CircMACF1 Attenuates Acute Myocardial Infarction Through miR-500b-5p-EMP1 Axis

Clinical Significance and Potential Mechanism of Circ_00008842 in Acute Myocardial Infarction

This study aimed to evaluate the clinical value of circ_0008842 in acute myocardial infarction (AMI) and explore the potential mechanisms.GSE149051 and GSE160717 datasets analyze common differentially expressed circRNAs (coDEcircRNA) in AMI. RT-qPCR analysis of circ_0008842 mRNA levels in patients with AMI. ROC curve assesses the diagnostic value of circ_0008842 in AMI. A cell model of AMI was constructed by hypoxia-reoxygenation (H/R) -induced H9c2. Cell viability and apoptosis were examined by CCK-8 and flow cytometry. Enzyme-linked immunosorbent assay was used to explore myocardial injury markers CK-MB and cTnI secretion. Dual luciferase reporter assays validate circ_0008842 binding to miRNA. PPI network and gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment reveal potential functions and pathways of targets from the miRNA in AMI.circ_0008842 is recognized as coDEcircRNA in AMI-related databases. circ_0008842 was greatly lower and miR-574-5p was significantly higher in patients with AMI than in healthy individuals. miR-574-5p is a target of circ_0008842. The sensitivity and specificity of circ_0008842 for diagnosing patients with AMI were 87.40% and 83.50%, respectively. Overexpression of circ_0008842 inhibited H/R induced apoptosis, increased cell viability, and decreased CK-MB and cTnI levels, which were partially abrogated by overexpression of miR-574-5p. Calmodulin-like protein 4 (CALML4) was the most connected hub gene in the PPI network of miR-574-5p predicted target genes.circ_0008842 is a diagnostic biomarker for AMI and participates in myocardial injury in AMI by regulating miR-574-5p. Our study provides new insights into the diagnosis for AMI.

Circ_005077 accelerates myocardial lipotoxicity induced by high-fat diet via CyPA/p47PHOX mediated ferroptosis

The long-term high-fat diet (HFD) can cause myocardial lipotoxicity, which is characterized pathologically by myocardial hypertrophy, fibrosis, and remodeling and clinically by cardiac dysfunction and heart failure in patients with obesity and diabetes. Circular RNAs (circRNAs), a novel class of noncoding RNA characterized by a ring formation through covalent bonds, play a critical role in various cardiovascular diseases. However, few studies have been conducted to investigate the role and mechanism of circRNA in myocardial lipotoxicity. Here, we found that circ_005077, formed by exon 2-4 of Crmp1, was significantly upregulated in the myocardium of an HFD-fed rat. Furthermore, we identified circ_005077 as a novel ferroptosis-related regulator that plays a role in palmitic acid (PA) and HFD-induced myocardial lipotoxicity in vitro and in vivo. Mechanically, circ_005077 interacted with Cyclophilin A (CyPA) and inhibited its degradation via the ubiquitination proteasome system (UBS), thus promoting the interaction between CyPA and p47phox to enhance the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase responsible for ROS generation, subsequently inducing ferroptosis. Therefore, our results provide new insights into the mechanisms of myocardial lipotoxicity, potentially leading to the identification of a novel therapeutic target for the treatment of myocardial lipotoxicity in the future.

Circular RNA: A new expectation for cardiovascular diseases

Circular RNA (circRNA) is a class of RNA with the 5' and 3' ends connected covalently to form a closed loop structure and characterized by high stability, conserved sequences and tissue specificity, which is caused by special reverse splicing methods. Currently, it has become a hot spot for research. With the discovery of its powerful regulatory functions and roles, the molecular mechanisms and future value of circRNA in participating in and regulating biological and pathological processes are becoming increasingly apparent. Among them is the increasing prevalence of cardiovascular diseases (CVDs). Many studies have elucidated that circRNA plays a crucial role in the development and progression of CVDs. Therefore, circRNA shows its advantages and brilliant expectations in the field of CVDs. In this review, we describe the biogenesis, bioinformatics detection and function of circRNA and discuss the role of circRNA and its effects on CVDs, including atherosclerosis, myocardial infarction, cardiac hypertrophy and heart failure, myocardial fibrosis, cardiac senescence, pulmonary hypertension, and diabetic cardiomyopathy by different mechanisms. That shows circRNA advantages and brilliant expectations in the field of CVDs.

Circ-SUZ12 Protects Cardiomyocytes from Hypoxia-Induced Dysfunction Through Upregulating SUZ12 Expression to Activate Wnt/β-catenin Signaling Pathway

Acute myocardial infarction (AMI) is a common coronary artery disease. This study attempted to reveal the impact of circ-SUZ12 (hsa_circ_0042961) on cardiomyocyte injury after exposure to hypoxia.Circ-SUZ12 was screened out from the GEO dataset GSE169594. RNA expression and protein level were detected by quantitative real-time PCR (qRT-PCR) and Western blot, respectively. The characteristics of circ-SUZ12 were identified by measuring its resistance to Rnase R or actinomycin D (Act D) treatment. CCK-8 and EdU assays were performed to explore the viability of AC16 cells. Cell apoptosis was assessed through TUNEL assay and flow cytometry analysis. Mechanism experiments were performed to investigate the downstream molecular mechanism of circ-SUZ12.Circ-SUZ12 was highly expressed in blood samples of AMI patients in the GEO dataset and lowly expressed in hypoxia-treated cardiomyocytes. Overexpression of circ-SUZ12 reversed hypoxia-induced cardiomyocyte injury. Circ-SUZ12 regulated SUZ12 polycomb repressive complex 2 subunit (SUZ12) expression by recruiting FUS protein. SUZ12 activated the Wnt/β-catenin signaling pathway by increasing the H3K27me3 level in microRNA (miR)-526b-5p promoter to release catenin beta 1 (CTNNB1). CTNNB1 depletion reversed the effect of circ-SUZ12 on the viability and apoptosis of hypoxia-induced cardiomyocytes.Circ-SUZ12 protects cardiomyocytes from hypoxia-induced dysfunction through upregulating SUZ12 expression to activate the Wnt/β-catenin signaling pathway.

Circ_0004771 Promotes Hypoxia/Reoxygenation Induced Cardiomyocyte Injury via Activation of Mitogen-Activated Protein Kinase Signaling Pathway

This study aimed to observe the mechanism and effect of circ_0004771 on cardiomyocyte injury in acute myocardial infarction (AMI). The differences in circ_0004771 expression in the blood of AMI patients and healthy volunteers were observed by Real-Time Quantitative Reverse Transcription-Polymerase Chain Reaction. AMI cell models were constructed by hypoxia/reoxygenation (H/R)-induced injury in human cardiomyocytes (AC16 cells). The changes of circ_0004771 expression in AMI cells were observed. After transfection with the knockdown or overexpression of circ_0004771 vector in AMI cells, Cell Counting Kit-8 (CCK-8) assay and propidium iodide/FITC-Annexin V staining were performed to detect cell proliferation and apoptosis levels, extracellular lactate dehydrogenase (LDH) activity, malondialdehyde (MDA) concentration, and superoxide dismutase (SOD) activity. Expression levels of Mitogen-activated protein kinase (MAPK) signaling pathway-related proteins (p-MEK1/2, MEK1/2, p-ERK1/2, ERK1/2), and endoplasmic reticulum (ER) stress proteins (GRP78 and CHOP-1) were observed in each group of cells by western blot method. The expression level of circ_0004771 was significantly reduced in both clinical samples and cells of AMI. When circ_0004771 was knocked down in AMI cells, it resulted in a decrease in cell proliferation level and significant increase in apoptosis level. The inhibition of circ_0004771 expression caused leakage of LDH in AMI cells, accumulation of intracellular MDA, and inhibition of SOD activity. In addition, the knockdown of circ_0004771 significantly increased the levels of p-MEK1/2, p-ERK1/2, GRP78, and CHOP-1 in H/R-induced AC16 cells. However, the overexpression of circ_0004771 resulted in the opposite result as when circ_0004771 was knocked down. A low level of circ_0004771 in AMI activates the MAPK signaling pathway in cardiomyocytes as well as encourages intracellular oxidative stress and ER stress, thereby inhibiting cell proliferation and promoting apoptosis.

CircMACF1 alleviates myocardial fibrosis after acute myocardial infarction by suppressing cardiac fibroblast activation via the miR-16-5p/SMAD7 axis

Circular RNAs (circRNAs) played a pivotal role in myocardial fibrosis after acute myocardial infarction (AMI). The activation of cardiac fibroblasts (CFs) and accumulation of extracellular matrix are the main characteristics of myocardial fibrosis. In our research, we aimed to elucidate the functional roles of circMACF1 in CF activation after AMI as well as the underlying mechanism. Human CFs were activated by TGF-β1 treatment. qPCR and western blotting were performed to investigate gene and protein expression. CCK-8 and transwell assays were carried out to measure cell proliferation, and migration. Immunofluorescence was used to investigate α-SMA level. The interaction between miR-16-5p and circMACF1 or SMAD7 was revealed by RIP or dual luciferase reporter gene assays. CircMACF1 and SMAD7 were repressed in AMI patients and CFs treated with TGF-β1, and miR-16-5p was increased. In addition, circMACF1 was resistant to RNase R and abundantly expressed in the cytoplasm. Overexpression of circMACF1 inhibited cell proliferation and migration and reduced the expression levels of fibrosis-related proteins, including Collagen I, Collagen III, and α-SMA. Furthermore, circMCAF1 could directly bind to miR-16-5p, and SMAD7 was a target gene of miR-16-5p. Knockdown of miR-16-5p suppressed the activation, proliferation, and migration of TGF-β1-treated CFs, but silencing circMACF1 or SMAD7 partially reversed this phenomenon. CircMACF1 attenuated the TGF-β1-induced activation, proliferation and migration of CFs via the miR-16-5p/SMAD7 signaling pathway, indicating that circMACF1 might be a new therapeutic target for AMI.

Circular RNAs: Biogenesis, Biological Functions, and Roles in Myocardial Infarction

Non-coding RNAs have been excavated as important cardiac function modulators and linked to heart diseases. Significant advances have been obtained in illuminating the effects of microRNAs and long non-coding RNAs. Nevertheless, the characteristics of circular RNAs are rarely mined. Circular RNAs (circRNAs) are widely believed to participate in cardiac pathologic processes, especially in myocardial infarction. In this review, we round up the biogenesis of circRNAs, briefly describe their biological functions, and summarize the latest literature on multifarious circRNAs related to new therapies and biomarkers for myocardial infarction.

Circular RNAs as a Diagnostic and Therapeutic Target in Cardiovascular Diseases

Circular RNAs (circRNAs) are a family of noncoding RNAs (ncRNAs) that are endogenous and widely distributed in different species, performing several functions, mainly their association with microRNAs (miRNAs) and RNA-binding proteins. CVDs remain the leading cause of death worldwide; therefore, the development of new therapies and strategies, such as gene therapies or nonpharmacological therapies, with low cost, such as physical exercise, to alleviate these diseases is of extreme importance for society. With increasing evidence of ncRNA participating in the progression of CVDs, several studies have reported these RNAs as promising targets for diagnosis and treatment. There are several studies of CVDs and the role of miRNAs and lncRNAs; however, little is known about the new class of RNAs, called circRNAs, and CVDs. In this mini review, we focus on the mechanisms of circRNAs and CVDs.

Silencing of Hsa_circ_0055440 Alleviates Hypoxia-Induced Cardiomyocyte Injury by Regulating the MiR-499b-5p/ACSL1 Axis

Circular RNAs (circRNAs) are a new type of regulatory RNAs, which are involved in various cardiac processes. However, the role of circRNA hsa_circ_0055440 (circ-USP39) in acute myocardial infarction regulation has not been studied yet.This study aims to explore the effect of circ-USP39 on hypoxia-induced cardiomyocyte injury.The head-to-tail splicing of circ-USP39 was verified by agarose gel electrophoresis. AC16 cell viability was detected using 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide assays. The apoptosis of the AC16 cell was determined by flow cytometry and detection of caspase-3 activity. The levels of creatine kinase-muscle/brain and cTnl were evaluated by specific detection kits. The interactions between miR-499b-5p and circ-USP39 (or acyl-CoA synthetase long-chain family member-1 (ACSL1) ) were verified by luciferase reporter assays.After confirming the circular characteristics of circ-USP39, we further found that the circ-USP39 expression was upregulated in hypoxia-induced cardiomyocytes and the circ-USP39 knockdown facilitated the viability of hypoxia-induced AC16, while suppressing cardiomyocyte apoptosis and injury. Importantly, circ-USP39 negatively regulated miR-499b-5p expression. As a downstream target of miR-499b-5p, ACSL1 partially counteracted the protective effect of circ-USP39 depletion on cardiomyocyte injury.Silencing of circ-USP39 alleviates hypoxia-induced cardiomyocyte injury via the miR-499b-5p/ACSL1 axis.

CircRNA02318 Exerts Therapeutic Effects on Myocardial Ischemia-Reperfusion Injury Rats by Regulating the Nox1/Akt Through Inhibiting Drebrin

Our research aims to explore the therapeutic effect of circRNA02318 on MIRI rats and the functional mechanism. The MIRI model was constructed in rats. CircRNA02318 overexpressing adenovirus was injected in situ during MIRI perfusion. H9C2 cells were treated with hypoxia for 6 h and reoxygenation for 3 h. Overexpression of circRNA02318 downregulated Drebrin, Nox1, cleaved caspase-3 and Bax in H/R H9C2 cells and MIRI rat heart tissues, promoted the expression of p-Akt/Akt and Bcl-2, and inhibited the apoptosis of H9C2 cells. The volume of myocardial infarction and the release of LDH and TnI in MIRI rats were suppressed by circRNA02318. The Nox1, cleaved caspase-3 and Bax levels were promoted, the level of p-Akt/Akt and Bcl-2 was repressed, and the apoptosis was facilitated by the Drebrin overexpression. Furthermore, the effect of Drebrin overexpression on H9C2 cells was abolished by circRNA02318. Collectively, circRNA02318 exerted therapeutic effects on MIRI rats by inhibiting Drebrin.

Epigenetic regulation in myocardial infarction: Non-coding RNAs and exosomal non-coding RNAs

Myocardial infarction (MI) is one of the leading causes of deaths globally. The early diagnosis of MI lowers the rate of subsequent complications and maximizes the benefits of cardiovascular interventions. Many efforts have been made to explore new therapeutic targets for MI, and the therapeutic potential of non-coding RNAs (ncRNAs) is one good example. NcRNAs are a group of RNAs with many different subgroups, but they are not translated into proteins. MicroRNAs (miRNAs) are the most studied type of ncRNAs, and have been found to regulate several pathological processes in MI, including cardiomyocyte inflammation, apoptosis, angiogenesis, and fibrosis. These processes can also be modulated by circular RNAs and long ncRNAs via different mechanisms. However, the regulatory role of ncRNAs and their underlying mechanisms in MI are underexplored. Exosomes play a crucial role in communication between cells, and can affect both homeostasis and disease conditions. Exosomal ncRNAs have been shown to affect many biological functions. Tissue-specific changes in exosomal ncRNAs contribute to aging, tissue dysfunction, and human diseases. Here we provide a comprehensive review of recent findings on epigenetic changes in cardiovascular diseases as well as the role of ncRNAs and exosomal ncRNAs in MI, focusing on their function, diagnostic and prognostic significance.

Expression Profiles and Functional Analysis of Plasma Exosomal Circular RNAs in Acute Myocardial Infarction

Acute myocardial infarction (AMI) is a common cardiovascular disease with high rates of morbidity and mortality globally. The dysregulation of circular RNAs (circRNAs) has been shown to be closely related to various pathological aspects of AMI. However, the function of exosomal circRNAs in AMI has yet to be investigated. The purpose of this study was to investigate the expression profiles of plasma exosomal circRNAs in AMI and explore their potential functionality. The expression profiles of plasma exosomal circRNAs in patients with AMI, stable coronary heart atherosclerotic disease (CAD), and healthy controls were obtained from a GEO expression dataset (GSE159657). We also analyzed bioinformatics functionality, potential pathways, and interaction networks related to the microRNAs associated with the differentially expressed circRNAs. A total of 253 exosomal circRNAs (184 up- and 69 down-regulated) and 182 exosomal circRNAs (94 up- and 88 down-regulated) were identified as being differentially expressed between the control group and the AMI and CAD patients, respectively. Compared with the CAD group, 231 different exosomal circRNAs (177 up- and 54 down-regulated) were identified in the AMI group. Functional analysis suggested that the parental genes of exosomal has_circ_0061776 were significantly enriched in the biological process of lysine degradation. Pathway interaction network analysis further indicated that exosomal has_circ_0061776 was associated with has-miR-133a, has-miR-214, has-miR-423, and has-miR-217 and may play a role in the pathogenesis of AMI through the MAPK signaling pathway. This study identified the differential expression and functionality of exosomal circRNAs in AMI and provided further understanding of the potential pathogenesis of an exosomal circRNA-related competing endogenous RNA (ceRNA) network in AMI.

The circRNA-miRNA/RBP regulatory network in myocardial infarction

Myocardial infarction (MI) is a serious heart disease that causes high mortality rate worldwide. Noncoding RNAs are widely involved in the pathogenesis of MI. Circular RNAs (circRNAs) are recently validated to be crucial modulators of MI. CircRNAs are circularized RNAs with covalently closed loops, which make them stable under various conditions. CircRNAs can function by different mechanisms, such as serving as sponges of microRNAs (miRNAs) and RNA-binding proteins (RBPs), regulating mRNA transcription, and encoding peptides. Among these mechanisms, sponging miRNAs/RBPs is the main pathway. In this paper, we systematically review the current knowledge on the properties and action modes of circRNAs, elaborate on the roles of the circRNA-miRNA/RBP network in MI, and explore the value of circRNAs in MI diagnosis and clinical therapies. CircRNAs are widely involved in MI. CircRNAs have many advantages, such as stability, specificity, and wide distribution, which imply that circRNAs have a great potential to act as biomarkers for MI diagnosis and prognosis.

CircSLC8A1 Exacerbates Hypoxia-Induced Myocardial Injury via Interacting with MiR-214-5p to Upregulate TEAD1 Expression

Circular RNAs (circRNAs) act as important regulators in myocardial infarction (MI). This study aimed to explore the regulatory mechanism of circRNA solute carrier family 8 member A1 antisense RNA 1 (circSLC8A1) in hypoxia-induced myocardial injury.Exosomes were isolated by ultracentrifugation and identified by microscopic observation or protein detection. Protein levels were examined by Western blot. CircSLC8A1, microRNA-214-5p (miR-214-5p), and TEA domain transcription factor 1 (TEAD1) levels were determined via quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability and apoptosis were analyzed by 3-(4,5-dimethylthiazol-2-y1)-2,5-diphenyl tetrazolium bromide (MTT) and flow cytometry, respectively. Inflammatory cytokines were measured using enzyme-linked immunosorbent assay (ELISA). Oxidative stress was assessed by reactive oxygen species (ROS) production, malondialdehyde (MDA) level, and superoxide dismutase (SOD) activity through the corresponding detection kits. Target analysis was performed by dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, and pull-down assay.Exosomes released circSLC8A1 from hypoxic cardiomyocytes. Exosomal circSLC8A1 exacerbated hypoxia-induced repression of cell viability but promotion of cell apoptosis, inflammation, and oxidative stress. Knockdown of circSLC8A1 ameliorated hypoxia-mediated cell injury. CircSLC8A1 directly targeted miR-214-5p and miR-214-5p downregulation reverted the effects of si-circSLC8A1 on hypoxia-treated cardiomyocytes. TEAD1 was a target of miR-214-5p and circSLC8A1 upregulated TEAD1 level via targeting miR-214-5p. In addition, miR-214-5p inhibited hypoxia-caused cell injury by downregulating the expression of TEAD1.These results suggested that circSLC8A1 aggravated cell damages in hypoxia-treated cardiomyocytes by the regulation of TEAD1 via sponging miR-214-5p.

CircR2Disease v2.0: An Updated Web Server for Experimentally Validated circRNA-disease Associations and Its Application

With accumulating dysregulated circular RNAs (circRNAs) in pathological processes, the regulatory functions of circRNAs, especially circRNAs as microRNA (miRNA) sponges and their interactions with RNA-binding proteins (RBPs), have been widely validated. However, the collected information on experimentally validated circRNA-disease associations is only preliminary. Therefore, an updated CircR2Disease database providing a comprehensive resource and web tool to clarify the relationships between circRNAs and diseases in diverse species is necessary. Here, we present an updated CircR2Disease v2.0 with the increased number of circRNA-disease associations and novel characteristics. CircR2Disease v2.0 provides more than 5-fold experimentally validated circRNA-disease associations compared to its previous version. This version includes 4201 entries between 3077 circRNAs and 312 disease subtypes. Secondly, the information of circRNA-miRNA, circRNA-miRNA-target, and circRNA-RBP interactions has been manually collected for various diseases. Thirdly, the gene symbols of circRNAs and disease name IDs can be linked with various nomenclature databases. Detailed descriptions such as samples and journals have also been integrated into the updated version. Thus, CircR2Disease v2.0 can serve as a platform for users to systematically investigate the roles of dysregulated circRNAs in various diseases and further explore the posttranscriptional regulatory function in diseases. Finally, we propose a computational method named circDis based on the graph convolutional network (GCN) and gradient boosting decision tree (GBDT) to illustrate the applications of the CircR2Disease v2.0 database. CircR2Disease v2.0 is available at http://bioinfo.snnu.edu.cn/CircR2Disease_v2.0 and https://github.com/bioinforlab/CircR2Disease-v2.0.

CircZDBF2 up-regulates RNF145 by ceRNA model and recruits CEBPB to accelerate oral squamous cell carcinoma progression via NFκB signaling pathway

Background

Oral squamous cell carcinoma (OSCC), as one of the commonest malignancies showing poor prognosis, has been increasingly suggested to be modulated by circular RNAs (circRNAs). Through GEO (Gene Expression Omnibus) database, a circRNA derived from ZDBF2 (circZDBF2) was uncovered to be with high expression in OSCC tissues, while how it may function in OSCC remains unclear.

Methods

CircZDBF2 expression was firstly verified in OSCC cells via qRT-PCR. CCK-8, along with colony formation, wound healing, transwell and western blot assays was performed to assess the malignant cell behaviors in OSCC cells. Further, RNA pull down assay, RIP assay, as well as luciferase reporter assay was performed to testify the interaction between circZDBF2 and RNAs.

Results

CircZDBF2 expressed at a high level in OSCC cells and it accelerated OSCC cell proliferation, migration, invasion as well as EMT (epithelial-mesenchymal transition) process. Further, circZDBF2 sponged miR-362-5p and miR-500b-5p in OSCC cells to release their target ring finger protein 145 (RNF145). RNF145 expressed at a high level in OSCC cells and circZDBF2 facilitated RNF145 transcription by recruiting the transcription factor CCAAT enhancer binding protein beta (CEBPB). Moreover, RNF145 activated NFκB (nuclear factor kappa B) signaling pathway and regulated IL-8 (C-X-C motif chemokine ligand 8) transcription.

Conclusion

CircZDBF2 up-regulated RNF145 expression by sponging miR-362-5p and miR-500b-5p and recruiting CEBPB, thereby promoting OSCC progression via NFκB signaling pathway. The findings recommend circZDBF2 as a probable therapeutic target for OSCC.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03347-1.

CircRbms1 knockdown alleviates hypoxia-induced cardiomyocyte injury via regulating the miR-742-3p/FOXO1 axis

Background

Circular RNA (circRNA) has been shown to play an important role in a variety of cardiovascular diseases, including myocardial infarction (MI). However, the role of circRbms1 in MI progression remains unclear.

Methods

An MI mouse model was constructed in vivo, and cardiomyocytes were cultured under hypoxia condition to induce a cardiomyocyte injury model in vitro. The expression levels of circRbms1, microRNA (miR)-742-3p, and forkhead box O1 (FOXO1) were determined by quantitative real-time PCR. Cell viability, migration, invasion, and apoptosis were measured using Cell Counting Kit-8 assay, transwell assay, and flow cytometry. Meanwhile, western blot analysis was used to examine the protein levels of apoptosis markers and FOXO1. Additionally, dual-luciferase reporter assay, RNA pull-down assay, and RIP assay were employed to verify the interactions between miR-742-3p and circRbms1 or FOXO1.

Results

CircRbms1 was upregulated in the heart tissues of MI mice and hypoxia-induced cardiomyocytes. Hypoxia induced cardiomyocyte injury by suppressing cell viability, migration, and invasion, and promoting apoptosis. Function experiments showed that circRbms1 overexpression aggravated hypoxia-induced cardiomyocyte injury, while its silencing relieved cardiomyocyte injury induced by hypoxia. Furthermore, circRbms1 sponged miR-742-3p. MiR-742-3p overexpression alleviated hypoxia-induced cardiomyocyte injury, and its inhibitor reversed the suppressive effect of circRbms1 silencing on hypoxia-induced cardiomyocyte injury. Further experiments showed that FOXO1 was a target of miR-742-3p, and its expression was positively regulated by circRbms1. The inhibitory effect of miR-742-3p on hypoxia-induced cardiomyocyte injury was reversed by FOXO1 overexpression.

Conclusion

CircRbms1 regulated the miR-742-3p/FOXO1 axis to mediate hypoxia-induced cardiomyocyte injury, suggesting that circRbms1 might be an effective target for MI treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-022-00330-y.

CircTRRAP Knockdown Has Cardioprotective Function in Cardiomyocytes via the Signal Regulation of miR-370-3p/PAWR Axis

Background

Circular RNA Transformation/Transcription Domain Associated Protein (circTRRAP, hsa_circ_0081241) was abnormally upregulated in acute myocardial infarction (AMI) patients. However, its biological role and functional mechanism in AMI remain to be researched.

Methods

Human cardiomyocyte AC16 was exposed to hypoxia to induce cell injury. Cell viability was detected through Cell Counting Kit-8. CircTRRAP, microRNA-370-3p (miR-370-3p), and Pro-Apoptotic WT1 Regulator (PAWR) levels were assayed by reverse transcription-quantitative polymerase chain reaction. Cell proliferation analysis was performed via 5-ethynyl-2′-deoxyuridine (EdU) assay. Cell apoptosis was assessed using flow cytometry and caspase-3 activity assay. The protein levels were measured through western blot. Enzyme-linked immunosorbent assay was used to examine the release of inflammatory cytokines. Oxidative stress was assessed by the commercial kits. Dual-luciferase reporter assay, RNA immunoprecipitation, and RNA pull-down assays were performed for the validation of target interaction.

Results

CircTRRAP was highly expressed following hypoxia treatment in AC16 cells. Downregulation of circTRRAP promoted cell growth but inhibited apoptosis, inflammation, and oxidative stress in hypoxic cells. CircTRRAP could target miR-370-3p, and the regulatory effects of circTRRAP on the hypoxic cells were associated with the sponge function of miR-370-3p. PAWR served as the target for miR-370-3p, and it was regulated by circTRRAP/miR-370-3p axis. The protective role of miR-370-3p was achieved by downregulating the PAWR expression in hypoxia-treated AC16 cells.

Conclusion

These findings demonstrated that silence of circTRRAP exerted the protection against the hypoxia-induced damages in cardiomyocytes through regulating the miR-370-3p and PAWR levels.

Circ-SWT1 Ameliorates H2O2-Induced Apoptosis, Oxidative Stress and Endoplasmic Reticulum Stress in Cardiomyocytes via miR-192-5p/SOD2 Axis

Acute myocardial infarction (AMI) is a most serious cardiovascular disease. Increasing findings have indicated that circular RNAs (circRNAs) serve as competent biomarkers in the process of AMI. Herein, our study aimed to probe the functions of circ-SWT1 in cardiomyocyte injury after AMI. H₂O₂-induced human cardiomyocyte cell line AC16 were used for expression and function analyses. The levels of genes and proteins were detected by qRT-PCR and western blotting. Cell apoptosis was analyzed by flow cytometry and caspase3 activity analysis. The oxidative stress injury was evaluated by detecting the levels of reactive oxygen species (ROS), malondialdehyde and superoxide dismutase (SOD). Western blotting was used to detect the expressions of apoptosis-related markers and endoplasmic reticulum stress (ERS) markers. Dual-luciferase reporter, RIP and pull-down assays were applied to confirm the interaction between miR-192-5p and circ-SWT1 or SOD2. H₂O₂ treatment significantly decreased circ-SWT1 expression in cardiomyocytes, functionally, ectopic expression of circ-SWT1 attenuated H₂O₂-triggered apoptosis, oxidative stress and endoplasmic reticulum (ER) stress in cardiomyocytes in vitro. Mechanistically, circ-SWT1 competitively bound to miR-192-5p to relieve the repression of miR-192-5p on its target SOD2. Further rescue experiments showed that miR-192-5p upregulation reversed the inhibitory effects of circ-SWT1 on H₂O₂-induced cardiomyocyte injury. Moreover, miR-192-5p inhibition protected cardiomyocytes against H₂O₂-evoked apoptosis, oxidative stress and ER stress, which were abolished by SOD2 silencing. Circ-SWT1 ameliorates H₂O₂-induced apoptosis, oxidative stress and ER stress in cardiomyocytes via miR-192-5p/SOD2 axis, suggesting the potential involvement of circ-SWT1 in AMI process.

Targeting Epigenetics and Non-coding RNAs in Myocardial Infarction: From Mechanisms to Therapeutics

Myocardial infarction (MI) is a complicated pathology triggered by numerous environmental and genetic factors. Understanding the effect of epigenetic regulation mechanisms on the cardiovascular disease would advance the field and promote prophylactic methods targeting epigenetic mechanisms. Genetic screening guides individualised MI therapies and surveillance. The present review reported the latest development on the epigenetic regulation of MI in terms of DNA methylation, histone modifications, and microRNA-dependent MI mechanisms and the novel therapies based on epigenetics.

Emerging roles of circRNAs in the pathological process of myocardial infarction

Myocardial infarction (MI) is defined as cardiomyocyte death in a clinical context consistent with ischemic insult. MI remains one of the leading causes of morbidity and mortality worldwide. Although there are a number of effective clinical methods for the diagnosis and treatment of MI, further investigation of novel biomarkers and molecular therapeutic targets is required. Circular RNAs (circRNAs), novel non-coding RNAs, have been reported to function mainly by acting as microRNA (miRNA) sponges or binding to RNA-binding proteins (RBPs). The circRNA-miRNA-mRNA (protein) regulatory pathway regulates gene expression and affects the pathological mechanisms of various diseases. Undoubtedly, a more comprehensive understanding of the relationship between MI and circRNA will lay the foundation for the development of circRNA-based diagnostic and therapeutic strategies for MI. Therefore, this review summarizes the pathophysiological process of MI and various approaches to measure circRNA levels in MI patients, tissues, and cells; highlights the significance of circRNAs in the regulation MI pathogenesis and development; and provides potential clinical insight for the diagnosis, prognosis, and treatment of MI.

miR profile in pagetic osteoclasts: from large-scale sequencing to gene expression study

Paget's disease of bone (PDB) is characterized by excessive and disorganized bone remodeling, in which bone-resorbing osteoclasts play a key role. We investigated microRNA (miR) expression in osteoclasts derived from the blood of 40 PDB patients and 30 healthy controls. By deep sequencing, a preliminary analysis identified differentially expressed miRs in a discovery cohort of 9 PDB patients and 9 age and sex-matched healthy controls. Six mature miRs, miR-29b1-3p, miR-15b-5p, miR-181a-5p, let-7i-3p, miR-500b-5p, and miR-1246, were found to be significantly decreased in pagetic overactive osteoclasts. The differential expression of the miRs was confirmed by the analysis of a larger independent cohort using qPCR. In an integrative network biology analysis of the miR candidates, we identified strong validated interactions between the miRs and some pathways, primarily apoptosis, and major osteoclast signaling pathways including PI3K/Akt, IFNγ, or TGFβ, as well as c-Fos, a transcription factor, and MMP-9, a metalloprotease. In addition, other genes like CCND2, CCND1, WEE1, SAMHD1, and AXIN2 were revealed in this network of interactions. Our results enhance the understanding of osteoclast biology in PDB; our work may also provide fresh perspectives on the research or therapeutic development of other bone diseases. KEY MESSAGES: miR profile in overactive osteoclasts from patients with Paget's disease of bone. Six mature miRs were significantly decreased in pagetic osteoclasts vs controls. miRs of interest: let7i-3p, miR-15b-5p, -29b1-3p, -181a-5p, -500b-5p, and -1246. Target genes and enriched pathways highlight the importance of apoptotic pathways.

Circular RNAs as Competing Endogenous RNAs in Cardiovascular and Cerebrovascular Diseases: Molecular Mechanisms and Clinical Implications

Circular RNAs (circRNAs) represent a novel class of widespread and diverse endogenous RNA molecules. This unusual class of RNA species is generated by a back-splicing event of exons or introns, resulting in a covalently closed circRNA molecule. Accumulating evidence indicates that circRNA plays an important role in the biological functions of a network of competing endogenous RNA (ceRNA). CircRNAs can competitively bind to miRNAs and abolish the suppressive effect of miRNAs on target RNAs, thus regulating gene expression at the posttranscriptional level. The role of circRNAs as ceRNAs in the pathogenesis of cardiovascular and cerebrovascular diseases (CVDs) has been recently reported and highlighted. Understanding the underlying molecular mechanism could aid the discovery of therapeutic targets or strategies against CVDs. Here, we review the progress in studying the role of circRNAs as ceRNAs in CVDs, with emphasis on the molecular mechanism, and discuss future directions and possible clinical implications.

Circle the Cardiac Remodeling With circRNAs

Cardiac remodeling occurs after the heart is exposed to stress, which is manifested by pathological processes such as cardiomyocyte hypertrophy and apoptosis, dendritic cells activation and cytokine secretion, proliferation and activation of fibroblasts, and finally leads to heart failure. Circular RNAs (circRNAs) are recently recognized as a specific type of non-coding RNAs that are expressed in different species, in different stages of development, and in different pathological conditions. Growing evidences have implicated that circRNAs play important regulatory roles in the pathogenesis of a variety of cardiovascular diseases. In this review, we summarize the biological origin, characteristics, functional classification of circRNAs and their regulatory functions in cardiomyocytes, endothelial cells, fibroblasts, immune cells, and exosomes in the pathogenesis of cardiac remodeling.

Insights into circular RNAs: their biogenesis, detection, and emerging role in cardiovascular disease

Circular RNAs (circRNAs) are an evolutionarily conserved form of noncoding RNA with covalently closed loop structures. Initial studies established a functional role for circRNAs as potent microRNA sponges and many other studies have focussed solely on this. However, the biological functions of most circRNAs are still undetermined and other functional roles are gaining traction. These include protein sponges and regulators, and coding for proteins with an alternative mechanism of translation, potentially opening up a whole new transcriptome. The first step to gaining insight into circRNA function is accurate identification and various software platforms have been developed. Specialized detection software has now evolved into whole bioinformatics pipelines that can be used for detection, de novo identification, functional prediction, and validation of circRNAs. However, few cardiovascular circRNA studies have utilized these tools. This review summarizes current knowledge of circRNA biogenesis, bioinformatic detection tools and the emerging role of circRNAs in cardiovascular disease.

Circular RNAs in Sudden Cardiac Death Related Diseases: Novel Biomarker for Clinical and Forensic Diagnosis

The prevention and diagnosis of sudden cardiac death (SCD) are among the most important keystones and challenges in clinical and forensic practice. However, the diagnostic value of the current biomarkers remains unresolved issues. Therefore, novel diagnostic biomarkers are urgently required to identify patients with early-stage cardiovascular diseases (CVD), and to assist in the postmortem diagnosis of SCD cases without typical cardiac damage. An increasing number of studies show that circular RNAs (circRNAs) have stable expressions in myocardial tissue, and their time- and tissue-specific expression levels might reflect the pathophysiological status of the heart, which makes them potential CVD biomarkers. In this article, we briefly introduced the biogenesis and functional characteristics of circRNAs. Moreover, we described the roles of circRNAs in multiple SCD-related diseases, including coronary artery disease (CAD), myocardial ischemia or infarction, arrhythmia, cardiomyopathy, and myocarditis, and discussed the application prospects and challenges of circRNAs as a novel biomarker in the clinical and forensic diagnosis of SCD.

Salidroside inhibits apoptosis and autophagy of cardiomyocyte by regulation of circular RNA hsa_circ_0000064 in cardiac ischemia-reperfusion injury

Salidroside (Sal), a natural extract of Rhodiola rosea, shows a latent effect on protecting cardiovascular system. Our study explored the effect of salidroside on ischemia-reperfusion (I/R) injury in rat heart. I/R was performed on Wistar rat hearts, and Sal pretreatment was performed in I/R rats. Cardiac marker enzyme, myocardial infarct size, malondialdehyde (MDA) and superoxide dismutase (SOD) content were then measured. Compared with the untreated group, Sal pretreatment observably ameliorated the cardiac function, decreased the myocardial infarct size, reduced the levels of cardiac lactate creatine kinase-MB (CK-MB) and dehydrogenase (LDH), and inhibited the anti-oxidative stress. In addition, Sal treatment also significantly inhibited autophagy and apoptosis, which could be partially reversed by Rapamycin (RAPA), an autophagic agonist. Furthermore, Sal treatment attenuated autophagy by up-regulating the expression of hsa_circ_0000064 (circ-0000064) and Rapamycin (RAPA) treatment abolished it. Our study showed that Sal protected the heart from I/R injury, which might berelated to the upregulation of circ-0000064 and the inhibition of autophagy.