Mechanism of biliary atresia caused by T follicular helper cells-induced immune injury.

BACKGROUND: Biliary atresia (BA) has diverse and unclear pathogenesis, which may be related to immune response in response to a foreign stimulus. T follicular helper (Tfh) cells have been found to play an important role in various immune diseases. AIMS: To investigate the expression of Tfh cells in BA and non-BA cholestatic diseases in children. METHODS: Transcriptome sequencing and Gene Ontology (GO) enrichment analysis were performed to investigate the differences in gene expression between the BA group and the non-BA cholestasis group. Study the distribution of Tfh cells in liver tissues of the BA and non-BA cholestatic groups through single sample gene set enrichment analysis (ssGSEA). Tfh cells (CD3+Bcl6+) in liver tissues from BA patients were labeled by double immunofluorescent staining to verify their distribution in the liver. RESULTS: Transcriptome sequencing showed differences in gene expression between the BA group and the non-BA cholestasis group. A total of 808 genes were up-regulated and 405 genes were down-regulated in BA, suggesting that there might be a specific immune response in BA. GO enrichment analysis showed that BA group had augmented response to foreign stimulus and increased metabolic process compared to the non-BA cholestatic group. The relative proportion of immune cells was analyzed by ssGSEA method. The proportions of Tfh cells, activated B cells, CD4+ T cells, memory B cells and Th2 cells were higher in the BA group than in the non-BA cholestatic group. Fluorescence immunostaining showed that Tfh cells were significantly increased in liver tissue samples of the BA group compared to the non-BA cholestasis group, which was consistent with the transcriptome sequencing results. CONCLUSION: Tfh cells share in immune cascade involvement in BA. Our work support immune pathogenesis of the in response to a stimulus that might be foreign in BA.

Cholestasis-induced phenotypic transformation of neutrophils contributes to immune escape of colorectal cancer liver metastasis.

BACKGROUND: Cholestasis is a common yet severe complication that occurs during the advancement of liver metastasis. However, how cholestasis impacts the development, treatment, and tumor microenvironment (TME) of liver metastasis remains to be elucidated. METHODS: Extrahepatic and intrahepatic cholestatic mouse models with liver metastasis were established to detect the differential expression levels of genes, infiltration of immune cells and change in bile acid-associated metabolites by using RNA-Sequencing, flowcytometry, and liquid chromatography and mass spectrometry. Western blot was applied to neutrophils under the stimulation of primary bile acids (BAs) in vitro to study the mechanism of phenotypic alteration. In vitro coculture of BA-treated neutrophils with CD8+ T cells were performed to study the immune-suppressive effect of phenotypic-altered neutrophils. Clinical samples collected from colorectal cancer patients with liver metastasis and cholestasis were applied to RNA-Seq. RESULTS: Compared to non-cholestatic mice, the progression of liver metastasis of cholestatic mice was significantly accelerated, which was associated with increased neutrophil infiltration and T-cell exclusion. Both neutrophils and T cells expressed higher immunosuppressive markers in the cholestatic mouse model, further indicating that an immunosuppressive tumor microenvironment was induced during cholestasis. Although neutrophils deletion via anti-Ly6G antibody partially hindered liver metastasis progression, it reduced the overall survival of mice. Tauro-ß-muricholic acid (Tß-MCA) and Glycocholic acid (GCA), the two most abundant cholestasis-associated primary BAs, remarkably promoted the expression of Arg1 and iNOS on neutrophils via p38 MAPK signaling pathway. In addition, BAs-pretreated neutrophils significantly suppressed the activation and cytotoxic effects of CD8+ T cells, indicating that the immunosuppressive phenotype of neutrophils was directly induced by BAs. Importantly, targeting BA anabolism with Obeticholic acid (OCA) under cholestasis effectively suppressed liver metastasis progression, enhanced the efficacy of immune checkpoint blockade, and prolonged survival of mice. CONCLUSIONS: Our study reveals the TME of cholestasis-associated liver metastasis and proposes a new strategy for such patients by targeting bile acid anabolism.

Blockade of neutrophil extracellular trap components ameliorates cholestatic liver disease in Mdr2 (Abcb4) knockout mice.

Primary sclerosing cholangitis (PSC) is an (auto)immune-mediated cholestatic liver disease with a yet unclear etiology. Increasing evidence points to an involvement of neutrophils in chronic liver inflammation and cirrhosis but also liver repair. Here, we investigate the role of the neutrophil extracellular trap (NET) component myeloperoxidase (MPO) and the therapeutic potential of DNase I and of neutrophil elastase (NE) inhibitor GW311616A on disease outcome in the multidrug resistance 2 knockout (Mdr2-/-) mouse, a PSC animal model. Initially, we observed the recruitment of MPO expressing cells and the formation of NETs in liver biopsies of PSC patients and in Mdr2-/- livers. Furthermore, sera of Mdr2-/- mice contained perinuclear anti-neutrophil cytoplasmic antibody (p-ANCA)-like reactivity similar to PSC patient sera. Also, hepatic NE activity was significantly higher in Mdr2-/- mice than in wild type littermates. Flow cytometry analyses revealed that during disease development a highly active neutrophil subpopulation established specifically in the liver of Mdr2-/- mice. However, absence of their MPO activity, as in MPO-deficient Mdr2-/- mice, showed no effect on hepatobiliary disease severity. In contrast, clearance of extracellular DNA by DNase I reduced the frequency of liver-resident neutrophils, plasmacytoid dendritic cells (pDCs) and CD103+ conventional DCs and decreased cholangiocyte injury. Combination of DNase I with a pDC-depleting antibody was additionally hepatocyte-protective. Most importantly, GW311616A, an orally bioavailable inhibitor of human NE, attenuated hepatobiliary injury in a TNFα-dependent manner and damped hyperproliferation of biliary epithelial cells. Further, hepatic immigration and activity of CD11b+ DCs as well as the secretion of IFNγ by hepatic CD4 and CD8 T cells were reduced. Our findings delineate neutrophils as important participants in the immune cell crosstalk that drives cholestatic liver disease and identify NET components as potential therapeutic targets.

Immunotherapy-based targeting of MSLN+ activated portal fibroblasts is a strategy for treatment of cholestatic liver fibrosis.

We investigated the role of mesothelin (Msln) and thymocyte differentiation antigen 1 (Thy1) in the activation of fibroblasts across multiple organs and demonstrated that Msln-/- mice are protected from cholestatic fibrosis caused by Mdr2 (multidrug resistance gene 2) deficiency, bleomycin-induced lung fibrosis, and UUO (unilateral urinary obstruction)-induced kidney fibrosis. On the contrary, Thy1-/- mice are more susceptible to fibrosis, suggesting that a Msln-Thy1 signaling complex is critical for tissue fibroblast activation. A similar mechanism was observed in human activated portal fibroblasts (aPFs). Targeting of human MSLN+ aPFs with two anti-MSLN immunotoxins killed fibroblasts engineered to express human mesothelin and reduced collagen deposition in livers of bile duct ligation (BDL)-injured mice. We provide evidence that antimesothelin-based therapy may be a strategy for treatment of parenchymal organ fibrosis.

Mast Cells Regulate Ductular Reaction and Intestinal Inflammation in Cholestasis Through Farnesoid X Receptor Signaling.

BACKGROUND AND AIMS: Cholestasis is characterized by increased total bile acid (TBA) levels, which are regulated by farnesoid X receptor (FXR)/FGF15. Patients with primary sclerosing cholangitis (PSC) typically present with inflammatory bowel disease (IBD). Mast cells (MCs) (i) express FXR and (ii) infiltrate the liver during cholestasis promoting liver fibrosis. In bile-duct-ligated (BDL) MC-deficient mice (B6.Cg-KitW-sh /HNihrJaeBsmJ [KitW-sh ]), ductular reaction (DR) and liver fibrosis decrease compared with BDL wild type, and MC injection exacerbates liver damage in normal mice. APPROACH AND RESULTS: In this study, we demonstrated that MC-FXR regulates biliary FXR/FGF15, DR, and hepatic fibrosis and alters intestinal FXR/FGF15. We found increased MC number and biliary FXR expression in patients with liver injury compared with control. Histamine and FGF19 serum levels and small heterodimer partner expression increase in patients PSC and PSC-IBD compared with healthy controls. MC injection increased liver damage, DR, inflammation, biliary senescence/senescence-associated secretory phenotype (SASP), fibrosis, and histamine in KitW-sh mice. Inhibition of MC-FXR before injection reduced these parameters. BDL and KitW-sh mice injected with MCs displayed increased TBA content, biliary FXR/FGF15, and intestinal inflammation, which decreased in BDL KitW-sh and KitW-sh mice injected with MC-FXR. MCs increased ileal FXR/FGF15 expression in KitW-sh mice that was reduced following FXR inhibition. BDL and multidrug resistance 2/ATP-binding cassette family 2 member 4 knockout (Mdr2-/- ) mice, models of PSC, displayed increased intestinal MC infiltration and FXR/FGF15 expression. These were reduced following MC stabilization with cromolyn sodium in Mdr2-/- mice. In vitro, MC-FXR inhibition decreased biliary proliferation/SASP/FGF and hepatic stellate cell activation. CONCLUSIONS: Our studies demonstrate that MC-FXR plays a key role in liver damage and DR, including TBA regulation through alteration of intestinal and biliary FXR/FGF15 signaling.

An insight into the mechanism and molecular basis of dysfunctional immune response involved in cholestasis.

Cholestasis is one of the most common clinical symptom of liver diseases. If patients do not receive effective treatment, cholestasis can evolve into liver fibrosis, cirrhosis and ultimately liver failure requiring liver transplantation. Currently, only ursodeoxycholic acid, obeticholic acid and bezafibrate are FDA-approved drugs, thereby requiring a breakthrough in new mechanisms and therapeutic development. Inflammation is one of the common complications of cholestasis. Hepatic accumulation of toxic hydrophobic bile acids is a highly immunogenic process involving both resident and immigrating immune cells. And the resulting inflammation may further aggravate hepatocyte injury. Though, great investigations have been made in the immune responses during cholestasis, the relationship between immune responses and cholestasis remains unclear. Moreover, scarce reviews summarize the immune responses during cholestasis and the efficacy of therapies on immune response. The main purpose of this paper is to review the existing literature on dysfunctional immune response during cholestasis and the effect of treatment on immune response which may provide an insight for researchers and drug development.

Substance-P prevents the cholestatic liver injury by regulating inflammatory responses.

Substance-P (SP) is a neuropeptide that modulates immune responses and accelerates tissue repair in critical inflammatory disease. Liver fibrosis and cirrhosis are the ultimate outcomes of almost all chronic liver diseases caused by viral infection, steatohepatitis, autoimmune, and cholestatic injury. Despite the development of new drugs, liver transplantation is still the only fundamental treatment; thus, new therapeutic approaches to mitigate liver fibrosis and chronic inflammation are constantly being needed. The aim of this study was to examine the effect of SP on liver damage due to cholestatic stress. To induce cholestatic injury, common bile duct ligation (CBDL) was attempted, followed by systemic application of SP. SP treatment increased IL-10 and decreased TNF-α in serum with increasing levels of circulating regulatory T cells (Tregs) from the early stage of CBDL. Moreover, SP decreased CBDL-induced TGF-ß1 expression in the circulation. This could create anti-inflammatory/anti-fibrotic environment under CBDL, which might ameliorate the progression of liver fibrosis in CBDL. Histological and molecular analysis revealed that SP treatment reduced ductular reaction, hepatic damage, and apoptotic hepatocytes, accompanied by diminishing type I collagen and upregulating MMP-9. These studies found that SP is a promising therapeutic candidate for immune-related liver disease as well as cholestatic liver disease, by providing hepatic protective effects via immune suppression.

Complement Inhibition Alleviates Cholestatic Liver Injury Through Mediating Macrophage Infiltration and Function in Mice.

Background and Aims: Cholestatic liver injury (CLI), which is associated with inflammatory reactions and oxidative stress, is a serious risk factor for postoperative complications. Complement system is involved in a wide range of liver disorders, including cholestasis. The present study assessed the role of complement in CLI and the therapeutic effect of the site-targeted complement inhibitor CR2-Crry in CLI. Methods: Wild-type and complement gene deficient mice underwent common bile duct ligation (BDL) to induce CLI or a sham operation, followed by treatment with CR2-Crry or GdCl3. The roles of complement in CLI and the potential therapeutic effects of CR2-Crry were investigated by biochemical analysis, flow cytometry, immunohistochemistry, ELISA, and quantitative RT-PCR. Results: C3 deficiency and CR2-Crry significantly reduced liver injuries in mice with CLI, and also markedly decreasing the numbers of neutrophils and macrophages in the liver. C3 deficiency and CR2-Crry also significantly reduced neutrophil expression of Mac-1 and liver expression of VCAM-1. More importantly, C3 deficiency and CR2-Crry significantly inhibited M1 macrophage polarization in these mice. Intravenous injection of GdCl3 inhibited macrophage infiltration and activation in the liver. However, the liver injury increased significantly. BDL significantly increased the level of lipopolysaccharide (LPS) in portal blood, but not in peripheral blood. GdCl3 significantly increased LPS in peripheral blood, suggesting that macrophages clear portal blood LPS. Oral administration of ampicillin to in GdCl3 treated mice reduced LPS levels in portal blood and alleviated liver damage. In contrast, intraperitoneal injection LPS increased portal blood LPS and reversed the protective effect of ampicillin. Interestingly, C3 deficiency did not affect the clearance of LPS. Conclusions: Complement is involved in CLI, perhaps mediating the infiltration and activation of neutrophils and macrophage M1 polarization in the liver. C3 deficiency and CR2-Crry significantly alleviated CLI. Inhibition of complement could preserve the protective function of macrophages in clearing LPS, suggesting that complement inhibition could be useful in treating CLI.

Inflammation Drives MicroRNAs to Limit Hepatocyte Bile Acid Transport in Murine Biliary Atresia.

BACKGROUND: Biliary atresia (BA) is an inflammatory pediatric cholangiopathy with only surgical means for treatment. Many contributors to bile acid synthesis and transport have previously been reported to be downregulated in patients with BA; yet, the driving factors of the abnormal bile acid synthesis and transport in regard to BA have not been previously studied. MATERIALS AND METHODS: Wild type or Ig-α-/- mice were injected with salt solution (control) or rotavirus on day of life 0, and analyses were performed on day of life 14. The mRNA levels of bile acid transporters/nuclear receptors and liver microRNAs (miRNAs) were compared between groups. A mouse hepatocyte cell line was used to examine the effects of innate cytokines on miRNA levels and bile acid transporter/nuclear receptor expression and miRNAs on bile acid transporter/nuclear receptor expression. RESULTS: BA mice had significantly increased mRNA expression of innate cytokines and miRNAs known to bind bile acid transporters/nuclear receptors (miRNAs -22-5p, -34a-5p, and -222-3p) and decreased mRNA expression of bile acid transporters and nuclear receptors. In vitro, TNF-α and IL-1ß decreased BSEP and CYP7A1 while increasing miRNA-34a-5p and miRNA 222-3p. LXR, SHP, CYP7A1, NTCP, and MRP2 were decreased by miRNA-34a-5p, whereas miRNA-222-3p decreased NTCP and MRP4. TNF-α and IL-1ß increased expression of miRNAs 34a-5p and 222-3p and these miRNAs then decrease expression of multiple bile acid transporters and nuclear receptors. CONCLUSIONS: Loss of bile acid transporters increases hepatotoxicity via bile acid retention. Therapeutic agents that increase bile acid transport or nuclear receptor functioning should be investigated in BA.

Cholestasis and disseminated histoplasmosis in a psoriatic patient on infliximab: case report and review of literature.

BACKGROUND: Histoplasma capsulatum is the most common endemic mycosis in the United States and frequently presents as an opportunistic infection in immunocompromised hosts. Though liver involvement is common in disseminated histoplasmosis, primary gastrointestinal histoplasmosis of the liver in absence of lung involvement is rare. Similarly, cholestatic granulomatous hepatitis in liver histoplasmosis is rarely seen. CASE PRESENTATION: We present a rare case of primary gastrointestinal histoplasmosis manifesting with acute granulomatous hepatitis and cholestasis in a 48-year-old female with psoriatic arthritis, receiving methotrexate and infliximab. The epidemiology, risk factors, clinical presentation, diagnosis, and treatment of histoplasmosis is discussed. Furthermore, we review the published cases of biopsy-proven disseminated histoplasmosis with cholestatic jaundice to highlight histoplasmosis involvement in the liver. CONCLUSION: Histoplasmosis should be considered in immunosuppressed patients with fever, chills, abdominal pain and cholestasis with progressive jaundice, particularly in subjects without evidence of biliary obstruction. Future studies are needed to accurately assess the risk of this fungal infection, specifically in patients on immunomodulatory therapy for autoimmune disease.

Assessment of Selected Parameters of Liver Fibrosis and Inflammation in Patients with Diagnosed Cystic Fibrosis.

Changes in the liver and bile ducts observed in patients diagnosed with cystic fibrosis result from inflammatory processes as well as fibrosis, remodeling, apoptosis, and cholestasis. As a consequence, portal hypertension, cirrhosis, and hepatic failure may develop. So far, the complexity of these processes has not been elucidated. Study Objectives. The aim of the study was to evaluate the selected parameters of hepatitis and fibrosis (Fibrotest, Actitest, and APRI) in patients diagnosed with cystic fibrosis. Material and Methods. The study included 79 patients with cystic fibrosis, aged 1 to 20 years (mean age 9.8 years), 49 girls (62%) and 30 boys (38%). The analysis involved the following: age, sex, clinical manifestations, laboratory tests evaluating pancreas function, parameters of liver damage, and cholestasis. Fibrotest, Actitest, and APRI were performed in all subjects. Results. Elevated parameters of hepatic cell damage (hypertransaminasemia) were found in 31/79 (39.2%) patients, while abnormal cholestasis parameters in 21/79 (26.6%). The abnormal results of Fibrotest were reported in 15% of patients (12/79), while of Actitest in 10% (8/79). In contrast, elevated APRI values were found in only 7.6% (6/79) of subjects. There was a statistically significant correlation between APRI and age (higher values were observed in younger children) and between Fibrotest and Actitest and pancreatic insufficiency (higher values were found in subjects without this abnormality). Moreover, Fibrotest values were significantly higher in girls. There was no correlation between Fibrotest, Actitest, and APRI values and the type of mutation. Conclusion. It appears that Fibrotest may be used as an early marker of liver fibrosis in patients with cystic fibrosis. Increased APRI values were only found in subjects with advanced hepatic lesions, most often in the form of portal hypertension.

Blockade of BAFF Reshapes the Hepatic B Cell Receptor Repertoire and Attenuates Autoantibody Production in Cholestatic Liver Disease.

Defects in biliary transport proteins, MDR3 in humans and Mdr2 in mice, can lead to a spectrum of cholestatic liver disorders. Although B cell disorders and the aberrant Ab production are the leading extrahepatic manifestations of cholestatic liver diseases, the mechanism underlying this phenomenon is incompletely understood. Using mice with deficiency of Mdr2 that progressively develop cholestatic liver disease, we investigated the contributions of BAFF to aberrant IgG autoantibody production and hepatic fibrosis. In Mdr2-/- mice, hepatic B lymphocytes constitutively produced IgG during fibrosis progression, which correlated with elevated serum levels of BAFF, antinuclear Abs (ANA) and immune complexes. The elevated BAFF and ANA titers were also detected in human patients with primary sclerosing cholangitis and hepatobiliary cholangiopathies. Consistent with the higher BAFF levels, liver-specific selection of the focused BCR IgH repertoire was found on hepatic B cells in Mdr2-/- mice. Interestingly, the administration of anti-BAFF mAb in Mdr2-/- mice altered the BCR repertoire on hepatic B lymphocytes and resulted in reduced ANA and immune complex titers. However, anti-BAFF treatment did not attenuate hepatic fibrosis as measured by collagen deposition, hepatic expressions of collagen-1a, α-smooth muscle actin, and mononuclear cell infiltration (CD11b+ Ly-6chi monocytes and CD11b+ Gr1+ neutrophils). Importantly, depletion of B cells by anti-CD20 mAb reduced both hepatic fibrosis and serum levels of ANA and immune complexes. Our findings implicate B cells as the potential therapeutic targets for hepatic fibrosis and targeting BAFF specifically for attenuating the autoantibody production associated with cholestatic liver disease.

Gut-Liver Axis and Inflammasome Activation in Cholangiocyte Pathophysiology.

The Nlrp3 inflammasome is a multiprotein complex activated by a number of bacterial products or danger signals and is involved in the regulation of inflammatory processes through caspase-1 activation. The Nlrp3 is expressed in immune cells but also in hepatocytes and cholangiocytes, where it appears to be involved in regulation of biliary damage, epithelial barrier integrity and development of fibrosis. Activation of the pathways of innate immunity is crucial in the pathophysiology of hepatobiliary diseases, given the strong link between the gut and the liver. The liver secretes bile acids, which influence the bacterial composition of the gut microbiota and, in turn, are heavily modified by microbial metabolism. Alterations of this balance, as for the development of dysbiosis, may deeply influence the composition of the bacterial products that reach the liver and are able to activate a number of intracellular pathways. This alteration may be particularly important in the pathogenesis of cholangiopathies and, in particular, of primary sclerosing cholangitis, given its strong association with inflammatory bowel disease. In the present review, we summarize current knowledge on the gut-liver axis in cholangiopathies and discuss the role of Nlrp3 inflammasome activation in cholestatic conditions.

Intestinal Microbiome-Macrophage Crosstalk Contributes to Cholestatic Liver Disease by Promoting Intestinal Permeability in Mice.

BACKGROUND AND AIMS: Mounting evidence supports an association between cholestatic liver disease and changes in the composition of the microbiome. Still, the role of the microbiome in the pathogenesis of this condition remains largely undefined. APPROACH AND RESULTS: To address this, we have used two experimental models, administering alpha-naphtylisocyanate or feeding a 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine diet, to induce cholestatic liver disease in germ-free mice and germ-free mice conventionalized with the microbiome from wild-type, specific pathogen-free animals. Next, we have inhibited macrophage activation by depleting these cells using clodronate liposomes and inhibiting the inflammasome with a specific inhibitor of NOD-, LRR-, and pyrin domain-containing protein 3. Our results demonstrate that cholestasis, the accumulation of bile acids in the liver, fails to promote liver injury in the absence of the microbiome in vivo. Additional in vitro studies supported that endotoxin sensitizes hepatocytes to bile-acid-induced cell death. We also demonstrate that during cholestasis, macrophages contribute to promoting intestinal permeability and to altered microbiome composition through activation of the inflammasome, overall leading to increased endotoxin flux into the cholestatic liver. CONCLUSIONS: We demonstrate that the intestinal microbiome contributes to cholestasis-mediated cell death and inflammation through mechanisms involving activation of the inflammasome in macrophages.

Consenso de hiperbilirrubinemia del primer trimestre de la vida / Consensus on hyperbilirubinemia of the first trimester of life

La presencia de ictericia en la etapa neonatal puede responder a diversas causas, desde situaciones fisiológicas hasta enfermedades graves. En los neonatos de término que persisten ictéricos más allá de los 14 días de vida, debe determinarse si la hiperbilirrubinemia es no conjugada o conjugada para establecer, a la brevedad, el plan de estudios etiológicos y la terapéutica correspondiente. La hiperbilirrubinemia conjugada (colestasis) refleja una disfunción hepática en la mayoría de los casos, cuyas consecuencias son alteraciones del flujo biliar secundarias a anormalidades estructurales o moleculares del hígado y/o del tracto biliar.Durante la última década, los nuevos estudios moleculares revolucionaron el abordaje de los pacientes colestáticos, lo que permitió el diagnóstico de diversas entidades genéticas. La etiología de la hiperbilirrubinemia del primer trimestre debe determinarse con urgencia, ya que, en muchos casos, el tratamiento instituido de modo precoz puede modificar sustancialmente la evolución de la enfermedad o salvar la vida del paciente.

Neonatal jaundice may be due to different causes, ranging from physiological conditions to severe diseases. In term neonates with persistent jaundice beyond 14 days of life, it should be determined whether hyperbilirubinemia is unconjugated or conjugated, in order to study the etiology and start early treatment. In the majority of cases, conjugated hyperbilirubinemia (cholestasis) is a sign of liver dysfunction possibly associated with alterations in the bile flow secondary to structural or molecular abnormalities of the liver and/or the biliary tract. Over the past decade, new molecular studies have revolutionized the approach of cholestatic patients, leading to the identification of different genetic entities. It is important to determine the etilogy of neonatal hyperbilirubinemia since in many cases early treatment will substantially improve morbidity and mortality.

Deficiency of TGR5 exacerbates immune-mediated cholestatic hepatic injury by stabilizing the ß-catenin destruction complex.

Intrahepatic cholestasis induced by drug toxicity may cause cholestatic hepatic injury (CHI) leading to liver fibrosis and cirrhosis. The G protein-coupled bile acid receptor 1 (TGR5) is a membrane receptor with well-known roles in the regulation of glucose metabolism and energy homeostasis. However, the role and mechanism of TGR5 in the context of inflammation during CHI remains unclear. Wild-type (WT) and TGR5 knockout (TGR5-/-) mice with CHI induced by bile duct ligation (BDL) were involved in vivo, and WT and TGR5-/- bone marrow-derived macrophages (BMDMs) were used in vitro. TGR5 deficiency significantly exacerbated BDL-induced liver injury, inflammatory responses and hepatic fibrosis compared with WT mice in vivo. TGR5-/- macrophages were more susceptible to lipopolysaccharide (LPS) stimulation than WT macrophages. TGR5 activation by its ligand suppressed LPS-induced pro-inflammatory responses in WT but not TGR5-/- BMDMs. Notably, expression of ß-catenin was effectively inhibited by TGR5 deficiency. Furthermore, TGR5 directly interacted with Gsk3ß to repress the interaction between Gsk3ß and ß-catenin, thus disrupting the ß-catenin destruction complex. The pro-inflammatory nature of TGR5-knockout was almost abolished by lentivirus-mediated ß-catenin overexpression in BMDMs. BMDM migration in vitro was accelerated under TGR5-deficient conditions or supernatant from LPS-stimulated TGR5-/- BMDMs. From a therapeutic perspective, TGR5-/- BMDM administration aggravated BDL-induced CHI, which was effectively rescued by ß-catenin overexpression. Our findings reveal that TGR5 plays a crucial role as a novel regulator of immune-mediated CHI by destabilizing the ß-catenin destruction complex, with therapeutic implications for the management of human CHI.

Inflammation: Cause or consequence of chronic cholestatic liver injury.

Cholestasis is a result of obstruction of the biliary tracts. It is a common cause of liver pathology after exposure to toxic xenobiotics and during numerous other liver diseases. Accumulation of bile acids in the liver is thought to be a major driver of liver injury during cholestasis and can lead to eventual liver fibrosis and cirrhosis. As such, current therapy in the field of chronic liver diseases with prominent cholestasis relies heavily on increasing choleresis to limit accumulation of bile acids. Many of these same diseases also present with autoimmunity before the onset of cholestasis though, indicating the inflammation may be an initiating component of the pathology. Moreover, cytotoxic inflammatory mediators accumulate during cholestasis and can propagate liver injury. Anti-inflammatory biologics and small molecules have largely failed clinical trials in these diseases though and as such, targeting inflammation as a means to address cholestatic liver injury remains debatable. The purpose of this review is to understand the different roles that inflammation can play during cholestatic liver injury and attempt to define how new therapeutic targets that limit or control inflammation may be beneficial for patients with chronic cholestatic liver disease.

Fragile X mental retardation protein protects against tumour necrosis factor-mediated cell death and liver injury.

OBJECTIVE: The Fragile X mental retardation (FMR) syndrome is a frequently inherited intellectual disability caused by decreased or absent expression of the FMR protein (FMRP). Lack of FMRP is associated with neuronal degradation and cognitive dysfunction but its role outside the central nervous system is insufficiently studied. Here, we identify a role of FMRP in liver disease. DESIGN: Mice lacking Fmr1 gene expression were used to study the role of FMRP during tumour necrosis factor (TNF)-induced liver damage in disease model systems. Liver damage and mechanistic studies were performed using real-time PCR, Western Blot, staining of tissue sections and clinical chemistry. RESULTS: Fmr1null mice exhibited increased liver damage during virus-mediated hepatitis following infection with the lymphocytic choriomeningitis virus. Exposure to TNF resulted in severe liver damage due to increased hepatocyte cell death. Consistently, we found increased caspase-8 and caspase-3 activation following TNF stimulation. Furthermore, we demonstrate FMRP to be critically important for regulating key molecules in TNF receptor 1 (TNFR1)-dependent apoptosis and necroptosis including CYLD, c-FLIPS and JNK, which contribute to prolonged RIPK1 expression. Accordingly, the RIPK1 inhibitor Necrostatin-1s could reduce liver cell death and alleviate liver damage in Fmr1null mice following TNF exposure. Consistently, FMRP-deficient mice developed increased pathology during acute cholestasis following bile duct ligation, which coincided with increased hepatic expression of RIPK1, RIPK3 and phosphorylation of MLKL. CONCLUSIONS: We show that FMRP plays a central role in the inhibition of TNF-mediated cell death during infection and liver disease.