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

The Impact of Toll-Like Receptor 5 on Liver Function in Age-Related Metabolic Disorders

Toll-like receptor 5 (TLR5) plays a critical role beyond its traditional function in innate immunity, significantly impacting metabolic regulation and liver health. Previously, we reported that TLR5 activation extends the healthspan and lifespan of aging mice. This study demonstrates that TLR5 deficiency leads to pronounced metabolic abnormalities with age, primarily affecting liver metabolic functions rather than intestinal inflammation. Comprehensive RNA sequencing analysis revealed that TLR5 deficiency induces gene expression changes in liver tissue similar to those caused by the methionine-choline deficient (MCD) diet, particularly affecting lipid metabolism and circadian rhythm-related genes. TLR5 knockout (TLR5 KO) mice displayed an increased propensity for liver fibrosis and lipid accumulation under the MCD diet, exacerbating liver pathology. Both hepatocytes and hepatic stellate cells in TLR5 KO mice were functionally impacted, leading to metabolic dysfunction and fibrosis. These findings suggest that TLR5 could be a significant target for addressing metabolic diseases that arise and worsen with aging. Furthermore, understanding the mechanisms by which TLR5 activation extends healthspan could provide valuable insights into therapeutic strategies for enhancing longevity and managing age-related metabolic disorders.

Postbiotic Impact on Host Metabolism and Immunity Provides Therapeutic Potential in Metabolic Disease

The gut microbiota influences aspects of metabolic disease, including tissue inflammation, adiposity, blood glucose, insulin, and endocrine control of metabolism. Prebiotics or probiotics are often sought to combat metabolic disease. However, prebiotics lack specificity and can have deleterious bacterial community effects. Probiotics require live bacteria to find a colonization niche sufficient to influence host immunity or metabolism. Postbiotics encompass bacterial-derived components and molecules, which are well-positioned to alter host immunometabolism without relying on colonization efficiency or causing widespread effects on the existing microbiota. Here, we summarize the potential for beneficial and detrimental effects of specific postbiotics related to metabolic disease and the underlying mechanisms of action. Bacterial cell wall components, such as lipopolysaccharides, muropeptides, lipoteichoic acids and flagellin, have context-dependent effects on host metabolism by engaging specific immune responses. Specific types of postbiotics within broad classes of compounds, such as lipopolysaccharides and muropeptides, can have opposing effects on endocrine control of host metabolism, where certain postbiotics are insulin sensitizers and others promote insulin resistance. Bacterial metabolites, such as short-chain fatty acids, bile acids, lactate, glycerol, succinate, ethanolamine, and ethanol, can be substrates for host metabolism. Postbiotics can fuel host metabolic pathways directly or influence endocrine control of metabolism through immunomodulation or mimicking host-derived hormones. The interaction of postbiotics in the host-microbe relationship should be considered during metabolic inflammation and metabolic disease.

Sappanone A alleviates metabolic dysfunction-associated steatohepatitis by decreasing hepatocyte lipotoxicity via targeting Mup3 in mice

BACKGROUND AND PURPOSE

Metabolic dysfunction-associated steatohepatitis (MASH) is an inflammatory lipotoxic disorder marked by hepatic steatosis, hepatocyte damage, inflammation, and varying stages of fibrosis. Sappanone A (SA), a flavonoid, exhibits anti-inflammatory and hepatoprotection activities. Nevertheless, the effects of SA on MASH remain ambiguous. We evaluated the effects of SA on hepatocyte lipotoxicity, inflammation, and fibrosis conditions in MASH mice, as well as the underlying mechanisms.

METHODS

A conventional murine MASH model fed a methionine-choline-deficient (MCD) diet was utilized to assess the role of SA on MASH in vivo. Drug target prediction and liver transcriptomics were employed to elucidate the potential actions of SA. AML12 cells were applied to further explore the effects and mechanisms of SA in vitro.

RESULTS

The in silico prediction indicated that SA could modulate inflammation, insulin resistance, lipid metabolism, and collagen catabolic process. Treating with SA dose-dependently lessened the elevated levels of serum ALT and AST in mice with diet-triggered MASH, and high-dose SA treatment exhibited a similar effect to silymarin. Additionally, SA treatment significantly reduced lipid deposition, inflammation, and fibrosis subjected to metabolic stress in a dose-dependent manner. Besides, SA mitigated palmitate-triggered lipotoxicity in hepatocytes. Liver transcriptomics further confirmed the aforementioned findings. Of note, mRNA-sequencing analysis and molecular biology experiments demonstrated that SA statistically up-regulated the hepatic expression of major urinary protein 3 (Mup3), thereby facilitating lipid transportation and inhibiting lipotoxicity. Furthermore, Mup3 knockdown in hepatocytes significantly abolished the hepatoprotection provided by SA.

CONCLUSION

SA alleviates MASH by decreasing lipid accumulation and lipotoxicity in hepatocytes, at least partially by targeting Mup3, and subsequently blocks MASH process. Therefore, SA could be a promising hepatoprotective agent in the context of MASH.

Fibrosis and Hepatocarcinogenesis: Role of Gene-Environment Interactions in Liver Disease Progression

The liver is a complex organ that performs vital functions in the body. Despite its extraordinary regenerative capacity compared to other organs, exposure to chemical, infectious, metabolic and immunologic insults and toxins renders the liver vulnerable to inflammation, degeneration and fibrosis. Abnormal wound healing response mediated by aberrant signaling pathways causes chronic activation of hepatic stellate cells (HSCs) and excessive accumulation of extracellular matrix (ECM), leading to hepatic fibrosis and cirrhosis. Fibrosis plays a key role in liver carcinogenesis. Once thought to be irreversible, recent clinical studies show that hepatic fibrosis can be reversed, even in the advanced stage. Experimental evidence shows that removal of the insult or injury can inactivate HSCs and reduce the inflammatory response, eventually leading to activation of fibrolysis and degradation of ECM. Thus, it is critical to understand the role of gene-environment interactions in the context of liver fibrosis progression and regression in order to identify specific therapeutic targets for optimized treatment to induce fibrosis regression, prevent HCC development and, ultimately, improve the clinical outcome.

Role of pattern recognition receptors in the development of MASLD and potential therapeutic applications

Metabolic dysfunction-associated steatotic liver disease (MASLD) has become one of the most prevalent liver diseases worldwide, and its occurrence is strongly associated with obesity, insulin resistance (IR), genetics, and metabolic stress. Ranging from simple fatty liver to metabolic dysfunction-associated steatohepatitis (MASH), even to severe complications such as liver fibrosis and advanced cirrhosis or hepatocellular carcinoma, the underlying mechanisms of MASLD progression are complex and involve multiple cellular mediators and related signaling pathways. Pattern recognition receptors (PRRs) from the innate immune system, including Toll-like receptors (TLRs), C-type lectin receptors (CLRs), NOD-like receptors (NLRs), RIG-like receptors (RLRs), and DNA receptors, have been demonstrated to potentially contribute to the pathogenesis for MASLD. Their signaling pathways can induce inflammation, mediate oxidative stress, and affect the gut microbiota balance, ultimately resulting in hepatic steatosis, inflammatory injury and fibrosis. Here we review the available literature regarding the involvement of PRR-associated signals in the pathogenic and clinical features of MASLD, in vitro and in animal models of MASLD. We also discuss the emerging targets from PRRs for drug developments that involved agent therapies intended to arrest or reverse disease progression, thus enabling the refinement of therapeutic targets that can accelerate drug development.

Molecular insights into experimental models and therapeutics for cholestasis

Cholestatic liver disease (CLD) is a range of conditions caused by the accumulation of bile acids (BAs) or disruptions in bile flow, which can harm the liver and bile ducts. To investigate its pathogenesis and treatment, it is essential to establish and assess experimental models of cholestasis, which have significant clinical value. However, owing to the complex pathogenesis of cholestasis, a single modelling method can merely reflect one or a few pathological mechanisms, and each method has its adaptability and limitations. We summarize the existing experimental models of cholestasis, including animal models, gene-knockout models, cell models, and organoid models. We also describe the main types of cholestatic disease simulated clinically. This review provides an overview of targeted therapy used for treating cholestasis based on the current research status of cholestasis models. In addition, we discuss the respective advantages and disadvantages of different models of cholestasis to help establish experimental models that resemble clinical disease conditions. In sum, this review not only outlines the current research with cholestasis models but also projects prospects for clinical treatment, thereby bridging basic research and practical therapeutic applications.

Gut microbiota in MAFLD: therapeutic and diagnostic implications

Metabolic dysfunction-associated fatty liver disease (MAFLD), formerly known as nonalcoholic fatty liver disease, is becoming a significant contributor to chronic liver disease globally, surpassing other etiologies, such as viral hepatitis. Prevention and early treatment strategies to curb its growing prevalence are urgently required. Recent evidence suggests that targeting the gut microbiota may help treat and alleviate disease progression in patients with MAFLD. This review aims to explore the complex relationship between MAFLD and the gut microbiota in relation to disease pathogenesis. Additionally, it delves into the therapeutic strategies targeting the gut microbiota, such as diet, exercise, antibiotics, probiotics, synbiotics, glucagon-like peptide-1 receptor agonists, and fecal microbiota transplantation, and discusses novel biomarkers, such as microbiota-derived testing and liquid biopsy, for their diagnostic and staging potential. Overall, the review emphasizes the urgent need for preventive and therapeutic strategies to address the devastating consequences of MAFLD at both individual and societal levels and recognizes that further exploration of the gut microbiota may open avenues for managing MAFLD effectively in the future.

ANGPTL3 negatively regulates IL-1β-induced NF-κB activation by inhibiting the IL1R1-associated signaling complex assembly

Interleukin-1β (IL-1β)-induced signaling is one of the most important pathways in regulating inflammation and immunity. The assembly of the receptor complex, consisting of the ligand IL-1β, the IL-1 receptor (IL-1R) type 1 (IL1R1), and the IL-1R accessory protein (IL1RAP), initiates this signaling. However, how the IL1R1-associated complex is regulated remains elusive. Angiopoietin like 3 (ANGPTL3), a key inhibitor of plasma triglyceride clearance, is mainly expressed in the liver and exists in both intracellular and extracellular secreted forms. Currently, ANGPTL3 has emerged as a highly promising drug target for hypertriglyceridemia and associated cardiovascular diseases. However, most studies have focused on the secreted form of ANGPTL3, while its intracellular role is still largely unknown. Here, we report that intracellular ANGPTL3 acts as a negative regulator of IL-1β-triggered signaling. Overexpression of ANGPTL3 inhibited IL-1β-induced NF-κB activation and the transcription of inflammatory genes in HepG2, THP1, and HEK293T cells, while knockdown or knockout of ANGPTL3 resulted in opposite effects. Mechanistically, ANGPTL3 interacted with IL1R1 and IL1RAP through its intracellular C-terminal fibrinogen-like domain and disrupted the assembly of the IL1R1-associated complex. Taken together, our study reveals a novel role for ANGPTL3 in inflammation, whereby it inhibits the physiological interaction between IL1R1 and IL1RAP to maintain immune tolerance and homeostasis in the liver.

Immunology of gut microbiome and liver in non-alcoholic fatty liver disease (NAFLD): mechanisms, bacteria, and novel therapeutic targets

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the world. Most important contributors to its development are diet and obesity. Gut microbiome's importance for immune system and inflammatory pathways more widely accepted as an important component in NAFLD and other liver diseases' pathogenesis. In this article we review potential mechanisms of microbiome alteration of local and systemic immune responses leading to NAFLD's development, and how can modulate them for the treatment. Our review mentions different immune system pathways and microorganisms regulating metabolism, liver inflammation and fibrosis. We specifically point out TLR-4 as a potential key immune pathway activated by bacterial lipopolysaccharides producing pro-inflammatory cytokines in NAFLD. Also, we discuss three endotoxin-producing strains (Enterobacter cloacae B29, Escherichia coli PY102, Klebsiella pneumoniae A7) that can promote NAFLD development via TLR4-dependent immune response activation in animal models and how they potentially contribute to disease progression in humans. Additionally, we discuss their other immune and non-immune mechanisms contributing to NAFLD pathogenesis. In the end we point out gut microbiome researches' future perspective in NAFLD as a potential new target for both diagnostic and treatment.

Monocyte-derived Kupffer cells dominate in the Kupffer cell pool during liver injury

Healthy Kupffer cell (KC) pool is dominated by embryonic KCs (EmKCs), preserving liver homeostasis. How the KC pool varies upon injury remains unclear. Using chimeric mice with bone marrow (BM) cells labeled with enhanced green fluorescent protein, we identify that BM monocyte-derived KCs (MoKCs) become dominant in cholestatic- or toxic-injured livers via immunofluorescence and mass cytometry. Single-cell RNA sequencing (scRNA-seq) unveils the enhanced proliferative, anti-apoptotic properties and repair potential of MoKCs compared with EmKCs, which are confirmed in vivo and ex vivo through flow cytometry, qPCR, Cell Counting Kit-8, and immunofluorescence. Furthermore, compared with EmKC-dominated livers, MoKC-dominated livers exhibit less functional damage, necrosis, and fibrosis under damage, as tested by serum alanine aminotransferase activity detection, H&E and Sirius red staining, qPCR, and western blot. Collectively, we highlight that MoKCs dominate the KC pool in injured livers and show enhanced proliferative and anti-apoptotic properties while also promoting repair and attenuating fibrosis.

Sappanone A Alleviates the Severity of Carbon Tetrachloride-Induced Liver Fibrosis in Mice

Liver fibrosis is a major challenge to global health because of its various complications, including cirrhosis and hepatocarcinoma, while no effective treatment is available for it. Sappanone A (SA) is a homoisoflavonoid extracted from the heartwood of Caesalpinia sappan Linn. with anti-inflammatory and antioxidant properties. However, the effects of SA on hepatic fibrosis remain unknown. This study aimed to investigate the protective effects of SA on carbon tetrachloride (CCl4)-induced liver fibrosis in mice. To establish a liver fibrosis model, mice were treated intraperitoneally (i.p.) with CCl4 for 4 weeks. SA (25, 50, and 100 mg/kg body weight) was i.p. injected every other day during the same period. Our data indicated that SA decreased liver injury, fibrotic responses, and inflammation due to CCl4 exposure. Consistently, SA reduced oxidative stress and its-mediated hepatocyte death in fibrotic livers. Of note, SA could not directly affect the activation of hepatic stellate cells. Mechanistically, SA treatment lessened oxidative stress-triggered cell death in hepatocytes after CCl4 exposure. SA down-regulated the expression of M1 macrophage polarization markers (CD86 and iNOS) and up-regulated the expression of M2 macrophage polarization markers (CD163, IL-10, and Arg1) in livers and macrophages. Meanwhile, SA induced the activation of peroxisome proliferator-activated receptor gamma (PPARγ). However, decreased inflammatory responses and the trend of M2 macrophage polarization provided by SA were substantially abolished by SR202 (a PPARγ inhibitor) treatment in macrophages. Additionally, SA treatment promoted fibrosis regression. Taken together, our findings revealed that treatment with SA alleviated CCl4-induced fibrotic liver in mice through suppression of oxidative stress-mediated hepatocyte death and promotion of M2 macrophage polarization via PPARγ. Thus, SA might pave the way for a new hepatoprotective agent to treat liver fibrosis.

Escherichia coli Promotes Endothelial to Mesenchymal Transformation of Liver Sinusoidal Endothelial Cells and Exacerbates Nonalcoholic Fatty Liver Disease Via Its Flagellin

BACKGROUND＆AIMS: Gut bacteria translocate into the liver through a disrupted gut vascular barrier, which is an early and common event in the development of nonalcoholic fatty liver disease (NAFLD). Liver sinusoidal endothelial cells (LSECs) are directly exposed to translocated gut microbiota in portal vein blood. Escherichia coli, a commensal gut bacterium with flagella, is markedly enriched in the gut microbiota of patients with NAFLD. However, the impact of E coli on NAFLD progression and its underlying mechanisms remains unclear.

METHODS

The abundance of E coli was analyzed by using 16S ribosomal RNA sequencing in a cohort of patients with NAFLD and healthy controls. The role of E coli was assessed in NAFLD mice after 16 weeks of administration, and the features of NAFLD were evaluated. Endothelial to mesenchymal transition (EndMT) in LSECs induced by E coli was analyzed through Western blotting and immunofluorescence.

RESULTS

The abundance of gut Enterobacteriaceae increased in NAFLD patients with severe fat deposition and fibrosis. Importantly, translocated E coli in the liver aggravated hepatic steatosis, inflammation, and fibrosis in NAFLD mice. Mechanistically, E coli induced EndMT in LSECs through the TLR5/MYD88/TWIST1 pathway during NAFLD development. The toll-like receptor 5 inhibitor attenuated E coli-induced EndMT in LSECs and liver injury in NAFLD mice. Interestingly, flagellin-deficient E coli promoted less EndMT in LSECs and liver injury in NAFLD mice.

CONCLUSIONS

E coli promoted the development of NAFLD and promoted EndMT in LSECs through toll-like receptor 5/nuclear factor kappa B-dependent activation of TWIST1 mediated by flagellin. Therapeutic interventions targeting E coli and/or flagellin may represent a promising candidate for NAFLD treatment.

Toll-like receptor 5 tunes hepatic and pancreatic stellate cells activation

OBJECTIVE

Stellate cells are responsible for liver and pancreas fibrosis and strictly correlate with tumourigenesis. Although their activation is reversible, an exacerbated signalling triggers chronic fibrosis. Toll-like receptors (TLRs) modulate stellate cells transition. TLR5 transduces the signal deriving by the binding to bacterial flagellin from invading mobile bacteria.

DESIGN

Human hepatic and pancreatic stellate cells were activated by the administration of transforming growth factor-beta (TGF-β). TLR5 was transiently knocked down by short-interference RNA transfection. Reverse Transcription-quantitativePCR and western blot were performed to analyse the transcript and protein level of TLR5 and the transition players. Fluorescence microscopy was performed to identify these targets in spheroids and in the sections of murine fibrotic liver.

RESULTS

TGF-β-activated human hepatic and pancreatic stellate cells showed an increase of TLR5 expression. TLR5 knockdown blocked the activation of those stellate cells. Furthermore, TLR5 busted during murine liver fibrosis and co-localised with the inducible Collagen I. Flagellin suppressed TLR5, COL1A1 and ACTA2 expression after the administration of TGF-β. Instead, the antagonist of TLR5 did not block the effect of TGF-β. Wortmannin, a specific AKT inhibitor, induced TLR5 but not COL1A1 and ACTA2 transcript and protein level.

CONCLUSION

TGF-β-mediated activation of hepatic and pancreatic stellate cells requires the over-expression of TLR5. Instead, its autonomous signalling inhibits the activation of the stellate cells, thus prompting a signalling through different regulatory pathways.

Toll-like receptor-7 signaling in Kupffer cells exacerbates concanavalin A-induced liver injury in mice

Concanavalin A (ConA) is a plant lectin that can induce immune-mediated liver damage. ConA induced liver damage animal model is a widely accepted model that can mimic clinical acute hepatitis and immune-mediated liver injury in humans. Toll-like receptor-7 (TLR7), a member of the TLR family, plays a key role in pathogen recognition and innate immune activation. The aim of this study was to examine the role of TLR7 in the pathogenesis of ConA-induced liver injury. Acute liver injury was induced by intravenous injection with ConA in WT (wild-type) and TLR7 knockout (KO) mice. Results showed that attenuated liver injury in TLR7-deficient mice, as indicated by increased survival rate, decreased aminotransferase levels, and reduced pathological lesions, was associated with decreased release of pro-inflammatory cytokines in livers. Consistently, significantly decreased proliferation of CD4⁺ T cell was detected in ConA-stimulated TLR7-deficient splenocytes, but not in CD3/CD28 stimulated TLR7-deficient CD4⁺ T cells. Moreover, TLR7 deficiency in KCs specifically suppressed the expression of TNF-α (tumor necrosis factor-α). Depletion of KCs abolished the detrimental role of TLR7 in ConA-induced liver injury. Taken together, these results demonstrate that TLR7 can regulate the expression of TNF-α in KCs, which is necessary for the full progression of ConA-induced liver injury.

Evaluation of transcriptomic molecular classification, biological behavior, and clinicopathological features in hepatocellular carcinoma

BACKGROUND

Studies in France, Korea, and Singapore found that G1-G6 transcriptomes are involved in hepatocellular carcinoma (HCC) carcinogenesis. However, the suitability of this method in Chinese HCC patients has remained unknown.

METHODS

The correlation between the G1-G6 molecular classification and clinicopathological features were analyzed in 107 Chinese HCC patients through the retrospective cohort study. RNA sequencing and bioinformatics analysis were performed to screen related targets and molecular signaling pathways.

RESULTS

We found that the G1-G3 subgroups were associated with high serum alpha-fetoprotein (AFP) level, high copy number of hepatitis B virus (HBV) DNA, complex histopathological structure, macrovascular invasion. The G1 subgroup was mainly related to liver cancer stemness, and G3 subgroup showed the worst prognosis. The G5 and G6 subgroups were associated with activation of the Wnt/β-catenin pathway. Compared with the G4-G6 group, the G1-G3 group showed significantly higher expression levels of regenerating family member 1 beta (REG1B), regenerating family member 3 gamma (REG3G), and inositol 1,4,5-trisphosphate receptor type 1 (ITPR1), and enriched calcium signaling pathway.

CONCLUSIONS

This study enhances our understanding of the heterogenicity of China HCC and indicates that the G1-G6 signatures can be used to identify predictive biomarkers against HCC patients in China.

Sappanone A ameliorates acetaminophen-induced acute liver injury in mice

Sappanone A (SA), a homoisoflavonoid compound extracted from the heartwood of Caesalpinia sappan Linn., exerts anti-inflammatory and antioxidant activities. However, the effects of SA on acetaminophen (APAP) overdose-induced acute liver injury (ALI) have not been determined yet. This study aims to explore the protective effects of SA and the potential mechanisms of action. Mice were pretreated with SA (25, 50, and 100 mg/kg) by intraperitoneal (i.p.) injection for seven days prior to APAP (300 mg/kg, i.p.) administration. At 12 h after APAP injection, serum and liver samples were collected. Primary murine hepatocytes were used to investigate the underlying mechanisms. SA pretreatment dose-dependently attenuated APAP-induced ALI, as validated by reduced serum alanine/aspartate aminotransferase levels, histopathologic lesions, and oxidative stress. Consistently, pretreatment with SA reduced the formation of APAP protein adducts in damaged livers of mice. Mechanistically, SA could facilitate the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and thus promote cellular glutathione (GSH) synthesis. The hepatoprotective outcomes provided by SA were significantly abolished by treatment with ML385, a Nrf2 inhibitor. Besides, anti-inflammatory property of SA reduced inflammatory reaction in injured livers of mice. Of note, posttreatment with SA reveals significant therapeutic influences against APAP-induced ALI in mice. Collectively, our findings demonstrated that pretreated-SA ameliorated APAP-mediated ALI in mice, at least in part, by reducing the generation of APAP protein adducts via Nrf2-enhanced GSH synthesis, and by diminishing hepatic inflammation. Therefore, SA could be a potential hepatoprotective agent for treating ALI.

The Role of Atypical Chemokine Receptor D6 (ACKR2) in Physiological and Pathological Conditions; Friend, Foe, or Both?

Chemokines exert crucial roles in inducing immune responses through ligation to their canonical receptors. Besides these receptors, there are other atypical chemokine receptors (ACKR1–4) that can bind to a wide range of chemokines and carry out various functions in the body. ACKR2, due to its ability to bind various CC chemokines, has attracted much attention during the past few years. ACKR2 has been shown to be expressed in different cells, including trophoblasts, myeloid cells, and especially lymphoid endothelial cells. In terms of molecular functions, ACKR2 scavenges various inflammatory chemokines and affects inflammatory microenvironments. In the period of pregnancy and fetal development, ACKR2 plays a pivotal role in maintaining the fetus from inflammatory reactions and inhibiting subsequent abortion. In adults, ACKR2 is thought to be a resolving agent in the body because it scavenges chemokines. This leads to the alleviation of inflammation in different situations, including cardiovascular diseases, autoimmune diseases, neurological disorders, and infections. In cancer, ACKR2 exerts conflicting roles, either tumor-promoting or tumor-suppressing. On the one hand, ACKR2 inhibits the recruitment of tumor-promoting cells and suppresses tumor-promoting inflammation to blockade inflammatory responses that are favorable for tumor growth. In contrast, scavenging chemokines in the tumor microenvironment might lead to disruption in NK cell recruitment to the tumor microenvironment. Other than its involvement in diseases, analyzing the expression of ACKR2 in body fluids and tissues can be used as a biomarker for diseases. In conclusion, this review study has tried to shed more light on the various effects of ACKR2 on different inflammatory conditions.

The anti-inflammatory effects of Akkermansia muciniphila and its derivates in HFD/CCL4-induced murine model of liver injury

Inflammation plays a critical role in the promotion of hepatocyte damage and liver fibrosis. In recent years the protective role of Akkermansia muciniphila, a next-generation beneficial microbe, has been suggested for metabolic and inflammatory disorders. In this study, we aimed to evaluate the effects of live and pasteurized A. muciniphila and its extra cellular vesicles (EVs) on inflammatory markers involved in liver fibrosis in a mouse model of a high-fat diet (HFD)/carbon tetrachloride (CCl₄)-induced liver injury. Firstly, the responses of hepatic stellate cells (HSCs) to live and pasteurized A. muciniphila and its EVs were examined in the quiescent and LPS-activated LX-2 cells. Next, the anti-inflammatory effects of different forms of A. muciniphila were examined in the mouse model of HFD/CCl₄-induced liver injury. The gene expression of various inflammatory markers was evaluated in liver, colon, and white adipose tissues. The cytokine secretion in the liver and white adipose tissues was also measured by ELISA. The results showed that administration of live and pasteurized A. muciniphila and its EVs leads to amelioration in HSCs activation. Based on data obtained from the histopathological analysis, an improvement in gut health was observed through enhancing the epithelium and mucosal layer thickness and strengthening the intestinal integrity in all treatments. Moreover, live A. muciniphila and its EVs had inhibitory effects on liver inflammation and hepatocytes damage. In addition, the tissue cytokine production and inflammatory gene expression levels revealed that live A. muciniphila and its EVs had more pronounced anti-inflammatory effects on liver and adipose tissues. Furthermore, EVs had better effects on the modulation of gene expression related to TLRs, PPARs, and immune response in the liver. In conclusion, the present results showed that oral administration of A. muciniphila and its derivatives for four weeks could enhance the intestinal integrity and anti-inflammatory responses of the colon, adipose, and liver tissues and subsequently prevent liver injury in HFD/CCL₄ mice.

STING signaling activation inhibits HBV replication and attenuates the severity of liver injury and HBV-induced fibrosis

The covalently closed circular DNA (cccDNA) of HBV plays a crucial role in viral persistence and is also a risk factor for developing HBV-induced diseases, including liver fibrosis. Stimulator of interferon genes (STING), a master regulator of DNA-mediated innate immune activation, is a potential therapeutic target for viral infection and virus-related diseases. In this study, agonist-induced STING signaling activation in macrophages was revealed to inhibit cccDNA-mediated transcription and HBV replication via epigenetic modification in hepatocytes. Notably, STING activation could efficiently attenuate the severity of liver injury and fibrosis in a chronic recombinant cccDNA (rcccDNA) mouse model, which is a proven suitable research platform for HBV-induced fibrosis. Mechanistically, STING-activated autophagic flux could suppress macrophage inflammasome activation, leading to the amelioration of liver injury and HBV-induced fibrosis. Overall, the activation of STING signaling could inhibit HBV replication through epigenetic suppression of cccDNA and alleviate HBV-induced liver fibrosis through the suppression of macrophage inflammasome activation by activating autophagic flux in a chronic HBV mouse model. This study suggests that targeting the STING signaling pathway may be an important therapeutic strategy to protect against persistent HBV replication and HBV-induced fibrosis.

ACKR2 limits skin fibrosis and hair loss through IFN-β

The resolution of inflammation facilitates proper wound healing and limits tissue repair short of exaggerated fibrotic scarring. The atypical chemokine receptor (ACKR)2/D6 scavenges inflammatory chemokines, while IFN-β is a recently unveiled pro-resolving cytokine. Both effector molecules limit acute inflammatory episodes and promote their resolution in various organs. Here, we found fibrotic skin lesions from ACKR2^-/- mice presented increased epidermal and dermal thickening, atrophy of the subcutaneous adipose tissue, augmented disorientation of collagen deposition, and enhanced deformation and loss of hair follicles compared to WT counterparts. In addition, affected skin sections from ACKR2^-/- mice contained reduced levels of the pro-resolving mediators IFN-β and IL-10, but increased levels of the pro-inflammatory chemokines CCL2 and 3, the pro-fibrotic cytokine TGF-β, and the immune-stimulating cytokine IL-12. Notably, treatment with exogenous IFN-β rescued, at least in part, all the pro-fibrotic outcomes and lesion size in ACKR2^-/- mice and promoted expression of the pro-resolving enzyme 12/15-lipoxygenase (LO) in both ACKR2^-/- and WT mice. Moreover, Ifnb^-/- mice displayed enhanced pro-fibrotic indices upon exposure to bleomycin. These findings suggest ACKR2 is an important mediator in limiting inflammatory skin fibrosis and acts via IFN-β production to promote the resolution of inflammation and minimize tissue scaring.

A genetic variant in toll-like receptor 5 is linked to chemokine levels and hepatocellular carcinoma in steatohepatitis

BACKGROUND & AIMS

Bacterial translocation drives liver disease progression. We investigated whether functional genetic variants in toll-like receptor 5 (TLR5), the receptor for bacterial flagellin, affect the risk for hepatocellular carcinoma (HCC).

METHODS

Healthy controls (n = 212), patients with alcohol abuse without liver disease (n = 382), and patients from a discovery cohort of alcohol-associated cirrhosis (n = 372 including 79 HCC cases), a validation cohort of alcohol-associated cirrhosis (n = 355 including 132 HCC cases), and a cohort of cirrhosis due to nonalcoholic steatohepatitis (NASH) (n = 145 including 62 HCC cases) were genotyped for the TLR5 rs5744174 and rs5744168 polymorphisms. Chemokine levels were measured by ELISA in patients' sera and supernatants of flagellin-stimulated healthy monocytes.

RESULTS

Frequency of the TLR5 rs5744174 TT genotype was similar in healthy controls (33%), controls with alcohol abuse (34%), and patients with alcohol-associated cirrhosis in the discovery (28%), validation (33%), and NASH cohort (31%). The TT genotype was enriched in patients with versus without HCC in the discovery, validation, and NASH cohort (41% vs 25%; 39% vs 29%; 40% vs 24%; p < .05 each). This genotype remained a risk factor for HCC (OR = 1.9; p = .01) after multivariate correction for age, gender, diabetes, and carriage of the PNPLA3 148M variant. Interleukin-8 induction in monocytes from healthy controls and serum levels of interleukin-8 and CXCL1 from cirrhotic patients with the TT genotype were significantly increased versus C allele carriers.

CONCLUSION

The TLR5 rs5744174 polymorphism, affecting immune response to flagellin, is linked to occurrence of HCC in cirrhosis caused by steatohepatitis.

Exogenous activation of toll-like receptor 5 signaling mitigates acetaminophen-induced hepatotoxicity in mice

Acetaminophen (APAP) poisoning is the most common cause of drug-induced acute liver injury (ALI). Our results showed that toll-like receptor 5 (TLR5) was abundantly expressed in hepatocytes and dramatically downregulated in the toxic mouse livers. Hence, we herein investigated the role of TLR5 signaling after APAP overdose. Mice were intraperitoneally (i.p.) injected with APAP to induce ALI, and then injected with flagellin at one hour after APAP administration. Flagellin attenuated APAP-induced ALI based on decreased histopathologic lesions, serum biochemical, oxidative stress, and inflammation. Furthermore, the protective effects of flagellin were abolished by TH1020 (a TLR5 antagonist) treatment. These results suggest that flagellin exerted protective effects on ALI via TLR5 activation. Mechanistically, flagellin injection promoted the translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) to the nucleus in hepatocytes. Consistent with the in vivo results, flagellin increased the activation of Nrf2 in hepatocytes, resulting in decreased APAP toxicity. ML385, a selective inhibitor of Nrf2, abolished the flagellin-mediated hepatoprotective effects in damaged livers and hepatocytes. Additionally, the flagellin-induced Nrf2 translocation was dependent upon the activation of TLR5-JNK/p38 pathways. These findings suggest that TLR5 signaling-induced Nrf2 activation, at least partially, contributed to the protection against APAP-induced ALI by flagellin treatment.

Indoleamine 2,3-dioxygenase 1 limits hepatic inflammatory cells recruitment and promotes bile duct ligation-induced liver fibrosis

Liver fibrosis is a course of chronic liver dysfunction, can develop into cirrhosis and hepatocellular carcinoma. Inflammatory insult owing to pathogenic factors plays a crucial role in the pathogenesis of liver fibrosis. Indoleamine 2,3-dioxygenase 1 (IDO1) can affect the infiltration of immune cells in many pathology processes of diseases, but its role in liver fibrosis has not been elucidated completely. Here, the markedly elevated protein IDO1 in livers was identified, and dendritic cells (DCs) immune-phenotypes were significantly altered after BDL challenge. A distinct hepatic population of CD11c+DCs was decreased and presented an immature immune-phenotype, reflected by lower expression levels of co-stimulatory molecules (CD40, MHCII). Frequencies of CD11c+CD80+, CD11c+CD86+, CD11c+MHCII+, and CD11c+CD40+ cells in splenic leukocytes were reduced significantly. Notably, IDO1 overexpression inhibited hepatic, splenic CD11c+DCs maturation, mature DCs-mediated T-cell proliferation and worsened liver fibrosis, whereas above pathological phenomena were reversed in IDO1-/- mice. Our data demonstrate that IDO1 affects the process of immune cells recruitment via inhibiting DCs maturation and subsequent T cells proliferation, resulting in the promotion of hepatic fibrosis. Thus, amelioration of immune responses in hepatic and splenic microenvironment by targeting IDO1 might be essential for the therapeutic effects on liver fibrosis.

Dual TBK1/IKKε inhibitor amlexanox mitigates palmitic acid-induced hepatotoxicity and lipoapoptosis in vitro

The common causes of Non-alcoholic fatty liver disease (NAFLD) are obesity, dyslipidemia, and insulin resistance. Metabolic disorders and lipotoxic hepatocyte damage are hallmarks of NAFLD. Even though amlexanox, a dual inhibitor of TRAF associated nuclear factor κB (NF-κB) activator-binding kinase 1 (TBK1) and IκB kinase epsilon (IKKε), has been reported to effectively improve obesity-related metabolic dysfunctions in mice models, its molecular mechanism has not been fully investigated. This study was designed to investigate the effects of amlexanox on in vitro nonalcoholic steatohepatitis (NASH) model induced by treatment of palmitic acid (PA, 0.4 mM), using a trans-well co-culture system of hepatocytes and Kupffer cells (KCs). Stimulation with PA significantly increased the phosphorylation levels of TBK1 and IKKε in both hepatocytes and KCs, suggesting a potential role of TBK1/IKKε in PA-induced NASH progression. Treatment of amlexanox (50 μM) showed significantly reduced phosphorylation of TBK1 and IKKε and hepatotoxicity as confirmed by decreased levels of lactate dehydrogenase released from hepatocytes. Furthermore, PA-induced inflammation and lipotoxic cell death in hepatocytes were significantly reversed by amlexanox treatment. Intriguingly, amlexanox inhibited the activation of KCs and induced polarization of KCs towards M2 phenotype. Mechanistically, amlexanox treatment decreased the phosphorylation of interferon regulator factor 3 (IRF3) and NF-κB in PA-treated hepatocytes. However, decreased phosphorylation of NF-κB, not IRF3, was found in PA-treated KCs upon amlexanox treatment. Taken together, our findings show that treatment of amlexanox attenuated the severity of PA-induced hepatotoxicity in vitro and lipoapoptosis by the inhibition of TBK1/IKKε-NF-κB and/or IRF3 pathway in hepatocytes and KCs.

A Network Pharmacology Approach to Explore the Mechanisms of Shugan Jianpi Formula in Liver Fibrosis

Purpose

We explored the mechanism of Shugan Jianpi Formula (SGJPF) and its effective components for the treatment of liver fibrosis (LF).

Materials and Methods

We collected the active ingredients in SGJPF through the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform and screened the effective components by absorption, distribution, metabolism, and excretion. Herb-associated target proteins were predicted and screened based on the Bioinformatics Analysis Tool for Molecular Mechanism of Traditional Chinese Medicine and Search Tool for Interactions of Chemicals databases. LF-associated target proteins were predicted and screened based on the Online Mendelian Inheritance in Man® Database and Comparative Toxicogenomics Database. Common genes with LF and herbs were selected, and Cytoscape 3.5.1 software was used to construct an herb pathway and component-LF common target network. The Search Tool for the Retrieval of Interacting Genes/Proteins was used to build a protein-protein interaction, and quantitative PCR was used to verify the related target genes. Finally, clusterProfiler was applied for the analysis of Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways.

Results

The pharmacological network contained 252 active compounds (e.g., Astragaloside A, saikosaponin, linoleic acid, and Poria acid A), 84 common target genes, and 94 significant signaling pathways. Among them, interleukin 6 (IL-6), tumor protein 53 p53 (TP53), prostaglandin-endoperoxide synthase 2 (PTGS2), AKT1, IL-1β, and the nucleotide-binding and oligomerization domain-like receptor and Janus kinase-signal transducer and activator of transcription signaling pathways were selected as the critical target gene and critical signal pathway, respectively.

Conclusion

The mechanisms of SGJPF in protecting against LF include the regulation of multiple targets such as IL-6, TP53, PTGS2, and AKT1. These target proteins affect LF through various signal transduction pathways.