Overexpression of hsa_circ_0001445 reverses oxLDL‑induced inhibition of HUVEC proliferation via SRSF1

Role of mRNA-binding proteins in retinal neovascularization

Retinal neovascularization (RNV) is a pathological process that primarily occurs in diabetic retinopathy, retinopathy of prematurity, and retinal vein occlusion. It is a common yet debilitating clinical condition that culminates in blindness. Urgent efforts are required to explore more efficient and less limiting therapeutic strategies. Key RNA-binding proteins (RBPs), crucial for post-transcriptional regulation of gene expression by binding to RNAs, are closely correlated with RNV development. RBP-RNA interactions are altered during RNV. Here, we briefly review the characteristics and functions of RBPs, and the mechanism of RNV. Then, we present insights into the role of the regulatory network of RBPs in RNV. HuR, eIF4E, LIN28B, SRSF1, METTL3, YTHDF1, Gal-1, HIWI1, and ZFR accelerate RNV progression, whereas YTHDF2 and hnRNPA2B1 hinder it. The mechanisms elucidated in this review provide a reference to guide the design of therapeutic strategies to reverse abnormal processes.

Tanshinone IIA attenuates ox-LDL-induced endothelial cell injury by inhibiting NF-kapaB pathway via circ_0000231/miR-590-5p/TXNIP axis

Tanshinone IIA (TSIIA) exhibits inhibitory function in atherosclerosis (AS) progression, and circular RNAs (circRNAs) are pivotal regulators in AS. However, the relation between TSIIA and circ_0000231 in AS pathogenesis remains unknown. In this study, oxidized low-density lipoprotein (ox-LDL) was used to establish AS cell model. Treatment of ox-LDL inhibited cell growth but promoted apoptosis, inflammation, and oxidative stress. Then, TSIIA was shown to attenuate ox-LDL-induced endothelial injury. Furthermore, the protective effect of TSIIA against ox-LDL-induced endothelial cell injury was reversed by circ_0000231. Circ_0000231 was identified as a miR-590-5p sponge. Also, miR-590-5p downregulation restored the protection of TSIIA for endothelial cell function. Moreover, circ_0000231 was found to upregulate thioredoxin interacting protein (TXNIP) level via targeting miR-590-5p. TXNIP overexpression mitigated the regulatory function of circ_0000231 knockdown after co-treatment with ox-LDL and TSIIA. TXNIP upregulation recovered the inhibitory regulation of TSIIA in ox-LDL-induced cell damage. In addition, TSIIA inactivated NF-kapaB (NF-κB) signaling pathway via regulating miR-590-5p/TXNIP axis by downregulating circ_0000231. All these results suggested that TSIIA inhibited ox-LDL-induced AS progression in endothelial cells by affecting NF-κB pathway via circ_0000231/miR-590-5p/TXNIP.

Exploring the Multifaceted Biologically Relevant Roles of circRNAs: From Regulation, Translation to Biomarkers

CircRNAs are a category of regulatory RNAs that have garnered significant attention in the field of regulatory RNA research due to their structural stability and tissue-specific expression. Their circular configuration, formed via back-splicing, results in a covalently closed structure that exhibits greater resistance to exonucleases compared to linear RNAs. The distinctive regulation of circRNAs is closely associated with several physiological processes, as well as the advancement of pathophysiological processes in several human diseases. Despite a good understanding of the biogenesis of circular RNA, details of their biological roles are still being explored. With the steady rise in the number of investigations being carried out regarding the involvement of circRNAs in various regulatory pathways, understanding the biological and clinical relevance of circRNA-mediated regulation has become challenging. Given the vast landscape of circRNA research in the development of the heart and vasculature, we evaluated cardiovascular system research as a model to critically review the state-of-the-art understanding of the biologically relevant functions of circRNAs. We conclude the review with a discussion of the limitations of current functional studies and provide potential solutions by which these limitations can be addressed to identify and validate the meaningful and impactful functions of circRNAs in different physiological processes and diseases.

Circular RNAs in vascular diseases

Vascular diseases are the leading cause of morbidity and mortality worldwide and are urgently in need of diagnostic biomarkers and therapeutic strategies. Circular RNAs (circRNAs) represent a unique class of RNAs characterized by a circular loop configuration and have recently been identified to possess a wide variety of biological functions. CircRNAs exhibit exceptional stability, tissue specificity, and are detectable in body fluids, thus holding promise as potential biomarkers. Their encoding function and stable gene expression also position circRNAs as an excellent alternative to gene therapy. Here, we briefly review the biogenesis, degradation, and functions of circRNAs. We summarize circRNAs discovered in major vascular diseases such as atherosclerosis and aneurysms, with a particular focus on molecular mechanisms of circRNAs identified in vascular endothelial cells and smooth muscle cells, in the hope to reveal new directions for mechanism, prognosis and therapeutic targets of vascular 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.

CircSHOC2 Knockdown Alleviates High Glucose-Induced Vascular Endothelial Cell Pyroptosis via Targeting miR-145/FOXO1 Axis In Vitro Condition

Emerging evidence indicates that pyroptosis participates in the pathogenic process of vascular endothelial cells in cardiovascular system complications of diabetes. The roles of circular RNAs (circRNAs) in high glucose (HG)-induced vascular endothelial cells are still unclear. Here, our research investigated the function and mechanism of circRNA circSHOC2 in pyroptosis of vascular endothelial cells. Results indicated that circSHOC2 was up-regulated in HG-induced human umbilical vein endothelial cells (HUVECs). Functionally, cellular assays indicated that circSHOC2 silencing repressed HG-induced HUVECs pyroptosis. Moreover, circSHOC2 targeted miR-145 through miRNA sponge, and FOXO1 functioned as downstream target of miR-145. In conclusion, these findings suggested the potential roles of circSHOC2 on HG-induced vascular endothelial cells in vitro condition, providing new insights for cardiovascular system complications of diabetes.

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.

CircSMARCA5: A key circular RNA in various human diseases

Circular RNAs (circRNAs) are recognized as a novel type of single-stranded endogenous noncoding RNA molecule with the characteristics of tissue specificity, sequence conservation and structural stability. Accumulating studies have shown that circRNAs play a unique biological role in different kinds of diseases. CircRNAs can affect tumor proliferation, migration, metastasis and other behaviors by modulating the expression of downstream genes. CircSMARCA5, an example of a circRNA, is dysregulated in various noninfectious diseases, such as tumors, osteoporosis, atherosclerosis and coronary heart disease. Furthermore, recent studies have demonstrated that circSMARCA5 is associated with the occurrence and development of a variety of tumors, including gastric cancer, glioblastoma, hepatocellular carcinoma, multiple myeloma, colorectal cancer, breast cancer and osteosarcoma. Mechanistically, circSMARCA5 primarily acts as a sponge of miRNAs to regulate the expression of downstream genes, and can serve as a potential biomarker for the diagnosis of malignant tumors. This review summarizes the biological roles of circSMARCA5 and its molecular mechanism of action in various diseases. Moreover, the meta-analysis of some publications showed that the expression of circSMARCA5 was significantly correlated with the prognosis of patients and tumor TNM stage, showing that circSMARCA5 has the potential to be a prognostic marker.

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.

Hsa_circ_0001879 promotes the progression of atherosclerosis by regulating the proliferation and migration of oxidation of low density lipoprotein (ox-LDL)-induced vascular endothelial cells via the miR-6873-5p-HDAC9 axis

Atherosclerosis (AS) is a typical vascular disease. Emerging evidence has shown that circRNAs play key roles in the progression of AS, but the potential function and underlying mechanism of hsa_circ_0001879 remains unknown. We detected the expression level of hsa_circ_0001879 was determined by qRT-PCR, and the proliferation rate and migration ability of HUVECs were measured by CCK-8 assay and Transwell assay, respectively. Proliferative markers and epithelium mesenchymal transition (EMT) markers were measured through immunoblotting. A dual luciferase activity assay was performed to detect the interaction between circRNAs, miRNAs, and mRNAs. Hsa_circ_0001879 was upregulated in AS patients. Hsa_circ_0001879 inhibited the proliferation and migration ability of Human umbilical vein endothelial cells (HUVECs). Hsa_circ_0001879 directly bound to miR-6873-5p and acted as a sponge. miR-6873-5p-induced HDAC9 mRNA degradation was inhibited by hsa_circ_0001879. Hsa_circ_0001879 decreased the proliferation and migration of HUVECs by inhibiting miR-6873-5p-induced HDAC9 degradation.