Hsa_circRNA_102541 regulates the development of atherosclerosis by targeting miR-296-5p/PLK1 pathway

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.

Circular RNAs Variously Participate in Coronary Atherogenesis

Over the past decade, numerous studies have shown that circular RNAs (circRNAs) play a significant role in coronary artery atherogenesis and other cardiovascular diseases. They belong to the class of non-coding RNAs and arise as a result of non-canonical splicing of premature RNA, which results in the formation of closed single-stranded circRNA molecules that lack 5'-end caps and 3'-end poly(A) tails. circRNAs have broad post-transcriptional regulatory activity. Acting as a sponge for miRNAs, circRNAs compete with mRNAs for binding to miRNAs, acting as competing endogenous RNAs. Numerous circRNAs are involved in the circRNA-miRNA-mRNA regulatory axes associated with the pathogenesis of cardiomyopathy, chronic heart failure, hypertension, atherosclerosis, and coronary artery disease. Recent studies have shown that сirc_0001445, circ_0000345, circ_0093887, сircSmoc1-2, and circ_0003423 are involved in the pathogenesis of coronary artery disease (CAD) with an atheroprotective effect, while circ_0002984, circ_0029589, circ_0124644, circ_0091822, and circ_0050486 possess a proatherogenic effect. With their high resistance to endonucleases, circRNAs are promising diagnostic biomarkers and therapeutic targets. This review aims to provide updated information on the involvement of atherogenesis-related circRNAs in the pathogenesis of CAD. We also discuss the main modern approaches to detecting and studying circRNA-miRNA-mRNA interactions, as well as the prospects for using circRNAs as biomarkers and therapeutic targets for the treatment of cardiovascular diseases.

Circular RNA as Therapeutic Targets in Atherosclerosis: Are We Running in Circles?

Much attention has been paid lately to harnessing the diagnostic and therapeutic potential of non-coding circular ribonucleic acids (circRNAs) and micro-RNAs (miRNAs) for the prevention and treatment of cardiovascular diseases. The genetic environment that contributes to atherosclerosis pathophysiology is immensely complex. Any potential therapeutic application of circRNAs must be assessed for risks, benefits, and off-target effects in both the short and long term. A search of the online PubMed database for publications related to circRNA and atherosclerosis from 2016 to 2022 was conducted. These studies were reviewed for their design, including methods for developing atherosclerosis and the effects of the corresponding atherosclerotic environment on circRNA expression. Investigated mechanisms were recorded, including associated miRNA, genes, and ultimate effects on cell mechanics, and inflammatory markers. The most investigated circRNAs were then further analyzed for redundant, disparate, and/or contradictory findings. Many disparate, opposing, and contradictory effects were observed across experiments. These include levels of the expression of a particular circRNA in atherosclerotic environments, attempted ascertainment of the in toto effects of circRNA or miRNA silencing on atherosclerosis progression, and off-target, cell-specific, and disease-specific effects. The high potential for detrimental and unpredictable off-target effects downstream of circRNA manipulation will likely render the practice of therapeutic targeting of circRNA or miRNA molecules not only complicated but perilous.

Diagnostic value of peripheral blood miR-296 combined with vascular endothelial growth factor B on the degree of coronary artery stenosis in patients with coronary heart disease

OBJECTIVE

Coronary heart disease (CHD) is a disorder resulting from organic and functional coronary artery stenosis (CAS), thus causing reduced oxygenated blood in the heart. miRNAs are useful biomarkers in the diagnosis of atherosclerosis, CHD, and acute coronary syndrome. Vascular endothelial growth factor (VEGF) is closely related to CHD. This study explored the correlation of miR-296 and VEGF-B expression levels in peripheral blood with CAS degree in CHD patients.

METHODS

Totally 220 CHD patients were enrolled and classified into mild-(71 cases)/moderate-(81 cases)/severe-CAS (68 cases) groups, with another 80 healthy cases as controls. The serum miR-296 and VEGF-B expression levels were detected using reverse transcription quantitative polymerase chain reaction. The correlation between miR-296 and CAS-related indexes was assessed via Pearson analysis. The binding relationship of miR-296 and VEGF-B was first predicted and their correlation was further analyzed via the Pearson method. The clinical diagnostic efficacy of miR-296 or VEGF-B on CAS degree was evaluated by the receiver operating characteristic curve.

RESULTS

Serum miR-296 was downregulated in CHD patients and was the lowest in patients with severe-CAS. miR-296 was negatively-correlated with high-sensitivity C-reactive protein, brain natriuretic peptide, and cardiac troponin I. miR-296 targeted VEGF-B. VEGF-B was upregulated in CHD patients and inversely-related to miR-296. Low expression of miR-296 and high expression of VEGF-B both had high clinical diagnostic values on CAS degree in CHD patients. miR-296 combined with VEGF-B increased the diagnostic value on CAS.

CONCLUSION

Low expression of miR-296 combined with high expression of its target VEGF-B predicts CAS degree in CHD patients.

CircRnas in atherosclerosis, with special emphasis on the spongy effect of circRnas on miRnas

Atherosclerosis (AS) is a chronic inflammatory disease, which leads to atherosclerotic rupture, lumen stenosis and thrombosis, and often endangers life. Circular RNAs (circRNAs) are a special class of non-coding RNA molecules, whose abnormal expression has been proved to be closely related to human diseases, including AS. Both the abnormal regulation of circRNAs and the sponging effect on miRNAs would lead to changes in gene expression in the form of epigenetic modification, ultimately leading to the formation of AS. CircRNAs can be used as peripheral blood markers of AS, and play an important regulatory role in the proliferation, migration, inflammation and apoptosis of vascular smooth muscle cells, endothelial cells and macrophage, which are key cells for the development of AS. The in-depth understanding of circRNAs in AS not only provides a new method for the diagnosis of AS, but also provides a new idea for the treatment of AS.

Circular RNA circ_0026218 Suppressed Atherosclerosis Progression via miR-338-3p/SIRT6 Axis

Background

Multiple circular RNAs (circRNAs) are implicated in atherosclerosis (AS) pathogenesis. In fact, how circRNA 0026218 (circ_0026218) functions in AS remains unknown, and thus the functions and mechanisms of circ_0026218 in the injury of vascular endothelial cells are to be investigated.

Methods

Microarray analysis was employed to screen out differentially expressed circRNAs in AS. A cell model was mimicked by treating Human umbilical vein endothelial cells (HUVECs) with oxidized low-density lipoprotein (ox-LDL). circ_0026218, microRNA-338-3p (miR-338-3p) and silent information regulator 6 (SIRT6) expressions in HUVECs with ox-LDL treatment were probed by qRT-PCR. The cell proliferative capabilities were exposed by CCK-8 assay. The contents of interleukin 6 (IL-6), interleukin 1β (IL-1β), and tumor necrosis factor α (TNF-α) were measured by ELISA. Oxidative stress kits were utilized to detect the levels of reactive oxygen species (ROS), superoxide dismutase (SOD), and malondialdehyde (MDA). Flow cytometry was adopted to analyze the level of apoptosis of HUVECs. Dual-luciferase reporter gene assay and RIP assay were leveraged to expose the interplay between miR-338-3p and circ_0026218 or SIRT6 3'-UTR, respectively. In addition, the impacts of circ_0026216 and miR-338-3p on SIRT6 protein expressions were subjected to Western blot.

Results

circ_0026218 was greatly depleted in ox-LDL-stimulated HUVECs. circ_0026218 overexpression promoted viability of HUVECs in vitro and inhibited inflammatory response, oxidative stress, and apoptosis. circ_0026218 could adsorb miR-338-3p and positively modulated SIRT6 expressions via sponging miR-338-3p. Upregulation of this miRNA reversed the influence of circ_0026218 overexpression on ox-LDL-caused injury and apoptosis of HUVECs.

Conclusion

Collectively, circ_0026218 upregulates SIRT6 expression through decoying miR-338-3p, thereby inhibiting ox-LDL-initiated injury of HUVECs. circ_0026218 is involved in the pathogenesis of AS.

PLK1 promotes cholesterol efflux and alleviates atherosclerosis by up-regulating ABCA1 and ABCG1 expression via the AMPK/PPARγ/LXRα pathway

Polo-like kinase 1 (PLK1) is a serine/threonine kinase involving lipid metabolism and cardiovascular disease. However, its role in atherogenesis has yet to be determined. The aim of this study was to observe the impact of PLK1 on macrophage lipid accumulation and atherosclerosis development and to explore the underlying mechanisms. We found a significant reduction of PLK1 expression in lipid-loaded macrophages and atherosclerosis model mice. Lentivirus-mediated overexpression of PLK1 promoted cholesterol efflux and inhibited lipid accumulation in THP-1 macrophage-derived foam cells. Mechanistic analysis revealed that PLK1 stimulated the phosphorylation of AMP-activated protein kinase (AMPK), leading to activation of the peroxisome proliferator-activated receptor γ (PPARγ)/liver X receptor α (LXRα) pathway and up-regulation of ATP binding cassette transporter A1 (ABCA1) and ABCG1 expression. Injection of lentiviral vector expressing PLK1 increased reverse cholesterol transport, improved plasma lipid profiles and decreased atherosclerotic lesion area in apoE-deficient mice fed a Western diet. PLK1 overexpression also facilitated AMPK and HSL phosphorylation and enhanced the expression of PPARγ, LXRα, ABCA1, ABCG1 and LPL in the aorta. In summary, these data suggest that PLK1 inhibits macrophage lipid accumulation and mitigates atherosclerosis by promoting ABCA1- and ABCG1-dependent cholesterol efflux via the AMPK/PPARγ/LXRα pathway.

Hsa_circ_0030042 Ameliorates Oxidized Low-Density Lipoprotein-Induced Endothelial Cell Injury via the MiR-616-3p/RFX7 Axis

Atherosclerosis (AS) is a common etiology of cardiovascular disease. As an emerging functional biomarker, circular RNAs (circRNAs) are involved in various diseases, including cardiovascular disease. However, the mechanism of action of circ_0030042 in AS has not been reported.Human umbilical vein endothelial cells (HUVECs) stimulated by ox-LDL served as a cellular model of AS. Gene expression was detected using quantitative real-time polymerase chain reaction. The influence of circ_0030042 on cell viability, proliferation, and apoptosis was verified using Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine, and flow cytometry assays. An enzyme-linked immunosorbent assay was performed to measure the contents of tumor necrosis factor-α, interleukin (IL) -6, and IL-1β. Western blot assay was utilized to determine the protein levels of Bax, Bcl-2, PCNA, and regulatory factor X 7 (RFX7). The interrelationship between miR-616-3p and circ_0030042 or RFX7 was validated using dual-luciferase reporter, RNA immunoprecipitation, and RNA pull-down assays.The expression of circ_0030042 was downregulated in ox-LDL-induced HUVECs. It was found that overexpression of circ_0030042 facilitated cell proliferation, repressed apoptosis, and reduced the level of inflammatory factors in HUVECs. Circ_0030042 and miR-616-3p had a targeting relationship, and the miR-616-3p mimic eliminated the effects of overexpressed circ_0030042 on ox-LDL-induced HUVECs. RFX7 was a downstream gene of miR-616-3p and was lowly expressed in ox-LDL-induced HUVECs. The miR-616-3p inhibitor stimulated cell proliferation, arrested apoptosis, and caused a decline in the levels of inflammatory factors, whereas knockdown of RFX7 abolished the effects.Circ_0030042 weakened ox-LDL-induced HUVEC injury by regulating the miR-616-3p/RFX7 pathway, thereby influencing AS progression. Circ_0030042 is likely to be a potential biomarker for the future treatment of patients with AS.

Circular RNAs and Their Role in Exosomes

As a novel class of endogenous non-coding RNAs discovered in recent years, circular RNAs (circRNAs) are highly conserved and stable covalently closed ring structures with no 5'-end cap or 3'-end poly(A) tail. CircRNAs are formed by reverse splicing, mainly by means of a noose structure or intron complementary pairing. Exosomes are tiny discoid vesicles with a diameter of 40-100 nm that are secreted by cells under physiological and pathological conditions. Exosomes play an important role in cell-cell communication by carrying DNA, microRNAs, mRNAs, proteins and circRNAs. In this review, we summarize the biological functions of circRNAs and exosomes, and further reveal the potential roles of exosomal circRNAs in different diseases, providing a scientific basis for the diagnosis, treatment, and prognosis of a wide variety of diseases.