Dual TBK1/IKKɛ inhibitor amlexanox attenuates the severity of hepatotoxin-induced liver fibrosis and biliary fibrosis in mice

The role of 2'-5'-oligoadenylate synthase-like protein (OASL1) in biliary and hepatotoxin-induced liver injury in mice

Following an injury, the liver embarks on a process that drives the accumulation and reformation of the extracellular matrix, leading to hepatic fibrosis. Type I interferons (IFNs), including IFN-α and IFN-β, play a crucial role in averting chronic liver injury through the activation of IFN-stimulated genes (ISGs), which are instrumental in sculpting adaptive immunity. The role of 2'-5'-oligoadenylate synthase-like protein 1 (OASL1), an antiviral ISG, in the context of liver fibrosis remains to be elucidated. To elicit liver fibrosis, a diet containing 0.1% diethoxycarbonyl-1,4-dihydrocollidine (DDC) and carbon tetrachloride (CCl4) were employed to induce cholestatic- and hepatotoxin-mediated liver fibrosis, respectively. Histological analyses of both models revealed that OASL1-/- mice exhibited reduced liver damage and, consequently, expressed lower levels of fibrotic mediators, notably α-smooth muscle actin. OASL1-/- mice demonstrated significantly elevated IFN-α and IFN-β mRNA levels, regulated by the IFN regulatory factor 7 (IRF7). Additionally, OASL1-/- ameliorated chronic liver fibrosis through the modulation of nuclear factor-κB (NF-κB) signaling. The effect of OASL1 on type I IFN production in acute liver damage was further explored and OASL1-/- mice consistently showed lower alanine transaminase levels and pro-inflammatory cytokines, but IFN-α and IFN-β mRNA levels were upregulated, leading to amelioration of acute liver injury. Additionally, the study discovered that F4/80-positive cells were observed more frequently in OASL1-/- CCl4 acutely treated mice. This implies that there is a significant synergy in the function of macrophages and OASL1 deficiency. These results demonstrate that in instances of liver injury, OASL1 inhibits the production of type I IFN by modulating the NF-κB signaling pathway, thereby worsening disease.

cGAS/STING signalling pathway in senescence and oncogenesis

The cGAS/STING signaling pathway is a crucial component of the innate immune system, playing significant roles in sensing cytosolic DNA, regulating cellular senescence, and contributing to oncogenesis. Recent advances have shed new lights into the molecular mechanisms governing pathway activation in multiple pathophysiological settings, the indispensable roles of cGAS/STING signaling in cellular senescence, and its context-dependent roles in cancer development and suppression. This review summarizes current knowledge related to the biology of cGAS/STING signaling pathway and its participations into senescence and oncogenesis. We further explore the clinical implications and therapeutic potential for cGAS/STING targeted therapies, and faced challenges in the field. With a focus on molecular mechanisms and emerging pharmacological targets, this review underscores the importance of future studies to harness the therapeutic potential of the cGAS/STING pathway in treating senescence-related disorders and cancer. Advanced understanding of the regulatory mechanisms of cGAS/STING signaling, along with the associated deregulations in diseases, combined with the development of new classes of cGAS/STING modulators, hold great promises for creating novel and effective therapeutic strategies. These advancements could address current treatment challenges and unlock the full potential of cGAS/STING in treating senescence-related disorders and oncogenesis.

cGAS-STING, an important signaling pathway in diseases and their therapy

Since cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway was discovered in 2013, great progress has been made to elucidate the origin, function, and regulating mechanism of cGAS-STING signaling pathway in the past decade. Meanwhile, the triggering and transduction mechanisms have been continuously illuminated. cGAS-STING plays a key role in human diseases, particularly DNA-triggered inflammatory diseases, making it a potentially effective therapeutic target for inflammation-related diseases. Here, we aim to summarize the ancient origin of the cGAS-STING defense mechanism, as well as the triggers, transduction, and regulating mechanisms of the cGAS-STING. We will also focus on the important roles of cGAS-STING signal under pathological conditions, such as infections, cancers, autoimmune diseases, neurological diseases, and visceral inflammations, and review the progress in drug development targeting cGAS-STING signaling pathway. The main directions and potential obstacles in the regulating mechanism research and therapeutic drug development of the cGAS-STING signaling pathway for inflammatory diseases and cancers will be discussed. These research advancements expand our understanding of cGAS-STING, provide a theoretical basis for further exploration of the roles of cGAS-STING in diseases, and open up new strategies for targeting cGAS-STING as a promising therapeutic intervention in multiple diseases.

Amlexanox attenuates LPS-induced neuroinflammatory responses in microglial cells via inhibition of NF-κB and STAT3 signaling pathways

Amlexanox is an anti-inflammatory and anti-allergic agent used clinically for the treatment of aphthous ulcers, allergic rhinitis, and asthma. Recent studies have demonstrated that amlexanox, a selective inhibitor of IkB kinase epsilon (IKKε) and TANK-binding kinase 1 (TBK1), suppresses a range of diseases or inflammatory conditions, such as obesity-related metabolic dysfunction and type 2 diabetes. However, the effects of amlexanox on neuroinflammatory responses to amlexanox have not yet been comprehensively studied. In this study, we investigated the novel therapeutic effect of amlexanox on LPS-induced neuroinflammation in vivo, and intraperitoneal injection of amlexanox markedly reduced LPS-induced IKKε levels, proinflammatory cytokines, and microglial activation, as evidenced by ionized calcium-binding adapter molecule 1 (Iba1) immunostaining. Furthermore, amlexanox significantly reduced proinflammatory cytokines and chemokines in LPS-induced bone marrow-derived macrophages (BMDM), murine BV2, and human HMC3 microglial cells. This data provided considerable evidence that amlexanox can be used as a preventive and curative therapy for neuroinflammatory and neurodegenerative diseases. In terms of mechanism aspects, our results demonstrated that the anti-inflammatory action of amlexanox in BV2 microglial cells was through the downregulation of NF-κB and STAT3 signaling pathways. In addition, the combination of amlexanox and SPI (a STAT3 selective inhibitor) showed high efficiency in inhibiting the production of neurotoxic and pro-inflammatory mediators. Overall, our data provide rational insights into the mechanisms of amlexanox as a potential therapeutic strategy for neuroinflammation-related diseases.

CXCL5 promotes lipotoxicity of hepatocytes through upregulating NLRP3/Caspase-1/IL-1β signaling in Kupffer cells and exacerbates nonalcoholic steatohepatitis in mice

Immune-inflammatory responses play a key role in the development of nonalcoholic steatohepatitis (NASH). Previous studies have demonstrated that CXC motif chemokine ligand 5 (CXCL5) correlates positively with obesity and type 2 diabetes. This study is to explore the functional role of CXCL5 in the pathogenesis of NASH. To establish a NASH model, mice were fed with methionine-and choline-deficient high-fat diet for 6 weeks and anti-CXCL5 mAb was injected during the same period. An in vitro NASH model was established by treating palmitic acid (PA), using a trans-well co-culture system of mouse primary hepatocytes and Kupffer cells (KCs), and recombinant mouse (rm) CXCL5 was treated after PA administration. Our data showed that hepatic CXCL5 levels were highly expressed in the NASH mouse model. CXCL5 neutralization significantly alleviated the severity of NASH livers, demonstrated by pathological analysis, decreased biochemicals, and inflammation. Besides, neutralizing CXCL5 reduced lipid accumulation, cell death, and fibrosis in injured livers. In vitro, rmCXCL5 could not affect the activation of hepatic stellate cells. Also, rmCXCL5 exacerbated PA-induced hepatotoxicity and lipid deposition in hepatocytes co-cultured with KCs rather than in single-cultured hepatocytes. Mechanistically, rmCXCL5 not only promoted NOD-like receptor pyrin domain-containing protein 3 (NLRP3) expression, Cleaved caspase-1 expression, and interleukin 1 beta (IL-1β) secretion in single-cultured and co-cultured KCs but also increased lipid deposition in co-cultured hepatocytes. In addition, MCC950, an inhibitor of NLRP3, almost abolished the effects of rmCXCL5 on PA-treated co-culture system. Therefore, CXCL5 could exacerbate NASH by promoting lipotoxicity of hepatocytes via upregulating NLRP3/Caspase-1/IL-1β signaling in KCs.

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.

Mesenchymal stem cells-based therapy in liver diseases

Multiple immune cells and their products in the liver together form a complex and unique immune microenvironment, and preclinical models have demonstrated the importance of imbalances in the hepatic immune microenvironment in liver inflammatory diseases and immunocompromised liver diseases. Various immunotherapies have been attempted to modulate the hepatic immune microenvironment for the purpose of treating liver diseases. Mesenchymal stem cells (MSCs) have a comprehensive and plastic immunomodulatory capacity. On the one hand, they have been tried for the treatment of inflammatory liver diseases because of their excellent immunosuppressive capacity; On the other hand, MSCs have immune-enhancing properties in immunocompromised settings and can be modified into cellular carriers for targeted transport of immune enhancers by genetic modification, physical and chemical loading, and thus they are also used in the treatment of immunocompromised liver diseases such as chronic viral infections and hepatocellular carcinoma. In this review, we discuss the immunological basis and recent strategies of MSCs for the treatment of the aforementioned liver diseases. Specifically, we update the immune microenvironment of the liver and summarize the distinct mechanisms of immune microenvironment imbalance in inflammatory diseases and immunocompromised liver diseases, and how MSCs can fully exploit their immunotherapeutic role in liver diseases with both immune imbalance patterns.

Inhibitory targeting cGAS-STING-TBK1 axis: Emerging strategies for autoimmune diseases therapy

The cGAS-STING signaling plays an integral role in the host immune response, and the abnormal activation of cGAS-STING is highly related to various autoimmune diseases. Therefore, targeting the cGAS-STING-TBK1 axis has become a promising strategy in therapy of autoimmune diseases. Herein, we summarized the key pathways mediated by the cGAS-STING-TBK1 axis and various cGAS-STING-TBK1 related autoimmune diseases, as well as the recent development of cGAS, STING, or TBK1 selective inhibitors and their potential application in therapy of cGAS-STING-TBK1 related autoimmune diseases. Overall, the review highlights that inhibiting cGAS-STING-TBK1 signaling is an attractive strategy for autoimmune disease therapy.

The TBK1/IKKε inhibitor amlexanox improves dyslipidemia and prevents atherosclerosis

Cardiovascular diseases, especially atherosclerosis and its complications, are a leading cause of death. Inhibition of the noncanonical IκB kinases TANK-binding kinase 1 and IKKε with amlexanox restores insulin sensitivity and glucose homeostasis in diabetic mice and human patients. Here we report that amlexanox improves diet-induced hypertriglyceridemia and hypercholesterolemia in Western diet-fed (WD-fed) Ldlr-/- mice and protects against atherogenesis. Amlexanox ameliorated dyslipidemia, inflammation, and vascular dysfunction through synergistic actions that involve upregulation of bile acid synthesis to increase cholesterol excretion. Transcriptomic profiling demonstrated an elevated expression of key bile acid synthesis genes. Furthermore, we found that amlexanox attenuated monocytosis, eosinophilia, and vascular dysfunction during WD-induced atherosclerosis. These findings demonstrate the potential of amlexanox as a therapy for hypercholesterolemia and atherosclerosis.

I-κB kinase-ε deficiency improves doxorubicin-induced dilated cardiomyopathy by inhibiting the NF-κB pathway

Dilated cardiomyopathy (DCM) can lead to heart expansion and severe heart failure, but its specific pathogenesis is still elusive. In many cardiovascular diseases, I-κB kinase-ε (IKKε) has been recognized as a pro-inflammatory molecule. In this study, wild-type mice (WT, n = 14) and IKKε knockout mice (IKKε-KO, n = 14) were intraperitoneally injected with a cumulative dose of 25 mg/kg with Dox or Saline five times in 30 days. Finally, the experimental mice were divided into WT + Saline group、WT + DOX group、IKKε-KO + Saline group and IKKε-KO + Dox group. Echocardiography was performed to assess cardiac structure and function. Moreover, the mechanism was validated by immunohistochemistry and western blotting. Our results demonstrated that compared to WT + Dox mice, IKKε-KO + Dox mice exhibited attenuation of dilated cardiomyopathy-related morphological changes and alleviation of heart failure. Additionally, compared to the WT mice after Dox-injected, the expression of fibrosis and proinflammatory were decreased in IKKε-KO mice, and the expression of cardiac gap junction proteins was much higher in IKKε-KO mice. Further testing found that pyroptosis and apoptosis in the myocardium were also ameliorated in IKKε-KO mice compared to WT mice after Dox was injected. Mechanistically, our results showed that deficiency of IKKε might inhibit the phosphorylation of IκBα, p65, RelB, and p100 in mouse heart tissues after Dox stimulation. In summary, our research suggests that IKKε might play an essential role in the development of Dox-induced dilated cardiomyopathy and may be a potential target for the treatment of dilated cardiomyopathy in the future.

Pharmacological Inhibition of STING/TBK1 Signaling Attenuates Myeloid Fibroblast Activation and Macrophage to Myofibroblast Transition in Renal Fibrosis

Renal fibrosis is an important pathological biomarker of chronic kidney disease (CKD). Stimulator of interferon genes/TANK binding kinase 1 (STING/TBK1) axis has been identified as the main regulator of innate immune response and closely related to fibrotic disorder. However, the role of STING/TBK1 signaling pathway in kidney fibrosis is still unknown. In this study, we investigated the effect of pharmacological inhibition of STING/TBK1 signaling on renal fibrosis induced by folic acid (FA). In mice, TBK1 was significantly activated in interstitial cells of FA-injured kidneys, which was markedly inhibited by H-151 (a STING inhibitor) treatment. Specifically, pharmacological inhibition of STING impaired bone marrow-derived fibroblasts activation and macrophage to myofibroblast transition in folic acid nephropathy, leading to reduction of extracellular matrix proteins expression, myofibroblasts formation and development of renal fibrosis. Furthermore, pharmacological inhibition of TBK1 by GSK8612 reduced myeloid myofibroblasts accumulation and impeded macrophage to myofibroblast differentiation, resulting in less deposition of extracellular matrix protein and less severe fibrotic lesion in FA-injured kidneys. In cultured mouse bone marrow-derived monocytes, TGF-β1 activated STING/TBK1 signaling. This was abolished by STING or TBK1 inhibitor administration. In addition, GSK8612 treatment decreased levels of α-smooth muscle actin and extracellular matrix proteins and prevents bone marrow-derived macrophages to myofibroblasts transition in vitro. Collectively, our results revealed that STING/TBK1 signaling has a critical role in bone marrow-derived fibroblast activation, macrophages to myofibroblasts transition, and kidney fibrosis progression.

RESISTANCE EXERCISE ATTENUATES IKKε PHOSPHORYLATION AND HEPATIC FAT ACCUMULATION OF OBESE MICE

Obesity is associated with low-grade inflammation and disturbances in hepatic metabolism. This study aimed to investigate the effects of resistance exercise on inflammatory signaling related to IKKepsilon protein (IKKɛ) and on hepatic fat accumulation in obese mice. Male Swiss mice were distributed into three groups: control (CTL) fed with standard chow; obese (OB) mice induced by a high-fat diet (HFD); obese exercised (OB+RE) mice fed with HFD and submitted to a resistance exercise training. The resistance exercise training protocol consisted of 20 sets/3 ladder climbs for eight weeks, three times/week on alternate days. The training overload was equivalent to 70% of the maximum load supported by the rodent. Assays were performed to evaluate weight gain, hepatic fat content, fasting glucose, insulin sensitivity, IKKɛ phosphorylation, and proteins related to insulin signaling and lipogenesis in the liver. Mice that received the high-fat diet showed greater adiposity, impaired insulin sensitivity, increased fasting glucose, and increased hepatic fat accumulation. These results were accompanied by an increase in IKKɛ phosphorylation and lipogenesis-related proteins such as cluster of differentiation 36 (CD36) and fatty acid synthase (FAS) in the liver of obese mice. In contrast, exercised mice showed lower body weight and adiposity evolution throughout the experiment. In addition, resistance exercise suppressed the effects of the high-fat diet by reducing IKKɛ phosphorylation and hepatic fat content. In conclusion, resistance exercise training improves hepatic fat metabolism and glycemic homeostasis, which are, at least in part, linked to the antiinflammatory effect of reduced IKKɛ phosphorylation in the liver of obese mice. This article is protected by copyright. All rights reserved.

Role of IKKε in the Metabolic Diseases: Physiology, Pathophysiology, and Pharmacology

IKKε (inhibitor of nuclear factor kappa-B kinase ε) is a member of the noncanonical NF-κB pathway. It participates in the inflammatory response and innate immunity against bacteria. In recent decades, IKKε has been closely associated with metabolic regulation. Inhibition of the IKKε pathway can improve fat deposition in the liver, reduce subcutaneous fat inflammation, and improve liver gluconeogenesis in obesity. IKKε is expected to be a new therapeutic target for metabolic diseases such as nonalcoholic fatty liver disease, diabetes, and obesity. Herein, we summarize the structural characterization, physiological function, and pathological role of IKKε in metabolic diseases and small molecule inhibitors of IKKε.

Nintedanib exerts anti-pulmonary fibrosis activity via inhibiting TANK-binding kinase 1 (TBK1) phosphorylation

Since triple angiokinase inhibitor could not fully explain the anti-pulmonary fibrosis activity of nintedanib (NDNB), the chemoproteomic strategy was performed to identify TANK-binding kinase 1 (TBK1) as the key target of NDNB in human pulmonary fibroblasts (HPFs). Functionally, NDNB exerts anti-fibrosis activity through impairing the p-TBK1-mediated Yes-associated protein (YAP)/transcriptional cofactor with PDZ-binding motif (TAZ) nuclear translocation.

The potential value of amlexanox in the treatment of cancer: Molecular targets and therapeutic perspectives

Amlexanox (AMX) is an azoxanthone drug used for decades for the treatment of mouth aphthous ulcers and now considered for the treatment of diabetes and obesity. The drug is usually viewed as a dual inhibitor of the non-canonical IκB kinases IKK-ɛ (inhibitor-kappaB kinase epsilon) and TBK1 (TANK-binding kinase 1). But a detailed target profile analysis indicated that AMX binds directly to twelve protein targets, including different enzymes (IKK-ɛ, TBK1, GRK1, GRK5, PDE4B, 5- and 12-lipoxygenases) and non-enzyme proteins (FGF-1, HSP90, S100A4, S100A12, S100A13). AMX has been demonstrated to have marked anticancer effects in multiple models of xenografted tumors in mice, including breast, colon, lung and gastric cancers and in onco-hematological models. The anticancer potency is generally modest but largely enhanced upon combination with cytotoxic (temozolide, docetaxel), targeted (selumetinib) or biotherapeutic agents (anti-PD-1 and anti-CTLA4 antibodies). The multiple targets participate in the anticancer effects, chiefly IKK-ɛ/TBK1 but also S100A proteins and PDE4B. The review presents the molecular basis of the antitumor effects of AMX. The capacity of the drug to block nonsense-mediated mRNA decay (NMD) is also discussed, as well as AMX-induced reduction of cancer-related pain. Altogether, the analysis provides a survey of the anticancer action of AMX, with the implicated protein targets. The use of this well-tolerated drug to treat cancer should be further considered and the design of newer analogues encouraged.

Isoproterenol-Induced Cardiomyopathy Recovery Intervention: Amlexanox and Forskolin Enhances the Resolution of Catecholamine Stress-Induced Maladaptive Myocardial Remodeling

The increasing incidence of stress-induced cardiomyopathy is due to the complexities of our modern-day lives, which constantly elicit stress responses. Herein, we aimed to explore the therapeutic potential of Amlexanox and Forskolin in promoting the recovery from stress-induced cardiomyopathy. Isoproterenol-induced cardiomyopathy (ICM) models were made, and the following treatment interventions were administered: 5% v/v DMSO as a placebo, Amlexanox (2.5 mg/100 g/day) treatment, Forskolin (0.5 mg/100 g/day), and Amlexanox and Forskolin combination, at their respective aforementioned dosages. The effects of Amlexanox and Forskolin treatment on ICM models were assessed by eletrocardiography and echocardiography. Also, using histological analysis and ELISA, their impact on myocardial architecture and inflammation were ascertained. ICM mice had excessive myocardial fibrosis, hypertrophy, and aggravated LVSDs which were accompanied by massive CD86+ inflammatory cells infiltration. Amlexanox treatment attenuated the myocardial hypertrophy, fibrosis, and inflammation and also slightly improved systolic functions. Meanwhile, forskolin treatment resulted in arrhythmias but significantly enhanced the resolution of myocardial fibrosis and inflammation. Intriguingly, Amlexanox and Forskolin combination demonstrated the most potency at promoting the recovery of the ICM from LVSD by attenuating maladaptive myocardial hypertrophy, fibrosis, and inflammatory responses. Our findings highlight the Amlexanox and Forskolin combination as a potential therapeutic intervention for enhancing cardiac function recovery from stress-induced cardiomyopathy by promoting the resolution of maladaptive cardiac remodeling.

TANK-binding kinase 1 (TBK1): An emerging therapeutic target for drug discovery

Dysregulation of TANK-binding kinase 1 (TBK1) homeostasis leads to the occurrence and progression of many diseases, such as inflammation, autoimmune diseases, metabolic diseases, and cancer. Therefore, there is a need to develop TBK1 inhibitors as therapeutic agents. In this review, we highlight the diverse biological functions of TBK1 and summarize the promising small-molecule inhibitors of TBK1 that have the potential to be developed as therapeutic candidates.

TANK-Binding Kinase 1 (TBK1) Serves as a Potential Target for Hepatocellular Carcinoma by Enhancing Tumor Immune Infiltration

Background

Numerous cancer types present the aberrant TANK-binding kinase 1 (TBK1) expression, which plays an important role in driving inflammation and innate immunity. However, the prognostic role of TBK1 and its relationship with immune cell infiltration in hepatocellular carcinoma (HCC) remain unclear.

Methods

The expression and prognostic value of TBK1 was analyzed by Tumor Immune Estimation Resource (TIMER), Kaplan-Meier plotter and Gene Expression Profiling Interactive Analysis (GEPIA), Clinical Proteomic Tumor Analysis Consortium (CPTAC) and further confirmed in the present cohort of patients with HCC. The association between TBK1 and HCC immune infiltrates, and its potential mechanism were investigated via analyses of the Tumor Immune Estimation Resource, tumor-immune system interactions database (TISIDB), CIBERSORT, STRING, and Metascape. The effect of TBK1 on immune infiltrates and the therapeutic value of targeting TBK1 were further investigated in a HCC mouse model by treatment with a TBK1 antagonist.

Results

The level of TBK1 expression in HCC was higher than that measured in normal tissues, and associated with poorer overall survival (GEPIA: hazard ratio [HR]=1.80, P=0.038; Kaplan-Meier plotter: HR=1.87, P<0.001; CPTAC: HR=2.23, P=0.007; Our cohort: HR=2.92, P=0.002). In addition, high TBK1 expression was found in HCC with advanced TNM stage and identified as an independent poor prognostic factor for overall survival among patients with HCC. In terms of immune infiltration, tumor tissues from HCC patients with high TBK1 expression had a low proportion of CD8+ T cells, and TBK1 expression did not show prognostic value in HCC patients with enriched CD8+ T cells. Furthermore, TBK1 expression was positively correlated with the markers of T cell exhaustion and immunosuppressive cells in the HCC microenvironment. Mechanistically, the promotion of HCC immunosuppression by TBK1 was involved in the regulation of inflammatory cytokines. In vivo experiments revealed that treatment with a TBK1 antagonist delayed HCC growth by increasing the number of tumor-infiltrating CD8+ T cells.

Conclusions

The up-regulated expression of TBK1 may be useful in predicting poor prognosis of patients with HCC. In addition, TBK1, which promotes the HCC immunosuppressive microenvironment, may be a potential immunotherapeutic target for patients with HCC.

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.

Orostachys japonicus ameliorates acetaminophen-induced acute liver injury in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Orostachys japonicus A. Berger (O. japonicus), referred to as Wa-song in Korea is a traditional and herbal medicine. Even though it has been traditionally used to treat inflammation- and toxicity-related diseases, the effects of ethanol extract of O. japonicus (OJE) on acetaminophen (N-acetyl-p-aminophenol, APAP) overdose-induced hepatotoxicity have not been determined yet.

AIM OF THE STUDY

The present study was aimed to investigate the effects of OJE against APAP-induced acute liver injury (ALI) and explore the underlying mechanisms.

MATERIALS AND METHODS

Mice were treated orally with OJE (50, 100, or 200 mg/kg) for seven days before APAP (300 mg/kg) injection. After 12 h of APAP treatment, serum and liver tissues were collected. An in vitro system using primary hepatocytes was also applied in this study.

RESULTS

Pretreatment with OJE, especially at a dose of 200 mg/kg, reduced APAP overdose-induced ALI in mice, as evidenced by decreased serum alanine/aspartate aminotransferase levels, histopathological damage, and inflammation. Consistently, OJE pretreatment reduced the gene transcription of cytochrome P450 (CYP) 3A11 and CYP1A2 in livers of mice injected with or without APAP, at least in part, via inactivation of nuclear receptor pregnane X receptor (PXR). Furthermore, the role of PXR in mediating the OJE regulation of CYPs was confirmed in primary hepatocytes, which showed that OJE pretreatment inhibited PXR activity and APAP hepatotoxicity enhanced by pregnenolone 16α-carbonitrile, a mouse agonist of PXR. Besides, the antioxidative activity provided by OJE, involving increases in hepatic glutathione (GSH) content and decreases in malondialdehyde levels, has been shown to exert hepatoprotective effects in normal and injured livers. Moreover, APAP-activated c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) in mice liver were indirectly inhibited by pretreatment with OJE.

CONCLUSIONS

Taken together, our findings showed that OJE attenuated APAP-induced ALI by decreasing APAP-metabolizing enzymes via inactivation of PXR and the restoration of hepatic GSH content. Therefore, OJE could be a promising hepatoprotective agent.

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.

AK-1, a Sirt2 inhibitor, alleviates carbon tetrachloride-induced hepatotoxicity in vivo and in vitro

Background/Aim: Acute liver injury (ALI) is a life-threatening clinical syndrome that is usually caused by toxic chemicals, drugs, or pathogen infections. Sirtuin2 (Sirt2), an NAD⁺-dependent deacetylase, appears to play detrimental roles in liver injury. Here, we evaluated the therapeutic application targeting Sirt2 in carbon tetrachloride (CCl₄)-induced ALI, by using AK-1 (a Sirt2 inhibitor).Methods: For in vivo experiments, a single injection of CCl₄ was used to induce ALI. One hour later, mice were intraperitoneally injected with AK-1 and were sacrificed 24 h after CCl₄ administration. For in vitro experiments, primary mouse hepatocytes were used to determine the effects of AK-1 on oxidative stress and hepatocellular death induced by CCl₄.Results: AK-1 alleviated CCl₄-induced ALI as confirmed by histopathologic analysis, and decreased levels of serum biochemicals and inflammatory cytokines. Although it barely affected the expression of hepatic cytochrome P450 enzymes, AK-1 attenuated CCl₄-induced oxidative stress and its related cell death. Mechanistically, Sirt2 inhibition significantly increased the nuclear protein level of nuclear factor erythroid 2-related factor 2 (Nrf2), and meanwhile decreased phosphorylation of c-Jun N-terminal kinases (JNK), in normal and injured livers. Similar results were observed in vitro. AK-1 significantly attenuated CCl₄-induced cytotoxicity and oxidative stress by up-regulating the activity of Nrf2, and down-regulating JNK signaling in hepatocytes.Conclusions: Our results suggest that AK-1 treatment attenuated oxidative stress and cell death in the ALI model, at least partially, via activating Nrf2 and inhibiting JNK signaling, and that Sirt2 inhibition might be a potential approach to cure ALI.

Dual TBK1/IKKɛ inhibitor amlexanox attenuates the severity of hepatotoxin-induced liver fibrosis and biliary fibrosis in mice

Although numerous studies have suggested that canonical IκB kinases (IKK) play a key role in the progression of liver fibrosis, the role of non-canonical IKKε and TANK-binding kinase 1 (TBK1) on the development and progression of liver fibrosis remains unclear. To demonstrate such issue, repeated injection of CCl4 was used to induce hepatotoxin-mediated chronic liver injury and biliary fibrosis was induced by 0.1% diethoxycarbonyl-1, 4-dihydrocollidine diet feeding for 4 weeks. Mice were orally administered with amlexanox (25, 50, and 100 mg/kg) during experimental period. Significantly increased levels of TBK1 and IKKε were observed in fibrotic livers or hepatic stellate cells (HSCs) isolated from fibrotic livers. Interestingly, amlexanox treatment significantly inhibited the phosphorylation of TBK1 and IKKε accompanied by reduced liver injury as confirmed by histopathologic analysis, decreased serum biochemical levels and fibro-inflammatory responses. Additionally, treatment of amlexanox promoted the fibrosis resolution. In accordance with these findings, amlexanox treatment suppressed HSC activation and its related fibrogenic responses by partially inhibiting signal transducer and activator of transcription 3. Furthermore, amlexanox decreased the activation and inflammatory responses in Kupffer cells. Collectively, we found that inhibition of the TBK1 and IKKε by amlexanox is a promising therapeutic strategy to cure liver fibrosis.