MFG-E8 Knockout Aggravated Nonalcoholic Steatohepatitis by Promoting the Activation of TLR4/NF-κB Signaling in Mice

Transcriptomic evaluation of N6-methyladenosine modification can be used to identify differentially gene and immune-related biological processes in TX mice with liver fibrosis

BACKGROUND

N6-methyladenosine (m6A) modification controls the stability, splicing, and translation of mRNA, which is important in the development of illnesses. Wilson's disease (WD) is an autosomal recessive liver copper metabolic disorder that causes liver fibrosis. The role of m6A methylation in WD-induced liver fibrosis development is still unclear. Thus, the goal of this study was to examine the scope of m6A methylation and further explore the potential targets related to WD-induced liver fibrosis.

RESULTS

A total of 1930 significantly different m6A peaks were found on 1737 mRNAs, of which 993 were hypermethylated and 744 were hypomethylated when comparing normal and WD-induced liver fibrosis mice (n = 3). In parallel, 1261 differentially expressed mRNAs, comprising 557 upregulated and 704 downregulated mRNAs, were found. Overall, 114 mRNAs with significant changes in m6A levels and RNA expression were identified via joint analysis. Then, through PPI network construction and functional enrichment analysis, 12 hub genes were identified, these genes were mainly enriched in the inflammatory response and immunomodulation, and they are associated with immune cell infiltration.

CONCLUSIONS

The significant difference in the amount of mRNA m6A modifications indicates that m6A modification is involved in the progression of WD-induced liver fibrosis, and theidentified hub genes are involved in inflammation and immune infiltration. These results may provide insights for subsequent studies on potential regulatory mechanisms.

Mechanisms and Therapeutic Strategies for MAFLD Targeting TLR4 Signaling Pathways

BACKGROUND

Metabolic-associated fatty liver disease (MAFLD) is one of the most common chronic liver diseases. The underlying pathophysiological mechanisms are intricate and involve various factors. Unfortunately, there is currently a lack of available effective treatment options. Toll-like receptors (TLRs) are a group of pattern-recognition receptors that are responsible for activating the innate immune system. Research has demonstrated that TLR4 plays a pivotal role in the progression of MAFLD by facilitating the pathophysiological mechanisms.

SUMMARY

Lipid peroxidation, pro-inflammatory factors, insulin resistance (IR), and dysbiosis of intestinal microbiota are considered as the pathogenic mechanisms of MAFLD. This review summarizes the impact of TLR4 signaling pathways on the progression of MAFLD, specifically in relation to lipid metabolic disorders, IR, oxidative stress, and gut microbiota disorders. Additionally, we emphasize the potential therapeutic approaches for MAFLD that target TLR4 signaling pathways, including the use of plant extracts, traditional Chinese medicines, probiotics, pharmaceuticals such as peroxisome proliferator-activated receptor antagonists and farnesol X agonists, and lifestyle modifications such as dietary changes and exercise also considered. Furthermore, TLR4 signaling pathways have also been linked to the lean MAFLD.

KEY MESSAGES

TLR4 plays a crucial role in MAFLD by triggering IR, buildup of lipids, imbalance in gut microbiota, oxidative stress, and initiation of immune responses. The mitigation of MAFLD can be accomplished by suppressing the TLR4 signaling pathway. In the future, it could potentially emerge as a therapeutic target for the condition.

Role of targeting TLR4 signaling axis in liver-related diseases

Toll-like receptor 4 (TLR4) plays an important role as a key signal-receiving transmembrane protein molecule in the liver, and substances that target the liver exert therapeutic effects via TLR4-related signaling pathways. This article provides a comprehensive review of targeting the TLR4 signaling axis to play an important role in the liver based on endogenous substances. Articles were divided into 5 major types of liver disease, acute liver injury, viral hepatitis, alcoholic and non-alcoholic liver disease, cirrhosis, and liver cancer, to elucidate how various endogenous substances affect the liver via the TLR4 pathway and the important role of the pathway itself in liver-related diseases to discover the potential therapeutic implications of the TLR4-related pathway in the liver. The results indicate that activation of the TLR4-related signaling axis primarily plays a role in promoting disease progression in liver-related diseases, and the TLR4/MyD88/NF-κB axis plays the most dominant role. Therefore, exploring the full effects of drugs targeting the TLR4-related signaling axis in the liver and the new use of old drugs may be a new research direction.

TAK-242 Ameliorates Hepatic Fibrosis by Regulating the Liver-Gut Axis

Objective. The aims of this study were to investigate the impact of TAK-242 on the Toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)/nuclear transcription factor-κB (NF-κB) signal transduction pathway in rats with hepatic fibrosis (HF) using the liver gut axis and to investigate the molecular mechanism of its intervention on HF. Methods. SPF grade SD male rats were randomly allocated to the control, model, and TAK-242 groups. For 8 weeks, the model and TAK-242 groups received 3 mL·kg-1 (the initial dose 5 mL·kg-1) intraperitoneal injections of 40% CCL4 olive oil solution. TAK-242 (5 mg·kg-1) was administered once a day for 5 days after modeling. The pathological alterations of liver and small intestine tissues in each group were observed using H&E and Masson staining. ELISA was used to measure serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), direct bilirubin (DBIL), total bilirubin (TBIL), interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α). RT-qPCR was utilized to identify the mRNA expression level of IL-1β, IL-6, TNF-α, TLR4, MyD88, and NF-κB in rat liver and small intestine tissues. The protein level of IL-1β, IL-6, TNF-α, TLR4, MyD88, and NF-κB protein in rat liver and small intestine tissues was determined utilizing Western blot and IHC. Results. TAK-242 significantly reduced AST, ALT, TBIL, and DBIL expression in HF rats’ serum ( $P<0.01$ ) and alleviated liver tissue injury. Hematoxylin-eosin (H&E) and Masson staining revealed inflammatory cell infiltration and fibrous proliferation in the liver and small intestine tissue in the model group and partial cell swelling in the TAK-242 group, which indicated a considerable improvement compared to the model group. RT-qPCR, Western blot, and IHC data indicated that TAK-242 reduced the IL-1β, IL-6, TNF-α, TLR4, MyD88, and NF-κB expression in the liver and small intestine tissues of HF rats. Conclusion. TAK-242 might downregulate the TLR4/MyD88/NF-κB signal pathway through the liver-gut axis, suppress the inflammatory response, and eventually alleviate HF in rats.