Noncoding RNAs in Hypertension.

High blood pressure or hypertension is an outstanding public health problem affecting nearly 40% of the World’s adult population. Prevalence of hypertension has a strong socioeconomic impact and health burden. Recently, hypertension has reached epidemic proportions, and it is estimated that ≈25% of adult individuals will be hypertensive in the World by 2025.[1] Untreated hypertension can result in various health complications, such as stroke, myocardial infarction, vascular disease, and chronic kidney diseases.[2]

Generally, hypertension is categorized as either primary or secondary according to its cause. However, there are several types of hypertension that are more or less common such as essential hypertension (EHT), pulmonary hypertension (PHT), pulmonary arterial hypertension (PAHT), white coat hypertension, and nocturnal hypertension. This article focuses on the 3 first types for which a significant amount of information on the role of noncoding RNAs (ncRNAs) is available. Essential, primary, or idiopathic hypertension refers to elevated blood pressure in which secondary causes such as renovascular disease, renal failure, pheochromocytoma, aldosteronism, or other causes of secondary hypertension, or Mendelian forms are not present.[3] EHT is the most frequent type of hypertension, which accounts for 95% of all cases.

PHT refers to an elevation of the pulmonary arterial pressure above 25 mm Hg at rest as assessed by right heart catheterization.[4] This elevation can be caused by different underlying diseases, such as liver disease, thromboembolic disease, rheumatic disorders, lung conditions, including tumors, chronic obstructive pulmonary disease, pulmonary fibrosis, or cardiovascular diseases, including aortic valve disease, heart failure, and congenital heart disease. According to the latest World Health Organization classification, PHT is classified depending on its cause into 5 groups: PAHT, PHT caused by left heart disease, PHT caused by lung disease, PHT caused by chronic blood clots, and PHT associated with other unclear conditions.

PAHT is defined as pulmonary vasculopathy and progressive pulmonary vasculature remodeling that cause the rise of pulmonary arterial pressure.[5] Although PAHT is classified as a specific subgroup of PHT, in the literature, PHT is often used instead of PAHT. Thus, while PHT refers to an elevation of pressure in the lung arteries caused by a side disease, PAHT is caused by remodeling of pulmonary blood vessels.

Owing to the fact that blood pressure is regulated by multiple physiological pathways, it is difficult to decipher a single causative agent of hypertension. Recent studies have shown that complex multifactorial cause of hypertension results from a dynamic interplay of genetic and environmental factors.[6] Polygenic nature of hypertension involves many genes each with mild cumulative effects reacting to environmental factors that contribute to hypertension. Population-based studies have demonstrated that Mendelian forms of hypertension can be found in about 20% of families and reach 60% in twins.[7,8] Integration of data from genome-wide linkage and association studies and system genetics approaches allowed the identification of >100 single nucleotide polymorphisms implicated in high blood pressure.[9,10] Studies aiming to decipher the molecular pathways of high blood pressure have identified genes involved in the renin-angiotensin-aldosterone system (RAAS), signaling through G protein-coupled receptors, vascular inflammation, remodeling, and in the structure and regulation of vascular senescence and developmental programming.[11]

Although significant progress has been achieved in elucidating the molecular pathways involved in the pathophysiology of hypertension, the regulatory function of these pathways remains to be fully elucidated. Recent advances in epigenetics may provide at least some of the missing pieces of the hereditary puzzle that can explain the fact that a same genome can provide distinct phenotypes, without alterations in primary DNA structure.[12] The key factor in figuring out the complex multifactorial nature of hypertension might well hence be the dark matter of the human genome. Indeed, while it used to be commonly accepted that each of human genes would encode proteins, it has more recently been discovered that the majority (>95%) of these genes are unable to produce proteins.[13] These genes are transcribed into ncRNA molecules and they play multiple important roles in regulating protein-coding genes. The ubiquitous expression of ncRNAs allows them to regulate many physiological and pathological processes, in virtually all cell types. Because their discovery, ncRNAs have attracted an exponential interest by the biomedical research community, notably in the area of cardiovascular diseases and their major risk factor, hypertension.[14] NcRNAs have been arbitrarily classified into short and long ncRNAs with a threshold of 200 nucleotides.[15] In addition, ncRNAs have been classified according to their cellular localization (nuclear versus cytoplasmic), mechanism of action and structure.[15,16] This review presents a comprehensive overview of the current knowledge of the role of ncRNAs in the complex regulatory processes involved in the pathophysiology of hypertension. We focus on microRNAs (miRNAs), long ncRNAs (lncRNAs), and circular RNAs (circRNAs). Because different ncRNAs regulate different types of hypertension, we separately review existing data on the 3 most prevalent types of hypertension, namely EHT, PHT, and PAHT.

Search Strategy, Data Synthesis, and Data Analysis

We searched all published studies in the PubMed database (up to March 31, 2019) using the following combination of keywords: “noncoding RNA AND hypertension” (Figure 1A). Furthermore, manual searches for related articles were performed to avoid missing any relevant study. A total of 1476 records were initially identified by searching the PubMed database. After reading the titles and abstracts, we excluded 269 articles with inadequate data, 6 articles not written in English, 39 reviews or commentaries, and 1046 that did not focus on ncRNAs and hypertension (Figure 1B). The remaining 116 full articles were then assessed according to following criteria: studies aimed to investigate the relationship between ncRNAs and hypertension, clinical, animal, in vitro and in silico studies, available data on ncRNAs expression levels, proposed functional role, target gene, and biomarker potential. This filtering step resulted in excluding 14 articles focused on other cardiovascular disease than hypertension, messenger RNAs (mRNAs) or single nucleotide polymorphisms in hypertension. Finally, 102 original articles were included in the present review and were stratified according to the type of hypertension (Figure 1B). The following information was extracted from each article: first author, year of publication, type of ncRNAs, method of detection, species, type of samples, expression of ncRNAs in hypertension, ncRNA’s target gene and method of target gene detection, and proposed role of ncRNAs in hypertension.

Figure 1.

Literature search. A, Flow chart methodology used for data extraction (original articles). PubMed search was performed using the keywords “noncoding RNA AND hypertension.” B, Distribution of evaluated and included original articles according to type of hypertension. CVD indicates cardiovascular disease; EHT, essential hypertension; mRNA, messenger RNA; ncRNA, noncoding RNA; NHT, nocturnal hypertension; OA, original articles; PAHT, pulmonary arterial hypertension; PHT, pulmonary hypertension; SNPs, single nucleotide polymorphisms; and WCHT, white coat hypertension.

MiRNAs and Hypertension

MiRNAs are short endogenous conserved ncRNAs with important roles in regulating gene expression programs that underlie normal and pathological cellular processes, including cardiovascular diseases.[17] Individual miRNAs have the capacity to simultaneously regulate a large number of genes through their coordinated activities on different pathways and networks. Increasing data have revealed that abnormal miRNAs expression and function can be related to pathogenesis or target organ damages of hypertension. MiRNAs are remarkably stable and are present in circulating cells or exosomes found in body fluids, such as blood, serum, and urine.[14] Because of miRNAs presence in body fluids and their altered expression levels in elevated blood pressure, they have drawn attention as potential biomarkers for different types of hypertension.

MiRNAs in EHT

The expression profiles, target genes, and proposed functional roles of miRNAs shown to be associated with EHT are shown in Table 1. Regulation of miRNA expression levels was obtained either by comparing patients with hypertension and healthy individuals, or in animal models of hypertension, or in cultured cells. This heterogeneity accounts for some of the variability between reports. Owing to the fact that miRNAs and their target genes are involved in a complex molecular network of vascular metabolism, they may affect EHT development in several ways.

Table 1.

MicroRNAs Associated With EHT

The RAAS represents a well-tuned network of peptides, substrates, enzymes, hormones, and receptors that act together to regulate blood pressure. Multiple miRNAs interact with the RAAS system. Downregulated miR-34b, miR-361-5p, miR-362-5p, and miR-181a, acting via their target genes, may alter homeostasis of the RAAS.[18-20] MiR-29b alters Sp1-TGF (transforming growth factor)-β/Smad-nuclear factor-kappa B signaling pathways in human and rats.[21] Furthermore, upregulation of miR-34c-5p, miR-449b, miR-571, miR-765, miR-483-3p, miR-143/145, miR-21, miR-126, miR-196a, miR-132, miR-212, and miR-451 may induce an imbalance in RAAS system resulting in elevated blood pressure.[45] MiR-663 can regulate REN (renin) and APOE (apolipoprotein E) mRNA levels via binding to REN and APOE 3′ untranslated regions whereas miR-181a regulates REN and AIFM1 (apoptosis-inducing factor mitochondria-associated 1) mRNAs.[22] Three studies reported that downregulation of miR-31a-5p,[23] miR-142-3p,[24] miR-4763-5p,[25] and miR-4717-3p[25] can induce a loss of control of cell proliferation and apoptosis in pulmonary artery smooth muscle cell (PASMCs) and platelets in rats, while downregulated miR-4709-3p via target gene apolipoprotein L3 gene (APOL3) induces apoptosis of human peripheral blood mononuclear cells.[25] Cardiac hypertrophy in patients with EHT might be caused by the presence of the C allele of rs17168525 located in the let-7/miR-98-binding site of myotrophin gene (MTPN).[26] Thus, let-7c overexpression can cause a significant decrease in the level of myotrophin protein. Furthermore, overexpression of miR-103a-2-5p or miR-585-5p may affect oxidative DNA damage and cell survival by regulating poly-(ADP-ribose) polymerase 1 (PARP-1) gene expression in human aortic endothelial cells (ECs) and human umbilical vein ECs.[30]

It is widely known that elevated oxygen levels may induce vascular wall remodeling associated with endothelial dysfunction, inflammation, and cell migration. Overexpression of miR-21 is positively correlated with elevated blood pressure in humans, and it has been shown to directly target mitochondrial genome-encoded cytochrome b (mt-Cytb), thereby enhancing the production of reactive oxygen species in the spontaneously hypertensive rat model.[31] Moreover, overexpression of miR-21 can trigger the atherosclerotic process in patients with EHT by targeting eNOS (endothelial nitric oxide synthase).[32] Upregulation of miR-135a, miR-376a, hcmv-miR-UL112, miR-296-5p, and miR-let-7e may induce neuromodulation and catecholaminergic regulation, together with immunologic, inflammatory, and anti-infection responses in human and rat.[33,34] In addition to hypothalamic hormone regulation of blood pressure, hypothalamic inflammation can be a trigger of pathological events, such as oxidative stress and endothelial dysfunction in hypertensive patients.

ECs play a crucial role in the development, maintenance, and remodeling of vascular network.[46] Dysfunctional vascular endothelium leads to impaired vasodilatation and a proinflammatory and prothrombic phenotype of the vessel wall.[47] MiRNAs play significant roles in the vascular wall and their deregulation may alter the function of ECs. MiR-505 and miR-126 are necessary for angiogenesis and endothelial migration.[35,46] MiR-130a and miR-487b regulate the proliferation of vascular smooth muscle cells (VSMCs) and medial smooth muscle cells via downregulation of GAX (growth arrest homeobox transcription factor)[36] and IRS1 (insulin receptor substrate 1)[37] expression, which may contribute to vascular remodeling in vascular disorders such as EHT. Finally, many of the miRNAs listed in Table 1 have been shown to be downregulated or upregulated in hypertensive subjects or in animal models,[27-29,38-44] although their role in the development and progression of EHT remains to be elucidated.

MiRNAs in PHT

MiRNAs have an important role in the maintenance of pulmonary vascular homeostasis and in the pathogenesis of PHT[48] (Table 2). MiR-let-7b might be involved in the pathogenesis of chronic thromboembolic PHT by affecting ET-1 (endothelin-1) expression and the migration of pulmonary artery ECs and PASMCs.[49] Downregulation of miR-208 was observed during the progression towards right ventricular failure and its inhibition activates the complex mediator of transcription 13/nuclear receptor corepressor 1 axis, which, in turn, promotes Mef2 inhibition.[50] By targeting androgen receptor and protein kinase C-α, miR-3148, which is downregulated in chronic thromboembolic PHT, might play a role in the development of chronic thromboembolic PHT.[51] In female mice carrying a heterozygous mutation of the bone morphogenetic protein receptor II gene (BMPRII), downregulation of miR-96 was associated with a concomitant upregulation of the 5-hydroxytryptamine 1B receptor and an increase in the proliferation of PASMCs, which may explain the association between miR-96 and the development of PHT in women.[52]

Table 2.

MicroRNAs Associated With PHT

The ubiquitous miR-21 display upregulated expression levels in plasma samples from humans and mice with PHT, lung, right ventricular tissues, and human pulmonary arterial ECs.[53,54] Integration of data obtained by different approaches such as combination of in silico predictions, cell culture data, and animal experiments, demonstrated that miR-21 acts in Rho/Rho kinase signaling pathway as well as in pathways associated with hypoxia, inflammation, and genetic haploinsufficiency of the BMPRII gene to control the development of PHT.[53]

MiRNA-328 regulates hypoxic PHT by targeting IGF-1R (insulin growth factor 1 receptor) and L-type calcium channel-1C (CaV1.2), causing pulmonary vascular remodeling in human and rats.[55] Upregulated miR-214 and miR-125a may cause proliferation of PASMCs and pulmonary ECs in PHT.[56-58] The miR-130/301 family plays an important role in the regulation of multiple proliferation pathways in PHT, such as apelin-miR-424/503-FGF2 signaling in smooth muscular cells, miR-130/301 modulated STAT3-miR-204 signaling, and endothelial signaling.[59,60] Thus, these findings suggest that inhibition of miR-130/301 may prevent PHT pathogenesis.

MiRNAs in PAHT

A summary of miRNAs, their targets and proposed role associated with PAHT is presented in Table 3. MiR-124, via targeting the splicing factor PTPB1 (polypyrimidine-tract binding protein) and PKM1/PKM2 (pyruvate kinase M2), may cause highly proliferative, migratory, inflammatory and metabolic abnormalities in PASMCs and fibroblasts.[64] Modification of the dysregulated miR-124, PTBP1 and PKM2 pathways may restore the normal glycolytic flux in ECs. The association between PAHT and APLN (apelin) and FGF (fibroblast growth factor) signaling pathways in the pulmonary vasculature is mediated by miR-424 and miR-503.[65] MiR-125-3p, miR-148-3p, and miR-193 may contribute to PAHT pathogenesis via dysregulation of TGF-β pathway, which plays an important role in pulmonary blood vessel angiogenesis, macrophage infiltration, and cytokine expression in the lungs.[66] The miR-143/145 cluster is abundantly expressed in smooth muscle cells, and its promoter responds to TGF-β by increasing the expression of mature forms of miRNAs.[67] Moreover, miR-22, miR-30, miR-let-7f,[68] and miR-140-5p[69] have been reported as important players in the dysregulation of TGF-β and BMP (bone morphogenetic protein) signaling pathways in PAHT. Downregulation of miR-140-5p and upregulation of TNF-α (tumor necrosis factor-α) may induce pathological events in PAHT.[70]

Table 3.

MicroRNAs Associated With PAHT

Several miRNAs are involved in the regulation of VEGFA (vascular endothelial growth factor A) pathway. Specifically, miR-126 is enriched in ECs and its dysregulation enhances the proangiogenic response of ECs to VEGF by repressing mRNA expression of VEGFA suppressor SPRED-1 (Sprouty-related EVH1 domain-containing protein 1) and PI3KR2 (phosphatidylinositol 3-kinase regulatory subunit β).[71,72] In addition, loss of miR-126 diminishes MAPK (mitogen-activated protein kinase) signaling in response to VEGFA and FGF, whereas gain of miR-126 enhances angiogenesis signaling.[73]

While most miRNAs are synthesized by a canonical pathway, deep sequencing technologies have revealed a class of miRNAs that can be generated by noncanonical biogenesis. Interestingly, mutations in BMPRII (causing heritable PAHT) or downstream mediator mothers against decapentaplegic homolog 9 (SMAD9) abrogated noncanonical processing of miR-21 and miR-27a which show antiproliferative properties on human pulmonary artery ECs and human PASMCs, providing a link between miR-21, miR-27a, and PAHT.[74] These findings emphasize the importance of the identification of heterozygous mutations of SMAD9 gene that can effectively distinguish between the canonical and noncanonical pathways in the pathogenesis of PAHT.

Downregulated miR-223 in human and rat lung tissue can be correlated to pathological DNA repair, increased proliferation, and suppressed apoptosis.[75] MiR-204 and its putative targets are implicated in pathways correlated to cell proliferation and resistance to apoptosis. Despite the fact that miR-204 might regulate several pathways in PAH-PASMCs including Rho-associated, coiled-coil–containing protein kinase (RhoA-ROCK), and NFAT (nuclear factor of activated T cells) pathways, aberrant expression of miR-204 might be critical for PAHT pathogenesis.[76] However, downregulation of several miRNAs might protect against the development of PAHT. MiR-145 was shown to be abundantly expressed in the vessel wall,[88] and mutations in BMPRII lead to upregulation of miR-145 in mice and patients with PAHT.[68] In line with these findings, manipulation of miR-145 may represent a novel strategy in PAHT treatment. Wnt/β-catenin signaling pathway is a key mediator of cell-cell signaling during embryonic development, cell proliferation, cell migration, cell polarity, neural patterning, and carcinogenesis. It is a highly conserved pathway that consists of the canonical or Wnt/β-catenin dependent pathway and the noncanonical or β-catenin–independent pathway. Interestingly, the Wnt/β-catenin signaling pathway is one of the critical pathways in PAHT pathogenesis. Aberrantly expressed miR-let-7a-5p, miR-26b-5p, miR-27b-3p, miR-199a-3p, miR-656,[78] and miR-199a-3p[79] strongly correlate to major PAHT-related pathways, including Wnt/β-catenin signaling pathway. Moreover, upregulated miR-27b targets NOTCH1 (notch receptor 1)[80] and PPAR-γ (peroxisome proliferator-activated receptor γ)[81] in the NOTCH, Hsp90-eNOS, and nitric oxide signaling pathways respectively, leading to progression of PAHT.

A common feature of miRNAs is their pleiotropic effects because of regulation of several target genes and thereby several biological pathways. As an example, miR-23a has shown a pleiotropic effect on the function of several PAHT-related genes including PGC1-α (PPAR-γ coactivator 1-α), CYTC (cytochrome C), SOD (superoxide dismutase), NRF2 (nuclear factor 2), and HO1 (heme oxygenase 1).[82]

Right ventricular hypertrophy and lung vascular remodeling are strongly correlated with PAHT. Reduced miR-322-5p contributes to the PAH-related right ventricular hypertrophy by increasing the expression of IGF-1 (insulin-like growth factor 1).[83] Overexpression of miR-130a in lung microvascular ECs is critical in lung vascular remodeling, an effect involving its target gene BMPRII.[84] Multiple other miRNAs have been shown to be aberrantly expressed, and their role in the pathogenesis of PAHT needs to be further explored.[77,85-87]

Common miRNAs in EHT, PHT, and PAHT Pathogenesis

Integration of published data revealed that multiple miRNAs are associated with the pathogenesis of different types of hypertension (Figure 2). This was expected considering their pleiotropic properties, their ability to regulate the expression of numerous target genes, and their involvement in complex regulatory networks. However, only 2 miRNAs, miR-21 and miR-130a, were found to be upregulated in EHT, PHT, and PAHT. MiR-21 is highly expressed and its role in VSMC proliferation and apoptosis, cardiac cell growth and death, cardiac fibroblast functions, and hypertension has been extensively reported.[89] Blood pressure-related changes in circulating concentrations of miR-21 may play a role in the increased risk of vascular disease and associated events in adults with hypertension.[90] The dysregulation of miR-21 expression induced by the hypobaric hypoxia closely correlates to decreased arterial blood oxygen content parameters in healthy humans that may cause proliferative status of PASMCs and pulmonary artery ECs in the early phase of hypoxic exposure.[91] Increased levels of miR-21 and BNP (B-type natriuretic peptide) have been shown in patients with pregnancy-induced hypertension.[92] Additionally, the elevated expression of miR-21 correlates with white coat hypertension.[93,94]

Figure 2.

Venn diagram of the number of microRNAs (miRNAs) overlap between different types of hypertension. MiRNA-21↑ and miR-130a↑ are upregulated in all types of hypertension. MiRNA-126↓ and miR-145↑ are common for essential hypertension (EHT) and pulmonary arterial hypertension (PAHT), while miR-204↓, miR-424↓ and miR-503↓ are downregulated in PAHT and PHT. ↑, upregulated; ↓, downregulated.

MiRNA-130a is the most abundantly expressed member of the miR-130 family and correlates with vascular remodeling. Recent data offer evidence that the elevated expression levels of miR-130a may participate in the pathogenesis of different types of hypertension through pleiotropic effects on several target genes involved in vascular remodeling.[95] However, its therapeutic potential in hypertension remains to be addressed. Additionally, we observed that downregulated miR-126 and upregulated miR-145 are common for EHT and PAHT, while miR-204, miR-424, and miR-503 are downregulated in PAHT and PHT. These findings motivate future research on the role of miRNAs in the complex regulatory networks responsible for the development of different types of hypertension.

Interaction Between Host miRNAs and the Gut Microbiota in Hypertension

In the last decade, the role of gut microbiota in the pathogenesis of hypertension has attracted some interest. The gut microbiota consists of a plethora of different microbes that play essential roles in the development of immune function, cell proliferation, and metabolism, by regulating roughly 10% of the host’s transcriptome.[96] Increased population of 2 main species of microbes in the gut, Firmicutes and Bacterioidetes, has been shown in experimental models of hypertension, including spontaneously hypertensive rats, salt-induced models, and Ang II (angiotensin II)–induced hypertension.[97] Recent data suggest the existence of a crosstalk between host cells and microbes that could be mediated through host miRNAs. Microbes might take up host miRNAs that are able to affect their microbiome, while they might also produce metabolites that can regulate the expression of host genes, including miRNAs.[98] The gut microbiota could cause endothelial dysfunction through downregulation of miR-204 expression in the vessel wall.[99] The expression of miR-21-5p could be induced by commensal microbiota, such as Helicobacter pylori, Salmonella typhimurium, and Mycobacterium species, leading to excessive immune responses.[100] Overall, the significance of a crosstalk between host miRNAs and the gut microbiota in the pathophysiology of hypertension remains to be further explored.

LncRNAs and Hypertension

LncRNAs are transcripts of >200 nucleotides without known protein-coding function. They are implicated in epigenetic processes in the nucleus, including chromatin modification, transcription modulation, and alternative splicing regulation, while cytoplasmic lncRNAs interact with proteins and other RNAs to modulate gene expression.[15] Despite remarkable breakthroughs of high-throughput sequencing technologies, the function and biological significance of lncRNAs in the cardiovascular system including pathological events related to hypertension is still limited. A few studies showed that lncRNAs are expressed in the circulation and might be useful disease markers.[101,102] Yet, their potential biomarker value in the context of hypertension has received little attention.

LncRNAs shown to be associated with elevated blood pressure are summarized in Table 4. The GAS5 (growth arrest-specific 5) lncRNA is widely expressed in adult tissues and, during embryonic development, it regulates ECs and VSMCs function through β-catenin signaling.[103] Because dysfunction of ECs and VSMCs strongly correlates to vascular remodeling, these data suggest that GAS5 may play an important role in EHT.[103] Using a sequence-based bioinformatics method named LncDisease to predict potential associations between lncRNAs and specific diseases, 3 lncRNAs (lnc-C16orf95–1:5, lnc-SPATA9-1:2, lnc-SLC17A9–1:1) have been shown to be downregulated in Ang II–treated VSMCs.[104] However, this method did not predict an association between the lncRNA GAS5 and EHT, as suggested by a previous study.[103] In a discovery phase with RNA-sequencing and a validation phase by quantitative polymerase chain reaction, 2 lncRNAs (TCONS_00028980 and TCONS_00029009) displayed differential expression between Dahl salt-sensitive rats and salt-insensitive, congenic Brown Norway SS.13 rats exposed to a high-salt diet, suggesting a role for these 2 lncRNAs in hypertension.[105] Results from a genetic study in human support a role for polymorphisms rs10757274, rs2383207, rs10757278, and rs1333049 within the lncRNA CDKN2B-AS1 in increasing the susceptibility to develop EHT.[106] A microarray analysis of ipsilateral renal cortex tissue revealed 145 differentially expressed lncRNAs between spontaneously hypertensive rats and normotensive Wistar-Kyoto rats, thus further supporting that lncRNAs might be involved in the pathogenesis of hypertension.[107] Additionally, the 4 lncRNAs TCONS_00052110, TCONS_00201718, TCONS_00094247, and TCONS_00296056 were upregulated in failing right ventricles of Sprague-Dawley rats treated with monocrotaline to establish PAHT and lipopolysaccharide to induce acute inflammation and heart failure.[5] A lncRNA termed MANTIS was downregulated in patients with PAHT, as well as in rats after administration of monocrotaline, and played a role in the angiogenic function of ECs.[108] Inhibition of MANTIS through CRISPR/Cas9-mediated gene editing, small interfering RNAs, or GapmeRs had favorable effects on ECs subjected to shear stress, suggesting that this lncRNA, which is also altered in patients with PAHT, might constitute an interesting therapeutic option for hypertension.[108] A lncRNA called Giver (growth factor- and proinflammatory cytokine-induced vascular cell-expressed RNA) is involved in Ang II–mediated VSMC dysfunction, is upregulated in arteries from hypertensive patients and downregulated after treatment with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, observations that support its potential as antihypertensive drug.[109] The lncRNA H19 was upregulated in serum and lung samples from rats and mice after monocrotaline treatment, and this was associated with PASMCs proliferation.[110] Knocking-down H19 had protective effects on pulmonary artery remodeling and PAHT development in mice treated with monocrotaline.[110] The lncRNA-AK098656 was upregulated in the plasma of patients with hypertension and promoted VSMC proliferation.[111] LncRNA-AK098656 transgenic rats developed spontaneous hypertension with narrowed resistant arteries.[111] Depletion of LnRPT (lncRNA regulated by platelet-derived growth factor and TGF-β) promoted PASMCs proliferation and this lncRNA was downregulated in pulmonary arteries from rats after monocrotaline-induced PAHT, consistent with a role in the development of PAHT.[112] LncRNA MRAK048635_P1 was weakly expressed in spontaneously hypertensive rats and its downregulation in VSMC stimulated the proliferation and migration of VSMCs, concomitantly with a phenotypic switch from a contractile to a secretory phenotype, key features of EHT.[113] Two lncRNAs, UCA1 and Hoxaas3, participated in the induction of proliferation of PASMCs on hypoxic stress.[114,115] Together, these preclinical studies support a role for lncRNAs in the development of hypertension and the potential for drugs targeting lncRNAs to treat hypertension.

Table 4.

Long and Circular Noncoding RNAs Associated With Hypertension

CircRNAs and Hypertension

CircRNAs are lncRNAs characterized by their structure and highly evolutionary conservation. Unlike linear lncRNAs, circRNAs have a covalently closed loop structure generated during a back-splicing event between 2 or more exons.[120,121] This loop structure protects circRNAs from degradation by exonucleases and thereby confers them with a high stability, in opposite to linear lncRNAs which are relatively unstable because of digestion by exonucleases. Although circRNAs are still looking for a place in the complex regulatory network of gene expression, they have been reported to orchestrate gene expression either by acting as miRNA sponges or through interactions with RNA binding proteins.[122] Recently, circRNAs have gained attention in cardiovascular pathology, because of their tissue-specificity and their presence in the circulation, which makes them potential disease markers.[123,124] However, their role in hypertension is still poorly characterized.

The latest findings of the role of circRNAs in hypertension are summarized in Table 4. The hsa_circ_0037911 has been suggested to play a role in the development of EHT because of significantly increased expression in patients with hypertension.[116] The 4 circRNAs hsa-circ-0000437, hsa-circ-0008139, hsa-circ-0040809, and hsa-circ-0005870 seem to be dysregulated in plasma samples obtained from patients with EHT.[117] Hsa_circ_0014243 is upregulated in whole blood of patients with EHT.[118] The rat circRNA rno_circRNA_006016 may play a role in the regulatory network of blood pressure through circRNA-miRNA-gene interaction in different signaling pathways such as the small GTPase-mediated signal transduction, ion transmembrane transport regulation of N-methyl-D-aspartate selective glutamate receptor activity, MAPK, and Wnt signaling pathways.[119] Hsa_circ_0002062 and hsa_circ_0022342 are associated with chronic thromboembolic PHT development.[51]

Biomarker Potential of ncRNAs in Hypertension

Several properties of ncRNAs suggest their potential value as biomarkers of hypertension: they are present and stable in the circulation, they are measurable using reliable and sensitive techniques, their expression is dynamic and changes on disease status, and they participate in disease evolution.

Among ncRNAs, miRNAs have been mostly investigated and their diagnostic potential for different types of hypertension has been suggested. Reports (61–64) have shown that miR-206, miR-451, miR-1246, miR-23b, miR-130a, miR-191, miR-451, and miR-26a are dysregulated in human blood samples. Several miRNAs, such as miR-199a-3p, miR-208a-3p, 122-5p, and 223-3p have shown good diagnostic performance for hypertension.[125] Dysregulation of those miRNAs may impact risk of EHT. Downregulated (miR-451 and miR-1246) and upregulated (miR-23b, miR-130a, and miR-191) may be considered as potential biomarker for early detection of PHT.[62] Combination of expression levels of plasma miR-451 with echocardiography may serve as a diagnostic reference for PHT.[63] Enhanced expression of circulating miR-19a in PAHT suggests that it may be proposed as novel biomarker for the diagnosis of PAHT.[85] A muscle-specific miRNA, miR-206 regulates the growth of cardiac myocytes and PASMCs. Combination of dysregulated miR-206 expression, cardiac remodeling, and neuroendocrine biomarkers may be helpful for the screening and identification of PHT.[61] The diagnostic or prognostic value of lncRNAs and circRNAs for hypertension has been so far poorly addressed. Differentially expressed lncRNAs: NR_027032, NR_034083, and NR_104181 in patients with hypertension and healthy individuals, support their roles in the pathogenesis of EHT.[126] The circRNAs hsa_circ_0014243 may find utility as a diagnostic biomarker of EHT.[118] Additionally, the combination of hsa_circ_0037911 and hsa-miR-637 may serve as significant biomarker for early diagnosis of EHT.[127]

Therapeutic Potential of ncRNAs in Hypertension

Despite continuous progress in the development of antihypertensive drugs, an epidemic proportion of hypertension worldwide pinpoints necessity for identification of novel and vigorous antihypertensive therapy. Multiple advantages of miRNAs, such as small size, evolutionary conservation among species, and their known sequence, are promising features for tailoring new therapeutic strategies for different diseases, including hypertension. Restoring altered miRNAs expression in hypertension can be achieved by introducing miRNA mimetics (miRNA-mimic) or anti-miRNA oligonucleotide inhibitors known as antagomiRs. Recent evidence has demonstrated the antihypertensive effect of recombinant adeno-associated virus-mediated delivery of miR-21-3p in hypertensive rats via miR-21-3p-mediated positive modulation of mt-Cytb translation in mitochondria.[128] AntagomiR-155 markedly decreased systolic and diastolic blood pressures, jointly with an elevation of the cell cycle regulator p27 (a direct target of miR-155) and α-smooth muscle actin expression in thoracic aortic media and a reduction of the thickness of tunica media in a rat model of hypertension.[129] Therapeutic inhibition of cardiac-specific miR-208a by subcutaneous delivery of miR-208a antisense prevents pathological cardiac remodeling during hypertension-induced heart failure in rats.[130] In experimental models of PAHT induced by hypoxia or monocrotaline in rodents, injection of antagomiRs against miR-17 improved cardiac and pulmonary function through interference with pulmonary and right ventricular vascular remodeling.[131] AntagomiR-20a prevented the development of vascular remodeling, in parallel with a restoration of functional levels of BMPRII, in a hypoxia-induced mouse model of PHT.[132] Although miRNAs have demonstrated some therapeutic potential in preclinical studies, the implementation of miRNAs antihypertension therapy in patients should be considered with caution due notably to their pleiotropic nature associated with multiple cellular pathways in different cell types and tissues. Modulation of a miRNA could be beneficial in a particular cell type or tissue but may also induce detrimental side effects. To date, whether targeting lncRNAs and circRNAs may help to treat hypertension remains an open question.

Conclusions and Future Directions

The available data summarized in this review article provide evidence that ncRNAs control numerous genes and biological processes, as well as navigate different signaling pathways involved in the regulatory network of hypertension. Furthermore, a dysregulation of ncRNAs expression can trigger cellular dysfunction and promote the development of pathological events related to hypertension. Owing to a certain tissue-specificity, ncRNAs might be considered as a novel class of antihypertensive drugs. AntagomiRs against miR-20a and miR-155 showed interesting protective effects in rodent models of hypertension. MiR-21 and miR-130a seem to be commonly regulated in EHT, PHT, and PAHT, while most miRNAs show distinct profiles of regulation between different types of hypertension, consistently with different features of each type of hypertension. It is tempting to speculate that miRNAs might be used both as diagnostic markers and therapeutic targets and thereby have the capacity to move the Theranostics field a step forward.

The present review shows that only a fraction of hypertension-related lncRNAs and circRNAs have been discovered and studied. Only a couple of lncRNAs have been tested for their ability to prevent or treat hypertension. No circRNAs have, so far, been engaged in such studies. The biomarker potential of lncRNAs and circRNAs as well has been poorly addressed. As a matter of fact, there is a substantial gap in knowledge of diagnostic and therapeutic potential for hypertension between miRNAs and other types of lncRNAs or circRNAs. Although significant progress has been made in the technologies used for the discovery and validation of novel ncRNAs, their clinical applicability (both as biomarker and therapeutic target) still needs to be demonstrated. Suitable delivery methods shall be implemented and the side effects and toxicity of modulating gene expression needs to be carefully examined. Properly sized and properly designed patient cohorts shall be engaged into biomarker studies. Use of extensively validated and homogenized experimental protocols is paramount to generate robust and reproducible results translatable into high-impact outcomes for public health. Finally, whether ncRNAs have the capacity to aid in advancing personalized healthcare is still an open question.

Sources of Funding

This work is supported by COST (European Cooperation in Science and Technology) Action EU-CardioRNA CA17129. Y. Devaux is funded by the National Research Fund (grants nos. C14/BM/8225223 and C17/BM/11613033), the Ministry of Higher Education and Research, and the Society for Research on Cardiovascular Diseases of Luxembourg.

Disclosures

None.