Circular RNAs in atherosclerosis

Shear-Sensitive circRNA-LONP2 Promotes Endothelial Inflammation and Atherosclerosis by Targeting NRF2/HO1 Signaling

Hemodynamic shear stress is a frictional force that acts on vascular endothelial cells and is essential for endothelial homeostasis. Physiological laminar shear stress (LSS) suppresses endothelial inflammation and protects arteries from atherosclerosis. Herein, we screened differentially expressed circular RNAs (circRNAs) that were significantly altered in LSS-stimulated endothelial cells and found that circRNA-LONP2 was involved in modulating the flow-dependent inflammatory response. Furthermore, endothelial circRNA-LONP2 overexpression promoted endothelial inflammation and atherosclerosis in vitro and in vivo. Mechanistically, circRNA-LONP2 competitively sponged miR-200a-3p and subsequently promoted Kelch-like ECH-associated protein 1, Yes-associated protein 1, and enhancer of zeste homolog 2 expression, thereby inactivating nuclear factor erythroid 2-related factor 2/heme oxygenase-1 signaling, promoting oxidative stress and endothelial inflammation, and accelerating atherosclerosis. LSS-induced down-regulation of circRNA-LONP2 suppresses endothelial inflammation, at least in part, by activating the miR-200a-3p-mediated nuclear factor erythroid 2-related factor 2/heme oxygenase-1 signaling pathway. CircRNA-LONP2 may serve as a new therapeutic target for atherosclerosis.

The Role of Circular RNA for Early Diagnosis and Improved Management of Patients with Cardiovascular Diseases

Cardiovascular diseases (CVDs) are responsible for approximately 17.9 million deaths every year. There is growing evidence that circular RNAs (circRNAs) may play a significant role in the early diagnosis and treatment of cardiovascular diseases. As regulatory molecules, circular RNAs regulate gene expression, interact with proteins and miRNAs, and are translated into proteins that play a key role in a wide variety of biological processes, including the division and proliferation of cells, as well as the growth and development of individuals. An overview of the properties, expression profiles, classification, and functions of circRNAs is presented here, along with an explanation of their implications in cardiovascular diseases including heart failure, hypertension, ischemia/reperfusion injury, myocardial infarction, cardiomyopathies, atherosclerosis, and arrhythmia.

Hsa_circ_0032389 Enhances Proliferation and Migration in PDGF-BB-Induced Human Aortic Vascular Smooth Muscle Cells

Circular RNA (circRNAs) has been confirmed to participate in atherosclerosis (AS) progression. However, the role and mechanism of hsa_circ_0032389 in AS process still need to be further revealed. This study evaluates the role and mechanism of hsa_circ_0032389 in AS process. Platelet-derived growth factor-BB (PDGF-BB) was used to induce human aortic vascular smooth muscle cells (HA-VSMCs). The expression levels of hsa_circ_0032389, microRNA (miR)-513a-5p, and fibroblast growth factor receptor substrate 2 (FRS2) were examined by quantitative real-time PCR. Cell proliferation and migration were analyzed using cell counting kit 8 assay, flow cytometry, EdU assay, transwell assay, and wound healing assay. Protein expression was assessed using western blot analysis. Dual-luciferase reporter and RIP assays were used to confirm RNA interaction. Hsa_circ_0032389 was overexpressed in PDGF-BB-induced HA-VSMCs, and its downregulation inhibited HA-VSMC viability, cell cycle, EdU positive cell rate, migratory cell number, and wound closure rate under PDGF-BB treatment. The luciferase activity of hsa_circ_0032389wt could be reduced by miR-513a-5p mimic, and both hsa_circ_0032389 and miR-513a-5p were enriched in anti-Ago2, confirming that miR-513a-5p could be sponged by hsa_circ_0032389. MiR-513a-5p inhibitor reversed the effect of hsa_circ_0032389 knockdown on PDGF-BB-induced HA-VSMC viability, cell cycle, EdU positive cell rate, migratory cell number, and wound closure rate. Moreover, the luciferase activity of FRS2wt was reduced by miR-513a-5p mimic, and both FRS2 and miR-513a-5p were enriched in anti-Ago2, verifying that FRS2 was targeted by miR-513a-5p. MiR-513a-5p suppressed PDGF-BB-induced HA-VSMC viability, cell cycle, EdU positive cell rate, migratory cell number, and wound closure rate by targeting FRS2. Our results indicated that hsa_circ_0032389 enhanced PDGF-BB-induced HA-VSMC proliferation and migration via regulating miR-513a-5p/FRS2 axis.

The potential role and mechanism of circRNAs in foam cell formation

Atherosclerosis is a significant risk factor for coronary heart disease (CHD) and myocardial infarction (MI). Atherosclerosis develops during foam cell generation, which is caused by an imbalance in cholesterol uptake, esterification, and efflux. LOX-1, SR-A1, and CD36 all increased cholesterol uptake. ACAT1 and ACAT2 promote free cholesterol (FC) esterification to cholesteryl esters (CE). The hydrolysis of CE to FC was aided by nCEH. FC efflux was promoted by ABCA1, ABCG1, ADAM10, and apoA-I. SR-BI promotes not only cholesterol uptake but also FC efflux. Circular RNAs (circRNAs), which are single-stranded RNAs with a closed covalent circular structure, have emerged as promising biomarkers and therapeutic targets for atherosclerosis due to their highly tissue, cell, and disease state-specific expression profiles. Numerous studies have shown that circRNAs regulate foam cell formation, acting as miRNA sponges to influence atherosclerosis development by regulating the expression of SR-A1, CD36, ACAT2, ABCA1, ABCG1, ADAM10, apoA-I, SR-B1. Several circRNAs, including circ-Wdr91, circ 0004104, circRNA0044073, circRNA_0001805, circDENND1B, circRSF1, circ 0001445, and circRNA 102682, are potential biomarkers for atherosclerosis to better evaluate cardiovascular risk. It is difficult to deliver synthetic therapeutic circRNAs to the desired target tissues. Nanotechnology, such as GA-RM/GZ/PL, may be an important solution to this problem. In this review, we focus on the potential role and mechanism of circRNA/miRNA axis in foam cell formation in the hopes of discovering new targets for the diagnosis, prevention, and treatment of atherosclerosis.

Extracellular vesicles in atherosclerosis and vascular calcification: the versatile non-coding RNAs from endothelial cells and vascular smooth muscle cells

Atherosclerosis (AS) is characterized by the accumulation of lipids, fibrous elements, and calcification in the innermost layers of arteries. Vascular calcification (VC), the deposition of calcium and phosphate within the arterial wall, is an important characteristic of AS natural history. However, medial arterial calcification (MAC) differs from intimal calcification and cannot simply be explained as the consequence of AS. Endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) are directly involved in AS and VC processes. Understanding the communication between ECs and VSMCs is critical in revealing mechanisms underlying AS and VC. Extracellular vesicles (EVs) are found as intercellular messengers in kinds of physiological processes and pathological progression. Non-coding RNAs (ncRNAs) encapsulated in EVs are involved in AS and VC, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). The effects of ncRNAs have not been comprehensively understood, especially encapsulated in EVs. Some ncRNAs have demonstrated significant roles in AS and VC, but it remains unclear the functions of the majority ncRNAs detected in EVs. In this review, we summarize ncRNAs encapsulated in EC-EVs and VSMC-EVs, and the signaling pathways that are involved in AS and VC.

A review on circular RNAs and bacterial infections

Bacterial infections and related diseases have been a major burden on social public health and economic stability around the world. However, the effective diagnostic methods and therapeutic approaches to treat bacterial infections are still limited. As a group of non-coding RNA, circular RNAs (circRNAs) that were expressed specifically in host cells and played a key regulatory role have the potential to be of diagnostic and therapeutic value. In this review, we systematically summarize the role of circRNAs in common bacterial infections and their potential roles as diagnostic markers and therapeutic targets.

RNA Sequencing Reveals the Differentially Expressed circRNAs between Stable and Unstable Carotid Atherosclerotic Plaques

Objective. This study aimed to identify circular RNA profiles (circRNAs) via high-throughput RNA sequencing and distinguish the differentially expressed (DE) circRNAs between stable and unstable plaques. Methods. RNA sequencing was performed on unstable and stable carotid plaque samples obtained from patients with carotid artery stenosis. DE circRNAs were screened, and six DE circRNAs were verified using quantitative real-time PCR (qRT-PCR). Functional evaluation of the DE circRNAs was conducted via Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Results. We screened 344 DE circRNAs in unstable plaques, consisting of 342 upregulated and 2 downregulated circRNAs. GO analysis showed that the host genes of the upregulated circRNAs were related to ER to Golgi transport vesicle membrane, endocytic vesicle membrane, and Ran GTPase binding. KEGG analysis revealed that the host genes of the upregulated circRNAs were primarily associated with protein processing in endoplasmic reticulum, lysine degradation, homologous recombination, epithelial cell signaling in Helicobacter pylori infection, and yersinia infection. The results of qRT-PCR verified three upregulated DE circRNAs and two downregulated DE circRNAs in unstable plaques. Conclusion. Hsa-circ-0001523, hsa-circ-0008950, hsa-circ-0000571, hsa-circ-0001946, and hsa-circ-0000745 may be involved in regulating the stability of atherosclerotic plaques and serves as a therapeutic target for unstable plaques.

Circular RNA circ_0029589 promotes ox-LDL-induced endothelial cell injury through regulating RAB22A by serving as a sponge of miR-1197

BACKGROUND

Dysfunction of endothelial cells is now considered a vital contributor to the pathogenesis of atherosclerosis (AS). Moreover, circular RNA (circRNA) circ_0029589 has been found to be involved in the regulation of oxidized low-density lipoprotein (ox-LDL)-induced endothelial cell damage. Nevertheless, its molecular mechanism in ox-LDL-triggered endothelial cell injury is poorly defined.

METHODS

Human umbilical vein endothelial cells (HUVECs) treated with ox-LDL were applied as cell models of AS. Circ_0029589, microRNA-1197 (miR-1197), and Ras-related protein Rab-22A (RAB22A) expression were detected using real-time quantitative polymerase chain reaction (RT-qPCR). Cell proliferation, apoptosis, angiogenesis, and invasion were detected using 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT), 5-ethynyl-2'-deoxyuridine (EdU), flow cytometry, tube formation, and transwell assays. Western blot analysis of Cleaved-caspase-3, B-cell lymphoma-2 related X protein (Bax), and RAB22A. IL-6, IL-1β, and Tumor necrosis factor α (TNF-α) levels were gauged using ELISA kits. Superoxide Dismutase (SOD) activity and Malondiahyde (MDA) level were assessed using special kits. Bioinformatics software predicted the binding between miR-1197 and circ_0029589 or RAB22A, which was proved using dual-luciferase reporter and RNA pull-down assays.

RESULTS

Circ_0029589 and RAB22A expression were strengthened, and miR-1197 was reduced in ox-LDL-treated HUVECs. Importantly, circ_0029589 silencing ameliorated ox-LDL-triggered HUVEC damage via promoting cell proliferation, tube formation ability, invasion, and repressing cell apoptosis, inflammation, and oxidative stress. Mechanical analysis suggested that circ_0029589 might affect RAB22A content through sponging miR-1197.

CONCLUSION

Circ_0090231 might protect against ox-LDL-mediated HUVEC injury via the miR-1197/RAB22A axis, which provides a therapeutic strategy for endothelial cell damage of AS.

Ox-LDL-Induced Vascular Smooth Muscle Cell Dysfunction Partly Depends on the Circ_0044073/miR-377-3p/AURKA Axis in Atherosclerosis

Atherosclerosis (AS) is the main reason for most cardiovascular diseases. Circular RNA hsa_circ_0044073 (circ_0044073) has been found to promote AS progression. However, the specific regulatory mechanism of circ_0044073 in AS progression remains unclear.In this study, oxidized low-density lipoprotein (Ox-LDL) -stimulated human vascular smooth muscle cells (VSMCs) were used as AS cell models. The expression changes of circ_0044073 in serum samples and Ox-LDL-stimulated human VSMCs were assessed via real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability, proliferation, colony formation, migration, and invasion were assessed using 3- (4,5-Dimethylthiazol-2-yl) -2,5-Diphenyltetrazolium Bromide (MTT), 5-ethynyl-2'-deoxyuridine (EDU), colony formation, and transwell assays. Some protein levels were detected via Western blotting. The regulatory mechanism of circ_0044073 was predicted using bioinformatics analysis and validated by dual-luciferase reporter and RNA pull-down assays.We observed an overt increase in circ_0044073 expression in serum samples derived from AS patients and Ox-LDL-stimulated human VSMCs. Circ_0044073 was identified as a miR-377-3p sponge. Either circ_0044073 knockdown or miR-377-3p overexpression could impair Ox-LDL-induced human VSMC proliferation, migration, invasion, and inflammation. AURKA served as a miR-377-3p target, and circ_0044073 regulated AURKA expression by adsorbing miR-377-3p. Furthermore, AURKA overexpression partly reversed the effects of circ_0044073 inhibition on Ox-LDL-induced human VSMC proliferation, migration, invasion, and inflammation.Circ_0044073 promoted AS progression by elevating AURKA expression by functioning as a miR-377-3p sponge. Providing a proof-of-concept demonstration to support circ_0044073 might be a target for AS treatment.

circHECTD1 Promotes the Proliferation and Migration of Human Brain Vascular Smooth Muscle Cells via Interacting with KHDRBS3 to Stabilize EZH2 mRNA Expression

Purpose

The objective of this paper is to explore the role of circHECTD1 in vascular smooth muscle cells (VSMCs) and atherosclerosis (AS).

Methods

VSMCs were treated with platelet-derived growth factor-BB (PDGF-BB) in vitro, and the level of circHECTD1 was determined using qRT-PCR. Cell proliferation, migration, and invasion were analyzed using CCK8 and transwell assays. Cell apoptosis and cell cycle were analyzed using flow cytometry. The binding interaction between circHECTD1 and KHDRBS3 or EZH2 was investigated using the RIP, RNA pull-down.

Results

CircHECTD1 was upregulated in PDGF-BB-induced VSMCs with a dose-dependent and time-dependent manner. Knockdown of circHECTD1 suppressed VSMCsproliferation and migration and enhanced cell apoptosis in VSMCs, while circHECTD1 overexpression yielded opposite effects. Mechanistically, circHECTD1 could interact with KHDRBS3, thus enhanced the stability of EZH2 mRNA and increased EZH2 protein level. In addition, silencing EZH2 in VSMCs reversed the proliferation-enhancing effect of circHECTD1 overexpression.

Conclusion

Our findings provided providing a potential prognostic and therapy biomarker for AS.

Non-Coding RNAs in Regulating Plaque Progression and Remodeling of Extracellular Matrix in Atherosclerosis

Non-coding RNAs (ncRNAs) regulate cell proliferation, migration, differentiation, inflammation, metabolism of clinically important biomolecules, and other cellular processes. They do not encode proteins but are involved in the regulatory network of various proteins that are directly related to the pathogenesis of diseases. Little is known about the ncRNA-associated mechanisms of atherosclerosis and related cardiovascular disorders. Remodeling of the extracellular matrix (ECM) is critical in the pathogenesis of atherosclerosis and related disorders; however, its regulatory proteins are the potential subjects to explore with special emphasis on epigenetic regulatory components. The activity of regulatory proteins involved in ECM remodeling is regulated by various ncRNA molecules, as evident from recent research. Thus, it is important to critically evaluate the existing literature to enhance the understanding of nc-RNAs-regulated molecular mechanisms regulating ECM components, remodeling, and progression of atherosclerosis. This is crucial since deregulated ECM remodeling contributes to atherosclerosis. Thus, an in-depth understanding of ncRNA-associated ECM remodeling may identify novel targets for the treatment of atherosclerosis and other cardiovascular diseases.

Role of circular RNAs in disease progression and diagnosis of cancers: An overview of recent advanced insights

Tumor microenvironment (TME) is a crucial regulator of tumor progression and cells in the TME release a number of molecules that are responsible for anaplasticity, invasion, metastasis of tumor, establishing stem cell niches, up-regulation and down-regulation of various pathways in cancer cells, interfering with immune surveillance and immune escape. Moreover, they can serve as diagnostic markers, and determine effective therapies. Among them, CircRNAs have gained special attention due to their involvement in mutated pathways in cancers. By functioning as a molecular sponge for miRNAs, binding with proteins, and directing selective splicing. CircRNAs modify the immunological environment of cancers to promote their growth. Besides of critical role in tumor growth, circRNAs are emerging as potential candidates as biomarkers for diagnosis cancer therapy. Also, circRNAs vaccination even offers a novel approach to tumor immunotherapy. Over the recent years, studies are advocating that circRNAs have tissue specific tumor specific expression patterns, which indicates their potential clinical utility. Especially, circRNAs have emerged as potential predictive and prognostic biomarkers. Although, there has been significant progress in deciphering the role of circRNA in cancers, literature lacks comprehensive overview on this topic. Keeping in view of these significant discoveries, this review systematically discusses circRNA and their role in the tumor in different dimensions.

Viral Circular RNAs and Their Possible Roles in Virus-Host Interaction

Circular RNAs (circRNAs) as novel regulatory molecules have been recognized in diverse species, including viruses. The virus-derived circRNAs play various roles in the host biological process and the life cycle of the viruses. This review summarized the circRNAs from the DNA and RNA viruses and discussed the biogenesis of viral and host circRNAs, the potential roles of viral circRNAs, and their future perspective. This review will elaborate on new insights gained on viruses encoded circRNAs during virus infection.