Ribonucleosides from tRNA in hyperglycemic mammalian cells and diabetic murine cardiac models

NAT10 Modulates Atherosclerosis Progression Mediated by Macrophage Polarization Through Regulating ac4C Modification of TLR9

Atherosclerosis (AS) is an inflammatory disease affected by macrophage polarization. N4-acetylcytosine (ac4C) modification mediated by N-acetyltransferase 10 (NAT10). In this study, we aimed to elucidate the role of ac4C modification mediated macrophage polarization in AS through in vivo and in vitro experiments. The ac4C level was measured using dot blot. Macrophage polarization was assessed by quantitative real-time PCR and flow cytometry. Underlying mechanism was analyzed by methylated RNA Immunoprecipitation (MeRIP), RIP and dual luciferase report. Results showed that the NAT10 expression and ac4C level were increased in patients with AS. Additionally, NAT10 knockdown promoted M1 to M2 polarization and suppressed TLR9 ac4C level. TLR9 overexpression reversed macrophage polarization regulated by NAT10 knockdown. Furthermore, M1 polarization and atherosclerosis in vivo was inhibited by NAT10 knockdown. In conclusion, we demonstrated that NAT10 regualted AS progression mediated by macrophage polarization through regulating ac4C modification of TLR9 and provided a new theoretical basis.

Abnormal ac4C modification in metabolic dysfunction associated steatotic liver cells

The pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD) remains unclear due to the complexity of its etiology. The emerging field of the epitranscriptome has shown significant promise in advancing the understanding of disease pathogenesis and developing new therapeutic approaches. Recent research has demonstrated that N4-acetylcytosine (ac4C), an RNA modification within the epitranscriptome, is implicated in progression of various diseases. However, the role of ac4C modification in MASLD remains unexplored. Herein, we performed acRIP-ac4c-seq and RNA-seq analysis in free fatty acids-induced MASLD model cells, identifying 2128 differentially acetylated ac4C sites, with 1031 hyperacetylated and 1097 hypoacetylated peaks in MASLD model cells. Functional enrichments analysis showed that ac4C differentially modified genes were significantly involved in processes related to MASLD, such as nuclear transport and MAP kinase (MAPK) signaling pathway. We also identified 341 differentially expressed genes (DEGs), including 61 lncRNAs and 280 mRNAs, between control and MASLD model cells. Bioinformatics analysis showed that DEGs were significantly enriched in long-chain fatty acid biosynthetic process. Notably, 118 genes exhibited significant changes in both ac4C modification and expression levels in MASLD model cells. Among these proteins, JUN, caveolin-1 (CAV1), fatty acid synthase (FASN), and heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) were identified as core proteins through protein-protein interaction (PPI) network analysis using cytoscape software. Collectively, our findings establish a positive correlation between ac4C modification and the pathogenesis of MASLD and suggest that ac4C modification may serve as a therapeutic target for MASLD.

Methylation modifications in tRNA and associated disorders: Current research and potential therapeutic targets

High-throughput sequencing has sparked increased research interest in RNA modifications, particularly tRNA methylation, and its connection to various diseases. However, the precise mechanisms underpinning the development of these diseases remain largely elusive. This review sheds light on the roles of several tRNA methylations (m1A, m3C, m5C, m1G, m2G, m7G, m5U, and Nm) in diverse biological functions, including metabolic processing, stability, protein interactions, and mitochondrial activities. It further outlines diseases linked to aberrant tRNA modifications, related enzymes, and potential underlying mechanisms. Moreover, disruptions in tRNA regulation and abnormalities in tRNA-derived small RNAs (tsRNAs) contribute to disease pathogenesis, highlighting their potential as biomarkers for disease diagnosis. The review also delves into the exploration of drugs development targeting tRNA methylation enzymes, emphasizing the therapeutic prospects of modulating these processes. Continued research is imperative for a comprehensive comprehension and integration of these molecular mechanisms in disease diagnosis and treatment.

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.

Emerging roles of RNA ac4C modification and NAT10 in mammalian development and human diseases

RNA ac4C modification is a novel and rare chemical modification observed in mRNA. Traditional biochemical studies had primarily associated ac4C modification with tRNA and rRNA until in 2018, Arango D et al. first reported the presence of ac4C modification on mRNA and demonstrated its critical role in mRNA stability and translation regulation. Furthermore, they established that the ac4C modification on mRNA is mediated by the classical N-acetyltransferase NAT10. Subsequent studies have underscored the essential implications of NAT10 and mRNA ac4C modification across both physiological and pathological regulatory processes. In this review, we aimed to explore the discovery history of RNA ac4C modification, its detection methods, and its regulatory mechanisms in disease and physiological development. We offer a forward-looking examination and discourse concerning the employment of RNA ac4C modification as a prospective therapeutic strategy across diverse diseases. Furthermore, we comprehensively summarize the functions and mechanisms of NAT10 in gene expression regulation and pathogenesis independent of RNA ac4C modification.

TRIB1 regulates liver regeneration by antagonizing the NRF2-mediated antioxidant response

Robust regenerative response post liver injuries facilitates the architectural and functional recovery of the liver. Intrahepatic redox homeostasis plays a key role in liver regeneration. In the present study, we investigated the contributory role of Tribbles homolog 1 (Trib1), a pseudokinase, in liver regeneration and the underlying mechanism. We report that Trib1 expression was transiently down-regulated in animal and cell models of liver regeneration. Further analysis revealed that hepatocyte growth factor (HGF) repressed Trib1 transcription by evicting liver X receptor (LXRα) from the Trib1 promoter. Knockdown of Trib1 enhanced whereas over-expression of Trib1 suppressed liver regeneration after partial hepatectomy in mice. Of interest, regulation of liver regenerative response by Trib1 coincided with alterations of intracellular ROS levels, GSH levels, and antioxidant genes. Transcriptional assays suggested that Trib1 influenced cellular redox status by attenuating nuclear factor erythroid 2-related factor 2 (Nrf2) activity. Mechanistically, Trib1 interacted with the C-terminus of Nrf2 thus masking a potential nuclear localization signal (NLS) and blocking nuclear accumulation of Nrf2. Finally, correlation between Trib1 expression, Nrf2 nuclear localization, and cell proliferation was identified in liver specimens taken from patients with acute liver failure. In conclusion, our data unveil a novel pathway that depicts Trib1 as a critical link between intracellular redox homeostasis and cell proliferation in liver regeneration.