Interferon-β Mediates Signaling Pathways Uniquely Regulated in Hepatic Stellate Cells and Attenuates the Progression of Hepatic Fibrosis in a Dietary Mouse Model

Loss of Toll-like receptor 9 protects from hepatocellular carcinoma in murine models of chronic liver disease

BACKGROUND & AIMS

Toll-like receptor 9 (Tlr9) is a pathogen recognition receptor detecting unmethylated DNA derivatives of pathogens and damaged host cells. It is therefore an important modulator of innate immunity. Here we investigated the role of Tlr9 in fibrogenesis and progression of hepatocellular carcinoma in chronic liver disease.

MATERIALS AND METHODS

We treated mice with a constitutive deletion of Tlr9 (Tlr9-/-) with DEN/CCl4 for 24 weeks. As a second model, we used hepatocyte-specific Nemo knockout (NemoΔhepa) mice and generated double knockout (NemoΔhepaTlr9-/-) animals.

RESULTS

We show that Tlr9 is in the liver primarily expressed in Kupffer cells, suggesting a key role of Tlr9 in intercellular communication during hepatic injury. Tlr9 deletion resulted in reduced liver fibrosis as well as tumor burden. We observed down-regulation of hepatic stellate cell activation and consequently decreased collagen production in both models. Tlr9 deletion was associated with decreased apoptosis and compensatory proliferation of hepatocytes, modulating the initiation and progression of hepatocarcinogenesis. These findings were accompanied by a decrease in interferon-β and an increase in chemokines having an anti-tumoral effect.

CONCLUSIONS

Our data define Tlr9 as an important receptor involved in fibrogenesis, but also in the initiation and progression of hepatocellular carcinoma during chronic liver diseases.

Exploring the Impact of Different Inflammatory Cytokines on Hepatitis C Virus Infection

Hepatitis C virus (HCV) infection is a global health concern affecting millions worldwide. Chronic HCV infection often leads to liver inflammation and can progress to cirrhosis and hepatocellular carcinoma. Inflammatory cytokines are crucial in modulating the immune response during HCV infection. This review aims to investigate the impact of different inflammatory cytokines on HCV infection and associated immune responses. This review was conducted to identify relevant studies on the interplay between inflammatory cytokines and HCV infection. The analysis focused on the effects of key inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-1 (IL-1), and interferon-gamma (IFN-γ), on HCV replication, immune cell activation, and liver inflammation. The findings reveal that these inflammatory cytokines can significantly influence HCV infection and the subsequent immune response. TNF-α, IL-6, and IL-1 have been shown to enhance HCV replication, while IFN-γ exerts antiviral effects by inhibiting viral replication and promoting immune cell-mediated clearance of infected hepatocytes. Moreover, these cytokines contribute to the recruitment and activation of immune cells, such as natural killer cells, T cells, and macrophages, which play critical roles in controlling HCV infection. Understanding the precise mechanisms by which inflammatory cytokines impact HCV infection is crucial for developing more targeted therapeutic strategies. Modulating the levels or activity of specific cytokines may provide opportunities to attenuate HCV replication, reduce liver inflammation, and improve treatment outcomes. In conclusion, this review highlights the significance of inflammatory cytokines in influencing HCV infection and associated immune responses.

TRIF-dependent signaling and its role in liver diseases

TIR domain-containing adaptor inducing IFN-β (TRIF) is a crucial adaptor molecule downstream of toll-like receptors 3 (TLR3) and 4 (TLR4). TRIF directly binds to TLR3 through its TIR domain, while it associates with TLR4 indirectly through the bridge adaptor molecule TRIF-related adaptor molecule (TRAM). TRIF plays a pivotal role in regulating interferon beta 1 (IFN-β) response, nuclear factor kappa B (NF-κB) signaling, apoptosis, and necroptosis signaling mediated by TLR3 and TLR4. It accomplishes these by recruiting and activating various kinases or transcription factors via its distinct domains. In this review, we comprehensively summarize the TRIF-dependent signaling pathways mediated by TLR3 and TLR4, elucidating key target molecules and downstream pathways. Furthermore, we provide an overview of TRIF's impact on several liver disorders, including drug-induced liver injury, ischemia-reperfusion liver injury, autoimmune hepatitis, viral hepatitis, alcohol-associated liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH). We also explore its effects on liver steatosis, inflammation, fibrosis, and carcinogenesis. A comprehensive understanding of the TRIF-dependent signaling pathways, as well as the intricate relationship between TRIF and liver diseases, can facilitate the identification of potential drug targets and the development of novel and effective therapeutics against hepatic disorders.

Differential effects of PGAM5 knockout on high fat high fructose diet and methionine choline-deficient diet induced non-alcoholic steatohepatitis (NASH) in mice

BACKGROUND

Phosphoglycerate mutase 5 (PGAM5), a phosphatase involved in mitochondrial homeostasis, is reported to be closely related to the metabolic stress induced by high-fat diet (HFD) or cold. In this study, we aimed to investigate the effects of PGAM5 on hepatic steatosis, inflammation and fibrosis in nonalcoholic steatohepatitis (NASH).

METHODS AND RESULTS

We generated PGAM5 global knockout (GKO) mice and their wildtype (WT) littermates using CRISPR/CAS9. The mice were fed with a high fat high fructose (HFHF) diet for 12 weeks or a methionine choline-deficient (MCD) diet (methionine choline supplemented (MCS) as control) for 6 weeks. Hepatic PGAM5 expression was up-regulated in humans with NASH and WT mice fed with HFHF and MCS, and reduced in WT mice fed with MCD diet. In HFHF-fed mice, GKO had reduced body weight, hepatic triglyceride (TG) content and serum transaminase along with decreased hepatic pro-inflammatory and pro-fibrotic responses compared with their WT control. GKO had increased expression of antioxidative gene glutathione peroxidase-6 (GPX6) and activation of mammalian target of rapamycin (mTOR). In mice fed with MCS diet, GKO significantly increased serum TNF-α and IL-6 and decreased hepatic GPX6 mRNA expression. There was no difference in hepatic steatosis, inflammation or fibrosis between GKO and WT mice fed with MCD diet. We investigated the role of PGAM5 deficiency in a variety of cell types. In differentiated THP-1 cells, PGAM5 silencing significantly increased pro-inflammatory cytokine secretion and decreased antioxidative proteins, including nuclear factor erythroid 2- related factors (NRF2), heme oxygenase-1 (HO-1) and GPX6 without affecting mTOR activity. In HepG2 cells with steatosis, PGAM5 knockdown reduced insulin sensitivity, increased mTOR phosphorylation and reduced the expression of NRF2, catalase (CAT), HO-1 and GPX6. Conversely, PGAM5 knockdown reduced TG accumulation, increased insulin sensitivity, and increased antioxidative genes in 3T3-L1 cells, despite the up-regulation in mTOR phosphorylation.

CONCLUSIONS

PGAM5-KO relieved hepatic steatosis and inflammation in HFHF model, promoted inflammation in MCS-fed mice and had no effects on the MCD-fed model. The distinct effects may be owing to the different effects of PGAM5-KO on anti-oxidative pathways in energy-dependent, possible involves mTOR, and/or cell type-dependent manner. Our findings suggest that PGAM5 can be a potential therapeutic target for NASH.

Therapeutic effect of fenofibrate for non-alcoholic steatohepatitis in mouse models is dependent on regime design

Background: Non-alcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver diseases. In most cases, NAFLD progresses from benign steatosis to steatohepatitis (NASH), and then to cirrhosis. No treatment is currently approved for NAFLD/NASH in the clinic. Fenofibrate (FENO) has been clinically used to treat dyslipidemia for more than a half century, but its effects on NASH are not established. FENO's half-life is quite different between rodent and human. The aim of this study was to investigate the potential of pharmacokinetic-based FENO regime for NASH treatment and the underlying mechanisms. Methods: Two typical mouse NASH models, methionine-choline deficient (MCD) diet-fed mice and choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD)-fed mice, were used. MCD model was designed as therapeutic evaluation in experiment 1 and CDAHFD model was designed as preventive in experiment 2. Three doses of FENO (5, 25, 125 mg/kg), two times a day (BID), were administered to the above models. Serum markers of liver injury, cholestasis, and the histology of liver tissues were investigated. Normal mice were used as a model in experiment 3 for toxicity evaluation, Quantitative-PCR and Western Blot assays were used to investigate the inflammatory responses, bile acid synthesis as well as lipid catabolism. Results: Mice on the MCD and CDAHFD diets developed steatohepatitis as expected. Treatment with FENO (25 mg/kg·BID) significantly decreased hepatic steatosis, inflammation and fibrosis in both therapeutic and preventive models. In the MCD model, the therapeutic action of FENO (25 mg/kg·BID) and 125 mg/kg·BID on histopathology and the expression of inflammatory cytokines were comparable. In reducing macrophage infiltration and bile acid load, FENO (25 mg/kg·BID) was superior to 125 mg/kg·BID. In all the aspects mentioned above, FENO (25 mg/kg·BID) was the best among the 3 doses in the CDAHFD model. In a third experiment, the effects of FENO (25 mg/kg·BID) and 125 mg/kg·BID on lipid catabolism were comparable, but 125 mg/kg·BID increased the expression of inflammatory factors and bile acid load. In both models, FENO (5 mg/kg·BID) showed little effect in hepatic steatosis and inflammation, neither the adverse effects. FENO (125 mg/kg·BID) aggravated liver inflammation, increased bile acid synthesis, and promoted the potential of liver proliferation. In toxicity risk assay, FENO (25 mg/kg·BID) treatment showed low potential to trigger bile acid synthesis, inflammation and hepatocyte proliferation. Conclusion: A new regime, FENO (25 mg/kg·BID) is potentially a therapeutic strategy for the NASH treatment. Translational medicine is warranted to prove its effectiveness in the clinic.

Type I and II interferon signaling in colorectal cancer liver metastasis

Metastatic colorectal cancer is one of the leading causes of cancer-related deaths worldwide. Traditional chemotherapy extended the lifespan of cancer patients by only a few months, but targeted therapies and immunotherapy prolonged survival and led to long-term remissions in some cases. Type I and II interferons have direct pro-apoptotic and anti-proliferative effects on cancer cells and stimulate anti-cancer immunity. As a result, interferon production by cells in the tumor microenvironment is in the spotlight of immunotherapies as it affects the responses of anti-cancer immune cells. However, promoting effects of interferons on colorectal cancer metastasis have also been reported. Here we summarize our knowledge about pro- and anti-metastatic effects of type I and II interferons in colorectal cancer liver metastasis and discuss possible therapeutic implications.

Co-expression of fibrotic genes in inflammatory bowel disease; A localized event?

Introduction

Extracellular matrix turnover, a ubiquitous dynamic biological process, can be diverted to fibrosis. The latter can affect the intestine as a serious complication of Inflammatory Bowel Diseases (IBD) and is resistant to current pharmacological interventions. It embosses the need for out-of-the-box approaches to identify and target molecular mechanisms of fibrosis.

Methods and results

In this study, a novel mRNA sequencing dataset of 22 pairs of intestinal biopsies from the terminal ileum (TI) and the sigmoid of 7 patients with Crohn's disease, 6 with ulcerative colitis and 9 control individuals (CI) served as a validation cohort of a core fibrotic transcriptomic signature (FIBSig), This signature, which was identified in publicly available data (839 samples from patients and healthy individuals) of 5 fibrotic disorders affecting different organs (GI tract, lung, skin, liver, kidney), encompasses 241 genes and the functional pathways which derive from their interactome. These genes were used in further bioinformatics co-expression analyses to elucidate the site-specific molecular background of intestinal fibrosis highlighting their involvement, particularly in the terminal ileum. We also confirmed different transcriptomic profiles of the sigmoid and terminal ileum in our validation cohort. Combining the results of these analyses we highlight 21 core hub genes within a larger single co-expression module, highly enriched in the terminal ileum of CD patients. Further pathway analysis revealed known and novel inflammation-regulated, fibrogenic pathways operating in the TI, such as IL-13 signaling and pyroptosis, respectively.

Discussion

These findings provide a rationale for the increased incidence of fibrosis at the terminal ileum of CD patients and highlight operating pathways in intestinal fibrosis for future evaluation with mechanistic and translational studies.

Kuhuang alleviates liver fibrosis by modulating gut microbiota-mediated hepatic IFN signaling and bile acid synthesis

Background: Liver fibrosis is a common outcome of the pathological progression of chronic liver disease; however, no specific and effective therapeutic agent has been approved for its treatment. We investigated the effects of Kuhuang on liver fibrosis and the underlying mechanisms of action. Materials and methods: To induce hepatic fibrosis, either 3,5-diethoxycarbonyl-1,4-dihydro-collidine (DDC) diet was administered, or bile duct ligation (BDL) surgery was performed on C57BL/6 mice. Kuhuang was orally administered to mice for 7 days before and after bile duct ligation or 4 weeks with a DDC diet. Hematoxylin and eosin, Sirius red staining, and immunohistochemical analyses were performed to evaluate hepatic pathology. Hepatic interferon-β (IFN-β) levels were measured using an enzyme-linked immunosorbent assay. RNA sequencing was performed to examine the gene expression profiles of liver tissues. The mRNA expression of inflammatory, profibrotic, and bile acid (BA)-related genes was further validated by qRT-PCR. A targeted metabolomics assay revealed the alteration of the hepatic bile acid (BA) composition. The composition of the gut microbiota was determined via 16S rRNA sequencing. Results: Treatment with Kuhuang attenuated liver fibrosis and reduced the inflammatory response in bile duct ligation and DDC mouse models. In addition, the hepatic IFN signaling pathway was activated following Kuhuang treatment. Kuhuang treatment also significantly decreased hepatic levels of both primary and secondary BAs. In addition, Kuhuang treatment altered gut microbiota composition, with an increased abundance of interferon-inducing Akkermansia and decreased abundance of bile salt hydrolase-producing Lactobacillus, Clostridium, and Bifidobacterium. Furthermore, the abundance of Akkermansia was positively correlated with the hepatic mRNA expression levels of Ifna4, Ifnb, and Isg15, whereas that of Lactobacillus, Clostridium _- sensu _- stricto _- 1, and Bifidobacterium was positively correlated with levels of bile acid synthesis-related genes. Conclusion: Our results suggest that Kuhuang plays a protective role during the progression of liver fibrosis, potentially by altering the composition of the gut microbiota, which consequently activates interferon signaling and inhibits bile acid synthesis in the liver.

Addressing the liver progenitor cell response and hepatic oxidative stress in experimental non-alcoholic fatty liver disease/non-alcoholic steatohepatitis using amniotic epithelial cells

Background

Non-alcoholic fatty liver disease is the most common liver disease globally and in its inflammatory form, non-alcoholic steatohepatitis (NASH), can progress to cirrhosis and hepatocellular carcinoma (HCC). Currently, patient education and lifestyle changes are the major tools to prevent the continued progression of NASH. Emerging therapies in NASH target known pathological processes involved in the progression of the disease including inflammation, fibrosis, oxidative stress and hepatocyte apoptosis. Human amniotic epithelial cells (hAECs) were previously shown to be beneficial in experimental models of chronic liver injury, reducing hepatic inflammation and fibrosis. Previous studies have shown that liver progenitor cells (LPCs) response plays a significant role in the development of fibrosis and HCC in mouse models of fatty liver disease. In this study, we examined the effect hAECs have on the LPC response and hepatic oxidative stress in an experimental model of NASH.

Methods

Experimental NASH was induced in C57BL/6 J male mice using a high-fat, high fructose diet for 42 weeks. Mice received either a single intraperitoneal injection of 2 × 10⁶ hAECs at week 34 or an additional hAEC dose at week 38. Changes to the LPC response and oxidative stress regulators were measured.

Results

hAEC administration significantly reduced the expansion of LPCs and their mitogens, IL-6, IFNγ and TWEAK. hAEC administration also reduced neutrophil infiltration and myeloperoxidase production with a concurrent increase in heme oxygenase-1 production. These observations were accompanied by a significant increase in total levels of anti-fibrotic IFNβ in mice treated with a single dose of hAECs, which appeared to be independent of c-GAS-STING activation.

Conclusions

Expansion of liver progenitor cells, hepatic inflammation and oxidative stress associated with experimental NASH were attenuated by hAEC administration. Given that repeated doses did not significantly increase efficacy, future studies assessing the impact of dose escalation and/or timing of dose may provide insights into clinical translation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02476-6.

Toll-Like Receptor 5 Signaling Ameliorates Liver Fibrosis by Inducing Interferon β-Modulated IL-1 Receptor Antagonist in Mice

Bacterial flagellin, recognized by cell surface of Toll-like receptor (TLR) 5, is a potent activator of many types of cells, leading to the activation of innate or adaptive immunity, which are pivotal in regulating fibrotic process. However, the exact role of TLR5 signaling in hepatic fibrogenesis remains unclear, and this study aims to elucidate its underlying mechanisms. Flagellin was injected to hepatotoxin- and cholestasis-induced liver fibrosis murine models. Flagellin-induced TLR5 activation significantly decreased the severity of liver fibrosis. Interestingly, the expression levels of IL-1 receptor antagonist (IL1RN) and interferon (IFN)β markedly increased in fibrotic livers on flagellin treatment. Consistently, in vivo activation of TLR5 signaling markedly increased IFNβ and IL1RN expression in the livers. Notably, flagellin injection significantly exacerbated the severity of liver fibrosis in IFN-α/β receptor 1 (IFNAR1) knockout mice. Furthermore, hepatic expression of IL1RN in the fibrotic livers of IFNAR1 knockout mice was significantly lower than those of wild-type mice. In support of these findings, flagellin-mediated IL1RN production is not sufficient to alleviate the severity of hepatic fibroinflammatory responses in IFNAR1-deficient milieu. Finally, hepatic stellate cells treated with IL1RN had significantly decreased cellular activation and its associated fibrogenic responses. Collectively, manipulation of TLR5 signaling may be a promising therapeutic strategy for the treatment of liver fibrosis.

Transcriptional Dysregulation of Upstream Signaling of IFN Pathway in Chronic HCV Type 4 Induced Liver Fibrosis

IFN orchestrates the expression of various genes to halt hepatitis C virus (HCV) replication with the possibility of either reduced or increased liver fibrosis; due to controlled viral replication or overproduction of inflammatory mediators, repectively. In this study, we examined the transcriptional profiling of type I IFN related genes in HCV-chronically infected patients with varying degrees of liver fibrosis. PCR array was used to examine the expression of 84 type I IFN related genes in peripheral blood mononuclear cells (PBMCs) RNA from 12 treatment-naïve chronic HCV patients (5 F0-F1 and 7 F2-F4) and 5 healthy subjects. We further validated our results by quantitative real time PCR (qRT-PCR) in 103 treatment-naïve chronic HCV patients (43 F0-F1 and 60 F2-F4) and 15 controls. PCR array data revealed dysregulation in TLR7 pathway. The expression of TLR7 was decreased by 4 folds and MyD88 was increased by 3 folds in PBMCs of F2-F4 patients when compared to the healthy volunteers (p = 0.03 and 0.002, respectively). In addition, IRF7 and TLR7 showed dramatic downregulation (6 and 8 folds, respectively) in F2-F4 patients when compared to F0-F1 ones. qRT-PCR confirmed the altered expression patterns of TLR7 and MyD88 in F2-F4 patients when compared to either controls or F0-F1 patients. However, by qRT-PCR, IRF7 and NF-κB1 (TLR7 pathway transcription factors) exhibited similar mRNA abundance among F2-F4 and F0-F1 patients. These results suggest that TLR7 and MyD88 are possible candidates as biomarkers for the progression of HCV-induced liver fibrosis and/ or targets for therapeutic intervention.