Interleukin-33 drives hepatic fibrosis through activation of hepatic stellate cells. Cell Mol Immunol. 2018;15:388-398. [PMID: 28194023 DOI: 10.1038/cmi.2016.63]

Analysis of Immunometabolic Profiles in Patients With Chronic Drug-Induced Liver Injury and Validation in Mice to Reveal Potential Mechanisms

BACKGROUND

The mechanism underlying chronic drug-induced liver injury (DILI) remains unclear. Immune activation is a common feature of DILI progression and is closely associated with metabolism. We explored the immunometabolic profile of chronic DILI and the potential mechanism of chronic DILI progression.

METHODS

Plasma and peripheral blood mononuclear cells from patients with chronic DILI were analyzed using multiplex immunoassays and untargeted metabolomics to reveal their immunometabolic profile. The effects and potential mechanisms of chronic DILI-related metabolite on acute or chronic liver injury induced by LPS or CCl4 in mice were investigated.

RESULTS

Patients with chronic DILI exhibited elevated plasma IL-6, IL-12p70, IL-15 and reduced IL-10 levels. The percentage of IL-12+ monocytes was higher, while that of CD206+ monocytes, IL-10+ monocytes, Th2, Treg, and IL-10+ CD4+ T cells were lower in patients with chronic DILI compared to those with acute DILI. We identified the most significantly increased metabolite in patients with chronic DILI was cis-aconitic acid (CAA). Administration of CAA can attenuate liver injury in mice with acute liver injury induced by LPS or CCl4 and promote the spontaneous resolution of liver fibrosis in mice with chronic live injury induced by CCl4. The protective mechanism of CAA against liver injury is associated with the inhibition of hepatic macrophage infiltration and polarization, which is achieved by inhibiting the secretion of neutrophil-derived IL-33 and subsequent phosphorylation of GATA3.

CONCLUSIONS

CAA, which is elevated in patients with chronic DILI, protects against liver injury by inhibiting hepatic macrophage infiltration and polarization through the suppression of the IL-33/GATA3 pathway, suggesting that CAA may serve as a potential target for regulating tissue repair in liver injury.

Single-cell RNA sequencing advances in revealing the development and progression of MASH: the identifications and interactions of non-parenchymal cells

Developing drugs for the treatment of Metabolic Associated Steatohepatitis (MASH) has always been a significant challenge. Researchers have been dedicated to exploring drugs and therapeutic strategies to alleviate disease progression, but treatments remain limited. This is partly due to the complexity of the pathophysiological processes, and inadequate knowledge of the cellular and molecular mechanisms in MASH. Especially, the liver non-parenchymal cells (NPCs) like Kupffer cells, hepatic stellate cells and sinusoidal endothelial cells which play critical roles in live function, immune responses, fibrosis and disease progression. Deciphering how these cells function in MASH, would help understand the pathophysiological processes and find potential drug targets. In recent years, new technologies have been developed for single-cell transcriptomic sequencing, making cell-specific transcriptome profiling a reality in healthy and diseased livers. In this review, we discussed how the use of single-cell transcriptomic sequencing provided us with an in-depth understanding of the heterogeneous, cellular interactions among non-parenchymal cells and tried to highlight recent discoveries in MASH by this technology. It is hoped that the summarized features and markers of various subclusters in this review could provide a technical reference for further experiments and a theoretical basis for clinical applications.

The role of the interleukin family in liver fibrosis

Liver fibrosis represents a wound-healing response to chronic liver injury caused by viral infections, alcohol, and chemicals agents. It is a critical step in the progression from chronic liver disease to cirrhosis and hepatocellular carcinoma. No chemical or biological drugs have been approved for the treatment of liver fibrosis. Relevant studies have demonstrated that effective inhibition of hepatitis B virus (HBV) replication by nucleoside (acid) analogs or polyethylene glycol alpha-interferon can lead to recovery in some patients with hepatitis B liver fibrosis, However, some patients with liver fibrosis do not show improvement, even after achieving a complete serologic and virologic response. A similar situation occurs in patients with hepatitis C-related liver fibrosis. The liver, with its unique anatomical and immunological structure, is the largest immune organ and produces a large number of cytokines in response to external stimuli, which are crucial for the progression of liver fibrosis. cytokines can act either by directly affecting hepatic stellate cells (HSCs) or by indirectly regulating immune target cells. Among these, the interleukin family activates a complex cascade of responses, including cytokines, chemokines, adhesion molecules, and lipid mediators, playing a key role in the initiation and regulation of inflammation, as well as innate and adaptive immunity. In this paper, we systematically summarize recent literature to elucidate the pathogenesis of interleukin-mediated liver fibrosis and explore potential therapeutic targets for liver fibrosis treatment.

Inflammatory Gene Expression in Livers Undergoing Ex Situ Normothermic Perfusion Is Attenuated by Leukocyte Removal From the Perfusate

BACKGROUND

Ex situ normothermic perfusion (ESNP) is a method to evaluate and potentially recondition organs before transplantation. However, increased expression of inflammatory molecules, including by tissue-resident immune cells, may occur during the perfusion process, potentially negating the beneficial effects of perfusion.

METHODS

We used RNA sequencing to assess gene expression in 31 livers undergoing ESNP, including 23 donated after circulatory death (DCD) and 8 donated after brain death. In 7 DCD livers, a leucocyte filter was added to the circuit during perfusion. Biopsies were available for transcriptomic assessment in all cases at the start of perfusion and at varying time points postperfusion.

RESULTS

During ESNP in DCD livers, we observed an increase in proinflammatory, profibrinolytic, and prorepair pathway genes. SERPINE1 , encoding plasminogen activator inhibitor-1, was among the genes most significantly upregulated during perfusion in DCD livers, potentially promoting fibrin clot persistence in vasculature. We also found increased expression of monocyte and neutrophil recruiting chemokine and proinflammatory cytokine transcripts during ESNP, but several prorepair molecules, including thymic stromal lymphopoietin, were also upregulated. In both DCD and donation after brain death livers, interferon-gamma response genes were enriched, whereas oxidative phosphorylation genes decreased in organs with high perfusate alanine transaminase, a biomarker associated with adverse clinical outcomes. The inclusion of a leukocyte filter in the perfusion circuit mitigated the induction of inflammation/immune pathway genes during perfusion and was associated with enrichment in oxidative phosphorylation genes.

CONCLUSIONS

Leukocyte removal during ESNP abrogates transcriptional changes that are associated with unfavorable clinical outcomes, potentially benefiting human livers undergoing ESNP.

Metabolism of hepatic stellate cells in chronic liver diseases: emerging molecular and therapeutic interventions

Chronic liver diseases, primarily metabolic dysfunction-associated steatotic liver disease (MASLD), metabolic and metabolic dysfunction-associated alcoholic liver disease (MetALD), and viral hepatitis, can lead to liver fibrosis, cirrhosis, and cancer. Hepatic stellate cell (HSC) activation plays a central role in the development of myofibroblasts and fibrogenesis in chronic liver diseases. However, HSC activation is influenced by the complex microenvironments within the liver, which are largely shaped by the interactions between HSCs and various other cell types. Changes in HSC phenotypes and metabolic mechanisms involve glucose, lipid, and cholesterol metabolism, oxidative stress, activation of the unfolded protein response (UPR), autophagy, ferroptosis, senescence, and nuclear receptors. Clinical interventions targeting these pathways have shown promising results in addressing liver inflammation and fibrosis, as well as in modulating glucose and lipid metabolism and metabolic stress responses. Therefore, a comprehensive understanding of HSC phenotypes and metabolic mechanisms presents opportunities for novel therapeutic approaches aimed at halting or even reversing chronic liver diseases.

Transient receptor potential channel 6 knockout ameliorates hepatic fibrosis by inhibiting the activation and proliferation of hepatic stellate cells

BACKGROUND AND AIM

Hepatic fibrosis is a common outcome of chronic liver injury and can eventually lead to cirrhosis, which is a major public health concern. Hepatic stellate cells (HSCs) are the major producers of extracellular matrix (ECM) and regulate the synthesis and decomposition of ECM, but the specific mechanism of them remains unclear. Transient receptor potential channel 6 (TRPC6), a non-selective cation channel, plays an important role in organic fibrosis. However, the role of TRPC6 in liver fibrosis is rarely studied.

METHODS

Here, we investigated the function of TRPC6 in the activation of the human hepatic stellate cell line LX-2 in vitro and bile duct ligation (BDL)-induced hepatic fibrosis in vivo by western blot, Ca2+ imaging, and immunohistochemistry.

RESULTS

We first found that TRPC6 was upregulated in fibrotic liver tissues and TRPC6 knockout inhibited BDL-induced hepatic fibrosis. Transforming growth factor-β1 (TGF-β1) treatment increased TRPC6 expression and thapsigargin (Tg)-mediated SOCE in LX-2 cells, which was decreased by the TRPC6 specific inhibitor SAR7334. Blockage of TRPC6 by SAR7334 or TRPC6-shRNA transfection attenuated TGF-β1-induced LX-2 cell activation and proliferation via the PI3K/AKT/p70S6K signaling pathway.

CONCLUSIONS

These observations suggested that TRPC6 contribute to LX-2 cell activation and hepatic fibrosis, and downregulation of TRPC6 may become a therapeutic strategy for the treatment of hepatic fibrosis in the future.

Live-cell imaging of human liver fibrosis using hepatic micro-organoids

Due to the limitations of available in vitro systems and animal models, we lack a detailed understanding of the pathogenetic mechanisms of and have minimal treatment options for liver fibrosis. Therefore, we engineered a live-cell imaging system that assessed fibrosis in a human multilineage hepatic organoid in a microwell (i.e., microHOs). Transcriptomic analysis revealed that TGFB converted mesenchymal cells in microHOs into myofibroblast-like cells resembling those in fibrotic human liver tissue. When pro-fibrotic intracellular signaling pathways were examined, the antifibrotic effect of receptor-specific tyrosine kinase inhibitors was limited to the fibrosis induced by the corresponding growth factor, which indicates their antifibrotic efficacy would be limited to fibrotic diseases solely mediated by that growth factor. Based upon transcriptomic and transcription factor activation analyses in microHOs, glycogen synthase kinase 3β and p38 MAPK inhibitors were identified as potential new broad-spectrum therapies for liver fibrosis. Other new therapies could subsequently be identified using the microHO system.

Immunological mechanisms in steatotic liver diseases: An overview and clinical perspectives

Steatotic liver diseases (SLD) are the principal worldwide cause of cirrhosis and end-stage liver cancer, affecting nearly a quarter of the global population. SLD includes metabolic dysfunction-associated alcoholic liver disease (MetALD) and metabolic dysfunction-associated steatotic liver disease (MASLD), resulting in asymptomatic liver steatosis, fibrosis, cirrhosis and associated complications. The immune processes include gut dysbiosis, adiposeliver organ crosstalk, hepatocyte death and immune cell-mediated inflammatory processes. Notably, various immune cells such as B cells, plasma cells, dendritic cells, conventional CD4+ and CD8+ T cells, innate-like T cells, platelets, neutrophils and macrophages play vital roles in the development of MetALD and MASLD. Immunological modulations targeting hepatocyte death, inflammatory reactions and gut microbiome include N-acetylcysteine, selonsertib, F-652, prednisone, pentoxifylline, anakinra, JKB-121, HA35, obeticholic acid, probiotics, prebiotics, antibiotics and fecal microbiota transplantation. Understanding the immunological mechanisms underlying SLD is crucial for advancing clinical therapeutic strategies.

Mitochondrial GRIM19 Loss Induces Liver Fibrosis through NLRP3/IL33 Activation via Reactive Oxygen Species/NF-кB Signaling

Background and Aims

Hepatic fibrosis (HF) is a critical step in the progression of hepatocellular carcinoma (HCC). Gene associated with retinoid-IFN-induced mortality 19 (GRIM19), an essential component of mitochondrial respiratory chain complex I, is frequently attenuated in various human cancers, including HCC. Here, we aimed to investigate the potential relationship and underlying mechanism between GRIM19 loss and HF pathogenesis.

Methods

GRIM19 expression was evaluated in normal liver tissues, hepatitis, hepatic cirrhosis, and HCC using human liver disease spectrum tissue microarrays. We studied hepatocyte-specific GRIM19 knockout mice and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 (Cas9) lentivirus-mediated GRIM19 gene-editing in murine hepatocyte AML12 cells in vitro and in vivo. We performed flow cytometry, immunofluorescence, immunohistochemistry, western blotting, and pharmacological intervention to uncover the potential mechanisms underlying GRIM19 loss-induced HF.

Results

Mitochondrial GRIM19 was progressively downregulated in chronic liver disease tissues, including hepatitis, cirrhosis, and HCC tissues. Hepatocyte-specific GRIM19 heterozygous deletion induced spontaneous hepatitis and subsequent liver fibrogenesis in mice. In addition, GRIM19 loss caused chronic liver injury through reactive oxygen species (ROS)-mediated oxidative stress, resulting in aberrant NF-кB activation via an IKK/IкB partner in hepatocytes. Furthermore, GRIM19 loss activated NLRP3-mediated IL33 signaling via the ROS/NF-кB pathway in hepatocytes. Intraperitoneal administration of the NLRP3 inhibitor MCC950 dramatically alleviated GRIM19 loss-driven HF in vivo.

Conclusions

The mitochondrial GRIM19 loss facilitates liver fibrosis through NLRP3/IL33 activation via ROS/NF-кB signaling, providing potential therapeutic approaches for earlier HF prevention.

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.

Therapeutic potential of natural products in schistosomiasis-associated liver fibrosis

Schistosomiasis is a parasitic disease that endangers human health and social development. The granulomatous reaction of Schistosoma eggs in the liver is the main cause of hepatosplenomegaly and fibrotic lesions. Anti liver fibrosis therapy is crucial for patients with chronic schistosomiasis. Although Praziquantel is the only clinical drug used, it is limited in insecticide treatment and has a long-term large-scale use, which is forcing the search for cost-effective alternatives. Previous research has demonstrated that plant metabolites and extracts have effective therapeutic effects on liver fibrosis associated with schistosomiasis. This paper summarizes the mechanisms of action of metabolites and some plant extracts in alleviating schistosomiasis-associated liver fibrosis. The analysis was conducted using databases such as PubMed, Google Scholar, and China National Knowledge Infrastructure (CNKI) databases. Some plant metabolites and extracts ameliorate liver fibrosis by targeting multiple signaling pathways, including reducing inflammatory infiltration, oxidative stress, inhibiting alternate macrophage activation, suppressing hepatic stellate cell activation, and reducing worm egg load. Natural products improve liver fibrosis associated with schistosomiasis, but further research is needed to elucidate the effectiveness of natural products in treating liver fibrosis caused by schistosomiasis, as there is no reported data from clinical trials in the literature.

Oxidative stress promotes liver fibrosis by modulating the microRNA-144 and SIN3A-p38 pathways in hepatic stellate cells

Background & Aims: Reactive oxygen species (ROS) act as modulators triggering cellular dysfunctions and organ damage including liver fibrosis in which hepatic stellate cell (HSC) activation plays a key role. Previous studies suggest that microRNA-144 (miR-144) acts as a pro-oxidant molecule; however, whether and how miR-144 affects HSC activation and liver fibrosis remain unknown. Methods: Carbon tetrachloride (CCl4) and bile duct ligation (BDL)-induced experimental liver fibrosis models were used. Hepatic miR-144 expression was analyzed by miRNA in situ hybridization with RNAscope probe. The in vivo effects of silencing or overexpressing miR-144 were examined with an adeno-associated virus 6 (AAV6) carrying miR-144 inhibitor or mimics in fibrotic mouse experimental models. Results: In this study, we demonstrated that ROS treatment significantly upregulated miR-144 in HSCs, which further promoted HSC activation in vitro. Interestingly, miR-144 was preferentially elevated in HSCs of experimental liver fibrosis in mice and in human liver fibrotic tissues. Furthermore, in vivo loss or gain-of-function experiments via AAV6 carrying miR-144 antagomir or agomir revealed that blockade of miR-144 in HSCs mitigated, while overexpression of miR-144 in HSCs accelerated the development of experimental liver fibrosis. Mechanistically, SIN3 transcription regulator family member A (SIN3A), a transcriptional repressor, was identified to be the target of miR-144 in HSCs. MiR-144 downregulated Sin3A, and in line with this result, specific knockdown of Sin3a in HSCs remarkedly activated p38 MAPK signaling pathway to promote HSC activation, eventually exacerbating liver fibrosis. Conclusions: Oxidative stress-driven miR-144 fuels HSC activation and liver fibrogenesis by limiting the SIN3A-p38 axis. Thus, a specific inhibition of miR-144 in HSCs could be a novel therapeutic strategy for the treatment of liver fibrosis.

Viscoelastic parameters derived from multifrequency MR elastography for depicting hepatic fibrosis and inflammation in chronic viral hepatitis

OBJECTIVES

The capability of MR elastography (MRE) to differentiate fibrosis and inflammation, and to provide precise diagnoses is crucial, whereas the coexistence of fibrosis and inflammation may obscure the diagnostic accuracy.

METHODS

In this retrospective study, from June 2020 to December 2022, chronic viral hepatitis patients who underwent multifrequency MRE (mMRE) were included in, and further divided into, training and validation cohorts. The hepatic viscoelastic parameters [shear wave speed (c) and loss angle (φ) of the complex shear modulus] were obtained from mMRE. The logistic regression and receiver operating characteristic (ROC) curves were generated to evaluate performance of viscoelastic parameters for fibrosis and inflammation.

RESULTS

A total of 233 patients were assigned to training cohort and validation cohorts (mean age, 52 years ± 13 (SD); 51 women; training cohort, n = 170 (73%), and validation cohort, n = 63 (27%)). Liver c exhibited superior performance in detecting fibrosis with ROC (95% confidence interval) of ≥ S1 (0.96 (0.92-0.99)), ≥ S2 (0.86 (0.78-0.92)), ≥ S3 (0.89 (0.84-0.95)), and S4 (0.88 (0.83-0.93)). Similarly, φ was effective in diagnosing inflammation with ROC values of ≥ G2 (0.72 (0.63-0.81)), ≥ G3 (0.88 (0.83-0.94)), and G4 (0.92 (0.87-0.98)). And great predictive discrimination for fibrosis and inflammation were shown in validation cohort (all AUCs > 0.75).

CONCLUSION

The viscoelastic parameters derived from multifrequency MRE could realize simultaneous detection of hepatic fibrosis and inflammation.

CRITICAL RELEVANCE STATEMENT

Fibrosis and inflammation coexist in chronic liver disease which obscures the diagnostic performance of MR elastography, whereas the viscoelastic parameters derived from multifrequency MR elastography could realize simultaneous detection of hepatic fibrosis and inflammation.

KEY POINTS

• Hepatic biomechanical parameters derived from multifrequency MR elastography could effectively detect fibrosis and inflammation. • Liver stiffness is useful for detecting fibrosis independent of inflammatory activity. • Fibrosis could affect the diagnostic efficacy of liver viscosity in inflammation, especially in early-grade of inflammation.

Evaluation of soluble suppression of tumorigenicity 2 (sST2) as serum marker for liver fibrosis

BACKGROUND & AIMS

With the increase in patients at risk of advanced liver disease due to the obesity epidemic, there will be a need for simple screening tools for advanced liver fibrosis. Soluble suppression of tumorigenicity 2 (sST2) is a serum biomarker for fibrotic processes. The aim of this study was to evaluate sST2 as marker for liver fibrosis in patients successfully treated for chronic hepatitis C.

METHODS

424 patients from the Swiss Hepatitis C Cohort Study were screened for inclusion in this post-hoc cohort study. Inclusion criteria were sustained virological response (SVR), available elastography (VCTE) and serum samples for biomarker analysis before and after treatment. For the validation of sST2, values were compared to VCTE, FIB-4 and APRI using Spearman's correlation and AUROC analyses.

RESULTS

Data of 164 subjects were finally analyzed. Median sST2 values slightly increased with VCTE-derived fibrosis stages and remained stable after reaching SVR within the respective fibrosis stage, suggesting that sST2 is not influenced by liver inflammation. However, correlation of sST2 pre- and post-treatment with VCTE was fair (Spearman's rho = 0.39 and rho = 0.36). The area under the curve (AUROC) for sST2 in detecting VCTE-defined F4 fibrosis (vs. F0-F3) before therapy was 0.74 (95%CI 0.65-0.83), and 0.67(95%CI 0.56-0.78) for the discrimination of F3/F4 fibrosis vs. F0-F2. Adding sST2 to either APRI or FIB-4, respectively, increased diagnostic performance of both tests.

CONCLUSIONS

sST2 can potentially identify patients with advanced fibrosis as a single serum marker and in combination with APRI and FIB-4.

Hepatocyte GPCR signaling regulates IRF3 to control hepatic stellate cell transdifferentiation

BACKGROUND

Interferon Regulatory Factor 3 (IRF3) is a transcription factor that plays a crucial role in the innate immune response by recognizing and responding to foreign antigens. Recently, its roles in sterile conditions are being studied, as in metabolic and fibrotic diseases. However, the search on the upstream regulator for efficient pharmacological targeting is yet to be fully explored. Here, we show that G protein-coupled receptors (GPCRs) can regulate IRF3 phosphorylation through of GPCR-Gα protein interaction.

RESULTS

IRF3 and target genes were strongly associated with fibrosis markers in liver fibrosis patients and models. Conditioned media from MIHA hepatocytes overexpressing IRF3 induced fibrogenic activation of LX-2 hepatic stellate cells (HSCs). In an overexpression library screening using active mutant Gα subunits and Phos-tag immunoblotting, Gαs was found out to strongly phosphorylate IRF3. Stimulation of Gαs by glucagon or epinephrine or by Gαs-specific designed GPCR phosphorylated IRF3. Protein kinase A (PKA) signaling was primarily responsible for IRF3 phosphorylation and Interleukin 33 (IL-33) expression downstream of Gαs. PKA phosphorylated IRF3 on a previously unrecognized residue and did not require reported upstream kinases such as TANK-binding kinase 1 (TBK1). Activation of Gαs signaling by glucagon induced IL-33 production in hepatocytes. Conditioned media from the hepatocytes activated HSCs, as indicated by α-SMA and COL1A1 expression, and this was reversed by pre-treatment of the media with IL-33 neutralizing antibody.

CONCLUSIONS

Gαs-coupled GPCR signaling increases IRF3 phosphorylation through cAMP-mediated activation of PKA. This leads to an increase of IL-33 expression, which further contributes to HSC activation. Our findings that hepatocyte GPCR signaling regulates IRF3 to control hepatic stellate cell transdifferentiation provides an insight for understanding the complex intercellular communication during liver fibrosis progression and suggests therapeutic opportunities for the disease. Video Abstract.

Inhibition of IL-33 signaling ameliorate hepatic fibrosis with decreasing MCP-1 in a mouse model of diabetes and non-alcoholic steatohepatitis; comparison for luseogliflozin, an SGLT2 inhibitor

Non-alcoholic fatty liver disease (NAFLD) is increasing globally, and seeking therapeutic molecule targets is urgent. Several studies have demonstrated that IL-33 plays an important role in the progression of Non-alcoholic steatohepatitis (NASH) with fibrosis and the proliferation of hepatocellular carcinoma (HCC). However, whether the inhibition of IL-33 signaling prevents NAFLD from progressing to NASH and HCC has not been clarified. We investigated the effects of a novel antibody, IL-33RAb, and luseogliflozin, a SGLT2 inhibitor, when administered to a model mouse for NASH and HCC, and their effects were compared to investigate the mechanisms of how IL-33 is involved in the pathogenesis of NASH progression. Compared with the positive control of luseogliflozin, inhibition of IL-33 signaling ameliorated decreasing hepatic fibrosis via decreasingαSMA and MCP-1, and also partially suppressed the progression of the HCC cell line in in vitro experiments. These findings suggest that inhibition of IL-33 possibly prevents progression from NASH to HCC, and their effect may be a newly arrived therapeutic agent.

Th2 Cell Activation in Chronic Liver Disease Is Driven by Local IL33 and Contributes to IL13-Dependent Fibrogenesis

BACKGROUND & AIMS

Type 2 immune responses contribute to liver fibrosis in parasite infections, but their role in other liver diseases is less well understood. Here, we aimed at unravelling mechanisms involved in T helper 2 (Th2) T-cell polarization, activation, and recruitment in human liver fibrosis and cirrhosis.

METHODS

Tissues, cells, and serum from human livers were analyzed using quantitative reverse-transcription polymerase chain reaction, enzyme-linked immunosorbent assay, fluorescence in situ hybridization, immunostaining, flow cytometry, and various functional in vitro assays. Cellular interactions and soluble mediators involved in T-cell polarization and recruitment were studied, as well as their effect on hepatic stellate cell (HSC) activation, proliferation, and extracellular matrix synthesis.

RESULTS

In human liver fibrosis, a stage-dependent increase in Th2-related transcription factors, Th2 cytokines, and trans-acting T-cell-specific transcription factor-expressing T cells was observed, and was highest in cirrhotic livers. The alarmin interleukin (IL)33 was found to be increased in livers and sera from patients with cirrhosis, to act as a chemotactic agent for Th2 cells, and to induce type 2 polarization of CD4+ T cells. Oval cells, liver sinusoidal endothelial cells, intrahepatic macrophages, and migrating monocytes were identified as sources of IL33. IL33-activated T cells, but not IL33 alone, induced HSC activation, as shown by Ki67 and α-smooth muscle actin staining, increased collagen type I alpha 1 chain messenger RNA expression, and wound healing assays. The profibrotic effect of IL33-activated T cells was contact-independent and could be antagonized using monoclonal antibodies against IL13.

CONCLUSION

In patients with chronic liver disease, the alarmin IL33 promotes the recruitment and activation of CD4+ T cells with Th2-like properties, which activate paracrine HSC in an IL13-dependent manner and promotes fibrogenesis.

Knockdown of TXNDC5 alleviates CCL4-induced hepatic fibrosis in mice by enhancing endoplasmic reticulum stress

BACKGROUND

Hepatic fibrosis is a common pathological process in many chronic liver diseases. TXNDC5 has been shown to be involved in the progression of renal and pulmonary fibrosis. However, the role of TXNDC5 in hepatic fibrosis is unknown. The purpose of this study is to explore the role and mechanism of TXNDC5 in hepatic fibrosis.

METHODS

We used TGF-β1 to activate LX-2 cells and reduced TXNDC5 expression by short hairpin RNA. Cell viability was assessed by CCK-8 assay. Cell apoptosis was analyzed by flow cytometry or Tunel assay. The fibrosis-related proteins and endoplasmic reticulum stress (ERs)-related proteins were measured by western blot. ELISA was performed to detect COL1AL levels and MMP2/9 activities in cell medium. A mouse model of hepatic fibrosis was constructed by intraperitoneal injection of CCL4. HE and Masson staining were performed to assess fibrosis in mouse liver tissue.

RESULTS

The results show that TXNDC5 was up-regulated in activated LX-2 cells and CCL4-induced hepatic fibrosis mice. Knockdown of TXNDC5 inhibited the viability of activated LX-2 cells and the production of collagen COL1A1. Knockdown of TXNDC5 promoted apoptosis of activated LX-2 cells. Mechanically, inhibition of TXNDC5 enhanced ERs, and the ERs inhibitor 4-Phenylbutyric acid (4-PBA) reversed the effect of TXNDC5 on activated LX-2 cells. More importantly, knockdown of TXNDC5 alleviated CCl4-induced hepatic fibrosis in mice.

CONCLUSIONS

Knockdown of TXNDC5 may reduce hepatic fibrosis by regulating ERs, and targeting TXNDC5 seems to be a candidate treatment for hepatic fibrosis.

Hepatic inflammatory responses in liver fibrosis

Chronic liver diseases such as nonalcoholic fatty liver disease (NAFLD) or viral hepatitis are characterized by persistent inflammation and subsequent liver fibrosis. Liver fibrosis critically determines long-term morbidity (for example, cirrhosis or liver cancer) and mortality in NAFLD and nonalcoholic steatohepatitis (NASH). Inflammation represents the concerted response of various hepatic cell types to hepatocellular death and inflammatory signals, which are related to intrahepatic injury pathways or extrahepatic mediators from the gut-liver axis and the circulation. Single-cell technologies have revealed the heterogeneity of immune cell activation concerning disease states and the spatial organization within the liver, including resident and recruited macrophages, neutrophils as mediators of tissue repair, auto-aggressive features of T cells as well as various innate lymphoid cell and unconventional T cell populations. Inflammatory responses drive the activation of hepatic stellate cells (HSCs), and HSC subsets, in turn, modulate immune mechanisms via chemokines and cytokines or transdifferentiate into matrix-producing myofibroblasts. Current advances in understanding the pathogenesis of inflammation and fibrosis in the liver, mainly focused on NAFLD or NASH owing to the high unmet medical need, have led to the identification of several therapeutic targets. In this Review, we summarize the inflammatory mediators and cells in the diseased liver, fibrogenic pathways and their therapeutic implications.

Amphiregulin couples IL1RL1+ regulatory T cells and cancer-associated fibroblasts to impede antitumor immunity

Regulatory T (Treg) cells and cancer-associated fibroblasts (CAFs) jointly promote tumor immune tolerance and tumorigenesis. The molecular apparatus that drives Treg cell and CAF coordination in the tumor microenvironment (TME) remains elusive. Interleukin 33 (IL-33) has been shown to enhance fibrosis and IL1RL1+ Treg cell accumulation during tumorigenesis and tissue repair. We demonstrated that IL1RL1 signaling in Treg cells greatly dampened the antitumor activity of both IL-33 and PD-1 blockade. Whole tumor single-cell RNA sequencing (scRNA-seq) analysis and blockade experiments revealed that the amphiregulin (AREG)-epidermal growth factor receptor (EGFR) axis mediated cross-talk between IL1RL1+ Treg cells and CAFs. We further demonstrated that the AREG/EGFR axis enables Treg cells to promote a profibrotic and immunosuppressive functional state of CAFs. Moreover, AREG mAbs and IL-33 concertedly inhibited tumor growth. Our study reveals a previously unidentified AREG/EGFR-mediated Treg/CAF coupling that controls the bifurcation of fibroblast functional states and is a critical barrier for cancer immunotherapy.

Oxidative Stress in Liver Pathophysiology and Disease

The liver is an organ that is particularly exposed to reactive oxygen species (ROS), which not only arise during metabolic functions but also during the biotransformation of xenobiotics. The disruption of redox balance causes oxidative stress, which affects liver function, modulates inflammatory pathways and contributes to disease. Thus, oxidative stress is implicated in acute liver injury and in the pathogenesis of prevalent infectious or metabolic chronic liver diseases such as viral hepatitis B or C, alcoholic fatty liver disease, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). Moreover, oxidative stress plays a crucial role in liver disease progression to liver fibrosis, cirrhosis and hepatocellular carcinoma (HCC). Herein, we provide an overview on the effects of oxidative stress on liver pathophysiology and the mechanisms by which oxidative stress promotes liver disease.

Crosstalk between Interleukin-1 Receptor-Like 1 and Transforming Growth Factor-β Receptor Signaling Promotes Renal Fibrosis

IL-33, a member of the IL-1 family, acts as an alarmin in immune response. Epithelial-mesenchymal transition and transforming growth factor-β (TGF-β)–induced fibroblast activation are key events in the development of renal interstitial fibrosis. The current study found increased expression of IL-33 and interleukin-1 receptor-like 1 (IL1RL1, alias ST2), the receptor for IL-33, in human fibrotic renal tissues. In addition, IL-33– or ST2-deficient mice showed significantly reduced levels of fibronectin, α-smooth muscle actin, and vimentin, and increased E-cadherin levels. In HK-2 cells, IL-33 promotes the phosphorylation of the TGF-β receptor (TGF-βR), Smad2, and Smad3, and the production of extracellular matrix (ECM), with reduced expression of E-cadherin. Blocking TGF-βR signaling or suppressing ST2 expression impeded Smad2 and Smad3 phosphorylation, thereby reducing ECM production, suggesting that IL-33–induced ECM synthesis requires cooperation between the two pathways. Mechanistically, IL-33 treatment induced a proximate interaction between ST2 and TGF-βRs, activating downstream Smad2 and Smad3 for ECM production in renal epithelial cells. Collectively, this study identified a novel and essential role for IL-33 in promoting TGF-β signaling and ECM production in the development of renal fibrosis. Therefore, targeting IL-33/ST2 signaling may be an effective therapeutic strategy for renal fibrosis.

The association of serum IL-33/ST2 expression with hepatocellular carcinoma

BACKGROUND

IL-33 is a multifunctional cytokine with dual functions. However, the clinicopathological and prognostic significance of IL-33 in cancer patients, especially in patients with hepatocellular carcinoma (HCC), remains controversial. Therefore, we conducted a study of 565 patients with HCC and 561 healthy controls and performed a meta-analysis to quantitatively evaluate the above problems.

METHODS

We collected blood from 565 patients with HCC and 561 healthy controls. ELISA was used to detect the concentrations of IL-33 and ST2 in the serum, and RT‒PCR was used to detect the levels of IL-33 and ST2 mRNA. Meanwhile, we collected comprehensive literature on IL-33 and the clinical characteristics of cancer patients retrieved from the PubMed, Web of Science and CNKI databases as of December 2022. An odds ratio (OR) with a 95% confidence interval (CI) was used to estimate the impact through overall and stratified analyses.

RESULTS

Compared with the healthy control group, the levels of ST2 mRNA and serum in the peripheral blood of HCC patients increased (p < 0.05), while the levels of IL-33 mRNA and serum showed no significant difference between the two groups (p > 0.05). In the meta-analysis section, at the tissue level, the overall analysis showed that the expression of IL-33 was positively correlated with tumor stage, histological grade, distant metastasis, and tumor size. Compared with patients with low IL-33 expression, the 3-year overall survival (OS) rate (OR = 3.467, p < 0.001) and 5-year OS rate (OR = 2.784, p < 0.001) of patients with high IL-33 expression were lower. At the serum expression level, the overall analysis showed that the expression of IL-33 increased the risk of cancer, and the serum level of IL-33 was positively correlated with tumor stage and vascular invasion.

CONCLUSION

IL-33/ST2 is a useful predictive or prognostic biomarker in clinical evaluation and may be used as a potential therapeutic target, but much research is needed to verify this hypothesis.

Interleukin-1 family cytokines in liver cell death: a new therapeutic target for liver diseases

INTRODUCTION

Liver cell death represents a basic biological process regulating the progression of liver diseases via distinct mechanisms. Accumulating evidence has uncovered participation of interleukin (IL)-1 family cytokines in liver cell death. Upon activation of cell death induced by hepatotoxic stimuli, IL1 family cytokines released by hepatic dead cells stimulate recruitment of immune cells, which in turn influence inflammation and subsequent liver injury, thus highlighting their potential as therapeutic targets in liver diseases. Enhancing our comprehension of mechanisms underlying IL1 family cytokine signaling in cell death responses could pave the way for novel therapeutic interventions aimed at addressing liver cell death-related liver pathologies.

AREAS COVERED

This review summarizes the recent findings reported in preclinical and clinical studies on mechanisms of liver cell death, alongside participation of IL1 family members consisting of IL1α, ILβ, IL18, and IL33 in liver cell death and their significant implications in liver diseases.

EXPERT OPINION

Discovery of new and innovative therapeutic approaches for liver diseases will need close cooperation between fundamental and clinical scientists to better understand the multi-step processes behind IL1 family cytokines' contributions to liver cell death.

Role of the IL-33/ST2 Activation Pathway in the Development of the Hepatic Fibrosis Induced by Schistosoma mansoni Granulomas in Mice

Schistosoma mansoni eggs retained in host tissues induce innate cytokine release, contributing to the induction of Type-2 immune responses and granuloma formation, important to restrain cytotoxic antigens, but leading to fibrosis. Interleukin(IL)-33 participates in experimental models of inflammation and chemically induced fibrosis, but its role in S. mansoni-induced fibrosis is still unknown. To explore the role of the IL-33/suppressor of the tumorigenicity 2 (ST2) pathway, serum and liver cytokine levels, liver histopathology, and collagen deposition were comparatively evaluated in S. mansoni-infected wild-type (WT) and IL-33-receptor knockout (ST2-/-) BALB/c mice. Our data show similar egg counts and hydroxyproline in the livers of infected WT and ST2-/- mice; however, the extracellular matrix in ST2-/- granulomas was loose and disorganised. Pro-fibrotic cytokines, such as IL-13 and IL-17, and the tissue-repairing IL-22 were significantly lower in ST2-/- mice, especially in chronic schistosomiasis. ST2-/- mice also showed decreased α-smooth muscle actin (α-SMA) expression in granuloma cells, in addition to reduced Col III and Col VI mRNA levels and reticular fibres. Therefore, IL-33/ST2 signalling is essential for tissue repairing and myofibroblast activation during S. mansoni infection. Its disruption results in inappropriate granuloma organisation, partly due to the reduced type III and VI collagen and reticular fibre formation.

Macrophage in liver Fibrosis: Identities and mechanisms

Liver fibrosis is a chronic disease characterized by the deposition of extracellular matrix and continuous loss of tissues that perform liver functions. Macrophages are crucial modulators of innate immunity and play important roles in liver fibrogenesis. Macrophages comprise heterogeneous subpopulations that exhibit different cellular functions. Understanding the identity and function of these cells is essential for understanding the mechanisms of liver fibrogenesis. According to different definitions, liver macrophages are divided into M1/M2 macrophages or monocyte-derived macrophages/Kupffer cells. Classic M1/M2 phenotyping corresponds to pro- or anti-inflammatory effects, and, therefore, influences the degree of fibrosis in later phases. In contrast, the origin of the macrophages is closely associated with their replenishment and activation during liver fibrosis. These two classifications of macrophages depict the function and dynamics of liver-infiltrating macrophages. However, neither description properly elucidates the positive or negative role of macrophages in liver fibrosis. Critical tissue cells mediating liver fibrosis include hepatic stellate cells and hepatic fibroblasts, with hepatic stellate cells being of particular interest because of their close association with macrophages in liver fibrosis. However, the molecular biological descriptions of macrophages are inconsistent between mice and humans, warranting further investigations. In liver fibrosis, macrophages can secrete various pro-fibrotic cytokines, such as TGF-β, Galectin-3 and interleukins (ILs), and fibrosis-inhibiting cytokines, such as IL10. These different secretions may be associated with the specific identity and spatiotemporal characteristics of macrophages. Furthermore, during fibrosis dissipation, macrophages may degrade extracellular matrix by secreting matrix metalloproteinases (MMPs). Notably, using macrophages as therapeutic targets in liver fibrosis has been explored. The current therapeutic approaches for liver fibrosis can by categorized as follows: treatment with macrophage-related molecules and macrophage infusion therapy. Although there have been limited studies, macrophages have shown reliable potential for liver fibrosis treatment. In this review, we focu on the identity and function of macrophages and their relationship to the progression and regression of liver fibrosis.

Group 2 innate lymphoid cells constrain type 3/17 lymphocytes in shared stromal niches to restrict liver fibrosis

Group 2 innate lymphoid cells (ILC2s) cooperate with adaptive Th2 cells as key organizers of tissue type 2 immune responses, while a spectrum of innate and adaptive lymphocytes coordinate early type 3/17 immunity. Both type 2 and type 3/17 lymphocyte associated cytokines are linked to tissue fibrosis, but how their dynamic and spatial topographies may direct beneficial or pathologic organ remodelling is unclear. Here we used volumetric imaging in models of liver fibrosis, finding accumulation of periportal and fibrotic tract IL-5 + lymphocytes, predominantly ILC2s, in close proximity to expanded type 3/17 lymphocytes and IL-33 high niche fibroblasts. Ablation of IL-5 + lymphocytes worsened carbon tetrachloride-and bile duct ligation-induced liver fibrosis with increased niche IL-17A + type 3/17 lymphocytes, predominantly γδ T cells. In contrast, concurrent ablation of IL-5 + and IL-17A + lymphocytes reduced this progressive liver fibrosis, suggesting a cross-regulation of type 2 and type 3 lymphocytes at specialized fibroblast niches that tunes hepatic fibrosis.

RIPK3 promoter hypermethylation in hepatocytes protects from bile acid-induced inflammation and necroptosis

Necroptosis facilitates cell death in a controlled manner and is employed by many cell types following injury. It plays a significant role in various liver diseases, albeit the cell-type-specific regulation of necroptosis in the liver and especially hepatocytes, has not yet been conceptualized. We demonstrate that DNA methylation suppresses RIPK3 expression in human hepatocytes and HepG2 cells. In diseases leading to cholestasis, the RIPK3 expression is induced in mice and humans in a cell-type-specific manner. Overexpression of RIPK3 in HepG2 cells leads to RIPK3 activation by phosphorylation and cell death, further modulated by different bile acids. Additionally, bile acids and RIPK3 activation further facilitate JNK phosphorylation, IL-8 expression, and its release. This suggests that hepatocytes suppress RIPK3 expression to protect themselves from necroptosis and cytokine release induced by bile acid and RIPK3. In chronic liver diseases associated with cholestasis, induction of RIPK3 expression may be an early event signaling danger and repair through releasing IL-8.

Full-length IL-33 augments pulmonary fibrosis in an ST2- and Th2-independent, non-transcriptomic fashion

Mature IL-33 (MIL33) acting through its receptor, ST2, is known to regulate fibrosis. The precursor, full-length IL-33 (FLIL33), may function differently from MIL33 and independently of ST2. Here we report that genetic deletion of either IL-33 or ST2 attenuates pulmonary fibrosis in the bleomycin model, as does Cre-induced IL-33 deficiency in response to either acute or chronic bleomycin challenge. However, adenovirus-mediated gene delivery of FLIL33, but not MIL33, to the lungs of either wild-type or ST2-deficient mice potentiates the profibrotic effect of bleomycin without inducing a Th2 phenotype. In cultured mouse lung cells, FLIL33 overexpression induces moderate and distinct transcriptomic changes compared with a robust response induced by MIL33, whereas ST2 deletion abrogates the effects of both IL-33 forms. Thus, FLIL33 may contribute to fibrosis in an ST2-independent, Th2-independent, non-transcriptomic fashion, suggesting that pharmacological targeting of both FLIL33 and MIL33 may prove efficacious in patients with pulmonary fibrosis.

Therapeutic Perspectives of IL1 Family Members in Liver Diseases: An Update

Interleukin (IL) 1 superfamily members are a cornerstone of a variety of inflammatory processes occurring in various organs including the liver. Progression of acute and chronic liver diseases regardless of etiology depends on the stage of hepatocyte damage, the release of inflammatory cytokines and disturbances in gut microbiota. IL1 cytokines and receptors can have pro- or anti-inflammatory roles, even dual functionalities conditioned by the microenvironment. Developing novel therapeutic strategies to block the IL1/IL1R signaling pathways seems like a reasonable option. This mode of action is now exploited by anakinra and canakinumab, which are used to treat different inflammatory illnesses, and studies in liver diseases are on the way. In this mini review, we have focused on the IL1 superfamily members, given their crucial role in liver inflammation diseases, specifically discussing their potential role in developing new treatment strategies.

MAIT cells ameliorate liver fibrosis by enhancing the cytotoxicity of NK cells in cholestatic murine models

BACKGROUND AND AIMS

Mucosal-associated invariant T (MAIT) cells are innate-like lymphocytes that display a critical role in various liver diseases. However, the role of MAIT cells in cholestatic liver fibrogenesis remains obscure. Our study aims to assess the contribution of MAIT cells and underlying mechanisms during this process.

METHODS

Cholestatic murine models using MAIT cell-deficient (MR1^- /^- ) and wild-type (WT) mice were established by feeding a 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-enriched diet or bile duct ligation (BDL). Liver samples were collected to determine the severity of fibrosis. Lymphocytes of the liver were isolated for analysing the phenotype and function of MAIT cells. Cell co-culture experiments were performed to investigate the cross-talk between MAIT and NK cells.

RESULTS

Liver MAIT cells were more activated with increased cytokines in cholestatic mice models than in control mice, although their frequency was decreased. MAIT cell deficiency led to severe liver inflammation and fibrosis with more activated HSCs in cholestatic mice. In addition, MR1^- /^- mice had an increased frequency of NK cells with higher expression of stimulatory receptors relative to WT mice. Paradoxically, activated MAIT cells significantly promoted the anti-fibrotic ability of NK cells by enhancing their cytotoxicity against HSCs in co-culture experiments. Importantly, this effect depended on direct cell-cell contact and TNF-α produced by MAIT cells.

CONCLUSION

Our findings indicate that MAIT cells ameliorate cholestatic liver fibrosis by enhancing the cytotoxicity of NK cells against HSCs. An in-depth understanding of the MAIT cell-mediated regulatory effect will provide more valuable immunotherapy strategies to treat liver fibrosis.

Interleukin-33 deficiency prevents biliary injuries and repairments caused by Clonorchis sinensis via restraining type 2 cytokines

Background

Clonorchiasis caused by Clonorchis sinensis is a zoonotic parasitic disease characterized by cholangitis, biliary proliferation, biliary fibrosis, and even cholangiocarcinoma. Our previous study showed that the expression of interleukin (IL)-33 is increased in both humans and mice infected by C. sinensis, suggesting that IL-33 is potentially involved in the pathogenesis of clonorchiasis. However, the roles and potential mechanism of IL-33 underlying remain unknown.

Methods

Wild-type (WT) and IL-33 knockout (KO) mice (BALB/c female mice) were orally infected with 45 metacercariae of C. sinensis for 8 weeks. Biliary injuries and fibrosis were extensively evaluated. Hepatic type II cytokines (IL-4, IL-13, and IL-10) were detected by ELISA.

Results

For wild-type mice, we found that the mice infected with C. sinensis showed severe biliary injuries and fibrosis compared with the normal mice that were free from worm infection. In addition, the levels of type II cytokines such as IL-4, IL-13, and IL-10 in infected wild-type mice were significantly higher than in the control mice without infection (P < 0.05). However, IL-33 deficiency (IL-33 KO) prevents the augmentation of biliary injuries and fibrosis caused by C. sinensis infection. Furthermore, the increased levels of these type II cytokines induced by worm infection were also reversed in IL-33 KO mice.

Conclusion

Our present study demonstrates that IL-33 contributes to the pathogenesis of C. sinensis-induced biliary injuries and repair, which can potentially orchestrate type 2 responses. These findings highlight the pathophysiological role of IL-33 in the progression of clonorchiasis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05490-6.

The role of interleukin-33 in organ fibrosis

Interleukin (IL)-33 is highly expressed in the nucleus of cells present at barrier sites and signals via the ST2 receptor. IL-33 signalling via ST2 is essential for return to tissue homeostasis after acute inflammation, promoting fibrinogenesis and wound healing at injury sites. However, this wound-healing response becomes aberrant during chronic or sustained inflammation, leading to transforming growth factor beta (TGF-β) release, excessive extracellular matrix deposition, and fibrosis. This review addresses the role of the IL-33 pathway in fibrotic diseases of the lung, liver, gastrointestinal tract, skin, kidney and heart. In the lung and liver, IL-33 release leads to the activation of pro-fibrotic TGF-β, and in these sites, IL-33 has clear pro-fibrotic roles. In the gastrointestinal tract, skin, and kidney, the role of IL-33 is more complex, being both pro-fibrotic and tissue protective. Finally, in the heart, IL-33 serves cardioprotective functions by favouring tissue healing and preventing cardiomyocyte death. Altogether, this review indicates the presence of an unclear and delicate balance between resolving and pro-fibrotic capabilities of IL-33, which has a central role in the modulation of type 2 inflammation and fibrosis in response to tissue injury.

Natural polysaccharides as potential anti-fibrotic agents: A review of their progress

Fibrosis, as a common disease which could be found in nearly all organs, is normally initiated by organic injury and eventually ended in cellular dysfunction and organ failure. Currently, effective and safe therapeutic strategies targeting fibrogenesis still in highly demand. Natural polysaccharides derived from natural resources possess promising anti-fibrosis potential, with no deleterious side effects. Based on the etiology and pathogenesis of fibrosis, this review summarizes the intervention effects and mechanisms of natural polysaccharides in the prevention and treatment of fibrosis. Natural polysaccharides are able to regulate each phase of the fibrogenic response, including primary injury to organs, activation of effector cells, the elaboration of extracellular matrix (ECM) and dynamic deposition. In addition, polysaccharides significantly reduce fibrosis levels in multiple organs including heart, lung, liver and kidney. The investigation of the pathogenesis of fibrosis indicates that mechanisms including the inhibition of TGF-β/Smad, NF-κB, HMGB1/TLR4, cAMP/PKA signaling pathways, MMPs/TIMPs system as well as microRNAs are promising therapeutic targets. Natural polysaccharides can target these mediators or pathways to alleviate fibrosis. The information reviewed here offer new insights into the understanding the protective role of natural polysaccharides against fibrosis, help design further experimental studies related to polysaccharides and fibrotic responses, and shed light on a potential treatment for fibrosis.

Hepatic damage caused by long-term high cholesterol intake induces a dysfunctional restorative macrophage population in experimental NASH

Excessive dietary cholesterol is preferentially stored in the liver, favoring the development of nonalcoholic steatohepatitis (NASH), characterized by progressive hepatic inflammation and fibrosis. Emerging evidence indicates a critical contribution of hepatic macrophages to NASH severity. However, the impact of cholesterol on these cells in the setting of NASH remains elusive. Here, we demonstrate that the dietary cholesterol content directly affects hepatic macrophage global gene expression. Our findings suggest that the modifications triggered by prolonged high cholesterol intake induce long-lasting hepatic damage and support the expansion of a dysfunctional pro-fibrotic restorative macrophage population even after cholesterol reduction. The present work expands the understanding of the modulatory effects of cholesterol on innate immune cell transcriptome and may help identify novel therapeutic targets for NASH intervention.

The Immune Pathogenesis of Acute-On-Chronic Liver Failure and the Danger Hypothesis

Acute-on-chronic liver failure (ACLF) is a group of clinical syndromes related to severe acute liver function impairment and multiple-organ failure caused by various acute triggering factors on the basis of chronic liver disease. Due to its severe condition, rapid progression, and high mortality, it has received increasing attention. Recent studies have shown that the pathogenesis of ACLF mainly includes direct injury and immune injury. In immune injury, cytotoxic T lymphocytes (CTLs), dendritic cells (DCs), and CD4⁺ T cells accumulate in the liver tissue, secrete a variety of proinflammatory cytokines and chemokines, and recruit more immune cells to the liver, resulting in immune damage to the liver tissue, massive hepatocyte necrosis, and liver failure, but the key molecules and signaling pathways remain unclear. The “danger hypothesis” holds that in addition to the need for antigens, damage-associated molecular patterns (DAMPs) also play a very important role in the occurrence of the immune response, and this hypothesis is related to the pathogenesis of ACLF. Here, the research status and development trend of ACLF, as well as the mechanism of action and research progress on various DAMPs in ACLF, are summarized to identify biomarkers that can predict the occurrence and development of diseases or the prognosis of patients at an early stage.

IL-33 Promotes ST2-Dependent Fibroblast Maturation via P38 and TGF-β in a Mouse Model of Epidural Fibrosis

BACKGROUND

Recent evidence suggests that IL-33, a novel member of the IL-1β family, is involved in organ fibrosis. However, the roles of IL-33 and its receptor ST2 in epidural fibrosis post spine operation remain elusive.

METHODS

A mouse model of epidural fibrosis was established after laminectomy. IL-33 in the wound tissues post laminectomy was measured with Western blotting, ELISA and immunoflurosence imaging. The fibroblast cell line NIH-3T3 and primary fibroblasts were treated with IL-33 and the mechanisms of maturation of fibroblasts into myofibroblasts were analyzed. To explore roles of IL-33 and its receptor ST2 in vivo, IL-33 knockout (KO) and ST2 KO mice were employed to construct the model of laminectomy. The epidural fibrosis was evaluated using H&E and Masson staining, western-blotting, ELISA and immunohistochemistry.

RESULTS

As demonstrated in western blotting and ELISA, IL-33 was increased in epidural wound tissues post laminectomy. The immunoflurosence imaging revealed that endothelial cells (CD31⁺) and fibroblasts (α-SAM⁺) were major producers of IL-33 in the epidural wound tissues. In vitro, IL-33 promoted fibroblast maturation, which was blocked by ST2 neutralization antibody, suggesting that IL-33-promoted-fibroblasts maturation was ST2 dependent. Further, IL-33/ST2 activated MAPK p38 and TGF-β pathways. Either p38 inhibitor or TGF-β inhibitor decreased fibronectin and α-SAM production from IL-33-treated fibroblasts, suggesting that p38 and TGF-β were involved with IL-33/ST2 signal pathways in the fibroblasts maturation. In vivo, IL-33 KO or ST2 KO decreased fibronectin, α-SMA and collagen deposition in the wound tissues of mice that underwent spine surgery. In addition, TGF-β1 was decreased in IL-33 KO or ST2 KO epidural wound tissues.

CONCLUSION

In summary, IL-33/ST2 promoted fibroblast differentiation into myofibroblasts via MAPK p38 and TGF-β in a mouse model of epidural fibrosis after laminectomy.

Interleukin-33/ Suppression of Tumorigenicity 2 in Renal Fibrosis: Emerging Roles in Prognosis and Treatment

Chronic kidney disease (CKD) is a major public health problem that affects more than 10% of the population worldwide and has a high mortality rate. Therefore, it is necessary to identify novel treatment strategies for CKD. Incidentally, renal fibrosis plays a central role in the progression of CKD to end-stage renal disease (ESRD). The activation of inflammatory pathways leads to the development of renal fibrosis. In fact, interleukin-33 (IL-33), a newly discovered member of the interleukin 1 (IL-1) cytokine family, is a crucial regulator of the inflammatory process. It exerts pro-inflammatory and pro-fibrotic effects via the suppression of tumorigenicity 2 (ST2) receptor, which, in turn, activates other inflammatory pathways. Although the role of this pathway in cardiac, pulmonary, and hepatic fibrotic diseases has been extensively studied, its precise role in renal fibrosis has not yet been completely elucidated. Recent studies have shown that a sustained activation of IL-33/ST2 pathway promotes the development of renal fibrosis. However, with prolonged research in this field, it is expected that the IL-33/ST2 pathway will be used as a diagnostic and prognostic tool for renal diseases. In addition, the IL-33/ST2 pathway seems to be a new target for the future treatment of CKD. Here, we review the mechanisms and potential applications of the IL-33/ST2 pathway in renal fibrosis; such that it can help clinicians and researchers to explore effective treatment options and develop novel medicines for CKD patients.

Macrophages Modulate Hepatic Injury Involving NLRP3 Inflammasome: The Example of Efavirenz

Drug-induced liver injury (DILI) constitutes a clinical challenge due to the incomplete characterization of the mechanisms involved and potential risk factors. Efavirenz, an anti-HIV drug, induces deleterious actions in hepatocytes that could underlie induction of the NLRP3 inflammasome, an important regulator of inflammatory responses during liver injury. We assessed the potential of efavirenz to modulate the inflammatory and fibrogenic responses of major liver cell types involved in DILI. The effects of efavirenz were evaluated both in vitro and in vivo. Efavirenz triggered inflammation in hepatocytes, in a process that involved NF-κB and the NLRP3 inflammasome, and activated hepatic stellate cells (HSCs), thereby enhancing expression of inflammatory and fibrogenic markers. The NLRP3 inflammasome was not altered in efavirenz-treated macrophages, but these cells polarized towards the anti-inflammatory M2 phenotype and displayed upregulated anti-inflammatory mediators. Conversely, no evidence of damage was observed in efavirenz-treated animals, except when macrophages were depleted, which resulted in the in vivo manifestation of the deleterious effects detected in hepatocytes and HSCs. Efavirenz elicits a cell-specific activation of the NLRP3 inflammasome in hepatocytes and HSCs, but macrophages appear to counteract efavirenz-induced liver injury. Our results highlight the dynamic nature of the interaction among liver cell populations and emphasize the potential of targeting macrophage polarization as a strategy to treat NLRP3 inflammasome-induced liver injury.

Association between Melatonin Value and Interleukins1B, -18, and -33 Levels in Patients with Different Stages of Non-Alcoholic Fatty Liver Disease

BACKGROUND: Interaction between immune modulators and inflammatory factors is considered as one of the main underlying pathologies of non-alcoholic fatty liver disease (NAFLD). Hence we aimed to assess the association between these cytokines and melatonin. METHODS: We enrolled adult patients diagnosed with fatty liver by ultrasonography in a crosssectional study. All of them underwent Fibroscan evaluation. The subjects who met the inclusion and exclusion criteria for NAFLD were involved. A normal group who did not have NAFLD, viral or non-viral hepatitis, and without a history of pancreatobiliary surgery, bariatric surgery, and intake of any medication that influence the liver was also selected. The participants were categorized into the three following groups: 1) fibrosis>9.1 kPa and steatosis>290 dbm, 2) fibrosis: 6-9.0 kPa and steatosis 240-290 dbm, and 3) normal group with fibrosis<6.0 kPa and steatosis<240 dbm. Laboratory assessment and a questionnaire including demographic, anthropometric, laboratories, and clinical data were completed for each of them. RESULTS: Totally 97 subjects were enrolled in the present study. The mean age of the subjects was 42.2±11.3 years. 60% of them (59 patients) were female. Serum levels of melatonin, interleukin (IL)-1B, IL-18, and IL-33 increased according to the advancing of NAFLD state. Based on multiple linear regression model, melatonin was significantly associated with IL-1B (β=2.8, P<0.001,95% CI=1.41-4.19), IL-18 (β=0.018, P=0.0005, 95% CI=0.006-0.03), and IL-33 (β=0.31, P=0.045, 95% CI=0.008-0.62) after adjustment for other variables. CONCLUSION: Melatonin level has a strong association with these cytokines. This linkage probably influences on the development and progression of NAFLD. Therefore it can be hypothesized that the therapeutic approach that affects this process may have a significant impact.

Therapeutic potential of targeting regulatory mechanisms of hepatic stellate cell activation in liver fibrosis

Hepatic fibrosis is a manifestation of different etiologies of liver disease with the involvement of multiple mediators in complex network interactions. Activated hepatic stellate cells (aHSCs) are the central driver of hepatic fibrosis, given their potential to induce connective tissue formation and extracellular matrix (ECM) protein accumulation. Therefore, identifying the cellular and molecular pathways involved in the activation of HSCs is crucial in gaining mechanistic and therapeutic perspectives to more effectively target the disease. In addition to a comprehensive summary of our current understanding of the role of HSCs in liver fibrosis, we also discuss here the proposed therapeutic strategies based on targeting HSCs.

The Role of Cancer-Associated Fibroblasts in Hepatocellular Carcinoma and the Value of Traditional Chinese Medicine Treatment

Invasion and metastasis are the main reasons for the high mortality of liver cancer, which involve the interaction of tumor stromal cells and malignant cells. Cancer-associated fibroblasts (CAFs) are one of the major constituents of tumor stromal cells affecting tumor growth, invasion, and metastasis. The heterogeneous properties and sources of CAFs make both tumor-supporting and tumor-suppression effects possible. The mechanisms for CAFs in supporting hepatocellular carcinoma (HCC) progression can be categorized into upregulated aggressiveness and stemness, transformed metabolism toward glycolysis and glutamine reductive carboxylation, polarized tumor immunity toward immune escape of HCC cells, and increased angiogenesis. The tumor-suppressive effect of fibroblasts highlights the functional heterogenicity of CAF populations and provides new insights into tumor–stromal interplay mechanisms. In this review, we introduced several key inflammatory signaling pathways in the transformation of CAFs from normal stromal cells and the heterogeneous biofunctions of activated CAFs. In view of the pleiotropic regulation properties of traditional Chinese medicine (TCM) and heterogeneous effects of CAFs, we also introduced the application and values of TCM in the treatment of HCC through targeting CAFs.

Quantifying the progression of non-alcoholic fatty liver disease in human biomimetic liver microphysiology systems with fluorescent protein biosensors

Metabolic syndrome is a complex disease that involves multiple organ systems including a critical role for the liver. Non-alcoholic fatty liver disease (NAFLD) is a key component of the metabolic syndrome and fatty liver is linked to a range of metabolic dysfunctions that occur in approximately 25% of the population. A panel of experts recently agreed that the acronym, NAFLD, did not properly characterize this heterogeneous disease given the associated metabolic abnormalities such as type 2 diabetes mellitus (T2D), obesity, and hypertension. Therefore, metabolic dysfunction-associated fatty liver disease (MAFLD) has been proposed as the new term to cover the heterogeneity identified in the NAFLD patient population. Although many rodent models of NAFLD/NASH have been developed, they do not recapitulate the full disease spectrum in patients. Therefore, a platform has evolved initially focused on human biomimetic liver microphysiology systems that integrates fluorescent protein biosensors along with other key metrics, the microphysiology systems database, and quantitative systems pharmacology. Quantitative systems pharmacology is being applied to investigate the mechanisms of NAFLD/MAFLD progression to select molecular targets for fluorescent protein biosensors, to integrate computational and experimental methods to predict drugs for repurposing, and to facilitate novel drug development. Fluorescent protein biosensors are critical components of the platform since they enable monitoring of the pathophysiology of disease progression by defining and quantifying the temporal and spatial dynamics of protein functions in the biosensor cells, and serve as minimally invasive biomarkers of the physiological state of the microphysiology system experimental disease models. Here, we summarize the progress in developing human microphysiology system disease models of NAFLD/MAFLD from several laboratories, developing fluorescent protein biosensors to monitor and to measure NAFLD/MAFLD disease progression and implementation of quantitative systems pharmacology with the goal of repurposing drugs and guiding the creation of novel therapeutics.

Type 2 Innate Lymphoid Cells: Protectors in Type 2 Diabetes

Type 2 innate lymphoid cells (ILC2) are the innate counterparts of Th2 cells and are critically involved in the maintenance of homeostasis in a variety of tissues. Instead of expressing specific antigen receptors, ILC2s respond to external stimuli such as alarmins released from damage. These cells help control the delicate balance of inflammation in adipose tissue, which is a determinant of metabolic outcome. ILC2s play a key role in the pathogenesis of type 2 diabetes mellitus (T2DM) through their protective effects on tissue homeostasis. A variety of crosstalk takes place between resident adipose cells and ILC2s, with each interaction playing a key role in controlling this balance. ILC2 effector function is associated with increased browning of adipose tissue and an anti-inflammatory immune profile. Trafficking and maintenance of ILC2 populations are critical for tissue homeostasis. The metabolic environment and energy source significantly affect the number and function of ILC2s in addition to affecting their interactions with resident cell types. How ILC2s react to changes in the metabolic environment is a clear determinant of the severity of disease. Treating sources of metabolic instability via critical immune cells provides a clear avenue for modulation of systemic homeostasis and new treatments of T2DM.

Genetic variants in IL33 and IL1RL1 genes confer susceptibility to HBV-related liver cirrhosis in Chinese Han population

INTRODUCTION

Previous studies indicate that the IL-33/ST2 pathway is involved in hepatitis B virus (HBV) -related liver diseases. This study aimed to determine the relationship between genetic variants in IL-33/ST2 pathway with susceptibility to liver cirrhosis.

MATERIALS AND METHODS

A total of 2632 Han Chinese samples met the inclusion and exclusion criteria, including 840 negative controls (NeC), 691 chronic hepatitis B (CHB), 680 HBV-related liver cirrhosis (LC) and 421 HBV-related hepatocellular carcinoma (HCC) (without LC) patients. Four polymorphisms (IL33-rs4742170, rs1048274, rs10975519 and IL1RL1-rs1041973) were selected and genotyping was performed. All statistical analyses were performed by SPSS21.0, mainly using the Hardy-Weinberg equilibrium test, Pearson chi-square, unconditional Logistic regression and haplotype analysis.

RESULTS

After adjusting for age, sex, smoking and drinking, significant associations were observed between IL33-rs4742170, rs1048274 and rs10975519 polymorphisms with LC risk. NeC with IL33-rs4742170 CC genotype was 1.80 times more likely to develop LC compared with TT genotype, while NeC with rs10975519(TC + CC) genotype was 1.32 times more likely to develop LC when compared with the TT genotype. CHB cases with rs4742170(CC + TC) genotype had 1.30 times higher susceptibility to develop LC compared with the TT genotype. The IL33-rs1048274G allele occurred more frequently in the LC group compared with the HCC group in codominant model (AG/AA: P = 0.001, OR = 1.66, 95%CI = 1.22-2.25; GG/AA: P = 0.018, OR = 1.54, 95%CI = 1.08-2.20). The IL33 haplotype CG conformed by rs10975519C and rs1048274G was more frequent in the LC group than in the NeC group and CHB group. Moreover, the IL33 haplotype CCG conformed by rs4742170C, rs10975519C and rs1048274G was found to be more frequent in the LC group than the HCC group. However, there was no association between IL1RL1-rs1041973 and LC risk.

CONCLUSION

Our findings demonstrate the association between genetic variants in IL33 with susceptibility to liver cirrhosis. IL33-rs4742170C, rs1048274G and rs10975519C could serve as biomarkers of LC.

Fasudil prevents liver fibrosis via activating natural killer cells and suppressing hepatic stellate cells

BACKGROUND

Fasudil, as a Ras homology family member A (RhoA) kinase inhibitor, is used to improve brain microcirculation and promote nerve regeneration clinically. Increasing evidence shows that Rho-kinase inhibition could improve liver fibrosis.

AIM

To evaluate the anti-fibrotic effects of Fasudil in a mouse model of liver fibrosis induced by thioacetamide (TAA).

METHODS

C57BL/6 mice were administered TAA once every 3 d for 12 times. At 1 wk after induction with TAA, Fasudil was intraperitoneally injected once a day for 3 wk, followed by hematoxylin and eosin staining, sirius red staining, western blotting, and quantitative polymerase chain reaction (qPCR), and immune cell activation was assayed by fluorescence-activated cell sorting. Furthermore, the effects of Fasudil on hepatic stellate cells and natural killer (NK) cells were assayed in vitro.

RESULTS

First, we found that TAA-induced liver injury was protected, and the positive area of sirius red staining and type I collagen deposition were significantly decreased by Fasudil treatment. Furthermore, western blot and qPCR assays showed that the levels of alpha smooth muscle actin (α-SMA), matrix metalloproteinase 2 (MMP-2), MMP-9, and transforming growth factor beta 1 (TGF-β1) were inhibited by Fasudil. Moreover, flow cytometry analysis revealed that NK cells were activated by Fasudil treatment in vivo and in vitro. Furthermore, Fasudil directly promoted the apoptosis and inhibited the proliferation of hepatic stellate cells by decreasing α-SMA and TGF-β1.

CONCLUSION

Fasudil inhibits liver fibrosis by activating NK cells and blocking hepatic stellate cell activation, thereby providing a feasible solution for the clinical treatment of liver fibrosis.

Interleukin 33 mediates hepatocyte autophagy and innate immune response in the early phase of acetaminophen-induced acute liver injury

Despite interleukin 33 (IL-33) functions as an "alarmin" released from hepatic dead cells in response to tissue damages, the interrelationship between IL-33-mediated hepatocyte autophagy and innate immune response in the acetaminophen (APAP)-induced liver injury (AILI) process remains obscure. This study aimed to explore the regulation of IL-33 on hepatocyte autophagy and macrophage polarization after APAP challenge in vivo and vitro. We found IL-33 released from hepatic necrosis was elevated in the AILI mouse model. Blockage of IL-33 exacerbated liver injury by consuming liver-resident macrophages cells (Kupffer cells, KCs) and promoting hepatic inflammatory factors secretion, such as TNF-α, IL-6 and IL-1β in the early phase of liver injury. Interestingly, IL-33 deficiency further activated hepatocyte autophagy and disrupted M2 macrophage polarization post-APAP challenge in vivo and vitro, which can be reversed by recombinant IL-33 treatment. Mechanistically, administration of IL-33 can directly enhance M2 polarization via PI3K/Akt signaling pathway and activate protective hepatocyte autophagy via AMPKα/mTOR signaling pathway in the AILI process. In conclusion, our data firstly demonstrates that IL-33 exerts protective effects on hepatocytes through the activation of autophagy and functions as an innate immunity regulator mediating macrophage polarization in the early phase of AILI.