METTL3-mediated N6-methyladenosine exacerbates ferroptosis via m6A-IGF2BP2-dependent mitochondrial metabolic reprogramming in sepsis-induced acute lung injury

Targeting ferroptosis offers therapy choice in sepsis-associated acute lung injury

Sepsis-associated acute lung injury (SALI) is a common complication of sepsis, consisting of a dysfunctional host response to infection-mediated heterogenous complexes. SALI is reported in up to 50 % of patients with sepsis and causes poor outcomes. Despite high incidence, there is a lack of understanding in its pathogenesis and optimal treatment. A better understanding of the molecular mechanisms underlying SALI may help produce better therapeutics. The effects of altered cell-death mechanisms, such as non-apoptotic regulated cell death (RCD) (i.e., ferroptosis), on the development of SALI are beginning to be discovered, while targeting ferroptosis as a meaningful target in SALI is increasingly being recognized. Here, we outline how a susceptible lung alveoli may develop SALI. Then we discuss the general mechanisms underlying ferroptosis, and how it contributes to SALI. We then outline the chemical structures of the emerging agents or compounds that can protect against SALI by inhibiting ferroptosis, summarizing their potential pharmacological effects. Finally, we highlight key limitations and possible strategies to overcome them. This review suggests that a detailed mechanistic and biological understanding of ferroptosis can foster the development of pharmacological antagonists in the treatment of SALI.

Interactions between ferroptosis and tumour development mechanisms: Implications for gynaecological cancer therapy (Review)

Ferroptosis is a form of programmed cell death that is distinct from apoptosis. The mechanism involves redox‑active metallic iron and is characterized by an abnormal increase in iron‑dependent lipid reactive oxygen species, which results in high levels of membrane lipid peroxides. The relationship between ferroptosis and gynaecological tumours is complex. Ferroptosis can regulate tumour proliferation, metastasis and chemotherapy resistance, and targeting ferroptosis is a promising antitumour approach. Ferroptosis interacts with mechanisms related to tumorigenesis and development, such as macrophage polarization, the neutrophil trap network, mitochondrial autophagy and cuproptosis. The present review examines recent information on the interaction between the molecular mechanism of ferroptosis and other tumour‑related mechanisms, as well as the involvement of ferroptosis in gynaecological tumours, to identify implications for gynaecological cancer therapy.

Immunologic role of macrophages in sepsis-induced acute liver injury

Sepsis-induced acute liver injury (SALI), a manifestation of sepsis multi-organ dysfunction syndrome, is associated with poor prognosis and high mortality. The diversity and plasticity of liver macrophage subpopulations explain their different functional responses in different liver diseases. Kupffer macrophages, liver capsular macrophages, and monocyte-derived macrophages are involved in pathogen recognition and clearance and in the regulation of inflammatory responses, exacerbating the progression of SALI through different pathways of pyroptosis, ferroptosis, and autophagy. Concurrently, they play an important role in maintaining hepatic homeostasis and in the injury and repair processes of SALI. Other macrophages are recruited to diseased tissues under pathological conditions and are polarized into various phenotypes (mainly M1 and M2 types) under the influence of signaling molecules, transcription factors, and metabolic reprogramming, thereby exerting different roles and functions. This review provides an overview of the immune role of macrophages in SALI and discusses the multiple roles of macrophages in liver injury and repair to provide a reference for future studies.

METTL3, m6A modification, and EGR1: interplay affecting myocardial I/R injury outcomes

The occurrence of severe myocardial ischemia/reperfusion (I/R) injury is associated with the clinical application of reestablishment technique for heart disease, and understanding its underlying mechanisms is currently an urgent issue. Prior investigations have demonstrated the potential enhancement of MIRI through EGR1 suppression, although the precise underlying regulatory pathways require further elucidation. The core focus of this investigation is to examine the molecular pathways through EGR1 regulates mitophagy-mediated myocardial cell pyroptosis and its impact on MIRI. Cardiomyocyte hypoxia/reoxygenation (H/R) injury models and mouse models of myocardial I/R injury were used to investigate the involvement of EGR1 in regulating mitophagy-mediated myocardial cell pyroptosis in myocardial I/R injury. The research outcomes demonstrated that under H/R conditions, EGR1 expression was upregulated and inhibited the JAK2/STAT3 pathway, leading to enhanced mitophagy and disrupted mitochondrial fusion/fission dynamics, ultimately resulting in myocardial cell pyroptosis. Further research revealed that the upregulation of EGR1 expression was mediated by methyltransferase like 3 (METTL3)-mediated m6A modification of EGR1 mRNA and depended on the binding of insulin like growth factor 2 mrna binding protein 2 (IGF2BP2) to the N6-methyladenosine (m6A) modification site to enhance mRNA stability. In vivo animal experiments confirmed that METTL3 upregulated EGR1 expression through IGF2BP2 and suppressed activation of the janus kinase 2 (JAK2) /signal transducer and activator of transcription 3 (STAT3) pathway, thereby inhibiting mitophagy, disrupting mitochondrial dynamics, promoting myocardial cell pyroptosis, and exacerbating I/R injury.

3-Acetyldeoxynivalenol induces pyroptosis in leydig cells via METTL3-mediated N6-methyladenosine modification of NLRP3

3-acetyldeoxynivalenol (3-ADON), an acetylated derivative of deoxynivalenol, is a prevalent contaminant found in food products contaminated with mycotoxins. While the toxicological effects of 3-ADON on human and animal health are well-documented, its specific impact on the reproductive system remains underexplored. In this study, we comprehensively examined the toxicological effects of 3-ADON on TM3 Leydig cells through both in vivo and in vitro experimental models. Our results demonstrate that 3-ADON exposure leads to substantial testicular damage in vivo and significantly reduces cell viability while increasing mortality in TM3 cells in vitro (P = 0.012). Mechanistic investigations further revealed that 3-ADON exposure triggers pyroptosis in TM3 cells, as evidenced by upregulation of NLRP3, activation of caspase-1, ASC, and GSDMD. Moreover, 3-ADON treatment resulted in a significant upregulation of METTL3 expression and increased global mRNA m6A modification levels. m6A sequencing and functional assays established that METTL3-mediated m6A modification of NLRP3 mRNA enhances its stability and expression. RNA immunoprecipitation (RIP) assays further demonstrated that IGF2BP1 selectively recognizes m6A-modified NLRP3 mRNA, contributing to its stabilization. Notably, IGF2BP1 was found to inhibit the recruitment of the BTG2/CCR4-NOT complex by competitively binding to PABPC1, thereby preventing the deadenylation of NLRP3 mRNA and maintaining its expression. Additionally, we identified that METTL3 also methylates and stabilizes c-MyB mRNA, which subsequently binds to the promoter region of NLRP3, thereby enhancing its transcription. Collectively, our findings reveal a novel mechanism by which 3-ADON exerts its reproductive toxicity, underscoring the pivotal role of METTL3-mediated m6A modifications in regulating Leydig cell dysfunction.

The roles of lactate and the interplay with m6A modification in diseases

Lactate exhibits various biological functions, including the mediation of histone and non-histone lactylation to regulate gene transcription, influencing the activity of T lymphocytes, NK cells, and macrophages in immune suppression, activating G protein-coupled receptor 81 for signal transduction, and serving as an energy substrate. The m6A modification represents the most prevalent post-transcriptional epigenetic alteration. It is regulated by m6A-related regulatory enzymes (including methyltransferases, demethylases, and recognition proteins) that control the transcription, splicing, stability, and translation of downstream target RNAs. Lactate-mediated lactylation at histone H3K18 can modulate downstream target m6A modifications by enhancing the transcriptional expression levels of m6A-related regulatory enzymes. These enzymes play a crucial role in the progression of diseases such as cancer, fibrosis (in both liver and lung), myocardial ischemia, cerebral hemorrhage, and sepsis. Furthermore, m6A-related regulatory enzymes are also subject to lactylation by lactate. In turn, these regulatory enzymes can influence key glycolytic pathway enzymes or modify lactate transporter MCT4 via m6A alterations to impact lactate levels and subsequently affect lactylation processes.

Ubiquitination in pyroptosis pathway: A potential therapeutic target for sepsis

Sepsis remains a significant clinical challenge, causing numerous deaths annually and representing a major global health burden. Pyroptosis, a unique form of programmed cell death characterized by cell lysis and the release of inflammatory mediators, is a crucial factor in the pathogenesis and progression of sepsis, septic shock, and organ dysfunction. Ubiquitination, a key post-translational modification influencing protein fate, has emerged as a promising target for managing various inflammatory conditions, including sepsis. This review integrates the current knowledge on sepsis, pyroptosis, and the ubiquitin system, focusing on the molecular mechanisms of ubiquitination within pyroptotic pathways activated during sepsis. By exploring how modulating ubiquitination can regulate pyroptosis and its associated inflammatory signaling pathways, this review provides insights into potential therapeutic strategies for sepsis, highlighting the need for further research into these complex molecular networks.

1,3-Dichloro-2-propanol Induced Renal Cell Ferroptosis via the Circadian Clock Protein BMAL1 Targeting GPX4

1,3-Dichloro-2-propanol (1,3-DCP), a representative chloropropyl alcohol contaminant in food, has shown toxic effects on the kidney. Ferroptosis is a newly identified cell death driven by iron-dependent lipid peroxidation that is associated with renal injury. However, the role of 1,3-DCP in ferroptosis in renal cells remains unclear. In this study, we found that ferroptosis was involved in a 1,3-DCP-induced renal injury. Mechanistically, we revealed that 1,3-DCP triggered ferroptosis by inhibiting GPX4 activity and disturbing iron homeostasis in NRK-52E cells. The circadian clock is crucial in modulating physiological cellular functions through the regulation of various downstream proteins. Furthermore, our findings also showed that 1,3-DCP triggered ferroptosis through interference with the circadian clock. The data showed that the expression of GPX4 was regulated by clock core protein BMAL1. 1,3-DCP interfered with GPX4 rhythmic expression through disordering BMAL1 and led to lipid peroxidation, ultimately inducing ferroptosis. In conclusion, our study uncovered that BMAL1 was responsible for controlling GPX4 to mediate 1,3-DCP-induced ferroptosis. The BMAL1/GPX4 axis may be a potentially novel pathway for ferroptosis. Our work may offer a fresh perspective for toxicological research examining the interactions between food pollutants, circadian clock, and ferroptosis.

rTM reprograms macrophages via the HIF-1α/METTL3/PFKM axis to protect mice against sepsis

The metabolic reprogramming of macrophages is a potential therapeutic strategy for sepsis treatment, but the mechanism underlying this reprogramming remains unclear. Since glycolysis can drive macrophage phenotype switching, the rate-limiting enzymes in glycolysis may be key to treating sepsis. Here, we found that, compared with other isoenzymes, the expression of 6-phosphofructokinase, muscle type (PFKM) was the most upregulated in monocytes from septic patients. Recombinant thrombomodulin (rTM) treatment downregulated the protein expression of PFKM in macrophages. Both rTM treatment and Pfkm knockout protected mice from sepsis and reduced the production of the proinflammatory cytokines IL-1β, IL-6, TNF-α, and IL-27, whereas PFKM overexpression increased the production of these cytokines. Mechanistically, rTM treatment inhibited glycolysis in macrophages by decreasing PFKM expression in a hypoxia-inducible factor-1α (HIF-1α)-dependent manner. HIF-1α overexpression increased methyltransferase-like 3 (METTL3) expression, elevated the m6A level on Pfkm, and upregulated the protein expression of PFKM. METTL3 silence attenuated HIF-1α-mediated PFKM expression. These findings provide insight into the underlying mechanism of macrophage reprogramming for the treatment of sepsis.

METTL3 mediated ferroptosis in chondrocytes and promoted pain in KOA via HMGB1 m6A modification

Methyltransferase-like 3 (METTL3) plays a role in the development of knee osteoarthritis (KOA). However, the mechanism underlying the role of METTL3 in KOA is unclear. This work investigated the effects of MELLT3 on ferroptosis and pain relief in in vitro and in vivo KOA models. Chondrocytes were treated with 10 ng/mL interleukin-1β (IL-1β) or 5 μM Erastin (ferroptosis inducer). IL-1β or Erastin treatment inhibited cell viability and glutathione levels; increased Fe2+, lipid reactive oxygen species and malondialdehyde production; and decreased glutathione peroxidase 4, ferritin light chain and solute carrier family 7 member 11 levels. The overexpression of METTL3 facilitated the N6-methyladenosine methylation of high mobility group box 1 (HMGB1). HMGB1 overexpression reversed the effect of sh-METTL3 on IL-1β-treated chondrocytes. A KOA rat model was established by the injection of monosodium iodoacetate into the joints and successful model establishment was confirmed by haematoxylin and eosin staining and Safranin O/Fast Green staining. METTL3 depletion alleviated cartilage damage, the inflammatory response, ferroptosis and knee pain in KOA model rats, and these effects were reversed by the addition of HMGB1. In conclusion, METTL3 depletion inhibited ferroptosis and the inflammatory response, and ameliorated cartilage damage and knee pain during KOA progression by regulating HMGB1.

FMRP protects breast cancer cells from ferroptosis by promoting SLC7A11 alternative splicing through interacting with hnRNPM

Ferroptosis is a unique modality of regulated cell death that is driven by iron-dependent phospholipid peroxidation. N6-methyladenosine (m6A) RNA modification participates in varieties of cellular processes. However, it remains elusive whether m6A reader Fragile X Mental Retardation Protein (FMRP) are involved in the modulation of ferroptosis in breast cancer (BC). In this study, we found that FMRP expression was elevated and associated with poor prognosis and pathological stage in BC patients. Overexpression of FMRP induced ferroptosis resistance and exerted oncogenic roles by positively regulating a critical ferroptosis defense gene SLC7A11. Mechanistically, upregulated FMRP catalyzes m6A modification of SLC7A11 mRNA and further influences the SLC7A11 translation through METTL3-dependent manner. Further studies revealed that FMRP interacts with splicing factor hnRNPM to recognize the splice site and then modulated the exon skip splicing event of SLC7A11 transcript. Interestingly, SLC7A11-S splicing variant can effectively promote FMRP overexpression-induced ferroptosis resistance in BC cells. Moreover, our clinical data suggested that FMRP/hnRNPM/SLC7A11 expression were significantly increased in the tumor tissues, and this signal axis was important evaluation factors closely related to the worse survival and prognosis of BC patients. Overall, our results uncovered a novel regulatory mechanism by which high FMRP expression protects BC cells from undergoing ferroptosis. Targeting the FMRP-SLC7A11 axis has a dual effect of inhibiting ferroptosis resistance and tumor growth, which could be a promising therapeutic target for treating BC.

Understanding how methyltransferase-like 3 functions in lung diseases: From pathogenesis to clinical application

Lung diseases have complex pathogenesis and treatment challenges, showing an obvious increase in the rate of diagnosis and death every year. Therefore, elucidating the mechanism for their pathogenesis and treatment ineffective from novel views is essential and urgent. Methyltransferase-like 3 (METTL3) is a novel post-transcriptional regulator for gene expression that has been implicated in regulating lung diseases, including that observed in chronic conditions such as pulmonary fibrosis (PF), pulmonary arterial hypertension (PAH), and chronic obstructive pulmonary disease (COPD), as well as acute conditions such as pneumonia, severe acute respiratory syndrome coronavirus 2 infection, and sepsis-induced acute respiratory distress syndrome. Notably, a comprehensive summary and analysis of findings from these studies might help understand lung diseases from the novel view of METTL3-regulated mechanism, however, such a review is still lacking. Therefore, this review aims to bridge such shortage by summarising the roles of METTL3 in lung diseases, establishing their interrelationships, and elucidating the potential applications of METTL3 regarding diagnosis, treatment, and prognosis. The analysis collectively suggests METTL3 is contributable to the onset and progression of these lung diseases, thereby prospecting METTL3 as a valuable biomarker for their diagnosis, treatment, and prognosis. In conclusion, this review offers elucidation into the correlation between METTL3 and lung diseases in both research and clinical settings and highlights potential avenues for exploring the roles of METTL3 in the respiratory system.

The m6A eraser FTO suppresses ferroptosis via mediating ACSL4 in LPS-induced macrophage inflammation

Acute lung injury (ALI) is a serious disorder characterized by the release of pro-inflammatory cytokines and cascade activation of macrophages. Ferroptosis, a form of iron-dependent cell death triggered by intracellular phospholipid peroxidation, has been implicated as an internal mechanism underlying ALI. In this study, we investigated the effects of m6A demethylase fat mass and obesity-associated protein (FTO) on the inhibition of macrophage ferroptosis in ALI. Using a mouse model of lipopolysaccharide (LPS)-induced ALI, we observed the induction of ferroptosis and its co-localization with the macrophage marker F4/80, suggesting that ferroptosis might be induced in macrophages. Ferroptosis was promoted during LPS-induced inflammation in macrophages in vitro, and the inflammation was counteracted by the ferroptosis inhibitor ferrostatin-1 (fer-1). Given that FTO showed lower expression levels in the lung tissue of mice with ALI and inflammatory macrophages, we further dissected the regulatory capacity of FTO in ferroptosis. The results demonstrated that FTO alleviated macrophage inflammation by inhibiting ferroptosis. Mechanistically, FTO decreased the stability of ACSL4 mRNA via YTHDF1, subsequently inhibiting ferroptosis and inflammation by interrupting polyunsaturated fatty acid consumption. Moreover, FTO downregulated the synthesis and secretion of prostaglandin E2, thereby reducing ferroptosis and inflammation. In vivo, the FTO inhibitor FB23-2 aggravated lung injury, the inflammatory response, and ferroptosis in mice with ALI; however, fer-1 therapy mitigated these effects. Overall, our findings revealed that FTO may function as an inhibitor of the inflammatory response driven by ferroptosis, emphasizing its potential as a target for ALI treatment.

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.

m6A methylation in myocardial tissue of septic mice analyzed using MeRIP/m6A-sequencing and RNA-sequencing

Septic cardiomyopathy is a secondary myocardial injury caused by sepsis. N6-methyl-adenosine (m6A) modification is involved in the pathological progression of septic cardiomyopathy; however, the pathological mechanism remains unclear. In this study, we identified the overall m6A modification pattern in septic myocardial injury and determined its potential interactions with differentially expressed genes (DEGs). A sepsis mouse model exhibiting septic symptoms and myocardial tissue damage was induced by lipopolysaccharide (LPS). LPS-induced septic myocardial tissues and control myocardial tissues were subjected to methylated RNA immunoprecipitation sequencing and RNA sequencing to screen for differentially expressed m6A peaks and DEGs. We identified 859 significantly m6A-modified genes in septic myocardial tissues, including 432 upregulated and 427 downregulated genes. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed to explore the biological importance of differentially expressed m6A methylated genes and DEGs. Differentially expressed m6A methylated genes were enriched in immune- and inflammation-related pathways. Conjoint analysis revealed co-expression of differentially expressed m6A genes and DEGs, including genes that were upregulated or downregulated and those showing opposite trends. High expression of m6A-related genes (WTAP and IGF2BP2), interleukin-17, and interleukin-17 pathway-related genes (MAPK11 and TRAF3IP2) was verified using reverse transcription-quantitative PCR. We confirmed the presence of m6A modification of the transcriptome and m6A-mediated gene expression in septic myocardial tissues.

NAT10-mediated ac4C acetylation of TFRC promotes sepsis-induced pulmonary injury through regulating ferroptosis

BACKGROUND

Sepsis-induced pulmonary injury (SPI) is a common complication of sepsis with a high rate of mortality. N4-acetylcytidine (ac4C) is mediated by the ac4C "writer", N-acetyltransferase (NAT)10, to regulate the stabilization of mRNA. This study aimed to investigate the role of NAT10 in SPI and the underlying mechanism.

METHODS

Twenty-three acute respiratory distress syndrome (ARDS) patients and 27 non-ARDS volunteers were recruited. A sepsis rat model was established. Reverse transcription-quantitative polymerase chain reaction was used to detect the expression of NAT10 and transferrin receptor (TFRC). Cell viability was detected by cell counting kit-8. The levels of Fe2+, glutathione, and malondialdehyde were assessed by commercial kits. Lipid reactive oxygen species production was measured by flow cytometric analysis. Western blot was used to detect ferroptosis-related protein levels. Haematoxylin & eosin staining was performed to observe the pulmonary pathological symptoms.

RESULTS

The results showed that NAT10 was increased in ARDS patients and lipopolysaccharide-treated human lung microvascular endothelial cell line-5a (HULEC-5a) cells. NAT10 inhibition increased cell viability and decreased ferroptosis in HULEC-5a cells. TFRC was a downstream regulatory target of NAT10-mediated ac4C acetylation. Overexpression of TFRC decreased cell viability and promoted ferroptosis. In in vivo study, NAT10 inhibition alleviated SPI.

CONCLUSION

NAT10-mediated ac4C acetylation of TFRC aggravated SPI through promoting ferroptosis.

Monosome Stalls the Translation Process Mediated by IGF2BP in Arcuate Nucleus for Puberty Onset Delay

Puberty onset through hypothalamic-pituitary-gonad (HPG) axis as an important reproductive event in postnatal development is initiated from hypothalamic arcuate nucleus (ARC). The growing evidence indicates that translational control also plays an essential role in the final expression of gonadotropin genes. To investigate the role of protein translation and behavior of ribosomes in pubertal onset, the global profiles of transcriptome, single ribosome (monosome), polysome, and tandem mass tag proteome were comprehensively investigated in rat hypothalamic ARCs of different pubertal stages using RNA sequencing, polyribo sequencing, and mass spectrum. Transcriptome-wide enrichments of N6-methyladenosine and IGF2BP2 were investigated using meRIP and RIP sequencing. Monosome was robustly enriched on a large proportion of mRNA in early puberty rats (postnatal day (PND)-25) compared to late puberty (PND-35 and PND-45). Monosome-enriched mRNAs, including HPG axis-related genes, had a large number of upstream ORFs (uORF, < 100 nt) and displayed translational repression in early puberty. Furthermore, insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2) could particularly interact with and facilitate monosome to bind with mRNA in early puberty. Finally, ectopic over-expression of IGF2BP2 in hypothalamic ARC via lateral ventricle injection in vivo could recruit monosome to aggregate on mRNA and delay puberty onset. We uncovered a novel regulatory mechanism of IGF2BP2 and monosome for translational control in puberty onset, which shed light on the neuroendocrine regulatory network involved in HPG axis activation.

Neutrophil extracellular traps trigger alveolar epithelial cell necroptosis through the cGAS-STING pathway during acute lung injury in mice

Extensive loss of alveolar epithelial cells (AECs) undergoing necroptosis is a crucial mechanism of acute lung injury (ALI), but its triggering mechanism needs to be thoroughly investigated. Neutrophil extracellular traps (NETs) play a significant role in ALI. However, the effect of NETs on AECs' death has not been clarified. Our study found that intratracheal instillation of NETs disrupted lung tissue structure, suggesting that NETs could induce ALI in mice. Moreover, we observed that NETs could trigger necroptosis of AECs in vivo and in vitro. The phosphorylation levels of RIPK3 and MLKL were increased in MLE12 cells after NETs treatment (P < 0.05). Mechanistically, NETs taken up by AECs through endocytosis activated the cGAS-STING pathway and triggered AECs necroptosis. The expression of cGAS, STING, TBK1 and IRF3 were increased in MLE12 cells treated with NETs (P < 0.05). Furthermore, the cGAS inhibitor RU.521 inhibited NETs-triggered AECs necroptosis and alleviated the pulmonary damage induced by NETs in mice. In conclusion, our study demonstrates that NETs taken up by AECs via endocytosis can activate the cGAS-STING pathway and trigger AECs necroptosis to promote ALI in mice. Our findings indicate that targeting the NETs/cGAS-STING/necroptosis pathway in AECs is an effective strategy for treating ALI.

The crosstalk between cellular survival pressures and N6-methyladenosine modification in hepatocellular carcinoma

BACKGROUND

Within the tumor microenvironment, survival pressures are prevalent with potent drivers of tumor progression, angiogenesis, and therapeutic resistance. N6-methyladenosine (m6A) methylation has been recognized as a critical post-transcriptional mechanism regulating various aspects of mRNA metabolism. Understanding the intricate interplay between survival pressures and m6A modification provides new insights into the molecular mechanisms underlying hepatocellular carcinoma (HCC) progression and highlights the potential for targeting the survival pressures-m6A axis in HCC diagnosis and treatment.

DATA SOURCES

A literature search was conducted in PubMed, MEDLINE, and Web of Science for relevant articles published up to April 2024. The keywords used for the search included hepatocellular carcinoma, cellular survival, survival pressure, N6-methyladenosine, tumor microenvironment, stress response, and hypoxia.

RESULTS

This review delves into the multifaceted roles of survival pressures and m6A RNA methylation in HCC, highlighting how survival pressures modulate the m6A landscape, the impact of m6A modification on survival pressure-responsive gene expression, and the consequent effects on HCC cell survival, proliferation, metastasis, and resistance to treatment. Furthermore, we explored the therapeutic potential of targeting this crosstalk, proposing strategies that leverage the understanding of survival pressures and m6A RNA methylation mechanisms to develop novel, and more effective treatments for HCC.

CONCLUSIONS

The interplay between survival pressures and m6A RNA methylation emerges as a complex regulatory network that influences HCC pathogenesis and progression.

Histone lactylation-regulated METTL3 promotes ferroptosis via m6A-modification on ACSL4 in sepsis-associated lung injury

Elevated lactate levels are a significant biomarker of sepsis and are positively associated with sepsis-related mortality. Sepsis-associated lung injury (ALI) is a leading cause of poor prognosis in clinical patients. However, the underlying mechanisms of lactate's involvement in sepsis-associated ALI remain unclear. In this study, we demonstrate that lactate regulates N6-methyladenosine (m6A) modification levels by facilitating p300-mediated H3K18la binding to the METTL3 promoter site. The METTL3-mediated m6A modification is enriched in ACSL4, and its mRNA stability is regulated through a YTHDC1-dependent pathway. Furthermore, short-term lactate stimulation upregulates ACSL4, which promotes mitochondria-associated ferroptosis. Inhibition of METTL3 through knockdown or targeted inhibition effectively suppresses septic hyper-lactate-induced ferroptosis in alveolar epithelial cells and mitigates lung injury in septic mice. Our findings suggest that lactate induces ferroptosis via the GPR81/H3K18la/METTL3/ACSL4 axis in alveolar epithelial cells during sepsis-associated ALI. These results reveal a histone lactylation-driven mechanism inducing ferroptosis through METTL3-mediated m6A modification. Targeting METTL3 represents a promising therapeutic strategy for patients with sepsis-associated ALI.

PAI-1 Deficiency Promotes NET-mediated Pyroptosis and Ferroptosis during Pseudomonas Aeruginosa-induced Acute Lung Injury by Regulating the PI3K/MAPK/AKT Axis

Circulating neutrophil extracellular trap (NET) formation is an adaptive process during acute lung injury (ALI). The important role of plasminogen activator inhibitor (PAI)-1 in NET formation during ALI remains unclear. This research intends to examine the impacts of the decrease in PAI-1 levels on NET formation and the underlying mechanism. We found a relative association between the increase in plasma NET levels and thromboinflammation-induced lung damage in patients with ARDS. PAI-1 knockout (KO) mice exhibited significant increases in Pseudomonas aeruginosa (PAO1 strain)-induced ALI, inflammation, inflammatory cell accumulation, and proinflammatory cytokine secretion, and wild-type mice exhibited the opposite changes. During PAO1-induced ALI, PAI-1 KO increased NET release and the levels of prothrombotic markers in mice. PAI-1 deficiency also promoted NET formation and NET-mediated pyroptosis and ferroptosis by activating the PI3K/MAPK/AKT pathway in a PAO1-induced ALI mouse model. In conclusion, PAI-1 KO exacerbated PAO1-induced pneumonia-associated injury and contributed to NET-mediated pyroptosis and ferroptosis through PI3K/MAPK/AKT pathway activation. Thus, targeting PAI-1 and NETs may be a promising therapeutic approach for ameliorating pneumonia and thromboinflammation-associated ALI.

Role and regulators of N6-methyladenosine (m6A) RNA methylation in inflammatory subtypes of asthma: a comprehensive review

Asthma is a common chronic inflammatory disease of the lungs and airway, yet its inflammatory subtypes and potential pathogenesis have not been completely elucidated and require further study. With advances in epigenetic development, methylation has emerged as a new direction for identifying and decoding the occurrence and subtype manifestations of asthma. N6-methyladenosine (m6A), an RNA methylation modification occurring in the N6-position of adenosine, is a prevalent epigenetic modification observed in eukaryotes. It exerts significant control over mRNA metabolism by regulating alternative splicing, stability, export, and translation. The dynamic process of m6A methylation plays a crucial role in the pathogenesis of asthma and is tightly regulated by three types of regulators: writers, readers, and erasers. This article provides a comprehensive review of the association between m6A regulators and the pathogenesis of inflammatory subtypes of asthma, such as involvement of inflammatory cells and related inflammatory response. Furthermore, the findings presented herein provide new insights and a solid foundation for further research on m6A mRNA methylation as biomarkers for the diagnosis and development of personalized treatment for different subtypes of asthma, particularly neutrophilic asthma and eosinophilic asthma.

S100A8/A9hi neutrophils induce mitochondrial dysfunction and PANoptosis in endothelial cells via mitochondrial complex I deficiency during sepsis

S100a8/a9, largely released by polymorphonuclear neutrophils (PMNs), belongs to the S100 family of calcium-binding proteins and plays a role in a variety of inflammatory diseases. Although S100a8/a9 has been reported to trigger endothelial cell apoptosis, the mechanisms of S100a8/a9-induced endothelial dysfunction during sepsis require in-depth research. We demonstrate that high expression levels of S100a8/a9 suppress Ndufa3 expression in mitochondrial complex I via downregulation of Nrf1 expression. Mitochondrial complex I deficiency contributes to NAD+-dependent Sirt1 suppression, which induces mitochondrial disorders, including excessive fission and blocked mitophagy, and mtDNA released from damaged mitochondria ultimately activates ZBP1-mediated PANoptosis in endothelial cells. Moreover, based on comprehensive scRNA-seq and bulk RNA-seq analyses, S100A8/A9hi neutrophils are closely associated with the circulating endothelial cell count (a useful marker of endothelial damage), and S100A8 is an independent risk factor for poor prognosis in sepsis patients.

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.

Neutrophil Extracellular Traps Upregulate p21 and Suppress Cell Cycle Progression to Impair Endothelial Regeneration after Inflammatory Lung Injury

Background: Sepsis is a major cause of ICU admissions, with high mortality and morbidity. The lungs are particularly vulnerable to infection and injury, and restoration of vascular endothelial homeostasis after injury is a crucial determinant of outcome. Neutrophil extracellular trap (NET) release strongly correlates with the severity of lung tissue damage. However, little is known about whether NETs affect endothelial cell (EC) regeneration and repair. Methods: Eight- to ten-week-old male C57BL/6 mice were injected intraperitoneally with a sublethal dose of LPS to induce acute lung inflammatory injury or with PBS as a control. Blood samples and lung tissues were collected to detect NET formation and lung endothelial cell proliferation. Human umbilical vein endothelial cells (HUVECs) were used to determine the role of NETs in cell cycle progression in vitro. Results: Increased NET formation and impaired endothelial cell proliferation were observed in mice with inflammatory lung injury following septic endotoxemia. Degradation of NETs with DNase I attenuated lung inflammation and facilitated endothelial regeneration. Mechanistically, NETs induced p21 upregulation and cell cycle stasis to impair endothelial repair. Conclusions: Our findings suggest that NET formation impairs endothelial regeneration and vascular repair through the induction of p21 and cell cycle arrest during inflammatory lung injury.

Ferritin-mediated neutrophil extracellular traps formation and cytokine storm via macrophage scavenger receptor in sepsis-associated lung injury

BACKGROUND

Sepsis is a severe systemic inflammatory disorder manifested by a dysregulated immune response to infection and multi-organ failure. Numerous studies have shown that elevated ferritin levels exist as an essential feature during sepsis and are able to suggest patients' prognoses. At the same time, the specific mechanism of ferritin-induced inflammatory injury remains unclear.

METHODS

Hyper-ferritin state during inflammation was performed by injecting ferritin into a mouse model and demonstrated that injection of ferritin could induce a systemic inflammatory response and increase neutrophil extracellular trap (NET) formation.Padi4-/-, Elane-/- and Cybb-/- mice were used for the NETs formation experiment. Western blot, immunofluorescence, ELISA, and flow cytometry examined the changes in NETs, inflammation, and related signaling pathways.

RESULTS

Ferritin induces NET formation in a peptidylarginine deiminase 4 (PAD4), neutrophil elastase (NE), and reactive oxygen species (ROS)-dependent manner, thereby exacerbating the inflammatory response. Mechanistically, ferritin induces the expression of neutrophil macrophage scavenger receptor (MSR), which promotes the formation of NETs. Clinically, high levels of ferritin in patients with severe sepsis correlate with NETs-mediated cytokines storm and are proportional to the severity of sepsis-induced lung injury.

CONCLUSIONS

In conclusion, we demonstrated that hyper-ferritin can induce systemic inflammation and increase NET formation in an MSR-dependent manner. This process relies on PAD4, NE, and ROS, further aggravating acute lung injury. In the clinic, high serum ferritin levels are associated with elevated NETs and worse lung injury, which suggests a poor prognosis for patients with sepsis. Our study indicated that targeting NETs or MSR could be a potential treatment to alleviate lung damage and systemic inflammation during sepsis. Video Abstract.

METTL14 contributes to acute lung injury by stabilizing NLRP3 expression in an IGF2BP2-dependent manner

Acute lung injury (ALI) as well as its more severe form, acute respiratory distress syndrome (ARDS), frequently leads to an uncontrolled inflammatory response. N6-methyladenosine (m6A) modification was associated with the progression of several inflammatory diseases. However, the role of methyltransferase-like 14 (METTL14)-mediated m6A methylation in ALI/ARDS remains unclear. Here, we reported an increase in overall expression levels of m6A and METTL14 in circulating monocyte-derived macrophages recruited to the lung following ALI, which is correlated with the severity of lung injury. We further demonstrated the critical function of METTL14 in activating NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome in vitro and in mouse models of ALI/ARDS, and validated NLRP3 as the downstream target of METTL14 by the m6A RNA immunoprecipitation (MeRIP) and RIP assays. Mechanistically, METTL14-methylated NLRP3 transcripts were subsequently recognized by insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2), an m6A reader, which stabilized NLRP3 mRNA. Furthermore, we observed that IGF2BP2 knockdown diminished LPS-induced ALI in mice by downregulating NLRP3 expression. In summation, our study revealed that the molecular mechanism underlying the pathogenesis of ALI/ARDS involves METTL14-mediated activation of NLRP3 inflammasome in an IGF2BP2 dependent manner, thereby demonstrating the potential of METTL14 and IGF2BP2 as promising biomarkers and therapeutic targets for ALI/ARDS treatment.

Neutrophil extracellular traps and their implications in airway inflammatory diseases

Neutrophil extracellular traps (NETs) are essential for immune defense and have been increasingly recognized for their role in infection and inflammation. In the context of airway inflammatory diseases, there is growing evidence suggesting the involvement and significance of NETs. This review aims to provide an overview of the formation mechanisms and components of NETs and their impact on various airway inflammatory diseases, including acute lung injury/ARDS, asthma, chronic obstructive pulmonary disease (COPD) and cystic fibrosis. By understanding the role of NETs in airway inflammation, we can gain valuable insights into the underlying pathogenesis of these diseases and identify potential targets for future therapeutic strategies that either target NETs formation or modulate their harmful effects. Further research is warranted to elucidate the complex interactions between NETs and airway inflammation and to develop targeted therapies that can effectively mitigate their detrimental effects while preserving their beneficial functions in host defense.

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.