The N6-Methyladenosine mRNA Methylase METTL3 Controls Cardiac Homeostasis and Hypertrophy

Vascular wall microenvironment: Endothelial cells original exosomes mediated melatonin-suppressed vascular calcification and vascular ageing in a m6A methylation dependent manner

Vascular calcification and vascular ageing are "silent" diseases but are highly prevalent in patients with end stage renal failure and type 2 diabetes, as well as in the ageing population. Melatonin (MT) has been shown to induce cardiovascular protection effects. However, the role of MT on vascular calcification and ageing has not been well-identified. In this study, the aortic transcriptional landscape revealed clues for MT related cell-to-cell communication between endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) in vascular calcification and vascular ageing. Furthermore, we elucidated that it was exosomes that participate in the information transportation from ECs to VSMCs. The exosomes secreted from melatonin-treated ECs (MT-ECs-Exos) inhibited calcification and senescence of VSMCs. Mechanistically, miR-302d-5p was highly enriched in MT-ECs-Exos, while depletion of miR-302d-5p blocked the ability of MT-ECs-Exos to suppress VSMC calcification and senescence. Notably, Wnt3 was a bona fide target of miR-302d-5p and modulated VSMC calcification and senescence. Furthermore, we found that maturation of endothelial derived exosomal miR-302d-5p was promoted by WTAP in an N6-methyladenosine (m6A)-dependent manner. Interestingly, MT alleviated vascular calcification and ageing in 5/6-nephrectomy (5/6 NTP) mice, a chronic kidney disease (CKD) induced vascular calcification and vascular ageing mouse model. MT-ECs-Exos was absorbed by VSMCs in vivo and effectively prevented vascular calcification and ageing in 5/6 NTP mice. ECs-derived miR-302d-5p mediated MT induced anti-calcification and anti-ageing effects in 5/6 NTP mice. Our study suggests that MT-ECs-Exos alleviate vascular calcification and ageing through the miR-302d-5p/Wnt3 signaling pathway, dependent on m6A methylation.

Molecular mechanism of Wilms tumour 1-associated protein in diabetes-related dry eye disease by mediating m6A methylation modification of lncRNA NEAT1

Background: Dry eye disease (DED) is often secondary to diabetes mellitus (DM).Purpose: This study is to explore the action of Wilms tumor 1-associated protein (WTAP) in DM-DED via lncRNA NEAT1 m6A methylation.Methods: DM-DED mouse models were treated with sh-WTAP/sh-NEAT1, followed by assessment of corneal epithelial damage/histopathological changes. HCE-2 cells were exposed to hyperosmotic conditions to establish in vitro DED models and treated with oe-NEAT1/sh-NEAT1/sh-WTAP/nigericin (an NLRP3 inflammasome inducer). Cell viability/apoptosis were evaluated by CCK-8/TUNEL. Levels of WTAP/NEAT1/inflammatory factors/NLRP3 inflammasome- and apoptosis-related markers were determined. m6A modification was examined by MeRIP-qPCR and NEAT1 stability was also detected.Results: DM-DED mice exhibited up-regulated WTAP/NEAT1 expression and severe corneal damage, whereas WTAP/NEAT1 knockdown alleviated inflammation/corneal damage. In hyperosmolarity-induced HCE-2 cells, NEAT1 aggravated inflammation and apoptosis, while NEAT1 knockdown suppressed NLRP3 inflammasome activation and ameliorated cell injury. Hyperosmolarity-induced WTAP expression increased m6A modification and NEAT1 mRNA stability. WTAP mediated m6A methylation of NEAT1 and NLRP3 inflammasome activation in DM-DED mice.

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.

The role of m6A modification in cardiovascular disease: A systematic review and integrative analysis

BACKGROUND AND AIMS

This study focused on the recent advancements in understanding the association between N6-methyladenosine (m6A) modification and cardiovascular disease (CVD).

METHODS

The potential mechanisms of m6A related to CVD were summarized by literature review. Associations between m6A levels and CVD were explored across 8 electronic databases: PubMed, Embase, Web of Science, Cochrane Library, Sinomed, Wan Fang, CNKI, and Vip. Standard mean difference (SMD) and 95 % confidence interval (95 % CI) were calculated to assess the total effect in integrated analysis.

RESULTS

The systematic review summarized previous studies on the association between m6A modification and CVD, highlighting the potential role of m6A in CVD progression. A total of 11 studies were included for integrative analysis. The mean m6A levels were significantly higher in CVD than those in normal controls (SMD = 1.86, 95 % CI: 0.16-3.56, P < 0.01).

CONCLUSIONS

This systematic review provided new targets for early detection and treatment for CVD. And the integrated analysis showed that increased level of m6A was associated with CVD.

Epigenetic regulation of cardiovascular diseases induced by behavioral and environmental risk factors: Mechanistic, diagnostic, and therapeutic insights

Behavioral and environmental risk factors are critical in the development and progression of cardiovascular disease (CVD). Understanding the molecular mechanisms underlying these risk factors will offer valuable insights for targeted preventive and therapeutic strategies. Epigenetic modifications, including DNA methylation, histone modifications, chromatin remodeling, noncoding RNA (ncRNA) expression, and epitranscriptomic modifications, have emerged as key mediators connecting behavioral and environmental risk factors to CVD risk and progression. These epigenetic alterations can profoundly impact on cardiovascular health and susceptibility to CVD by influencing cellular processes, development, and disease risk over an individual's lifetime and potentially across generations. This review examines how behavioral and environmental risk factors affect CVD risk and health outcomes through epigenetic regulation. We review the epigenetic effects of major behavioral risk factors (such as smoking, alcohol consumption, physical inactivity, unhealthy diet, and obesity) and environmental risk factors (including air and noise pollution) in the context of CVD pathogenesis. Additionally, we explore epigenetic biomarkers, considering their role as causal or surrogate indicators, and discuss epigenetic therapeutics targeting the mechanisms through which these risk factors contribute to CVD. We also address future research directions and challenges in leveraging epigenetic insights to reduce the burden of CVD related to behavioral and environmental factors and improve public health outcomes. This review aims to provide a comprehensive understanding of behavioral and environmental epigenetics in CVD and offer valuable strategies for therapeutic intervention.

m6A reader YTHDF2 governs the onset of atrial fibrillation by modulating Cacna1c translation

Atrial fibrillation (AF) is the most common arrhythmia, which is tightly associated with the abnormal expression and function of ion channels in the atrial cardiomyocytes. N6-methyladenosine (m6A), a widespread chemical modification in eukaryotic mRNA, is known to play a significant regulatory role in the pathogenesis of heart disease. However, the significance of m6A regulatory proteins in the onset of AF remains unclear. Here, we demonstrate that the m6A reader protein YTHDF2 regulates atrial electrical remodeling and AF onset by modulating the Cav1.2 expression. Firstly, YTHDF2 expression was selectively upregulated in rat atrial cardiomyocytes with AF. Secondly, YTHDF2 knockout reduced AF susceptibility in mice. Thirdly, the knockout of YTHDF2 increased Cav1.2 protein levels in an m6A-in-dependent manner, ultimately prolonging the atrial myocardial refractory period, a critical electrophysiological substrate for the onset of AF. Fourthly, the N-terminal domain of YTHDF2 was identified as critical for Cacna1c mRNA translation regulation. Overall, our findings unveil that YTHDF2 can alter Cav1.2 protein expression in an m6A-independent manner, thereby facilitating the onset of AF. Our study suggests that YTHDF2 may be a potential intervention target for AF.

Mettl1 knockdown alleviates cardiac I/R injury in mice by inactivating the Mettl1-CYLD-P53 positive feedback loop

The N7-methylguanosine (m7G) methyltransferase Mettl1 has been recently implicated in cardiac repair and fibrosis. In this study we investigated the role of Mettl1 in mouse cardiomyocytes injury and the underlying mechanisms. Cardiac ischemia/reperfusion (I/R) I/R model was established in mice by ligation of the left anterior descending coronary artery (LAD) for 45 min followed by reperfusion for 24 h. We showed the mRNA and protein levels of Mettl1 were significantly upregulated in mouse I/R hearts and H2O2-treated neonatal mouse cardiomyocytes (NMCMs). Mettl1 knockdown markedly ameliorated cardiac I/R injury, evidenced by decreased infarct size, apoptosis, and improved cardiac function. Overexpression of Mettl1 triggered cardiomyocytes apoptosis in vivo and in vitro. By performing RNA sequencing combined with m7G methylated RNA sequencing in Mettl1-overexpressing mouse hearts, we revealed that Mettl1 catalyzed m7G modification of the deubiquitinase cylindromatosis (CYLD) mRNA to increase the expression of CYLD, which enhanced the stability of P53 via abrogating its ubiquitination degradation. Vice versa, P53 served as a transcriptional factor to positively regulate Mettl1 expression during I/R injury. Knockdown of CYLD mitigated cardiomyocytes apoptosis induced by Mettl1 overexpression or oxidative stress. From the available drug-targets databases and literature, we identified 4 small molecule inhibitors of m7G modification. Sinefungin, one of the Mettl1 inhibitors exerted profound protection against cardiac I/R injury in vivo and in vitro. Collectively, this study has identified Mettl1 as a key regulator of cardiomyocyte apoptosis, and targeting the Mettl1-CYLD-P53 positive feedback circuit may represent a novel therapeutic avenue for alleviating cardiac I/R injury.

Screening of key genes related to M6A methylation in patients with heart failure

OBJECTIVE

This study aims to identify m6A methylation-related and immune cell-related key genes with diagnostic potential for heart failure (HF) by leveraging various bioinformatics techniques.

METHODS

The GSE116250 and GSE141910 datasets were sourced from the Gene Expression Omnibus (GEO) database. Correlation analysis was conducted between differentially expressed genes (DEGs) in HF and control groups, alongside differential m6A regulatory factors, to identify m6A-related DEGs (m6A-DEGs). Subsequently, candidate genes were narrowed down by intersecting key module genes derived from weighted gene co-expression network analysis (WGCNA) with m6A-DEGs. Key genes were then identified through the Least Absolute Shrinkage and Selection Operator (LASSO) analysis. Correlation analyses between key genes and differentially expressed immune cells were performed, followed by the validation of key gene expression levels in public datasets. To ensure clinical applicability, five pairs of blood samples were collected for quantitative real-time fluorescence PCR (qRT-PCR) validation.

RESULTS

A total of 93 m6A-DEGs were identified (|COR| > 0.6, P < 0.05), and five key genes (LACTB2, NAMPT, SCAMP5, HBA1, and PRKAR2A) were selected for further analysis. Correlation analysis revealed that differential immune cells were negatively associated with the expression of LACTB2, NAMPT, and PRKAR2A (P < 0.05), while positively correlated with SCAMP5 and HBA1 (P < 0.05). Subsequent expression validation confirmed significant differences in key gene expression between the HF and control groups, with consistent expression trends observed across both training and validation sets. The expression trends of LACTB2, PRKAR2A, and HBA1 in blood samples from the qRT-PCR assay aligned with the results derived from public databases.

CONCLUSION

This study successfully identified five m6A methylation-related key genes with diagnostic significance, providing a theoretical foundation for further exploration of m6A methylation's molecular mechanisms in HF.

Loss of NAT10 Reduces the Translation of Kmt5a mRNA Through ac4C Modification in Cardiomyocytes and Induces Heart Failure

BACKGROUND

In the past decade, the biological functions of various RNA modifications in mammals have been uncovered. N4-acetylcytidine (ac4C), a highly conserved RNA modification, has been implicated in human diseases. Despite this, the involvement of RNA ac4C modification in cardiac physiology and pathology remains incompletely understood. NAT10 (N-acetyltransferase 10) stands as the sole acetyltransferase known to catalyze RNA ac4C modification. This study aims to explore the role of NAT10 and ac4C modification in cardiac physiology and pathology.

METHODS AND RESULTS

Cardiac-specific knockout of NAT10, leading to reduced RNA ac4C modification, during both neonatal and adult stages resulted in severe heart failure. NAT10 deficiency induced cardiomyocyte apoptosis, a crucial step in heart failure pathogenesis, supported by in vitro data. Activation of the p53 signaling pathway was closely associated with enhanced apoptosis in NAT10-deficient cardiomyocytes. As ac4C modification on mRNA influences translational efficiency, we employed ribosome footprints coupled with RNA sequencing to explore genome-wide translational efficiency changes caused by NAT10 deficiency. We identified and validated that the translational efficiency of Kmt5a was suppressed in NAT10 knockout hearts due to reduced ac4C modification on its mRNA. This finding was consistent with the observation that Kmt5a protein levels were reduced in heart failure despite unchanged mRNA expression. Knockdown of Kmt5a in cardiomyocytes recapitulated the phenotype of NAT10 deficiency, including increased cardiomyocyte apoptosis and activated p53 signaling. Finally, overexpression of Kmt5a rescued cardiomyocyte apoptosis and p53 activation induced by NAT10 inhibition.

CONCLUSIONS

Our study highlights the significance of NAT10 in cardiomyocyte physiology, demonstrating that NAT10 loss is sufficient to induce cardiomyocyte apoptosis and heart failure. NAT10 regulates the translational efficiency of Kmt5a, a key mediator, through mRNA ac4C modification during heart failure.

m6A control programmed cell death in cardiac fibrosis

N6-methyladenosine (m6A) modification is closely related to cardiac fibrosis. As the most common and abundant form of mRNA modification in eukaryotes, m6A is deposited by methylases ("writers"), recognized and effected by RNA-binding proteins ("readers"), and removed by demethylases ("erasers"), achieving highly dynamic reversibility. m6A modification is involved in regulating the entire biological process of target RNA, including transcription, processing and splicing, export from the nucleus to the cytoplasm, and enhancement or reduction of stability and translation. Programmed cell death (PCD) comprises many forms and pathways, with apoptosis and autophagy being the most common. Other forms include pyroptosis, ferroptosis, necroptosis, mitochondrial permeability transition (MPT)-dependent necrosis, and parthanatos. In recent years, increasing evidence suggests that m6A modification can mediate PCD, affecting cardiac fibrosis. Since the correlation between some PCD types and m6A modification is not yet clear, this article mainly introduces the relationship between four common PCD types (apoptosis, autophagy, pyroptosis, and ferroptosis) and m6A modification, as well as their role and influence in cardiac fibrosis.

Methyl-Transferase-Like Protein 16 (METTL16): The Intriguing Journey of a Key Epitranscriptomic Player Becoming an Emerging Biological Target

Key epitranscriptomic players have been increasingly characterized for their structural features and their involvement in several diseases. Accordingly, the design and synthesis of novel epitranscriptomic modulators have started opening a glimmer for drug discovery. m6A is a reversible modification occurring on a specific site and is catalyzed by three sets of proteins responsible for opposite functions. Writers (e.g., methyl-transferase-like protein (METTL) 3/METTL14 complex and METTL16) introduce the methyl group on adenosine N-6, by transferring the methyl group from the methyl donor S-adenosyl-methionine (SAM) to the substrate. Despite the rapidly advancing drug discovery progress on METTL3/METTL14, the METTL16 m6A writer has been marginally explored so far. We herein provide the first comprehensive overview of structural and biological features of METTL16, highlighting the state of the art in the field of its biological and structural characterization. We also showcase initial efforts in the identification of structural templates and preliminary structure-activity relationships for METTL16 modulators.

METTL3-mediated m6A modification of OTUD1 aggravates press overload induced myocardial hypertrophy by deubiquitinating PGAM5

Background: Pathological cardiac hypertrophy, a condition that contributes to heart failure, is characterized by its intricate pathogenesis. The meticulous regulation of protein function, localization, and degradation is a crucial role played by deubiquitinating enzymes in cardiac pathophysiology. This study clarifies the participation and molecular mechanism of OTUD1 (OTU Deubiquitinase 1) in pathological cardiac hypertrophy. Methods: We generated a cardiac-specific Otud1 knockout mouse line (Otud1-CKO) and adeno-associated virus serotype 9-Otud1 mice to determine the role of Otud1 in cardiac hypertrophy. Its impact on cardiomyocytes enlargement was investigated using the adenovirus. RNA immunoprecipitation was used to validate the specific m6a methyltransferase interacted with OTUD1 transcript. RNA sequencing in conjunction with immunoprecipitation-mass spectrometry analysis was employed to identify the direct targets of OTUD1. A series of depletion mutant plasmids were constructed to detect the interaction domain of OTUD1 and its targets. Results: Ang II-stimulated neonatal rat cardiac myocytes and mice hearts subjected to transverse aortic constriction (TAC) showed increased protein levels of Otud1. Cardiac hypertrophy and dysfunction were less frequent in Otud1-CKO mice during TAC treatment, while Otud1 overexpression worsened cardiac hypertrophy and remodeling. METTL3 mediated m6A modification of OTUD1 transcript promoted mRNA stability and elevated protein expression. In terms of pathogenesis, Otud1 plays a crucial role in cardiac hypertrophy by targeting Pgam5, leading to the robust activation of the Ask1-p38/JNK signal pathway to accelerate cardiac hypertrophy. Significantly, the pro-hypertrophy effects of Otud1 overexpression were largely eliminated when Ask1 knockdown. Conclusion: Our findings confirm that targeting the OTUD1-PGAM5 axis holds significant potential as a therapeutic approach for heart failure associated with pathological hypertrophy.

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.

The Biological Mechanisms and Clinical Roles of RNA-Binding Proteins in Cardiovascular Diseases

RNA-binding proteins (RBPs) have pivotal roles in cardiovascular biology, influencing various molecular mechanisms underlying cardiovascular diseases (CVDs). This review explores the significant roles of RBPs, focusing on their regulation of RNA alternative splicing, polyadenylation, and RNA editing, and their impact on CVD pathogenesis. For instance, RBPs are crucial in myocardial injury, contributing to disease progression and repair mechanisms. This review systematically analyzes the roles of RBPs in myocardial injury, arrhythmias, myocardial infarction, and heart failure, revealing intricate interactions that influence disease outcomes. Furthermore, the potential of RBPs as therapeutic targets for cardiovascular dysfunction is explored, highlighting the advances in drug development and clinical research. This review also discusses the emerging role of RBPs as biomarkers for cardiovascular diseases, offering insights into their diagnostic and prognostic potential. Despite significant progress, current research faces several limitations, which are critically examined. Finally, this review identifies the major challenges and outlines future research directions to advance the understanding and application of RBPs in cardiovascular medicine.

Single-cell transcriptomics reveals writers of RNA modification-mediated immune microenvironment and cardiac resident Macro-MYL2 macrophages in heart failure

BACKGROUND

Heart failure (HF), which is caused by cardiac overload and injury, is linked to significant mortality. Writers of RNA modification (WRMs) play a crucial role in the regulation of epigenetic processes involved in immune response and cardiovascular disease. However, the potential roles of these writers in the immunological milieu of HF remain unknown.

METHODS

We comprehensively characterized the expressions of 28 WRMs using datasets GSE145154 and GSE141910 to map the cardiac immunological microenvironment in HF patients. Based on the expression of WRMs, the immunological cells in the datasets were scored.

RESULTS

Single-cell transcriptomics analysis (GSE145154) revealed immunological dysregulation in HF as well as differential expression of WRMs in immunological cells from HF and non-HF (NHF) samples. WRM-scored immunological cells were positively correlated with the immunological response, and the high WRM score group exhibited elevated immunological cell infiltration. WRMs are involved in the differentiation of T cells and myeloid cells. WRM scores of T cell and myeloid cell subtypes were significantly reduced in the HF group compared to the NHF group. We identified a myogenesis-related resident macrophage population in the heart, Macro-MYL2, that was characterized by an increased expression of cardiomyocyte structural genes (MYL2, TNNI3, TNNC1, TCAP, and TNNT2) and was regulated by TRMT10C. Based on the WRM expression pattern, the transcriptomics data (GSE141910) identified two distinct clusters of HF samples, each with distinct functional enrichments and immunological characteristics.

CONCLUSION

Our study demonstrated a significant relationship between the WRMs and immunological microenvironment in HF, as well as a novel resident macrophage population, Macro-MYL2, characterized by myogenesis. These results provide a novel perspective on the underlying mechanisms and therapeutic targets for HF. Further experiments are required to validate the regulation of WRMs and Macro-MYL2 macrophage subtype in the cardiac immunological milieu.

The potential of RNA methylation in the treatment of cardiovascular diseases

RNA methylation has emerged as a dynamic regulatory mechanism that impacts gene expression and protein synthesis. Among the known RNA methylation modifications, N6-methyladenosine (m6A), 5-methylcytosine (m5C), 3-methylcytosine (m3C), and N7-methylguanosine (m7G) have been studied extensively. In particular, m6A is the most abundant RNA modification and has attracted significant attention due to its potential effect on multiple biological processes. Recent studies have demonstrated that RNA methylation plays an important role in the development and progression of cardiovascular disease (CVD). To identify key pathogenic genes of CVD and potential therapeutic targets, we reviewed several common RNA methylation and summarized the research progress of RNA methylation in diverse CVDs, intending to inspire effective treatment strategies.

Peptide Degrader-Based Targeting of METTL3/14 Improves Immunotherapy Response in Cutaneous Melanoma

METTL3 has emerged as a promising therapeutic target in cancer treatment, although its oncogenic functions in melanoma development and potential for therapeutic targeting drug have not been fully explored. In this study, we define the oncogenic role of METTL3 in melanoma development and progression. Building on this insight, we examine our recently designed peptide inhibitor RM3, which targets the binding interface of METTL3/14 complex for disruption and subsequent ubiquitin-mediated proteasomal degradation via the E3 ligase STUB1. RM3 treatment reduces proliferation, migration, and invasion, and induces apoptosis in melanoma cells in vitro and in vivo. Subsequent transcriptomic analysis identified changes in immuno-related genes following RM3-mediated suppression of METTL3/14 N6-methyladenosine (m6A) methyltransferase activity, suggesting a potential for interaction with immunotherapy. A combination treatment of RM3 with anti-PD-1 antibody results in significantly higher beneficial tumor response in vivo, with a good safety profile. Collectively, these findings not only delineate the oncogenic role of METTL3 in melanoma but also showcase RM3, acting as a peptide degrader, as a novel and promising strategy for melanoma treatment.

Endogenous RBM4 prevents Ang II-induced cardiomyocyte hypertrophy via downregulating the expression of PTBP1

Aberrant gene expression in cardiomyocyte has been revealed to be the fundamental essence of pathological cardiac hypertrophy. However, the detailed mechanisms are not fully understood. The underlying regulators of gene expression involved in cardiac hypertrophy remain to be further identified. Here, we report that the RNA-binding protein RNA-binding motif protein 4 (RBM4) functions as an endogenic protector that is able to fight against cardiomyocyte hypertrophy in vitro. Under pro-hypertrophic stimulation of angiotensin II (Ang II), the protein level of RBM4 in cardiomyocyte and myocardium is elevated. Knockdown of RBM4 can further aggravate cardiomyocyte hypertrophy, while over-expression of RBM4 represses cardiomyocyte hypertrophy. Mechanistically, RBM4 is localized in the nucleus and down-regulates the expression of polypyrimidine tract-binding protein 1 (PTBP1), which has been shown to aggravate cardiomyocyte hypertrophy. In addition, we suggest that the up-regulation of RBM4 in cardiomyocyte hypertrophy is caused by N6-methyladenosine (m6A). Ang II induces m6A methylation of RBM4 mRNA, which further enhances the YTH domain-containing family protein 1 (YTHDF1)-mediated translation of RBM4. Thus, our results reveal a novel pathway consisting of m6A, RBM4 and PTBP1, which is involved in cardiomyocyte hypertrophy.

Recent advances of PIWI-interacting RNA in cardiovascular diseases

BACKGROUND

The relationship between noncoding RNAs (ncRNAs) and human diseases has been a hot topic of research, but the study of ncRNAs in cardiovascular diseases (CVDs) is still in its infancy. PIWI-interacting RNA (piRNA), a small ncRNA that binds to the PIWI protein to maintain genome stability by silencing transposons, was widely studied in germ lines and stem cells. In recent years, piRNA has been shown to be involved in key events of multiple CVDs through various epigenetic modifications, revealing the potential value of piRNA as a new biomarker or therapeutic target.

CONCLUSION

This review explores origin, degradation, function, mechanism and important role of piRNA in CVDs, and the promising therapeutic targets of piRNA were summarized. This review provide a new strategy for the treatment of CVDs and lay a theoretical foundation for future research.

KEY POINTS

piRNA can be used as a potential therapeutic target and biomaker in CVDs. piRNA influences apoptosis, inflammation and angiogenesis by regulating epigenetic modificaions. Critical knowledge gaps remain in the unifying piRNA nomenclature and PIWI-independent function.

The m7G Methyltransferase Mettl1 Drives Cardiac Hypertrophy by Regulating SRSF9-Mediated Splicing of NFATc4

Cardiac hypertrophy is a key factor driving heart failure (HF), yet its pathogenesis remains incompletely elucidated. Mettl1-catalyzed RNA N7-methylguanosine (m7G) modification has been implicated in ischemic cardiac injury and fibrosis. This study aims to elucidate the role of Mettl1 and the mechanism underlying non-ischemic cardiac hypertrophy and HF. It is found that Mettl1 is upregulated in human failing hearts and hypertrophic murine hearts following transverse aortic constriction (TAC) and Angiotensin II (Ang II) infusion. YY1 acts as a transcriptional factor for Mettl1 during cardiac hypertrophy. Mettl1 knockout alleviates cardiac hypertrophy and dysfunction upon pressure overload from TAC or Ang II stimulation. Conversely, cardiac-specific overexpression of Mettl1 results in cardiac remodeling. Mechanically, Mettl1 increases SRSF9 expression by inducing m7G modification of SRSF9 mRNA, facilitating alternative splicing and stabilization of NFATc4, thereby promoting cardiac hypertrophy. Moreover, the knockdown of SRSF9 protects against TAC- or Mettl1-induced cardiac hypertrophic phenotypes in vivo and in vitro. The study identifies Mettl1 as a crucial regulator of cardiac hypertrophy, providing a novel therapeutic target for HF.

RNA epigenetic modifications in digestive tract cancers: Friends or foes

Digestive tract cancers are among the most common malignancies worldwide and have high incidence and mortality rates. Thus, the discovery of more effective diagnostic and therapeutic targets is urgently required. The development of technologies to accurately detect RNA modification has led to the identification of numerous RNA chemical modifications in humans (epitranscriptomics) that are involved in the occurrence and development of digestive tract cancers. RNA modifications can cooperatively regulate gene expression to facilitate normal physiological functions of the digestive system. However, the dysfunction of relevant RNA-modifying enzymes ("writers," "erasers," and "readers") can lead to the development of digestive tract cancers. Consequently, targeting dysregulated enzyme activity could represent a potent therapeutic strategy for the treatment of digestive tract cancers. In this review, we summarize the most widely studied roles and mechanisms of RNA modifications (m6A, m1A, m5C, m7G, A-to-I editing, pseudouridine [Ψ]) in relation to digestive tract cancers, highlight the crosstalk between RNA modifications, and discuss their roles in the interactions between the digestive system and microbiota during carcinogenesis. The clinical significance of novel therapeutic methods based on RNA-modifying enzymes is also discussed. This review will help guide future research into digestive tract cancers that are resistant to current therapeutics.

YTHDF1 is pivotal for maintenance of cardiac homeostasis

The YTH-domain family (YTHDF) of RNA binding proteins can control gene expression at the post-transcriptional level by regulating mRNAs with N6-methyladenosine (m6A) modifications. Despite the established importance of m6A in the heart, the cardiac role of specific m6A-binding proteins remains unclear. Here, we characterized the function of YTHDF1 in cardiomyocytes using a newly generated cardiac-restricted mouse model. Deletion of YTHDF1 in adult cardiomyocytes led to hypertrophy, fibrosis, and dysfunction. Using mass spectrometry, we identified the necessity of YTHDF1 for the expression of cardiomyocyte membrane raft proteins. Specifically, YTHDF1 bound to m6A-modified Caveolin 1 (Cav1) mRNA and favored its translation. We further demonstrated that YTHDF1 regulates downstream ERK signaling. Altogether, our findings highlight a novel role for YTHDF1 as a post-transcriptional regulator of caveolar proteins which is necessary for the maintenance of cardiac function.

N6-Methyladenosine in Vascular Aging and Related Diseases: Clinical Perspectives

Aging leads to progressive deterioration of the structure and function of arteries, which eventually contributes to the development of vascular aging-related diseases. N6-methyladenosine (m6A) is the most prevalent modification in eukaryotic RNAs. This reversible m6A RNA modification is dynamically regulated by writers, erasers, and readers, playing a critical role in various physiological and pathological conditions by affecting almost all stages of the RNA life cycle. Recent studies have highlighted the involvement of m6A in vascular aging and related diseases, shedding light on its potential clinical significance. In this paper, we comprehensively discuss the current understanding of m6A in vascular aging and its clinical implications. We discuss the molecular insights into m6A and its association with clinical realities, emphasizing its significance in unraveling the mechanisms underlying vascular aging. Furthermore, we explore the possibility of m6A and its regulators as clinical indicators for early diagnosis and prognosis prediction and investigate the therapeutic potential of m6A-associated anti-aging approaches. We also examine the challenges and future directions in this field and highlight the necessity of integrating m6A knowledge into patient-centered care. Finally, we emphasize the need for multidisciplinary collaboration to advance the field of m6A research and its clinical application.

Systemic aging fuels heart failure: Molecular mechanisms and therapeutic avenues

Systemic aging influences various physiological processes and contributes to structural and functional decline in cardiac tissue. These alterations include an increased incidence of left ventricular hypertrophy, a decline in left ventricular diastolic function, left atrial dilation, atrial fibrillation, myocardial fibrosis and cardiac amyloidosis, elevating susceptibility to chronic heart failure (HF) in the elderly. Age-related cardiac dysfunction stems from prolonged exposure to genomic, epigenetic, oxidative, autophagic, inflammatory and regenerative stresses, along with the accumulation of senescent cells. Concurrently, age-related structural and functional changes in the vascular system, attributed to endothelial dysfunction, arterial stiffness, impaired angiogenesis, oxidative stress and inflammation, impose additional strain on the heart. Dysregulated mechanosignalling and impaired nitric oxide signalling play critical roles in the age-related vascular dysfunction associated with HF. Metabolic aging drives intricate shifts in glucose and lipid metabolism, leading to insulin resistance, mitochondrial dysfunction and lipid accumulation within cardiomyocytes. These alterations contribute to cardiac hypertrophy, fibrosis and impaired contractility, ultimately propelling HF. Systemic low-grade chronic inflammation, in conjunction with the senescence-associated secretory phenotype, aggravates cardiac dysfunction with age by promoting immune cell infiltration into the myocardium, fostering HF. This is further exacerbated by age-related comorbidities like coronary artery disease (CAD), atherosclerosis, hypertension, obesity, diabetes and chronic kidney disease (CKD). CAD and atherosclerosis induce myocardial ischaemia and adverse remodelling, while hypertension contributes to cardiac hypertrophy and fibrosis. Obesity-associated insulin resistance, inflammation and dyslipidaemia create a profibrotic cardiac environment, whereas diabetes-related metabolic disturbances further impair cardiac function. CKD-related fluid overload, electrolyte imbalances and uraemic toxins exacerbate HF through systemic inflammation and neurohormonal renin-angiotensin-aldosterone system (RAAS) activation. Recognizing aging as a modifiable process has opened avenues to target systemic aging in HF through both lifestyle interventions and therapeutics. Exercise, known for its antioxidant effects, can partly reverse pathological cardiac remodelling in the elderly by countering processes linked to age-related chronic HF, such as mitochondrial dysfunction, inflammation, senescence and declining cardiomyocyte regeneration. Dietary interventions such as plant-based and ketogenic diets, caloric restriction and macronutrient supplementation are instrumental in maintaining energy balance, reducing adiposity and addressing micronutrient and macronutrient imbalances associated with age-related HF. Therapeutic advancements targeting systemic aging in HF are underway. Key approaches include senomorphics and senolytics to limit senescence, antioxidants targeting mitochondrial stress, anti-inflammatory drugs like interleukin (IL)-1β inhibitors, metabolic rejuvenators such as nicotinamide riboside, resveratrol and sirtuin (SIRT) activators and autophagy enhancers like metformin and sodium-glucose cotransporter 2 (SGLT2) inhibitors, all of which offer potential for preserving cardiac function and alleviating the age-related HF burden.

ALKBH5 induces fibroblast-to-myofibroblast transformation during hypoxia to protect against cardiac rupture after myocardial infarction

INTRODUCTION

N6-methyladenosine (m6A) methylation produces a marked effect on cardiovascular diseases. The m6A demethylase AlkB homolog 5 (ALKBH5), as an m6A "eraser", is responsible for decreased m6A modification. However, its role in cardiac fibroblasts during the post-myocardial infarction (MI) healing process remains elusive.

OBJECTIVES

To investigate the effect of ALKBH5 in cardiac fibroblasts during infarct repair.

METHODS

MI was mimicked by permanent left anterior descending artery ligation in global ALKBH5-knockout, ALKBH5-knockin, and fibroblast-specific ALKBH5-knockout mice to study the function of ALKBH5 during post-MI collagen repair. Methylated RNA immunoprecipitation sequencing was performed to explore potential ALKBH5 targets.

RESULTS

Dramatic alterations in ALKBH5 expression were observed during the early stages post-MI and in hypoxic fibroblasts. Global ALKBH5 knockin reduced infarct size and ameliorated cardiac function after MI. The global and fibroblast-specific ALKBH5-knockout mice both exhibited low survival rates along with poor collagen repair, impaired cardiac function, and cardiac rupture. Both in vivo and in vitro ALKBH5 loss resulted in impaired fibroblast activation and decreased collagen deposition. Additionally, hypoxia, but not TGF-β1 or Ang II, upregulated ALKBH5 expression in myofibroblasts by HIF-1α-dependent transcriptional regulation. Mechanistically, ALKBH5 promoted the stability of ErbB4 mRNA and the degradation of ST14 mRNA via m6A demethylation. Fibroblast-specific ErbB4 overexpression ameliorated the impaired fibroblast-to-myofibroblast transformation and poor post-MI repair due to ALKBH5 knockout.

CONCLUSION

Fibroblast ALKBH5 positively regulates post-MI healing by stabilization of ErbB4 mRNA in an m6A-dependent manner. ALKBH5/ErbB4 might be potential therapeutic targets for post-MI cardiac rupture.

Liquid-liquid phase separation in diseases

Liquid-liquid phase separation (LLPS), an emerging biophysical phenomenon, can sequester molecules to implement physiological and pathological functions. LLPS implements the assembly of numerous membraneless chambers, including stress granules and P-bodies, containing RNA and protein. RNA-RNA and RNA-protein interactions play a critical role in LLPS. Scaffolding proteins, through multivalent interactions and external factors, support protein-RNA interaction networks to form condensates involved in a variety of diseases, particularly neurodegenerative diseases and cancer. Modulating LLPS phenomenon in multiple pathogenic proteins for the treatment of neurodegenerative diseases and cancer could present a promising direction, though recent advances in this area are limited. Here, we summarize in detail the complexity of LLPS in constructing signaling pathways and highlight the role of LLPS in neurodegenerative diseases and cancers. We also explore RNA modifications on LLPS to alter diseases progression because these modifications can influence LLPS of certain proteins or the formation of stress granules, and discuss the possibility of proper manipulation of LLPS process to restore cellular homeostasis or develop therapeutic drugs for the eradication of diseases. This review attempts to discuss potential therapeutic opportunities by elaborating on the connection between LLPS, RNA modification, and their roles in diseases.

Insights into the role of RNA m6A modification in the metabolic process and related diseases

According to the latest consensus, many traditional diseases are considered metabolic diseases, such as cancer, type 2 diabetes, obesity, and cardiovascular disease. Currently, metabolic diseases are increasingly prevalent because of the ever-improving living standards and have become the leading threat to human health. Multiple therapy methods have been applied to treat these diseases, which improves the quality of life of many patients, but the overall effect is still unsatisfactory. Therefore, intensive research on the metabolic process and the pathogenesis of metabolic diseases is imperative. N6-methyladenosine (m6A) is an important modification of eukaryotic RNAs. It is a critical regulator of gene expression that is involved in different cellular functions and physiological processes. Many studies have indicated that m6A modification regulates the development of many metabolic processes and metabolic diseases. In this review, we summarized recent studies on the role of m6A modification in different metabolic processes and metabolic diseases. Additionally, we highlighted the potential m6A-targeted therapy for metabolic diseases, expecting to facilitate m6A-targeted strategies in the treatment of metabolic diseases.

The m6A methyltransferase METTL3 drives neuroinflammation and neurotoxicity through stabilizing BATF mRNA in microglia

Persistent neuroinflammation and progressive neuronal loss are defining features of acute brain injury including traumatic brain injury (TBI) and cerebral stroke. Microglia, the most abundant type of brain-resident immune cells, continuously surveil the environment and play a central role in shaping the inflammatory state of the central nervous system (CNS). In the study, we discovered that the protein expression of METTL3 (a m6A methyltransferase) was upregulated in inflammatory microglia independent of increased Mettl3 gene transcription following TBI in both human and mouse subjects. Subsequently, we identified TRIP12, a HECT-domain E3 ubiquitin ligase, as a negative regulator of METTL3 protein expression by facilitating METTL3 K48-linked polyubiquitination. Importantly, selective ablation of Mettl3 inhibited microglial pathogenic activities, diminished neutrophil infiltration, rescued neuronal loss and facilitated functional recovery post-TBI. Using MeRIP-seq and CUT&Tag sequencing, we identified that METTL3 promoted the expression of Basic Leucine Zipper Transcriptional Factor ATF-Like (BATF), which in turn directly bound to a cohort of characteristic inflammatory cytokines and chemokine genes. Enhanced activities of BATF in microglia elicited TNF-dependent neurotoxicity and can also promote neutrophil recruitment through releasing CXCL2. Pharmacological inhibition of METTL3 using a BBB-penetrating drug-loaded nano-system showed satisfactory therapeutic effects in both TBI and stroke mouse models. Collectively, our findings identified METTL3-m6A-BATF axis as a potential therapeutic target for terminating detrimental neuroinflammation and progressive neuronal loss following acute brain injury. METTL3 protein is significantly up-regulated in inflammatory microglia due to the decreased proteasomal degradation mediated by TRIP12 and ERK-USP5 pathways. METTL3 stabilized BATF mRNA stability and promoted BATF expression through the m6A-IGF2BP2-dependent mechanism. Elevated expression of BATF elicits a pro-inflammatory gene program in microglia, and aggravates neuroinflammatory response including local immune responses and peripheral immune cell infiltration. Genetic deletion or pharmaceutically targeting METTL3-BATF axis suppressed microglial pro-inflammatory activities and promoted neurological recovery following TBI and stroke.

m6A epitranscriptomic modification of inflammation in cardiovascular disease

Cardiovascular disease is currently the number one cause of death endangering human health. There is currently a large body of research showing that the development of cardiovascular disease and its complications is often accompanied by inflammatory processes. In recent years, epitranscriptional modifications have been shown to be involved in regulating the pathophysiological development of inflammation in cardiovascular diseases, with 6-methyladenine being one of the most common RNA transcriptional modifications. In this review, we link different cardiovascular diseases, including atherosclerosis, heart failure, myocardial infarction, and myocardial ischemia-reperfusion, with inflammation and describe the regulatory processes involved in RNA methylation. Advances in RNA methylation research have revealed the close relationship between the regulation of transcriptome modifications and inflammation in cardiovascular diseases and brought potential therapeutic targets for disease diagnosis and treatment. At the same time, we also discussed different cell aspects. In addition, in the article we also describe the different application aspects and clinical pathways of RNA methylation therapy. In summary, this article reviews the mechanism, regulation and disease treatment effects of m6A modification on inflammation and inflammatory cells in cardiovascular diseases in recent years. We will discuss issues facing the field and new opportunities that may be the focus of future research.

RNA-binding proteins in cardiovascular biology and disease: the beat goes on

Cardiac development and function are becoming increasingly well understood from different angles, including signalling, transcriptional and epigenetic mechanisms. By contrast, the importance of the post-transcriptional landscape of cardiac biology largely remains to be uncovered, building on the foundation of a few existing paradigms. The discovery during the past decade of hundreds of additional RNA-binding proteins in mammalian cells and organs, including the heart, is expected to accelerate progress and has raised intriguing possibilities for better understanding the intricacies of cardiac development, metabolism and adaptive alterations. In this Review, we discuss the progress and new concepts on RNA-binding proteins and RNA biology and appraise them in the context of common cardiovascular clinical conditions, from cell and organ-wide perspectives. We also discuss how a better understanding of cardiac RNA-binding proteins can fill crucial knowledge gaps in cardiology and might pave the way to developing better treatments to reduce cardiovascular morbidity and mortality.

RNA-mediated epigenetic regulation in exercised heart: Mechanisms and opportunities for intervention

Physical exercise has been widely acknowledged as a beneficial lifestyle alteration and a potent non-pharmacological treatment for heart disease. Extensive investigations have revealed the beneficial effects of exercise on the heart and the underlying mechanisms involved. Exercise is considered one of the key factors that can lead to epigenetic alterations. The increasing number of identified molecules in the exercised heart has led to many studies in recent years that have explored the cellular function of ncRNAs and RNA modifications in the heart. Investigating the regulatory role of RNA-mediated epigenetic regulation in exercised hearts will contribute to the development of therapeutic strategies for the management of heart diseases. This review aims to summarize the positive impact of exercise on cardiac health. We will first provide an overview of the mechanisms through which exercise offers protection to the heart. Subsequently, we will delve into the current understanding of ncRNAs, specifically miRNAs, lncRNAs, and circRNAs, as well as RNA modification, focusing on RNA m6A and RNA A-to-I editing, and how they contribute to exercise-induced benefits for the heart. Lastly, we will explore the emerging therapeutic strategies that utilize exercise-mediated RNA epigenetic regulation in the treatment of heart diseases, while also addressing the challenges faced in this field.

Upregulation of eIF2α by m6A modification accelerates the proliferation of pulmonary artery smooth muscle cells in MCT-induced pulmonary arterial hypertension rats

Pulmonary arterial hypertension (PAH) is a malignant cardiovascular disease. Eukaryotic initiation factor 2α (eIF2α) plays an important role in the proliferation of pulmonary artery smooth muscle cells (PASMCs) in hypoxia-induced pulmonary hypertension (HPH) rats. However, the regulatory mechanism of eIF2α remains poorly understood in PAH rats. Here, we discover eIF2α is markedly upregulated in monocrotaline (MCT)-induced PAH rats, eIF2α can be upregulated by mRNA methylation, and upregulated eIF2α can promote PASMC proliferation in MCT-PAH rats. GSK2606414, eIF2α inhibitor, can downregulate the expression of eIF2α and alleviate PASMC proliferation in MCT-PAH rats. And we further discover the mRNA of eIF2α has a common sequence with N 6-methyladenosine (m6A) modification by bioinformatics analysis, and the expression of METTL3, WTAP, and YTHDF1 is upregulated in MCT-PAH rats. These findings suggest a potentially novel mechanism by which eIF2α is upregulated by m6A modification in MCT-PAH rats, which is involved in the pathogenesis of PAH.

Inhibition of METTL3 ameliorates doxorubicin-induced cardiotoxicity through suppression of TFRC-mediated ferroptosis

BACKGROUND

Doxorubicin (DOX) is a chemotherapeutic drug, while its clinical use is greatly limited by the life-threatening cardiotoxicity. N6-methyladenosine (m6A) RNA modification participates in varieties of cellular processes. Nonetheless, it remains elusive whether m6A modification and its methyltransferase METTL3 are involved in the progression of DOX-induced cardiotoxicity (DIC).

METHODS

Mice were administrated with DOX (accumulative dosage of 20 mg/kg) repeatedly to establish a chronic DIC model. Cardiomyocyte-specific conditional METTL3 knockout mice were employed to evaluate the effects of altered m6A RNA modification on DIC. The effects of METTL3 on cardiomyocyte ferroptosis were also examined in response to DOX stimulation.

RESULTS

DOX led to increased levels in m6A modification and METTL3 expression in cardiomyocytes in a c-Jun-dependent manner. METTL3-knockout mice exhibited improved cardiac function, remodeling and injury following DOX insult. Besides, inhibition of METTL3 alleviated DOX-induced iron accumulation and ferroptosis in cardiomyocytes, whereas METTL3 overexpression exerted the opposite effects. Mechanistically, METTL3 promoted m6A modification of TFRC mRNA, a critical gene governing iron uptake, and enhanced its stability through recognition of the m6A reader protein, IGF2BP2. Moreover, pharmacological administration of a highly selective METTL3 inhibitor STM2457 effectively ameliorated DIC in mice.

CONCLUSION

METTL3 plays a cardinal role in the etiology of DIC by regulating cardiac iron metabolism and ferroptosis through TFRC m6A modification. Inhibition of METTL3 might be a potential therapeutic avenue for DIC.

The m6A methylation enzyme METTL14 regulates myocardial ischemia/reperfusion injury through the Akt/mTOR signaling pathway

Herein, we investigated the role of the m6A methylation enzyme METTL14 in regulating myocardial ischemia/reperfusion injury (IR/I) through the Akt/mTOR signaling pathway and related biological mechanisms. Enzyme-linked immunosorbent assay (ELISA) and fluorescence quantitative polymerase chain reaction (qPCR) were performed to detect the m6A mRNA and METTL3, METTL14, WTAP, and KIAA1429 levels in a mouse myocardial IR/I model. An oxygen-glucose deprivation/reperfusion (OGD/R) model was constructed by transfecting neonatal rat cardiomyocytes (NRCM) with METTL14-knockdown lentivirus. METTL14, Bax, and cleaved-caspase3 mRNA expression levels were detected using fluorescence qPCR. Apoptosis was detected using TUNEL staining. After the IR/I surgery following the adeno-associated virus injection, the METTL14 mRNA and apoptosis-related BAX/BCL2 protein expression was detected using fluorescence qPCR and western blotting, respectively. Degree of cell necrosis was detected using an LDH assay. The oxidative stress response of the myocardial tissue was detected, and IL-6 and IL-1β serum levels were detected using ELISAs. The mice injected with METTL14-knockdown AAV9 adeno-associated virus underwent IR/I surgery after the injection of an Akt/mTOR pathway inhibitor (MK2206) into the myocardial layer. Elevated mRNA m6A modification and m6A methyltransferase METTL14 levels were observed in the IR/I-injured mouse heart tissues. METTL14 knockdown significantly inhibited the OGD/R- and IR/I-induced apoptosis and necrosis in cardiac myocytes, inhibited IR/I-induced oxidative stress and inflammatory factor secretion, and activated the Akt/ mTOR pathway in vitro and in vivo. Akt/mTOR pathway inhibition significantly attenuated the alleviating effect of METTL14 knockdown on myocardial IR/I injury-induced apoptosis. Knocking down m6A methylase METTL14 inhibits IR/I-induced myocardial apoptosis and necrosis, inhibits myocardial oxidative stress and secretion of inflammatory cytokines, and activates the Akt/mTOR signaling pathway. Hence, METTL14 regulated myocardial apoptosis and necrosis in mice with IR/I through the Akt/mTOR signaling pathway.

RNA binding proteins as mediators of pathological cardiac remodeling

RNA binding proteins (RBPs) play a central in the post-transcriptional regulation of gene expression, which can account for up to 50% of all variations in protein expression within a cell. Following their binding to target RNAs, RBPs most typically confer changes in gene expression through modulation of alternative spicing, RNA stabilization/degradation, or ribosome loading/translation rate. All of these post-transcriptional regulatory processes have been shown to play a functional role in pathological cardiac remodeling, and a growing body of evidence is beginning to identify the mechanistic contribution of individual RBPs and their cardiac RNA targets. This review highlights the mechanisms of RBP-dependent post-transcriptional gene regulation in cardiomyocytes and fibroblasts and our current understanding of how RNA binding proteins functionally contribute to pathological cardiac remodeling.

AVCAPIR: A Novel Procalcific PIWI-Interacting RNA in Calcific Aortic Valve Disease

BACKGROUND

Calcification of the aortic valve leads to increased leaflet stiffness and consequently results in the development of calcific aortic valve disease (CAVD). However, the underlying molecular and cellular mechanisms of calcification remain unclear. Here, we identified a novel aortic valve calcification-associated PIWI-interacting RNA (piRNA; AVCAPIR) that increases valvular calcification and promotes CAVD progression.

METHODS

Using piRNA sequencing, we identified piRNAs contributing to the pathogenesis of CAVD that we termed AVCAPIRs. High-cholesterol diet-fed ApoE-/- mice with AVCAPIR knockout were used to examine the role of AVCAPIR in aortic valve calcification (AVC). Gain- and loss-of-function assays were conducted to determine the role of AVCAPIR in the induced osteogenic differentiation of human valvular interstitial cells. To dissect the mechanisms underlying AVCAPIR-elicited procalcific effects, we performed various analyses, including an RNA pulldown assay followed by liquid chromatography-tandem mass spectrometry, methylated RNA immunoprecipitation sequencing, and RNA sequencing. RNA pulldown and RNA immunoprecipitation assays were used to study piRNA interactions with proteins.

RESULTS

We found that AVCAPIR was significantly upregulated during AVC and exhibited potential diagnostic value for CAVD. AVCAPIR deletion markedly ameliorated AVC in high-cholesterol diet-fed ApoE-/- mice, as shown by reduced thickness and calcium deposition in the aortic valve leaflets, improved echocardiographic parameters (decreased peak transvalvular jet velocity and mean transvalvular pressure gradient, as well as increased aortic valve area), and diminished levels of osteogenic markers (Runx2 and Osterix) in aortic valves. These results were confirmed in osteogenic medium-induced human valvular interstitial cells. Using unbiased protein-RNA screening and molecular validation, we found that AVCAPIR directly interacts with FTO (fat mass and obesity-associated protein), subsequently blocking its N6-methyladenosine demethylase activity. Further transcriptomic and N6-methyladenosine modification epitranscriptomic screening followed by molecular validation confirmed that AVCAPIR hindered FTO-mediated demethylation of CD36 mRNA transcripts, thus enhancing CD36 mRNA stability through the N6-methyladenosine reader IGF2BP1 (insulin-like growth factor 2 mRNA binding protein 1). In turn, the AVCAPIR-dependent increase in CD36 stabilizes its binding partner PCSK9 (proprotein convertase subtilisin/kexin type 9), a procalcific gene, at the protein level, which accelerates the progression of AVC.

CONCLUSIONS

We identified a novel piRNA that induced AVC through an RNA epigenetic mechanism and provide novel insights into piRNA-directed theranostics in CAVD.

RBM15 Protects From Myocardial Infarction by Stabilizing NAE1

RNA-binding proteins play multiple roles in several biological processes. However, the roles of RBM15-an important RNA-binding protein and a significant regulator of RNA methylation-in cardiovascular diseases remain elusive. This study aimed to investigate the biological function of RBM15 and its fundamental mechanisms in myocardial infarction (MI). Methylated RNA immunoprecipitation sequencing was used to explore the N6-methyladenosine (m6A) difference between MI and normal tissues. Our findings showed the elevated level of m6A in MI, and its transcription profile in both MI and normal tissues. RBM15 was the main regulator and its overexpression attenuated apoptosis in cardiomyocytes and improved cardiac function in mice after MI. Then, we used one target NEDD8 activating enzyme E1 subunit and its inhibitor (MLN4924) to investigate the impact of RBM15 targets on cardiomyocytes. Finally, the enhanced m6A methylation in the presence of RBM15 overexpression led to the increased expression and stability of NEDD8 activating enzyme E1 subunit. Our findings suggest that the enhanced m6A level is a protective mechanism in MI, and RBM15 is significantly upregulated in MI and promotes cardiac function. This study showed that RBM15 affected MI by stabilizing its target on the cell apoptosis function, which might provide a new insight into MI therapy.

Sex-based differences in short- and longer-term diet-induced metabolic heart disease

Sex-based differences in the development of obesity-induced cardiometabolic dysfunction are well documented, however, the specific mechanisms are not completely understood. Obesity has been linked to dysregulation of the epitranscriptome, but the role of N6-methyladenosine (m6A) RNA methylation has not been investigated in relation to the sex differences during obesity-induced cardiac dysfunction. In the current study, male and female C57BL/6J mice were subjected to short- and long-term high-fat/high-sucrose (HFHS) diet to induce obesogenic stress. Cardiac echocardiography showed males developed systolic and diastolic dysfunction after 4 mo of diet, but females maintained normal cardiac function despite both sexes being metabolically dysfunctional. Cardiac m6A machinery gene expression was differentially regulated by duration of HFHS diet in male, but not female mice, and left ventricular ejection fraction correlated with RNA machinery gene levels in a sex- and age-dependent manner. RNA-sequencing of cardiac transcriptome revealed that females, but not males may undergo protective cardiac remodeling early in the course of obesogenic stress. Taken together, our study demonstrates for the first time that cardiac RNA methylation machinery genes are regulated early during obesogenic stress in a sex-dependent manner and may play a role in the sex differences observed in cardiometabolic dysfunction.NEW & NOTEWORTHY Sex differences in obesity-associated cardiomyopathy are well documented but incompletely understood. We show for the first time that RNA methylation machinery genes may be regulated in response to obesogenic diet in a sex- and age-dependent manner and levels may correspond to cardiac systolic function. Our cardiac RNA-seq analysis suggests female, but not male mice may be protected from cardiac dysfunction by a protective cardiac remodeling response early during obesogenic stress.

N6-methyladenosine in myeloid cells: a novel regulatory factor for inflammation-related diseases

N6-methyladenosine (m6A) is one of the most abundant epitranscriptomic modifications on eukaryotic mRNA. Evidence has highlighted that m6A is altered in response to inflammation-related factors and it is closely associated with various inflammation-related diseases. Multiple subpopulations of myeloid cells, such as macrophages, dendritic cells, and granulocytes, are crucial for the regulating of immune process in inflammation-related diseases. Recent studies have revealed that m6A plays an important regulatory role in the functional of multiple myeloid cells. In this review, we comprehensively summarize the function of m6A modification in myeloid cells from the perspective of myeloid cell production, activation, polarization, and migration. Furthermore, we discuss how m6A-mediated myeloid cell function affects the progression of inflammation-related diseases, including autoimmune diseases, chronic metabolic diseases, and malignant tumors. Finally, we discuss the challenges encountered in the study of m6A in myeloid cells, intended to provide a new direction for the study of the pathogenesis of inflammation-related diseases.

Lipotoxicity as a therapeutic target in obesity and diabetic cardiomyopathy

Unhealthy sources of fats, ultra-processed foods with added sugars, and a sedentary lifestyle make humans more susceptible to developing overweight and obesity. While lipids constitute an integral component of the organism, excessive and abnormal lipid accumulation that exceeds the storage capacity of lipid droplets disrupts the intracellular composition of fatty acids and results in the release of deleterious lipid species, thereby giving rise to a pathological state termed lipotoxicity. This condition induces endoplasmic reticulum stress, mitochondrial dysfunction, inflammatory responses, and cell death. Recent advances in omics technologies and analytical methodologies and clinical research have provided novel insights into the mechanisms of lipotoxicity, including gut dysbiosis, epigenetic and epitranscriptomic modifications, dysfunction of lipid droplets, post-translational modifications, and altered membrane lipid composition. In this review, we discuss the recent knowledge on the mechanisms underlying the development of lipotoxicity and lipotoxic cardiometabolic disease in obesity, with a particular focus on lipotoxic and diabetic cardiomyopathy.

Epitranscriptomic Regulations in the Heart

RNA modifications affect key stages of the RNA life cycle, including splicing, export, decay, and translation. Epitranscriptomic regulations therefore significantly influence cellular physiology and pathophysiology. Here, we selected some of the most abundant modifications and reviewed their roles in the heart and in cardiovascular diseases: N6-methyladenosine (m6A), N6,2'-O-dimethyladenosine (m6Am), N1-methyladenosine (m1A), pseudouridine (?), 5 methylcytidine (m5C), and inosine (I). Dysregulation of epitranscriptomic machinery affecting these modifications vastly changes the cardiac phenotype and is linked with many cardiovascular diseases such as myocardial infarction, cardiomyopathies, or heart failure. Thus, a deeper understanding of these epitranscriptomic changes and their regulatory mechanisms can enhance our knowledge of the molecular underpinnings of prevalent cardiac diseases, potentially paving the way for novel therapeutic strategies. Keywords: Epitranscriptomics, RNA modifications, Epigenetics, m6A, RNA, Heart.

Silencing of METTL3 suppressed ferroptosis of myocardial cells by m6A modification of SLC7A11 in a YTHDF2 manner

Myocardial infarction (MI) is the main cause of heart failure (HF). N6-methyladenosine (m6A) methylation is associated with the progression of HF. The study aimed to explore whether METTL3 regulates ferroptosis of cardiomyocytes in HF. We evaluated ferroptosis by detecting lactic dehydrogenase (LDH) release, lipid reactive oxygen species (ROS), Fe2+, glutathione (GSH), and malonaldehyde (MDA) levels. M6A methylation was assessed using methylated RNA immunoprecipitation assay. The binding relationship was assessed using RNA immunoprecipitation assays. The mRNA stability was assessed using actinomycin D treatment. The results showed that METTL3 was upregulated in oxygen glucose deprivation/recovery (OGD/R) cells, which knockdown suppressed OGD/R-induced ferroptosis. Moreover, METTL3 could bind to SLC7A11, promoting m6A methylation of SLC7A11. Silencing of SLC7A11 abrogated the suppression of ferroptosis induced by METTL3 knockdown. Additionally, YTHDF2 was the reader that recognized the methylation of SLC7A11, reducing the stability of SLC7A11. The silencing of METTL3 inhibited OGD/R-induced ferroptosis by suppressing the m6A methylation of SLC7A11, which is recognized by YTHDF2. The findings suggested that METTL3-mediated ferroptosis might be a new strategy for MI-induced HF therapy.

Unlocking the dark matter: noncoding RNAs and RNA modifications in cardiac aging

Cardiac aging is a multifaceted process that encompasses structural and functional alterations culminating in heart failure. As the elderly population continues to expand, there is a growing urgent need for interventions to combat age-related cardiac functional decline. Noncoding RNAs have emerged as critical regulators of cellular and biochemical processes underlying cardiac disease. This review summarizes our current understanding of how noncoding RNAs function in the heart during aging, with particular emphasis on mechanisms of RNA modification that control their activity. Targeting noncoding RNAs as potential novel therapeutics in cardiac aging is also discussed.

Downregulation of Wtap causes dilated cardiomyopathy and heart failure

RNA binding proteins have been shown to regulate heart development and cardiac diseases. However, the detailed molecular mechanisms is not known. In this study, we identified Wilms' tumor 1-associating protein (WTAP, a key regulatory protein of the m6A RNA methyltransferase complex) as a key regulator of heart function and cardiac diseases. WTAP is associated with heart development, and its expression is downregulated in both human and mice with heart failure. Cardiomyocyte-specific knockout of Wtap (Wtap-CKO) induces dilated cardiomyopathy, heart failure and neonatal death. Although WTAP deficiency in the heart decreases METTL3 (methyltransferase-like 3) protein levels, cardiomyocyte-specific overexpression of Mettl3 in Wtap-CKO mice does not rescue the phenotypes of Wtap-CKO mice. Instead, WTAP deficiency in the heart decreases chromatin accessibility in the promoter regions of Mef2a (myocyte enhancer factor-2α) and Mef2c, leading to reduced mRNA and protein levels of these genes and lower expression of their target genes. Conversely, WTAP directly binds to the promoter of the Mef2c gene and increases its promoter luciferase activity and expression. These data demonstrate that WTAP plays a key role in heart development and cardiac function by maintaining the chromatin accessibility of cardiomyocyte specific genes.

Suxiao Jiuxin Pill alleviates myocardial ischemia/reperfusion-induced autophagy via miR-193a-3p/ALKBH5 pathway

BACKGROUND

Myocardial ischemia/reperfusion injury (MIRI) poses a formidable challenge to cardiac reperfusion therapy due to the absence of effective clinical interventions. Methylation of N6-methyladenosine (m6A), which is the most common post-transcriptional modifications occurring within mammalian mRNA, is believed to be involved in MIRI by modulating autophagy. MicroRNAs (miRNAs) play a crucial role in regulating gene expression at the post-transcriptional level and have been implicated in the regulation of m6A methylation. Suxiao Jiuxin Pill (SJP) is extensively used in China for the clinical treatment of angina pectoris and confers benefits to patients with acute coronary syndrome who have received percutaneous coronary intervention. However, the precise mechanisms underlying SJP intervention in MIRI remain unclear.

PURPOSE

This study aimed to demonstrate, both in vivo and in vitro, that SJP could alleviate autophagy in MIRI by regulating miR-193a-3p to target and upregulate the demethylase ALKBH5.

METHODS

An in vitro hypoxia/reoxygenation model was established using H9c2 cells, while an in vivo MIRI model was established using Wistar rats. A lentivirus harboring the precursor sequence of miR-193a-3p was employed for its overexpression. Adeno-associated viruses were used to silence both miR-193a-3p and ALKBH5 expressions. Cardiac function, infarct size, and tissue structure in rats were assessed using echocardiography, triphenyl tetrazolium chloride (TTC) staining, and HE staining, respectively. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) was employed to detect the levels of apoptosis in rat cardiac tissue. m6A methylation levels were assessed using colorimetry. GFP-RFP-LC3B was used to monitor autophagic flux and transmission electron microscopy was used to evaluate the development of autophagosomes. Western Blot and qRT-PCR were respectively employed to assess the levels of autophagy-related proteins and miR-193a-3p.

RESULTS

SJP alleviated autophagy, preserved cardiac function, and minimized myocardial damage in the hearts of MIRI rats. SJP attenuated autophagy in H/R H9C2 cells. Elevated levels of miR-193a-3p were observed in the cardiac tissues of MIRI rats and H/R H9C2 cells, whereas SJP downregulated miR-193a-3p levels in these models. ALKBH5, a target gene of miR-193, is negatively regulated by miR-193a-3p. Upon overexpression of miR-193a-3p or silencing of ALKBH5, m6A methylation decreased, and the autophagy-attenuating effects of SJP and its components, senkyunolide A and l-borneol, were lost in H/R H9C2 cells, whereas in MIRI rats, these effects were not abolished but merely weakened. Further investigation indicated that the METTL3 inhibitor STM2475, combined with the silencing of miR-193a-3p, similarly attenuated autophagy in the hearts of MIRI rats. This suggests that a reduction in m6A methylation is involved in autophagy alleviation.

CONCLUSION

We demonstrated that SJP mitigates autophagy in MIRI by downregulating miR-193a-3p, enhancing ALKBH5 expression, and reducing m6A methylation, a mechanism potentially attributed to its constituents, senkyunolide A and l-borneol.

Reduced DNMT1 levels induce cell apoptosis via upregulation of METTL3 in cardiac hypertrophy

DNA methylation is also involved in the development and progression of cardiac diseases. Although studies have shown that DNA methylation and RNA m6A methylation play an important role in the development of myocardial hypertrophy, whether DNA methylation and RNA m6A methylation have a coordinated role in the development of myocardial hypertrophy and influence each other is still unknown. Here, we found that DNMT1 expression was downregulated in TAC mice and Ang II-treated NRCMs. Moreover, DNMT1 overexpression inhibited Ang II-induced apoptosis of NRCMs. Furthermore, we found that the expression of METTL3 was up-regulated after inhibiting the expression of DNMT1 by a DNMT1 inhibitor or small interfering RNA. In addition, ectopic expression DNMT1 inhibited METTL3 expression in NRCMs. Furthermore, METTL3 expression was elevated in NRCMs treated with Ang II, and suppression of METTL3 inhibited cell apoptosis induced by Ang II in NRCMs.In addition, this study revealed that the DNMT1/METTL3 pathway affected Ang II-induced apoptosis in NRCMs. Finally, this study found that DNMT1, but not METTL3, might directly regulated the ANP and BNP expression. Collectively, our findings revealed the role of the DNMT1/METTL3 pathway in cardiac hypertrophy and provided a novel molecular mechanism describing the physiological and pathological processes.