N6-methyladenosine (m6A) methyltransferase METTL3 regulates sepsis-induced myocardial injury through IGF2BP1/HDAC4 dependent manner

METTL3: a multifunctional regulator in diseases

N6-methyladenosine (m6A) methylation is the most prevalent and abundant internal modification of mRNAs and is catalyzed by the methyltransferase complex. Methyltransferase-like 3 (METTL3), the best-known m6A methyltransferase, has been confirmed to function as a multifunctional regulator in the reversible epitranscriptome modulation of m6A modification according to follow-up studies. Accumulating evidence in recent years has shown that METTL3 can regulate a variety of functional genes, that aberrant expression of METTL3 is usually associated with many pathological conditions, and that its expression regulatory mechanism is related mainly to its methyltransferase activity or mRNA posttranslational modification. In this review, we discuss the regulatory functions of METTL3 in various diseases, including metabolic diseases, cardiovascular diseases, and cancer. We focus mainly on recent progress in identifying the downstream target genes of METTL3 and its underlying molecular mechanisms and regulators in the above systems. Studies have revealed that the use of METTL3 as a therapeutic target and a new diagnostic biomarker has broad prospects. We hope that this review can serve as a reference for further studies.

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.

Molecular mechanism of METTL3 regulating hippocampal neuronal injury induced by sepsis-associated encephalopathy

OBJECTIVE

This study explores the mechanism of methyltransferase like 3 (METTL3) on sepsis-associated encephalopathy (SAE)-induced hippocampal neuronal injury.

METHODS

A murine model of SAE was established by caecal ligation and puncture. Hippocampal cells were induced by lipopolysaccharide (LPS). The mouse survival was observed and behavioural tests evaluated cognitive function. METTL3 and glutamic-oxaloacetic transaminase 1 (GOT1) expressions were detected via RT-qPCR and Western blot. Immunofluorescence staining examined the co-localization of NeuN and METTL3. The m6A enrichment on GOT1 was determined by MeRIP.

RESULTS

METTL3 and GOT1 were highly expressed in SAE mice and LPS-stimulated hippocampal cells. SAE mice exhibited cognitive function impairment, reduced survival rate, and decreased neuronal cells. LPS induction increased hippocampal cell apoptosis and enhanced inflammation. Silence of METTL3 reduced hippocampal neuronal injury in SAE mice and LPS-induced hippocampal cell injury.

CONCLUSION

METTL3-mediated m6A modification on GOT1 mRNA elevates GOT1 expression, thereby aggravating SAE-induced hippocampal neuronal injury.

Melatonin antagonizes bone loss induced by mechanical unloading via IGF2BP1-dependent m6A regulation

Disuse bone loss is prone to occur in individuals who lack mechanical stimulation due to prolonged spaceflight or extended bed rest, rendering them susceptible to fractures and placing an enormous burden on social care; nevertheless, the underlying molecular mechanisms of bone loss caused by mechanical unloading have not been fully elucidated. Numerous studies have focused on the epigenetic regulation of disuse bone loss; yet limited research has been conducted on the impact of RNA modification bone formation in response to mechanical unloading conditions. In this study, we discovered that m6A reader IGF2BP1 was downregulated in both osteoblasts treated with 2D clinostat and bone tissue in HLU mice. Supplementing IGF2BP1 could promote osteoblast proliferation and partially alleviate the adverse effects of mechanical unloading on bone formation. Mechanistically, IGF2BP1 inhibited the degradation of Lef1 mRNA by directly binding to its mRNA and recognizing the m6A modification. Furthermore, LEF1 promoted osteoblast proliferation by upregulating c-Myc and Cyclin D1 expression, as well as participated in mediating IGF2BP1-induced osteoblast activity under mechanical unloading. Notably, Melatonin (MT) might participate in the regulation of the IGF2BP1/LEF1 axis, thereby regulating the proliferation of osteoblasts and bone formation. Collectively, this study revealed a new insight into the regulation of the MT/IGF2BP1/LEF1 pathway in the process of unloading-induced bone loss, which could potentially contribute to establishing therapeutic strategies for disuse osteoporosis.

METTL3/YTHDF1-mediated m6A modification stabilizes USP12 to deubiquitinate FOXO3 and promote apoptosis in sepsis-induced myocardial dysfunction

Sepsis-induced myocardial dysfunction (SIMD) is a life-threatening complication primarily driven by inflammation, yet its molecular mechanisms remain unclear. In this study, we identified significant upregulation of the m6A methyltransferase METTL3 (methyltransferase-like 3), the m6A reader protein YTHDF1 (YTH N6-methyladenosine RNA binding protein 1), as well as increased expression levels of USP12 (ubiquitin-specific peptidase 12), FOXO3 (forkhead box O3), and key molecules in the intrinsic apoptotic pathway, PUMA (p53 upregulated modulator of apoptosis) and BAX (Bcl-2-associated X), through proteomic profiling in an LPS (Lipopolysaccharide)-induced SIMD mouse model. In vitro and in vivo experiments demonstrated that METTL3 and YTHDF1 regulated USP12 mRNA expression and stability through m6A modification. Elevated USP12 interacted with FOXO3, preventing its ubiquitin-mediated degradation, which enhanced FOXO3 binding to the PUMA promoter, leading to upregulation of PUMA. PUMA upregulation initiated the intrinsic apoptotic pathway, activating downstream BAX, Apaf1 (apoptotic protease-activating factor 1), and Caspases, ultimately driving SIMD. Inhibition of METTL3 (with STM2457), YTHDF1 (with Ebselen), or PUMA (with CLZ-8) significantly suppressed intrinsic apoptosis and alleviated SIMD symptoms. These findings underscore the critical role of METTL3/YTHDF1-dependent m6A modification in modulating the USP12-FOXO3-PUMA-BAX-Apaf1-Caspases signaling axis in SIMD, and suggest that targeting this pathway may offer a potential therapeutic strategy for SIMD.

Utilizing omics technologies in the investigation of sepsis-induced cardiomyopathy

Sepsis-induced cardiomyopathy (SIC) is a common and high-mortality complication among critically ill patients. Uncertainties persist regarding the pathogenesis, pathophysiology, and diagnosis of SIC, underscoring the necessity to investigate potential biological mechanisms. With the rise of omics technologies, leveraging their high throughput and big data advantages, a systems biology perspective is employed to study the biological processes of SIC. This approach aids in gaining a better understanding of the disease's onset, progression, and outcomes, ultimately providing improved guidance for clinical practices. This review summarizes the currently applied omics technologies, omics studies related to SIC, and relevant omics databases.

METTL3-mediated TIM1 promotes macrophage M1 polarization and inflammation through IGF2BP2-dependent manner

Macrophage polarization and inflammation may play an important role in the development of sepsis. T-cell immunoglobulin mucin 1 (TIM1) has been demonstrated to promote macrophage inflammatory responses. However, whether TIM1 regulates macrophage polarization and inflammation to affect sepsis development remains unclear. Human monocytic leukemia cell line was induced into macrophages, followed by stimulated with LPS and IL-4 to induce M1 polarization and M2 polarization. The expression levels of TIM1, methyltransferase 3 (METTL3), and insulin like growth factor 2 mRNA binding protein 2 (IGF2BP2) were examined by qRT-PCR and western blot. IL-6, IL-1β, and TNF-α levels were tested by ELISA. CD86+cell rate was analyzed by flow cytometry. The m6A methylation level of TIM1 was assessed by MeRIP assay. The interaction of between TIM1 and METTL3 or IGF2BP2 was assessed by dual-luciferase reporter assay and RIP assay. TIM1 knockdown repressed LPS-induced macrophage M1 polarization and inflammation. In terms of mechanism, METTL3 promoted TIM1 expression through m6A modification, and this modification could be recognized by IGF2BP2. Besides, knockdown of METTL3/IGF2BP2 suppressed LPS-induced macrophage M1 polarization and inflammation, while this effect could be eliminated by TIM1 overexpression. METTL3/IGF2BP2/TIM1 axis promoted macrophage M1 polarization and inflammation, which might provide potential target for sepsis treatment.

Diagnostic and Predictive Value of LncRNA MCM3AP-AS1 in Sepsis and Its Regulatory Role in Sepsis-Induced Myocardial Dysfunction

The present study focused on exploring the clinical value and molecular mechanism of LncRNA MCM3AP antisense RNA 1 (MCM3AP-AS1) in sepsis and sepsis-induced myocardial dysfunction (SIMD). 122 sepsis patients and 90 healthy were included. Sepsis patients were categorized into SIMD and non-MD. The expression levels of MCM3AP-AS1 and miRNA were examined using RT-qPCR. Diagnostic value of MCM3AP-AS1 in sepsis assessed by ROC curves. Logistic regression to explore risk factors influencing the occurrence of SIMD. Cardiomyocytes were induced by LPS to construct cell models in vitro. CCK-8, flow cytometry, and ELISA to analyze cell viability, apoptosis, and inflammation levels. Serum MCM3AP-AS1 was upregulated in patients with sepsis. The sensitivity and specificity of MCM3AP-AS1 were 75.41% and 93.33%, for recognizing sepsis from healthy controls. Additionally, elevated MCM3AP-AS1 is a risk factor for SIMD and can predict SIMD development. Compared with the LPS-induced cardiomyocytes, inhibition of MCM3AP-AS1 significantly attenuated LPS-induced apoptosis and inflammation; however, this attenuation was partially reversed by lowered miR-28-5p, but this reversal was partially eliminated by CASP2. MCM3AP-AS1 may be a novel diagnostic biomarker for sepsis and can predict the development of SIMD. MCM3AP-AS1 probably participated in SIMD progression by regulating cardiomyocyte inflammation and apoptosis through the target miR-28-5p/CASP2 axis.

Insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) in hematological diseases

The oncofetal mRNA-binding protein IGF2BP1 belongs to a conserved family of RNA-binding proteins. It primarily promotes RNA stability, regulates translation and RNA localization, and mediates gene expression through its downstream effectors. Numerous studies have demonstrated that IGF2BP1 plays crucial roles in embryogenesis and carcinogenesis. IGF2BP1-modulated cell proliferation, invasion, and chemo-resistance in solid tumors have attracted researchers' attention. Additionally, several studies have highlighted the importance of IGF2BP1 in hematologic malignancies and hematological genetic diseases, positioning it as a promising therapeutic target for hematological disorders. However, there is a lack of systematic summaries regarding the IGF2BP1 gene within the hematological field. In this review, we provide a comprehensive overview of the discovery and molecular structure of IGF2BP1, along with recent studies on its role in regulating embryogenesis. We also focus on the mechanisms by which IGF2BP1 regulates hematological malignancies through its interactions with its targeted mRNAs. Furthermore, we systematically elucidate the function and mechanism of IGF2BP1 in promoting fetal hemoglobin expression in adult hematopoietic stem/progenitor cells. Finally, we discuss the limitations and challenges of IGF2BP1 as a therapeutic target, offering insights into its prospects.

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.

α-Ketoglutarate plays an inflammatory inhibitory role by regulating scavenger receptor class a expression through N6-methyladenine methylation during sepsis

Sepsis arises from an uncontrolled inflammatory response triggered by infection or stress, accompanied by alteration in cellular energy metabolism, and a strong correlation exists between these factors. Alpha-ketoglutarate (α-KG), an intermediate product of the TCA cycle, has the potential to modulate the inflammatory response and is considered a crucial link between energy metabolism and inflammation. The scavenger receptor (SR-A5), a significant pattern recognition receptor, assumes a vital function in anti-inflammatory reactions. In the current investigation, we have successfully illustrated the ability of α-KG to mitigate inflammatory factors in the serum of septic mice and ameliorate tissue damage. Additionally, α-KG has been shown to modulate metabolic reprogramming and macrophage polarization. Moreover, our findings indicate that the regulatory influence of α-KG on sepsis is mediated through SR-A5. We also elucidated the mechanism by which α-KG regulates SR-A5 expression and found that α-KG reduced the N6-methyladenosine level of macrophages by up-regulating the m6A demethylase ALKBH5. α-KG plays a crucial role in inhibiting inflammation by regulating SR-A5 expression through m6A demethylation during sepsis. The outcomes of this research provide valuable insights into the relationship between energy metabolism and inflammation regulation, as well as the underlying molecular regulatory mechanism.

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.

RNA m6A methylation regulators in sepsis

N6-methyladenosine (m6A) modification is a class of epitope modifications that has received significant attention in recent years, particularly in relation to its role in various diseases, including sepsis. Epigenetic research has increasingly focused on m6A modifications, which is influenced by the dynamic regulation of three protein types: ‟Writers" (such as METTL3/METTL14/WTAP)-responsible for m6A modification; ‟Erasers" (FTO and ALKBH5)-involved in m6A de-modification; and ‟Readers" (YTHDC1/2, YTHDF1/2/3)-responsible for m6A recognition. Sepsis, a severe and fatal infectious disease, has garnered attention regarding the crucial effect of m6A modifications on its development. In this review, we attempted to summarize the recent studies on the involvement of m6A and its regulators in sepsis, as well as the significance of m6A modifications and their regulators in the development of novel drugs and clinical treatment. The potential value of m6A modifications and modulators in the diagnosis, treatment, and prognosis of sepsis has also been discussed.

Post-translational modifications in sepsis-induced organ dysfunction: mechanisms and implications

As a grave and highly lethal clinical challenge, sepsis, along with its consequent multiorgan dysfunction, affects millions of people worldwide. Sepsis is a complex syndrome caused by a dysregulated host response to infection, leading to fatal organ dysfunction. An increasing body of evidence suggests that the pathogenesis of sepsis is both intricate and rapid and involves various cellular responses and signal transductions mediated by post-translational modifications (PTMs). Hence, a comprehensive understanding of the mechanisms and functions of PTMs within regulatory networks is imperative for understanding the pathological processes, diagnosis, progression, and treatment of sepsis. In this review, we provide an exhaustive and comprehensive summary of the relationship between PTMs and sepsis-induced organ dysfunction. Furthermore, we explored the potential applications of PTMs in the treatment of sepsis, offering a forward-looking perspective on the understanding of infectious diseases.

LINC00313 suppresses autophagy and promotes stemness of nasopharyngeal carcinoma cells through PTBP1/STIM1 axis

BACKGROUND

Nasopharyngeal carcinoma (NPC) is a kind of malignant head and neck tumor with high mortality. lncRNAs are valuable diagnostic biomarkers and therapeutic targets for various tumors. This study investigated the effects and mechanism of LINC00313 in nasopharyngeal carcinoma.

METHODS

Cell Counting Kit-8 (CCK-8) and immunohistochemistry were used for assessing cell proliferation. The levels of autophagy-related proteins, and stem cell markers were detected. Immunofluorescence assay was used for LC3 detection. Methylated RNA Immunoprecipitation (meRIP) of LINC00313 in NPC cells was assessed. The localization of LINC00313 was verified by luorescence in situ hybridization (FIHS). The interaction between LINC00313 and the downstream targets were analyzed and confirmed by immunoprecipitation (RIP). Besides, the tumorigenesis roles of LINC00313 were confirmed in tumor growth mice model.

RESULTS

LINC00313 was increased in NPC tissues and cells. LINC00313 knockdown enhanced autophagy, and decreased stemness and cell viability of NPC cells through regulating STIM1. METTL3/IGF2BP1-mediated m6A modification promoted the stabilization and up-regulation of LINC00313. LINC00313 activated AKT/mTOR pathway in NPC cells through PTBP1/STIM1 axis. Moreover, LINC00313 promoted tumor growth and metastasis in xenograft model.

CONCLUSION

Upregulation of LINC00313 suppressed autophagy and promoted stemness of NPC cells through PTBP1/STIM1 axis.

m6A epitranscriptomic and epigenetic crosstalk in cardiac fibrosis

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

A review on the role of RNA methylation in aging-related diseases

Senescence is the underlying mechanism of organism aging and is robustly regulated at the post-transcriptional level. This regulation involves the chemical modifications, of which the RNA methylation is the most common. Recently, a rapidly growing number of studies have demonstrated that methylation is relevant to aging and aging-associated diseases. Owing to the rapid development of detection methods, the understanding on RNA methylation has gone deeper. In this review, we summarize the current understanding on the influence of RNA modification on cellular senescence, with a focus on mRNA methylation in aging-related diseases, and discuss the emerging potential of RNA modification in diagnosis and therapy.

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

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

N6-methyladenosine modification: Regulatory mechanisms and therapeutic potential in sepsis

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection and is characterized by multiple biological and clinical features. N6-methyladenosine (m6A) modification is the most common type of RNA modifications in eukaryotes and plays an important regulatory role in various biological processes. Recently, m6A modification has been found to be involved in the regulation of immune responses in sepsis. In addition, several studies have shown that m6A modification is involved in sepsis-induced multiple organ dysfunctions, including cardiovascular dysfunction, acute lung injury (ALI), acute kidney injury (AKI) and etc. Considering the complex pathogenesis of sepsis and the lack of specific therapeutic drugs, m6A modification may be the important bond in the pathophysiological process of sepsis and even therapeutic targets. This review systematically highlights the recent advances regarding the roles of m6A modification in sepsis and sheds light on their use as treatment targets for sepsis.

Epitranscriptomics as a New Layer of Regulation of Gene Expression in Skeletal Muscle: Known Functions and Future Perspectives

Epitranscriptomics refers to post-transcriptional regulation of gene expression via RNA modifications and editing that affect RNA functions. Many kinds of modifications of mRNA have been described, among which are N6-methyladenosine (m6A), N1-methyladenosine (m1A), 7-methylguanosine (m7G), pseudouridine (Ψ), and 5-methylcytidine (m5C). They alter mRNA structure and consequently stability, localization and translation efficiency. Perturbation of the epitranscriptome is associated with human diseases, thus opening the opportunity for potential manipulations as a therapeutic approach. In this review, we aim to provide an overview of the functional roles of epitranscriptomic marks in the skeletal muscle system, in particular in embryonic myogenesis, muscle cell differentiation and muscle homeostasis processes. Further, we explored high-throughput epitranscriptome sequencing data to identify RNA chemical modifications in muscle-specific genes and we discuss the possible functional role and the potential therapeutic applications.

RNA methylation, homologous recombination repair and therapeutic resistance

Homologous recombination (HR) repair of DNA double-strand breaks (DSBs) is critical for maintaining genomic integrity and stability. Defects in HR increase the risk of tumorigenesis. However, many human tumors exhibit enhanced HR repair capabilities, consequently endowing tumor cells with resistance to DNA-damaging chemotherapy and radiotherapy. This review summarizes the role of RNA methylation in HR repair and therapeutic resistance in human tumors. We also analyzed the interactions between RNA methylation and other HR-modulating modifications including histone acetylation, histone deacetylation, ubiquitination, deubiquitination, protein arginine methylation, and gene transcription. This review proposes that targeting RNA methylation is a promising approach to overcoming HR-mediated therapeutic resistance.

Transcriptome-wide identification of altered RNA m6A profiles in cardiac tissue of rats with LPS-induced myocardial injury

Purpose

Myocardial injury is a common complication in patients with endotoxaemia/sepsis, especially in children. Moreover, it develops through an unclear pathophysiological mechanism, and effective therapies are lacking. Recently, RNA modification, particularly N ⁶-methyladenosine (m⁶A) modification, has been found to be involved in various physiological processes and to play important roles in many diseases. However, the role of m⁶A modification in endotoxaemia/sepsis-induced myocardial injury is still in its infancy. Therefore, we attempted to construct the m⁶A modification map of myocardial injury in a rat model treated by lipopolysaccharide (LPS) and explore the role of m⁶A modification in LPS-induced myocardial injury.

Method

Myocardial injury adolescent rat model was constructed by intraperitoneal injection of LPS. m⁶A RNA Methylation Quantification Kit was used to detect overall level of m⁶A modification in rat cardiac tissue. m⁶A-specific methylated RNA immunoprecipitation followed by high-throughput sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) were conducted to identify the altered m⁶A-modified genes and differentially expressed genes in cardiac tissue of rats treated by LPS and control rats (6 versus. 6). Bioinformatics was used to analyze the functions of differentially m⁶A modified genes, differentially expressed genes, and genes with both differential m⁶A modification and differential expression. qPCR was used to detect expression of m⁶A modification related enzymes.

Result

We found that the overall level of m⁶A modification in cardiac tissue of the LPS group was up-regulated compared with that of the control group. MeRIP-seq and RNA-seq results showed that genes with differential m⁶A modification, genes with differential expression and genes with both differential m⁶A modification and differential expression were closely associated with inflammatory responses and apoptosis. In addition, we found that m⁶A-related enzymes (Mettl16, Rbm15, Fto, Ythdc2 and Hnrnpg) were differentially expressed in the LPS group versus. the control group.

Conclusion

m⁶A modification is involved in the pathogenesis process of LPS-induced myocardial injury, possibly through the regulation of inflammatory response and apoptosis-related pathways. These results provide valuable information regarding the potential pathogenic mechanisms underlying LPS-induced myocardial injury.

Immune dysregulation and RNA N6-methyladenosine modification in sepsis

Sepsis is defined as life-threatening organ dysfunction caused by the host immune dysregulation to infection. It is a highly heterogeneous syndrome with complex pathophysiological mechanisms. The host immune response to sepsis can be divided into hyper-inflammatory and immune-suppressive phases which could exist simultaneously. In the initial stage, systemic immune response is activated after exposure to pathogens. Both innate and adaptive immune cells undergo epigenomic, transcriptomic, and functional reprogramming, resulting in systemic and persistent inflammatory responses. Following the hyper-inflammatory phase, the body is in a state of continuous immunosuppression, which is related to immune cell apoptosis, metabolic failure, and epigenetic reprogramming. Immunosuppression leads to increased susceptibility to secondary infections in patients with sepsis. RNA N6-Methyladenosine (m6A) has been recognized as an indispensable epitranscriptomic modification involved in both physiological and pathological processes. Recent studies suggest that m6A could reprogram both innate and adaptive immune cells through posttranscriptional regulation of RNA metabolism. Dysregulated m6A modifications contribute to the pathogenesis of immune-related diseases. In this review, we summarize immune cell changes and the potential role of m6A modification in sepsis. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA Processing > RNA Editing and Modification.

LPS-aggravated Ferroptosis via Disrupting Circadian Rhythm by Bmal1/AKT/p53 in Sepsis-Induced Myocardial Injury

Circadian disruption is involved in the progress of sepsis-induced cardiomyopathy (SICM), one of the leading causes of death in sepsis. The molecular mechanism remains ambiguous. In this study, LPS was used to build SICM model in H9c2 cell. The results suggested that LPS induced cytotoxicity via increasing ferroptosis over the time of course. After screening the expressions of six circadian genes, the circadian swing of Bmal1 was dramatically restrained by LPS in H9c2 cell of SIMC vitro model. PcDNA and siRNA were used to upregulate and downregulate Bmal1 and confirmed that Bmal1 inhibited LPS-triggered ferroptosis in H9c2 cells. Then, the results suggested that AKT/p53 pathway was restrained by LPS in H9c2 cell. Rescue test indicated that Bmal1 inhibited LPS-triggered ferroptosis via AKT/p53 pathway in H9c2 cells. In summary, our findings demonstrated that LPS induced cytotoxicity via increasing ferroptosis over the time of course in H9c2 cells and Bmal1 inhibited this toxicity of LPS via AKT/p53 pathway. Although further studies are needed, our findings may contribute to a new insight to mechanism of SICM.

MetBil as a novel molecular regulator in ischemia-induced cardiac fibrosis via METTL3-mediated m6A modification

Cardiac fibrosis is a common pathological manifestation in multiple cardiovascular diseases and often results in myocardial stiffness and cardiac dysfunctions. LncRNA (long noncoding RNA) participates in a number of pathophysiological processes. However, its role in cardiac fibrosis remains unclear. The purpose of this study was to investigate the role and molecular mechanism of MetBil in regulating cardiac fibrosis. Our data showed that METTL3 binding lncRNA (MetBil) was significantly increased both in fibrotic tissue following myocardial infarction (MI) in mice and in cardiac fibroblasts (CFs) exposed to TGF-β1 (20 ng/mL) or 20% FBS. Overexpression of MetBil augmented collagen deposition, CF proliferation and activation while silencing MetBil exhibited the opposite effects. Importantly, heterozygous knockout of MetBil alleviated cardiac fibrosis and improved cardiac function after MI. RNA pull-down and RNA-binding protein immunoprecipitation assay showed that METTL3 is a direct downstream target of MetBil; consistently, MetBil and METTL3 were co-localized in both the nucleus and cytoplasm of CFs. Interestingly, MetBil regulated METTL3 expression at protein level, but not mRNA level, in ubiquitin-proteasome pathway. Enforced expression of METTL3 canceled the antifibrotic effects of silencing MetBil reflected by increased collagen production, CF proliferation and activation. Most notably, the m6A-modified fibrosis-regulated genes mediated by METTL3 are profoundly involved in the regulation of MetBil in the cardiac fibrosis following MI. Our study reveals that MetBil as a novel regulator of fibrosis promotes cardiac fibrosis via interacting with METTL3 and regulating the expression of the methylated fibrosis-associated genes, providing a new intervening target for fibrosis-associated cardiac diseases.

N6-methyladenosine (m6A) reader IGF2BP1 facilitates clear-cell renal cell carcinoma aerobic glycolysis

Emerging articles have reported that N⁶-methyladenosine (m⁶A) modification is mainly involved in clear-cell renal cell carcinoma (ccRCC) tumorigenesis. However, the regulatory mechanisms of m⁶A reader IGF2BP1 involved in ccRCC tumor energy metabolism are currently unknown. Results showed that the m⁶A reader IGF2BP1 exhibited significantly higher expression in ccRCC cells. Functionally, results by gain/loss functional assays indicated that IGF2BP1 promoted the glycolytic characteristics, including glucose uptake, lactate production and extracellular acidification rate (ECAR). Mechanistically, IGF2BP1 recognized the m⁶A modified sites on LDHA mRNA and enhanced its mRNA stability, thereby accelerating tumor energy metabolism. Thus, our work reveals a novel facet of the m⁶A that promoted mRNA stability and highlighted the functional importance of IGF2BP1 as m⁶A readers in post-transcriptional gene regulation.

N6-methyladenosine writer METTL3 accelerates the sepsis-induced myocardial injury by regulating m6A-dependent ferroptosis

Ferroptosis is an iron-dependent and phospholipid peroxidation-mediated cell death, which has been identified to be involved in sepsis-induced injury. However, the in-depth molecular mechanisms of N⁶-methyladenosine (m⁶A) and ferroptosis on sepsis-induced myocardial injury are still unclear. Here, in the septic myocardial injury, m⁶A methyltransferase METTL3 level and methylation level high-expressed in lipopolysaccharide (LPS)-induced cardiomyocytes (H9C2). Functionally, METTL3 silencing repressed the ferroptosis phenotype induced by LPS. Mechanistically, METTL3-mediated m⁶A methylation on solute carrier family 7 member 11 (SLC7A11) empowered its mRNA with high methylation level. Moreover, YTHDF2 directly bound to the m⁶A modification sites of SLC7A11 to mediate the mRNA degradation. The m⁶A modified SLC7A11 mRNA was recognized by YTHDF2, which promoted the decay of SLC7A11 mRNA, consequently up-regulating ferroptosis in sepsis-induced myocardial injury. Together, these findings establish a role of METTL3 in the ferroptosis of LPS-induced cardiomyocytes, and provide potential therapeutic target to treat the sepsis-induced myocardial injury.

Inhibition of the intracellular domain of Notch1 results in vascular endothelial cell dysfunction in sepsis

Background

Notch signaling is critical for regulating the function of vascular endothelial cells (ECs). However, the effect of the intracellular domain of Notch1 (NICD) on EC injury in sepsis remains unclear.

Methods

We established a cell model of vascular endothelial dysfunction and induced sepsis in a mouse model via lipopolysaccharide (LPS) injection and cecal ligation and puncture (CLP). Endothelial barrier function and expression of endothelial-related proteins were determined using CCK-8, permeability, flow cytometry, immunoblot, and immunoprecipitation assays. The effect of NICD inhibition or activation on endothelial barrier function was evaluated in vitro. Melatonin was used for NICD activation in sepsis mice. The survival rate, Evans blue dye of organs, vessel relaxation assay, immunohistochemistry, ELISA, immunoblot were used to explore the specific role of melatonin for sepsis induced vascular dysfunction in vivo.

Results

We found that LPS, interleukin 6, and serum collected from septic children could inhibit the expression of NICD and its downstream regulator Hes1, which impaired endothelial barrier function and led to EC apoptosis through the AKT pathway. Mechanistically, LPS decreased the stability of NICD by inhibiting the expression of a deubiquitylating enzyme, ubiquitin-specific proteases 8 (USP8). Melatonin, however, upregulated USP8 expression, thus maintaining the stability of NICD and Notch signaling, which ultimately reduced EC injury in our sepsis model and elevated the survival rate of septic mice.

Conclusions

We found a previously uncharacterized role of Notch1 in mediating vascular permeability during sepsis, and we showed that inhibition of NICD resulted in vascular EC dysfunction in sepsis, which was reversed by melatonin. Thus, the Notch1 signaling pathway is a potential target for the treatment of sepsis.

Inhibition of IGF2BP1 attenuates renal injury and inflammation by alleviating m6A modifications and E2F1/MIF pathway

Septic acute kidney injury (AKI) is characterized by inflammation. Pyroptosis often occurs during AKI and is associated with the development of septic AKI. This study found that induction of insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1) to a higher level can induce pyroptosis in renal tubular cells. Meanwhile, macrophage migration inhibitory factor (MIF), a subunit of NLRP3 inflammasomes, was essential for IGF2BP1-induced pyroptosis. A putative m6A recognition site was identified at the 3'-UTR region of E2F transcription factor 1 (E2F1) mRNA via bioinformatics analyses and validated using mutation and luciferase experiments. Further actinomycin D (Act D) chase experiments showed that IGF2BP1 stabilized E2F1 mRNA dependent on m6A. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) indicated that E2F1 acted as a transcription factor to promote MIF expression. Thus, IGF2BP1 upregulated MIF through directly upregulating E2F1 expression via m6A modification. Experiments on mice with cecum ligation puncture (CLP) surgery verified the relationships between IGF2BP1, E2F1, and MIF and demonstrated the significance of IGF2BP1 in MIF-associated pyroptosis in vivo. In conclusion, IGF2BP1 was a potent pyroptosis inducer in septic AKI through targeting the MIF component of NLRP3 inflammasomes. Inhibiting IGF2BP1 could be an alternate pyroptosis-based treatment for septic AKI.

An overview of the effects and mechanisms of m6 A methylation on innate immune cells in sepsis

Introduction

Sepsis is a severe clinical syndrome caused by dysregulated systemic inflammatory responses to infection. Methylation modification, as a crucial mechanism of RNA functional modification, can manipulate the immunophenotype and functional activity of immune cells to participate in sepsis progression. This study aims to explore the mechanism of N6-methyladenosine (m6A) methylation modification in immune cell-mediated sepsis through keyword search.

Methods

Literature retrieval.

Results and Discussion

Literature retrieval reveals that m6A methylation is implicated in sepsis-induced lung injury and myocardial injury,as well as sepsis-related encephalopathy. Furthermore, it is found that m6A methylation can regulate sepsis by inhibiting the chemotaxis of neutrophils and the formation of neutrophil extracellular traps and suppressing macrophage phagocytosis, thereby playing a role in sepsis.