m6A mRNA modification maintains colonic epithelial cell homeostasis via NF-κB-mediated antiapoptotic pathway

Interplay of m6A RNA methylation and gut microbiota in modulating gut injury

The gut microbiota undergoes continuous variations among individuals and across their lifespan, shaped by diverse factors encompassing diet, age, lifestyle choices, medication intake, and disease states. These microbial inhabitants play a pivotal role in orchestrating physiological metabolic pathways through the production of metabolites like bile acids, choline, short-chain fatty acids, and neurotransmitters, thereby establishing a dynamic "gut-organ axis" with the host. The intricate interplay between the gut microbiota and the host is indispensable for gut health, and RNA N6-methyladenosine modification, a pivotal epigenetic mark on RNA, emerges as a key player in this process. M6A modification, the most prevalent internal modification of eukaryotic RNA, has garnered significant attention in the realm of RNA epigenetics. Recent findings underscore its potential to influence gut microbiota diversity and intestinal barrier function by modulating host gene expression patterns. Conversely, the gut microbiota, through its impact on the epigenetic landscape of host cells, may indirectly regulate the recruitment and activity of RNA m6A-modifying enzymes. This review endeavors to delve into the biological functions of m6A modification and its consequences on intestinal injury and disease pathogenesis, elucidating the partial possible mechanisms by which the gut microbiota and its metabolites maintain host intestinal health and homeostasis. Furthermore, it also explores the intricate crosstalk between them in intestinal injury, offering a novel perspective that deepens our understanding of the mechanisms underlying intestinal diseases.

Downregulation of METTL3 enhances TRADD-mediated apoptosis in inflammatory bowel disease

Dysregulation of RNA N6-methyladenosine (m6A) modification in intestinal epithelial cells (IECs) compromises intestinal homeostasis, which is critical for maintaining gastrointestinal functions, immunity, and barrier integrity in inflammatory bowel disease (IBD). Here we explored the role of m6A modification, particularly through methyltransferase like 3 (METTL3), in IBD pathology and the apoptosis of intestinal stem cells (ISCs). Reduced m6A RNA methylation and METTL3 expression were detected in IBD tissues, which correlated with increased ISC apoptosis and spontaneous enteritis in METTL3-deficient models; mechanistically, Mettl3 depletion increased TRADD expression in a m6A-dependent manner, thereby augmenting the TNF-induced apoptosis pathway, whereas pharmacological inhibition of TRADD ameliorated the apoptotic phenotype in METTL3-deficient models and improved survival rates in the enteritis mouse model, suggesting a novel therapeutic avenue for IBD management. Collectively, METTL3-mediated m6A RNA methylation plays a pivotal role in maintaining intestinal homeostasis and is activated in ISCs to mitigate the hyperactivity of endogenous inflammatory signals; by modulating TRADD transcript metabolism, METTL3 limits excessive ISC apoptosis, providing insights into IBD pathogenesis and treatment strategies.

The role and intrinsic connection of cellular senescence and cell death in inflammatory bowel disease

Cellular senescence in the intestine can induce cell death, which extends beyond the mere clearance of senescent cells. This phenomenon is prevalent in inflammatory and immune-related diseases, particularly in inflammatory bowel disease (IBD). IBD is characterized by recurrent and chronic intestinal inflammation, with the occurrence and development of the disease being influenced by multiple factors, including genetics, environment, lifestyle, intestinal immunity, and gut microbiota. Chronic intestinal inflammation drives aging of the IBD immune system, reducing its efficiency and impairing the clearance of senescent cells. The disruption of cell death regulation and the interplay between cell death and cellular senescence contribute to disease progression in IBD, with inflammaging and immunosenescence playing the key role in this process. However, the mechanisms underlying the interplay between cell death and cellular senescence in the context of IBD remain unclear. Therefore, this paper comprehensively reviews the impact of cellular death and cellular senescence on intestinal aging in IBD, emphasizing the exploration of their potential interrelationships.

RNA modification: a promising code to unravel the puzzle of autoimmune diseases and CD4+ T cell differentiation

Dynamic changes in various forms of RNA modification are critical to the functional homeostasis of the immune system and the pathophysiology of autoimmune diseases. RNA modification-related proteins play an essential role in these processes. At present, the research methods of RNA modification in autoimmune diseases are mainly to detect the expression changes of RNA modification-related proteins in tissues or cells, but there is a lack of explorations of target RNAs and in-depth mechanisms. Considering the important role of CD4+ T cell dysfunction in the pathogenesis and progression of autoimmune diseases, the regulatory effect of abnormal RNA modification on CD4+ T cells deserves attention, which will provide a perspective for further exploring the mechanism of RNA modification in autoimmune diseases. In this Review, we discuss the abnormal RNA modification changes in patients with autoimmune diseases and highlight the effects of these abnormal changes on CD4+ T cells.

The Role of M6A Modification in Autoimmunity: Emerging Mechanisms and Therapeutic Implications

N6-methyladenosine (m6A), a prevalent and essential RNA modification, serves a key function in driving autoimmune disease pathogenesis. By modulating immune cell development, activation, migration, and polarization, as well as inflammatory pathways, m6A is crucial in forming innate defenses and adaptive immunity. This article provides a comprehensive overview of m6A modification features and reveals how its dysregulation affects the intensity and persistence of immune responses, disrupts immune tolerance, exacerbates tissue damage, and promotes the development of autoimmunity. Specific examples include its contributions to systemic autoimmune disorders like lupus and rheumatoid arthritis, as well as conditions that targeting specific organs like multiple sclerosis and type 1 diabetes. Furthermore, this review explores the therapeutic promise of target m6A-related enzymes ("writers," "erasers," and "readers") and summarizes recent advances in intervention strategies. By focusing on the mechanistic and therapeutic implications of m6A modification, this review sheds light on its role as a promising tool for both diagnosis and treatment in autoimmune disorders, laying the foundation for advancements in customized medicine.

Bacteroides fragilis Toxin Suppresses METTL3-Mediated m6A Modification in Macrophage to Promote Inflammatory Bowel Disease

BACKGROUND AND AIMS

Bacteroides fragilis toxin (BFT), produced by enterotoxigenic B. fragilis (ETBF), is crucial for ETBF-induced colitis. This study aims to investigate the impact of BFT-host interactions on N6-methyladenosine (m6A) modification of host mRNA and its underlying mechanisms.

METHODS

Single-cell sequencing was employed to identify the cell types involved in ETBF-induced colitis in inflammatory bowel disease patients and dextran sodium sulfate-induced colitis mice. An ETBF strain with the bft gene deleted (ETBF[Δbft]) was utilized to investigate the role of ETBF components. The biological functions and mechanisms of BFT-induced m6A modifications, as well as the target genes, were explored in vitro and in vivo.

RESULTS

Inflammatory macrophages are enriched in the intestinal mucosal tissue of both inflammatory bowel disease patients and mice with high levels of ETBF. Additionally, ETBF triggers the activation of inflammatory macrophages, subsequently inducing downstream inflammatory responses. Remarkably, BFT secreted by ETBF reduced METTL3 transcription by inhibiting FOXD3 expression and induced a dramatic reduction of m6A modifications in inflammatory macrophages. Moreover, BFT promotes the expression of its target ITGA5 expression by diminishing YTHDF2-dependent mRNA degradation. Targeting integrin subunit alpha 5 using Cilengitide significantly alleviated ETBF-induced colitis by decreasing the level of inflammatory factors in macrophages.

CONCLUSIONS

Our study reveals that BFT produced by ETBF leads to a reduction of m6A modifications by reducing METTL3 transcription and promotes ITGA5 expression in inflammatory macrophages. These findings provide new insights into the modulation of human m6A epitranscriptome in macrophages by gut microbiota and its significance in inflammatory bowel disease progression.

Regulation of autophagy and cellular signaling through non-histone protein methylation

Autophagy is a highly conserved catabolic pathway that is precisely regulated and plays a significant role in maintaining cellular metabolic balance and intracellular homeostasis. Abnormal autophagy is directly linked to the development of various diseases, particularly immune disorders, neurodegenerative conditions, and tumors. The precise regulation of proteins is crucial for proper cellular function, and post-translational modifications (PTMs) are key epigenetic mechanisms in the regulation of numerous biological processes. Multiple proteins undergo PTMs that influence autophagy regulation. Methylation modifications on non-histone lysine and arginine residues have been identified as common PTMs critical to various life processes. This paper focused on the regulatory effects of non-histone methylation modifications on autophagy, summarizing related research on signaling pathways involved in autophagy-related non-histone methylation, and discussing current challenges and clinical significance. Our review concludes that non-histone methylation plays a pivotal role in the regulation of autophagy and its associated signaling pathways. Targeting non-histone methylation offers a promising strategy for therapeutic interventions in diseases related to autophagy dysfunction, such as cancer and neurodegenerative disorders. These findings provide a theoretical basis for the development of non-histone-methylation-targeted drugs for clinical use.

Overexpression of ALKBH5 alleviates LPS induced neuroinflammation via increasing NFKBIA

Sepsis-associated encephalopathy (SAE) is a serious condition in which the immune system uncontrollably responds to infection, causing organ dysfunction. Neuroinflammation is one of the primary mechanisms underlying SAE. N6-methyladenosine (m6A) methylation is a common and reversible chemical modification of RNA molecules. Increasing evidence suggests that this modification plays a vital role in the inflammatory immune response. AlkB homolog 5 (ALKBH5) is an enzyme responsible for removing m6A modifications from RNA molecules and is known as a demethylase. However, the specific role of ALKBH5 in neuroinflammation remains unclear. To explore the role of ALKBH5 in neuroinflammation, researchers have used lipopolysaccharide (LPS) to induce inflammation in BV2 cells and mice. This study found that treatment of BV2 cells with LPS (1 μg/mL) significantly increased the total RNA m6A level and the ALKBH5 protein decreased significantly. Meanwhile, the NF-κB inflammatory signaling pathway was activated, leading to an obvious increase in IL-1β, IL-6, and TNF-α mRNA. The LPS-induced inflammatory response was alleviated when ALKBH5 was overexpressed in BV2 cells. This is due to a slower degradation rate of NFKBIA mRNA, an increase in NFKBIA protein levels, and inhibition of the NF-κB inflammatory signal pathway. When ALKBH5 was overexpressed in mice, as expected, there was an improvement in behavioral abnormalities induced by LPS. Compared to healthy volunteers, ALKBH5 mRNA levels were significantly decreased in peripheral blood mononuclear cells (PBMCs) from patients with sepsis and correlated with GCS and IL-6 levels. In summary, this study suggested that ALKBH5 is a potential therapeutic target for enhancing NFKBIA mRNA stability and alleviating neuroinflammation. Thus, ALKBH5 may provide new insights into the diagnosis and treatment of SAE.

Polymerization of dietary fructans differentially affects interactions among intestinal microbiota of colitis mice

The intestinal microbiota plays a critical role in maintaining human health and can be modulated by dietary interventions and lifestyle choices. Fructans, a dietary carbohydrate, are selectively utilized by the intestinal microbiota to confer health benefits. However, the specific effects of different fructan types on microbial changes and functions remain incompletely understood. Here, we investigated how the intestinal microbiota responds to fructans with varying degrees of polymerization in the context of gut dysbiosis. Both low molecular weight fructo-oligosaccharides and high molecular weight levan suppressed intestinal inflammation in a colitis mouse model, mitigating intestinal fibrosis and dysbiosis. Although both the effects of fructo-oligosaccharides and levan are microbiota-dependent, distinct modulation patterns of the intestinal microbiota were observed based on the molecular weight of the fructans. Levan had a more pronounced and persistent impact on gut microbiota compared to fructo-oligosaccharides. Levan particularly promoted the abundance of Dubosiella newyorkensis, which exhibited preventive effects against colitis. Our findings highlight the importance of polymerization levels of dietary fructans in microbiota alterations and identify Dubosiella newyorkensis as a potential probiotic for treating inflammatory diseases.

Modified Jiaoqi Powder enhances epithelial autophagy against TNF-triggered apoptosis in chronic ulcerative colitis

BACKGROUND

A vicious cycle of dysregulated intestinal epithelial cell death, intestinal barrier defect, and subsequent inflammation response is core to chronic ulcerative colitis (UC). Modified Jiaoqi Powder (MJQP), a traditional Chinese medicine formula, has been clinically applied to treat chronic relapsing and chronic persistent types of UC. Nevertheless, the underlying mechanisms of MJQP in chronic UC remains unknown.

PURPOSE

The present study aimed to demonstrate the favorable effects and potential molecular mechanisms of MJQP in chronic UC.

METHODS

The chemical components of MJQP and MJQP drug serum were identified by LC-MS/MS. The curative effects of MJQP were evaluated in a well-established DSS-induced chronic UC mice model by measuring body weight, colon length, disease activity index (DAI) and histological scores. Serum cytokines, including interleukin (IL)-1β, IL-12, IL-13, IL-4, tumor necrosis factor-alpha (TNF-α), and IFN-γ were measured using enzyme-linked immunosorbent assay. Western blotting, immunofluorescence, and MTT assay were used to analyze the effects of MJQP on colonic barrier function in chronic UC mice and human epithelial cell lines. TUNEL assay, western blotting, and flow cytometry were used to examine the related apoptosis indicators. An electron microscope was used to observe autophagosomes and autolysosomes, while western blotting and immunofluorescence were used to detect autophagy-associated proteins. Network pharmacology was used to predict potential targets and pathways of MJQP in UC. Finally, the TNF pathway-related proteins were detected by immunohistochemistry and western blotting.

RESULTS

MJQP administration prevented the UC progression, as evidenced by faster weight gain, longer colon length, lower histological scores and DAI, and up-/down- regulation of inflammatory factors. The expression of tight junction proteins, ki67, and E-cadherin increased dose-dependently after MJQP intervention. Moreover, MJQP treatment promoted the viability of NCM460 and Caco2 cells in a concentration-dependent manner. MJQP dose-dependently decreased the proportion of TUNEL-positive cells and attenuated the pro-apoptotic proteins cleaved-caspase 8 and cleaved-caspase 3 in colonic tissues. Flow cytometry also showed that MJQP dose-dependently decreased the apoptotic cell population of LPS-induced NCM460 and Caco2 cells. Electron microscopy revealed that autophagosomes and autolysosomes were significantly improved in the MJQP-treated groups. Additionally, autophagy-related proteins were significantly expressed after MJQP treatment. Network pharmacological analysis predicted that MJQP may alleviate chronic UC by promoting intestinal epithelial cell proliferation and affecting TNF-related signaling pathways. As anticipated, the TNF pathway-associated proteins were attenuated dose-dependently in colonic tissues after MJQP treatment.

CONCLUSION

These results provide novel therapeutic strategies indicating that MJQP may be a promising candidate treatment for chronic UC by promoting epithelial barrier restitution by enhancing epithelial autophagy against TNF-mediated apoptosis.

PI(4,5)P2 alleviates colitis by inhibiting intestinal epithelial cell pyroptosis through NNMT-mediated RBP4 m6A modification

Lipid metabolism disorder is a critical feature of Crohn's disease (CD). Phosphatidylinositol (PI) and its derivative, phosphatidylinositol bisphosphate (PIP2), are associated with CD. The mechanisms underlying such association remain unknown. In this study, we explored the role played by the major PI derivative, phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], in CD pathogenesis. The relationship between CD activity and PI or PIP2 was analyzed via lipidomics. The mucosal expression of PI(4,5)P2 in patients with CD was measured using immunofluorescence. The function and mechanism of PI(4,5)P2 were examined in dextran sulfate sodium (DSS)-induced colitis mice and lipopolysaccharide (LPS)-induced Caco-2 cell models, along with MeRIP and mRNA sequencing. The results suggested lipid PI and PIP2 were substantially negatively associated with disease activity and high-sensitivity C-reactive protein. PI(4,5)P2 was substantially downregulated in the inflamed mucosa of patients with CD. PI(4,5)P2 alleviated mouse colitis, with improvements in survival rate, colon length, weight, and disease activity index. PI(4,5)P2 also alleviated DSS-induced tissue damage, tight junction loss, and intestinal epithelial cell (IEC) pyroptosis. In the in vitro LPS-induced cell model, PI(4,5)P2 inhibited pyroptosis, as well as NLRP3, and caspase-1 expression, in addition to reducing interleukin (IL)-18, IL-1β, and lactate dehydrogenase (LDH) secretion. PI(4,5)P2 mediated NNMT upregulation in mice and Caco-2 cells and suppressed pyroptosis in IECs. NNMT knockdown restricted the inhibitory effect of PI(4,5)P2 on IEC pyroptosis. NNMT inhibited the stability of RBP4 mRNA via m6A modification, thereby preventing pyroptosis following PI(4,5)P2 treatment. Significant correlations were also observed between PI(4,5)P2 and NNMT, NNMT and RBP4, and RBP4 and GSDMD expression in the intestinal tissues from patients with CD. Our results indicated that PI(4,5)P2 ameliorates colitis by inhibiting IEC pyroptosis via NNMT-mediated RBP4 m6A modification. Thus, PI(4,5)P2 shows potential as a therapeutic target in CD.

Downregulated KLF4, induced by m6A modification, aggravates intestinal barrier dysfunction in inflammatory bowel disease

BACKGROUND

Krüppel-like factor 4 (KLF4), a transcription factor, is involved in various biological processes. However, the role of KLF4 in regulating the intestinal epithelial barrier (IEB) in inflammatory bowel disease (IBD) and its mechanism have not been extensively studied.

METHODS

KLF4 expression in IBD patients and colitis mice was analyzed using Gene Expression Omnibus(GEO) database, immunohistochemistry (IHC) and Western blot. The roles of KLF4 in IEB and colitis symptoms were verified in dextran sulfate sodium (DSS)-induced and 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis model mice using an adenovirus carrying KLF4 shRNA (shKLF4-Adv). Furthermore, the influence of KLF4 on trans-epithelium electrical resistance (TEER), paracellular permeability, apical junction complex (AJC) protein expression and apoptosis was assessed in vitro and in vivo. MeRIP and RIP assays were used to verify the effects of m6A modification on KLF4 expression.

RESULTS

KLF4 expression was significantly decreased in IBD patients and was negatively associated with inflammatory features. KLF4 deletion aggravated colitis symptoms and IEB injuries by reducing AJC protein expression and increasing apoptosis in mice with colitis. Furthermore, KLF4 transcriptionally regulated the expression of AJC proteins and inhibited apoptosis by reducing cellular ROS levels and proinflammatory cytokine expression. Moreover, we observed that METTL3/ALKBH5/YTHDF2-mediated m6A modification led to a decrease in KLF4 expression in Caco-2 cells. In addition, APTO-253, an inducer of KLF4, exhibited a synergistic effect with mesalazine on IEB function.

CONCLUSIONS

Our study demonstrated that KLF4 is a crucial regulator of IEB, suggesting that targeting KLF4 may be a promising therapeutic alternative for IBD.

Modulation of host N6-methyladenosine modification by gut microbiota in colorectal cancer

As a research hotspot in the field of molecular biology, N6-methyladenosine (m6A) modification has made progress in the treatment of colorectal cancer (CRC), leukemia and other cancers. Numerous studies have demonstrated that the tumour microenvironment (TME) regulates the level of m6A modification in the host and activates a series of complex epigenetic signalling pathways through interactions with CRC cells, thus affecting the progression and prognosis of CRC. However, with the diversity in the composition of TME factors, this action is reciprocal and complex. Encouragingly, some studies have experimentally revealed that the intestinal flora can alter CRC cell proliferation by directly acting on m6A and thereby altering CRC cell proliferation. This review summarizes the data, supporting the idea that the intestinal flora can influence host m6A levels through pathways such as methyl donor metabolism and thus affect the progression of CRC. We also review the role of m6A modification in the diagnosis, treatment, and prognostic assessment of CRC and discuss the current status, limitations, and potential clinical value of m6A modification in this field. We propose that additional in-depth research on m6A alterations in CRC patients and their TME-related targeted therapeutic issues will lead to better therapeutic outcomes for CRC patients.

hucMSC-Ex alleviates inflammatory bowel disease in mice by enhancing M2-type macrophage polarization via the METTL3-Slc37a2-YTHDF1 axis

Human umbilical cord mesenchymal stem cell-derived exosomes (hucMSC-Ex) have emerged as a new treatment strategy for inflammatory bowel disease (IBD) due to their immunoregulatory function. N6-methyladenosine (m6A) plays a crucial role in regulating intestinal immunity, especially in IBD where macrophages play an important role, although its mechanism is not yet fully understood. From this perspective, this research aimed to evaluate the effect of hucMSC-Ex on m6A modification of macrophages in IBD. In the process of alleviating inflammation, hucMSC-Ex promotes macrophage polarization toward the M2 type and regulates intracellular m6A levels by upregulating the expression of m6A "Writer" METTL3 and "Reader" YTHDF1. Solute Carrier Family 37 Member 2 (Slc37a2) was identified by Methylation RNA immunoprecipitation sequencing as the target molecule of the hucMSC-Ex. Mechanically, hucMSC-Ex promoted the binding of METTL3 to the Slc37a2 mRNA complex, and enhanced the binding of Slc37a2 to YTHDF1 to upregulate the intracellular expression of Slc37a2, thereby attenuating the pro-inflammatory function of macrophage. This study confirms the modulatory role of hucMSC-Ex on the m6A modification of macrophages in IBD, providing a new scientific basis for the treatment of IBD with hucMSC-Ex.

The Role of m6A Methylation in Tumor Immunity and Immune-Associated Disorder

N6-methyladenosine (m6A) represents the most prevalent and significant internal modification in mRNA, with its critical role in gene expression regulation and cell fate determination increasingly recognized in recent research. The immune system, essential for defense against infections and maintaining internal stability through interactions with other bodily systems, is significantly influenced by m6A modification. This modification acts as a key post-transcriptional regulator of immune responses, though its effects on different immune cells vary across diseases. This review delineates the impact of m6A modification across major system-related cancers-including those of the respiratory, digestive, endocrine, nervous, urinary reproductive, musculoskeletal system malignancies, as well as acute myeloid leukemia and autoimmune diseases. We explore the pathogenic roles of m6A RNA modifications within the tumor immune microenvironment and the broader immune system, highlighting how RNA modification regulators interact with immune pathways during disease progression. Furthermore, we discuss how the expression patterns of these regulators can influence disease susceptibility to immunotherapy, facilitating the development of diagnostic and prognostic models and pioneering new therapeutic approaches. Overall, this review emphasizes the challenges and prospective directions of m6A-related immune regulation in various systemic diseases throughout the body.

METTL3 restricts RIPK1-dependent cell death via the ATF3-cFLIP axis in the intestinal epithelium

Intestinal epithelial cells (IECs) are pivotal for maintaining intestinal homeostasis through self-renewal, proliferation, differentiation, and regulated cell death. While apoptosis and necroptosis are recognized as distinct pathways, their intricate interplay remains elusive. In this study, we report that Mettl3-mediated m6A modification maintains intestinal homeostasis by impeding epithelial cell death. Mettl3 knockout induces both apoptosis and necroptosis in IECs. Targeting different modes of cell death with specific inhibitors unveils that RIPK1 kinase activity is critical for the cell death triggered by Mettl3 knockout. Mechanistically, this occurs via the m6A-mediated transcriptional regulation of Atf3, a transcription factor that directly binds to Cflar, the gene encoding the anti-cell death protein cFLIP. cFLIP inhibits RIPK1 activity, thereby suppressing downstream apoptotic and necroptotic signaling. Together, these findings delineate the essential role of the METTL3-ATF3-cFLIP axis in homeostatic regulation of the intestinal epithelium by blocking RIPK1 activity.

RNA epigenetic modifications in digestive tract cancers: Friends or foes

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

Changes in M6A methylation: A key factor in the vicious cycle of flora -gut aging

The aging process significantly impacts the gastrointestinal tract and various bodily systems, exacerbating age-related diseases. Research suggests a correlation between an imbalance in intestinal flora and gut aging, yet the precise mechanism remains incompletely elucidated. Epigenetic modifications, particularly m6A methylation, play a pivotal role in driving aging and are closely associated with gut aging. Maintaining a healthy balance of intestinal microbes is contingent upon m6A methylation, which is believed to be crucial in the vicious cycle of gut aging and intestinal flora. This article highlights the importance of m6A methylation in the nexus between gut aging and flora. It proposes the potential for targeted m6A methylation to break the vicious cycle of gut aging and flora imbalance, offering novel perspectives on attenuating or reversing gut aging.

Specific deletion of Mettl3 in IECs triggers the development of spontaneous colitis and dysbiosis of T lymphocytes in mice

The enzymatic core component of m6A writer complex, Mettl3, plays a crucial role in facilitating the development and progress of gastric and colorectal cancer (CRC). However, its underlying mechanism in regulating intestinal inflammation remains unclear and poorly investigated. First, the characteristics of Mettl3 expression in inflammatory bowel diseases (IBD) patients were examined. Afterward, we generated the mice line with intestinal epithelial cells (IECs)-specific deletion of Mettl3 verified by various experiments. We continuously recorded and compared the physiological status including survival rate etc. between the two groups. Subsequently, we took advantage of staining assays to analyze mucosal damage and immune infiltration of Mettl3WT and Mettl3KO primary IECs. Bulk RNA sequencing was used to pursuit the differential expression of genes (DEGs) and associated signaling pathways after losing Mettl3. Pyroptosis-related proteins were to determine whether cell death was caused by pyroptosis. Eventually, CyTOF was performed to probe the difference of CD45+ cells, especially CD3e+ T-cell clusters after losing Mettl3. In IBD patients, Mettl3 was highly expressed in the inner-nucleus of IECs while significantly decreased upon acute intestinal inflammation. IECs-specific deletion of Mettl3 KO mice triggered a wasting phenotype and developed spontaneous colitis. The survival rate, body weight, and intestinal length observed from 2 to 8 weeks of Mettl3KO mice were significantly lower than Mettl3WT mice. The degree of mucosal damage and immune infiltration in Mettl3KO were even more serious than in their WT littermate. Bulk RNA sequencing demonstrated that DEGs were dramatically enriched in NOD-signaling pathways due to the loss of Mettl3. The colonic epithelium was more prone to pyroptosis after losing Mettl3. Subsequently, CyTOF revealed that T cells have altered significantly in Mettl3KO. Furthermore, there was abnormal proliferation of CD4+ T and markedly exhaustion of CD8 + T in Mettl3KO mice. In severe IBD patients, Mettl3 is located in the inner-nucleus of IECs and declined when intestinal inflammation occurs. Subsequently, Mettl3 prevented mice from developing colitis.

YTHDC1 inhibits autophagy-dependent NF-κB signaling by stabilizing Beclin1 mRNA in macrophages

BACKGROUND

YTHDC1, a key m(6)A nuclear reader, plays a crucial role in regulating mRNA splicing, export, and stability. However, the functional significance and regulatory mechanisms of YTHDC1 in inflammatory bowel disease (IBD) remain to be explored.

METHODS

We established a dextran sulfate sodium (DSS)-induced murine colitis model in vivo and LPS/IFN-γ-stimulated macrophage inflammation in vitro. The expression of YTHDC1 was determined. Colocalization of YTHDC1 and macrophages was assayed by immunofluorescence staining. LV-YTHDC1 or shYTHDC1 lentiviruses were applied for YTHDC1 overexpression or inhibition. For NF-κB inhibition, JSH-23 was utilized. The interaction of YTHDC1 and Beclin1 mRNA was determined by RIP, and the m6A modification of Beclin1 was confirmed by MeRIP.

RESULTS

In DSS-induced colitis and LPS/IFN-γ-treated RAW264.7 macrophages, we observed a significant downregulation of YTHDC1. Overexpression of YTHDC1 resulted in decreased levels of iNOS, CD86, and IL-6 mRNA, along with inhibited NF-κB activation in LPS/IFN-γ-treated RAW264.7 cells. Conversely, downregulation of YTHDC1 promoted iNOS expression and inhibited autophagy. Additionally, the effect of YTHDC1 knockdown on CD86 and IL-6 mRNA induced by LPS/IFN-γ was abolished by the NF-κB inhibitor JSH-23. Mechanistically, YTHDC1 interacted with Beclin1 mRNA, thereby stabilizing Beclin1 mRNA and enhancing Beclin1 expression and autophagy. These effects ultimately led to the inhibition of NF-κB signaling in LPS/IFN-γ-challenged macrophages.

CONCLUSIONS

YTHDC1 inhibited the macrophage-mediated inflammatory response by stabilizing Beclin1 mRNA, which may be a potential therapeutic target for the treatment of IBD.

Nurturing gut health: role of m6A RNA methylation in upholding the intestinal barrier

The intestinal lumen acts as a critical interface connecting the external environment with the body's internal state. It's essential to prevent the passage of harmful antigens and bacteria while facilitating nutrient and water absorption. The intestinal barriers encompass microbial, mechanical, immunological, and chemical elements, working together to maintain intestinal balance. Numerous studies have associated m6A modification with intestinal homeostasis. This review comprehensively outlines potential mechanisms through which m6A modification could initiate, exacerbate, or sustain barrier damage from an intestinal perspective. The pivotal role of m6A modification in preserving intestinal equilibrium provides new insights, guiding the exploration of m6A modification as a target for optimizing preventive and therapeutic strategies for intestinal homeostasis.

Taurine Alleviates Experimental Colitis by Enhancing Intestinal Barrier Function and Inhibiting Inflammatory Response through TLR4/NF-κB Signaling

Taurine (Tau) is a semiessential amino acid in mammals with preventive and therapeutic effects on several intestinal disorders. However, the exact function of taurine in ulcerative colitis (UC) is still largely unclear. In this study, we used two taurine-deficient mouse models (CSAD-/- and TauT-/- mice) to explore the influence of taurine on the progression of UC in both dextran sulfate sodium (DSS)-induced colitis and LPS-stimulated Caco-2 cells. We found that cysteine sulfinic acid decarboxylase (CSAD) and taurine transporter (TauT) expressions and taurine levels were markedly reduced in colonic tissues of mice treated with DSS. The CSAD and TauT knockouts exacerbated DSS-induced clinical symptoms and pathological damage and aggravated the intestinal barrier dysfunction and the colonic mucosal inflammatory response. Conversely, taurine pretreatment enhanced the intestinal barrier functions by increasing goblet cells and upregulating tight junction protein expression. Importantly, taurine bound with TLR4 and inhibited the TLR4/NF-κB pathway, ultimately reducing proinflammatory factors (TNF-α and IL-6) and oxidative stress. Our findings highlight the essential role of taurine in maintaining the intestinal barrier integrity and inhibiting intestinal inflammation, indicating that taurine is a promising supplement for colitis treatment.

RNA methylation: A potential therapeutic target in autoimmune disease

Autoimmune diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and inflammatory bowel disease (IBD) are caused by the body's immune response to autoantigens. The pathogenesis of autoimmune diseases is unclear. Numerous studies have demonstrated that RNA methylation plays a key role in disease progression, which is essential for post-transcriptional regulation and has gradually become a broad regulatory mechanism that controls gene expression in various physiological processes, including RNA nuclear output, translation, splicing, and noncoding RNA processing. Here, we outline the writers, erasers, and readers of RNA methylation, including N6-methyladenosine (m6A), 2'-O-methylation (Nm), 2'-O-dimethyladenosine (m6Am), N1-methyladenosine (m1A), 5-methylcytidine (m5C) and N7-methylguanosine (m7G). As the role of RNA methylation modifications in the immune system and diseases is explained, the potential treatment value of these modifications has also been demonstrated. This review reports the relationship between RNA methylation and autoimmune diseases, highlighting the need for future research into the therapeutic potential of RNA modifications.

DHX9 maintains epithelial homeostasis by restraining R-loop-mediated genomic instability in intestinal stem cells

Epithelial barrier dysfunction and crypt destruction are hallmarks of inflammatory bowel disease (IBD). Intestinal stem cells (ISCs) residing in the crypts play a crucial role in the continuous self-renewal and rapid recovery of intestinal epithelial cells (IECs). However, how ISCs are dysregulated in IBD remains poorly understood. Here, we observe reduced DHX9 protein levels in IBD patients, and mice with conditional DHX9 depletion in the intestinal epithelium (Dhx9ΔIEC) exhibit an increased susceptibility to experimental colitis. Notably, Dhx9ΔIEC mice display a significant reduction in the numbers of ISCs and Paneth cells. Further investigation using ISC-specific or Paneth cell-specific Dhx9-deficient mice demonstrates the involvement of ISC-expressed DHX9 in maintaining epithelial homeostasis. Mechanistically, DHX9 deficiency leads to abnormal R-loop accumulation, resulting in genomic instability and the cGAS-STING-mediated inflammatory response, which together impair ISC function and contribute to the pathogenesis of IBD. Collectively, our findings highlight R-loop-mediated genomic instability in ISCs as a risk factor in IBD.

m6A Methylated Long Noncoding RNA LOC339803 Regulates Intestinal Inflammatory Response

Cytokine mediated sustained inflammation increases the risk to develop different complex chronic inflammatory diseases, but the implicated mechanisms remain unclear. Increasing evidence shows that long noncoding RNAs (lncRNAs) play key roles in the pathogenesis of inflammatory disorders, while inflammation associated variants are described to affect their function or essential RNA modifications as N6-methyladenosine (m6A) methylation, increasing predisposition to inflammatory diseases. Here, the functional implication of the intestinal inflammation associated lncRNA LOC339803 in the production of cytokines by intestinal epithelial cells is described. Allele-specific m6A methylation is found to affect YTHDC1 mediated protein binding affinity. LOC339803-YTHDC1 interaction dictates chromatin localization of LOC339803 ultimately inducing the expression of NFκB mediated proinflammatory cytokines and contributing to the development of intestinal inflammation. These findings are confirmed using human intestinal biopsy samples from different intestinal inflammatory conditions and controls. Additionally, it is demonstrated that LOC339803 targeting can be a useful strategy for the amelioration of intestinal inflammation in vitro and ex vivo. Overall, the results support the importance of the methylated LOC339803 lncRNA as a mediator of intestinal inflammation, explaining genetic susceptibility and presenting this lncRNA as a potential novel therapeutic target for the treatment of inflammatory intestinal disorders.

Whole genome sequencing analysis of Limosilactobacillus reuteri from the intestinal tract of mice recovering from ulcerative colitis and preliminary study on anti-inflammatory effects of its derived peptides

Limosilactobacillus reuteri is an indigenous inhabitant of the animal gut known for its probiotic effects on the host. In our previous study, a large number of L. reuteri strains were isolated from the gastrointestinal tract of mice recovering from ulcerative colitis, from which we randomly selected L. reuteri RE225 for whole genome sequencing to explore its probiotic properties. The results of next-generation sequencing and third-generation single molecule sequencing showed that L. reuteri RE225 contained many genes encoding functional proteins associated with adhesion, anti-inflammatory and pathogen inhibition. And compared to other L. reuteri strains in NCBI, L. reuteri RE225 has unique gene families with probiotic functions. In order to further explore the probiotic effect of the L. reuteri RE225, the derived peptides were identified by LC-MS/MS, and the peptides with tumor necrosis factor-α binding ability were screened by reverse molecular docking and microscale thermophoresis. Finally, cell experiments demonstrated the anti-inflammatory ability of the peptides. Western blotting and qPCR analyses confirmed that the selected peptides might alleviate LPS-induced inflammation in NCM460 cells by inhibiting JAK2/STAT3 pathway activation.

NF-κB in biology and targeted therapy: new insights and translational implications

NF-κB signaling has been discovered for nearly 40 years. Initially, NF-κB signaling was identified as a pivotal pathway in mediating inflammatory responses. However, with extensive and in-depth investigations, researchers have discovered that its role can be expanded to a variety of signaling mechanisms, biological processes, human diseases, and treatment options. In this review, we first scrutinize the research process of NF-κB signaling, and summarize the composition, activation, and regulatory mechanism of NF-κB signaling. We investigate the interaction of NF-κB signaling with other important pathways, including PI3K/AKT, MAPK, JAK-STAT, TGF-β, Wnt, Notch, Hedgehog, and TLR signaling. The physiological and pathological states of NF-κB signaling, as well as its intricate involvement in inflammation, immune regulation, and tumor microenvironment, are also explicated. Additionally, we illustrate how NF-κB signaling is involved in a variety of human diseases, including cancers, inflammatory and autoimmune diseases, cardiovascular diseases, metabolic diseases, neurological diseases, and COVID-19. Further, we discuss the therapeutic approaches targeting NF-κB signaling, including IKK inhibitors, monoclonal antibodies, proteasome inhibitors, nuclear translocation inhibitors, DNA binding inhibitors, TKIs, non-coding RNAs, immunotherapy, and CAR-T. Finally, we provide an outlook for research in the field of NF-κB signaling. We hope to present a stereoscopic, comprehensive NF-κB signaling that will inform future research and clinical practice.

RNA methylation in inflammatory bowel disease

RNA modifications, including the renowned m6A, have recently garnered significant attention. This chemical alteration, present in mRNA, exerts a profound influence on protein expression levels by affecting splicing, nuclear export, stability, translation, and other critical processes. Although the role of RNA methylation in the pathogenesis and progression of IBD and colorectal cancer has been reported, many aspects remain unresolved. In this comprehensive review, we present recent studies on RNA methylation in IBD and colorectal cancer, with a particular focus on m6A and its regulators. We highlight the pivotal role of m6A in the pathogenesis of IBD and colorectal cancer and explore the potential applications of m6A modifications in the diagnosis and treatment of these diseases.

Disruption of CerS6-mediated sphingolipid metabolism by FTO deficiency aggravates ulcerative colitis

BACKGROUND AND AIMS

Deregulation of RNA N6-methyladenosine (m6A) modification in intestinal epithelial cells (IECs) influences intestinal immune cells and leads to intestinal inflammation. We studied the function of fat mass-and obesity-associated protein (FTO), one of the m6A demethylases, in patients with ulcerative colitis (UC).

METHODS

We analysed colon tissues of Ftoflox/flox; Villin-cre mice and their Ftoflox/flox littermates with dextran sulfate sodium (DSS) using real-time PCR and 16s rRNA sequencing. RNA and methylated RNA immunoprecipitation sequencing were used to analyse immunocytes and IECs. Macrophages were treated with conditioned medium of FTO-knockdown MODE-K cells or sphingosine-1-phosphate (S1P) and analysed for gene expression. Liquid chromatograph mass spectrometry identified C16-ceramide.

RESULTS

FTO downregulation was identified in our in-house cohort and external cohorts of UC patients. Dysbiosis of gut microbiota, increased infiltration of proinflammatory macrophages, and enhanced differentiation of Th17 cells were observed in Ftoflox/flox;Villin-cre mice under DSS treatment. FTO deficiency resulted in an increase in m6A modification and a decrease in mRNA stability of CerS6, the gene encoding ceramide synthetase, leading to the downregulation of CerS6 and the accumulation of S1P in IECs. Subsequentially, the secretion of S1P by IECs triggered proinflammatory macrophages to secrete serum amyloid A protein 1/3, ultimately inducing Th17 cell differentiation. In addition, through bioinformatic analysis and experimental validation, we identified UC patients with lower FTO expression might respond better to vedolizumab treatment.

CONCLUSIONS

FTO downregulation promoted UC by decreasing CerS6 expression, leading to increased S1P accumulation in IECs and aggravating colitis via m6A-dependent mechanisms. Lower FTO expression in UC patients may enhance their response to vedolizumab treatment.

Epigenetic modification of m6A methylation: Regulatory factors, functions and mechanism in inflammatory bowel disease

Although the exact cause of inflammatory bowel disease (IBD) is still unknown, there is a lot of evidence to support the notion that it results from a combination of environmental factors, immune system issues, gut microbial changes, and genetic susceptibility. In recent years, the role of epigenetics in the pathogenesis of IBD has drawn increasing attention. The regulation of IBD-related immunity, the preservation of the intestinal epithelial barrier, and autophagy are all significantly influenced by epigenetic factors. The most extensive epigenetic methylation modification of mammalian mRNA among them is N6-methyladenosine (m6A). It summarizes the general structure and function of the m6A regulating factors, as well as their complex effects on IBD by regulating the intestinal mucous barrier, intestine mucosal immunity, epidermal cell death, and intestinal microorganisms.This paper provides key insights for the future identification of potential new targets for the diagnosis and treatment of IBD.

Intestinal transit-amplifying cells require METTL3 for growth factor signaling and cell survival

Intestinal epithelial transit-amplifying cells are essential stem progenitors required for intestinal homeostasis, but their rapid proliferation renders them vulnerable to DNA damage from radiation and chemotherapy. Despite these cells' critical roles in intestinal homeostasis and disease, few studies have described genes that are essential to transit-amplifying cell function. We report that RNA methyltransferase-like 3 (METTL3) is required for survival of transit-amplifying cells in the murine small intestine. Transit-amplifying cell death after METTL3 deletion was associated with crypt and villus atrophy, loss of absorptive enterocytes, and uniform wasting and death in METTL3-depleted mice. Sequencing of polysome-bound and methylated RNAs in enteroids and in vivo demonstrated decreased translation of hundreds of methylated transcripts after METTL3 deletion, particularly transcripts involved in growth factor signal transduction such as Kras. Further investigation verified a relationship between METTL3 and Kras methylation and protein levels in vivo. Our study identifies METTL3 as an essential factor supporting the homeostasis of small intestinal tissue via direct maintenance of transit-amplifying cell survival. We highlight the crucial role of RNA modifications in regulating growth factor signaling in the intestine with important implications for both homeostatic tissue renewal and epithelial regeneration.

Muc2 mucin O-glycosylation interacts with enteropathogenic Escherichia coli to influence the development of ulcerative colitis based on the NF-kB signaling pathway

BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory disease of the intestine characterized by a compromised intestinal epithelial barrier. Mucin glycans are crucial in preserving barrier function during bacterial infections, although the underlying mechanisms remain largely unexplored.

METHODS

A cohort comprising 15 patients diagnosed with UC and 15 healthy individuals was recruited. Stool samples were collected to perform 16S rRNA gene sequencing, while biopsy samples were subjected to nanocapillary liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS) to assess O-glycosylation. Gene expression was evaluated through qPCR analysis and Western blotting. Furthermore, animal experiments were conducted to investigate the effects of Escherichia coli and/or O-glycan inhibitor benzyl-α-GalNAc on the development of colitis in mice.

RESULTS

Our findings revealed that the mucus barrier was disrupted during the early stages of UC, while the MUC2 protein content remained unaltered. Additionally, a noteworthy reduction in the O-glycosylation of MUC2 was observed, along with significant changes in the intestinal microbiota during the early stages of UC. These changes included a decrease in intestinal species richness and an increase in the abundance of Escherichia coli (E. coli). Moreover, subsequent to the administration of galactose or O-glycan inhibitor to intestinal epithelial cells, it was observed that the cell culture supernatant had the ability to modify the proliferation and adhesive capacity of E. coli. Furthermore, when pathogenic E. coli or commensal E. coli were cocultured with intestinal epithelium, both strains elicited activation of the NF-KB signaling pathway in epithelial cells and facilitated the expression of serine protease in comparison to the untreated control. Consistently, the inhibition of O-glycans has been observed to enhance the pathogenicity of E. coli in vivo. Furthermore, a correlation has been established between the level of O-glycans and the development of ulcerative colitis. Specifically, a reduction in the O-glycan content of MUC2 cells has been found to increase the virulence of E. coli, thereby compromising the integrity of the intestinal epithelial barrier.

CONCLUSIONS

Together, there exist complex interactions between the intestinal epithelium, O-glycans, and the intestinal microbiota, which may inform the development of novel therapeutic strategies for the treatment of ulcerative colitis.

RIPK1 and RIPK3 inhibitors: potential weapons against inflammation to treat diabetic complications

Diabetes mellitus is a metabolic disease that is characterized by chronic hyperglycemia due to a variety of etiological factors. Long-term metabolic stress induces harmful inflammation leading to chronic complications, mainly diabetic ophthalmopathy, diabetic cardiovascular complications and diabetic nephropathy. With diabetes complications being one of the leading causes of disability and death, the use of anti-inflammatories in combination therapy for diabetes is increasing. There has been increasing interest in targeting significant regulators of the inflammatory pathway, notably receptor-interacting serine/threonine-kinase-1 (RIPK1) and receptor-interacting serine/threonine-kinase-3 (RIPK3), as drug targets for managing inflammation in treating diabetes complications. In this review, we aim to provide an up-to-date summary of current research on the mechanism of action and drug development of RIPK1 and RIPK3, which are pivotal in chronic inflammation and immunity, in relation to diabetic complications which may be benefit for explicating the potential of selective RIPK1 and RIPK3 inhibitors as anti-inflammatory therapeutic agents for diabetic complications.

Phase separation of BuGZ regulates gut regeneration and aging through interaction with m6A regulators

Exploring the role of phase separation in intracellular compartment formation is an active area of research. However, the associations of phase separation with intestinal stem cell (ISC)-dependent regeneration and aging remain unclear. Here, we demonstrate that BuGZ, a coacervating mitotic effector, shows age- and injury-associated condensation in Drosophila ISC nuclei during interphase. BuGZ condensation promotes ISC proliferation, affecting Drosophila gut repair and longevity. Moreover, m6A reader YT521-B acts as the transcriptional and functional downstream of BuGZ. The binding of YT521-B promotor or m6A writer Ime4/ Mettl14 to BuGZ controls its coacervation, indicating that the promotor may accelerate the phase transition of its binding transcription factor. Hence, we propose that phase separation and m6A regulators may be critical for ameliorating ISC-dependent gut regeneration and aging and requires further study.

Colonic stem cell from severe ulcerative colitis maintains environment-independent immune activation by altering chromatin accessibility and global m6A loss

Ulcerative colitis (UC) is a chronic inflammatory disease of colon, which is characterized by cryptarchitectural distortion. Alternation of colonic stem cell (CoSC) contributed to the occurrence of UC, yet the regulatory mechanisms remain unclear. To investigate the dysregulation of transcriptional and post-transcriptional regulation, we performed RNA-seq, ATAC-seq, and m6A meRIP-seq analysis of the cultured CoSCs that were isolated from UC patients. The transcriptome analysis revealed distinct expression signatures of UC patients in mild and severe stages. We observed abnormal activation of immune and extracellular matrix-related genes in patients affected by severe UC. The chromatin accessibility at the promoter regions of these genes was also specifically increased in the severe stage. In addition, we identified that a global loss of RNA m6A modification in the severe stage was accompanied by higher expression of the m6A demethylase FTO. The aberrant activation of a large number of immune and extracellular matrix-related genes, including IL4R, HLA-DPA1, and COL6A1, was related to both the gain of chromatin accessibility and the loss of m6A in severe UC patients. Our finding revealed an environment-independent immune activation of CoSCs in UC and provided FTO as a potential therapeutic target.

Role of TNF-α-induced m6A RNA methylation in diseases: a comprehensive review

Tumor Necrosis Factor-alpha (TNF-α) is ubiquitous in the human body and plays a significant role in various physiological and pathological processes. However, TNF-α-induced diseases remain poorly understood with limited efficacy due to the intricate nature of their mechanisms. N6-methyladenosine (m6A) methylation, a prevalent type of epigenetic modification of mRNA, primarily occurs at the post-transcriptional level and is involved in intranuclear and extranuclear mRNA metabolism. Evidence suggests that m6A methylation participates in TNF-α-induced diseases and signaling pathways associated with TNF-α. This review summarizes the involvement of TNF-α and m6A methylation regulators in various diseases, investigates the impact of m6A methylation on TNF-α-induced diseases, and puts forth potential therapeutic targets for treating TNF-α-induced diseases.

Biological function and research progress of N6-methyladenosine binding protein heterogeneous nuclear ribonucleoprotein A2B1 in human cancers

N6-methyladenosine (m6A) is the most prevalent internal modification found in both mRNA and lncRNA. It exerts reversible regulation over RNA function and affects RNA processing and metabolism in various diseases, especially tumors. The m6A binding protein, hnRNPA2B1, is extensively studied as a member of the heterogeneous nuclear ribonucleoprotein (hnRNP) protein family. It is frequently dysregulated and holds significant importance in multiple types of tumors. By recognizing m6A sites for variable splicing, maintaining RNA stability, and regulating translation and transport, hnRNPA2B1 plays a vital role in various aspects of tumor development, metabolism, and regulation of the immune microenvironment. In this review, we summarized the latest research on the functional roles and underlying molecular mechanisms of hnRNPA2B1. Moreover, we discussed its potential as a target for tumor therapy.

Polysaccharide from Strongylocentrotus nudus eggs regulates intestinal epithelial autophagy through CD36/PI3K-Akt pathway to ameliorate inflammatory bowel disease

Sea urchin is a popular food all over the world, of which eggs are main edible part. Previous studies suggested that polysaccharides from eggs of Strongylocentrotus nudus (SEP) exhibited immunomodulatory activities during anti-tumor therapy, nevertheless, effects of SEP on inflammatory bowel disease and its underlying mechanisms have never been reported. In the present study, we showed that the SEP inhibited dextran sodium sulfate-induced ulcerative colitis characterized by decreased disease activity index, restored colon length and body weight, improved histopathological changes, down-regulation of inflammatory cytokines levels and Th17/Treg ratios in C57BL/6 J mice. Moreover, immunofluorescence analysis suggested that SEP repaired gut barrier in UC mice, while 16S rDNA sequencing exhibited improved intestinal flora. Mechanistically, we found SEP significantly modulated autophagy-related factors in intestinal epithelial cells (IECs), while might contributed to pathogenesis of UC. Furthermore, we demonstrated PI3K/Akt pathway was involved in regulatory effect of SEP on lipopolysaccharide-induced autophagy of HT-29 cells. Besides, among possible polysaccharide binding receptors, change of the CD36 expression was most significant, which was associated with PI3K/Akt signals. Collectively, our study showed for the first time that the SEP might be used a prebiotic agent to improve IBD through regulating CD36-PI3K/Akt mediated autophagy of IECs.

Modulation of stem cell fate in intestinal homeostasis, injury and repair

The mammalian intestinal epithelium constitutes the largest barrier against the external environment and makes flexible responses to various types of stimuli. Epithelial cells are fast-renewed to counteract constant damage and disrupted barrier function to maintain their integrity. The homeostatic repair and regeneration of the intestinal epithelium are governed by the Lgr5⁺ intestinal stem cells (ISCs) located at the base of crypts, which fuel rapid renewal and give rise to the different epithelial cell types. Protracted biological and physicochemical stress may challenge epithelial integrity and the function of ISCs. The field of ISCs is thus of interest for complete mucosal healing, given its relevance to diseases of intestinal injury and inflammation such as inflammatory bowel diseases. Here, we review the current understanding of the signals and mechanisms that control homeostasis and regeneration of the intestinal epithelium. We focus on recent insights into the intrinsic and extrinsic elements involved in the process of intestinal homeostasis, injury, and repair, which fine-tune the balance between self-renewal and cell fate specification in ISCs. Deciphering the regulatory machinery that modulates stem cell fate would aid in the development of novel therapeutics that facilitate mucosal healing and restore epithelial barrier function.

The role of mesenchymal stem cell-derived exosome in epigenetic modifications in inflammatory diseases

Epigenetic modification is a complex process of reversible and heritable alterations in gene function, and the combination of epigenetic and metabolic alterations is recognized as an important causative factor in diseases such as inflammatory bowel disease (IBD), osteoarthritis (OA), systemic lupus erythematosus (SLE), and even tumors. Mesenchymal stem cell (MSC) and MSC-derived exosome (MSC-EXO) are widely studied in the treatment of inflammatory diseases, where they appear to be promising therapeutic agents, partly through the potent regulation of epigenetic modifications such as DNA methylation, acetylation, phosphorylation, and expression of regulatory non-coding RNAs, which affects the occurrence and development of inflammatory diseases. In this review, we summarize the current research on the role of MSC-EXO in inflammatory diseases through their modulation of epigenetic modifications and discuss its potential application in the treatment of inflammatory diseases.

Intestinal transit amplifying cells require METTL3 for growth factor signaling, KRAS expression, and cell survival

Intestinal epithelial transit amplifying cells are essential stem progenitors required for intestinal homeostasis, but their rapid proliferation renders them vulnerable to DNA damage from radiation and chemotherapy. Despite their critical roles in intestinal homeostasis and disease, few studies have described genes that are essential to transit amplifying cell function. We report that the RNA methyltransferase, METTL3, is required for survival of transit amplifying cells in the murine small intestine. Transit amplifying cell death after METTL3 deletion was associated with crypt and villus atrophy, loss of absorptive enterocytes, and uniform wasting and death in METTL3-depleted mice. Ribosome profiling and sequencing of methylated RNAs in enteroids and in vivo demonstrated decreased translation of hundreds of unique methylated transcripts after METTL3 deletion, particularly transcripts involved in growth factor signal transduction such as Kras. Further investigation confirmed a novel relationship between METTL3 and Kras methylation and protein levels in vivo. Our study identifies METTL3 as an essential factor supporting the homeostasis of small intestinal tissue via direct maintenance of transit amplifying cell survival. We highlight the crucial role of RNA modifications in regulating growth factor signaling in the intestine, with important implications for both homeostatic tissue renewal and epithelial regeneration.

N6 - Methyladenosine defines a new checkpoint in γδ T cell development

T cells, which are derived from hematopoietic stem cells (HSCs), are the most important components of adaptive immune system. Based on the expression of αβ and γδ receptors, T cells are mainly divided into αβ and γδ T cells. In the thymus, they share common progenitor cells, while undergoing a series of well-characterized and different developmental processes. N⁶ -Methyladenosine (m⁶ A), one of the most abundant modifications in mRNAs, plays critical roles in cell development and maintenance of function. Recently, we have demonstrated that the depletion of m⁶ A demethylase ALKBH5 in lymphocytes specifically induces an expansion of γδ T cells through the regulation of Jag1/Notch2 signaling, but not αβ T cells, indicating a checkpoint role of ALKBH5 and m⁶ A modification in the early development of γδ T cells. Based on previous studies, many key pathway molecules, which exert dominant roles in γδ T cell fate determination, have been identified as the targets regulated by m⁶ A modification. In this review, we mainly summarize the potential regulation between m⁶ A modification and these key signaling molecules in the γδ T cell lineage commitment, to provide new perspectives in the checkpoint of γδ T cell development.

m6A modification in inflammatory bowel disease provides new insights into clinical applications

Inflammatory bowel disease (IBD) results from a complex interplay between genetic predisposition, environmental factors, and gut microbes. The role of N6-methyladenosine (m6A) methylation in the pathogenesis of IBD has attracted increasing attention. m6A modification not only regulates intestinal mucosal immunity and intestinal barrier function, but also affects apoptosis and autophagy in intestinal epithelial cells. Additionally, m6A modification participated in the interaction between gut microbes and the host, providing a novel direction to explore the molecular mechanisms of IBD and the theoretical basis for specific microorganism-oriented prevention and treatment measures. m6A regulators are expected to be biomarkers for predicting the prognosis of IBD patients. m6A methylation may be utilized as a novel target in the management of IBD. This review focused on the recent advances in how m6A modification causes the initiation and development of IBD, and provided new insights into optimal prevention and treatment measures for IBD.

Activation of MyD88-Dependent TLR Signaling Modulates Immune Response of the Mouse Heart during Pasteurella multocida Infection

Pasteurella multocida (P. multocida) is an important zoonotic pathogen. In addition to lung lesions, necropsies have revealed macroscopic lesions in the heart in clinical cases. However, most previous studies focused on lung lesions while ignoring heart lesions. Therefore, to investigate the immune response of the P. multocida-infected heart, two murine infection models were established by using P. multocida serotype A (Pm HN02) and D (Pm HN01) strains. Histopathological examination revealed heterogeneous inflammatory responses, including immune cell infiltration in the epicardial and myocardial areas of the heart. Transcriptome sequencing was performed on infected cardiac tissues. To explore the traits of immune responses, we performed the functional enrichment analysis of differentially expressed genes, gene set enrichment analysis and gene set variation analysis. The results showed that the innate immune pathways were significantly regulated in both groups, including the NOD-like receptor signaling pathway, the complement and coagulation cascade and cytokine-cytokine receptor interaction. The Toll-like receptor signaling pathway was only significantly activated in the Pm HN02 group. For the Pm HN02 group, immunohistochemistry analysis further verified the significant upregulation of the hub component MyD88 at the protein level. In conclusion, this study reveals critical pathways for host heart recognition and defense against P. multocida serotypes A and D. Moreover, MyD88 was upregulated by P. multocida serotype A in the heart, providing a theoretical basis for future prevention, diagnosis and treatment research.

METTL14 Regulates Intestine Cellular Senescence through m6A Modification of Lamin B Receptor

N-6-Methyladenosine (m⁶A) modification is involved in multiple biological processes including aging. However, the regulation of m⁶A methyltransferase-like 14 (METTL14) in aging remains unclear. Here, we revealed that the level of m⁶A modification and the expression of METTL14 were particularly decreased in the intestine of aged mice as compared to young mice. Similar results were confirmed in Drosophila melanogaster. Knockdown of Mettl14 in Drosophila resulted in a short lifespan, associated disrupted intestinal integrity, and reduced climbing ability. In human CCD-18Co cells, knockdown of METTL14 accelerated cellular senescence, and the overexpression of METTL14 rescued senescent phenotypes. We also identified the lamin B receptor (LBR) as a target gene for METTL14-mediated m⁶A modification. Knockdown of METTL14 decreased m⁶A level of LBR, resulted in LBR mRNA instability, and thus induced cellular senescence. Our findings suggest that METTL14 plays an essential role in the m⁶A modification-dependent aging process via the regulation of LBR and provides a potential target for cellular senescence.

New insights into bacterial mechanisms and potential intestinal epithelial cell therapeutic targets of inflammatory bowel disease

The global incidence of inflammatory bowel disease (IBD) has increased rapidly in recent years, but its exact etiology remains unclear. In the past decade, IBD has been reported to be associated with dysbiosis of gut microbiota. Although not yet proven to be a cause or consequence of IBD, the common hypothesis is that at least some alterations in the microbiome are protective or pathogenic. Furthermore, intestinal epithelial cells (IECs) serve as a protective physical barrier for gut microbiota, essential for maintaining intestinal homeostasis and actively contributes to the mucosal immune system. Thus, dysregulation within the intestinal epithelium increases intestinal permeability, promotes the entry of bacteria, toxins, and macromolecules, and disrupts intestinal immune homeostasis, all of which are associated with the clinical course of IBD. This article presents a selective overview of recent studies on bacterial mechanisms that may be protective or promotive of IBD in biological models. Moreover, we summarize and discuss the recent discovery of key modulators and signaling pathways in the IECs that could serve as potential IBD therapeutic targets. Understanding the role of the IECs in the pathogenesis of IBD may help improve the understanding of the inflammatory process and the identification of potential therapeutic targets to help ameliorate this increasingly common disease.

The Role of N6-Methyladenosine in Inflammatory Diseases

N⁶-Methyladenosine (m⁶A) is the most abundant epigenetic RNA modification in eukaryotes, regulating RNA metabolism (export, stability, translation, and decay) in cells through changes in the activity of writers, erasers, and readers and ultimately affecting human life or disease processes. Inflammation is a response to infection and injury in various diseases and has therefore attracted significant attention. Currently, extensive evidence indicates that m⁶A plays an essential role in inflammation. In this review, we focus on the mechanisms of m⁶A in inflammatory autoimmune diseases, metabolic disorder, cardio-cerebrovascular diseases, cancer, and pathogen-induced inflammation, as well as its possible role as targets for clinical diagnosis and treatment.

Lycopene attenuates the inflammation and apoptosis in aristolochic acid nephropathy by targeting the Nrf2 antioxidant system

Lycopene (LYC) is a carotenoid, has antioxidant properties. This study investigated whether lycopene attenuates aristolochic acids (AAs) -induced chronic kidney disease. In this experiment, lycopene was used to intervene C57BL/6 mice with renal injury induced by aristolochic acid exposure. The histomorphological changes and serological parameters of the kidney were measured in order to assess the alleviating effect of lycopene on renal injury in aristolochic acid nephropathy. In vitro and in vivo experiments were carried out to verify the main mechanism of action and drug targets of lycopene in improving aristolochic acid nephropathy (AAN) and by various experimental methods such as ELISA, immunohistochemistry, immunofluorescence, Western-blot and qRT-PCR. The results showed that oxidative stress injury was induced in the kidney of mice after AAI exposure, resulting in inflammatory response and tubular epithelial cell apoptosis. The results showed that the Nrf2/HO-1 antioxidant signaling pathway was inhibited after AAI exposure. AAI induces oxidative stress injury in the kidney, which ultimately leads to inflammation and tubular epithelial cell apoptosis. After LYC intervened in the body, it activated Nrf2 nuclear translocation and its downstream HO-1 and NQO1 antioxidant signaling pathways. LYC inhibited ROS production by renal tubular epithelial cells, and alleviated mitochondrial damage. LYC further modulated the TNF-α/NF-κB signaling cascade, thereby reduced the accumulation of inflammatory factors in the renal interstitium. Moreover, LYC was able to up-regulate the expression of Bcl-2, down-regulate Bax expression and inhibit the activation of cleaved forms of Caspase-9 and Caspase-3, which finally attenuated the apoptosis of the mitochondrial pathway induced by AAI exposure. It was concluded that lycopene was able to activate the Nrf2 antioxidant signaling pathway to maintain the homeostasis of renal oxidative stress and ultimately attenuated renal inflammatory response and apoptosis. These results suggested that lycopene can be used as a drug to relieve AAN.