m6A epitranscriptomic and epigenetic crosstalk in cardiac fibrosis

Novel epitranscriptomic and epigenetic therapeutic strategies and targets for ferroptosis in liver fibrosis

Liver fibrosis is characterized by an excessive accumulation of extracellular matrix (ECM) and the activation of hepatic stellate cells (HSCs), which are influenced by epitranscriptomic and epigenetic factors. Recent advancements in epigenetic and epitranscriptomic research have revealed new opportunities for therapeutic interventions, particularly through the regulation of ferroptosis, a type of programmed cell death that is specifically linked to iron-dependent lipid peroxidation. In the context of liver fibrosis, a progressive scarring process that can progress to cirrhosis and ultimately end-stage liver disease, targeting these regulatory mechanisms to modulate ferroptosis presents a promising therapeutic strategy. This review aims to consolidate current knowledge on the epigenetic and epitranscriptomic control of ferroptosis and investigate its potential implications for the treatment of liver fibrosis.

The epigenetic regulation of crosstalk between cardiac fibroblasts and other cardiac cell types during stress

With the global impact of cardiovascular disease, there is a dire need to understand the mechanisms in the heart during injury and stress. It has been shown that the regulation of the extracellular matrix via cardiac fibroblasts plays a major role in the progression of heart failure and worsening function of the heart. Importantly, it has been suggested that crosstalk between other cardiac cells like cardiomyocytes, immune cells, and endothelial cells are influenced by the pathological function of the fibroblasts. This decline in function across all cardiac cells is seemingly irreversible. However, epigenetic mechanisms have been shown to regulate functionality across cardiac cells and improve outcomes during stress or injury. This epigenetic regulation has also been shown to control communication between different cell types and influence the role of multiple cardiac cell types during injury. The goal of this review is to summarize and discuss the current research of epigenetic regulation of cardiac fibroblasts and the subsequent crosstalk with other cardiac cell types in cardiovascular disease states.

Deciphering single-cell landscape unravels cell-type-specific functional roles of RNA m6A modification in atherosclerosis

Background: Atherosclerosis is a chronic inflammatory disease that is the major cause of mortality worldwide. Although several studies have assessed the function of m6A (N6-methyladenosine) modification in atherosclerosis, its regulatory mechanism at the single-cell level remains unclear. This study provides a comprehensive single-cell atlas of m6A modification regulating cell-type-specific functions in atherosclerosis. Methods: We analyzed single-cell sequencing data derived from atherosclerosis patients to elucidate the influence of m6A modification on diverse cell types. We demonstrated the potential regulatory functions of m6A regulators across various cell types and key transcription factors involved. Furthermore, we discovered m6A regulators mediated intercellular communication in important biological processes. In vitro experiments were conducted to further investigate the effects of ALKBH5, WTAP and METTL3 on atherosclerosis. Results: ALKBH5 upregulated in endothelial cells induced cell proliferation and migration involved in sprouting angiogenesis. In smooth muscle cells, upregulation of WTAP enhanced proliferation, migration and phenotypic transformation. Upregulation of METTL3 and YTHDF2 promoted macrophage activation and differentiation. Furthermore, we identified abnormally activated transcription factors could regulate m6A regulators in a cell-type-specific manner. Moreover, we revealed that m6A regulators were implicated in dysregulated intercellular communication in atherosclerosis. And a series of experimental validations supported the conclusion that m6A regulators exert cell-type-specific regulatory functions. Conclusion: Our study provided evidence for the roles of ALKBH5, WTAP and METTL3 in orchestrating atherosclerotic cell-type-specific functions, representing promising targets for precision medicine.

METTL14 depletion induces trophoblast cell dysfunction by inhibiting miR-21-5p processing in an m6A-dependent manner

Spontaneous abortion (SA) is a devastating, but common outcome for expectant parents and their families. However, the mechanism of SA occurrence remains mostly unknown. Herein, we examined human SA villi samples and found decreased N6-methyladenosine (m6A) levels and methyltransferase-like protein 14 (METTL14) expression compared with those in healthy women. Knockdown of METTL14 in trophoblast HTR8 cells induced cellular dysfunction. We identified candidate differentially expressed microRNAs and found that METTL14 accelerated miR-21-5p processing by modulating its m6A modification level. Exogenous miR-21-5p expression attenuated METTL14 knockdown-induced cellular dysfunction. Subsequently, we found that SMAD family member 7 (SMAD7) expression is inhibited by miR-21-5p and that knockdown of SMAD7 rescued the trophoblast cell dysfunction induced by miR-21-5p inhibitors. Then, we revealed that METTL14 can regulate the SMAD7 pathway by modulating miR-21-5p. Finally, we found that exposing pregnant mice to an m6A inhibitor caused embryo loss and reduced expression levels of Mettl14 and miR-21-5p while increasing Smad7 levels. Taken together, this study establishes the involvement of m6A in SA and identified a novel SA signaling pathway. These results reveal the underlying molecular mechanisms of trophoblast cell dysfunction induced by m6A modification and provide new strategies to identify and mitigate SA.

Epigenetic regulation of diverse regulated cell death modalities in cardiovascular disease: Insights into necroptosis, pyroptosis, ferroptosis, and cuproptosis

Cell death constitutes a critical component of the pathophysiology of cardiovascular diseases. A growing array of non-apoptotic forms of regulated cell death (RCD)-such as necroptosis, ferroptosis, pyroptosis, and cuproptosis-has been identified and is intimately linked to various cardiovascular conditions. These forms of RCD are governed by genetically programmed mechanisms within the cell, with epigenetic modifications being a common and crucial regulatory method. Such modifications include DNA methylation, RNA methylation, histone methylation, histone acetylation, and non-coding RNAs. This review recaps the roles of DNA methylation, RNA methylation, histone modifications, and non-coding RNAs in cardiovascular diseases, as well as the mechanisms by which epigenetic modifications regulate key proteins involved in cell death. Furthermore, we systematically catalog the existing epigenetic pharmacological agents targeting novel forms of RCD and their mechanisms of action in cardiovascular diseases. This article aims to underscore the pivotal role of epigenetic modifications in precisely regulating specific pathways of novel RCD in cardiovascular diseases, thus offering potential new therapeutic avenues that may prove more effective and safer than traditional treatments.

N6-Methyladenosine-mediated phase separation suppresses NOTCH1 expression and promotes mitochondrial fission in diabetic cardiac fibrosis

BACKGROUND

N6-methyladenosine (m6A) modification of messenger RNA (mRNA) is crucial for liquid-liquid phase separation in mammals. Increasing evidence indicates that liquid-liquid phase separation in proteins and RNAs affects diabetic cardiomyopathy. However, the molecular mechanism by which m6A-mediated phase separation regulates diabetic cardiac fibrosis remains elusive.

METHODS

Leptin receptor-deficient mice (db/db), cardiac fibroblast-specific Notch1 conditional knockout (POSTN-Cre × Notch1flox/flox) mice, and Cre mice were used to induce diabetic cardiac fibrosis. Adeno-associated virus 9 carrying cardiac fibroblast-specific periostin (Postn) promoter-driven small hairpin RNA targeting Alkbh5, Ythdf2, or Notch1, and the phase separation inhibitor 1,6-hexanediol were administered to investigate their roles in diabetic cardiac fibrosis. Histological and biochemical analyses were performed to determine how Alkbh5 and Ythdf2 regulate Notch1 expression in diabetic cardiac fibrosis. NOTCH1 was reconstituted in ALKBH5- and YTHDF2-deficient cardiac fibroblasts and mouse hearts to study its effects on mitochondrial fission and diabetic cardiac fibrosis. Heart tissue samples from patients with diabetic cardiomyopathy were used to validate our findings.

RESULTS

In mice with diabetic cardiac fibrosis, decreased Notch1 expression was accompanied by high m6A mRNA levels and mitochondrial fission. Fibroblast-specific deletion of Notch1 enhanced mitochondrial fission and cardiac fibroblast proliferation and induced diabetic cardiac fibrosis in mice. Notch1 downregulation was associated with Alkbh5-mediated m6A demethylation in the 3'UTR of Notch1 mRNA and elevated m6A mRNA levels. These elevated m6A levels in Notch1 mRNA markedly enhanced YTHDF2 phase separation, increased the recognition of m6A residues in Notch1 mRNA by YTHDF2, and induced Notch1 degradation. Conversely, epitranscriptomic downregulation rescues Notch1 expression, resulting in the opposite effects. Human heart tissues from patients with diabetic cardiomyopathy were used to validate the findings in mice with diabetic cardiac fibrosis.

CONCLUSIONS

We identified a novel epitranscriptomic mechanism by which m6A-mediated phase separation suppresses Notch1 expression, thereby promoting mitochondrial fission in diabetic cardiac fibrosis. Our findings provide new insights for the development of novel treatment approaches for patients with diabetic cardiac fibrosis.

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.

Role of M6a Methylation in Myocardial Ischemia-Reperfusion Injury and Doxorubicin-Induced Cardiotoxicity

Cardiovascular disease remains the leading cause of death worldwide, with acute myocardial infarction and anticancer drug-induced cardiotoxicity being the significant factors. The most effective treatment for acute myocardial infarction is rapid restoration of coronary blood flow by thrombolytic therapy or percutaneous coronary intervention. However, myocardial ischemia-reperfusion injury (MI/RI) after reperfusion therapy is common in acute myocardial infarction, thus affecting the prognosis of patients with acute myocardial infarction. There is no effective treatment for MI/RI. Anthracyclines such as Doxorubicin (DOX) have limited clinical use due to their cardiotoxicity, and the mechanism of DOX-induced cardiac injury is complex and not yet fully understood. N6-methyladenosine (m6A) plays a crucial role in many biological processes. Emerging evidence suggests that m6A methylation plays a critical regulatory role in MI/RI and DOX-induced cardiotoxicity (DIC), suggesting that m6A may serve as a novel biomarker and therapeutic target for MI/RI and DIC. M6A methylation may mediate the pathophysiological processes of MI/RI and DIC by regulating cellular autophagy, apoptosis, oxidative stress, and inflammatory response. In this paper, we first focus on the relationship between m6A methylation and MI/RI, then further elucidate that m6A methylation may mediate the pathophysiological process of MI/RI through the regulation of cellular autophagy, apoptosis, oxidative stress, and inflammatory response. Finally, briefly outline the roles played by m6A in DIC, which will provide a new methodology and direction for the research and treatment of MI/RI and DIC.

ALKBH5-mediated m6A demethylation ameliorates extracellular matrix deposition in cutaneous pathological fibrosis

BACKGROUND

Elevated extracellular matrix (ECM) accumulation is a major contributing factor to the pathogenesis of fibrotic diseases. Recent studies have indicated that N6-methyladenosine (m6A) RNA modification plays a pivotal role in modulating RNA stability and contribute to the initiation of various pathological conditions. Howbeit, the precise mechanism by which m6A influences ECM deposition remains unclear.

METHODS

In this study, we used hypertrophic scars (HTSs) as a paradigm to investigate ECM-related diseases. We focused on the role of ALKBH5-mediated m6A demethylation within the pathological progression of HTSs and examined its correlation with clinical stages. The effects of ALKBH5 ablation on ECM components were studied both in vivo and in vitro. Downstream targets of ALKBH5, along with their underlying mechanisms, were identified using integrated high-throughput analysis, RNA-binding protein immunoprecipitation and RNA pull-down assays. Furthermore, the therapeutic potential of exogenous ALKBH5 overexpression was evaluated in fibrotic scar models.

RESULTS

ALKBH5 was decreased in fibroblasts derived from HTS lesions and was negatively correlated with their clinical stages. Importantly, ablation of ALKBH5 promoted the expression of COL3A1, COL1A1, and ELN, leading to pathological deposition and reconstruction of the ECM both in vivo and in vitro. From a therapeutic perspective, the exogenous overexpression of ALKBH5 significantly inhibited abnormal collagen deposition in fibrotic scar models. As determined by integrated high-throughput analysis, key ECM components including COL3A1, COL1A1, and ELN are direct downstream targets of ALKBH5. By means of its mechanism, ALKBH5 inhibits the expression of COL3A1, COL1A1, and ELN by removing m6A from mRNAs, thereby decreasing their stability in a YTHDF1-dependent manner.

CONCLUSIONS

Our study identified ALKBH5 as an endogenous suppressor of pathological ECM deposition, contributing to the development of a reprogrammed m6A-targeted therapy for HTSs.

m6A RNA methylation: The latent string-puller in fibrosis

Fibrosis is a pathological phenomenon characterized by the aberrant accumulation of extracellular matrix (ECM) in tissues. Fibrosis is a universally age-related disease involving that many organs and is the final stage of many chronic inflammatory diseases, which often threaten the patient's health. Undoubtedly, fibrosis has become a serious economic and health burden worldwide, However, the pathogenesis of fibrosis is complex. Further, the key molecules still remain to be unraveled. Hence, so far, there have been no effective treatments designed against the key targets of fibrosis. The methylation modification on the nitrogen atom at position 6 of adenine (m6A) is the most common mRNA modification in mammals. There is increasing evidence that m6A is actively involved in the pathogenesis of fibrosis. This review aims to highlight m6A-associated mechanisms and functions in several organic fibrosis, which implies that m6A is universal and critical for fibrosis and summarize the outlook of m6A in the treatment of fibrosis. This may light up the unknown aspects of this condition for researchers interested to explore fibrosis further.