CircUSP36 knockdown alleviates oxidized low‑density lipoprotein‑induced cell injury and inflammatory responses in human umbilical vein endothelial cells via the miR‑20a‑5p/ROCK2 axis

Circular RNAs: Regulators of endothelial cell dysfunction in atherosclerosis

Endothelial cell (EC) dysfunction is associated with atherosclerosis. Circular RNAs (circRNAs) are covalently closed loops formed by back-splicing, are highly expressed in a tissue-specific or cell-specific manner, and regulate ECs mainly through miRNAs (mircoRNAs) or protein sponges. This review describes the regulatory mechanisms and physiological functions of circRNAs, as well as the differential expression of circRNAs in aberrant ECs. This review focuses on their roles in inflammation, proliferation, migration, angiogenesis, apoptosis, senescence, and autophagy in ECs from the perspective of signaling pathways, such as nuclear factor κB (NF-κB), nucleotide-binding domain, leucine-rich-repeat family, pyrin-domain-containing 3 (NLRP3)/caspase-1, Janus kinase/signal transducer and activator of transcription (JAK/STAT), and phosphoinositide-3 kinase/protein kinase B (PI3K/Akt). Finally, we address the issues and recent advances in circRNAs as well as circRNA-mediated regulation of ECs to improve our understanding of the molecular mechanisms underlying the progression of atherosclerosis and provide a reference for studies on circRNAs that regulate EC dysfunction and thus affect atherosclerosis.

LncRNA/CircRNA-miRNA-mRNA Axis in Atherosclerotic Inflammation: Research Progress

Atherosclerosis is characterized by chronic inflammation of the arterial wall. However, the exact mechanism underlying atherosclerosis-related inflammation has not been fully elucidated. To gain insight into the mechanisms underlying the inflammatory process that leads to atherosclerosis, there is need to identify novel molecular markers. Non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-protein-coding RNAs (lncRNAs) and circular RNAs (circRNAs) have gained prominence in recent years. LncRNAs/circRNAs act as competing endogenous RNAs (ceRNAs) that bind to miRNAs via microRNA response elements (MREs), thereby inhibiting the silencing of miRNA target mRNAs. Inflammatory mediators and inflammatory signaling pathways are closely regulated by ceRNA regulatory networks in atherosclerosis. In this review, we discuss the role of LncRNA/CircRNA-miRNA-mRNA axis in atherosclerotic inflammation and how it can be targeted for early clinical detection and treatment.

CircCHMP5 Contributes to Ox-LDL-induced Endothelial Cell Injury Through the Regulation of MiR-532-5p/ROCK2 axis

BACKGROUND

Aberrant expression of circular RNA (circRNA) has been demonstrated to be related to atherosclerosis (AS) formation. However, the mechanism of circCHMP5 (also known as hsa_circ_0003575) in AS formation remains unclear.

METHODS

Oxidized low-density lipoprotein (ox-LDL) was used to treat human umbilical vein endothelial cells (HUVECs) to construct a cell injury model. The expression level of circCHMP5, miR-532-5p, and Rho-associated protein kinase 2 (ROCK2) was measured using quantitative real-time PCR. Cell cycle, apoptosis, proliferation, and angiogenesis were determined by flow cytometry, 5-ethynyl-2'-deoxyuridine (EdU) assay, and tube formation assay. In addition, the protein expression of apoptosis markers, inflammation factors, and ROCK2 was detected by western blot analysis. The interaction between miR-532-5p and circCHMP5 or ROCK2 was assessed by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay.

RESULTS

Our results indicated that circCHMP5 was overexpressed in ox-LDL-induced HUVECs. CircCHMP5 knockdown promoted cell cycle, proliferation, and angiogenesis while inhibiting apoptosis and inflammation in ox-LDL-induced HUVECs. MiR-532-5p could be sponged by circCHMP5, and its inhibitor reversed the negative regulation of si-circCHMP5 on ox-LDL-induced HUVECs injury. ROCK2, a target of miR-532-5p, reversed the inhibition effect of miR-532-5p on ox-LDL-induced HUVECs injury. Furthermore, we confirmed that circCHMP5 upregulated ROCK2 by sponging miR-532-5p.

CONCLUSION

To sum up, our data showed that circCHMP5 regulated the miR-532-5p/ROCK2 axis to accelerate ox-LDL-induced HUVECs injury, confirming that circCHMP5 might be a potential target for AS treatment.

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.

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.

m6A 'writer' KIAA1429 regulates the proliferation and migration of endothelial cells in atherosclerosis

Increasing evidences have illustrated the important role of N⁶-methyladenosine (m⁶A) in atherosclerosis (AS). However, the role of m⁶A modification in AS pathophysiological process is still unknown. Here, the present work tried to investigate the expression and function of m⁶A methyltransferase KIAA1429 in AS pathology and explored its undergoing m⁶A-dependent molecular mechanism. Results indicated that KIAA1429 remarkedly up-regulated in oxidative low-density lipoprotein (ox-LDL)-treated human umbilical vein endothelial cells (HUVECs). KIAA1429 over-expression inhibited the proliferation/migration in ox-LDL-treated HUVECs, while, KIAA1429 knockdown up-regulated the proliferation and migration. Mechanistically, via m⁶A modification sites binding, ROCK2 mRNA was post-transcriptionally upregulated by KIAA1429 in response to Actinomycin D. Collectively, our study demonstrated the regulation of KIAA1429 on ox-LDL-induced HUVECs via m⁶A/ROCK2 pathway. These findings provide new insights for m⁶A-mediated epigenetics in AS.

Circ_0004104 participates in the regulation of ox-LDL-induced endothelial cells injury via miR-942-5p/ROCK2 axis

BACKGROUND

Cardiovascular disease was the most common disease among the elderly with high morbidity and mortality. Circ_0004104 was demonstrated to be involved in the regulation of atherosclerosis.

METHODS

Quantitative real-time polymerase chain reaction was employed to measure the expression of circ_0004104, miR-942-5p and Rho associated coiled-coil containing protein kinase 2 (ROCK2). Cell proliferation was tested by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay. Cell apoptosis was measured by flow cytometry, and tube formation assay was used to detect the angiogenesis ability of cells. Western blot assay was performed to assess protein levels. Enzyme‑linked immunosorbent assay was used to detect the release of IL-1β and TNF-α. The relationship between miR-942-5p and circ_0004104 or ROCK2 was identified by dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, and RNA pull-down assay.

RESULTS

Oxidized low-density lipoprotein (ox-LDL) inhibited the proliferation of human umbilical vein endothelial cells (HUVECs) and promoted apoptosis in a dose-dependent manner. Circ_0004104 was increased in serum of atherosclerosis patients and ox-LDL-treated HUVECs, and silence of circ_0004104 promoted the proliferation of ox-LDL-exposed HUVECs and inhibited cell apoptosis. MiR-942-5p downregulation reversed si-circ_0004104-mediated influences in HUVECs upon ox-LDL exposure. ROCK2 was the target of miR-942-5p and circ_0004104 regulated the expression of ROCK2 through sponging miR-942-5p. ROCK2 abated the influences of miR-942-5p in ox-LDL-stimulated HUVECs. Circ_0004104 was increased in the exosomes derived from ox-LDL-exposed HUVECs, and the expression of circ_0004104 was promoted in HUVECs after stimulation with ox-LDL-treated HUVECs cells-derived exosomes.

CONCLUSION

Circ_0004104 downregulation receded ox-LDL-induced injury in HUVECs through miR-942-5p and ROCK2.

Knockdown of lncRNA H19 alleviates ox-LDL-induced HCAECs inflammation and injury by mediating miR-20a-5p/HDAC4 axis

BACKGROUND

Coronary artery disease (CAD) seriously disturbs the life of people. LncRNA H19 is reported to promote the progression of CAD; Nevertheless, the detailed mechanism by which H19 modulates CAD development is unclear.

METHODS

Clinical samples of CAD patients were collected, meanwhile we established in vitro and in vivo models of CAD by treating HCAECs with ox-LDL and feeding ApoE^-/- mice with high fat diets (HFD). MTT assay was adopted to assess the cell viability. Transwell detection was applied to test the migration, and apoptosis was tested by flow cytometry. The levels of inflammatory cytokines were examined by ELISA. The relation among H19, miR-20a-5p and HDAC4 was explored by dual luciferase reporter and RIP assay.

RESULTS

H19 and HDAC4 levels were elevated, while miR-20a-5p was reduced in plasma of CAD patients and ox-LDL-treated HCAECs. ox-LDL increased H19 level and induced apoptosis and inflammation in HCAECs, while silencing of H19 rescued this phenomenon. In addition, the level of H19 was negatively correlated with miR-20a-5p, and miR-20a-5p inhibitor restored the effect of H19 silencing on HCAECs function. HDAC4 was the downstream mRNA of miR-20a-5p, and miR-20a-5p upregulation reversed ox-LDL-induced HCAECs injury through targeting HDAC4. Furthermore, H19 silencing significantly alleviated the coronary atherosclerotic plaques and inhibited the inflammatory responses in vivo.

CONCLUSIONS

We proved that knockdown of H19 alleviated ox-LDL-induced HCAECs injury via miR-20a-5p/HDAC4 axis, which might provide a new tactics against CAD.

Hsa_circ_0045932 regulates the progression of colorectal cancer by regulating HK2 through sponging miR-873-5p

Background

Circular RNAs (circRNAs) have been confirmed to be key regulators for colorectal cancer (CRC) progression. The purpose of this research was to explore the biological role and mechanism of hsa_circ_0045932 in CRC.

Methods

RT‐qPCR and Western blot (WB) were applied to examine RNA and protein levels, respectively. MTT assay, EdU assay, and transwell assay were used to detect cell proliferative, migration, and invasion. Glucose uptake and lactic acid level were determined to assess cellular glycolysis. Dual‐luciferase reporter and RIP assays were carried out to detect the relationship between miR‐873‐5p and hsa_circ_0045932 or hexokinase 2 (HK2). Xenograft mice model was established to confirm the function of hsa_circ_0045932 in vivo.

Results

Hsa_circ_0045932 was overexpressed in CRC tissue samples and cells. Hsa_circ_0045932 knockdown repressed CRC cell proliferation, invasion, migration, and glycolysis abilities in vitro. MiR‐873‐5p could be sponged by hsa_circ_0045932, and its inhibitor also reversed the inhibitory effect of hsa_circ_0045932 knockdown on CRC cell progression. HK2 was targeted by miR‐873‐5p, and hsa_circ_0045932 regulated HK2 expression through targeting miR‐873‐5p. Overexpression of HK2 reversed the repressive effect of hsa_circ_0045932 knockdown on CRC cell malignant behaviors. Furthermore, the pro‐tumor role of hsa_circ_0045932 in vivo was also confirmed using animal experiments.

Conclusion

Hsa_circ_0045932 promoted CRC progression through sponging miR‐873‐5p to up‐regulate HK2, which might offer novel therapeutic target for CRC clinical intervention.

Study on the Mechanism of circRNA-0024103 Reducing Endothelial Cell Injury by Regulating miR-363/MMP-10

Cardiovascular diseases could damage the heart and blood vessels, which cause mortality and morbidity. It is of great significance to explore targeted therapeutic approaches for atherosclerosis that is one of the most common vascular lesions and the main pathological basis of cardiovascular disease. However, the function of circRNA-0024103 in cardiovascular diseases is still not clear. Therefore, we aim to observe the effect of circRNA-0024103 modulation of miR-363/MMP-10 axis on biological behaviors such as proliferation and migration of endothelial cells after ox-LDL induction. The effects on the proliferation ability of endothelial cells were observed by CCK-8 assay and EdU assay based on overexpression of circRNA-0024103 in combination with miR-363 mimic or MMP-10 siRNA, and then, the effects on apoptosis were detected by flow cytometry analysis. The effects on cell migration, invasion, and angiogenesis were further examined by scratch assay, transwell assay, and tube formation assay. The results in CCK-8 and EdU assays showed that miR-363 mimic or MMP-10siRNA significantly attenuated the proliferation-promoting effect of overexpressed circRNA-0024103 on cell proliferation. In flow cytometry assays to detect apoptosis, overexpression of circRNA-0024103 inhibited apoptosis of endothelial cells, and the intervention of combined miR-363 mimic or MMP-10 siRNA counteracted the inhibitory effect of overexpression of circRNA-0024103 on apoptosis, resulting in a significant increase in the number of endothelial cells undergoing apoptosis. The migration, invasion, and tube-forming ability of endothelial cells were significantly enhanced when circRNA-0024103 was overexpressed, while the promotion of migration, invasion, and the tube-forming ability by overexpression of circRNA-0024103 alone was counteracted when combined with miR-363 mimic or MMP-10 siRNA. circRNA-0024103 regulates the biological behaviors of endothelial cells such as proliferation, apoptosis, migration, and invasion through the miR-363/MMP-10 axis. Our finding provides a new therapeutic target for the treatment of atherosclerosis.

Circ_0068087 Promotes High Glucose-Induced Human Renal Tubular Cell Injury through Regulating miR-106a-5p/ROCK2 Pathway

<b><i>Background:</i></b> Many studies have confirmed that circular RNA (circRNA) is an important target for regulating human disease progression. This study aimed to explore the role of circ_0068087 in diabetic nephropathy (DN) progression. <b><i>Methods:</i></b> High glucose (HG)-induced renal tubular cells (HK2) were used to mimic DN cell models in vitro. The expression levels of circ_0068087, microRNA (miR)-106a-5p, and Rho-associated coiled-coil-containing kinase 2 (ROCK2) were detected by quantitative real-time PCR. Cell proliferation and apoptosis were examined by cell counting kit-8 assay, 5-ethynyl-2′-deoxyuridine assay, colony formation assay, and flow cytometry. The protein levels were examined by Western blot analysis. Cell oxidative stress was assessed by measuring MDA level and SOD activity, and cell inflammation was evaluated by detecting the concentrations of inflammatory factors. RNA interaction was verified by dual-luciferase reporter assay and RNA pull-down assay. <b><i>Results:</i></b> The present study showed that circ_0068087 was highly expressed in the serum of DN patients and HG-induced HK2 cells. Interference of circ_0068087 alleviated HG-induced apoptosis, oxidative stress, inflammation, and fibrosis in HK2 cells, while accelerated cell proliferation. miR-106a-5p could be sponged by circ_0068087, and its inhibitor eliminated the regulation of circ_0068087 knockdown on HG-induced HK2 cell injury. ROCK2 was a target of miR-106a-5p, and its expression was suppressed by circ_0068087 knockdown. miR-106a-5p overexpression suppressed HG-induced HK2 cell injury, and this effect was reversed by ROCK2 upregulation. <b><i>Conclusion:</i></b> Our data indicated that circ_0068087 downregulation mitigated HG-induced HK2 cell injury through the miR-106a-5p/ROCK2 axis, providing a potential circRNA-targeted therapy for DN.

Mechanisms of Oxidized LDL-Mediated Endothelial Dysfunction and Its Consequences for the Development of Atherosclerosis

Atherosclerosis is an immuno-metabolic disease involving chronic inflammation, oxidative stress, epigenetics, and metabolic dysfunction. There is compelling evidence suggesting numerous modifications including the change of the size, density, and biochemical properties in the low-density lipoprotein (LDL) within the vascular wall. These modifications of LDL, in addition to LDL transcytosis and retention, contribute to the initiation, development and clinical consequences of atherosclerosis. Among different atherogenic modifications of LDL, oxidation represents a primary modification. A series of pathophysiological changes caused by oxidized LDL (oxLDL) enhance the formation of foam cells and atherosclerotic plaques. OxLDL also promotes the development of fatty streaks and atherogenesis through induction of endothelial dysfunction, formation of foam cells, monocyte chemotaxis, proliferation and migration of SMCs, and platelet activation, which culminate in plaque instability and ultimately rupture. This article provides a concise review of the formation of oxLDL, enzymes mediating LDL oxidation, and the receptors and pro-atherogenic signaling pathways of oxLDL in vascular cells. The review also explores how oxLDL functions in different stages of endothelial dysfunction and atherosclerosis. Future targeted pathways and therapies aiming at reducing LDL oxidation and/or lowering oxLDL levels and oxLDL-mediated pro-inflammatory responses are also discussed.

CircRNA-miRNA interactions in atherogenesis

Atherosclerosis is the major cause of coronary artery disease (CAD) which includes unstable angina, myocardial infarction, and heart failure. The onset of atherogenesis, a process of atherosclerotic lesion formation in the intima of arteries, is driven by lipid accumulation, a vicious cycle of reactive oxygen species (ROS)-induced oxidative stress and inflammatory reactions leading to endothelial cell (EC) dysfunction, vascular smooth muscle cell (VSMC) activation, and foam cell formation which further fuel plaque formation and destabilization. In recent years, there is a surge in the number of publications reporting the involvement of circular RNAs (circRNAs) in the pathogenesis of cardiovascular diseases, cancers, and metabolic syndromes. These studies have advanced our understanding on the biological functions of circRNAs. One of the most common mechanism of action of circRNAs reported is the sponging of microRNAs (miRNAs) by binding to the miRNAs response element (MRE), thereby indirectly increases the transcription of their target messenger RNAs (mRNAs). Individual networks of circRNA-miRNA-mRNA associated with atherogenesis have been extensively reported, however, there is a need to connect these findings for a complete overview. This review aims to provide an update on atherogenesis-related circRNAs and analyze the circRNA-miRNA-mRNA interactions in atherogenesis. The atherogenic mechanisms and clinical relevance of each atherogenesis-related circRNA were systematically discussed for better understanding of the knowledge gap in this area.

Regulatory mechanism of miR-20a-5p expression in Cancer

MicroRNAs(miRNAs) are non-coding single-stranded RNA molecules encoded by endogenous genes with a length of about 22 nucleotides. The dysregulation of miRNAs has been proven to be one of the vital causes of cancer, which makes them a biomarker for cancer diagnosis and prognosis. Compared with surgery and chemotherapy, nucleic acid therapy targeting specific miRNAs is a promising candidate for cancer treatment. miR-20a-5p plays an anticancer role in high-incidence human cancers such as cervical cancer, breast cancer and leukemia, which is of great importance in the diagnosis of cancers. The up-regulation and down-regulation of miR-20a-5p offers a possible breakthrough for the treatment of cancers. In this paper, we aim to investigate the functional significance of miR-20a-5p in different cancers, reviewing the expression differences of miR-20a-5p in cancer, while systematically summarizing the changes of circRNA-miR-20a-5p networks, and probe how it promotes messenger RNA (mRNA) degradation or inhibits mRNA translation to regulate downstream gene expression. We've also summarized the biogenesis mechanism of miRNAs, and emphasized its role in cell proliferation, cell apoptosis and cell migration. On this basis, we believe that miR-20a-5p is a promising and effective marker for cancer diagnosis, prognosis and treatment.

Emerging Roles of Extracellular Vesicle-Delivered Circular RNAs in Atherosclerosis

Atherosclerosis (AS) is universally defined as chronic vascular inflammation induced by dyslipidaemia, obesity, hypertension, diabetes and other risk factors. Extracellular vesicles as information transmitters regulate intracellular interactions and their important cargo circular RNAs are involved in the pathological process of AS. In this review, we summarize the current data to elucidate the emerging roles of extracellular vesicle-derived circular RNAs (EV-circRNAs) in AS and the mechanism by which EV-circRNAs affect the development of AS. Additionally, we discuss their vital role in the progression from risk factors to AS and highlight their great potential for use as diagnostic biomarkers of and novel therapeutic strategies for AS.

A circular RNA, circUSP36, accelerates endothelial cell dysfunction in atherosclerosis by adsorbing miR-637 to enhance WNT4 expression

Atherosclerosis is a fatal disorder that is fundamental to various cardiovascular diseases and severely threatens people’s health worldwide. Several studies have demonstrated the role of circular RNAs (circRNAs) in the pathogenesis of atherosclerosis. circUSP36 acts as a key modulator in the progression of atherosclerosis, but the molecular mechanism underlying this role is as yet unclear. This study aimed to elucidate the mechanism by which circUSP36 exerts its function in an in vitro cell model of endothelial cell dysfunction, which is one of pathological features of atherosclerosis. The circRNA traits of circUSP36 were confirmed, and we observed high expression of circUSP36 in endothelial cells exposed to oxidized low-density lipoprotein (ox-LDL). Functional assays revealed that overexpression of circUSP36 suppressed proliferation and migration of ox-LDL-treated endothelial cells. In terms of its mechanism, circUSP36 adsorbed miR-637 by acting as an miRNA sponge. Moreover, enhanced expression of miR-637 abated the impact of circUSP36 on ox-LDL-treated endothelial cell dysregulation. Subsequently, the targeting relationship between miR-637 and WNT4 was predicted using bioinformatics tools and was confirmed via luciferase reporter and RNA pull-down assays. Notably, depletion of WNT4 rescued circUSP36-mediated inhibition of endothelial cell proliferation and migration. In conclusion, circUSP36 regulated WNT4 to aggravate endothelial cell injury caused by ox-LDL by competitively binding to miR-637; this finding indicates circUSP36 to be a promising biomarker for the diagnosis and therapy of atherosclerosis.