N6-methyladenosine methyltransferase plays a role in hypoxic preconditioning partially through the interaction with lncRNA H19

A comprehensive review of m6 A methylation in coronary heart disease

The morbidity and mortality rates of coronary heart disease (CHD) are high worldwide. The primary pathological changes in CHD involve stenosis and ischemia caused by coronary atherosclerosis (AS). Extensive research on the pathogenesis of AS has revealed chronic immunoinflammatory processes and cell proliferation in all layers of coronary vessels, including endothelial cells (ECs), vascular smooth muscle cells, and macrophages. m6 A methylation is a common posttranscriptional modification of RNA that is coordinated by a variety of regulators (writers, readers, erasers) to maintain the functional stability of modified mRNAs and ncRNAs. In recent years, there has been increasing focus on the involvement of m6 A methylation in the incidence and progression of CHD, which starts with atherosclerotic plaque formation, leads to myocardial ischemia, and ultimately results in the occurrence of myocardial infarction (MI). m6 A regulators modulate relevant signaling pathways to participate in the inflammatory response, programmed death of cardiomyocytes, and fibrosis. Therefore, diagnostic models based on m6 A profiling are helpful for the early detection of CHD, and m6 A methylation shows promise as a sensitive target for new drugs to treat CHD in the future.

Recent Advances in the Mutual Regulation of m6A Modification and Non-Coding RNAs in Atherosclerosis

Atherosclerosis, a progressive inflammatory disease of the arteries, remains a leading cause of cardiovascular morbidity and mortality worldwide. Recent years have witnessed the pivotal role of N6-methyladenosine (m6A) RNA methylation in regulating various biological processes, including those implicated in atherosclerosis. Current evidence suggested that m6A regulators (writers, erasers, and readers) participated in the modification of multiple non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), thereby affecting their metabolism and functions. Meanwhile, ncRNAs have also emerged as key modulator of m6A regulators expression in turn. Therefore, understanding the mutual regulation between m6A modifications and ncRNAs is of great significance to identify novel therapeutic targets for atherosclerosis and has great clinical application prospects. This review aims to summarize the recent advances in the reciprocal regulation and provide insights into the interaction between m6A modification and ncRNAs in the context of atherosclerosis.

LncRNA UCA1 enhances NRF2 expression through the m6A pathway to mitigate oxidative stress and ferroptosis in aging cardiomyocytes

To explore the regulatory mechanism of lncRNA UCA1 and NRF2 in cardiomyocyte aging. In this study, we explored how lncRNA UCA1 regulates NRF2 and its effect on cardiomyocyte aging. H9c2 cardiomyocytes were cultured and treated with H2O2 to simulate cardiomyocyte aging in vitro. The expression levels of lncRNA UCA1 and NRF2 in cells were detected using qRT-PCR. Cell viability was assessed using the CCK8 assay, and cell aging was detected via Sa-β-gal staining. The levels of oxidative stress markers (SOD, MDA, ROS) and the expressions of ferroptosis-related proteins (ACSL4, TFR1, FTH1, GPX4) were measured. The regulatory mechanism between UCA1 and NRF2 was investigated using RIP-qPCR. Additionally, changes in m6A modification levels and the expression of m6A modification-related proteins in cells after UCA1 overexpression were analyzed by western blot. Our results indicate that H2O2 treatment significantly downregulated the expression of lncRNA UCA1 and NRF2. UCA1 overexpression promoted H9c2 cell proliferation, inhibited cell aging, increased SOD activity and the expression of FTH1 and GPX4 proteins, and decreased MDA and ROS content as well as ACSL4 and TFR1 protein expression. RIP-qPCR verified that UCA1 can promote the expression of NRF2 in cells. Overexpression of UCA1 significantly increased the expression of the demethylase FTO, leading to a reduction in m6A modification levels. Furthermore, there was significant enrichment between FTO and NRF2, and overexpression of FTO improved the expression of NRF2 protein in cells. Taken together, lncRNA UCA1 inhibits oxidative stress and ferroptosis, thereby preventing cardiomyocyte aging. This protective effect is likely mediated by increasing the expression of demethylase FTO and reducing m6A modification, which promotes the expression of NRF2.

M6A modification in cardiovascular disease: With a focus on programmed cell death

N6-methyladenosine (m6A) methylation is one of the most predominant internal RNA modifications in eukaryotes and has become a hot spot in the field of epigenetics in recent years. Cardiovascular diseases (CVDs) are a leading cause of death globally. Emerging evidence demonstrates that RNA modifications, such as the m6A modification, are associated with the development and progression of many diseases, including CVDs. An increasing body of studies has indicated that programmed cell death (PCD) plays a vital role in CVDs. However, the molecular mechanisms underlying m6A modification and PCD in CVDs remain poorly understood. Herein, elaborating on the highly complex connections between the m6A mechanisms and different PCD signaling pathways and clarifying the exact molecular mechanism of m6A modification mediating PCD have significant meaning in developing new strategies for the prevention and therapy of CVDs. There is great potential for clinical application.

Unravelling the impact of RNA methylation genetic and epigenetic machinery in the treatment of cardiomyopathy

Cardiomyopathy (CM) represents a heterogeneous group of diseases primarily affecting cardiac structure and function, with genetic and epigenetic dysregulation playing a pivotal role in its pathogenesis. Emerging evidence from the burgeoning field of epitranscriptomics has brought to light the significant impact of various RNA modifications, notably N6-methyladenosine (m6A), 5-methylcytosine (m5C), N7-methylguanosine (m7G), N1-methyladenosine (m1A), 2'-O-methylation (Nm), and 6,2'-O-dimethyladenosine (m6Am), on cardiomyocyte function and the broader processes of cardiac and vascular remodelling. These modifications have been shown to influence key pathological mechanisms including mitochondrial dysfunction, oxidative stress, cardiomyocyte apoptosis, inflammation, immune response, and myocardial fibrosis. Importantly, aberrations in the RNA methylation machinery have been observed in human CM cases and animal models, highlighting the critical role of RNA methylating enzymes and their potential as therapeutic targets or biomarkers for CM. This review underscores the necessity for a deeper understanding of RNA methylation processes in the context of CM, to illuminate novel therapeutic avenues and diagnostic tools, thereby addressing a significant gap in the current management strategies for this complex disease.

Risk of Fat Mass- and Obesity-Associated Gene-Dependent Obesogenic Programming by Formula Feeding Compared to Breastfeeding

It is the purpose of this review to compare differences in postnatal epigenetic programming at the level of DNA and RNA methylation and later obesity risk between infants receiving artificial formula feeding (FF) in contrast to natural breastfeeding (BF). FF bears the risk of aberrant epigenetic programming at the level of DNA methylation and enhances the expression of the RNA demethylase fat mass- and obesity-associated gene (FTO), pointing to further deviations in the RNA methylome. Based on a literature search through Web of Science, Google Scholar, and PubMed databases concerning the dietary and epigenetic factors influencing FTO gene and FTO protein expression and FTO activity, FTO's impact on postnatal adipogenic programming was investigated. Accumulated translational evidence underscores that total protein intake as well as tryptophan, kynurenine, branched-chain amino acids, milk exosomal miRNAs, NADP, and NADPH are crucial regulators modifying FTO gene expression and FTO activity. Increased FTO-mTORC1-S6K1 signaling may epigenetically suppress the WNT/β-catenin pathway, enhancing adipocyte precursor cell proliferation and adipogenesis. Formula-induced FTO-dependent alterations of the N6-methyladenosine (m6A) RNA methylome may represent novel unfavorable molecular events in the postnatal development of adipogenesis and obesity, necessitating further investigations. BF provides physiological epigenetic DNA and RNA regulation, a compelling reason to rely on BF.

Hypoxia triggers cardiomyocyte apoptosis via regulating the m6A methylation-mediated LncMIAT/miR-708-5p/p53 axis

Long-time hypoxia induced cardiomyocyte apoptosis is an important mechanism of myocardial ischemia (MI) injury. Interestingly, long noncoding RNA myocardial infarction-associated transcript (LncMIAT) has been involved in the regulation of MI injury; however, the underlying mechanism by which LncMIAT affects the progression of hypoxia-induced cardiomyocyte apoptosis remains unclear. In the present study, hypoxia was found to promote cardiomyocyte apoptosis through an increased expression of LncMIAT in vitro. Biological investigations and dual-luciferase gene reporter assay further revealed that LncMIAT was able to bind with miR-708-5p to upregulate the p53-mediated cell death of the cardiomyocytes. Silencing of LncMIAT or overexpression of miR-708-5p led to a significant reduction in p53-mediated cardiomyocyte apoptosis. The methylated RNA immunoprecipitation (MeRIP)-qPCR results showed that hypoxia exerted its effects on LncMIAT through AKLBH5-N6-methyladenosine (m6A) methylation and therefore hypoxia was shown to trigger HL-1 cardiomyocyte apoptosis via the m6A methylation-mediated LncMIAT/miR-708-5p/p53 axis. Silencing of AKLBH5 significantly alleviated the m6A methylation-mediated LncMIAT upregulation and p53-mediated cardiomyocyte apoptosis, while promoted miR-708-5p expression. Taken together, the present study highlighted that LncMIAT could act as a key biological target during hypoxia-induced cardiomyocyte apoptosis. In addition, it was shown that hypoxia could promote cardiomyocyte apoptosis through regulation of the m6A methylation-mediated LncMIAT/miR-708-5p/p53 signaling axis.

N6-Methyladenosine in Cell-Fate Determination of BMSCs: From Mechanism to Applications

The methylation of adenosine base at the nitrogen-6 position is referred to as "N6-methyladenosine (m6A)" and is one of the most prevalent epigenetic modifications in eukaryotic mRNA and noncoding RNA (ncRNA). Various m6A complex components known as "writers," "erasers," and "readers" are involved in the function of m6A. Numerous studies have demonstrated that m6A plays a crucial role in facilitating communication between different cell types, hence influencing the progression of diverse physiological and pathological phenomena. In recent years, a multitude of functions and molecular pathways linked to m6A have been identified in the osteogenic, adipogenic, and chondrogenic differentiation of bone mesenchymal stem cells (BMSCs). Nevertheless, a comprehensive summary of these findings has yet to be provided. In this review, we primarily examined the m6A alteration of transcripts associated with transcription factors (TFs), as well as other crucial genes and pathways that are involved in the differentiation of BMSCs. Meanwhile, the mutual interactive network between m6A modification, miRNAs, and lncRNAs was intensively elucidated. In the last section, given the beneficial effect of m6A modification in osteogenesis and chondrogenesis of BMSCs, we expounded upon the potential utility of m6A-related therapeutic interventions in the identification and management of human musculoskeletal disorders manifesting bone and cartilage destruction, such as osteoporosis, osteomyelitis, osteoarthritis, and bone defect.

m6A epitranscriptomic and epigenetic crosstalk in cardiac fibrosis

Cardiac fibrosis, a crucial pathological characteristic of various cardiac diseases, presents a significant treatment challenge. It involves the deposition of the extracellular matrix (ECM) and is influenced by genetic and epigenetic factors. Prior investigations have predominantly centered on delineating the substantial influence of epigenetic and epitranscriptomic mechanisms in driving the progression of fibrosis. Recent studies have illuminated additional avenues for modulating the progression of fibrosis, offering potential solutions to the challenging issues surrounding fibrosis treatment. In the context of cardiac fibrosis, an intricate interplay exists between m6A epitranscriptomic and epigenetics. This interplay governs various pathophysiological processes: mitochondrial dysfunction, mitochondrial fission, oxidative stress, autophagy, apoptosis, pyroptosis, ferroptosis, cell fate switching, and cell differentiation, all of which affect the advancement of cardiac fibrosis. In this comprehensive review, we meticulously analyze pertinent studies, emphasizing the interplay between m6A epitranscriptomics and partial epigenetics (including histone modifications and noncoding RNA), aiming to provide novel insights for cardiac fibrosis treatment.

Electroacupuncture Alleviates Cerebral Ischemia-reperfusion Injury by Regulating the S1PR2/TLR4/NLRP3 Signaling Pathway via m6A Methylation of lncRNA H19

Electroacupuncture (EA) treatment plays a protective role in cerebral ischemiareperfusion (CIR) injury. However, the underlying molecular mechanism is still not fully elucidated.

METHODS

All rats were randomly divided into five groups: the SHAM group, MCAO group, MCAO+EA (MEA) group, MCAO+METTL3 overexpression+EA (METTL3) group and MCAO+lncRNA H19 overexpression+EA (lncRNA H19) group. The middle cerebral artery occlusion (MCAO) rats were established to mimic CIR injury. The overexpression of lncRNA H19 and METTL3 was induced by stereotactic injection of lentiviruses into the rat lateral ventricles. The rats in the MEA, METTL3, and lncRNA H19 groups were treated with EA therapy on "Renzhong" (DU26) and "Baihui" (DU20) acupoints (3.85/6.25Hz; 1mA). Besides, the neurological deficit scoring, cerebral infarction area, pathological changes in brain tissue, total RNA m6A level, and the expression of METTL3, S1PR2, TLR4, NLRP3 and lncRNA H19 were detected in this experiment.

RESULTS

EA improved the neurological deficit scoring, cerebral infarction area, and pathological injury in MCAO rats, while these beneficial effects of EA on CIR injury were attenuated by the overexpression of METTL3 or lncRNA H19. More importantly, EA down-regulated the total RNA m6A level and the expression of METTL3, S1PR2, TLR4, NLRP3 and lncRNA H19 in MCAO rats. Instead, the overexpression of METTL3 or lncRNA H19 was found to reverse the EA-induced down-regulation.

CONCLUSION

The findings indicated that EA might down-regulate the S1PR2/TLR4/NLRP3 signaling pathway via m6A methylation of lncRNA H19 to alleviate CIR injury. Our findings provide a new insight into the molecular mechanism of EA on CIR injury.

Novel insights into the regulatory role of N6-methyladenosine methylation modified autophagy in sepsis

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. It is characterized by high morbidity and mortality and one of the major diseases that seriously hang over global human health. Autophagy is a crucial regulator in the complicated pathophysiological processes of sepsis. The activation of autophagy is known to be of great significance for protecting sepsis induced organ dysfunction. Recent research has demonstrated that N6-methyladenosine (m6A) methylation is a well-known post-transcriptional RNA modification that controls epigenetic and gene expression as well as a number of biological processes in sepsis. In addition, m6A affects the stability, export, splicing and translation of transcripts involved in the autophagic process. Although it has been suggested that m6A methylation regulates the biological metabolic processes of autophagy and is more frequently seen in the progression of sepsis pathogenesis, the underlying molecular mechanisms of m6A-modified autophagy in sepsis have not been thoroughly elucidated. The present article fills this gap by providing an epigenetic review of the processes of m6A-modified autophagy in sepsis and its potential role in the development of novel therapeutics.

Critical roles of m6A methylation in cardiovascular diseases

Cardiovascular diseases (CVDs) have been established as a major cause of mortality globally. However, the exact pathogenesis remains obscure. N6-methyladenosine (m⁶A) methylation is the most common epigenetic modification on mRNAs regulated by methyltransferase complexes (writers), demethylase transferases (erasers) and binding proteins (readers). It is now understood that m⁶A is a major player in physiological and pathological cardiac processes. m⁶A methylation are potentially involved in many mechanisms, for instance, regulation of calcium homeostasis, endothelial function, different forms of cell death, autophagy, endoplasmic reticulum stress, macrophage response and inflammation. In this review, we will summarize the molecular functions of m⁶A enzymes. We mainly focus on m⁶A-associated mechanisms and functions in CVDs, especially in heart failure and ischemia heart disease. We will also discuss the potential application and clinical transformation of m⁶A modification.

The significance of N6-methyladenosine-modified non-coding RNAs in different disorders

N6-methyladenosine (m6A) is the most widespread endogenous modification affecting the expression of eukaryotic mRNA transcripts. Recent studies have shown that the m6A marks within non-coding RNAs can affect their functions and expression in a manner similar to that of mRNA-coding genes. Since non-coding RNAs are involved in the pathophysiology of several disorders, identification of the role of m6A marks in the regulation of expression of non-coding RNAs can open a new era for identifying underlying mechanisms of several disorders and designing novel therapeutic modalities for a variety of disorders, particularly cancers. Moreover, a number of non-coding RNAs can affect m6A levels. In the current review, we discuss the impacts of m6A marks on the expression of non-coding RNAs in the context of different disorders, such as bone, gastrointestinal, neurologic, renal, pulmonary, hepatic and other disorders.

METTL3-mediated long non-coding RNA MIR99AHG methylation targets miR-4660 to promote bone marrow mesenchymal stem cell osteogenic differentiation

Whether long non-coding RNA Mir-99a-Let-7c Cluster Host Gene (LncRNA MIR99AHG) is involved in osteoporosis (OP) remains vague, so we hereby center on its implication. Old C57BL/6J mice were injected with the silencing lentivirus of MIR99AHG and subjected to microCT analysis and immunohistochemistry on osteogenic cells. The osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) with or without transfection was determined by alkaline phosphatase (ALP) and Alizarin Red S staining. Total N(6)-methyladenosine (m6A) on the bone marrow mesenchymal stem cells (BMSCs) was quantified. The potential methylation site and the complementary binding sites with candidate microRNA (miR) were predicted via bioinformatic analyses, with the latter being confirmed via dual-luciferase reporter, RNA immunoprecipitation and RNA pull-down assays. Quantitative real-time PCR and Western blot were used for quantification assays. MIR99AHG was decreased during the osteogenic differentiation of BMSCs, where increased Osterix (OSX), Collagen, Type I, Alpha 1 (Col1A1), Osteocalcin (OCN) and RUNX Family Transcription Factor 2 (RUNX2) as well as more color-stained areas were found. Also, silencing MIR99AHG relieved the OP in mice and reduced the loss of osteogenic cells. M6A methylation in undifferentiated BMSCs was low and MIR99AHG overexpression abolished the effects of overexpressed METTL3 on promoting osteogenic differentiation. MiR-4660, which was downregulated in BMSCs without differentiation but increased during osteogenic differentiation, could bind with MIR99AHG. Furthermore, miR-4660 promoted osteogenic differentiation and reversed the effects of overexpressed MIR99AHG. The present study demonstrated that METTL3-mediated LncRNA MIR99AHG methylation enhanced the osteogenic differentiation of BMSCs via targeting miR-4660.

N6-methyladenosine in macrophage function: a novel target for metabolic diseases

N6-methyladenosine (m⁶A) is one of the most prevalent internal transcriptional modifications. Evidence has highlighted changes in m⁶A in metabolic disorders and various metabolic diseases. However, the precise mechanisms of these m⁶A changes in such conditions are not understood. Macrophages are crucial for the innate immune system and exert either beneficial or harmful roles in metabolic disease. Notably, m⁶A was found to be closely related to macrophage phenotype and dysfunction. In this review, we summarize m⁶A in macrophage function from the perspective of macrophage development, activation, and polarization, pyroptosis, and metabolic disorders. Furthermore, we discuss how m⁶A-mediated macrophage function affects metabolic diseases, including atherosclerosis and nonalcoholic fatty liver disease (NAFLD). Finally, we discuss challenges and prospects for m⁶A in macrophage and metabolic diseases with the aim of providing guidance for the treatment of metabolic diseases.

Emerging roles of the RNA modifications N6-methyladenosine and adenosine-to-inosine in cardiovascular diseases

Cardiovascular diseases lead the mortality and morbidity disease metrics worldwide. A multitude of chemical base modifications in ribonucleic acids (RNAs) have been linked with key events of cardiovascular diseases and metabolic disorders. Named either RNA epigenetics or epitranscriptomics, the post-transcriptional RNA modifications, their regulatory pathways, components, and downstream effects substantially contribute to the ways our genetic code is interpreted. Here we review the accumulated discoveries to date regarding the roles of the two most common epitranscriptomic modifications, N6-methyl-adenosine (m6A) and adenosine-to-inosine (A-to-I) editing, in cardiovascular disease.

N(6)-methyladenosine modification: A vital role of programmed cell death in myocardial ischemia/reperfusion injury

N(6)-methyladenosine (m⁶A) modification is closely associated with myocardial ischemia/reperfusion injury (MIRI). As the most common modification among RNA modifications, the reversible m⁶A modification is processed by methylase ("writers") and demethylase ("erasers"). The biological effects of RNA modified by m⁶A are regulated under the corresponding RNA binding proteins (RBPs) ("readers"). m⁶A modification regulates the whole process of RNA, including transcription, processing, splicing, nuclear export, stability, degradation, and translation. Programmed cell death (PCD) is a regulated mechanism that maintains the internal environment's stability. PCD plays an essential role in MIRI, including apoptosis, autophagy, pyroptosis, ferroptosis, and necroptosis. However, the relationship between PCD modified with m⁶A and MIRI is still not clear. This review summarizes the regulators of m⁶A modification and their bioeffects on PCD in MIRI.

m6A RNA methylation: A dynamic regulator of cardiac muscle and extracellular matrix

Post-transcriptional modifications encompass a large group of RNA alterations that control gene expression. Methylation of the N⁶-Adenosine (m⁶A) of mRNA is a prevalent modification which alters the life cycle of transcripts. The roles that m⁶A play in regulating cardiac homeostasis and injury response are an active area of investigation, but it is clear that this chemical modification is a critical controller of fibroblast to myofibroblast transition, cardiomyocyte hypertrophy and division, and the structure and function of the extracellular matrix. Here we discuss the latest findings of m⁶A in cardiac muscle and matrix.

LncRNA H19 inhibits oxidative stress injury of cochlear hair cells by regulating miR-653-5p/SIRT1 axis

Oxidative stress is one of the important mechanisms of inner ear cell damage, which can lead to age-related hearing loss (ARHL). LncRNA H19 is significantly downregulated in the cochlea of old mouse, however, the role of H19 in the development of ARHL remains unclear. In this study, we aim to investigate the expression and function of H19 in oxidative stress injury of cochlear hair cells induced by HO. RT-qPCR and western blot analysis confirms that HEI-OC1 cells stimulated with HO decreases the expressions of H19 and SIRT1, but increases the expression of miR-653-5p. Overexpression of H19 could increase cell viability, ATP level and mitochondrial membrane potential, but reduce mitochondrial ROS generation and cell apoptosis ratio in HO-stimulated HEI-OC1 cells. MiR-653-5p is a target of H19, which can bind to the 3'-UTR of SIRT1. H19 is found to regulate the expression of SIRT1 through miR-653-5p. Further experiments demonstrates that H19 regulates HEI-OC1 cell viability, ATP level, mitochondrial membrane potential, mitochondrial ROS generation, and cell apoptosis ratio via the miR-653-5p/SIRT1 axis. In conclusion, lncRNA H19 inhibits oxidative stress injury of cochlear hair cells via the miR-653-5p/SIRT1 axis.

Long Non-Coding RNA Epigenetics

Long noncoding RNAs exceeding a length of 200 nucleotides play an important role in ensuring cell functions and proper organism development by interacting with cellular compounds such as miRNA, mRNA, DNA and proteins. However, there is an additional level of lncRNA regulation, called lncRNA epigenetics, in gene expression control. In this review, we describe the most common modified nucleosides found in lncRNA, 6-methyladenosine, 5-methylcytidine, pseudouridine and inosine. The biosynthetic pathways of these nucleosides modified by the writer, eraser and reader enzymes are important to understanding these processes. The characteristics of the individual methylases, pseudouridine synthases and adenine-inosine editing enzymes and the methods of lncRNA epigenetics for the detection of modified nucleosides, as well as the advantages and disadvantages of these methods, are discussed in detail. The final sections are devoted to the role of modifications in the most abundant lncRNAs and their functions in pathogenic processes.

RNA modifications in cardiovascular diseases, the potential therapeutic targets

More than one hundred RNA modifications decorate the chemical and topological properties of these ribose nucleotides, thereby executing their biological functions through post-transcriptional regulation. In cardiovascular diseases, a wide range of RNA modifications including m⁶A (N6-adenosine methylation), m⁵C (5-methylcytidin), Nm (2'-O-ribose-methylation), Ψ (pseudouridine), m⁷G (N7-methylguanosine), and m¹A (N1-adenosine methylation) have been found in tRNA, rRNA, mRNA and other noncoding RNA, which can function as a novel mechanism in metabolic syndrome, heart failure, coronary heart disease, and hypertension. In this review, we will summarize the current understanding of the regulatory roles and significance of several types of RNA modifications in CVDs (cardiovascular diseases) and the interplay between RNA modifications and noncoding RNA, epigenetics. Finally, we will focus on the potential therapeutic strategies by using RNA modifications.