The development and compensation of biliary cirrhosis in interleukin-6-deficient mice

The two facets of gp130 signalling in liver tumorigenesis

The liver is a vital organ with multiple functions and a large regenerative capacity. Tumours of the liver are the second most frequently cause of cancer-related death and develop in chronically inflamed livers. IL-6-type cytokines are mediators of inflammation and almost all members signal via the receptor subunit gp130 and the downstream signalling molecule STAT3. We here summarize current knowledge on how gp130 signalling and STAT3 in tumour cells and cells of the tumour micro-environment drives hepatic tumorigenesis. We furthermore discuss very recent findings describing also anti-tumorigenic roles of gp130/STAT3 and important considerations for therapeutic interventions.

Fibrotic Events in the Progression of Cholestatic Liver Disease

Cholestatic liver diseases including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are associated with active hepatic fibrogenesis, which can ultimately lead to the development of cirrhosis. However, the exact relationship between the development of liver fibrosis and the progression of cholestatic liver disease remains elusive. Periductular fibroblasts located around the bile ducts seem biologically different from hepatic stellate cells (HSCs). The fibrotic events in these clinical conditions appear to be related to complex crosstalk between immune/inflammatory mechanisms, cytokine signalling, and perturbed homeostasis between cholangiocytes and mesenchymal cells. Several animal models including bile duct ligation (BDL) and the Mdr2-knockout mice have improved our understanding of mechanisms underlying chronic cholestasis. In the present review, we aim to elucidate the mechanisms of fibrosis in order to help to identify potential diagnostic and therapeutic targets.

Network Pharmacology-Based Investigation of the Therapeutic Mechanisms of Action of Danning Tablets in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a rising global public health concern due to its prevalence. Danning Tablets (DNt), a composite prescription of Chinese herbal medicine, shows significant curative effects on NAFLD in clinical application. This study aimed to decipher the bioactive substances and potential mechanisms of action of DNt in the treatment of NAFLD, applying an integrated network pharmacology approach. First, the bioactive compounds of DNt were screened based on their pharmacokinetic properties, and the corresponding drug targets were predicted. Then, the NAFLD-related targets were collected. The overlapping targets between the putative targets of DNt and NAFLD-related targets were identified as the potential therapeutic targets of DNt against NAFLD. Subsequently, the networks were constructed and analyzed, and the key bioactive compounds and targets were screened out depending on their importance in the networks. Functional enrichment analysis was carried out to elucidate the potential mechanisms of DNt acting on NAFLD. Finally, a molecular docking simulation was implemented to assess the potential binding affinity between the key targets and the bioactive compounds. As a result, 43 bioactive compounds of DNt and 69 putative targets were identified. Based on the network analysis, we found seven key bioactive compounds (quercetin, ß-sitosterol, luteolin, kaempferol, supraene, curcumenolactone C, and stigmasterol) of DNt might treat NAFLD via intervening IL6, MAPK8, VEGFA, CASP3, ALB, APP, MYC, PPARG, and RELA. The functional enrichment analysis revealed that DNt might affect NAFLD by modulating the signaling pathways involved in lipid metabolism, inflammation, oxidation, insulin resistance (IR), atherosclerosis, and apoptosis. Furthermore, most key bioactive compounds might bind firmly with the key targets. This study predicted the multicomponent, multitarget, and multipathway mechanisms of DNt in the treatment of NAFLD from a holistic perspective. DNt could be a promising agent for NAFLD, but further experimental verifications are still needed.

Comparing distress of mouse models for liver damage

In order to foster animal welfare as well as high quality of research, many countries regulate by law that the severity of animal experiments must be evaluated and considered when performing biomedical research. It is well accepted that multiple parameters rather than a single readout parameter should be applied to describe animal distress or suffering. However, since the performance of readout parameters for animal distress is rarely defined and methods for multivariate analysis have only in rare cases been used, it is not known which methodology is most appropriate to define animal distress. This study used receiver operating characteristic curve analysis to quantify the performance of burrowing activity, body weight change and a distress score of mice after induction of liver damage by bile duct ligation or carbon tetrachloride. In addition, Support Vector Machine classification was used to compare the distress of these mouse models. This approach demonstrated that bile duct ligation causes much more distress than carbon tetrachloride-induced liver damage. This study, therefore, provides a prototype how to compare two animal models by considering several readout parameters. In the future these or similar methods for multivariate analysis will be necessary, when assessing and comparing the severity of animal models.

RTK signaling requires C3ar1/C5ar1 and IL-6R joint signaling to repress dominant PTEN, SOCS1/3 and PHLPP restraint

How receptor tyrosine kinase (RTK) growth signaling is controlled physiologically is incompletely understood. We have previously provided evidence that the survival and mitotic activities of vascular endothelial cell growth factor receptor-2 (VEGFR2) signaling are dependent on C3a/C5a receptor (C3ar1/C5ar1) and IL-6 receptor (IL-6R)-gp130 joint signaling in a physically interactive platform. Herein, we document that the platelet derived and epidermal growth factor receptors (PDGFR and EGFR) are regulated by the same interconnection and clarify the mechanism underlying the dependence. We show that the joint signaling is required to overcome dominant restraint on RTK function by the combined repression of tonically activated PHLPP, SOCS1/SOCS3, and CK2/Fyn dependent PTEN. Signaling studies showed that augmented PI-3Kɣ activation is the process that overcomes the multilevel growth restraint. Live-cell flow cytometry and single-particle tracking indicated that blockade of C3ar1/C5ar1 or IL-6R signaling suppresses RTK growth factor binding and RTK complex formation. C3ar1/C5ar1 blockade abrogated growth signaling of four additional RTKs. Active relief of dominant growth repression via joint C3ar1/C5ar1 and IL-6R joint signaling thus enables RTK mitotic/survival signaling.

Significance of IL-6 Deficiency in Recognition Memory in Young Adult and Aged Mice

Chronic peripheral elevation of interleukin 6 (IL-6) in humans is associated with cognitive deficits. 4- and 24-month-old IL-6-deficient C57BL/6J (IL-6KO) and reference wild-type (WT) mice were tested in an object recognition test. Discrimination ratios and recognition indexes were significantly lower in 4-month-old IL-6KO and in 24-month-old WT mice vs 4-month-old WT animals. Their discrimination ratios had negative values and recognition indexes were below 50% indicating inability to differentiate the novel from the familiar object after 1-hour delay. In 24-month-old IL-6KO mice recognition index reached 53.17% indicating that their recognition memory was not worsened with age in comparison with younger IL-6-deficient animals. Results of holeboard and elevated plus maze indicated that this effect was memory specific. Inborn IL-6 deficiency attenuated recognition memory in 4-month-old mice and did not altered recognition memory in aged animals. IL-6 signalling may constitute a target for development of the protection against memory disturbances connected with IL-6 overexpression.

VEGFR2 survival and mitotic signaling depends on joint activation of associated C3ar1/C5ar1 and IL-6R-gp130

Purified vascular endothelial cell (EC) growth factor receptor-2 (VEGFR2) auto-phosphorylates upon VEGF-A occupation in vitro, arguing that VEGR2 confers its mitotic and viability signaling in and of itself. Herein, we show that, in ECs, VEGFR2 function requires concurrent C3a/C5a receptor (C3ar1/C5ar1) and IL-6 receptor (IL-6R)-gp130 co-signaling. C3ar1/C5ar1 or IL-6R blockade totally abolished VEGFR2 auto-phosphorylation, downstream Src, ERK, AKT, mTOR and STAT3 activation, and EC cell cycle entry. VEGF-A augmented production of C3a/C5a/IL-6 and their receptors via a two-step p-Tyk2/p-STAT3 process. Co-immunoprecipitation analyses, confocal microscopy, ligand pulldown and bioluminescence resonance energy transfer assays all indicated that the four receptors are physically interactive. Angiogenesis in murine day 5 retinas and in adult tissues was accelerated when C3ar1/C5ar1 signaling was potentiated, but repressed when it was disabled. Thus, C3ar1/C5ar1 and IL-6R-gp130 joint activation is needed to enable physiological VEGFR2 function.

Effect of the transdifferentiation of BECs into myofibroblasts on the pathogenesis of secondary cholestatic hepatic fibrosis

The present study investigated the effect of the transdifferentiation of bile duct epithelial cells (BECs) into myofibroblasts on the pathogenesis of secondary cholestatic hepatic fibrosis and examined the underlying mechanisms. A total of 60 male rats with hepatic fibrosis were randomly divided into two groups: A secondary cholestatic hepatic fibrosis model group induced by ligation of the bile duct (BDL) and a sham group, which only underwent segregation of the choledochus. Rats in the BDL group were dynamically observed after week 1, 2, 3 and 4 post-BDL, and the remaining rats were sacrificed after week 5 to determine histological changes and hydroxyproline content. The cellular co-localization of cytokeratin (CK)7/α-smooth muscle actin (SMA) or α-SMA/desmin was detected by immunofluorescence staining and laser confocal microscopy, while the protein expression levels of CK7, α-SMA and desmin were determined by western blot analysis. Sirius red staining was also performed and quantified. The results revealed a significant correlation between the protein expression of CK7 and α-SMA (r=0.9692, P<0.01). Furthermore, a predominant correlation between the number of cells stained for CK7/α-SMA and collagen deposition in liver tissues was identified, while the correlation of cells with co-localized α-SMA and desmin was less pronounced. The transdifferentiation of BECs into myofibroblasts may be a key pathological factor in secondary cholestatic hepatic fibrosis formation.

Inflammation and the Gut-Liver Axis in the Pathophysiology of Cholangiopathies

Cholangiocytes, the epithelial cells lining the bile ducts, represent the unique target of a group of progressive diseases known as cholangiopathies whose pathogenesis remain largely unknown. In normal conditions, cholangiocytes are quiescent and participate to the final bile volume and composition. Following exogenous or endogenous stimuli, cholangiocytes undergo extensive modifications of their phenotype. Reactive cholangiocytes actively proliferate and release a set of proinflammatory molecules, which act in autocrine/paracrine manner mediating the cross-talk with other liver cell types and innate and adaptive immune cells. Cholangiocytes themselves activate innate immune responses against gut-derived microorganisms or bacterial products that reach the liver via enterohepatic circulation. Gut microbiota has been implicated in the development and progression of the two most common cholangiopathies, i.e., primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC), which have distinctive microbiota composition compared to healthy individuals. The impairment of intestinal barrier functions or gut dysbiosis expose cholangiocytes to an increasing amount of microorganisms and may exacerbate inflammatory responses thus leading to fibrotic remodeling of the organ. The present review focuses on the complex interactions between the activation of innate immune responses in reactive cholangiocytes, dysbiosis, and gut permeability to bacterial products in the pathogenesis of PSC and PBC.

The STAT3-IL-10-IL-6 Pathway Is a Novel Regulator of Macrophage Efferocytosis and Phenotypic Conversion in Sterile Liver Injury

The disposal of apoptotic bodies by professional phagocytes is crucial to effective inflammation resolution. Our ability to improve the disposal of apoptotic bodies by professional phagocytes is impaired by a limited understanding of the molecular mechanisms that regulate the engulfment and digestion of the efferocytic cargo. Macrophages are professional phagocytes necessary for liver inflammation, fibrosis, and resolution, switching their phenotype from proinflammatory to restorative. Using sterile liver injury models, we show that the STAT3-IL-10-IL-6 axis is a positive regulator of macrophage efferocytosis, survival, and phenotypic conversion, directly linking debris engulfment to tissue repair.

The Cholangiocyte Adenosine-IL-6 Axis Regulates Survival During Biliary Cirrhosis

Epithelial response to injury is critical to the pathogenesis of biliary cirrhosis, and IL-6 has been suggested as a mediator of this phenomenon. Several liver cell types can secrete IL-6 following activation by various signaling molecules including circulating adenosine. The aims of this study were to assess whether adenosine can induce IL-6 secretion by cholangiocytes via the A2b adenosine receptor (A2bAR) and to determine the effect of A2bAR-sensitive IL-6 release on injury response in biliary cirrhosis. Human normal cholangiocyte H69 cells were used for in vitro studies to determine the mechanism by which adenosine and the A2bAR induce release of IL-6. In vivo, control and A2bAR-deficient mice were used to determine the roles of A2bAR-sensitive IL-6 release in biliary cirrhosis induced by common bile duct ligation (BDL). Additionally, the response to exogenous IL-6 was assessed in C57BL/6 and A2bAR-deficient mice. Adenosine induced IL-6 mRNA expression and protein secretion via A2bAR activation. Although activation of A2bAR induced cAMP and intracellular Ca2+ signals, only the Ca2+ signals were linked to IL-6 upregulation. After BDL, A2bAR-deficient mice have impaired survival, which is further impaired by exogenous IL-6; however, decreased survival is not due to changes in fibrosis and no changes in inflammatory cells. Exogenous IL-6 is associated with the increased presence of bile infarcts. Extracellular adenosine induces cholangiocyte IL-6 release via the A2bAR. This signaling pathway is important in the pathogenesis of injury response in biliary cirrhosis but does not alter fibrosis. Adenosine upregulates IL-6 release by cholangiocytes via the A2bAR in a calcium-sensitive fashion. Mice deficient in A2bAR experience impaired survival after biliary cirrhosis induced by common bile duct ligation independent of changes in fibrosis.

Huang Qi Decoction Prevents BDL-Induced Liver Fibrosis Through Inhibition of Notch Signaling Activation

Notch signaling has been demonstrated to be involved in ductular reactions and fibrosis. Previous studies have shown that Huang Qi Decoction (HQD) can prevent the progression of cholestatic liver fibrosis (CLF). However, whether HQD affects the Notch signaling pathway is unclear. In this study, CLF was established by common bile duct ligation (BDL) in rats. At the end of the first week, the rats were randomly divided into a model group (i.e., BDL), an HQD group, and a sorafenib positive control group (SORA) and were treated for 3 weeks. Bile duct proliferation and liver fibrosis were determined by tissue staining. Activation of the Notch signaling pathway was evaluated by analyzing expressions of Notch-1, -2, -3, and -4, Jagged (JAG) 1, and Delta like (DLL)-1, -3, and -4. The results showed that HQD significantly reduced the deposition of collagen and the Hyp content of liver tissue and inhibited the activation of HSCs compared with the BDL group. In addition, HQD significantly decreased the protein and mRNA expressions of TGF-[Formula: see text]1 and [Formula: see text]-SMA. In contrast, HQD significantly enhanced expression of the Smad 7 protein. HQD also reduced biliary epithelial cell proliferation, and reduced the mRNA levels of CK7, CK8, CK18, SRY-related high mobility group-box gene (SOX) 9, epithelial cell adhesion molecule (EpCAM) and the positive areas of CK19 and OV6. In addition, the mRNA and protein expressions of Notch-3, -4, JAG1, and DLL-1, -3 were significantly reduced in the HQD compared to the BDL group. These results demonstrated that HQD may prevent biliary liver fibrosis through inhibition of the Notch signaling pathway, and it may be a potential treatment for cholestatic liver disease.

Epidermal growth factor signaling protects from cholestatic liver injury and fibrosis

We have demonstrated that the signal transducer and activator of transcription 3 (STAT3) protects from cholestatic liver injury. Specific ablation of STAT3 in hepatocytes and cholangiocytes (STAT3∆hc) aggravated liver damage and fibrosis in the Mdr2-/- (multidrug resistance 2) mouse model for cholestatic disease. Upregulation of bile acid biosynthesis genes and downregulation of epidermal growth factor receptor (EGFR) expression were observed in STAT3∆hc Mdr2-/- mice but the functional consequences of these processes in cholestatic liver injury remained unclear. Here, we show normal canalicular architecture and bile flow but increased amounts of bile acids in the bile of STAT3∆hc Mdr2-/- mice. Moreover, STAT3-deficient hepatocytes displayed increased sensitivity to bile acid-induced apoptosis in vitro. Since EGFR signaling has been reported to protect hepatocytes from bile acid-induced apoptosis, we generated mice with hepatocyte/cholangiocyte-specific ablation of EGFR (EGFR∆hc) and crossed them to Mdr2-/- mice. Importantly, deletion of EGFR phenocopied deletion of STAT3 and led to aggravated liver damage, liver fibrosis, and hyperproliferation of K19+ cholangiocytes. Our data demonstrate hepatoprotective functions of the STAT3-EGFR signaling axis in cholestatic liver disease.

KEY MESSAGE

STAT3 is a negative regulator of bile acid biosynthesis. STAT3 protects from bile acid-induced apoptosis and regulates EGFR expression. EGFR signaling protects from cholestatic liver injury and fibrosis.

Antifibrotic Effects of Human Amniotic Membrane Transplantation in Established Biliary Fibrosis Induced in Rats

Liver fibrosis is characterized by excessive accumulation of extracellular matrix components in the liver parenchyma that distorts the normal architecture and hepatic function. Progressive fibrosis could end in the advanced stage known as cirrhosis, resulting in the need to resort to liver transplantation. Amniotic membrane (AM) has emerged as an innovative therapeutic approach for chronic liver diseases due to its anti-inflammatory, antiscarring, and wound-healing effects. We have recently shown that AM can be used as a patch on the liver surface at the same time of fibrosis induction, resulting in significantly reduced progression and severity of biliary fibrosis. Here we investigated the effects of human AM on the established rat model of liver fibrosis, induced by the bile duct ligation (BDL). We also explored the effect of AM on the expression of transforming growth factor-1 (TGF-1), the main profibrogenic factor in hepatic fibrosis, and the proinflammatory cytokines, tumor necrosis factor- (TNF-), interleukin-6 (IL-6), and anti-inflammatory cytokine IL-10. Two weeks after BDL, the liver was covered with a fragment of AM or left untreated. Six weeks later, the fibrosis was first assessed by the semiquantitative Knodell and the METAVIR scoring systems and, thereafter, by CellProfiler digital image analysis to quantify the area occupied by collagen deposition, ductular reactions (DRs), activated myofibroblasts, and TGF-1. The hepatic cytokines were determined by ELISA. AM-treated rats showed a significantly lower score compared to the control BDL rats (2.50.9 vs. 3.50.3, respectively; p0.05). The collagen deposition, DRs, number of activated myofibroblasts, and TGF-1 were all reduced to about 50% of levels observed in untreated BDL rats. These findings suggest that AM, when applied as a patch onto the liver surface, is useful for treating well-established cholestatic fibrosis, and the mechanism was partly by means of downregulating the profibrotic factor TGF-1 and IL-6.

Inhibition of notch signaling pathway prevents cholestatic liver fibrosis by decreasing the differentiation of hepatic progenitor cells into cholangiocytes

Although hepatic progenitor cells (HPCs) are known to contribute to cholestatic liver fibrosis (CLF), how Notch signaling modulates the differentiation of HPCs to cholangiocytes in CLF is unknown. Thus, using a rat model of CLF that is induced by bile duct ligation, we inhibited Notch signaling with DAPT. In vivo, CK19, OV6, Sox9, and EpCAM expression was increased significantly. Notch signaling increased after bile duct ligation, and DAPT treatment reduced the expression of CK19, OV6, Sox9, and EpCAM and blocked cholangiocyte proliferation and CLF. In vitro, treatment of a WB-F344 cell line with sodium butyrate resulted in increased mRNA and protein expression of CK19, Sox9, and EpCAM, but Notch signaling was activated. Both of these processes were inhibited by DAPT. This study reveals that Notch signaling activation is required for HPC differentiation into cholangiocytes in CLF, and inhibition of the Notch signaling pathway may offer a therapeutic approach for treating CLF.

Interleukin‑6 induces epithelial‑mesenchymal transition in human intrahepatic biliary epithelial cells

The aim of the present study was to determine the role of interleukin-6 (IL-6) in the epithelial-mesenchymal transition (EMT) of human intrahepatic biliary epithelial cell (HIBEC) lines in vitro. HIBECs were stimulated with IL-6 at concentrations of 0, 10, 20, 50 and 100 µg/l for 24 h. A wound healing and Transwell assay were performed to determine the migratory and invasive capacity of HIBECs, respectively. Following 24 h of incubation, IL-6 at 10 and 20 µg/l significantly increased the number of migrated and invaded cells (P<0.05), while stimulation with 50 and 100 µg/l IL-6 resulted in a further increase of the migratory and invasive capacity compared to that in all other groups (P<0.05). Furthermore, reverse-transcription quantitative polymerase chain reaction and western blot analyses were used to detect the mRNA and protein expression of EMT markers E-cadherin and vimentin in HIBECs. Decreased mRNA levels of E-cadherin accompanied by higher mRNA levels of vimentin were observed in the 10, 20, 50, 100 µg/l IL-6 groups compared to those in the 0 µg/l group (all P<0.05). Furthermore, the protein expression of E-cadherin was decreased, while that of vimentin was increased in the 50 and 100 µg/l IL-6 groups compared to those in the 0, 10 and 20 µg/l IL-6 groups (all P<0.05). The present study therefore indicated that IL-6 promoted the process of EMT in HIBECs as characterized by increased migration and invasion of HIBECs and the typical changes in mRNA and protein expression of the EMT markers E-cadherin and vimentin.

Mice with Hepatic Loss of the Desmosomal Protein γ-Catenin Are Prone to Cholestatic Injury and Chemical Carcinogenesis

γ-Catenin, an important component of desmosomes, may also participate in Wnt signaling. Herein, we dissect the role of γ-catenin in liver by generating conditional γ-catenin knockout (KO) mice and assessing their phenotype after bile duct ligation (BDL) and diethylnitrosamine-induced chemical carcinogenesis. At baseline, KO and wild-type littermates showed comparable serum biochemistry, liver histology, and global gene expression. β-Catenin protein was modestly increased without any change in Wnt signaling. Desmosomes were maintained in KO, and despite no noticeable changes in gene expression, differential detergent fractionation revealed quantitative and qualitative changes in desmosomal cadherins, plaque proteins, and β-catenin. Enhanced association of β-catenin to desmoglein-2 and plakophilin-3 was observed in KO. When subjected to BDL, wild-type littermates showed specific changes in desmosomal protein expression. In KO, BDL deteriorated baseline compensatory changes, which manifested as enhanced injury and fibrosis. KO also showed enhanced tumorigenesis to diethylnitrosamine treatment because of Wnt activation, as also verified in vitro. γ-Catenin overexpression in hepatoma cells increased its binding to T-cell factor 4 at the expense of β-catenin-T-cell factor 4 association, induced unique target genes, affected Wnt targets, and reduced cell proliferation and viability. Thus, γ-catenin loss in liver is basally well tolerated. However, after insults like BDL, these compensations at desmosomes fail, and KO show enhanced injury. Also, γ-catenin negatively regulates tumor growth by affecting Wnt signaling.

Interactions between Myc and Mediators of Inflammation in Chronic Liver Diseases

Most chronic liver diseases (CLDs) are characterized by inflammatory processes with aberrant expressions of various pro- and anti-inflammatory mediators in the liver. These mediators are the driving force of many inflammatory liver disorders, which often result in fibrosis, cirrhosis, and liver tumorigenesis. c-Myc is involved in many cellular events such as cell growth, proliferation, and differentiation. c-Myc upregulates IL-8, IL-10, TNF-α, and TGF-β, while IL-1, IL-2, IL-4, TNF-α, and TGF-β promote c-Myc expression. Their interactions play a central role in fibrosis, cirrhosis, and liver cancer. Molecular interference of their interactions offers possible therapeutic potential for CLDs. In this review, current knowledge of the molecular interactions between c-Myc and various well known inflammatory mediators is discussed.

Astragaloside prevents BDL-induced liver fibrosis through inhibition of notch signaling activation

ETHNOPHARMACOLOGICAL RELEVANCE

Huangqi decoction was first described in Prescriptions of the Bureau of Taiping People׳s Welfare Pharmacy in the Song Dynasty (AD1078). It consists of Radix Astragali (Astragalus membranceus (Fisch.) Bge. Root, Huangqi) and Radix Glycyrrhizae (Glycyrrhiza uralensis Fisch., root and rhizome, Gancao), and it is an effective recipe that is usually used to treat consumptive disease and chronic liver diseases. Astragaloside (AS) is a main component of Radix Astragali had an effect similar to the Huangqi decoction on hepatic fibrosis.

AIM OF THE STUDY

Cholestasis is associated with a number of chronic liver diseases and Notch signaling has been demonstrated to be involved in ductular reaction. Previous studies have shown that AS can prevent the progression of cholestatic liver fibrosis, however, whether AS affects the Notch signaling pathway is unclear.

MATERIALS AND METHODS

Cholestatic liver fibrosis was established by common bile duct ligation (BDL) in rats. At first weekend, the rats were randomly divided into a model group (BDL), an AS group, and a Sorafenib positive control group (SORA) and treated for 3 weeks. Bile duct proliferation and liver fibrosis were determined by tissue staining. Activation of the Notch signaling pathway was evaluated by analyzing expressions of Notch-1, -2, -3, -4, Jagged 1 (JAG1), Delta-like (DLL)-1, -3, -4, Hes1, Numb and RBP-Jκ. Activation of the Wnt signaling pathway was evaluated by analyzing expressions of Wnt-4, -5a, -5b, Frizzled (Fzd)-2, -3, -6 and β-catenin.

RESULTS

(1) Compared with the BDL group, AS significantly reduced the deposition of collagen and the Hyp content of liver tissue and inhibited the activation of HSCs. In addition, AS significantly decreased the protein and mRNA expressions of TGF-β1 and α-SMA. In contrast, AS significantly enhanced expression of the Smad 7 protein. AS also reduced biliary epithelial cell proliferation, and reduced the mRNA and protein expressions of CK7, CK8, CK18, CK19, OV6, Sox9 and EpCAM. (2) The mRNA and protein expressions of Notch-2, -3, -4 and JAG1 were significantly reduced in the AS compared to the BDL group. In contrast, the mRNA and protein level of Numb was clearly enhanced after AS treatment.

CONCLUSION

AS may prevent biliary liver fibrosis via inhibition of the Notch signaling pathway, thereby inhibiting the abnormal proliferation of biliary epithelial cells. Results indicate that AS may be a potential therapeutic drug for cholestatic liver disease.

Dysregulated miR-124 and miR-200 expression contribute to cholangiocyte proliferation in the cholestatic liver by targeting IL-6/STAT3 signalling

BACKGROUND & AIMS

Cholestatic liver disease is associated with dysregulated expression of microRNAs (miRNAs). However, it remains unknown whether miRNAs are involved in the cholestasis-induced proliferation of cholangiocytes. In this study, we tested the hypothesis that miRNAs modulate cholangiocyte proliferation through effects on the IL-6 pathway, a known regulator of cholangiocyte proliferation.

METHODS

Expression of IL-6, Foxa2, and phosphorylated signal transducer activator of transcription 3 (STAT3) was investigated in patients with biliary atresia (BA) and in rats subjected to bile duct ligation (BDL). miRNA expression was determined in BA patients and BDL rats, with miRNA array and quantitative real-time PCR. Biological functions of miRNAs were studied using immunoblot, immunohistochemical and proliferation assays. Luciferase reporter assays and Western blots were performed to identify miRNA targets.

RESULTS

Hepatic interleukin-6 (IL-6) expression was significantly elevated in BA patients and BDL rats, while the expression of miR-124 was dramatically decreased in comparison to controls. Moreover, mRNA levels of STAT3 and IL-6 receptor (IL-6R) were inversely correlated with those of miR-124. Ectopic expression of miR-124 inhibited IL-6-mediated cholangiocyte proliferation in vitro and cholangiocyte hyperplasia in vivo, through a mechanism involving direct targeting of the 3'-untranslated region of STAT3 and IL-6R. We further demonstrated that miR-200 family members were significantly upregulated in cholestasis and inhibited FOXA2 expression in cholangiocytes, which further enhanced the expression of IL-6.

CONCLUSIONS

Our findings suggest that downregulation of miR-124 and upregulation of miR-200 collaboratively promote bile duct proliferation through the IL-6/STAT3 pathway.

Impact of serum levels of interleukin-6 and adiponectin on all-cause, liver-related, and liver-unrelated mortality in chronic hepatitis C patients

BACKGROUND AND AIM

Various inflammatory cytokines and adipokines have been implicated in hepatitis C virus (HCV)-mediated liver disease, and interleukin-6 (IL-6) and adiponectin may play key roles. In addition, these factors may be associated with chronic hepatitis C (CHC)-induced extrahepatic manifestations. However, little data are available on the role of these factors on future outcomes of CHC patients. This study aims to evaluate the impact of serum levels of IL-6 and adiponectin on all-cause mortality, liver-related mortality, and liver-unrelated mortality.

METHODS

A long-term follow-up study was conducted, consisting of 325 CHC patients, for which we previously reported positive associations between these factors (Serum levels of IL-6 and adiponectin) and hepatocellular carcinoma (HCC) development.

RESULTS

During the follow-up period (mean, 13.0 year), there were 92 events consisting of 91 deaths (liver related, 72; liver unrelated, 19) and 1 liver transplantation due to liver failure. High IL-6 and adiponectin levels, defined as being higher than each median value at baseline, were associated with significantly higher incidences of not only HCC development but also all-cause mortality. Interestingly, high IL-6 was strongly associated with only liver-related mortality, whereas high-serum adiponectin was associated with not only liver-related, but also liver-unrelated mortality. Multivariate analysis identified high IL-6 as an independent risk factor for liver-related mortality and high adiponectin as an independent risk factor for liver-unrelated mortality.

CONCLUSION

High serum levels of IL-6 and adiponectin were associated with higher all-cause and liver-related mortality in CHC patients. In addition, high adiponectin was associated with liver-unrelated mortality. The measurement of these factors may provide information useful for predicting future outcomes in CHC patients.

Cytokine single nucleotide polymorphisms in patients' with gallstone: dose TGF-β gene variants affect gallstone formation?

Gallstone is a common biliary disorder with several risk factors. Immune responses and inflammatory cytokines are important in this disease; as a result, some cytokines can be detected in bile fluid. In this research, cytokine gene polymorphisms were studied, and their effects on gallstone formation were evaluated. On 158 gallstone patients and 254 normal subjects, by PCR- RFLP method, IL-4-C590T polymorphism and by ARMS-PCR method, IFN-γ T+874A, TNF-α-A308G, IL-6 G-174C and TGF-β T+869C variants were studied. Pathologic evaluations were done on surgical specimens. There were no significant differences in distribution of evaluated polymorphisms between patient group and normal control group (P > 0.05), except TGF-β +869T allele (P = 0.04, OR = 1.23, 95 % CI = 1-1.79) which was higher in patients with gallstone. Although the pro-inflammatory cytokines such as TNF-α and IL-6 may promote gallstone formation, in this study no significant correlation between TNF-α and IL-6 polymorphisms and gallstone formation was seen. It is taught that TGF-β may affect gallbladder cells to promote gallstone formation and higher producer TGF-β +869T allele can be a risk factor of gallstone disease, so further studies would be more elucidative

Efficacy of HGF carried by ultrasound microbubble-cationic nano-liposomes complex for treating hepatic fibrosis in a bile duct ligation rat model, and its relationship with the diffusion-weighted MRI parameters

Hepatic fibrosis is a major consequence of liver aggression. Finding novel ways for counteracting this damaging process, and for evaluating fibrosis with a non-invasive imaging approach, represent important therapeutic and diagnostic challenges. Hepatocyte growth factor (HGF) is an anti-fibrosis cell growth factor that induces apoptosis in activated hepatic stellate cells, reduces excessive collagen deposition, and stimulates hepatocyte regeneration. Thus, using HGF in gene therapy against liver fibrosis is an attractive approach. The aims of the present study were: (i) to explore the efficacy of treating liver fibrosis using HGF expression vector carried by a novel ultrasound microbubble delivery system; (ii) to explore the diagnostic interest of diffusion-weighted MRI (DWI-MRI) in evaluating liver fibrosis. We established a rat model of hepatic fibrosis. The rats were administered HGF linked to novel ultrasound micro-bubbles. Progression of hepatic fibrosis was evaluated by histopathology, hydroxyproline content, and DWI-MRI to determine the apparent diffusion coefficient (ADC). Our targeted gene therapy produced a significant anti-fibrosis effect, as shown by liver histology and significant reduction of hydroxyproline content. Moreover, using DWI-MRI, the b value (diffusion gradient factor) was equal to 300s/mm(2), and the ADC values significantly decreased as the severity of hepatic fibrosis increased. Using this methodology, F0-F2 could be distinguished from F3 and F4 (P<0.01). This is the first in vivo report of using an ultrasound microbubble-cationic nano-liposome complex for gene delivery. The data indicate that, this approach is efficient to counteract the fibrosis process. DWI-MRI appears a promising imaging technique for evaluating liver fibrosis.

Oroxylin A accelerates liver regeneration in CCl₄-induced acute liver injury mice

Introduction

Based on the previous research that oroxylin A can suppress inflammation, we investigated the hepatoprotective role of oroxylin A against CCl₄-induced liver damage in mice and then studied the possible alteration of the activities of cytokine signaling participating in liver regeneration. Wild type (WT) mice were orally administrated with oroxylin A (60 mg/kg) for 4 days after CCl₄ injection, the anti-inflammatory effects of oroxylin A were assessed directly by hepatic histology and indirectly by measuring serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and Albumin. Proliferating cell nuclear antigen (PCNA) staining was performed to evaluate the role of oroxylin A in promoting hepatocyte proliferation. Serum IL-1β, TNF-α, IL-6 and IL-1Ra levels were measured by enzyme-linked immunosorbent assay (ELISA) and liver HGF, EGF, TNF-α, IL-6, IL-1Ra and IL-1β gene expression was determined by quantitative real-time PCR. The data indicated that the IL-6 and TNF-α mRNA of oroxylin A administered group significantly increased higher than the control within 12 hours after CCl₄ treatment. Meanwhile, oroxylin A significantly enhanced the expression of IL-1Ra at the early phase, which indicated that oroxylin A could facilitate the initiating events in liver regeneration by increasing IL-1Ra which acts as an Acute-Phase Protein (APP). In addition, a lethal CCl₄-induced acute liver failure model offers a survival benefit in oroxylin A treated WT mice. However, oroxylin A could not significantly improve the percent survival of IL-1RI^−/− mice with a lethal CCl₄-induced acute liver failure.

Conclusions

Our study confirmed that oroxylin A could strongly promote liver structural remodeling and functional recovery through IL-1Ra/IL-1RI signaling pathway. All these results support the possibility of oroxylin A being a therapeutic candidate for acute liver injury.

Preexisting epithelial diversity in normal human livers: a tissue-tethered cytometric analysis in portal/periportal epithelial cells

Routine light microscopy identifies two distinct epithelial cell populations in normal human livers: hepatocytes and biliary epithelial cells (BECs). Considerable epithelial diversity, however, arises during disease states when a variety of hepatocyte-BEC hybrid cells appear. This has been attributed to activation and differentiation of putative hepatic progenitor cells (HPC) residing in the canals of Hering and/or metaplasia of preexisting mature epithelial cells. A novel analytic approach consisting of multiplex labeling, high-resolution whole-slide imaging (WSI), and automated image analysis was used to determine if more complex epithelial cell phenotypes preexist in normal adult human livers, which might provide an alternative explanation for disease-induced epithelial diversity. "Virtually digested" WSI enabled quantitative cytometric analyses of individual cells displayed in a variety of formats (e.g., scatterplots) while still tethered to the WSI and tissue structure. We employed biomarkers specifically associated with mature epithelial forms (HNF4α for hepatocytes, CK19 and HNF1β for BEC) and explored for the presence of cells with hybrid biomarker phenotypes. The results showed abundant hybrid cells in portal bile duct BEC, canals of Hering, and immediate periportal hepatocytes. These bipotential cells likely serve as a reservoir for the epithelial diversity of ductular reactions, appearance of hepatocytes in bile ducts, and the rapid and fluid transition of BEC to hepatocytes, and vice versa.

CONCLUSION

Novel imaging and computational tools enable increased information extraction from tissue samples and quantify the considerable preexistent hybrid epithelial diversity in normal human liver. This computationally enabled tissue analysis approach offers much broader potential beyond the results presented here.

Mesenchymal stem cells and Interleukin-6 attenuate liver fibrosis in mice

BACKGROUND

Mesenchymal stem cell (MSC) transplantation has emerged as a promising therapy for liver fibrosis. Issues concerning poor MSC survival and engraftment in the fibrotic liver still persist and warrant development of a strategy to increase MSC potency for liver repair. The present study was designed to examine a synergistic role for Interleukin-6 (IL-6) and MSCs therapy in the recovery of carbon tetrachloride (CCl(4)) induced injured hepatocytes in vitro and in vivo.

METHODS

Injury was induced through 3 mM and 5 mM CCl(4) treatment of cultured hepatocytes while fibrotic mouse model was established by injecting 0.5 ml/kg CCl(4) followed by treatment with IL-6 and MSCs. Effect of MSCs and IL-6 treatment on injured hepatocytes was determined by lactate dehydrogenase release, RT-PCR for (Bax, Bcl-xl, Caspase3, Cytokeratin 8, NFκB, TNF-α) and annexin V apoptotic detection. Analysis of MSC and IL-6 treatment on liver fibrosis was measured by histopathology, PAS, TUNEL and Sirius red staining, RT-PCR, and liver function tests for Bilirubin and Alkaline Phosphatase (ALP).

RESULTS

A significant reduction in LDH release and apoptosis was observed in hepatocytes treated with a combination of MSCs and IL-6 concomitant with upregulation of anti-apoptotic gene Bcl-xl expression and down regulation of bax, caspase3, NFκB and TNF-α. Adoptive transfer of MSCs in fibrotic liver pretreated with IL-6 resulted increased MSCs homing and reduced fibrosis and apoptosis. Hepatic functional assessment demonstrated reduced serum levels of Bilirubin and ALP.

CONCLUSION

Pretreatment of fibrotic liver with IL-6 improves hepatic microenvironment and primes it for MSC transplantation leading to enhanced reduction of liver injury after fibrosis. Synergistic effect of IL-6 and MSCs seems a favored therapeutic option in attenuation of liver apoptosis and fibrosis accompanied by improved liver function.

Hepatoprotective effects of baicalein against CCl4-induced acute liver injury in mice

AIM: To investigate the hepatoprotective effect of baicalein against carbon tetrachloride (CCl₄)-induced liver damage in mice.

METHODS: Mice were orally administered with baicalein after CCl₄ injection, and therapeutic baicalein was given twice a day for 4 d. The anti-inflammation effects of baicalein were assessed directly by hepatic histology and serum alanine aminotranferease and aspartate aminotransferase measurement. Proliferating cell nuclear antigen was used to evaluate the effect of baicalein in promoting hepatocyte proliferation. Serum interleukin (IL)-6, IL-1β and tumor necrosis factor-α (TNF-α) levels were measured by enzyme-linked immunosorbent assay and liver IL-6, TNF-α, transforming growth factor-α (TGF-α), hepatocyte growth factor (HGF) and epidermal growth factor (EGF) genes expression were determined by quantitative real-time polymerase chain reaction.

RESULTS: CCl₄-induced acute liver failure model offers a survival benefit in baicalein-treated mice. The data indicated that the mRNA levels of IL-6 and TNF-α significantly increased within 12 h after CCl₄ treatment in baicalein administration groups, but at 24, 48 and 72 h, the expression of IL-6 and TNF-α was kept at lower levels compared with the control. The expression of TGF-α, HGF and EGF was enhanced dramatically in baicalein administration group at 12, 24, 48 and 72 h. Furthermore, we found that baicalein significantly elevated the serum level of TNF-α and IL-6 at the early phase, which indicated that baicalein could facilitate the initiating events in liver regeneration.

CONCLUSION: Baicalein may be a therapeutic candidate for acute liver injury. Baicalein accelerates liver regeneration by regulating TNF-α and IL-6 mediated pathways.

Advances in cholangiocyte immunobiology

Cholangiocytes, or bile duct epithelia, were once thought to be the simple lining of the conduit system comprising the intra- and extrahepatic bile ducts. Growing experimental evidence demonstrated that cholangiocytes are in fact the first line of defense of the biliary system against foreign substances. Experimental advances in recent years have unveiled previously unknown roles of cholangiocytes in both innate and adaptive immune responses. Cholangiocytes can release inflammatory modulators in a regulated fashion. Moreover, they express specialized pattern-recognizing molecules that identify microbial components and activate intracellular signaling cascades leading to a variety of downstream responses. The cytokines secreted by cholangiocytes, in conjunction with the adhesion molecules expressed on their surface, play a role in recruitment, localization, and modulation of immune responses in the liver and biliary tract. Cholangiocyte survival and function is further modulated by cytokines and inflammatory mediators secreted by immune cells and cholangiocytes themselves. Because cholangiocytes act as professional APCs via expression of major histocompatibility complex antigens and secrete antimicrobial peptides in bile, their role in response to biliary infection is critical. Finally, because cholangiocytes release mediators critical to myofibroblastic differentiation of portal fibroblasts and hepatic stellate cells, cholangiocytes may be essential in the pathogenesis of biliary cirrhosis.

Attenuation of early liver fibrosis by pharmacological inhibition of smoothened receptor signaling

Hedgehog (Hh) signaling is involved in the pathogenesis of liver fibrosis. It has been previously shown that Hh-inhibitor cyclopamine (CYA) can reduce liver fibrosis in rats. However, CYA is not stable in vivo, which limits its clinical application. This study compares the antifibrotic potential of two known Hh antagonists, vismodegib (GDC-0449, abbreviated to GDC) and CYA. GDC is a synthetic molecule presently in clinical cancer trials and has been reported to be safe and efficacious. These drugs attenuated early liver fibrosis in common bile duct ligated rats, improved liver function, and prevented hepatic stellate cell (HSC) activation, thereby suppressing epithelial to mesenchymal transition (EMT). While both CYA and GDC increased the number of proliferating cell nuclear antigen positive liver cells in vivo, only CYA increased Caspase-3 expression in HSCs in rat livers, suggesting that while GDC and CYA effectively attenuate early liver fibrosis, their hepatoprotective effects may be mediated through different modes of action. Thus, GDC has the potential to serve as a new therapeutic agent for treating early liver fibrosis.

Animal models of cutaneous and hepatic fibrosis

Fibrosis occurs as a part of normal wound healing. However, excessive or dysregulated fibrosis can lead to severe organ dysfunction and is a feature of a variety of diseases. Due to its insidious onset, fibrosis tends to go undetected in its early stages. This is in part why these diseases remain so poorly understood. Animal models have provided a means to examine these early stages and to isolate and understand the effect of perturbations in signaling pathways, chemokines, and cytokines. Here, we summarize recent progress in the understanding of the molecular pathogenesis of fibrosis, both its initiation and its maintenance phases, from animal models of fibrosis in the skin and liver. Due to these organs' properties, modeling fibrosis in them poses unique challenges. Elegant solutions have therefore been developed for modeling fibrosis in each, and now, great potential for animal models to contribute to our understanding appears scientifically imminent.

Cyclopamine attenuates acute warm ischemia reperfusion injury in cholestatic rat liver: hope for marginal livers

Cholestasis is a significant risk factor for immediate hepatic failure due to ischemia reperfusion (I/R) injury in patients undergoing liver surgery or transplantation. We recently demonstrated that inhibition of Hedgehog (Hh) signaling with cyclopamine (CYA) before I/R prevents liver injury. In this study we hypothesized that Hh signaling may modulate I/R injury in cholestatic rat liver. Cholestasis was induced by bile duct ligation (BDL). Seven days after BDL, rats were exposed to either CYA or vehicle for 7 days daily before being subjected to 30 min of ischemia and 4 h of reperfusion. Expression of Hh ligands (Sonic Hedgehog, Patched-1 and Glioblastoma-1), assessment of liver injury, neutrophil infiltration, cytokines, lipid peroxidation, cell proliferation and apoptosis were determined. Significant upregulation of Hh ligands was seen in vehicle treated BDL rats. I/R injury superimposed on these animals resulted in markedly elevated serum alanine transaminase (ALT), aspartate transaminase (AST), total bilirubin accompanied with increased neutrophil recruitment and lipid peroxidation. Preconditioning with CYA reduced the histological damage and serum liver injury markers. CYA also reduced neutrophil infiltration, proinflammatory cytokines such as TNF-α and IL-1β expression of α-smooth muscle actin and type 1 collagen resulting in reduced fibrosis. Furthermore CYA treated animals showed reduced cholangiocyte proliferation, and apoptosis. Hepatoprotection by CYA was conferred by reduced activation of protein kinase B (Akt) and extracellular signal regulated kinase (ERK). Endogenous Hh signaling in cholestasis exacerbates inflammatory injury during liver I/R. Blockade of Hh pathway represents a clinically relevant novel approach to limit I/R injury in cholestatic marginal liver.

Interleukin-6 plays a protective role in development of cisplatin-induced acute renal failure through upregulation of anti-oxidative stress factors

AIMS

Cisplatin, a major chemotherapeutic agent, accumulates in proximal tubules of the kidneys and causes acute renal failure dose-dependently. We previously reported that cisplatin induced more severe renal dysfunction in interleukin-6 (IL-6) knockout (IL-6(-/-)) mice than in wild-type (WT) mice. Expression of a pro-apoptotic protein was significantly increased with cisplatin in IL-6(-/-) mice compared to that in WT mice. IL-6, locally expressed in renal tubular cells after cisplatin administration, prevents the development of renal dysfunction at an early stage. In the present study, we focused on downstream signals of IL-6 and oxidative stress induced by cisplatin in order to evaluate the protective role of IL-6 in the development of acute renal failure.

MAIN METHODS

WT and IL-6(-/-) mice were given either cisplatin (30 mg/kg) or saline intraperitoneally. Blood and kidney samples were collected at 24h and 72 h after cisplatin administration. The changes in expression of 4-hydroxy-2-nonenal protein (4-HNE, oxidative stress marker) and cyclooxygenase-2 (cox-2), activities of superoxide dismutases and caspase-3, and phosphorylation of extracellular signal-regulated kinase (ERK) were examined.

KEY FINDINGS

Cisplatin increased the expression of 4-HNE and cox-2, and phosphorylation of ERK in IL-6(-/-) mice than in WT mice. On the other hand, activity of superoxide dismutase, an anti-oxidative enzyme, was significantly decreased in the kidney obtained from IL-6(-/-) mice after cisplatin administration.

SIGNIFICANCE

Our findings suggest that IL-6 plays a protective role in the development of cisplatin-induced acute renal failure through upregulation of anti-oxidative stress factors.

Animal models for the study of liver fibrosis: new insights from knockout mouse models

Fibrosis arises as part of a would-healing response that maintains organ structure and integrity following tissue damage but also contributes to a variety of human pathologies such as liver fibrosis. Liver fibrosis is an abnormal response of the liver to persistent injury with the excessive accumulation of collagenous extracellular matrices. Currently there is no effective treatment, and many patients end up with a progressive form of the disease, eventually requiring a liver transplant. The clarification of mechanisms underlying pathogenesis of liver fibrosis and the development of effective therapy are of clinical importance. Experimental animal models, in particular targeted gene knockouts (loss of function) in mice, have become a powerful resource to address the molecular mechanisms or significance of the targeted gene in hepatic functions and diseases. This review will focus on the recent advances in knowledge obtained from genetically engineered mice that provide novel insights into the pathophysiology of liver fibrosis.

NK cells suppress experimental cholestatic liver injury by an interleukin-6-mediated, Kupffer cell-dependent mechanism

BACKGROUND & AIMS

Natural killer (NK) cells are innate immune effector cells first characterized by their ability to lyse susceptible tumor cells. Recent studies demonstrated their role in initiating and modulating adaptive immunity. NK cells represent a larger percentage of the lymphoid population in liver than other organs, suggesting that hepatic NK cells express some unique function. Here, we examined the response of NK cells to liver injury that occurs in a mouse model of biliary obstruction.

METHODS

Bile duct ligations (BDL) were performed in mice previously depleted or not depleted of NK cells. NK cell activation, interleukin (IL)-6 mRNA expression and protein production by Kupffer cells, and the ability of exogenous IL-6 to ameliorate liver injury in NK cell-depleted mice, were determined.

RESULTS

The number of activated hepatic NK cells increased markedly following BDL. Activation was suppressed in mice rendered Kupffer cell-depleted prior to ligation. Increased liver injury occurred in NK cell-depleted mice correlating with a reduction in IL-6 production. Purified Kupffer cells, obtained from NK cell-depleted or anti-interferon (IFN)-γ monoclonal antibody-pretreated mice following BDL, produced less IL-6 in culture than did Kupffer cells derived from control animals. In culture, hepatic NK cells derived from BDL mice stimulated IFN-γ-dependent IL-6 production by Kupffer cells; splenic NK cells obtained from the same animals had a negligible effect. Treatment with recombinant murine IL-6 reduced liver injury in BDL, NK cell-depleted mice.

CONCLUSIONS

Hepatic NK cells suppress cholestatic liver injury by stimulating Kupffer cell-dependent IL-6 production.

Impact of HIV on liver fibrosis in men with hepatitis C infection and haemophilia

Hepatitis C virus (HCV) is the major cause of liver disease in haemophilia. Few data exist on the proportion with liver fibrosis in this group after long-term HCV and HIV co-infection. We conducted a cross-sectional multi-centre study to determine the impact of HIV on the prevalence and risk factors for fibrosis in haemophilic men with chronic hepatitis C. Biopsies were independently scored by Ishak, Metavir and Knodell systems. Variables were tested for associations with fibrosis using logistic regression and receiver operating curves (ROC). Of 220 biopsied HCV(+) men, 23.6% had Metavir ≥ F3 fibrosis, with higher mean Metavir fibrosis scores among HIV/HCV co-infected than HCV mono-infected, 1.6 vs. 1.3 (P = 0.044). Variables significantly associated with fibrosis included AST, ALT, APRI score (AST/ULN × 100/platelet × 10(9) /L), alpha-fetoprotein (all P < 0.0001), platelets (P = 0.0003) and ferritin (P = 0.0008). In multiple logistic regression of serum markers, alpha-fetoprotein, APRI and ALT were significantly associated with ≥ F3 fibrosis [AUROC = 0.77 (95% CI 0.69, 0.86)]. Alpha-fetoprotein, APRI and ferritin were significant in HIV(-) [AUROC = 0.82 (95% CI 0.72, 0.92)], and alpha-fetoprotein and platelets in HIV(+) [AUROC = 0.77 (95% CI 0.65, 0.88]. In a multivariable model of demographic and clinical variables, transformed (natural logarithm) of alpha-fetoprotein (P = 0.0003), age (P = 0.006) and HCV treatment (P = 0.027) were significantly associated with fibrosis. Nearly one-fourth of haemophilic men have Metavir ≥ 3 fibrosis. The odds for developing fibrosis are increased in those with elevated alpha-fetoprotein, increasing age and past HCV treatment.

Deletion of interleukin-6 in mice with the dominant negative form of transforming growth factor beta receptor II improves colitis but exacerbates autoimmune cholangitis

The role of interleukin-6 (IL-6) in autoimmunity attracts attention because of the clinical usage of monoclonal antibodies to IL-6 receptor (IL-6R), designed to block IL-6 pathways. In autoimmune liver disease, activation of the hepatocyte IL-6/STAT3 (signal transducer and activator of transcription 3) pathway is associated with modulating pathology in acute liver failure, in liver regeneration, and in the murine model of concanavalin A-induced liver inflammation. We have reported that mice expressing a dominant negative form of transforming growth factor beta receptor II (dnTGFbetaRII) under control of the CD4 promoter develop both colitis and autoimmune cholangitis with elevated serum levels of IL-6. Based on this observation, we generated IL-6-deficient mice on a dnTGF-betaRII background (dnTGFbetaRII IL-6(-/-)) and examined for the presence of antimitochondrial antibodies, levels of cytokines, histopathology, and immunohistochemistry of liver and colon tissues. As expected, based on reports of the use of anti-IL-6R in inflammatory bowel disease, dnTGFbetaRII IL-6(-/-) mice manifest a dramatic improvement in their inflammatory bowel disease, including reduced diarrhea and significant reduction in intestinal lymphocytic infiltrates. Importantly, however, autoimmune cholangitis in dnTGFbetaRII IL-6(-/-) mice was significantly exacerbated, including elevated inflammatory cytokines, increased numbers of activated T cells, and worsening hepatic pathology.

CONCLUSION

The data from these observations emphasize that there are distinct mechanisms involved in inducing pathology in inflammatory bowel disease compared to autoimmune cholangitis. These data also suggest that patients with inflammatory bowel disease may not be the best candidates for treatment with anti-IL-6R if they have accompanying autoimmune liver disease and emphasize caution for therapeutic use of anti-IL-6R antibody.

Signal transducer and activator of transcription 3 protects from liver injury and fibrosis in a mouse model of sclerosing cholangitis

BACKGROUND & AIMS

Signal transducer and activator of transcription 3 (Stat3) is the main mediator of interleukin-6-type cytokine signaling required for hepatocyte proliferation and hepatoprotection, but its role in sclerosing cholangitis and other cholestatic liver diseases remains unresolved.

METHODS

We investigated the role of Stat3 in inflammation-induced cholestatic liver injury and used mice lacking the multidrug resistance gene 2 (mdr2(-/-)) as a model for SC.

RESULTS

We show that conditional inactivation of Stat3 in hepatocytes and cholangiocytes (stat3(Deltahc)) of mdr2(-/-) mice strongly aggravated bile acid-induced liver injury and fibrosis. A similar phenotype was observed in mdr2(-/-) mice lacking interleukin-6 production. Biochemical and molecular characterization suggested that Stat3 exerts hepatoprotective functions in both hepatocytes and cholangiocytes. Loss of Stat3 led to increased expression of tumor necrosis factor alpha, which might reduce the barrier function of bile ducts. Moreover, Stat3-deficient hepatocytes displayed up-regulation of bile acid biosynthesis genes and down-regulation of hepatoprotective epidermal growth factor receptor and insulin-like growth factor 1 signaling pathways. Consistently, stat3(Deltahc) mice were more sensitive to cholic acid-induced liver damage than control mice.

CONCLUSIONS

Our data suggest that Stat3 prevents cholestasis and liver damage in sclerosing cholangitis via regulation of pivotal functions in hepatocytes and cholangiocytes.

Foxa1 and Foxa2 regulate bile duct development in mice

The forkhead box proteins A1 and A2 (Foxa1 and Foxa2) are transcription factors with critical roles in establishing the developmental competence of the foregut endoderm and in initiating liver specification. Using conditional gene ablation during a later phase of liver development, we show here that deletion of both Foxa1 and Foxa2 (Foxa1/2) in the embryonic liver caused hyperplasia of the biliary tree. Abnormal bile duct formation in Foxa1/2-deficient liver was due, at least in part, to activation of IL-6 expression, a proliferative signal for cholangiocytes. The glucocorticoid receptor is a negative regulator of IL-6 transcription; in the absence of Foxa1/2, the glucocorticoid receptor failed to bind to the IL-6 promoter, causing enhanced IL-6 expression. Thus, after liver specification, Foxa1/2 are required for normal bile duct development through prevention of excess cholangiocyte proliferation. Our data suggest that Foxa1/2 function as terminators of bile duct expansion in the adult liver through inhibition of IL-6 expression.

Lack of glycoprotein 130/signal transducer and activator of transcription 3-mediated signaling in hepatocytes enhances chronic liver injury and fibrosis progression in a model of sclerosing cholangitis

The 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) model leads to chronic cholestatic liver injury and therefore resembles human diseases such as sclerosing cholangitis and forms of metabolic liver diseases. The role of the interleukin-6/glycoprotein 130 (gp130) system in this context is still undefined. Therefore, conditional gp130 knockout and knockin mice were used to achieve hepatocyte-specific deletions of gp130 (gp130(Deltahepa)), gp130-dependent ras (gp130(DeltahepaRas)), and signal transducer and activator of transcription (STAT) (gp130(DeltahepaSTAT)) activation. These mice were treated with a DDC-containing diet and analyzed over time. Mice deficient in hepatic gp130 and STAT signaling showed increased and earlier mortality than wild-type and gp130(DeltahepaRas) animals. Over time, significantly more apoptosis and cholestasis became evident in gp130(Deltahepa) and gp130(DeltahepaSTAT) mice. These mice also displayed increased tumor necrosis factor-alpha expression, a diminished acute-phase response (lack of STAT3 and serum amyloid A activation), and enhanced immune cell infiltration in the liver. These were associated with stronger periportal oval cell activation. In addition, DDC treatment in gp130(Deltahepa) and gp130(DeltahepaSTAT) mice resulted in significantly stronger hepatic stellate cell activation. Long-term analysis revealed the development of severe liver fibrosis in gp130(Deltahepa) and gp130(DeltahepaSTAT) animals, as evidenced by increased collagen accumulation. Here we demonstrate that gp130/STAT signaling in hepatocytes provides protection in a cholestatic hepatitis mouse model. STAT3-dependent signaling pathways in hepatocytes protect from apoptosis and tissue injury, which subsequently reduce oval cell activation and prevent fibrosis progression.

Rapamycin inhibits cholangiocyte regeneration by blocking interleukin-6-induced activation of signal transducer and activator of transcription 3 after liver transplantation

Cholangiocyte proliferation is necessary for biliary recovery from cold ischemia and reperfusion injury (CIRI), but there are few studies on its intracellular mechanism. In this process, the role of rapamycin, a new immunosuppressant used in liver transplantation, is still unknown. In order to determine whether rapamycin can depress cholangiocyte regeneration by inhibiting signal transducer and activator of transcription 3 (STAT3) activation, rapamycin (0.05 mg/kg) was administered to rats for 3 days before orthotopic liver transplantation. The results indicated that cholangiocytes responded to extended cold preservation (12 hours) with severe bile duct injures, marked activation of the interleukin-6 (IL-6)/STAT3 signal pathway, and increased expression of cyclin D1 until 7 days after transplantation, and this was followed by compensatory cholangiocyte regeneration. However, rapamycin treatment inhibited STAT3 activation and resulted in decreased cholangiocyte proliferation and delayed biliary recovery after liver transplantation. On the other hand, rapamycin showed no effect on the expression of IL-6. We conclude that the IL-6/STAT3 signal pathway is involved in initiating cholangiocytes to regenerate and repair CIRI. Rapamycin represses cholangiocyte regeneration by inhibiting STAT3 activation, which might have a negative effect on the healing and recovery of bile ducts in grafts with extended cold preservation. Insights gained from this study will be helpful in designing therapy using rapamycin in clinical patients after liver transplantation.

Interleukin-6 deficiency accelerates cisplatin-induced acute renal failure but not systemic injury

Cisplatin (CDDP), a major chemotherapeutic agent used to treat solid tumors, is known to induce acute renal failure (ARF). The progression of tissue injury involves the coordination of inflammatory and repair responses. Interleukin-6 (IL-6) has been suggested to modulate inflammatory and repair processes in various tissue injuries. In this study, we analyzed IL-6 regulation during CDDP-induced ARF in wild-type (WT) mice and determined the pathological role of IL-6 using IL-6 knockout ((-/-)) mice. A correlation between increase in serum IL-6 level and blood urea nitrogen level was found in WT mice. Renal IL-6 expression in most proximal tubular cells and suppressor of cytokine signaling 3 (SOCS3) gene expression significantly increased in WT mice after administration of CDDP, suggesting active IL-6 signaling during CDDP-induced ARF development. Interestingly, renal dysfunction occurred soon after administration of CDDP and became more severe in IL-6(-/-) mice than that in WT mice. In contrast, the survival rate of IL-6(-/-) mice (50% at 8 days) was better than that of WT mice (10%). Induction levels of proapoptotic Bcl-2 associated X protein (Bax) in renal proximal tubular cells was significantly higher in IL-6(-/-) mice than in WT mice at 24h after CDDP injection. Levels of antiapoptotic proteins, Bcl-2 and Bcl-extra large (Bcl-x(L)), in IL-6(-/-) groups were significantly higher than those in CDDP-treated WT groups throughout the experimental period. Bax might contribute to the development of CDDP-induced ARF at 24h; however, high expression levels of Bcl-x(L) and Bcl-2 might overcome the proapoptosis signaling at 72 h in IL-6(-/-) mice. These results indicated that local and systemic elevation of IL-6 contributes to the development of CDDP-induced ARF and that IL-6 produced in renal tubular cells prevents progression of ARF at the early stage. IL-6 deficiency accelerates CDDP-induced ARF but not development of systemic injury.

Involvement of sphingosine 1-phosphate (SIP)/S1P3 signaling in cholestasis-induced liver fibrosis

Bioactive sphingosine 1-phosphate (S1P) and S1P receptors (S1PRs) have been implicated in many critical cellular events, including inflammation, cancer, and angiogenesis. However, the role of S1P/S1PR signaling in the pathogenesis of liver fibrosis has not been well documented. In this study, we found that S1P levels and S1P(3) receptor expression in liver tissue were markedly up-regulated in a mouse model of cholestasis-induced liver fibrosis. In addition, the S1P(3) receptor was also expressed in green fluorescent protein transgenic bone marrow (BM)-derived cells found in the damaged liver of transplanted chimeric mice that underwent bile duct ligation. Silencing of S1P(3) expression significantly inhibited S1P-induced BM cell migration in vitro. Furthermore, a selective S1P(3) receptor antagonist, suramin, markedly reduced the number of BM-derived cells during cholestasis. Interestingly, suramin administration clearly ameliorated bile duct ligation-induced hepatic fibrosis, as demonstrated by attenuated deposition of collagen type I and III, reduced smooth muscle alpha-actin expression, and decreased total hydroxyproline content. In conclusion, our data suggest that S1P/S1P(3) signaling plays an important role in cholestasis-induced liver fibrosis through mediating the homing of BM cells. Modulation of S1PR activity may therefore represent a new antifibrotic strategy.

Foxa1 and Foxa2 regulate bile duct development in mice

The forkhead box proteins A1 and A2 (Foxa1 and Foxa2) are transcription factors with critical roles in establishing the developmental competence of the foregut endoderm and in initiating liver specification. Using conditional gene ablation during a later phase of liver development, we show here that deletion of both Foxa1 and Foxa2 (Foxa1/2) in the embryonic liver caused hyperplasia of the biliary tree. Abnormal bile duct formation in Foxa1/2-deficient liver was due, at least in part, to activation of IL-6 expression, a proliferative signal for cholangiocytes. The glucocorticoid receptor is a negative regulator of IL-6 transcription; in the absence of Foxa1/2, the glucocorticoid receptor failed to bind to the IL-6 promoter, causing enhanced IL-6 expression. Thus, after liver specification, Foxa1/2 are required for normal bile duct development through prevention of excess cholangiocyte proliferation. Our data suggest that Foxa1/2 function as terminators of bile duct expansion in the adult liver through inhibition of IL-6 expression.

Transcriptional regulation of IL-6 in bile duct epithelia by extracellular ATP

The inflammatory cytokine IL-6 is essential for cell survival after liver injury. Bile duct epithelia (BDE) markedly upregulate IL-6 release after liver injury, but the mechanisms regulating this have not been defined. Purinergic signals induce multiple potent downstream effects in BDE, so the goals of this study were to determine whether extracellular ATP regulates BDE IL-6 transcription and to identify the molecular mechanisms regulating this process. Effects of extracellular nucleotides on IL-6 transcription in primary rat bile duct epithelia were assessed. The relative effects of cAMP and cytosolic calcium were determined by use of agonists and antagonists. The role of the cAMP response element (CRE) was determined by site-directed mutagenesis. We found that ATP potently upregulated IL-6 mRNA, and that the pharmacological profile for IL-6 upregulation was most consistent with the newly identified P2Y11 receptor. This occurred in a cAMP-dependent and calcium-dependent fashion. The effect of cAMP and calcium agonists on IL-6 promoter activity was synergistic, and mutation of the IL-6 CRE blocked upregulation by ATP. Taken together, these data show that extracellular ATP acts through a mechanism involving a rat P2Y receptor functionally related to the P2Y11 receptor, cAMP, and calcium signals and that the IL-6 promoter CRE to upregulate transcription of IL-6 in BDE. Since IL-6 has such critical importance in the liver, it is likely that this pathway is of great relevance to the understanding of hepatic response to injury.

Single administration of thrombopoietin prevents progression of liver fibrosis and promotes liver regeneration after partial hepatectomy in cirrhotic rats

OBJECTIVE

To evaluate the effect of thrombopoietin on liver regeneration after hepatectomy and antifibrosis under conditions of liver cirrhosis in rats.

SUMMARY BACKGROUND DATA

We revealed that platelets induced by thrombopoietin administration promote liver regeneration after hepatectomy in the normal liver.

METHODS

Seventy percent hepatectomy was carried out in rats, which were subsequently divided into 4 groups: (1) normal group without any treatment, (2) liver cirrhosis (LC) group, (3) combined thrombopoietin and liver cirrhosis (LC+TPO) group, and (4) combined thrombopoietin, antiplatelet serum and liver cirrhosis (LC+TPO+APS) group. Growth kinetics in the liver regeneration and growth factors were analyzed. Liver fibrotic area and activation of hepatic stellate cells were also investigated.

RESULTS

In LC group, liver regeneration was significantly delayed compared with normal group 24 hours after hepatectomy. On the other hand, liver regeneration of LC+TPO group increased significantly compared with LC group, to a level that was the same as that recorded in normal group. In LC group, liver fibrotic area before hepatectomy was significantly higher compared with the normal group. Liver fibrosis of LC+TPO group was significantly reduced compared with LC group. The antifibrotic and liver regeneration promoting effects of LC+TPO group were inhibited by antiplatelet serum in LC+TPO+APS group.

CONCLUSION

The administration of thrombopoietin reduces liver fibrosis and stimulates regeneration after hepatectomy through increment and accumulation of platelets in the cirrhotic liver. This could be a potentially useful treatment for liver cirrhosis.