Circular RNAs as Novel Biomarkers for Cardiovascular Diseases. In: Xiao J, editor. Circular RNAs. Singapore: Springer; 2018. pp. 159-70. [DOI: 10.1007/978-981-13-1426-1_13]

Detailed profiling of m6A modified circRNAs and synergistic effects of circRNA and environmental risk factors for coronary artery disease

The modification of N6-methyladenosine (m6A) modification is implicated in human diseases. However, considerable uncertainty is associated with the regulatory mechanisms of m6A circRNAs in coronary artery disease (CAD), which require further clarification. In this study, m6A-modified RNA immunoprecipitation sequencing (MeRIP-seq) was conducted to investigate m6A-modified circRNAs in human coronary artery smooth muscle cells (HCASMCs) and to identify potential biomarkers for CAD. A total of 830 and 331 up- and down-regulated m6A peaks, (corresponding to 463 and 243 up- and down-regulated circRNAs, respectively), were identified in HCASMCs in a pathological condition. Functional analysis suggested that these circRNAs appeared to participate in intracellular protein, histone deacetylase complex, ATP-dependent activity, autophagy, and AMPK signaling pathway. Four candidate circRNAs were selected for further evaluation in HCASMCs and human samples. The results suggested that hsa_circHECTD1 and hsa_circZBTB46 were significantly increased in patients with CAD (p-value = 0.039 and p-value = 0.014) and may act as potential diagnostic biomarkers of CAD. Furthermore, statistical results showed that hsa_circHECTD1 and hsa_circSEC62 were positively correlated with triglyceride (TG) (r = 0.213, p-value = 0.014) and Gensini Score (used to quantify the severity of CAD) (r = 0.349, p-value <0.001), respectively. Logistic regression revealed that hsa_circZBTB46 was strongly correlated with the incidence of CAD, and the synergistic effects of circRNAs and hypertension enhanced the risk of CAD. These results show that hsa_circHECTD1 and hsa_circZBTB46 may be new targets for further studies, and this study enhances our understanding of the effects of m6A-circRNAs on the pathogenesis of CAD.

The Role of BTBD7 in Normal Development and Tumor Progression

BTB/POZ domain-containing protein 7 (BTBD7) has a relative molecular weight of 126KD and contains two conserved BTB/POZ protein sequences. BTBD7 has been shown to play an essential role in normal human development, precancerous lesions, heat-stress response, and tumor progression. BTBD7 promotes branching morphogenesis during development and participates in the salivary gland, lung, and tooth formation. Furthermore, many studies have shown that aberrant expression of BTBD7 promotes heat stress response and the progression of precancerous lesions. BTBD7 has also been found to play an important role in cancer. High expression of BTBD7 affects tumor progression by regulating multiple pathways. Therefore, a complete understanding of BTBD7 is crucial for exploring human development and tumor progression. This paper reviews the research progress of BTBD7, which lays a foundation for the application of BTBD7 in regenerative medicine and as a biomarker for tumor prediction or potential therapeutic target.

Circular RNAs Regulate Vascular Remodelling in Pulmonary Hypertension

Circular RNAs (circRNAs) are a newly identified type of noncoding RNA molecule with a unique closed-loop structure. circRNAs are widely expressed in different tissues and developmental stages of many species, participating in many important pathophysiological processes and playing an important role in the occurrence and development of diseases. This article reviews the discovery, characteristics, formation, and biological function of circRNAs. The relationship between circRNAs and vascular remodelling, as well as the current status of research and potential application value in pulmonary hypertension (PH), is discussed to promote a better understanding of the role of circRNAs in PH. circRNAs are closely related to the remodelling of vascular endothelial cells and vascular smooth muscle cells. circRNAs have potential application prospects for in-depth research on the possible pathogenesis and mechanism of PH. Future research on the role of circRNAs in the pathogenesis and mechanism of PH will provide new insights and promote screening, diagnosis, prevention, and treatment of this disease.

RNA Sequencing Demonstrates That Circular RNA Regulates Avian Influenza Virus Replication in Human Cells

Circular RNAs (circRNAs) are involved in diverse biological processes. Avian influenza virus (AIV) can cross the species barrier to infect humans. Here, we employed RNA sequencing technology to profile circRNA, microRNA, and mRNA expression in human lung carcinoma cells in response to AIV or human influenza A virus (IAV) infection at viral replication. The analysis revealed that the expression of 475 common circRNAs were significantly regulated. The 381 and 1163 up-regulated circRNAs were induced by AIV at 8 and 16 h, respectively. Subsequently, gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses were also conducted for the AIV-specific up-regulated circRNAs. Moreover, the circRNAs were characterized, of which six were verified by quantitative real-time PCR. We further confirmed that expression of the selected circRNAs only increased following AIV infection. Knocking down the selected circRNAs promoted AIV proliferation, and overexpression of three of the candidate circRNAs restricted AIV replication and proliferation. We further analyzed that AIV-specific up-regulated circRNA mechanisms might function through the ceRNA network to affect the “Endocytosis” pathway and the “Cell cycle process”. These data provide the first expression profile of AIV-specific up-regulated circRNAs and shed new light on the pathogenesis of AIV infection. Our findings also suggest that these circRNAs serve an important role in AIV infection.

Extracellular Vesicle-Derived circITGB1 Regulates Dendritic Cell Maturation and Cardiac Inflammation via miR-342-3p/NFAM1

Acute myocardial infarction (AMI) is a complication of atherosclerosis-related cardiovascular illness that is caused by prolonged ischemia. Circular RNAs (circRNAs) are concentrated in extracellular vesicles (EVs) and have been linked to cardiovascular disease. However, additional research is needed into the expression and function of circRNAs in AMI. In this study, circITGB1 (has_circRNA_0018146), derived from exon 1 of the ITGB1 gene localized on chromosome 10, was shown to be considerably increased in plasma from patients with AMI compared to healthy controls, as demonstrated by the comparison of EV-circRNA expression patterns. Using a luciferase screening assay and a biotin-labeled circITGB1 probe to identify microRNA(s) complementary to circITGB1 sequences, we discovered that circITGB1 competitively binds to miR-342-3p and inhibits its expression, which in turn increase the expression of NFAT activating molecule 1 (NFAM1). Based on western blotting and immunological studies, circITGB1 controls dendritic cell maturation by targeting miR-342-3p and NFAM1. circITGB1 also exacerbated cardiac damage and regulated miR-342-3p and NFAM1 expression in a mouse AMI model. This implies that EV-circITGB1 is involved in dendritic cell maturation and cardiac damage via miR-342-3p/NFAM1, and that is linked to AMI-associated pathogenic processes.

Circ-TLR4 promotes cardiac hypertrophy through recruiting FUS to stabilize TLR4 mRNA

BACKGROUND

Cardiac hypertrophy is an adaptive and compensatory mechanism preserving cardiac output during detrimental stimuli. Circular RNAs (circRNAs) have been illustrated to exert important implications in the pathogenesis of multiple cardiovascular diseases (CVD) including demonstrated cardiac hypertrophy. Toll-like receptor 4 (TLR4) has been previously reported to be a crucial regulator in inflammatory response and cardiac hypertrophy. However, the role of circular isoforms derived from TLR4 in cardiac hypertrophy remains unclear.

METHODS

Expression of circ-TLR4 and TLR4 in cardiomyocytes was detected by RT-qPCR. The indicators of cardiac hypertrophy responses, including cell surface area, atrial natriuretic factor (ANF), B-type natriuretic peptide (BNP) and β-myosin heavy chain (β-MHC) were measured by immunofluorescence staining and western blot. RIP assay was used to validate the interaction between circ-TLR4 and TLR4.

RESULTS

Circ-TLR4 and TLR4 was up-regulated in cellular models of cardiac hypertrophy. Circ-TLR4 knockdown attenuated angiotensin II (Ang II)-induced hypertrophy responses in cardiomyocytes. Moreover, circ-TLR4 positively regulated TLR4 expression through recruiting FUS to stabilize TLR4 mRNA. Furthermore, TLR4 overexpression rescued the cardiac responses mediated by circ-TLR4 silencing.

CONCLUSION

Circ-TLR4 promotes cardiac hypertrophy through recruiting FUS to stabilize TLR4 mRNA.

GEO Database Screening Combined with In Vitro Experiments to Study the Mechanism of hsa_circ_0003570 in Infantile Hemangiomas

Objective

In this study, we screened out a type of differentially expressed circular RNA in infantile hemangioma (IH) cells and analyzed the mechanism in the malignant biological behavior of IH.

Methods

Based on the GSE98795, GSE100682, and GSE43742 datasets, differential expression analysis of circRNAs, microRNAs, and mRNAs was performed. The relative expression level of RNA was detected by quantitative real-time polymerase chain reaction (qRT-PCR). MTT assay, Transwell, flow cytometry analysis, and western blot were used to study the effects of hsa_circ_0003570, hsa-miR-138-5p, and RGS5 on the proliferation and apoptosis of hemangioma endothelial cells (HEMECs).

Results

The hsa_circ_0003570 and RGS5 mRNA were upregulated in HEMECs, but hsa-miR-138-5p was downregulated. Silencing of hsa_circ_0003570 inhibited the proliferation of HEMECs and promoted the apoptosis of HEMECs. The malignant biological behaviors of hsa_circ_0003570 on the proliferation and apoptosis of HEMECs were reversed by hsa-miR-138-5p. Hsa_circ_0003570 acted as the ceRNA of hsa-miR-138-5p and upregulated the expression of RGS5. Silencing of RGS5 inhibited the proliferation, migration, and invasion of HEMECs and promoted apoptosis.

Conclusion

Hsa_circ_0003570 promotes IH cell proliferation and inhibits IH cell apoptosis through hsa-miR-138-5p/RGS5 axis.

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.

The Preventive Effect of Cardiac Sympathetic Denervation Induced by 6-OHDA on Myocardial Ischemia-Reperfusion Injury: The Changes of lncRNA/circRNAs-miRNA-mRNA Network of the Upper Thoracic Spinal Cord in Rats

In this study, we investigated whether chemical 6-hydroxydopamine (6-OHDA) stimuli caused cardiac sympathetic denervation (SD), and we analyzed gene expression profiles to determine the changes in the lncRNA/circRNAs-miRNA-mRNA network in the affected spinal cord segments to identify putative target genes and molecular pathways in rats with myocardial ischemia–reperfusion injury (MIRI). Our results showed that cardiac sympathetic denervation induced by 6-OHDA alleviated MIRI. Compared with the ischemia reperfusion (IR, MIRI model) group, there were 148 upregulated and 51 downregulated mRNAs, 165 upregulated and 168 downregulated lncRNAs, 70 upregulated and 52 downregulated circRNAs, and 12 upregulated and 11 downregulated miRNAs in the upper thoracic spinal cord of the SD-IR group. Furthermore, we found that the differential genes related to cellular components were mainly enriched in extracellular and cortical cytoskeleton, and molecular functions were mainly enriched in chemokine activity. Pathway analysis showed that the differentially expressed genes were mainly related to the interaction of cytokines and cytokine receptors, sodium ion reabsorption, cysteine and methionine metabolism, mucoglycan biosynthesis, cGMP-PKG signaling pathway, and MAPK signaling pathway. In conclusion, the lncRNA/circRNAs-miRNA-mRNA networks in the upper thoracic spinal cord play an important role in the preventive effect of cardiac sympathetic denervation induced by 6-OHDA on MIRI, which offers new insights into the pathogenesis of MIRI and provides new targets for MIRI.

Comprehensive Analysis of mRNA Expression Profiling and Identification of Potential Diagnostic Biomarkers in Coronary Artery Disease

The aim of this study is to investigate mRNA expression profiling by RNA sequencing (RNA-seq) in patients with coronary artery disease (CAD) and validate differentially expressed genes (DEGs) as novel biomarkers for CAD. Transcriptome-wide mRNA expression analysis of peripheral blood mononuclear cells was performed in five CAD patients and five controls. Functional enrichment analyses, protein-protein interaction network construction, and hub gene selection were further conducted. Relative expression levels of hub genes were validated by quantitative reverse transcription PCR in larger cohorts. Spearman correlation test and multiple linear regression analysis were applied to examine the relationship between confounding factors with severity of coronary artery atherosclerosis. Receiver operating characteristic (ROC) curve analysis was adopted to identify potentially diagnostic biomarkers for CAD. A total of 527 upregulated and 653 downregulated mRNAs were identified as DEGs in CAD patients. The relative expression levels of beta-transducin repeat containing E3 ubiquitin protein ligase (BTRC), F-box and leucine-rich repeat protein 4 (FBXL4), ubiquitin conjugating enzyme E2 D2 (UBE2D2), and ankyrin repeat and SOCS box containing 1 (ASB1) were significantly different between two groups (all p ≤ 0.05). The severity of coronary artery atherosclerosis was negatively associated with the BTRC gene relative expression level (r = -0.323, p < 0.001) and positively with UBE2D2 (r = 0.285, p < 0.001). ROC analysis of BTRC and UBE2D2 genes showed that the areas under the curve were 0.782 (95% CI: 0.720-0.845, p < 0.001) and 0.753 (95% CI: 0.681-0.824, p < 0.001), respectively. We described the characteristics of mRNA expression in the peripheral blood of CAD patients and controls by RNA-seq. Combined with Spearman correlation analysis and ROC analyses, BTRC and UBE2D2 genes had significantly diagnostic values, which may have potential to act as novel diagnostic biomarkers and therapeutic targets for CAD.

Knockdown of circ_0004104 Alleviates Oxidized Low-Density Lipoprotein-Induced Vascular Endothelial Cell Injury by Regulating miR-100/TNFAIP8 Axis

ABSTRACT

Coronary artery disease (CAD) is a common cardiovascular disease, mainly due to vascular endothelial cell (VEC) injury caused by atherosclerosis. Circular RNA has been shown to be involved in the regulation of various diseases. However, the role and mechanism of circ_0004104 in CAD are still unclear. Oxidized low-density lipoprotein (ox-LDL) was used to construct the VEC injury model in vitro. The expression levels of circ_0004104 and miR-100 were measured by quantitative real-time polymerase chain reaction. The proliferation of VECs was determined using 3-(45)-dimethylthiahiazo (-z-y1)-35-di-phenytetrazoliumromide assay and 5-ethynyl-2'-deoxyuridine staining assay. VEC apoptosis rate was assessed using flow cytometry, and caspase-3 activity was measured using a Caspase-3 Assay Kit. The protein expression levels of Ki-67, cleaved-caspase3, and tumor necrosis factor-α-induced protein 8 (TNFAIP8) were detected by western blot analysis. Furthermore, enzyme-linked immunosorbent assay was performed to assess the concentrations of inflammatory cytokines. In addition, the relationship between miR-100 and circ_0004104 or TNFAIP8 was confirmed by dual-luciferase reporter assay and biotin-labeled RNA pull-down assay. Our results revealed that circ_0004104 was upregulated and miR-100 was downregulated in patients with CAD and ox-LDL-induced VECs. Ox-LDL could inhibit the proliferation and promote the apoptosis and inflammation of VECs to induce VEC injury. However, silenced circ_0004104 could alleviate VEC injury induced by ox-LDL. Moreover, we found that circ_0004104 could sponge miR-100 and a miR-100 inhibitor could reverse the inhibition effect of circ_0004104 knockdown on ox-LDL-induced VEC injury. In addition, TNFAIP8 was a target of miR-100, and miR-100 alleviated ox-LDL-induced VEC injury by targeting TNFAIP8. Our data suggested that circ_0004104 promoted ox-LDL-induced VEC injury by the miR-100/TNFAIP8 axis, indicating that circ_0004104 might be a potential biomarker for CAD treatment.

Circ_0124644 Serves as a ceRNA for miR-590-3p to Promote Hypoxia-Induced Cardiomyocytes Injury via Regulating SOX4

Circular RNA (circRNA) is an important factor for regulating the progression of many cardiovascular diseases, including acute myocardial infarction (AMI). However, the role of circ_0124644 in AMI progression remains unclear. Hypoxia was used to induce cardiomyocytes injury. The expression of circ_0124644, microRNA (miR)-590-3p, and SRY-box transcription factor 4 (SOX4) mRNA was measured by qRT-PCR. Cell counting kit 8 (CCK8) assay and flow cytometry were utilized to detect cell viability, cell cycle progression, and apoptosis. The protein levels of apoptosis markers and SOX4 were determined by western blot (WB) analysis, and the levels of oxidative stress markers were assessed using commercial Assay Kits. Dual-luciferase reporter assay, RIP assay, and RNA pull-down assay were employed to confirm the interaction between miR-590-3p and circ_0124644 or SOX4. Circ_0124644 was upregulated in AMI patients and hypoxia-induced cardiomyocytes. Hypoxia could inhibit cardiomyocytes viability, cell cycle process, and promote apoptosis and oxidative stress, while silencing circ_0124644 could alleviate hypoxia-induced cardiomyocytes injury. In terms of mechanism, circ_0124644 could target miR-590-3p. MiR-590-3p overexpression could relieve hypoxia-induced cardiomyocytes injury. Also, the suppressive effect of circ_0124644 knockdown on hypoxia-induced cardiomyocytes injury could be reversed by miR-590-3p inhibitor. Moreover, SOX4 was found to be a target of miR-590-3p, and its overexpression also could reverse the regulation of miR-590-3p on hypoxia-induced cardiomyocytes injury. Circ_0124644 silencing could alleviate hypoxia-induced cardiomyocytes injury by regulating the miR-590-3p/SOX4 axis, suggesting that it might be a target for alleviating AMI.

CircRNA 010567 plays a significant role in myocardial infarction via the regulation of the miRNA-141/DAPK1 axis

Background

Myocardial infarction (MI), caused by temporary or permanent coronary artery occlusion, poses a serious threat to patients’ lives. Circular RNAs (circRNAs), a new kind of endogenous noncoding RNAs, have been widely studied recently. This study was designed to illustrate and potential molecular mechanisms of circRNA 010567 in hypoxia-induced cardiomyocyte injury in vitro, so as to provide new strategies for the therapy of MI.

Methods

H9c2 cells were cultured in anoxic conditions with 94% N₂, 5% CO₂, and 1% O₂ to establish the in vitro MI model. Cell viability and apoptosis were checked using MTT and flow cytometry assay, respectively, Moreover, the levels of circRNA 010567, miR-141, and DAPK1 was determined using qRT-PCR. The putative targets of circRNA 010567 and miR-141 were confirmed by dual-luciferase reporter system and the RNA immunoprecipitation (RIP) assay. The release of creatine kinase-MB (CK-MB), cardiac troponin I (cTnI), and the viability of mitochondria were detected using assay kits.

Results

The current study revealed that circRNA 010567 and DAPK1 were over-expressed, and miR-141 was low-expressed in hypoxia-induced MI. circRNA 010567 sponges miR-141 and DAPK1 was a direct target of miR-141. Mechanistic investigations revealed that circRNA 010567-siRNA impaired the release of CK-MB and cTnI, and promoted the viability of mitochondria in hypoxia-induced H9c2 cells, while these findings were reversed by the miR-141 inhibitor. In addition, the miR-141 mimic markedly reduced the release of CK-MB and cTnI, and promoted the viability of mitochondria, and these results were reversed by the DAPK1-plasmid. Subsequently, functional experiments revealed that hypoxia-stimulated decreases in H9c2 cell viability, as well as increases in apoptosis and caspase-3 activity, were induced by the miR-141 mimic and circRNA 010567-siRNA. However, these results were reversed by the miR-141 inhibitor and DAPK1-plasmid.

Conclusions

Our results demonstrated that circRNA 010567-siRNA played a protective role in hypoxia-induced cardiomyocyte damage via regulating the miR-141/DAPK1 axis, indicating that circRNA 010567-siRNA may be a promising target for MI therapy.

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.

Identification of Circular RNA hsa_circ_0001599 as a Novel Biomarker for Large-Artery Atherosclerotic Stroke

Circular RNAs (circRNAs) are a recently discovered noncoding RNA isoform capable of regulating neurological disease incidence. The present study was designed to characterize the circRNA expression profiles present in large-artery atherosclerosis (LAA)-type acute ischemic stroke patients and to detect biomarkers suitable for LAA-stroke detection. Using a RNA-seq-based approach, we characterized circRNA expression profiles in five LAA-stroke patients and four controls. We confirmed the differential expression of target circRNAs through quantitative real-time polymerase chain reaction (qRT-PCR), and used Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses to explore their functional roles. The diagnostic value of specific circRNAs was evaluated through a receiver operating characteristic (ROC) curve analysis. We identified 182 upregulated and 176 downregulated circRNAs in LAA-stroke patients and confirmed the differential expression of six circRNAs through qRT-PCR. These differentially expressed circRNAs are primarily associated with chromatin modification, autophagy, platelet activation, and neural precursor cell proliferation. The hsa_circRNA_0001599 expression levels were positively correlated with the National Institutes of Health Stroke Scale scores and infarct volumes, with an ROC analysis of hsa_circRNA_0001599 in LAA-stroke, yielding an area under the curve of 0.805 (95% confidence interval: 0.748-0.862; p < 0.001), consistent with sensitivity and specificity values of 64.41% and 89.93%, respectively, for the diagnosis of LAA-stroke. A transcriptome-wide survey of differential circRNA expression in LAA-stroke patients revealed hsa_circRNA_0001599 as a putative circRNA biomarker of LAA-stroke diagnosis.

Circular RNAs in childhood-related diseases and cancers: A review

Research into the diagnosis, treatment and prevention of childhood-related diseases is the key to reducing their morbidity and mortality. Circular RNAs (circRNAs) play critical roles, both in physiology and pathology, and there is ample evidence to show that they play varying roles in tissue development and gene regulation. Studies on circRNAs in different childhood-related diseases have confirmed their great potential for disease prevention and treatment. These breakthroughs highlight the pathological role of circRNAs in cancers, as well as cardiovascular and hereditary childhood illnesses. In this review, we summarize the role of circRNAs in childhood-related diseases and cancer, and provide an update of the possible diagnostic and therapeutic application of circRNAs.

Circular RNA ITCH mediates H2O2-induced myocardial cell apoptosis by targeting miR-17-5p via wnt/β-catenin signalling pathway

Cardiovascular disease is a severe threat health worldwide, and circRNAs have been shown to be correlated with the development of cardiovascular disease. Expression of circ-ITCH and miR-17a-5p was evaluated by RT-qPCR. Cell viability was measured using CCK-8. Flow cytometry was applied to measure apoptosis rate. Binding between miR-17-5p and circ-ITCH was detected via luciferase reporter assays. Levels of ATP in cells were examined with ATP testing. Western blot was used to evaluate apoptosis-related proteins and proteins in Wnt/β-catenin signalling pathway. H2O2 induced apoptosis of H9c2 cells and lowered cell viability as well as ATP levels and circ-ITCH expression. After overexpression, circ-ITCH enhanced cell viability and ATP concentration. Meanwhile, apoptosis was inhibited. MiR-17-5p was the target of circ-ITCH as evidenced by luciferase report assays, with higher expression in H2O2-induced H9c2 cells. Knockdown of miR-17-5p could promote cell viability and level of ATP and curb apoptosis and p53 and PARP expression. Moreover, overexpressed miR-17-5p could reverse the function of upregulated circ-ITCH. Wnt3a, Wnt5a and β-catenin in Wnt/β-catenin signalling pathway were increased after H2O2 induction. Suppression of Wnt/β-catenin signalling pathway could initiate the process of injury in H9c2 cells. Circ-ITCH could protect myocardial cells from injuries caused by H2O2 by suppressing apoptosis while miR-17-5p played a reverse role, which could upregulate apoptosis and inhibit cell viability via Wnt/β-catenin signalling pathway.

CircSAMD4A aggravates H/R-induced cardiomyocyte apoptosis and inflammatory response by sponging miR-138-5p

Hypoxia/reoxygenation (H/R)‐induced myocardial cell injury is the main cause of acute myocardial infarction (AMI). Many proofs show that circular RNA plays an important role in the development of AMI. The purpose of this study was to investigate the role of circSAMD4A in H/R‐induced myocardial injury. The levels of circular SAMD4A (circSAMD4A) were detected in the heart tissues of AMI mice and H/R‐induced H9C2 cells, and the circSAMD4A was suppressed in AMI mice and H/R‐induced H9C2 cells to investigate its’ function in AMI. The levels of circSAMD4A and miR‐138‐5p were detected by real‐time quantitative PCR, and MTT assay was used to detect cell viability. TUNEL analysis and Annexin V‐FITC were used to determine apoptosis. The expression of Bcl‐2 and Bax proteins was detected by Western blot. IL‐1β, TNF‐α and IL‐6 were detected by ELISA kits. The study found that the levels of circSAMD4A were up‐regulated after H/R induction and inhibition of circSAMD4A expression would reduce the H/R‐induced apoptosis and inflammation. MiR‐138‐5p was down‐regulated in H/R‐induced H9C2 cells. circSAMD4A was a targeted regulator of miR‐138‐5p. CircSAMD4A inhibited the expression of miR‐138‐5p to promote H/R‐induced myocardial cell injury in vitro and vivo. In conclusion, CircSAMD4A can sponge miR‐138‐5p to promote H/R‐induced apoptosis and inflammatory response.

Quantitative proteomics reveals the regulatory networks of circular RNA BTBD7_hsa_circ_0000563 in human coronary artery

BACKGROUND

BTBD7_hsa_circ_0000563, which is located on chromosome 14, contains conserved binding sites with miR-155/130a and RNA-binding proteins according to bioinformatic prediction. We investigated the association of BTBD7_hsa_circ_0000563 expression in coronary artery segments with atherosclerotic stenosis and identified the proteome-wide BTBD7_hsa_circ_0000563-regulated proteins in human coronary artery.

METHODS

The atherosclerotic grade and extent in coronary artery segments were determined by hematoxylin and eosin staining. BTBD7_hsa_circ_0000563 expression in eight coronary artery segments from one patient was quantified by RT-qPCR assay. A proteomic approach was adopted to reveal significant differences in protein expression between among four groups differing in their BTBD7_hsa_circ_0000563 expression levels.

RESULTS

The RT-qPCR assay revealed that coronary artery segments with severe atherosclerotic stenosis had significantly low BTBD7_hsa_circ_0000563 levels. The proteomic analysis identified 49 differentially expressed proteins among the segment groups with different BTBD7_hsa_circ_0000563 expression levels, of which 10 were downregulated and 39 were upregulated with increases in the BTBD7_hsa_circ_0000563 level. The 10 downregulated proteins were P61626 (LYSC_HUMAN), P02760 (AMBP_HUMAN), Q02985 (FHR3_HUMAN), P01701 (LV151_HUMAN), P06312(KV401_HUMAN), P01624 (KV315_HUMAN), P13671 (CO6_HUMAN), P01700(LV147_HUMAN), Q9Y287(ITM2B_HUMAN), and A0A075B6I0 (LV861_HUMAN). The top 10 upregulated proteins were Q92552 (RT27_HUMAN), Q9UJY1(HSPB8_HUMAN), Q9Y235(ABEC2_HUMAN), P19022 (CADH2_HUMAN), O43837(IDH3B_HUMAN), Q9H479(FN3K_HUMAN), Q9UM22(EPDR1_HUMAN), P48681(NEST_HUMAN), Q9NRP0(OSTC_HUMAN), and Q15628(TRADD_HUMAN).

CONCLUSION

BTBD7_hsa_circ_0000563 is involved in the atherosclerotic changes in human coronary artery segments. Verification, mechanistic, and function studies are needed to confirm whether patients with coronary artery disease would benefit from such personalized medicine in the future.

Knockdown of circular RNA UBAP2 inhibits the malignant behaviours of esophageal squamous cell carcinoma by microRNA-422a/Rab10 axis

Esophageal squamous cell carcinoma (ESCC) is a major type of esophageal cancer, accounting for about 90% of cases. Circular RNA UBAP2 (circUBAP2) is involved in the progression of several types of cancers. However, the role of circUBAP2 in ESCC remains unclear. In the present study, circUBAP2 expression was found to be upregulated in ESCC tumour tissues. Knockdown of circUBAP2 through infection with lentiviral vector encoding shRNA targeting circUBAP2 (sh-circUBAP2) inhibited the proliferation, migration and invasion of ESCC cells. In addition, circUBAP2 significantly promoted the proliferation, migration and invasion of ESCC cells. In vivo xenograft assay demonstrated that circUBAP2 downregulation suppressed the tumour growth of ESCC. Further mechanism investigations proved that circUBAP2 exerted its role via sponging microRNA (miR)-422a, and miR-422a directly targeted Rab10 in ESCC cells. These findings suggested that circUBAP2 acted as oncogene through regulating the miR-422a/Rab10 axis in ESCC.

Emerging Challenges of Radiation-Associated Cardiovascular Dysfunction (RACVD) in Modern Radiation Oncology: Clinical Practice, Bench Investigation, and Multidisciplinary Care

Radiotherapy (RT) is a crucial treatment modality in managing cancer patients. However, irradiation dose sprinkling to tumor-adjacent normal tissues is unavoidable, generating treatment toxicities, such as radiation-associated cardiovascular dysfunction (RACVD), particularly for those patients with combined therapies or pre-existing adverse features/comorbidities. Radiation oncologists implement several efforts to decrease heart dose for reducing the risk of RACVD. Even applying the deep-inspiration breath-hold (DIBH) technique, the risk of RACVD is though reduced but still substantial. Besides, available clinical methods are limited for early detecting and managing RACVD. The present study reviewed emerging challenges of RACVD in modern radiation oncology, in terms of clinical practice, bench investigation, and multidisciplinary care. Several molecules are potential for serving as biomarkers and therapeutic targets. Of these, miRNAs, endogenous small non-coding RNAs that function in regulating gene expression, are of particular interest because low-dose irradiation, i.e., 200 mGy (one-tenth of conventional RT daily dose) induces early changes of pro-RACVD miRNA expression. Moreover, several miRNAs, e.g., miR-15b and miR21, involve in the development of RACVD, further demonstrating the potential bio-application in RACVD. Remarkably, many RACVDs are late RT sequelae, characterizing highly irreversible and progressively worse. Thus, multidisciplinary care from oncologists and cardiologists is crucial. Combined managements with commodities control (such as hypertension, hypercholesterolemia, and diabetes), smoking cessation, and close monitoring are recommended. Some agents show abilities for preventing and managing RACVD, such as statins and angiotensin-converting enzyme inhibitors (ACEIs); however, their real roles should be confirmed by further prospective trials.

Circular RNA_101237 mediates anoxia/reoxygenation injury by targeting let‑7a‑5p/IGF2BP3 in cardiomyocytes

Circular RNAs (circRNAs) serve important roles in cardiovascular diseases, including myocardial infarction. However, the mechanisms underlying the roles of circRNAs in cardiomyocyte death induced by anoxia/reoxygenation (A/R) are not fully understood. In the present study, the roles of circRNA_101237 and let‑7a‑5p in cardiomyocyte death induced by A/R injury were investigated. It was identified that circRNA_101237 was induced by A/R injury in a time‑dependent manner and that circRNA_101237 knockdown protected cardiomyocytes from A/R‑mediated apoptosis. Additional mechanistic studies revealed that circRNA_101237 served as a sponge for let‑7a‑5p, subsequently regulating insulin‑like growth factor 2 mRNA‑binding protein 3 (IGF2BP3)‑dependent autophagy. IGF2BP3 downregulation decreased the levels of apoptosis and inhibited autophagy induced by A/R challenge in primary cardiomyocytes. These results identified circRNA_101237 as a novel circRNA that regulates cardiomyocyte death and autophagy, and demonstrated that the circRNA‑101237/let‑7a‑5p/IGF2BP3 axis, which serves as a regulator of cardiomyocyte death, may be a potential therapeutic target for the management of cardiovascular diseases.

Noncoding RNAs regulating cardiac muscle mass

Noncoding RNAs, including microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs) play roles in the development and homeostasis of nearly every tissue of the body, including the regulation of processes underlying heart growth. Cardiac hypertrophy can be classified as either physiological (beneficial heart growth) or pathological (detrimental heart growth), the latter of which results in impaired cardiac function and heart failure and is predictive of a higher incidence of death due to cardiovascular disease. Several miRNAs have a functional role in exercise-induced cardiac hypertrophy, while both miRNAs and lncRNAs are heavily involved in pathological heart growth and heart failure. The latter have the potential to act as an endogenous sponge RNA and interact with specific miRNAs to control cardiac hypertrophy, adding another level of complexity to our understanding of the regulation of cardiac muscle mass. In addition to tissue-specific effects, ncRNA-mediated tissue cross talk occurs via exosomes. In particular, miRNAs can be internalized in exosomes and secreted from various cardiac and vascular cell types to promote angiogenesis, as well as protection and repair of ischemic tissues. ncRNAs hold promising therapeutic potential to protect the heart against ischemic injury and aid in regeneration. Numerous preclinical studies have demonstrated the therapeutic potential of ncRNAs, specifically miRNAs, for the treatment of cardiovascular disease. Most of these studies employ antisense oligonucleotides to inhibit miRNAs of interest; however, off-target effects often limit their potential to be translated to the clinic. In this context, approaches using viral and nonviral delivery tools are promising means to provide targeted delivery in vivo.