZ, Pollock RA, Haudenschild CC and Liau G: H19, a marker of developmental transition, is reexpressed in human atherosclerotic plaques and is regulated by the insulin family of growth factors in cultured rabbit smooth muscle cells. J Clin Invest, 1996; 97: 12761285
77) Kim DK, Zhang L, Dzau VJ and Pratt RE: H19, a developmentally regulated gene, is reexpressed in rat vascular smooth muscle cells after injury. J Clin Invest, 1994; 93: 355-360 78) Gao W, Zhu M, Wang H, Zhao S, Zhao D, Yang Y, Wang ZM, Wang F, Yang ZJ, Lu X and Wang LS: Association of polymorphisms in long non-coding RNA H19 with coronary artery disease risk in a Chinese population. Mutation research, 2015; 772: 15-22 79) Wang J, Chen L, Li H, Yang J, Gong Z, Wang B and Zhao X: Clopidogrel reduces apoptosis and promotes proliferation of human vascular endothelial cells induced by palmitic acid via suppression of the long non-coding RNA HIF1A-AS1 in vitro. Molecular and cellular biochemistry, 2015; 404: 203-210 80) He Q, Tan J, Yu B, Shi W and Liang K: Long noncoding RNA HIF1A-AS1A reduces apoptosis of vascular smooth muscle cells: implications for the pathogenesis of thoracoabdominal aorta aneurysm. Die Pharmazie, 2015; 70: 310-315 81) Wang S, Zhang X, Yuan Y, Tan M, Zhang L, Xue X, Yan Y, Han L and Xu Z: BRG1 expression is increased in thoracic aortic aneurysms and regulates proliferation and apoptosis of vascular smooth muscle cells through the long non-coding RNA HIF1A-AS1 in vitro. European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery, 2015; 47: 439-446
Department of Cardiology, The Second Affiliated Hospital of Zhengzhou University, Henan, PR China. Department of Cardiology, the First Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang, PR China
Long noncoding RNAs (lncRNAs) were a group of non-protein-coding RNAs ＞ 200 nucleotides and participated in biological processes and pathophysiological conditions in vivo or in vitro. Recently, more and more lncRNAs interfering with the progress of atherosclerosis were identified and characterized in the atherogenic cells such as vascular smooth muscle cells (VSMCs), endothelial cells (ECs), and monocytes/macrophages showing that lncRNAs play an important role in the occurrence of atherosclerosis. In this review, we summarized and highlighted the lncRNAs that play a role in the process of atherosclerosis. This study may provide helpful insights regarding further study of lncRNAs associated with atherosclerosis. J Atheroscler Thromb, 2016; 23: 000-000. Key words: Long noncoding RNA, VSMCs, ECs, Monocyte/macrophages, Atherosclerosis
Introduction Cardiovascular disease (CVD) is the most important cause of mortality worldwide, and its underlying reason was atherosclerosis 1). In contrast to the small number of coding transcripts ( ＜ 3%) of the total genome, the majority of noncoding transcripts (＞ 80%) has been previously described as “junk” transcripts or transcriptional noise 2, 3). Because the first lncRNA X inactive specific transcript (XIST) was initially discovered in the 1990s 4, 5), several lncRNAs that play vital roles in cancer progression and metastasis, cell proliferation, and apoptosis were identified by a growing number of studies 6-8). Therefore, identifying the correlation between lncRNAs and atherosclerosis may help us better understand the pathogenesis of atherosclerosis and find new treatment for patients with CVD. This study will introduce lncRNAs and summarize the current understanding of lncRNAs in the process of atherosclerosis. Address for correspondence: Li Zhang, Department of Cardiology, the First Affiliated Hospital, School of Medicine, Zhejiang University, 79 Qingchun Road, Hangzhou, Zhejiang, 310003, PR China E-mail: [email protected] Received: September 18, 2015 Accepted for publication: November 4, 2015
Definition, Classification, and Functional Mechanisms of lncRNAs LncRNAs are broadly classified as transcripts nt with limited coding potential 9). RNA polymerase II processing, 5´ cap, and 3´ polyadenylation are common features of lncRNAs like protein-coding RNAs. However, they lack distinct open reading frames and are generally expressed at much lower levels in contrast to mRNAs 10-12). Recently, because of the high-throughput sequencing technologies, lncRNAs have been identified and found to be important regulators of gene transcription in cancers and other diseases including vascular disease 2, 13). There are 145331 and 74963 lncRNA genes for humans and mice, respectively, as shown in NONCODE database (version4.0; http:// www.noncode.org). However, whether all these lncRNAs have biological functions was unclear because only few of them have been characterized to date. Corresponding to their association with nearby mRNAs, the generally accepted categorization of lncRNAs was divided into five groups (Fig. 1): (a) Sense: the transcription product of protein-coding genes after splicing (from the same mRNA chain); (b) Antisense: produced by the complementary strand of protein-coding genes (from the opposite mRNA
＞ 200
2
Advance Publication Jian et al . Journal of Atherosclerosis and Thrombosis Accepted for publication: November 4, 2015 Published online: December 22, 2015
Fig. 1. The classification of lncRNAs. Yellow indicates mRNA coding genes and gray indicates the noncoding genes.
chain); (c) Intronic: stemming from the introns of the protein-coding genes; (d) Intergenic: located between two protein-coding genes [termed long intergenic noncoding RNAs (lincRNAs)]; and (e) Bidirectional: produced by the upstream sequence and the opposite direction of protein-coding genes 3, 14). Although the study of functional mechanisms of lncRNAs is yet in the infancy stage, in terms of our current understanding, the mechanism of lncRNAs can be briefly divided into the following categories. Epigenetic Regulation Epigenetics, which mostly consists of changes in histone post-translational modifications and chromatin structure, refers to the heritable changes in gene phenotypes without the DNA sequence changes 15-17). LncRNAs can regulate the gene expression at the epigenetic level. Researches demonstrate that lncRNA can combine with chromatin remodeling complexes resulting in a specific mode of histone modification, activating or inhibiting transcription; therefore, lncRNA play a key role in genomic imprinting and dosage compensation effect 18-21). For example, XIST is a well-known lncRNA which plays an important role in the X chromosome inactivation in female mammals 22). The 5´ end of XIST has a repeated motif known as “repeat A” which can directly bond to EZH2, the catalytic subunit of Polycomb repressive
complex 2 (PRC2). Then, PRC2 catalyzed repressive epigenetic modifications such as trimethylation of histone H3 lysine 27 (H3K27me3), which cause transcriptional silencing of the X chromosome 23-25). Mohammad et al 26) found that Kcnq1ot1 ncRNA was required for the maintenance of the ubiquitously imprinted gene (UIG) silencing and was involved in directing and maintaining the CpG methylation at somatic differentially methylated regions. Transcriptional Regulation LncRNAs can regulate gene transcription by regulating the activity of transcriptional factors, interfering with the adjacent gene expression, blocking the promoter regions, and regulating the combination with proteins. Berghoff and his colleagues 27) found that lncRNA-Evf2 could repress Dlx5/6 gene expression by regulating Dlx5/6 enhancer site-specific methylation. Martens et al 28) found that lncRNA-SRG1 transcript across the SER3 promoter interferes with the binding of activators, thus regulating SER3 repression. Martianov et al 29) demonstrated that noncoding RNA could directly interact with the general transcription factor IIB and format a stable complex, which could dissociate the preinitiation complex and major promoter, thus decreasing dihydrofolate reductase gene expression. Wang et al 30) found that ncRNA CCND1 could recruit an RNA-binding protein
Advance Publication LncRNAs in Atherosclerosis Journal of Atherosclerosis and Thrombosis 3 Accepted for publication: November 4, 2015 Published online: December 22, 2015
Fig. 2. The brief expression and functions of lncRNAs in pro-atherogenic cells.
TLS to the CCND1 promoter causing gene-specific repression of CCND1. Post-Transcriptional Regulation LncRNAs can regulate the alternative splicing, degradation, and stability of mRNA. Lin et al 31) found that perturbation of lncRNA ΣRNA (human MALAT1) altered splicing activity of genes that encode the RNA-binding proteins serine/arginine rich (SR) proteins and heterogeneous nuclear ribonucleoproteins (hnRNPs), which themselves participate in RNA processing. Souquere et al 32, 33) found that lncRNA-NEAT1 transcripts could constrain the geometry of paraspeckle bodies (PSPs), which prompt nuclear retention of mRNAs with A-I edition at the 3´ end noncoding regions, preventing mRNA translation into protein. Kretz 34) demonstrates that the lncRNA-terminal differentiation-induced ncRNA (TINCR could directly bind to mRNAs through a 25 nucleotide “TINCR box” motif, thus regulating the stability of target mRNAs. Molecular Sponges LncRNAs can act as endogenous decoys for miRNAs. For example, miR-135 and miR-133 could tar-
get MEF2C and MAML1, respectively, to regulate myoblast differentiation. A long intergenic noncoding RNA linc-MD1 has two miRNA bonding sites, which can sponge miR-135 and miR-133 y, thus regulating the expression levels of MEF2C and MAML1 2, 35). Long Noncoding RNAs in Atherogenic Cells Vascular smooth muscle cells (VSMCs), endothelial cells (ECs), and macrophages are the primary cells that contribute to atherosclerotic lesion formation 36-38). Therefore, we will elaborate lncRNAs associated with these three cell lines that may play a role in the process of atherosclerosis (Fig. 2). Moreover, we summarized the verified species and conditions of the known pro-atherogenic lncRNAs (Table 1). Long Noncoding RNAs in Vascular Physiological or Pathological Processes Recently, several studies demonstrated that the chromosome 9p21 (Chr9p21) locus is the strongest genetic risk factor for coronary artery disease 39, 40). This region is adjacent to INK4 locus that encodes a lncRNA termed ANRIL (also termed CDKN2B-AS). ANRIL expression was observed in several atherogenic
Advance Publication Jian et al . Journal of Atherosclerosis and Thrombosis Accepted for publication: November 4, 2015 Published online: December 22, 2015
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Table 1. The verified species of pro-atherogenic lncRNAs LncRNA
Species
Verified
MIAT MALAT1 ANRIL lincRNA-p21 lnc-Ang362 SENCR lnc-MC lincRNA-Cox2 lincRNA-DYNLRB2-2 APOA1-AS H19 HIF1A-AS1
Human/Mouse/Rat Human/Mouse Human Human/Mouse Rat Human Human Mouse Mouse Human/Monkey Human/Mouse Human
in vitro/in vivo in vitro/in vivo in vitro/in vivo in vitro/in vivo in vitro in vitro in vitro in vitro in vitro/in vivo in vitro/in vivo in vitro in vitro
cells and tissues such as SMCs, ECs, monocytederived macrophages, and RNA samples extracted from carotid and arterectomy 41). Moreover, the severity of atherosclerosis with ANRIL expression has been described 39, 42). Yap et al found that knockdown of ANRIL was associated with increased cyclin-dependent kinase inhibitors 2A (CDKN2A) expression and decreased H3K27me3 43). However, Kotake et al showed that ANRIL knockdown by shRNA resulted in increased CDKN2B expression by disturbing SUZ12 binding to the Chr9p21 locus 44). There are conflicts regarding CDKN2A or CDKN2B expression mediated by ANRIL knockdown, the significant decrease of cell proliferation, which play a key role in atherogenesis were observed 43-45). Moreover, Holdt et al found that Alu motifs are essential for the pro-atherogenic functions of ANRIL. ANRIL regulates target genes through the Alu motifs located in ANRIL and the promoters of target-genes resulting in increased cell proliferation, cell adhesion, and decreased apoptosis, which all play critical roles in the process of atherosclerosis 41). Differential transcript variants have different regulations and biological properties suggest a complex mechanism of ANRIL, which makes its function poorly understood 3). Jarinova et al 46) found that the levels of the short variants DQ485454 and EU741058 were increased and the long variant DQ485453 was decreased in the whole blood RNA from the carriers of the risk alleles. Another study confirmed the transcript EU741058 was increased, but the transcript variant DQ485454 showed no change in peripheral blood mononuclear cells and atherosclerotic plaques from risk haplotype carriers. Furthermore, the correlation of transcripts EU741058 and NR_003529 with the severity of atherosclerosis were further con-
firmed 47). Long Noncoding RNAs Regulate the Function of ECs Pathological angiogenesis, which was usually caused by cell proliferation, cell motility, immune or inflammation response, plays a critical role in atherosclerosis 48). Yan at al 48) found that lncRNA-MIAT (also termed retinal noncoding RNA 2 or Gomafu) can be induced by high glucose and MIAT knockdown inhibited endothelial cell proliferation, migration, and tube formation, thus ameliorating retinal microvascular dysfunction in diabetes mellitus – induced rats. Further study confirmed that VEGF, TNF-α, and intercellular adhesion molecule-1 (ICAM1) expressions were increased when MIAT was knockdown. Furthermore, VEGF has 3 miR-150-5p sites and luciferase assay showed that miR-150-5p could directly target and repress VEGF expression 48, 49). LncRNA-MIAT functions as miR-150-5p sponge and affecting the de-repression of VEGF in retinal endothelial cells. During the process of angiogenesis, lncRNA-MIAT is significantly upregulated and the sponge effect decreased the miR-150-5p level, thereby upregulating the level of VEGF, thus regulating endothelial cell function by a lncRNA-MIAT-miR-150-5pVEGF feedback loop. LncRNA MALAT1, which was first described as Metastasis Associated in Lung Adenocarcinoma Transcript, was recently found to regulate genes in endothelial cells and induce proliferation by bioinformatics analysis 50). Katharina et al 51) found that MALAT1 silencing by siRNA or LNA GapmeRs induced a phenotype switch of the endothelial cells from a proliferation state to a promigratory state. This type of phenotype switch results in a block in vessel outgrowth
Advance Publication LncRNAs in Atherosclerosis Journal of Atherosclerosis and Thrombosis 5 Accepted for publication: November 4, 2015 Published online: December 22, 2015 through increasing migratory and basal sprouting capacity, while inhibiting the cell cycle progression in vitro and in vivo. The mechanism was further demonstrated by quantitative reverse transcriptase-PCR that the cell cycle regulatory genes, particularly CCNA2, CCNB1, and CCNB2, were decreased, but the cell cycle inhibitory genes p21 and p27Kip1 were increased during MALAT1silencing. A recent study showed that MALAT1 is expressed in both endothelial and muscle cells and promotes skeletal muscle differentiation 52). Further study of MALAT1 in other pro-atherogenic cells such as myocytes or SMCs may be possible and meaningful.
expression and several SMC contractile proteins and increased two promigatory genes MDK and PTN, thus significantly increased SMC migration. The regulating targets of SENCR is unclear, but the induced promigratory effect by SENCR silencing can be inhibited by 2 upregulated genes, suggesting these 2 genes may participate in the phenotype of SENCR. Because SENCR was located in the cytoplasm and transcribed in antisense orientation to the Fli1 gene, but does not affect its expression, we may speculate that SENCR function as a miRNA sponge or exhibit RNA-protein interactions in the cytoplasm based on our current knowledge.
Long Noncoding RNAs in SMCs Vascular smooth muscle cells (VSMCs) proliferation and neointima formation play a dominant role in the process of atherosclerotic lesion development. As an essential and most important molecule in cell cycle and apoptosis control, p53 also plays a critical role in atherosclerosis 53-55). Several studies demonstrated that the development of atherosclerosis was accompanied with the inactivation of p53 56-58). Huarte et al found that lincRNA-p21, which was a p53-induced lncRNA and function as a component of the p53 pathway, could downregulate various p53 target genes by interacting with p53 repressive complex 59). Wu et al 60) confirmed that lincRNA-p21 suppresses cell proliferation and induces apoptosis and more importantly, lincRNA-p21 knockdown results in obvious neointimal hyperplasia. They found that lincRNA-p21 enhances p53 activity by directly binding to mouse double minute 2 (MDM2), thus decreasing MDM2-mediated inhibition of p53 and facilitating p53 binding to p300 for acetylation. A previous study has confirmed that angiotensin II could induce hyperproliferation and hypertrophy of VSMCs 61). Leung et al 62) identified a lncRNA in the angiotensin-induced SMCs and termed it lnc-Ang362. They found that lnc-Ang362 knockdown decreased the proliferation of SMCs and further confirmed that lnc-Ang362 was proximal to miR-221 and miR-222 and obviously attenuated the expression of the two miRNAs. Because miR-222 and miR-221 are wellknown participants in proliferation of VSMCs 63, 64), the proliferation-induced effects of lnc-Ang362 may represent the host transcript for the two miRNAs. Using of RNA-sequencing studies, Bell et al 65) revealed 31 unannotated lncRNAs from human coronary artery smooth muscle cells and investigated a lncRNA SENCR (smooth muscle and endothelial cell enriched migration/differentiation-associated lncRNA). SENCR knockdown decreased myocardin
Long Noncoding RNAs and Monocyte/ Macrophages Accumulation of cholesterol by macrophages is one of the pathological hallmarks of atherosclerosis 66). The differentiation of monocyte/macrophage is controlled by a complicated process including the coordinated expression of stage-specific transcription factors, various cytokines and ncRNAs 67, 68). Chen et al 69) found that PU.1-regulated two ncRNAs, lncRNA monocyte (lnc-MC) and miR-199a-5p, which have opposing roles during the differentiation of monocyte/ macrophage. Lnc-MC could promote monocyte/macrophage differentiation through function as a miR199a-5p sponge and decrease repression on ACVR1B (activin A receptor type 1B) expression, which was an important regulator of monocyte/macrophage differentiation. Carpenter et al 70) found that the lincRNACox2, which could be upregulated by TLR2-ligands in a MyD88 and NFκB dependent manner in murine macrophages, can both decrease (e.g., Ccl5) and induce (e.g., IL-6) expression of cytokines relevant in atherosclerosis. However, whether these lncRNAs have direct effects in the process of atherosclerosis and its detailed mechanisms requires further investigation. Other Long Noncoding RNAs Associated with Atherosclerosis Atherosclerosis is a complicated pathological process promoted by several factors. Except these lncRNAs directly acting on pro-atherogenic cells, there are various other lncRNAs play different kinds of roles in this process. For example, Hu et al 71) identified a lincRNA-DYNLRB2-2, which can be significantly induced by Ox-LDL, promoted cholesterol efflux mediated by ABCA1 and inhibited inflammation through GPR119 (G protein-coupled receptor 119) in THP-1 macrophage-derived foam cells, thus decreasing atherosclerosis in apoE−/− mice. Wang et
Advance Publication Jian et al . Journal of Atherosclerosis and Thrombosis Accepted for publication: November 4, 2015 Published online: December 22, 2015
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al 72) identified a dendritic cell-specific lncRNA termed lnc-DC playing a critical role in the differentiation of dendritic cells from human monocytes and mouse bone marrow, a cell type playing important roles in atherosclerosis 73). Another study has shown that lncRNA APOA1-AS function as a negative transcriptional regulator and distinct histone methylation patterns modulator of APOA1 74), a major component of HDL particles associated with reduced atherosclerosis 75). Former studies in human atherosclerotic plaques and carotid artery injury model of rat identified that lncRNA H19 is re-expressed 76, 77). Furthermore, Gao et al showed that H19 polymorphisms were associated with the risk of coronary artery disease (CAD). Furthermore, the T variant of rs217727 and the A variant of rs2067051 was associated with increased and decreased risk of CAD, respectively 78). Moreover, several studies confirm that lncRNA HIF1A-AS1 knockdown decreases apoptosis and promote proliferation VSMC 79-81), but whether it plays a role in atherosclerosis is yet unknown. Conclusion These studies suggest that lncRNAs are emerging important players in the process of atherosclerosis. However, only a small part of pro-atherogenic lncRNAs were identified and expounds up to present. Functional mechanism study of lncRNAs is yet in its infancy stages and requires further investigation. Actually, the poor conservative, various transcript variants, and low expression level of most lncRNAs challenged our further research. However, gain or loss of function approaches and pharmacological inhibition studies suggest that lncRNAs participate in atherosclerosis and may be potential therapeutic targets. As such, lncRNA research may provide a new breakthrough for the possibility of conquering atherosclerosis. Conflicts of Interest There are no funding sources or conflicts of interest to declare. References 1) Peters SA, den Ruijter HM, Bots ML, Moons KG. Improvements in risk stratification for the occurrence of cardiovascular disease by imaging subclinical atherosclerosis: a systematic review. Heart. 2012; 98: 177-184 2) Leung A, Natarajan R. Noncoding RNAs in vascular disease. Current opinion in cardiology. 2014; 29: 199-206 3) Uchida S, Dimmeler S. Long noncoding RNAs in cardiovascular diseases. Circulation research. 2015; 116: 737750
4) Kornfeld JW, Bruning JC. Regulation of metabolism by long, non-coding RNAs. Frontiers in genetics. 2014; 5: 57 5) Penny GD, Kay GF, Sheardown SA, Rastan S, Brockdorff N. Requirement for Xist in X chromosome inactivation. Nature. 1996; 379: 131-137 6) Arase M, Horiguchi K, Ehata S, Morikawa M, Tsutsumi S, Aburatani H, Miyazono K and Koinuma D: Transforming growth factor-beta-induced lncRNA-Smad7 inhibits apoptosis of mouse breast cancer JygMC(A) cells. Cancer science, 2014; 105: 974-982 7) Wang K, Long B, Zhou LY, Liu F, Zhou QY, Liu CY, Fan YY and Li PF: CARL lncRNA inhibits anoxia-induced mitochondrial fission and apoptosis in cardiomyocytes by impairing miR-539-dependent PHB2 downregulation. Nature communications, 2014; 5: 3596 8) Yang Y, Li H, Hou S, Hu B, Liu J, Wang J. The noncoding RNA expression profile and the effect of lncRNA AK126698 on cisplatin resistance in non-small-cell lung cancer cell. PloS one. 2013; 8: e65309 9) Klattenhoff CA, Scheuermann JC, Surface LE, Bradley RK, Fields PA, Steinhauser ML, Ding H, Butty VL, Torrey L, Haas S, Abo R, Tabebordbar M, Lee RT, Burge CB and Boyer LA: Braveheart, a long noncoding RNA required for cardiovascular lineage commitment. Cell, 2013; 152: 570-583 10) Cabili MN, Trapnell C, Goff L, Koziol M, Tazon-Vega B, Regev A and Rinn JL: Integrative annotation of human large intergenic noncoding RNAs reveals global properties and specific subclasses. Genes & development, 2011; 25: 1915-1927 11) Khalil AM, Guttman M, Huarte M, Garber M, Raj A, Rivea Morales D, Thomas K, Presser A, Bernstein BE, van Oudenaarden A, Regev A, Lander ES and Rinn JL: Many human large intergenic noncoding RNAs associate with chromatin-modifying complexes and affect gene expression. Proceedings of the National Academy of Sciences of the United States of America, 2009; 106: 1166711672 12) Guttman M, Garber M, Levin JZ, Donaghey J, Robinson J, Adiconis X, Fan L, Koziol MJ, Gnirke A, Nusbaum C, Rinn JL, Lander ES and Regev A: Ab initio reconstruction of cell type-specific transcriptomes in mouse reveals the conserved multi-exonic structure of lincRNAs. Nature biotechnology, 2010; 28: 503-510 13) Leung A, Stapleton K, Natarajan R. Functional Long Non-coding RNAs in Vascular Smooth Muscle Cells. Current topics in microbiology and immunology. 2015 14) Pan YF, Feng L, Zhang XQ, Song LJ, Liang HX, Li ZQ and Tao FB: Role of long non-coding RNAs in gene regulation and oncogenesis. Chinese medical journal, 2011; 124: 2378-2383 15) Ringrose L, Paro R. Epigenetic regulation of cellular memory by the Polycomb and Trithorax group proteins. Annual review of genetics. 2004; 38: 413-443 16) Moazed D. Mechanisms for the inheritance of chromatin states. Cell. 2011; 146: 510-518 17) Ragunathan K, Jih G, Moazed D. Epigenetics. Epigenetic inheritance uncoupled from sequence-specific recruitment. Science. 2015; 348: 1258699
Advance Publication LncRNAs in Atherosclerosis Journal of Atherosclerosis and Thrombosis 7 Accepted for publication: November 4, 2015 Published online: December 22, 2015 18) Rinn JL, Kertesz M, Wang JK, Squazzo SL, Xu X, Brugmann SA, Goodnough LH, Helms JA, Farnham PJ, Segal E and Chang HY: Functional demarcation of active and silent chromatin domains in human HOX loci by noncoding RNAs. Cell, 2007; 129: 1311-1323 19) Saxena A, Carninci P. Long non-coding RNA modifies chromatin: epigenetic silencing by long non-coding RNAs. BioEssays: news and reviews in molecular, cellular and developmental biology. 2011; 33: 830-839 20) Rizki G, Boyer LA. Lncing Epigenetic Control of Transcription to Cardiovascular Development and Disease. Circulation research. 2015; 117: 192-206 21) Mercer TR, Mattick JS. Structure and function of long noncoding RNAs in epigenetic regulation. Nature structural & molecular biology. 2013; 20: 300-307 22) Zhao J, Sun BK, Erwin JA, Song JJ, Lee JT. Polycomb proteins targeted by a short repeat RNA to the mouse X chromosome. Science. 2008; 322: 750-756 23) Plath K, Fang J, Mlynarczyk-Evans SK, Cao R, Worringer KA, Wang H, de la Cruz CC, Otte AP, Panning B and Zhang Y: Role of histone H3 lysine 27 methylation in X inactivation. Science, 2003; 300: 131-135 24) Wang J, Mager J, Chen Y, Schneider E, Cross JC, Nagy A and Magnuson T: Imprinted X inactivation maintained by a mouse Polycomb group gene. Nature genetics, 2001; 28: 371-375 25) Froberg JE, Yang L, Lee JT. Guided by RNAs: X-inactivation as a model for lncRNA function. Journal of molecular biology. 2013; 425: 3698-3706 26) Mohammad F, Pandey GK, Mondal T, Enroth S, Redrup L, Gyllensten U and Kanduri C: Long noncoding RNAmediated maintenance of DNA methylation and transcriptional gene silencing. Development, 2012; 139: 2792-2803 27) Berghoff EG, Clark MF, Chen S, Cajigas I, Leib DE, Kohtz JD. Evf2 (Dlx6as) lncRNA regulates ultraconserved enhancer methylation and the differential transcriptional control of adjacent genes. Development. 2013; 140: 4407-4416 28) Martens JA, Laprade L, Winston F. Intergenic transcription is required to repress the Saccharomyces cerevisiae SER3 gene. Nature. 2004; 429: 571-574 29) Martianov I, Ramadass A, Serra Barros A, Chow N, Akoulitchev A. Repression of the human dihydrofolate reductase gene by a non-coding interfering transcript. Nature. 2007; 445: 666-670 30) Wang X, Arai S, Song X, Reichart D, Du K, Pascual G, Tempst P, Rosenfeld MG, Glass CK and Kurokawa R: Induced ncRNAs allosterically modify RNA-binding proteins in cis to inhibit transcription. Nature, 2008; 454: 126-130 31) Lin R, Roychowdhury-Saha M, Black C, Watt AT, Marcusson EG, Freier SM and Edgington TS: Control of RNA processing by a large non-coding RNA overexpressed in carcinomas. FEBS letters, 2011; 585: 671676 32) Souquere S, Beauclair G, Harper F, Fox A, Pierron G. Highly ordered spatial organization of the structural long noncoding NEAT1 RNAs within paraspeckle nuclear bodies. Molecular biology of the cell. 2010; 21: 4020-
4027 33) Clemson CM, Hutchinson JN, Sara SA, Ensminger AW, Fox AH, Chess A and Lawrence JB: An architectural role for a nuclear noncoding RNA: NEAT1 RNA is essential for the structure of paraspeckles. Molecular cell, 2009; 33: 717-726 34) Kretz M, Siprashvili Z, Chu C, Webster DE, Zehnder A, Qu K, Lee CS, Flockhart RJ, Groff AF, Chow J, Johnston D, Kim GE, Spitale RC, Flynn RA, Zheng GX, Aiyer S, Raj A, Rinn JL, Chang HY and Khavari PA: Control of somatic tissue differentiation by the long non-coding RNA TINCR. Nature, 2013; 493: 231-235 35) Cesana M, Cacchiarelli D, Legnini I, Santini T, Sthandier O, Chinappi M, Tramontano A and Bozzoni I: A long noncoding RNA controls muscle differentiation by functioning as a competing endogenous RNA. Cell, 2011; 147: 358-369 36) Onat D, Brillon D, Colombo PC, Schmidt AM. Human vascular endothelial cells: a model system for studying vascular inflammation in diabetes and atherosclerosis. Current diabetes reports. 2011; 11: 193-202 37) Martinet W, Schrijvers DM, De Meyer GR. Molecular and cellular mechanisms of macrophage survival in atherosclerosis. Basic research in cardiology. 2012; 107: 297 38) Ho-Tin-Noe B, Michel JB. Initiation of angiogenesis in atherosclerosis: smooth muscle cells as mediators of the angiogenic response to atheroma formation. Trends in cardiovascular medicine. 2011; 21: 183-187 39) McPherson R, Pertsemlidis A, Kavaslar N, Stewart A, Roberts R, Cox DR, Hinds DA, Pennacchio LA, Tybjaerg-Hansen A, Folsom AR, Boerwinkle E, Hobbs HH and Cohen JC: A common allele on chromosome 9 associated with coronary heart disease. Science, 2007; 316: 1488-1491 40) Helgadottir A, Thorleifsson G, Manolescu A, Gretarsdottir S, Blondal T, Jonasdottir A, Jonasdottir A, Sigurdsson A, Baker A, Palsson A, Masson G, Gudbjartsson DF, Magnusson KP, Andersen K, Levey AI, Backman VM, Matthiasdottir S, Jonsdottir T, Palsson S, Einarsdottir H, Gunnarsdottir S, Gylfason A, Vaccarino V, Hooper WC, Reilly MP, Granger CB, Austin H, Rader DJ, Shah SH, Quyyumi AA, Gulcher JR, Thorgeirsson G, Thorsteinsdottir U, Kong A and Stefansson K: A common variant on chromosome 9p21 affects the risk of myocardial infarction. Science, 2007; 316: 1491-1493 41) Holdt LM, Hoffmann S, Sass K, Langenberger D, Scholz M, Krohn K, Finstermeier K, Stahringer A, Wilfert W, Beutner F, Gielen S, Schuler G, Gabel G, Bergert H, Bechmann I, Stadler PF, Thiery J and Teupser D: Alu elements in ANRIL non-coding RNA at chromosome 9p21 modulate atherogenic cell functions through trans-regulation of gene networks. PLoS genetics, 2013; 9: e1003588 42) Holdt LM and Teupser D: Recent studies of the human chromosome 9p21 locus, which is associated with atherosclerosis in human populations. Arteriosclerosis, thrombosis, and vascular biology, 2012; 32: 196-206 43) Yap KL, Li S, Munoz-Cabello AM, Raguz S, Zeng L, Mujtaba S, Gil J, Walsh MJ and Zhou MM: Molecular interplay of the noncoding RNA ANRIL and methylated histone H3 lysine 27 by polycomb CBX7 in transcrip-
8
Advance Publication Jian et al . Journal of Atherosclerosis and Thrombosis Accepted for publication: November 4, 2015 Published online: December 22, 2015
tional silencing of INK4a. Molecular cell, 2010; 38: 662674 44) Kotake Y, Nakagawa T, Kitagawa K, Suzuki S, Liu N, Jian et al. Kitagawa M and Xiong Y: Long non-coding RNA ANRIL is required for the PRC2 recruitment to and silencing of p15(INK4B) tumor suppressor gene. Oncogene, 2011; 30: 1956-1962 45) Lusis AJ: Atherosclerosis. Nature, 2000; 407: 233-241 46) Jarinova O, Stewart AF, Roberts R, Wells G, Lau P, Naing T, Buerki C, McLean BW, Cook RC, Parker JS and McPherson R: Functional analysis of the chromosome 9p21.3 coronary artery disease risk locus. Arteriosclerosis, thrombosis, and vascular biology, 2009; 29: 1671-1677 47) Holdt LM, Beutner F, Scholz M, Gielen S, Gabel G, Bergert H, Schuler G, Thiery J and Teupser D: ANRIL expression is associated with atherosclerosis risk at chromosome 9p21. Arteriosclerosis, thrombosis, and vascular biology, 2010; 30: 620-627 48) Yan B, Yao J, Liu JY, Li XM, Wang XQ, Li YJ, Tao ZF, Song YC, Chen Q and Jiang Q: lncRNA-MIAT regulates microvascular dysfunction by functioning as a competing endogenous RNA. Circulation research, 2015; 116: 11431156 49) Zachary I: VEGF signalling: integration and multi-tasking in endothelial cell biology. Biochemical Society transactions, 2003; 31: 1171-1177 50) Ji P, Diederichs S, Wang W, Boing S, Metzger R, Schneider PM, Tidow N, Brandt B, Buerger H, Bulk E, Thomas M, Berdel WE, Serve H and Muller-Tidow C: MALAT-1, a novel noncoding RNA, and thymosin beta4 predict metastasis and survival in early-stage non-small cell lung cancer. Oncogene, 2003; 22: 8031-8041 51) Michalik KM, You X, Manavski Y, Doddaballapur A, Zornig M, Braun T, John D, Ponomareva Y, Chen W, Uchida S, Boon RA and Dimmeler S: Long noncoding RNA MALAT1 regulates endothelial cell function and vessel growth. Circulation research, 2014; 114: 13891397 52) Watts R, Johnsen VL, Shearer J and Hittel DS: Myostatin-induced inhibition of the long noncoding RNA Malat1 is associated with decreased myogenesis. American journal of physiology Cell physiology, 2013; 304: C9951001 53) Guevara NV, Kim HS, Antonova EI and Chan L: The absence of p53 accelerates atherosclerosis by increasing cell proliferation in vivo. Nature medicine, 1999; 5: 335339 54) Merched AJ, Williams E and Chan L: Macrophage-specific p53 expression plays a crucial role in atherosclerosis development and plaque remodeling. Arteriosclerosis, thrombosis, and vascular biology, 2003; 23: 1608-1614 55) van Vlijmen BJ, Gerritsen G, Franken AL, Boesten LS, Kockx MM, Gijbels MJ, Vierboom MP, van Eck M, van De Water B, van Berkel TJ and Havekes LM: Macrophage p53 deficiency leads to enhanced atherosclerosis in APOE*3-Leiden transgenic mice. Circulation research, 2001; 88: 780-786 56) Mercer J and Bennett M: The role of p53 in atherosclerosis. Cell cycle, 2006; 5: 1907-1909 57) Jackson SP and Bartek J: The DNA-damage response in
human biology and disease. Nature, 2009; 461: 10711078 58) Mercer J, Figg N, Stoneman V, Braganza D and Bennett MR: Endogenous p53 protects vascular smooth muscle cells from apoptosis and reduces atherosclerosis in ApoE knockout mice. Circulation research, 2005; 96: 667-674 59) Huarte M, Guttman M, Feldser D, Garber M, Koziol MJ, Kenzelmann-Broz D, Khalil AM, Zuk O, Amit I, Rabani M, Attardi LD, Regev A, Lander ES, Jacks T and Rinn JL: A large intergenic noncoding RNA induced by p53 mediates global gene repression in the p53 response. Cell, 2010; 142: 409-419 60) Wu G, Cai J, Han Y, Chen J, Huang ZP, Chen C, Cai Y, Huang H, Yang Y, Liu Y, Xu Z, He D, Zhang X, Hu X, Pinello L, Zhong D, He F, Yuan GC, Wang DZ and Zeng C: LincRNA-p21 regulates neointima formation, vascular smooth muscle cell proliferation, apoptosis, and atherosclerosis by enhancing p53 activity. Circulation, 2014; 130: 1452-1465 61) Brasier AR, Recinos A, 3rd and Eledrisi MS: Vascular inflammation and the renin-angiotensin system. Arteriosclerosis, thrombosis, and vascular biology, 2002; 22: 1257-1266 62) Leung A, Trac C, Jin W, Lanting L, Akbany A, Saetrom P, Schones DE and Natarajan R: Novel long noncoding RNAs are regulated by angiotensin II in vascular smooth muscle cells. Circulation research, 2013; 113: 266-278 63) Zhu N, Zhang D, Chen S, Liu X, Lin L, Huang X, Guo Z, Liu J, Wang Y, Yuan W and Qin Y: Endothelial enriched microRNAs regulate angiotensin II-induced endothelial inflammation and migration. Atherosclerosis, 2011; 215: 286-293 64) Liu X, Cheng Y, Zhang S, Lin Y, Yang J and Zhang C: A necessary role of miR-221 and miR-222 in vascular smooth muscle cell proliferation and neointimal hyperplasia. Circulation research, 2009; 104: 476-487 65) Bell RD, Long X, Lin M, Bergmann JH, Nanda V, Cowan SL, Zhou Q, Han Y, Spector DL, Zheng D and Miano JM: Identification and initial functional characterization of a human vascular cell-enriched long noncoding RNA. Arteriosclerosis, thrombosis, and vascular biology, 2014; 34: 1249-1259 66) Glass CK and Witztum JL: Atherosclerosis. the road ahead. Cell, 2001; 104: 503-516 67) Friedman AD: Transcriptional control of granulocyte and monocyte development. Oncogene, 2007; 26: 6816-6828 68) El Gazzar M and McCall CE: MicroRNAs regulatory networks in myeloid lineage development and differentiation: regulators of the regulators. Immunology and cell biology, 2012; 90: 587-593 69) Chen MT, Lin HS, Shen C, Ma YN, Wang F, Zhao HL, Yu J and Zhang JW: PU.1-Regulated Long Noncoding RNA lnc-MC Controls Human Monocyte/Macrophage Differentiation through Interaction with MicroRNA 199a-5p. Molecular and cellular biology, 2015; 35: 32123224 70) Carpenter S, Aiello D, Atianand MK, Ricci EP, Gandhi P, Hall LL, Byron M, Monks B, Henry-Bezy M, Lawrence JB, O,Neill LA, Moore MJ, Caffrey DR and Fitzgerald KA: A long noncoding RNA mediates both activation
Advance Publication LncRNAs in Atherosclerosis Journal of Atherosclerosis and Thrombosis 9 Accepted for publication: November 4, 2015 Published online: December 22, 2015 and repression of immune response genes. Science, 2013; 341: 789-792 71) Hu YW, Yang JY, Ma X, Chen ZP, Hu YR, Zhao JY, Li SF, Qiu YR, Lu JB, Wang YC, Gao JJ, Sha YH, Zheng L and Wang Q: A lincRNA-DYNLRB2-2/GPR119/GLP1R/ABCA1dependent signal transduction pathway is essential for the regulation of cholesterol homeostasis. Journal of lipid research, 2014; 55: 681-697 72) Wang P, Xue Y, Han Y, Lin L, Wu C, Xu S, Jiang Z, Xu J, Liu Q and Cao X: The STAT3-binding long noncoding RNA lnc-DC controls human dendritic cell differentiation. Science, 2014; 344: 310-313 73) Manthey HD and Zernecke A: Dendritic cells in atherosclerosis: functions in immune regulation and beyond. Thrombosis and haemostasis, 2011; 106: 772-778 74) Halley P, Kadakkuzha BM, Faghihi MA, Magistri M, Zeier Z, Khorkova O, Coito C, Hsiao J, Lawrence M and Wahlestedt C: Regulation of the apolipoprotein gene cluster by a long noncoding RNA. Cell reports, 2014; 6: 222230 75) Lund-Katz S and Phillips MC: High density lipoprotein structure-function and role in reverse cholesterol transport. Sub-cellular biochemistry, 2010; 51: 183-227 76) Han DK, Khaing ZZ, Pollock RA, Haudenschild CC and Liau G: H19, a marker of developmental transition, is reexpressed in human atherosclerotic plaques and is regulated by the insulin family of growth factors in cultured rabbit smooth muscle cells. J Clin Invest, 1996; 97: 12761285
77) Kim DK, Zhang L, Dzau VJ and Pratt RE: H19, a developmentally regulated gene, is reexpressed in rat vascular smooth muscle cells after injury. J Clin Invest, 1994; 93: 355-360 78) Gao W, Zhu M, Wang H, Zhao S, Zhao D, Yang Y, Wang ZM, Wang F, Yang ZJ, Lu X and Wang LS: Association of polymorphisms in long non-coding RNA H19 with coronary artery disease risk in a Chinese population. Mutation research, 2015; 772: 15-22 79) Wang J, Chen L, Li H, Yang J, Gong Z, Wang B and Zhao X: Clopidogrel reduces apoptosis and promotes proliferation of human vascular endothelial cells induced by palmitic acid via suppression of the long non-coding RNA HIF1A-AS1 in vitro. Molecular and cellular biochemistry, 2015; 404: 203-210 80) He Q, Tan J, Yu B, Shi W and Liang K: Long noncoding RNA HIF1A-AS1A reduces apoptosis of vascular smooth muscle cells: implications for the pathogenesis of thoracoabdominal aorta aneurysm. Die Pharmazie, 2015; 70: 310-315 81) Wang S, Zhang X, Yuan Y, Tan M, Zhang L, Xue X, Yan Y, Han L and Xu Z: BRG1 expression is increased in thoracic aortic aneurysms and regulates proliferation and apoptosis of vascular smooth muscle cells through the long non-coding RNA HIF1A-AS1 in vitro. European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery, 2015; 47: 439-446
