Protective effect of quercetin against macrophage-mediated hepatocyte injury via anti-inflammation, anti-apoptosis and inhibition of ferroptosis.

Yinchenhao Decoction (YCHD) is a classic prescription in traditional Chinese medicine (TCM). It appears to play an important role in anti-inflammation and autoimmunity protection. As one of the key active ingredients in YCHD, quercetin is a novel anti-inflammatory metabolite that exerts protective effects in many autoimmune diseases. However, its role in autoimmune hepatitis (AIH)-related hepatic injury has not been studied. The aim of this study was to reveal the hepatocyte protective mechanism of quercetin. In this study, we used Concanavalin A (Con A) to establish an in vitro hepatocyte injury-associated AIH model. Brl3a hepatocyte injury was induced by the supernatant of J774A.1 cells treated with Con A. We found that quercetin mitigated Con A-induced via macrophage-mediated Brl3a hepatocyte injury. Quercetin administration reduced the levels of alanine transaminase (ALT) and aspartate transaminase (AST) in the supernatant of Con A-treated Brl3a cells and attenuated the infiltration of J774A.1 macrophages induced by Con A. Moreover, quercetin effectively inhibited the expression of proinflammatory cytokines including interleukin-1ß (IL-1ß) by Con A. Furthermore, quercetin decreased hepatocyte apoptosis and ferroptosis levels in the macrophage-induced hepatocyte injury model. In conclusion, our study indicates that quercetin alleviates macrophage-induced hepatocyte damage by reducing the inflammatory response, apoptosis and ferroptosis. Our work suggests that quercetin might be a potential therapeutic strategy for AIH.

Concanavalin A-induced autoimmune hepatitis model in mice: Mechanisms and future outlook.

The concanavalin A (Con A)-induced liver injury mouse model is a typical animal model focusing on T cell-dependent hepatic damage in the field of autoimmune hepatitis (AIH). However, the underlying mechanism of hepatic dysfunction due to cell activation or signaling pathways triggered by Con A has not been fully clarified. Therefore, the controversy on this model remains in the academic community. In this article, we first summarized the merit and demerit of this contentious model from the perspectives of cell dysfunction, microcirculation disturbance, involved signaling pathways, as well as the properties of Con A. Then, we summed up the scientific implications of the model in elucidating the pathogenesis of AIH, and the shortcomings of this model were also summarized to elucidate the pathogenesis and application prospect of this classical liver injury mouse model in the study of AIH.

Circular RNAs associated with a mouse model of concanavalin A-induced autoimmune hepatitis: preliminary screening and comprehensive functional analysis.

Without treatment, autoimmune hepatitis (AIH) often leads to cirrhosis, liver failure and, in some cases, death. However, the pathogenesis of AIH remains incompletely understood. Here, we explored the relationship between differentially expressed circular RNAs (DECs) and development of AIH by obtaining an expression profile of DECs in a concanavalin A-induced AIH mouse model by microarray. In total, we identified 27 DECs; the host genes of these DECs were annotated with 140 Gene Ontology terms and 19 pathways, revealing potential roles in the metabolism of cellular ions and regulation of protein expression, as well as possible involvement in endocytosis and apoptosis. We constructed a circular RNA-microRNA network that was used to infer that a mmu_circ_0001520/mmu-miR-193b-3p/MAPK10 network may be associated with the occurrence of AIH. These findings may help lay the foundation for validation of the potential roles of circular RNAs in AIH.

Characterization and functional prediction of the microRNAs differentially expressed in a mouse model of concanavalin A-induced autoimmune hepatitis.

In order to investigate the altered expression of microRNAs (miRNAs) in the development of autoimmune hepatitis (AIH), the aberrantly expressed miRNAs in the concanavalin A (Con A)-induced AIH mouse model were identified for the first time with microarray in this study. A total of 49 miRNAs (31 up- and 18 down-regulated) were screened out, and the qRT-PCR validation results of 12 chosen miRNAs were consistent with the microarray data. Combined with the profiling of differently expressed mRNAs in the same model (data not shown), 959 predicted target genes (601 for up- and 358 for down-regulated miRNAs) were obtained according to the intersection of databases miRWalk and miRDB, and several hub genes were obtained from the regulatory networks, including Cadm1 and Mier3. These target genes were significantly enriched in the Gene ontology (GO) terms of "transcription, DNA-templated", and were annotated in 47 signaling pathways, comprising "Wnt signaling pathway", "Hippo signaling pathway", "Ferroptosis" and "mitogen-activated protein kinase (MAPK) signaling pathway", according to the GO and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. In the miRNA-GO-network, mmu-miR-193b-3p were exhibited in 33 GO terms of biological processes (BP), and the most significantly regulated GO term in BP categories was "regulation of transcription, DNA-templated". While in the miRNA-pathway-network, mmu-miR-7005-5p were enriched in 37 pathways, which was more than the other specifically expressed miRNAs, and the most significantly enriched pathways were "Endocytosis" and "MAPK signaling pathway". In conclusion, these differently expressed miRNAs seemed to be associated with the onset of AIH, and have the potential to serve as the new targets on the treatment of this disease.

Microarray-based transcriptional profiling of a mouse model of autoimmune hepatitis.

Long noncoding RNAs (lncRNAs) are RNA molecules longer than 200 nucleotides that do not typically code for a protein. lncRNAs have regulatory roles in many physiological processes, and their dysregulation can contribute to cancer, cardiovascular and neurodegenerative diseases, as well as the onset of autoimmune diseases, including systemic lupus erythematosus and rheumatoid arthritis. However, lncRNA expression changes in autoimmune hepatitis (AIH), a form of inflammation induced by immunological tolerance disorders, are poorly understood. Here, for the first time to our knowledge, we used microarrays to profile 1161 differentially expressed lncRNAs (DELs; 608 up- and 553 down-regulated) and 11 512 differentially expressed mRNAs (DEMs; 5189 up- and 6323 down- regulated) in a concanavalin A-induced AIH mouse model. We used quantitative real-time PCR to confirm the expression of eight DELs and DEMs, and analyzed the coexpression relationship between them. Potential biological functions of screened DELs and DEMs were predicted with Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis. DEL-DEM interaction networks were also constructed. Our study revealed the roles of DELs and DEMs in the pathogenesis of AIH. We also provided potential candidate biomarkers that may have potential for future development into possible diagnostics or as a treatment for this disorder.

CD279 mediates the homeostasis and survival of regulatory T cells by enhancing T cell and macrophage interactions.

CD279 is a cell surface protein predominantly expressed on T cells. Its ligands CD273 and CD274 are expressed on antigen-presenting cells and tumors. CD279 has been shown to act as an important immune check point by inhibiting CD8 T cell activation, and antibodies against CD279 enhance T cell-mediated cytotoxic function. However, whether CD279 has other functions in CD4 T cell homeostasis or in mediating T cell interactions with antigen-presenting cells remains unclear. In the present study, we show that antibody-mediated inhibition of CD279 reduces T cell survival in bone marrow in vivo. Unexpectedly, CD279 blockade also compromised regulatory T cell and macrophage interactions by reducing their contact time. The observation that the CD273 antagonist had little effect suggests that CD274 (the second ligand of CD279) plays a more central role in contact between conventional T cells (Tcon) and macrophages. The results of the present study suggest that both CD279 ligands contribute to the interaction length between T cells and macrophages as a mechanism of maintaining Treg homeostasis. Furthermore, CD273 and CD274 are not redundant ligands because CD274 may have unique effects on Tcon in this complex immune axis. Therefore, ligand selection for check point blockade as a tool for cancer immunotherapy has important implications with respect to anti-tumor T cell activation and the avoidance of side effects.

A transendocytosis perspective on the CD28/CTLA-4 pathway.

T cell activation is a key event in the adaptive immune response and vital to the generation of both cellular and humoral immunity. Activation is required not only for effective CD4 T cell responses but also to provide help for B cells and the generation of cytotoxic T cell responses. Unsurprisingly, impaired T cell activation results in infectious pathology, whereas dysregulated activation can result in autoimmunity. The decision to activate is therefore tightly regulated and the CD28/CTLA-4 pathway represents this apical decision point at the molecular level. In particular, CTLA-4 (CD152) is an essential checkpoint control for autoimmunity; however, the molecular mechanism(s) by which CTLA-4 achieves its regulatory function are not well understood, especially how it functionally intersects with the CD28 pathway. In this chapter, we review the established molecular and cellular concepts relating to CD28 and CTLA-4 biology, and attempt to integrate these by discussing the transendocytosis of ligands as a new model of CTLA-4 function.