The circular RNA ACR attenuates myocardial ischemia/reperfusion injury by suppressing autophagy via modulation of the Pink1/ FAM65B pathway

Circular RNAs modulate cell death in cardiovascular diseases

Cardiovascular diseases (CVDs) remain a global health challenge, with programmed cell death (PCD) mechanisms like apoptosis and necroptosis playing key roles in the progression. Circular RNAs (circRNAs) have recently been recognized as crucial regulators of gene expression, especially in modulating PCD. In current researches, circRNA regulation of apoptosis is the most studied area, followed by autophagy and ferroptosis. Notably, the regulatory role of circRNAs in pyroptosis and necroptosis has also begun to attract attention. From a mechanistic perspective, circRNAs influence cellular processes through several modes of action, including miRNA sponging, protein interactions, and polypeptide translation. Manipulating circRNAs and their downstream targets through inhibition or overexpression offers versatile therapeutic options for CVD treatment. Continued investigation into circRNA-mediated mechanisms may enhance our understanding of CVD pathophysiology and underscore their potential as novel and promising therapeutic targets.

Comprehensive evaluation of non-coding RNA-mediated autophagy regulation in myocardial ischemia-reperfusion injury

Ischemic heart disease remains a major global health challenge, with myocardial ischemia-reperfusion injury (MIRI) being one of its most common and severe pathophysiological complications. The pathogenesis of MIRI is multifaceted, involving oxidative stress, inflammatory responses, apoptotic pathways, and autophagic regulation. Notably, autophagy exerts a dual regulatory effect, where maintaining optimal autophagic flux is essential for cardiac homeostasis. Emerging evidence underscores the crucial role of non-coding RNAs (ncRNAs) in modulating these pathological processes. In particular, long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs) have been identified as key regulators of autophagy-mediated MIRI progression through complex molecular networks. This review provides a systematic analysis of the molecular pathways through which ncRNAs influence MIRI pathogenesis, with a specific focus on their autophagy-regulatory mechanisms. These insights may enhance our understanding of MIRI pathobiology and facilitate the development of novel therapeutic strategies.

Emerging role and clinical applications of circular RNAs in human diseases

Circular RNAs (circRNAs) are a large family of non-coding RNAs characterized by a single-stranded, covalently closed structure, predominantly synthesized through a back-splicing mechanism. While thousands of circRNAs have been identified, only a few have been functionally characterized. Although circRNAs are less abundant than other RNA types, they exhibit exceptional stability due to their covalently closed structure and demonstrate high cell and tissue specificity. CircRNAs play a critical role in maintaining cellular homeostasis by influencing gene transcription, translation, and post-translation processes, modulating the immune system, and interacting with mRNA, miRNA, and proteins. Abnormal circRNA expression has been associated with a wide range of human diseases and various infections. Due to their remarkable stability in body fluids and tissues, emerging research suggests that circRNAs could serve as diagnostic and therapeutic biomarkers for these diseases. This review focuses on the emerging role of circRNAs in various human diseases, exploring their biogenesis, molecular functions, and potential clinical applications as diagnostic and therapeutic biomarkers with current evidence, challenges, and future perspectives. The key theme highlights the significance of circRNAs in regulating gene expression, their involvement in diseases like cancer, neurodegenerative disorders, cardiovascular diseases, and diabetes, and their potential use in translational medicine for developing novel therapeutic strategies. We also discuss recent clinical trials involving circRNAs. Thus, this review is important for both basic researchers and clinical scientists, as it provides updated insights into the role of circRNAs in human diseases, aiding further exploration and advancements in the field.

CircHIPK3 targets DRP1 to mediate hydrogen peroxide-induced necroptosis of vascular smooth muscle cells and atherosclerotic vulnerable plaque formation

INTRODUCTION

Necroptosis triggered by H2O2 is hypothesized to be a critical factor in the rupture of atherosclerotic plaques, which may precipitate acute cardiovascular events. Nevertheless, the specific regulatory molecules of this development remain unclear. We aims to elucidate a mechanism from the perspective of circular RNA.

OBJECTIVES

There are few studies on circRNA in VSMCs necroptosis. The objective of our research is to shed light on the intricate roles that circHIPK3 plays in the process of necroptosis in VSMCs and the development of atherosclerotic plaques that are prone to rupture. Our study elucidates the specific molecular mechanisms by which circHIPK3 regulates necroptosis and atherosclerotic vulnerable plaque formation through targeted proteins. Identifying this mechanism at the cellular level offers a molecular framework for understanding plaque progression and stability regulation, as well as a potential biomarker for the prognosis of susceptible atherosclerotic plaques.

METHODS

We collected clinical vascular tissue for HE staining and Masson staining to determine the presence and stability of plaques. Then, NCBI database was used to screen out circRNA with elevated expression level in plaque tissue, and the up-regulated circRNA, circHIPK3, was verified by qRT-PCR and FISH. Further, we synthesized circHIPK3's small interference sequence and overexpressed plasmid in vitro, and verified its regulation effect on necroptosis of VSMCs under physiological and pathological conditions by WB, qRT-PCR and PI staining. Through RNA pull down, mass spectrometry and RNA immunoprecipitation, DRP1 was identified as circHIPK3 binding protein and was positively regulated by circHIPK3. Meanwhile, on the basis of silencing of DRP1, the regulation of circHIPK3 on necroptosis is verified to be mediated by DRP1. Finally, we validated the regulation of circHIPK3 on vulnerable plaque formation in ApoE-/- mice.

RESULTS

We investigated that circHIPK3 was highly expressed in vulnerable plaques, and the increase in expression level promoted H2O2 induced necroptosis of VSMCs. CircHIPK3 targeted the protein DRP1, leading to an elevation in mitochondrial division rate, resulting in increased reactive oxygen species and impaired mitochondrial function, ultimately leading to necroptosis of VSMCs and vulnerable plaque formation.

CONCLUSION

CircHIPK3 interact with DRP1 involve in H2O2 induced Mitochondrial damage and necroptosis of VSMCs, and Silencing circHIPK3 in vivo can reduce atherosclerotic vulnerable plaque formation. Our research findings may have applications in providing diagnostic biomarkers for vulnerable plaques.

CircHIPK2 recruits SRSF1 to increase TXNIP mRNA stability and promotes autophagy-dependent ferroptosis and apoptosis in myocardial ischemia-reperfusion injury

BACKGROUND

Myocardial ischemia/reperfusion injury (MIRI) secondary to acute myocardial infarction (AMI) can lead to cardiomyocyte death and impaired cardiac function. Studies have confirmed that circular RNAs (circRNAs) play an important role in MIRI. In this study, the role and mechanism of circHIPK2 in MIRI were evaluated.

METHODS

Human cardiac myocytes (HCM) were cultured under Hypoxia/Reoxygenation (H/R) condition to establish a MIRI model in vitro. Expression of circHIPK2, SRSF1 and TXNIP was assessed using RT-qPCR. Protein levels of autophagy markers (LC3II/LC3I, Beclin1, p62) and ferroptosis markers (GPX4, FTH1, ACSL4) were detected by Western blot. Cell viability and apoptosis were assessed by CCK-8 and flow cytometry. Levels of oxidative stress markers (MDA, SOD) and inflammatory factors (IL-6, IL-1β, TNF-α) were tested by ELISA assay. Iron concentration was measured with an iron detection kit. Location of circHIPK2 in cells was detected by RNA-nucleosome separation assay. RIP and ChIP assays verified the relationship between circHIPK2, SRSF1 and TXNIP. TXNIP mRNA stability was dertermined by actinomycin D. Infarct area was examined by TTC staining in myocardial ischemia/reperfusion (I/R) mouse model. HE staining evaluated myocardial injury.

RESULTS

CircHIPK2 was increased in H/R-induced HCM cells. CircHIPK2 downregulation suppressed oxidative stress, inflammatory factors and autophagy-dependent ferroptosis in HCM cells induced by H/R. Additionally circHIPK2 recruited SRSF1 to target TXNIP and stabilized TXNIP mRNA expression. We further demonstrated that TXNIP upregulation overturned the therapeutic effects of circHIPK2 silencing on H/R model cells. In vivo, downregulation of circHIPK2 improved myocardial dysfunction caused by I/R.

CONCLUSION

Our results demonstrate that circHIPK2 contributes to MIRI through inducing oxidative stress and autophagy-dependent ferroptosis via SRSF1/TXNIP axis, offering new insights into MIRI treatment.

Exosomes and non-coding RNAs: Exploring their roles in human myocardial dysfunction

Myocardial dysfunction, characterized by impaired cardiac muscle function, arises from diverse etiologies, including coronary artery disease, myocardial infarction, cardiomyopathies, hypertension, and valvular heart disease. Recent advancements have highlighted the roles of exosomes and non-coding RNAs in the pathophysiology of myocardial dysfunction. Exosomes are small extracellular vesicles released by cardiac and other cells that facilitate intercellular communication through their molecular cargo, including ncRNAs. ncRNAs are known to play critical roles in gene regulation through diverse mechanisms, impacting oxidative stress, fibrosis, and other factors associated with myocardial dysfunction. Dysregulation of these molecules correlates with disease progression, presenting opportunities for therapeutic interventions. This review explores the mechanistic interplay between exosomes and ncRNAs, underscoring their potential as biomarkers and therapeutic agents in myocardial dysfunction. Emerging evidence supports the use of engineered exosomes and modified ncRNAs to enhance cardiac repair by targeting signaling pathways associated with fibrosis, apoptosis, and angiogenesis. Despite promising preclinical results, delivery, stability, and immunogenicity challenges remain. Further research is needed to optimize clinical translation. Understanding these intricate mechanisms may drive the development of innovative strategies for diagnosing and treating myocardial dysfunction, ultimately improving patient outcomes.

Evidence and perspectives on miRNA, circRNA, and lncRNA in myocardial ischemia-reperfusion injury: a bibliometric study

OBJECTIVE

miRNA, circRNA, and lncRNA play crucial roles in the pathogenesis and progression of myocardial ischemia-reperfusion injury (MI/RI). This study aims to provide valuable insights into miRNA, circRNA, lncRNA, and MI/RI from a bibliometric standpoint, with the goal of fostering further advancements in this area.

METHODS

The relevant literature in the field of miRNA, circRNA, lncRNA, and MI/RI was retrieved from the Science Citation Index Expanded (SCI-E) database within Web of Science. The "Analyze Results" and "Citation Report" functions in WOS were utilized to compile the annual publication and citation counts in this field. Microsoft Office Excel 2019 was used to organize and visualize the data. Furthermore, bibliometric and visualization analyses of countries/regions, institutions, authors, keywords, and references were conducted using the bibliometric visualization software CiteSpace.

RESULTS

A total of 858 publications were included for further analysis in this field. The literature was published across 297 journals, with Molecular Medicine Reports contributing the highest number of publications. Researchers from 45 countries participated in studies within this field, with those from China contributing the most publications. The research hotspots in this field primarily focus on three areas: the role of miRNA, circRNA, and lncRNA in the pathogenesis of MI/RI, their potential as therapeutic targets, and their role as biomarkers. Among these, circular RNA, therapy target, inflammatory response, and cardiomyocyte ferroptosis are likely to emerge as emerging trends in this field.

CONCLUSION

The overall development of research in this field is on the rise. The compilation of research hotspots and emerging trends in this area may provide researchers with more references and assistance in selecting research directions, ultimately benefiting MI/RI patients.

Circular RNA regulatory role in pathological cardiac remodelling

Cardiac remodelling involves structural, cellular and molecular alterations in the heart after injury, resulting in progressive loss of heart function and ultimately leading to heart failure. Circular RNAs (circRNAs) are a recently rediscovered class of non-coding RNAs that play regulatory roles in the pathogenesis of cardiovascular diseases, including heart failure. Thus, a more comprehensive understanding of the role of circRNAs in the processes governing cardiac remodelling may set the ground for the development of circRNA-based diagnostic and therapeutic strategies. In this review, the current knowledge about circRNA origin, conservation, characteristics and function is summarized. Bioinformatics and wet-lab methods used in circRNA research are discussed. The regulatory function of circRNAs in cardiac remodelling mechanisms such as cell death, cardiomyocyte hypertrophy, inflammation, fibrosis and metabolism is highlighted. Finally, key challenges and opportunities in circRNA research are discussed, and orientations for future work to address the pharmacological potential of circRNAs in heart failure are proposed. LINKED ARTICLES: This article is part of a themed issue Non-coding RNA Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v182.2/issuetoc.

CircCHSY1 protects hearts against ischaemia/reperfusion injury by enhancing heme oxygenase 1 expression via miR-24-3p

AIMS

Circular RNAs (circRNAs) are important players involved in a variety of physiological and pathological processes. However, their functions and mechanisms during myocardial ischaemic injury and protection remain largely unknown. We recently found significant alterations of many circRNAs including circCHSY1 following myocardial ischaemia/reperfusion (I/R) injury, whereas their exact functions are unclear. Here, we investigated the roles of circCHSY1 in the acute myocardial I/R injury and the potential mechanisms involved.

METHODS AND RESULTS

The expression of circCHSY1 was detected in cardiomyocytes from mouse, rat, and human embryonic stem cells (hESC-CMs). It was further up-regulated in mouse I/R (30 min/24 h) hearts, oxygen glucose deprivation/reperfusion (OGD/R, 6 h/2 h) primary neonatal rat ventricular cardiomyocytes (NRCMs) and OGD/R (48 h/2 h) hESC-CMs. Adenovirus-mediated circCHSY1 overexpression significantly decreased infarct size and lactate dehydrogenase (LDH) release in mouse I/R hearts. Consistently, circCHSY1 overexpression reduced the LDH release in the OGD/R NRCMs and hESC-CMs, improved cell viability, and preserved mitochondrial function in the OGD/R NRCMs, whereas there were no significant differences in cell viability and LDH release between the OGD/R NRCMs with and without small interfering RNA (siRNA)-mediated circCHSY1 knockdown. Mechanistically, circCHSY1 was detected to bind with miR-24-3p analysed by dual-luciferase assay and RNA pull-down assays. CircCHSY1 overexpression-mediated protective effects on cells and mitochondria in OGD/R NRCMs were reversed by the miR-24-3p mimic. Furthermore, dual-luciferase assay showed that miR-24-3p was directly bound to heme oxygenase 1 (HO1) via its 3'UTR. The protein level of HO1 was down-regulated by miR-24-3p mimic in OGD/R NRCMs but enhanced by the circCHSY1 overexpression in vitro and in vivo. Functionally, the HO1 knockdown by adenovirus in vivo and by siRNA in vitro eliminated cardioprotective effects of circCHSY1 overexpression.

CONCLUSION

CircCHSY1 is up-regulated following myocardial I/R injury. The higher level of circCHSY1 protects I/R hearts and cardiomyocytes. The protection of circCHSY1 is mediated through enhancement of the HO1 level, resulting in preserving mitochondrial homoeostasis via targeting miR-24-3p in cardiomyocytes. These findings suggest circCHSY1 as a protective factor.

Nucleic acid liquid biopsies in cardiovascular disease: Cell-free RNA liquid biopsies in cardiovascular disease

Cardiovascular diseases (CVD) and their complications continue to be the leading cause of mortality globally. With recent advancements in molecular analytics, individualized treatments are gradually applied to the diagnosis and treatment of CVD. In the field of diagnostics, liquid biopsy combined with modern analytical technologies is the most popular natural source to identify disease biomarkers, as has been successfully demonstrated in the cancer field. While it is not easy to obtain any diseased tissue for different types of CVD such as atherosclerosis, deep vein thrombosis or stroke, liquid biopsies provide a simple and non-invasive alternative to surgical tissue specimens to obtain dynamic molecular information reflecting disease states. The release of cell-free ribonucleic acids (cfRNA) from stressed/damaged/dying and/or necrotic cells is a common physiological phenomenon. CfRNAs are a heterogeneous population of various types of extracellular RNA found in body fluids (blood, urine, saliva, cerebrospinal fluid) or in association with vascular/atherosclerotic tissue, offering insights into disease pathology on a diagnostic front. In particular, cf-ribosomal RNA has been shown to act as a damaging molecule in several cardio-vascular disease conditions. Moreover, such pathophysiological functions of cfRNA in CVD have been successfully antagonized by the administration of RNases. In this review, we discuss the origin, structure, types, and potential utilization of cfRNA in the diagnosis of CVD. Together with the analysis of established CVD biomarkers, the profiling of cfRNA in body fluids may thereby provide a promising approach for early disease detection and monitoring.

Circular RNAs in programmed cell death: Regulation mechanisms and potential clinical applications in cancer: A review

Circular RNAs (circRNAs) are a novel class of non-coding RNAs with covalently closed structures formed by reverse splicing of precursor mRNAs. The widespread expression of circRNAs across species has been revealed by high-throughput sequencing and bioinformatics approaches, indicating their unique properties and diverse functions including acting as microRNA sponges and interacting with RNA-binding proteins. Programmed cell death (PCD), encompassing various forms such as apoptosis, necroptosis, pyroptosis, autophagy, and ferroptosis, is an essential process for maintaining normal development and homeostasis in the human body by eliminating damaged, infected, and aging cells. Many studies have demonstrated that circRNAs play crucial roles in tumourigenesis and development by regulating PCD in tumor cells, showing that circRNAs have the potential to be biomarkers and therapeutic targets in cancer. This review aims to comprehensively summarize the intricate associations between circRNAs and diverse PCD pathways in tumor cells, which play crucial roles in cancer development. Additionally, this review provides a detailed overview of the underlying mechanisms by which circRNAs modulate various forms of PCD for the first time. The ultimate objective is to offer valuable insights into the potential clinical significance of developing novel strategies based on circRNAs and PCD for cancer diagnosis, prognosis, and treatment.

GATA-4 overexpressing BMSC-derived exosomes suppress H/R-induced cardiomyocyte ferroptosis

Bone marrow mesenchymal stem cell (BMSC)-derived exosomes overexpressing GATA-4 (Exosoe-GATA-4) can protect cardiac function. Mitochondrial permeability transition pore (mPTP) has a crucial role in ferroptosis. This study aimed to assess the mechanism of Exosoe-GATA-4 in myocardial ischemia/reperfusion (I/R) injury. Exos were successfully excreted, and 185 differential expression miRNAs were obtained using bioinformatics. The Exosoe-GATA-4 effectively suppressed hypoxia/reoxygenation (H/R)-induced cardiomyocytes' ferroptosis, while the effects were reversed by miR-330-3p inhibitor. miR-330-3p targeted negative regulated BAP1. The effects of miR-330-3p inhibitor were reversed by knock-down BAP1. Also, BAP1 reversed the effects of Exosoe-GATA-4 on H/R-induced cardiomyocytes' ferroptosis by downregulating SLC7A11. Mechanistically, BAP1 interacted with IP3R and increased cardiomyocytes' Ca2+ level, causing mPTP opening and mitochondrial dysfunction, promoting H/R-induced cardiomyocytes' ferroptosis. Moreover, hydrogen sulfide (H2S) content was increased and regulated the keap1/Nrf2 signaling pathway by Exosoe-GATA-4 treated. Exosoe-GATA-4 effectively suppresses H/R-induced cardiomyocytes' ferroptosis by upregulating miR-330-3p, which regulates the BAP1/SLC7A11/IP3R axis and inhibits mPTP opening.

Overview of mechanism of electroacupuncture pretreatment for prevention and treatment of cardiovascular and cerebrovascular diseases

Cardio-cerebrovascular disease (CCVD) is a serious threat to huma strategy to prevent the occurrence and development of disease by giving electroacupuncture intervention before the disease occurs. EAP has been shown in many preclinical studies to relieve ischemic symptoms and improve damage from ischemia-reperfusion, with no comprehensive review of its mechanisms in cardiovascular disease yet. In this paper, we first systematically discussed the meridian and acupoint selection law of EAP for CCVD and focused on the progress of the mechanism of action of EAP for the prevention and treatment of CCVD. As a result, in preclinical studies, AMI and MCAO models are commonly used to simulate ischemic injury in CCVD, while MIRI and CI/RI models are used to simulate reperfusion injury caused by blood flow recovery after focal tissue ischemia. According to the meridian matching rules of EAP for CCVD, PC6 in the pericardial meridian is the most commonly used acupoint in cardiovascular diseases, while GV20 in the Du meridian is the most commonly used acupoint in cerebrovascular diseases. In terms of intervention parameters, EAP intervention generally lasts for 30 min, with acupuncture depths mostly between 1.5 and 5 mm, stimulation intensities mostly at 1 mA, and commonly used frequencies being low frequencies. In terms of molecular mechanisms, the key pathways of EAP in preventing and treating cardiovascular and cerebrovascular diseases are partially similar. EAP can play a protective role in cardiovascular and cerebrovascular diseases by promoting autophagy, regulating Ca2+ overload, and promoting vascular regeneration through anti-inflammatory reactions, antioxidant stress, and anti-apoptosis. Of course, both pathways involved have their corresponding specificities. When using EAP to prevent and treat cardiovascular diseases, it involves the metabolic pathway of glutamate, while when using EAP to prevent and treat cerebrovascular diseases, it involves the homeostasis of the blood-brain barrier and the release of neurotransmitters and nutritional factors. I hope these data can provide experimental basis and reference for the clinical promotion and application of EAP in CCVD treatment.

Regulation of autophagy by protein lipidation

Autophagy is a conserved catabolic recycling pathway that can eliminate cytosolic materials to maintain homeostasis and organelle functions. Many studies over the past few decades have demonstrated that abnormal autophagy is associated with a variety of diseases. Protein lipidation plays an important role in the regulation of autophagy by affecting protein trafficking, localization, stability, interactions and signal transduction. Here, we review recent advances in the understanding of the role of lipidation in autophagy, including S-palmitoylation, N-myristoylation, S-prenylation, glycosylphosphatidylinositol (GPI) anchor modification and cholesterylation. We comprehensively review the enzymes and catalytic mechanisms of lipidation and discuss the relationship between lipidation and autophagy, aiming to deepen the understanding of lipidation and promote the discovery of drug targets for the treatment of autophagy-related diseases.

Research trends and hotspots of circular RNA in cardiovascular disease: A bibliometric analysis

From a global perspective, cardiovascular diseases (CVDs), the leading factor accounting for population mortality, and circRNAs, RNA molecules with stable closed-loop structures, have been proven to be closely related. The latent clinical value and the potential role of circRNAs in CVDs have been attracting increasing, active research interest, but bibliometric studies in this field are still lacking. Thus, in this study, we conducted a bibliometric analysis by using software such as VOSviewer, CiteSpace, Microsoft Excel, and the R package to determine the current research progress and hotspots and ultimately provide an overview of the development trends and future frontiers in this field. In our study, based on our search strategy, a total of 1206 publications published before July 31, 2023 were accessed from the WOSCC database. According to our findings, there is a notable increasing trend in global publications in the field of circRNA in CVDs. China was found to be the dominant country in terms of publication number, but a lack of high-quality articles was a significant fault. A cluster analysis on the co-cited references indicated that dilated cardiomyopathy, AMI, and cardiac hypertrophy are the greatest objects of concern. In contrast, a keywords analysis indicated that high importance has been ascribed to MI, abdominal aortic aneurysm, cell proliferation, and coronary artery diseases.

Circular RNAs in human diseases

Circular RNAs (circRNAs) are a unique class of RNA molecules formed through back-splicing rather than linear splicing. As an emerging field in molecular biology, circRNAs have garnered significant attention due to their distinct structure and potential functional implications. A comprehensive understanding of circRNAs' functions and potential clinical applications remains elusive despite accumulating evidence of their involvement in disease pathogenesis. Recent research highlights their significant roles in various human diseases, but comprehensive reviews on their functions and applications remain scarce. This review provides an in-depth examination of circRNAs, focusing first on their involvement in non-neoplastic diseases such as respiratory, endocrine, metabolic, musculoskeletal, cardiovascular, and renal disorders. We then explore their roles in tumors, with particular emphasis on exosomal circular RNAs, which are crucial for cancer initiation, progression, and resistance to treatment. By detailing their biogenesis, functions, and impact on disease mechanisms, this review underscores the potential of circRNAs as diagnostic biomarkers and therapeutic targets. The review not only enhances our understanding of circRNAs' roles in specific diseases and tumor types but also highlights their potential as novel diagnostic and therapeutic tools, thereby paving the way for future clinical investigations and potential therapeutic interventions.

Research progress of circular RNAs in myocardial ischemia

Circular RNAs (circRNAs) are a type of single-stranded RNA that forms a covalently closed continuous loop. Its structure, stability, properties, and cell- and tissue-specificity have gained considerable recognition in the research and clinical sectors, as its role has been observed in different diseases, such as cardiovascular diseases, cancers, and central nervous system diseases, etc. Cardiovascular disease is still named as the number one cause of death globally, with myocardial ischemia (MI) accounting for 15 % of mortality annually. A number of circRNAs have been identified and are being studied for their ability to reduce MI by inhibiting the molecular mechanisms associated with myocardial ischemia reperfusion injury, such as inflammation, oxidative stress, autophagy, apoptosis, and so on. CircRNAs play a significant role as crucial regulatory elements at transcriptional levels, regulating different proteins, and at posttranscriptional levels, having interactions with RNA-binding proteins, ribosomal proteins, micro-RNAS, and long non-coding RNAS, making it possible to exert their effects through the circRNA-miRNA-mRNA axis. CircRNAs are a potential novel biomarker and therapeutic target for myocardial ischemia and cardiovascular diseases in general. The purpose of this review is to summarize the relationship, function, and mechanism observed between circRNAs and MI injury, as well as to provide directions for future research and clinical trials.

Insights into the post-translational modifications in heart failure

Heart failure (HF), as the terminal manifestation of multiple cardiovascular diseases, causes a huge socioeconomic burden worldwide. Despite the advances in drugs and medical-assisted devices, the prognosis of HF remains poor. HF is well-accepted as a myriad of subcellular dys-synchrony related to detrimental structural and functional remodelling of cardiac components, including cardiomyocytes, fibroblasts, endothelial cells and macrophages. Through the covalent chemical process, post-translational modifications (PTMs) can coordinate protein functions, such as re-localizing cellular proteins, marking proteins for degradation, inducing interactions with other proteins and tuning enzyme activities, to participate in the progress of HF. Phosphorylation, acetylation, and ubiquitination predominate in the currently reported PTMs. In addition, advanced HF is commonly accompanied by metabolic remodelling including enhanced glycolysis. Thus, glycosylation induced by disturbed energy supply is also important. In this review, firstly, we addressed the main types of HF. Then, considering that PTMs are associated with subcellular locations, we summarized the leading regulation mechanisms in organelles of distinctive cell types of different types of HF, respectively. Subsequently, we outlined the aforementioned four PTMs of key proteins and signaling sites in HF. Finally, we discussed the perspectives of PTMs for potential therapeutic targets in HF.

Epigenetic biomarkers in aging and longevity: Current and future application

The aging process has been one of the most necessary research fields in the current century, and knowing different theories of aging and the role of different genetic, epigenetic, molecular, and environmental modulating factors in increasing the knowledge of aging mechanisms and developing appropriate diagnostic, therapeutic, and preventive ways would be helpful. One of the most conserved signs of aging is epigenetic changes, including DNA methylation, histone modifications, chromatin remodeling, noncoding RNAs, and extracellular RNAs. Numerous biological processes and hallmarks are vital in aging development, but epigenomic alterations are especially notable because of their importance in gene regulation and cellular identity. The mounting evidence points to a possible interaction between age-related epigenomic alterations and other aging hallmarks, like genome instability. To extend a healthy lifespan and possibly reverse some facets of aging and aging-related diseases, it will be crucial to comprehend global and locus-specific epigenomic modifications and recognize corresponding regulators of health and longevity. In the current study, we will aim to discuss the role of epigenomic mechanisms in aging and the most recent developments in epigenetic diagnostic biomarkers, which have the potential to focus efforts on reversing the destructive signs of aging and extending the lifespan.

Circular RNA in Cardiovascular Diseases: Biogenesis, Function and Application

Cardiovascular diseases pose a significant public health challenge globally, necessitating the development of effective treatments to mitigate the risk of cardiovascular diseases. Recently, circular RNAs (circRNAs), a novel class of non-coding RNAs, have been recognized for their role in cardiovascular disease. Aberrant expression of circRNAs is closely linked with changes in various cellular and pathophysiological processes within the cardiovascular system, including metabolism, proliferation, stress response, and cell death. Functionally, circRNAs serve multiple roles, such as acting as a microRNA sponge, providing scaffolds for proteins, and participating in protein translation. Owing to their unique properties, circRNAs may represent a promising biomarker for predicting disease progression and a potential target for cardiovascular drug development. This review comprehensively examines the properties, biogenesis, and potential mechanisms of circRNAs, enhancing understanding of their role in the pathophysiological processes impacting cardiovascular disease. Furthermore, the prospective clinical applications of circRNAs in the diagnosis, prognosis, and treatment of cardiovascular disease are addressed.

Exploring circular RNAs as biomarkers for Parkinson's disease and their expression changes after aerobic exercise rehabilitation

Circular RNAs (circRNAs) are circularized single-stranded ribonucleic acids that interacts with DNA, RNA, and proteins to play critical roles in cell biology. CircRNAs regulate microRNA content, gene expression, and may code for specific peptides. Indeed, circRNAs are differentially expressed in neurodegenerative disorders like Parkinson's disease (PD), playing a potential role in the mechanisms of brain pathology. The RNA molecules with aberrant expression in the brain can cross the blood-brain barrier and reach the bloodstream, which enable their use as non-invasive PD disease biomarker. Promising targets with valuable discriminatory ability in combined circRNA signatures include MAPK9_circ_0001566, SLAIN1_circ_0000497, SLAIN2_circ_0126525, PSEN1_circ_0003848, circ_0004381, and circ_0017204. On the other hand, regular exercises are effective therapy for mitigating PD symptoms, promoting neuroprotective effects with epigenetic modulation. Aerobic exercises slow symptom progression in PD by improving motor control, ameliorating higher functions, and enhancing brain activity and neuropathology. These improvements are accompanied by changes circRNA expression, including hsa_circ_0001535 (circFAM13B) and hsa_circ_0000437 (circCORO1C). The sensitivity of current methods for detecting circulating circRNAs is considered a limitation. While amplification kits already exist for low-abundant microRNAs, similar kits are needed for circRNAs. Alternatively, the use of digital PCR can help overcome this constraint. The current review examines the potential use of circRNAs as non-invasive biomarkers of PD and to assess the effects of rehabilitation. Although circRNAs hold promise as targets for PD diagnosis and therapeutics, further validation is needed before their clinical implementation.

Therapeutic Potential of Natural Compounds Acting through Epigenetic Mechanisms in Cardiovascular Diseases: Current Findings and Future Directions

Cardiovascular diseases (CVDs) remain a leading global cause of morbidity and mortality. These diseases have a multifaceted nature being influenced by a multitude of biochemical, genetic, environmental, and behavioral factors. Epigenetic modifications have a crucial role in the onset and progression of CVD. Epigenetics, which regulates gene activity without altering the DNA's primary structure, can modulate cardiovascular homeostasis through DNA methylation, histone modification, and non-coding RNA regulation. The effects of environmental stimuli on CVD are mediated by epigenetic changes, which can be reversible and, hence, are susceptible to pharmacological interventions. This represents an opportunity to prevent diseases by targeting harmful epigenetic modifications. Factors such as high-fat diets or nutrient deficiencies can influence epigenetic enzymes, affecting fetal growth, metabolism, oxidative stress, inflammation, and atherosclerosis. Recent studies have shown that plant-derived bioactive compounds can modulate epigenetic regulators and inflammatory responses, contributing to the cardioprotective effects of diets. Understanding these nutriepigenetic effects and their reversibility is crucial for developing effective interventions to combat CVD. This review delves into the general mechanisms of epigenetics, its regulatory roles in CVD, and the potential of epigenetics as a CVD therapeutic strategy. It also examines the role of epigenetic natural compounds (ENCs) in CVD and their potential as intervention tools for prevention and therapy.

Circular RNAs: Epigenetic regulators of PTEN expression and function in cancer

Epigenetic regulation of gene expression, without altering the DNA sequence, is involved in many normal cellular growth and division events, as well as diseases such as cancer. Epigenetics is no longer limited to DNA methylation, and histone modification, but regulatory non-coding RNAs (ncRNAs) also play an important role in epigenetics. Circular RNAs (circRNAs), single-stranded RNAs without 3' and 5' ends, have recently emerged as a class of ncRNAs that regulate gene expression. CircRNAs regulate phosphatase and tensin homolog (PTEN) expression at various levels of transcription, post-transcription, translation, and post-translation under their own regulation. Given the importance of PTEN as a tumor suppressor in cancer that inhibits one of the most important cancer pathways PI3K/AKT involved in tumor cell proliferation and survival, significant studies have been conducted on the regulatory role of circRNAs in relation to PTEN. These studies will be reviewed in this paper to better understand the function of this protein in cancer and explore new therapeutic approaches.

Exosomes based strategies for cardiovascular diseases: Opportunities and challenges

Exosomes, as nanoscale extracellular vesicles (EVs), are secreted by all types of cells to facilitate intercellular communication in living organisms. After being taken up by neighboring or distant cells, exosomes can alter the expression levels of target genes in recipient cells and thereby affect their pathophysiological outcomes depending on payloads encapsulated therein. The functions and mechanisms of exosomes in cardiovascular diseases have attracted much attention in recent years and are thought to have cardioprotective and regenerative potential. This review summarizes the biogenesis and molecular contents of exosomes and details the roles played by exosomes released from various cells in the progression and recovery of cardiovascular disease. The review also discusses the current status of traditional exosomes in cardiovascular tissue engineering and regenerative medicine, pointing out several limitations in their application. It emphasizes that some of the existing emerging industrial or bioengineering technologies are promising to compensate for these shortcomings, and the combined application of exosomes and biomaterials provides an opportunity for mutual enhancement of their performance. The integration of exosome-based cell-free diagnostic and therapeutic options will contribute to the further development of cardiovascular regenerative medicine.

CircCUL1 inhibits trophoblast cell migration and invasion and promotes cell autophagy by sponging hsa-miR-30e-3p in fetal growth restriction via the ANXA1/PI3K/AKT axis

Fetal growth restriction (FGR) severely affects the health outcome of newborns and represents a major cause of perinatal morbidity. The precise involvement of circCULT1 in the progression of FGR remains unclear. We performed next-generation sequencing and RT-qPCR to identify differentially expressed circRNAs in placental tissues affected by FGR by comparing them with unaffected counterparts. Edu, flow cytometry, and transwell assay were conducted to detect HTR8/SVneo cell's function in regard to cell proliferation, migration, and invasion. The interaction between circCUL1 and hsa-miR-30e-3p was assessed through dual-luciferase reporter assays, validation of the interaction between circCUL1 and ANXA1 was performed using RNA pulldown and immunoprecipitation assays. Western blot analysis was performed to evaluate protein levels of autophagy markers and components of the PI3K/AKT signaling pathway. A knockout (KO) mouse model was established for homologous mmu-circ-0001469 to assess fetal mouse growth and development indicators. Our findings revealed an upregulation of circCUL1 expression in placental tissues from patients with FGR. We found that suppression of circCUL1 increased the trophoblast cell proliferation, migration, and invasion, circCUL1 could interact with hsa-miR-30e-3p. Further, circCUL1 stimulated autophagy, modulating trophoblast cell autophagy via the ANXA1/PI3K/AKT pathway, and a notable disparity was observed, with KO mice displaying accelerated embryo development and exhibiting heavier placentas in comparison to wild-type C57BL/6 mice. By modulating the ANXA1/PI3K/AKT signaling pathway through the interaction with hsa-miR-30e-3p, circCUL1 promotes autophagy while concurrently suppressing trophoblast cell proliferation, migration, and invasion. These findings offer novel insights into potential diagnostic markers and therapeutic targets for FGR research.

Queen bee acid pretreatment attenuates myocardial ischemia/reperfusion injury by enhancing autophagic flux

Queen bee acid (QBA), which is exclusively found in royal jelly, has anti-inflammatory, antihypercholesterolemic, and antiangiogenic effects. A recent study demonstrated that QBA enhances autophagic flux in the heart. Considering the significant role of autophagy in the development of myocardial ischemia/reperfusion (I/R) injury, we investigated the effect of pretreatment with QBA on myocardial damage. In an in vivo model, left coronary artery blockage for 30 min and reperfusion for 2 h were used to induce myocardial I/R. In an in vitro model, neonatal rat cardiomyocytes (NRCs) were exposed to 3 h of hypoxia and 3 h of reoxygenation (H/R). Our results showed that pretreatment with QBA increased the cell viability of cardiomyocytes exposed to H/R in a dose-dependent manner, and the best protective concentration of QBA was 100 μM. Next, we noted that QBA pretreatment (24h before H/R) enhanced autophagic flux and attenuated mitochondrial damage, cardiac oxidative stress and apoptosis in NRCs exposed to H/R injury, and these effects were weakened by cotreatment with the autophagy inhibitor bafilomycin A1 (Baf). In addition, similar results were observed when QBA (10 mg/kg) was injected intraperitoneally into I/R mice 30 min before ischemia. Compared to mice subjected to I/R alone, those treated with QBA had decreased myocardial infarct area and increased cardiac function, whereas, these effects were partly reversed by Baf. Notably, in NRCs exposed to H/R, tandem fluorescent mRFP-GFP-LC3 assays indicated increased autophagosome degradation due to the increase in autophagic flux upon QBA treatment, but coinjection of Baf blocked autophagic flux. In this investigation, no notable adverse effects of QBA were detected in either cellular or animal models. Our findings suggest that QBA pretreatment mitigates myocardial I/R injury by eliminating dysfunctional mitochondria and reducing reactive oxygen species via promoting autophagic flux.

Identification of circular RNAs regulating cardiomyocyte proliferation in neonatal pig hearts

Little is known about the expression patterns and functions of circular RNAs (circRNAs) in the heart of large mammals. In this study, we examined the expression profiles of circRNAs, microRNAs (miRNAs), and messenger RNAs (mRNAs) in neonatal pig hearts. Pig heart samples collected on postnatal days 1 (P1), 3 (P3), 7 (P7), and 28 (P28) were sent for total RNA sequencing. Our data revealed a total of 7,000 circRNAs in the 24 pig hearts. Pathway enrichment analysis of hallmark gene sets demonstrated that differentially expressed circRNAs were engaged in different pathways. The most significant difference was observed between P1 and the other 3 groups (P3, P7, and P28) in pathways related to cell cycle and muscle development. Out of the 10 circRNAs that were validated through real-time quantitative PCR to verify their expression, 6 exhibited significant effects on cell cycle activity in human induced pluripotent stem cell-derived cardiomyocytes following small interfering RNA-mediated knockdown. circRNA-miRNA-mRNA networks were constructed to understand the potential mechanisms of circRNAs in the heart. In conclusion, our study provided a data set for exploring the roles of circRNAs in pig hearts. In addition, we identified several circRNAs that regulate cardiomyocyte cell cycle.

Dihydroartemisinin alleviates doxorubicin-induced cardiotoxicity and ferroptosis by activating Nrf2 and regulating autophagy

Although the use of Doxorubicin (Dox) is extensive in the treatment of malignant tumor, the toxic effects of Dox on the heart can cause myocardial injury. Therefore, it is necessary to find an alternative drug to alleviate the Dox-induced cardiotoxicity. Dihydroartemisinin (DHA) is a semisynthetic derivative of artemisinin, which is an active ingredient of Artemisia annua. The study investigates the effects of DHA on doxorubicin-induced cardiotoxicity and ferroptosis, which are related to the activation of Nrf2 and the regulation of autophagy. Different concentrations of DHA were administered by gavage for 4 weeks in mice. H9c2 cells were pretreated with different concentrations of DHA for 24 h in vitro. The mechanism of DHA treatment was explored through echocardiography, biochemical analysis, real-time quantitative PCR, western blotting analysis, ROS/DHE staining, immunohistochemistry, and immunofluorescence. In vivo, DHA markedly relieved Dox-induced cardiac dysfunction, attenuated oxidative stress, alleviated cardiomyocyte ferroptosis, activated Nrf2, promoted autophagy, and improved the function of lysosomes. In vitro, DHA attenuated oxidative stress and cardiomyocyte ferroptosis, activated Nrf2, promoted clearance of autophagosomes, and reduced lysosomal destruction. The changes of ferroptosis and Nrf2 depend on selective degradation of keap1 and recovery of lysosome. We found for the first time that DHA could protect the heart from the toxic effects of Dox-induced cardiotoxicity. In addition, DHA significantly alleviates Dox-induced ferroptosis through the clearance of autophagosomes, including the selective degradation of keap1 and the recovery of lysosomes.

Circular RNAs: a small piece in the heart failure puzzle

Cardiovascular disease, specifically heart failure (HF), remains a significant concern in the realm of healthcare, necessitating the development of new treatments and biomarkers. The RNA family consists of various subgroups, including microRNAs, PIWI-interacting RNAs (piRAN) and long non-coding RNAs, which have shown potential in advancing personalized healthcare for HF patients. Recent research suggests that circular RNAs, a lesser-known subgroup of RNAs, may offer a novel set of targets and biomarkers for HF. This review will discuss the biogenesis of circular RNAs, their unique characteristics relevant to HF, their role in heart function, and their potential use as biomarkers in the bloodstream. Furthermore, future research directions in this field will be outlined. The stability of exosomal circRNAs makes them suitable as biomarkers, pathogenic regulators, and potential treatments for cardiovascular diseases such as atherosclerosis, acute coronary syndrome, ischemia/reperfusion injury, HF, and peripheral artery disease. Herein, we summarized the role of circular RNAs and their exosomal forms in HF diseases.

CIRC-MARC2 SILENCING PROTECTS HUMAN CARDIOMYOCYTES FROM HYPOXIA/REOXYGENATION-INDUCED INJURY BY MODULATING MIR-335-5P/TRPM7 AXIS

ABSTRACT

Myocardial ischemia-reperfusion injury (MIRI) is a vital risk factor for cardiovascular diseases. Some circular RNAs have been identified as modulators of MIRI. However, the effects of circ-mitochondrial amidoxime reducing component 2 (circ-MARC2) in MIRI are unclear. Our results showed that circ-MARC2 was overexpressed in hypoxia/reoxygenation (H/R)-treated AC16 cells. Circ-MARC2 silencing reversed the inhibitory effect of H/R treatment on cell proliferation and promoting effects on lactate dehydrogenase activity, creatine kinase activity, and cell apoptosis in AC16 cells. Moreover, circ-MARC2 served as the sponge for miR-335-5p and ameliorated H/R-induced AC16 cell damage by decoying miR-335-5p. In addition, transient receptor potential cation channel subfamily M member 7 (TRPM7) was identified as the target gene of miR-335-5p. Overexpression of miR-335-5p relieved H/R-induced AC16 cell damage, whereas TRPM7 elevation abolished the effect. Circ-MARC2 knockdown was able to relieve H/R-induced AC16 cell injury through miR-335-5p/TRPM7 axis.

CircTMEM165 facilitates endothelial repair by modulating mitochondrial fission via miR-192/SCP2 in vitro and in vivo

Constitutive explorations indicate a correlation between circular RNAs (circRNAs) and cardiovascular diseases. However, the involvement of circRNAs in endothelial recuperation and in-stent restenosis (ISR) remains underexplored. CircTMEM165 has first been reported to be highly expressed in hypoxic human umbilical vein endothelial cells (HUVECs). Here, we identified that circTMEM165 was downregulated in ISR patients, inversely correlating with ISR severity. Functionally, circTMEM165 was found to be abundant in endothelial cells, inhibiting inflammation, and adhesion. Particularly, we first observed that circTMEM165 could alleviate HUVECs apoptosis and mitochondrial fission induced by lipopolysaccharide (LPS). Mechanistically, circTMEM165, as a miR-192-3p sponge, enhancing SCP2 expression, which serves as a critical regulator of HUVECs biological functions. Moreover, in vivo, circTMEM165 attenuated intimal hyperplasia and facilitated repair following classic rat carotid artery balloon injury model. These findings investigated the circTMEM165-miR-192-3p-SCP2 axis as a critical determinant of endothelial health and a potential biomarker and therapeutic target for vascular disorders.

The Janus face of mitophagy in myocardial ischemia/reperfusion injury and recovery

In myocardial ischemia/reperfusion injury (MIRI), moderate mitophagy is a protective or adaptive mechanism because of clearing defective mitochondria accumulates during MIRI. However, excessive mitophagy lead to an increase in defective mitochondria and ultimately exacerbate MIRI by causing overproduction or uncontrolled production of mitochondria. Phosphatase and tensin homolog (PTEN)-induced kinase 1 (Pink1), Parkin, FUN14 domain containing 1 (FUNDC1) and B-cell leukemia/lymphoma 2 (BCL-2)/adenovirus E1B19KD interaction protein 3 (BNIP3) are the main mechanistic regulators of mitophagy in MIRI. Pink1 and Parkin are mitochondrial surface proteins involved in the ubiquitin-dependent pathway, while BNIP3 and FUNDC1 are mitochondrial receptor proteins involved in the non-ubiquitin-dependent pathway, which play a crucial role in maintaining mitochondrial homeostasis and mitochondrial quality. These proteins can induce moderate mitophagy or inhibit excessive mitophagy to protect against MIRI but may also trigger excessive mitophagy or insufficient mitophagy, thereby worsening the condition. Understanding the actions of these mitophagy mechanistic proteins may provide valuable insights into the pathological mechanisms underlying MIRI development. Based on the above background, this article reviews the mechanism of mitophagy involved in MIRI through Pink1/Parkin pathway and the receptor mediated pathway led by FUNDC1 and BNIP3, as well as the related drug treatment, aim to provide effective strategies for the prevention and treatment of MIRI.

CircBCL2L13 attenuates cardiomyocyte oxidative stress and apoptosis in cardiac ischemia‒reperfusion injury via miR-1246/PEG3 signaling

Ischemia‒reperfusion (I/R) is a common complication in the clinical treatment of acute myocardial infarction (MI), in which cardiomyocytes play a pivotal role in the recovery of cardiac function after reperfusion injury. The expression of numerous circular ribonucleic acids (circRNAs) is disrupted in I/R-induced cardiac damage, but the potential role of circRNAs in I/R damage has not been fully elucidated. The purpose of the present study was to clarify the biological action and molecular mechanism of circRNA 002166 (also termed circCL2L13) in postmyocardial I/R. Oxygen-glucose deprivation/reoxygenation (OGD/R) in an in vivo model was performed to simulate I/R damage. real-time polymerase chain reaction analysis was also conducted to evaluate the relationships of the SOD1, SOD2, NRF2, HO1 and GPX4 indicators with oxidative stress injury. TUNEL immunofluorescence was used to evaluate the degree of cardiomyocyte apoptosis in the different treatment groups. The circBCL2L13 level was markedly upregulated in myocardial tissues from a mouse I/R model. Overexpression of circBCL2L13 markedly attenuated the expression of oxidative stress-related genes and apoptosis in OGD/R-induced cardiomyocytes. A mechanistic study revealed that circBCL2L13 functions as a ceRNA for miR-1246 and modulates paternally expressed gene 3 (PEG3). Eventually, circBCL2L13 was proven to regulate PEG3 by targeting miR-1246, thereby protecting against OGD/R-induced cardiomyocyte oxidative damage and apoptosis. In conclusion, our study confirmed that the circBCL2L13/miR-1246/PEG3 axis suppressed the progression of OGD/R injury in cardiomyocytes, which might lead to new therapeutic strategies for cardiac I/R injury.

Hippo (YAP)-autophagy axis protects against hepatic ischemia-reperfusion injury through JNK signaling

BACKGROUND

Hepatic ischemia-reperfusion injury (HIRI) remains a common complication during liver transplantation (LT) in patients. As a key downstream effector of the Hippo pathway, Yes-associated protein (YAP) has been reported to be involved in various physiological and pathological processes. However, it remains elusive whether and how YAP may control autophagy activation during ischemia-reperfusion.

METHODS

Human liver tissues from patients who had undergone LT were obtained to evaluate the correlation between YAP and autophagy activation. Both an in vitro hepatocyte cell line and in vivo liver-specific YAP knockdown mice were used to establish the hepatic ischemia-reperfusion models to determine the role of YAP in the activation of autophagy and the mechanism of regulation.

RESULTS

Autophagy was activated in the post-perfusion liver grafts during LT in patients, and the expression of YAP positively correlated with the autophagic level of hepatocytes. Liver-specific knockdown of YAP inhibited hepatocytes autophagy upon hypoxia-reoxygenation and HIRI ( P <0.05). YAP deficiency aggravated HIRI by promoting the apoptosis of hepatocytes both in the in vitro and in vivo models ( P <0.05). Attenuated HIRI by overexpression of YAP was diminished after the inhibition of autophagy with 3-methyladenine. In addition, inhibiting autophagy activation by YAP knockdown exacerbated mitochondrial damage through increasing reactive oxygen species ( P <0.05). Moreover, the regulation of autophagy by YAP during HIRI was mediated by AP1 (c-Jun) N-terminal kinase (JNK) signaling through binding to the transcriptional enhanced associate domain (TEAD).

CONCLUSIONS

YAP protects against HIRI by inducing autophagy via JNK signaling that suppresses the apoptosis of hepatocytes. Targeting Hippo (YAP)-JNK-autophagy axis may provide a novel strategy for the prevention and treatment of HIRI.

Circular RNA-circLRP6 protects cardiomyocyte from hypoxia-induced apoptosis by facilitating hnRNPM-mediated expression of FGF-9

Coronary atherosclerosis-induced myocardial ischemia leads to cardiomyocyte apoptosis. The regulatory mechanisms for cardiomyocyte apoptosis have not been fully understood. Circular RNAs are non-coding RNAs which play important roles in heart function maintenance and progression of heart diseases by regulating gene transcription and protein translation. Here, we reported a conserved cardiac circular RNA, which is generated from the second exon of LRP6 and named circLRP62-2 . CircLRP62-2 can protect cardiomyocyte from hypoxia-induced apoptosis. The expression of circLRP62-2 in cardiomyocytes was down-regulated under hypoxia, while forced expression of circLRP62-2 inhibited cell apoptosis. Normally, circLRP62-2 was mainly localized in the nucleus. Under hypoxia, circLRP62-2 is associated with heterogeneous nuclear ribonucleoprotein M (hnRNPM) to be translocated into the cytoplasm. It recruited hnRNPM to fibroblast growth factor 9 (FGF9) mRNA to enhance the expression of FGF9 protein, promoting hypoxia-adaption and viability of cardiomyocytes. In summary, this study uncovers a new inhibitor of apoptosis and reveals a novel anti-apoptotic pathway composed of circLRP62-2 , hnRNPM, and FGF9, which may provide therapeutic targets for coronary heart disease and ischemic myocardial injury.

GSLCDA: An Unsupervised Deep Graph Structure Learning Method for Predicting CircRNA-Disease Association

Growing studies reveal that Circular RNAs (circRNAs) are broadly engaged in physiological processes of cell proliferation, differentiation, aging, apoptosis, and are closely associated with the pathogenesis of numerous diseases. Clarification of the correlation among diseases and circRNAs is of great clinical importance to provide new therapeutic strategies for complex diseases. However, previous circRNA-disease association prediction methods rely excessively on the graph network, and the model performance is dramatically reduced when noisy connections occur in the graph structure. To address this problem, this paper proposes an unsupervised deep graph structure learning method GSLCDA to predict potential CDAs. Concretely, we first integrate circRNA and disease multi-source data to constitute the CDA heterogeneous network. Then the network topology is learned using the graph structure, and the original graph is enhanced in an unsupervised manner by maximize the inter information of the learned and original graphs to uncover their essential features. Finally, graph space sensitive k-nearest neighbor (KNN) algorithm is employed to search for latent CDAs. In the benchmark dataset, GSLCDA obtained 92.67% accuracy with 0.9279 AUC. GSLCDA also exhibits exceptional performance on independent datasets. Furthermore, 14, 12 and 14 of the top 16 circRNAs with the most points GSLCDA prediction scores were confirmed in the relevant literature in the breast cancer, colorectal cancer and lung cancer case studies, respectively. Such results demonstrated that GSLCDA can validly reveal underlying CDA and offer new perspectives for the diagnosis and therapy of complex human diseases.

A review on regulation of DNA methylation during post-myocardial infarction

Myocardial infarction (MI) imposes a huge medical and economic burden on society, and cardiac repair after MI involves a complex series of processes. Understanding the key mechanisms (such as apoptosis, autophagy, inflammation, and fibrosis) will facilitate further drug development and patient treatment. Presently, a substantial body of evidence suggests that the regulation of epigenetic processes contributes to cardiac repair following MI, with DNA methylation being among the notable epigenetic factors involved. This article will review the research on the mechanism of DNA methylation regulation after MI to provide some insights for future research and development of related drugs.

A Novel Circular RNA circITGa9 Predominantly Generated in Human Heart Disease Induces Cardiac Remodeling and Fibrosis

Recent studies have highlighted the pivotal roles of circular RNAs (circRNAs) in cardiovascular diseases. Through high-throughput circRNA sequencing of both normal myocardial tissues and hypertrophic patients, we unveiled 32,034 previously undiscovered circRNAs with distinct cardiac expression patterns. Notably, circITGa9, a circRNA derived from integrin-α9, exhibited substantial up-regulation in cardiac hypertrophy patients. This elevation was validated across extensive sample pools from cardiac patients and donors. In vivo experiments revealed heightened cardiac fibrosis in mice subjected to transverse aortic constriction (TAC) after circITGa9 injection. We identified circITGa9 binding proteins through circRNA precipitation followed by liquid chromatography tandem-mass spectrometry. Furthermore, circRNA pull-down/precipitation assays demonstrated that increased circITGa9 expression facilitated binding with tropomyosin 3 (TPM3). Specific binding sites between circITGa9 and TPM3 were identified through computational algorithms and further validated by site-directed mutagenesis. We further showed that circITGa9 induced actin polymerization, characteristic of tissue fibrosis. Finally, we developed approaches that improved cardiac function and decreased fibrosis by delivering small interfering RNA targeting circITGa9 or blocking oligo inhibiting the interaction of circITGa9 and TPM3 into TAC mice, which is amenable for further preclinical and translational development. We conclude that elevated circITGa9 levels drive cardiac remodeling and fibrosis. By pinpointing circITGa9 as a therapeutic target, we open doors to innovative interventions for mitigating cardiac remodeling and fibrosis.

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.

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.

The circRNA MKLN1 regulates autophagy in the development of diabetic retinopathy

Diabetic retinopathy (DR) is a common complication in patients with diabetes and has become an important cause of blindness in working-age people. However, the mechanisms involved have not been fully elucidated. Circular RNAs (circRNAs) can play an important role in DR, and they can accurately regulate the expression of target genes through a new regulatory model: the competing endogenous RNA (ceRNA) model. We isolated total RNA from extracellular vesicles in the serum of healthy individuals (Con) and individuals with diabetes mellitus without DR (DM), nonproliferative DR (NPDR), or proliferative DR (PDR) and subjected them to deep sequencing. We found aberrantly high expression of circMKLN1. In a streptozotocin (STZ)-induced mice model of diabetes, the inhibition of circMKLN1 with AAV2 transduction markedly ameliorated retinal acellular vessels and vascular leakage, which was reversed by intravitreal injection of rapamycin, a potent autophagy inducer. In addition, circMKLN1 adsorbs miR-26a-5p as a molecular sponge and mediates high glucose (HG)/methylglyoxal (MG)-induced autophagy in hRMECs. CircMKLN1-silencing treatment reduces HG/MG-related reactive autophagy and inflammation. In addition, miR-26a-5p targeting by circMKLN1 plays an important role in the regulation of Rab11a expression. Thus, either new biomarkers or new therapeutic targets may be identified with the translation of these findings.

Circular RNA in Multiple Sclerosis: Pathogenicity and Potential Biomarker Development: A Systematic Review

Multiple sclerosis (MS) is a complex autoimmune disorder of the CNS that affects millions of people worldwide. The causes of the disease remain unknown despite extensive efforts to understand it. CircRNAs are a unique class of endogenous non-coding RNA that are abundant, stable, conserved, and specifically expressed molecules, making them a promising biomarker of diseases. This review investigates the role of circRNA in MS pathogenicity and their potential as a biomarker through a comprehensive literature search conducted in 8 scientific databases. The studies found that there are differentially expressed circRNAs in MS patients compared to healthy controls (HC), and this difference is even more pronounced in different MS subtypes. Enrichment of circRNAs in linkage disequilibrium (LD) blocks that harbor MS-associated SNPs suggests that these SNPs manipulate the levels of circRNAs in the surrounding area, contributing to disease pathogenicity. While circRNA shows promise as an indicator or biomarker for MS disease pathology, further research is needed to fully explore its potential and impact on human biology.

hucMSCs Treatment Ameliorated Pulmonary Fibrosis via Downregulating the circFOXP1-HuR-EZH2/STAT1/FOXK1 Autophagic Axis

This study was performed to determine the effect of human umbilical cord mesenchymal stem cells (hucMSCs) treatment on pulmonary fibrosis and investigate the circFOXP1-mediated autophagic mechanism of hucMSCs treatment. Pulmonary fibrosis models were established by spraying bleomycin in mice and TGF-β1 treatment of MRC-5 cells. Results showed that hucMSCs were retained in lung and hucMSCs treatment alleviated pulmonary fibrosis. Morphological staining indicated that hucMSCs-treated mice had thinner alveolar walls, effectively improved alveolar structure, significantly reduced alveolar inflammation, and decreased collagen deposition than control mice. Fibrotic proteins, including vimentin, α-SMA, collagens I and III, and the differentiation-related protein S100 calcium-binding protein A4 was reduced considerably in the hucMSCs-treated group. The mechanistic study revealed that the inhibition of hucMSCs treatment on pulmonary fibrogenesis depended on downregulating circFOXP1, in which hucMSCs treatment promoted circFOXP1-mediated autophagy process via blocking the nuclear human antigen R (HuR) translocation and promoting the HuR degradation, leading to a marked decrease in autophagy negative regulators EZH2, STAT1, and FOXK1. In conclusion, hucMSCs treatment significantly improved pulmonary fibrosis by downregulating the circFOXP1-HuR-EZH2/STAT1/FOXK1 autophagic axis. hucMSCs can act as an effective treatment for pulmonary fibrosis.

Knockdown of Mmu-circ-0001380 Attenuates Myocardial Ischemia/Reperfusion Injury via Modulating miR-106b-5p/Phlpp2 Axis

Myocardial ischemia/reperfusion (MI/R) injury induces myocardial damage and dysfunction. Increasing evidence has confirmed that circular RNAs (circRNAs) play crucial roles in regulating MI/R. Mmu-circ-0001380 has identified to be highly expressed in myocardium of MI/R mouse model. However, its biological function and molecular mechanism in MI/R injury are still unclear. Here, we demonstrated that knockdown of cric-0001380 attenuated myocardial injury of MI/R mice. In vitro, silence of circ-0001380 significantly enhanced viability, and inhibited apoptosis and oxidative stress in HL-1 cells under oxygen-glucose deprivation/reoxygenation (OGD/R). Mmu-miR-106b-5p interacted with circ-0001380, and suppressed the expression of pleckstrin homology domain and leucine rich repeat protein phosphatase 2 (Phlpp2). The miR-106b-5p/Phlpp2 axis mediated the effect of circ-0001380 on OGD/R-induced apoptosis through regulating the phosphorylation of p38, and further involved in regulating the viability and oxidative stress of HL-1 cells. In conclusion, circ-0001380 downregulation relieves MI/R injury via regulating the miR-106b-5p/Phlpp2 axis. The present study indicates that mmu-circ-0001380 exacerbates the myocardial ischemia/reperfusion injury through modulating the miR-106b-5p/Phlpp2 axis in vitro and in vivo.

Non-coding RNAs: The potential biomarker or therapeutic target in hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) is the major complication of liver surgery and liver transplantation, that may increase the postoperative morbidity, mortality, tumor progression, and metastasis. The underlying mechanisms have been extensively investigated in recent years. Among these, oxidative stress, inflammatory responses, immunoreactions, and cell death are the most studied. Non-coding RNAs (ncRNAs) are defined as the RNAs that do not encode proteins, but can regulate gene expressions. In recent years, ncRNAs have emerged as research hotspots for various diseases. During the progression of HIRI, ncRNAs are differentially expressed, while these dysregulations of ncRNAs, in turn, have been verified to be related to the above pathological processes involved in HIRI. ncRNAs mainly contain microRNAs, long ncRNAs, and circular RNAs, some of which have been reported as biomarkers for early diagnosis or assessment of liver damage severity, and as therapeutic targets to attenuate HIRI. Here, we briefly summarize the common pathophysiology of HIRI, describe the current knowledge of ncRNAs involved in HIRI in animal and human studies, and discuss the potential of ncRNA-targeted therapeutic strategies. Given the scarcity of clinical trials, there is still a long way to go from pre-clinical to clinical application, and further studies are needed to uncover their potential as therapeutic targets.

The regulation of circRNA and lncRNAprotein binding in cardiovascular diseases: Emerging therapeutic targets

Noncoding ribonucleic acids (ncRNAs) are a class of ribonucleic acids (RNAs) that carry cellular information and perform essential functions. This class encompasses various RNAs, such as small nuclear ribonucleic acids (snRNA), small interfering ribonucleic acids (siRNA) and many other kinds of RNA. Of these, circular ribonucleic acids (circRNAs) and long noncoding ribonucleic acids (lncRNAs) are two types of ncRNAs that regulate crucial physiological and pathological processes, including binding, in several organs through interactions with other RNAs or proteins. Recent studies indicate that these RNAs interact with various proteins, including protein 53, nuclear factor-kappa B, vascular endothelial growth factor, and fused in sarcoma/translocated in liposarcoma, to regulate both the histological and electrophysiological aspects of cardiac development as well as cardiovascular pathogenesis, ultimately leading to a variety of genetic heart diseases, coronary heart disease, myocardial infarction, rheumatic heart disease and cardiomyopathies. This paper presents a thorough review of recent studies on circRNA and lncRNAprotein binding within cardiac and vascular cells. It offers insight into the molecular mechanisms involved and emphasizes potential implications for treating cardiovascular diseases.

Propofol synergizes with circAPBB2 to protect against hypoxia/reoxygenation-induced oxidative stress, inflammation, and apoptosis of human cardiomyocytes

BACKGROUND

Myocardial injury is the main manifestation of cardiovascular diseases, and previous studies have shown that propofol (PPF) regulates myocardial injury. However, the mechanism of PPF in regulating myocardial injury remains to be further explored. This work aims to analyze the effects of PPF on human cardiomyocyte injury and the underlying mechanism.

METHODS

The regulatory and functional role of PPF and circAPBB2 in human cardiomyocyte injury were analyzed using an in vitro hypoxia/reoxygenation (H/R) cell model, which was established by treating human cardiomyocytes (AC16 cells) with H/R. The study evaluated AC16 cell injury by analyzing cytotoxicity, oxidative stress, inflammation and apoptosis of H/R-induced AC16 cells. Quantitative real-time polymerase chain reaction was performed to detect circAPBB2, miR-18a-5p and dual specificity phosphatase 14 (DUSP14) expression. Protein expression was analyzed by Western blot analysis assay. Dual-luciferase reporter assay, RNA pull-down assay and RNA immunoprecipitation assay were performed to identify the associations among circAPBB2, miR-18a-5p and DUSP14. Cytotoxicity was investigated by cell counting kit-8 assay and lactate dehydrogenase activity detection kit. Oxidative stress was evaluated by cellular reactive oxygen species assay kit and superoxide dismutase activity assay kit. The production of tumor necrosis factor-α and interleukin-1β was evaluated by enzyme-linked immunosorbent assays.

RESULTS

The expression of circAPBB2 and DUSP14 was significantly decreased, while miR-18a-5p was increased in H/R-induced AC16 cells when compared with controls. H/R treatment-induced cytotoxicity, oxidative stress, inflammation and cell apoptosis were attenuated after circAPBB2 overexpression or PPF treatment, whereas these effects were restored by increasing miR-18a-5p expression. PPF treatment improved the inhibitory effect of ectopic circAPBB2 expression on H/R-induced cell injury. MiR-18a-5p silencing ameliorated H/R-induced AC16 damage by interacting with DUSP14. Mechanically, circAPBB2 acted as a miR-18a-5p sponge, and miR-18a-5p targeted DUSP14 in AC16 cells.

CONCLUSION

PPF synergized with circAPBB2 to protect AC16 cells against H/R-induced oxidative stress, inflammation and apoptosis through the miR-18a-5p/DUSP14 pathway.

Progress in circRNA-Targeted Therapy in Experimental Parkinson's Disease

Circular RNAs (circRNAs) are single-stranded RNA molecules often circularized by backsplicing. Growing evidence implicates circRNAs in the underlying mechanisms of various diseases, such as Alzheimer's and Parkinson's disease (PD)-the first and second most prevalent neurodegenerative disorders. In this sense, circSNCA, circHIPK2, circHIPK3, and circSLC8A1 are circRNAs that have been related to the neurodegenerative process of PD. Gain-of-function and loss-of-function studies on circRNAs have shed light on their roles in the pathobiology of various diseases. Gain-of-function approaches typically employ viral or non-viral vectors that hyperexpress RNA sequences capable of circularizing to form the specific circRNA under investigation. In contrast, loss-of-function studies utilize CRISPR/Cas systems, antisense oligonucleotides (ASOs), or RNAi techniques to knock down the target circRNA. The role of aberrantly expressed circRNAs in brain pathology has raised a critical question: could circRNAs serve as viable targets for neuroprotective treatments? Translating any oligonucleotide-based therapy, including those targeting circRNAs, involves developing adequate brain delivery systems, minimizing off-target effects, and addressing the high costs of treatment. Nonetheless, RNAi-based FDA-approved drugs have entered the market, and circRNAs have attracted significant attention and investment from major pharmaceutical companies. Spanning from bench to bedside, circRNAs present a vast opportunity in biotechnology for oligonucleotide-based therapies designed to slow or even halt the progression of neurodegenerative diseases.

Effect and mechanism of circHMGA2 on ferroptosis and pyroptosis in myocardial ischemia-reperfusion model CircHMGA2 exacerbates MI/R injury

Myocardial ischemia-reperfusion (MI/R) injury is a common and serious complication following reperfusion treatment for myocardial infarction (MI). Increasing evidence has verified the crucial role of circular RNAs (circRNAs) in the MI/R injury processes. The objective of this study was to investigate the effects and potential regulatory mechanisms of circHMGA2 on MI/R injury. Hypoxia/reoxygenation (H/R) models were established using human cardiac myocytes (HCMs) and mice models were induced by MI/R. The level of circHMGA2 was detected by RT-qPCR. Myocardial function was evaluated by the hemodynamic parameters, the activity of serum myocardial enzymes, HE staining and TUNEL assays. Cell proliferation was measured by CCK-8 assay. The ferrous ion (Fe²⁺) level was determined with an iron assay kit. Ferroptosis- and pyroptosis-related proteins were determined using western blotting. The levels of oxidative stress and inflammatory factors were analyzed using DCFH-DA staining or ELISA assays. CircHMGA2 was upregulated in H/R-induced HCMs and myocardial tissues of MI/R mice. In vitro, circHMGA2 knockdown attenuated the proliferation inhibition, restrained the ferroptosis and pyroptosis in H/R-induced HCMs. This regulatory mechanism may be associated with the suppression of NLRP3 pathway. In vivo, circHMGA2 depletion attenuated myocardial tissue damage of MI/R mice through inhibiting the oxidative stress and pyroptosis. Taken together, CircHMGA2 enhanced MI/R injury via promoting ferroptosis and pyroptosis, providing new insights into the treatment of MI/R injury.

Circular RNA FEACR inhibits ferroptosis and alleviates myocardial ischemia/reperfusion injury by interacting with NAMPT

BACKGROUND

Emerging research has reported that circular RNAs (circRNAs) play important roles in cardiac cell death after myocardial ischemia and reperfusion (I/R). Ferroptosis, a new form of cell death discovered in recent years, has been proven to participate in the regulation of myocardial I/R. This study used circRNA sequencing to explore the key circRNA in the regulation of cardiac ferroptosis after I/R and study the mechanisms of potential circRNA function.

METHODS

We performed circRNA sequencing to explore circRNAs differentially expressed after myocardial I/R. We used quantitative polymerase chain reactions to determine the circRNA expression in different tissues and detect the circRNA subcellular localization in the cardiomyocyte. Gain- and loss-of-function experiments were aimed to examine the function of circRNAs in cardiomyocyte ferroptosis and cardiac tissue damage after myocardial I/R. RNA pull-down was applied to explore proteins interacting with circRNA.

RESULTS

Here, we identified a ferroptosis-associated circRNA (FEACR) that has an underlying regulatory role in cardiomyocyte ferroptosis. FEACR overexpression suppressed I/R-induced myocardial infarction and ameliorated cardiac function. FEACR inhibition induces ferroptosis in cardiomyocytes and FEACR overexpression inhibits hypoxia and reoxygenation-induced ferroptosis. Mechanistically, FEACR directly bound to nicotinamide phosphoribosyltransferase (NAMPT) and enhanced the protein stability of NAMPT, which increased NAMPT-dependent Sirtuin1 (Sirt1) expression, which promoted the transcriptional activity of forkhead box protein O1 (FOXO1) by reducing FOXO1 acetylation levels. FOXO1 further upregulated the transcription of ferritin heavy chain 1 (Fth1), a ferroptosis suppressor, which resulted in the inhibition of cardiomyocyte ferroptosis.

CONCLUSIONS

Our finding reveals that the circRNA FEACR-mediated NAMPT-Sirt1-FOXO1-FTH1 signaling axis participates in the regulation of cardiomyocyte ferroptosis and protects the heart function against I/R injury. Thus, FEACR and its downstream factors could be novel targets for alleviating ferroptosis-related myocardial injury in ischemic heart diseases.